The engine power system is designed for storing, cleaning and supplying fuel, cleaning air, preparing a combustible mixture and feeding it into the engine cylinders. At different operating modes of the engine, the quantity and quality of the combustible mixture must be different, and this is also provided by the power system.

The power system consists of:

Fuel tank;

Fuel lines;

Fuel filters;

Fuel pump;

Air filter;

Carburetor.

The fuel tank is a container for storing fuel. It is usually placed in the rear, more accident-safe part of the car. From the fuel tank to the carburetor, gasoline flows through fuel lines that run along the entire vehicle, usually under the underbody.

The first stage of fuel cleaning is a grid on the fuel intake inside the tank. It prevents large impurities and water contained in gasoline from entering the engine power system.

The driver can control the amount of gasoline in the tank by reading the fuel level indicator located on the instrument panel.

Average fuel tank capacity passenger car usually 40-50 liters. When the level of gasoline in the tank decreases to 5-9 liters, the corresponding yellow (or red) light on the instrument panel lights up - the fuel reserve lamp. This is a signal to the driver that it is time to think about refueling.

The fuel filter (usually installed independently) is the second stage of fuel purification. The filter is located in the engine compartment and is designed for fine cleaning of gasoline supplied to the fuel pump (it is possible to install a filter after the pump). Usually, a non-separable filter is used, if it gets dirty, it needs to be replaced.

Fuel pump - designed for forced supply of fuel from the tank to the carburetor.

Principle of operation:

When the lever pulls the stem with the diaphragm down, the diaphragm spring is compressed, and a vacuum is created above it, under which the inlet valve, overcoming the force of its spring, opens.

Through this valve, fuel from the tank is drawn into the space above the diaphragm. When the lever releases the diaphragm stem (the part of the lever associated with the stem moves upward), the diaphragm also moves upward under the action of its own spring, the intake valve closes, and gasoline is squeezed out through the discharge valve to the carburetor. This process takes place every time the eccentric drive shaft is turned.

Gasoline is pushed into the carburetor only by the force of the diaphragm spring when moving it up. When the carburetor is filled to the required level, its special needle valve will block the access of gasoline. Since there will be nowhere to pump fuel, the diaphragm of the fuel pump will remain in the lower position: its spring will be unable to overcome the created resistance.

The vehicle power system is used to prepare fuel mixture... It consists of two elements: fuel and air. The engine power system performs several tasks at once: purification of the mixture elements, obtaining the mixture and its supply to the engine elements. The composition of the combustible mixture differs depending on the vehicle power system used.

Types of power systems

There are the following types of engine power systems, which differ in the place of formation of the mixture:

1. inside the engine cylinders;
2. outside the engine cylinders.

When a mixture is formed outside the cylinder, the vehicle's fuel system is divided into:

• fuel system with carburetor
• using one injector (mono injection)
• injector

Purpose and composition of the fuel mixture

For smooth operation of a car engine, a certain fuel mixture is required. It consists of air and fuel mixed in a certain proportion. Each of these mixtures is characterized by the amount of air per unit of fuel (gasoline).

The enriched mixture is characterized by the presence of 13-15 parts of air per part of the fuel. This mixture is supplied at medium loads.

A rich mixture contains less than 13 parts of air. It is used for heavy loads. There is an increased consumption of gasoline.

A normal mixture has 15 parts of air per part of fuel.
The lean mixture contains 15-17 parts of air and is used at medium loads. Provides economical fuel consumption. A poor mixture contains more than 17 parts of air.

General structure of the power system

The engine power system has the following main parts:

• fuel tank. Serves for storing fuel, contains a pump for pumping fuel and sometimes a filter. Has a compact size
• fuel line. This device supplies fuel to a special mixing device. Consists of various hoses and tubes
• mixture formation device. Designed to obtain a fuel mixture and supply to the engine. Such devices can be an injection system, mono injection, carburetor
• control unit (for injectors). Comprises electronic unit, which controls the operation of the mixing system and signals the occurrence of malfunctions
• fuel pump. Required for the entry of fuel into the fuel line
• filters for cleaning. Necessary to obtain pure components of the mixture

Carburetor fuel supply system

This system is distinguished by the fact that mixture formation takes place in a special device - a carburetor. From it, the mixture enters the engine in the desired concentration. The engine power system device contains the following elements: a fuel tank, fuel cleaning filters, a pump, an air filter, two pipelines: inlet and outlet, and a carburetor.

The scheme of the engine power supply system is implemented as follows. The tank contains fuel that will be used for feeding to. It enters the carburetor through the fuel line. The feeding process can be realized with a pump or in a natural way using gravity.

In order for the fuel supply to be carried out into the carburetor chamber by gravity, then it (the carburetor) must be placed below the fuel tank. Such a scheme cannot always be implemented in a car. But the use of a pump makes it possible not to depend on the position of the tank relative to the carburetor.

The fuel filter cleans the fuel. Thanks to it, mechanical particles and water are removed from the fuel. Air enters the carburetor chamber through a special air filter that removes dust particles from it. In the chamber, two purified components of the mixture are mixed. Getting into the carburetor, fuel enters the float chamber. And then it is sent to the mixing chamber, where it is combined with air. Through the throttle valve, the mixture enters the intake manifold. From here it goes to the cylinders.

After exhausting the mixture, gases from the cylinders are removed using the exhaust manifold. Then they are sent from the manifold to the muffler, which suppresses their noise. From there, they enter the atmosphere.

Details about the injection system

At the end of the last century, carburetor power systems began to be intensively replaced by new systems operating on injectors. And for a reason. This arrangement of the engine power supply system had a number of advantages: less dependence on the properties of the environment, economical and reliable operation, and less toxic emissions. But they have a drawback - it is high sensitivity to the quality of gasoline. If this is not followed, then some system elements may malfunction.

"Injector" is translated from English as an injector. A single-point (single-injection) scheme of the engine power system looks like this: fuel is supplied to the injector. The electronic unit sends signals to it, and the nozzle opens at the right time. The fuel is directed to the mixing chamber. Then everything happens as in carburetor system: a mixture is formed. It then passes the intake valve and enters the engine cylinders.

The engine power system device, organized using injectors, is as follows. This system is characterized by the presence of several nozzles. These devices receive signals from a special electronic unit and open. All these injectors are connected to each other via a fuel line. There is always fuel in it. Excess fuel is removed through the fuel return line back to the tank.

The electric pump supplies fuel to the rail, where overpressure is generated. The control unit sends a signal to the injectors, and they open. Fuel is injected into the intake manifold. Air, passing through the throttle assembly, enters the same place. The resulting mixture enters the engine. The amount of mixture required is adjusted by opening the throttle valve. As soon as the injection stroke ends, the injectors close again and the fuel supply stops.

The power supply system is an integral part of any engine internal combustion... It is designed to solve the following tasks.

□ Fuel storage.

□ Cleaning fuel and feeding it to the engine.

□ Purification of the air used for the preparation of a combustible mixture.

□ Preparation of a combustible mixture.

□ Supply of a combustible mixture to the engine cylinders.

□ Discharge of exhaust (exhaust) gases into the atmosphere.

The power supply system of a passenger car includes the following elements: fuel tank, fuel hoses, fuel filter (there may be several of them), a fuel pump, an air filter, a carburetor (an injector or other device used to prepare a combustible mixture). Note that carburetors are rarely used in modern cars.

The fuel tank is located at the bottom or at the rear of the vehicle: these are the safest places. The fuel tank is connected to the appliance, which creates a combustible mixture, by means of fuel hoses that run through almost the entire vehicle (usually along the underbody).

