Introduction
1. The purpose of the braking system of the car……………………………………
2. The device of the brake system………………………………………………….
3. Arrangement of the main mechanisms and devices of the brake system
KAMAZ vehicles…………………………………………………………………
3.1. Brake mechanism…………………………………………………………
3.2. Adjusting lever……………………………………………………….
3.3. The mechanism of the auxiliary brake system…………………………..
3.4. Compressor…………………………………………………………………….
3.5. Dehumidifier…………………………………………………………………
3.6. Pressure regulator……………………………………………………………
3.7. Brake valve……………………………………………………………….
3.8. Automatic brake force regulator………………………………….
3.9. Four-circuit safety valve……………………………………….
3.10. Receivers…………………………………………………………………………
3.11. Brake chamber…………………………………………………………….
3.12. Pneumatic cylinders…………………………………………………..
3.13. Valves and gauges………………………………………………………………
4. Maintenance and repair of the brake system……………………...
Bibliography…………………………………………………………….
Introduction
KamAZ trucks are designed to work in all sectors of the national economy. The KamAZ association, which includes 10 main plants, produces vehicles with wheel formulas 4 × 2, 6 × 4 and 6 × 6 - for operation on roads with different coating and all-wheel drive - off-road.
Specialized equipment based on these vehicles is also produced (banking, fire, construction cranes, concrete mixers).
Figure 1 shows a diagram of a KamAZ-53215 vehicle with a 6 × 4 wheel arrangement, designed to transport goods weighing up to 10 tons on roads with improved coverage as part of a road train (with a trailer).
Figure 1 - Car KamAZ-53215
KamAZ vehicles, like other vehicles, consists of a number of systems (starting; fuel supply; lubrication; cooling; brake, etc.), their units and assemblies, as well as frames, cabs, platforms, engines, transmissions, etc.
Each system and unit performs its own functions to ensure the smooth and safe operation of the entire vehicle.
KamAZ vehicles and road trains are equipped with four autonomous brake systems: working, spare, parking, auxiliary and emergency brake release drive.
Although these systems have common elements, they work independently and provide high braking performance in all operating conditions.
1. The purpose of the braking system of the car
The service brake system is designed to reduce the speed of the vehicle or stop it completely. The brake mechanisms of the service brake system are installed on all six wheels of the vehicle. The drive of the working brake system is pneumatic double-circuit, it drives separately the brake mechanisms of the front axle and the rear bogie of the car. The drive is controlled by a foot pedal mechanically connected to the brake valve. The executive bodies of the drive of the working brake system are the brake chambers.
The spare brake system is designed to smoothly reduce the speed or stop a moving vehicle in the event of a complete or partial failure of the working system.
The parking brake system provides braking of the motionless car on a horizontal site, and also on a slope and in the absence of the driver.
The parking brake system on KamAZ vehicles is made as a single unit with the spare one, and to enable it, the handle of the manual crane should be set to the extreme (upper) fixed position.
The emergency release drive provides the possibility of resuming the movement of the car (road train) during its automatic braking due to leakage of compressed air, alarms and control devices that allow you to monitor the operation of the pneumatic drive.
Thus, in KamAZ vehicles, the brake mechanisms of the rear bogie are common for the working, spare and parking brake systems, and the last two have, in addition, a common pneumatic drive.
The brake auxiliary system of the car serves to reduce the load and temperature of the brake mechanisms of the working brake system. The auxiliary brake system on KamAZ vehicles is an engine retarder, when turned on, the engine exhaust pipes are blocked and the fuel supply is turned off.
emergency system brake release is designed to release spring energy accumulators when they are automatically activated and the vehicle stops due to leakage of compressed air in the drive.
The drive of the emergency release system is duplicated: in addition to the pneumatic drive, there are emergency release screws in each of the four spring-loaded energy accumulators, which makes it possible to release the latter mechanically.
The alarm and control system consists of two parts:
A) light and acoustic signaling of the operation of brake systems and their drives.
At various points of the pneumatic drive, pneumatic-electric sensors are built-in, which, under the action of any brake system, except for the auxiliary one, close the circuits of the “stop light” electric lamps.
Pressure drop sensors are installed in the actuator reservoirs and when insufficient pressure in the latter, they close the circuits of signal electric lamps located on the instrument panel of the car, as well as the circuit of the sound signal (buzzer).
B) valves of control outputs, with the help of which the diagnostics of the technical condition of the pneumatic brake actuator is carried out, as well as (if necessary) the selection of compressed air.
2. The device of the brake system
Figure 2 shows a diagram of the pneumatic drive of the brake mechanisms of KamAZ-43101, -43114 vehicles.
Compressor 9 is the source of compressed air in the drive. Compressor, pressure regulator 11, fuse 12 against freezing of condensate, condensate receiver 20 constitute the supply part of the drive, from which purified compressed air at a given pressure is supplied in the required amount to the remaining parts of the pneumatic brake drive and to others. compressed air consumers.
The pneumatic brake drive is divided into autonomous circuits, separated from each other by protective valves. Each circuit operates independently of other circuits, even in the event of a fault. The pneumatic brake actuator consists of five circuits separated by one double and one triple safety valve.
The circuit I of the drive of the working brake mechanisms of the front axle consists of a part of the triple protective valve 17; receiver 24 with a capacity of 20 l with a condensate drain valve and a pressure drop sensor 18 in the receiver, parts of a two-pointer pressure gauge 5; lower section of a two-section brake valve 16; control outlet valve 7 (C); pressure limiting valve 8; two brake chambers 1; brake mechanisms of the front axle of the tractor; pipelines and hoses between these devices.
In addition, the circuit includes a pipeline from the lower section of the brake valve 16 to the valve 81 for controlling the brake systems of the trailer with a two-wire drive.
The circuit II of the drive of the working brake mechanisms of the rear bogie consists of a part of the triple protective valve 17; receivers 22 with a total capacity of 40 liters with condensate drain valves 19 and a pressure drop sensor 18 in the receiver; parts of a two-pointer manometer 5; the upper section of the two-section brake valve 16; control output valve (D) of the automatic brake force regulator 30 with an elastic element; four brake chambers 26; brake mechanisms of the rear bogie (intermediate and rear axles); pipelines and hose between these devices. The circuit also includes a pipeline from the upper section of the brake valve 16 to the brake control valve 31 with a two-wire drive.
The circuit III of the drive of the mechanisms of the spare and parking brake systems, as well as the combined drive of the brake mechanisms of the trailer (semi-trailer) consists of a part of the double protective valve 13; two receivers 25 with a total capacity of 40 liters with a condensate drain valve 19 and a pressure drop sensor 18 in the receivers; two valves 7 of the control output (B and E) of the manual brake valve 2; accelerating valve 29; parts of the dual-line bypass valve 32; four spring energy accumulators 28 brake chambers; pressure drop sensor 27 in the line of spring energy accumulators; valve 31 for controlling the brake mechanisms of a trailer with a two-wire drive; single protective valve 35; valve 34 for controlling the brake mechanisms of a trailer with a single-wire drive; three uncoupling taps 37 three connecting heads; heads 38 type A single-wire trailer brakes and two heads 39 type "Palm" two-wire trailer brakes; two-wire trailer brake drive; pneumoelectric sensor 33 "stop lights", pipelines and hoses between these devices. It should be noted that the pneumoelectric sensor 33 in the circuit is installed in such a way that it ensures that the "stop light" lamps are turned on when the car is braked not only by the spare (parking) brake system, but also by the working one, as well as in the event of failure of one of the circuits of the latter .
Circuit IV of the drive of the auxiliary brake system and other consumers does not have its own receiver and consists of a part of a double protective valve 13; pneumatic valve 4; two cylinders 23 damper drive; cylinder 10 of the engine stop lever drive; pneumoelectric sensor 14; pipelines and hoses between these devices.
From circuit IV of the drive of the mechanisms of the auxiliary brake system, compressed air is supplied to additional (non-brake) consumers; pneumatic signal, pneumohydraulic clutch booster, control of transmission units, etc.
Circuit V of the emergency release drive does not have its own receiver and executive bodies. It consists of part of a triple safety valve 17; pneumatic valve 4; parts of the dual-line bypass valve 32; pipelines and hoses connecting the devices.
1 - type 24 brake chambers; 2 (A, B, C) - control conclusions; 3 - pneumoelectric switch of the electromagnetic valve of the trailer; 4 - control valve for the auxiliary brake system; 5 - two-pointer manometer; 6 - compressor; 7 - pneumatic cylinder of the drive of the engine stop lever; 8 - water separator; 9 - pressure regulator; 11 - two-line bypass valve; 12-4 circuit safety valve; 13 - parking brake control valve; 14 - heat exchanger; 15 - two-section brake valve; 17 - pneumatic cylinders for the drive of the dampers of the mechanism of the auxiliary brake system; 18 - receiver circuit I; 19 - consumer receiver; 20 - pressure drop alarm switch; 21 - receiver circuit III; 22 - receivers of circuit II; 23 - condensate drain valve; 24 - brake chambers of type 20/20 with spring energy accumulators; 25, 28 - accelerating valves; 26 - valve for controlling the brake systems of a trailer with a two-wire drive; 27 - switch of the signaling device of the parking brake system; 29 - valve for controlling the brake systems of a trailer with a single-wire drive; 30 - automatic connecting heads; 31 - connecting head type A; R - to the supply line of the two-wire drive; P - to the connecting line of a single-wire drive; N - to the control line of the two-wire drive; 31 - pressure drop sensor in the receivers of the 1st circuit; 32 - pressure drop sensor in the receivers of the second circuit; 33 - brake light sensor; 34-faucet emergency release
Figure 2 - Scheme of the pneumatic drive of the brake mechanisms of KamAZ-43101, 43114
Pneumatic brake drives of the tractor and trailer connect three lines: a single-wire drive line, supply and control (brake) lines of a two-wire drive. On the truck tractors connecting heads 38 and 39 are located at the ends of three flexible hoses of these lines, fixed on a supporting rod. On board vehicles, heads 38 and
39 are mounted on the rear cross member of the frame.
To improve moisture separation in the supply part of the brake drive of cars of models 53212, 53213, a dehumidifier is additionally installed on the first cross member in the section compressor - pressure regulator
A car in a zone of intense airflow.
For the same purpose, on all models of the KamAZ vehicle, a condensing receiver with a capacity of 20 liters is provided in the fuse-protective valves section against freezing. Dump truck 55111 does not have trailer brake control equipment, release valves, and coupling heads.
To monitor the operation of the pneumatic brake drive and timely signal its condition and malfunctions in the cab, the instrument panel has five signal lights, a two-pointer pressure gauge showing the pressure of compressed air in the receivers of two circuits (I and II) of the pneumatic drive of the working brake system, and a buzzer , signaling an emergency drop in compressed air pressure in the receivers of any brake circuit.
3. Arrangement of the main mechanisms and devices of the brake system
KamAZ vehicles
3.1. Brake mechanism
The brake mechanisms (Figure 3) are installed on all six wheels of the vehicle, the main assembly of the brake mechanism is mounted on a caliper 2 rigidly connected to the axle flange. On the eccentrics of axles 1, fixed in the caliper, two brake pads 7 with friction linings 9 attached to them, made along a sickle-shaped profile in accordance with the nature of their wear. Shoe axes with eccentric bearing surfaces make it possible to correctly center the shoes relative to the brake drum when assembling the brake mechanisms. The brake drum is attached to the wheel hub.
Five bolts.
When braking, the pads are moved apart by the S-shaped fist 12 and pressed against the inner surface of the drum. Rollers 13 are installed between the expanding fist 12 and pads 7, reducing friction and improving braking efficiency. The pads are returned to the braked state by four retracting springs 8.
Expanding fist 12 rotates in bracket 10, bolted to the caliper. The brake chamber is mounted on this bracket. At the end of the shaft of the expanding fist, a worm-type adjusting lever 14 is installed, connected to the rod of the brake chamber with a fork and a pin. A shield bolted to the caliper protects the brake mechanism from dirt.
1 - the axis of the block; 2 - support; 3 - shield; 4 - axle nut; 5 - lining of the axes of the pads;
6 - pin of the block axis; 7 - brake shoe; 8 - spring; 9 - friction lining; 10-bracket expanding fist; 11 - roller axis; 12 - expanding fist;
13 - roller; 14 - adjusting lever
Picture 3 - Brake mechanism
3.2. Adjusting lever
The adjusting lever is designed to reduce the gap between the shoes and the brake drum, which increases due to wear of the friction linings. The device of the adjusting lever is shown in Figure 4. The adjusting lever has a steel housing 6 with a bushing 7. The housing contains a worm gear 3 with splined holes for installation on an expanding fist and a worm 5 with an axle 11 pressed into it. locking device, the ball 10 of which enters the holes on the axis 11 of the worm under the action of the spring 9, abutting against the locking bolt 8. The gear wheel is kept from falling out by covers 1 attached to the body 6 of the lever. When turning the axis (at the square end), the worm turns the wheel 3, and with it the expanding fist turns, pushing the pads apart and reducing the gap between the pads and the brake drum. When braking, the adjusting lever is turned by the brake chamber rod.
Before adjusting the gap, the locking bolt 8 must be loosened by one or two turns, after adjustment, tighten the bolt securely.
1 - cover; 2 - rivet; 3 - gear wheel; 4 - plug; 5 - worm; 6 - body;
7 - bushing; 8 - locking bolt; 9 - retainer spring; 10 - retainer ball;
11 - worm axis; 12 - oiler
Picture 4 - Adjusting lever
3.3. Secondary Brake Mechanism
The mechanism of the auxiliary brake system is shown in Figure 5.
Housing 1 and damper 3 mounted on shaft 4 are installed in the exhaust pipes of the muffler. A rotary lever 2 is also fixed on the damper shaft, connected to the pneumatic cylinder rod. The lever 2 and the flap 3 associated with it have two positions. The inner cavity of the body is spherical. When the auxiliary brake system is turned off, damper 3 is installed along the exhaust gas flow, and when turned on, it is perpendicular to the flow, creating a certain counterpressure in the exhaust manifolds. At the same time, the fuel supply is cut off. The engine starts in compressor mode.
1 - body; 2 - rotary lever; 3 - damper; 4 - shaft
Figure 4 - The mechanism of the auxiliary brake system
3.4. Compressor
Compressor (Figure 5) piston type, single cylinder, single stage compression. The compressor is fixed on the front end of the engine flywheel housing.
The piston is aluminum, with a floating finger. From axial movement, the pin in the piston bosses is fixed by thrust rings. Air from the engine manifold enters the compressor cylinder through the reed inlet valve.
The air compressed by the piston is displaced into the pneumatic system through a lamellar discharge valve located in the cylinder head.
The head is cooled by liquid supplied from the engine cooling system. Oil is supplied to the rubbing surfaces of the compressor from the engine oil line: to the rear end of the compressor crankshaft and through the channels of the crankshaft to the connecting rod. The piston pin and cylinder walls are splash lubricated.
When the pressure in the pneumatic system reaches 800–2000 kPa, the pressure regulator communicates the pressure line with the environment, stopping the air supply to the pneumatic system.
When the air pressure in the pneumatic system drops to 650–50 kPa, the regulator closes the air outlet to the environment and the compressor starts again to pump air into the pneumatic system.
1- connecting rod; 2 - piston pin; 3 - oil scraper ring; 4 - compression ring;
5 - compressor cylinder housing; 6 - cylinder spacer; 7 - cylinder head;
8 - coupling bolt; 9 - nut; 10 - gaskets; 11 - piston; 12, 13 - sealing rings; 14 - plain bearings; 15 - rear crankcase cover; 16 - crankshaft; 17 - crankcase; 18 - drive gear; 19 - gear nut; I - input; II - output to the pneumatic system
Figure 5 - Compressor
3.5. water separator
The moisture separator is designed to separate condensate from compressed air and automatically remove it from the power part of the drive. The dehumidifier device is shown in Figure 6.
Compressed air from the compressor through inlet II is supplied to a finned aluminum cooler tube (radiator) 1, where it is constantly cooled by the oncoming air flow. Then the air passes through the centrifugal guide disks of the guide apparatus 4 through the hole of the hollow screw 3 in the housing 2 to the output I and further into the pneumatic brake actuator. The moisture released due to the thermodynamic effect, flowing down through the filter 5, accumulates in the bottom cover 7. When the regulator is triggered, the pressure in the dehumidifier drops, while the membrane 6 moves up. The condensate drain valve 8 opens, the accumulated mixture of water and oil is removed to the atmosphere through port III.
The direction of compressed air flow is shown by arrows on housing 2.
1 - radiator with finned tubes; 2 - body; 3 - hollow screw; 4 - guide apparatus; 5 - filter; 6 - membrane; 7 - cover; 8 - condensate drain valve;
I - to the pressure regulator; II - from the compressor; III - into the atmosphere
Figure 6 - Dehumidifier
3.6. pressure regulator
The pressure regulator (Figure 7) is intended for:
- to regulate the pressure of compressed air in the pneumatic system;
– protection of the pneumatic system from overload by excess pressure;
– purification of compressed air from moisture and oil;
– provision of tire inflation.
Compressed air from the compressor through output IV of the regulator, filter 2, channel 12 is fed into the annular channel. Through the check valve 11, compressed air enters the outlet II and further into the receivers of the vehicle's pneumatic system. At the same time, through channel 9, compressed air passes under piston 8, which is loaded with a balancing spring 5. At the same time, exhaust valve 4, connecting the cavity above the unloading piston 14 with the atmosphere through outlet I, is open, and inlet valve 13 is closed under the action of the spring. Under the action of the spring, the unloading valve 1 is also closed. In this state of the regulator, the system is filled with compressed air from the compressor. At a pressure in the cavity under piston 8 equal to 686.5 ... 735.5 kPa (7 ... 7.5 kgf / cm2), the piston, having overcome the force of the balancing spring 5, rises, valve 4 closes, inlet valve 13 opens.
Under the action of compressed air, the unloading piston 14 moves down, the unloading valve 1 opens, and the compressed air from the compressor through outlet III exits to the atmosphere along with the condensate accumulated in the cavity. In this case, the pressure in the annular channel drops and the check valve 11 closes. Thus, the compressor operates in unloaded mode without back pressure.
When the pressure in outlet II drops to 608...637.5 kPa, piston 8 moves down under the action of spring 5, valve 13 closes, and outlet valve 4 opens. In this case, the unloading piston 14 rises under the action of the spring, the valve 1 closes under the action of the spring, and the compressor pumps compressed air into the pneumatic system.
The unloading valve 1 also serves as a safety valve. If the regulator does not operate at a pressure of 686.5 ... 735.5 kPa (7 ... 7.5 kgf / cm2), then valve 1 opens, overcoming the resistance of its spring and piston spring 14. Valve 1 opens at a pressure of 980, 7... 1274.9 kPa (10... 13 kgf/cm2). The opening pressure is adjusted by changing the number of shims installed under the valve spring.
To join special devices the pressure regulator has an outlet that is connected to outlet IV through filter 2. This outlet is closed with a screw plug 3. In addition, an air bleed valve for tire inflation is provided, which is closed with a cap 17. air into the hose and blocking the passage of compressed air into the brake system. Before inflating the tires, the pressure in the reservoirs should be reduced to a pressure corresponding to the regulator switch-on pressure, since during idle move air sampling is not possible.
1 - unloading valve; 2 - filter; 3 - plug of the air sampling channel; 4 - exhaust valve; 5 - balancing spring; 6 - adjusting screw; 7 - protective cover; 8 - follower piston; 9, 10, 12 - channels; 11 - check valve;
13 - inlet valve; 14 - unloading piston; 15 - unloading valve seat; 16 - tire inflation valve; 17 - cap;
I, III - atmospheric conclusions; II - into the pneumatic system; IV - from the compressor;
C - cavity under the follower piston; D - cavity under the unloading piston
Picture 7 - Pressure regulator
3.7. Brake valve
A two-section brake valve (Figure 8) is used to control the actuators of the two-circuit drive of the vehicle's service brake system.
1 - pedal; 2 - adjusting bolt; 3 - protective cover; 4 - roller axis; 5 - roller; 6 - pusher; 7 - base plate; 8 - nut; 9 - plate; 10,16, 19, 27 - sealing rings; 11 - hairpin; 12 - spring follower piston; 13, 24 - valve springs; 14, 20 - plates of valve springs; 15 - small piston; 17 - lower section valve; 18 - small piston pusher; 21 - atmospheric valve; 22 - thrust ring; 23 - atmospheric valve body; 25 - lower body; 26 - small piston spring; 28 - large piston; 29 - valve of the upper section; 30 - follower piston; 31 - elastic element; 32 - upper body; A - hole; B - cavity above the large piston; I, II - input from the receiver; III, IV - output to the brake chambers, respectively, of the rear and front wheels
Figure 8 - Pedal-operated brake valve
The crane is controlled by a pedal directly connected to the brake valve.
