JP2018181935A - Piezoelectric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric actuator which is small-sized but capable of preventing a piezoelectric element part from being damaged or broken and improves durability.SOLUTION: A piezoelectric actuator 10 comprises: a shaft 12 which is a movable part; a substantially rectangular parallelepiped piezoelectric element part 20 including a first end face 20a to which the shaft is connected, and four side faces including mutually opposed two external electrode formation faces and mutually opposed two external electrode non-formation faces connecting the two external electrode formation faces, and connecting the first end face with a second end face 20b; an adhesive resin part 50 coupling the shaft with the piezoelectric element part; a coupling part 56 coupling a weight 40 with the piezoelectric element part; a first element protective layer 61 which is provided so as to be held between a first boundary part 51 in the adhesive resin part and external electrode formation faces 20c; and a second element protective layer which is provided so as to be held between a second boundary part in the adhesive resin part and the external electrode non-formation faces. An area of the first element protective layer is narrower than an area of the second element protective layer.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a piezoelectric actuator that drives a target member.

  Piezoelectric actuators are actuators that mutually convert mechanical displacement and electrical displacement using the piezoelectric effect and inverse piezoelectric effect of a piezoelectric element, and various types of linear actuators etc. that give linear displacement to an object Are used in various fields.

  Since the mechanical displacement obtained by the piezoelectric actuator is relatively minute, the actuator is suitably used for applications requiring precise and accurate control, for example, for driving a lens such as a camera. For example, as such a piezoelectric actuator, one in which a shaft which is a movable portion is connected to one end surface of a piezoelectric element portion and a weight which is an inertia portion is connected to the other end surface is proposed (see Patent Document 1) .

JP 2007-274777

  However, in recent years, with the miniaturization of the actuator, the shaft is relatively elongated relative to the piezoelectric element portion, and the cross-sectional area of the piezoelectric element portion also tends to be reduced. As a result, a situation occurs in which a larger stress is applied to the piezoelectric element portion of the actuator than in the prior art, and measures for preventing damage and breakage of the piezoelectric element portion are required.

  The present invention has been made in view of such an actual situation, and it is an object of the present invention to provide a piezoelectric actuator excellent in durability which can prevent damage and breakage of a piezoelectric element portion while being compact.

In order to achieve the above object, a piezoelectric actuator according to the present invention is
A shaft which is a movable part,
A weight which is an inertia part,
A first end face to which the shaft is connected, a second end face opposite to the first end face to which the weight is connected, and two external electrode forming surfaces facing each other are connected to two external electrode forming surfaces A substantially rectangular parallelepiped piezoelectric element portion having two external electrode non-formed surfaces facing each other and four side surfaces connecting the first end surface and the second end surface;
An adhesive resin portion connecting the shaft and the piezoelectric element portion;
A connecting portion connecting the weight and the piezoelectric element portion;
In a cross section perpendicular to the external electrode forming surface, the external electrode forming surface is sandwiched between a first boundary portion which is an end portion on the side close to the weight in the adhesive resin portion and the external electrode forming surface A first element protection layer provided on the
In a cross section perpendicular to the external electrode non-formed surface, the external electrode is sandwiched between a second boundary portion which is an end portion on the side close to the weight in the adhesive resin portion and the external electrode non-formed surface. And a second element protection layer provided on the non-formation surface,
The area of the first element protection layer may be smaller than the area of the second element protection layer.

  In the piezoelectric actuator according to the present invention, the first element protection layer is provided between the first boundary portion of the adhesive resin portion connecting the shaft and the piezoelectric element portion and the external electrode forming surface, and A second element protective layer is provided between the second boundary portion and the external electrode non-formed surface. Although there is a problem that damage such as a crack is likely to occur in the piezoelectric element part around the first boundary part and the second boundary part of the adhesive resin part after passing through cooling and thermal cycles etc. Since the first element protective layer and the second protective layer are provided, it is possible to prevent a problem such as occurrence of damage such as a crack in the piezoelectric element portion. In such a piezoelectric actuator, since the first and second boundary portions are connected to the external electrode formation surface and the external electrode non-formation surface through the first and second protective layers, the adhesive resin portion and the piezoelectric element portion It is thought that the stress which arises in a piezoelectric element part can be relieved from the difference in a linear expansion coefficient with the above. Further, since the area of the first element protective layer is smaller than the area of the second element protective layer, a wiring portion for applying a voltage to the piezoelectric element portion with respect to the external electrode formation surface exposed from the first element protective layer Etc. can be easily connected.

Also, for example, even if the adhesive resin portion has a first thickness change portion in which the thickness gradually increases from the first boundary portion toward the shaft in the cross section perpendicular to the external electrode formation surface. Often,
The first element protection layer may be provided so as to be sandwiched between the first thickness change portion and the external electrode formation surface.
The adhesive resin portion may have a second thickness change portion which gradually increases in thickness from the second boundary portion toward the shaft in a cross section perpendicular to the outer electrode non-formed surface.
The second element protective layer may be provided so as to be sandwiched between the second thickness-changed portion and the external electrode non-formed surface.

