EP1329629A2 - Double switching valve for fuel injection systems - Google Patents

Abstract

Pump/nozzle unit comprises a pump part, a nozzle part, an actuator (5), and a hydraulic coupling device (38) located downstream of the actuator and via which a valve needle (24) of a 2/2-way valve within a nozzle body (23) is operated. The actuator has a piezo crystal arrangement (7) acting on the hydraulic coupling device and impinging on an end face (40) of the valve needle which is adjusted into a first position (41) allowing a pressure increase. A further position of the valve needle allowing opening of a nozzle needle (29) is independently adjusted. Preferred Features: The hydraulic coupling device changes in the nozzle body into a needle guide (44) guiding the valve needle.

Description

Technical field

In the case of injection systems based on the UIS system (Unit Injector System), a Controls the high pressure chamber of a fuel injection pump via a hydraulic coupler locked. In the UI systems, the pressure is built up by a piston. The pressure opens the injection valve when a certain value is reached.

State of the art

With pump-nozzle systems (UI-Unit Injector systems) are now on auto-igniting Internal combustion engines generate mechanically-hydraulically controlled injection phases, which on the one hand contribute to noise reduction and on the other hand to minimize pollutants. A distinction can be made between four operating states in pump-nozzle systems. A pump piston is moved upwards via a return spring. The one under constant overpressure standing fuel flows from the low pressure part of the fuel supply via the Engine block-integrated inlet bores and the inlet channel in a valve chamber Solenoid valve. The solenoid valve is open. The passes through a connecting hole Fuel into the high pressure room.

When the drive cam rotates, the pump piston moves down. The Solenoid valve remains in its open position and the fuel is through the Pump piston via the return channel into the low-pressure part of the fuel supply pressed.

In a third phase of the injection process when using an electromagnetic valve the coil of the electromagnet by the control unit at a certain time energized so that the solenoid valve needle is pulled into a seat and the connection is closed between the high pressure chamber and the low pressure part. That time will also called "electrical start of spraying". The fuel pressure in the high pressure room increases continuously due to the movement of the pump piston, which also increases pressure increases at the injector. When a nozzle opening pressure is reached The nozzle needle is raised by approximately 300 bar, which brings fuel into the combustion chamber is injected. This time is also called the "actual start of spraying" or also referred to as the start of funding. Due to the high delivery rate of the pump piston the pressure continues to rise during the entire injection process. In a final Operating state, the coil of the electromagnet is switched off again, after which the solenoid valve opens after a short delay and the connection between high pressure chamber and low pressure part is released again. In this transition phase the peak pressure is reached, which, depending on the pump type, between a maximum 1800 and 2050 bar varies. Then the pressure breaks down very quickly. When falling short of the nozzle closing pressure closes the injection nozzle and ends the injection process. The rest from the pump element to the apex of the drive cam Pumped fuel is fed into the low pressure part of the fuel system via the return channel pressed.

Such pump nozzle systems used, for example, in truck injection systems usually include two actuators designed as electromagnets. With two digits the unit injector system (UIS) requires more installation space than in such applications Injection systems for commercial vehicles are available. The trained as solenoid valves Actuators can therefore be easily accommodated on truck diesel engines. at Passenger cars, however, is in the engine compartment, especially in the upper area of the Cylinder block, limited space available, what the external dimensions of a pump-nozzle system. Will be used instead of two as solenoid valves procured only used an electromagnetic valve, this goes with the The disadvantage is that this is only very imprecise and requires a lot of control in an intermediate position can be held.

Presentation of the invention

The advantages of the solution proposed according to the invention can be seen above all in that the closing of the high pressure chamber of the pump-nozzle system to build up pressure and the opening of the nozzle needle can be controlled separately. So that's the Injection pressure, i.e. the pressure at which the nozzle needle opens can be varied freely.

