For everyone modern cars from gasoline engines the fuel injection system is used, since it is more advanced than the carburetor system, despite the fact that it is structurally more complex.

The injection engine is not new, but it became widespread only after the development of electronic technology. This is because it was very difficult to mechanically organize the control of a system with high precision. But with the advent of microprocessors, this has become quite possible.

The injection system is distinguished by the fact that gasoline is supplied in strictly predetermined portions forcibly to the manifold (cylinder).

The main advantage possessed by the injector power supply system is the observance of the optimal proportions of the constituent elements of the combustible mixture in different operating modes power plant... This results in better power output and economical consumption of gasoline.

System design

The fuel injection system consists of electronic and mechanical components. The first controls the parameters of work power unit and on their basis gives signals for the actuation of the executive (mechanical) part.

The electronic component includes a microcontroller (electronic control unit) and a large number of tracking sensors:

• crankshaft position;
• mass air flow;
• throttle position;
• detonation;
• coolant temperature;
• air pressure in the intake manifold.

Injector system sensors

Some cars may have a few more additional sensors. They all have one task - to determine the operating parameters of the power unit and transfer them to the ECU

As for the mechanical part, it includes the following elements:

• electric fuel pump;
• fuel lines;
• filter;
• pressure regulator;
• fuel rail;
• nozzles.

Simple fuel injection system

How it works

Now we will consider the principle of operation of the injection engine separately for each component. With the electronic part, in general, everything is simple. Sensors collect information about rotation speed crankshaft, air (entering the cylinders, as well as its residual part in the exhaust gases), throttle position (associated with the accelerator pedal), coolant temperature. These data are constantly transmitted by the sensors to the electronic unit, due to which a high accuracy of gasoline dosage is achieved.

The ECU compares the information received from the sensors with the data entered in the cards, and already on the basis of this comparison and a number of calculations, it controls the executive part. The electronic unit contains the so-called cards with the optimal operating parameters of the power plant (for example, such conditions need to be applied as much some gasoline, others - so much).

First injection toyota engine 1973 year

To make it clearer, let us consider in more detail the algorithm of the electronic unit, but according to a simplified scheme, since in reality a very large amount of data is used in the calculation. In general, all this is aimed at calculating the time length of the electrical impulse that is supplied to the injectors.

Since the scheme is simplified, we will assume that the electronic unit calculates only a few parameters, namely the basic time pulse length and two coefficients - the coolant temperature and the oxygen level in the exhaust gases. To obtain the result, the ECU uses a formula in which all the available data is multiplied.

To obtain the basic pulse length, the microcontroller takes two parameters - the crankshaft rotation speed and the load, which can be calculated from the manifold pressure.

For example, the engine speed is 3000, and the load is 4. The microcontroller takes this data and compares it with the table entered in the map. In this case, we get a base time pulse length of 12 milliseconds.

But for the calculations, you also need to take into account the coefficients, for which readings are taken from the coolant temperature sensors and the lambda probe. For example, the temperature is 100 degrees, and the oxygen level in the exhaust gases is 3. The ECU takes this data and compares it with several more tables. Suppose the temperature coefficient is 0.8 and the oxygen coefficient is 1.0.

Having received all the necessary data, the electronic unit calculates. In our case, 12 is multiplied by 0.8 and 1.0. As a result, we get that the pulse should be 9.6 milliseconds.

The described algorithm is very simplified, in fact, more than a dozen parameters and indicators can be taken into account in the calculations.

Since the data is constantly fed to the electronic unit, the system almost instantly reacts to changes in the engine operating parameters and adapts to them, providing optimal mixture formation.

It is worth noting that the electronic unit controls not only the fuel supply, its task also includes adjusting the ignition angle to ensure optimal engine operation.

Now about the mechanical part. Everything is very simple here: a pump installed in the tank pumps gasoline into the system, moreover, under pressure to ensure a forced supply. The pressure must be certain, so a regulator is included in the circuit.

Gasoline is fed through the highways to the ramp, which connects all the injectors. An electrical impulse supplied from the ECU leads to the opening of the injectors, and since gasoline is under pressure, it is simply injected through the opened channel.

Types and types of injectors

There are two types of injectors:

1. With single point injection. This system is outdated and is no longer used on cars. Its essence is that there is only one injector installed in the intake manifold. This design did not provide an even distribution of fuel over the cylinders, so its operation was similar to the carburetor system.
2. Multipoint injection. This type is used on modern cars. Here, each cylinder has its own nozzle, so this system is characterized by high dosing accuracy. The injectors can be installed both in the intake manifold and in the cylinder itself (injection).

