EP2013468B1 - Injector - Google Patents

Abstract

The injector has a piezoactuator (5) for controlling and/or operating a nozzle needle(s) for controlling the injection of fuel at high pressure through an injection hole(s) (12), whereby the piezoactuator is arranged with its shaft (7) in an actuator chamber (9) of an injector body (2) and fuel under high pressure is passed to a high pressure path(s) (10) leading to the injection hole(s) through the actuator chamber. The piezoactuator has a foot (6) on the end remote from the nozzle needle that has a sealing profile (21) facing the needle that contacts a seal seat (22) on the injector body.

Description

Technical area

The present invention relates to an injector for supplying fuel to an internal combustion engine, in particular in a motor vehicle, having the features of the preamble of claim 1.

State of the art

Injectors of this type are for example from the DE 10 2004 027 824 A1 and from the EP 1 174 615 A2 are known and each comprise a piezoelectric actuator for driving or actuating at least one nozzle needle, with the aid of which an injection of high-pressure fuel is controlled by at least one injection hole. The piezoelectric actuator has a shaft which expands in its "energization" in its longitudinal direction and which resumes its original, shortened length in a "Entstromung". An injector body of the injector contains an actuator space in which the piezoelectric actuator is arranged with its shaft. In the case of the known injectors, it is also provided that a high-pressure path, which leads the high-pressure fuel to the at least one injection hole, is passed through said actuator space. As a result, the piezoelectric actuator is surrounded by the fuel under high pressure; The piezoelectric actuator is arranged "wet" or "floating".

In the known injectors can be driven by energizing and Entström the piezoelectric actuator, a control piston to lower the pressure in a control chamber for opening the nozzle needle. This is a direct, pressure controlled Needle control. In an inversely operated piezoelectric actuator, it is de-energized to open the nozzle needle while it is energized when the nozzle needle is closed (eg WO 2005/121544 ).

In other types of injectors, it is also possible to use the piezoelectric actuator directly to drive the nozzle needle or a needle assembly comprising the nozzle needle or, for example, to control a servo valve. Furthermore, other designs for injectors with piezoelectric actuator are conceivable.

In the case of the above-mentioned direct needle control, in order to reduce hydraulic translation devices, it is necessary to provide the piezoelectric actuator with a relatively long shaft in order to be able to realize the required strokes. In the production of the piezoelectric actuator and the injector body, however, plan and concentricity deviations due to manufacturing tolerances can not be avoided, which can lead to an axial and angular offset of the interacting components. To achieve an effective seal of the actuator space to the outside, however, the most accurate angular orientation of the piezoelectric actuator within the injector body is required. This requirement becomes more important the higher the high pressure is selected to apply to the fuel. In the meantime, the fuel in modern injection systems with a high pressure of 2,000 bar can be applied. For the injector then, for example, a pressure tightness to the outside to about 2,400 bar is desired in order to avoid leaks even when occurring during operation, dynamic pressure peaks.

Advantages of the invention

The injector according to the invention with the features of claim 1 has the advantage that the alignment of the piezoelectric actuator relative to the injector body is improved during assembly of the injector via the interaction of a sealing contour formed on an actuator body with a sealing seat formed on the injector body. It is of particular importance that the sealing contour of the actuator base of the nozzle needle faces and sits axially in the direction of the nozzle needle in the sealing seat. In particular, this makes it possible to match the sealing contour and the sealing seat to one another such that the actuator foot, with its sealing contour in the sealing seat, forms an actuator space seal closing the actuator space. Depending on which axial force the sealing contour in the sealing seat sits, a more or less effective seal of the actuator space can be achieved to the outside.

Particularly advantageous is a development in which the actuator foot is biased by means of a biasing device in the direction of the nozzle needle, such that the sealing contour is biased in the sealing seat. By selecting this axial preload, the tightness of the actuator chamber seal can be adjusted to the particular desired pressure value. In particular, the biasing device can also be designed so that it is designed to initiate a bias that is so great that it leads to plastic deformation of the sealing seat and / or on the sealing contour. In such an embodiment, even the smallest form deviations can be compensated by the deformation in order to improve the effectiveness of the actuator chamber seal.

