EP1831539B1 - Fuel injector with direct control of the injection valve body - Google Patents

Description

The invention relates to a fuel injector with direct control of the injection valve member according to the preamble of claim 1.

State of the art

DE 10 2004 028 522.5 refers to a fuel injector with variable Aktorhubübersetzung. The fuel injector comprises an actuator which actuates an injection valve member directly, which acts on the injection valve member, which is acted upon by a spring element in the closing direction. The fuel injector includes a hydraulic coupling space that hydraulically connects a booster piston and the injection valve member. At the injection valve member, a sleeve-shaped body is supported, which cooperates with an edge forming a Zwischenhubstellung the injection valve member edge. The sleeve-shaped body is movable relative to the injection valve member. With this solution, a two-stage translation can be achieved, wherein a first gear ratio is given by a stop.

Out DE 103 33 427 B3 a fuel injector is known. The fuel injection device comprises an injection valve which has a valve needle for opening and closing injection openings. There is provided a fuel injecting valve when operating under high pressure fuel supply line and an actuator and a hydraulic coupler having two cooperating via a coupling of a coupler, arranged linearly one behind the other piston. The coupler volume of the coupler is formed by leading columns of pistons arranged one behind the other through high-pressure fuel. At the ends of the pistons facing away from the actuator, a respective filling space is arranged and connected to a line, one of the pistons having a first cross-sectional area being connected to the actuator via a rod with an injection valve member designed as a nozzle needle. The two other ends of the pistons engage in associated compartments, which communicate hydraulically with each other via a duct.

A fuel injector with a direct control of an injection valve member is still off DE 102 25 686 A1 known. The actuator which actuates the injection valve member acts to open the injection valve member, so that the actuator is energized in the open position of the injection valve member and is not energized in the closed position of the injection valve member. To reverse the oppressive stroke of the actuator, a reversing device is provided which converts the pressing stroke of the actuator into a pulling stroke of the nozzle needle of the injection valve member.

Advantages of the invention

A fuel injector for high-pressure accumulator injection systems (common rail) is proposed, which has a direct needle control, in which an injector member which can be embodied as a nozzle needle is opened between an actuator; such as a piezoelectric actuator, and the injection valve member no hydraulic valve is interposed, with the opening of the injection valve member, the pressure in a control chamber is relieved. The actuator, which is preferably a piezocrystal stack having piezoelectric actuator, is inversely controlled, wherein the actuator is energized in the closed state of the injection valve member designed as a nozzle needle. To open the injector valve which can be embodied as a nozzle needle, the actuator is switched to a de-energized state, so that the length of the piezocrystal stack of the actuator is reduced. As a result, a reduction in pressure is brought about, which in turn entails an opening of the injection valve member which can be embodied as a nozzle needle.

According to the invention, a fuel injector is provided which enables direct control of the injection valve member which can be embodied as a nozzle needle with an extremely compact installation space. The proposed fuel injector is characterized by a small number of components and a low overall height, which is due to the fact that a hydraulic valve can be omitted for actuating the injection valve member which can be embodied as a nozzle needle.

In the fuel injector proposed according to the invention, a booster piston assigned to the actuator has a control chamber sleeve surrounding it, as a result of which an control chamber which is otherwise to be formed in the body of the fuel injector can be saved. The booster piston is advantageously designed such that it is both an internally formed Translator and also acted on in relation to the Einspritrventilglied outer control chamber. From the outside arranged control chamber, fuel flows into a rear space, which acts on the injection valve member which can be embodied as a nozzle needle.

In the closed position of the injection valve member which can be embodied as a nozzle needle, the actuator is energized. If the energization of the actuator is removed, the length of the piezocrystal stack is reduced, as a result of which the booster piston is withdrawn via a spring element assigned to it and the pressure in the internal booster chamber lowers. The reduction in pressure in the interrupter compartment results in a piston surrounding the injection valve member moving into the interrupter compartment. Due to the cancellation of the energization of the actuator and the pressure in a control chamber is lowered, as well as in a trained within the piston rear space of the injection needle member can be formed as a nozzle needle. For this purpose, the rear space and the control chamber are fluidically connected to each other via a channel containing a throttle point. If the piston travels due to the pressure reduction occurring in the booster chamber, in the control chamber and in the rear space of the injection valve member, the injection valve member which can be embodied as a nozzle needle is also wound, which is pulled along by a stop which can be embodied as a sleeve during the upward movement of the piston. Upon further pressure reduction in the rear space of the injection valve member that can be embodied as a nozzle needle, this lifts off from the stop embodied as a sleeve and continues to open.

