JP2016081986A - Piezoelectric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric actuator capable of appropriately transmitting displacement of a piezoelectric element.SOLUTION: A piezoelectric actuator includes: a piezoelectric element 40, which includes a piezoelectric material 41 having first and second principal surfaces 41a and 41b opposing each other, a first external electrode 42 formed on the first principal surface 41a, and a second external electrode 43 formed on the second principal surface 41b; and a support member that supports the piezoelectric element 40. The piezoelectric element 40 is bound and supported by the support member in a state where a binding force acting on the piezoelectric material 41 from a first principal surface 41a side is larger than a binding force acting on the piezoelectric material 41 from a second principal surface 41b side. The first principal surface 41a is a polished surface and the first external electrode 42 is formed on the first principal surface 41a, which is the polished surface, along the first principal surface 41a, while the second principal surface 41b is a natural face and the second external electrode 43 is formed on the second principal surface 41b, which is the natural face, along the second principal surface 41b.SELECTED DRAWING: Figure 2

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 formed on the first main surface; and a second external electrode formed 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, when the piezoelectric element is reduced in size or thickness, 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 formed on the main surface 101a, and a main surface 101b. And an external electrode 104 formed on the substrate. 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 fixed to the support member 111 mainly by the resin 113 and the conductive resin 114 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 bent and 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.

  The present inventors conducted research on a piezoelectric actuator capable of appropriately transmitting the displacement of the piezoelectric element. As a result, the present inventors have found the following facts.

  The piezoelectric element expresses piezoelectric characteristics by polarizing each crystal grain of the piezoelectric ceramic constituting the piezoelectric body. Each crystal grain of the piezoelectric ceramic is polarized with a change in shape. An external electrode is disposed on the piezoelectric body. For this reason, a crystal grain located in the interface with the external electrode in the piezoelectric body and in the vicinity of the interface (hereinafter simply referred to as “crystal grain located in the vicinity of the interface”) is prevented from changing in shape by the external electrode. Therefore, there is a fear that the polarization is inhibited.

  When an electric field is applied to the piezoelectric body by a pair of external electrodes to drive the piezoelectric element, the piezoelectric body tends to displace, but the external electrode itself does not attempt to displace. For this reason, the external electrode acts to inhibit the displacement of the piezoelectric body, and the displacement amount of the piezoelectric element may be reduced. That is, if the inhibition of the displacement of the piezoelectric body due to the external electrode is reduced, the displacement amount of the piezoelectric element can be improved.

  And the present inventors conducted further research and research, found the following facts, and came to conceive the present invention.

  When the main surface of the piezoelectric body is a polished surface and the external electrode is formed on the polished surface along the polished surface, the external electrode has a shape having peaks and valleys along the polished surface. The external electrode formed on the polished surface is easy to tolerate deformation of the external electrode in a direction parallel to the main surface, and when the crystal grains are polarized, deformation of the shape of the crystal grains located near the interface Reduce inhibition. Thereby, when the piezoelectric element is driven, the external electrode reduces the inhibition of the displacement of the piezoelectric body.

  Therefore, a piezoelectric actuator according to the present invention is formed on a piezoelectric body having first and second main surfaces facing each other, a first external electrode formed on the first main surface, and a second main surface. A piezoelectric element including a second external electrode, and a support member that supports the piezoelectric element. The piezoelectric element has a restraining force that acts on the piezoelectric body from the first main surface side and is piezoelectric from the second main surface side. The first main surface is a polished surface, and the first external electrode is a first main surface along the first main surface that is a polished surface. The second main surface is a natural surface, and the second external electrode is formed on the second main surface along the natural second surface.

  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, the first main surface is a polished surface, and the first external electrode is formed on the first main surface along the first main surface which is a polished surface, so that the inhibition of displacement of the piezoelectric body is reduced. To do. On the other hand, since the second main surface is a natural surface and the second external electrode is formed on the second main surface along the second main surface, which is a natural surface, obstruction of displacement of the piezoelectric body is reduced. hard. Thus, the obstruction of the displacement of the piezoelectric body by the first external electrode is reduced on the first main surface side which is the polished surface, whereas the piezoelectric body by the second external electrode is reduced on the second main surface side which is the natural surface. Since the inhibition of displacement is difficult to be reduced, the piezoelectric element is prevented from being bent so that the second main surface side is on the curved outer side. As a result, the bending deformation of the piezoelectric element is suppressed, and the displacement of the piezoelectric element can be appropriately transmitted to the support member.

  The polished surface may be a satin-like surface formed by blasting. In this case, it is possible to easily realize a polished surface in which Yamaya is further emphasized.

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

It is a schematic plan view which shows the suspension which concerns on this embodiment. 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, this embodiment 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 thickness of the base plate 13 is, for example, about 200 μm. 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.

