JP6659450B2 - Piezoelectric element and method of manufacturing piezoelectric element - Google Patents

Description

  The present invention relates to a piezoelectric element and a method for manufacturing a piezoelectric element.

  The piezoelectric element of Patent Document 1 includes a piezoelectric body and a plurality of electrodes embedded in the piezoelectric body.

JP 2005-191450 A

  In the above-described piezoelectric element, when a polarization process is performed by applying a voltage to a plurality of electrodes, only the region of the piezoelectric body sandwiched between the electrodes is polarized, and the piezoelectric element may be warped. Therefore, when the piezoelectric element is installed in a device or the like, a problem may occur.

  An object of the present invention is to provide a piezoelectric element in which warpage is suppressed and a method for manufacturing the same.

  (1) One aspect of the piezoelectric element according to the present invention is a piezoelectric element, a first electrode layer provided on the piezoelectric body, and a first electrode layer between the first electrode layer in a first direction. A second electrode layer embedded in the piezoelectric body with the first region interposed therebetween, and a second electrode layer provided on the first outer surface of the piezoelectric body in the first direction, at least a part of the first electrode layer or the The piezoelectric body is provided on the piezoelectric body with a second region of the piezoelectric body sandwiched between the piezoelectric body and the second electrode layer. The piezoelectric body is connected to the first electrode layer and the second electrode layer via the piezoelectric body. And a conductive layer having conductivity, wherein the first region and the second region of the piezoelectric body are polarized.

  (2) One embodiment of the piezoelectric element according to the present invention is a piezoelectric element, a first electrode layer provided on the piezoelectric body, and a first electrode layer between the first electrode layer in a first direction. A second electrode layer embedded in the piezoelectric body with the first region interposed therebetween, and a second electrode layer provided on the first outer surface of the piezoelectric body in the first direction, at least a part of the first electrode layer or the The piezoelectric body is provided on the piezoelectric body with a second region of the piezoelectric body sandwiched between the piezoelectric body and the second electrode layer. The piezoelectric body is connected to the first electrode layer and the second electrode layer via the piezoelectric body. And a conductive layer having conductivity, and the thickness of the conductive layer is selected in a range of 1 μm to 100 μm.

  (3) In one example of the piezoelectric element, the piezoelectric element includes a plurality of first electrode layers and a plurality of second electrode layers, and the plurality of first electrode layers are embedded in the piezoelectric body. The first electrode layers and the second electrode layers are alternately arranged at intervals in the first direction.

  (4) In one example of the piezoelectric element, a first connecting portion extending in a first direction and electrically connecting the plurality of first electrode layers, and a plurality of second connecting portions extending in a first direction are provided. And a second connection portion for electrically connecting the electrode layers.

  (5) In one example of the piezoelectric element, a first external electrode layer provided on a second outer surface of the piezoelectric body in the first direction and connected to the first connection portion; And a second external electrode layer provided on the second outer surface of the piezoelectric body in the direction of and connected to the second connection portion.

  (6) In one example of the piezoelectric element, one of the plurality of second electrode layers is arranged at a position closer to the second outer surface of the piezoelectric body than the plurality of first electrode layers. Then, at least a portion of the first external electrode layer sandwiches a third region of the piezoelectric body between the first external electrode layer and the second electrode layer in the first direction.

(7) In one example of the piezoelectric element, the first external electrode layer has a larger area than the second external electrode layer.
(8) In one example of the piezoelectric element, the first external electrode layer and the second external electrode layer are formed of the same material.

(9) In one example of the piezoelectric element, the conductive layer is formed of the same material as the first external electrode layer and the second external electrode layer.
(10) In one example of the piezoelectric element, the conductive layer, the first external electrode layer, and the second external electrode layer include silver.

(11) In one example of the piezoelectric element, the thickness of the conductive layer is substantially equal to the thickness of the first external electrode layer and the second external electrode layer.
(12) In one example of the piezoelectric element, the first electrode layer, the second electrode layer, the first connection part, and the second connection part are formed of the same material.

(13) In one example of the piezoelectric element, the first electrode layer, the second electrode layer, the first connection portion, and the second connection portion include silver and palladium.
(14) In one example of the piezoelectric element, the conductive layer covers at least half of the first outer surface.

  (15) One embodiment of the method for manufacturing a piezoelectric element according to the present invention is a method for manufacturing a piezoelectric element, comprising: a piezoelectric body, a first electrode layer provided on the piezoelectric body, and the first electrode layer in a first direction. A second electrode layer embedded in the piezoelectric body with a first region of the body interposed therebetween, wherein the piezoelectric element is provided on a first outer surface of the piezoelectric body in the first direction. And at least a portion is provided on the piezoelectric body with the first electrode layer or the second electrode layer and a second region of the piezoelectric body interposed therebetween, and the first electrode layer and the second electrode The method includes a step of forming a conductive layer which is connected to the layer via the piezoelectric body and has conductivity, and a step of applying a DC voltage to the first region and the second region.

  ADVANTAGE OF THE INVENTION The piezoelectric element of this invention and the manufacturing method of a piezoelectric element can suppress the warpage of a piezoelectric element.