The crane has two independent sections arranged in series. Inputs I and II of the crane are connected to the receivers of two separate drive circuits of the working brake system. From terminals III and IV, compressed air is supplied to the brake chambers. When you press the brake pedal, the force is transmitted through the pusher 6, the plate 9 and the elastic element 31 to the follower piston 30. Moving down, the follower piston 30 first closes the outlet of the valve 29 of the upper section of the brake valve, and then tears the valve 29 from the seat in the upper housing 32, opening the passage to compressed air through input II and output III and further to the actuators of one of the circuits. The pressure at terminal III rises until the force of pressing the pedal 1 is balanced by the force created by this pressure on the piston 30. This is how the follow-up action is carried out in the upper section of the brake valve. Simultaneously with the increase in pressure at port III, compressed air through hole A enters cavity B above the large piston 28 of the lower section of the brake valve. Moving down, the large piston 28 closes the valve outlet 17 and lifts it off the seat in the lower housing. Compressed air through input I enters output IV and then to the actuators of the primary circuit of the working brake system.
Simultaneously with the increase in pressure at port IV, the pressure under pistons 15 and 28 increases, as a result of which the force acting on piston 28 from above is balanced. As a result, pressure is also set at terminal IV, corresponding to the force on the brake valve lever. This is how the follow-up action is carried out in the lower section of the brake valve.
In the event of a failure in the operation of the upper section of the brake valve, the lower section will be mechanically controlled through the pin 11 and the pusher 18 of the small piston 15, fully maintaining its operability. In this case, the follow-up action is carried out by balancing the force applied to the pedal 1 by the air pressure on the small piston 15. If the lower section of the brake valve fails, the upper section operates as usual.
3.8. Automatic brake force regulator
The automatic brake force regulator is designed to automatically control the pressure of compressed air supplied to the brake chambers of the axles of the rear bogie of KamAZ vehicles during braking, depending on the current axial load.
The automatic brake force regulator is installed on bracket 1, fixed on the cross member of the vehicle frame (Figure 9). The regulator is attached to the bracket with nuts.
1 - regulator bracket; 2 - regulator; 3- lever; 4 - rod of the elastic element; 5 - elastic element; 6 - connecting rod; 7 - compensator; 8 - intermediate bridge; 9 - rear axle
Figure 9 - Installing the brake force regulator
The lever 3 of the regulator with the help of a vertical rod 4 is connected through the elastic element 5 and the rod 6 with the beams of the bridges 8 and 9 of the rear bogie. The regulator is connected to the axles in such a way that misalignment of the axles during braking on rough roads and twisting of the axles due to the action of the braking torque do not affect the correct regulation of the braking forces. The regulator is installed in a vertical position. The length of the lever arm 3 and its position with the unloaded axle are selected according to a special nomogram depending on the suspension travel when the axle is loaded and the ratio of the axial load in the laden and unladen state.
The device of the automatic brake force regulator is shown in Fig.
Ke 10. When braking, compressed air from the brake valve is supplied to the output I of the regulator and acts on the upper part of the piston 18, causing it to move down. At the same time, compressed air through the tube 1 enters under the piston 24, which moves up and is pressed against the pusher 19 and the ball joint 23, which, together with the regulator lever 20, is in a position depending on the load on the bogie axle. When the piston 18 moves down, the valve 17 is pressed against the outlet seat of the pusher 19. With further movement of the piston 18, the valve 17 breaks away from the seat in the piston and compressed air from outlet I enters outlet II and then to the brake chambers of the axles of the rear bogie car.
At the same time, compressed air through the annular gap between the piston 18 and the guide 22 enters the cavity A under the membrane 21 and the latter begins to put pressure on the piston from below. When pressure is reached at port II, the ratio of which to the pressure at port I corresponds to the ratio of the active areas of the upper and lower sides of the piston 18, the latter rises up until the valve 17 is seated on the inlet seat of the piston 18. The flow of compressed air from port I to port II stops. In this way, the follow-up action of the regulator is carried out. The active area of the upper side of the piston, which is affected by the compressed air supplied to port 7, always remains constant.
The active area of the lower side of the piston, which is affected by the compressed air through the membrane 21, which has passed into port II, is constantly changing due to a change in the relative position of the inclined ribs 11 of the moving piston 18 and the fixed insert 10. The mutual position of the piston 18 and insert 10 depends on the position of the lever 20 and associated with it through the heel 23 of the pusher 19. In turn, the position of the lever 20 depends on the deflection of the springs, that is, on the relative position of the bridge beams and the vehicle frame. The lower the lever 20, the heel 23, and hence the piston 18, falls, the greater the area of the ribs 11 comes into contact with the membrane 21, that is, the active area of the piston 18 from below becomes larger. Therefore, at the extreme lower position of the pusher 19 (minimum axial load), the difference in compressed air pressures in terminals I and II is the largest, and at the extreme upper position of the pusher 19 (maximum axial load), these pressures are equalized. Thus, the brake force regulator automatically maintains a compressed air pressure in port II and in the brake chambers associated with it, which provides the required braking force proportional to the axial load acting during braking.
When the brake is released, the pressure in port I drops. Piston 18, under compressed air pressure acting on it through membrane 21 from below, moves up and tears off valve 17 from the outlet seat of pusher 19. Compressed air from outlet II exits through the hole of the pusher and outlet III into the atmosphere, while squeezing the edges of the rubber valve 4.
1 - pipe; 2, 7 - sealing rings; 3 - lower body; 4 - valve; 5 - shaft;
6, 15 - thrust rings; 8 - membrane spring; 9 - membrane washer; 10 - insert; 11 - piston fins; 12 - cuff; 13 - valve spring plate; 14 - upper body; 16 - spring; 17 - valve; 18 - piston; 19 - pusher; 20 - lever; 21 - membrane; 22 - guide; 23 - ball heel; 24 - piston; 25 - guide cap; I - from the brake valve; II - to brake chambers rear wheels; III - into the atmosphere
Figure 10 - Automatic brake force regulator
The elastic element of the brake force regulator is designed to prevent damage to the regulator if the displacement of the axles relative to the frame is greater than the allowable stroke of the regulator lever.
The elastic element 5 of the brake force regulator is installed (Figure 11) on
Rod 6, located between the beams of the rear axles in a certain way.
The point of connection of the element with the regulator rod 4 is located on the axis of symmetry of the bridges, which does not move in the vertical plane when the bridges are twisted during braking, as well as with a one-sided load on an uneven road surface and when the bridges are skewed on curved sections when turning. Under all these conditions, only vertical movements from static and dynamic changes in the axial load are transmitted to the regulator lever.
The device of the elastic element of the brake force regulator is shown in Figure 11. When the bridges move vertically within the allowable stroke of the brake force regulator lever, the ball pin 4 of the elastic element is at the neutral point. With strong shocks and vibrations, as well as when the bridges move beyond the allowable stroke of the brake force regulator lever, the rod 3, overcoming the force of the spring 2, rotates in the housing 1. In this case, the rod 5 connecting the elastic element with the brake force regulator rotates relative to the deflected rod 3 around the ball pin 4.
After the termination of the force that deflects the rod 3, the pin 4 under the action of the spring 2 returns to its original neutral position.
1 - body; 2 - spring; 3 - rod; 4 - ball pin; 5 - regulator rod
Figure 11 - Elastic element of the brake force regulator
3.9. Four-circuit protective valve
The four-circuit protective valve (Figure 12) is designed to separate the compressed air coming from the compressor into two main and one additional circuits: for automatic shutdown of one of the circuits in case of violation of its tightness and preservation of compressed air in sealed circuits; to save compressed air in all circuits in case of leakage of the supply line; to supply an additional circuit from two main circuits (until the pressure in them drops to a predetermined level).
The four - circuit protective valve is attached to the side member of the vehicle frame .
1 - protective cap; 2 - spring plate; 3, 8, 10 - springs; 4 - spring guide; 5 - membrane; 6 - pusher; 7, 9 - valves; 11, 12 - screws; 13 - traffic jam; 14 - body; 15 - cover
Figure 12 - Four-circuit protective valve
The compressed air entering the four-circuit safety valve from the supply line, upon reaching the predetermined opening pressure set by the force of the springs 3, opens the valves 7, acting on the membrane 5, raises it, and enters through the outlets into the two main circuits. After opening the check valves, compressed air enters the valves 7, opens them and passes through the outlet to the additional circuit.
If the tightness of one of the main circuits is violated, the pressure in this circuit, as well as at the inlet to the valve, drops to a predetermined value. As a result, the valve of the healthy circuit and the check valve of the additional circuit are closed, preventing a decrease in pressure in these circuits. Thus, in good circuits, pressure will be maintained corresponding to the opening pressure of the valve of the faulty circuit, while excess compressed air will exit through the faulty circuit.
If the auxiliary circuit fails, the pressure drops in the two main circuits and at the inlet to the valve. This happens until valve 6 of the additional circuit closes. With further supply of compressed air to the protective valve 6 in the main circuits, the pressure will be maintained at the level of the opening pressure of the valve of the additional circuit.
3.10. receivers
The receivers are designed to accumulate compressed air produced by the compressor and to supply it to pneumatic brake drive devices, as well as to supply other pneumatic components and vehicle systems.
Six receivers with a capacity of 20 liters each are installed on the KamAZ vehicle, and four of them are interconnected in pairs, forming two tanks with a capacity of 40 liters each. The receivers are fixed with clamps on the brackets of the car frame. Three receivers are combined into a block and mounted on a single bracket.
Condensate drain valve (Figure 13) is designed for forced draining of condensate from the pneumatic brake drive receiver, as well as for releasing compressed air from it if necessary. The condensate drain valve is screwed into the threaded boss on the bottom of the receiver housing. The connection between the tap and the receiver boss is sealed with a gasket.
1 - stock; 2 - spring; 3 - body; 4 - support ring; 5 - washer; 6 - valve
Figure 13 - Condensate drain valve
3.11. brake chamber
A brake chamber with a spring-loaded energy accumulator type 20/20 is shown in Figure 14. It is designed to actuate the brake mechanisms of the wheels of the rear bogie of the car when the working, spare and parking brake systems are turned on.
Spring-loaded energy accumulators together with brake chambers are mounted on the brackets of the expanding cams of the brake mechanisms of the rear bogie and secured with two nuts and bolts.
When braking by the working brake system, compressed air from the brake valve is supplied to the cavity above the membrane 16. The membrane 16, bending, acts on the disk 17, which moves the stem 18 through the washer and locknut and turns the adjusting lever with the expanding fist of the brake mechanism. Thus, braking of the rear wheels occurs in the same way as braking of the front wheels with a conventional brake chamber.
When the spare or parking brake system is turned on, that is, when air is released from the cavity under the piston 5 by a manual valve, the spring 8 is decompressed and the piston 5 moves down. The thrust bearing 2 through the membrane 16 acts on the bearing of the rod 18, which, moving, turns the adjusting lever of the brake mechanism associated with it. The vehicle is braking.
When braking, compressed air enters through the outlet under the piston 5. The piston, together with the pusher 4 and the thrust bearing 2, moves upward, compressing the spring 8 and allowing the rod 18 of the brake chamber to return to its original position under the action of the return spring 19.
1 - body; 2 - thrust bearing; 3 - sealing ring; 4 - pusher; 5 - piston;
6 - piston seal; 7 - power accumulator cylinder; 8 - spring; 9 - screw of the emergency release mechanism; 10 - thrust nut; 11- cylinder branch pipe; 12 - drainage tube; 13 - thrust bearing; 14 - flange; 15 - branch pipe of the brake chamber; 16 - membrane; 17 - support disk; 18 - stock; 19 - return spring
Figure 14 - Brake chamber type 20/20 with spring energy accumulator
With an excessively large gap between the shoes and the brake drum, that is, with an excessively large stroke of the brake chamber rod, the force on the rod may not be sufficient for effective braking. In this case, turn on the reverse-acting hand brake valve and release air from under the piston 5 of the spring-loaded energy accumulator. The thrust bearing 2 under the action of the power spring 8 will push through the middle of the membrane 16 and advance the rod 18 to the available additional stroke, ensuring the braking of the car.
If the tightness is broken and the pressure in the reservoir of the parking brake system is reduced, the air from the cavity under piston 5 will escape into the atmosphere through the outlet through the damaged part of the drive and the vehicle will automatically brake with spring-loaded energy accumulators.
3.12. Pneumatic cylinders
Pneumatic cylinders are designed to actuate the mechanisms of the auxiliary brake system.
Three pneumatic cylinders are installed on KamAZ vehicles:
- two cylinders with a diameter of 35 mm and a piston stroke of 65 mm (Figure 15, a) for control throttle valves installed in the exhaust pipes of the engine;
- one cylinder with a diameter of 30 mm and a piston stroke of 25 mm (Figure 15, b) to control the lever of the high pressure fuel pump regulator.
Pneumatic cylinder 035x65 is hinged on the bracket with a pin. The cylinder rod is connected with a threaded fork to the damper control lever. When the auxiliary brake system is turned on, compressed air from the pneumatic valve through the outlet in the cover 1 (see Fig. 311, a) enters the cavity under the piston 2. The piston 2, overcoming the force of the return springs 3, moves and acts through the rod 4 on the control lever damper, moving it from the "OPEN" position to the "CLOSED" position. When the compressed air is released, the piston 2 with the rod 4 returns to its original position under the action of the springs 3. In this case, the damper rotates to the "OPEN" position.
Pneumatic cylinder 030x25 is pivotally mounted on the cover of the high pressure fuel pump regulator. The cylinder rod is connected by a threaded fork to the regulator lever. When the auxiliary brake system is turned on, compressed air from the pneumatic valve through the outlet in the cover 1 of the cylinder enters the cavity under the piston 2. Piston 2, overcoming the force of the return spring 3, moves and acts through the rod 4 on the fuel pump regulator lever, transferring it to the zero supply position . The throttle linkage system is connected to the cylinder rod in such a way that the pedal does not move when the auxiliary brake system is applied. When the compressed air is released, the piston 2 with the rod 4 returns to its original position under the action of the spring 3.
1 - cylinder cover; 2 - piston; 3 - return springs; 4 - rod; 5 - body;
6 - cuff
Figure 15 - Pneumatic cylinders of the mechanism damper drive
Auxiliary brake system (a) and lever drive
Engine stops (b)
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3.13. Valves and sensors
Control outlet valve (Fig. 312) is designed to be connected to the drive of control and measuring devices in order to check the pressure, as well as to extract compressed air. There are five such valves on KamAZ vehicles - in all circuits of the pneumatic brake drive. To connect to the valve, hoses and measuring devices with a union nut M 16x1.5 should be used.
When measuring pressure or for extracting compressed air, unscrew the cap 4 of the valve and screw on the housing 2 the union nut of the hose connected to the control pressure gauge or any consumer. When screwing on, the nut moves the pusher 5 with the valve, and air enters the hose through the radial and axial holes in the pusher 5. After disconnecting the hose, the pusher 5 with the valve under the action of the spring 6 is pressed against the seat in the housing 2, closing the compressed air outlet from the pneumatic actuator.
1 - fitting; 2 - body; 3 - loop; 4 - cap; 5 - pusher with valve;
6 - spring
Figure 16 - Control output valve
The pressure drop sensor (Figure 17) is a pneumatic switch designed to close the circuit of electric lamps and an alarm signal (buzzer) in case of pressure drop in the pneumatic brake actuator receivers. The sensors, using an external thread on the housing, are screwed into the receivers of all brake circuits, as well as into the fittings of the parking and reserve brake circuits, and when they are turned on, the red control lamp on the instrument panel and the brake signal lamps light up.
The sensor has normally closed central contacts, which open when the pressure rises above 441.3 ... 539.4 kPa.
When the specified pressure is reached in the drive, the membrane 2 bends under the action of compressed air and through the pusher 4 acts on the movable contact 5. The latter, having overcome the force of the spring 6, breaks away from the fixed contact 3 and breaks the electrical circuit of the sensor. Closing the contact, and consequently, turning on the control lamps and the buzzer, occurs when the pressure drops below the specified value.
1 - body; 2 - membrane; 3 - fixed contact; 4 pusher; 5 - mobile contact; 6 - spring; 7 - adjusting screw; 8 - insulator
Figure 17 - Pressure drop sensor
The brake signal switch (Figure 18) is a pneumatic switch designed to close the circuit of electrical signal lamps when braking. The sensor has normally open contacts that close at a pressure of 78.5 ... 49 kPa and open when the pressure drops below 49 ... 78.5 kPa. Sensors are installed in highways,
Giving compressed air to the actuators of the brake systems.
When compressed air is supplied under the membrane, the latter bends, and the movable contact 3 connects the contacts 6 of the electrical circuit of the sensor.
1 - body; 2-membrane; 3 - movable contact; 4 - spring; 5 - output of a fixed contact; 6 - fixed contact; 7 - cover
Figure 18 - Brake signal enable sensor
The trailer brake control valve with a two-wire drive (Figure 19) is designed to actuate the brake drive of the trailer (semi-trailer) when any of the separate drive circuits of the working brake system of the tractor is turned on, as well as when the spring energy accumulators of the drive of the spare and parking brake systems of the tractor are turned on.
The valve is attached to the tractor frame with two bolts.
Membrane 1 is clamped between the lower 14 and middle 18 housings, which is fixed between two washers 17 on the lower piston 13 with a nut 16 sealed with a rubber ring. An outlet window 15 with a valve is attached to the lower body with two screws, which protects the device from dust and dirt. When one of the screws is loosened, the outlet window 15 can be turned and access to the adjusting screw 8 through the hole of the valve 4 and the piston 13 is opened. 12 holds the piston 13 in the down position. At the same time, output IV connects the trailer brake control line with atmospheric output VI through the central hole of valve 4 and lower piston 13.
1 - membrane; 2 - spring; 3 - unloading valve; 4 - inlet valve; 5 - upper body; 6 - upper large piston; 7 - spring plate; 8 - adjusting screw; 9 - spring; 10 - small upper piston; 11 - spring; 12 - middle piston; 13 - lower piston; 14 - lower case; 15 - outlet window; 16 - nut;
17 - membrane washer; 18 - medium body; I - output to the section of the brake valve;
II - output to the parking brake control valve; III - output to the section of the brake valve; IV - output to the brake line of the trailer; V - output to the receiver; VI - atmospheric output
Figure 19 - Trailer brake control valve with a two-wire drive
When compressed air is supplied to terminal III, the upper pistons 10 and 6 simultaneously move down. Piston 10 first sits with its seat on valve 4, blocking the atmospheric outlet in the lower piston 13, and then separates valve 4 from the seat of the middle piston 12. Compressed air from outlet V connected to the receiver enters outlet IV and then into the brake control line trailer. The supply of compressed air to terminal IV continues until its effect from below on the upper pistons 10 and 6 is balanced by the pressure of compressed air supplied to terminal III on these pistons from above. After that, the valve 4 under the action of the spring 2 blocks the access of compressed air from port V to port IV. Thus, a follow-up action is carried out. With a decrease in compressed air pressure at outlet III from the brake valve, i.e. when braking, the upper piston 6 under the action of the spring 11 and the pressure of compressed air from below (in port IV) moves upwards together with piston 10. The piston seat 10 comes off valve 4 and communicates port IV with atmospheric output VI through the holes of valve 4 and piston 13.
When compressed air is supplied to outlet I, it enters under the membrane 1 and moves the lower piston 13 together with the middle piston 12 and valve 4 upwards. The valve 4 reaches the seat in the small upper piston 10, closes the atmospheric outlet, and with further movement of the middle piston 12 is separated from its inlet seat. Air enters from outlet V, connected to the receiver, to outlet IV and then into the trailer brake control line until its effect on the middle piston 12 from above is equalized by pressure on the membrane 1 from below. After that, valve 4 blocks the access of compressed air from port V to port IV. Thus, a follow-up action is carried out with this version of the device operation. When the compressed air pressure drops at outlet I and under the membrane, the lower piston 13 moves down together with the middle piston 12. Valve 4 breaks away from the seat in the upper small piston 10 and communicates output IV with the atmospheric output VI through the holes in valve 4 and piston 13.
With the simultaneous supply of compressed air to terminals I and III, the large and small upper pistons 10 and 6 simultaneously move down, and the lower piston 13 with the middle piston 12 moves up. Filling the trailer brake control line through terminal IV and venting compressed air from it proceeds in the same way as described above.
When the compressed air is released from port II (during braking with the emergency or parking brake system of the tractor), the pressure above the diaphragm drops. Under the action of compressed air from below, the middle piston 12, together with the lower piston 13, move upwards. Filling the trailer brake control line through terminal IV and braking occurs in the same way as when compressed air is supplied to terminal I. The follow-up action in this case is achieved by balancing the compressed air pressure on the middle piston 12 and the sum of the pressure from above on the middle piston 12 and membrane 1.