However, any fuel must undergo preliminary purification, which can include several stages. If you are filling fuel from a canister, use a funnel with a strainer. Remember that gasoline is more fluid than water, so very fine mesh can be used to filter it, in which the cells are almost invisible. If your gasoline contains an admixture of water, then after filtration through a fine mesh, water will remain on it, and gasoline will leak out.

Cleaning fuel when filling it into the fuel tank is called pre-cleaning or the first stage of cleaning - because on the way of fuel to the engine it will go through a similar procedure more than once.

The second stage of cleaning is carried out using a special mesh located on the fuel intake inside the fuel tank. Even if some impurities remain in the fuel at the first stage of cleaning, they will be removed at the second stage.

For the highest quality (fine) cleaning of the fuel entering the fuel pump, a fuel filter (Fig. 2.9) located in the engine compartment is used. By the way, in some cases the filter is installed both before and after the fuel pump - in order to improve the quality of cleaning the fuel entering the engine.

Important.

The fuel filter should be changed every 15,000 - 25,000 km (depending on the specific make and model of the vehicle).

A fuel pump is used to provide fuel to the engine. It usually includes the following parts: body, diaphragm with actuator and spring, inlet and outlet (discharge) valves. There is also another mesh filter in the pump: it provides the last, fourth stage of fuel purification before feeding it to the engine. Among other parts of the fuel pump, we note the rod, the delivery and suction nozzles, the manual fuel pump lever, etc.

The fuel pump can be driven by the oil pump drive shaft or by camshaft engine. When any of these shafts rotate, the eccentric on them exerts pressure on the fuel pump drive rod. The stem, in turn, presses on the lever, and the lever on the diaphragm, causing it to go down. After that, a vacuum is formed above the diaphragm, under the influence of which the inlet valve overcomes the spring force and opens. As a result, a certain amount of fuel is sucked from the fuel tank into the space above the diaphragm.

When the eccentric then "releases" the fuel pump rod, the lever stops pressing on the diaphragm, as a result of which, due to the rigidity of the spring, it rises up. In this case, pressure is formed, under the action of which the inlet valve closes tightly, and the discharge valve opens. Fuel above the diaphragm is directed to the carburetor (or other device used to prepare a combustible mixture - for example, an injector). When the eccentric once again starts to press on the rod, fuel is sucked in and the process is repeated again.

However, it is not only the fuel that should be cleaned, but also the air used to prepare the combustible mixture. For this, a special device is used - an air filter. It is installed in a special case after the air intake and closed with a cover (Fig. 2.10).

The air passing through the filter leaves on it all the contained debris, dust, impurities, etc., and is used in a purified form to prepare a combustible mixture.

Remember this.

The air filter is a consumable item that should be replaced after a certain gap (usually 10,000 - 15,000 km). A clogged filter makes it difficult for air to pass through. This becomes the cause of excessive consumption of fuel, since the combustible mixture will contain a lot of fuel and little air.

The purified components of the combustible mixture (gasoline and air), each on their own way, enter the carburetor or other device specially designed to create a combustible mixture from gasoline and air vapors. The finished mixture is fed into the engine cylinders.

Note.

The carburetor automatically regulates the composition of the combustible mixture (the ratio of gasoline vapor to air), as well as its amount supplied to the cylinders, depending on the engine operating mode (idle, measured driving, acceleration, etc.). As we noted earlier, on modern cars, carburetors are rarely used (everything is controlled by electronics, the most famous such device is the injector), but Soviet and russian cars (VAZ, AZLK, GAZ, ZAZ) were produced with a carburetor. Since half of Russia still drives such cars today, we will further consider in detail the principle of operation and the structure of the carburetor.

The carburetor (fig.2.11) consists of a large number different parts and includes a number of systems necessary for stable engine operation.

The key elements of a typical carburetor are: a float chamber, a float with a needle valve, a mixing chamber, an atomizer, an air damper, a throttle valve, a diffuser, fuel and air passages with jets.

In general, the principle of producing a combustible mixture in a carburetor looks like this.

When the piston, when the fuel mixture is injected into the cylinder, begins to move from TDC to BDC, a vacuum is formed above it in accordance with the laws of physics. Accordingly, the air stream after preliminary cleaning with an air filter and passing through the carburetor enters this zone (in other words, it is sucked in there).

When the purified air passes through the carburetor, fuel is sucked in from the float chamber through the atomizer. This sprayer is located at the narrowest point of the mixing chamber called the "diffuser". By the incoming stream of purified air, gasoline flowing out of the sprayer is "crushed", after which it mixes with air, and the so-called initial mixing takes place. The final mixing of gasoline with air is carried out at the outlet of the diffuser, and then the combustible mixture enters the engine cylinders.

In other words, the carburetor uses the principle of a conventional spray gun to produce a combustible mixture.

However, the engine will operate stably and reliably only when the gasoline level in the carburetor's float chamber is constant. If it rises above the set limit, there will be too much fuel in the mixture. If the level of gasoline in the float chamber is below the set limit, the combustible mixture will be too lean. To solve this problem, a special float is designed in the float chamber, as well as a needle shut-off valve. When there is too little gasoline in the float chamber, the float is lowered together with the needle shut-off valve, thereby allowing gasoline to flow into the chamber unhindered. When there is enough fuel, the float floats up and the valve closes the path of gasoline flow. To see this principle in action, look at how a simple toilet cistern works.

The harder the driver presses on the gas pedal, the more the throttle valve opens (in the initial position it is closed). This allows more gas and air to flow into the carburetor. The more the driver releases the accelerator pedal, the more the throttle valve closes, and less gasoline and air enters the carburetor. The motor works less intensively (rpm drops), so the torque transmitted to the wheels of the car decreases, respectively - the car slows down.

But even when you fully release the gas pedal (and close the throttle), the engine will not stall. This is due to the fact that when the engine is running at idle a different principle applies. Its essence lies in the fact that the carburetor is equipped with channels specially designed so that air can penetrate under the throttle valve, mixing with gasoline along the way. With the throttle valve closed (at idle speed), air is forced into the cylinders through these channels. At the same time, it "sucks" gasoline from the fuel channel, mixes with it, and this mixture enters the throttle space. In this space, the mixture finally assumes the required state and enters the engine cylinders.

Note.

For most engines, when idling, the optimum crankshaft speed is 600-900 rpm.

Depending on the current operating mode of the engine, the carburetor prepares a fuel mixture of the required quality. In particular, when starting a cooled engine, the combustible mixture must contain more fuel than when a warm engine is running. It should be noted that the most economical operating mode of the engine is smooth driving in the highest gear at a speed of about 60–90 km / h. When driving in this mode, the carburetor creates a lean mixture.

Note.

Car carburetors come in a variety of models and designs. Here we will not give a description of various modifications of carburetors, since it is enough for us to have at least a general idea of \u200b\u200bthe carburetor operation. Detailed information how the carburetor functions in a particular car can be found in the operation and repair manual for that car.

As we noted above, exhaust gases are generated during the operation of an internal combustion engine. They are a product of combustion of the working mixture in the engine cylinders.

It is the exhaust gases that are removed from the cylinder during the last, fourth stroke of its working cycle, which is called the release. Then they are released into the atmosphere. For this, each car has an exhaust gas release mechanism, which is part of the power system. Moreover, its task is not only to remove them from the cylinders and release them into the atmosphere, which of course, but also to reduce the noise that accompanies this process.

The fact is that the release of exhaust gases from the engine cylinder is accompanied by a very loud noise. It is so strong that without a silencer ( special deviceabsorbing noise, Fig. 2.12) the operation of cars would be impossible: it would be impossible to stay near a running car because of the noise it produces.

