EP1452727A1 - Fuel injector - Google Patents

Abstract

A fuel injection valve for a combustion engine with a piezoelectric or magnetorestrictive actuator comprises a valve body and seat and a hydraulic fluid coupling having two movable pistons (9,10) and a coupling volume connected by a throttle to an equalization space(12) in a flexible section (13) which is constrained by an outside contacting body (33).

Description

State of the art

The invention is based on a fuel injector according to the genus of the main claim.

EP 0 477 400 A1 describes an arrangement for an in Adaptive mechanical acting stroke direction Tolerance compensation for a displacement transformer piezoelectric actuator for a fuel injector known. The stroke of the actuator is over a Transfer hydraulic chamber. The hydraulic chamber has one defined leak with a defined leak rate. The hub the actuator is inserted into the Hydraulic chamber initiated and on a slave piston transfer an element to be driven. This element is for example a valve needle Fuel injector.

A slave piston is guided in the master cylinder Master cylinder also closes and thereby the Hydraulic chamber forms. There is one in the hydraulic chamber Spring arranged the master cylinder and the slave piston presses apart. If the actuator on the master cylinder one Transmits stroke movement, this stroke movement by the Pressure of a hydraulic fluid in the hydraulic chamber on the Transfer slave piston because the hydraulic fluid in the Hydraulic chamber can not be compressed and only one low proportion of hydraulic fluid through the annular gap can escape during the short period of a stroke. In the idle phase when the actuator does not exert any pressure on the Master cylinder exerts, is the spring of the slave piston pushed out of the cylinder and by the resulting Vacuum penetrates the hydraulic fluid through the annular gap the hydraulic space and refills it. Thereby the hydraulic coupler sets up automatically Linear expansion and expansion due to pressure Fuel injector. Sealing the Hydraulic medium takes place via sealing rings.

Are also from the prior art Fuel injectors are known for being flexible Sections, for example in corrugated pipe or bellows-shaped design, seal hydraulic medium.

A disadvantage of this known prior art is that the flexible section, for example at maximum Load, is not supported by a stop and so is disadvantageously exposed to high loads. This reduces the lifespan and increases the Manufacturing effort through appropriately reinforced design of the flexible section.

Advantages of the invention

The fuel injector according to the invention with the has characteristic features of the main claim in contrast the advantage that the flexible section reliable against impermissibly high elongation or stress is protected and so the coupler is simple and inexpensive producible, less complex and reliable is durable.

By the measures listed in the subclaims advantageous developments of the main claim specified fuel injector possible.

In a first development, the stop body shaped like a sleeve. The stop body can be so easy to manufacture and assemble.

Furthermore, it is advantageous if the slave piston at least partly from a cup-shaped first slave section exists, the bottom of which partially limits the coupler volume, and the master piston partially the first slave section cup-shaped encloses. This makes it possible to Slave piston-master piston arrangement particularly simple build. It is also advantageous if the upper end the first slave section over the upper end of the The piston.

In a further development, the slave piston has one second slave section on the first Slave section is fixedly connected or the second Slave section also has a diameter shoulder whose diameter is larger than that of the first Slave section and is approximately as large as the diameter of the master piston. This makes the coupler particularly easy compact design and the flexible section in particular advantageous to integrate in the coupler.

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

This is also an advantageous simple construction given that the throttle in the bottom of the first Slave section is arranged.

Does the throttle include a throttle ball that with a Throttle gap is guided in an opening, the throttle be built particularly easily and if the Throttle ball on a surface delimiting the coupler volume supports the master piston for the function of the coupler be built up advantageously.

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

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

At least one recess is advantageous trough-shaped. This allows the end of the in the recess engaging flexible section particularly easy against axial displacements can be secured.

It is also advantageous if the stop body at least one of the ends of the flexible portion in at least one of the recesses form and / or is non-positive and hermetically sealed. The coupler can be built particularly compact.

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

It is also particularly advantageous if the stop is on Has evasive volume. The flexible section can thereby in a precisely defined place and in one by the Form of the alternative volume defined advantageous form expand.

