EP2456970A1

EP2456970A1 - Piezoactuator having electrical contact

Info

Publication number: EP2456970A1
Application number: EP10734999A
Authority: EP
Inventors: Reinhard Gabl; Jan-Thorsten Reszat; Markus Laussermayer
Original assignee: Epcos AG
Current assignee: TDK Electronics AG
Priority date: 2009-07-21
Filing date: 2010-07-20
Publication date: 2012-05-30
Also published as: JP5717736B2; CN102472213B; US8441175B2; JP2012533897A; WO2011009866A1; US20120202382A1; DE102009034099A1; EP2799703A1; CN102472213A

Abstract

The present invention relates to a piezoactuator (10) having multilayer construction, wherein piezoelectric layers (14) and electrode layers (12) are alternatingly disposed one over the other in a stack (16). A plurality of the electrode layers (12) are electrically conductively connected to a contact pin (24), wherein a continuation (30) is electrically conductively disposed on the contact pin (24). The continuation (30) has a contact point (32) with the contact pin (24) and a free end (34) for producing an electrical connection of the piezoactuator (10). A straight line extending through the contact point (32) and the free end (34) of the continuation encloses an angle (μ) with the longitudinal axis (18) of the contact pin (24) that is greater than 0° and less than 180°.

Description

description

Piezo actuator with electrical contact

A piezoactuator in multilayer construction is described in which piezoelectric layers and electrode layers are arranged alternately one above the other to form a stack. When applying an electrical voltage to the

Electrode layers expands the stack along the electric field direction resulting from the applied voltage.

By means of such a piezoelectric actuator, for example, a valve piston of a control valve is actuated, which as

Injection valve in a motor vehicle is used.

A piezoelectric actuator is for example in the publications

DE 199 45 933 C1 or WO 2005/035971 Al.

It is an object to be solved to provide a piezoelectric actuator, which has a high reliability and is suitable for a variety of possible applications and installation locations.

This object is solved by the independent claim.

Advantageous embodiments and further developments of

Invention will be apparent from the dependent claims.

A piezoactuator in multilayer construction is specified in which piezoelectric layers and electrode layers are arranged alternately one above the other to form a stack. For example, the stack has four side surfaces and two end surfaces. The piezoelectric actuator can be clamped to the end faces, which provides a mechanical bias along the longitudinal axis of the stack.

For example, the stack comprises a plurality of thin foils made of piezoceramic, which comprise, for example, a material such as lead zirconate titanate. A piezoelectric layer may comprise one or more of these films. Between these layers of piezoceramic electrode layers are arranged. Depending on the desired voltage-dependent

Behavior of the piezoelectric actuator does not necessarily follow an electrode layer on each piezoelectric layer.

One possible material for the electrode layer is

Silver palladium or copper. This can be applied to the piezoelectric layer as a paste by means of a screen printing process, and then the stack can be sintered.

The electrode layers can be applied continuously to the

be applied to piezoelectric layers or they may only partially cover the cross-sectional area of the piezoelectric layers. The embodiment of the electrical contacting of the electrode layers depends on whether the electrode layers are arranged continuously on the surface of the piezoelectric layers.

Several of the electrode layers are electrically connected to a contact pin. At the contact pin can a

Continuation be arranged so that it connects the contact pin and continuation electrically conductive.

In particular, the continuation has a contact point with the contact pin. The contact point is designed to to connect the continuation with the contact pin electrically conductive. The continuation has a free end, which is provided for producing an electrical connection. A straight line that passes through the contact point and the free end of the continuation includes an angle with the longitudinal axis of the contact pin, which is greater than 0 ° and less than 180 °.

In one embodiment, the contact point for

Producing the connection between the continuation and the contact pin along the stack of piezoelectric

Layers and electrode layers arranged. In particular, the contact point is arranged between an upper end and a lower end of the stack.

In an embodiment in which the electrode layers are made continuous, the applied

Electrode layers on all side surfaces of the stack out of this. The electrical connection of the electrode layers to the contact pin may, for example, be realized by thin wires which individually connect each second electrode layer to the contact pin on a side surface of the stack.

