WO2012122975A2

WO2012122975A2 - Method and device for producing a piezoelectric actuator component

Info

Publication number: WO2012122975A2
Application number: PCT/DE2012/100051
Authority: WO
Inventors: Jörg WALLASCHEK; Sebastian Mojrzisch; Ilja GORELIK; Marcus Neubauer; Florian Schiedeck; Andreas Renner
Original assignee: Gottfried Wilhelm Leibniz Universität Hannover
Priority date: 2011-03-17
Filing date: 2012-03-01
Publication date: 2012-09-20
Also published as: DE102011001359A1; WO2012122975A3

Abstract

The invention relates to a method and a device for producing a piezoelectric actuator component, which has a layer structure of several layers of an active material, in particular a piezoelectric ceramic, and conductive electrodes arranged respectively between the layers of an active material. For this purpose, a plurality of in particular parallel, spaced sections of a wire are wound on a coil form (8) as windings (5), wherein the windings (5) are disconnected after being fastened. In this way, several parallel sections of the wire (6) of various windings (5) form the electrode. It has been show that, thanks to the method according to the invention, the parallel wires (6) can be produced in a surprisingly simple manner by first fabricating said parallel wires in the form of a plurality of windings of a single wire (6) as a winding on the coil form (8) and then separating said parallel wires along the circumference of the layer surface according to the desired dimensions.

Description

Method and device for producing a piezoactuator component

The invention relates to a method for producing a piezoelectric actuator component with a layer structure of a plurality of layers of an active material, in particular a piezoceramic, and each arranged between the layers of an active material conductive electrodes consisting of a plurality of parallel conductors, and an apparatus for producing a piezoelectric actuator.

The use of piezo actuators in industry is expanding. If electromagnets have been used in the past, the advantages of piezoelectric elements are in particular the speed of movement and the continuous loadability. Common rail piezo injectors in diesel engines, for example, are no longer conceivable without piezo elements. Piezo actuators usually consist of a plurality of piezo elements arranged in a stack. Each of these elements in turn consists of a piezoceramic layer, which is provided on both sides with metallic electrodes. If a voltage is applied to these electrodes, the piezoceramic layer reacts with a lattice distortion, which leads along a main axis to a usable linear expansion. Since this in turn is less than two parts per thousand of the layer thickness along the main axis, a correspondingly higher layer thickness of active piezoceramic must be provided in order to achieve a desired absolute linear expansion. However, as the layer thickness of the piezoceramic layer of a single piezoelectric element increases, so does the voltage required to respond to the piezoelectric element. Consequently, a plurality of piezoelectric elements provided with electrodes must be stacked one above the other. When an electric field is applied, for example, in the polarity direction to the ceramic, it expands in the field direction, which is referred to as a so-called longitudinal effect (d ₃₃ effect), while it contracts orthogonally thereto (d ₃ i effect). The type of deformation thus depends on the direction of the applied field relative to the poling direction of the ceramic. The d ₃ i effect is only about one-third the size of the d ₃₃ effect, ie the deformation in the field direction. When using piezoelectric ceramics as actuators in the art, therefore, the aim is usually to use the d ₃₃ effect. In order to ensure a maximum deflection of the actuator, therefore, the d ₃₃ effect is used, the mechanical force acting parallel to the applied field. The electrodes required for this purpose consist of two intermeshing electrode combs, each with positive and negative potential. These electrodes are referred to as "interdigital electrodes" (IDE).

In the IDE design, the length is not determined by the number of levels. Rather, the planes are parallel to the longitudinal extent, so that the length is determined by mere trimming. The electrodes as a separate component, here a wire, are parallel to the planes of the electrodes.

In practice, customary production methods for producing such piezoelectric actuator components are printing and foiling, wherein sputtering is used.

In a not yet sintered, relatively soft ceramic, an electrode is produced in the printing process, wherein a conductive, later curing in the sintering process medium is applied, which later forms the electrode. During foliation, individual layers are produced by sputtering and then introduced layer by layer into the ceramic layers to be excited.

