EP1452727B1 - Fuel injector - Google Patents

Description

State of the art

The invention relates to a fuel injection valve according to the preamble of the main claim.

EP 0 477 400 A1 discloses an arrangement for an adaptive mechanical tolerance compensation acting in the stroke direction for a travel transformer of a piezoelectric actuator for a fuel injection valve. The stroke of the actuator is transmitted via a hydraulic chamber. The hydraulic chamber has a defined leak with a defined leak rate. The stroke of the actuator is introduced via a master piston in the hydraulic chamber and transmitted via a slave piston to a driven element. This element is for example a valve needle of a fuel injection valve.

In the master cylinder, a slave piston is guided, which also closes the master cylinder and thereby forms the hydraulic chamber. In the hydraulic chamber, a spring is arranged, which presses apart the master cylinder and the slave piston. When the actuator transmits to the master cylinder a lifting movement, this stroke movement is due to the pressure of a hydraulic fluid in the hydraulic chamber on the Transfer slave piston, since the hydraulic fluid in the hydraulic chamber can not compress and only a small proportion of the hydraulic fluid can escape through the annular gap during the short period of a stroke. In the resting phase, when the actuator exerts no pressure force on the master cylinder, the slave piston is pushed out of the cylinder by the spring and by the resulting negative pressure penetrates through the annular gap, the hydraulic fluid in the hydraulic chamber and fills it again. As a result, the hydraulic coupler automatically adjusts to length expansions and pressure-related expansions of a fuel injection valve. The sealing of the hydraulic medium takes place via sealing rings.

In addition, fuel injection valves are known from the prior art, which seal hydraulic medium by flexible sections, for example in corrugated or bellows-shaped design.

A disadvantage of this known prior art that the flexible portion, for example, at maximum load, is not supported by a stop and is exposed to unfavorably high loads. This reduces the life and increases the manufacturing cost by correspondingly increased execution of the flexible section.

From DE 199 50 760 A1 a further embodiment is known.

Advantages of the invention

The fuel injection valve according to the invention with the characterizing features of the main claim has the advantage that the flexible section is reliably protected from unacceptably high strain or stress and so the coupler simple and inexpensive to produce, less expensive and reliable reliable running.

The stopper body is shaped like a sleeve. The stopper body can be so easy to manufacture and assemble.

The measures listed in the dependent claims advantageous developments of the fuel injection valve specified in the main claim are possible.

It is advantageous if the slave piston at least partially consists of a cup-shaped first slave section, the bottom of which partially limits the coupler volume, and the master piston encloses the first slave section in a partially cup-shaped manner. This makes it possible to build the slave piston-master piston assembly very easy. It is likewise advantageous if the upper end of the first slave section projects beyond the upper end of the master piston.

In a further development, the slave piston has a second slave section which is immovably connected to the first slave section or the second slave section additionally has a diameter shoulder whose diameter is greater than that of the first slave section and which is about the same size as the master piston diameter. As a result, the coupler can be built very compact and integrate the flexible section particularly advantageous in the coupler.

It is also advantageous if the diameter shoulder rests on the upper end of the first slave section or the upper end of the first slave section is beyond the upper end of the master piston. This also makes a very compact design possible.

An advantageous simple construction is also given by the fact that the throttle is arranged in the bottom of the first slave section.

If the throttle comprises a throttle ball, which is guided with a throttle gap in an opening, the throttle can be constructed in a particularly simple manner and, if the throttle ball is supported on a surface bounding the coupler volume of the master piston, be advantageously constructed for the function of the coupler.

It is also advantageous if one end of the flexible portion on the slave piston and / or the other end of the flexible portion is hermetically sealed to the master piston, in particular positive and / or non-positive. The flexible section can be particularly easily integrated into the coupler.

In a further development, at least one respective recess is arranged in the radial outer surfaces of the master piston and / or the slave piston, which is in particular annular and in which engages at least one of the ends of the flexible portion.