At the contact pin a continuation may be appropriate. This continuation is with the contact pin on a

Contact point electrically connected. For example, the continuation is firmly connected to the contact pin, for example, soldered to this or by means of an eyelet, which firmly surrounds the contact pin, attached to the contact pin.

All other mounting options that provide a conductive contact between the contact pin and the continuation However, allow and sufficient stability with respect to an electrical connection offers, are also conceivable.

The continuation comprises, for example, a flexible conductor wire. Preferably, the continuation comprises a rigid pin-shaped element. A combination of these two possibilities would also be conceivable.

The continuation is attached to the contact pin. The angle at which the continuation is attached to the contact pin should be between 0 ° and 180 ° with respect to the longitudinal axis of the contact pin. By being able to choose different angles, an individual alignment of the electrical connections can be achieved and a lateral further contact of the stack via the continuation is made possible.

The free end of the continuation may be oriented outwardly as viewed from the center of the stack. This free end can be used to apply a voltage between the

Electrode layers serve and thus an electrical

Form the connection of the stack.

Preferably, the electrode layers lead out of the stack alternately on opposite side surfaces and a plurality of the electrode layers are connected by means of a

Outside electrode, which is applied laterally on the stack, contacted.

In a stack in which the electrode layers mutually lead out of this, the electrode layers do not cover the entire surface of a piezoelectric layer. The areas of the stack in which adjacent electrode layers do not overlap in the stacking direction become inactive Called zones. The areas of the stack in which adjacent electrode layers overlap in the stacking direction are called active zones.

Such a construction of the stack allows, for example, a common electrical contacting of all electrode layers, which lead out of the stack on the same side, via a common outer electrode.

The outer electrode is for example by means of a

Baking paste, which by a screen printing process on the

Outside of the stack is applied, prepared and then sintered with the stack.

In an advantageous embodiment, the contact pin is arranged parallel to the longitudinal axis of the stack.

Since the continuation is attached to the contact pin, a fixed orientation of the contact pin with respect to the stack also results in a fixed orientation of the continuation to the stack. In particular, the angle between the contact pin and the continuation is fixed in this case. This can be very helpful to the location of the free end of the

Continuation and thus adjust the subsequent electrical connection of the piezoelectric actuator, since only the angle of the

Continuation must be taken into account with respect to the contact pin and not the angle between the continuation and the longitudinal axis of the stack.

In the production of the piezoelectric actuator and the contact pin with a continuation may have been prefabricated and the resulting component can in a single

Step be attached for example via an intermediate element on the stack. Because of the orientation of the Continuation with respect to the contact pin is already established, the orientation of the continuation is fixed with respect to the stack in a parallel arrangement between the contact pin and stack.

In addition, a parallel orientation of the contact pin with respect to the stack saves space.

In a further advantageous embodiment, an electrically conductive intermediate element between the outer electrode and the contact pin is arranged, which the

External electrode and the contact pin electrically conductively connects.

The intermediate element may comprise one or more individual elements. For example, it can be an elastic component that adapts to the movements of the stack. This prevents a loss of electrical

Connection between the outer electrode and the contact pin and ensures a stable operation of the

Piezoelectric actuator. In particular, the tearing of the connection between the contact pin and the intermediate element and between

Intermediate element and outer electrode are prevented.

Such a tearing off of the electrical connection between the contact pin and the electrode layers could cause a failure of the piezoelectric actuator. If the piezoelectric actuator, for example, a valve piston of a control valve

actuate, which serves as an injection valve in a motor vehicle, then the piezoelectric actuator must be replaced immediately to ensure further operation of the injector and thus the engine. Furthermore, it can be provided that the electrically conductive intermediate element comprises wires arranged in parallel, which connects the outer electrode to the contact pin in an electrically conductive manner. For example, the parallel wires may be aligned perpendicular to the longitudinal axis of the stack.

To connect the outer electrode with the contact pin electrically conductive, for example, a so-called Harhtharfe use. This includes a plurality of thinner,

electrically conductive wires. The wire can with the

Be soldered outside electrode and the contact pin.