Further important features and advantages of the injector according to the invention will become apparent from the subclaims, from the drawings and from the associated description of the figures with reference to the drawings.

drawings

Fig. 1

einen vereinfachten Längsschnitt durch einen Injektor,

Fig. 2

eine vergrößerte Darstellung im Halbschnitt eines Ausschnitts II aus Fig. 1,

Fig. 3

eine weiter vereinfachte Darstellung im Längsschnitt eines Injektors, jedoch bei einer anderen Ausführungsform.

Embodiments of the injector according to the invention are illustrated in the drawings and are explained in more detail below, wherein like reference numerals refer to the same or similar or functionally identical components. Show, in each case schematically,

Fig. 1

a simplified longitudinal section through an injector,

Fig. 2

an enlarged view in half section of a section II Fig. 1 .

Fig. 3

a further simplified representation in longitudinal section of an injector, but in another embodiment.

Description of the embodiments

According to the Fig. 1 to 3 comprises an injector 1 of an injection device, which for supplying an internal combustion engine, in particular in a motor vehicle, with fuel serves, an injector body 2, in which at least one nozzle needle 3 and a nozzle needle 3 comprehensive nozzle body 4 is arranged. The nozzle body 4 is fixed by means of an overspent nozzle retaining nut 46 on the rest of the injector body 2. Furthermore, the injector 1 comprises a piezoactuator 5 with an actuator foot 6, an actuator shaft 7 and an actuator head 8. The injector body 2 contains an actuator chamber 9, in which the piezoactuator 5 is arranged at least with its shaft 7.

In the injector body 2, a high pressure path 10 is also formed, which leads from a trained on the injector 2 high pressure port 11 of the injector 1 to at least one also formed on the nozzle body 4 injection hole 12 of the injector 1 and in operation of the injector 1 under high pressure fuel for at least one Spray hole 12 leads. The high-pressure path 10 is moved through the actuator chamber 9, that is, the actuator chamber 9 forms part of the high-pressure path 10 and is flowed through by the high-pressure fuel.

The piezoelectric actuator 5 is used to control or to actuate the nozzle needle 3, such that with the nozzle needle 3, the injection of high-pressure fuel through the at least one injection hole 12 in a respective injector 1 associated injection chamber 13 is controllable. For controlling the injection through the at least one injection hole 12, the nozzle needle 3 cooperates with a needle seat 14 in a known manner. In order to move the nozzle needle 3 out of the needle seat 14, it must perform an opening stroke parallel to a longitudinal axis 15 of the injector 1 or the injector body 2. For this purpose, the pressure is lowered in a control chamber 16 by a corresponding actuation of the piezoelectric actuator 5. Said control chamber 16 is limited in the radial direction by a control sleeve 17. In the axial direction of the control chamber 16 is limited to the nozzle needle 3 through an intermediate plate 18 and the piezoelectric actuator 5 through a control piston 19. The control piston 19 is firmly connected to the actuator head 8 and immersed in the control sleeve 17 a. The control sleeve 17 is mounted on the control piston 19 adjustable in stroke and supported by a closing compression spring 20 on the actuator head 8. About the closing pressure spring 20, the control sleeve 17 is axially biased against the intermediate plate 18.

The piezoelectric actuator 5 may be operated inversely, for example. That is, in the initial state shown, in which the nozzle needle 3 is seated in the needle seat 14 and assumes its closed position, the piezoelectric actuator 5 is energized and is thus axially expanded. To open the nozzle needle 3, the piezoelectric actuator 5 is de-energized, whereby it is parallel to the longitudinal axis 15 measured length reduced. Since the actuator foot 6 is fixedly arranged on the injector body 2, the actuator head 8 retracts from the nozzle needle 3 during the shortening of the actuator shaft 7. As a result, the control piston 19 is moved away from the, nozzle needle 3, whereby the pressure in the control chamber 16 drops. As a result, the pressure-controlled nozzle needle 3 can lift off the needle seat 14 and the injection process begins.

