The structure of the carburetor. Design and principle of operation of the carburetor

The question is, why do we need to know the structure of the carburetor, because today there is a service station on every corner, where they will always find a breakdown and fix it in a timely manner. Everyone has read in the traffic rules about faults with which you can’t move at all or you can drive to the nearest service station, but how can you determine where the fault actually is and whether it is dangerous for movement? That’s why you should know at least at a basic level the structure of your car and its main components.

Carburetor - what is it and how does it work?

This device performs two main functions in the engine. The first is to spray and mix fuel with air. This process occurs in this way: an air jet is introduced into the fuel stream under high pressure, and due to the difference in speeds, the first is atomized. Moreover, it is worth clearly distinguishing that the carburetor sprays and does not evaporate fuel. The latter occurs already in the engine cylinder and in the intake manifold.

Another task of the carburetor is to create an optimal fuel-air mixture ratio to ensure efficient combustion. Basically, this ratio is 14.7 parts air to 1 part fuel. However, it changes, for example, to drive at high speeds, accelerate and start a cold engine, a rich mixture (less than 14.7:1) is required. To drive at average speed or start a warm engine, a lean mixture will be required (the amount of air must exceed 14.7 parts). In general, these values ​​range from 8:1 to 22:1.

Carburetor design: principle of operation

This car unit consists of the following elements: a float chamber, a throttle valve, a nozzle with a spray and a diffuser. The carburetor circuit, or rather the principle of its operation, looks something like this. Fuel (from the fuel tank) flows through a special hose and enters the float chamber, where there is a brass hollow float, which, using a shut-off needle, regulates its quantity. But as soon as you start the engine, fuel will be consumed, and accordingly its level drops, along with the float and shut-off needle.

Thus, the same level of gasoline is constantly maintained in the float chamber, which is very important for engine operation.

Next, the jets are used, it is through them that the fuel from the float chamber enters the atomizer. Thanks to the special air cushion in which the diffuser is located, outside air also enters the cylinder. In order for the air supply speed to be maximum, the sprayer is located in the narrowest part of the diffuser. Throttle valves regulate the amount of fuel that enters the cylinder. In cars, throttle valves are driven by a foot drive, in motorcycles - by a hand drive.

Carburetor circuit and malfunctions

Since the carburetor is directly connected to the car’s engine, any problems that arise with it can cause significant damage to your “iron horse”. Absolutely all its problems affect the operation of the engine. In some cases it refuses to work at all, in others it works poorly. Below are the main problems that can occur in the carburetor and their characteristic symptoms:

• If, then, despite the fact that the fuel level is normal and the car engine itself is in order, it still will not start. This is a very serious problem and its cause, most often, is a violation of the self-cleaning regime.
• If the emulsion nozzle becomes clogged, it will happen immediately after you release the gas pedal.
• Black smoke pours out of the exhaust pipe - this is a characteristic sign that there is more fuel in the float chamber than there should be. You should check the condition of the float and valves.
• A small gap in the breaker contacts will lead to unstable operation of the engine.
• If the tightness of the fuel pump valves is broken, the fuel in the carburetor may evaporate. In this case, you will have to turn the starter for a long time before the float chamber is filled.

In advertisements for the sale of a car you can find many offers of not new, but quite decent cars in good condition. As they say, “drive and ride.” But here’s the problem: the selected car has a carburetor. This is a rather old device, which scares off modern car enthusiasts, especially young people, due to its complexity, possible lack of repair parts and possible breakdowns. Whether to buy a car with a carburetor or find a more modern design with a fuel injection system - you can make a decision only after you understand the nuances of the operation and design of this device.

What is a carburetor and what is it for?

In order for an internal combustion engine to operate optimally, it is necessary to mix fuel and air in a certain proportion and feed this mixture into the combustion chamber. The mixture parameters can change depending on the operating mode of the internal combustion engine, fuel consumption too, which means you need a device that will do all this automatically.