  In the adhesive resin portion having the first and second thickness change portions, stress tends to be concentrated in the vicinity of the first and second boundaries and the piezoelectric element portion facing the first and second thickness change portions. However, by arranging the first and second element protective layers between the first and second thickness change portions and the external electrode formation surface and the external electrode non-formation surface, the first and second thicknesses in the piezoelectric element portion can be obtained. It is possible to prevent the problem of concentration of stress on the part facing the change part.

  Also, for example, the elastic modulus of the first element protective layer and the second element protective layer may be lower than the elastic modulus of the adhesive resin portion.

  Since the first and second element protective layers can be easily deformed in the first and second element protective layers having a low elastic modulus, when the adhesive resin portion expands or contracts due to a temperature change, the first and second element protective layers It is possible to prevent the force associated with the deformation from being transmitted to the piezoelectric element portion, and to prevent the problem of the generation of stress in the piezoelectric element portion.

  Also, for example, the thickness of the first element protection layer in a cross section perpendicular to the external electrode formation surface may be thinner than the thickness of the second element protection layer in a cross section perpendicular to the external electrode non-formation surface.

  The external electrode formed on the external electrode formation surface is disposed between the element body of the piezoelectric element portion and the adhesive resin portion, so that the force accompanying the deformation of the adhesive resin portion is the same as the first element protective layer. The effect of preventing transmission to the piezoelectric element portion is achieved. Therefore, by thinning the first element protective layer and thickening the second element protective layer, the external electrode forming surface side of the piezoelectric element portion and the external electrode non-forming surface side can be similarly protected.

FIG. 1 is a schematic perspective view showing a piezoelectric actuator according to a first embodiment of the present invention. FIG. 2 is a perspective view showing a piezoelectric element portion, a first element protection layer, and a second element protection layer included in the piezoelectric actuator shown in FIG. FIG. 3 is a partial cross-sectional view perpendicular to the external electrode formation surface of the piezoelectric actuator shown in FIG. FIG. 4 is a partial cross-sectional view perpendicular to the external electrode non-forming surface of the piezoelectric actuator shown in FIG. FIG. 5 is a schematic perspective view showing a piezoelectric actuator according to a second embodiment of the present invention. FIG. 6 is a partial cross-sectional view perpendicular to the external electrode formation surface of the piezoelectric actuator shown in FIG. FIG. 7 is a partial cross-sectional view perpendicular to the external electrode non-forming surface of the piezoelectric actuator shown in FIG. FIG. 8 is a schematic perspective view showing a piezoelectric actuator according to a third embodiment of the present invention. FIG. 9 is a schematic perspective view showing a piezoelectric actuator according to a fourth embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described based on the drawings.

First Embodiment FIG. 1 is a schematic perspective view showing a piezoelectric actuator 10 according to a first embodiment of the present invention. As shown in FIG. 1, the piezoelectric actuator 10 includes a shaft 12, a piezoelectric element portion 20, a wiring portion 30, a weight 40, an adhesive resin portion 50, a connecting portion 56, a first element protection layer 61, a second element protection layer 62, etc. Have.

  The shaft 12 of the piezoelectric actuator 10 is connected to a first end surface 20 a which is an end surface of the piezoelectric element unit 20 in the positive Z-axis direction. The shaft 12 is a movable portion that is displaced with the deformation of the piezoelectric element portion 20. For example, when the piezoelectric actuator 10 is used as a lens drive module, a moving member (not shown) is movably engaged with the shaft 12. The moving member holds an optical system or the like, and the moving member and the optical system held thereby can be displaced in the Z-axis direction along the shaft 12 by the driving force of the piezoelectric actuator 10.

  The shaft 12 of the piezoelectric actuator 10 is cylindrical, and the area of the shaft facing surface 12 a facing the first end surface 20 a of the piezoelectric element portion 20 in the shaft 12 is larger than the area of the first end surface 20 a. Further, the length of the shaft 12 in the Z-axis direction is longer than the length of the piezoelectric element portion 20 in the Z-axis direction, whereby the moving distance of the moving member can be increased. However, the shape and size of the shaft 12 are not particularly limited, and the shaft 12 may have a columnar or rod shape other than a cylindrical shape, and the area of the shaft opposing surface 12a may be smaller than the area of the first end face 20a.

  Although the material of the shaft 12 is not particularly limited, for example, metal, carbon, resin or the like can be adopted.