To be able to support the piezoelectric actuator 5 in the area of its actuator core 6 on the injector body 2 in a fixed manner, the actuator foot 6 has a sealing contour 21 which faces the nozzle needle 3 and bears against a sealing seat 22 which faces away from the nozzle needle 3 and at the injector body 2 is formed. As a result, the actuator foot 6 can be supported axially on the injector body 2 in the direction of the nozzle needle 3.

Preferably, sealing contour 21 and sealing seat 22 are matched to one another such that the actuator foot 6 forms, together with its sealing contour 21 in the sealing seat 22, an actuator space seal 23 which closes the actuator space 9. With the help of this Aktorraumdichtung 23 while the actuator chamber 9 is axially closed at its end facing away from the nozzle needle 3. In order to realize the desired Aktorraumdichtung 23, the sealing contour 21 and the sealing seat 22 are each designed annularly closed, wherein they rotate with respect to the longitudinal axis 15 in the circumferential direction. Furthermore, sealing contour 21 and sealing seat 22 are preferably aligned concentrically to the longitudinal axis 15.

In addition to the realizability of the actuator space seal 23, the sealing contour 21 and the sealing seat 22 can also be utilized to align the piezoactuator 5 as exactly as possible concentrically with the longitudinal central axis 15 during assembly of the injector 1. Particularly advantageous is an embodiment in which the sealing contour 21 is designed spherical, such that the sealing contour 21 extends spherically along a spherical section. The associated virtual sphere is designated 24 in the figures. Preferably, a center 25 of the ball 24 is arranged centrally in the actuator base 6. The spherical sealing contour 21 simplifies the axial alignment of the piezoelectric actuator 5 relative to the injector body 2, whereby the functionality of the interaction between the control sleeve 17 and the control piston 19 is improved. This design is particularly advantageous when the piezoelectric actuator 5 has a comparatively long shaft 7, for example, in Fig. 1 is clearly shortened.

The sealing seat 22 preferably has a conical shape, whereby a linear contact between sealing contour 21 and sealing seat 22 is achieved regardless of manufacturing tolerances. As a result, a closed and thus effective Aktorraumdichtung 23 is realized.

In order to increase the effectiveness of the actuator chamber seal 23, the actuator foot 6 is prestressed in the direction of the nozzle needle 3, as a result of which the sealing contour 21 is seated with axial prestress in the sealing seat 22. The selected axial preload can be comparatively large, for example, the set preload can be so large that it comes to tolerated plastic deformation of the sealing seat 22 and / or on the sealing contour 21. The above-mentioned linear contact between sealing contour 21 and sealing seat 22 is thereby virtually strip-shaped.

In order to be able to introduce the desired axial prestress into the actuator foot 6, the injector 1 is equipped with a pretensioning device 26. In the embodiments shown, the biasing means 26 comprises a clamping screw 27 and a clamping member 28, wherein it is also possible in principle, the here separately formed clamping member 28 integrally formed on the clamping screw 27 and to form the clamping member 28 by the clamping screw 27. Likewise, instead of a clamping screw 27 and a clamping nut can be used.

The tendon 28 has a support seat 29 which faces the nozzle needle 3. On the actuator base 6, a support contour 30 is formed on a side facing away from the nozzle needle 3, which abuts axially in the support seat 29 and is supported. In order to initiate the highest possible axial forces in the actuator base 6, it is expedient to design the support contour 30 and the support seat 29 closed in an annular manner and preferably to arrange it concentrically with respect to the longitudinal axis 15. Furthermore, it may also be advantageous here to design the support contour 30 spherical. The support contour 30 then extends spherically in a spherical section. The support contour 30 associated ball may have a different radius than the sealing contour 21 associated ball. In the preferred example shown, on the one hand, the balls of the two contours 21, 30 are the same size and are preferably identical. That is, in the example shown, the spherical support contour 30 is also on the virtual ball 24 with the center 25th

The support seat 29 is preferably configured conical, whereby a linear contact is achieved between the support contour 30 and support seat 29. Depending on the biasing force, plastic deformation may also occur on the support seat 29 and / or on the support contour 30.

