How does an injector and fuel injection system work? - "What is fuel injection" What is the injection system

Modern cars are equipped with different fuel injection systems. In gasoline engines, a mixture of fuel and air is forcibly ignited by a spark.

The fuel injection system is an integral part. The injector is the main working element of any injection system.

Gasoline engines are equipped with injection systems, which differ from each other in the way that a mixture of fuel and air is formed:

central injection systems;
multipoint injection systems;
direct injection systems.

Central injection, or otherwise it is called monojetronic, is carried out by a single central electromagnetic injector, which injects fuel into the intake manifold. It is a bit like a carburetor. Now cars with such an injection system are not produced, since a car with such a system also has low environmental properties of the car.

The multipoint injection system has been continuously improved over the years. The system started K-jetronic... The injection was mechanical, which gave it good reliability, but the fuel consumption was quite high. Fuel was supplied not impulsively, but constantly. This system was replaced by the system KE-jetronic.

She was not fundamentally different from K-jetronic, but an electronic control unit (ECU) appeared, which made it possible to slightly reduce fuel consumption. But this system did not bring the expected results either. The system appeared L-jetronic.

In which the ECU received signals from sensors and sent an electromagnetic pulse to each injector. The system had good economic and environmental performance, but the designers did not stop there, and developed a completely new system Motronic.

The control unit began to control both the fuel injection and the ignition system. The fuel burns better in the cylinder, the engine power has increased, the consumption and harmful emissions of the car have decreased. In all these systems presented above, injection is carried out by a separate nozzle for each cylinder into the intake manifold, where a mixture of fuel and air is formed, which enters the cylinder.

The most promising system today is the direct injection system.

The essence of this system is that fuel is injected directly into the combustion chamber of each cylinder, and already there it mixes with air. The system determines and delivers the optimal mixture composition to the cylinder, which provides good power at various engine operating modes, good economy and high environmental properties of the engine.

But on the other hand, engines with this injection system have a higher price than their predecessors, due to the complexity of their design. Also, this system is very demanding on the quality of the fuel.

The main disadvantage Vehicle staffed by gasoline engines with a carburetor - the fuel in them does not burn completely. Since by operational characteristics fuel supply is determined by environmental friendliness, power, efficiency of the machine, there is a need for devices that regulate this process, focusing on the mode of operation.

Such units are called injection systems. In injection engines, fuel is delivered at a predetermined time in a predetermined dosage. Various fuel injection systems have been developed for gasoline and diesel engines.

Classification and structure of injection systems

The differences in injection mechanisms are determined by the method used to make a mixture of gasoline with air.

The classification is mainly carried out by the type of injection:

central injection;
distributive;
direct;
combined.

Central injection (single injection)

This system replaces the carburetor, operates on one injector. Mono injection is almost never used due to non-compliance with environmental standards, it is found on very old cars. But these mechanisms are simple and reliable due to the location of the nozzle in place with good air exchange, in the starting manifold.

Monosystem elements:

pressure regulator - prevents the formation of air congestion, provides a constant pressure of 0.1 MPa;
nozzle - provides gasoline supply to the manifold;
throttle(mechanical, electrical) - regulates the air supply;
control unit (memory, microprocessor) - contains information required for injection;
temperature sensors, condition of the crankshaft, throttle valve.

This type is more modern and environmentally friendly. Although, the only distinctive feature is that in this system there is already a separate nozzle for each cylinder. Only it is also mounted in the intake manifold, only each in its own separate branch pipe. Electronic systems control the dosage of fuel. The most progressive injectors in this regard belong to Bosch.

Direct injection

Gasoline is simultaneously supplied with air directly to the combustion chambers. The advantage of the direct injection system is the accurate calculation of the constituents for the fuel mixture. The percentage of environmentally hazardous emissions is reduced due to almost one hundred percent combustion of the fuel mixture.

Mechanism device with direct injection:

gasoline pump;
pressure regulating device;
ramp equipped with a safety valve;
a sensor displaying pressure parameters;
nozzles.

Disadvantages:

high requirements for the quality composition of the fuel;
complex design for manufacturers;
the need for a pressure of 5 MPa.

But injection systems of this type are the most modern and promising.

Combined injection

In order to reduce emissions and meet Euro 6 requirements, Volkswagen has developed a combined injection system, combining a distribution system with a direct one. Systems by the control unit are activated in turn, focusing on the operating mode. This power system is the most promising from the point of view of environmental safety.