In US 5,113,566 A, for example, the electrode layers are produced by vapor deposition. The individual layers are offset from one another during the stacking process. US 2005/0120528 A1 describes the application of conductive metal layers in the form of a paste, similar to the production of the ceramic layers.

DE 689 26 166 T2 describes a method for producing a piezoelectric stacking device. Here, on the one hand, wire nets are used as electrodes, which are introduced as layers into the ceramic elements, on the other hand electrode arrangements are described from parallel bars, which are then introduced into the ceramic elements. WO 2007/104784 A1 relates to a method for producing a monolithic multilayer actuator, wherein the inner electrodes of both polarities are applied as interconnects on each active film, the laminating directions of all active films are arranged at right angles to the longitudinal axis of the multilayer actuator and the films together with the inner electrodes in one cofiring process in which the internal electrodes are completely laminated and sintered together with the ceramic.

Characterized in that arranged on each active film, the inner electrodes of both polarities as interconnects, the layering directions of all active films arranged at right angles to the longitudinal axis of the multilayer actuator and the films are sintered together with the inner electrodes in a cofiring process, multi-layer actuators (d ₃₃ actuators) a required, for example, valve actuators high altitude can be easily manufactured. The internal electrodes are incorporated as conductor tracks with the finest possible conductors in the actuators. The inner electrodes of both polarities are comb-like, each with a base conductor and formed by this substantially perpendicular outgoing comb conductors, wherein the comb conductor tracks of both polarities intermesh so that each Kammleiterbahn one polarity between two Kammleiterbahnen the other polarity is arranged except for the edge region of the films. These comb-shaped interlocking internal electrodes form interdigital electrodes. The base conductor tracks are preferably arranged adjacent to opposite sides of the film.

Furthermore, WO 01/35468 A2 relates to a method for producing a piezoelectric transducer, which consists of piezoelectric fibers in a polymer matrix and are applied to the electrodes for driving the fibers. In this case, the enveloping of the piezoelectric fibers is carried out with a liquid polymer composition such that there is no parallel alignment in the polymer mass, but a distribution of longitudinal axes of at least portions of the fibers or fiber pieces to the preferred direction, wherein the fibers or fiber pieces are compacted before curing with each other , All known from the prior art methods are time-consuming and costly in terms of their implementation. For example, sputtering requires special atmospheres and has low coating rates. The surface to be sputtered must be specially cleaned and may be damaged during the process. The printing process, in turn, in particular the screen printing process, can not produce the necessary for the IDE actuators thin printed conductors, as the pressing of the layers leads to a lateral displacement of the metal paste. Even if wires are used as electrodes, they must be agile to braids are processed. Wire mesh must first be produced and can not be obtained inexpensively as semi-finished products.

The object of the invention is thus to provide a method and a device for producing a piezoelectric actuator component which offers economic advantages over the prior art.

The first object is achieved by a method according to the features of claim 1. The further embodiment of the invention can be taken from the subclaims.

According to the invention, the production of a piezoelectric actuator component takes place in that a plurality of, in particular, parallel, mutually spaced sections of a wire are wound as windings on a winding body which rotates about an axis of rotation, wherein the desired spacing of the adjacent turns is fixed and the windings are subsequently interrupted such that a plurality of parallel sections of the wire of different turns form the electrodes associated with a layer. It has been found that the parallel wires can be produced by the method according to the invention in a surprisingly simple manner in that they are first produced as a plurality of turns of a single wire as a winding on the winding body and then corresponding to the desired dimensions along the circumference of the layer surface be separated. It goes without saying that the wire has been previously fixed accordingly, so that the parallel arrangement generated by the windings can be maintained accordingly. The invention is therefore also based on the surprising finding that the production of wires of the electrodes arranged in a common plane does not require fabrication on a flat base by arranging a plurality of individual wires, but rather the principle of a winding for the first time a considerably more economical one Production permitted. For this purpose, the windings on the circumference of the winding body, for example, on strips which extend substantially parallel to the axis of rotation, and between which the turns of the wire according to its bias in a common plane, preferably without further support extend. In this way, electrodes can be produced or separated from a multiplicity of parallel, single-layer windings. The wire could be fed by means of the wire guide such that it extends in a plane not perpendicular to the axis of rotation of the winding body, so that solely by the orientation of the wire feed the parallel spaced course of the turns results. By contrast, a modification of the method in which the wire guide for adjusting the spacing of the adjacent turns during the winding process, in particular parallel to the axis of rotation, for example, is continuously or continuously moved, is particularly advantageous. As a result, the spacing of the adjacent windings, in particular also for each turn, is achieved in a simple manner by the movement of the wire guide, which can be arranged to be movable or pivotable along an axis parallel to the axis of rotation of the winding body. The movement of the wire guide is preferably carried out continuously or continuously, so as to achieve a constant distance for all turns. The oblique course of the turns with respect to the cross-sectional plane can be taken into account accordingly in the subsequent relative orientation of the layers to the wires.