For closing the injection valve member that can be embodied as a nozzle needle, the actuator is energized again, so that the booster piston, which acts on both the booster chamber and the control chamber, moves again in the direction of these spaces and causes an increase in pressure in them. The injection valve member is returned to its closed position via the channel containing a throttle point between the control chamber and the rear space of the injection valve member which can be embodied as a nozzle needle, and consequently seals the injection openings opening into the combustion chamber of the internal combustion engine.

Consequently, in the case of a fuel injector with an actuator that is actuated inversely, opening of the nozzle needle that can be formed as a nozzle needle

Injection valve member by forcibly entrained the same at pressure loading of the booster chamber and achieved a further opening movement of the injection valve member thereby caused that the back space of the injection valve member is further pressure-loaded at pressure loading of the control room. When closing the injector valve element which can be embodied as a nozzle needle, when the actuator is energized, the translator piston retracts into both the translator chamber and the control chamber, whereby the piston surrounding the injection valve member is pressurized and the rear chamber of the injection valve member is pressurized.

drawing

Reference to the drawings, the invention will be explained in more detail below.

Figur 1

einen Schnitt durch den erfindungsgemäß vorgeschlagenen Kraftstoffinjektor mit direkter Steuerung des Einspritzventilgliedes und inverser Ansteuerung eines Aktors, und

Figur 2

eine weitere Ausführungsvariante des erfindungsgemäß vorgeschlagenen Kraftstoffinjektors.

It shows:

FIG. 1

a section through the inventively proposed fuel injector with direct control of the injection valve member and inverse control of an actuator, and

FIG. 2

a further embodiment of the present invention proposed fuel injector.

embodiments

The representation according to the FIG. 1 is a fuel injector 10 can be seen, which has a cavity 12 in which a preferably designed as a piezoelectric actuator 14 is added. In the cavity 12 opens a supply line 20 of a fuel injector 10 arranged outside the high-pressure source 22, such as a high-pressure accumulation chamber (common rail).

The actuator 14, preferably a piezoactuator, comprises a number of stacked stacked piezocrystals and is controlled inversely. This means that the actuator 14 is energized in the closed state of a injection valve member 48 designed as a nozzle needle, that is to say when the injection openings 86 are closed, whereas to open the injection valve member 48 it is switched to a de-energized state, which takes place via an activation not shown in the drawing ,

At one of the actuator 14 assigning end 26 of a booster piston 24 designed as a tubular spring spring element 16 is employed. The booster piston 24 has an annular surface 28, which engages over a further spring element 30, which in turn engages over a control chamber sleeve 31. About the employed by the booster piston 24 to the control chamber sleeve 31 further spring element 30, the control chamber sleeve 31 is employed with a biting edge 84 to a first end face 70 of a washer 68 of the fuel injector 10.

The control piston 24 has an extension 32 which on the one hand serves as a guide for an inner spring element 34 and on the other hand delimits a translator chamber 36 formed by an inner peripheral surface 40 of the booster piston 24 and a piston 44. In the translator room 36 there is a pressure level, which is designated by p ₁ .

The pressurized via the supply line 20 under high pressure fuel cavity 12 of the fuel injector 10 has an inlet 38, 74, via which the fuel from the cavity 12 a nozzle chamber 78 flows. The nozzle chamber 78 surrounds the injection valve member 48 which can be formed as a nozzle needle.

The booster piston 24 also has an annular surface 42 which delimits a control chamber 46. The control chamber 46 is limited by the mentioned annular surface 42 of the booster piston 24 and by the inner peripheral surface of the control chamber sleeve 31 and the washer 68 of the fuel injector 10. The enclosing the piston 44 Control chamber 46 is connected via a channel in which a throttle point 56 is formed with a rear space 54 in connection. Within the rear space 54, an injector member 48 which can be embodied as a nozzle needle is accommodated. The closing spring 52 is supported on the one hand on an end face 50 of the injection valve member 48 and on the other hand on the inside of the piston 44 from. About the channel with orifice 56 are the back space 54, in which a pressure level p ₃ prevails and the control chamber 46, in which a pressure level of p ₂ prevails, with each other in hydraulic communication.