The combined device consists of:

fuel supply pump;
parts of the direct mechanism (nozzles installed in the combustion chambers, a ramp that maintains a pressure of 20 MPa);
elements of the distribution system (nozzles installed in the manifold channels, low pressure ramps).

Principle of operation

Aggregates injection engine with a single nozzle they operate according to the following scheme:

the motor starts;
sensors read and transmit information to the control unit;
real data are compared with reference data, the moment of opening of the injector is calculated;
a signal is transmitted to the solenoid coil;
gasoline is supplied to the manifold for mixing with air;
the fuel mixture is supplied to the cylinders.

Distributed injection unit functioning:

the motor is supplied with air;
sensors determine the volume, temperature, crankshaft indicators, valve position;
the volume of fuel for the supplied air is calculated by the control unit;
a signal is given to the injectors;
they open at the programmed time.
mixing of gasoline with air takes place in the manifold, the mixture is fed into the cylinders.

Instructional video of the principle of operation of distributed injection

How direct injection works depends on method of mixing gasoline with air:

layer by layer;
stoichiometrically;
homogeneous.

Layered mixing is used at medium speed, the air flow rate is high, gasoline is fed into the cylinder through the nozzle, lights up after mixing with air.

When mixing stoichiometric type, the process starts at the moment you press the gas. The throttle valve opens, gasoline and air are supplied at the same time, they burn out completely.

When mixing homogeneous like, first, air movement in the cylinders is created, then gasoline is injected.

Video explanation of the principle of operation of the direct injection injector

The operation of the combined system is completely dependent on the load on the motor:

direct injection starts during start-up, warm-up, maximum load, the number of injections depends on the mode;
distributed injection is started while driving at medium speed with frequent stops.

With distributed injection, the direct nozzles are periodically opened. This prevents clogging.

Injection systems are equipped not only with gasoline, but also diesel engines... The first can be called spark motors, as the mixture of gasoline and air is ignited by a spark.

Major malfunctions

Most often, injection failures are manifested by several malfunctions:

the motor does not start (the main relay is faulty, the pump does not work, there is no voltage on the injectors);
works unstable cold engine(temperature sensor is faulty);
the motor does not work well at transitions (pump or nozzle is faulty);
the engine stalls (the fuel system is out of order, the air inlet is depressurized).

Advantages and disadvantages

Here, as in any system, there are advantages and disadvantages.

Pluses of injectors (when compared with the carburetor):

reduction of fuel consumption by 2 times;
increase in power;
simplified (automated) launch;
easy control;
reducing the release of toxins several times;
self-tuning, simplifying maintenance;
repair is reduced to the replacement of parts;
reducing the height of the hood due to the placement of injection elements on the sides of the engine;
independence from the pressure of the atmosphere, the position of the car (the work of the carburetors is disturbed during rolls).

Cons of injection systems:

relatively high production cost;
high requirements for the quality of gasoline;
the need for special equipment for diagnostics;
dependence on electricity;
increasing the likelihood of fire in an accident due to the supply of gasoline under pressure.

The last drawback is partially compensated by the installation of a controller that turns off the supply on impact.

Several types of injection systems made it possible to equip most passenger cars released after the eighties. The control is mechanical or electronic, fuel can be supplied continuously or in pulses.

Regardless of the structure and principle of operation of the fuel injection system, it will last longer without repair, if you refuse to manipulate the power supply, do not disconnect the mass unnecessarily, do not start by towing. Injection systems do not tolerate moisture, if water penetrates into them in winter, there is a high probability of failure of the nozzles. The fuel must be clean, special attention should be paid to the condition of the filter installed in front of the pump. In the presence of impurities in the fuel, the pump and control system fail very soon.

Direct injection (also used the term "direct injection", or GDI) began to appear on cars not so long ago. However, the technology is gaining popularity and is increasingly found on the engines of new cars. Today we will try to answer in general terms, what is direct injection technology and is it worth it to be afraid?

To begin with, it should be noted that the main distinguishing feature of the technology is the location of the nozzles, which are located directly in the cylinder head, respectively, and the injection under enormous pressure occurs directly into the cylinders, in contrast to the long-established better side fuel into the intake manifold.

Direct injection was first tested in series production by the Japanese automaker Mitsubishi. Operation has shown that among the advantages, the main advantages are efficiency - from 10% to 20%, power - plus 5% and environmental friendliness. The main disadvantage is that the injectors are extremely demanding on the quality of the fuel.