Exhaust gas release mechanism standard car includes the following building blocks:

□ outlet valve;

□ outlet channel;

□ front exhaust pipe (in the driver's slang - "pants");

□ additional muffler (resonator);

□ main muffler;

□ connecting clamps with which parts of the muffler are connected to each other.

In addition to the listed elements, many modern cars also use a special catalyst for neutralizing exhaust gases. The name of the device speaks for itself: it is designed to reduce the amount of harmful substances contained in the exhaust gases of a car.

The exhaust mechanism works quite simply. From the engine cylinders, they enter the exhaust pipe of the muffler, which is connected to an additional muffler, and that, in turn, to the main muffler (the end of which is the exhaust pipe protruding from the rear of the car). The resonator and the main silencer inside have a rather complex structure: this is how there are numerous holes, as well as small chambers that are staggered, resulting in a complex intricate maze. When the exhaust gases pass through this labyrinth, they greatly reduce their speed and go out of exhaust pipe almost silent.

Note that the exhaust gases of a car contain many harmful substances: carbon monoxide (the so-called carbon monoxide), nitric oxide, hydrocarbon compounds, etc. Therefore, never warm up the car indoors - this is deadly: there are a lot of cases when people died in own garages from carbon monoxide.

OPERATING MODES OF THE POWER SYSTEM

Depending on the goals and road conditions, the driver can apply different driving modes. They also correspond to certain operating modes of the power system, each of which has a fuel-air mixture of a special quality.

1. The mixture will be rich when starting a cold engine. At the same time, air consumption is minimal. In this mode, the possibility of movement is categorically excluded. Otherwise, this will lead to increased fuel consumption and wear of parts of the power unit.
2. The composition of the mixture will be enriched when using the "idle" mode, which is used when "coasting" or running the engine in a warm state.
3. The mixture will be lean when driving at partial loads (for example, on a flat road at medium speed in high gear).
4. The mixture will be enriched at full load while driving at high speed.
5. The composition of the mixture will be rich, close to rich, when driving under conditions of sharp acceleration (for example, when overtaking).

The choice of operating conditions for the power supply system, therefore, must be justified by the need for movement in a certain mode.

FAULTS AND SERVICE

During the operation of the vehicle, the fuel system of the vehicle is under stress, leading to its unstable operation or failure. The following faults are considered the most common.

INSUFFICIENT SUPPLY (OR LACK OF SUPPLY) OF FUEL INTO ENGINE CYLINDERS

Low-quality fuel, long service life, environmental impacts lead to contamination and clogging of fuel lines, tank, filters (air and fuel) and technological openings of the combustible mixture preparation device, as well as damage to the fuel pump. The system will require repair, which will consist of timely replacement filter elements, periodic (every two to three years) cleaning the fuel tank, carburetor or injector nozzles, and replacing or repairing the pump.

LOSS OF ICE POWER

Malfunction fuel system in this case, it is determined by a violation of the regulation of the quality and quantity of the combustible mixture entering the cylinders. Elimination of the malfunction is associated with the need to diagnose the device for preparing a combustible mixture.

FUEL LEAK

Fuel leakage is a very dangerous and categorically unacceptable phenomenon. This malfunction is included in the "List of malfunctions ...", with which the movement of the car is prohibited. The causes of the problems lie in the loss of tightness by the components and assemblies of the fuel system. Elimination of the malfunction consists either in replacing damaged system elements, or in tightening the fasteners of the fuel lines.

Thus, the power supply system is important element The internal combustion engine of a modern car is responsible for the timely and uninterrupted supply of fuel to the power unit.

Organizational part (15 min.).

Lesson 6. Fuel supply system of the Rotax 912 engine

TOPIC 4. Fuel supply system power plant Rotax 912.

Astana 2012

EDUCATIONAL AND EDUCATIONAL OBJECTIVES

POWER PLANT CONSTRUCTION

TOPIC 4. Fuel supply system of the Rotax 912 engine

1. To acquaint cadets with the structure of the fuel supply system of an internal combustion engine, with the general purpose of its units and systems.

2. Remind the students of some physics data.

3. To acquaint the cadets with the basic technical data of the Rotax 912 engine fuel supply system.

4. To instill in cadets the ability to act competently when possible failures fuel supply systems of the Rotax 912 engine.

TIME:3 hours

METHOD:lecture

A PLACE:classroom

DESIGNED BY: N.N.

Issues under study:

6.1. Organizational part (15 min.).

6.2. Purpose and design of the fuel supply system for internal combustion engines. (50 min.).

6.3. Composition, general diagram and operation of the fuel supply system for the Rotax 912 engine. (45 min.).

6.4. Basic data of the power supply system of the Rotax 912 engine (20 min.).

6.5. The final part (5 min.).

Poll on topic # 3.

The order of studying topic number 4.

Supply system fuelm of the internal combustion engine of the engine is intended for storing, cleaning and supplying fuel, cleaning air, preparing a combustible mixture and feeding it into the engine cylinders. At different operating modes of the engine, the quantity and quality of the combustible mixture must be different, and this is also provided by the fuel supply system. Since we are considering the operation of the carburetor gasoline engine, then in the future, fuel will mean exactly gasoline.

Ri.s 6.1. The layout of the power system elements
1 - filler neck with plug; 2 - fuel tank; 3 - fuel level indicator sensor with a float; 4 - fuel intake with filter; 5 - fuel lines; 6 - fine fuel filter; 7 - fuel pumps; 8 - carburetor float chamber with a float; 9 - air filter; 10 - carburetor mixing chamber; 11 - inlet valve; 12 - inlet pipeline; 13 - combustion chamber

The power supply system (see figure 6.1.) Consists of:

fuel tank;

fuel filters;

fuel pump,

air filter,

carburetor;

fuel lines,

The fuel tank is a container for storing fuel. It is usually located in the safer part of the aircraft (in the fuselage, in the wing). Gasoline flows from the fuel tank to the carburetor through fuel lines. For a prudent driver, the first stage of gasoline purification occurs when it is poured into the fuel tank. To do this, a strainer or some other filter should be installed in the filler neck of the tank. The second stage of fuel cleaning is a grid on the fuel intake inside the tank. It does not allow the remaining impurities and water to get into the engine power system. The presence and amount of gasoline in the tank is monitored according to the fuel level indicator. When the fuel remains at a minimum, the corresponding red light on the instrument panel lights up - the reserve lamp. Fuel consumption is controlled according to the readings of the flow meter displayed on the engine parameters control device.

Fuel filter - the next, third stage of fuel purification. The filter is located in the engine compartment and is designed for fine cleaning of gasoline supplied to the fuel pump (it is possible to install a filter after the pump).

Fuel pump - designed for forced supply of fuel from the tank to the carburetor. The pump consists of (see fig. 6.2.):

body, diaphragm with spring and drive mechanism, intake and discharge (exhaust) valves. It also contains a mesh filter for the next - fourth stage of gasoline purification. The fuel pump is driven from the engine camshaft. When the shaft rotates, the eccentric on them runs onto the fuel pump drive rod. The stem begins to press on the lever, which, in turn, forces the diaphragm to go down. Above it, a vacuum is created and the inlet valve, overcoming the force of the spring, opens. A portion of the fuel from the tank is sucked into the space above the diaphragm. When the eccentric escapes from the stem, the diaphragm is released from the action of the lever and, due to the rigidity of the spring, rises up. The resulting pressure closes the inlet valve and opens the delivery valve. Gasoline above the diaphragm is sent to the carburetor. With the next run of the eccentric on the rod, gasoline is sucked in and the process is repeated. Please note that the supply of gasoline to the carburetor is only due to the force of the spring, which raises the diaphragm. This means that when the carburetor's float chamber is full and the needle valve (see Fig. 6.1.) Blocks the path of gasoline, the diaphragm of the fuel pump will remain in the lower position. And until the engine has consumed part of the fuel from the carburetor, the spring will not be able to "push" the next portion of gasoline from the pump.