Furthermore, it proves to be particularly expedient if a non-rotationally symmetrical winding with a particularly polygonal cross-sectional shape is generated on the winding body. Each of these sections of the winding winding between the support points on the winding body forms the desired comb-like electrode, which would only have to be interconnected. The parallel orientation created by the winding process is determined only by the fixation of the wires in their respective end region before separating out the corresponding regions from the winding.

The method is not limited to a specific format electrodes to be produced. Rather, each turn can be separated several times according to the format to be produced, so that a universal use of the winding in a desired electrode format can be achieved.

Furthermore, it proves to be particularly practical if the windings are simultaneously mounted on a plurality of flat, releasably arranged on the winding body support frame. As a result, the prerequisites for economical production of piezoelectric actuator components are created by combining the required parallel conductors on the support frame into a structural unit and, in a largely automated subsequent method step, in each case being used for the layer construction with alternating layers of the active material.

For this purpose, each support frame preferably has opposing support frames, on which the parallel turns are fixed to a molding. The support frame are for example provided with a groove-shaped recess which is spanned by the turns and in which the wire by means of an adhesion or a Clamp connection is fixed. The joint is separated between the layers of active material following the attachment of the electrodes and the wire debris is released from the molding. By defining the turns on the formations of each support frame, the support frames can be separated by separating the turns and the support frames can then be inserted between two layers of the active material without losing the parallel orientation of the wires. The electrodes are thus available as an intermediate for an industrial production of actuators, which can be done independently of the production of the winding on the winding body. In another, also particularly promising embodiment of the invention, a layer of the active material is applied to the winding body in a first step, then applied a winding with several parallel turns on this layer of active material, which finally on the parallel, the electrode forming Windings another layer is applied, which fixes the turns, and the windings are separated accordingly, wherein on the outer layer, if necessary, alternately more windings and layers of the active material can be applied. In this case, therefore, the layer structure arises in a sequence of turns as electrodes and of the active material on the circumference of the wound body. Characterized in that at the same time a plurality of unsintered ceramic components are applied as layers of the active material on the peripheral surface of the winding body to collectively applied to this one made of a single wire winding, a further substantial cost optimization is achieved and the production at the same time significantly accelerated. After attaching the winding on the ceramic component, the further ceramic layer is preferably pressed onto the winding, so that the windings can be separated according to the circumference of the covering layer.

The wire tension is ensured by the tension created during winding on the winding drum. On the other hand, it is particularly promising if the wire is loaded with a predetermined, in particular constant prestressing. As a result, a constant tension over the entire circumference is achieved, which is not dependent on the angle of rotation, in particular even in the case of a polygonal cross-sectional shape. Thereby, a transient voltage fluctuation with the result of wireless can be avoided and the positioning accuracy when mounting the parallel windings can be improved.