FIG. 2 is a schematic diagram of a strain sensor including the piezoelectric element according to the embodiment. The top view of the piezoelectric element of FIG. FIG. 2 is a bottom view of the piezoelectric element of FIG. 1. FIG. 4 is a sectional view taken along line 4-4 of FIG. 2. 3 is a flowchart illustrating a method for manufacturing the piezoelectric element of FIG. Sectional drawing which shows the process of forming the connection part of the manufacturing method of a piezoelectric element. FIG. 4 is a cross-sectional view illustrating a step of forming a first electrode layer in the method for manufacturing a piezoelectric element. FIG. 6 is a cross-sectional view illustrating a step of forming a second electrode layer in the method for manufacturing a piezoelectric element. Sectional drawing which shows the process of laminating the piezoelectric layer of the manufacturing method of a piezoelectric element. Sectional drawing which shows the process of baking of the piezoelectric layer of the manufacturing method of a piezoelectric element. FIG. 6 is a sectional view showing a second step of the method for manufacturing a piezoelectric element. Sectional drawing of the piezoelectric element of a modification.

The strain sensor 10 including the piezoelectric element 20 of the embodiment will be described with reference to FIGS.
As shown in FIG. 1, the strain sensor 10 includes a circuit section 12 and a piezoelectric element 20. The strain sensor 10 detects a strain of the detection body X to which the piezoelectric element 20 is attached. The detection object X is a part of a bicycle or a part of a bicycle component, and is, for example, a pedal shaft, a crankshaft, a crank arm, a frame, and the like of the bicycle (all not shown).

  The circuit section 12 is connected to the piezoelectric element 20. The circuit unit 12 includes an amplifier circuit (not shown) that amplifies the current from the piezoelectric element 20, a communication unit (not shown) that outputs a signal amplified by the amplifier circuit to an external device, and the like. The circuit unit 12 may further include a calculation unit (not shown) that calculates a distortion generated in the piezoelectric element 20 based on a current input from the piezoelectric element 20. When the circuit unit 12 includes a calculation unit, the communication unit outputs a result calculated by the calculation unit to an external device. The communication unit may perform wired communication or wireless communication.

  The piezoelectric element 20 includes a piezoelectric body 22, a first electrode layer 24 (see FIG. 4), a second electrode layer 26 (see FIG. 4), and a conductive layer 28. In one example, the piezoelectric element 20 includes a first connection portion 30 (see FIG. 4), a second connection portion 32 (see FIG. 4), a first external electrode layer 34, and a second external electrode layer 36. In addition. The piezoelectric element 20 is preferably attached to a flat surface of the detection object X, but may be attached to a curved surface when the detection object X has a curved surface such as a cylindrical or cylindrical shaft. The piezoelectric element 20 has a substantially rectangular parallelepiped shape. The piezoelectric element 20 is a so-called laminated piezoelectric element.

  As shown in FIG. 2, on the top surface 20B side of the piezoelectric element 20, a part of the second outer surface 22B of the piezoelectric body 22, a first external electrode layer 34, and a second external electrode layer 36 are provided. Exposed. As shown in FIG. 3, a part of the first outer surface 22A of the piezoelectric body 22 and the conductive layer 28 are exposed on the bottom surface 20A side of the piezoelectric element 20. The piezoelectric body 22 is exposed on the four side surfaces 20C of the piezoelectric element 20.

  As shown in FIG. 4, a plurality of first electrode layers 24 are provided. The first electrode layer 24 is provided on the piezoelectric body 22. The first electrode layer 24 is embedded in the piezoelectric body 22. The first electrode layer 24 is formed in a sheet shape. The first electrode layer 24 extends in a direction intersecting the first direction A of the piezoelectric body 22, and preferably extends in a second direction B orthogonal to the first direction A. The first direction A is the direction in which the first electrode layer 24 and the second electrode layer 26 are stacked, and is parallel to the direction from the top surface 20B of the piezoelectric element 20 to the bottom surface 20A. The second direction B is a direction along one side of the rectangular parallelepiped shape.

  A plurality of second electrode layers 26 are provided. The second electrode layer 26 is provided on the piezoelectric body 22. The second electrode layer 26 is embedded in the piezoelectric body 22 with the first region R1 of the piezoelectric body 22 interposed between the second electrode layer 26 and the first electrode layer 24 in the first direction A. The second electrode layer 26 is formed in a sheet shape. The second electrode layer 26 extends in a direction intersecting the first direction A of the piezoelectric body 22, and preferably extends in a second direction B orthogonal to the first direction A. The first electrode layers 24 and the second electrode layers 26 are alternately arranged at intervals in the first direction A. The second electrode layer 26X, which is one of the plurality of second electrode layers 26, is arranged at a position closer to the second outer surface 22B of the piezoelectric body than the plurality of first electrode layers 24. It is preferable that a total of 3 to 20 first electrode layers 24 and second electrode layers 26 are provided. In this case, there are 2 to 19 regions R1 of the piezoelectric body 22 sandwiched between the first electrode layer 24 and the second electrode layer 26.