Figure: 6.2. The scheme of the fuel pump a) fuel suction, b) fuel injection

1 - discharge pipe; 2 - coupling bolt; 3 - cover; 4 - suction pipe; 5 - inlet valve with spring; 6 - body; 7 - pump diaphragm; 8 - manual pumping lever; 9 - thrust; 10 - mechanical pumping lever; 11 - spring; 12 - stock; 13 - eccentric; 14 - pressure valve with a spring; 15 - fuel filter

Since the fuel tank is located below the carburetor, there is a need for a forced supply of gasoline. In this case, an electric pump is used to pump fuel.

Air filter (Fig. 6.3.) is designed to clean the air entering the engine cylinders. The filter is installed on top of the carburetor air intake. Clogging the filter increases the resistance to air movement, which can lead to increased consumption fuel, as the combustible mixture will be too rich in gasoline.

Figure: 6.3. Air filter

The carburetor is designed for preparing a combustible mixture and feeding it into the engine cylinders. Depending on the operating modes of the engine, the carburetor changes the quality (ratio of gasoline and air) and the amount of this mixture. The carburetor is one of the most complex devices in a car. It consists of many parts and has several systems that take part in the preparation of the combustible mixture, ensuring the smooth operation of the engine. Let's look at the device and the principle of operation of the carburetor in a somewhat simplified diagram (Figure 6.4.).

Figure: 6.4. The scheme of the simplest carburetor

1 - fuel pipe; 2 - float with a needle valve; 3 - fuel jet; 4 - sprayer; 5 - carburetor body; 6 - air damper; 7 - diffuser; 8 - throttle valve

The simplest carburetor consists of: a float chamber, a float with a needle shut-off valve, an atomizer, a mixing chamber, a diffuser, an air and throttle valve, fuel and air channels with jets.

How is the combustible mixture prepared? When the piston moves in the cylinder from the top dead center to the bottom (intake stroke), a vacuum is created above it. The air flow through the air filter and carburetor rushes into the vacated volume of the cylinder. When air passes through the carburetor, fuel is sucked out of the float chamber through the sprayer, which is located at the narrowest point of the mixing chamber - the diffuser. This is due to the pressure difference in the carburetor's float chamber, which is connected to the atmosphere, and in the diffuser, where a significant vacuum is created. The air stream crushes the fuel flowing out of the atomizer and mixes with it. At the outlet of the diffuser, the final mixing of gasoline with air takes place, and then the ready-made combustible mixture enters the cylinders.

From the operation diagram of the simplest carburetor (see Fig. 6.4.), It can be understood that the engine will not work normally if the fuel level in the float chamber is higher than normal, since in this case more gasoline will be poured out than necessary. If the level of gasoline is less than the norm, then its content in the mixture will be less, which will again disrupt the correct operation of the engine. Based on this, the amount of gasoline in the chamber should be unchanged. The fuel level in the carburetor's float chamber is regulated by a special float, which, dropping together with a needle shut-off valve, allows gasoline to enter the chamber. When the float chamber begins to fill, the float floats up and closes the gas passage with its valve.

Throttle valve, by means of levers or a cable, connected to the engine control handle. In the initial position, the damper is closed. when the throttle valve is opened, the air flow through the carburetor increases. In this case, the more the throttle valve opens, the more fuel is sucked out, since the volume and speed of the air flow passing through the diffuser increases and the “sucking” vacuum increases. When the throttle valve is closed, the air flow decreases, and less and less combustible mixture enters the cylinders. The engine "loses speed", the engine torque decreases. When the throttle valve is fully closed, the engine is idling, the carburetor has its own channels through which air can still get under the throttle valve, mixing with gasoline along the way (see Figure 6.5.).

Figure: 6.5. Idling system operation diagram

1 - fuel channel of the idle system; 2 - fuel jet of the idling system; 3 - needle valve of the carburetor float chamber; 4 - fuel jet; 5 - throttle valve; 6 - screw "quality" of the idling system; 7 - air jet of the idle system; 8 - air damper

With the throttle valve closed, the air has no other way but to pass through the idle channel into the cylinders. And on the way, it sucks gasoline from the fuel channel and, mixing with it, again turns into a combustible mixture. The mixture, almost ready to "use", enters the throttle space, where it is finally mixed and then enters the engine cylinders.

When starting a cold engine, use the control knob throttle (choke handle) that controls air damper carburetor. If you close this flap (pull the "suction" handle towards you), then the vacuum in the mixing chamber of the carburetor will increase. As a result, the fuel from the float chamber begins to be sucked out more intensively and the combustible mixture is enriched, which is necessary to start a cold engine.

The combustible mixture is called normal, if one part of gasoline accounts for 15 parts of air (1:15). This ratio may vary depending on various factors, and will change accordingly mix quality. If there is more air, then the mixture is called impoverished or poor. If there is less air - enriched or rich.The lean and lean mixture is hungry food for the engine, it contains less fuel. Enriched and rich mix - too high-calorie food, as it contains more fuel than necessary.

Purpose, design and operation of the fuel supply system

The engine fuel supply system is designed to accommodate the fuel supply on the car, clean, spray fuel and distribute it evenly over the cylinders in accordance with the engine operation order.

The KamAZ-740 engine uses a separate fuel supply system (that is, the functions of the high-pressure fuel pump and the nozzle are separated). It includes (Fig. 37) fuel tanks, a coarse fuel filter, a fine fuel filter, a low pressure fuel priming pump *, a manual fuel priming pump, a high pressure fuel pump (HPP) with an all-mode regulator and an automatic fuel injection advance clutch, injectors, high and low pressure fuel lines and instrumentation.

Fuel from the fuel tank under the action of a vacuum created by the fuel priming pump through coarse and fine filters through low pressure fuel lines is supplied to the high pressure fuel pump. In accordance with the order of engine operation (1-5-4-2-6-3-7-8), the injection pump delivers fuel under high pressure and in certain portions through the nozzles into the combustion chambers of the engine cylinders. The fuel is atomized by the nozzles. Excess fuel, and with it the air that has entered the system, is discharged into the fuel tank through the high-pressure fuel pump bypass valve and fine filter nozzle valve. Fuel seeping through the gap

Figure: 37. Engine fuel supply system:
1 - fuel tank; 2 - fuel line to the coarse filter; 3 - tee; 4 - coarse fuel filter; 5 - drain drainage fuel line of the left row injectors; 6 - nozzle; 7 - fuel supply line to the low pressure pump; 8 - high pressure fuel line; 9 - manual fuel pump; 10 - low pressure fuel pump; 11 - fuel line to the fine filter; 12 - high pressure fuel pump; 13 - fuel line to the solenoid valve; 14 - electromagnetic valve; / 5-drain fuel drain line of the right row injectors; 16 - torch candle; P - drainage fuel line of the high pressure pump; 18 - fine fuel filter; 19 - fuel supply line to the high pressure pump; 20 - drainage fuel line of the fine fuel filter; 21 - drain fuel line; 22 - distribution valve

Figure: 38. Fuel tank:
1 - bottom; 2 - partition; 3 - body; 4 - plug of the drain valve; 5 - filling pipe; 6 - filler pipe plug; 7 - tie tape; 8 - tank mounting bracket

Fuel tanks (fig. 38) are designed to accommodate and store a certain amount of fuel on the vehicle. The KamAZ-4310 has two tanks with a capacity of 125 liters each. They are located on both sides of the vehicle on the frame side members. The tank consists of two halves, stamped from sheet steel and connected by welding; lead-coated from the inside to protect against corrosion.

