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Fuel pump danfoss. The device of high and low pressure fuel pumps. Single plunger pump with electronic control

Used on a variety of types of transport and equipment, it is based on the combustion of the fuel-air mixture and the energy released as a result of this process. But in order for the power plant to function, fuel must be supplied in portions at strictly defined moments. And this task lies with the power supply system included in the design of the motor.

Engine fuel supply systems are made up of a number of components, each with a different task. Some of them filter the fuel, removing contaminants from it, others meter and supply it to the intake manifold or directly to the cylinder. All these elements perform their function with the fuel that still needs to be supplied to them. And this is provided by the fuel pumps used in the designs of the systems.

Complete pump

Like any liquid pump, the task of the assembly used in the design of the motor is to pump fuel into the system. Moreover, almost everywhere it is necessary that it be supplied under a certain pressure.

Fuel pump types

Different types of engines use their own types of fuel pumps. But in general, all of them can be divided into two categories - low and high pressure. Which node to use depends on design features and the principle of operation of the power plant.

So, for gasoline engines, since the flammability of gasoline is much higher than diesel fuel, and at the same time the fuel-air mixture from a third-party source ignites, high pressure in the system is not required. Therefore, low pressure pumps are used in the design.

Gasoline engine pump

But it is worth noting that in the latest generation gasoline injection systems, fuel is supplied directly to the cylinder (), so gasoline must already be supplied at high pressure.

As for diesel engines, their mixture ignites under the influence of pressure in the cylinder and temperature. In addition, the fuel itself has direct injection into the combustion chambers, therefore, in order for the nozzle to be able to inject it, significant pressure is needed. And for this, a high-pressure pump (TNVD) is used in the design. But we note that it was not possible to do without the use of a low-pressure pump in the design of the power system, since the high-pressure fuel pump itself cannot pump fuel, because its task is only to compress and supply to the nozzles.

All used pumps on power plants different types can also be divided into mechanical and electrical. In the first case, the assembly is powered by a power plant (a gear drive is used or from shaft cams). As for the electric ones, they are driven by their electric motor.

More specifically, on gasoline engines, power systems use only low-pressure pumps. And only in the direct injection injector there is a high-pressure fuel pump. At the same time, in carburetor models, this unit had a mechanical drive, but in injection models, electrical elements are used.

Mechanical fuel pump

In diesel engines, two types of pumps are used - low pressure, which pumps fuel, and high pressure, which compresses diesel fuel before it enters the nozzles.

The diesel fuel priming pump is usually mechanically driven, although there are also electric models. As for the high-pressure fuel pump, it is put into operation from the power plant.

The difference in pressure generated between low and high pressure pumps is very striking. So, for the operation of the injection power system, only 2.0-2.5 bar is enough. But this is the working pressure range of the injector itself. The fuel pumping unit, as usual, provides it with a little excess. So, the pressure of the fuel injector pump varies from 3.0 to 7.0 bar (depending on the type and condition of the element). As for carburetor systems, gasoline is supplied there with practically no pressure.

But in diesel engines, very high pressure is needed to supply fuel. If we take the latest generation Common Rail system, then in the “high-pressure fuel pump-injector” circuit, diesel fuel pressure can reach 2200 bar. Therefore, the pump is powered by a power plant, since it requires a lot of energy to operate, and it is not advisable to install a powerful electric motor.

Naturally, the operating parameters and the pressure generated affect the design of these units.

Types of gasoline pumps, their features

We will not disassemble the device of the gasoline pump of the carburetor engine, since such a power system is no longer used, and structurally it is very simple, and there is nothing special about it. But the electric fuel injection pump should be considered in more detail.

It should be noted that different machines use different types fuel pumps, differing in design. But in any case, the assembly is divided into two components - mechanical, which provides fuel injection, and electrical, which drives the first part.

Pumps can be used on injection vehicles:

  • vacuum;
  • roller;
  • Gear;
  • centrifugal;

Rotary pumps

And the difference between them basically comes down to the mechanical part. And only the device of the vacuum type fuel pump is completely different.

Vacuum

The operation of the vacuum pump is based on a conventional gasoline pump of a carburetor engine. The only difference is in the drive, but the mechanical part itself is almost identical.

There is a membrane dividing the working module into two chambers. In one of these chambers there are two valves - inlet (connected with a channel to the tank) and outlet (leading to the fuel line that supplies fuel further to the system).

This membrane, during translational movement, creates a vacuum in the chamber with valves, which leads to the opening of the inlet element and the pumping of gasoline into it. During reverse movement, the intake valve closes, but the exhaust valve opens and the fuel is simply pushed into the line. In general, everything is simple.

As for the electrical part, it works on the principle of a solenoid relay. That is, there is a core and a winding. When voltage is applied to the winding, the magnetic field that arises in it draws in the core associated with the membrane (its translational movement occurs). As soon as the voltage disappears, the return spring returns the diaphragm to its original position (return movement). The supply of impulses to the electrical part is controlled by the electronic control unit of the injector.

Roller

As for the other types, their electrical part is, in principle, identical and is a conventional electric motor direct current, powered by a 12 V network. But the mechanical parts are different.

Roller fuel pump

In a roller type pump, the working elements are a rotor with grooves made in which the rollers are installed. This design is placed in a housing with an internal cavity of complex shape, having chambers (inlet and outlet, made in the form of grooves and connected to the supply and exhaust lines). The essence of the work boils down to the fact that the rollers simply distill gasoline from one chamber to the second.

gear

The gear type uses two gears mounted one inside the other. The inner gear is smaller and moves along the path of the eccentric. Due to this, there is a chamber between the gears, in which fuel is captured from the supply channel and pumped into the exhaust channel.

Gear pump

centrifugal type

Roller and gear types of electric gasoline pumps are less common than centrifugal, they are also turbine.