  The piezoelectric body 41 has a rectangular shape in plan view, and is a flat plate-shaped piezoelectric body. The piezoelectric body 41 has first and second main surfaces 41a and 41b facing each other. The first major surface 41a is a polished surface having a valley. In the present embodiment, the first main surface 41a is entirely a polished surface. In addition, the 1st main surface 41a should just be a grinding | polishing surface at least one part. On the other hand, the second main surface 41b is a natural surface. The piezoelectric body 41 has a pair of end faces 41c and 41d that face each other in the longitudinal direction. The external 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 is made of, for example, a piezoelectric ceramic material such as PZT.

  The first external electrode 42 is formed on the first main surface 41a. The first external electrode 42 is formed on the first main surface 41a along the first main surface 41a which is a polishing surface. The first external electrode 42 is formed so as to cover the entire first main surface 41a. The thickness of the first external electrode 42 is set to, for example, about 200 to 500 nm.

  The second external electrode 43 is formed on the second main surface 41b. The second external electrode 43 is formed on the second main surface 41b along the second main surface 41b which is a natural surface. The second external electrode 43 is formed so as to cover the entire second main surface 41b. The thickness of the second external electrode 43 is set to be the same as the thickness of the first external electrode 42. That is, the thickness of the second external electrode 43 is set to, for example, about 200 to 500 nm.

  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).

  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 is fixed to the intermediate portion 32 with a resin 50 so as to be supported by the intermediate portion 32 of the hinge member 14 on one end side in the longitudinal direction of the piezoelectric element 40. 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 fixed to the intermediate portion 32 via the resin 50. . The resin 50 is an insulating resin. In addition, a conductive resin 51 is formed on the second external electrode 43 on one end side in the longitudinal direction of the piezoelectric element 40. The second external electrode 43 is connected to an electrical wiring (not shown) by a conductive resin 51. The conductive resin 51 is a resin containing a conductive material (for example, metal particles).

  Each piezoelectric element 40 is fixed to the base 30 with a conductive resin 51 so as to be supported by the base 30 of the hinge member 14 on the other end side in the longitudinal direction of the piezoelectric element 40. 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 (first external electrode 42) are fixed to the base 30 via the conductive resin 51. ing. The first external electrode 42 is connected to an electrical wiring (not shown) by a conductive resin 51.

  As described above, the piezoelectric element 40 is restrained and supported by the intermediate portion 32 and the base portion 30 of the hinge member 14. The intermediate portion 32 and the base portion 30 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. And supported by the base 30). In the present embodiment, the suspension 10 includes a piezoelectric actuator including the piezoelectric element 40 and support members (the intermediate portion 32 and the base portion 30).

  Next, a method for manufacturing the piezoelectric element 40 described above will be described.

  First, a piezoelectric ceramic powder paste is obtained, and a green sheet having a predetermined thickness is prepared from the paste (sheet method). An electrode may be printed on the green sheet. Alternatively, green sheets may be stacked to form a laminate. Next, the green sheet or the laminated body is pressed in the laminating direction to obtain piezoelectric green. The press treatment is preferably performed at, for example, about 100 MPa. Subsequently, the obtained piezoelectric green is subjected to binder removal processing and then fired to obtain a piezoelectric substrate.

  Next, a polishing process is performed on one main surface of the piezoelectric substrate to form a polished surface. The polishing process is, for example, a blast process, a lapping process, and an etching process. The blasting process may be either a wet blasting process or a dry blasting process. The other main surface of the piezoelectric substrate is not subjected to polishing treatment and is left as a natural surface.

  Here, the natural surface is a surface constituted by the surface of crystal grains grown by firing, and exhibits a shape having gentle peaks and valleys due to the crystal grains. The polished surface formed by the blasting process has a shape in which natural peaks and valleys are emphasized. The polished surface formed by the lapping process and the etching process has such a shape that a natural peak portion is cut off, the peaks and valleys are smoothed, and a plurality of fine peaks and valleys are formed. For example, a polished surface formed by blasting is a textured surface rougher than a natural surface. The polished surface has a larger surface area than the natural surface.

  After the blast treatment, an electrode film is formed on each main surface of the piezoelectric substrate. Each electrode film is formed by a printing method, a sputtering method, a vapor deposition method, or the like. Through the above steps, a piezoelectric element substrate including a piezoelectric substrate and an electrode film is obtained. The piezoelectric substrate is in a state in which a plurality of piezoelectric bodies 41 in an individualized state are connected, and each electrode film is connected in a plurality of first and second electrode films 42, 43 in an individualized state. The piezoelectric element substrate is in a state where a plurality of piezoelectric elements 40 in a state of being separated are connected.