  As shown in FIG. 1, the adhesive resin unit 50 connects the shaft 12 and the piezoelectric element unit 20. The adhesive resin portion 50 is made of a resin such as an epoxy resin or an acrylic resin. For example, the adhesive resin portion 50 is formed of an adhesive curing portion in which an epoxy resin adhesive or the like for fixing the shaft 12 and the piezoelectric element portion 20 is cured. . The adhesive resin portion 50 is formed to surround the outer periphery of the first end face 20 a of the piezoelectric element portion 20.

  In the description of the piezoelectric actuator 10 shown in FIG. 1 etc., the normal direction of the first and second end faces 20a and 20b (see FIG. 2) of the piezoelectric element portion 20 is the Z axis direction, and the external electrodes of the piezoelectric element portion 20 are formed. The normal direction of the surface 20c will be described as the Y-axis direction, and the normal direction of the external electrode non-forming surface 20e of the piezoelectric element unit 20 as the X-axis direction.

  As shown in FIG. 1, a weight 40 is connected to a second end face 20 b which is an end face in the Z-axis negative direction of the piezoelectric element portion 50. In the piezoelectric element portion 20, the second end face 20b faces the first end face 20a to which the shaft 12 is connected.

  The weight 40 is an inertia part and functions as an inertia body for displacing the shaft 12 connected to the first end face 20a. The weight 40 is made of, for example, a material having a specific gravity larger than that of the piezoelectric element portion 20 and the shaft 12. Although the material of the weight 40 is not particularly limited, for example, a metal having a large specific gravity such as tungsten or an alloy containing such a metal can be adopted.

  The weight 40 has a rectangular parallelepiped outer shape, and in the weight 40, the area of the opposing surface facing the second end surface 20b of the piezoelectric element portion 20 is larger than the area of the second end surface 20b. However, the shape of the weight 40 is not limited to a rectangular parallelepiped, and may be another shape such as a flat plate shape or a cylindrical shape.

  As shown in FIG. 1, the connecting portion 56 connects the weight 40 and the piezoelectric element portion 20. The connection portion 56 is made of resin or the like, and, for example, is formed of an adhesive-cured portion in the same manner as the adhesive resin portion. The connecting portion 56 is formed so as to surround the outer periphery of the second end face 20 b of the piezoelectric element portion 20.

  The connection portion 56 covers the connection portion between the external electrode 24 and the wiring portion 30 and prevents the problem that the electrical connection between the wiring portion 30 and the external electrode 24 is released due to an external force or the like. As shown in FIG. 1, wiring portions 30 are connected to the two external electrodes 24 of the piezoelectric element portion 20, respectively. A voltage can be applied to the piezoelectric element unit 20 through the wiring unit 30, and the piezoelectric element unit 20 deforms in accordance with the applied voltage. The wiring portion 30 is formed of, for example, a covered wire, a lead frame or the like, but may be anything as long as a voltage can be applied to the piezoelectric element portion 20.

  FIG. 2 is a perspective view showing the piezoelectric element unit 20 and a first element protection layer 61 and a second element protection layer 62 provided on the surface of the piezoelectric element unit 20. FIG. As shown in FIG. 2, the piezoelectric element portion 20 has a substantially rectangular outer shape, and has two end surfaces and four side surfaces. The shaft 12 shown in FIG. 1 is connected to a first end face 20 a facing the Z-axis positive direction among the two end faces of the piezoelectric element unit 20. As shown in FIG. 1, the shaft 12 and the piezoelectric element portion 20 are connected by an adhesive resin portion 50.

  The weight 40 is connected to the 2nd end surface 20b which faces the Z-axis negative direction side among two end surfaces which the piezoelectric element part 20 has. The first end face 20 a and the second end face 20 b face each other, and the piezoelectric element portion 20 is sandwiched by the shaft 12 and the weight 40 on both sides in the Z direction.

  The four side surfaces of the piezoelectric element portion 20 all connect the first end surface 20a and the second end surface 20b. The four side surfaces of the piezoelectric element portion 20 are composed of two external electrode forming surfaces 20c facing each other and two external electrode non-forming surfaces 20e facing each other. While the external electrodes 24 electrically connected to the wiring portion 30 are formed in layers on the external electrode forming surface 20c, the external electrodes 24 are not formed on the external electrode non-forming surface 20e. . Further, the external electrode forming surface 20c connects two external electrode non-forming surfaces 20e, and the external electrode non-forming surface 20e connects two external electrode forming surfaces 20c.

  FIG. 3 is a partial cross-sectional view perpendicular to the external electrode forming surface 20c of the piezoelectric actuator 10 shown in FIG. The piezoelectric element portion 20 has an element main body 21 which is a laminated body in which internal electrode layers 22 and piezoelectric layers 23 are alternately stacked in the Z-axis direction, and an external electrode 24 formed on the surface of the element main body 21. . The element body 21 has a rectangular parallelepiped shape slightly smaller than the entire piezoelectric element portion 20. The thickness of the external electrode 24 is not particularly limited, but is about 0.1 to 20 m.