Centrifugal pump

This type of fuel pump device includes an impeller with a large number of blades. When rotating, this turbine creates a swirl of gasoline, which ensures its suction into the pump and further pushing into the line.

We examined the arrangement of fuel pumps in a slightly simplified way. Indeed, in their design there are additional intake and pressure reducing valves, the task of which is to supply fuel in only one direction. That is, gasoline that has entered the pump can only return to the tank along the return line, passing through all the constituent elements of the power system. Also, the task of one of the valves includes locking and stopping the injection under certain conditions.

Turbine pump

As for high-pressure pumps used in diesel engines, the principle of operation is radically different there, and you can learn more about such components of the power system here.

The fuel pump (abbreviated as high pressure fuel pump) is designed to perform the following functions - supplying a combustible mixture under high pressure to the internal combustion engine fuel system, as well as regulating its injection at certain points. That is why the fuel pump is considered the most important device for diesel and petrol engines.

Mostly injection pumps are used, of course, in diesel engines. And in gasoline engines, high-pressure fuel pumps are found only in those units that use a direct fuel injection system. At the same time, the pump in a gasoline engine works with a much lower load, since such a high pressure as in a diesel engine is not required.

The main structural elements of the fuel pump are a plunger (piston) and a cylinder (sleeve) of small size, which are combined into a single plunger system (pair) made of high-strength steel with great accuracy.

In fact, the manufacture of a plunger pair is a rather difficult task, requiring special high-precision machines. For the whole Soviet Union there was, if memory serves, only one factory where plunger pairs were made.

How plunger pairs are made in our country today can be seen in this video:

A very small gap is provided between the plunger pair, the so-called precision mating. This is perfectly shown in the video when the plunger enters the cylinder very smoothly, hovering under its own weight.

So, as we said earlier, the fuel pump is used not only for the timely supply of a combustible mixture to the fuel system, but also for distributing it through the nozzles into the cylinders in accordance with the type of engine.

The nozzles are the link in this chain, so they are connected to the pump by pipelines. The nozzles are connected to the combustion chamber by the lower spray part, equipped with small holes for efficient fuel injection with its further ignition. The advance angle allows you to determine the exact moment of injection of the vehicle into the combustion chamber.

Fuel pump types

Depending on the design features, there are three main types of injection pumps - distribution, in-line, main.

Inline injection pump

This type of high pressure fuel pump is equipped with plunger pairs located next to each other (hence the name). Their number strictly corresponds to the number of working cylinders of the engine.

Thus, one plunger pair supplies fuel to one cylinder.

The vapors are installed in the pump housing, which has inlet and outlet channels. The plunger is started using a camshaft, connected, in turn, to the crankshaft, from which rotation is transmitted.

The camshaft of the pump, when rotated by the cams, acts on the pushers of the plungers, forcing them to move inside the pump bushings. In this case, the inlet and outlet openings are opened and closed alternately. When the plunger moves up the sleeve, the pressure necessary to open the delivery valve is created, through which fuel under pressure is directed through the fuel line to a specific nozzle.

The moment of fuel supply and the adjustment of its amount required at a particular point in time can be carried out either using a mechanical device or using electronics. Such an adjustment is needed to adjust the fuel supply to the engine cylinders depending on the crankshaft speed (engine speed).

Mechanical control is provided through the use of a special centrifugal type clutch, which is mounted on the cam shaft. The principle of operation of such a clutch lies in the weights that are inside the clutch and have the ability to move under the action of centrifugal force.

The centrifugal force changes with an increase (or decrease) in the engine speed, due to which the weights either diverge towards the outer edges of the coupling, or again approach the axis. This leads to a displacement of the camshaft relative to the drive, due to which the operating mode of the plungers changes and, accordingly, with an increase in the engine speed, early fuel injection is provided, and late, as you guessed, with a decrease in speed.

In-line fuel pumps are very reliable. They are lubricated by engine oil coming from the engine lubrication system. They are absolutely not picky about the quality of fuel. To date, the use of such pumps due to their bulkiness is limited to medium and heavy trucks. Until about 2000, they were also used on passenger diesel engines.

Distribution injection pump

Unlike an in-line high-pressure pump, a distribution high-pressure fuel pump can have either one or two plungers, depending on the engine size and, accordingly, the required amount of fuel.

And these one or two plungers serve all the engine cylinders, which can be 4, 6, 8, and 12. uniform fuel supply.

The main disadvantage of this type of pumps is their relative fragility. Distribution pumps are only installed in cars.

Distribution injection pump can be equipped with various types of plunger drives. All these types of drive are cam and are: end, internal, external.

The most efficient are face and internal drives, which are devoid of loads created by fuel pressure on the drive shaft, as a result of which they last somewhat longer than pumps with an external cam drive.

By the way, it is worth noting that the imported pumps from Bosch and Lucas, which are most often used in the automotive industry, are equipped with an end and internal drive, and domestically produced pumps of the ND series have an external drive.

Face cam drive

In this type of drive, used in Bosch VE pumps, the main element is the distribution plunger, designed to create pressure and distribute fuel in the fuel cylinders. In this case, the distributor plunger performs rotational and reciprocating movements during rotational movements of the cam.

The reciprocating movement of the plunger is carried out simultaneously with the rotation of the cam, which, relying on the rollers, moves along the fixed ring along the radius, that is, it runs around it, as it were.

The impact of the washer on the plunger provides high fuel pressure. The return of the plunger to its original state is carried out thanks to the spring mechanism.

The distribution of fuel in the cylinders occurs due to the fact that the drive shaft provides the rotational movement of the plunger.

The amount of fuel supply can be provided by an electronic (solenoid valve) or mechanical (centrifugal clutch) device. Adjustment is carried out by turning a fixed (not rotating) adjusting ring by a certain angle.