  Next, polarization processing is performed on the piezoelectric element substrate. In the polarization treatment, for example, a voltage with an electric field strength of 2 kV / mm is applied at a temperature of 100 ° C. for about 5 minutes. Subsequently, the piezoelectric element substrate after the polarization treatment is cut into a product shape. Thereby, the piezoelectric element 40 including the piezoelectric body 41 and the first and second external electrodes 42 and 43 that are separated into pieces is obtained.

  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.

  The first main surface 41a is a polished surface, and the first external electrode 42 is formed on the first main surface 41a along the first main surface 41a, which is a polished surface. Therefore, the displacement of the piezoelectric body 41 is inhibited. Reduce. On the other hand, the second main surface 41b is a natural surface, and the second external electrode 43 is formed on the second main surface 41b along the second main surface 41b which is a natural surface. It is difficult to reduce the inhibition of 41 displacement. As described above, on the first main surface 41a side which is the polished surface, the obstruction by the first external electrode 42 with respect to the displacement of the piezoelectric body 41 is reduced, whereas on the second main surface 41b side which is the natural surface, the piezoelectric body Inhibition by the second external electrode 43 with respect to the displacement of 41 is difficult to be reduced. 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 part 32 and the base part 30) are restrained and supported. Therefore, in a state where the piezoelectric element 40 is supported by being supported by the support members (the intermediate portion 32 and the base portion 30), the region on the first main surface 41 a side of the piezoelectric body 41 is the same as the second portion of the piezoelectric body 41. The displacement is more likely to be inhibited than in the region on the main surface 41b side. 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.

  When both the first and second main surfaces 41a and 41b are polished surfaces, the first and second external electrodes 42 and 43 both reduce the inhibition of displacement of the piezoelectric body 41. Therefore, it is difficult to suppress the second main surface 41b from being bent so that the second main surface 41b is on the curved outer side in a state in which a restraining force acts on the piezoelectric body 41 from the first main surface 41a side by the support member.

  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 transmitted to the support members (the intermediate portion 32 and the base portion 30). Can do.

  As described above, in the present embodiment, in the suspension 10, the piezoelectric element 40 is supported by the support members (the intermediate portion 32 and the base portion 30) provided on the first main surface 41a side. That is, since 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 piezoelectric element 40 is driven. Then, the piezoelectric element 40 tries to bend so that the second main surface 41b side is on the curved outer side. At this time, the first main surface 41a is a polishing surface, and the first external electrode 42 is formed on the first main surface 41a along the first main surface 41a that is the polishing surface. Reduce the inhibition of displacement. On the other hand, the second main surface 41b is a natural surface, and the second external electrode 43 is formed on the second main surface 41b along the second main surface 41b which is a natural surface. It is difficult to reduce the inhibition. As described above, on the first main surface 41a side which is the polished surface, the obstruction by the first external electrode 42 with respect to the displacement of the piezoelectric body 41 is reduced, whereas on the second main surface 41b side which is the natural surface, the piezoelectric body Since the inhibition by the second external electrode 43 with respect to the displacement of 41 is difficult to be reduced, the piezoelectric element 40 is prevented from being bent so that the second main surface 41b side is on the curved outer side. As a result, the bending deformation of the piezoelectric element 40 is suppressed, and the displacement of the piezoelectric element 40 can be appropriately transmitted to the support member (the intermediate portion 32 and the base portion 30).

  In the piezoelectric element 40, since the first main surface 41a of the piezoelectric body 41 is a polished surface and the second main surface 41b is a natural surface, the difference between the first and second main surfaces 41a and 41b is utilized using the difference in gloss. Discriminability can be improved. In the conventional piezoelectric element, it is necessary to provide, for example, an identification mark in order to identify the front and back. According to the piezoelectric element 40 of the present embodiment, such an identification mark can be omitted.

  When the piezoelectric element 40 is bent and deformed, the piezoelectric element 40 is easily peeled off from the support member (the intermediate portion 32 and the base portion 30). In this embodiment, since the bending deformation of the piezoelectric element 40 is suppressed, occurrence of such peeling can be suppressed. Further, in the piezoelectric element 40, the first main surface 41a of the piezoelectric body 41 is a polished surface, so that the adhesion between the first main surface 41a and the first external electrode 42 and the first external electrode 42 and the support member ( Adhesiveness with the intermediate portion 32 and the base portion 30) is high, and peeling between them is difficult to occur.

  The polishing surface of the first main surface 41a is a polishing surface formed by blasting. According to the blasting process, it is possible to easily realize a polished surface in which the peaks and valleys are further emphasized. Further, as a result of further emphasizing the peaks and valleys, inhibition of displacement of the piezoelectric body 41 by the first external electrode 42 on the first main surface 41a side is further reduced. Thereby, it is further suppressed that the piezoelectric element 40 bends so that the second main surface 41b side becomes the curved outer side. As a result of the bending deformation of the piezoelectric element 40 being further suppressed as described above, it becomes easy to appropriately transmit the displacement of the piezoelectric element 40 to the support member (the intermediate portion 32 and the base portion 30). Furthermore, since the peaks and valleys are further emphasized, the distinguishability of the first and second main surfaces 41a and 41b can be further enhanced.