  As shown in FIG. 3, the external electrode forming surface 20 c of the piezoelectric element unit 20 is configured of an external electrode 24. The external electrode 24 is formed to cover the side surface of the element main body 21 facing the Y-axis positive direction side. Half of the internal electrode layers 22 included in the element main body 21 is connected to the external electrode 24 formed on the side surface of the element main body 21 facing the Y-axis positive direction side. Although not shown in FIG. 3, the external electrodes 24 forming the external electrode forming surface 20 c are formed on the side surface of the element main body 21 facing the negative Y-axis direction, as in the positive Y-axis direction. The other half of the internal electrode layer 22 included in the element main body 21 is connected to the external electrode 24 facing the Y-axis negative direction side.

The thickness of the piezoelectric layer 23 in the piezoelectric element portion 20 is not particularly limited, but is preferably about 5 to 50 μm. The material of the piezoelectric layer 23 is not particularly limited as long as it exhibits a piezoelectric effect or an inverse piezoelectric effect, and examples thereof include PbZr _x Ti _1-x O ₃ and BaTiO ₃ . Moreover, the component for the characteristic improvement etc. may be contained, and the content may be suitably determined according to the desired characteristic.

  Examples of the conductive material constituting the internal electrode layer 22 include noble metals such as Ag, Pd, Au, and Pt, and alloys thereof (such as Ag-Pd), or base metals such as Cu, Ni, and alloys thereof. There is no particular limitation. The conductive material which comprises the external electrode 24 is not specifically limited, either, The material similar to the conductive material which comprises an internal electrode can be used. Furthermore, plated layers or sputtered layers of the above-described various metals may be formed on the outer side of the external electrode 24.

  As shown in FIGS. 2 and 3, a first element protection layer 61 is provided on the external electrode forming surface 20 c of the piezoelectric element unit 20. The first element protection layer 61 is sandwiched between the first boundary portion 51 of the adhesive resin portion 50 and the external electrode forming surface 20 c in a cross section (cross section shown in FIG. 3) perpendicular to the external electrode forming surface 20 c. It is arranged. As shown in FIG. 1, the first boundary 51 is perpendicular to the external electrode forming surface 20 c at the end closer to the weight 40 in the adhesive resin portion 50 connecting the shaft 12 and the piezoelectric element portion 20. Part that appears on the

  As shown in FIGS. 2 and 3, the first element protection layer 61 is provided on the external electrode 24 formed on the external electrode formation surface 20 c so as to overlap a part of the external electrode 24. However, the area of the first element protection layer 61 is smaller than that of the second element protection layer 62 provided on the external electrode non-formation surface 20 e and the external electrode 24 formed under the first element protection layer 61. A portion of the portion 24, in particular, a portion close to the weight 40 is not covered with the first element protection layer 61, and the wiring portion 30 shown in FIG. 1 covers the first element protection layer 61 of the external electrode 24. It is connected to the part not covered.

  As shown in FIGS. 2 and 3, the first element protection layer 61 is provided on the outer electrode forming surface 20 c on the side closer to the shaft 12 in the Z-axis direction. As shown in FIG. 3, the portion on the side closer to the shaft 12 in the external electrode forming surface 20c is covered with the adhesive resin portion 50 connected to the shaft 12, and the adhesive resin portion 50 of this portion is shown in FIG. In such a cross section perpendicular to the external electrode forming surface 20 c, the first thickness change portion 50 a has a thickness gradually increasing from the first boundary portion 51 toward the shaft 12.

  As shown in FIG. 3, the first element protection layer 61 is provided so as to be sandwiched between the first thickness change portion 50 a and the external electrode formation surface 20 c, and the first thickness change portion 50 a and the first boundary The portion 51 does not directly face the external electrode forming surface 20 c and is not directly connected. The adhesive resin portion 50 is not directly opposed to the external electrode forming surface 20 c due to the first element protective layer 61 being disposed, but the adhesive resin portion 50 is not provided to the first end face 20 a of the piezoelectric element portion 20. Directly facing and connecting. Although not shown in FIGS. 2 and 3, the first element protection is also applied to the external electrode forming surface 20c facing the Y-axis negative direction side, similarly to the external electrode forming surface 20c facing the Y-axis positive direction side. Layer 61 is provided.

  FIG. 4 is a partial cross-sectional view perpendicular to the external electrode non-forming surface 20 e of the piezoelectric actuator 10 shown in FIG. As shown in FIG. 4, the external electrode 24 is not formed on the external electrode non-forming surface 20 e of the piezoelectric element unit 20. That is, the external electrode non-forming surface 20 e facing the negative direction of the X-axis is configured by the internal electrode layer 22 and the piezoelectric layer 23 in the element main body 21. In the internal electrode layer 22 constituting the external electrode non-formed surface 20 e shown in FIG. 4, the internal electrode layer 22 connected to one external electrode 24 (Y-axis positive direction side) and the other external electrode 24 (Y-axis negative) Both of the internal electrode layers 22 connected to the direction side) are included. Although not shown in FIG. 4, the external electrode non-formed surface 20 e facing in the positive direction of the X-axis is also composed of the internal electrode layer 22 and the piezoelectric layer 23.

