EP1613855B1 - Fuel injector provided with a servo leakage free valve - Google Patents

Description

Technical area

For introducing fuel into direct-injection internal combustion engines, stroke-controlled injection systems with high-pressure storage space are used. The advantage of these injection systems is that the injection pressure can be adapted to load and speed in a wide range. To reduce emissions and achieve high specific power, high injection pressure is required. The achievable pressure level of high-pressure fuel pumps is limited for reasons of strength, so that pressure amplifiers in the fuel injectors are used to further increase the pressure in fuel injection systems.

State of the art

From the post-published document WO 2004/036027 A1 a fuel injection device with an injection valve member and a pressure booster or pressure booster is known. The pressure booster device has a pressure booster piston, which is exposed as a stepped piston with pressure surfaces a working space, a differential pressure chamber and a high-pressure chamber. The pressure booster piston and the injection valve member are actuated by a switching valve that drives a hydraulic servo valve piston. The servo valve piston seals a control chamber, a first hydraulic chamber and a second hydraulic chamber by means of a first sealing seat against a low-pressure side return. A formed on the servo valve piston second sealing seat separates in the activated state of the pressure booster connected to the return second hydraulic space from the first hydraulic space connected to the system pressure of the common rail. The servo valve piston is exposed to the high-pressure connected first hydraulic chamber with an end face end face.

Another fuel injector with an integrated pressure booster device is off DE 102 18 904 A1 known, which also has a servohydraulisches switching valve for controlling the pressure booster and the Spritzvenfilglieds. The switching valve is driven by a piezoelectric actuator which acts on a valve element via a power transmission piston or coupler piston. The valve element closes by means of a first sealing seat a hydraulic space which is hydraulically brewed with the differential pressure chamber, from a hydraulic control chamber, which in turn is connected to the low pressure / return. A control chamber opposite the second sealing seat separates in the open state of the first sealing seat, the hydraulic space acted upon by the system pressure working space, so that the differential pressure chamber via the control chamber in the return pressure is relieved to activate the pressure booster.

Out WO 2004/003376 A1 a fuel injector with a pressure booster device and with a servohydraulic switching valve, in which the switching valve is a 2/2-way valve that uses a single sealing seat in the deactivated state of the pressure booster separates the connected via the control room with system pressure differential pressure chamber from the system pressure and connects to the return ,

DE 101 23 914 A1 relates to a fuel injector for internal combustion engine with a fuel injector which can be supplied by a high-pressure fuel source. Between the fuel injector and the high-pressure fuel source is connected to a movable pressure booster piston having pressure booster. The pressure booster piston separates a connectable to the high-pressure fuel source space from a high-pressure chamber connected to the fuel injector. By filling a backspace of Pressure booster with fuel or by emptying the back space of fuel, the fuel pressure in the high-pressure chamber can be varied. The fuel injector has a movable closing piston for opening and closing injection openings. The closing piston protrudes into a closing pressure chamber, so that the closing piston can be acted upon by fuel pressure in order to achieve a force acting on the closing piston in the closing direction. The closing pressure chamber and the rear space are formed by a common closing pressure-return chamber, with all sub-areas of the closing pressure-return space permanently for replacement connected by fuel. There is provided a pressure space for supplying the injection openings with fuel and for acting on the closing piston with a force acting in the opening direction. A high-pressure chamber communicates with the high-pressure fuel source in such a way that, apart from pressure oscillations, at least the fuel pressure of the high-pressure fuel source can constantly be present in the high-pressure chamber. The pressure chamber and the high pressure chamber are formed by a common injection space, wherein all portions of the injection chamber are permanently connected to each other for the exchange of fuel.

DE 102 294 18.6 refers to a fuel injector for injecting fuel into the combustion chamber of an internal combustion engine. The fuel injection device comprises a high pressure source, a pressure booster and a metering valve. The pressure booster comprises a working space and a control space, which are separated from each other by a piston, wherein a pressure change in the control chamber of the pressure booster causes a pressure change in a compression space. The compression chamber acts on a fuel inlet to a nozzle chamber surrounding an injection valve member. A nozzle control chamber which acts upon the injection valve member can be filled from the compression region both on the high pressure side via a line containing an inlet throttle point and can also be connected to a space of the pressure booster via a line containing an outlet throttle point.