  The size of the first electrode layer 24 and the size of the second electrode layer 26 are substantially equal. The first electrode layer 24 extends in the second direction B orthogonal to the first direction A to the first side surface 22C side of the piezoelectric body 22 beyond the second electrode layer 26. The second electrode layer 26 extends in the second direction B from the first electrode layer 24 to the second side surface 22D of the piezoelectric body 22.

The conductive layer 28 is provided on the first outer surface 22A of the piezoelectric body 22 in the first direction A. The conductive layer 28 covers at least half of the first outer surface 22A. At least a portion of the conductive layer 28 is provided on the piezoelectric body 22 with the second region R2 of the piezoelectric body 22 interposed between the conductive layer 28 and the second electrode layer 26. The conductive layer 28 has conductivity. The conductive layer 28 is connected to the first electrode layer 24 and the second electrode layer 26 via the piezoelectric body 22. The conductive layer 28 does not directly contact the first electrode layer 24, the second electrode layer 26, the first connection portion 30, and the second connection portion 32. The surface of the conductive layer 28 opposite to the piezoelectric body 22 is attached to the detection body X in a state of being in contact with the detection body X (see FIG. 1). The surface of the conductive layer 28 opposite to the piezoelectric body 22 may be attached to the detection body X via an adhesive. One A1-side surface of the piezoelectric body 22 in the first direction A and a second outer surface 22 B, and the other A2-side surface of the piezoelectric body 22 in the first direction A and the first outer surface 22 A .

  The first connection part 30 extends in the first direction A and electrically connects the plurality of first electrode layers 24. The first connection portion 30 is provided in a hole 27 </ b> A formed in the piezoelectric body 22. The first connection part 30 forms one of a positive electrode and a negative electrode of the piezoelectric element 20 together with the plurality of first electrode layers 24. The second connection part 32 extends in the first direction A and electrically connects the plurality of second electrode layers 26. The second connection part 32 is provided in a hole 27 </ b> B formed in the piezoelectric body 22. The second connection part 32 forms the other of the positive electrode and the negative electrode together with the plurality of second electrode layers 26.

  The first external electrode layer 34 is provided on the second outer surface 22B of the piezoelectric body 22 in the first direction A. The first external electrode layer 34 is connected to the first connection part 30. At least a part of the first external electrode layer 34 sandwiches the third region R3 of the piezoelectric body 22 between the first external electrode layer 34 and the second electrode layer 26 in the first direction A. As shown in FIG. 1, a first electric wire C1 is connected to the first external electrode layer.

  As shown in FIG. 4, the second external electrode layer 36 is provided on the second outer surface 22B of the piezoelectric body 22 in the first direction A. The first external electrode layer 34 and the second external electrode layer 36 are provided on the second outer surface 22B so as not to contact each other on the second outer surface 22B of the piezoelectric body 22. As shown in FIG. 2, the first external electrode layer 34 and the second external electrode layer 36 are arranged in the second direction B and spaced from each other in the second direction B. In the second direction B, the second external electrode layer 36 is provided on the second side face 22D of the piezoelectric body 22 more than the first external electrode layer 34. The second external electrode layer 36 is connected to the second connection part 32. The first external electrode layer has a larger area than the second external electrode layer. Specifically, the area where the first external electrode layer 34 is in contact with the second outer surface 22B of the piezoelectric body 22 is different from the area where the second external electrode layer 36 is in contact with the second outer surface 22B of the piezoelectric body 22. It is larger than the contact area. The first external electrode layer 34 preferably has an area at least twice as large as the second external electrode layer 36. As shown in FIG. 1, a second electric wire C2 is connected to the second external electrode layer 36. In the piezoelectric body 22 shown in FIG. 4, the first region R1 and the second region R2 are polarized. The third region R3 of the piezoelectric body 22 is polarized.

The thickness of each member of the piezoelectric element 20 will be described.
The thickness D1 of the first electrode layer 24 is selected in the range of 0.2 μm to 2 μm. The thickness D2 of the second electrode layer 26 is selected in the range of 0.2 μm to 2 μm. It is preferable that the thickness D1 of the first electrode layer 24 and the thickness D2 of the second electrode layer 26 are substantially equal. The average thickness of the thickness D1 of the first electrode layer 24 and the thickness D2 of the second electrode layer 26 is, for example, 1.5 μm.

  The thickness D3 of the conductive layer 28 is selected in the range of 1 μm to 100 μm. In one example, the thickness D3 of the conductive layer 28 is selected in a range of 5 μm to 20 μm. The thickness D4 of the first external electrode layer 34 is selected in the range of 1 μm to 100 μm. In one example, the thickness D4 of the first external electrode layer 34 is selected in a range of 5 μm to 20 μm. The thickness D5 of the second external electrode layer 36 is selected in the range of 1 μm to 100 μm. In one example, the thickness D5 of the second external electrode layer 36 is selected in a range of 5 μm to 20 μm. The thickness D3 of the conductive layer 28 is preferably substantially equal to the thickness D4 of the first external electrode layer 34 and the thickness D5 of the second external electrode layer 36.