When compressed air is supplied to terminal III (or when air is simultaneously supplied to terminals III and I), the pressure in terminal IV connected to the trailer brake control line exceeds the pressure supplied to terminal III. This ensures the advancing action of the brake system of the trailer (semi-trailer). The maximum overpressure at port IV is 98.1 kPa, the minimum is about 19.5 kPa, and the nominal is 68.8 kPa. The overpressure value is controlled by screws 8: when the screw is screwed in, it increases, and when it is turned out, it decreases.
4. Maintenance and repair of the brake system
During daily maintenance checks:
– tightness of connecting heads;
– the condition of the hoses for connecting the brake system of the trailer (for a road train);
- the presence, condition and draining of condensate from the system receivers (Condensate is drained from the receivers at a nominal air pressure in the pneumatic drive, pulling the drain valve stem aside at the end of the shift. The stem is pulled down. An increased oil content in the condensate indicates a compressor malfunction. When condensate freezes in receivers, they are heated with hot water or warm air.It is forbidden to use an open flame for heating.After draining the condensate, the air pressure in the pneumatic system will be brought to the nominal);
– during inspection, twisting and contact with sharp edges of other parts of the thermoses hoses is not allowed.
At TO-1:
- external inspection of the elements and according to the indications of standard devices of the car
Bill checks the brake system.
- the detected malfunctions are eliminated by adjusting and replacing failed units, assemblies and parts, topping up or replacing oil and alcohol;
– parts are lubricated according to the lubrication map.
Checking the performance of the pneumatic brake drive consists in determining the output parameters of the air pressure along the circuits using control pressure gauges and standard instruments in the cab (two-pointer pressure gauge and a block of control lamps for the brake system). The check is carried out on the valves of the control outputs installed in all circuits of the pneumatic drive, and the connecting heads of the Palm type of the supply (emergency) and control (brake) lines of the two-wire drive and type A of the connecting line of the single-wire brake drive of the trailer. The location of the valves is indicated in the instructions.
Brake system repair
To improve the reliability and reliability of the brake system, it is recommended to carry out a mandatory check and sorting of brake devices once every two years, regardless of their technical condition.
Subject to compulsory sorting: pressure regulator; brake force regulators; brake chambers type 20/20; brake chamber type 24 (membrane); double safety valve; 4-circuit protective valve; manual brake valve; two-section brake valve; pressure limiting valve; accelerating valve; trailer brake control valve (one- and two-wire drives); pneumatic crane.
Forcibly removed or discovered during control check defective devices must be repaired with repair kits, checked for operation and compliance with the characteristics.
The procedure for assembling and testing devices is set out in special instructions. Their repair is carried out by persons who have undergone the necessary training.
Bibliography
1. KAMAZ vehicles. Models with wheel arrangement 6x4 and 6x6. Guide
Operation, repair and maintenance. M., 2004. 314 p.
2. Manual for the repair and maintenance of vehicles
KAMAZ. M., 2001.289 p.
3. Parchment L.R. The driver of the KamAZ car. M., 1982. 160 p.
4. STP SGUPS 01.01–2000. Course and diploma projects. Requirements for the
Lenia. Novosibirsk, 2000. 44 p.
Scheme of the pneumatic drive of the brake systems of the KamAZ-4310 carThe separation of the brake system of KamAZ 5320 (4310) vehicles allows each circuit to operate independently, which is important in the event of a malfunction.
TOontur I
This front axle brake circuit consists of a 20-liter reservoir with a pressure drop sensor and a stopcock, a triple safety valve, a two-pointer pressure gauge, a pressure limiting valve, a control outlet valve, a lower section of the brake valve, two brake chambers and other brake mechanisms, hoses and pipelines. In addition, the first circuit includes a pipeline from the trailer brake system valve to the lower section of the brake valve.
Circuit II
This is the rear bogie brake circuit.
The device of the brakes of the bogie of Kamaz 5320 (4310) vehicles consists of the upper section of the brake valve, part of the triple safety valve, receivers with a total capacity of 40 liters with a pressure sensor and condensate drain valves, a control output valve for the automatic brake force regulator, a two-pointer pressure gauge, four brake chambers, brake mechanisms of the intermediate and rear axles of the bogie, hose and pipelines. The circuit includes a pipeline from the brake control valve to the upper section of the brake valve.
Circuit III
This is the circuit of the parking, spare brake systems and the combined drive of the brake mechanisms of the semi-trailer (trailer). It consists of:
- double safety valve
- two receivers with a total capacity of 40 liters, a pressure sensor and a condensate drain cock,
- two control output valves of the manual brake valve,
- relay valve,
- four spring-loaded brake chambers with a pressure sensor,
- parts of a dual-line bypass valve,
- control valve with a two-wire drive of the trailer brake system,
- single safety valve,
- trailer brake control valve with single-wire drive,
- "A" type heads for a single-wire drive and two "Palm" heads for a two-wire trailer brake drive,
- three disconnecting taps, three connecting heads,
- pneumoelectric sensor "stop light",
- two-wire trailer brake drive,
- hoses and pipelines.
Circuit IV
This circuit of the auxiliary brake system does not have its own receiver. It consists of a pneumatic valve, a part of a double safety valve, two damper actuator cylinders, a pneumoelectric sensor, an engine stop lever actuator cylinder, pipelines and hoses.
Contour V
This emergency release circuit does not have executive bodies and its own receiver.
It consists of a part of a double-line bypass valve, a pneumatic valve, a part of a triple safety valve, hoses and pipelines connecting the apparatus.
The pneumatic brake drives of the Kamaz vehicle and the trailer are connected by three lines: a brake line of a two-wire drive, a supply line and a line of a single-wire drive. In the supply part of the brake drive of models 53212 and 53213, to improve moisture separation in the “pressure regulator - compressor” section, a dehumidifier is provided, installed in the zone of intensive airflow on the first cross member of the vehicle. On all KAMAZ models, for the same purpose, a condensate receiver with a capacity of 20 liters protects against freezing in the "protective valves - fuse" section.
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Scheme of the pneumatic actuator of the brake systems of the KamAZ-5320 car
Technical description
KamAZ vehicles and road trains are equipped with four independent brakes: working, spare, parking and auxiliary. Although these brakes have common elements, they work independently and provide high braking performance in all operating conditions. In addition, the vehicle is equipped with an emergency brake release drive that enables the vehicle (road train) to move during its automatic braking due to compressed air leakage, alarms and control devices that allow monitoring the operation of the pneumatic drive.
service brake It is designed for service and emergency braking of the car or its complete stop. The service brake drive is pneumatic, dual-circuit, it actuates the brakes of the front axle and the rear bogie separately. The drive is controlled by a foot pedal mechanically connected to the brake valve. The executive bodies of the service brake drive are the brake chambers on the wheels.
Emergency brake designed to smoothly reduce speed or stop a moving vehicle in the event of a complete or partial failure of the service brake.
Parking brake on KamAZ vehicles it is made as a single unit with a spare. To turn it on, the handle of the manual crane should be set to the extreme (upper) fixed position. Thus, on KamAZ vehicles, the brake mechanisms of the rear bogie are common to the working, spare and parking brakes.
Auxiliary brake of the car serves to reduce the load and temperature of the brake mechanisms of the service brake. The auxiliary brake on KamAZ vehicles is the engine retarder, when turned on, the engine exhaust pipes are blocked and the fuel supply is turned off.
Emergency release system is designed to release spring energy accumulators when they are automatically activated and the vehicle stops due to leakage of compressed air in the drive. The emergency braking system drive is duplicated: in addition to the pneumatic drive, there are mechanical release screws in each of the four spring-loaded energy accumulators, which makes it possible to release the latter mechanically.
Alarm and control system consists of two parts:
1. Light and acoustic signaling of the operation of the brakes and their drives.
2. Valves of control outputs, with the help of which the technical condition of the pneumatic brake actuator is diagnosed, as well as (if necessary) the selection of compressed air.
Below is the technical specification of the braking system:
| Brake mechanisms | drum type with two internal shoes and an expander with an S-shaped fist |
| Drum diameter, mm | 400 |
| Overlay width, mm | 140 |
| Total area of pads, mm 2 | 6300 |
| Adjustment lever length, mm: | |
| 125 | |
| middle and rear axles: | |
| KAMAZ-5320, -5410, -55102 | 125 |
| KAMAZ-5511, -53212, -54112 | 150 |
| Brake chamber stroke, mm: | |
| front axle KAMAZ-5320, -5410, -55102, -5511, -53212, -54112 | 20-30 |
| middle and rear axles: | |
| KAMAZ-5320, -5410, -55102 | 20-30 |
| KAMAZ-5511, -53212, -54112 | 25-35 |
| brake chambers |
front type 24, middle and back type 20/20 |
| Compressor | piston type, two-cylinder |
| Cylinder diameter and piston stroke, mm | 60X38 |
| Delivery at backpressure 7 kgf/cm 2 and speed 2200 rpm, l/min | 220 |
| Drive unit | gear, from timing gears |
| gear ratio | 0,94 |
| Receivers: | |
| Total | 6 |
| total capacity, l | 120 |
| Frost protection capacity, ml | 200 and 1000 |
| Back pressure in exhaust system with closed dampers of the auxiliary brake, kgf / cm 2 | 1,7-1,9 |
Brake mechanisms (Fig. 203) are installed on all six wheels of the vehicle. The main assembly of the brake mechanism is mounted on a caliper 2 rigidly connected to the bridge flange. On the eccentrics of the axles 7, fixed in the caliper, two brake pads 7 freely rest with friction linings 9 riveted to them, made along a sickle-shaped profile in accordance with the nature of their wear. Shoe axes with eccentric bearing surfaces make it possible to correctly center the shoes with the brake drum when assembling the brake. The brake drum is attached to the wheel hub with five bolts.
When braking, the pads move apart with an S-shaped fist 12 and are pressed against the inner surface of the drum. Rollers 13 are installed between the expanding fist and the pads, reducing friction and improving braking efficiency. The pads are returned to the braked state by four retracting springs 8.
The expanding fist rotates in the bracket 10, bolted to the caliper. The brake chamber is fixed on this bracket. At the end of the shaft of the expanding fist, an adjusting lever 14 of the worm type is installed, connected to the rod of the brake chamber with the help of a fork and a finger. A brake shield bolted to the caliper protects the brake mechanism from dirt.
Rice. 203. Brake mechanism: 1-axis pads; - 2-caliper; 3-shield; 4-axle nut; 5-pad axle pads; 6-pin axle pads; 7-brake shoe; 8-spring; 9 friction lining; 10-bracket expanding fist; 11-axis roller; 12-expanding fist; 13-roller; 14-adjustment lever
Adjustment lever designed to reduce the gap between the pads and the brake drum when the friction linings are worn. It has a housing 7 (Fig. 204) with a bushing 6. The housing contains a worm gear 10 with a splined hole for installation on an expanding fist and a worm 8 with an axis 2 pressed into it. To fix the worm axis there is a locking device, the ball 3 of which is included in holes on the axis 2 of the worm under the action of the spring 4, abutting against the plug 5. The gear is kept from falling out by covers 12 attached to the body 7 of the lever. When the axis is rotated (by the square shank), the worm turns gear 10, and with it the expanding fist rotates, pushing the pads apart and reducing the gap between the pads and the brake drum. When braking, the adjusting lever is turned by the brake chamber rod.
Rice. 204. Adjusting lever: 1-oiler; 2-axis worm; 3-ball retainer; 4-spring latch; 5-retainer plug; 6-sleeve; 7-body; 8-worm; 9-plug; 10-gear; 11-rivet; 12-cap
On the levers of the rear bogie of KamAZ-5511, -54112, -53212, instead of plug 5, a locking bolt is installed, which increases the reliability of locking the worm pair of the lever. Before adjusting the clearance, the lock bolt must be loosened by one or two turns, and after adjustment, the bolt must be tightened securely.
The source of compressed air in the pneumatic brake actuator is compressor 1 (Fig. 205). The compressor, pressure regulator 2, fuse 3 against freezing of condensate in compressed air and condensate receiver 6 constitute the supply part of the drive, from which purified compressed air at a given pressure is supplied to the rest of the pneumatic brake drive and to other consumers of compressed air. The pneumatic brake drive is divided into autonomous circuits, separated from each other by protective valves. Each circuit operates independently of other circuits, even in the event of a fault. The pneumatic brake drive of KamAZ vehicles includes five circuits separated by one double and one triple protective valves.
Rice. 205. Scheme of the pneumatic drive of the brake mechanisms: A-valve of the control output of the IV circuit; B, D - control output valves of the third circuit; B - valve of the control output of the I circuit; G-valve of the control output of the P circuit; K, L-additional control output valves; I-brake (control) line of a two-wire drive; Zh-connecting line of a single-wire drive; E-feeding line of a two-wire drive; I-compressor; 2-pressure regulator; 3-fuse against freezing; 4-double safety valve; 5-triple safety valve; 6- condensing receiver; 7-cock for draining condensate; 8-receiver III circuit; 9-air receiver of the I circuit; 10-receiver of the II circuit; 11-sensor pressure drop in the receiver; 12-valve control output; 13-pneumatic crane; 14-sensor for switching on the electromagnetic valve of the trailer brakes; 15-pneumatic cylinder for engine stop lever drive; 16-pneumatic auxiliary brake damper actuator cylinder; 17-brake two-section crane; 18-double needle manometer; 19-brake chamber type 24; 20-pressure limiting valve; 21-crane control parking and spare brakes; 22-accelerator valve; 23-brake chamber type 20/20 with spring energy accumulator; 24 - two-line bypass valve; 25-trailer brake control valve with two-wire drive; 26-protective single valve; 27-trailer brake control valve with a single-wire drive; 28-uncoupling tap; 29-connecting head type "Palm"; 30 - type A connection head; 31-sensor "stop light"; 32-automatic brake force regulator; 33-air bleed valve; 34- rechargeable batteries; 35-block of control lamps and buzzer; 36-rear light; 37-sensor parking brake
The circuit I of the drive of the service brakes of the front axle consists of: part of the triple protective valve 5, the receiver 9 with a capacity of 20 liters with a condensate drain valve 7 and a pressure drop sensor 11 in the receiver; parts of a two-pointer manometer 18; the lower section of the two-section brake valve 17; control output valve 12 (B); pressure limiting valve 20; two brake chambers 19; brake mechanisms of the front axle of the tractor; pipelines and hoses between these devices. In addition, the circuit includes a pipeline from the lower section of the brake valve 17 to the trailer brake control valve 25 with a two-wire drive.
Circuit II of the drive of the service brakes of the rear bogie consists of: part of the triple protective valve 5; receivers 10 with a total capacity of 40 liters with a condensate drain valve 7 and a pressure drop sensor 11 in the receiver; parts of a two-pointer manometer 18; the upper section of the two-section brake valve 17; valve 12 control output (D) automatic regulator 32 brake forces with an elastic element; four brake chambers 23; brake mechanisms of the rear bogie (middle and rear axles); pipelines and hose between these devices. The circuit also includes a pipeline from the upper section of the brake valve 17 to the trailer brake control valve 25 with a two-wire drive.
Circuit III of the drive of the spare and parking brakes, as well as the combined drive of the brakes of the trailer (semi-trailer) consists of: part of the double protective valve 4; receivers 8 with a total capacity of 40 liters with a condensate drain valve 7 and a pressure drop sensor 11 in the receiver; two valves 12 control outputs (B and D); manual brake valve 21; accelerating valve 22; parts of the dual-line bypass valve 24; four spring energy accumulators of brake chambers 23; the second pressure drop sensor in the line of spring energy accumulators; trailer brake control valve 25 with a two-wire drive; single protective valve 26; trailer brake control valve 27 with a single-wire drive; uncoupling taps 28; connecting heads; type A heads 30 for a single-wire trailer brake drive and two Palm-type heads 29 for a two-wire trailer brake drive; pneumoelectric sensor 31 brake light; pipelines and hoses between these devices. It should be noted. that the pneumoelectric sensor 31 in the circuit is installed in such a way that it ensures that the stop lamps are turned on when the vehicle is braked not only by the spare (parking) brake, but also by the working one, and also in case of failure of one of the circuits of the latter.
Circuit IV of the auxiliary brake drive and other consumers consists of: part of the double safety valve 4; pneumatic valve 13; two cylinders 16 of the engine brake damper drive; cylinder 15 of the engine stop lever drive; pneumoelectric sensor 14; pipelines and hoses between these devices. Air enters the circuit from the condensation receiver 6.
From circuit IV of the auxiliary brake drive, compressed air is supplied to additional (not brake) consumers: a pneumatic signal, a pneumohydraulic clutch booster, and transmission unit control.
Circuit V of the automatic release drive does not have its own receiver and executive bodies. It consists of a part of a triple protective valve 5, a pneumatic valve 13, a part of a two-way bypass valve 24, pipelines and hoses connecting the devices.
The pneumatic brake drives of the tractor and trailer connect three lines: a single-wire drive line, the supply and control (brake) lines of a two-wire drive. On truck tractors, connecting heads 29 and 30 are located at the ends of three flexible hoses of the indicated lines, fixed on a supporting rod. On board vehicles, heads 29 and 30 are mounted on the rear cross member of the frame.
To improve moisture separation in the supply part of the brake drive of KamAZ-53212 vehicles, a water separator is additionally provided in the compressor-pressure regulator section, installed on the first cross member of the frame in the zone of intensive airflow.
The KamAZ-5511 dump truck does not have trailer brake control equipment, uncoupling valves, and coupling heads.
To monitor the operation of the pneumatic brake actuator and timely signal its condition and malfunctions in the cab, the instrument panel has four signal lamps, a two-pointer pressure gauge showing the compressed air pressure in the receivers of two circuits (I and II) of the service brake pneumatic actuator, and a buzzer, signaling an emergency drop in compressed air pressure in the receivers of any brake circuit.
Auxiliary brake mechanisms (Fig. 206) are installed in the exhaust pipes of the muffler. Each mechanism consists of a housing 1 and a damper 3 fixed on the shaft 4, a rotary lever 2 is also fixed on the damper shaft, connected to the pneumatic cylinder rod. The lever and associated shutter have two positions. The inner cavity of the body is spherical. When the auxiliary brake is turned off, the damper is installed along the exhaust gas flow, and when the brake is turned on, it is perpendicular to the exhaust gas flow, creating a certain back pressure in exhaust manifolds. At the same time, the fuel supply is cut off. The engine starts to work in braking mode.
Rice. 206. Auxiliary brake mechanism
Pneumatic brake drive devices.
Compressor (Fig. 207) is installed on the front end of the engine flywheel housing.
The block and head are cooled by liquid supplied from the engine cooling system. Oil under pressure through the mechanical seal is supplied from the engine oil line to the rear end of the compressor crankshaft and through the crankshaft channels to the connecting rod bearings. Main ball bearings, piston pins and cylinder walls are splash lubricated.
When the pressure in the pneumatic system reaches 7.0-7.5 kgf/cm 2 , the pressure regulator communicates the discharge line with the atmosphere, thereby stopping the air supply to the pneumatic system. When the air pressure in the pneumatic system drops to 6.2-6.5 kgf/cm 2 , the regulator closes the air outlet to the atmosphere and the compressor starts again to pump air into the pneumatic system.
Rice. 207. Compressor: 1-gear drive; 2-lock washer; 3-gear nut; 4-seal; 5-spring seal; 6-segment key; 7-crankshaft; 8-ball bearing; 9-carter; 10- connecting rod insert; 11-rod; 12-cork; 13-oil scraper ring; 14-piston pin; 15-compression ring; 16-piston; 17-cylinder head; 18-cylinder head gasket; 19-cylinder block: 20-angle coolant supply; 21-reflective plate; 22- gasket of the rear crankcase cover; 23-rear crankcase cover; 24-gasket of the lower cover of the compressor; 25-lower crankcase cover
water separator (Fig. 208) is designed to separate condensate from compressed air and automatically remove it from the power part of the drive.
Compressed air from the compressor through inlet 8 is supplied to the finned aluminum cooler tube 1, where it is gradually cooled by the oncoming air flow. Then the air passes through the centrifugal guide vane 5, through the hollow screw 3 into the housing 2 to the outlet 4 and then into the pneumatic brake actuator. The moisture released due to the thermodynamic effect, flowing down through the grid 6, accumulates in the cover 9. When the regulator is triggered, the pressure in the water separator drops, while the diaphragm 7 moves up. The condensate drain valve 10 opens, the accumulated mixture of water and oil is removed to the atmosphere through outlet 11.
The direction of compressed air flow is indicated by arrows on the housing.
Rice. 208. Water separator
pressure regulator (fig. 209) is intended for:
Regulating the pressure of compressed air in the pneumatic system;
Protection of the pneumatic system from overload by excessive pressure;
Purification of compressed air from moisture and oil;
Providing tire inflation.