Advantageously, at least one recess is trough-shaped. As a result, the end of the recess engaging in the flexible portion can be particularly easily secured against axial displacements.

It is also advantageous if the stopper body is fixed in at least one of the ends of the flexible portion in at least one of the recesses positively and / or non-positively and hermetically sealed. The coupler can be made very compact.

If the ends of the flexible section are thickened, they can be fixed hermetically tight in the coupler with very little effort.

It is also particularly advantageous if the stop has an evasive volume. The flexible section can thereby at a well-defined place and in a through the Extend shape of the escape volume fixed advantageous shape.

It is also advantageous to arrange the evasion volume approximately at the level of the middle of the flexible section. The flexible section can thereby be evenly loaded.

It is also advantageous to widen a part of the axial course of the stopper body to the outside, in particular round or circular segment, thereby forming the escape volume. The evasive volume can be made particularly easy.

It is furthermore advantageous to design the stop body at least in two parts in a first stop section and a second stop section, wherein the two stop sections are divided by a particular annular stop gap.

The stop gap is advantageously arranged at the height of the center of the escape volume. The flexible section is characterized mechanically stressed evenly and the stop gap can be easily mounted, for example, by laser welding after mounting on the coupler.

drawing

Fig. 1

einen schematischen Schnitt durch ein Brennstoffeinspritzventil gemäß dem Stand der Technik,

Fig. 2

einen schematischen Ausschnitt eines Brennstoffeinspritzventils im Bereich des Kopplers gemäß dem Stand der Technik, ähnlich dem in Fig. 1 dargestellten Brennstoffeinspritzventil,

Fig. 3

ein erstes Ausführungsbeispiel eines erfindungsgemäßen Brennstoffeinspritzventils im Bereich des Kopplers und

Fig. 4

ein zweites Ausführungsbeispiel eines erfindungsgemäßen Brennstoffeinspritzventils im Bereich des Kopplers.

Embodiments of the invention are shown in simplified form in the drawing and explained in more detail in the following description. Show it:

Fig. 1

a schematic section through a fuel injection valve according to the prior art,

Fig. 2

a schematic section of a fuel injection valve in the region of the coupler according to the prior art, similar to the fuel injection valve shown in Fig. 1,

Fig. 3

a first embodiment of a fuel injection valve according to the invention in the region of the coupler and

Fig. 4

A second embodiment of a fuel injection valve according to the invention in the region of the coupler.

Description of the embodiments

Hereinafter, embodiments of the invention will be described by way of example.

Before the invention is described in more detail with reference to preferred embodiments, a fuel injection valve according to the prior art in its essential components in FIGS. 1 and 2 is briefly explained for better understanding. Matching components are provided in the figures with corresponding reference numerals.

The fuel injection valve 1 shown in FIG. 1 is in the form of a fuel injection valve 1 for fuel injection systems of mixture-compression spark-ignition internal combustion engines. The fuel injection valve 1 is suitable in particular for the direct injection of fuel into a combustion chamber, not shown, of an internal combustion engine.

The fuel injection valve 1 comprises a housing 2, in which a provided with an Aktorumspritzung 3 piezoelectric or magnetostrictive actuator 4 is arranged. The actuator 4 can be supplied by means of an electrical line 5, to which a protruding from the housing 2 electrical terminal 6, an electrical voltage can be supplied. The actuator 4 is supported on the inflow side a master piston 9 of a hydraulic coupler 7 and downstream of an actuator head 8 from. The hydraulic coupler 7 further comprises a slave piston 10, a compression spring 11, which biases the hydraulic coupler 7, and a compensation chamber 12, which is filled with a hydraulic medium. The fuel is fed centrally via an inlet 14.

A detailed description of the coupler 7 and its function is the description of FIG. 2 can be seen.