The cycle of the pump operation consists of the following stages: pumping a portion of fuel into the space above the plunger, pressurizing due to compression and distributing the fuel over the cylinders. Then the plunger returns to its original position and the cycle repeats again.

Internal cam drive

The internal drive is used in distribution injection pumps of rotary type, for example, in pumps Bosch VR, Lucas DPS, Lucas DPC. In this type of pump, the supply and distribution of fuel is carried out through two devices: a plunger and a distribution head.

The camshaft is equipped with two oppositely located plungers, which provide the fuel injection process, the smaller the distance between them, the higher the fuel pressure. After pressurizing, the fuel rushes to the injectors through the channels of the distributor head through the delivery valves.

The fuel supply to the plungers is provided by a special booster pump, which may differ depending on the type of its design. It can be either a gear pump or a rotary vane pump. The booster pump is located in the pump housing and is driven by a drive shaft. Actually, it is installed right on this shaft.

We will not consider a distribution pump with an external drive, since, most likely, their star is close to sunset.

Main injection pump

This type of fuel pump is used in the Common Rail fuel supply system, in which the fuel first accumulates in the fuel rail before it reaches the injectors. The main pump is able to provide high fuel supply - over 180 MPa.

The main pump can be one-, two- or three-plunger. The plunger drive is provided by a cam washer or a shaft (also cam, of course), which perform rotational movements in the pump, in other words, they spin.

At the same time, in a certain position of the cams, under the action of a spring, the plunger moves down. At this moment, the compression chamber expands, due to which the pressure in it decreases and a vacuum is formed, which causes the intake valve to open, through which fuel passes into the chamber.

Raising the plunger is accompanied by an increase in intra-chamber pressure and closing of the inlet valve. When the pressure to which the pump is set is reached, the exhaust valve opens, through which fuel is pumped into the rail.

In the main pump, the fuel supply process is controlled by a fuel metering valve (which opens or closes by the required amount) using electronics.

Like the human heart, the fuel pump circulates fuel through the fuel system. For gasoline engines, this role is performed by an electric fuel pump, and for diesel engines, a high-pressure fuel pump (TNVD).

This unit performs two functions: it pumps fuel into the nozzles in a strictly defined amount and determines the moment when it is injected into the cylinders. The second task is similar to changing the ignition timing for gasoline engines. However, since the introduction of battery injection systems, the injection timing is controlled by the electronics that control the injectors.

The main element of the high pressure fuel pump is a plunger pair. Its structure and principle of operation will not be considered in detail in this article. In short, the plunger pair is a long piston of small diameter (its length is several times greater than the diameter), and the working cylinder, very precisely and tightly fitted to each other, the gap is a maximum of 1-3 microns (for this reason, in the case failure, the whole pair changes). The cylinder has one or two inlet channels, through which fuel enters, which is then pushed out by a piston (plunger) through the exhaust valve.

The principle of operation of a plunger pair is similar to the operation of a two-stroke internal combustion engine. Moving down, the plunger creates a vacuum inside the cylinder and opens the intake port. Fuel, obeying the laws of physics, rushes to fill the rarefied space inside the cylinder. After that, the piston begins to rise. First, it closes the intake port, then raises the pressure inside the cylinder, as a result of which the exhaust valve opens, and fuel under pressure enters the nozzle.

Types of high pressure fuel pumps

There are three types of injection pumps, they have a different device, but one purpose:

  • in-line;
  • distributive;
  • trunk.

In the first of them, a separate plunger pair pumps fuel into each cylinder, respectively, the number of pairs is equal to the number of cylinders. The scheme of the high-pressure distribution fuel pump differs significantly from the in-line scheme. The difference lies in the fact that the fuel is pumped to all cylinders by means of one or more plunger pairs. The main pump pumps fuel into the accumulator, from which it is subsequently distributed among the cylinders.

In cars with gasoline engines, with a direct injection system, the fuel is pumped by an electric high-pressure fuel pump, but it (pressure) is many times less there.

In-line high pressure fuel pump

As already mentioned, it has plunger pairs according to the number of cylinders. Its device is quite simple. Pairs are placed in a housing, inside which there are underwater and outlet fuel channels. At the bottom of the housing is a camshaft driven by a crankshaft, the plungers are constantly pressed against the cams by springs.


The principle of operation of such a fuel pump is not very complicated. The cam, during rotation, runs into the plunger pusher, forcing it and the plunger to move up, compressing the fuel in the cylinder. After the outlet and inlet channels are closed (exactly in this sequence), the pressure begins to rise to a value after which the discharge valve opens, after which diesel fuel is supplied to the corresponding nozzle. This scheme resembles the operation of the gas distribution mechanism of the engine.

To regulate the amount of incoming fuel, and the moment of its supply, either a mechanical method or an electric one is used (such a scheme assumes the presence of control electronics). In the first case, the amount of fuel supplied is changed by turning the plunger. The scheme is very simple: it has a gear, it is engaged with a rack, which, in turn, is connected to the accelerator pedal. The upper surface of the plunger has a slope, due to which the closing moment of the inlet in the cylinder changes, and hence the amount of fuel.

The moment of fuel supply must be changed when the crankshaft speed changes. To do this, there is a centrifugal clutch on the cam shaft, inside which weights are located. With an increase in speed, they diverge, and the camshaft rotates relative to the drive. As a result, with an increase in speed, the fuel pump provides an earlier injection, and with a decrease - a later one.


The device of in-line injection pumps provides them with very high reliability and unpretentiousness. Since lubrication occurs with engine oil from the lubrication system of the power unit, this makes them suitable for operation on low-quality diesel fuel.

In-line injection pumps are installed on medium and heavy trucks. They were completely discontinued on passenger cars in 2000.

High pressure distribution fuel pump

Unlike the in-line fuel pump, the distribution pump has only one or two plunger pairs that supply fuel to all cylinders. The main advantages of such fuel pumps are lower weight and dimensions, as well as a more uniform fuel supply. The main disadvantage is one - their service life is much less due to the heavy load, so they are used only on cars.

