JP2015216722A - Piezoelectric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric actuator capable of suitably transmitting displacement of a piezoelectric element.SOLUTION: The piezoelectric actuator includes: a piezoelectric substance 41 having a first principal surface 41a and a second principal surface 41b which are opposed to each other; a piezoelectric element 40 including a first external electrode 42 arranged on the first principal surface 41a and a second external electrode 43 arranged on the second principal surface 41b; and a support member for restricting and supporting the piezoelectric element 40. The piezoelectric element 40 is restricted and supported by the support member in a state where restriction force applied from the first principal surface 41a side to the piezoelectric substance 41 is larger than restriction force applied from the second principal surface 41b side to the piezoelectric substance 41. Restriction force applied from the second external electrode 43 to the piezoelectric substance 41 is larger than restriction force applied from the first external electrode 42 to the piezoelectric substance 41.

Description

  The present invention relates to a piezoelectric actuator.

  A piezoelectric element comprising: a piezoelectric body having first and second main surfaces facing each other; a first external electrode disposed on the first main surface; and a second external electrode disposed on the second main surface. A piezoelectric actuator including a piezoelectric element and a support member that supports the piezoelectric element is known (see, for example, Patent Document 1). In the piezoelectric actuator described in Patent Document 1, the actuator base of a suspension for a hard disk drive (HDD) corresponds to the support member, and the piezoelectric element transmits the displacement to the actuator base.

JP 2002-184140 A

  In recent years, electronic devices have been reduced in size or thickness. Accordingly, miniaturization or thinning is also required for piezoelectric elements mounted on electronic devices. However, in other words, when the piezoelectric element is downsized or thinned, the rigidity of the piezoelectric element (piezoelectric body) is lowered, and there is a possibility that the displacement of the piezoelectric element is not easily transmitted to the support member. .

  Hereinafter, the above-described problem that the displacement of the piezoelectric element is not easily transmitted to the support member will be described with reference to FIGS. 5 and 6.

  As shown in FIG. 5A, the piezoelectric element 100 includes a piezoelectric body 101 having a pair of opposed main surfaces 101a and 101b, an external electrode 103 disposed on the main surface 101a, and a main surface 101b. The external electrode 104 is provided. The thickness of the external electrode 103 is equal to the thickness of the external electrode 104. As shown in FIG. 5B, when the piezoelectric element 100 is driven by applying a predetermined electric field to the piezoelectric body 101 through the external electrodes 103 and 104, as shown in FIG. 5B, the pair of main surfaces 101a. , 101b extend in a direction D0 orthogonal to the facing direction.

  The piezoelectric element 100 is provided in the piezoelectric actuator 110 as shown in FIG. That is, the piezoelectric actuator 110 includes a piezoelectric element 100 and a support member 111 that supports the piezoelectric element 100. The piezoelectric element 100 is mainly fixed to the supporting member 111 with an adhesive 113 on the main surface 101b side. Specifically, the piezoelectric element 100 is supported by being restrained by the support member 111 in a state where the restraining force acting on the piezoelectric body 101 from the main surface 101b side is larger than the restraining force acting on the piezoelectric body 101 from the main surface 101a side. ing.

  When the piezoelectric element 100 is driven by applying the predetermined electric field to the piezoelectric body 101, the piezoelectric element 100 extends in the direction D0. At this time, if the rigidity of the piezoelectric element 100 (piezoelectric body 101) is lowered, as shown in FIG. 6B, the piezoelectric element 100 causes the displacement of the piezoelectric element 100 (piezoelectric body 101) to be a support member. The main surface 101a is bent so that the main surface 101a is on the curved outer side. That is, the piezoelectric element 100 (piezoelectric body 101) itself is deformed.

  Since the piezoelectric element 100 is supported and supported by the support member 111 in the above-described state, the piezoelectric element 100 bends so that the principal surface 101a side with a small restraining force is on the curved outer side. As described above, when the piezoelectric element 100 is deformed, the displacement of the piezoelectric element 100 is not easily transmitted to the support member 111. The rigidity of the piezoelectric element 100 decreases as the thickness of the piezoelectric body 101 decreases, and decreases as the width of the piezoelectric body 101 (length in the direction orthogonal to the direction D0) decreases.

  Accordingly, an object of the present invention is to provide a piezoelectric actuator that can appropriately transmit displacement of a piezoelectric element.