  The thickness D6 of the first region R1 is selected, for example, in the range of 10 μm to 50 μm. In one example, the thickness D6 of the first region R1 is 30 μm. The thickness D7 of the second region R2 is selected, for example, in the range of 10 μm to 50 μm. In one example, the thickness D7 of the second region R2 is 30 μm. The thickness D8 of the third region R3 is selected, for example, in the range of 10 μm to 50 μm. In one example, the thickness D8 of the third region R3 is 30 μm. It is preferable that the thickness D6 of the first region R1, the thickness D7 of the second region R2, and the thickness D8 of the third region R3 are substantially equal.

The material of each member of the piezoelectric element 20 will be described.
The piezoelectric body 22 includes a material having piezoelectric characteristics. In one example, the piezoelectric body 22 includes lead zirconate titanate. In another example, the piezoelectric body 22 includes barium titanate or lead titanate. The piezoelectric body 22 is fired by adding an additive to a material having piezoelectric characteristics.

  The first electrode layer 24, the second electrode layer 26, the first connection part 30, and the second connection part 32 are formed of the same material. The first electrode layer 24, the second electrode layer 26, the first connection portion 30, and the second connection portion 32 are formed of a highly conductive metal material. The first electrode layer 24, the second electrode layer 26, the first connection part 30, and the second connection part 32 include silver and palladium. In one example, an example of a metal synthesis ratio of silver and palladium is 90:10 or 80:20 for silver: palladium.

  The first external electrode layer 34 and the second external electrode layer 36 are formed of the same material. The conductive layer 28 is formed of the same material as the first external electrode layer 34 and the second external electrode layer 36. The first external electrode layer 34, the second external electrode layer 36, and the conductive layer 28 are formed of a highly conductive metal material. The conductive layer 28, the first external electrode layer 34, and the second external electrode layer 36 include silver.

A method of manufacturing the piezoelectric element 20 will be described with reference to FIGS.
The method of manufacturing the piezoelectric element 20 includes a step of forming the conductive layer 28 and a step of applying a DC voltage to the first region R1 and the second region R2 (hereinafter, referred to as “polarizing”). In one example, the method of manufacturing the piezoelectric element 20 includes a first step of forming the piezoelectric layer 22X, a second step of forming the connection portions 30 and 32, and a second step of forming the first and second electrode layers 24 and 26. The method further includes a third step, a fourth step of laminating the piezoelectric layer 22X, a fifth step of firing the piezoelectric layer 22X, and a sixth step of forming the external electrode layers 34 and 36. The step of forming the conductive layer 28 (hereinafter, “seventh step”) and the step of polarizing (hereinafter, “eighth step”) are performed after the sixth step.

  The first step is a step of mixing and stirring the material of the piezoelectric body 22 to form a slurry, a step of forming the slurry-like material into a sheet, a step of drying the formed sheet, and a step of drying the dried sheet. Is cut into a predetermined size to form a piezoelectric layer 22X. The material of the piezoelectric body 22 includes a powder of lead zirconate titanate, an organic solvent, and a resin binder. In the step of forming the piezoelectric layer 22X, for example, a lip coater is used. Since the thickness D9 (see FIG. 6) of the piezoelectric layer 22X is reduced by the step of firing the piezoelectric layer 22X, the thickness D9 is preferably set to about 120% of a desired thickness after firing. When the thicknesses D4 to D6 (see FIG. 4) of the first to third regions after firing are 30 μm, the thickness D9 of the piezoelectric layer 22X is set to 36 μm.

  The second step of forming the connection portions 30 and 32 shown in FIG. 6 includes a step of forming a through hole 22Y in the piezoelectric layer 22X and a step of filling the through hole 22Y with the material of the connection portions 30 and 32. The piezoelectric layer 22X in which the through holes 22Y are formed is referred to as a piezoelectric layer 22X1, and the piezoelectric layer 22X in which the through holes 22Y are not formed is referred to as a piezoelectric layer 22X2 (see FIG. 9). FIG. 6 shows only a portion of the piezoelectric layer 22X corresponding to one piezoelectric element 20, but actually, a plurality of piezoelectric layers 22X of a unit shown in FIG. 6 are connected in a matrix.

  In the third step of forming the electrode layers 24 and 26 shown in FIGS. 7 and 8, only one of the first electrode layer 24 and the second electrode layer 26 is printed on one surface in the thickness direction of the piezoelectric layer 22X1. The step of performing The first electrode layer 24 shown in FIG. 7 is printed on the surface of the piezoelectric layer 22X1 so as to be in contact with the first connection portion 30 and not to be in contact with the second connection portion 32. The second electrode layer 26 shown in FIG. 8 is printed on the surface of the piezoelectric layer 22X1 so as to be in contact with the second connection portion 32 and not to be in contact with the first connection portion 30. As a printing method, for example, screen printing is used. The piezoelectric layer 22X1 on which the first electrode layer 24 is printed is referred to as a first piezoelectric layer with electrode layer 23X. The piezoelectric layer 22X1 on which the second electrode layer 26 is printed is a second piezoelectric layer with electrode layer 23Y.

