WO2002014679A1

WO2002014679A1 - Piezoelectric actuator, especially for actuating a valve in a motor vehicle

Info

Publication number: WO2002014679A1
Application number: PCT/DE2001/002950
Authority: WO
Inventors: Wolfgang Stoecklein; Dietmar Schmieder
Original assignee: Robert Bosch Gmbh
Priority date: 2000-08-11
Filing date: 2001-08-09
Publication date: 2002-02-21
Also published as: DE10039218A1

Abstract

The invention relates to a piezoelectric actuator comprised of an actuator housing (10) having a receiving opening (14), which is axially open at one end, of an axially elongated lifting body (16), which can be inserted into said receiving opening and which is made of a piezoelectric material, of an electrode (22), which is placed against the piezoelectric material, and of electric supply means (24, 32) for supplying voltage. The invention provides that the supply means (24, 32) are brought into contact with the electrode (22) in the area of the first longitudinal end (18) of the lifting body. From there, the supply means run along the lifting body at least until they are approximately in the area of an axially opposed second longitudinal end (20) of the lifting body and are subsequently led out through an outlet channel.

Description

Piezoelectric actuator arrangement, in particular for actuating a valve in a motor vehicle

State of the art

The invention relates to a piezoelectric actuator arrangement, in particular for actuating a valve in a motor vehicle, comprising an actuator housing with a housing axis and a receiving opening that is axially open at one end and closed at the other end, an axially elongated, with a first longitudinal end ahead through the open one End of the receiving opening into this insertable lifting body made of piezoelectric material, an electrode arrangement applied to the piezoelectric material and electrical supply means for supplying voltage to the electrode arrangement.

Piezoelectric actuators are used, for example, for valve actuation in fuel injection systems in motor vehicles. With generic actuator arrangements, it is necessary to contact the electrode Arrangement of the piezo material is known to solder or weld electrical conductor wires in the region of the first longitudinal end of the lifting body to the electrode arrangement and to guide the conductor wires to the outside through a housing bore in the region of the closed end of the receiving opening of the actuator housing. The first longitudinal end of the lifting body is supported in the area of the closed end of the receiving opening against axial movements, while the axially opposite second longitudinal end of the lifting body forms a lifting end which carries out axial strokes when the voltage is applied to the electrode arrangement. For this reason, the conductor wires are fastened to the lifting body in the region of the first longitudinal end because this prevents the conductor wires from moving along and possibly causing cracks in the soldering or welding points.

This known solution has the technical assembly problem that when the lifting body is inserted into the receiving opening of the actuator housing, the previously soldered or welded-on conductor wires must be threaded blindly into the housing bore. Automatic assembly is not possible here, but manual assembly also poses great difficulties for the workforce. This is because the conductor wires cannot be guided specifically into the housing bore by hand, since the lifting body hides them as soon as they are inserted into the receiving opening. It can then only be relied on to hit the conductor wires in the housing bore by turning the slide body back and forth. The uncertainty as to whether the housing bore is is hit, the time required is due to inevitable failed attempts, so that overall there is a time-consuming and cumbersome assembly.

Advantages of the invention

The invention provides that in the case of an actuator arrangement of the type described in the introduction, the supply means are contacted with the electrode arrangement in the region of the first longitudinal end of the lifting body, from there within the receiving opening along the lifting body at least up to approximately the area of an axially opposite second longitudinal end of the Lift body run and are then led out of the actuator housing through an outlet channel.

This can make installation considerably easier. By initially guiding the supply means from the point of their contacting with the electrode arrangement to the second longitudinal end, no leading parts of the supply means need to be blindly threaded into any housing bore when the lifting body is inserted into the housing. In the area of the second longitudinal end of the lifting body, it will be much easier to access the feed means, even if the lifting body is already fully inserted into the receiving opening of the actuator housing. The threading of the feed means into the outlet channel and thus the removal of the feed means from the actuator housing can then be considerably more convenient and, above all, under manage constant visual observation. False attempts are no longer to be expected per se. In particular, the solution according to the invention enables the assembly process to be automated to a greater extent, the reliefs mentioned naturally also being apparent in the case of manual assembly.