Compressed air from the compressor through input IV of the regulator, filter 2, channel 11 is supplied to the annular channel 8. Through the check valve 9, compressed air enters output II and further into the receivers of the vehicle's pneumatic system. At the same time, through channel 7, compressed air passes into cavity G under piston 6, which is loaded with a balancing spring 5. At the same time, exhaust valve 4, connecting cavity B above unloading piston 12 with the atmosphere through outlet 1, is open, and inlet valve 10, through which compressed air is supplied to cavity B, closed under the action of a spring. Under the action of the spring, the unloading valve 1 is also closed. In this state of the regulator, the system is filled with compressed air from the compressor. At a pressure in cavity G equal to 7.0-7.5 kgf / cm 2, piston 6, having overcome the force of the balancing spring 5, rises, valve 4 closes, inlet valve 10 opens and compressed air from cavity G enters cavity C.
Under the action of compressed air, the unloading piston 12 moves down, the unloading valve 1 opens and the compressed air from the compressor through outlet III goes out into the atmosphere along with the condensate accumulated in the cavity. In this case, the pressure in the annular channel 8 drops and the check valve 9 closes. Thus, the compressor operates in unloaded mode without back pressure.
When the pressure in outlet II and cavity G drops to 6.2-6.5 kgf / cm 2, piston 6 moves down under the action of spring 5, valve 10 closes, and exhaust valve 4 opens, communicating cavity B with the atmosphere through outlet I. In this case, the unloading piston 12 rises under the action of the spring, the valve 1 closes under the action of the spring, and the compressor pumps compressed air into the pneumatic system.
The unloading valve 1 also serves as a safety valve. If the regulator does not work at a pressure of 7.0-7.5 kgf/cm 2, then valve 1 opens, overcoming the resistance of its spring and the piston spring 12. Valve 1 opens at a pressure of 10-13 kgf/cm 2. The opening pressure is adjusted by changing the number of shims installed under the valve spring.
To connect special devices, the pressure regulator has an outlet that is connected to outlet IV through filter 2. This outlet is closed with a screw plug 3. In addition, an air bleed valve for tire inflation is provided, which is closed with a cap 15. When screwing on the hose fitting for tire inflation, the valve is sunk , opening access to compressed air in the hose and blocking the passage of compressed air into the brake system. Before inflating the tires, the pressure in the reservoirs should be reduced to a pressure corresponding to the pressure on the regulator, since air cannot be taken during idling.
Rice. 209. Pressure regulator: B-cavity above the unloading piston; G - cavity under the follower piston; I, III-atmospheric output; III-output to the pneumatic system; IV-input from the compressor; 1-unloading valve; 2- filter; 3-plug of the air sampling channel; 4 outlet valve; 5-balancing spring; 6-following piston; 7, 11-channels; 8-ring channel: 9-check valve; 10-inlet valve; 12-unloading piston; 13-saddle of the unloading valve; 14-valve for tire inflation; 15-cap
Frost protector (Fig. 210) is designed to prevent freezing of condensate in pipelines and devices of the pneumatic brake drive. It is mounted on the right side member of the frame behind the pressure regulator in a vertical position and fastened with two bolts.
The lower case 2 of the fuse is connected with the upper case 7 by four bolts. Both cases are made of aluminum alloy. To seal the joint between the housings, a sealing ring 4 is laid. A switching device is mounted in the upper housing, consisting of a rod 10 with a handle pressed into it, a thrust limiter 8 and a plug 6 with a sealing ring. The thrust in the upper housing is sealed with a rubber ring 9. In the upper housing there is also a clip 11 with a sealing ring 12, held by a thrust ring 13. A wick 3 is installed between the bottom of the lower housing and plug 6, stretched by spring 1. The wick is fixed to the spring with the help of a rod shank and plugs 14.
A plug with an alcohol level indicator is installed in the filling hole of the upper body. The drain hole in the lower housing is plugged with a plug 14 with a sealing washer 15. A nozzle 5 is also installed in the upper housing to equalize the air pressure in the lower housing in the off position. The capacity of the fuse reservoir can be 200 or 1000 cm 3 .
When the thrust handle is in the upper position, the air pumped by the compressor into the receiver passes by the wick 3 and takes alcohol with it, which takes moisture from the air and turns it into non-freezing condensate.
At an ambient temperature above +5°C, the fuse should be turned off. To do this, the rod is lowered to its lowest position, rotated and fixed with the help of a thrust limiter. Cork 6, compressing the spring located inside the wick, enters the holder and separates the lower housing containing alcohol from the pneumatic drive, as a result of which the evaporation of alcohol stops.
Rice. 210. Fuse from freezing: 1-spring; 2-lower body; 3-wick; 4, 9, 12 - sealing rings; 5-nozzle; 6-plug with sealing ring; 7-upper case; 8-thrust limiter; 10-thrust; 11-clip; 13 - thrust ring; 14-cork; 15-sealing washer
Double safety valve (Fig. 211) is designed to divide the line coming from the compressor into two independent circuits to automatically turn off one of the circuits in case of a violation of its tightness and to maintain compressed air in a healthy circuit, as well as to preserve compressed air in both circuits in case of violation tightness of the line coming from the compressor.
Rice. 211. Double protective valve: 1-spring; 2, 5, 6 sealing rings; 3-piston spring; 4-support washer; 7- cover; 8-adjusting washer; 9-protective cap; 10-central piston; 11-case; 12-valve; 13-valve spring; 14-thrust piston; 15-cap cap
A double safety valve is installed inside the right side member of the vehicle frame and is connected to the pipeline from the antifreeze, according to the arrow printed on the valve body, indicating the direction of compressed air flow.
The aluminum body 11 of the valve has three outputs: from compressor-I and to circuits II and III. Adjusting washers 8 are used to regulate the force of spring 1, which determines the compressed air pressure at which the damaged circuit is turned off. Central piston 10 is held in the middle position by springs 3 installed between covers 7 and support washers 4. I, opens the check valves 12 and passes to the conclusions II and III of the individual circuits of the pneumatic actuator. Upon reaching the outputs II and III pressure equal to the pressure at the output 1, the valves 12 are closed.
If, due to leaks in the circuit, the line of which is connected to terminal II, there is a decrease in pressure in this outlet, then the central piston 10 with the check valve 12 will move towards outlet II under the influence of the pressure difference in outlets II and III. The bottom valve 12 will close, press against the thrust piston 14 and move it down. The stroke of the central piston will be limited by a special stop on the cover 7. At the same time, compressed air from the compressor through port I will replenish the circuit connected to port III when air is consumed in it, and compressed air will not enter the damaged circuit connected to port II.
If the pressure of the compressed air supplied to port III exceeds a certain value, the bottom valve 12 will open and allow excess compressed air to pass through port II into the leaky circuit. If during braking in one of the circuits the compressed air consumption is higher than in the other, then during the subsequent filling, the circuit with a lower pressure drop will be filled first. The other circuit will start filling only when the pressure in the first exceeds the set value.
Triple safety valve (Fig. 212) is intended for: separation of compressed air coming from the compressor into two main and one additional circuits; automatic shutdown one of the circuits in case of violation of its tightness and the preservation of compressed air in sealed circuits; preservation of compressed air in all circuits in case of leakage of the supply line; supply of an additional circuit from two main circuits (until the pressure in them drops to a predetermined level).
A triple safety valve is installed inside the right side member of the vehicle frame and is connected to the supply pipe coming from the antifreeze.
The aluminum valve body 1 has four leads: one large (from the compressor) and three small ones. A rubber ring is installed between the body 1 and the guide 20 for sealing. The force of the springs 6, 9 and 18 is adjusted using screws 8 installed in the covers 2. Rubber plugs 7 are inserted into the threaded holes of the covers 2, protecting the threads and internal cavities of the covers from contamination, as well as closing the atmospheric openings in them.
Compressed air entering the triple safety valve from the supply line, upon reaching the predetermined opening pressure set by the force of springs 6 and 9, opens valves 3 and 12 and enters through the outlets into two main circuits. At the same time, compressed air, acting on diaphragms 5 and 11, raises them. After opening the check valves 13 and 14, compressed air enters the valve 15, opens it, passes through the outlet into the additional circuit, while simultaneously raising the diaphragm 16.
When one of the main circuits is depressurized, a pressure drop occurs inside the housing. As a result, the valve of the healthy main circuit and the check valve of the additional circuit are closed, preventing pressure drop in these circuits. When the pressure at the inlet to the housing decreases to a predetermined level, the valve of the faulty circuit closes. Compressed air from the compressor replenishes the serviceable main circuit through the check valve. No air enters the damaged circuit. When the air pressure at the valve inlet is higher than the predetermined level, the valve of the faulty circuit opens and excess air escapes through it into the atmosphere. At the same time, the pressure is maintained constant and air does not enter the serviceable circuits. Further filling with compressed air of serviceable circuits will occur only after a pressure drop in these circuits due to air consumption. The valves of serviceable circuits open under the action of the pressure of the air present in these circuits on the diaphragms and the air pressure in the cavity under the valves, which facilitates the opening of the valves of serviceable circuits. Thus, in good circuits, the pressure corresponding to the opening pressure of the valve of the faulty circuit will be maintained, and excess compressed air will exit through the faulty circuit.
If the auxiliary circuit fails, the pressure drops in the two main circuits and at the inlet to the valve. This happens until the valve 15 of the additional circuit closes. With further supply of compressed air to the triple safety valve in the main circuits, the pressure will be maintained at the level of the opening pressure of the valve 15 of the additional circuit.
If the compressed air supply to the triple safety valve is interrupted, valves 3 and 12 of the main circuits are closed, thereby preventing a pressure drop in all three circuits.
The receivers are designed to accumulate compressed air produced by the compressor and to supply it to pneumatic brake drive devices, as well as to supply other pneumatic components and vehicle systems.
Six receivers with a volume of 20 liters each are installed on the KamAZ vehicle, and four of them are interconnected in pairs and form single tanks with a volume of 40 liters each. The receivers are fixed with clamps on the brackets of the car frame. To improve moisture separation, a condensate receiver with an air bleed valve is provided in the supply part of the brake drive.
Rice. 212. Triple protective valve: 1-body; 2-lid; 3, 12, 15 valves; 4, 10, 17 guide springs; 5, 11, 16 apertures; 6, 9, 18-springs; 7-stub; 8-adjusting screw; 13, 14 check valves; 19-spring plate; 20-guide; 21-check valve spring; 22-plate spring check valve; 23-valve spring
Condensate drain valve is designed for forced draining of condensate from the air brake drive receiver, as well as for releasing compressed air from it if necessary. The edge is screwed into a threaded boss on the bottom of the receiver case.
The connection between the tap and the receiver boss is sealed with a gasket.
Two-piece brake valve (Fig. 213) is designed to control the actuators of the two-circuit drive of the vehicle's service brake.
The brake valve is mounted on a bracket, which is attached to the left side member of the frame from the inside.
Conclusions I to II of the crane are connected to the receivers of two separate circuits of the service brake drive. From terminals III and IV, compressed air is supplied to the brake chambers. When you press the brake pedal, the force is transmitted through the system of levers and drive rods to the lever 1 of the crane and then through the pusher 6, the plate 9 and the elastic element 31 to the follower piston 30. Moving down, the piston 30 first closes the outlet valve 29 of the upper section of the brake valve, and then opens the valve 29 from the seat in the upper housing 32, opening the passage of compressed air from port II to port III and further to the actuators of one of the circuits. The pressure at terminal III is increased until the pressing force on the lever I is balanced by the force generated by the pressure on the upper piston 30. In this way, a follow-up action is carried out in the upper section of the brake valve. Simultaneously with the increase in pressure at port III, compressed air through hole A enters cavity B above the large piston 28 of the lower section of the brake valve. Moving down, the large piston closes the valve outlet 17 and lifts it off the seat in the lower housing. Compressed air from terminal I is supplied to terminal IV and then to the actuators of another service brake circuit.
Simultaneously with the increase in pressure at port IV, the pressure under pistons 15 and 28 increases, as a result of which the force acting on piston 28 from above is balanced. As a result, pressure is also set at terminal IV, corresponding to the force on the brake valve lever. Thus, a follow-up action is carried out in the lower section of the brake valve.
In the event of a failure in the operation of the upper section of the brake valve, the lower section will be mechanically controlled through the pin 11 and the pusher 18 of the small piston 15, fully maintaining its performance. If the lower section of the brake valve fails, the upper section operates as usual.
Rice. 213. Two-section brake valve: 1-lever: 2-thrust lever screw; 3-protective cover; 4-axis roller; 5-roller; 6-pusher; 7- lever body; 8-nut; 9-plate; 10, 16, 19, 27 O-rings; 11-hairpin; 12-spring follower piston; 13, 24-springs; 14, 20-plates of valve springs; 15-small piston; 17-valve of the lower section; 18-pusher of the small piston; 21-atmospheric valve; 22-thrust ring; 23-housing atmospheric valve; 25-lower case; 26-spring of a small piston; 28- large piston; 29-valve of the upper section; 30-following piston; 31-elastic element; 32- upper body; 33-plate; I, II-conclusions to air cylinders; III, IV-conclusions to the brake chambers, respectively, of the rear and front wheels
Pedal 7 brake valve drive (Fig. 214) is mounted on a bracket fixed on the cabin floor. The lower arm of the pedal passes through a hole in the floor and is connected by a rod 6 with an adjusting fork 5 to the front lever. The fork 5 is designed to adjust the position of the pedal 7 of the brake valve. To ensure the return of the pedal to its original position, its lower arm is connected by a return spring 2 to the bracket 3 of the front lever 4, which is attached from below to the cab floor. Front lever mounted on the axis of the bracket 3. The long arm of the lever is connected to the rod 6 of the pedal, the short arm is connected to the rod I of the drive of the intermediate lever 9 of the pendulum type.
To enable regulation of the stroke of the lever of the brake valve 13 rod 1 in the area of the intermediate lever 9 also has a threaded fork. Brake valve 13 on the bracket is attached to the left side member from the inside in the area where the fuel tank bracket is attached.
Rice. 214. The drive of a two-section brake valve: 1-thrust intermediate; 2-spring; 3-front bracket; 4-front lever; 5-adjusting fork; 6-pedal thrust; 7-pedal brake valve; 8-protective cover; 9-intermediate lever; 10-intermediate bracket; 11-rear thrust; 12-brake valve bracket; 13-brake valve
Parking brake control valve (Fig. 215) is designed to control the spring-loaded power accumulators of the parking and emergency brakes.
The crane is fixed with two bolts on the engine niche inside the cab to the right of the driver's seat. The air coming out of the valve during braking is discharged outside through a pipeline connected to the atmospheric outlet of the edge.
When the car is moving, the handle 14 of the valve is in its lowest position and compressed air from the receiver of the parking and spare brakes is supplied to terminal I. Under the action of spring 6, stem 16 is in its lowest position, and valve 22 is pressed against outlet seat 21 under the action of spring 2 rod 16. Compressed air through the holes in the piston 23 enters the cavity A, and from there through the inlet valve seat 22, which is made at the bottom of the piston 23, enters the cavity B. Then, through the vertical channel in the housing 3, the air passes to the outlet III and then to spring energy accumulators of the drive.
When the handle 14 is turned, the guide cap 15 rotates together with the cover 13. Sliding along the helical surfaces of the ring 9, the cap 15 rises, dragging the stem 16 with it. 23.
As a result, the passage of compressed air from port I to port III is stopped. Through the open outlet seat 21 on the stem 16, compressed air through the central hole of the valve 22 exits from outlet III to atmospheric outlet II until the air pressure in cavity A under piston 23 overcomes the forces of the balancing spring 5 and the air pressure above the piston in cavity B Overcoming the force of the spring 5, the piston 23 together with the valve 22 rises until the valve contacts the outlet seat 21 of the stem 16, after which the air release stops. Thus, the follow-up action of the crane is carried out.
The stopper 20 of the crane has a profile that automatically returns the handle to the lower position when it is released. Only in the uppermost position, the latch 18 of the handle 14 enters the special cutout of the stopper 20 and fixes the handle. In this case, the air from outlet III completely exits into the atmospheric outlet II, since the piston 23 abuts against the plate 7 of the spring 5 and the valve 22 does not reach the outlet seat 21 of the stem. To release the spring energy accumulators, the handle must be pulled out in the radial direction, while the latch 18 comes out of the stopper groove and the handle 14 freely returns to the lower position.
Rice. 215. Parking brake control valve: I-output to the receiver; II-atmospheric output; III-output of the control line of the accelerating valve: 1-thrust ring; 2-valve spring; 3-body; 4, 24-sealing rings; 5-balancing spring; 6-rod spring; 7- balance spring plate; 8- rod guide; 9- figured ring; 10-thrust ring; 11-pin; 12-cap spring; 13- cover; 14- crane handle; 15-guide cap; 16-stock; 17-axis roller; 18- latch; 19-roller; 20-stopper; 21-way valve seat on stem; 22- valve; 23-follower piston
Pneumatic crane (Fig. 216) with push-button control is designed to supply and disable compressed air. Two such cranes are installed on the KamAZ vehicle. One controls the emergency braking system of spring energy accumulators, the second controls the pneumatic cylinders of the engine brake.
A filter 3 is installed in the atmospheric outlet II of the pneumatic valve, which prevents dirt and dust from entering the valve.
Compressed air enters the pneumatic valve through outlet I. When button 8 is pressed, pusher 9 moves down and presses valve 15 with its outlet seat, separating outlet III from atmospheric outlet II. Then the pusher 9 presses the valve 15 from the inlet seat of the body, thereby opening the compressed air passage from port I to port III and further into the line to the pneumatic actuator.
When the button 8 is released, the pusher 9 returns to the upper position under the action of the spring 13. In this case, the valve 15 closes the hole in the body 2, stopping the further supply of compressed air to the outlet III. and the pusher seat 9 breaks away from the valve 15, thereby communicating output III with atmospheric output II. Compressed air from outlet III through hole A in the pusher 9 and outlet II goes into the atmosphere.
Rice. 216. Pneumatic valve: I-output to the receiver; II-atmospheric output; III-output to pneumatic cylinders; 1, 11, 12-thrust rings; 2-body; 3- filter; 4-plate spring rod; 5, 10, 14 sealing rings; 6-sleeve; 7-protective cover; 8-button; 9-pusher; 13-pusher spring; 15-valve; 16-valve spring; 17-valve guide
Pressure limiting valve (Fig. 217) is designed to reduce the pressure in the brake chambers of the front axle of the car during braking with low intensity (to improve the controllability of the car on slippery roads), as well as to quickly release air from the brake chambers when braking.
Atmospheric output III in the lower part of housing 1 is closed with a rubber valve 18, which protects the device from dust and dirt ingress and is attached to the housing with a rivet. When braking, the compressed air coming from the brake valve to port II acts on the small piston 14 and moves it down together with valves 15 and 17. Piston 13 remains in place until the pressure at port II reaches the level set by adjusting the preload balancing spring 12. When the piston 14 moves down, the exhaust valve 17 closes, and the inlet valve 15 opens and compressed air flows from output II to outputs I and then to the brake chambers of the front axle. Compressed air is supplied to terminals I until its pressure on the lower end of the piston 14 (which has a larger area than the upper one) is balanced by the air pressure from outlet II to the upper end and the valve 15 closes. Thus, pressure is set in ports I, corresponding to the ratio of the areas of the upper and lower ends of the piston 14. This ratio is maintained until the pressure in port II reaches a predetermined level, after which piston 13 is put into operation, which also begins to move down, increasing the force acting on the upper side of the piston 14. With a further increase in pressure in port II, the pressure difference in ports II to I decreases, and when a predetermined level is reached, the pressure in ports II to I equalizes. In this way, a follow-up action is carried out over the entire operating range of the pressure limiting valve.
When the pressure in output II decreases (brake valve is released), pistons 13 and 14, together with valves 15 and 17, move upwards. The inlet valve 15 closes, and the outlet valve 17 opens and the compressed air from outlets I, i.e. the brake chambers of the front axle, escapes into the atmosphere through outlet III.
Rice. 217. Pressure limiting valve: I-outlet to the brake chambers of the front wheels; II-output to the brake valve; III-atmospheric output; 1-case; 2-inlet valve spring plate; 3-spring; 4, 5, 8, 11 - sealing rings; 6-thrust ring; 7- washer; 9-cover; 10-adjusting gasket; 12-balancing spring; 13-big piston; 14-small piston; 15-inlet valve; 16-valve stem; 17 outlet valve; 18 atmospheric valve
Automatic brake force regulator is designed for automatic control of the pressure of compressed air supplied to the brake chambers of the axles of the rear bogie of KamAZ vehicles during braking, depending on the current axial load. The regulator is mounted on a bracket 1 (Fig. 218), fixed on the cross member of the vehicle frame. The regulator is attached to the bracket with nuts.