If a piezo actuator is used, its stroke can be changed by changing the voltage vary as desired on the piezo actuator. The actuator of the pump-nozzle unit designed as a piezo actuator (PDE) can be used to implement the required travel distances within the A hydraulic pressure intensifier can be connected downstream of the housing of the pump-nozzle unit. An actuator designed as a piezo actuator can be energized in accordance with transfer different switching positions. In a de-energized, de-energized state of the piezo actuator, the nozzle needle assumes an open position, i.e. Fuel comes with low pressure by the fuel feed pump by the unit injector (PDE) pumped. In this position of the nozzle needle are the inlet and the low pressure side Inlet to a high-pressure pump chamber connected in a short circuit, because the openings corresponding to these within the housing of the unit injector are released by the nozzle needle.

When the piezo actuator is energized to the maximum, the nozzle needle is moved downwards, i.e. the low-pressure inlet and high-pressure inlet to the pump room are both locked. In this phase, the pressure builds up without the needle passing through the steadily increasing pressure would be opened. However, is the desired injection pressure built in the pump-nozzle unit (PDE), the current supply to the piezo actuator is withdrawn, whereby the nozzle needle opens with pressure support.

The end of the injection is brought about by opening the return line, which is what Closing the nozzle needle results. This solution can be used as a piezo actuator Trained actuator on a unit injector (PDE) building up pressure and opening the nozzle needle can be controlled separately from each other, giving freedom of choice in terms of the built-up injection pressure allowed.

drawing

The invention is described in more detail below with reference to the drawing.

Figur 1

eine Pumpe-Düse-Einheit (PDE), welche mittels eines Magnetventils betätigbar ist,

Figur 2.1

einen Piezoaktor mit hydraulischem Kopplungsraum in einer ersten Schaltstellung,

Figur 2.2

den Piezosteller mit nachgeschaltetem hydraulischen Kopplungsraum mit vollständig geschlossener Düsennadel,

Figur 2.3

den Piezosteller mit nachgeschaltetem hydraulischen Kopplungsraum in einer druckunterstützt angesteuerten Zwischenposition und

Figur 3

das Spannungsprofil, mit dem der Piezoaktor ansteuerbar ist.

It shows:

Figure 1

a pump-nozzle unit (PDE) which can be actuated by means of a solenoid valve,

Figure 2.1

a piezo actuator with hydraulic coupling space in a first switching position,

Figure 2.2

the piezo actuator with a downstream hydraulic coupling chamber with a completely closed nozzle needle,

Figure 2.3

the piezo actuator with downstream hydraulic coupling chamber in a pressure-assisted intermediate position and

Figure 3

the voltage profile with which the piezo actuator can be controlled.

variants

Figure 1 shows a pump-nozzle unit (PDE), which is designed as a piezo actuator Actuator is actuated.

The illustration according to FIG. 1 shows that the pump-nozzle unit shown there 1 comprises a pump part 2 and a nozzle part 3. The nozzle part 3 of the pump-nozzle unit 1 (PDE) is in the cylinder head 4 of a self-igniting, not shown here Internal combustion engine inserted. The nozzle part 3 of the pump-nozzle unit 1 is screwed into a cylinder head bore 22 and by means of a spacer 32 and with the help of O-rings 33 in the cylinder head bore 22 sealed.

On the side of the pump part 2 of the pump nozzle unit 1, an actuator 5 is received, which as Is formed piezo actuator and comprises a piezo crystal arrangement in stack form. The electrical control of the piezocrystal stack 7 takes place via a switch 5 on the side Recorded plug connection 6. The actuator 5 is on the side of the pump housing 8 of the Pump part 2 of the pump-nozzle unit 1 is added and acts on a hydraulic Coupler 38, the one in a nozzle body 23 of the via a coupler line 39 Nozzle part 3 displaceably arranged valve needle 24 acted on the end face. In the pump housing 8 of the pump part 2 of the pump nozzle unit 1, a pump piston 9 is embedded, which is operated via a rocker arm 17 controlled by camshafts. The face 11 of the pump piston 9 delimits a pressure chamber 10 which is in the pump housing 8 of the pump part 2 of the pump-nozzle unit 1 is added.