  The fourth step of laminating the piezoelectric layers 22X shown in FIG. 9 is a step of laminating the plurality of piezoelectric layers 22X, a step of crimping the laminated piezoelectric layers 22X, and a step of cutting the crimped piezoelectric layers 22X to predetermined dimensions. Process. In the step of stacking the plurality of piezoelectric layers 22X, the first piezoelectric layers with electrode layers 23X and the second piezoelectric layers with electrode layers 23Y are alternately stacked. In FIG. 9, the first electrode layer-attached piezoelectric layer 23X and the second electrode layer-attached piezoelectric layer 23X are arranged such that the first electrode layer 24 and the second electrode layer 26 face the other direction A2 in the first direction A. And a layer 23Y. Further, when viewed from the first direction A, the first electrode-attached piezoelectric layer 23X and the second electrode-attached piezoelectric layer 23X are arranged such that the first connection portions 30 and the second connection portions 32 overlap each other. 23Y are stacked. The piezoelectric layer 22X2 is stacked on the piezoelectric layer 23Y disposed at the other end A2 in the first direction A on the other end A2 in the first direction A. By the fourth step, a stacked body 25 in which the first piezoelectric layer with an electrode layer 23X, the second piezoelectric layer with an electrode layer 23Y, and the piezoelectric layer 22X are stacked is formed. The number of piezoelectric layers 22X laminated in the fourth step is at least plural, for example, selected from 4 to 12, and is selected as 6 in the example shown in FIG.

In the fifth step of firing the piezoelectric layer 22X, the stacked body 25 formed in the fourth step is fired. The firing temperature is set to be higher than the melting points of the electrode layers 24 and 26 and the connection parts 30 and 32. When the electrode layers 24 and 26 and the connection parts 30 and 32 contain silver and palladium, the firing temperature is set to 950 ° C. to 1030 ° C. in one example. Each piezoelectric layer 22X is integrated by sintering to form the piezoelectric body 22 as shown in FIG. 10, and the first electrode layer 24, the second electrode layer 26, the first connecting portion 30, and the second The connection portion 32 is buried inside the piezoelectric body 22. In FIG. 10, the plurality of through holes 22Y on one side in the second direction B form one hole 27A, and the first connection portion 30 of each piezoelectric layer 22X provided in the hole 27A is continuous. In FIG. 10, the plurality of through holes 22Y on the other side in the second direction B form one hole 27B, and the second connection portion 32 of each piezoelectric layer 22X provided in the hole 27B is continuous. None of the first electrode layer 24, the second electrode layer 26, the first connection part 30, and the second connection part 32 are exposed on the first outer surface 22A of the piezoelectric body 22.

  In the sixth step of forming the external electrode layers 34 and 36 shown in FIG. 11, the first external electrode layer 34 and the second external electrode layer 36 are printed and baked on the second outer surface 22B of the piezoelectric body 22. Process. The first external electrode layer 34 is formed on the second outer surface 22B so as to be in contact with the first connection portion 30 and not to be in contact with the second connection portion 32. The second external electrode layer 36 is formed on the second outer surface 22 </ b> B so as to be in contact with the second connection part 32 and not to be in contact with the first connection part 30. The temperature at which the external electrode layers 34, 36 are baked on the first outer surface 22A is a temperature equal to or higher than the melting point of the material of the external electrode layers 34, 36. When the external electrode layers 34 and 36 include silver, the baking temperature is set to 550 degrees in one example.

  The seventh step of forming the conductive layer 28 includes a step of printing and printing the conductive layer 28 on the first outer surface 22A of the piezoelectric body 22. The temperature at which the conductive layer 28 is baked on the first outer surface 22A is a temperature equal to or higher than the melting point of the material of the external electrode layers 34 and 36. When the conductive layer 28 contains silver, the baking temperature is set to 550 degrees in one example. The conductive layer 28 is connected to the first electrode layer 24 and the second electrode layer 26 via the piezoelectric body 22. Note that the order of the steps of forming the external electrode layers 34 and 36 and the step of forming the conductive layer 28 can be interchanged. Further, regarding the melting point of each material and the temperature used in each step, “the firing temperature> the melting point of the material of the conductive layer 28 and the external electrode layers 34 and 36> the melting point of the material of the electrode layers 24 and 26 and the connecting portions 30 and 32> "Baking temperature of conductive layer 28 and external electrode layers 34 and 36" or "Melting point of material of conductive layer 28 and external electrode layers 34 and 36> Firing temperature> Melting point of material of electrode layers 24 and 26 and connecting portions 30 and 32> It is preferable that the relationship of “baking temperature of the conductive layer 28 and the external electrode layers 34 and 36” is satisfied.