A carburetor is a device for mixing air with fuel. As a result of its operation, at the right moment, atomized gasoline mixed with air enters the combustion chamber of the engine, ready for ignition. Despite the fact that there is only one carburetor for several cylinders, the mixture always gets to the right place through the intake manifold thanks to the coordinated operation of all internal combustion engine elements.

Carburetor design

To this day, we have received mainly float models - the latest and most improved. So you can find them on most cars.

Design of a float carburetor: 1 - adjusting screw of the starting device; 2 — lever pin 24, included in the groove of lever 3; 3 — air damper control lever; 4 — screw securing the air damper drive rod; 5 - adjusting screw for slightly opening the throttle valve of the first chamber; 6 — throttle lever of the first chamber; 7 — axis of the throttle valve of the first chamber; 8 — throttle drive lever of the second chamber; 9 — adjusting screw for the amount of idle mixture; 10 — axis of the throttle valve of the second chamber; 11 — throttle lever of the second chamber; 12 — pipe for suction of crankcase gases into the rear throttle space of the carburetor; 13 — throttle valve of the second chamber; 14 — outlet openings of the transition system of the second chamber; 15 — throttle body; 16 — sprayer of the main dosing system of the second chamber; 17 — small diffuser; 18 — fuel nozzle housing of the transition system of the second chamber; 19 — accelerator pump nozzle; 20 — fuel supply pipe to the carburetor; 21 — econostat sprayer; 22 — air damper; 23 — starting rod; 24 — air damper lever; 25 — starter cover; 26 — lever pin 24, operating from the rod 23 of the starting device; 27 — air damper axis; 28 — carburetor cover; 29 — tube with econostat fuel jet; 30 — fuel filter; 31 — needle valve; 32 — emulsion tube of the second chamber; 33 - float; 34 — main fuel jet of the second chamber; 35 — accelerator pump bypass jet; 36 — throttle valve drive lever; 37 — accelerator pump drive lever; 38 — accelerator pump diaphragm; 39 — adjusting screw for the quality (composition) of the idle mixture; 40 — vacuum intake pipe of the vacuum ignition timing regulator. 41 — carburetor housing. 42 - solenoid shut-off valve; 43 — adjusting screw for additional air for factory adjustment of the idle speed system; 44 - trigger diaphragm.

A float carburetor consists of many elements.

1. A float chamber, which is responsible for maintaining a certain fuel level.
2. A float with a shut-off needle, designed for automatic dosing of the fuel level in the float chamber.
3. Mixing chamber in which the main mixing of atomized (fine) fuel and air occurs
4. A diffuser is a narrowed area through which the air flow accelerates its movement.
5. A nozzle with a nozzle connecting the float and mixing chambers, through which fuel passes directly to the diffuser.
6. Throttle valve - regulates the flow of mixture entering the cylinders.
7. Air damper - regulates the air flow entering the carburetor. Thanks to it, you can make the mixture “poor”, normal or “rich”. Diagram of the dependence of power on the amount of air in the fuel mixture

   The diagram shows that a normal mixture is when there is about 15 times more air than fuel. Under such conditions, there will be complete combustion of gasoline and maximum power.

8. Idle system - supplies fuel bypassing the mixing chamber when the throttle valve is fully closed. Through special channels, gasoline and air pass into the throttle body.
9. Economizers and econostats are devices for additional fuel supply when the engine is operating at maximum load. In this case, economizers have forced control, and econostats operate from air rarefaction.
10. Fuel suction is a system for forced enrichment of the fuel mixture. By pulling the lever, the driver slightly opened the throttle valve, as a result of which air passed more intensely through the mixing chamber and took in more fuel. The result is a rich mixture, convenient for starting a cold engine.

The principle of operation of the carburetor

After watching the video below, you will clearly see the structure and principle of operation of the carburetor in different operating modes. The video, although old, is still relevant today. Don’t be lazy and watch to the end if you want to fully understand the topic.

Well, let’s summarize below - the operation of all float carburetors is carried out according to a typical scheme.