On multipoint injection system fuel supply can use several types of injection:

1. Simultaneous. In this type, an impulse from the ECU goes to all injectors at once, and they open together. Now this injection is not used.
2. Paired, it is also paralleled. In this type, the nozzles work in pairs. Interestingly, only one of them supplies fuel directly in the intake stroke, while the second does not match. But since the engine is 4-stroke, with a valve timing system, the timing mismatch does not affect the engine's performance.
3. Phased. In this type, the ECU sends signals to open for each injector separately, so the injection occurs with the same stroke.

It is noteworthy that a modern fuel injection system can use several types of injection. So, in normal mode, phased injection is used, but in the event of a transition to emergency operation (for example, one of the sensors has failed), injection engine switches to twin injection.

Sensor feedback

One of the main sensors, on the readings of which the ECU regulates the opening time of the injectors, is the lambda probe installed in the exhaust system. This sensor detects the residual (unburned) amount of air in the gases.

Evolution of the lambda probe from Bosch

Thanks to this sensor, the so-called " feedback". Its essence is as follows: the ECU carried out all the calculations and gave an impulse to the injectors. Fuel entered, mixed with air and burned out. The resulting exhaust gases with unburned particles of the mixture are removed from the cylinders through the exhaust system exhaust gasesin which the lambda probe is installed. On the basis of its readings, the ECU determines whether all the calculations were carried out correctly and, if necessary, makes adjustments to obtain the optimal composition. That is, on the basis of the already carried out stage of fuel supply and combustion, the microcontroller makes calculations for the following.

It should be noted that during the operation of the power plant there are certain modes in which the readings oxygen sensor will be incorrect, which may disrupt the operation of the motor, or a mixture with a certain composition is required. In such modes, the ECU ignores the information from the lambda probe, and it sends signals to supply gasoline based on the information stored in the cards.

In different modes, the feedback works like this:

• Starting the motor. For the engine to start, a rich fuel mixture with an increased percentage of fuel is needed. And the electronic unit provides this, and for this it uses the given data, and it does not use the information from the oxygen sensor;
• Warming up. To make the injection engine quickly gain working temperature The ECU sets an increased engine speed. At the same time, he constantly monitors its temperature, and as it warms up, he adjusts the composition of the combustible mixture, gradually depleting it until its composition becomes optimal. In this mode, the electronic unit continues to use the data specified in the cards, still not using the readings of the lambda probe;
• Idling. In this mode, the engine is already fully warmed up, and the exhaust gas temperature is high, therefore, the conditions for the correct operation of the lambda probe are met. The ECU is already starting to use the readings of the oxygen sensor, which makes it possible to establish the stoichiometric composition of the mixture. With this composition, the greatest power output of the power plant is provided;
• Movement with a smooth change in engine speed. To achieve economical fuel consumption at maximum power output, a mixture with a stoichiometric composition is needed, therefore, in this mode, the ECU regulates the supply of gasoline based on the readings of the lambda probe;
• A sharp increase in revs. In order for the injection engine to react normally to such an action, a somewhat enriched mixture is needed. To provide it, the ECU uses map data, and not the readings of the lambda probe;
• Braking by the motor. Since this mode does not require power output from the motor, it is enough that the mixture simply does not allow the power plant to stop, and a lean mixture is suitable for this. For its manifestation, the readings of the lambda probe are not needed, therefore the ECU does not use them.

As you can see, although the lambda probe is very important for the operation of the system, the information from it is not always used.

Finally, we note that, although the injector is a structurally complex system and includes many elements, the breakdown of which immediately affects the functioning of the power plant, but it provides more rational gasoline consumption, and also increases the environmental friendliness of the car. Therefore, there is no alternative to this power system yet.

Carburetor appearance:
1 - throttle valve zone heating unit;
2 - engine crankcase ventilation fitting;
3 - cover of the accelerating pump;
4 - electromagnetic shut-off valve;
5 - carburetor cover;
6 - air filter mounting stud;
7 - air damper control lever;
8 - starter cover;
9 - sector of the throttle valve drive lever;
10 - block of wire of the EPHH sensor-screw;
11 - adjusting screw for the amount of mixture idle move;
12 - economizer cover;
13 - carburetor body;
14 - fuel supply union;
15 - fuel outlet fitting;
16 - adjusting screw for the quality of the idle mixture (arrow);
17 - connection for supplying vacuum to the vacuum ignition regulator

For the engine to work, it is necessary to prepare a combustible mixture of air and fuel vapor, which must be homogeneous, that is, well mixed and have a specific composition to ensure the most efficient combustion. The power supply system of a gasoline internal combustion engine with spark ignition is used to prepare a combustible mixture and supply it to the engine cylinders and remove exhaust gases from the cylinders.
The process of preparing a combustible mixture is called carburetion... For a long time, a unit called a carburetor was used as the main device for preparing a mixture of gasoline and air and supplying it to the engine cylinders.