It is also worth noting that a similar system has been successfully installed on. However, it was on gasoline engines the application of the technology was fraught with a number of difficulties that have not yet been finally resolved.

A video from the YouTube channel "Savagegeese" explains what direct injection is and what can go wrong when using a vehicle with this system. In addition to the main pros and cons, the video also explains the intricacies of preventive system maintenance. In addition, the video touches on the topic of intake injection systems, which can be observed in abundance on older engines, as well as those that use both methods of fuel injection. Using Bosch diagrams, the presenter explains how it all works.

To find out all the nuances, we suggest watching the video below (turning on the translation of subtitles will help you figure it out if you don't know English very well). For those who are not too interested in watching, you can read about the main pros and cons of direct petrol injection below, after the video:

So, environmental friendliness and economy are good goals, but here is what the use of modern technology in your car is fraught with:

Minuses

1. A very complex structure.

2. Hence follows the second important problem... Since the young gasoline technology implies major changes in the design of the engine cylinder heads, the design of the injectors themselves and the concomitant change in other engine parts, for example, high pressure fuel pump (high pressure fuel pump), the cost of cars with direct fuel injection is higher.

3. The production of the parts of the power system themselves must also be extremely precise. The nozzles develop a pressure of 50 to 200 atmospheres.

Add to this the work of the injector in close proximity to the combustible fuel and the pressure inside the cylinder and you have the need to produce very high strength components.

4. Since the nozzles of the injectors face the combustion chamber, all gasoline combustion products are also deposited on them, gradually clogging or disabling the injector. This is perhaps the most serious disadvantage of using the GDI construction in Russian realities.

5. In addition, it is necessary to very carefully monitor the condition of the engine. If oil burns out in the cylinders, the products of its thermal decomposition will quickly disable the nozzle, clog the intake valves, forming indelible deposits on them. Do not forget that classic injection with injectors located in the intake manifold cleans the intake valves well, washing them under pressure with fuel.

6. Expensive repairs and the need for preventive maintenance, which is also expensive.

In addition, it also explains that improper use on direct injection vehicles can cause valve clogging and performance degradation, especially on turbocharged engines.

V modern cars in gasoline power plants the principle of operation of the power supply system is similar to that used on diesel engines. In these engines, it is divided into two - intake and injection. The first provides air and the second supplies fuel. But due to the design and operational features, the functioning of the injection is significantly different from that used on diesel engines.

Note that the difference in the injection systems of diesel and gasoline engines is increasingly erased. To receive best qualities designers borrow design solutions and apply them to different types power systems.

The device and principle of operation of the injection injection system

The second name for injection systems for gasoline engines is injection. Its main feature is the precise dosage of fuel. This is achieved by using injectors in the design. Device injection injection the engine includes two components - executive and control.

The task of the executive part includes the supply of gasoline and its spraying. It includes not so many constituent elements:

Pump (electric).
Filter element (fine cleaning).
Fuel lines.
Ramp.
Injectors.

But these are only the main components. The executive component may include a number of additional units and parts - a pressure regulator, a system for draining excess gasoline, an adsorber.

The task of these elements is to prepare the fuel and ensure its supply to the injectors, which are used to inject them.

The principle of operation of the executive component is simple. When the ignition key is turned (on some models, when the driver's door is opened), an electric pump turns on, which pumps gasoline and fills the rest of the elements with it. The fuel is cleaned and enters the rail through the fuel lines, which connects the injectors. Due to the pump, the fuel in the entire system is under pressure. But its value is lower than on diesel engines.

The injectors are opened by electrical impulses supplied from the control part. This component of the fuel injection system consists of a control unit and a whole set of tracking devices - sensors.

These sensors track indicators and parameters of work - rotation speed crankshaft, amount of air supplied, coolant temperature, throttle position. The readings are sent to the control unit (ECU). He compares this information with the data stored in the memory, on the basis of which the length of the electrical impulses supplied to the injectors is determined.

The electronics used in the control part of the fuel injection system are needed to calculate the time for which the nozzle should open in a particular mode of operation of the power unit.

Types of injectors

But note that this is the general design of the gasoline engine supply system. But several injectors have been developed, and each of them has its own design and operating features.

On cars, engine injection systems are used:

central;
distributed;
direct.