The lever 3 of the regulator with the help of a vertical rod 4 is connected through the elastic element 5 and the rod 6 with the beams of the bridges 8 and 9 of the rear bogie. The regulator is connected to the axles in such a way that misalignment of the axles during braking on rough roads and twisting of the axles due to the action of the braking torque do not affect the correct regulation of the braking forces. The regulator is installed in a vertical position. The length of the lever arm 3 and its position with the unloaded axle are selected according to a special nomogram depending on the suspension travel when the axle is loaded and the ratio of the axial load in the laden and unladen state.
Rice. 218. Installing the brake force regulator: 1-regulator bracket; 2 - regulator; 3 - lever; 4 - rod of the elastic element; 5 - elastic element; 6 - connecting rod; 7 - compensator; 8 - middle bridge; 9 - rear axle
When braking, compressed air from the brake valve is supplied to the output I (Fig. 219) of the regulator and acts on the upper part of the piston 18, causing it to move down. At the same time, compressed air through the tube 1 enters under the piston 24, which moves up and is pressed against the pusher 19 and the ball joint 23, which, together with the regulator lever 20, is in a position depending on the load on the bogie axle. When the piston 18 moves down, the valve 17 is pressed against the exhaust seat of the pusher. When the piston 18 moves further, the valve 17 opens from the seat in the piston and compressed air from port I enters port 11 and then to the brake chambers of the axles of the rear bogie of the vehicle.
Rice. 219. Automatic brake force regulator: I-outlet to the emergency release valve; II-output to the accelerating valve; III-atmospheric output; 1-tube; 2, 7-sealing rings; 3-lower body; 4, 17 valves; 5-shaft; 6, 15-thrust rings; 8-diaphragm spring; 9-diaphragm washer; 10-insert; 11-ribs of the piston; 12-cuff; 13-valve spring plate; 14-upper body; 16-spring; 18, 24 - pistons; 19-pusher; 20-lever; 21-diaphragm; 22-guide; 23-ball heel; 25 - guide cap
At the same time, compressed air through the annular gap between the piston 18 and the guide 22 enters the cavity A under the diaphragm 21 and the latter begins to put pressure on the piston from below. When pressure is reached at port 11, the ratio of which to the pressure at port 1 corresponds to the ratio of the active areas of the upper and lower sides of the piston 18, the latter rises up until the valve 17 is seated on the inlet seat of the piston 18. The flow of compressed air from port 1 to port And stops. In this way, the follow-up action of the regulator is carried out. The active area of the upper side of the piston, which is affected by compressed air supplied to port I, remains always constant.
The active area of the lower side of the piston, which is affected by the compressed air through the diaphragm 21, which has passed into the output II, is constantly changing due to a change in the relative position of the inclined ribs II of the moving piston 18 and the fixed insert 10. The mutual position of the piston 18 and the insert 10 depends on the position of the lever 20 and connected with it through the heel 23 of the pusher 19. In turn, the position of the lever 20 depends on the deflection of the springs, i.e., on the relative position of the bridge beams and the vehicle frame. The lower the lever 20, the heel 23, and hence the piston 18, are lowered, the greater the area of the ribs 11 comes into contact with the diaphragm 21, i.e., the active area of the piston 18 from below becomes larger. Therefore, at the extreme lower position of the pusher 19 (minimum axial load), the difference in compressed air pressures in terminals I and II is the largest, and at the extreme upper position of the pusher 19 (maximum axial load), these pressures are equalized. Thus, the brake force regulator automatically maintains a compressed air pressure in port II and in the brake chambers associated with it, which provides the required braking force proportional to the axial load acting during braking.
When the brake is released, the pressure in port I drops. Piston 18, under the pressure of compressed air acting on it through diaphragm 21 from below, moves up and tears off valve 17 from the outlet seat of pusher 19. Compressed air from outlet II exits through the hole of the pusher and outlet III into the atmosphere, while squeezing the edges of the rubber valve 4.
Elastic element of the brake force regulator designed to prevent damage to the governor if the axle travel relative to the frame is greater than the allowable travel of the governor lever.
The elastic element 5 (see Fig. 218) of the brake force regulator is mounted on a rod 6 located between the rear axle beams in a certain way. The point of connection of the element with the regulator rod is located on the axis of symmetry of the bridges, which does not move in the vertical plane when the bridges are twisted during braking, as well as with a one-sided load on an uneven road surface and when the bridges are skewed on curved sections when turning. Under all these conditions, only vertical movements from static and dynamic changes in the axial load are transmitted to the regulator lever.
At vertical movements bridges within the allowable stroke of the brake force regulator lever, the ball pin 2 (Fig. 220) of the elastic element is at the neutral point.
With strong shocks and vibrations, as well as when the bridges move beyond the limits of the allowable travel of the brake force regulator lever, the rod 3, overcoming the force of the spring 4, rotates in the housing 5. In this case, the rod 1 connecting the elastic element with the brake force regulator rotates relative to the deflected rod around ball finger. After the termination of the force that deflects the rod, the finger returns to its original neutral position under the action of the spring.
Rice. 220. Elastic element of the brake force regulator
Relay valve (Fig. 221) is designed to reduce the actuation time of the spare brake drive by reducing the length of the compressed air inlet line to the spring energy accumulators and the release of air from them directly through the accelerating valve into the atmosphere. valve installed on inside of the right side member of the vehicle frame in the area of the rear bogie.
Conclusion III is supplied with compressed air from the receiver. Conclusion IV is connected to the control device - parking brake valve, and output I-c spring power accumulator.
In the absence of pressure in port IV, piston 3 is in the upper position. Inlet valve 4 is closed by spring 5 and outlet valve I is open. Through the open exhaust valve and output I, the spring energy accumulators communicate with the atmospheric output II. The car is braked by spring energy accumulators.
When compressed air is supplied to terminal IV from the manual brake valve, air enters the above-piston space - chamber 2. The piston moves down under the action of compressed air and first closes the exhaust valve, and then opens the intake valve. Cylinders of spring energy accumulators connected to output I are filled with compressed air from the receiver through output III and an open inlet valve.
The proportionality of the control pressure at port IV and the output pressure at port I is carried out by the piston. When a pressure is reached in port I corresponding to the pressure at port IV, the piston moves up until the intake valve closes, moving under the action of a spring. With a decrease in pressure in the control line (i.e. at port IV), the piston moves upwards due to the higher pressure at port I and breaks away from the exhaust valve. Compressed air from spring energy accumulators through an open exhaust valve, a hollow body of 6 valves and an atmospheric valve is released into the atmosphere and the car is braked.
Rice. 221. Accelerator valve: I-output to the cylinders of energy accumulators; II-atmospheric output; III-output to the receiver; IV-outlet to the parking brake control valve
Dual line bypass valve (Fig. 222) is designed to provide control of one actuator using two independent controls.
On the one hand, a line is connected to it from the parking brake valve (terminal I), on the other, from the parking brake emergency release valve (terminal II). The output line (terminal III) is connected to the spring-loaded energy accumulators of the brake mechanisms of the rear bogie of the car.
The dual-line valve is installed inside the right side member of the vehicle frame next to the relay valve.
The valve is connected according to the arrow on the body. When compressed air is supplied to outlet I from the manual brake valve (through the accelerating valve), seal 1 moves to the left and sits on the seat in cover 3, closing outlet II. In this case, terminal III is connected to terminal I, compressed air passes into the spring energy accumulators and the car is released.
When compressed air is supplied to outlet II from the pneumatic emergency release valve, the seal moves to the right and sits on the seat in housing 2, closing outlet I. At the same time, outlet III is connected to outlet II, compressed air also passes into the spring energy accumulators and the car is released. When braking, i.e., when air is released from the spring energy accumulators, the seal remains pressed against the seat to which it has moved, and compressed air flows freely from the spring energy accumulators through terminal III to terminals I and II.
In the case of simultaneous supply of compressed air to terminals I and II, the seal takes a neutral position and does not interfere with the passage of air to terminal III and further into the spring energy accumulators.
Rice. 222. Dual-line bypass valve: I-outlet to the emergency release valve; II-output to the accelerating valve; III-output to the cylinders of energy accumulators; 1-seal; 2-body; 3-lid; 4-ring sealing
Brake chamber type 24 (Fig. 223) is designed to convert the energy of compressed air into work to actuate the front wheel brakes.
The cavity above the diaphragm through the threaded boss 1 in the cover 2 is connected to the service brake supply line.
The cavity below the diaphragm is connected to the atmosphere through drainage holes made in 8 camera body. The camera is attached to the bracket with two bolts 13, welded to the flange 9, which is inserted into the camera body from the inside and pressed against the bottom of the body by a return spring 5. To prevent dirt from entering the body, a rubber cover is put on the camera stem. When braking, i.e. when compressed air is supplied through output I, diaphragm 3 bends, acts on disk 4 and moves rod 7, which rotates the brake adjusting lever together with the expanding fist. The fist presses the pads against the brake drum with a force proportional to the pressure of the compressed air supplied to the brake chamber.
When braking, i.e., when air is released from the chamber, under the action of a spring, the disk with the rod and the diaphragm return to its original position. The adjusting lever with a fist and pads under the action of the coupling springs of the brake mechanism returns to the braked position.
Rice. 223. Brake chamber type 24: I-outlet of compressed air; 1-boss; 2-lid; 3-diaphragm; 4-disk; 5-spring; 6 clamp; 7-rod; 8-body; 9-flange; 10-nut; 11-protective cover; 12-fork; 13-bolt
Brake chamber type 20/20 with spring energy accumulator (Fig. 224) is designed to actuate the brake mechanisms of the wheels of the rear bogie of the car when the service, spare and parking brakes are turned on.
Rice. 224. Brake chamber with spring energy accumulator type 20/20: 1-case; 2-pusher; 3-ring sealing; 4-pipe; 5-piston; 6-seal; 7- cylinder; 8-spring; 9-screw; 10-boss; 11, 15 branch pipes; 12-hose; 13-thrust ring; 14-flange; 16-diaphragm; 17-disk; 18- stock; 19-return spring
Spring energy accumulators together with brake chambers are installed on the brackets of the expanding knuckles of the rear bogie.
The brake chamber with a spring energy accumulator type 20/20 consists of the actual brake chamber, the device of which is no different from the device of the brake chamber shown in Fig. 223, and spring energy storage. Inside pipe 4 (see Fig. 224) a device for mechanical retraction of the spring energy accumulator is mounted.
When braking with a service brake, compressed air from the brake valve is supplied to the cavity above the diaphragm 16. The diaphragm, bending, acts on the disk 17, which moves the rod 18 through the washer and locknut and turns the adjusting lever with the expanding fist of the brake mechanism. Thus, braking of the rear wheels occurs in the same way as braking of the front wheels with a conventional brake chamber.
When the spare or parking brakes are turned on, that is, when air is released using a manual valve from the cavity under the piston 5, the spring 8 is decompressed and the piston moves down. The pusher 2 through the diaphragm acts on the thrust bearing, which, moving, turns the brake adjustment lever associated with it. The vehicle is braking.
When braking, compressed air enters through the outlet under the piston. The piston, together with the pipe and the pusher, moves up, compresses the spring 8 and allows the brake chamber rod to return to its original position under the action of the return spring 19.
With an excessively large gap between the shoes and the brake drum, i.e. with an excessively large stroke of the brake chamber rod, the force on the rod may not be sufficient for effective braking. In this case, turn on the hand brake valve and release air from under the piston of the spring-loaded energy accumulator. The pusher under the action of the power spring 8 will push through the middle of the diaphragm and advance the rod to the available additional stroke, ensuring the braking of the car.
In the event of a leak and a decrease in pressure in the parking brake reservoir, air from the cavity under the piston through the outlet and the damaged part of the drive will go into the atmosphere and the car will automatically brake with spring-loaded energy accumulators.
Pneumatic cylinders are designed to actuate the mechanisms of the engine brake.
Three pneumatic cylinders are installed on KamAZ vehicles:
Two cylinders Ø 35 mm and with a piston stroke of 65 mm (Fig. 225, a) for controlling throttle valves installed in the engine exhaust pipes;
One cylinder Ø 30 mm and with a piston stroke of 25 mm (Fig. 225, b) to control the lever of the high pressure fuel pump regulator.
Rice. 225. Pneumatic drive cylinders: a-flap mechanism of the auxiliary brake; b-engine stop lever; 1-cylinder cover; 2-piston; 3-return spring; 4-rod; 5-case; 6-cuff
The pneumatic cylinder Ø 35x 65 is hinged on the bracket with a pin. The cylinder rod is connected with a threaded fork to the damper control lever. When the auxiliary brake is turned on, compressed air from the pneumatic valve through the outlet in the cover 1 (see Fig. 225, a) enters the cavity under the piston 2. The piston, overcoming the force of the return springs 3, moves and acts through the rod 4 on the engine brake damper control lever by moving the damper from the "open" position to the "closed" position. When the compressed air is released, the piston with the rod returns to its original position under the action of the springs. In this case, the damper rotates to the "open" position.
Pneumatic cylinder Ø 30X 25 is pivotally mounted on the cover of the high pressure fuel pump regulator. The cylinder rod is connected by a threaded fork to the regulator lever. When the auxiliary brake is turned on, compressed air from the pneumatic valve through the outlet in the cover 1 (see Fig. 225, b) of the cylinder enters the cavity under the piston 2. The piston, overcoming the force of the return spring 3, moves and acts through the rod 4 on the fuel pump regulator lever , moving it to the zero feed position. The throttle linkage system is connected to the cylinder rod in such a way that the pedal does not move when the engine brake is applied. When the compressed air is released, the piston with the rod returns to its original position under the action of the spring.
Check outlet valve (fig. 226) is intended for connection to the drive of instrumentation for checking pressure, as well as for extracting compressed air. There are five such valves on KamAZ vehicles - in all circuits of the pneumatic brake drive. To connect to the valve, hoses and measuring instruments with a union nut M16X1.5 should be used.
When measuring pressure or for extracting compressed air, unscrew the cap 4 of the valve and screw on the housing 2 the union nut of the hose connected to the control pressure gauge or any consumer. When screwing on, the nut moves the pusher 5 with the valve and air enters the hose through the radial and axial holes in the pusher. After disconnecting the hose, the pusher with the valve is pressed against the seat in the housing under the action of spring 6, closing the compressed air outlet from the pneumatic actuator.
Rice. 226. Control outlet valve: 1-fitting; 2-body; 3-loop; 4-cap; 5-pusher with valve; 6-spring
pressure drop sensor (Fig. 227) is a pneumatic switch designed to close the circuit of electric lamps and an alarm signal (buzzer) in case of pressure drop in the pneumatic brake actuator receivers. The sensors are screwed into the receivers of all circuits of the brake drive, as well as into the fittings of the circuit of the parking brake drive circuit, using an external thread on the housing. Since the drive of these systems works with the release of compressed air, in this case the pressure drop sensor serves as a sensor for the start of braking, and when it is turned on, the red control lamp on the instrument panel and the brake signal lamps light up.
The sensor has normally closed central contacts, which open when the pressure drops below 4.8-5.2 kgf/cm 2 . When the specified pressure is reached in the actuator, the diaphragm 2 bends under the action of compressed air and through the pusher 4 acts on the movable contact 5. The latter, having overcome the force of the spring 6, breaks away from the fixed contact 3 and breaks the electrical circuit of the sensor. Closing of contacts, and, consequently, switching on of control lamps and a buzzer, occurs when the pressure drops below the specified value.
Rice. 227. Pressure drop sensor: 1-case; 2-diaphragm; 3-fixed contact; 4-pusher; 5-moving contact; 6- spring; 7-adjusting screw; 8-insulator
Brake signal switch (Fig. 228) is a pneumatic switch designed to close the circuit of electrical signal lamps when braking. The sensor has normally open contacts that close at a pressure of 0.1-0.5 kgf/cm 2 and open when the pressure drops below 0.5-0.4 kgf/cm 2 . The sensors are installed in the lines supplying compressed air to the brake actuators.
When compressed air is supplied under the diaphragm, the latter bends and the movable contact 3 connects the contacts 6 of the sensor electrical circuit.
Rice. 228. The sensor of inclusion of a stoplight: 1 case; 2-diaphragm; 3-moving contact; 4-spring; 5-terminal fixed contact; 6-fixed contact; 7-cap
Single safety valve (Fig. 229) is designed to protect the pneumatic brake drive of the tractor from the loss of compressed air in case of damage to the supply line connecting the tractor with the trailer (semi-trailer). When the pressure in the brake drive of the tractor vehicle decreases due to leakage or leakage in the trailer drive (for example, when the line connecting the car with the trailer breaks), the safety valve disconnects the pneumatic brake drives of the car and trailer. In addition, a single safety valve prevents compressed air from escaping from the trailer (semi-trailer) line in the event of a leak in the brake drive of the towing vehicle, thereby preventing automatic braking of the trailer.
A single protective valve is installed on the trailer brake supply pipeline at the rear of the frame of the tractor vehicle and is connected according to the arrow printed on its body and indicating the direction of air flow.
Compressed air through outlet I enters cavity A under diaphragm 13, which is pressed by springs 7 and 8 through piston 6 to the seat in housing 1, blocking the access of air to cavity B. When the predetermined opening pressure is reached, compressed air, overcoming the force of the springs, lifts the diaphragm and passes into cavity B. Then, by opening check valve 2, it enters terminal II.
When the pressure in port I drops below a predetermined value, the diaphragm lowers under the action of springs on the seat and separates outputs I and II. At the same time, the non-return valve closes and prevents the reverse flow of compressed air (from port II to port I). The valve is adjusted in such a way that air enters outlet II at a pressure at outlet I equal to 5.5-5.55 kgf/cm 2 . In this case, the closing of the valve will occur when the pressure at port I drops to 5.45 kgf/cm 2 .
When the adjusting screw 10 is screwed into the cover, the valve opening pressure increases, and when turned out, it decreases.
Rice. 229. Single protective valve: I - output to the receiver; II-output to the supply line of the trailer; 1-case; 2-return valve; 3-check valve spring; guide sleeve; 5-thrust ring; 6-piston; 7, 8-piston springs; 9-cover; 10- adjusting screw; 11-piston spring plate; 12 washer; 13-aperture
Trailer brake control valve with two-wire actuator (Fig. 230) is designed to actuate the trailer (semi-trailer) brake drive when any of the separate tractor service brake drive circuits are turned on, as well as when the spring-loaded power accumulators of the tractor spare and parking brake drives are turned on. The valve is attached to the tractor frame with two bolts.
Between the lower 14 and middle 18 housings, a rubber diaphragm I is clamped, which is fixed between two washers 17 on the lower piston 13 with a nut 16 sealed with a rubber ring. An outlet window 15 is attached to the lower body with two screws, which has holes covered with a dirt-proof valve. By loosening one of the screws, the outlet port can be rotated and access to the adjusting screw 8 through the opening of the valve 4 and piston 13 can be made.
The trailer brake control valve with a two-wire drive generates a control command for the trailer (semi-trailer) brake air distributor from three independent commands, acting both simultaneously and separately. In this case, a direct action command (to increase pressure) is given to terminals I and III, and a reverse action command to terminal II (to decrease pressure). The valve leads are connected as follows; I - with the lower section of the brake valve, II - with a reverse action valve with manual control, III - with the upper section of the brake valve, IV - with the trailer brake control line, V - with the car's reservoir, VI - with the atmosphere.
In the braked state, compressed air is constantly supplied to terminals II and V, which, acting from above on the diaphragm I and from below on the middle piston 12, keeps the piston 13 in the lower position. At the same time, output VI connects the trailer brake control line with atmospheric output VI through the central hole of valve 4 and the lower piston
When compressed air is supplied to terminal III, the upper pistons 10 to 6 simultaneously move down. Piston 10 first sits with its seat on valve 4, blocking the atmospheric outlet in the lower piston 13, and then separates valve 4 from the seat of the middle piston. Compressed air from outlet V connected to the receiver enters outlet IV and further into the trailer brake control line. The supply of compressed air to terminal IV continues until its effect from below on the upper pistons 10 and 6 is balanced by the pressure of compressed air supplied to terminal III on these pistons from above. After that, the valve 4 under the action of the spring 2 blocks the access of compressed air from port V to port IV. Thus, a follow-up action is carried out. When the pressure of compressed air at port III from the brake valve decreases, i.e. when braking, the upper piston 6 moves upwards together with piston 10 under the action of spring II and the pressure of compressed air from below (at port IV) together with piston 10. The piston seat 10 comes off valve 4 and communicates output IV with the atmospheric output VI through the holes of valve 4 and piston 13.