There are three types of distribution injection pumps:

  1. with end cam drive;
  2. with internal cam drive (rotary pumps);
  3. with external cam drive.

The device of the first two types of pumps provides them with a longer service life, compared to the last, because there are no power loads on the drive shaft units, from fuel pressure, in them.

The scheme of operation of the distribution fuel pump of the first type is as follows. The main element is the distributor plunger, which, in addition to the forward-return movement, rotates around its axis, and thereby pumps and distributes fuel between the cylinders. It is driven by a cam that runs around a fixed ring on rollers.


The amount of incoming fuel is regulated both mechanically, using the centrifugal clutch described above, and by means of an electromagnetic valve, to which an electrical signal is applied. The fuel injection advance is determined by turning the fixed ring through a certain angle.

The rotary circuit assumes a slightly different arrangement of the distribution fuel pump. The operating conditions of such a pump are somewhat different from how the high pressure fuel pump works with a front cam drive. The fuel is pumped and distributed, respectively, by two opposing plungers and a distributor head. The rotation of the head ensures the redirection of fuel to the appropriate cylinders.

Main injection pump

The main fuel pump drives fuel into the fuel rail and provides higher pressure compared to in-line and distribution pumps. The scheme of his work is somewhat different. Fuel can be pumped by one, two or three plungers driven by a cam or shaft.


The fuel supply is controlled by an electronic metering valve. The normal state of the valve is open, when an electrical signal is received, it partially closes and thereby regulates the amount of fuel entering the cylinders.

What is TNND

The low pressure fuel pump is required to supply fuel to the high pressure fuel pump. It is usually installed either on the injection pump housing or separately, and pumps fuel from the gas tank through coarse filters, and after fine filters, directly into the high pressure pump.

The principle of its work is the following. It is driven by an eccentric located on the camshaft of the injection pump. The pusher, pressed against the rod, causes the piston rod to move. The pump housing has inlet and outlet channels, which are blocked by valves.


The scheme of operation of TNND is as follows. The duty cycle of the low pressure fuel pump consists of two cycles. During the first, preparatory, the piston moves down and fuel is sucked into the cylinder from the tank, while the discharge valve is closed. When the piston moves upwards, the inlet channel is blocked by the suction valve, and under increasing pressure, the exhaust valve opens, through which the fuel enters the fine filter and then to the high-pressure fuel pump.

Since the low pressure fuel pump has a capacity greater than that required for the engine to work, therefore, part of the fuel is pushed into the cavity under the piston. As a result, the piston loses contact with the pusher and freezes. As the fuel runs out, the piston lowers again and the pump resumes operation.

Instead of a mechanical one, an electric low-pressure fuel pump can be installed on the car. Quite often it is found on machines that are equipped with Bosch pumps (Opel, Audi, Peugeot, etc.). An electric pump is installed only on cars and small minibuses. In addition to the main function, it serves to stop the supply of fuel in the event of an accident.

The electric injection pump starts working simultaneously with the starter and continues to pump fuel at a constant speed until the engine is turned off. Excess fuel is drained back to the tank through the bypass valve. An electric pump is placed either inside the fuel tank or outside it, between the tank and the fine filter.

Any car engine has a power system that ensures the mixing of the components of the combustible mixture and their supply to the combustion chambers. The design of the power system depends on what fuel the power plant runs on. But the most common is the unit that runs on gasoline.

In order for the power system to be able to mix the components of the mixture, it must also receive them from the container in which the gasoline is located - the fuel tank. And for this, a pump is included in the design, which provides the supply of gasoline. And it seems that this component is not the most important, but without its operation, the engine simply will not start, since gasoline will not flow into the cylinders.

Types of gasoline pumps and the principle of their operation

Two types of gasoline pumps are used on cars, which differ not only in design, but also in the place of installation, although they have one task - to pump gasoline into the system and ensure its supply to the cylinders.

According to the type of construction, gasoline pumps are divided into:

  1. Mechanical;
  2. Electrical.

1. Mechanical type

A mechanical type gas pump is used on. It is usually located on the head of the power plant block, since it is driven from the camshaft. The injection of fuel in it is carried out due to the vacuum created by the membrane.

Its design is quite simple - there is a membrane (diaphragm) in the body, which is spring-loaded from below and attached to the rod connected to the drive lever along the central part. In the upper part of the pump there are two valves - inlet and outlet, as well as two fittings, one of them draws gasoline into the pump, and from the second it exits and enters the carburetor. The working area of ​​the mechanical type is the cavity above the membrane.

The fuel pump works according to this principle - there is a special eccentric cam on the camshaft that drives the pump. During engine operation, the shaft, rotating, acts on the pusher with the top of the cam, which presses the drive lever. That, in turn, pulls down the rod along with the membrane, overcoming the force of the spring. Because of this, a vacuum is created in the space above the membrane, due to which the intake valve opens and gasoline is pumped into the cavity.

Video: How the fuel pump works

As soon as the shaft turns, the spring returns the pusher, drive lever and diaphragm together with the stem. Because of this, pressure rises in the cavity above the membrane, due to which the inlet valve closes and the outlet valve opens. The same pressure pushes the gasoline out of the cavity and into the outlet port and it flows into the carburetor.

That is, all the work of a mechanical type of non-pump is built on pressure drops. But we note that the entire carburetor power system does not require a lot of pressure, therefore the pressure that the mechanical fuel pump creates is small, the main thing is that this assembly provides the necessary amount of gasoline in the carburetor.

The fuel pump runs continuously as long as the engine is running. When the power unit stops, the supply of gasoline stops, since the pump also stops pumping. To ensure that there is enough fuel to start the engine and operate it until the system is filled due to vacuum, there are chambers in the carburetor into which gasoline is poured even during the previous operation of the engine.

