Hyundai Elantra

since 2000-2004 of release

Repair and car operation

Fuel system Common Rail

System of injection of Common Rail fuel

The fuel system Common Rail includes a step of supply of fuel under low pressure and a step of supply of fuel under a high pressure and ECU (11).

Supply of fuel under low pressure

Supply of fuel under low pressure of Common Rail system includes:

– a fuel tank with the preliminary fuel filter;
– the pumping-up fuel pump;
– fuel filter;
– топливопроводы low pressure.

The pumping-up fuel pump

The electric pumping-up fuel pump with the preliminary fuel filter continuously submits certain amount of fuel from a fuel tank to the fuel pump of a high pressure. The pump not only submits fuel, but within work of system of safety should stop supply of fuel in case of failure, i.e. at the included ignition and the stopped engine.

The fuel pump consists of three basic elements:

– pump;
– electric motor;
– covers.

Fuel filter

Insufficient purification of fuel can lead to damage of knots of the fuel pump of a high pressure, delivery valves and sprays of nozzles. The fuel filter clears fuel before its receipt in the fuel pump of a high pressure and thus prevents premature wear in sensitive knots of the pump.

Diesel fuel (emulsion), or in a free form (for example, condensation паров waters can contain water or in the connected form at temperature change). If water gets to injection system, it can lead to corrosion of elements of system of injection therefore the precautionary alarm system which includes a control lamp in combinations of devices if it is necessary to merge water from the fuel filter is established.

Supply of fuel under a high pressure

Supply of fuel under a high pressure of Common Rail system includes:

– the fuel pump of a high pressure with the valve of adjustment of pressure;
– топливопроводы high pressure;
– the accumulator of a high pressure (rail) with the pressure sensor, the pressure limiter, the stream limiter, nozzles;
– returnable топливопровод.

Fuel pump of a high pressure

Fuel pump of a high pressure (the schematic image of longitudinal section)

Fuel pump of a high pressure (the schematic image of cross-section section)

The fuel pump of a high pressure through топливопроводы a high pressure submits fuel under the pressure of the 1350th bar to the accumulator of a high pressure.

The fuel pump of a high pressure is located on border of steps of a low and high pressure of fuel. At all operational modes service life of the fuel pump corresponds to car service life.
The fuel pump is greased with diesel fuel. Fuel is compressed by three pistons established radially at an angle 120 ° to each other. The pump submits three portions of fuel for one turn of a cranked shaft. For the diesel engine with working volume of 2,0 l, rotation of a cranked shaft working with nominal frequency and created pressure the 1350th bar, the capacity of 3,8 kW is necessary for a drive of the pump taking into account mechanical к.п.д. about 90 %.

Pump functioning

The pumping-up fuel pump submits fuel via the filter with a water separator to an entrance and a safety valve of the fuel pump of a high pressure. Fuel through a throttle opening of a safety valve greases mobile elements of the pump, and also cools it. The power shaft with ekstsentrikovy cams is moved by three plunzher of the pump up and down according to a cam form. As soon as pressure of giving exceeds pressure of opening of a safety valve (0,5... 1,5 bar), forces fuel to pass pumping-up pump through the inlet valve of the fuel pump of a high pressure in a compartment of the pump element which piston moves down (an admission step). The inlet valve is closed, when the piston of the pump passes through NMT and as fuel cannot flow out from a compartment of a pump element, it is compressed irrespective of pressure of giving.

Increasing pressure opens the final valve and as soon as the pressure equal to pressure in the accumulator is reached, the compressed fuel is included into a contour of a high pressure. The piston of the pump continues to deliver fuel, yet does not reach VMT (a delivery course) then pressure decreases and the final valve is closed. The fuel remaining in a compartment of a pump element, extends and the piston of the pump moves down. As soon as pressure in a compartment of a pump element decreases below the pressure created by the pumping-up pump, the inlet valve opens and process repeats.

As productivity of the pump exceeds fuel consumption by the engine, superfluous fuel under a high pressure via the valve of adjustment of pressure comes back to a fuel tank. It leads to unnecessary heating of fuel and decrease in the general efficiency.

Accumulator of a high pressure (rail)

The pressure created by the fuel pump of a high pressure, extends via the accumulator and топливопроводы to a nozzle. At the same time, at the expense of fuel volume in the accumulator fluctuations of pressure the fuels created by the fuel pump of a high pressure and opening nozzles decrease. Compressibility of fuel as a result of a high pressure is used for achievement of effect of the accumulator. Pressure of fuel is measured by the sensor and supported at demanded level by the valve of regulation of pressure.

Toplivoprovoda of a high pressure

Toplivoprovoda of a high pressure are intended for fuel transfer from the accumulator of a high pressure to nozzles and should resist to the high-frequency fluctuations of pressure arising at operation of the engine. Toplivoprovoda are made of steel and have external diameter of 6 mm and internal diameter of 2,4 mm. All топливопроводы a high pressure should have identical length. The distance difference between the accumulator and each fuel nozzle is compensated for the bending account топливопроводов.

Pressure sensor

The sensor of pressure transmits a signal of ECU which corresponds to real pressure in the pressure accumulator.

The sensor of pressure consists of the following elements:

– the incorporated element of the sensor welded on the case;
– the printed-circuit board with an electric contour;
– sensor cases with the electric socket.

Fuel under pressure through an opening influences a sensor diaphragm on which the sensor element (the semi-conductor device) reformative pressure in an electric signal is established. Through contacts of the socket both an electric chain the generated and strengthened signal is transferred to ECU. The sensor works as follows: at change of a form of a diaphragm electric resistance of the layers pasted to a diaphragm changes. Change of pressure upon the 1500th bar leads to change of a form of a diaphragm on 1 mm.