  A piezoelectric actuator according to the present invention includes a piezoelectric body having first and second main surfaces facing each other, a first external electrode disposed on the first main surface, and a second external electrode disposed on the second main surface. And a supporting member that restrains and supports the piezoelectric element, and the piezoelectric element has a restraining force that acts on the piezoelectric body from the first main surface side and the piezoelectric body from the second main surface side. The restraining force acting on the piezoelectric body from the second external electrode is made larger than the restraining force acting on the piezoelectric body from the second external electrode. ing.

  In the piezoelectric actuator according to the present invention, the piezoelectric element is restrained by the support member in a state where the restraining force acting on the piezoelectric body from the first principal surface side is larger than the restraining force acting on the piezoelectric body from the second principal surface side. Since it is supported, when the piezoelectric element is driven, the piezoelectric element tends to bend so that the second main surface side is outside the curve. At this time, since the restraining force that acts on the piezoelectric body from the second external electrode is made larger than the restraining force that acts on the piezoelectric body from the first external electrode, the piezoelectric element has a first main surface side that is curved outward. Therefore, the piezoelectric element is restrained from being bent so that the second main surface side is on the curved outer side. As a result, the deformation of the piezoelectric element is suppressed, and the displacement of the piezoelectric element can be appropriately transmitted to the support member.

  By setting the thickness of the second external electrode to be greater than the thickness of the first external electrode, the restraining force acting on the piezoelectric body from the second external electrode is greater than the restraining force acting on the piezoelectric body from the first external electrode. It may be enlarged. In addition, since the rigidity of the second external electrode is set to be higher than the rigidity of the first external electrode, the restraining force that acts on the piezoelectric body from the second external electrode is changed to the restraining force that acts on the piezoelectric body from the first external electrode. It may be made larger. In any case, it is possible to easily realize a configuration in which the restraining force acting on the piezoelectric body from the second external electrode can be made larger than the restraining force acting on the piezoelectric body from the first external electrode.

  ADVANTAGE OF THE INVENTION According to this invention, the piezoelectric actuator which can transmit the displacement of a piezoelectric element appropriately can be provided.

1 is a schematic plan view showing a suspension according to an embodiment of the present invention. It is a figure for demonstrating the cross-sectional structure along the II-II line shown by FIG. It is a figure for demonstrating operation | movement of the piezoelectric element which concerns on this embodiment. It is a figure for demonstrating operation | movement of the suspension which concerns on this embodiment. It is a figure for demonstrating operation | movement of the conventional piezoelectric element. It is a figure for demonstrating operation | movement of the conventional piezoelectric actuator.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  The configuration of the piezoelectric actuator according to this embodiment will be described with reference to FIGS. In this embodiment, the HDD suspension 10 includes a piezoelectric actuator. FIG. 1 is a schematic plan view showing a suspension according to the present embodiment. FIG. 2 is a view for explaining a cross-sectional configuration along the line II-II shown in FIG.

  The dual actuator type suspension 10 shown in FIG. 1 includes a load beam 11, a microactuator unit 12, a base plate 13, and a hinge member 14.

  The load beam 11 is made of a metal plate having a spring property. The thickness of the load beam 11 is, for example, about 100 μm. A flexure 15 is attached to the tip of the load beam 11. The flexure 15 is made of a thin metal spring that is thinner than the load beam 11. A slider 16 constituting a magnetic head is disposed at the front end of the flexure 15.

  A circular boss hole 21 is formed in the base portion 20 of the base plate 13. Between the base portion 20 and the front end portion 22 of the base plate 13, a pair of openings 23 having a size capable of accommodating a piezoelectric element 40 described later is formed. Between the pair of openings 23, a band-shaped connecting portion 24 extending in the front-rear direction of the base plate 13 (longitudinal direction of the suspension 10) is provided. The connecting portion 24 is configured to allow a predetermined range of bending in the width direction of the base plate 13 (direction intersecting the longitudinal direction of the suspension 10).

  The base 20 of the base plate 13 is fixed to the tip of an actuator arm that is driven by a voice coil motor (not shown). Thereby, the base plate 13 is pivotally driven by the voice coil motor. The base plate 13 is made of a metal plate such as stainless steel. The base plate 13 has a thickness of about 200 μm, for example. In the case of the present embodiment, the actuator base 25 is configured by the base plate 13 and the hinge member 14.

  The hinge member 14 includes a base portion 30, a bridge portion 31, an intermediate portion 32, a pair of hinge portions 33, and a distal end portion 34. The base 30 is overlapped and fixed on the base 20 of the base plate 13. The bridge portion 31 has a belt shape and is formed at a position corresponding to the connecting portion 24 of the base plate 13. The intermediate portion 32 is formed at a position corresponding to the front end portion 22 of the base plate 13. Each hinge part 33 has the flexibility which can be elastically deformed in a plate | board thickness direction. The distal end portion 34 is fixed to the load beam 11. The hinge member 14 is made of a metal plate having a spring property. The thickness of the hinge member 14 is, for example, about 50 μm.