When compressed air is supplied to outlet I, it enters under the diaphragm 1 and moves the lower piston 13 upwards together with the middle piston 12 and valve 4 upwards. The valve 4 reaches the seat in the small upper piston 10, closes the atmospheric outlet, and with further movement of the middle piston 12 is separated from its inlet seat. Air enters from outlet V, connected to the receiver, to outlet IV and then into the trailer brake control line until its effect on the middle piston 12 from above is equalized by pressure on the diaphragm 1 from below. After that, valve 4 blocks the access of compressed air from port V to port IV. Thus, a follow-up action is carried out with this version of the device operation. When the compressed air pressure drops at outlet I and under diaphragm 1, the lower piston 13 moves down together with the middle piston 12. Valve 4 breaks away from the seat in the upper small piston 10 and communicates output IV with the atmospheric output VI through the holes in valve 4 and piston 13.
With the simultaneous supply of compressed air to terminals I and III, the large and small upper pistons 10 and 6 simultaneously move down, and the lower piston 13 with the middle piston 12 moves up. The filling of the trailer brake control line through terminal IV and the release of compressed air from it proceed in the same way as described above.
When compressed air is released from port II (during braking by the spare or parking brake systems of the tractor), the pressure above diaphragm 1 drops. Under the action of compressed air from below, the middle piston 12 moves upwards together with the lower piston 13. Filling the trailer brake control line through terminal IV and braking occurs in the same way as when compressed air is supplied to terminal I. The follow-up action in this case is achieved by balancing the pressure of compressed air from below on the middle piston 12 and the sum of the pressure from above on the middle piston and diaphragm 1.
When compressed air is supplied to terminal III (or when air is simultaneously supplied to terminals III and I), the pressure in terminal IV connected to the trailer brake control line exceeds the pressure supplied to terminal III. This ensures the advancing action of the brakes of the trailer (semi-trailer). Maximum excess pressure at port IV is 1 kgf / cm 2, the minimum is about 0.2 kgf / cm 2, the nominal is 0.6 kgf / cm 2. Exceeding pressure is regulated by screw 8; turning the screw in increases the pressure, turning it out decreases it.
Rice. 230. Trailer brake control valve with a two-wire drive: I-outlet to the lower section of the brake valve; II-output to the parking brake control valve; III-output to the upper section of the brake valve; IV-outlet to the brake line of the trailer; V- output to the receiver; VI-atmospheric output; 1-diaphragm; 2, 9, 11-springs; 3-unloading valve; 4-inlet valve; 5-upper case; 6-upper large piston; 7-spring plate; 8-adjusting screw; 10-upper small piston; 12-middle piston; 13-lower piston; 14-lower case; 15 outlet window; 16-nut; 17-diaphragm washer; 18-medium body
Trailer brake control valve with single-wire actuator (Fig. 231) is designed to actuate the trailer (semi-trailer) brake drive when the tractor brake systems are operating, as well as to limit the compressed air pressure in the trailer (semi-trailer) pneumatic drive to prevent the latter from self-braking due to pressure fluctuations in the pneumatic brake drive of the tractor vehicle . The valve is mounted on the vehicle frame and secured with two bolts.
Compressed air from the receiver of the tractor vehicle is supplied to terminal I and passes through channel A into the cavity above the stepped piston 8. In the decelerated state, the spring 14, acting on the plate 15, holds the diaphragm 16 together with the pusher 19 in the lower position. In this case, the outlet valve 20 is closed, and the inlet 21 is open and compressed air flows from outlet I to outlet II and further into the connecting line of the trailer. When a certain pressure is reached in port II, which is set using the adjusting screw 24, the piston 4 overcomes the force of the spring 23 and lowers, as a result of which the inlet valve 21 sits on the seat in the piston 4. Thus, in the braked position in the trailer line, a pressure less than in the pneumatic drive of the tractor.
When the tractor is braked, compressed air is supplied to terminal IV and fills the subdiaphragmatic cavity B. Overcoming the force of the spring 14, the diaphragm 16 rises up along with the pushers 19. This first closes the inlet valve 21, and then the outlet valve 20 opens and the air from the connecting line of the trailer through the outlet II, the pusher 19 and output III in the cover 12 goes into the atmosphere. Air exits from outlet II until the pressure in cavity B under the diaphragm 16 and the cavity under the stepped piston 8 is balanced by the pressure in the cavity above the stepped piston. With a further decrease in pressure at outlet II, the piston 8 descends and moves down the plunger 19, which closes the exhaust valve 20, as a result of which the air is released from outlet II. Thus, a follow-up action is carried out and the braking of the trailer (semi-trailer) occurs with an efficiency proportional to the value of the compressed air pressure supplied to terminal IV.
A further increase in pressure at port IV leads to the complete release of compressed air from port II and thus to the most effective braking of the trailer. When the tractor is braked, i.e., when the pressure drops at port IV and in cavity B under diaphragm 16, the latter returns to its original lower position under the action of spring 14. Together with the diaphragm, the pusher 19 is lowered. This closes the exhaust valve 20 and opens the inlet valve 21. Compressed air from outlet I enters outlet II and then into the connecting line of the trailer (semi-trailer), as a result of which the trailer (semi-trailer) is braked.
Rice. 231. Trailer brake control valve with a single-wire drive: I - output to the receiver; II-output to the connecting line; III-output to the atmosphere; IV-outlet to the trailer brake control valve with a two-wire drive, 1-spring plate; 2-bottom cover; 3, 11-thrust rings; 4-lower piston; 5-valve spring; 6-exhaust valve seat; 7-tracking camera; 8-stage piston; 9-working chamber; 10, 17 - ring springs; 12-top cover; 13-protective cap; 14-diaphragm spring; 15- diaphragm spring plate; 16-diaphragm; 18-support; 19-pusher; 20 outlet valve; 21-inlet valve; 22-case; 23-spring; 24-adjusting screw: 25 - locknut
Uncoupling tap (Fig. 232) is designed to block, if necessary, the pneumatic line connecting the tractor with the trailer (semi-trailer). Three disconnecting valves are installed on KamAZ tractors: on flatbed tractors - on the rear cross member of the frame in front of the connecting heads, on saddle trucks - behind the cab on the right on a special bracket in front of the connecting flexible hoses. Each crane is attached with two bolts.
Terminal II is connected to the trailer brake control line; compressed air is supplied through port I.
If the handle 9 is located along the axis of the valve, the pusher 8 together with the stem 6 are in the lower position and the valve 4 is open. Compressed air from outlet I through an open valve and outlet II flows from the tractor to the trailer (semi-trailer).
When the handle 9 is turned by 90°, the rod 6 together with the diaphragm rises up under the action of the spring 5 and air pressure. Valve 4 sits on the seat in housing 2, separating conclusions I and II. The stroke of the stem, determined by the screw profile of the cover 7, is greater than the stroke of the valve 4. The stem departs from the valve, the compressed air from the connecting line through port II, the axial and radial holes in the stem exits into the atmosphere through port III in the cover 7.
The coupling heads can then be disengaged.
Rice. 232. Dissociative faucet: a-faucet is open; b-faucet is closed; 1-cork; 2-body; 3-valve spring; 4-valve; 5-rod spring; 6-rod with diaphragm; 7-cover; 8-pusher; 9-handle
Connecting heads type "Palm" (Fig. 233) are designed to connect the lines of the two-wire pneumatic brake drive of the trailer (semi-trailer) and the tractor.
On board tractors KAMAZ one connecting head of the "Palm" type of the supply line, painted in red (or with a red cover), is installed on the rear cross member of the frame with right side(along the way). Another "Palm" connection head of the control line, painted blue (or with a yellow cover), is fixed in the same place on the left side. Both heads are installed in such a way that the connecting holes in them are directed to the right. On KAMAZ truck tractors, the coupling heads are mounted on flexible hoses and, after being disconnected from the semi-trailer, are attached behind the cab to special brackets. The color of the heads is the same as on the flatbed tractors.
When connecting heads of the "Palm" type, it is necessary to take aside the protective covers 4 of both heads. The heads are joined by seals 3 and rotate until the protrusion of the head enters the corresponding groove of the other, i.e. until the insert 2 is connected to the latch 5. This prevents spontaneous separation of the connecting heads. The sealing of the joint of two heads is provided by compression of the seals 3.
When disconnecting the tractor and trailer, the coupling heads are rotated in the opposite direction until the insert 2 leaves the groove of the latch 5. After disconnection, the coupling heads should be closed with covers 4.
Rice. 233. Connecting head type "Palm": a-connecting head; b-connection of the heads of the tractor and trailer; 1-case; 2-insert; 3- seal; 4-lid; 5-retainer
Connection head type "A" (fig. 234) is designed for installation on tractors and serves to connect a single-wire pneumatic drive of trailer and semi-trailer brakes, as well as to automatically close the connecting line of the tractor in case of spontaneous separation of the heads (for example, when the trailer is torn off).
On KamAZ flatbed tractors, the type “A” coupling head, painted black, is installed on the rear cross member of the frame on the left side (along the way) in such a way that the connecting hole in it is directed to the right. On KAMAZ truck tractors, the type “A” coupling head is also painted black and installed on a flexible hose. After detaching from the semi-trailer, the head is attached behind the cab to a special bracket.
When the tractor vehicle is coupled to the trailer, the protective cover 5 is set aside at the connecting head. The head of type “A” of the tractor is joined to the head of type “B” of the trailer by seals 4. In this case, the rod 7 of the head of type “B” enters the spherical recess of the valve 3 of the head type "A" and separates the valve from the seal. After that, the heads are rotated until the protrusion of one head enters the corresponding groove of the other head. Head lock type "B" fits into the groove of the guide head type "A", preventing spontaneous separation of the heads. The sealing of the joint of the heads is achieved by compressing the seals. When the tractor and trailer are disconnected, the connecting heads are rotated in the opposite direction until the protrusion of one head leaves the groove of the other, after which the heads are separated. In this case, the valve, under the action of a spring, is pressed against the seal and automatically closes the connecting line, preventing the release of compressed air from the pneumatic brake drive of the towing vehicle. After disconnection, the head should be closed with a cap.
Rice. 234. Connecting head type "A": a-connecting head; b-connection of heads of type "A" and "B": I - body; 2-valve spring; 3-check valve; 4-seal; 5-lid; 6 ring nut; 7-rod
Features of the pneumatic drive of the brakes of cars produced before May 1983 Five receivers are installed on the cars (Fig. 235): two with a volume of 40 liters and three with a volume of 20 liters, two of the latter are interconnected and form a single volume of 40 liters. Circuit IV (auxiliary brake drive and other consumers) has its own receiver 10. A condensing receiver is not provided in the pneumatic drive.
Rice. 235. Location of brake system devices on a KamAZ-5320 car (until May 1983): 1-crane for emergency release of the parking brake; 2- pneumatic cylinder of the engine stop lever; 3-crane parking brake control; 4- pressure regulator; 5-fuse against freezing; 6-compressor; 7- double protective valve; 8-triple safety valve; 9-receiver II circuit; 10-receiver IV circuit; 11-pressure drop sensor; 12 - receiver of the III circuit; 13-brake chamber with a spring-loaded energy accumulator; 14-sensor on the parking brake; 15-two-main bypass valve; 16-accelerator valve; 17-brake SNL regulator; 18- control output valve; 19-uniary protective valve; 20-uncoupling tap; 21-connecting head type "Palm"; 22-connecting head type "A"; 23-trailer brake control valve with a single-wire drive; 24-trailer brake control valve with two-wire drive; 25-elastic element; 26-receiver of the I circuit; 27-pneumatic cylinder of the auxiliary brake drive; 28 two-section brake valve; 29-pressure limiting valve; 30-brake chamber type 24; 31-crane for switching on the auxiliary brake
Maintenance
When inspecting the brake system hoses, do not allow them to be twisted or come into contact with sharp edges of other parts. To eliminate leaks in connection heads, replace defective heads or o-rings in them.
When operating a car without a trailer, close the coupling heads with a cover to protect them from dirt, snow, moisture; on truck tractors, connect the heads to the false heads installed behind the cab.
Drain the condensate from the receivers at nominal air pressure in the system, moving aside the ring 2 (Fig. 236) stem 1 of the drain cock. Do not pull the stem down or push it up. An increased oil content in the condensate indicates a compressor failure.
Rice. 236. Condensate drain valve
If condensate freezes in the brake reservoirs, heat them with hot water or warm air. Forbidden use an open flame for heating.
After draining the condensate, bring the air pressure in the pneumatic system to the nominal value.
When changing alcohol in the fuse, drain the sediment from the filter housing by unscrewing drain plug. To fill in alcohol and control its level, lower the handle of the thrust 1 (Fig. 237) to the lower position and lock it by turning it 90 ° (with the lower position of the thrust, the fuse is off). Then unscrew the plug with level indicator 2, fill in 0.2 or 1 l of alcohol and close the filler hole. To turn on the fuse, lift the traction handle up.
To increase the efficiency of the fuse, it is recommended to press the traction handle 5-8 times when filling the pneumatic system with air.
Rice. 237. Turning on the fuse from freezing condensate: a - the fuse is off; b - the fuse is on
At TO-1 perform the following operations: lubricate the bushings of the expander shafts through the grease fittings, making no more than five strokes with a syringe; lubricate the adjusting levers of the brake mechanisms through the grease fittings until fresh grease is squeezed out; adjust the stroke of the brake chamber rods.
Brake chamber stroke Adjust with cold brake drums and disengaged parking brake.
Measure the stroke of the rods with a ruler, setting it parallel to the rod and resting it with its end into the brake chamber housing. Mark the location of the extreme point of the rod on the scale of the ruler. Press the brake pedal to the stop (at nominal air pressure in the system) and again note the location of the same point on the rod on the scale. The difference between the results obtained will give the value of the stroke of the rod.
Turning axis 1 (Fig. 238) of the worm of the adjusting lever, set the smallest stroke of the brake chamber rod. Make sure that when turning on and off the compressed air supply, the brake chamber rods move quickly, without jamming. Check the rotation of the reels. They should rotate freely and evenly without touching the pads. The smallest stroke for models 5320, 5410 and 55102 is 20 mm, and for models 5511, 53212 and 54112 it is 25 mm. The greatest stroke of the rods is allowed - 40 mm.
Rice. 238. Adjusting lever of the brake mechanism: 1-axis worm; 2-window for checking gaps; 3-oil can
It is necessary that the rods of the right and left chambers on each axle have the same stroke as possible (permissible difference is not more than 2-3 mm) in order to obtain the same braking efficiency of the right and left wheels.
At TO-2 check the operability of the pneumatic drive of the brakes on the valves of the control outputs. Visually check the splint of the pins of the brake chamber rods. Tighten the nuts securing the brake chambers to the brackets and the nuts of the bolts securing the brake chamber brackets to the caliper.
Adjust the position of the brake pedal relative to the cabin floor, ensuring that the brake valve lever has full travel.
Checking the performance of the pneumatic brake drive consists in determining the output parameters of air pressure along the circuits using control pressure gauges and standard instruments in the driver's cab (two-pointer pressure gauge and a block of control lamps for the brake system). Check the control output valves installed in all circuits of the pneumatic drive, and the connecting heads of the Palm type of the supply and control (brake) lines of the two-wire drive and type A of the connecting line of the single-wire trailer brake drive.
Valves 12 (see Fig. 205) of the control outlet are located in the following places of the drive circuits:
Service brakes of the front axle - on the pressure limiting valve;
Service brakes of the rear bogie - on the left (along the vehicle) side member of the frame in the rear axle area;
Parking and spare brakes - on the right side member of the frame in the area of the rear axle and on the receiver of the circuit;
Auxiliary brakes and consumers - on the condensing receiver.
Before checking, eliminate compressed air leakage from the pneumatic system. As control process pressure gauges, use pressure gauges with a measurement range of 0-10 kgf / cm 2 of accuracy class 1.5. Check the performance of the pneumatic brake drive in the following sequence:
Fill the pneumatic system with air until pressure regulator 2 operates. In this case, the pressure in all circuits of the brake drive and the connecting head 29 of the Palm type of the supply line of the two-wire trailer brake drive (terminal E) should be 6.2-7.5 kgf / cm 2, and in the connecting head 30 of type "A" of the single-wire drive (output F) - 4.8-5.3 kgf / cm 2. The signal lamps of the block of control lamps of the brake system should go out when the pressure in the circuits reaches 4.5-5.5 kgf / cm 2. At the same time, the sound signaling device (buzzer) stops working;
Fully depress the service brake pedal. The pressure on the two-pointer pressure gauge in the driver's cab should drop sharply (by no more than 0.5 kgf / cm 2). In this case, the pressure in the control outlet valve B must be equal to the upper scale reading of the two-pointer pressure gauge in the driver's cab. The pressure in the control output valve G must be at least 2.3-2.7 kgf / cm 2 (for an unloaded car). Raise the vertical rod of the brake force regulator drive 32 by the amount of static suspension deflection:
The pressure in the brake chambers 23 must be equal to the indication of the lower scale of the two-pointer pressure gauge, the pressure in the connecting head 29 of the Palm type of the brake line of the two-wire drive (pin I) must be 6.2-7.5 kgf / cm 2, in the connecting head 30 type “A” of the connecting line (terminal G), the pressure should drop to 0;
Set the crane drive handle 21 to the front fixed position. The pressure in the control output valve D must be equal to the pressure in the receiver 8 of the parking and spare circuits and be in the range of 6.2-7.5 kgf / cm 2, the pressure in the connecting head 29 of the Palm type of the brake line of the two-wire drive (output And) should be equal to 0, in the connecting head 30 type "A" (output G) -4.8-5.3 kgf / cm 2;
Set the parking brake valve 21 to the rear fixed position. The parking brake warning light on the brake warning lamp unit should illuminate in flashing mode. The pressure in the valve of the control output D and in the connecting head 30 of type "A" (output G) should drop to 0, and in the connecting head 29 of the type "Palm" of the brake line of the two-wire drive (output I) should be 6.2-7.5 kgf / cm 2;
With the handle of the crane 21 in the rear fixed position, press the button of the emergency release valve 13. The pressure in the control output valve D must be equal to the reading of the two-pointer pressure gauge 18 in the driver's cab. The rods of the brake chambers of the mechanisms of the middle and rear axles must return to their original position;
Release the emergency release button. The pressure in the control output valve D should drop to 0;
Press the button of the crane 13 of the auxiliary brake. The rods of the cylinders 16 for controlling the dampers of the engine brake and the pneumatic cylinder 15 for turning off the fuel supply must extend. The air pressure in the brake chambers of the trailer (semi-trailer) should be 0.6-0.7 kgf / cm 2.
In the process of checking the operability of the pneumatic brake actuator, when the pressure in the circuits drops to 4.5-5.5 kgf / cm 2, the buzzer should turn on and the control lamps of the corresponding circuits on the instrument panel should light up.
Adjust the position of the brake pedal relative to the cabin floor, ensuring the full travel of the brake valve lever. The full travel of the brake pedal should be 100-130 mm, of which 20-40 mm is free play. When fully depressed, the pedal should not reach the cabin floor by 10-30 mm. Measure the pedal travel with a ruler along the upper end of the pedal. The end of the freewheel is taken as the moment when the rods of the brake chambers start to extend or the moment when the brake lights come on. If necessary, adjust the pedal stroke by changing the length of the rod 6 (see Fig. 214) with an adjusting fork 5.
At full pedal travel, the stroke of the brake valve lever should be 31.1-39.1 mm.
At STO: check the condition of the brake drums, shoes, linings, coupling springs and expanding fists; troubleshoot. Attach the receiver brackets to the frame.
When servicing the brake mechanism pay attention to the distance from the surface of the lining to the heads of the rivets. If it is less than 0.5 mm, change the brake pads. Protect the linings from getting oil on them, as the friction properties of oiled linings cannot be fully restored by cleaning and rinsing. If you need to replace one of the left or right brake linings, change all linings on both brake mechanisms (left and right wheels). After installing new friction linings, the block must be processed.
For a new drum, the block radius should be 199.6-200 mm. After the drum is bored during repair, the block radius must be equal to the radius of the bored drum. Drums are allowed to be bored up to a diameter of not more than 406 mm.
The expander shaft must rotate in the bracket without jamming. Otherwise, clean the bearing surfaces of the shaft and bracket, check the condition of the shaft sealing rings, then lubricate them through a grease fitting.
The axis of the worm of the adjusting lever should turn without jamming. Otherwise, flush the inside of the lever, dry and fill the adjusting lever with fresh grease.
Before In-Depth Check * parameters of the pneumatic actuator of the brake system, perform the following operations:
Tighten the compressor mounting bolts and the compressor cylinder head mounting nuts;
Drain the condensate from the receivers; remove the pressure regulator filter, wash it with kerosene, dry it, blow it with compressed air and reinstall it;
Remove the auxiliary brake mechanisms, clean their internal surfaces from carbon deposits, wash in kerosene, blow with compressed air and reinstall;
Inspect pipelines, hoses, covers of brake chambers and brake valve, brake valve drive, troubleshoot.
(* Only persons with the necessary training may be allowed to inspect the brake actuator.)