  The eighth step of performing polarization includes a step of disposing the piezoelectric body 22 on the conductive plate P such that the conductive plate P having conductivity and the conductive layer 28 are in contact with each other, and a step of disposing the first external electrode layer 34 and the conductive plate. Connecting the first electric wire C1 to P and connecting the second electric wire C2 to the second external electrode layer 36; and applying a DC voltage to the first electric wire C1 and the second electric wire C2. . One of the first electric wire C1 and the second electric wire C2 is connected to a negative electrode of the power supply BT, and the other of the first electric wire C1 and the second electric wire C2 is connected to a positive electrode of the power supply BT.

A first region R1 sandwiched between the first electrode layer 24 and the second electrode layer 26 by application of a DC voltage, and a second region sandwiched between the second electrode layer 26 and the conductive layer 28 R2 and the third region R3 sandwiched between the first external electrode layer 34 and the second electrode layer 26 are polarized.

In a piezoelectric element in which the conductive layer 28 is not provided, no DC voltage is applied to a region of the piezoelectric body 22 closer to the second A2 side than the second electrode layer 26 on the other A2 side in the first direction A. , Not polarized. Residual displacement occurs in the polarized first region R1 of the piezoelectric body 22 due to the application of the DC voltage. For this reason, the internal stress generated between the non-polarized region and the first region R1 having the residual displacement may cause warpage or deflection. In the piezoelectric element 20, the second region R 2 to be similarly uniform voltage to the first region R1 is formed between the second electrode layer 26 and the first outer surface 22A is polarized is applied You. For this reason, the displacement of the piezoelectric body 22 in the second direction B due to the application of the DC voltage becomes uniform, and the occurrence of warpage and bending can be suppressed.

  In the piezoelectric element 20, the first connection part 30 and the second connection part 32 are not exposed on the side surface 20C of the piezoelectric element 20, so that the first connection part 30 and the second connection part 32 It is difficult for electrical connection to occur between them. For this reason, erroneous detection hardly occurs in the output of the strain sensor 10.

  At least a part of the first external electrode layer 34 sandwiches the third region R3 of the piezoelectric body 22 between the first external electrode layer 34 and the second electrode layer 26 in the first direction A. For this reason, the third region R3 is also polarized, so that the piezoelectric body 22 is less likely to warp and bend.

  The conductive layer 28 is formed of the same material as the first external electrode layer 34 and the second external electrode layer 36. Therefore, in the step of polarizing the piezoelectric body 22, a DC voltage can be appropriately applied to the second region R2.

(Modification)
The description relating to each of the above embodiments is an example of a form that can be taken by the piezoelectric element and the method for manufacturing the piezoelectric element according to the present invention, and is not intended to limit the form. The piezoelectric element and the method of manufacturing the piezoelectric element according to the present invention can take a form in which, for example, a modification of each of the above-described embodiments described below and at least two modifications that do not contradict each other are combined.

  -The 1st connection part 30 and the 2nd connection part 32 may be changed into the 1st connection part 38 and the 2nd connection part 40 shown in FIG. The first connection portion 38 and the second connection portion 40 of FIG. 12 are provided on the first side surface 22C and the second side surface 22D of the piezoelectric body 22, respectively. The first electrode layer 24 is exposed on the first side face 22C. The first connection portion 38 contacts the first electrode layer 24 exposed on the first side surface 22C and the first external electrode layer 34. The second electrode layer 26 is exposed on the second side face 22D. The second connection portion 40 contacts the second electrode layer 26 exposed on the second side surface 22D and the second external electrode layer 36. In this case, the material of the first connection part 38 and the material of the second connection part 40 are preferably equal to the material of the first external electrode layer 34 and the second external electrode layer 36.

- a first electrode layer 24 may be disposed on the second outer surface 22 on the B. In this case, the first electrode layer 24 functions as a first external electrode layer.
-The first electrode layer 24 and the second electrode layer 26 can be exchanged. In this case, the conductive layer 28 is provided on the piezoelectric body 22 with the second region R2 of the piezoelectric body 22 interposed between the conductive layer 28 and the first electrode layer 24 closest to the first outer surface 22A.

  A: first direction, 20: piezoelectric element, 22: piezoelectric body, 22A: first outer surface, 22B: second outer surface, R1: first region, R2: second region, R3: first Region 3, 24 first electrode layer, 26 second electrode layer, 28 conductive layer, 30 first connection portion, 32 second connection portion, 34 first external electrode layer, 36 ... second external electrode layer.

Claims (19)