The central injection is considered the first injector. Its peculiarity lies in the use of only one injector, which injected gasoline into the intake manifold at the same time for all cylinders. Initially, it was mechanical and no electronics were used in the design. If we consider the device of a mechanical injector, then it is similar to a carburetor system, with the only difference that a mechanically driven injector was used instead of a carburetor. Over time, the central feed was made electronic.

Now this type is not used due to a number of disadvantages, the main of which is the uneven distribution of fuel over the cylinders.

Distributed injection is currently the most common system. The design of this type of injector is described above. Its peculiarity lies in the fact that the fuel for each cylinder is supplied by its own injector.

In this type of design, the injectors are installed in the intake manifold and are located next to the cylinder head. The distribution of fuel among the cylinders makes it possible to ensure an accurate dosage of gasoline.

Direct injection is currently the most advanced type of gasoline delivery. In the previous two types, gasoline was fed into the passing air stream, and mixture formation began to take place even in the intake manifold. The design of the same injector copies the diesel injection system.

In a direct injection injector, the injector nozzles are located in the combustion chamber. As a result, the components of the air-fuel mixture are fed into the cylinders separately, and they are mixed in the chamber itself.

The peculiarity of this injector is that high fuel pressure is required to inject gasoline. And its creation is provided by another unit added to the device of the executive part - a high-pressure pump.

Diesel engine power systems

And diesel systems are being upgraded. If earlier it was mechanical, now diesel engines are equipped with electronic control... It uses the same sensors and control unit as the gasoline engine.

Three types of diesel injections are currently used on cars:

With distribution injection pump.
Common Rail.
Unit injectors.

As in gasoline engines, the diesel injection design consists of an executive and a control part.

Many elements of the executive part are the same as those of the injectors - the tank, fuel lines, filter elements. But there are also nodes that are not found on gasoline engines - a fuel priming pump, a high-pressure fuel pump, high-pressure fuel lines.

In mechanical systems of diesel engines, in-line injection pumps were used, in which the fuel pressure for each nozzle was created by its own separate plunger pair. These pumps were highly reliable, but bulky. The injection moment and the amount of injected diesel fuel were regulated by a pump.

In engines equipped with a distribution injection pump, only one plunger pair is used in the pump design, which pumps fuel for the injectors. This node is compact in size, but its resource is lower than in-line ones. Such a system is used only in light vehicles.

Common Rail is considered one of the most efficient diesel engine injection systems. Its general concept is largely borrowed from the split-feed injector.

In such a diesel engine, the moment of the beginning of the supply and the amount of fuel is "in charge" of the electronic component. The task of the high pressure pump is only to pump diesel fuel and create high pressure. Moreover, diesel fuel is not supplied immediately to the injectors, but to the ramp connecting the injectors.

Unit injectors are another type of diesel injection. In this design, the high pressure fuel pump is absent, and the plunger pairs that create the diesel fuel pressure enter the injector device. This design solution allows you to create the highest fuel pressure values among the existing types of injection on diesel units.

Finally, we note that information on the types of injection of engines is given here in general. To understand the design and features of these types, they are considered separately.

Video: Fuel injection system control

The direct fuel injection system in gasoline engines is by far the most advanced and modern solution. The main feature of direct injection is that the fuel is fed directly into the cylinders.

For this reason this system also often referred to as direct fuel injection. In this article, we will look at how a direct fuel injection engine works, as well as what advantages and disadvantages such a scheme has.

Read in this article

Direct fuel injection: design of a direct injection system

As mentioned above, the fuel in these is supplied directly to the combustion chamber of the engine. This means that the injectors do not spray gasoline into, after which the fuel-air mixture enters the cylinder through it, and injects fuel directly into the combustion chamber.

The first gasoline engines with direct injection steel. In the future, the scheme became widespread, as a result of which today with such a fuel supply system can be found in the lineup of many well-known car manufacturers.

For example, the VAG concern presented a number of Audi models and Volkswagen with naturally aspirated and turbocharged engines, which received direct fuel injection. Direct injection engines are also produced by BMW, Ford, GM, Mercedes and many others.

Direct fuel injection is so widespread thanks to high efficiency systems (about 10-15% compared to distributed injection), as well as more complete combustion of the working mixture in the cylinders and a decrease in the level of toxicity of exhaust gases.