The metering valve according to the solution described above is designed as a 3/2-valve, which controls a occurring according to this solution with pressure booster high return flow. Although a simplified and cost-effective production can be achieved when the metering valve is designed as a 3/2 servo valve, it is disadvantageous to have a leakage gap which sets in the quiescent state of the fuel injector and forms between the control chamber of the servo piston of the servo valve and a return line. By the leakage gap effluent actuating fluid deteriorates the system efficiency and requires a large guide length of the sealing gap. A large guide length of the sealing gap in turn pulls a large length of the valve body of the servo valve after what is undesirable in terms of the available installation space, since the smallest possible size of a fuel injector with integrated pressure booster is sought.

Presentation of the invention

The proposed design of the inventively proposed servo valve for a fuel injector with pressure booster for direct-injection internal combustion engines has at rest no leakage on the piston of the servo valve. As a result, the leakage amount is significantly reduced, whereby the efficiency of the fuel injector can be significantly improved. Due to the selected design of a 3/2-Servovalve required on the servo piston guide lengths can be significantly reduced, whereby the length of the servo valve and the space occupied by this significantly decreases. As a result, a very compact servo valve can be realized for controlling a fuel injector having a pressure intensifier.

The trained as 3/2 valve servo valve can be designed as a seat-seat valve. For this purpose, the valve is designed with a one-piece servo valve piston and a multi-part valve body. When executing a sealing seat on the servo valve, an axial offset of a multi-part servo valve housing can be compensated. The proposed design of the 3/2-Servoventiles as a seat-seat valve, the occurring when using slide seals with small overlap lengths wear and tolerance problems can be avoided. The easy accessibility of the valve seats ensures easy manufacturability.

drawing

With reference to the drawing, the invention will be described below in more detail.

Figur 1

eine Ausführungsvariante eines Servoventiles mit leckagefrei ausgebildetem Servoventilkolben, welches einem Kraftstoffinjektor mit Druckübersetzer zugeordnet ist und

Figur 2

eine weitere konstruktive Ausführungsvariante eines Servoventiles mit einem als Kegelsitz ausgebildeten Dichtsitz und einteiligem Ventilgehäuse.

It shows:

FIG. 1

an embodiment of a servo valve with leak-free trained Servoventilkolben, which is associated with a fuel injector with pressure booster and

FIG. 2

a further constructive embodiment of a servo valve with a conical seat formed as a sealing seat and one-piece valve body.

variants

Via a pressure source 1, which can be formed as a high-pressure accumulation chamber of a fuel injection system, a high-pressure line 2 is acted upon by high-pressure fuel. The high pressure line 2 opens into a working space 5 of a pressure booster 3. The working space 5 is permanently acted upon by the high pressure fuel of the pressure source 1. The working space 5 of the pressure booster 3 is separated by a booster piston 4 from a differential pressure chamber 6 (back space) of the pressure booster 3. The booster piston 4 of the pressure booster 3 is acted upon by a return spring 8, which is supported on a support plate 7, which in turn is received in an injector 19 of the fuel injector 18. By means of the booster piston 4 of the pressure booster 3, a compression chamber 9 of the pressure booster 3 is acted upon. The booster piston 4 comprises, at its end facing the compression space 9, an end face 20 which, upon activation of the pressure booster 3, enters the compression space 9 of the pressure booster 3 and compresses the fuel contained therein.

The differential pressure chamber 6 (back space) of the pressure booster 3 is connected via an overflow 10 with an injection valve 14 acting on a control chamber 12 in connection. In the overflow line 10 between the differential pressure chamber 6 (back space) and the control chamber 12 for the injection valve member 14 is a first throttle point 11, lying in the flow direction of the fuel in front of the control chamber 12, respectively. In addition, the control chamber 12 is for the injection valve member 14 via a second throttle body 15 containing line with the compression chamber 9 of the pressure booster 3 in combination. Within the control chamber 12 for the injection valve member 14, a spring 13 is received, which acts on the upper end face of the needle-shaped injection valve member 14. The injection valve member 14 comprises a pressure stage, which is enclosed by a nozzle chamber 16 formed in a nozzle body. From the control chamber 16, the volume of fuel entering via a nozzle chamber inlet 17 from the compression chamber 9 into the nozzle chamber 16 flows along an annular gap at the combustion chamber end of the injection valve member 14 injection ports and is injected into the combustion chamber of the internal combustion engine upon release of the injection openings through the needle-shaped injection valve member 14.