In the piston 44 can be formed as a nozzle needle injection valve member 48 is movably received. For this purpose, located on the piston 44 on the side facing the nozzle chamber 78 a bell 60, which may be non-positively or positively connected to a caulking 58 with the piston 44. The bell 60 in the lower region of the piston 44 encloses a stop 62 which can be embodied as a sleeve. In the stop 62, the injection valve member 48 which can be embodied as a nozzle needle is movably guided in the axial direction. The stop 62 which can be formed as a sleeve comprises a first side 64 and a second side 66 facing the bell 60. The piston 44 with the bell 60 accommodated on it is movably guided in the nozzle body 76 of the fuel injector 10 in the vertical direction.

From the nozzle chamber 78, fuel flows toward a tip 80 of the injection valve member 48 which can be embodied as a nozzle needle, which in its closed position is placed in a seat 82 at the combustion chamber end. As a result, injection ports 86 opening into a combustion chamber 88 of an internal combustion engine are closed.

Reference numeral 90 designates a guide surface between the booster piston 24 and the piston 44 surrounding the injection valve member 48.

The actuator 14, which acts on the end face 26 of the booster piston 24, is driven inversely. This means that the actuator 14 is energized in the closed state of the injection valve member 48, however, is not energized to open the injection valve member 48 can be formed as a nozzle needle.

When energized actuator 14 and consequently closed injection valve member 48, the injection valve member 48 is placed in its the injection ports 86 closing seat 82. The stacked piezocrystals of the actuator 14 are elongated against the action of the formable as a tubular spring spring element 16. The end face 26 of the booster piston 24 is acted upon by the piezoelectric actuator 14. The booster piston 24 thus maintains a pressure in the booster chamber 36 and is retracted with its annular surface 42 into the control chamber 46, so that in this also an increased pressure prevails. The pressure prevailing in the control chamber 46 increased pressure is above the channel, which the rear space 54 hydraulically connects to the control chamber 46 at. Due to the pressure prevailing in the interrupter chamber 36 and the pressure prevailing in the rear chamber 54, both the piston 44 is pressurized and the end face 50 of the injection valve member designed as a nozzle needle 48. The over the high-pressure inlet 38, 74 in the nozzle chamber 78 pending fuel volume, since the injection openings 86th are closed by the injection valve member 48, are not injected into the combustion chamber 88 of the internal combustion engine. In the closed position of the injection valve member 48 which can be embodied as a nozzle needle, it rests against the first side 64 of the stop 62 which can be embodied as a sleeve. The formable as a sleeve stop 62 is also fixed by the bell 60 on its second side 66. The piston 44 together with the bell 60 received thereon is placed in the nozzle body 76 due to the pressure prevailing in the booster chamber 36 pressure and is in its lower stop position.

When opening the injection valve member 48 which can be embodied as a nozzle needle, the energization of the actuator 14 is canceled, so that the length of the piezocrystal stack of the actuator 14 is reduced. Due to the action of the formable as a tubular spring spring element 16 of the booster piston 24 is pulled into the cavity 12. This is accompanied both a pressure relief of the booster chamber 36 by extending the extension 32 from this, as well as a pressure relief of the control chamber 46 by extending the annular surface 42 of the booster piston 24 from this. Due to the pressure relief in the control chamber 46, a, albeit time-delayed, pressure relief of the back space 54 takes place on the back of the injection valve member 48 which can be embodied as a nozzle needle. With an extension movement of the booster piston 24, a simultaneous pressure relief of the booster chamber 36 and the control chamber 46 takes place 36 with its end face limiting piston 44 moves into the booster chamber 36 a. Arranged on the piston 44, the stop 62 enclosing the bell 60 causes the nozzle needle 48 is engaged in a Auffahrbewegung of the piston 44 in the booster chamber 36 and consequently follows the vertical upward movement of the piston 44. Since at the same time due to the pressure relief in the control chamber 46 by the extending out of this annular surface 42 of the booster piston 24 and a pressure reduction in the rear 54, the end face 50 of the nozzle needle formable injection valve member 48 moves against the action of the closing spring 52 in the rear space 54 and lifts from the first side 64 of the stop 62. Consequently, there is a further opening movement of the injection valve member 48 into the rear space 54, which is limited by the spring force of the closing spring 52. The fuel present in the nozzle chamber 78 can now be injected via the released Einspritzöff openings 86 at the combustion chamber end of the fuel injector 10 into the combustion chamber 88 of the internal combustion engine.