The principle of operation of the simplest carburetor:
1 - fuel line;
2 - needle valve;
3 - hole in the float chamber cover;
4 - sprayer;
5 - air damper;
6 - diffuser;
7 - throttle valve;
8 - mixing chamber;
9 - fuel jet;
10 - float;
11 - float chamber
In the simplest carburetor, the fuel is kept in a float chamber where the fuel level is kept constant. The float chamber is connected by a channel to the mixing chamber of the carburetor. The mixing chamber contains diffuser - local narrowing of the chamber. The diffuser makes it possible to increase the speed of the air passing through the mixing chamber. In the narrowest part of the diffuser, sprayconnected by a channel to the float chamber. At the bottom of the mixing chamber there is throttle, which turns when the driver presses the gas pedal.
When the engine is running, air flows through the carburetor mixer. In the diffuser, the air speed increases, and a vacuum is formed in front of the atomizer, which leads to the flow of fuel into the mixing chamber, where it mixes with air. Thus, the carburetor, working on the principle of the atomizer, creates fuel-air combustible mixture... By pressing the gas pedal, the driver turns throttle carburetor, changes the amount of mixture entering the engine cylinders, and therefore, its power and speed.
Due to the fact that gasoline and air have different densities, when you turn the throttle valve, not only the amount of the combustible mixture supplied to the combustion chambers changes, but also the ratio between the amount of fuel and air in it. For complete combustion of the fuel, the mixture must be stoichiometric.
When starting a cold engine, it is necessary to enrich the mixture, since the condensation of fuel on the cold surfaces of the combustion chamber impairs the starting properties of the engine. Some enrichment of the combustible mixture is required when idling, when it is necessary to obtain maximum power, sharp acceleration of the car.
According to the principle of its operation, the simplest carburetor constantly enriches the fuel-air mixture as the throttle valve opens, therefore it cannot be used for real engines cars. For car engines carburetors are used that have several special systems and devices: a starting system (air damper), an idle system, an economizer or econostat, an accelerator pump, etc.
As the requirements for fuel economy and exhaust gas toxicity increased, carburetors became much more complex, and even electronic devices appeared in the latest carburetor versions.

Organizational part (15 min.).

Lesson 6. Fuel supply system of the Rotax 912 engine

TOPIC 4. Fuel supply system of the power plant Rotax 912.

Astana 2012

EDUCATIONAL AND EDUCATIONAL OBJECTIVES

POWER PLANT CONSTRUCTION

TOPIC 4. Fuel supply system of the engine Rotax 912

1. To acquaint cadets with the structure of the engine fuel supply system internal combustion, 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 scheme 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 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 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 - float chamber of the carburetor 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 indications of 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 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 camshaft engine. 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 runs off the rod, 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 out of 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 mounted 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, air and throttle valves, fuel and air channels with jets.

How is the combustible mixture prepared? When the piston moves in the cylinder from top dead points 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 atomizer, 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 flow 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 a simple 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 pour 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 increase 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, the throttle grip (choke knob) is used to control the 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 than normal. Enriched and rich mix - too high-calorie food, as it contains more fuel than necessary.

The main elements, which are nozzles.

To the power supply system carburetor engine are included: fuel tank, sump filter, fuel lines, fuel pump, fine fuel filter, air cleaner, intake pipe, exhaust pipe, intake pipes, muffler, fuel level control devices.

Work power system

When the engine is running the fuel pump sucks fuel from the fuel tank and feeds it through the filters to the carburetor float chamber. During the intake stroke, a vacuum is created in the engine cylinder and air, passing through the air cleaner, enters the carburetor, where it mixes with fuel vapors and is fed into the cylinder in the form of a combustible mixture, and there, mixing with the remaining exhaust gases, a working mixture is formed. After completing the working stroke, the exhaust gases are pushed out by the piston into the exhaust pipe and through the intake pipes through the muffler into the environment.