For example, two outer electrodes on the stack

be attached, which alternately contact the electrode layers. To make the wire harp, a thin, electrically conductive wire is wound in a plurality of turns around the stack. After soldering the wire to the outer electrodes, the wire connection between the two outer electrodes can be severed and the connection

completely removed. Thus, the outer electrodes are electrically isolated from each other.

Preferably, the straight line passing through the contact point between the continuation and the contact pin and the free end of the continuation, with the longitudinal axis of the

Contact pin an angle of 90 °.

The continuation can be arranged perpendicular to the contact pin. If the contact pin is also arranged parallel to the longitudinal axis of the stack, then the continuation is arranged not only perpendicular to the contact pin but also perpendicular to the longitudinal axis of the stack. This orientation is advantageous for a connection of the piezoelectric actuator to a voltage source, since a lateral electrical further contact of the piezoelectric actuator in this way is possible. In an advantageous embodiment, the piezoelectric actuator has a housing.

This housing may for example be a casting of an elastic material, such as silicone or include such a potting. Ideally, the housing encloses at least the side surfaces of the stack. All other forms of housing that do not hinder the operation of the piezoelectric actuator are conceivable. A housing can provide protection against environmental influences such as moisture.

In a further advantageous embodiment of the

Contact pin completely enclosed by the housing.

Since the contact pin no longer directly to the connection of the

Stack is needed to a voltage source, it may be appropriate to leave it completely in the housing. A lateral connection is advantageous in some applications, since the mechanical contact surfaces, which are located, for example, at the end faces of the stack, are separated from the electrical connections.

Preferably, the continuation projects out of a side surface of the housing.

In this way, an electrical Weitererkontaktierung on a side surface of the housing is made possible.

Furthermore, it can be provided that the continuation is connected at a free end with a connection element and the piezoelectric actuator can be controlled via this connection element. The connection element serves to apply an electrical voltage between the electrode layers. The amount of voltage applied can be used to control the behavior of the stack. The connection element may be a

Essay on the continuation act. Such an attachment can be applied to any continuation. Also, two essays can be integrated in one component and together form a connection element.

The connection element can also be a part of an electrical continuation contact, which is arranged at the installation location of the piezoelectric actuator. The continuations can be connected to the further contact, for example via a plug connection. Via the further contact, a voltage can be applied to the stack and also regulated.

In an advantageous embodiment, the piezoelectric actuator has two contact pins and the electrode layers are alternately electrically conductively connected to a respective contact pin. Each of the contact pins has a continuation. Over the free ends of the continuations, a voltage can be applied between adjacent electrode layers.

For example, the electrode layers are alternately on opposite side surfaces of the stack with a

Contact pin connected. At the contact pin is a

Continuation attached.

In the case of continuous electrode layers, every second electrode layer may be connected to a contact pin by means of a conductive wire. Since a continuation is attached to the contact pin, in this way becomes an electric conductive connection between the electrode layers and the continuation made.

Another possibility would be to produce a conductive connection between the electrode layers and the continuation via an outer electrode and an intermediate element. This is particularly advantageous in the case that the

Electrode layers do not cover the entire cross-sectional area of the piezoelectric layer.

A voltage can then be applied to the continuations via the connection element. Depending on the desired

Execution of the connection, the continuation can be oriented differently with respect to the longitudinal axis of the stack.

In the case of two continuations, the Weitererkontaktierung can be done in any orientation of the continuations to each other. As a result, the piezoelectric actuator can be made individually, depending on which orientation of the free ends of the continuations is desired.

For example, the free ends of the continuations may be arranged on the same side surface of the piezoelectric actuator.

Such an arrangement of the free ends of the continuations is very space-saving, for example. In this case, further electrical contact is necessary even over only one side surface. This is often preferred for reasons of space and the installation of such a piezoelectric actuator is under circumstances

lighter than in the case of an arrangement of the continuations on different side surfaces.

The free ends of the continuations can be arranged one above the other with respect to the longitudinal axis of the stack. Here, the free ends of the continuations in

different height of the stack on the same side surface of the piezoelectric actuator or on different side surfaces

be arranged.

In a further embodiment, the free ends of the continuation are arranged side by side with respect to the longitudinal axis of the stack.

The free ends of the continuations can be arranged at the same height on the same side surface of the piezoelectric actuator or at the same height at different side surfaces of the piezoelectric actuator.