Direct injection system: design features

So let's take as an example FSI engine with its so-called "stratified" injection. The system includes the following elements:

high pressure circuit;
gasoline;
pressure regulator;
fuel rail;
high pressure sensor;
injection nozzles;

Let's start with the fuel pump. The specified pump creates high pressure, under which fuel is supplied to the fuel rail, as well as to the injectors. The pump has plungers (there can be several plungers or one in rotary-type pumps) and is driven from the inlet camshaft.

RTD (fuel pressure regulator) is integrated into the pump and is responsible for the metered fuel supply, which corresponds to the injection of the injector. The fuel rail (fuel rail) is needed in order to distribute fuel to the injectors. Also, the presence of this element allows you to avoid pressure surges (pulsations) of the fuel in the circuit.

By the way, the circuit uses a special safety valve, which is in the rail. The specified valve is needed in order to avoid too high fuel pressure and thereby protect individual elements of the system. An increase in pressure can occur due to the fact that the fuel tends to expand when heated.

A high pressure sensor is a device that measures the pressure in the fuel rail. The signals from the sensor are transmitted to, which, in turn, is able to change the pressure in the fuel rail.

As for the injector nozzle, the element ensures that fuel is supplied and atomized in the combustion chamber on time to create the required air-fuel mixture. Note that the described processes are controlled. The system has a group of various sensors, an electronic control unit, and actuators.

If we talk about a direct injection system, together with a high-pressure fuel sensor for its operation, the following are involved:, DPRV, an air temperature sensor in the intake manifold, a coolant temperature sensor, etc.

Thanks to the operation of these sensors, the necessary information is sent to the ECU, after which the unit sends signals to the actuators. This allows to achieve well-coordinated and accurate operation of solenoid valves, injectors, safety valve and a number of other elements.

How the direct fuel injection system works

The main advantage of direct injection is the ability to achieve different types mixture formation. In other words, such a power supply system is able to flexibly change the composition of the working fuel-air mixture, taking into account the operating mode of the engine, its temperature, the load on the internal combustion engine, etc.

It is necessary to highlight layer-by-layer mixture formation, stoichiometric, as well as homogeneous. It is this mixture formation that ultimately allows the most efficient fuel consumption. The mixture always turns out to be of high quality, regardless of the mode ICE operation, gasoline burns fully, the engine becomes more powerful, while the toxicity of the exhaust is simultaneously reduced.

Layer-by-layer mixture formation is activated when the engine load is low or medium, and the crankshaft speed is low. To put it simply, in such modes, the mixture is somewhat leaner in order to save money. Stoichiometric mixing involves the preparation of a mixture that is highly flammable without being too rich.
Homogeneous mixture formation allows to obtain the so-called "power" mixture, which is needed at high engine loads. On a lean homogeneous mixture for additional savings power unit works in transient modes.
When stratified mode is engaged, the throttle valve is wide open with the intake flaps closed. Air is fed into the combustion chamber at a high speed, and air currents arise. Fuel is injected towards the end of the compression stroke and is injected into the spark plug area.

A short time before the spark appears on the spark plug, a fuel-air mixture is formed, in which the excess air ratio is 1.5-3. The mixture is then ignited by a spark, while a sufficient amount of air is retained around the ignition zone. This air acts as a temperature "insulator".

If we consider homogeneous stoichiometric mixture formation, such a process occurs when the intake valves are open, while the throttle valve is also open to one or another angle (depending on the degree of pressing the accelerator pedal).

In this case, fuel is injected during the intake stroke, as a result of which a homogeneous mixture is obtained. Excess air has a coefficient close to unity. Such a mixture is highly flammable and fully burns throughout the entire volume of the combustion chamber.

A lean homogeneous mixture is created when the throttle valve is fully open and the intake flaps are closed. In this case, air actively moves in the cylinder, and fuel injection occurs at the intake stroke. The ECM maintains excess air at 1.5.

Exhaust gases can be added to the clean air. This is due to work. As a result, the exhaust “burns out” again in the cylinders without damaging the engine. At the same time, the level of emission of harmful substances into the atmosphere is reduced.

What is the bottom line

As you can see, direct injection allows you to achieve not only fuel economy, but also a good return from the engine both in low and medium and high load modes. In other words, the presence of direct injection means that the optimal composition of the mixture will be maintained at all operating modes of the internal combustion engine.

As for the disadvantages, the disadvantages of direct injection include only the increased complexity during the repair and the price of spare parts, as well as the high sensitivity of the system to the quality of fuel and the condition of the fuel and air filters.