Downstream of the actuator head 8, an actuating body 15 is arranged, which acts on a valve needle 16. The valve needle 16 has at its downstream end a valve closing body 17. This acts together with a valve seat surface 18, which is formed on a nozzle body 19, to form a sealing seat. A return spring 20 acts on the valve needle 16 so that the fuel injection valve 1 remains in the de-energized state of the actuator 4 in the closed state. Furthermore, it ensures the return of the valve needle 16 after the injection phase.

The nozzle body 19 is fixed by means of a weld 21 in an inner housing 22, which seals the actuator 4 against the fuel. The fuel flows from the inlet 14 between the housing 2 and the inner housing 22 to the sealing seat.

FIG. 2 shows a coupler 7 constructed similarly to the coupler shown in FIG.

Hydraulic couplers 7 in fuel injection valves 1 are usually designed on the one hand for conversion or translation of the stroke of the actuator 4 on the valve needle 16 and / or on the other hand to compensate for temperature-induced changes in length of the actuator 4 and the housing 2. The latter is realized, as shown in the exemplary embodiment, by means of the coupler 7 designed as a second medium coupler, which contains a hydraulic medium not in contact with the fuel. The hydraulic medium fills the compensation chamber 12 and a coupler volume 23 formed between master piston 9 and slave piston 10, which is connected to the compensation chamber 12 via a throttle 24.

The compensation chamber 12 is disposed inside and outside the slave piston 10, wherein the two parts are connected by a transverse bore 31 and the outboard part of the compensation chamber 12 is sealed by means of a corrugated pipe seal designed as flexible portion 13 relative to the fuel injector 1 flowing through the fuel. In the event of temperature changes, hydraulic medium is exchanged between the coupler volume 23 via the throttle 24 with the compensation chamber 12.

The necessary filling pressure is applied via the pressure piston 11 arranged in the slave piston 10 in a pressure storage chamber 32. This is arranged between a first closure body 25 and a second closure body 26, the former having a groove 27 with a sealing ring 28 arranged therein for sealing the coupler space 12.

The filling of the coupler 7, for example in the production, with hydraulic medium takes place through a channel 29, which may be closed, for example by means of a pressed-in closure ball 30.

FIG. 3 shows an exemplary embodiment of a coupler 7 for a fuel injection valve 1 configured according to the invention. The slave piston 10 engages with a cup-shaped first slave section 34 in the hollow-cylindrical master piston 9 closed on one side. The slave piston 10 or the first slave section 34 is axially movably guided in the master piston 9 with a guide gap 38. The guide gap 38 is relatively small, wherein the amount flowing through the guide gap 38 of hydraulic medium very is small. In other embodiments, the guide gap 38 may exert a throttle function.

In this embodiment, the slave piston 10 of the first slave portion 34 and a second slave portion 35. The first slave section 34 defines with its closed end together with the bottom of the master piston 9, the coupler volume 23, wherein centered in the closed end of the first slave section 34, the throttle 24th is arranged. The throttle 24 consists of an opening 36 centered in the bottom of the cup-shaped first slave section 24 and a throttle ball 39 guided therein with a throttle gap 37.

The open, the coupler volume 23 facing away from the end of the first slave section 34 is closed by the second slave section 35. The second slave section 35 engages partially in the first slave section 34 and is joined, for example by pressing or welding with this motion. Between the engaging in the first slave section 34 end of the second slave section 35 and the throttle ball 39, the compression spring 11 is arranged with a bias in a arranged in the first slave section 34 spring chamber 45. The compression spring 11 is spirally and presses on the throttle ball 39 with the interposition of a spring plate 40, wherein the throttle ball 39 is supported at the bottom of the master piston 9 in the coupler volume 23.