There are two partitions inside the tank, which serve to cushion hydraulic shocks of fuel against the walls when the vehicle is moving. The tank is equipped with a filler neck with a retractable pipe, a filter mesh and a sealed cover. In the upper part of the tank there is a rheostat-type fuel level indicator sensor, a tube that acts as an air valve. In the lower part of the tank there is a suction pipe and a fitting with a valve for draining the sediment. There is a strainer at the end of the intake tube.

The coarse fuel filter (Fig. 39) is designed for preliminary cleaning of fuel supplied to the fuel pump. Installed on the left side of the vehicle frame. It consists of a housing, a reflector with a filter mesh, a distributor, a damper, a filter cup, inlet and outlet fittings with gaskets. The glass with the lid is connected with four bolts through a rubber gasket. A drain plug is screwed into the lower part of the glass.

Fuel coming from the fuel tank through the inlet connection is supplied to the distributor. Large foreign particles and water collect in the bottom of the glass. From the upper part, the fuel is supplied through a strainer to the outlet fitting, and from it to the fuel pump.

The fine fuel filter (Fig. 40) is designed for final cleaning of fuel before it enters the high pressure fuel pump. The filter is installed at the rear of the engine at the highest point in the power system. Such an installation provides for the collection of air that has entered the power supply system and its removal into the fuel tank through the nozzle valve. The filter consists of a body,

two filter elements, two caps with welded rods, an orifice valve, inlet and outlet fittings with gaskets, sealing elements. The body is cast from an aluminum alloy. It has channels for supplying and removing fuel, a cavity for installing a nozzle valve and annular grooves for installing caps.

Replaceable cardboard filter elements are made of highly porous ETFZ cardboard. The elements are sealed by upper and lower seals. The tight fit of the elements to the filter housing is ensured by springs mounted on the cap rods.

The jet valve is designed to remove air that has entered the power system. It is installed in the filter housing and consists of a cap, valve spring, plug, adjusting washer, and sealing washer. The nozzle valve opens when the pressure in the cavity in front of the valve is 0.025 ... 0.045 MPa (0.25 ... 0.45 kgf / cm2), and at a pressure of 0.22 ± 0.02 MPa (2.2 ± 0.2 kgf / cm2), fuel starts to flow.

Fuel under pressure from the fuel priming pump fills the inner cavity of the bell and is pushed through the filter element, on the surface of which mechanical impurities remain. The cleaned fuel from the inner cavity of the filter element is supplied to the inlet cavity of the injection pump.

Figure: 39. Coarse fuel filter:
1 - drain plug; 2 - glass; 3 - sedative; 4 - filtering mesh; 5 - reflector; 6 - distributor; 7- bolt; 8- flange; 9- sealing ring; 10 - case

The low pressure fuel priming pump is designed to supply fuel through coarse and fine filters to the inlet cavity of the injection pump. The pump is a piston type driven by an eccentric cam shaft of the injection pump. Supply pressure 0.05 ... 0.1 MPa (0.5 ... 1 kgf / cm2). The pump is installed on the back cover of the injection pump. The fuel priming pump (Fig. 41, 42) consists of a housing, a piston, a piston spring, a piston pusher, a pusher rod, a pusher spring, a rod guide sleeve, an inlet valve, a pressure valve.

Cast iron pump casing. It has channels and cavities for the piston and valves. The cavities under the piston and above the piston are connected by a channel through a discharge valve.

The pusher is designed to transmit force from the cam shaft eccentric to the piston. Roller type pusher.

The cam shaft eccentric of the injection pump through the pusher and the rod imparts a reciprocating movement to the pump piston (see Fig. 41).

Figure: 40. Fine fuel filter:
1 - case; 2 - bolt; 3 - sealing washer; 4 - plug; 5, 6 - gaskets; 7 - filter element; 8 - cap; 9 - filter element spring; 10 - drain plug; 11 - rod

When the pusher is lowered, the piston moves downward under the action of the spring. A vacuum is created in the suction cavity a, the intake valve opens and lets fuel into the over-piston cavity. At the same time, fuel from the sub-piston cavity through a fine filter enters the inlet channels of the high-pressure fuel pump. When the piston moves up, the inlet valve closes and fuel from the above-piston cavity through the discharge valve enters the cavity under the piston. When the pressure in the delivery line b rises, the piston stops moving down after the pusher, but remains in a position determined by the balance of forces from the fuel pressure on one side and the spring force on the other. Thus, the piston does not make a full stroke, but a partial one. Thus, the pump performance will be determined by the fuel consumption.

The manual fuel priming pump (see fig. 42) is used to fill the system with fuel and remove air from it. The pump is a piston type, mounted on the body of the fuel-priming pump through a sealing copper washer.

The pump consists of a body, a piston, a cylinder, a piston rod and a handle, a support plate, an inlet valve (common with the fuel priming pump).

The system is filled and pumped by moving the handle with the stem up and down. When the handle moves up, a vacuum is created in the sub-piston space. The inlet valve opens and fuel flows into the cavity above the fuel pump piston. When the handle moves down, the delivery valve of the fuel priming pump opens and pressurized fuel enters the delivery line. Then the process is repeated.

After bleeding, the handle should be tightly screwed onto the upper threaded shank of the cylinder. In this case, the piston is pressed against the rubber gasket, sealing the inlet cavity of the fuel priming pump.

Figure: 41. Scheme of operation of the low pressure fuel priming pump and manual fuel priming pump:
1 - eccentric pump drive; 2 - pusher; 3 - piston; l - inlet valve; 5 - hand pump; 6 - discharge valve 4

The high pressure fuel pump (TNVD) is designed to supply metered portions of fuel under high pressure to the engine cylinders in accordance with the order of their operation.

Figure: 42. Fuel pump:
1 - eccentric pump drive; 2 - pusher roller; 3 - pump body (cylinder); 4 - pusher spring; 5 - pusher rod; 6 - stem sleeve; 7 - piston; 8 - piston spring; 9 - high pressure pump body; 10 - inlet valve saddle; 11- low pressure fuel priming pump body; 12 - inlet valve; 13 - valve spring; / 4 - manual booster pump; 15 - washer; 16 - plug of the discharge valve; 17 - pressure valve spring; 18 - discharge valve of the low pressure fuel pump

Figure: 43. High pressure fuel pump: 1 - rear cover of the regulator; 2, 3 - leading and intermediate gears of the speed controller; 4- driven gear wheel of the regulator with a holder of weights; 5 - load axis; 6 - cargo; 7-clutch of weights; 8 - lever finger; 9 - proofreader; 10 - lever of the regulator spring; 11 - rail; 12 - rack bushing; 13 - pressure reducing valve; 14 - rail plug; 15 - fuel injection advance coupling; 16 - camshaft; 17, - pump casing; 18 - pump section

The pump is installed in the camber of the cylinder block and is driven from the camshaft gear through the pump drive gear. The direction of rotation of the camshaft from the drive side is right.

The pump consists of a housing, a camshaft (see Fig. 43), eight pump sections, an all-speed governor, a fuel injection advance clutch and a fuel pump drive.