The formable as a sleeve stop 62 allows on the one hand at pressure relief of the booster chamber 36 entrainment movement of the injector valve can be formed as a nozzle needle 48 at Auffahrbewegung of the piston 44 in the booster chamber 36; On the other hand, lifting of the injector valve element 48 that can be embodied as a nozzle needle is made possible by the first side 64 of the stop 62 when the back space 54 is relieved of pressure and the control chamber 46 is relieved of pressure. The opening movement of the injection valve member 48 when the actuator 14 is de-energized thus takes place by a superposition of the Auffahrbewegung of the piston 44 in the booster chamber 36 at pressure relief of the same and parallel running pressure relief of the back space 54 in the likewise pressure-relieved control chamber 46, whereby the end face 50 the injection valve member 48 on enters the rear space 54. When closing, that is, when energizing the piezoelectric actuator 14, however, there is a pressure increase in the booster chamber 36, whereby the piston 44 is pressed down in the direction of the combustion chamber end of the fuel injector 10 in the nozzle body and a pressure increase in the back space 54, the over the channel with Throttle 56 hydraulically communicates with the control chamber 46, in which also due to the retraction of the booster piston 24 with its annular surface 42, the pressure increases. Advantageously, the control chamber sleeve 31 is formed so that it on the one hand limits the booster chamber 36 and on the other hand forms the control chamber 46 together with the annular surface 42 of the booster piston 24 and a surface area of a first planar surface 70 of the washer 68. A second plane surface of the washer 68 is designated by reference numeral 72.

Due to the interlocking of the booster piston 24 and guided in this, acted upon by the inner spring member 34 piston 44, a particularly compact structure of a direct actuation of the injection valve member 48 enabling fuel injector 10 can be provided, in which advantageously the control chamber 46 by using a relative to the booster piston 24 movable control chamber sleeve 31 is formed. This allows the waiver of the production of the control chamber 46 in the injector body. Through the control chamber sleeve 31, the control chamber 46 can be formed in the cavity 12 of the fuel injector 10. The filling of the booster chamber 36 and the control chamber 46 via the production-related adjusting column on the guide surface 90 between the booster piston 24 and the piston 44 and the first planar surface 70 and the biting edge 84 on the underside of the control chamber sleeve 31. Instead of the illustrated in the figure Calking 58 between the bell 60 and the piston 44 can also be a different type of connection can be selected to connect the bell 60 with the piston 44. At position 58, a cohesive connection in the form of a weld between the piston 44 and the bell 60 can be formed, wherein the material connection after insertion of the injector valve 48 can be formed as a nozzle needle and subsequent assembly of the stopper 62 between the piston 44 and the bell 60 is made. Depending on the dimensions of the closing spring 52 received in the rear space 54, the stroke of the injection valve member 48 can be defined relative to the piston 44.

In the rear space 54 within the piston 44, which communicates hydraulically with the control chamber 46 via the channel containing the throttle point 56, arises upon pressure relief of the control chamber 46 due to the dimensioning of the throttle body 56 during opening, that is, when the energization of the piezoelectric actuator 14 , a correspondingly delayed pressure build-up with which an influencing of the time profile of the injected into the combustion chamber 88 via the injection ports 86 fuel volume can be brought about.

FIG. 2 shows a further embodiment of the present invention proposed fuel injector.

In the in FIG. 2 illustrated embodiment is - analogous to FIG. 1 - The booster piston 24 is acted upon directly by the inversely actuated actuator 14. The booster piston 24 is analogous to the representation according to FIG. 1 enclosed by a spring element 30 designed as a spiral spring, which adjusts the control chamber sleeve 31 against the nozzle body 76. The control piston 24 encloses the rear space 54 of the injection valve member 48, in which an inner spring element 34 is arranged, which in turn acts on the end face 50 of the injection valve member 48. In this embodiment variant of the fuel injector proposed according to the invention, a pressure booster 100 comprises only two hydraulic chambers, namely the rear chamber 54 and the control chamber 46, while in the in FIG. 1 dargstellten embodiment of the pressure booster 100 includes the translator 36, the control chamber 46 and the rear 54.