Carry out the check in accordance with the list of controlled parameters given in the protocol for an in-depth check of the parameters of the pneumatic drive of the brake system (Table 27) using a kit (Fig. 239), which includes: control pressure gauges 2 class 1.5, connecting hoses 1, connecting 4 heads of “A”, “B” and “Palm” types, 5 control outlet valves, a set of fittings and sealing washers, a set of 3 most commonly used keys (19X22; 24X27).
Rice. 239. Pneumatic actuator test kit
If possible, check the braking properties of the car on a brake stand * type STP-3.
(* In the absence of a stand, the effectiveness of the car's brakes can be assessed by road tests using a special method. In this case, the efficiency criterion is braking distances and vehicle behavior on the road.
The criterion for evaluating the effectiveness of brakes is the specific braking force:
Q = ∑T/P,
where ∑T is the total braking force of all wheels of the vehicle;
P is the weight of the car.
The specific braking force must be at least 0.56 when checking the service brakes and 0.28 when checking the spare brake.
In addition, determine the difference in the braking forces of the right and left wheels of the same axle on the stand. The difference should not exceed 15% (for run-in brake linings).
Inaccuracy of readings of a standard two-pointer pressure gauge determine by comparison with the readings of control pressure gauges. Connect the latter instead of threaded plugs to the receiver 9 (see Fig. 205) of the first circuit and to the receiver 10 of the second circuit. Gradually increasing and then lowering the pressure in the system, check the readings of the standard and control pressure gauges.
Determine the pressure for turning on the brake light at a nominal pressure in the system with a control pressure gauge, which is connected to the control output I. Slowly pressing the brake pedal, record the pressure for turning on and off the brake light when the lights come on. Also determine the brake light on and off pressure by gently actuating the hand brake valve.
Switch-off pressure* (switch-on) of control lamps define for all pneumatic drive circuits. To do this, connect control pressure gauges to the receiver 8, 9, 10 (see Fig. 205) of all circuits, start the engine and bring the air pressure in the system to the nominal value.
(* Before determining the cut-off pressure, check that the pilot lamps are working by pressing the control button.)
Slowly releasing air (for example, by opening a condensate drain valve) from the receiver 9 of circuit I, record the ignition pressure of the control lamp of the primary circuit on the control pressure gauge. Also determine the pressure of turning off (on) the control lamps of the second and third circuits of the pneumatic drive.
Switch-off and switch-on pressure of the pressure regulator determine by a regular two-pointer pressure gauge, the error of which has been previously verified. The car must be disinhibited, i.e. the position of the brake pedal and the parking brake valve must ensure the movement of the car. Compressed air consumers must be switched off.
Start the engine and, while increasing the air pressure in the system, record on the pressure gauge the moment when air begins to escape from the atmospheric outlet of the pressure regulator (switch-on pressure).
Press the brake pedal several times, while watching the pressure gauge for a decrease in pressure in the system and fix the moment when air stops coming out of the atmospheric outlet of the pressure regulator (cut-off pressure).
Pressure protection double safety valve determine by control pressure gauges by connecting them to control output valves A and B (see Fig. 205).
After starting the engine, fill the system with air to the nominal pressure and, by opening the condensate drain valve, bleed air from the reservoir 8 of the spare and parking brakes. Read the pressure on the test gauge connected to outlet A valve.
Refill the system with air to the nominal pressure, stop the engine and bleed the air from the reservoir 6 of the auxiliary brake system. Read the pressure on the control pressure gauge connected to the outlet B valve.
Pressure protection triple safety valve determine by three control pressure gauges connected instead of threaded plugs to receivers 9 and 10 and to the control output valve D (see Fig. 205).
Fill the system with air to nominal pressure and stop the engine. Having opened the condensate drain cock, bleed the air from the receiver 9 of the primary circuit and fix the pressure on the pressure gauge connected to the receiver 10 of the second circuit.
Refill the system with air to the nominal pressure, stop the engine, bleed the air from the second circuit receiver 10 and record the pressure on the pressure gauge connected to the primary circuit receiver 9.
Repeatedly pressing the emergency release button on the pressure gauge connected to the output valve D, fix the pressure in the receivers, at which the supply of compressed air to the emergency release circuit stops.
Determine the pressure drop in the actuator using the control pressure gauges connected to all actuator reservoirs.
After starting the engine, fill the system with air to the nominal pressure. Stop the engine and record the pressure drop on the pressure gauges after 15 minutes. The position of the brake pedal and the parking brake valve must ensure the movement of the vehicle.
Determine in turn the pressure drop in the receivers from the nominal pressure in 15 minutes with the brake pedal depressed or the parking brake valve turned on.
pressure drop in the receivers for one braking, determine by the control pressure gauges connected instead of the screw plugs to the receivers 9 and 10 (see Fig. 205), or by the checked standard pressure gauge.
After starting the engine, fill the system with air to the nominal pressure. Stop the engine, fully depress the brake pedal (consumers of compressed air must be turned off) and record the pressure drop in the receivers using the pressure gauges.
Pressure advance in the control line in relation to the pressure at the outlet of the brake valve, determine from the control pressure gauges by connecting them to the valves of the control outputs I and K (see Fig. 205).
After starting the engine, fill the system with air to the nominal pressure. Stop the engine and, gently pressing the brake pedal, fix the pressure on the pressure gauge at the output And, with the following indications of the pressure gauge connected to the output K: 6, 5, 4, 3, 2 and 1 kgf / cm 2.
The pressure difference in the outputs And and K will give the value of the pressure advance in the control line.
TABLE 27
| Controlled parameter, kgf/cm 2 | Connection point for control pressure gauges (see fig. 205) | Value | |
| control | actual (filled in according to the results of measurements) | ||
| Inaccuracy of standard pressure gauge readings, no more | 9, 10 | ||
| Stop lamp pressure | AND | ||
| The time of filling the drive with air (until the control lamps go out) from the compressor with a warm engine running at a crankshaft speed of 2200 rpm, min | - | 8 | |
| Turn-off (turn-on) pressure of control lamps | B, 9, 10 | 4,5-5,5 | |
| Pressure regulator cut-off pressure | 18 | 7,0-7,5 | |
| Pressure regulator cut-in pressure | A, B, 9, 10 | 6,2-6,5 | |
| Difference between switch-on pressure and switch-off pressure | - | 0,5-1,1 | |
| Protection Pressure: | |||
| double safety valve | A, B | 5,6-6,0 | |
| triple » » | 9, 10 | 5,4-5,7 | |
| Pressure drop in the drive for 15 min (from nominal): | D | 4,9-5,2 | |
| with the controls turned off, no more | A, B, 9, 10 | 0,15 | |
| with the included controls, no more | A, B, 9, 10 | 0,3 | |
| Pressure drop in receivers during one braking, no more | 18, 9, 10 | 0,5 | |
| Pressure in connection heads: | |||
| disengaged car: | |||
| E | 6,5-7,5 | ||
| AND | 0 | ||
| type "A" | F | 4,8-5,3 | |
| during service braking: | |||
| type "Palm" supply line | E | 6,5-7,5 | |
| type "Palm" control line | AND | 6,5-7,5 | |
| type "A" | F | 0 | |
| parking brake: | |||
| type "Palm" supply line | E | 6,5-7,5 | |
| type "Palm" control line | AND | 6,5-7,5 | |
| type "A" | F | 0 | |
| The pressure in the front brake chambers at the pressure at the outlet of the brake valve (control output "L"): | |||
| 2,0 | IN | 1,0 | |
| 3,5 | IN | 2,0 | |
| 5,0 | IN | 4,5 | |
| 6,0 | IN | 6,0 | |
| Pressure in the rear brake chambers: | |||
| for an empty car, not less than | G | 2,2-2,5 | |
| when simulating a loaded car | G | Not lower than the pressure in the receiver 10 (see Fig. 250) | |
| Single safety valve opening pressure | E | 5,5 | |
|
Leading pressure in the control line in relation to the pressure at the outlet of the brake valve |
I, K | 0,6 | |
| Reducing the pressure in the connecting line | W, K or L | 1,3-1,8 | |
Repair
Faulty devices found during the control check must be repaired using repair kits, checked for operability and compliance with the characteristics. The procedure for assembling and testing devices is set out in special instructions. Their repair is carried out by persons who have undergone the necessary training.
Full adjustment* of the brake mechanism carry out after replacing the brake linings in the following order:
Release the parking brake;
Loosen the nuts securing the axles of the pads and bring the eccentrics together by turning the axles with the marks towards each other.
(* Before adjusting, check the tightness of the wheel bearings. The brake drums must be cold.)
The marks are placed on the outer ends of the axles. Loosen the nuts securing the expander bracket;
Supply compressed air to the brake chamber at a pressure of 0.5-0.7 kgf / cm 2 (depress the brake pedal if there is air in the system or use compressed air from the installation). In the absence of compressed air, remove the pin of the brake chamber rod and, pressing the adjusting lever in the direction of the stroke of the brake chamber rod during braking, press the shoes against the brake drum. By turning the eccentrics in one direction or another, center the pads relative to the drum, ensuring that they fit snugly against the drum. Check the fit of the shoes to the drum with a feeler gauge through the windows in the brake shield, located at a distance of 20-30 mm from the outer ends of the linings. A probe 0.1 mm thick should not run along the entire width of the lining;
Without stopping the supply of compressed air to the brake chamber, and in the absence of compressed air, without releasing the adjusting lever and holding the axles of the shoes from turning, securely tighten the nuts of the axles and the nuts of the bolts that fasten the expander bracket to the brake caliper;
Stop the compressed air supply, and in the absence of compressed air, release the adjusting lever and attach the brake chamber rod;
Rotate the adjusting lever worm shafts so that the stroke of the brake chamber rod is within the prescribed limits. Make sure that when turning on and off the air supply, the brake chamber rods move quickly, without jamming;
Check the rotation of the reels. They should rotate freely and evenly without touching the pads. After the specified adjustment, the following gaps can be between the brake drum and the shoes: at the expanding fist 0.4 mm, at the axes of the shoes 0.2 mm.
Assembly and adjustment of the brake valve drive run in the following order:
Install the parts of the brake valve drive located on the cab to achieve the required pedal travel;
Link 11 connect the brake valve drive lever with the pendulum lever 9;
Connect the lower end of the intermediate lever 4 with the free end of the pendulum lever 9 with a rod 1 with a threaded fork, selecting the gaps in the brake valve drive and at the same time eliminating the possibility of forced movement of the brake valve lever. In this case, the length of the rod 1 together with the fork along the axes of the holes of the forks should be approximately 895-900 mm;
Cotter all connecting pins of the drive;
When you press the brake pedal, the total pedal travel should be 100-140 mm, of which 20-40 mm is free travel. When fully depressed, the pedal should not reach the cabin floor by 10-30 mm. Measure the pedal travel with a ruler at the top end of the pedal. At full pedal travel, the stroke of the brake valve lever should be 31.1 - 39.1 mm.
The assembled brake valve drive must work without jamming and fully return to its original position.
When installing the brake force regulator after replacing the middle and rear axles, pay attention to the fact that the regulator 2 (see Fig. 218) and the rod 4 connecting the regulator lever with the elastic element are installed vertically. The elastic element 5 must be in a horizontal position (neutral). The length of lever 3 must correspond to the value indicated below:
After setting the desired lever length, tighten the lever mounting bolt on the regulator. After installation, check the outlet pressure of the brake force regulator. To do this, fill the pneumatic system with compressed air to a control pressure of 6.5 kgf/cm 2 . With the pedal fully depressed, the pressure in the control output valve D (see Fig. 205) should be equal to 2.2-2.5 kgf / cm 2 (for an empty car). If the pressure in the output valve D differs from the specified one, then bring it into line with the change in the length of the vertical rod 4 (see Fig. 235), moving it in a rubber coupling. Check the stability of the pressure produced by the brake force regulator by pressing the brake pedal repeatedly, then tighten the clamp on the coupling.
Having raised the tip of the elastic element by the value of the static deflection of the suspension (see above), make sure that the pressure in the brake chambers of the rear bogie has become equal to the control one, i.e. 6 kgf / cm 2. If this does not happen, correct the length of lever 3 and rod 4. It should be remembered that the rod must enter the regulator coupling to a depth of at least 45 mm. Finally secure all connections.
When removing the brake chamber with spring accumulator:
Brake the car with a parking brake;
Unscrew the bolt of the mechanical release of the spring energy accumulator to the stop. Make sure that the brake chamber rod is retracted;
Disconnect the supply pipelines, loosen the fastening of the brake chamber, disconnect the stem fork from the adjusting lever;
Remove the brake chamber.
Possible malfunctions of the pneumatic drive of the brake system , their search and methods of elimination are described in Table. 28.
TABLE 28
| Cause of malfunction | Finding a reason | Remedy |
| 1. Air reservoirs do not fill or fill slowly | ||
| The pneumatic system has a significant leakage of compressed air |
Locate compressed air leaks by hearing or touch Leaks can be caused by: |
|
| damaged hoses and pipelines, insufficient tightening of the joints of pipelines, hoses, connecting and adapter fittings | Replace hoses and lines. Tighten the connections. Replace defective fittings and seals | |
| insufficient tightening of body parts of devices | Tighten the fastening of body parts | |
| body parts of the devices are leaking due to poor-quality casting | Replace device | |
| the presence of nicks, dents on the end surfaces of the bosses for supplying (removing) compressed air. Significant non-perpendicularity of the end surfaces relative to the axes of the threaded holes | Sand small nicks, dents, eliminate the non-perpendicularity of the ends | |
| device is defective. Leakage occurs through the atmospheric outlet of the apparatus | Replace device | |
| receiver leaking | » receiver | |
| 2. The pressure regulator often works when the pneumatic system is filled | ||
| Leakage of compressed air in the line from the compressor to the block of protective valves | Locate compressed air leaks by hearing or touch | Eliminate the leak in the ways indicated in paragraph 1 of the table |
| 3. Receivers of the pneumatic system are not filled (the pressure regulator works) | ||
| The pressure regulator actuation pressure is determined by the standard pressure gauge in the driver's cab | Adjust the pressure regulator with the adjusting screw, replace the pressure regulator if necessary | |
| The flow area of the pipelines from the pressure regulator to the block of protective valves is blocked |
Look at the pipeline route. If necessary, remove the pipelines: The reason for the overlap can be: |
|
| the presence of kinks and collapses of pipelines | Replace pipeline | |
| the presence of a transport plug or foreign bodies in the pipeline | Remove the plug and foreign objects, blow out the pipeline with compressed air | |
| 4. Receivers of III and IV circuits are not filled | ||
| Disconnect the supply pipelines III and IV circuits. By touch, check the passage of compressed air through the valve | ||
| Check pipelines by blowing out | ||
| Deformation of the body of the double protective valve due to the tightening of the valve attachment to the frame side member | - | Adjust the tightening of the double safety valve to the frame side member |
| 5. Receivers of I and II circuits are not filled | ||
| Triple safety valve defective | Disconnect the supply pipes of I and II circuits from the triple safety valve. Feel the flow of compressed air through the valve |
Replace defective machine |
| Clogged supply lines | Purge the pipelines | Remove foreign objects from the pipeline |
| The triple safety valve is tightly pressed against the frame side member during installation | Check for clearance between the frame side member and the rubber plugs on the triple safety valve covers. | If there is no clearance, increase the length of the double safety valve mounting spacers by installing additional flat washers |
| 6. Receivers of the trailer (semi-trailer) are not filled | ||
| Faulty: | ||
| trailer brake control devices located on the tractor | Check the compressed air pressure in the connection heads. If there is no pressure at port E (see Fig. 205), the single safety valve is faulty. In the absence of the necessary pressure at terminal G and the presence of appropriate pressures at terminals I and E, the trailer brake control valve for a single-wire drive is faulty | |
| trailer (semi-trailer) brake devices |
Check the condition of the coupling heads and the quality of their connections, as well as the passage of compressed air through the devices of the trailer (semi-trailer) |
Replace defective devices |
| Clogged supply lines | Disconnect the supply pipes, check their patency | Blow out the pipes with compressed air. Replace if necessary |
| 7. The pressure in the receivers of the I and II circuits is above or below the norm when the pressure regulator is working | ||
| Defective two-pointer manometer | Check the pressure in the receivers using a control process pressure gauge, for which screw an additional control output valve into the receivers instead of a plug. Compare the indications of the control pressure gauge with the indication of the corresponding scale of the standard two-pointer pressure gauge | Replace double gauge |
| Pressure regulator incorrectly adjusted | Check the control pressure gauge on and off pressure of the pressure regulator | Adjust the pressure regulator with the adjusting screw. Replace pressure regulator if necessary. |
| 8. Ineffective braking or no braking of the vehicle by the service brake when the brake pedal is fully depressed | ||
| Faulty brake valve | Connect a control pressure gauge to the conclusions of the brake valve K and L (see. Fig. 205) through an additional control output valve. Press the brake valve lever fully (manually). The pressure on the control pressure gauge must be equal to the pressure indicated by the two-pointer pressure gauge in the driver's cab | Replace brake valve |
| Contamination of the cavity under the rubber boot of the drive lever of the two-section brake valve. The cover is torn or removed from the seat | - | Clean the cavities under the rubber boot from dirt. Replace case if necessary |
| The presence of a significant leakage of compressed air in the lines of I and II circuits after the brake valve | Find the place of compressed air leakage by hearing or by touch in accordance with paragraph 1 of the table | |
| Brake valve not adjusted | Check the correct adjustment of the brake valve drive | Adjust the brake valve drive |
| Incorrect installation of the brake force regulator drive | Check the installation of the brake force regulator | Adjust the setting of the brake force regulator or replace the brake force regulator |
| Defective pressure relief valve | Check pressure at terminals L and B (see fig. 205) | Replace pressure relief valve |
| Check the strokes of the brake chamber rods | Adjust stroke | |
| 9. Ineffective braking or lack of braking of the car by parking, emergency brakes | ||
| Faulty: accelerating valve; parking brake valve; emergency release valve | Check pressure at terminals B and D (see Fig. 205) | Replace defective brake apparatus |
| Pipelines or hoses of the third circuit are clogged | Check the passage of compressed air in the sections "reservoir of the III circuit - parking brake valve", "parking brake valve - accelerator valve", "accelerator valve - spring energy accumulators", "receiver of the III circuit - accelerating valve" | Clean the pipes and blow them out with compressed air. Replace with correct ones if necessary. |
| Faulty spring energy accumulators | Check the stroke of the brake chamber rods with spring-loaded energy accumulators when the parking brake and emergency release valve are actuated | Replace defective brake chambers with spring-loaded energy accumulators |
| The strokes of the brake chamber rods exceed the set value (40 mm) | Check the stroke of the brake chamber rods | Adjust stroke |
| 10. When installing the parking brake valve handle in a horizontal position, the car does not brake | ||
| Air leakage from the pipelines of the III circuit, from the atmospheric outlet of the accelerating valve | Locate the compressed air leak by hearing or touching | Eliminate the leak using the methods indicated in paragraph 1 of the table |
| The thrust bearing of the spring energy accumulator has failed | When the spring energy accumulator is mechanically released, the bolt can be easily turned out, the brake chamber rod is not removed | Replace defective spring-loaded brake chamber |
| 11. When the vehicle is moving, the rear bogie is braked without actuating the brake pedal and the parking brake valve | ||
| Faulty two-section brake valve. Brake valve drive incorrectly adjusted | See point 8 | See point 8 |
| The seal between the cavity of the spring energy accumulator and the working chamber is broken | By ear or touch, determine the leakage of compressed air from the brake force regulator, the atmospheric outlet of the two-section brake valve. There is pressure in outlet D (see Fig. 205) | Replace brake chamber with spring-loaded energy accumulator |
| 12. Inefficient braking of the trailer (semi-trailer) or lack of braking when the brake pedal is depressed or the emergency brake is on | ||
| Compressed air leak | Locate the leak by ear or touch in accordance with paragraph 1 of the table | Eliminate in the ways indicated in paragraph 1 |
| The following drive devices are faulty: a single protective valve, a trailer brake control valve for a single-wire drive, a trailer brake control valve for a two-wire drive, disconnecting valves, connecting heads | Check the pressure in the control output valve of the trailer (semi-trailer) and in the connecting heads E, G, I (see Fig. 205) of the tractor | Replace defective devices |
| 13. There is no braking of the road train when the auxiliary brake is turned on | ||
| Faulty: | ||
| pneumatic valve for switching on the auxiliary brake | After disconnecting the air outlet pipe from the tap, check the passage of air through the tap with the button pressed | Replace faucet |
| pneumatic cylinders for auxiliary brake damper drive, fuel shut-off cylinder | Check the function of the cylinders when compressed air is supplied to them and the disconnecting rods | Replace bad cylinders |
| damper mechanisms | Having disconnected the rods of the pneumatic cylinders, manually check the smoothness of the rotation of the dampers. Seizures should not be | If necessary, remove the auxiliary brake components, clean from carbon deposits, rinse and dry |
| auxiliary brake switch | Check with a test light for voltage on the contacts of the sensor and the solenoid valve when the auxiliary brake valve is turned on | Replace sensor |
| solenoid valve | Check the passage of air through the solenoid valve in the presence of voltage on its contacts | » valve |
| Compressed air leak | Determine the place of compressed air leakage by ear or touch in accordance with paragraph 1 of the table | Eliminate the leak in the ways indicated in point 1 |
| Clogged pipelines | - | Remove pipes and blow with compressed air |
| 14. Brake mechanisms are not released when the tractor emergency brake release valve is pressed or the trailer release valve button is pulled out | ||
| Triple safety valve defective | If the pressure in I and II circuits of the tractor is not less than 5.7 kgf / cm 2, disconnect the emergency release valve, pipeline from the triple safety valve, check the air intake through the triple safety valve | Replace triple safety valve |
| The pipelines of the emergency release circuit are leaking or their flow area is blocked | Determine by ear or touch the tightness of pipelines. Determine the blocking of the flow section by blowing compressed air of the dismantled pipeline | Replace pipelines |
| 15. When you press the brake pedal or when you apply the parking brake, the brake lights do not light up | ||
| Faulty brake light sensor or pneumatic actuators | With the brake control actuated, check for pressure in the "Palm" type connection head of the two-wire actuator control line and the absence of pressure in the "L" head of the single-wire actuator connecting line. If the pressure does not correspond to the prescribed one, then the trailer brake control devices are faulty. If the pressure is as specified, then the brake light sensor or wiring is faulty. | Replace defective sensor or devices |
| 16. The presence of a significant amount of oil in the pneumatic system | ||
| Wear of piston rings, compressor cylinders | Estimate the amount of oil ejected by the compressor by the diameter of the oil spot on a piece of writing paper that does not absorb oil. Set the paper at a distance of 50 mm from the outlet of the compressor. At an engine crankshaft speed of 1700 rpm for 10 s, the diameter of a continuous oil spot should not exceed 20 mm. In addition, check the reliability of the connection of the compressor air intake pipe with the engine intake air duct, the degree of contamination air filter engine | Replace compressor |
Depending on the various models of KAMAZ vehicles, their wheel arrangement, purpose, operating conditions, different KAMAZ brake system diagrams. Usually, when buying spare parts for the KAMAZ brake system, many questions, as practice shows, arise on the device brake system KAMAZ 5320. Below is scheme of the brake system of the car KAMAZ-5320, which will help you determine the entire range of spare parts for this brake system KAMAZ with the purpose of its quality repair.