The pump piston 9 is moved in the pump housing 8 in the axial direction and is through a spring element 12 configured here as a spiral spring is biased. That as a spiral spring 12 trained spring element is supported on the one hand on a collar 13 of the pump housing 8 and on the other hand on a spring plate 14, which is penetrated by a pressure pin 15. The pressure pin 15 in turn is supported on a ball socket element 16 and acts on the end face of the pump piston 9 facing away from the pump chamber 11. The pressure pin 15, which is received with its lower end in a pin socket 16 is at its end opposite the pin socket 16 by a rocker arm 17 enclosed, which is rotatable about a rocker arm axis 18. On the pressure pin 15 opposite end of the rocker arm 17, a rocker arm roller 19 is rotatably supported, which runs with its outer peripheral surface on an eccentric cam 21, which is on a camshaft 20 is formed. Due to the outer peripheral contour of the eccentric cam 21 the axial movement of the pump piston 9 transmitted via the rocker arm 17 within of the pump housing 8 of the pump part 2 of the pump-nozzle unit 1 generated.

The nozzle body 23 of the nozzle part 3 which is let into the cylinder head bore 22 comprises a valve needle 24 which is moved in the axial direction within the nozzle body 23. The upper end face 40 of the valve needle 24 is connected to the hydraulic via the coupler line 39 Coupler 38 in connection, which in turn by the piezocrystal stack arrangement 7 of the actuator 5 is applied. In addition, the valve needle 24 of the 2/2-way valve in the nozzle body 23 is acted upon by a return spring. The Return spring assigned to the end face of the valve needle 24 facing away from the end face 40 is, in turn, supported on a disc-shaped element, which by a Nozzle needle spring 35 is acted upon. From the pump chamber 11 in the pump housing 8 of the Pump part 2 branches off a high-pressure line, which via the control chamber inlet 26 Control chamber 25 acts on the valve needle 24 and at the same time via the nozzle chamber inlet 27 the nozzle chamber 28 in the nozzle body 23 with fuel under high pressure acted upon, which receives the nozzle needle 29 slidably received in the nozzle body 23. The fuel under high pressure flows from the nozzle chamber 28 over one Annular gap 30 in the direction of the nozzle tip, at which at least one injection opening 31 is formed, which in a combustion chamber, not shown in Figure 1, of a self-igniting Internal combustion engine protrudes. The nozzle needle 29 is in the combustion chamber end of the nozzle body 23 and biased by the nozzle needle spring 35. The axial position of the nozzle body 23 in the cylinder head 4 is due to the thickness of a spacer 32 determined. The sealing function between the combustion chamber and cylinder head 4 is performed by the Spacer 32 and a number of O-rings 33 taken over.

Associated to the side of the nozzle body 23 within the cylinder head 4 is a Fuel return identified by reference numeral 36, the one above that by reference numeral 37 designated fuel inlet to the nozzle body 23 is arranged. The nozzle body 23 is with the combustion chamber of the self-igniting internal combustion engine part assigned via a nozzle clamping nut 34. This seals the two Parts of the nozzle body 23 against each other and creates a fuel-tight connection between the pump chamber 11 of the pump part 2 and the high pressure inlets 26, 27 to the control room 25 or to the nozzle room 28.

Figure 2.1 shows a piezo actuator with a hydraulic coupling space, which is in a first switch position is set.