1. Gasoline is pumped into the float chamber through the fuel line from the tank to the required level, which is regulated and maintained by a float and a shut-off needle.
2. The sprayer, located in the lower part of the float chamber, uses a nozzle to transfer a strictly dosed portion of fuel to the mixing chamber. At the same time, the fuel flow is atomized for better mixing with air and combustion.
3. The fuel from the atomizer is dispersed over a diffuser, which is designed to create a rapid flow of air and better mix it with the already atomized gasoline.
4. The mixture of fuel and air flows to the throttle valve, which is directly connected to the gas pedal. The more fuel the engine needs, the more the throttle is open and the more active the carburetor is.
5. From the carburetor, the fuel-air mixture passes through the intake manifold to the cylinder in which the piston is currently descending with the simultaneous opening of the intake valve.
6. The piston works like a pump, drawing in the mixture already prepared in the carburetor.

Despite the rather simple operating principle, a well-tuned carburetor ensures excellent engine power delivery, good fuel economy and system reliability.

Types of carburetors

The predecessors of the float carburetor already discussed were the membrane-needle and bubbling carburetors. These are already outdated designs that today cannot be found on cars for everyday use (but these rarities still exist on “old cars”).

Membrane-needle The carburetor consists of several chambers separated by membranes. The membranes rest on springs of a given stiffness and are connected to each other by a rod. The membrane chambers have an outlet to the mixing chamber and are also connected to the fuel supply channel. The movement of the rod activated the membranes of the chambers, causing them to pump fuel into the mixing cavity. Yes, the system is somewhat cumbersome and slow to respond to changes in engine operating mode, but at the same time it is reliable to such an extent that it was installed on aircraft engines.

Scheme of a membrane-needle carburetor

Bubbler The carburetor is the first design and the first attempt to create such a device. It was a blank lid that covered the gas tank at some distance from the fuel. Two pipes were connected to the cover: one inlet for air, the second to the engine. The air, passing under the lid, was saturated with gasoline vapor and in this form was sent to the combustion chamber. This is the first device designed to work with fuel vapors.

Diagram of a bubble carburetor: 1 - pipeline; 2 - hole in the float chamber; 3 - diffuser; 4 - sprayer; 5 - throttle valve; 6 - mixing chamber; 7 - jet; 8 - float chamber; 9 - float; 10 - needle valve.

The classification of other types of carburetors depends on the design features. Based on the cross-section of the sprayer, devices with constant vacuum(models made in Japan with the highest performance characteristics), with constant spray cross section(carburetors made in the USSR and Russia) and with spool throttling(horizontal carburetors, intended mainly for motorcycles).

Based on the direction of movement of the finished mixture, designs with horizontal And vertical flow (of the latter, the system with a downward flow turned out to be the most effective).

Float carburetors may have one or more mixing chambers. Single-chamber units were in use until the 1960s, when engine developments required increased carburetor capacity.

The creation of multi-chamber carburetors with multiple throttle valves solved this problem. Varieties appeared: carburetors with the simultaneous opening of two throttle valves, each of which fed certain cylinders, and carburetors with the sequential opening of two valves, which were connected to the entire engine and operated in accordance with its mode.

As engine power increased, so did carburetors. Three- and four-chamber types appeared, several carburetors were installed on the car, various options for preparing the fuel mixture were configured (for example, an over-enriched mixture was made in one chamber, and a lean mixture in the other two).

Advantages and disadvantages of carburetors

Only the deaf have never heard of the horrors of constant carburetor repair. But what really? What are the advantages of this device and is there any point in dealing with it at all? Strange as it may sound in our technological age, the carburetor has several serious advantages.

1. Simplicity of design. No, the point is not that this is a very simple mechanism. But compared to the electronic components of today's cars, the carburetor is much easier to repair, maintain, and even operate. Most carburetors do not have any electronics, only mechanical devices, which means that a person with “straight hands” can repair and maintain it himself. The “old guard” – our parents, who are accustomed to delving into their “beloved” Zhiguli and Cossacks – remember this well.
2. Maintainability. Anything that breaks in the carburetor can be repaired without “excess blood.” The necessary spare parts can be purchased (there are manufacturers that still produce repair kits. Why not?).