A piezoelectric body,
A first electrode layer provided on the piezoelectric body;
A second electrode layer embedded in the piezoelectric body with a first region of the piezoelectric body interposed between the first electrode layer and the first electrode layer in a first direction;
The first direction is provided on the first outer surface of the piezoelectric body in the first direction, and at least a part of the piezoelectric body sandwiches the second region of the piezoelectric body between the first electrode layer and the second electrode layer. A conductive layer provided on the piezoelectric body, connected to the first electrode layer and the second electrode layer via the piezoelectric body, and having conductivity.
A connection portion provided in a hole formed in the piezoelectric body and electrically connected to the first electrode layer or the second electrode layer,
In the piezoelectric body, the first region and the second region are polarized ,
A first connection part electrically connected to the first electrode layer, not electrically connected to the second electrode layer, and a first connection part electrically connected to the second electrode layer; A second connection portion that is not electrically connected to the first electrode layer;
A first external electrode layer provided on the second outer surface of the piezoelectric body in the first direction and connected to the first connection portion;
A second external electrode layer provided on the second outer surface of the piezoelectric body in the first direction and connected to the second connection portion;
The piezoelectric element , wherein the conductive layer is formed of the same material as the first external electrode layer and the second external electrode layer . A piezoelectric body,
A first electrode layer provided on the piezoelectric body;
A second electrode layer embedded in the piezoelectric body with a first region of the piezoelectric body interposed between the first electrode layer and the first electrode layer in a first direction;
The first direction is provided on the first outer surface of the piezoelectric body in the first direction, and at least a part of the piezoelectric body sandwiches the second region of the piezoelectric body between the first electrode layer and the second electrode layer. A conductive layer provided on the piezoelectric body, connected to the first electrode layer and the second electrode layer via the piezoelectric body, and having conductivity.
A connection portion provided in a hole formed in the piezoelectric body and electrically connected to the first electrode layer or the second electrode layer,
The thickness of the conductive layer is selected in a range of 1 μm to 100 μm ,
A first connection part electrically connected to the first electrode layer, not electrically connected to the second electrode layer, and a first connection part electrically connected to the second electrode layer; A second connection portion that is not electrically connected to the first electrode layer;
A first external electrode layer provided on the second outer surface of the piezoelectric body in the first direction and connected to the first connection portion;
A second external electrode layer provided on the second outer surface of the piezoelectric body in the first direction and connected to the second connection portion;
The piezoelectric element , wherein the conductive layer is formed of the same material as the first external electrode layer and the second external electrode layer . A piezoelectric body,
A first electrode layer provided on the piezoelectric body;
A second electrode layer embedded in the piezoelectric body with a first region of the piezoelectric body interposed between the first electrode layer and the first electrode layer in a first direction;
The first direction is provided on the first outer surface of the piezoelectric body in the first direction, and at least a part of the piezoelectric body sandwiches the second region of the piezoelectric body between the first electrode layer and the second electrode layer. A conductive layer provided on the piezoelectric body, connected to the first electrode layer and the second electrode layer via the piezoelectric body, and having conductivity.
A connection portion provided in a hole formed in the piezoelectric body and electrically connected to the first electrode layer or the second electrode layer,
In the piezoelectric body, the first region and the second region are polarized ,
A first connection part electrically connected to the first electrode layer, not electrically connected to the second electrode layer, and a first connection part electrically connected to the second electrode layer; A second connection portion that is not electrically connected to the first electrode layer;
A first external electrode layer provided on the second outer surface of the piezoelectric body in the first direction and connected to the first connection portion;
A second external electrode layer provided on the second outer surface of the piezoelectric body in the first direction and connected to the second connection portion;
The piezoelectric element , wherein a thickness of the conductive layer is substantially equal to thicknesses of the first external electrode layer and the second external electrode layer . A piezoelectric body,
A first electrode layer provided on the piezoelectric body;
A second electrode layer embedded in the piezoelectric body with a first region of the piezoelectric body interposed between the first electrode layer and the first electrode layer in a first direction;
The first direction is provided on the first outer surface of the piezoelectric body in the first direction, and at least a part of the piezoelectric body sandwiches the second region of the piezoelectric body between the first electrode layer and the second electrode layer. A conductive layer provided on the piezoelectric body, connected to the first electrode layer and the second electrode layer via the piezoelectric body, and having conductivity.
A connection portion provided in a hole formed in the piezoelectric body and electrically connected to the first electrode layer or the second electrode layer,
The thickness of the conductive layer is selected in a range of 1 μm to 100 μm ,
A first connection part electrically connected to the first electrode layer, not electrically connected to the second electrode layer, and a first connection part electrically connected to the second electrode layer; A second connection portion that is not electrically connected to the first electrode layer;
A first external electrode layer provided on the second outer surface of the piezoelectric body in the first direction and connected to the first connection portion;
A second external electrode layer provided on the second outer surface of the piezoelectric body in the first direction and connected to the second connection portion;
The piezoelectric element , wherein a thickness of the conductive layer is substantially equal to thicknesses of the first external electrode layer and the second external electrode layer . The piezoelectric element according to claim 3 , wherein the conductive layer is formed of the same material as the first external electrode layer and the second external electrode layer. A plurality of said first electrode layers;
A plurality of the second electrode layers,
The plurality of first electrode layers are embedded in the piezoelectric body,