  As shown in FIGS. 2 and 4, a second element protection layer 62 is provided on the external electrode non-formed surface 20 e of the piezoelectric element unit 20. The second element protection layer 62 is sandwiched between the second boundary portion 52 of the adhesive resin portion 50 and the external electrode non-formation surface 20 e in a cross section (cross section shown in FIG. 4) perpendicular to the external electrode non-formation surface 20 e. It is arranged as. The second boundary 52 is, as shown in FIG. 1, at the outer electrode non-formed surface 20 e of the end close to the weight 40 in the adhesive resin 50 connecting the shaft 12 and the piezoelectric element 20. It is a part that appears in the vertical cross section.

  As shown in FIGS. 2 and 4, the second element protection layer 62 is provided to cover the external electrode non-formation surface 20e, and covers the entire external electrode non-formation surface 20e. However, the second element protective layer 62 may cover a part of the external electrode non-formed surface 20 e.

  As shown in FIGS. 2 and 4, the second element protection layer 62 is provided so as to be continuous in the Z-axis direction on the external electrode non-formed surface 20 e. As shown in FIG. 4, the portion on the side closer to the shaft 12 in the external electrode non-forming surface 20e is covered with the adhesive resin portion 50 connected to the shaft 12 as in the electrode forming surface 20c shown in FIG. The adhesive resin portion 50 of this portion has a second thickness gradually increasing from the second boundary portion 52 toward the shaft 12 in a cross section perpendicular to the external electrode forming surface 20c as shown in FIG. It is a change part.

  As shown in FIG. 4, the portion on the side closer to the shaft 12 in the second element protective layer 62 is provided so as to be sandwiched between the second thickness change portion 50 b and the external electrode non-formed surface 20 e. Therefore, the second thickness change portion 50b and the second boundary portion 52 of the adhesive resin portion 50 do not directly face the external electrode non-formed surface 20e and are not directly connected. Although not shown in FIGS. 2 and 4, the second external electrode non-forming surface 20 e facing the X-axis positive direction side is the same as the second external electrode non-forming surface 20 e facing the X-axis negative direction. An element protective layer 62 is provided.

  The first element protective layer 61 and the second element protective layer 62 can be made of a resin such as urethane resin, vinyl chloride resin, acrylic resin, epoxy resin, etc., but the first element protective layer 61 and the second element protective layer The constituent material is not particularly limited as long as 62 can relieve the stress generated in the piezoelectric element portion 20. Here, the elastic modulus of the first element protective layer 61 and the second element protective layer 62 is preferably lower than the elastic modulus of the adhesive resin portion 50. The first and second element protection layers 61 and 62 having a low elastic modulus can be easily deformed by external force and stress, so that when the adhesive resin portion 50 expands or contracts due to a temperature change, It is possible to prevent the force associated with the deformation from being transmitted to the piezoelectric element unit 20, and to prevent the problem of the generation of stress in the piezoelectric element unit 20.

  For example, the elastic modulus of the first element protective layer 61 and the second element protective layer 62 can be approximately 2.0 to 5.0 GPa, and the elastic modulus of the adhesive resin portion 50 is 4.0 to 7.0 GPa. The degree can be. Thereby, while the piezoelectric element portion 20 and the shaft 12 are reliably connected by the adhesive resin portion 50, it is possible to preferably prevent the concentration of stress in the piezoelectric element portion 20 and the occurrence of a crack and the like.

  The thickness of the first element protective layer 61 can be, for example, 5 to 20 μm, and the thickness of the second element protective layer 62 can be, for example, 10 to 30 μm. Here, the thickness of the first element protection layer 61 shown in FIG. 3 is preferably thinner than the thickness of the second element protection layer 62 shown in FIG. 4. The external electrode 24 is disposed between the element body 21 of the piezoelectric element portion 20 and the adhesive resin portion 50, so that the force associated with the deformation of the adhesive resin portion 50 is a piezoelectric element, as in the first element protection layer 61. The effect of preventing transmission to the unit 20 is achieved. Therefore, by thickening the second element protection layer 62 provided on the external electrode non-formation surface 20e, the external electrode non-formation surface 20e side of the piezoelectric element portion 20 and the external electrode non-formation surface 20e side are similarly protected. be able to.

