Piezoelectric Actuator

Abstract

To provide a piezoelectric actuator that can transmit vibration to a drive object without reducing the vibration efficiency of a piezoelectric element.SOLUTION: A piezoelectric actuator 100 comprises: a piezoelectric element 1 that has a piezoelectric element body 2 and an external electrode 6 arranged on the piezoelectric element body 2; a wiring member 40 connected with the external electrode 6; a housing 80 that has an arrangement surface 82s on which the piezoelectric element 1 is arranged via the wiring member 40; and a first support member 50 and a second support member 60 that support the piezoelectric element 1. The arrangement surface 82s includes: a first region R1 abutting on the wiring member 40; and a second region R2 provided so as to correspond to the external electrode 6, not abutting on the wiring member 40.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a piezoelectric actuator.

Background Art

[0002] Patent Document 1 describes a holding device for a piezoelectric vibrator used as a piezoelectric actuator. In this holding device, since the piezoelectric vibrator is held by a leaf spring fixed to the side portion of the piezoelectric vibrator, the loss of vibration energy of the piezoelectric vibrator is small.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] One aspect of the present disclosure provides a piezoelectric actuator capable of transmitting vibration to a driven object without reducing the vibration efficiency of a piezoelectric element.

Means for Solving the Problems

[0005] A piezoelectric actuator according to one aspect of the present disclosure is a piezoelectric actuator that drives a driven object, and includes a piezoelectric element having a piezoelectric body and a first external electrode disposed on the piezoelectric body, a wiring member connected to the first external electrode, a housing having an arrangement surface on which the piezoelectric element is disposed via the wiring member, and a support member that supports the piezoelectric element. The arrangement surface includes a first region that abuts on the wiring member and a second region that is provided corresponding to the first external electrode and does not abut on the wiring member.

[0006] In the piezoelectric actuator described above, since the first external electrode protrudes from the surface of the piezoelectric element by the thickness thereof, it is likely to interfere with the placement surface via the wiring member. Since the placement surface of the housing is provided corresponding to the first external electrode and includes a second region that does not contact the wiring member, interference between the first external electrode and the placement surface via the wiring member is suppressed. Therefore, vibration can be transmitted to the object to be driven without reducing the vibration efficiency of the piezoelectric element.

[0007] When viewed from a direction orthogonal to the placement surface, the second region may have a size that covers the entire first external electrode. In this case, interference between the first external electrode and the placement surface via the wiring member is surely suppressed. Therefore, vibration can be surely transmitted to the object to be driven.

[0008] The piezoelectric element may further have a second external electrode disposed on the piezoelectric element, and the first region may be provided corresponding to the second external electrode. In this case, since the wiring member and the placement surface are in a state close to point contact, the position where the piezoelectric element is pressed is accurately determined and the vibration is stabilized.

[0009] The second region may be disposed between a pair of first regions. In this case, the piezoelectric element is supported by the placement surface in the pair of first regions via the wiring member. By being supported at two locations in this way, the piezoelectric element is stably disposed on the placement surface.

[0010] The second region may be constituted by a recess or a through hole provided in the placement surface. In this case, a configuration in which the second region does not contact the wiring member can be easily realized.

[0011] The piezoelectric element has a rectangular shape and includes a pair of main surfaces facing each other, a first end surface and a second end surface facing each other in the long side direction of the pair of main surfaces, and a first side surface and a second side surface facing each other in the short side direction of the pair of main surfaces. The support member includes a first support member facing the object to be driven in the long side direction via the piezoelectric element and supporting the first end surface, and a second support member facing the arrangement surface of the housing in which the piezoelectric element is arranged in the short side direction via the piezoelectric element and supporting the first side surface. The first support member may be provided movably in accordance with the deformation of the first end surface, and the second support member may be provided movably in accordance with the deformation of the first side surface. In this case, since the first support member and the second support member are provided movably separately, the vibration of the piezoelectric element is hardly inhibited.