It is also advantageous to approximately increase the escape volume Arrange the height of the center of the flexible section. The flexible section can be loaded evenly.

It is also advantageous to use a part of the axial Widen the course of the stop body to the outside, in particular round or segment of a circle to thereby To form alternative volume. The escape volume can thereby be manufactured particularly easily.

It is also advantageous, at least the stop body two parts in a first stop section and one second stop section, the two Stop sections by a particularly annular Stop gap are divided.

The stop gap is advantageously at the level of Arranged in the middle of the escape volume. The flexible one Section is mechanically evenly stressed and the stop gap can be easily after the Assembly on the coupler, for example by laser welding be attached.

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

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

Fig. 2

3 shows a schematic section of a fuel injection valve in the area 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 injector according to the invention in the area of the coupler and

Fig. 4

a second embodiment of a fuel injector according to the invention in the area of the coupler.

Description of the embodiments

The following are exemplary embodiments of the invention described as an example.

Before the invention based on preferred embodiments is described in more detail for better understanding Fuel injector according to the prior art in its essential components in FIGS. 1 and 2 briefly explained. Matching components are in the Figures with matching reference numerals.

The fuel injector 1 shown in FIG. 1 is in the form of a fuel injector 1 for Fuel injection systems from mixture-compressing, spark-ignition internal combustion engines. The Fuel injection valve 1 is particularly suitable for not directly injecting fuel into one Shown combustion chamber of an internal combustion engine.

The fuel injector 1 comprises a housing 2, in which is provided with an actuator extrusion coating 3 piezoelectric or magnetostrictive actuator 4 arranged is. The actuator 4 can by means of an electrical line 5, on which an electrical protruding from the housing 2 Connection 6 can be formed, an electrical voltage are fed. The actuator 4 is supported on the inflow side a master piston 9 of a hydraulic coupler 7 and on the downstream side at an actuator head 8. The hydraulic one Coupler 7 further comprises a slave piston 10, one Compression spring 11, which the hydraulic coupler 7 with a Preloaded, and a compensation chamber 12, which is filled with a hydraulic medium. The Fuel is supplied centrally via an inlet 14.

A detailed description of the coupler 7 and its Function can be found in the description of FIG. 2.

An actuator body 15 is located on the downstream side of the actuator head 8 arranged, which acts on a valve needle 16. The Valve needle 16 has one at its downstream end Valve closing body 17. This works with one Valve seat 18, which on a nozzle body 19th is formed to form a sealing seat. A Return spring 20 acts on the valve needle 16 so that the fuel injector 1 in the de-energized state of the Actuator 4 remains in the closed state. Still worries them after the injection phase for resetting the Valve needle 16.

The nozzle body 19 is in one by means of a weld seam 21 Fixed inner housing 22, which the actuator 4 against the Fuel seals. The fuel flows from the inlet 14 between the housing 2 and the inner housing 22 for Sealing seat.

Fig. 2 shows a similar to that shown in Fig. 1 Coupler built coupler 7.

Hydraulic couplers 7 in fuel injection valves 1 are usually on the one hand to translate or translate the hub of the Actuator 4 on the valve needle 16 and / or on the other hand Compensation of temperature-related changes in length of the actuator 4 and the housing 2 designed. The latter, as in the Embodiment shown using the as Realized coupler 7 implemented second medium coupler, which is one that does not come into contact with the fuel Contains hydraulic medium. The hydraulic medium fills the Compensation chamber 12 and one between master piston 9 and Slave piston 10 formed coupler volume 23, which with the compensation chamber 12 is connected via a throttle 24.

The compensation space 12 is inside and outside of the Slave piston 10 arranged, the two parts by a transverse bore 31 are interconnected and the outside part of the compensation space 12 by means of a Flexible section 13 designed as a corrugated pipe seal compared to which the fuel injector 1 flowing fuel is sealed. at Temperature changes will occur between the hydraulic medium Coupler volume 23 via the throttle 24 with the compensation space 12 exchanged.