The high-pressure fuel pump housing is designed to accommodate the pump sections, camshaft and speed regulator. Cast from an aluminum alloy, it has inlet and shut-off channels and cavities for installing and fixing pump sections, a camshaft with bearings, regulator drive gears, inlet and outlet fuel fittings... At the rear end of the pump housing, a regulator cover is attached, in which a low pressure fuel priming pump with a manual fuel priming pump is located. A nipple with an oil supply pipe is screwed in from the top of the cover for lubricating the injection pump parts under pressure. Oil from the pump is drained through a pipe connecting the lower hole of the regulator cover with the hole in the camber of the block. The upper cavity of the injection pump housing is closed by a cover (see Fig. 44), on which the control levers of the speed regulator and two protective casings of the pump fuel sections are located. The cover is mounted on two pins and bolted, and protective covers - two screws. At the front end of the pump casing at the outlet of the cut-off channel, a fitting with a ball-type bypass valve is screwed in, maintaining an excess fuel pressure in the pump of 0.06 ... 0.08 MPa (0.6 ... 0.8 kgf / cm2). In the lower part of the pump housing there is a cavity for the camshaft.

The camshaft is designed to communicate the movement of the plungers of the pumping sections and ensure timely fuel supply to the engine cylinders. The camshaft is made of steel. The working surfaces of the cams and bearing journals are cemented to a depth of 0.7 ... 1.2 mm. Due to the K-type pump design, the camshaft is shorter and therefore more rigid. The shaft rotates in two tapered bearings, the inner races of which are pressed onto the shaft journals. The axial clearance of the camshaft of 0.1 mm is adjusted by shims installed under the bearing cover. There is a rubber seal in the cover to seal the camshaft. An automatic fuel injection timing clutch is installed on the front tapered end of the camshaft on a segmented key. Mounted on the rear end of the camshaft is a thrust bushing, governor drive gear assembly, and on a key, the governor drive gear flange. The flange is made together with the eccentric of the drive of the fuel pump. The torque from the camshaft to the drive gear of the governor is transmitted through the flange by means of rubber nuts. When the camshaft rotates, the force is transmitted to the roller pushers and through the pusher heels to the plungers of the pump sections. Each pusher is fixed from rotation with a cracker, the protrusion of which enters the groove of the pump housing. By changing the thickness of the heel, the start of the fuel supply is regulated. When installing a thicker foot, the fuel starts to flow earlier.

Figure: 44. Regulator cover:
1 - bolt for adjusting the starting feed; 2 - stop lever; 3 - bol * regulation of the stop lever stroke; 4 - bolt for limiting the maximum speed; 5 - regulator control lever (fuel pump rail); 6 - bolt for limiting the minimum speed; I - work; It - off

The pump section (Fig. 45, a) is a part of the high-pressure fuel pump, which measures and supplies fuel to the injector. Each pumping section consists of a housing, a plunger pair, a rotary sleeve, a plunger spring, a discharge valve, and a pusher.

The section casing has a flange, by means of which the section is fixed on studs screwed into the pump casing. The stud holes are oval in shape. This allows the pump section to be rotated to regulate the uniformity of the fuel delivery in individual sections. When the section is turned counterclockwise, the cycle feed increases, clockwise - decreases. The section housing has two holes for the passage of fuel from the channels in the pump to the holes in the plunger sleeve (A, B), a hole for installing a pin that fixes the position of the sleeve and the plunger relative to the section body, and a slot for accommodating the leash of the rotary sleeve.

Plunger pair (Fig. 45, b) - pump section unit, directly intended for metering and supplying fuel. The plunger pair includes a plunger sleeve and a plunger. They are a precision pair. Manufactured from chrome-molybdenum steel, hardened and then deep cold treated to stabilize material properties. The bushing and plunger working surfaces are nitrided.

Figure: 45. High pressure fuel pump section:
a - construction; b - diagram of the upper part of the plunger pair; A - injection chamber of the fuel pump; B - cut-off cavity; 1 - pump housing; 2- section pusher; 3 - pusher heel; 4 - spring: 5, 14 - section plunger; 6, 13 - plunger sleeve; 7 - discharge valve; 8 - fitting; 9 - section body; 10 - cut-off edge of the plunger screw groove; 11 - rail; 12 - swivel plug of the plunger

The plunger is a moving part of the plunger pair and acts as a piston. The plunger in the upper part has axial drilling, two spiral grooves made on both sides of the plunger, and a radial drilling connecting the axial drilling and grooves. The spiral groove is designed to change the cyclic fuel supply due to the rotation of the plunger, and hence the groove relative to the shut-off hole of the plunger sleeve. The rotation of the plunger relative to the sleeve is carried out by the fuel pump rack through the plunger pins. There is a mark on the outer surface of one spike. When assembling the section, the mark on the spike of the plunger and the slot in the body of the section for installing the driver of the swivel sleeve must be on one side. The presence of the second groove provides hydraulic unloading of the plunger from lateral forces. This increases the reliability of the pump section.

The seal between the bushing and the section casing is provided by a ring made of oil and petrol resistant rubber installed in the annular groove of the bushing.

The discharge valve and its seat are made of steel, hardened and deep cold worked. The valve and the seat constitute a precision pair, in which replacement of one part with the same part from another set is not allowed.

The discharge valve is located at the upper end of the sleeve and is pressed against the seat by a spring. The discharge valve seat is pressed against the plunger sleeve by the end face of the fitting through a sealing textolite gasket.

Mushroom type discharge valve with cylindrical guide part. A radial hole with a diameter of 0.3 mm is used to correct the cycle feed at a camshaft rotation frequency of 600 ... 1000 min-1. The correction is carried out due to an increase in the throttling action of the valve during the cutoff period, as a result of which the amount of fuel flowing from the high-pressure fuel line to the above-plunger space is reduced. Unloading the fuel line from high pressure is carried out by moving when the valve guide is seated in the seat channel. The upper part of the guide acts as a piston that sucks fuel from the fuel line.

All-mode speed controller. Internal combustion engines must operate at a given steady state (equilibrium) mode, characterized by a constant crankshaft speed, coolant temperature and other parameters. This mode of operation can be maintained only if the engine torque is equal to the moment of resistance to motion. However, during operation, this equality is often violated due to a change in the load or the specified mode, therefore the value of the parameters (rotation frequency, etc.) deviates from the specified ones. To restore the disturbed engine operation, regulation is applied. Regulation can be carried out manually by acting on the control element (fuel pump rail) or using a special device called an automatic speed controller. Thus, the speed regulator is designed to maintain the crankshaft speed set by the driver by automatically changing the cycle fuel supply depending on the load.

The KAMAZ engine is equipped with a direct-acting all-mode centrifugal speed controller. It is located in the collapse of the injection pump housing, and the control is brought to the pump cover.

The regulator has the following elements (fig. 46):
- master device;
- sensitive element;
- a comparison device;
- actuating mechanism;
- regulator drive.

The setting device includes a regulator control lever, a spring lever, a regulator spring, a regulator lever, a lever with a corrector, adjusting bolts for speed limiting.

The sensitive element includes a regulator shaft with a weight holder, weights with rollers, a thrust bearing, a regulator sleeve with a heel.

The comparison device includes the weight clutch lever, with the help of which the movement of the regulator clutch is transmitted to the actuator (racks).

The actuator includes the fuel pump rails, rack lever (differential lever).

The drive of the regulator includes the drive gear of the regulator, the intermediate gear 6, the gear of the regulator, made in one piece with the shaft of the all-mode regulator.

To stop the engine, there is a device that includes a stop lever, a stop lever spring, a start spring, a stop lever travel adjustment bolt, and a starting feed adjustment bolt.

Fuel supply is controlled by foot and hand drives.

The rotation of the drive gear of the regulator is transmitted through rubber rusks. Crackers, being elastic elements, dampen vibrations associated with uneven shaft rotation. Reducing high-frequency vibrations leads to a decrease in wear on the joints of the main parts of the regulator. From the drive gear, rotation to the driven gear is transmitted through the idler gear.