The clamping screw 27 has an external thread 31 which cooperates with a complementary internal thread 32 which is formed on the injector body 2. Thus, the clamping screw 27 is axially screwed into the injector 2. The clamping screw 27 presses the clamping member 28 in the axial direction against the actuator base. 6

The tendon 28 may be secured by means of a rotation lock 33 against a rotational adjustment about the longitudinal axis 15. For example, the anti-rotation device 33 is formed by a locking pin 34 which is supported on the injector body 2 and engages radially in a securing slot 35 formed on the outside of the tensioning element 28. Furthermore, the tendon 28 is preferably annular, thereby including a central opening 36. In addition, the clamping screw 27 may be configured as sleeve-shaped here, whereby it has a central passage 37. Opening 36 and passage 37 form a connection channel 38, through which electrical connections 39 of the piezoelectric actuator 5 to the actuator foot 6 and through the actuator foot 6 are led through to the actuator shaft 7 equipped with the piezoelectric elements. For this connection channel 38, the actuator foot 6 together with its support seat 29 resting on the support contour 30 form a connection channel seal 45, which closes the connection channel 38 on the actuator foot 6 to the outside.

The injector 1 according to the invention is characterized in particular by the fact that its piezoactuator 5 can be aligned relatively exactly axially parallel to the longitudinal axis 15 during assembly, which is achieved by the targeted shaping and interaction of sealing contour 21 and sealing seat 22. Furthermore, with the help of the clamping member 28, which is secured against rotation on the injector body 2, the introduction of very high biasing forces on the clamping screw 27 allows, without causing a change in the set orientation between the piezoelectric actuator 5 and injector 2. Because the rotational movement of the clamping screw 27 is not transmitted to the actuator base 6 via the non-rotatable clamping member 28.

Via the high-pressure connection 11, the injector 1 can be connected to a high-pressure source which provides the high-pressure fuel. For example, the high pressure port 11 is connected to a high pressure line, which in turn is connected to a high pressure pump. If a plurality of injectors 1 is connected to a common high pressure line, it is a so-called "common rail system".

In the in the Fig. 1 and 2 In the embodiment shown, the injector body 2 is made in one piece in the region containing the actuator chamber 9. At the in Fig. 3 In the illustrated embodiment, the injector body 2 is made in the area surrounding the actuator chamber 9 at least in two parts or assembled from two parts, namely from a first injector body part 40 and from a second injector body part 41. The first injector body part 40 contains the actuator foot 6. The second injector body part 41 adjoins the first injector body part 40 in the direction of the nozzle needle 3. The second injector body part 41 contains the entire or at least a substantial proportion of the actuator chamber 9. The first injector body part 40 may contain a comparatively small proportion of the actuator chamber 9. In the present case, the high-pressure port 11 is formed on the first injector body part 40. The two injector body parts 40, 41 are fastened to one another via a connecting element 42, which may be designed in particular sleeve-shaped. In order to achieve the desired pressure-tightness at the connection point designated 43 between the two injector body parts 40, 41, an annular seal 44 is additionally provided here.

By the in Fig. 3 shown multi-part construction of the injector body 2, it is for example possible to form the second injector body part 41 as a standard component, which is used identically in different variants of the injector 1. The first injector body part 40 can then be designed differently for different variants of the injector 1. By mounting different first injector body parts 40 on the standardized second injector body part 41, different variants of the injector 1 can then be realized comparatively inexpensively.