In addition to the overflow 10 branches off the differential pressure chamber 6 (back space) of the pressure booster from a Absteuerleitung 21. This runs through the injector 19 of the fuel injector 18 and opens into a second hydraulic chamber 38 above of the pressure booster 3 is located. Above the injector body 19 of the fuel injector 18 is a servo valve 22 which, in the embodiment variant shown in FIG. 1, has a valve body 26 which comprises a first valve body part 27 and a second valve body part 28. The valve body 26 encloses a servo valve piston 23 with which a first sealing seat 24 and a second sealing seat 25 can be released or closed. In the illustration according to FIG. 1, a sealing edge 29 is formed on the first valve body component 27, to which a conical surface 33 of the servo valve piston 23 can be made to seal, whereby the second sealing seat 25 is represented. At the end opposite the control chamber 36 of the servo valve 22, the servo valve piston 23 has a first sealing seat 24 designed here as a flat seat, with which a flow control chamber 35 from which a first return 30 branches off can be released or closed. The actuation of the servo valve piston 23 of the servo valve 22 via a switching valve 32, which releases a second return 31 to a fuel reservoir, not shown in Figure 1 or closes. The fuel volume contained in the control chamber 36 of the servo valve 22 acts on an end face 39 of the servo valve piston 23. The filling of both the control chamber 36 and a first hydraulic chamber 37 in the first valve body part 27 via a pressure line, which branches off from the working space 5 of the pressure booster 3. Before the confluence of this pressure line in the control chamber 36 of the servo valve 22, a throttle point 47 is provided.

In the embodiment variant shown in FIG. 1, the servo valve piston 23 has a mushroom-shaped configured section, the upper side of which is formed by the conical surface 33. The mushroom-shaped portion is bounded on the conical surface 33 opposite side by an annular surface 34.

The servovalve piston 23 of the servo valve 22 shown in FIG. 1 is acted on at the end face 39 by the fuel volume contained in the control chamber 36 of the servo valve 22. In the idle state of the servo valve 22, this is closed, ie, the second sealing seat 25 is opened, while the first sealing seat 24 is closed to the flow control chamber 35. The servo valve piston 23 is guided in the first valve body part 27 of the valve body 26 high pressure-tight with respect to the control chamber 36 and the first hydraulic chamber 37. At this guide area is in the idle state of the servo valve 22 system pressure; ie both the control chamber 36 and the first hydraulic chamber 37 have the same pressure, so that no leakage flow in the direction of the first return 30 occurs. The entire area of the servo valve piston 23 of the servo valve 22 according to the embodiment variant shown in FIG. 1 is under system pressure with respect to the control chamber 36, the first and second hydraulic 37 and 38 and the second sealing seat 25.

Due to the closed first sealing seat 24 above the drain control space 35, this system is leak-proof sealed against the first return 30.

Figure 2 shows a variant of the first sealing seat of the servo valve, which is designed in this embodiment as a conical sealing seat, while the further sealing seat of the servo valve piston is designed as a slide seal.

In contrast to the embodiment variant of the servo valve shown in FIG. 1, the servo valve piston 46 in FIG. 2 is provided in the region of its first sealing seat 24 above the flow control space 35 for the first return 30 with a conical surface 40 which has a sealing edge formed above the flow control chamber in a one-piece valve body 41 35 interacts. The servo valve piston 46 of the servo valve 22 according to FIG. 2 has a slide portion 43, which is formed in the same diameter as the piston part of the servo valve piston 46, which separates the control chamber 36 in the first hydraulic chamber 37. The first hydraulic chamber 37 and the control chamber 36 in the one-piece valve body 41 are supplied from the work dream 5 of the pressure booster 3 - analogous to the representation of Figure 1 - with fuel. In the control chamber 36 and the first hydraulic chamber 37 in the one-piece valve body 41 of the servo valve 22 is at system pressure. Also, according to this embodiment, no leakage current occurs between said hydraulic chambers 36 and 37, respectively. Also according to this embodiment, the entire area of the servo valve piston 46, i. the control chamber 36, the first hydraulic chamber 37 and the second hydraulic chamber 38 and the second sealing seat 25 acted upon by system pressure. If the first sealing seat 24 of the servo valve 22 is closed, leakage does not occur according to this embodiment of the servo valve 22 against the first return 30, which branches off from the outlet control chamber 35.

The trained on the servo valve piston 46 slide portion 43 has a slide edge 45 which cooperates with a slide edge 44 on the one-piece valve body 41 of the servo valve 22.

Instead of the embodiment variants of the first sealing seat 24 shown in FIG. 1 or FIG. 2 as a flat seat (FIG. 1) or as a conical seat (FIG. 2 reference 40) or of the second sealing seat 25 as a conical surface 33 cooperating with a sealing edge 29 or as a slide seal 44, 45 combinations of flat seat, conical seat, ball seat or slide edges can be used in any arrangement. To support the lifting movement of the servo valve piston 23 and 46, spring elements not explicitly shown in FIGS. 1 and 2 can also be used.