The driven gear is made integrally with the weight holder rotating on two ball bearings. When the holder rotates, the weights diverge under the action of centrifugal forces and the clutch is moved through the thrust bearing, the clutch, resting on the finger, in turn, moves the weight clutch lever.

The weight clutch lever is attached at one end to the axis of the regulator levers, with the other through a pin connected to the fuel pump rail. A regulator lever is also attached to the axle, the other end of which moves to the stop in the fuel supply adjusting bolt. The weight clutch lever acts on the adjuster lever through the corrector. The governor control lever is rigidly connected to the governor spring lever.

Figure: 46. \u200b\u200bSpeed \u200b\u200bcontroller:
1 - back cover; 2 - nut; 3 - washer; 4 - bearing; 5 - adjusting gasket; 6 - intermediate gear; 7 - gasket for the rear cover of the regulator; 8 - retaining ring; 9- cargo holder; 10 - cargo axis; 11 - thrust bearing; 12 - clutch; 13 - cargo; 14 - finger; 15 - proofreader; 16 - return spring of the stop lever; 17 - bolt; 18 - bushing; 19 - ring; 20 - regulator spring lever; 21 - the driving gear wheel: 22 - rusk of the driving gear wheel; 23 - drive gear flange; 24 - adjusting bolt of fuel supply; 25 - starting lever

The starting spring is attached to the starting spring arm and the rack arm. The slats, in turn, are connected to the rotating sleeves of the pump sections. Reducing the degree of unevenness of the regulator at low speeds of rotation of the crankshaft is achieved by changing the arm of the application of the force of the regulator spring to the regulator lever.

An increase in the sensitivity of the regulator is ensured by high-quality processing of the rubbing surfaces of the moving parts of the regulator and the pump, their reliable lubrication and an increase in the angular speed of rotation of the weights clutch twice in relation to the camshaft of the pump due to the gear ratio of the drive gears of the regulator.

The engine has a speed regulator with a smoke corrector, which is built into the weight clutch lever. The corrector, by decreasing the fuel supply, allows to reduce engine smoke at low crankshaft speed (1000 ... 1400 min).

The preset high-speed operating mode of the engine is set by the regulator control lever, which turns and increases its tension through the spring lever. Under the influence of this spring, the lever, through the corrector, acts on the clutch lever, which moves the racks connected to the rotary plugs of the plungers in the direction of increasing the fuel supply. The crankshaft speed increases.

The centrifugal force of the rotating weights through the thrust bearing, the clutch and the weight clutch lever is transmitted to the fuel pump rail, which is connected to another rail via a differential lever. The movement of the rods by the centrifugal force of the weights causes a decrease in the fuel supply.

The regulated speed mode depends on the ratio of the regulator spring force and the centrifugal force of the weights at a set crankshaft speed. The more the regulator spring is tensioned, the higher the speed mode its weights can change the position of the regulator lever towards limiting the fuel supply to the engine cylinders. Stable operation of the engine will be in the event that the centrifugal force of the weights is equal to the force of the regulator spring. Each position of the governor control lever corresponds to a certain speed of the crankshaft.

With a given position of the governor control lever in the event of a decrease in the engine load (downhill movement), the crankshaft rotation speed, and, consequently, the governor drive shaft, increases. In this case, the centrifugal force of the weights increases and they diverge.

The weights act on the thrust bearing and, overcoming the spring force set by the driver, turn the regulator lever and move the racks in the direction of decreasing feed until the fuel supply is established corresponding to the driving conditions. The preset high-speed mode of engine operation will be restored.

With an increase in the load (movement uphill), the rotational speed and, consequently, the centrifugal forces of the loads decrease. The force of the spring through the levers 31, 32, acting on the clutch, moves it and brings the loads closer together. In this case, the racks move in the direction of increasing the fuel supply until the crankshaft speed reaches the value specified by the driving conditions.

Thus, the all-mode regulator maintains any driving mode specified by the driver.

When the engine is running at the rated speed and full fuel supply, the L-shaped lever 31 rests against the adjusting bolt 24. If the load increases, the speed of the crankshaft and governor shaft begins to decrease. In this case, the balance between the force of the regulator spring and the centrifugal force of its weights, reduced to the axis of the regulator lever, is disturbed. And due to the excess force of the corrector spring, the corrector plunger moves the clutch lever in the direction of increasing fuel supply.

Thus, the speed regulator not only maintains the engine at a given mode, but also ensures the supply of additional portions of fuel to the cylinders when working with overload.

Turning off the fuel supply (stopping the engine) is carried out by turning the stop lever until it stops against the stop lever stroke adjustment bolt. The lever, overcoming the force of the spring (installed on the lever), will turn the regulator lever by the finger. The racks move until the fuel supply is completely turned off. The engine stops. After stopping, the stop lever returns to the RUN position under the action of the return spring, and the starting spring through the rack lever will return the fuel pump racks towards the starting fuel supply (195 ... 210 mm3 / cycle).

Automatic fuel injection advance clutch. In diesel engines, fuel is injected into an air charge. The fuel cannot instantly ignite, but must go through a preparatory phase, during which the fuel is mixed with air and evaporated. When the autoignition temperature is reached, the mixture ignites and quickly begins to burn. This period is accompanied by a sharp rise in pressure and temperature rise. In order to obtain the highest power, it is necessary that the combustion of the fuel occurs in the minimum volume, that is, when the piston is at TDC. For this purpose, fuel is always injected even before the piston reaches TDC.

The angle that determines the position of the crankshaft relative to TDC at the time of the start of fuel injection is called the fuel injection advance angle. The design of the drive of the fuel pump of the KamAZ diesel engine provides fuel injection 18 ° before the piston reaches TDC during the compression stroke.

With an increase in the engine crankshaft speed, the preparatory process time decreases and ignition can begin after TDC, which will lead to a decrease in useful work. In order to get the greatest work with an increase in the crankshaft speed, the fuel must be injected earlier, i.e., the fuel injection advance angle must be increased. This can be done by turning the camshaft in the direction of rotation relative to the drive. For this purpose, a fuel injection advance clutch is installed between the camshaft of the injection pump and its drive. The use of the clutch significantly improves the starting qualities of the diesel engine and its efficiency at various speed modes.

Thus, the fuel injection advance clutch is designed to change the moment of the start of fuel supply depending on the engine crankshaft speed.

On KamAZ-740, an automatic centrifugal-type clutch of direct action is used. The range of adjustment of the fuel injection advance angle is 18 ... 28 °.

The clutch is mounted on the tapered end of the camshaft of the injection pump on a segmented key and is secured with an annular nut with a spring washer. It changes the moment of fuel injection due to additional rotation of the pump camshaft during engine operation relative to the high pressure pump drive shaft (Fig. 47).

The automatic clutch (Fig. 47, a) consists of a body, a leading half-coupling with pins, a driven half-coupling with cargo axles, weights with pins, spacers, spring cups, springs, shims and thrust washers.

The body of the coupling is cast iron. At the front end there are two threaded holes for filling the coupling engine oil... The body is screwed onto the driven half-coupling and locked. The seal between the body and the driving half-coupling and the hub of the driven half-coupling is carried out by two rubber cuffs, and between the body and the driven coupling half - by a ring made of oil and petrol-resistant rubber.

The driving half of the coupling is installed on the driven hub and can rotate relative to it. The clutch is driven from the drive shaft of the injection pump (Fig. 47, b). In the leading half of the coupling there are two pins on which spacers are installed. The spacer rests against one end of the load finger, while the other slides along the profile projection of the load.