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

The filling of the coupler 7, for example in the Manufacturing, with hydraulic medium is done through a channel 29, which for example by means of a pressed Locking ball 30 can be closed.

Fig. 3 shows an embodiment of a coupler 7 for a fuel injector designed according to the invention 1. The slave piston 10 engages with a cup-shaped first slave section 34 in the closed on one side hollow cylindrical master piston 9 a. The slave piston 10 or the first slave section 34 is axial in the master piston 9 movably guided with a guide gap 38. The Guide gap 38 is relatively small, the by the Guide gap 38 flowing amount of hydraulic medium very much is small. In other embodiments, the Guide gap 38 perform a throttle function.

In this embodiment, the slave piston 10 from the first slave section 34 and a second Slave section 35. The first slave section 34 delimits with its closed end together with the bottom of the Master piston 9, the coupler volume 23, being in the closed The throttle 24 centers the end of the first slave section 34 is arranged. The throttle 24 consists of a centered in the bottom of the cup-shaped first slave section 24 arranged opening 36 and one therein with a Throttle gap 37 guided throttle ball 39.

The open end of the first, facing away from the coupler volume 23 Slave section 34 is through second slave section 35 locked. The second slave section 35 engages partially into the first slave section 34 and is for example by pressing or welding with it joined motionless. Between that in the first Slave section 34 engaging end of the second Slave section 35 and the throttle ball 39 is the Compression spring 11 with a bias in one in the first Slave section 34 arranged spring chamber 45 arranged. The Compression spring 11 is spiral and presses on the Throttle ball 39 with the interposition of a spring plate 40, the throttle ball 39 at the bottom of the master piston 9 is supported in the coupler volume 23.

The upper ends of the coupler volume facing away from the first slave section 34 and the master piston 9 about the same height, with the end of the first Slave section 34 slightly above the end of the master piston 9 protrudes. Partially in the first slave section 34 engaging second slave section 35 extends its Diameter through a step 44 above the upper end of the first slave section 34 to a flange-like Diameter step 46, the diameter step 46 in this embodiment with its lower, the first Slave section 34 facing side on the upper end of the first slave section 34 rests. The diameter paragraph 46 has approximately the diameter of the master piston 9.

The compensation space 12 is through the flexible section 13, the second slave section 35 with its diameter shoulder 46, the master piston 9 and the first slave section 34 limited, the compensation chamber 12 via the cross hole 31 and the spring chamber 45 with the throttle 24 in connection stands. The channel 29 with the locking ball 30 is coaxial second slave section 35 realized by a bore, which opens into the spring chamber 45.

The flexible section 13 can be elastic and is made preferably made of an elastomer. In this The embodiment is the flexible section 13 hollow cylindrical or sleeve-shaped and coaxial to the pistons 9, 10 arranged, the ends or the lower and upper Edge is thickened in each case.

The flexible section 13 lies in one with the upper end trough-shaped first recess 42, which in the radial Outer surface of the second slave section 35 and the Diameter paragraph 46 is formed, and with his lower end in a trough-shaped second recess 43, which in the area of the outer surface of the upper end of the Master piston 9 is arranged. The axial extent of the Recesses 42, 43 are each slightly larger than that axial expansion of the thickened ends. This is especially the assembly easier.

A two-part in the embodiment sleeve-shaped stop body 33 is a precise fit over the Diameter paragraph 46, the flexible section 13 and the pulled the upper area of the master piston 9. The Stop body 33 consists of an upper first Stop section 47 and a lower second Stop section 48. The first stop section 47 is non-moving with the slave piston 10 or the second Slave section 35 added, for example by welding or presses. The second stop section 48 is joined to the master piston 9 in a manner fixed against movement, for example by welding or pressing. On his second The end facing away from the stop section 48 has the first Stop section 47 on a feeder 49 on which the Diameter of the first stop section 47 tapers. This makes the first stop section 47 easier to be assembled.