Depending on enclosed pressure target tension of the sensor changes from 0 to 70 мВ and after strengthening makes 0,5–4,5 Century. Exact measurement of pressure in the accumulator is necessary for the correct functioning of system of injection of fuel. In a working range measuring accuracy should be in limits ±2 %. At an exit of the sensor of pressure out of operation the valve of adjustment of pressure passes to the diaphragm mode and injection system, using spare (soft) function, accepts in advance set size of pressure.

Valve of restriction of pressure

The valve of restriction of pressure carries out the same function, as the valve of superfluous pressure. In case of superfluous pressure the valve opening limits pressure in the accumulator. Pressure of opening of the valve of restriction of pressure – the 1500th bar.

The valve of restriction of pressure – the mechanical device which is switching on the following elements:

– the case with an external carving for a vvorachivaniye in the pressure accumulator;
– connection of a tube of return of fuel in a fuel tank;
– mobile plunzher;
– spring.

Nozzles

Nozzle: A–the nozzle is closed (a motionless condition); In – the nozzle is open (fuel injection)

The nozzle provides giving of the necessary amount of fuel in the combustion chamber. During precisely established moment of ECU transmits a signal of excitement to the nozzle solenoid that means the beginning of supply of fuel. The amount of injected fuel is defined by the period of opening of a spray and pressure in system. The fuel which is coming back from the valve of regulation of pressure and a step of low pressure, moves in a collector together with fuel which carried out greasing of the fuel pump of a high pressure.

The nozzle consists of the following knots:

– spray;
– hydraulic system;
– solenoidal valve.

Fuel from carving connection of a high pressure via the channel moves to a spray and through a giving opening in a compartment of management of the valve. The compartment of management is connected by the valve with returnable toplivoprovody through the opening of leak connected to the solenoidal valve. When closing an opening of leak the hydraulic effort enclosed to a plunzher of management of the valve, exceeds effort from pressure upon a konusny end face of a needle of a spray. As a result the needle of a spray falls down and tightly blocks supply of fuel under a high pressure in the combustion chamber.

When opening the solenoidal valve of a nozzle the leak opening that leads to pressure decrease in a compartment of management of the valve therefore hydraulic pressure on a plunzher also decreases opens. As soon as the hydraulic effort becomes lower than effort from pressure upon a konusny end face of a needle of a spray, the needle of a spray opens and fuel is injected into the combustion chamber. This indirect management of a spray needle with use of hydraulic system of increase in effort is applied because forces which are required for fast opening of a needle, cannot be generated by directly solenoidal valve. The so-called amount of fuel for the management, necessary for opening of a needle of a spray, moves in addition to amount of fuel which is necessary for entering actually into the cylinder, and it through the opening of leak connected to the solenoidal valve, moves in returnable топливопровод.

In addition to amount of fuel for management also there is a fuel loss in directing a pusher of the valve and a spray needle.

Nozzle action at operation of the engine and pressure creation by the fuel pump of a high pressure is subdivided into the following four stages:

– the nozzle is closed (with the appendix of a high pressure);
– the nozzle opens (the beginning of injection of fuel);
– the nozzle is open completely;
– nozzle closing (completion of injection of fuel).

At the switched-off engine and lack of pressure in the pressure accumulator the spring of a spray closes a nozzle.

The nozzle is closed

The solenoidal valve of a nozzle is not raised in a motionless condition and consequently is closed. The opening of leak is closed and the spring of the valve presses a ball to a nest of an opening of leak. The high pressure from the accumulator of pressure increases in a compartment of management of the valve and at the same time is present at volume of a compartment of a needle of a spray. Pressure from the pressure accumulator, enclosed in a face surface of a plunzher of management, together with force of a spring of a needle of a spray holds a needle in a closed position, counteracting against the forces of opening enclosed in a stage of pressure.

The nozzle opens

The nozzle is in motionless situation. The solenoidal valve is raised by a current which provides fast opening of the valve. Immediately big current submitted to the solenoid, decreases to a current, sufficient for deduction of the solenoidal valve in open situation. When the leak opening opens, fuel follows from a compartment of management of the valve in a cavity located over the valve, and from there via the returnable pipeline in a fuel tank.

The effort created by the solenoid, exceeds effort of a spring and the leak opening that leads to pressure decrease in a compartment of management of the valve therefore hydraulic pressure on a plunzher also decreases opens. As soon as the hydraulic effort becomes lower than effort from pressure upon a konusny end face of a needle of a spray, the needle of a spray opens and fuel is injected into the combustion chamber.

Speed of opening of a needle of a spray is defined by a difference in speed of a stream by an opening of leak and a giving opening. Plunzher of management reaches the top situation where there is the pillow of fuel formed by a stream of fuel between openings of leak and supply of fuel. In this situation the spray of a nozzle is completely open and fuel is injected into the combustion chamber under the pressure equal to pressure in the accumulator of pressure.

Nozzle closing

After tension interruption of supply to the solenoidal valve the klapanny spring moves an anchor down and the ball closes a leak opening. The anchor consists of two parts. However, in spite of the fact that the plate of an anchor copes to a coat hanger when moving down, it can «отпружинить» with a returnable spring so that there will be no the forces operating down on an anchor and a ball.

When closing an opening of leak the hydraulic effort enclosed to a plunzher of management of the valve, exceeds effort from pressure upon a konusny end face of a needle of a spray. As a result the needle of a spray falls down and tightly blocks supply of fuel under a high pressure in the combustion chamber. Speed of movement of a needle of a spray is defined by a stream by a giving opening.