The space available at the installation location of the actuator arrangement often requires that a plug connection serving to connect a voltage supply cable be arranged in a region of the actuator housing close to the first longitudinal end of the lifting body. In order to guide the supply means in a protected manner into this housing area, the outlet channel in the housing wall of the actuator housing can run approximately parallel or at an acute angle to the housing axis in the direction from the second longitudinal end of the lifting body to the first longitudinal end and extend beyond the latter.

A preferred development of the invention provides that the supply means are formed at least over a substantial part of their length running within the receiving opening by a strip material arrangement made of sheet metal. The rigidity of the sheet ensures that the lifting body can be inserted safely and precisely into the receiving opening without the parts of the supply means located within the receiving opening hindering this by undesired tangling, as can occur with conductor wires, for example. In terms of assembly technology, it is particularly favorable if the strip material arrangement on the lifting body can be mounted before its insertion into the receiving opening.

The strip material arrangement preferably extends into the region of the first longitudinal end of the lifting body and is contacted there with the electrode arrangement, in particular on the outer jacket of the lifting body. For this purpose, the strip material arrangement can be soldered or welded to the electrode arrangement. A permanently secure electrical contact results if the

The electrode arrangement surrounds the strip material arrangement for contacting it on the edge.

The strip material arrangement will expediently be covered with an electrically insulating material layer on at least part of its side facing the lifting body. In particular in the case of an actuator housing made of a metallic material, it is also advisable to avoid electrical short circuits that the strip material arrangement is also covered with an electrically insulating material layer on at least part of its side facing the peripheral jacket of the receiving opening.

The strip material arrangement should advantageously extend axially at least up to approximately in the region of the second longitudinal end of the lifting body, preferably even extending beyond it. A conductor wire arrangement led out of the actuator housing through the outlet channel can then be connected to the strip material arrangement within the receiving opening. On simple connection of the conductor wire arrangement is possible, for example, in that the strip material arrangement has at least one U-shaped pocket into which the conductor wire arrangement engages. For reliable contact establishment, it may already be sufficient if the conductor wire arrangement is clamped in the pocket by squeezing it. Alternatively or additionally, the conductor wire arrangement can also be soldered or welded in the pocket.

Occasionally, the actuator housing will have a configuration in which it extends axially substantially beyond the second longitudinal end of the lifting body. The housing areas axially beyond the lifting body can serve, for example, to accommodate a plunger or piston which transmits the axial strokes of the lifting body. If a one-piece actuator housing is used in such a case, access to the conductor wire arrangement can be difficult if the lifting body is already fully inserted into the actuator housing. It may then have to be reached deep into the actuator housing in order to get hold of the conductor wire arrangement. In order to avoid this, it is recommended to design the actuator housing with two housing parts which are divided axially, in particular approximately in the region of the second longitudinal end of the lifting body, one of which at least largely accommodates the lifting body and the other essentially the part of the actuator which extends beyond the second longitudinal end of the lifting body. tuatorgehäuses forms, where the two housing parts after connecting the conductor wire arrangement to the strip material arrangement are assembled. All the necessary work at the interface between the strip material arrangement and the conductor wire arrangement can then be carried out conveniently before the housing parts are assembled.

In a solution, known from practice, of a generic actuator arrangement, electrical conductor wires are led out of the actuator housing and connected outside the actuator housing with connector lugs, which are then encapsulated with a plastic material. In this way, a plug is made in situ, ie directly at the location of the actuator housing, to which a voltage supply cable can be connected. In order to hold the

To ensure the connector on the actuator housing, this is overmolded. It is easy to understand that this type of connector production is very complex, on the one hand because the connector tabs have to be positioned exactly on the actuator housing, and on the other hand because the actuator housing is often made of metal and the injection molding of a plastic part onto a metal part is difficult.