In an advantageous embodiment, the free ends of the continuations are arranged on different side surfaces of the piezoelectric actuator.

Such an arrangement of the free ends of the continuations has the advantage that the Weitererkontaktierung can be spatially separated from each other.

In the following, the specified piezoelectric actuator and its preferred embodiments will be explained with reference to schematic and not to scale figures. Show it:

1 shows a piezoelectric actuator with a connected via an intermediate element with the electrode layers

Contact pin to which a continuation is attached,

2a shows a cross section through a piezoelectric actuator with two perpendicular to the longitudinal axis of the stack arranged continuations, 2b shows a cross section through a piezoelectric actuator with two continuations, which at opposite

Sides of the stack are arranged

3a shows a side view of the piezoelectric actuator as shown in FIG

2a is shown

Figure 3b is a side view of the piezoelectric actuator as shown in FIG

2b is shown and

Figure 3c is a side view of a piezoelectric actuator with two

with respect to the longitudinal axis of the piezoelectric actuator

superimposed continuations.

FIG. 1 schematically shows a piezoelectric actuator 10. The electrode layers 12 can clearly be seen, which lead alternately out of the stack 16 in the embodiment shown here. On the opposite sides of the stack 16, an outer electrode 20 is mounted, wherein in the here

used view only an outer electrode 20 can be seen.

On the outer electrode 20, a conductive intermediate member 22 is arranged, which is formed from thin conductive wires 23. These parallel wires 23 connect the outer electrode 20 with a rigid

Contact pin 24. At this rigid contact pin 24 is a continuation 30, which consists of a metallic pin

exists, firmly soldered. The contact pin 24 is arranged parallel to the longitudinal axis 18 of the stack 16.

The point at which the electrical contact between the

Continuation 30 and the contact pin 24 is made, the contact point 32. The free end 34 of the continuation 30 shows in a stack 16 facing away from the direction. Placing a straight line through the contact point 32 and the free end 34 of the continuation 30, so includes this straight line with the longitudinal axis 18 of the contact pin 24 an angle μ, which is 90 ° in the example shown.

FIG. 2 a shows a cross section perpendicular to the longitudinal axis 18 of a piezoactuator 10 with two continuations 30 arranged perpendicular to the longitudinal axis 18 of the stack 16.

In the center of the figure, the stack 16 can be seen, on each of which an outer electrode 20 is applied on two opposite side surfaces 19. These outer electrodes 20 are conductively connected via a bent intermediate element 22, each with a contact pin 24.

At the contact pin 24, a continuation 30 is electrically conductively soldered. To this arrangement, a potting compound 42 is injected, which forms the housing 40 of the piezoelectric actuator 10 together with a sleeve 44. The potting compound 42 may comprise an elastic material, such as silicone.

It can be seen on the right side of FIG. 2a that only the two continuations 30 protrude out of the housing 40. At the free ends 34 of the continuations 30 connecting contacts 36 are attached, via which a voltage to the

Electrode layers 12 is applied in the piezoelectric actuator 10. The continuations 30 protrude from the housing 40 on the same side surface 46.

FIG. 2b shows a structure similar to that in FIG. 2a, with the difference that the continuations 30 on the opposite side surfaces 46 of the housing 40 protrude therefrom.

FIG. 3a shows a side view of the piezoactuator 10, as already shown in cross section in FIG. 2a. It is clear to see that the continuations 30 are arranged at an angle μ = 90 ° to the longitudinal axis 18 of the piezoelectric actuator 10 back.

It can also be seen that the continuations 30

are arranged side by side perpendicular to the longitudinal axis 18 of the piezoelectric actuator 10.

FIG. 3b shows a side view of the piezoactuator 10, as already shown in cross section in FIG. 2b. It can clearly be seen that the continuations 30 are arranged at an angle μ = 90 ° to the longitudinal axis 18 of the piezoelectric actuator 10.

It can also be seen that the continuations 30 on opposite side surfaces 46 lead out of the housing 40 of the piezoactuator 10 at the same height therefrom.

FIG. 3c shows a side view of a piezoactuator 10.