Analogous to the representation in FIG. 1 is in the in FIG. 2 illustrated embodiment of the actuator 14 received in a cavity 12 which is acted upon by the supply line 20 with fuel under system pressure. From the cavity 12, the fuel under system pressure flows through the injector body to the channels 74, which open into the nozzle chamber 78. In the nozzle chamber 78 is a pressure stage 92 which is formed on the needle-shaped injection valve member 48 formed. In the in FIG. 2 illustrated embodiment, the back space 54 and the control chamber 46 via a channel 94 with throttle point 56 in connection. The injection valve member 48 according to the embodiment in FIG. 2 includes a piston-shaped projection 44, which is enclosed by an annular surface 98 of the booster piston 24. In the illustration according to FIG. 2 is the piston-shaped projection 44 of the injection valve member 48 on the annular surface 98 of the booster piston 24.

From the nozzle chamber 78, an annular gap extends to the seat 82 of the injection valve member 48. In the in FIG. 2 illustrated closed position of the injector valve can be formed as a nozzle needle 48 are formed below the seat 82, opening into the combustion chamber 88 Einspritzöfihungen 86 closed.

To open the injection valve member 48 is a partial or complete cancellation of the energization of the actuator 14. This causes the booster piston 24 of the pressure booster 100 is pulled into the cavity 12. The pressure in the control chamber 46 decreases, whereby the pressure in the rear chamber 54 decreases, as these two hydraulic chambers 54, 46 via the throttle 56 and the channel 94 are hydraulically in communication. Upon retraction of the booster piston 24 into the cavity 12, the annular surface 98, which engages under the piston-shaped projection 44 of the injection valve member 48, pulls the injection valve member 48. Since the pressure drops in the rear space 54 when the pressure in the control chamber 46 drops by extending the booster piston 54, the piston-shaped projection 44 of the injection valve member 48 lifts from the annular surface 98 and moves, guided in a piston guide 96 of the transmission piston 24, with its end face 50 in the rear space 54, whereby the injector valve can be formed as a nozzle needle 48 quickly opens completely with minimal stroke of the actuator 14.

To close the injection valve member 48 is energized by the actuator 14, whereby the piezocrystal stack lengthens and the booster piston 24 is pressurized. Its end face 42 moves into the control chamber 46, in which as a result of which the pressure rises. Due to the hydraulic connection between the control chamber 46 and the rear space 54 through the throttle point 56 with channel 94 increases in the rear space 54 of the pressure. The increased pressure in the rear space 54 acts on the end face 50 on the piston-shaped projection 44 of the injection valve member 48 and provides it against the hydraulic force acting in the nozzle chamber 78 at the pressure stage 92 formed therein back into the seat 82 so that the injection openings opening into the combustion chamber 88 86 be closed again.

Compared to in FIG. 1 illustrated embodiment of the fuel injector comprises in FIG. 2 illustrated embodiment of the fuel injector a pressure booster 100 with two hydraulic chambers, namely the rear chamber 54 and the control chamber 46, which are hydraulically connected to each other via a duct system with throttle body 56.

While the mechanical coupling between the injection valve member 48 and the piston 44 via a sleeve-shaped stop 62 in the embodiment according to FIG. 1 is formed, embraces in the embodiment according to FIG. 2 the booster piston 42 the piston-shaped Approach 44 on the injection valve member 48 with an annular surface 98. In both variants, preferably designed as a nozzle needle injection valve member 48 is wound by the inverse actuated actuator 14 at partial or complete cancellation of the energization thereof, the further opening of the injection valve member 48 according to the embodiment in FIG. 1 by entering into the rear space 54 and according to the embodiment in FIG. 2 is carried out by retracting the end face 50 of the piston-shaped projection 44 of the injection valve member 48 in the rear space 54, which has a rapid opening of the preferred designed as a nozzle needle injection valve member 48 result.