  The piezoelectric actuator 10 shown in FIG. 1 is manufactured, for example, by the following process. First, the piezoelectric element portion 20 shown in FIG. 2 is manufactured, and then, the first element protection layer 61 is formed on the external electrode formation surface 20c of the piezoelectric element portion 20, and the second element protection layer 62 is formed on the external electrode non-formation surface 20d. Form The piezoelectric element portion 20 is manufactured by laminating green sheets composed of the raw materials of the internal electrode layer 22 and the piezoelectric layer 23 to produce a green sheet laminate, and firing the green sheet laminate to form the element body 21. This is performed by forming an external electrode 24 on a pair of opposing side surfaces of the element body 21. The formation of the external electrode 24 can be performed by plating or the like.

  In the process of forming the first element protection layer 61 on the external electrode formation surface 20c and forming the second element protection layer 62 on the external electrode non-formation surface 20e, the first element protection layer 61 and the second element protection layer 62 are formed. The resin paste, which is a raw material of the above, is applied to the external electrode forming surface 20c and the external electrode non-forming surface 20e, and dried or the like. Either of the first element protective layer 61 and the second element protective layer 62 may be formed first, and the material of the first element protective layer 61 and the material of the second element protective layer 62 are: It may be the same or different. In the embodiment shown in FIGS. 3 and 4, the first end face 20a and the second end face 20b of the piezoelectric element portion 20 are provided with a resin layer such as the first element protection layer 61 or the second element protection layer 62. Although not shown, the materials of the first element protective layer 61 and the second element protective layer 62 may extend to the first end face 20a and the second end face 20b.

  Furthermore, for the piezoelectric element portion 20 provided with the first element protection layer 61 and the second element protection layer 62 on the side surface as shown in FIG. The piezoelectric actuator 10 as shown in FIG. 1 is obtained by joining the weight 40 to the first end face 20a and the second end face 20b. Bonding of the shaft 12 and the piezoelectric element portion 20 and bonding of the weight 40 and the piezoelectric element portion 20 are performed, for example, by applying an adhesive to the bonding surface, bonding the respective members, and curing the applied adhesive. Can. In this case, the adhesive resin 50 is formed by curing the adhesive for bonding the shaft 12 and the piezoelectric element unit 20, and the connector 56 is formed when the adhesive for bonding the weight 40 and the piezoelectric element unit 20 is cured. .

  As described above, in the piezoelectric actuator 10 shown in FIGS. 1 to 4, the first boundary portion 51 and the second boundary portion 52 of the adhesive resin portion 50 connecting the shaft 12 and the piezoelectric element portion 20 directly form the piezoelectric element portion 20 is not connected to the surface of the element main body 21 or the surface of the external electrode 24, and is connected via the first element protection layer 61 and the second element protection layer 62. The first element protection layer 61 and the second element protection layer 62 change the temperature environment by relieving stress generated in the piezoelectric element portion 20 due to the difference in linear expansion coefficient between the adhesive resin portion 50 and the piezoelectric element portion 20, etc. It is possible to prevent the problem that a crack occurs in the piezoelectric element unit 20 or the piezoelectric element unit 20 is damaged due to, for example.

  Further, in the piezoelectric actuator 10, since the adhesive resin portion 50 has the first thickness changing portion 50a and the second thickness changing portion 50b, it is possible to firmly bond the piezoelectric element portion 20 and the shaft 12. Moreover, in the structure having the first thickness change portion 50a and the second thickness change portion 50b, the stress is concentrated on the piezoelectric element portion 20 around the first boundary portion 51 and the second boundary portion 52 after passing through the cooling and heating cycle and the like. In the piezoelectric actuator 10 according to this embodiment, the first and second element protection layers 61 and 62 are provided between the piezoelectric element unit 20 and the first boundary 51 and the second boundary 52. Therefore, such a problem can be suitably prevented.

  Further, in the piezoelectric actuator 10, since the area of the first element protection layer 61 is smaller than the area of the second element protection layer 62 and the area of the external electrode 24, a part of the external electrode 24 is covered with the first element protection layer 61 I will not. Therefore, even after the first element protection layer 61 is provided on the external electrode formation surface 20c, the wiring portion 30 can be easily connected to the external electrode 24, and assembly is easy.

Second Embodiment FIG. 5 is a schematic perspective view showing a piezoelectric actuator 110 according to a second embodiment of the present invention. The piezoelectric actuator 110 according to the second embodiment relates to the first embodiment except that the thickness of the shaft 112 which is a movable portion and the shape of the adhesive resin portion 150 connecting the shaft 112 and the piezoelectric element portion 20 are different. The same as the piezoelectric actuator 10. Therefore, in the description of the piezoelectric actuator 110, only the differences from the piezoelectric actuator 10 according to the first embodiment will be described, and the description of the common points will be omitted.

  As shown in FIG. 5, in the shaft 112 of the piezoelectric actuator 110, the area of the shaft facing surface 112a (see FIGS. 6 and 7) opposed to the first end face 20a of the piezoelectric element portion 20 is narrower than the area of the first end face 20a. .