In the solution according to the invention, on the other hand, it is preferably provided that the supply means extend over part of their length in a connector component which is prefabricated separately from the actuator housing and which can be fixedly but detachably mounted on the actuator housing and forms a plug connection for a voltage supply cable. On the one hand, this facilitates the manufacture of the Plug component itself, on the other hand, this enables a separate test of the plug component, for example with regard to electrical properties and tightness against moisture penetration. If it turns out during this test that the plug component is faulty, it can be thrown away as a committee without having to throw away the actuator housing at the same time, as may be necessary in the known solution with a molded plug. If necessary, the plug component can also be replaced at a later time if it suffers damage during operation.

For the idea of producing a plastic plug component separately from the actuator housing, in particular when the actuator housing is made of a metallic material, such as steel, and to fix the plug component firmly but releasably to the actuator housing, the invention relates to The right to claim independent protection is reserved, regardless of the specific course of the supply means in the actuator housing and regardless of the specific design of the supply means.

A very good seal between the plug component and the actuator housing can be achieved if the plug component has a plug housing with a housing extension, in particular molded on in one piece, with which it engages in the outlet channel. At the same time, the housing extension can be used as a positioning aid for correct right positioning of the connector component relative to the actuator housing.

According to a preferred variant, the housing extension is designed as an elongated mandrel, which extends essentially through the entire outlet channel and, if desired, extends into the receiving opening of the actuator housing, the feed means running through the mandrel. This measure ensures a particularly simple assembly of the actuator arrangement because the housing mandrel can be very easily inserted into the outlet channel from the outside.

Further advantages and developments of the subject matter of the invention result from the patent claims, the description and the drawing.

drawing

An embodiment of the invention is explained below with reference to the accompanying drawings. It represent

FIG. 1 shows an axial longitudinal section through an exemplary embodiment of the actuator arrangement according to the invention;

Figure 2 shows a section corresponding to II-II of Figure 1;

Figure 3 is an enlargement of a section A of Figure 2; and

FIG. 4 shows an enlargement of a section B of FIG. 2. Description of the embodiment

The actuator arrangement shown in the figures serves to actuate a control or injection valve (not shown in more detail) in a fuel injection system, for example a common rail diesel injection system. It comprises a cylindrical actuator housing 10 with a housing axis 12 and an axial receiving opening 14. The actuator housing 10 can be made of a metal, preferably steel, which will be the case especially if it contains channels which are part of a high-pressure line system for Are fuel. Manufacturing from plastic is, however, by no means excluded within the scope of the invention. An axially elongated lifting body 16 made of piezoelectric material is inserted into the actuator housing 10 through an open axial end of the receiving opening 14.

In the area of a closed bag end of the receiving opening 14, the lifting body 16 is axially immovably supported on the actuator housing 10 with a first axial end, generally designated 18. With its axially opposite end 20, the lifting body 16 carries out axial lifting movements when an electrical voltage is applied to the piezo material, which are transmitted to an actuating plunger or piston, also not shown, which is also accommodated in the actuator housing 10. In order to achieve the largest possible axial strokes, the lifting body 16 is formed from a large number of individual layers of piezo material stacked axially one above the other, between which thin metal layers are located. Find. The metal layers are alternately connected to two flat electrodes 22 arranged on the outer jacket of the lifting body 16, which serve to supply voltage to the metal layers. Details of such a lifting body can be found, for example, in DE 199 09 452 Cl.

Before the lifting body 16 is installed in the actuator housing 10, each of the electrodes 22 is contacted near the immovable lifting body end 18 with a strip-shaped conductor plate 24 which extends axially to the lifting body end 20 and somewhat beyond. The electrodes 22 are placed around the narrow edges of the metal strips 24 in order to ensure better contact.

This can be seen particularly well in FIG. 3 in an area identified by reference numeral 26. In this area 26, where the electrodes 22 overlap the conductor plates 24, the conductor plates 24 are also expediently soldered or welded to the electrodes 22, so that the conductor plates 24 are held firmly on the lifting body 16.