Approximately at the middle of the flexible section 13 is the Stop body 33 on an evasion section 51, for example round and in particular segmented, from flexible section 13 bent away. This creates between the flexible section 13 and the stop body 33 or the escape section 51, an escape volume 52, in which the flexible section 13 from the inflow of hydraulic medium can expand the coupler volume 23. The stop body 33 limits the expansion of the flexible portion 13 that with one with the axial axis of movement of the pistons 9, 10 radial directional directional movement takes place, and protects it from damage. The axial extent of the Dodge section 51 extends between the thickened Ends of the flexible portion 13 and closes it not one, so that the thickened ends reliably from Stop body 33 hermetically sealed in the recesses 42, 43 can be pressed. A stop gap 50 separates the two stop sections 47, 48.

Long acting axially on the coupler 7 Forces such as those caused by temperature Expansion of the actuator 4 occur, cause a Reduction of the coupler volume 23 by draining Hydraulic medium from the coupler volume 23 through the throttle 24 via the spring chamber 45 and the transverse bore 31 in the Compensation chamber 12 through the elastic and membrane-like flexible section 13 partially limited is. By biasing the compression spring 11 is a Coupler volume 23 increasing pressure on the Hydraulic medium exerted.

The dynamic stiffness of the coupler 7 becomes particular by the size and shape of the throttle gap 37 and possibly by determines the size and shape of the guide gap 38.

Fig. 4 shows a second embodiment of a Fuel injector according to the invention in the area of Coupler 7.

The cup-shaped slave piston 10 engages with its open one End ahead in the one-sided closed a hollow cylindrical master piston 9, the open End of the slave piston 10 with a throttle disk 41 is closed. The slave piston 10 is in the master piston 9 axially movable with a guide gap 38. The Guide gap 38 is relatively small, the by the Guide gap 38 flowing amount of hydraulic medium very much is small. In other embodiments, the Guide gap 38 perform a throttle function.

The slave piston 10 is limited by its Throttle disc 41 closed end together with the bottom of the master piston 9, the coupler volume 23. In the Throttle disk 41 is centered as a relatively thin Bore throttle 24 arranged. The one through the Lock ball 30 closed channel 29 is centered in the master piston 9 and opens directly into the coupler volume 23. The in the slave piston 10 above the upper edge of the Master piston 9 arranged transverse bore 31 connects via the Interior of the slave piston 10, the compensation chamber 12 with the Throttle 24.

The compensation space 12 is through the upper edge of the Master piston 9, the slave piston 10 and the flexible Section 13 limited. The flexible section 13 consists of an elastomer and is shaped like a sleeve, whereby its diameter tapers upwards from the master piston 9. The upper end of the flexible section 13 is between one the slave piston 10 in the upper area upwards diameter-reducing piston stage 54 and one the upper Area of the slave piston 10 comprising cover 53 clamped. The lower end of the flexible section 13 is in the outer surface of the master piston 9 arranged second recess 43 through the in this Embodiment also sleeve-shaped and Master piston 9 precisely fitting stop body 33 clamped.

The invention is not shown on the Embodiments limited and for any design of fuel injection valves 1, especially for Fuel injection valves 1 for self-igniting Internal combustion engines and / or inward opening Fuel injectors, suitable. The characteristics of the Exemplary embodiments can be combined with one another as desired.

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 body

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

Indent

50

stop gap

51

escape portion

52

dodge volume

53

cover

54

piston step

Claims (29)