2. Electric fuel pump, their types

In injection fuel systems, gasoline is injected by injectors, and for this it is necessary that the fuel comes to them already under pressure. Therefore, the use of a mechanical type pump is not possible here.

An electric fuel pump is used to supply gasoline to the fuel injection system. Such a pump is located in the fuel line or directly in the tank, which ensures that gasoline is pumped under pressure into all components of the power system.

Let's mention a little the most modern injection system - with direct injection. It works on the principle of a diesel system, that is, gasoline is injected directly into the cylinders at high pressure, which a conventional electric pump cannot provide. Therefore, in such a system, two nodes are used:

  1. The first of them is electric, installed in the tank, and it ensures the filling of the system with fuel.
  2. The second pump is a high pressure pump (TNVD), has a mechanical drive and its task is to provide significant fuel pressure before supplying it to the nozzles.

But we will not consider high-pressure fuel pumps for now, but we will go through conventional electric gasoline pumps, which are located either near the tank and are cut into the fuel line, or are installed directly into the tank.

Video: Gasoline pump, check-test

There are a large number of species, but three types are most widespread:

  • rotary roller;
  • gear;
  • centrifugal (turbine);

Rotary roller electric pump refers to pumps that are installed in the fuel line. Its design includes an electric motor, on the rotor of which a disk with rollers is installed. All this is placed in the holder of the supercharger. Moreover, the rotor is slightly offset in relation to the supercharger, that is, there is an eccentric arrangement. Also, the supercharger has two outlets - through one gasoline enters the pump, and through the second it exits.

It works like this: when the rotor rotates, the rollers pass through the inlet area, due to which a vacuum is formed and gasoline is pumped into the pump. Its rollers are captured and transferred to the outlet zone, but due to the eccentric arrangement, the fuel is compressed, which is how the pressure is achieved.

Due to the eccentric movement, a gear-type pump also works, which is also installed in the fuel line. But instead of a rotor and a supercharger, it has two internal gears in its design, that is, one of them is placed inside the second. In this case, the internal gear is the leading one, it is connected to the electric motor shaft and is offset relative to the second - the driven one. During operation of such a pump, fuel is pumped by gear teeth.

But on a car, a centrifugal electric fuel pump is most often used, which is installed directly in the tank, and the fuel line is already connected to it. Its fuel supply is carried out by an impeller having a large number blades and placed inside a special chamber. During the rotation of this impeller, turbulences are created that contribute to the suction of gasoline and its compression, which provides pressure before it enters the fuel line.

These are simplified diagrams of the most common electric fuel pumps. In fact, their design includes valves, contact systems for connecting to the on-board network, etc.

Note that already during the start of the injection power plant, fuel under pressure should already be in the system. Therefore, the electric fuel pump is controlled by the electronic control unit, and it is turned on before the starter is activated.

The main malfunctions of the fuel pump

Video: When the fuel pump "gets sick"

All gasoline pumps have a fairly long service life due to a relatively simple design.

In mechanical assemblies, problems are rare at all. They occur most often due to a rupture of the membrane or wear of the drive elements. In the first case, the pump stops pumping fuel altogether, and in the second case, it does not supply enough fuel.

Checking such a gasoline pump is not difficult, just remove the top cover and assess the condition of the membrane. You can also disconnect the fuel line from the carburetor from the assembly, lower it into a container and start the engine. In a serviceable element, fuel is supplied in uniform portions by a sufficiently powerful jet.

In injection engines, a malfunction of the electric fuel pump has certain signs - the car does not start well, a drop in power is noticeable, and interruptions in the operation of the engine are possible.

Of course, such signs can cause malfunctions in different systems, so additional diagnostics will be required in which the pump performance is checked by measuring pressure.

But the list of malfunctions due to which this node does not work correctly is not so much. So, the pump may stop working due to severe and systematic overheating. This happens due to the habit of pouring small portions of gasoline into the tank, because the fuel acts as a coolant for this unit.

Refueling with low-quality fuel can easily lead to malfunctions. The impurities and foreign particles present in such gasoline, getting inside the assembly, lead to increased wear of it. constituent parts.

Problems can also arise through the electrical part. Oxidation of the wiring and its damage can lead to the fact that insufficient energy is supplied to the pump.

Note that most of the malfunctions that occur due to damage or wear to the components of the fuel pump are difficult to eliminate, so often if it fails, it is simply replaced.

In the previous series of articles on the structure of the fuel system of a gasoline engine, the topic of a high-pressure fuel pump for a diesel engine and gasoline engines with direct (direct) fuel injection was touched upon more than once.

This article is a separate material that describes the design of a high-pressure diesel fuel pump, its purpose, potential malfunctions, the scheme and principles of operation using the example of a device for such a fuel supply system for this type. So, let's get straight to the point.

Read in this article

What is TNVD?

The high pressure fuel pump is abbreviated as . This device is one of the most complex in the design of a diesel engine. The main task of such a pump is the supply of diesel fuel under high pressure.

Pumps provide fuel supply to the cylinders of a diesel engine under a certain pressure, and also strictly at a certain moment. The portions of the supplied fuel are measured very accurately and correspond to the degree of load on the engine. High pressure fuel pumps are distinguished by the injection method. There are direct acting pumps as well as accumulator injection pumps.

Direct acting fuel pumps have a mechanical plunger drive. The processes of injection and injection of fuel proceed at the same time. A certain section of the high-pressure fuel pump delivers the required dose of fuel to each individual cylinder of a diesel engine. The pressure required for effective atomization is generated by the movement of the fuel pump plunger.

High pressure fuel pump with battery injection is different in that the drive of the working plunger is affected by the pressure forces of compressed gases in the cylinder of the internal combustion engine itself or the impact is exerted by means of springs. There are fuel pumps with a hydraulic accumulator, which are used in powerful low-speed diesel internal combustion engines.