In the first position 41 of the valve needle 24 in the nozzle body 23 shown in FIG. 2.1 the piezo crystal stack arrangement 7 of the actuator 5 is de-energized. Accordingly, the hydraulic Coupler 38 is not applied. The valve needle 24 in the nozzle part 3 of the pump-nozzle unit 1 is located around a first stroke 45 in relation to its nozzle body side Seat, opened. In this switch position, the inlet 37, which is above the Return 36 is arranged in the nozzle body 23 and the return 36 both opened. In in FIG. 2.1 shown voltage-free state of the actuator 5, the valve needle 25 is open, the fuel is pumped through the low pressure fuel feed pump Nozzle part 2 of the pump-nozzle unit 1 promoted. In this first position 41 of the valve needle 25 is the actuator 5, i.e. whose piezocrystal stack arrangement 7 does not energize what corresponds to the voltage level according to FIG. 3 before the rising edge 50 of the voltage.

In Figure 2.2, the piezo actuator with downstream hydraulic coupler 38 with maximum voltage energized according to the first voltage level 54 shown in Figure 3. As a result, the piezo-crystal stack arrangement 7 of the actuator 5 travels in the hydraulic manner Coupler 38 that that via the coupler line 39 shown in Figure 1 Face 40 of the valve needle 24 is subjected to high pressure. This causes the nozzle needle to move 24 of the 2/2-way valve completely inside the needle guide 44 down and closes the inlet 37 and the return 36 at the same time. In the second, in FIG 2.2 shown position 42 of the nozzle needle 24, the pressure builds up in the high pressure chamber, i.e. in the pump chamber 11 of the pump part 2. The second position 42 of the valve needle 24 is held during the pressure build-up phase 52. During the pressure build-up phase 52 (see voltage profile representation according to FIG. 3), the pressure builds up in the high-pressure chamber, i.e. in the pump chamber 11 within the pump housing 8 until a desired one Pressure level is reached.

Figure 2.3 shows the piezo actuator with a downstream hydraulic coupler in one further, the third position 43.

To achieve a switching state corresponding to the third position of the valve needle 24 the valve needle 24 becomes the energization of the piezo crystal stack arrangement 7 of the actuator 5 withdrawn to a second voltage level 56 (cf. illustration according to FIG. 3). The voltage drops in accordance with a first falling voltage edge 55 first voltage level 54, which during the second position 42 of the valve needle 24 is held back to a second, lower voltage level 56 (see illustration according to Figure 3).

As a result, the pressure in the hydraulic coupler 38 and the coupler line 39 increases so that the valve needle 24, the end face 40 of which is acted upon by the high pressure, by a second stroke 46 in the vertical direction with respect to the nozzle body 23 opens up. In the third position 43 of the valve needle 24, the return 36 is open, while the inlet 37 continues through the valve needle 24, analogous to the illustration in FIG Figure 2.2, remains closed. The nozzle needle 29 (cf. illustration according to FIG. 1) is thereby opened with pressure support. The injection ends by opening the return 36, since the opening of the return 36 an immediate pressure reduction and the closing of the nozzle needle 29 results.

FIG. 3 shows the voltage profile with which the 2/2-way valve, which is designed as a piezo actuator double switching piezo actuator is controlled.

