Tightening torques vase. How and with what force to tighten the connecting rod and main bearings

Many motorists who are used to repairing their car themselves know firsthand that engine repair is a very difficult and responsible task.

Since the repair of the power unit requires from the motorist not only certain skills, but also knowledge for the correct execution technological process. Today in the article we will briefly consider the crank mechanism, its role in the car engine.

In addition, we will also talk about the importance of observing the tightening torque of the main and connecting rod bearings, the nuances and sequence of this operation, and other important aspects. Therefore, it will be useful for beginners to somewhat expand their knowledge on the topic by reading our article.

The concept of KShM

The crank mechanism, abbreviated as KShM, is the most important unit of the unit for the engine. The main task of this mechanism is to change the rectilinear movements of the piston into rotational, and vice versa. This moment of rotation occurs due to the combustion of fuel in the engine cylinders.

As you know, combustion gases fuel mixture have the ability to expand. Then, under high pressure, they push the engine pistons down, and they, in turn, transfer force to the connecting rods and the crankshaft. It is due to the specific shape of the crankshaft in the motor that one movement is converted into another, which ultimately allows the wheels of the machine to rotate.

In terms of its functions, the crankshaft is the most loaded mechanism of the engine. It is this node that determines which form this or that will have. power unit and how the cylinders will be located in it. This is due to the fact that each type of engine is created for a specific purpose. Some vehicles require maximum engine power, light weight and dimensions, while others prioritize ease of maintenance, reliability and durability. Therefore, manufacturers and produce for different types engines different kinds crank mechanisms. KShM are divided into single-row and double-row.

The role of the crankshaft liners

The crankshaft must withstand heavy loads during engine operation. But bearings for this device cannot be used. This role was taken over by the main and connecting rod bearings. Although in their task they perform the functions of plain bearings. The liners are made from a bimetallic strip consisting of low carbon steel, copper and lead, as well as ACM aluminum alloy or babbitt.

It is thanks to the liners that the free rotation of the crankshaft is ensured. To ensure durability and wear resistance, the liners are coated with a thin, micron-sized layer of oil during engine operation. But for their complete and high-quality lubrication, high oil pressure is simply necessary. This role was taken over by the engine lubrication system. All these conditions just help to reduce the friction force and increase the life of the engine.

Types and sizes of liners

In general, crankshaft liners are divided into two groups:

1. The first type is called root bearings. They are located between the crankshaft and the places of its passage through the motor housing. They bear the greatest load, since it is on them that the crankshaft is fixed and rotates.
2. The second group includes connecting rod bearings. They are located between the connecting rods and the crankshaft, its necks. They also carry huge loads.

Main and connecting rod bearings are made for each type of engine individually with their own dimensions. And for the majority automotive engines in addition to the nominal, factory sizes, there are also repair liners. The outer size of the repair liners remains unchanged, while the inner diameter is adjusted by increasing the thickness of the liner. In total there are four such sizes with a step of 0.25 mm.

It is no secret that with high mileage of the car, not only the main and connecting rod bearings wear out, but also the crankshaft journals. These circumstances lead to the need to replace liners of nominal sizes with repair ones. To put one or another repair insert, the neck is bored to a certain diameter. Moreover, the diameter is selected for each of the dimensions of the liner individually.

If, for example, a repair size of 0.25 mm has already been used, then when getting rid of flaws on the crankshaft journals, a size of 0.5 mm should be used, and for serious scuffing, 0.75 mm. At correct replacement liners, the engine must work for more than one thousand kilometers, unless, of course, other car systems are working.

There are also options when boring is not required and the liners are simply changed to new ones. But people who do this professionally do not advise simply changing the liners to new ones. This is explained by the fact that during the operation and operation of the liners, microdefects still occur on the shaft, which are not visible at first glance. In general, without grinding, there is a possibility of rapid wear and a small KShM resource.

Signs of wear on the crankshaft bearings

In the conversations of motorists, the phrases are often heard: “The engine knocked” or “The liners cranked”, these words most often refer to the wear of the liners. This, in turn, is a serious breakdown in the motor. The first signs of such malfunctions are loss of oil pressure or the appearance of extraneous sounds when the engine is running. It will be difficult for an inexperienced motorist to determine the signs of a malfunction of the liners, so it is better to immediately contact a specialist.

For a professional to listen and make a diagnosis will not be serious problems. Typically, this procedure is performed on idling engine by sharply pressing the gas pedal. It is believed that if the sound is a dull tone or iron grinding, then the problem is in the main bearings. If the connecting rod bearings fail, the knock is louder and stronger.

There is another way to check wear. It is necessary to alternately unscrew the spark plugs or nozzles for diesel engines. If the knock disappears when you unscrew a candle, then this is the cylinder in which there are problems.

Problem low pressure oil may appear not necessarily from the wear of the liners. It is possible that the oil pump, the pressure reducing valve is faulty, or the camshaft bed is worn out. Therefore, we first check all the nodes of the lubrication system and only after that we draw conclusions about what exactly to repair.