It should be noted that hydraulic accumulator systems are characterized by separate injection and injection processes. High-pressure fuel is pumped by the fuel pump into the accumulator, and only then it enters the fuel injectors. This approach provides efficient atomization and optimal mixture formation, which is suitable for the entire range of loads on the diesel unit. The disadvantages of this system include the complexity of the design, which became the reason for the unpopularity of such a pump.

Modern diesel installations use a technology that is based on the control of the injector solenoid valves from an electronic control unit with a microprocessor. This technology is called Common Rail.

The main causes of malfunctions

High pressure fuel pump is an expensive device that is very demanding on the quality of fuel and lubricants. If the car is operated on low quality fuel, such fuel necessarily contains particulate matter, dust, water molecules, etc. All this leads to failure of the plunger pairs, which are installed in the pump with a minimum tolerance, measured in microns.

Low-quality fuel easily disables the nozzles that are responsible for the process of spraying and fuel injection.

Common signs of malfunctions in the operation of the injection pump and injectors are the following deviations from the norm:

  • fuel consumption is markedly increased;
  • there is an increased opacity of the exhaust;
  • during operation there are extraneous sounds and noise;
  • power and output from the internal combustion engine drop noticeably;
  • there is a difficult start;

Modern engines with injection pumps are equipped with electronic system fuel injection. doses the fuel supply to the cylinders, distributes this process over time, determines the required amount of diesel fuel. If the owner notices the slightest interruption in the operation of the engine, then this is an immediate reason for immediately contacting the service. The power plant and fuel system are carefully examined using professional diagnostic equipment. During the diagnosis, specialists determine numerous indicators, among which the primary ones are:

  • the degree of uniformity of fuel supply;
  • pressure and its stability;
  • shaft speed;

Device evolution

The tightening of environmental regulations and requirements regarding the emission of harmful substances into the atmosphere has led to the fact that mechanical high-pressure fuel pumps for diesel vehicles began to be replaced by systems with electronic adjustment. The mechanical pump simply could not provide fuel dosing with the required high accuracy, and was also not able to respond as quickly as possible to dynamically changing engine operating modes.

  1. injection start sensor;
  2. crankshaft and TDC speed sensor;
  3. air flow meter;
  4. coolant temperature sensor;
  5. gas pedal position sensor;
  6. Control block;
  7. device for starting and warming up the internal combustion engine;
  8. device for controlling the exhaust gas recirculation valve;
  9. a device for controlling the fuel injection advance angle;
  10. device for controlling the drive of the dosing clutch;
  11. dispenser stroke sensor;
  12. fuel temperature sensor;
  13. high pressure fuel pump;

The key element in this system is the device for moving the injection pump metering sleeve (10). The control unit (6) controls the fuel supply processes. Information enters the unit from sensors:

  • injection start sensor, which is installed in one of the nozzles (1);
  • TDC and crankshaft speed sensor (2);
  • air flow meter (3);
  • coolant temperature sensor (4);
  • accelerator pedal position sensor (5);

The preset optimal characteristics are stored in the memory of the control unit. Based on the information from the sensors, the ECU sends signals to the mechanisms for controlling the cyclic feed and injection advance angle. This is how the amount of cyclic fuel supply is adjusted in various modes of operation of the power unit, as well as at the time of a cold start of the engine.

The actuators have a potentiometer that sends a feedback signal to the computer, which determines the exact position of the metering sleeve. The fuel injection advance angle is adjusted in a similar way.

The ECU is responsible for creating signals that provide regulation for numerous processes. The control unit stabilizes the speed in idling mode, regulates the exhaust gas recirculation with the determination of indicators based on the signals of the mass air flow sensor. The block compares real-time signals from sensors with those values ​​that are programmed in it as optimal. Next, the output signal from the ECU is transmitted to the servo mechanism, which ensures the required position of the metering sleeve. This achieves high accuracy regulation.

This system has a self-diagnosis program. This allows you to work out emergency modes to ensure movement vehicle even in the presence of a number of certain malfunctions. A complete failure occurs only when the computer microprocessor breaks down.

The most common cyclic flow control solution for a single plunger high pressure distributor type pump is to use an electromagnet (6). Such a magnet has a rotary core, the end of which is connected by means of an eccentric to a dosing sleeve (5). Electricity passes in the winding of the electromagnet, while the angle of rotation of the core can be from 0 to 60 °. This is how the metering sleeve (5) moves. This clutch ultimately regulates the cyclic supply of the injection pump.

Single plunger pump with electronic control

  1. injection pump;
  2. solenoid valve for controlling the automatic fuel injection advance;
  3. jet;
  4. injection advance cylinder;
  5. dispenser;
  6. electromagnetic device for changing the fuel supply;
  7. temperature sensor, boost pressure, position of the fuel supply regulator;
  8. control lever;
  9. fuel return;
  10. fuel supply to the nozzle;

The injection advance control is controlled by a solenoid valve (2). This valve regulates the fuel pressure that acts on the piston of the machine. The valve is characterized by operation in a pulsed mode according to the principle of "opening - closing". This allows you to modulate the pressure, which depends on the speed of the internal combustion engine shaft. At the moment the valve opens, the pressure drops, and this entails a decrease in the injection advance angle. A closed valve provides an increase in pressure, which moves the piston of the machine to the side when the injection advance angle is increased.

These EMC pulses are determined by the ECU and depend on the operating mode and temperature indicators of the engine. The injection start moment is determined by the fact that one of the nozzles is equipped with an inductive needle lift sensor.

The actuators that act on the fuel supply controls in the distributor-type injection pump are proportional electromagnetic, linear, torque or stepper motors that act as a drive for the fuel dispenser in these pumps.