Power supply and exhaust systems of the car engine:

1 - channel for supplying air to the air filter; 2 - air filter; 3 - carburetor; 4 - handle for manual control of the air damper; 5 - handle for manual control of the throttle valves; 6 - throttle valve control pedal; 7 - fuel wires; 8 - filter-settler; 9 - muffler; 10 - receiving pipes; 11 - outlet pipeline; 12 - fine fuel filter; 13 - fuel pump; 14 - fuel level indicator; 15 - fuel level indicator sensor; 16 - fuel tank; 17 - fuel tank filler cap; 18 - crane; 19 - exhaust pipe of the muffler.

Fuel. Gasoline, which is obtained from oil refining, is usually used as fuel in carburetor engines.

Automobile gasolines, depending on the amount of easily evaporating fractions, are divided into summer and winter.

For automobile carburetor engines, gasolines A-76, AI-92, AI-98, etc. are produced. The letter "A" denotes that gasoline is automobile, the number is the lowest octane number that characterizes the detonation resistance of gasoline. Isooctane has the highest detonation resistance (its resistance is taken as 100), the least is n-heptane (its resistance is 0). Octane number, which characterizes the detonation resistance of benzene, is the percentage of isooctane in such a mixture with n-heptane, which in terms of detonation resistance is equivalent to the test fuel. For example, the fuel under study detonates in the same way as a mixture of 76% iso-octane and 24% n-heptane. The octane number of this fuel is 76. The octane number is determined by two methods: motor and research. When determining the octane number by the second method, the letter "I" is added in the marking of gasoline. The octane number determines the allowable compression ratio.

Fuel tank. One or more fuel tanks are installed on the car. The volume of the fuel tank should provide 400-600 km of the vehicle's mileage without refueling. The fuel tank consists of two stamped, lead-steel, welded halves. There are partitions inside the tank, which give rigidity to the structure and prevent the formation of waves in the fuel. A filler neck is welded in the upper part of the tank, which is closed with a stopper. Sometimes, for the convenience of filling the tank with fuel, a retractable neck with a mesh filter is used. The fuel level indicator sensor and fuel intake pipe with a mesh filter are mounted on the top wall of the tank. In the bottom of the tank there is a threaded hole for draining sediment and removing mechanical impurities, which is closed with a plug. The filler neck of the tank is tightly closed with a plug, in the body of which there are two valves - steam and air. The steam valve opens when the pressure in the tank rises and releases steam to the environment. The air valve opens when fuel is consumed and vacuum is generated.

Fuel filters. To clean the fuel from mechanical impurities, coarse and fine filters are used. A coarse filter settling tank separates fuel from water and large mechanical impurities. The filter-sump consists of a body, a sump and a filter element, which is assembled from plates with a thickness of 0.14 mm. The plates have holes and projections with a height of 0.05 mm. The plate pack is installed on a rod and is pressed against the body by a spring. When assembled, there are slots between the plates through which the fuel passes. Large mechanical impurities and water are collected at the bottom of the sump and are periodically removed through the plug hole in the bottom.

Fuel tank (a) and operation of outlet (b) and inlet (c) valves: 1 - filter-sump; 2 - tank mounting bracket; 3 - tank fastening clamp; 4 - fuel level indicator sensor in the tank; 5 - fuel tank; 6 - crane; 7 - tank plug; 8 - neck; 9 - cork lining; 10 - rubber gasket; P - plug body; 12 - outlet valve; 13 - exhaust valve spring; 14 - inlet valve; 15 - tank plug lever; 16 - inlet valve spring.

Sump filter: 1 - fuel line to the fuel pump; 2 - body gasket; 3 - case-cover; 4 - fuel wire from the fuel tank; 5 - gasket of the filter element; 6 - filter element; 7 - stand; 8 - sump; 9- drain plug; 10 - the rod of the filter element; 11 - spring; 12 - filter element plate; 13 - hole in the plate for the passage of cleaned fuel; 14 - projections on the plate; 15 - hole in the plate for racks; 16 - plug; 17 - bolt for fastening the body-cover

Fine fuel filters with filter elements: a - mesh; b - ceramic; 1 - body; 2 - inlet; 3 - gasket; 4 - filter element; 5 - removable sump bowl; 6 - spring; 7 — screw for fastening the glass; 8 — channel for fuel removal.

Fine filter. To clean the fuel from small mechanical impurities, fine filters are used, which consist of a body, a settling glass and a filtering mesh or ceramic element. The ceramic filter element is a porous material that provides labyrinthine fuel movement. The filter is held in place by a bracket and a screw.
Fuel wires connect the fuel system devices and are made of copper, brass and steel pipes.