As in FIG. 3 a, the continuations 30 on the same side surface 46 of the housing 40 lead out of this. In this example, however, they are arranged one above the other vertically along the longitudinal axis 18.

The invention is not limited to the preferred embodiments described above. Rather, a variety of variants and modifications is possible, which also make use of the inventive idea and therefore fall within the scope. List of reference numbers:

10 piezo actuator

12 electrode layer

14 piezoelectric layer

16 piles

18 longitudinal axis

19 side surface of the stack

20 outer electrode

22 intermediate element

23 wire

24 contact pin

30 continuation

32 contact point

34 free end of continuation

36 connection element

40 housing

42 potting

44 sleeve

46 Side surface of the housing μ Angle between a straight line running through the contact point and the free end of the continuation and the

Claims

claims

1. Piezo actuator in multilayer construction, in which

piezoelectric layers (14) and electrode layers

(12) are arranged alternately one above the other to a stack (16), wherein a plurality of the electrode layers (12) with a contact pin (24) are electrically connected, wherein the contact pin (24) has a

Continuation (30) is arranged, which is a

Contact point (32) for producing an electrically conductive connection with the contact pin (24) and wherein the continuation (30) has a free end (34) for producing an electrical

Connection of the piezoelectric actuator (10), and wherein a straight line passing through the contact point (32) and the free end (34) of the continuation (30) extends with a longitudinal axis

(18) of the contact pin (24) forms an angle (μ)

which is larger than 0 ° and smaller than 180 °.

2. Piezoelectric actuator according to claim 1, wherein the electrode layers (12) alternately on opposite side surfaces

(19) lead out of the stack (16) and wherein a plurality of the electrode layers (12) by means of a

Outer electrode (20), which is laterally applied to the stack (16) are contacted.

3. Piezoelectric actuator according to claim 1 or 2, wherein the

Contact pin (24) parallel to the longitudinal axis (18) of the

Stack (16) is arranged.

4. Piezoelectric actuator according to claim 2 or 3, wherein an electrically conductive intermediate element (22) between the Outer electrode (20) and the contact pin (24) is arranged and connects electrically conductive.

5. Piezoelectric actuator according to claim 4, wherein the electrically

conductive intermediate element (22) arranged in parallel

Includes wires which electrically conductively connect the outer electrode (20) with the contact pin (24).

6. Piezoelectric actuator according to one of the preceding claims,

wherein the straight line passing through the contact point (32) between the continuation (30) and the contact pin (24) and the free end (34) of the continuation (30), with the longitudinal axis (18) of the contact pin (24) at an angle (μ) of 90 °.

7. Piezoelectric actuator according to one of the preceding claims, comprising a housing (40).

8. Piezoelectric actuator according to claim 7, wherein the contact pin (24) is completely enclosed by the housing (40).

9. Piezoelectric actuator according to claim 7 or 8, wherein the

Continuation (30) from a side surface (46) of the

Housing (40) protrudes.

10. Piezoelectric actuator according to one of the preceding claims,

wherein the continuation (30) at the free end (34) is connected to a connection element (36) and wherein the piezoactuator (10) is connected via the connection element (36).

can be controlled.

11. Piezoelectric actuator according to one of the preceding claims,

wherein the piezoactuator (10) has two contact pins (24) and wherein the electrode layers (12) alternately with one of the contact pins (24) are electrically connected and each of the

Contact pins (24) has a continuation (30) and wherein over the free ends (34) of the continuations (30), a voltage between adjacent electrode layers (12) of the stack (16) can be applied.

12. Piezoelectric actuator according to claim 11, wherein the free ends (34) of the continuations (30) on the same side surface (19) of the piezoelectric actuator (10) are arranged.

13. Piezoelectric actuator according to claim 12, wherein the free ends (34) of the continuations (30) are arranged one above the other with respect to the longitudinal axis (18) of the stack (16).

14. Piezoelectric actuator according to claim 12, wherein the free ends (34) of the continuations (30) are arranged side by side with respect to the longitudinal axis (18) of the stack (16).

15. Piezoelectric actuator according to one of claims 11, wherein the free ends (34) of the continuations (30) on different side surfaces (19) of the piezoelectric actuator (10) are arranged.