The upper, the coupler volume 23 facing away from the ends of the first slave section 34 and the master piston 9 are approximately at the same height, the end of the first slave section 34 projects slightly beyond the end of the master piston 9. The second slave section 35 partially engaging the first slave section 34 extends its diameter through a step 44 above the upper end of the first slave section 34 to a flange-like diameter shoulder 46, the diameter shoulder 46 in this embodiment having its lower, first Nehmerabschnitt 34 facing side rests on the upper end of the first slave section 34. The diameter shoulder 46 has approximately the diameter of the master piston 9.

The compensation chamber 12 is limited by the flexible portion 13, the second slave portion 35 with its diameter shoulder 46, the master piston 9 and the first slave section 34, wherein the compensation chamber 12 via the transverse bore 31 and the spring chamber 45 communicates with the throttle 24. The channel 29 with the closure ball 30 is realized coaxially in the second slave section 35 through a bore which opens into the spring chamber 45.

The flexible portion 13 may be elastic and is preferably made of an elastomer. In this embodiment, the flexible portion 13 is a hollow cylindrical or sleeve-shaped and arranged coaxially with the pistons 9, 10, wherein the ends and the lower and upper edges are each thickened.

The flexible portion 13 lies with the upper end in a trough-shaped first recess 42 which is formed in the radial outer surface of the second slave portion 35 and the Durchmesserabsatzes 46, and with its lower end in a trough-shaped second recess 43, which in the region of the outer surface the upper end of the master piston 9 is arranged. The axial extent of the recesses 42, 43 is in each case slightly larger than the axial extent of the thickened ends. As a result, in particular the assembly is facilitated.

A two-part executed in the exemplary embodiment sleeve-shaped stopper body 33 is precisely aligned over the diameter shoulder 46, the flexible portion 13 and the upper portion of the master piston 9 pulled. The stopper body 33 consists of an upper first stopper portion 47 and a lower second stopper portion 48. The first stopper portion 47 is fixed to movement with the slave piston 10 and the second Nehmerabschnitt 35 joined, for example by welding or pressing. The second stopper portion 48 is immovably joined to the master piston 9, for example by welding or pressing. At its end remote from the second stop section 48, the first stop section 47 has a retraction 49, at which the diameter of the first stop section 47 tapers. Thereby, the first stopper portion 47 can be mounted more easily.

Approximately at the level of the middle of the flexible portion 13 of the stopper body 33 is bent away at an alternate portion 51, for example, round and in particular circular segment-shaped, from the flexible portion 13. This creates between the flexible portion 13 and the stopper body 33 and the escape portion 51, an evasive volume 52, in which the flexible portion 13 can expand at inflow of hydraulic medium from the coupler volume 23. The stopper body 33 limits the extension of the flexible portion 13, which takes place with a movement directed towards the axial movement axis of the pistons 9, 10 with a radial direction component, and protects it from damage. The axial extent of the escape portion 51 extends between the thickened ends of the flexible portion 13 and does not enclose them, so that the thickened ends can be reliably pressed by the stopper body 33 hermetically sealed in the recesses 42, 43. A stop gap 50 separates the two stop sections 47, 48.

Over long periods on the coupler 7 axially acting forces, such as occur in a temperature-induced expansion of the actuator 4, cause a reduction in the Kopplervolumens 23 by flow of hydraulic fluid from the coupler volume 23 through the throttle 24 via the spring chamber 45 and the transverse bore 31 in the Compensation space 12, which is partially limited by the elastic and membrane-like flexible portion 13. By a bias of the compression spring 11 is a Coupler volume 23 exerted increasing pressure on the hydraulic medium.

The dynamic stiffness of the coupler 7 is determined in particular by the size and shape of the throttle gap 37 and possibly by the size and shape of the guide gap 38.

4 shows a second exemplary embodiment of a fuel injection valve according to the invention in the region of the coupler 7.

The cup-shaped slave piston 10 engages with its open end first in the one-sided closed hollow-cylindrical master piston 9, wherein the open end of the slave piston 10 is closed with a throttle disk 41. The slave piston 10 is axially movably guided in the master piston 9 with a guide gap 38. The guide gap 38 is relatively small, wherein the amount of hydraulic medium flowing through the guide gap 38 is very small. In other embodiments, the guide gap 38 may exert a throttle function.