The driven coupling half is installed on the tapered part of the camshaft of the injection pump. Two weight axles are pressed into the half-coupling and a mark is applied to set the fuel injection advance angle. Loads swing on axles in a plane perpendicular to the coupling rotation axis. The weights have profile projections and pins. The forces of the springs act on the weights.

Figure: 47. Automatic fuel injection advance clutch:
a - automatic clutch: 1 - leading half-clutch; 2, 4 - cuffs; 3 - bushing of the leading half-coupling; 5 - case; 6 - an adjusting gasket; 7 - spring glass; 8 - spring; 9, 15 - washers; 10 - ring; 11 - weight with a finger; 12 - pro-rate with an axis; 13 - driven half-coupling; 14 - sealing ring; 16 - axis of loads
b - drive of an automatic clutch and its installation according to marks; 1 - mark nya rear flange of the coupling half; II - mark on the injection advance clutch; III - mark on the body of the fuel pump; 1 - automatic injection advance clutch; 2 - driven drive half-coupling; 3 - bolt; 4 - drive half-coupling flange

At the minimum crankshaft speed, the centrifugal force of the weights is small and they are held by the force of the springs. In this case, the distance between the axles of the weights (on the driven coupling half) and the fingers of the driving coupling half will be maximum. The driven part of the coupling lags behind the leading part by the maximum angle. Therefore, the fuel injection advance angle will be minimal.

With an increase in the crankshaft rotation frequency, the weights under the action of centrifugal forces, overcoming the resistance of the springs, diverge. The spacers slide along the profile projections of the weights and pivot around the axes of the weights pins. Since the fingers of the driving half of the coupling enter the hole of the spacers, the divergence of the weights leads to the fact that the distance between the fingers of the driving half of the coupling and the axes of the weights will decrease, i.e., the angle of lag of the driven half from the leading one will also decrease. The driven half of the coupling rotates relative to the leading half by a certain angle along the direction of rotation of the coupling (the direction of rotation is right). Rotation of the driven coupling half causes the camshaft of the injection pump to rotate, which leads to earlier fuel injection relative to TDC.

With a decrease in the speed of the engine crankshaft, the centrifugal force of the weights decreases and they begin to converge under the action of a spring. The driven half of the coupling turns relative to the leading one in the direction opposite to rotation, decreasing the fuel injection advance angle.

The injector is designed for injecting fuel into the cylinders of the engine, atomizing and distributing it throughout the volume of the combustion chamber. The KamAZ-740 engine is equipped with closed-type nozzles with a multi-hole sprayer and a hydraulically controlled needle. The pressure of the beginning of the needle lift is 20 ... 22.7 MPa (200 ... 227 kgf / cm2). The injector fits into the cylinder head socket and is secured with a bracket. The injector is sealed in the cylinder head socket in the upper belt with a rubber ring 7 (Fig. 48), in the lower one - with a cone of the spray nut and a copper washer. The nozzle consists of a body 6, a nozzle nut 2, a nozzle, a spacer 3, a rod 5, a spring, support and adjusting washers and a nozzle fitting with a filter.

The nozzle body is made of steel. In the upper part of the body there are threaded holes for installing a filter connection and a drain pipe connection (see Fig. 37). A fuel supply channel and a channel for removing fuel leaking into the inner cavity of the body are made in the body.

Figure: 48. Nozzle:
a - with adjusting washers; b - with external adjustment; 1 - sprayer body; 2 - spray nut; 3 - spacer; 4 - locating pins; 5 - barbell; 6 - body; 7 and 16 - sealing rings; 8 - fitting; 9 - filter; 10 - sealing sleeve; 11 and 12 - adjusting washers; 13 - spring; 14 - spray needle; 15 - spring stop;. 17 - eccentric

The nozzle nut is used to connect the nozzle to the nozzle body.

Sprayer - a nozzle assembly that atomizes and forms jets of injected fuel.

The atomizer body and the needle are a precision pair, in which the replacement of any one part is not allowed. The body is made of chromium-nickel-vanadium steel and subjected to a special heat treatment (carburizing, quenching, followed by deep cold treatment) to obtain high hardness and wear resistance of the working surfaces. An annular groove and a channel for supplying fuel to the cavity of the atomizer body, as well as two holes for pins are made in the atomizer body, which ensure fixation of the atomizer body relative to the nozzle body. Four nozzle holes are made in the lower part of the body. Their diameter is 0.3 mm. To ensure uniform distribution of fuel throughout the volume of the combustion chamber, the nozzle openings are made at different angles. This is due to the fact that the nozzle is located at an angle of 21 ° relative to the cylinder axis.

The spray needle is designed to close the spray holes after fuel injection. The needle is made of tool steel and has also been specially treated. In order to increase the service life of the atomizer and the needle, the closure part of the needle is made with a double cone.

The spacer is designed to fix the nozzle body relative to the nozzle body.

The rod is a moving part of the nozzle, designed to transfer the force from the nozzle spring to the spray needle.

The nozzle spring is designed to provide the required needle lift pressure. The spring is tensioned by adjusting washers, which are installed between the support washer and the end of the inner cavity of the nozzle body. A change in the thickness of the washers by 0.05 mm leads to a change in the pressure of the beginning of the rise of the needle by 0.3 ... 0.35 MPa (3 ... 3.5 kgf / cm2). In nozzles of the second type (Fig. 48.6), the spring is adjusted by turning the eccentric 17.

Joint work of the pump section of the injection pump and the nozzle. The driver, acting on the fuel delivery pedal through the system of rods and levers, the setting device of the all-mode regulator, fuel pump racks, swivel bushings, turns the plunger. Thus, it sets a certain distance between the cutoff hole and the cutoff edge of the helical groove, providing a certain cyclic fuel supply.

The plunger, under the action of the camshaft, reciprocates. When the plunger moves down, the spring-loaded discharge valve is closed and a vacuum is created in the supra-plunger cavity.

After the upper edge of the plunger opens the inlet in the bushing, the fuel from the fuel channel at a pressure of 0.05 ... 0.1 MPa (0.5 ... 1 kgf / cm2) from the fuel pump enters the space above the plunger (Fig. 49, a).

At the beginning of the movement (Fig. 49, b) of the plunger upward, part of the fuel is displaced through the inlet and cutoff holes of the sleeve into the fuel supply channel. The moment of the beginning of fuel delivery is determined by the moment when the upper edge of the plunger closes the inlet of the bushing. From this moment, when the plunger moves upwards, the fuel is compressed in the above-plunger cavity, and after reaching the pressure at which the discharge valve opens, in the high-pressure pipeline and the nozzle.

Figure: 49. Scheme of the pumping section:
a - filling the supra-plunger cavity; b - the beginning of the feed; at - end of feed

When the fuel pressure in the specified cavity becomes more than 20 MPa (200 kgf / cm2), the nozzle needle rises and opens fuel access to the nozzle openings of the nozzle, through which fuel is injected at high pressure into the combustion chamber.

When the plunger moves up, when the cut-off edge of the helical groove reaches the level of the cut-off hole, the moment of the end of the fuel supply comes (Fig. 49, a). With further upward movement of the plunger, the supra-plunger cavity through the vertical channel, the diametral channel, the helical groove communicates with the cut-off channel. As a result, the pressure in the supra-plunger cavity drops, the discharge valve, under the action of the spring and the fuel pressure in the pump union, sits in the seat and the flow of fuel to the injector stops, although the plunger can still move upward. When the pressure in the fuel line drops below the force created by the spring, the nozzle needle moves downward under the action of the spring and blocks the access of fuel to the nozzle openings of the nozzle, thereby stopping the fuel supply to the engine cylinder. The fuel leaked through the gap in the pair of the needle - the nozzle body is discharged through a channel in the nozzle body to the drain pipe and further into the fuel tank.