  6 is a partial cross-sectional view perpendicular to the external electrode forming surface 20c of the piezoelectric actuator 110 shown in FIG. As shown in FIG. 6, unlike the adhesive resin portion 50 according to the first embodiment, the adhesive resin portion 150 connecting the shaft 112 and the piezoelectric element portion 20 to the Z axis from the first end face 20 a of the piezoelectric element portion 20. The portion located on the positive direction side (shaft 112 side) is large. However, a part of the adhesive resin portion 150 extends to the Z-axis negative direction side (the weight 40 side) from the first end face 20a, and a part thereof is perpendicular to the external electrode forming surface 20c as shown in FIG. In the cross section, the first thickness change portion 150a has a thickness gradually increasing from the first boundary portion 151 toward the shaft 12 side.

  Further, the first boundary portion 151 of the adhesive resin portion 150 shown in FIG. 6 is also the first element protection layer with respect to the external electrode forming surface 20c of the piezoelectric element portion 20, similarly to the first boundary portion 51 shown in FIG. 61 are facing each other. That is, the first element protection layer 61 is sandwiched between the first boundary portion 151 of the adhesive resin portion 150 and the external electrode forming surface 20c in a cross section (cross section shown in FIG. 6) perpendicular to the external electrode forming surface 20c. It is arranged as.

  Furthermore, although the first thickness change portion 150a of the adhesive resin portion 150 is smaller than the first thickness change portion 50a shown in FIG. 3, like the first thickness change portion 50a shown in FIG. By sandwiching the protective layer 61, it does not directly face the external electrode formation surface 20c and is not directly connected.

  FIG. 7 is a partial cross-sectional view perpendicular to the external electrode non-forming surface 20 e of the piezoelectric actuator 110 shown in FIG. The adhesive resin portion 150 has a second thickness change portion 150b whose thickness gradually increases from the second boundary portion 152 toward the shaft 12 in a cross section perpendicular to the external electrode non-forming surface 20e as shown in FIG. Have. The second thickness change portion 150b of the adhesive resin portion 150 is smaller than the second thickness change portion 50b shown in FIG. 4, but like the second thickness change portion 50b shown in FIG. By sandwiching 62, it does not directly oppose to the external electrode non-formed surface 20e, and is not directly connected.

  Further, the second boundary portion 152 of the adhesive resin portion 150 shown in FIG. 7 also protects the second element with respect to the external electrode non-formed surface 20 e of the piezoelectric element portion 20 similarly to the second boundary portion 52 shown in FIG. The layers 62 are opposed to each other. That is, the second element protection layer 62 is located between the second boundary 152 of the adhesive resin portion 150 and the external electrode non-formation surface 20 e in a cross section (cross section shown in FIG. 7) perpendicular to the external electrode non-formation surface 20 e. It is arranged to be sandwiched.

  In the piezoelectric actuator 110 according to the second embodiment as well as the piezoelectric actuator 10, the first element protection layer 61 and the second element protection layer 62 have a difference in linear expansion coefficient between the adhesive resin portion 150 and the piezoelectric element portion 20, etc. Thus, the stress generated in the piezoelectric element portion 20 can be alleviated, and the problem of the occurrence of a crack in the piezoelectric element portion 20 or damage of the piezoelectric element portion 20 due to a change in temperature environment and the like can be prevented. Further, the piezoelectric actuator 110 according to the second embodiment has the same effect as the piezoelectric actuator 10 according to the first embodiment.

Third Embodiment FIG. 8 is a schematic perspective view showing a piezoelectric actuator 210 according to a third embodiment of the present invention. The piezoelectric actuator 210 according to the third embodiment is the same as the piezoelectric actuator 10 according to the first embodiment except that a resistive layer 264 is provided on the second element protective layer 62. Therefore, in the description of the piezoelectric actuator 210, only differences from the piezoelectric actuator 10 according to the first embodiment will be described, and the description of the common points will be omitted.

  As shown in FIG. 8, in the piezoelectric actuator 210, the external electrode non-forming surface 20 e of the piezoelectric element portion 20 is covered with the second element protective layer 62, and further, on the second element protective layer 62, a resistive layer is provided. H.264 is provided in piles. The resistance layer 264 has a strip shape crossing the second element protection layer 62 along the Y-axis direction, and the two external electrodes 24 formed on the two opposing external electrode formation surfaces 20c Connected

  The resistance layer 264 has an electric resistance lower than that of the second element protection layer 62 and higher than that of the external electrode 24 and the internal electrode layer 22 so that charges generated by the pyroelectric effect in the piezoelectric element portion 20 can move. ing. Thereby, the piezoelectric actuator 210 can prevent the decrease in the degree of polarization of the piezoelectric element portion 20 due to the pyroelectric effect. Further, since the resistance layer 264 is provided on the second element protection layer 62, the resistance layer 264 does not directly contact the internal electrode layer 22 of the element body 21. Such a resistance value of the resistance layer 264 can be accurately controlled by the cross-sectional area of the resistance layer 264 and the connection length connecting the external electrodes 24 by the resistance layer 264, so that the manufacturing error is small. The number of resistance layers 264 is not limited to two, and may be one or three or more.