Fuel pump system

The fuel pump is used to supply fuel through filters from the tank to the carburetor float chamber. They use diaphragm-type pumps driven by the camshaft eccentric. The pump consists of a body in which the drive is mounted - a two-armed lever with a spring, a head, where inlet and outlet valves with springs are located, and a cover. The edges of the diaphragm are clamped between the body and the head. The diaphragm stem is pivotally attached to the actuator arm, which allows the diaphragm to operate with variable stroke.
When the two-armed lever (rocker arm) lowers the diaphragm down, a vacuum is created in the cavity above the diaphragm, due to which the intake valve opens and the above-diaphragm cavity is filled with fuel. When the lever (pusher) escapes from the eccentric, the diaphragm rises upward under the action of the return spring. Above the diaphragm, the fuel pressure rises, the intake valve closes, the discharge valve opens, and fuel flows through a fine filter into the carburetor float chamber. When changing filters, the float chamber is filled with fuel using a manual pumping device. In the event of a diaphragm failure (crack, burst, etc.), fuel enters the lower part of the body and flows out through the control hole.

Air filter serves to clean the air entering the carburetor from dust. Dust contains tiny crystals of quartz, which, when deposited on the lubricated surfaces of parts, causes them to wear out.

Requirements for filters:

... efficiency of air cleaning from dust;
... low hydraulic resistance;
... sufficient dust holding capacity:
... reliability;
... ease of maintenance;
... manufacturability of the design.

According to the method of air purification, filters are divided into inertial oil and dry.
Inertial oil filter consists of a housing with an oil bath, a cover, an air intake and a filter element made of synthetic material.
When the engine is running, air passing through the annular slot inside the housing and contacting the oil surface sharply changes the direction of movement. As a result, large dust particles in the air adhere to the surface of the oil. Then the air passes through the filter element, is cleaned of small dust particles and enters the carburetor. Thus, the air is purified in two stages. If clogged, the filter is washed.
Dry type air filter consists of a housing, a cover, an air intake and a filtering element made of porous cardboard. Change the filter element if necessary.

The main the purpose of the vehicle fuel system are the supply of fuel from the tank, filtration, the formation of a combustible mixture and its supply to the cylinders. There are several types of fuel systems for. The most common in the 20th century was carburetor system fuel mixture supply. The next step was the development of fuel injection using a single nozzle, the so-called mono injection. The use of this system has reduced fuel consumption. Currently, the third fuel supply system is used - injection. In this system, pressurized fuel is supplied directly to the intake manifold. The number of injectors is equal to the number of cylinders.

injection andcarburetor option

Fuel system device

All engine power systems are similardiffer only in the methods of mixture formation. The fuel system includes the following elements:

1. The fuel tank is designed for storing fuel and is a compact container with a fuel intake device (pump) and, in some cases, coarse filtration elements.
2. Fuel lines are a set of fuel pipes, hoses and are designed to transport fuel to the mixing device.
3. Mixing devices ( carburetor, mono injection, injector) Is a mechanism in which fuel and air (emulsion) are combined for further supply to the cylinders at (intake stroke).
4. The control unit for the operation of the mixture formation device (injection power systems) is a complex electronic device for controlling the operation fuel injectors, cut-off valves, control sensors.
5. A fuel pump, usually a submersible pump, is designed to pump fuel into the fuel line. It is an electric motor connected to a liquid pump in a sealed case. Lubricated directly with fuel and long-term operation with a minimum amount of fuel, leads to engine failure... In some engines, the fuel pump is attached directly to the engine and is driven by rotation intermediate shaft, or camshaft.
6. Additional coarse and fine filters... Installed filter elements in the fuel supply chain.

How the fuel system works

Let's consider the operation of the entire system as a whole. Fuel from the tank is sucked in by the pump and is fed through the fuel line through the cleaning filters to the mixture formation device. In the carburetor, the fuel enters the float chamber, where it is then fed through calibrated jets to the mixture formation chamber. Having mixed with air, the mixture enters the intake manifold through the throttle valve. After opening the intake valve, it is fed into the cylinder. IN mono injection system fuel is supplied to the injector, which is controlled electronic unit... At the right time, the nozzle opens and the fuel enters the mixture formation chamber, where, as in carburetor system mixes with air. Further, the process is the same as in the carburetor.

IN injection system fuel is supplied to the injectors, which are opened by control signals from the control unit. The injectors are interconnected by a fuel line, which always contains fuel. In all fuel systems there is a return fuel line, through which excess fuel is drained into the tank.

Supply system diesel engine similar to gasoline. True, fuel is injected directly into the combustion chamber of the cylinder, under high pressure. Mixing takes place in the cylinder. A high pressure pump (high pressure fuel pump) is used to supply fuel under high pressure.