  A pair of piezoelectric elements 40 is disposed in the microactuator unit 12. Each piezoelectric element 40 includes a piezoelectric body 41, a first external electrode 42, and a second external electrode 43 as shown in FIG. 2.

The piezoelectric body 41 has a rectangular shape in plan view, and is a flat plate-shaped piezoelectric body. The piezoelectric body 41 has a first main surface 41a and a second main surface 41b facing each other. The dimensions of the piezoelectric body 41 are, for example, a longitudinal length of 1.0 mm, a lateral length of 0.3 mm, and a thickness of 0.05 mm. The piezoelectric body 41 is made of a piezoelectric ceramic. Examples of the piezoelectric ceramic include PZT [Pb (Zr, Ti) O ₃ ], PT [PbTiO ₃ ], PLZT [(Pb, La) (Zr, Ti) O ₃ ], or barium titanate [BaTiO ₃ ]. It is done.

  The piezoelectric body 41 has a rectangular flat plate shape, and has a first main surface 41a and a second main surface 41b facing each other. The piezoelectric body 41 has a pair of end faces 41c and 41d that face each other in the longitudinal direction. The dimensions of the piezoelectric body 41 are, for example, a longitudinal length of 1.0 mm, a lateral length of 0.3 mm, and a thickness of 0.05 mm. The piezoelectric body 41 is made of, for example, a piezoelectric ceramic material such as PZT.

  The first external electrode 42 is disposed on the first main surface 41a. The first external electrode 42 is formed so as to cover the entire area of the first main surface 41a. The second external electrode 43 is disposed on the second main surface 41b. The second external electrode 43 is formed so as to cover the entire area of the second main surface 41b.

  In the present embodiment, the first and second external electrodes 42 and 43 have a Cr / Ni—Cu / Au laminated structure (a structure in which a Cr layer, a Ni—Cu alloy layer, and an Au layer are laminated in this order from the piezoelectric body 41 side). It is said that. That is, the first and second external electrodes 42 and 43 have the same laminated structure. The first and second external electrodes 42 and 43 are formed by a sputtering method. The first and second external electrodes 42 and 43 may be formed by a method other than the sputtering method (for example, a baking method, an electrolytic plating method, or a vapor deposition method). The first and second external electrodes 42 and 43 may be formed as a single metal layer (such as a Cr layer, a Ni—Cu alloy layer, an Au layer, or a Ni layer).

  The thickness of the second external electrode 43 is set to be thicker than the thickness of the first external electrode 42. The thickness of the first external electrode 42 is set to, for example, about 200 to 500 nm. The thickness of the second external electrode 43 is set to about 400 to 1500 nm, for example. By setting the thickness described above, the rigidity of the second external electrode 43 is higher than the rigidity of the first external electrode 42.

  Each piezoelectric element 40 is accommodated in a corresponding opening 23 such that the longitudinal direction of the piezoelectric element 40 is along the front-rear direction of the base plate 13 (the axial direction of the suspension 10). That is, each piezoelectric element 40 is disposed in the corresponding opening 23.

  Each piezoelectric element 40 has an adhesive 50 on the intermediate portion 32 and the front end portion 22 so as to be supported by the intermediate portion 32 of the hinge member 14 and the front end portion 22 of the base plate 13 on one end side in the longitudinal direction of the piezoelectric element 40. It is fixed through. More specifically, the end surface 41 c of the piezoelectric body 41 and a part on the first main surface 41 a side and one end side of the piezoelectric element 40 (first external electrode 42) are connected to the intermediate portion 32 and the front end portion 22 via the adhesive 50. It is fixed to. An adhesive 50 is also applied to a part of the piezoelectric element 40 (second external electrode 43) on the second main surface 41b side and one end side.

  Each piezoelectric element 40 is supported on the base 30 and the base 20 via an adhesive 50 so as to be supported by the base 30 of the hinge member 14 and the base 20 of the base plate 13 on the other end side in the longitudinal direction of the piezoelectric element 40. It is fixed. Specifically, the end surface 41 d of the piezoelectric body 41 and a part on the first main surface 41 a side and the other end side of the piezoelectric element 40 (second external electrode 43) are attached to the base 30 and the base 20 via the adhesive 50. It is fixed.