A - valve for controlling the output of the IV circuit; B, D - control output valves III
contour; B - control output valve of the I circuit; G - control output valve of the second circuit; E - supply line of a two-wire drive; Zh - connecting line of a single-wire drive; I - brake (control) line of a two-wire drive; K, L - additional control outlet valves; 1 - compressor; 2 - pressure regulator, 3 - anti-freeze fuse; 4 - double protective valve; 5 - triple protective valve; 6 - condensation receiver; 7 - condensate drain valve; 8. 9. 10 - receivers, respectively, III, I and-II circuits; 11 - pressure drop sensor in the receiver; 12 - control outlet valve; 13 - pneumatic valve; 14 - sensor for switching on the electromagnetic valve of the trailer brakes; 15 - pneumatic cylinder drive of the engine stop lever; 16 -- pneumatic cylinder of the auxiliary brake damper actuator; 17. - brake two-section crane; 18 - two-pointer manometer; 19 - brake chamber type 24; 20 - pressure limiting valve; 21 - control valve for parking and spare brakes; 22 - accelerating valve; 23 - brake chamber type 20/20 with spring energy accumulator; 24 - two-way bypass valve; 25 - trailer brake control valve with a two-wire drive; 26 - protective single valve; 27 - trailer brake control valve with a single-wire drive; 28 - uncoupling tap; 29 - connecting head type "Palm"; 30 - connecting head type A; 31 - "stop light" sensor; 32 - automatic brake force regulator; 33 - air bleed valve; 34 - batteries; 35 - a block of control lamps and a buzzer; 36 - rear light; 37 - parking brake switch
The service brake system is designed to reduce the speed of the vehicle or stop it completely. The brake mechanisms of the service brake system are installed on all six wheels of the vehicle. The drive of the working brake system is pneumatic double-circuit, it drives separately the brake mechanisms of the front axle and the rear bogie of the car. The drive is controlled by a foot pedal mechanically connected to the brake valve. The executive bodies of the drive of the working brake system are the brake chambers.
The spare brake system is designed to smoothly reduce the speed or stop a moving vehicle in the event of a complete or partial failure of the working system.
The parking brake system provides braking of the motionless car on a horizontal site, and also on a slope and in the absence of the driver.
The parking brake system on KamAZ vehicles is made as a single unit with the spare one, and to enable it, the handle of the manual crane should be set to the extreme (upper) fixed position.
The emergency release drive provides the possibility of resuming the movement of the car (road train) during its automatic braking due to leakage of compressed air, alarms and control devices that allow you to monitor the operation of the pneumatic drive.
Thus, in KamAZ vehicles, the brake mechanisms of the rear bogie are common for the working, spare and parking brake systems, and the last two have, in addition, a common pneumatic drive.
The brake auxiliary system of the car serves to reduce the load and temperature of the brake mechanisms of the working brake system. The auxiliary brake system on KamAZ vehicles is an engine retarder, when turned on, the engine exhaust pipes are blocked and the fuel supply is turned off.
The emergency release system is designed to release spring-loaded energy accumulators when they are automatically activated and the vehicle stops due to leakage of compressed air in the drive.
The drive of the emergency release system is duplicated: in addition to the pneumatic drive, there are emergency release screws in each of the four spring-loaded energy accumulators, which makes it possible to release the latter mechanically.
The alarm and control system consists of two parts:
a) light and acoustic signaling of the operation of brake systems and their drives.
At various points of the pneumatic drive, pneumatic-electric sensors are built-in, which, under the action of any brake system, except for the auxiliary one, close the circuits of the “stop light” electric lamps.
Pressure drop sensors are installed in the drive receivers and, in case of insufficient pressure in the latter, they close the circuits of signal electric lamps located on the instrument panel of the car, as well as the audio signal (buzzer) circuit.
b) control output valves, which are used to diagnose the technical condition of the pneumatic brake drive, as well as (if necessary) to extract compressed air.
Elemental diagnostics are usually performed before TO-2 in order to conduct a detailed examination of the technical condition of the mechanism and identify: malfunctions and their causes.
Pre-repair diagnostics is carried out directly during maintenance and repair in order to clarify the need for performing individual operations.
The drive of the emergency release system is duplicated: in addition to the pneumatic drive, there are emergency release screws in each of the four spring-loaded energy accumulators, which makes it possible to release the latter mechanically.
The alarm and control system consists of two parts:
a) light and acoustic signaling of the operation of brake systems and their drives.
At various points of the pneumatic drive, pneumoelectric sensors are built-in, which, under the action of any brake
systems, except for the auxiliary one, close the circuits of the electric stop lamps.
Pressure drop sensors are installed in the drive receivers and, in case of insufficient pressure in the latter, they close the circuits of signal electric lamps located on the instrument panel of the car, as well as the audio signal (buzzer) circuit.
b) control output valves, which are used to diagnose the technical condition of the pneumatic brake drive, as well as (if necessary) to extract compressed air.
Figure 1 shows a diagram of the pneumatic drive of the brake mechanisms of the KamAZ - 5320 car
Figure 1 - Scheme of the pneumatic drive of the brake mechanisms: 1 - type 24 brake chambers; 2 - parking brake control valve; 3 - crane for emergency release of the parking brake system; 4 - control valve for the auxiliary brake system; 5 - two-pointer manometer; 6 - control lamps and a sound signaling device; 7 - control output valve; 8 - pressure limiting valve; 9 - compressor; 10 - pneumatic cylinder of the drive of the engine stop lever; 11 - pressure regulator; 12 - fuse against freezing; 13 - double protective valve; 14 - sensor for switching on the electromagnetic valve of the trailer brake mechanism; 15 - batteries; 16 - two-section brake valve; 17 - triple protective valve; 18 - pressure drop sensor in the receiver; 19 - condensate drain valves; 20 - condensing receiver; 21 - air bleed valve; 22 - receivers of circuit II; 23 - pneumatic cylinder of the auxiliary brake system damper drive; 24, 25 - receivers I and III circuits; 26 - brake chambers type 20x20; 27 - sensor for turning on the control lamp of the parking brake system; 28 - power accumulators; 29 - accelerating valve; 30 - automatic brake force regulator; 31 - trailer brake control valve with two-wire drive
To monitor the operation of the pneumatic brake drive, and timely signal its condition, and the malfunctions that occur in the cab, there are five signal lights on the instrument panel, a two-pointer pressure gauge showing the pressure of compressed air in the receivers of two circuits (I and II) of the pneumatic drive of the working brake system , and a buzzer signaling an emergency drop in compressed air pressure in the receivers of any brake drive circuit.
Figure 2 shows the brake mechanisms of the KamAZ-5320 vehicle. The brake mechanisms are installed on all six wheels of the vehicle, the main brake assembly is mounted on caliper 2, rigidly connected to the axle flange. On the eccentrics of the axles 1, fixed in the caliper, two brake pads 7 freely rest with friction linings 9 attached to them, made along a sickle-shaped profile in accordance with the nature of their wear. Shoe axes with eccentric bearing surfaces make it possible to correctly center the shoes relative to the brake drum when assembling the brake mechanisms. The brake drum is attached to the wheel hub with five bolts.
When braking, the pads move apart with an S-shaped fist 12 and are pressed against the inner surface of the drum. Rollers 13 are installed between the expanding fist 12 and pads 7, reducing friction and improving braking efficiency. The pads are returned to the braked state by four retracting springs 8.
Expanding fist 12 rotates in bracket 10, bolted to the caliper. The brake chamber is mounted on this bracket. At the end of the shaft of the expanding fist, a worm-type adjusting lever 14 is installed, connected to the rod of the brake chamber with a fork and a pin. A shield bolted to the caliper protects the brake mechanism from dirt.
Figure 2 - Brake mechanism: 1 - shoe axis; 2 - support; 3 - shield; 4 - axle nut; 5 - overlay of the axles of the pads; 6 - check of the axis of the pad; 7 - brake shoe; 8 - spring; 9 - friction lining; 10-bracket expanding fist; 11 - roller axis; 12 - expanding fist; 13 - roller; 14 - adjusting lever
The adjusting lever is designed to reduce the gap between the shoes and the brake drum, which increases due to wear of the friction linings. The device of the adjusting lever is shown in Figure 4. The adjusting lever has a steel body 6 with a bushing 7.
The housing contains a worm gear wheel 3 with splined holes for installation on an expanding fist and a worm 5 with an axis 11 pressed into it. locking bolt 8. The gear wheel is kept from falling out by covers 1 attached to the body 6 of the lever. When turning the axis (at the square end), the worm turns the wheel 3, and with it the expanding fist turns, pushing the pads apart and reducing the gap between the pads and the brake drum. When braking, the adjusting lever is turned by the brake chamber rod.
Before adjusting the gap, the locking bolt 8 must be loosened by one or two turns, after adjustment, tighten the bolt securely.
Figure 3 - Adjusting lever: 1 - cover; 2 - rivet; 3 - gear wheel; 4 - plug; 5 - worm; 6 - body; 7 - bushing; 8 - locking bolt; 9 - retainer spring; 10 - retainer ball; 11 - worm axis; 12 - oiler
The mechanism of the auxiliary brake system is shown in Figure 4.
Housing 1 and damper 3 are installed in the exhaust pipes of the muffler, mounted on shaft 4. A rotary lever 2 is also fixed on the damper shaft, connected to the pneumatic cylinder rod. The lever 2 and the flap 3 associated with it have two positions. The inner cavity of the body is spherical. When the auxiliary brake system is turned off, damper 3 is installed along the exhaust gas flow, and when turned on, it is perpendicular to the flow, creating a certain counterpressure in the exhaust manifolds. At the same time, the fuel supply is cut off. The engine starts in compressor mode.
The piston is aluminum, with a floating finger. From axial movement, the pin in the piston bosses is fixed by thrust rings. Air from the engine manifold enters the compressor cylinder through the reed inlet valve.
Figure 4 - The mechanism of the auxiliary brake system: 1 - housing; 2 - rotary lever; 3 - damper; 4 - shaft. Compressor (Figure 5) piston type, single cylinder, single stage compression. The compressor is fixed on the front end of the engine flywheel housing
The air compressed by the piston is displaced into the pneumatic system through a lamellar discharge valve located in the cylinder head.
The head is cooled by liquid supplied from the engine cooling system. Oil is supplied to the rubbing surfaces of the compressor from the engine oil line: to the rear end of the compressor crankshaft and through the channels of the crankshaft to the connecting rod. The piston pin and cylinder walls are splash lubricated.
When the pressure in the pneumatic system reaches 800-2000 kPa, the pressure regulator communicates the discharge line with the environment, stopping the air supply to the pneumatic system.
When the air pressure in the pneumatic system drops to 650-50 kPa, the regulator closes the air outlet to the environment and the compressor starts again to pump air into the pneumatic system.
The pressure regulator (Figure 6) is designed:
- - to regulate the pressure of compressed air in the pneumatic system;
- - protection of the pneumatic system from overload by excessive pressure;
- - purification of compressed air from moisture and oil;
- - provision of tire inflation.
Compressed air from the compressor through output IV of the regulator, filter 2, channel 12 is fed into the annular channel. Through the check valve 11, compressed air enters the outlet II and further into the receivers of the vehicle's pneumatic system. At the same time, through channel 9, compressed air passes under piston 8, which is loaded with a balancing spring 5. At the same time, exhaust valve 4,
connecting the cavity above the unloading piston 14 with the atmosphere through port I is open, and the inlet valve 13 is closed under the action of a spring. Under the action of the spring, the unloading valve 1 is also closed. In this state of the regulator, the system is filled with compressed air from the compressor. At a pressure in the cavity under the piston 8, equal to 686.5.. 735.5 kPa (7.. 7.5 kgf/cm2), the piston, having overcome the force of the balancing spring 5, rises, the valve 4 closes, the inlet valve 13 opens. Under the action of compressed air, the unloading piston 14 moves down, the unloading valve 1 opens, and the compressed air from the compressor through outlet III exits to the atmosphere along with the condensate accumulated in the cavity. In this case, the pressure in the annular channel drops and the check valve 11 closes. Thus, the compressor operates in unloaded mode without back pressure.
When the pressure in port II drops to 608..637.5 kPa, piston 8 moves down under the action of spring 5, valve 13 closes, and outlet valve 4 opens. In this case, the unloading piston 14 rises under the action of the spring, the valve 1 closes under the action of the spring, and the compressor pumps compressed air into the pneumatic system.
The unloading valve 1 also serves as a safety valve. If the regulator does not work at a pressure of 686.5.. 735.5 kPa (7.. 7.5 kgf / cm2), then valve 1 opens, overcoming the resistance of its spring and the piston spring 14. Valve 1 opens at a pressure of 980.7. .1274.9 kPa (10.. 13 kgf/cm2). The opening pressure is adjusted by changing the number of shims installed under the valve spring.
Figure 5 - Pressure regulator: 1 - unloading valve; 2 - filter; 3 - plug of the air sampling channel; 4 - exhaust valve; 5 - balancing spring; 6 - adjusting screw; 7 - protective cover; 8 - follower piston; 9, 10, 12 - channels; 11 - check valve; 13 - inlet valve; 14 - unloading piston; 15 - unloading valve seat; 16 - tire inflation valve; 17 - cap; I, III - atmospheric conclusions; II - into the pneumatic system; IV - from the compressor; C - cavity under the follower piston; D - cavity under the unloading piston
To connect special devices, the pressure regulator has an outlet that is connected to outlet IV through filter 2. This outlet is closed with a screw plug 3. In addition, an air bleed valve for tire inflation is provided, which is closed with a cap 17. When screwing on the hose fitting for tire inflation, the valve is sunk , opening access to compressed air in the hose and blocking the passage of compressed air into the brake system. Before inflating the tires, the pressure in the reservoirs should be reduced to a pressure corresponding to the pressure on the regulator, since air cannot be taken during idling.
The two-section brake valve (Figure 6) is used to control the actuators of the dual-circuit drive of the vehicle's service brake system.
Figure 6 - Brake valve driven by a pedal: 1 - pedal; 2 - adjusting bolt; 3 - protective cover; 4 - roller axis; 5 - roller; 6 - pusher; 7 - base plate; 8 - nut; 9 - plate; 10,16, 19, 27 - sealing rings; 11 - hairpin; 12 - spring follower piston; 13, 24 - valve springs; 14, 20 - plates of valve springs; 15 - small piston; 17 - lower section valve; 18 - small piston pusher; 21 - atmospheric valve; 22 - thrust ring; 23 - atmospheric valve body; 25 - lower body; 26 - small piston spring; 28 - large piston; 29 - valve of the upper section; 30 - follower piston; 31 - elastic element; 32 - upper body; A - hole; B - cavity above the large piston; I, II - input from the receiver; III, IV - output to the brake chambers, respectively
The crane is controlled by a pedal directly connected to the brake valve.
The crane has two independent sections arranged in series. Inputs I and II of the crane are connected to the receivers of two separate drive circuits of the working brake system. From terminals III and IV, compressed air is supplied to the brake chambers. When you press the brake pedal, the force is transmitted through the pusher 6, the plate 9 and the elastic element 31 to the follower piston 30. Moving down, the follower piston 30 first closes the outlet of the valve 29 of the upper section of the brake valve, and then tears the valve 29 from the seat in the upper housing 32, opening the passage to compressed air through input II and output III and further to the actuators of one of the circuits. The pressure at terminal III rises until the force of pressing the pedal 1 is balanced by the force created by this pressure on the piston 30. This is how the follow-up action is carried out in the upper section of the brake valve. Simultaneously with the increase in pressure at port III, compressed air through hole A enters cavity B above the large piston 28 of the lower section of the brake valve. Moving down, the large piston 28 closes the valve outlet 17 and lifts it off the seat in the lower housing.
Compressed air through input I enters output IV and then to the actuators of the primary circuit of the working brake system.
Simultaneously with the increase in pressure at port IV, the pressure under pistons 15 and 28 increases, as a result of which the force acting on piston 28 from above is balanced. As a result, pressure is also set at terminal IV, corresponding to the force on the brake valve lever. This is how the follow-up action is carried out in the lower section of the brake valve.
In the event of a failure in the operation of the upper section of the brake valve, the lower section will be mechanically controlled through the pin 11 and the pusher 18 of the small piston 15, fully maintaining its operability. In this case, the follow-up action is carried out by balancing the force applied to the pedal 1 by the air pressure on the small piston 15. If the lower section of the brake valve fails, the upper section operates as usual.
A brake chamber with a spring-loaded energy accumulator type 20/20 is shown in Figure 7. It is designed to actuate the brake mechanisms of the wheels of the rear bogie of the car when the working, spare and parking brake systems are turned on.
The spring energy accumulators together with the brake chambers are mounted on the brackets of the expanding cams of the brake mechanisms of the rear bogie and secured with two nuts and bolts.
When braking by the working brake system, compressed air from the brake valve is supplied to the cavity above the membrane 16. The membrane 16, bending, acts on the disk 17, which moves the stem 18 through the washer and locknut and turns the adjusting lever with the expanding fist of the brake mechanism.
Thus, braking of the rear wheels occurs in the same way as braking of the front wheels with a conventional brake chamber.
When the spare or parking brake system is turned on, that is, when air is released from the cavity under the piston 5 by a manual valve, the spring 8 is unclenched and the piston 5 moves down. The thrust bearing 2 through the membrane 16 acts on the bearing of the rod 18, which, moving, turns the adjusting lever of the brake mechanism associated with it. The vehicle is braking.
When braking, compressed air enters through the output under the piston 5. The piston, together with the pusher 4 and the thrust bearing 2, moves upward, compressing the spring 8 and allowing the rod 18 of the brake chamber to return to its original position under the action of the return spring 19.
Figure 7 - Brake chamber type 20/20 with a spring energy accumulator: 1 - body; 2 - thrust bearing; 3 - sealing ring; 4 - pusher; 5 - piston; 6 - piston seal; 7 - power accumulator cylinder; 8 - spring; 9 - screw of the emergency release mechanism; 10 - thrust nut; 11- cylinder branch pipe; 12 - drainage tube; 13 - thrust bearing; 14 - flange; 15 - branch pipe of the brake chamber; 16 - membrane; 17 - support disk; 18 - stock; 19 - return spring