In the de-energized state of the piezo actuator 5, the voltage corresponds to the level which in Figure 3 is present before the rising edge 50 of the voltage. The pressure build-up phase 52 will generated by the rising edge 50 of the voltage down to a first voltage level 54. The start of funding is shown with reference number 51. The pressure build-up phase 52 can are kept variable and is controlled by the actuation of the nozzle needle 29 the valve needle 24 independently, i.e. Cut. During the pressure build-up phase, the Piezo actuator 5 energized at the first voltage level 54. The pressure builds up without that the nozzle needle 29 by the pressure building up in the pump chamber 11 of the pump part 2 of the unit injector is opened. As soon as the desired spray pressure level as soon as the desired time for the start of injection 53 has been reached, the first Voltage level 54 lowered to a second voltage level 56. During the concern of the first voltage level 54 is the valve needle 24 of the 2/2-way valve the unit injector 1 in the second position, as shown in the illustration Figure 2.2 is identified by reference numeral 42, i.e. the inlet 37 and the return 36 to the pump room 11 are closed. If the first voltage level 54 is along the first falling voltage edge 55 lowered to the second voltage level 56 takes place a relief of the hydraulic coupler 38, since the piezocrystal arrangement 7 at Apply a low voltage level corresponding to the second voltage level 56 contracted. As a result, the valve needle 24 moves by the second stroke 46 in accordance with the representation in Figure 2.3 in its third position. In the third position, inlet 37 still closed, while the return 36 to the pump chamber 11 remains open. The second voltage level 56 is applied up to the delivery end 57 of the fuel pump drops to the 0 level in accordance with a further, second falling voltage edge 58 from. At the 0 level of the voltage U, the valve needle 24 again takes the one shown in FIG. 2.1 first position 41, in which the nozzle needle a first stroke 45 within the Nozzle body 23 covers and in which the inlet 37 and the return 36 together are short-circuited. Through the valve needle 24 of the 2/2-way valve inside the nozzle body 23 the closing of the high pressure space, i.e. the pump chamber 11 the pump part 2 to build up pressure and the opening of the nozzle needle 29 separately controlled. According to the activation time of the actuator 5, at which the first If the voltage level 54 is reduced to the second voltage level 56, the injection pressure can be reduced control freely, whereby the pressure build-up phase is unaffected.

Claims (10)

Pump-nozzle unit (1) for injecting fuel into the combustion chamber of a self-igniting internal combustion engine with a pump part (2) and a nozzle part (3) and an actuator (5), which is followed by a hydraulic coupler (38, 39) One valve needle (24) of a 2/2-way valve can be actuated within a nozzle body (23), characterized in that the actuator (5) comprises a piezo crystal arrangement (7) acting on the hydraulic coupler (38, 39) and acts on an end face (40) of the valve needle (24), which can be set into a first position (41) that enables pressure build-up, a further position (43) of the valve needle (24) that enables opening of a nozzle needle (29) to be set independently , Pump-nozzle unit according to claim 1, characterized in that the hydraulic coupler (38, 39) in the nozzle body (23) merges into a needle guide (44) guiding the valve needle (24). Pump-nozzle unit according to claim 1, characterized in that a control chamber inlet (26) and a nozzle chamber inlet (27) branch off from the pump chamber (10) of the pump part (2), which control chamber (25) of the valve needle (24) and one Actuate the nozzle chamber (28) surrounding the nozzle needle (29) at the same time. Pump-nozzle unit according to claim 1, characterized in that, seen in the longitudinal direction of the nozzle needle (29) in the nozzle body (23), the inlet (37) is arranged above the return (36). Pump-nozzle unit according to claim 4, characterized in that in the first position (41) of the valve needle (24) with the actuator (5) deenergized, an inlet (37) and the return (36) in the nozzle body (23) are short-circuited. Pump-nozzle unit according to claim 4, characterized in that when the actuator (5) is energized to a first voltage level (54) the inlet (37) and the return (36) are closed by the valve needle (24) and a pressure build-up ( 52) in the pump chamber (10) of the pump part (2). Pump-nozzle unit according to claim 4, characterized in that after the end of a pressure build-up phase (52) in the pump chamber (10) of the pump part (2) at the start of injection (53) the actuator (5) is subjected to a second voltage level (54) and the nozzle needle (29) opens with pressure support. Pump-nozzle unit according to claim 7, characterized in that the start of injection (53) and the pressure build-up phase (52) can be controlled separately from one another by closing the pump chamber (10). Pump-nozzle unit according to claim 5, characterized in that in the first position (41) of the valve needle (24), a first stroke (55) of the valve needle (24) is set, in which the inlet (37) and the return ( 36) are open. Pump-nozzle unit according to claim 7, characterized in that in a third position (43) of the valve needle (24) a second stroke path (46) of the valve needle (24) is set, at the return (36) to the pump chamber (10) is open.

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