  As described above, the piezoelectric element 40 is restrained and supported by the intermediate portion 32, the front end portion 22, the base portion 30, and the base portion 20. The intermediate portion 32, the front end portion 22, the base portion 30, and the base portion 20 function as a support member that restrains and supports the piezoelectric element 40. In other words, the piezoelectric element 40 is configured so that the restraining force acting on the piezoelectric body 41 from the first main surface 41a side is larger than the restraining force acting on the piezoelectric body 41 from the second main surface 41b side. The front end portion 22, the base portion 30, and the base portion 20) are restrained and supported. In the present embodiment, the suspension 10 includes a piezoelectric actuator including the piezoelectric element 40 and a support member (intermediate portion 32, front end portion 22, base portion 30, and base portion 20).

  In order to apply a voltage to the first external electrode 42 and the second external electrode 43, electrical wirings (not shown) are connected to the first external electrode 42 and the second external electrode 43, respectively. A conductive adhesive may be used as the adhesive 50, and the adhesive 50 may be used as part of the electrical wiring.

  Next, the operation of the suspension 10 (piezoelectric actuator) will be described with reference to FIGS. FIG. 3 is a diagram for explaining the operation of the piezoelectric element according to the present embodiment. FIG. 4 is a view for explaining the operation of the suspension according to the present embodiment.

  In the piezoelectric element 40 shown in each of FIG. 3 and FIG. 4A, no voltage is applied to the first and second external electrodes 42 and 43, and the piezoelectric element 40 passes through the first and second external electrodes 42 and 43. An electric field is not applied to the body 41. When a voltage is applied to the first and second external electrodes 42, 43 and a predetermined electric field is applied to the piezoelectric body 41 through the first and second external electrodes 42, 43, the piezoelectric element 40 is driven. As shown in FIG. 3B, the element 40 extends in a direction D1 orthogonal to the direction in which the first main surface 41a and the second main surface 41b face each other.

  Since the thickness of the second external electrode 43 is greater than the thickness of the first external electrode 42, the binding force that acts on the piezoelectric body 41 from the second external electrode 43 is the binding force that acts on the piezoelectric body 41 from the first external electrode 42. Larger than. For this reason, the region of the piezoelectric body 41 on the second main surface 41b side is more likely to be inhibited from displacement than the region of the piezoelectric body 41 on the first main surface 41a side. Therefore, when the piezoelectric element 40 itself extends in the above-described direction D1, as shown in FIG. 3B, the piezoelectric element 40 bends so that the first main surface 41a side is on the curved outer side.

  As described above, the piezoelectric element 40 is in a state where the restraining force acting on the piezoelectric body 41 from the first main surface 41a side is larger than the restraining force acting on the piezoelectric body 41 from the second main surface 41b side. The intermediate portion 32, the front end portion 22, the base portion 30, and the base portion 20) are restrained and supported. Therefore, in a state where the piezoelectric element 40 is supported by being supported by the support member (the intermediate portion 32, the front end portion 22, the base portion 30, and the base portion 20), the region on the first main surface 41a side of the piezoelectric body 41 is Similarly, displacement is more likely to be inhibited than in the region on the second main surface 41b side of the piezoelectric body 41. Therefore, the piezoelectric element 40 tries to bend so that the second main surface 41b side is on the curved outer side. However, as described above, the piezoelectric element 40 itself tends to bend so that the first main surface 41a side is on the outside of the curve. Therefore, as shown in FIG. 4B, the second main surface 41b side is The bending which becomes a curve outer side will be suppressed.

  From the above, in this embodiment, the bending deformation of the piezoelectric element 40 is suppressed, and the displacement (displacement in the extension direction) of the piezoelectric element 40 is appropriately supported by the support member (intermediate portion 32, front end portion 22, base portion 30, And the base 20).

  In the present embodiment, by setting the thickness of the second external electrode 43 to be greater than the thickness of the first external electrode 42, the binding force that acts on the piezoelectric body 41 from the second external electrode 43 is applied to the first external electrode 42. Thus, the restraining force acting on the piezoelectric body 41 is made larger. Thereby, the structure which can make the restraining force which acts on the piezoelectric body 41 from the 2nd external electrode 43 larger than the restraining force which acts on the piezoelectric body 41 from the 1st external electrode 42 is easily realizable.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, It deform | transforms in the range which does not change the summary described in each claim, or applied to another thing. There may be.