But there are also disadvantages due to which carburetor cars eventually disappeared from the world automotive arena.

1. Technology required a fuel supply system with flexible adjustments, rather than with constant parameters, in order to minimize fuel consumption (which no one had previously taken into account). Therefore, the carburetor was replaced by an injection system, which is still being developed and improved.
2. The second significant disadvantage is the dependence of the carburetor on weather conditions. During the cold season, condensation collects inside, interfering with operation; in winter, there is a risk of icing of the inside. At the same time, the summer heat also prevents it from working stably due to active evaporation - disruptions in the supply of the mixture begin.
3. Well, the third drawback is that the environmental performance is significantly lower compared to an injector. In the modern struggle for the environment, carburetor cars simply do not stand up to criticism, since their harmful emissions are much higher.

Main malfunctions of carburetors and their causes

Malfunctions in the carburetor are reflected in the operating mode of the engine, and it is by this that one can determine that not everything is normal with the fuel supply system.

1. It is difficult to start an engine that is not warmed up - most likely, there are problems in adjusting the throttle valve. It is necessary to adjust the damper drive so that when the suction is extended, it closes completely, or adjust the starting clearances.
2. An unheated engine starts and immediately stalls when the choke is fully extended - the problem, again, is in the throttle valve drive. Either the gaps are incorrectly adjusted, or the telescopic rod does not work and the damper does not open.
3. A warm engine is difficult to start - the fuel level in the float chamber has not been adjusted, the float mechanism or valve needle has failed, resulting in the fuel level being higher than normal.
4. Unstable engine operation at idle speed - there may be several reasons, and the main one is the adjustment of the idle system. Other reasons - the idle speed ecostat drive does not work or the shut-off valve does not work, the jets are clogged, air is leaking, the float in the float chamber is not working properly
5. When opening the throttle, there is no increase in power - the mixture is too rich or lean due to the accelerator pump nozzle not being sealed.
6. Low acceleration dynamics - lack of fuel due to a lean mixture or shutdown of the secondary chamber.

Conclusion

Despite their somewhat bulky design, carburetors faithfully serve owners of old cars. And, perhaps, the repairs and cleaning that car enthusiasts do on their own are several times cheaper than washing the injectors, which owners of injection-powered cars are forced to resort to.

Should you buy a car if it has a carburetor? Judging by the operating pattern, it is far from the weakest link in the car, and may not be bothered by any breakdowns for a long time. So carburetors, although outdated, are still ready to serve those who value simplicity and reliability.

A mixture of air and fuel is supplied to the cylinders through the carburetor. From this we can conclude that the carburetor is located between the fuel pump and the cylinder block. Where exactly depends on the make of the car. For example, in a VAZ-2106 the carburetor is located under the air filter to the right of the cylinder block, when viewed in the direction of travel of the car. Newer models usually use an injector instead of a carburetor.

Where is the carburetor located in the engine?

An internal combustion engine receives energy by burning strictly measured doses of fuel in the cylinders. In a four-stroke engine, fuel is ignited in turn in four cylinders. Combustion requires oxygen, so it is not pure fuel that enters the cylinders, but its mixture with air, which is formed in the carburetor.

In the cylinder block, ignition of each portion of the mixture must occur at equal intervals, and at the moment when the piston in the cylinders is in its lower position. If these conditions are not met:

• engine power drops,
• the engine starts to run rough
• the car stalls or roars,
• the amount of carbon dioxide in the exhaust increases.

The moment of ignition of the mixture depends on the ratio of fuel and air in the cylinder, which is formed in the carburetor. By adjusting the carburetor, the desired ratio is achieved experimentally. Of course, the carburetor is adjusted at the factory, but the ignition time also depends on the state of the atmosphere: temperature, humidity, altitude. Therefore, from time to time you have to do all the adjustments, for which you need to understand the principle of operation of the carburetor.

How does a carburetor work?

The air flow into the carburetor enters through the air filter, the amount of air is regulated by the gas pedal. Every time you step on the gas, more air enters the carburetor.