Claims (10)

1. Injector for supplying fuel to an internal combustion engine, in particular in a motor vehicle,

   - comprising a piezoactuator (5) for activating and/or actuating at least one nozzle needle (3) for controlling the injection of high-pressure fuel through at least one spray hole (12),

   - the piezoactuator (5) being arranged with its shank (7) in an actuator space (9) of an injector body (2),

   - a high-pressure path (10), which directs the high-pressure fuel to the spray hole (12), of which there is at least one, being passed through the actuator space (9),

   characterized in that the piezoactuator (5) has an actuator foot (6) at an end remote from the nozzle needle (3), said actuator foot (6) having a sealing contour (21) which faces the nozzle needle (3) and fits in a sealing seat (22) formed on the injector body (2) and facing away from the nozzle needle (3).
2. Injector according to Claim 1, characterized in that the actuator foot (6) forms an actuator-space seal (23) with its sealing contour (21), which fits in the sealing seat (22), which seal closes the actuator space (9).
3. Injector according to Claim 1 or 2,
   characterized in that the actuator foot (6) is preloaded towards the nozzle needle (3) by means of a preloading device (26) in such a way that the sealing contour (21) fits in the sealing seat (22) under a preload.
4. Injector according to Claim 3, characterized

   - in that the preloading device (26) has a clamping member (28), the actuator foot (6) having a supporting contour (30) which faces away from the nozzle needle (3) and fits in a supporting seat (29) formed on the clamping member (28) and facing the nozzle needle (3),
   and/or

   - in that the preloading device (26) has a clamping nut or clamping screw (27) which is screwed to the injector body (2) and which is the clamping member (28) preloaded against the actuator foot (6) or by means of which the clamping member (28) is preloaded against the actuator foot (6).
5. Injector according to Claim 4, characterized in that the clamping member (28) is secured against twisting about a longitudinal axis (15) of the injector body (2) by means of an anti-rotation device (33) supported on the injector body (2).
6. Injector according to Claim 4 or 5,
   characterized

   - in that the clamping member (28) is of annular configuration and has a central opening (36), and/or

   - in that the clamping nut or clamping screw (27) is of sleeve-shaped configuration and has a central passage (37), and/or

   - in that the electrical connections (39) of the piezoactuator (5) are passed through the actuator foot (6) and through a connection duct (38), which has the opening (36) of the clamping member (28) and the passage (37) of the clamping nut or clamping screw (27).
7. Injector according to Claim 6, characterized in that, with its supporting contour (30), which fits in the supporting seat (29), the actuator foot (6) forms a connection-duct seal (45) which seals the connection duct (38).
8. Injector according to one of Claims 3 to 7,
   characterized in that the preloading device (26) is designed to introduce a preload which leads to plastic deformations at the sealing seat (22) and/or at the sealing contour (21) and/or at the supporting seat (29) and/or at the supporting contour (30).
9. Injector according to one of Claims 1 to 8,
   characterized

   - in that the sealing contour (21) is of closed annular configuration, and/or

   - in that the sealing contour (21) is configured to be concentric to a longitudinal axis (15) of the injector body (2), and/or

   - in that the sealing contour (21) is of spherical configuration, and/or

   - in that the sealing seat (22) is of closed annular configuration, and/or

   - in that the sealing seat (22) is configured to be concentric to a longitudinal axis (15) of the injector body (2), and/or

   - in that the sealing seat (22) is of conical configuration, and/or

   - in that the supporting contour (30) is of closed annular configuration, and/or

   - in that the supporting contour (30) is configured to be concentric to a longitudinal axis (15) of the injector body (2), and/or

   - in that the supporting contour (30) is of spherical configuration, and/or

   - in that the supporting seat (29) is of closed annular configuration, and/or

   - in that the supporting seat (29) is configured to be concentric to a longitudinal axis (15) of the injector body (2), and/or

   - in that the supporting seat (29) is of conical configuration.
10. Injector according to one of Claims 1 to 9,
    characterized

    - in that the injector body (2) is assembled at least from a first injector-body part (40) containing the actuator foot (6) and from a second injector-body part (41) adjoining the first injector-body part (40) towards the nozzle needle (3), and

    - in that the two injector-body parts (40, 41) are secured on one another by means of a sleeve-shaped connecting element (42), and

    - in that the first injector-body part (40) has a high-pressure connection (11), via which the high-pressure path (10) can be connected to a high-pressure source which provides the fuel under high pressure.

Images