  Resistance layer 264 is formed of, for example, a resin containing a conductive filler. In addition, the piezoelectric actuator 210 according to the third embodiment has the same effect as the piezoelectric actuator 10 according to the first embodiment.

Fourth Embodiment FIG. 9 is a schematic perspective view showing a piezoelectric actuator 310 according to a fourth embodiment of the present invention. The piezoelectric actuator 310 according to the fourth embodiment is the same as the piezoelectric actuator 110 according to the second embodiment except that a resistive layer 264 is provided on the second element protective layer 62. Therefore, in the description of the piezoelectric actuator 310, only differences from the piezoelectric actuator 110 according to the second embodiment will be described, and the description of the common points will be omitted.

  As shown in FIG. 9, in the piezoelectric actuator 310, the external electrode non-forming surface 20e of the piezoelectric element portion 20 is covered with the second element protective layer 62, and further, on the second element protective layer 62, a resistive layer is provided. H.264 is provided in piles. The resistance layer 264 is the same as the resistance layer 264 included in the piezoelectric actuator 210 shown in FIG.

  Similarly to the piezoelectric actuator 210 according to the third embodiment, the piezoelectric actuator 310 can also prevent a decrease in the degree of polarization of the piezoelectric element portion 20 due to the pyroelectric effect. In addition, the piezoelectric actuator 310 according to the fourth embodiment has the same effects as the piezoelectric actuator 210 according to the second embodiment and the piezoelectric actuator 310 according to the third embodiment.

  Although the piezoelectric actuator 310 according to the present invention has been described above by the embodiment, the present invention is not limited to the above-described embodiment, and it goes without saying that it has many other embodiments and modifications. Yes. For example, the first element protective layer 61 and the second element protective layer 62 may have any shape as long as they are provided so as to be sandwiched between the side surface of the piezoelectric element portion 20 and the adhesive resin portion 150. , May have shapes other than those shown in the embodiment.

10, 110, 210, 310 ... Piezoelectric actuator 12, 112 ... Shaft 12a, 112a ... Shaft opposing surface 20 ... Piezoelectric element portion 20a ... First end surface 20b ... Second end surface 20c ... External electrode forming surface 20e ... External electrode non-forming surface 21 Element body 22 Internal electrode layer 23 Piezoelectric layer 24 External electrode 30 Wiring portion 40 Weight 50, 150 Adhesive resin portion 50a, 150a First thickness changing portion 50b, 150b Second thickness changing portion 51, 151 ... first boundary portion 52, 152 ... second boundary portion 56 ... connection portion 61 ... first element protection layer 62 ... second element protection layer 264 ... resistance layer

Claims (4)

A shaft which is a movable part,
A weight which is an inertia part,
A first end face to which the shaft is connected, a second end face opposite to the first end face to which the weight is connected, and two external electrode forming surfaces facing each other are connected to two external electrode forming surfaces A substantially rectangular parallelepiped piezoelectric element portion having two external electrode non-formed surfaces facing each other and four side surfaces connecting the first end surface and the second end surface;
An adhesive resin portion connecting the shaft and the piezoelectric element portion;
A connecting portion connecting the weight and the piezoelectric element portion;
In a cross section perpendicular to the external electrode forming surface, the external electrode forming surface is sandwiched between a first boundary portion which is an end portion on the side close to the weight in the adhesive resin portion and the external electrode forming surface A first element protection layer provided on the
In a cross section perpendicular to the external electrode non-formed surface, the external electrode is sandwiched between a second boundary portion which is an end portion on the side close to the weight in the adhesive resin portion and the external electrode non-formed surface. And a second element protection layer provided on the non-formation surface,
An area of the first element protection layer is smaller than an area of the second element protection layer. The adhesive resin portion has a first thickness change portion which gradually increases in thickness from the first boundary portion toward the shaft in a cross section perpendicular to the outer electrode forming surface,
The first element protection layer is provided so as to be sandwiched between the first thickness change portion and the external electrode formation surface,
The adhesive resin portion has a second thickness change portion whose thickness gradually increases from the second boundary portion toward the shaft in a cross section perpendicular to the external electrode non-formed surface,
The piezoelectric actuator according to claim 1, wherein the second element protection layer is provided so as to be sandwiched between the second thickness change portion and the external electrode non-formed surface.   The piezoelectric actuator according to claim 1, wherein an elastic modulus of the first element protective layer and the second element protective layer is lower than an elastic modulus of the adhesive resin portion.   The thickness of the first element protection layer in a cross section perpendicular to the external electrode formation surface is thinner than the thickness of the second element protection layer in a cross section perpendicular to the external electrode non-formation surface. The piezoelectric actuator according to any one of claims 3 to 10.

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