Fuel enters the carburetor through one, two or, at most, three special slots. Each socket is responsible for its own power: low speed (idle), high speed and, in rare cases, medium speed.

Needles that look like small cogs with pointed ends are inserted into the nests. The needles are not inserted into the sockets tightly: there is a gap between the walls of the socket and the needle, through which fuel enters the carburetor. The further the needle is inserted into the socket, the smaller the gap remains and the less fuel flows inside. Carburetor adjustment consists of selecting the correct clearance at the appropriate speed.

Inside the carburetor housing is the high speed needle. It regulates the flow of air at all speeds; the overall performance of the engine depends on it, although the fuel mixture for high speeds mainly depends on its position.

Then the low speed or idle speed needle comes into play. It is usually located inside the carburetor, and it regulates the amount of fuel entering after the first needle. Without it, there will be too much fuel in the mixture at low speeds. As the speed increases, the needle is removed from the socket, and as much fuel enters the cylinders as the first needle measured.

Carburetor, often called " carb" - part of the power system of a car engine, where certain compounds are formed when air and fuel are mixed. Subsequently, this air-fuel mixture enters the combustion chamber. This element, together with - is a fuel regulator, due to which the resulting mixture can be enriched or lean. The stoichiometric state of this fuel component is achieved at a ratio of 1 g of gasoline to 14.7 g of air, and to start a cold engine a ratio of 10 to 1 is required.

There are three types of carburetors:

• Bubbler(no longer used).
• Membrane-needle– the unit consists of several chambers separated by membranes and connected by a rod at the end of which there is a needle that closes/opens the fuel supply.
• Float– exists in many modifications of modern carburetors and is widely used.

Components of the carburetor system of a car

The carburetor design in a trivial version:

Carburetor design

1. float and mixing chambers
2. float with needle type shut-off valve
3. spray and diffuse systems
4. gasoline and air channels with
5. aero and throttle valves

Float chamber necessary to maintain a constant gasoline level. The air damper starts the vehicle's engine idle, enriching the air-fuel system. The idle system ensures the supply of gasoline when the main metering system is not functioning. Special screws regulate the fuel/air ratio in the carburetor.

Acceleration pump supplies additional fuel - the throttle valves open sharply so that you can prevent the engine from stopping and avoid malfunctions in the operation of the engine during acceleration of the car.

Transition system is responsible for the transition mode between the main dosing system and the vehicle idle.

Idle system ensures the supply of the required amount of fuel to the engine cylinders when operating without load (idling).

Main dosing system provides increased engine power due to a greater supply of fuel-air mixture while the vehicle is moving.

Carburetor design

A lot of passenger cars run on gasoline. More precisely, on a mixture of gasoline and air. Such engines are commonly called internal combustion engines. However, there are two types of internal combustion engines: engines running on gasoline and engines running on diesel (read the article for more details). Today we will talk specifically about gasoline engines, because it is in the structure of a gasoline engine that there is such equipment as a carburetor. The engine itself does not prepare the fuel mixture (air + gasoline) for use; it burns this mixture, pushing the pistons. But the device we will talk about prepares this mixture.

Carburetor – The engine attachment, which is designed to make the combustible mixture that is injected into the engine cylinders for further ignition, is usually located on top of the engine.

Principle of operation

Gasoline enters the carburetor through the fuel line and enters the mixing chamber, but the fuel is atomized through a system of special carburetor devices called jets, that is, the fuel takes the form of steam. Next, the air undergoes additional purification through a filter system and is supplied to the same chamber, which contains fuel vapor, mixing in the required proportion, this mixture is supplied to the engine cylinders, where this mixture is ignited with the help of engine spark plugs. Enriching the mixture in the carburetor leads to fast engine operation and vice versa, this is the work of the accelerator (gas pedal), the driver presses on the gas, the engine shaft rotates faster, the speed increases, if you release the gas pedal, the engine shaft will rotate more slowly, the speed will drop.

That's all, I think, it has now become clear what it is. Read our AUTO SITE