Fuel injection valve with a piezoelectric or magnetostrictive actuator (4), which actuates a valve closing body (17), which cooperates with a valve seat surface (18) to form a sealing seat, and with a hydraulic coupler (7), which has a master piston (9), a slave piston ( 10) and a coupler volume (23) formed therebetween, the master piston (9) and the slave piston (10) being axially movable relative to one another, the coupler volume (23) being connected to a compensation chamber (12) via a throttle (24) flexible section (13) at least partially delimits the compensation space (12) and the coupler volume (23), the throttle (24) and the compensation space (12) are filled with a hydraulic medium,
characterized in that the flexible section (13) is limited in its outward extension by a stop body (33). Fuel injection valve according to claim 1,
characterized in that the stop body (33) has the shape of a sleeve. Fuel injection valve according to claim 1 or 2,
characterized in that the slave piston (10) consists at least partially of a cup-shaped first slave portion (34), the bottom of which partially limits the coupler volume (23). Fuel injection valve according to claim 3,
characterized in that the master piston (9) partially encloses the first slave section (34) in a cup shape. Fuel injection valve according to claim 3 or 4,
characterized in that the upper end of the first slave section (34) projects beyond the upper end of the master piston (9). Fuel injection valve according to one of Claims 3 to 5,
characterized in that the slave piston (10) has a second slave section (35) which is connected to the first slave section (34) in a manner fixed against movement. Fuel injection valve according to Claim 6,
characterized in that the second slave section (35) has a diameter shoulder (46), the diameter of which is larger than that of the first slave section (34) and approximately as large as that of the master piston (9). Fuel injection valve according to claim 7,
characterized in that the diameter shoulder (46) rests on the upper end of the first slave section (34). Fuel injection valve according to one of Claims 3 to 8,
characterized in that the throttle (24) is arranged in the bottom of the cup-shaped first slave section (34). Fuel injection valve according to one of Claims 3 to 9,
characterized in that the upper axial end of the first slave section (34) facing away from the coupler volume (23) projects beyond the upper axial end of the master piston (9) facing away from the coupler volume (23). 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). Fuel injection valve according to Claim 11,
characterized in that the throttle ball (39) is supported on a surface of the master piston (9) delimiting the coupler volume (23). Fuel injection valve according to one of the preceding claims,
characterized in that one end of the flexible section (13) on the slave piston (10) and / or the other end of the flexible section (13) on the master piston (9) is hermetically sealed, in particular positive and / or non-positive. Fuel injection valve according to one of the preceding claims,
characterized in that at least one recess (42, 43) is arranged in each of the radial outer surfaces of the master piston (9) and / or the slave piston (10). Fuel injection valve according to claim 14,
characterized in that at least one of the recesses (42, 43) is in the form of an annular groove. Fuel injection valve according to claim 14 or 15,
characterized in that at least one of the ends of the flexible section (13) engages in at least one of the recesses (42, 43). Fuel injection valve according to one of Claims 14 to 16,
characterized in that at least one of the recesses (42, 43) is trough-shaped. Fuel injection valve according to one of Claims 14 to 17,
characterized in that the stop body (33) fixes at least one of the ends of the flexible section (13) in at least one of the recesses (42, 43) in a positive and / or non-positive and hermetically sealed manner. Fuel injection valve according to one of the preceding claims,
characterized in that the ends of the flexible portion (13) are thickened. Fuel injection valve according to one of the preceding claims,
characterized in that the stop body (33) has an escape volume (52). Fuel injector according to claim 20,
characterized in that the escape volume (52) is arranged approximately at the height of the center of the flexible section (13). A fuel injector according to claim 20 or 21,
characterized in that the flexible section (13) expands into the escape volume (52) when the coupler volume (23) is removed. Fuel injection valve according to one of Claims 20 to 22,
characterized in that the escape volume (52) is formed in that part of the axial course of the stop (33) is widened outwards. Fuel injection valve according to claim 23,
characterized in that the part of the axial course of the stop body (33) which forms the escape volume (52) is widened outward, in particular in the form of a segment of a circle. Fuel injection valve according to one of Claims 20 to 24,
characterized in that the stop body (33) is divided into at least a first stop section (47) and a second stop section (48). Fuel injection valve according to claim 25,
characterized in that the stop body (33) is divided by a stop gap (50), in particular an annular stop gap (50). Fuel injection valve according to claim 26,
characterized in that the stop gap (50) is arranged at the level of the center of the escape volume (52). Fuel injection valve according to one of the preceding claims,
characterized in that the compensation space (12) is delimited by the flexible section (13), the slave piston (10) and the master piston (9). Fuel injection valve according to one of the preceding claims,
characterized in that the flexible section (13) is elastic and in particular consists of an elastomer.

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