Nozzle with needle lift sensor

The electromagnetic actuator of the distributive type consists of a metering stroke sensor, the executing device itself, a metering device, a valve for changing the injection start angle, which is equipped with an electromagnetic drive. The nozzle has a built-in excitation coil (2) in its body. The ECU sends a certain reference voltage. This is done to maintain the current in the electrical circuit constant and regardless of temperature fluctuations.

The nozzle, equipped with a needle lift sensor, consists of:

  • adjusting screw (1);
  • excitation coils (2);
  • rod (3);
  • wiring (4);
  • electrical connector (4);

The specified current as a result ensures the creation of a magnetic field around the coil. At the moment the nozzle needle is lifted, the core (3) changes the magnetic field. This causes a change in voltage and signal. When the needle is in the process of lifting, then the pulse reaches its peak and is determined by the ECU, which controls the injection advance angle.

The electronic control unit compares the received impulse with the data in its memory, which correspond to various modes and operating conditions diesel unit. The ECU then sends a return signal to the solenoid valve. Said valve is connected to the working chamber of the injection advance machine. The pressure acting on the piston of the machine begins to change. The result is a movement of the piston under the action of the spring. This changes the injection advance angle.

The maximum pressure indicator, which is achieved using electronic fuel control based on the VE fuel pump, is 150 kgf / cm2. It is worth noting that this scheme is complex and outdated, the voltage in the cam drive has no further development prospects. The next stage in the development of high pressure fuel pumps are new generation schemes.

VP-44 pump and diesel direct injection system

This scheme is successfully used on the latest models of diesel vehicles from the world's leading concerns. These include BMW, Opel, Audi, Ford, etc. Pumps of this type allow you to get an injection pressure indicator of 1000 kgf / cm2.

The direct injection system with VP-44 fuel pump shown in the figure includes:

  • A-group of actuators and sensors;
  • B-group of devices;
  • C-circuit of low pressure;
  • D- system for providing air supply;
  • E- system for removing harmful substances from exhaust gases;
  • M-torque;
  • CAN-on-board communication bus;
  1. pedal control sensor for fuel control;
  2. clutch release mechanism;
  3. brake pad contact;
  4. vehicle speed controller;
  5. glow plug and starter switch;
  6. vehicle speed sensor;
  7. inductive crankshaft speed sensor;
  8. coolant temperature sensor;
  9. sensor for measuring the temperature of the air entering the intake;
  10. boost pressure sensor;
  11. film-type sensor for measuring intake air mass flow;
  12. combined dashboard;
  13. air conditioning system with electronic control;
  14. diagnostic connector for connecting a scanner;
  15. time control unit for glow plugs;
  16. injection pump drive;
  17. ECU for engine control and injection pump;
  18. injection pump;
  19. filter fuel element;
  20. fuel tank;
  21. nozzle sensor that controls the stroke of the needle in the 1st cylinder;
  22. pin type glow plug;
  23. power point;

This system has salient feature, which consists in a combined control unit for high-pressure fuel pumps and other systems. The control unit structurally has two parts, the final stages and the power supply of the electromagnets located on the fuel pump housing.

High pressure fuel pump device VP-44

  1. fuel pump;
  2. pump shaft position and frequency sensor;
  3. Control block;
  4. spool;
  5. supply electromagnet;
  6. injection timing solenoid;
  7. hydraulic drive executive mechanism to change the injection advance angle;
  8. rotor;
  9. cam washer;
  • a-cylinders four or six;
  • b-for six cylinders;
  • c-for four cylinders;
  1. cam washer;
  2. video clip;
  3. guide grooves of the drive shaft;
  4. roller shoe;
  5. injection plunger;
  6. distributor shaft;
  7. high pressure chamber;

The system works in such a way that the torque from the drive shaft is transmitted through the connecting washer and spline connection. Such a moment goes to the distributor shaft. The guide grooves (3) perform such a function that through the shoes (4) and the rollers (2) located in them, the injection plungers (5) are activated in such a way that this corresponds to the internal profile that the cam disk (1) has. The number of cylinders in a diesel engine is equal to the number of cams on the washer.

The injection plungers in the distributor shaft housing are located radially. For this reason, such a system was called high pressure fuel pump. The plungers carry out joint extrusion of the incoming fuel on the ascending cam profile. Next, the fuel enters the main high pressure chamber (7). In high pressure fuel pump there can be two, three or more injection plungers, which depends on the planned loads on the engine and the number of cylinders (a, b, c).

The process of distributing fuel using a distributor housing

This device is based on:

  • flange (6);
  • distribution sleeve (3);
  • the rear part of the distributor shaft (2) located in the distribution sleeve;
  • locking needle (4) of the high pressure solenoid valve (7);
  • accumulating membrane (10), which separates the cavities responsible for pumping and draining;
  • fittings of the high pressure line (16);
  • delivery valve (15);

In the figure below we see the distributor housing itself:

  • a - fuel filling phase;
  • b-phase of fuel injection;

This system consists of:

  1. plunger;
  2. distributor shaft;
  3. distribution sleeve;
  4. the locking needle of the high pressure solenoid valve;
  5. channels for fuel return;
  6. flange;
  7. high pressure solenoid valve;
  8. high pressure chamber channel;
  9. an annular inlet for fuel;
  10. an accumulative membrane for separating the pump and drain cavities;
  11. cavities behind the membrane;
  12. low pressure chambers;
  13. distribution groove;
  14. exhaust channel;
  15. delivery valve;
  16. high pressure line fitting;

During the filling phase, on the descending profile of the cams, the plungers (1), which move radially, move outward and move towards the surface of the cam. The locking needle (4) is now free and opens the fuel inlet. The fuel passes through the low pressure chamber (12), the annular channel (9) and the needle. Further, the fuel is directed from the fuel priming pump through the channel (8) of the distributor shaft and enters the high pressure chamber. All excess fuel flows back through the return drain channel (5).