We measure the gap between the liner and the crankshaft

Inserts are produced in 2 separate parts with special places for mounting. The main task during assembly should be to ensure the required clearance between the shaft journal and the liner. Usually, a micrometer is used to determine the working gap between them, and the inner diameter of the liners is measured with an inside gauge. After that, some calculations are made, which make it possible to identify the gap.

However, it is much easier to do such an operation using a special plastic calibrated wire. Pieces of the required size are placed between the liner and the neck, after which the bearing is clamped with the required force and disassembled again. Next, a special ruler is taken, which comes with the wire in the kit, and the width of the corresponding imprint on the shaft is measured. The wider the crushed measuring strip, the smaller the clearance in the bearing. This method allows you to control the required distance between the neck and the liner with high accuracy.

How and with what force is the main and connecting rod bearings tightened?

It is possible to tighten the main and connecting rod bearings with the required force with a special torque wrench. The wrench can be either with a ratchet or with an arrow. Both wrenches are stamped with the dimensions required to tighten nuts and bolts to any torque. To set up, you will need to set the required value on the key, and after that you can immediately start tightening.

At the same time, remember that for a force of less than 5 kg, there is no need to put a pipe on the wrench in order to create additional leverage. This can be done with one hand to avoid stripping the bolt threads.

Tightening torque for main and connecting rod bearings

Before installing the liners, the first step is to remove the preservative grease from them and apply a small layer of oil. Next, we install the main bearings in the bed of the main journals, while not forgetting that the middle liner is different from the others.

The next step is to put the covers on the beds and tighten them. Moreover, the tightening torque must be applied in accordance with the standards, which are sometimes indicated in the operating rules. vehicle. But most often there are cases when technical guidance for the car, the tightening torque of the main and connecting rod bearings is not specified. In such cases, it is recommended to look for this information in the special literature on the repair of a particular engine. For example, for Lada Priora cars, the tightening torque of the bed cover is from 64 N * m (6.97 kgf * m) to 81 N * m (8.61 kgf * m).

Next, we proceed to install the connecting rod bearings. In this case, you should pay attention to the correct installation of the covers, each of them is marked, so do not mix them up. The tightening torque they have is much less than that of the indigenous ones. For example, if you take the tighter model "Lada Priora", the tightening torque of the connecting rod bearings will start from about 43 N * m (4.42 kgf * m), up to 53 N * m (5.46 kgf * m).

Please note that the data given as an example assumes the use of new liners for repair, and not used parts. Otherwise, when using the old bushings, the tightening torque should be selected based on the upper limit of the recommended torque from the documentation for this engine. This is done due to the possible presence of some wear on old parts. Sometimes ignoring this fact can lead to significant deviations from the recommended norm.

When all the bolts are tightened for the first time, it is advisable to scroll the shaft. To do this, on the side of the crankshaft there is a place for a wrench, we calmly scroll it clockwise. If the ring burst or there is any other malfunction, then this will be immediately visible. Further, making sure that there are no problems, we check again all the bolts with a wrench at the moment of tightening.

It should be remembered that the tightness of the sliding bearings to crankshaft and, accordingly, the efficiency of the engine itself. Since if the bolt is not fully tightened, there will be excess oil, the entire lubrication cycle will be disrupted, and it can also lead to breakage of the liner. If we overtighten, then the liner will overheat, the lubricant will no longer be enough. Ultimately, the liner may even melt and turn, which will lead to overhaul engine.

Rating 3.50

Engine repair is considered the most difficult in a car, because no other part of it contains such a huge number of interconnected elements. On the one hand, this is very convenient, because in the event of a breakdown of one of them, there is no need to change the entire assembly, it is enough just to replace the failed part, on the other hand, the more components, the more complex the device and the more difficult it is to figure it out for someone who not very experienced in auto repair business. However, with a strong desire, everything is possible, especially if your zeal is supported by theoretical knowledge, for example, in the matter of determining the tightening torque of the main and connecting rod bearings. If, for now, this phrase is a set of incomprehensible words for you, be sure to read this article before getting into the engine.

Main and connecting rod bearings are two types of plain bearings. They are produced using the same technology and differ from each other only in the inner diameter (for connecting rod bearings, this diameter is smaller).

The main task of the liners is to convert translational movements (up and down) into rotational ones and ensure the smooth operation of the crankshaft so that it does not wear out ahead of time. It is for these purposes that the liners are installed under a strictly defined gap, in which a strictly specified oil pressure is maintained.

If this gap increases, the pressure engine oil it becomes smaller in it, which means that the necks of the gas distribution mechanism, crankshaft, and other important components wear out much faster. Needless to say, too much pressure (reduced clearance) also does not carry anything positive, since it creates additional obstacles in the operation of the crankshaft, it can begin to wedge. That is why it is so important to control this gap, which is impossible without the use of repair work a torque wrench, knowledge of the necessary parameters that are prescribed by the manufacturer in the technical literature for engine repair, as well as compliance with the tightening torque of the main and connecting rod bearings. By the way, the force (torque) of tightening the bolts of the connecting rod and main bearing caps is different.