The slave piston 10 is limited with its closed by the throttle disk 41 end together with the bottom of the master piston 9, the coupler volume 23. In the throttle disk 41 is centered which designed as a relatively thin bore throttle 24 is arranged. The sealed by the closure ball 30 channel 29 extends centered in the master piston 9 and opens directly into the coupler volume 23. The arranged in the slave piston 10 above the upper edge of the master piston 9 transverse bore 31 connects via the interior of the slave piston 10 the compensation chamber 12 with the throttle 24th

The compensation chamber 12 is bounded by the upper edge of the master piston 9, the slave piston 10 and the flexible portion 13. The flexible portion 13 is made of an elastomer and is sleeve-shaped, with its diameter tapers from the master piston 9 upwards. The The upper end of the flexible portion 13 is clamped between a piston 10 which tapers the diameter of the slave piston 10 in the upper region, and a cover 53 comprising the upper region of the slave piston 10. The lower end of the flexible portion 13 is clamped in the arranged in the outer surface of the master piston 9 second recess 43 through the sleeve-shaped in this embodiment, and the master piston 9 accurately comprehensive stop body 33.

The invention is not limited to the illustrated embodiments and suitable for any designs of fuel injectors 1, in particular for fuel injectors 1 for auto-ignition internal combustion engines and / or inwardly opening fuel injectors.

LIST OF REFERENCE NUMBERS

1

Fuel injector

2

casing

3

actuator extrusion coat

4

actuator

5

electrical line

6

Connection

7

coupler

8th

actuator head

9

master piston

10

slave piston

11

compression spring

12

compensation space

13

flexible section

14

Intake

15

operating body

16

valve needle

17

Valve closing body

18

Valve seat

19

nozzle body

20

Return spring

21

Weld

22

inner housing

23

coupler

24

throttle

25

first closure body

26

second closure body

27

groove

28

seal

29

channel

30

closing ball

31

cross hole

32

Pressure reservoir

33

stop bodies

34

first slave section

35

second slave section

36

opening

37

throttle gap

38

guide gap

39

throttle ball

40

spring plate

41

throttle disc

42

first recess

43

second recess

44

step

45

spring chamber

46

Diameter paragraph

47

first stop section

48

second stop section

49

collection

50

stop gap

51

escape portion

52

dodge volume

53

cover

54

piston step

Claims (28)