It said first electrode layer and the second electrode layer, said first direction at intervals are arranged alternately, the piezoelectric element according to any one of claims 1 to 5. The piezoelectric element according to claim 6 , wherein the connection portion extends in the first direction and electrically connects the plurality of first electrode layers. The piezoelectric element according to claim 6 , wherein the connection portion extends in the first direction and electrically connects the plurality of second electrode layers. A piezoelectric body,
A first electrode layer provided on the piezoelectric body;
A second electrode layer embedded in the piezoelectric body with a first region of the piezoelectric body interposed between the first electrode layer and the first electrode layer in a first direction;
The first direction is provided on the first outer surface of the piezoelectric body in the first direction, and at least a part of the piezoelectric body sandwiches the second region of the piezoelectric body between the first electrode layer and the second electrode layer. And the first electrode layer and the second electrode layer are connected to the first electrode layer and the second electrode layer via the piezoelectric body, and include a conductive layer having conductivity.
In the piezoelectric body, the first region and the second region are polarized,
The conductive layer is configured to be attachable to a portion of a bicycle or a portion of a bicycle component ;
A connection portion provided in a hole formed in the piezoelectric body and electrically connected to the first electrode layer or the second electrode layer;
A first connection part electrically connected to the first electrode layer, not electrically connected to the second electrode layer, and a first connection part electrically connected to the second electrode layer; A second connection portion that is not electrically connected to the first electrode layer;
A first external electrode layer provided on the second outer surface of the piezoelectric body in the first direction and connected to the first connection portion;
A second external electrode layer provided on the second outer surface of the piezoelectric body in the first direction and connected to the second connection portion,
The piezoelectric element , wherein the conductive layer is formed of the same material as the first external electrode layer and the second external electrode layer . A piezoelectric body,
A first electrode layer provided on the piezoelectric body;
A second electrode layer embedded in the piezoelectric body with a first region of the piezoelectric body interposed between the first electrode layer and the first electrode layer in a first direction;
The first direction is provided on the first outer surface of the piezoelectric body in the first direction, and at least a part of the piezoelectric body sandwiches the second region of the piezoelectric body between the first electrode layer and the second electrode layer. And the first electrode layer and the second electrode layer are connected to the first electrode layer and the second electrode layer via the piezoelectric body, and include a conductive layer having conductivity.
In the piezoelectric body, the first region and the second region are polarized,
The conductive layer is configured to be attachable to a portion of a bicycle or a portion of a bicycle component ;
A connection portion provided in a hole formed in the piezoelectric body and electrically connected to the first electrode layer or the second electrode layer;
A first connection part electrically connected to the first electrode layer, not electrically connected to the second electrode layer, and a first connection part electrically connected to the second electrode layer; A second connection portion that is not electrically connected to the first electrode layer;
A first external electrode layer provided on the second outer surface of the piezoelectric body in the first direction and connected to the first connection portion;
A second external electrode layer provided on the second outer surface of the piezoelectric body in the first direction and connected to the second connection portion;
The piezoelectric element , wherein a thickness of the conductive layer is substantially equal to thicknesses of the first external electrode layer and the second external electrode layer . The piezoelectric element according to claim 10 , wherein the conductive layer is formed of the same material as the first external electrode layer and the second external electrode layer. One of the plurality of second electrode layers is arranged at a position closer to the second outer surface of the piezoelectric body than the plurality of first electrode layers,
Wherein at least a portion of the first external electrode layer, sandwiching a third region of the piezoelectric body between the second electrode layer in the first direction, any one of claims 1 to 11 3. The piezoelectric element according to item 1. The piezoelectric element according to claim 1, wherein the first external electrode layer has a larger area than the second external electrode layer. The piezoelectric element according to any one of claims 1 to 13 , wherein the first external electrode layer and the second external electrode layer are formed of the same material. The piezoelectric element according to claim 1, wherein the conductive layer, the first external electrode layer, and the second external electrode layer include silver. The piezoelectric device according to any one of claims 1 to 15 , wherein the first electrode layer, the second electrode layer, the first connection portion, and the second connection portion are formed of the same material. element. The piezoelectric element according to claim 1, wherein the first electrode layer, the second electrode layer, the first connection part, and the second connection part include silver and palladium. .   The piezoelectric element according to claim 1, wherein the conductive layer covers at least half of the first outer surface. A piezoelectric body,
A first electrode layer provided on the piezoelectric body;
A second electrode layer embedded in the piezoelectric body with a first region of the piezoelectric body interposed between the first electrode layer and the first electrode layer in a first direction, the method comprising:
Forming a first hole and a second hole in the piezoelectric body, providing a first connection portion in the first hole, and providing a second connection portion in the second hole;
The first electrode layer electrically connected to the first connection portion and not electrically connected to the second connection portion, and the first electrode layer electrically connected to the second connection portion; Providing the connection portion with the second electrode layer that is not electrically connected;
A first external electrode layer provided on the second outer surface of the piezoelectric body in the first direction and connected to the first connection portion; and a second external electrode layer of the piezoelectric body in the first direction. Providing a second external electrode layer provided on the outer surface and connected to the second connection portion;
The piezoelectric element is provided on a first outer surface of the piezoelectric body in the first direction, and at least a part of the piezoelectric body is sandwiched between the first electrode layer or the second electrode layer and a second region of the piezoelectric body. And is connected to the first electrode layer and the second electrode layer via the piezoelectric body, and is formed of the same material as the first external electrode layer and the second external electrode layer. and forming a conductive layer having conductivity,
Applying a DC voltage to the first region and the second region.