  The rigidity of the second external electrode 43 may be made higher than the rigidity of the first external electrode 42 by making the configurations or materials of the first external electrode 42 and the second external electrode 43 different. For example, even if the thickness of the first external electrode 42 and the thickness of the second external electrode 43 are the same, the second external electrode 43 only needs to be harder than the first external electrode 42. As an example, a configuration in which the second external electrode 43 has a Cr / Ni—Cu / Au laminated structure and the first external electrode 42 has a Ni—Cu / Au laminated structure can be given. Cr is a relatively hard metal, and the second external electrode 43 is harder than the first external electrode 42 because the second external electrode 43 includes a Cr layer.

  Even when the second external electrode 43 is harder than the first external electrode 42, the rigidity of the second external electrode 43 is higher than the rigidity of the first external electrode 42. It tries to bend so that the 41a side becomes the curved outer side. That is, the restraining force acting on the piezoelectric body 41 from the second external electrode 43 is made larger than the restraining force acting on the piezoelectric body 41 from the first external electrode 42. Accordingly, similarly to the above-described embodiment, the bending deformation of the piezoelectric element 40 is suppressed, and the displacement (displacement in the extension direction) of the piezoelectric element 40 is appropriately supported by the support member (intermediate portion 32, front end portion 22, base portion 30, and To the base 20). Also in this case, it is possible to easily realize a configuration in which the restraining force acting on the piezoelectric body 41 from the second external electrode 43 can be made larger than the restraining force acting on the piezoelectric body 41 from the first external electrode 42.

  By differentiating the formation method of the first external electrode 42 and the formation method of the second external electrode 43, the restraining force acting on the piezoelectric body 41 between the second external electrode 43 and the first external electrode 42 may be different. Good. The sputtering method has higher adhesion than the baking method, the electrolytic plating method, and the vapor deposition method. Therefore, the external electrode including the layer formed by the sputtering method has a greater restraining force acting on the piezoelectric body 41 than the external electrode not including the layer formed by the sputtering method. For example, when the second external electrode 43 includes a layer formed by a sputtering method and the first external electrode 42 includes a layer formed by a method other than the sputtering method, The restraining force acting on 41 is greater than the restraining force acting on the piezoelectric body 41 from the first external electrode 42.

  The piezoelectric element 40 is supported by a supporting member on each of both end sides in the longitudinal direction of the piezoelectric element 40 on the two surfaces of the end surfaces 41c and 41d of the piezoelectric body 41 and the outer surface of the piezoelectric element 40 on the first main surface 41a side. However, the support structure to the support member is not limited to this. The piezoelectric element 40 may be supported by the support member at least on the outer surface of the piezoelectric element 40 on the first main surface 41a side on either side of the piezoelectric element 40 in the longitudinal direction. Thereby, the piezoelectric element 40 is restrained by the support member in a state where the restraining force acting on the piezoelectric body 41 from the first main surface 41a side is larger than the restraining force acting on the piezoelectric body 41 from the second main surface 41b side. Will be supported.

  The present invention can be used for piezoelectric actuators other than the microactuator portion 12 of the HDD suspension 10.

  DESCRIPTION OF SYMBOLS 10 ... Suspension, 11 ... Load beam, 12 ... Micro actuator part, 13 ... Base plate, 14 ... Hinge member, 40 ... Piezoelectric element, 41 ... Piezoelectric body, 41a ... First main surface, 41b ... Second main surface, 42 ... 1st external electrode, 43 ... 2nd external electrode.

Claims (3)

A piezoelectric element comprising: a piezoelectric body having first and second main surfaces facing each other; a first external electrode disposed on the first main surface; and a second external electrode disposed on the second main surface. When,
A support member that restrains and supports the piezoelectric element;
With
The piezoelectric element is supported by being restrained by the support member in a state where a restraining force acting on the piezoelectric body from the first principal surface side is larger than a restraining force acting on the piezoelectric body from the second principal surface side. And
The binding force that acts on the piezoelectric body from the second external electrode is greater than the binding force that acts on the piezoelectric body from the first external electrode.
Piezoelectric actuator. When the thickness of the second external electrode is set to be greater than the thickness of the first external electrode, a binding force acting on the piezoelectric body from the second external electrode is applied to the piezoelectric body from the first external electrode. It is larger than the binding force that acts,
The piezoelectric actuator according to claim 1. By setting the rigidity of the second external electrode to be higher than the rigidity of the first external electrode, a binding force acting on the piezoelectric body from the second external electrode is applied to the piezoelectric body from the first external electrode. It is larger than the binding force that acts,
The piezoelectric actuator according to claim 1 or 2.

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