Please note that the given standards are relevant only when using new sets of parts, since the assembly / disassembly of an assembly that was in operation due to its development cannot guarantee compliance with the necessary clearances. Alternatively, in this situation, when tightening the bolts, you can focus on the upper limit of the recommended torque, or you can use special repair inserts with four different sizes that differ from each other by 0.25 mm, provided that the crankshaft is ground until the minimum gap between rubbing elements will not be 0.025 / 0.05 / 0.075 / 0.1 / 0.125 (depending on the available clearance and the repair product used).

Examples of specific tightening torques for the bolts of the connecting rod and main bearing caps for some cars of the VAZ family.

Video.

Engine repair is considered the most difficult in a car, because no other part of it contains such a huge number of interconnected elements. On the one hand, this is very convenient, because in the event of a breakdown of one of them, there is no need to change the entire assembly, it is enough just to replace the failed part, on the other hand, the more components, the more complex the device and the more difficult it is to figure it out for someone who not very experienced in auto repair business. However, with a strong desire, everything is possible, especially if your zeal is supported by theoretical knowledge, for example, in the matter of determining the tightening torque of the main and connecting rod bearings. If, for now, this phrase is a set of incomprehensible words for you, be sure to read this article before getting into the engine.

Plain bearings, their types and role in the operation of internal combustion engines.

Main and connecting rod bearings are two types of plain bearings. They are produced using the same technology and differ from each other only in the inner diameter (for connecting rod bearings, this diameter is smaller).

The main task of the liners is to convert translational movements (up and down) into rotational ones and ensure the smooth operation of the crankshaft so that it does not wear out ahead of time. It is for these purposes that the liners are installed under a strictly defined gap, in which a strictly specified oil pressure is maintained.

If this gap increases, the pressure of the engine oil in it becomes less, which means that the necks of the gas distribution mechanism, crankshaft, and other important components wear out much faster. Needless to say, too much pressure (reduced clearance) also does not carry anything positive, since it creates additional obstacles in the operation of the crankshaft, it can begin to wedge. That is why it is so important to control this gap, which is impossible without the use of a torque wrench in repair work, knowledge of the necessary parameters that are prescribed by the manufacturer in the technical literature on engine repair, as well as compliance with the tightening torque of the main and connecting rod bearings. By the way, the force (torque) of tightening the bolts of the connecting rod and main bearing caps is different.

Please note that the given standards are relevant only when using new sets of parts, since the assembly / disassembly of an assembly that was in operation due to its development cannot guarantee compliance with the necessary clearances. Alternatively, in this situation, when tightening the bolts, you can focus on the upper limit of the recommended torque, or you can use special repair inserts with four different sizes that differ from each other by 0.25 mm, provided that the crankshaft is ground until the minimum gap between rubbing elements will not be 0.025 / 0.05 / 0.075 / 0.1 / 0.125 (depending on the available clearance and the repair product used).

Examples of specific tightening torques for the bolts of the connecting rod and main bearing caps for some cars of the VAZ family.

Video.

For products made of carbon steel of strength class - 2, numbers through a dot are indicated on the bolt head. Example: 3.6, 4.6, 8.8, 10.9, etc.

The first digit indicates 1/100 of the nominal value of the tensile strength, measured in MPa. For example, if the bolt head is marked 10.9, the first number 10 means 10 x 100 = 1000 MPa.

The second digit is the ratio of the yield strength to the tensile strength multiplied by 10. In the above example, 9 is the yield strength / 10 x 10. Hence the yield strength = 9 x 10 x 10 = 900 MPa.

The yield strength is the maximum working load of the bolt!

For stainless steel products, the steel marking is applied - A2 or A4 - and the tensile strength is 50, 60, 70, 80, for example: A2-50, A4-80.

The number in this marking means - 1/10 of the compliance with the tensile strength of carbon steel.

Unit conversion: 1 Pa = 1N/m2; 1 MPa = 1 N/mm2 = 10 kgf/cm2.
Limit tightening torques for bolts (nuts).

Torques for tightening bolts (nuts).

The table below shows the tightening torques for bolts and nuts. Do not exceed these values.

The above values ​​are given for standard bolts and nuts with
metric thread. For non-standard and special fasteners, see the repair manual for the repaired equipment.

Tightening torques for standard fasteners with US inch threads.

The following tables show general guidelines
tightening torques for bolts and nuts SAE class 5 and above.

1 newton meter (N.m) is equal to approximately 0.1 kGm.

ISO - International Standards Organization

Tightening torques for standard worm-type hose clamps

The table below gives the tightening torques
clamps during their initial installation on a new hose, and
also when reinstalling or tightening clamps
on used hoses

Tightening torque for new hoses at initial installation

Tightening torque table for typical threaded connections