1. Fuel injection valve having a piezoelectric or magnetostrictive actuator (4) which activates a valve-closing body (17) which interacts with a valve seat face (18) to form a sealing seat, and having a hydraulic coupler (7) which comprises a master piston (9), a slave piston (10) and a coupler volume (23) formed between them, the master piston (9) and the slave piston (10) being movable axially with respect to one another, the coupler volume (23) being connected to an equalization space (12) via a throttle (24), a flexible section (13) at least partially bounding the equalization space (12), and the coupler volume (23), the throttle (24) and the equalization space (12) being filled with a hydraulic medium, and the flexible section (13) being bounded by a stop element (33) in its outwardly directed extent, characterized in that the stop element (33) is in the form of a sleeve.
2. Fuel injection valve according to Claim 1, characterized in that the slave piston (10) is composed at least partially of a cup-shaped first slave section (34) whose base partially bounds the coupler volume (23) .
3. Fuel injection valve according to Claim 2, characterized in that the master piston (9) partially encloses the first slave section (34) in the form of a cup.
4. Fuel injection valve according to Claim 2 or 3, characterized in that the upper end of the first slave section (34) protrudes beyond the upper end of the master piston (9).
5. Fuel injection valve according to one of Claims 2 to 4, characterized in that the slave piston (10) has a second slave section (35) which is connected fixed in terms of movement to the first slave section (34).
6. Fuel injection valve according to Claim 5, characterized in that the second slave section (35) has a diameter shoulder (46) whose diameter is greater than that of the first slave section (34) and approximately as large as that of the master piston (9).
7. Fuel injection valve according to Claim 6, characterized in that the diameter shoulder (46) rests on the upper end of the first slave section (34).
8. Fuel injection valve according to one of Claims 2 to 7, characterized in that the throttle (24) is arranged in the base of the cup-shaped first slave section (34).
9. Fuel injection valve according to one of Claims 2 to 8, characterized in that the upper axial end of the first slave section (34) which faces away from the coupler volume (23) protrudes beyond the upper axial end of the master piston (9) which faces away from the coupler volume (23).
10. Fuel injection valve according to one of the preceding claims, characterized in that the throttle (24) comprises a throttle ball (39) which is guided with a throttle gap (37) in an opening (36).
11. Fuel injection valve according to Claim 10, characterized in that the throttle ball (39) is supported on a face of the master piston (9) which bounds the coupler volume (23).
12. Fuel injection valve according to one of the preceding claims, characterized in that one end of the flexible section (13) is fitted in a hermetically sealed fashion, in particular in a positively and/or frictionally locking fashion, onto the slave piston (10) and/or the other end of the flexible section (13) is fitted in a hermetically sealed fashion, in particular in a positively and/or frictionally locking fashion, onto the master piston (9).
13. Fuel injection valve according to one of the preceding claims, characterized in that in each case at least one recess (42, 43) is arranged in the radial outer faces of the master piston (9) and/or of the slave piston (10).
14. Fuel injection valve according to Claim 13, characterized in that at least one of the recesses (42, 43) is in the shape of an annular groove.
15. Fuel injection valve according to Claim 13 or 14, characterized in that at least one of the ends of the flexible section (13) engages in at least one of the recesses (42, 43).
16. Fuel injection valve according to one of Claims 13 to 15, characterized in that at least one of the recesses (42, 43) is trough-shaped.
17. Fuel injection valve according to one of Claims 13 to 16, characterized in that the stop element (33) of at least one of the ends of the flexible section (13) is secured in a positively and/or frictionally locking fashion and in a hermetically sealed fashion in at least one of the recesses (42, 43).
18. Fuel injection valve according to one of the preceding claims, characterized in that the ends of the flexible section (13) are thickened.
19. Fuel injection valve according to one of the preceding claims, characterized in that the stop element (33) has a compensation volume (52).
20. Fuel injection valve according to Claim 19, characterized in that the compensation volume (52) is arranged approximately at the level of the centre of the flexible section (13).
21. Fuel injection valve according to Claim 19 or 20, characterized in that the flexible section (13) expands into the compensation volume (52) when the coupler volume (23) is reduced.
22. Fuel injection valve according to one of Claims 19 to 21, characterized in that the compensation volume (52) is formed by a part of the axial profile of the stop (33) being widened outwards.
23. Fuel injection valve according to Claim 22, characterized in that the part of the axial profile of the stop element (33) which forms the compensation volume (52) is widened outwards in a round shape, in particular in the form of a circular segment.
24. Fuel injection valve according to one of Claims 19 to 23, characterized in that the stop element (33) is divided at least into a first stop section (47) and a second stop section (48).
25. Fuel injection valve according to Claim 24, characterized in that the stop element (33) is divided by a stop gap (50), in particular by an annular stop gap (50).
26. Fuel injection valve according to Claim 25, characterized in that the stop gap (50) is arranged at the level of the centre of the compensation volume (52).
27. Fuel injection valve according to one of the preceding claims, characterized in that the compensation space (12) is bounded by the flexible section (13), the slave piston (10) and the master piston (9).
28. Fuel injection valve according to one of the preceding claims, characterized in that the flexible section (13) is elastic and is composed in particular of an elastomer.

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