Following the area of their contact with the electrodes 22, the conductor plates 24 are provided on their two flat sides with an insulating layer 28, for example a glued-on insulating tape or an anodizing layer, in order to avoid electrical malfunctions when the metallic housing wall or the piezo material of the lifting body 16 comes into contact , The conductor plates 24 can be spaced from the outside of the lifting body. pers 16. Due to their insulation, however, they can also nestle against the outside of the lifting body 16.

As can be seen in particular in FIG. 4, the ends of the conductor plates 24 projecting beyond the lifting body 16 are bent into a U-shape to form pockets 30 which are used for connecting conductor wires 32. The contact between the conductor wires 32 and the pockets 30 can be established, for example, by placing the conductor wires 32 in the pockets 30 and clamping them there by squeezing the pockets 30 together. Of course, welding or soldering the conductor wires 32 in the pockets 30 is also possible.

In order to lead the conductor wires 32 to the outside, a housing bore 34 serving as an outlet channel is machined into the actuator housing 10 at a small acute angle to the axis 12. The housing bore 34 extends away from the lifting body end 20 axially beyond the lifting body end 18 and leads beyond this lifting body end 18 out of the actuator housing 10.

The attachment of the housing bore 34 is facilitated in that it opens out on an axial end face, which in the present example is formed by an annular shoulder 36 in an axial end region 38 of the actuator housing 10. Outside the housing bore 34, the conductor wires 32 end in a connector component, generally designated 40, which has a Plug connection 42 is designed for a voltage supply cable, not shown, coming from an actuator control.

The plug component 40 is a component manufactured separately from the actuator housing 10. It has a connector housing 44 made of plastic, preferably in an injection molding process, with a retaining ring 46, with which it can be axially attached to the axial end region 38 of the actuator housing 10 and clamped thereon, for example, by means of a clamping screw 48 indicated by a broken line. The annular shoulder 36 serves as an axial positioning stop for the plug component 40.

An elongate, spike-like housing extension 50 is formed in one piece with the plug housing 44, which engages with a precise fit in the housing bore 34 and extends through this into the receiving opening 14. In this way, a high degree of tightness against the ingress of dirt or moisture into the receiving opening 14 is achieved.

The conductor wires 32 are an integral part of the plug component 40. They run in the mandrel 50 and emerge from its tip which projects into the receiving opening 14. When assembling the actuator arrangement, the plug component 40 is inserted with its mandrel 50 into the housing bore 34, and the lifting body 16 prepared with the conductor plates 24 is inserted into the receiving opening 14. Then the run out of the mandrel 50 the ends of the conductor wires 32 contacted with the pockets 30 of the conductor plates 24. In order to have easy access to the pockets 30 and the wire ends during this contacting activity, the actuator housing 10 is of axially multi-part design.

Specifically, it has a first housing part 52 which is dimensioned axially in such a way that the lifting body 16 can be accommodated therein at least for the most part. A second housing part 54 axially connects to the first housing part 52. It extends far beyond the lifting body end 20 and is used, for example, to accommodate the actuating plunger mentioned above.

The housing bore 34 is located on the first housing part 52, so that first the plug component 40 can be mounted on the first housing part 52 and the connection of the conductor wires 32 to the metal sheets 24 can be made before the second housing part 54 and possibly further housing parts on the first housing part 52 are grown. In the present example, the first housing part 52 extends axially essentially to the lifting body end 20, the pockets 30 projecting axially beyond it, as can be seen particularly well in FIG. 4. The soldering, welding or clamping work on the pockets 30 can thus be carried out without hindrance.