As shown in FIG. 1, when the servo valve piston 23 is formed with a mushroom-shaped portion having a conical surface 33, a two-part servo valve housing 26 including a first valve body portion 27 and a second valve body portion 28 is advantageous. This facilitates the assembly. If the first sealing seat 24 according to the embodiment in FIG. 1 is designed as a flat seat, manufacturing tolerances in the axial offset of the two valve body parts 27 and 28 can be compensated for one another. The asked in the embodiment of Figure 1 in its closed position first sealing seat 24 - formed here as a flat seat - is hired by the prevailing in the control chamber 36 of the servo valve 22 large hydraulic force sealingly against the second valve body part 28, so that a tightness in today achievable manufacturing accuracies for is ensured under very high pressure fuel against the first return 30.

The mode of operation of the fuel injector shown in FIGS. 1 and 2 with a servo valve 22 which is leak-free in idle state will be described in more detail with reference to the embodiment variant shown in FIG.

The pressure booster 3 - here integrated in the injector 19 of the fuel injector 18 - has the working space 5 and the differential pressure chamber 6 (back space), which are separated from each other by the booster piston 4. The restoring force on the booster piston is applied by a restoring spring 8, which is supported on the support body 7 provided on the injector body side. The end face 20 of the booster piston 4 acts on a compression chamber 9, from which the nozzle chamber inlet 17 branches off to the nozzle chamber 16 in this body of the force injector 8. In the deactivated state of rest of the differential pressure chamber (back space) of the pressure booster on the open first sealing seat 25 and the branching off from the working space 5 of the pressure booster 3, leading to the first hydraulic chamber 37 and the control chamber 36 line is subjected to the same system pressure, under which the working space 5 of the pressure booster 3 stands. In this state of rest of the pressure booster 3 is pressure balanced and there is no pressure gain instead.

To activate the pressure booster 3, the differential pressure chamber 6 (back space) of the pressure booster 3 is depressurized. For this purpose, a control of the switching valve 32, which is opened, so that the control chamber 36 of the servo valve 22 is relieved of pressure in the second return 31. Due to this, due to the pressure force applied in the second hydraulic space 38, which acts on the annular surface 34 and adjusts the conical surface 33 to the sealing edge 29 of the first valve body part 27, the servo valve piston 23 moves upwardly and closes the second sealing seat 25, while in the latter Upward movement of the servo valve piston 23, the first sealing seat 24 opens. The opening degree of the first sealing seat 24 is dimensioned so that a residual pressure in the second hydraulic chamber 38 is maintained even in the open state of the first sealing seat 24. This ensures that the servo valve piston 23 of the servo valve 22 remains in its open position and the second sealing seat 25 is always closed.

When the first sealing seat 24 is opened, the differential pressure chamber 6 (back space) of the pressure booster 3 is decoupled from the high pressure accumulator 1 pending high pressure and pressure relief via the Absteuerleitung 21, the Absteuerraum 35 in the first return 30. Due to this, in the compression space 9 of the pressure booster 3, the pressure corresponding to the transmission ratio of the pressure booster 3 increases. About the nozzle space inlet 17 is this translated pressure in the nozzle chamber 16 at. Due to the translated in the nozzle chamber 16 translated pressure, which acts on the compression stage of the injection valve member 14, this opens, whereby the opening into the combustion chamber of the internal combustion engine injection openings are released and the injection process begins. When fully open injection valve member 14, the second throttle point 15 is closed, so that no leakage current occurs during the injection process.

To complete the injection process, the switching valve 32 of the servo valve 22 is closed, whereby 22 system pressure builds up in the control chamber 36 of the servo valve. The system pressure 36 acts on the end face 39 of the servo valve 23 and moves the servo valve piston 23 down to its initial position, whereby the second sealing seat 25 is opened and the first sealing seat 24 to the drain control chamber 35 and the first return 30 is closed again.

A pressure build-up in the differential pressure chamber 6 via the second hydraulic chamber 38 and the discharge line 21 takes place via the opened second sealing seat 25. Furthermore, the pressure prevailing in the pressure source 1 builds up over the working chamber 5, the first hydraulic chamber 37, the second hydraulic chamber 38, the diversion line 21, the differential pressure chamber 6 and the overflow line 10 also in the control chamber 12 for the injection valve member 14. As a result, the pressure in the compression chamber 9 and in the nozzle chamber 16, which are hydraulically connected to each other via the nozzle chamber inlet 17, falls. Due to the drop of the translated pressure in the nozzle chamber 16 and the compression chamber 9, the injection valve member 14 is supported by the action of the spring 13 is closed, whereby the injection is terminated.