LIST OF REFERENCE NUMBERS

10

fuel injector

12

cavity

14

Actuator (piezoelectric actuator)

16

feather

20

supply

22

High pressure source (common rail)

24

Booster piston

26

front

28

ring surface

30

spring element

31

Control chamber sleeve

32

extension

34

inner spring element

36

Translator room (p ₁ )

38

High-pressure inlet

40

Inner peripheral surface of the booster piston 24

42

Ring surface of the booster piston 24

44

piston

46

Control room (p ₂ )

48

Injection valve member

50

Front side injection valve member 48

52

Closing spring injection valve member 48

54

Rear space (p ₃ )

56

Channel with throttle point

58

junction

60

Bell jar

62

sleeve-shaped stop

64

first side sleeve-shaped stopper 62nd

66

second side sleeve-shaped stopper 62nd

68

washer

70

first plane surface

72

second plane surface

74

Continuation of high pressure feed

76

nozzle body

78

nozzle chamber

80

Tip injection valve member 48

82

Seat injection valve member 48

84

biting edge

86

Finspritzöffnung

88

combustion chamber

90

Guide surface Translator piston 24 / piston 44

92

pressure stage

94

channel

96

piston guide

98

ring surface

100

Pressure intensifier

Claims (12)

1. Fuel injector (10) with direct activation of an injection valve member (48) by means of an actuator (14) which is held in a cavity (12) which is acted on with highly pressurized fuel by means of a high-pressure source (22) arranged outside the fuel injector (10), the actuator (14) being supplied with electrical current in the closed position of the injection valve member (48) and not being supplied with electrical current in the open position of the injection valve member (48), with the actuator (14) acting on a booster piston (24) of a pressure booster (100) which acts on a control chamber (46) situated at the outside in relation to the injection valve member (48),
   characterized in that the control chamber (46) is connected to a rear chamber (54) of the injection valve member (48) by means of a duct which contains a throttle point (56), and in that a control chamber sleeve (31) which delimits the control chamber (46) is held on the booster piston (24), and in that the control chamber sleeve (31) is loaded with a biting edge (84) against a first planar Surface (70) of an intermediate disc (68) by means of a spring element (30).
2. Fuel injector according to Claim 1, characterized in that the booster piston (24) of the pressure booster (100) is acted on directly by the actuator (14).
3. Fuel injector according to Claim 1, characterized in that the booster piston (24) is assigned a spring element (16) which assists the restoring movement of said booster piston (24).
4. Fuel injector according to Claim 1, characterized in that the booster piston (24) acts on a booster chamber (36) and the control chamber (46) with pressure simultaneously or relieves a booster chamber (36) and the control chamber (46) of pressure simultaneously.
5. Fuel injector according to Claim 1, characterized in that a booster chamber (36) is delimited by the booster piston (24) and a piston (44) in which the injection valve member (48) is guided in a movable fashion.
6. Fuel injector according to Claim 1, characterized in that the control chamber (46) is delimited by the intermediate disc (68), the control chamber sleeve (31) and an annular surface (42) of the booster piston (24).
7. Fuel injector according to Claim 1, characterized in that an annular surface (98) which engages around the injection valve member (48) is formed on the booster piston (24).
8. Fuel injector according to Claim 5, characterized in that a stop (62) is arranged in the piston (44), against the first side (64) of which stop (62) the injection valve member (48) bears and over the second side (66) of which stop (62) the piston (44) engages.
9. Fuel injector according to Claim 8, characterized in that the stop (62) is fixed by a bell (60) which is held on the piston (44) in a cohesive, positively locking or non-positively locking fashion.
10. Fuel injector according to Claim 5, characterized in that, when the injection valve member (48) is closed and the actuator (14) is supplied with electrical current, the booster piston (24) acts on the piston (44) with pressure directly via the booster chamber (36) and pressurizes the rear chamber (54) of the injection valve member (48) indirectly via the control chamber (46).
11. Fuel injector according to Claim 5, characterized in that, when the supply of electrical current to the actuator (14) is switched off, the booster chamber (36) and the control chamber (46) are relieved of pressure, and a release of pressure from the rear chamber (54) of the injection valve member (48) takes place after a time delay.
12. Fuel injector according to Claim 11, characterized in that, when the rear chamber (54) is relieved of pressure, the injection valve member (48) lifts up from the stop (62).

Images