The second-mentioned object of providing a device for carrying out the method is achieved according to the invention in that the device has a rotation axis about one axis has rotatably driven bobbin, on the peripheral side of a receptacle for a releasably fixable support frame and / or is provided for a layer of an active material, and is equipped with a coil for a wire. With the device according to the invention, the production of a layer structure for a piezoelectric actuator component by a winding method is made possible for the first time and in a surprisingly simple manner. In order to achieve a flat layer structure, the winding body has a polygonal cross-sectional shape. Each of the at least three planar peripheral sections optionally carries a support frame on which the winding is first fixed, so that after the separation of the support frame along its circumference an intermediate product for a further, in particular also automated production is available. Alternatively, the receptacle can also serve directly as the temporary support of a ceramic disk as a layer of the active material, so that the layer structure is formed in layers on the circumference of the winding body. For this purpose, a common winding is simultaneously applied to a plurality of circumferentially arranged ceramic discs. After pressing with a further ceramic disk such that the disks enclose the winding between them, the winding is separated on each side of the ceramic disks. Subsequently, the next winding can be applied to the ceramic disk.

In practice, it makes sense if the winding body is constructed so adjustable or modular that different support frame and / or a different number of support frame can be fixed to it. In a simple embodiment, the winding body is limited to a hub with holding flanges arranged thereon. On the other hand, an embodiment in which the winding body has a polygonal cross-sectional shape and is thus optimally suited for arranging the receptacle for a releasably fixable supporting frame or the ceramic plates in the respective planar peripheral sections is particularly advantageous. In this case, a point-symmetrical with respect to the axis of rotation cross-sectional shape during winding proves to be advantageous in order to reduce the occurring imbalances. Furthermore, it proves to be promising if the device has a clamping means for transmitting a bias voltage to the wire. By loading the wire with an adjustable biasing force, the parallelism of the turns can be maintained with reproducible accuracy. In particular, a force-controlled control takes place. Alternatively, a rotation angle-dependent control can be realized, in which the polygonal shape and the associated cyclical change of the diameter during a complete revolution is taken into account. In a simple clamping means this spring preload is provided. Furthermore, it proves to be particularly promising if the winding body in the direction of the axis of rotation spaced slot-shaped or groove-shaped recesses, by which the distance between adjacent turns is defined. These comb-like recesses take the wire, for example, a form-fitting manner and thus ensure an exact distance of adjacent turns. Of course, the recesses may also be arranged on a releasably and exchangeably connected with the winding body shaped body.

The invention allows for various embodiments. To further clarify its basic principle, one of them is shown in the drawing and will be described below. This shows in

1 shows a schematic representation of an apparatus according to the invention for producing a piezoelectric actuator component.

Fig. 2 is a schematic diagram of a coil and a clamping means of

Contraption;

Fig. 3 is a perspective view of the device;

4 shows a layer structure of the piezoelectric actuator component to be produced.

The method and the device 1 for producing a piezoelectric actuator component 2 are explained in more detail below with reference to FIGS. 1 to 4. The piezoactuator component 2 to be produced comprises a layer structure comprising a plurality of layers of an active material 3, in particular a piezoceramic, and in each case an electrode 4 arranged between two layers of the active material 3, comprising sections of a plurality of turns 5 of a single wire 6 spaced parallel to one another.

The manufacturing method is based on the surprising finding that a winding method allows an economical production of the planar layer structure. For this purpose, an existing from a metal frame support frame 7 is covered with a plurality of turns 5 of the wire 6, wherein the support frame 7 are locked to a bobbin 8, for example by magnets. The turns 5 are fixed to opposite frame parts of the support frame 7 at 9 formations by gluing, welding or soldering. The covered support frames 7 can be used for the production of piezo actuators in industrial le, in particular automated manufacturing processes are involved. For example, the covered support frame 7 can be manufactured separately as semi-finished products, so that in a later manufacturing process, the support frame 7 are pressed only with their biased wires in ceramic elements.