Injection is carried out with the help of plungers (1) and a needle (4), which is closed. The plungers begin to move on the ascending profile of the cams towards the axis of the camshaft. This is how the pressure in the high pressure chamber increases.

The fuel, being already under high pressure, rushes through the channel of the high pressure chamber (8). It passes a distribution groove (13), which in this phase connects the camshaft (2) with the outlet channel (14), the fitting (16) with the pressure valve (15) and the high pressure line with the nozzle. The last step becomes the flow of diesel fuel into the combustion chamber of the power plant.

How does fuel dosing work? High pressure solenoid valve

The solenoid valve (valve for setting the injection start point) consists of the following elements:

  1. valve seat;
  2. valve closing direction;
  3. valve needle;
  4. armature of an electromagnet;
  5. coil;
  6. electromagnet;

The specified solenoid valve is responsible for the cyclic supply and dosing of fuel. This high pressure valve is built into the high pressure circuit of the injection pump. At the very beginning of the injection, the electromagnet coil (5) is energized by a signal from the control unit. The anchor (4) moves the needle (3) by pressing the latter against the seat (1).

When the needle is firmly pressed against the seat, then no fuel is supplied. For this reason, the fuel pressure in the circuit rises rapidly. This allows the corresponding nozzle to be opened. When the right amount of fuel is in the combustion chamber of the engine, then the voltage on the electromagnet coil (5) disappears. The high pressure solenoid valve opens, causing the pressure in the circuit to decrease. The decrease in pressure causes the fuel injector to close and stop injection.

All the precision with which this process directly depends on the solenoid valve. If you try to explain in more detail, then from the moment the valve ends. This moment is solely determined by the absence or presence of voltage on the solenoid valve coil.

Excess injected fuel, which continues to be injected until the plunger roller passes the top point of the cam profile, moves along a special channel. The end of the path for the fuel is the space behind the storage membrane. In the low pressure circuit, high pressure surges occur, which are damped by the storage membrane. Additional is that this space stores (accumulates) the accumulated fuel for filling before the next injection.

The engine is stopped by a solenoid valve. The fact is that the valve completely blocks the injection of fuel under high pressure. This solution completely eliminates the need for an additional stop valve, which is used in distribution injection pumps, where the control edge is controlled.

Process for damping pressure waves with a discharge valve with backflow throttling

This discharge valve (15) with reverse flow throttling prevents the next opening of the injector atomizer after completion of injection of a portion of fuel. This completely eliminates the phenomenon of post-injection resulting from pressure waves or their derivatives. This additional injection increases the toxicity of exhaust gases and is an extremely undesirable negative phenomenon.

When the fuel supply starts, then the valve cone (3) opens the valve. At this very moment, the fuel is already pumped through the fitting, penetrates the high pressure line and goes to the nozzle. The end of the injection of fuel causes a sharp drop in pressure. For this reason, the return spring forcefully presses the valve cone back against the valve seat. When the nozzle closes, reverse pressure waves occur. These waves are successfully extinguished by the delivery valve throttle. All these actions prevent unwanted injection of fuel into the working combustion chamber of a diesel engine.

injection advance device

This device consists of the following elements:

  1. cam washer;
  2. ball pin;
  3. plunger for setting the injection advance angle;
  4. underwater and outlet channel;
  5. adjustment valve;
  6. vane pump for pumping fuel;
  7. fuel withdrawal;
  8. fuel inlet;
  9. supply from the fuel tank;
  10. control piston spring;
  11. return spring;
  12. control piston;
  13. hydraulic stop ring chamber;
  14. throttle;
  15. solenoid valve (closed) for setting the injection start time;

The optimal combustion process and the best power characteristics in relation to a diesel internal combustion engine are possible only when the moment of the start of combustion of the mixture occurs in a certain position of the crankshaft or piston in the diesel engine cylinder.

The injection advance device performs one very important task, which is to increase the fuel injection start angle at the moment when the crankshaft speed increase occurs. This device constructively includes:

  • fuel injection pump drive shaft rotation angle sensor;
  • Control block;
  • solenoid valve for setting the injection start time;

The device provides the very optimal moment for the start of injection, which is ideally suited to the engine operating mode and load on it. There is a compensation of the time shift, which is determined by the reduction of the period of injection and ignition with increasing speed.

This device is equipped with a hydraulic drive and is built into the lower part of the injection pump housing in such a way as to be located across the longitudinal axis of the pump.

Injection advance device operation

The cam disc (1) enters with the ball pin (2) into the transverse hole of the plunger (3) in such a way that the translational movement of the plunger is transformed into a rotation of the cam disc. The plunger has a control valve (5) in the center. This valve opens and closes the control port in the plunger. Along the axis of the plunger (3) there is a control piston (12), which is loaded with a spring (10). The piston is responsible for the position of the control valve.

The solenoid valve for setting the injection start time (15) is located across the plunger axis. The electronic unit that controls the injection pump acts on the plunger of the injection advance device through this valve. The control unit delivers continuous current pulses. Such pulses are characterized by a constant frequency and a variable duty cycle. The valve changes the pressure that acts on the control piston in the design of the device.

Summing up

This material is aimed at the most accessible and understandable acquaintance of users of our resource with the complex device of a high-pressure fuel pump and an overview of its main elements. device and general principle The operation of the high-pressure fuel pump allows us to talk about trouble-free operation only if the diesel unit is filled with high-quality fuel and engine oil.

As you already understood, low-grade diesel fuel is the main enemy of complex and expensive diesel fuel equipment, the repair of which is often very expensive.

If you operate the diesel engine carefully, strictly observe and even shorten the service intervals for replacing the lubricant, take into account other important requirements and recommendations, then the high-pressure fuel pump will certainly respond to its caring owner with exceptional reliability, efficiency and enviable durability.