The first and the second sealing seat 24 or 25 may be formed as combinations of flat seat, conical seat, ball seat or slide seats (see illustration according to FIG.

The inventively proposed solution of a servo valve 22 without pilot leakage can be used in all fuel injectors with pressure booster 3, which are controlled by a pressure change of the differential pressure chamber 6 (back space).

LIST OF REFERENCE NUMBERS

1

Pressure source (high-pressure reservoir)

2

High-pressure line

3

Pressure intensifier

4

Booster piston

5

working space

6

Differential pressure chamber (backspace)

7

support disc

8th

Return spring

9

compression chamber

10

overflow

11

first throttle point

12

Control chamber injection valve member

13

feather

14

Injection valve member

15

second throttle point

16

nozzle chamber

17

Nozzle chamber inlet

18

fuel injector

19

injector

20

End face of the booster piston

21

diversion line

22

servo valve

23

Servo valve piston (1st variant)

24

first sealing seat

25

second sealing seat

26

valve body

27

first valve body part

28

second valve body part

29

sealing edge

30

first return

31

second return

32

switching valve

33

conical surface

34

ring surface

35

diversion chamber

36

Control room Servovalve

37

first hydraulic room

38

second hydraulic room

39

Face servovalve piston

40

conical surface

41

one-piece valve body

42

attack

43

slide portion

44

Slide edge housing

45

Slide edge Servo valve piston

46

Servo valve piston (2nd variant)

47

restriction

Claims (11)

1. Fuel injector (18) for injecting fuel into a combustion chamber of an internal combustion engine, having a pressure booster (3) whose booster piston (4) separates a working space (5), which is acted on permanently with fuel via a pressure source (1, 2), from a differential pressure space (6) which can be relieved of pressure, with a pressure variation in the differential pressure space (6) taking place by means of an actuation of a servo valve (22) whose control space (36) can be relieved of pressure by means of a switching valve (32) and which opens or closes off a hydraulic connection (21, 38, 30) of the differential pressure space (6) to a first low-pressure-side return (30), with a servo valve piston (23, 46) having a first sealing seat (24) which opens or closes off the first return (30), and a second sealing seat (25) which opens or closes off the first hydraulic space (37), and with a high-pressure region, which encompasses the control space (36), a first hydraulic space (37) and a second hydraulic space (38), of the servo valve (22) being sealed off from a low-pressure-side return (30) by means of the first sealing seat (24) in the deactivated state of the pressure booster (3), characterized in that the first sealing seat (24), which opens or closes off the first return (30), is formed on the servo valve piston (23) at the opposite end from the control space (36).
2. Fuel injector according to Claim 1, characterized in that the actuation of the servo valve (22) takes place by means of the switching valve (32) which connects the control space (36) to a second return (31).
3. Fuel injector according to Claim 1, characterized in that the control space (36) of the servo valve (22) and the first hydraulic space (37) are connected to a pressure source (1) via the working space (5) of the pressure booster (3).
4. Fuel injector according to Claim 1, characterized in that the second hydraulic space (38) is connected via a shutoff line (21) to the differential pressure space (6), by means of which shutoff line (21) said differential pressure space (6) can be connected to a first low-pressure-side return (30).
5. Fuel injector according to Claim 1, characterized in that the first sealing seat (24) is designed as a flat seat or conical seat (40).
6. Fuel injector according to Claim 1, characterized in that the first sealing seat (24) is designed as a conical seat or slide seal.
7. Fuel injector according to Claim 1, characterized in that the second sealing seat (25) is designed as a conical seat (29, 33).
8. Fuel injector according to Claim 1, characterized in that the second sealing seat (25) is provided as a slide seal (43, 44, 45).
9. Fuel injector according to Claim 4, characterized in that the servo valve piston (23) has a section which is enclosed by the second hydraulic space (38) and which has an annular face (34) against which is applied a residual pressure, which adjusts the servo valve piston (23) into its second sealing seat (25), when the first sealing seat (24) is open.
10. Fuel injector according to Claim 5, characterized in that the servo valve piston (23) is held with a first sealing seat (24), which is designed as a flat seat, in a valve body (26; 27, 28) which is of two-part design and compensates an axial offset.
11. Fuel injector according to Claim 1, characterized in that the servo valve piston (23, 46) is of single-part design.

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