The winding body 8 of the device 1 is connected by means of an endless drive belt 10 with an electric drive 1 1. A wire guide 12 of the device 1 is arranged to be movable substantially parallel to a rotation axis 13 of the winding body 8 by means of a threaded spindle 14. According to the feed rate of the wire guide 12 in relation to the rotational speed of the bobbin 8 so the distance of the turns 5 is set. At the same time serve nutenformige recesses 15 in a shaped body 16, which limits the planar peripheral regions of the bobbin 8, the reliable positioning. At the peripheral areas dowel pins for exact positioning of the support frame 7 are provided.

The winding body 8 can in principle accommodate any number of support frame 7 on the outside so as to be able to produce a plurality of comb-like supporting frame 7 with a single winding. The wire guide 12 has a wire nozzle 17 with an inside high surface hardness, so as to reduce the friction between the wire 6 and the wire nozzle 17. In addition, this design ensures that the wire 6 does not get dirty. Preferably, a diamantene inside can be provided here. In order to ensure a parallel distortion of the windings 5, the wire 6 provided on a coil 18, which can have both a round and a rectangular cross-sectional shape, is biased within its elastic region with a biasing force F counter to the winding, which is achieved by the biasing unit 19 is guaranteed. This can be carried out in such a way that a winding with a constant winding force is ensured by deflection rollers 20 which are provided with a force-measuring sensor 21. In this case, the wire beginning as well as the wire end of the first or the last turn 5 is locked to the device 1.

Claims

PATE N TAN SP RU CHE

1. A method for producing a Piezoaktorenkomponente (2) having a layer structure of several layers of an active material (3), in particular a piezoceramic, and each between the layers of an active material (3) arranged conductive electrodes (4) consisting of a plurality of parallel conductors , characterized in that a plurality of particularly parallel, mutually spaced sections of a wire (6) as windings (5) on a winding body (8) are wound, which rotates about an axis of rotation (13), wherein the desired distance of the adjacent turns (5 ) and the windings (5) are subsequently interrupted, so that a plurality of parallel sections of the wire (6) of different windings (5) form the electrodes (4) associated with a layer.

2. The method according to claim 1, characterized in that a wire guide (12) for adjusting the distance of the adjacent turns (5) during the winding process, in particular parallel to the rotation axis (13) is moved.

3. Process according to claims 1 or 2, characterized in that on the

Winding body (8) is generated a non-rotationally symmetric winding with a particular polygonal cross-sectional shape.

4. The method according to at least one of the preceding claims, characterized in that each turn (5) is separated according to the format to be produced several times.

5. The method according to at least one of the preceding claims, characterized in that the turns (5) at the same time on a plurality of flat, on the winding body (8) releasably arranged support frame (7) are applied.

6. The method according to claim 5, characterized in that each support frame (7) has mutually opposite frame members on which the parallel turns (5) are fixed to a molding (9).

7. The method according to claim 5 or 6, characterized in that the support frame (7) separated by separation of the windings (5) and the support frame (7) are then introduced between two layers of the active material (3).

8. The method according to at least one of the preceding claims, characterized in that in a first step, a layer of the active material (3) applied to the winding body (8), then a winding with a plurality of parallel turns (5) on this layer of the active material (3) is applied to the parallel electrode-forming windings (5) another layer, which fixes the windings (5) applied, and finally the winding is separated accordingly.

9. The method according to at least one of the preceding claims, characterized in that the wire (6) with a predetermined, in particular constant bias voltage (F) is charged.

10. Piezoelectric actuator, produced by a method according to at least one of the preceding claims.

1 device (1) having a about a rotational axis (13) rotatably driven bobbin (8), on the peripheral side of a receptacle for a releasably fixable support frame (7) and / or for a layer of an active material (3) is provided and a coil (18) for a wire (6).

12. Device (1) according to claim 1 1, characterized in that the winding body (8) has a polygonal cross-sectional shape.

13. Device (1) according to claim 1 1 or 12, characterized in that the device (1) comprises a biasing unit (19) for transmitting a biasing force (F) to the wire (6).

14. Device (1) according to at least one of claims 1 1 to 13, characterized in that the winding body (8) in the direction of the axis of rotation (13) spaced slot or groove-shaped recesses (15).