Claims

Expectations

1. Piezoelectric actuator arrangement, in particular for actuating a valve in a motor vehicle, comprising an actuator housing (10) with a housing axis (12) and an axially open end and axially other end at least substantially closed receiving opening (14); an axially elongated, with a first longitudinal end (18) ahead through the open end of the receiving opening (14) into this insertable lifting body (16) made of piezoelectric material; an electrode arrangement (22) applied to the piezoelectric material and electrical supply means (24, 32) for supplying voltage to the electrode arrangement (22), characterized in that the supply means (24, 32) in the region of the first longitudinal end (18) of the lifting body

(16) are in contact with the electrode arrangement (22), from there within the receiving opening (14) along the lifting body (16) at least up to approximately in the region of an axially opposite second longitudinal end (20) of the lifting body (16) and then through an outlet channel (34) is led out of the actuator housing (10).

2. Actuator arrangement according to claim 1, characterized in that the outlet channel (34) in the actuator housing (10) approximately parallel or at an acute angle to the housing axis (12) in the direction from the second longitudinal end (20) of the lifting body (16) to the first longitudinal end (18th ) runs and extends beyond the latter.

3. Actuator arrangement according to claim 1 or 2, characterized in that the feed means (24, 32) are formed at least over a substantial part of their length within the receiving opening (14) by a strip material arrangement (24) made of sheet metal.

4. Actuator arrangement according to claim 3, characterized in that the strip material arrangement (24) on the lifting body (16) prior to its introduction into the opening (14) can be mounted.

5. Actuator arrangement according to Claim 3 or 4, characterized in that the strip material arrangement (24) extends into the region of the first longitudinal end (18) of the lifting body (16) and is contacted there with the electrode arrangement (22), in particular on the outer jacket of the Lift body (16).

6. Actuator arrangement according to claim 5, characterized in that the strip material arrangement (24) to it rer contact is encompassed on the edge by the electrode arrangement.

7. Actuator arrangement according to one of claims 3 to 6, characterized in that the strip material arrangement (24) is coated at least on part of its side facing the lifting body (16) with an electrically insulating material layer (28).

8. Actuator arrangement according to Claim 7, characterized in that the strip material arrangement (24) is also coated at least on part of its side facing the peripheral jacket of the receiving opening (14) with an electrically insulating material layer (28).

9. Actuator arrangement according to one of claims 3 to 8, characterized in that the strip material arrangement (24) extends axially at least up to approximately in the region of the second longitudinal end (20) of the lifting body (16), preferably extends beyond this, and within the receiving opening ( 14) a conductor wire arrangement (32) led out of the actuator housing (10) through the outlet channel (34) is connected to the strip material arrangement (24).

10. Actuator arrangement according to claim 9, characterized in that the strip material arrangement (24) forms at least one U-shaped pocket (30) into which the conductor wire arrangement (32) engages for its connection.

11. Actuator arrangement according to claim 10, characterized in that the conductor wire arrangement (32) is clamped in the at least one pocket (30) and is preferably soldered or welded.

12. Actuator arrangement according to one of claims 9 to

11, characterized in that the actuator housing (10) extends axially substantially beyond the second longitudinal end (20) of the lifting body (16), the actuator housing (10) two in particular approximately in the region of the second longitudinal end (20) of the lifting body (16) comprises axially divided housing parts (52, 54), one (52) of which at least largely receives the lifting body (16) and the other (54) of which essentially extends beyond the second longitudinal end (20) of the lifting body (16)

Forms part of the actuator housing (10) and that the two housing parts (52, 54) can be assembled after connecting the conductor wire arrangement (32) to the strip material arrangement (24).

13. Actuator arrangement according to one of claims 1 to

12, characterized in that the supply means (24, 32) extend over part of their length in a connector component (40) which is prefabricated separately from the actuator housing (10) and which can be fixedly but detachably mounted on the actuator housing (10) and forms a plug connection (42) for an external power supply cable.

14. Actuator arrangement according to claim 13, characterized in that the plug component (40) is a plug housing. se (44) with an in particular integrally molded housing extension (50) with which it engages in the outlet channel (34).

15. Actuator arrangement according to claim 14, characterized in that the housing extension (50) is designed as an elongate mandrel which extends essentially through the entire outlet channel (34) and, if desired, into the receiving opening (14) of the actuator housing (10) and that the feed means (24, 32) extend through the mandrel (50).