  The piezoelectric element 40 may have a thickness of 0.2 mm or less, for example. As the thickness of the piezoelectric element 40 is reduced, the rigidity is reduced and the piezoelectric element 40 is easily bent. According to this embodiment, even when the thickness of the piezoelectric element 40 is 0.2 mm or less, the bending deformation of the piezoelectric element 40 can be suppressed.

  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.

  In addition to the first main surface 41 a being a polished surface, for example, the second external electrode 43 may be thicker than the first external electrode 42. In this case, the rigidity of the second external electrode 43 is higher than the rigidity of the first external electrode 42. Therefore, on the second main surface 41 b side, the inhibition by the second external electrode 43 with respect to the displacement of the piezoelectric body 41 becomes stronger. As a result, the bending deformation of the piezoelectric element 40 is more easily suppressed.

  The material of the second external electrode 43 may be a material harder than the material of the first external electrode 42. Also in this case, the rigidity of the second external electrode 43 is higher than the rigidity of the first external electrode 42. Therefore, on the second main surface 41 b side, the inhibition by the second external electrode 43 with respect to the displacement of the piezoelectric body 41 becomes stronger. As a result, the bending deformation of the piezoelectric element 40 is more easily suppressed.

  The second external electrode 43 may include a layer formed by a sputtering method, and the first external electrode 42 may not include a layer formed by a sputtering method. The sputtering method has high adhesion as compared with the baking method, the electrolytic plating method, the vapor deposition method, and the like. Therefore, the second external electrode 43 including the layer formed by the sputtering method has a greater restraining force acting on the piezoelectric body 41 than the first external electrode 42 not including the layer formed by the sputtering method. Therefore, on the second main surface 41 b side, the inhibition by the second external electrode 43 with respect to the displacement of the piezoelectric body 41 becomes stronger. As a result, the bending deformation of the piezoelectric element 40 is more easily suppressed.

  When the second external electrode 43 is thick as described above, when the second external electrode 43 is made of a hard material, and when the second external electrode 43 includes a layer formed by sputtering. In addition, the bending deformation of the piezoelectric element 40 can be suppressed, and as a result, the displacement amount of the piezoelectric element 40 can be improved. However, in these cases, bending deformation of the piezoelectric element 40 is suppressed by increasing the inhibition by the second external electrode 43 with respect to the displacement of the piezoelectric body 41 on the second main surface 41b side. For this reason, it is difficult to improve the displacement amount of the piezoelectric element 40. On the other hand, in the present embodiment, since the first main surface 41a is used as a polished surface and the inhibition of the displacement of the piezoelectric body 41 by the first external electrode 42 is reduced, the displacement amount of the piezoelectric element 40 can be improved more easily.

  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 41 c and 41 d of the piezoelectric body 41 and the outer surface of the piezoelectric element 40 on the first main surface 41 a side. However, the support structure to the support member is not limited to this. The piezoelectric element 40 is supported by being restrained by a 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. Just do it. Therefore, the piezoelectric element 40 is only required to be supported by at least the support member on the outer surface of the piezoelectric element 40 on the first main surface 41a side. In addition to this, the end surfaces 41c and 41d of the piezoelectric body 41 and the first surface of the piezoelectric element 40 are the same. The outer surface on the second main surface 41b side, and the end surface 41c and the end surface 41d are connected to each other and supported on one of the two side surfaces of the piezoelectric body 41 that connects the first main surface 41a and the second main surface 41b. It may be supported by the member.

  Although the intermediate portion 32 and the base portion 30 of the hinge member 14 function as support members, in addition to this, for example, the front end portion 22, the base portion 20, and the connecting portion 24 of the base plate 13 may function as support members.

  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 ... Microactuator part, 13 ... Base plate, 14 ... Hinge member, 25 ... Actuator base, 30 ... Base part, 32 ... Middle part, 40 ... Piezoelectric element, 41 ... Piezoelectric body, 41a ... 1st main surface, 41b ... 2nd main surface, 42 ... 1st external electrode, 43 ... 2nd external electrode.

Claims (2)

A piezoelectric body having first and second main surfaces facing each other, a first external electrode formed on the first main surface, and a second external electrode formed on the second main surface. A piezoelectric element;
A support member for supporting the piezoelectric element,
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 first main surface is a polishing surface, and the first external electrode is formed on the first main surface along the first main surface which is the polishing surface,
The second main surface is a natural surface, and the second external electrode is formed on the second main surface along the second main surface which is the natural surface.
Piezoelectric actuator. The polished surface is a satin-like surface formed by blasting,
The piezoelectric actuator according to claim 1.

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