[0012] The first support member may have a facing portion facing the second support member in the long side direction and a protruding portion protruding in the long side direction from the facing portion and contacting the second support member. In this case, the position of the second support member with respect to the first support member is easily determined during assembly. Therefore, the assembly is easy.

[0013] The distance at which the contact portion of the protruding portion with the second support member is separated from the piezoelectric element in the short side direction may be 0.3 times or more and 0.7 times or less the length of the piezoelectric element in the short side direction. In this case, even if the first support member and the second support member move in accordance with the vibration of the piezoelectric element, interference between the first support member and the second support member is suppressed. Therefore, inhibition of the vibration of the piezoelectric element is suppressed.

[0014] The piezoelectric actuator may further include a first biasing member that biases the first support member in the long side direction and contacts the piezoelectric element, and a second biasing member that biases the second support member in the short side direction and contacts the piezoelectric element. In this case, a configuration in which the first support member is movable in accordance with the deformation of the first end surface is easily realized. A configuration in which the second support member is movable in accordance with the deformation of the first side surface is easily realized.

[0015] The piezoelectric actuator further includes a first biasing member that biases the first support member in the long side direction and abuts against the piezoelectric element, and a second biasing member that biases the second support member in the short side direction and abuts against the piezoelectric element. The second support member has a pair of support portions that are spaced apart from each other in the long side direction and support the first side surface. The second biasing member may be located between the pair of support portions in the long side direction. In this case, a configuration in which the first support member is movable in response to deformation of the first end surface can be easily realized. A configuration in which the second support member is movable in response to deformation of the first side surface can be easily realized. Since the second support member supports the first side surface with the pair of support portions, the first side surface can be reliably supported. Since the second biasing member is located between the pair of support portions in the long side direction, a biasing force can be imparted to the pair of support portions in a well-balanced manner.

[0016] The second support member may have a pair of support portions that are spaced apart from each other in the long side direction and support the first side surface. In this case, since the second support member supports the first side surface with the pair of support portions, the first side surface can be reliably supported.

[0017] The first support member may have a positioning portion that defines the position of the piezoelectric element in the short side direction. In this case, movement of the piezoelectric element in the short side direction on the first support member can be suppressed.

Advantages of the Invention

[0018] According to one aspect of the present invention, there is provided a piezoelectric actuator capable of transmitting vibration to a driven object without reducing the vibration efficiency of the piezoelectric element.

Brief Description of the Drawings

[0019]

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MODE FOR CARRYING OUT THE INVENTION

[0020] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0021] [First Embodiment] As shown in FIGS. 1 to 3, a piezoelectric actuator 100 according to a first embodiment includes a piezoelectric element 1, a wiring member 40, a contact 46, a first support member 50, a second support member 60, a first biasing member 71, a second biasing member 72, and a housing 80. The piezoelectric actuator 100 is used as an ultrasonic motor and is configured to be able to drive a moving body 200, which is an object to be driven, in a driving direction Dd. In FIG. 3, the illustration of the moving body 200 is omitted.

[0022] (Moving body) The moving body 200 includes a rail 201, a shaft member 202, a plurality of pairs of bearings 203, and a sliding plate 204. The rail 201 is a groove-shaped member having a U-shaped cross section and extending in the driving direction Dd. The rail 201 has a bottom portion 201a and a pair of side portions 201b facing each other. A groove extending in the driving direction Dd is provided on the inner surface of each side portion 201b. The shaft member 202 is a bar-shaped member having a rectangular cross section and extending in the driving direction Dd. The shaft member 202 is fitted into the groove of the rail 201. A groove extending in the driving direction Dd is provided on the outer surface of the shaft member 202 at a position facing the groove provided on the inner surface of each side portion 201b.

[0023] The bearing 203 is disposed between the groove of the side portion 201b of the rail 201 and the groove of the shaft member 202. The sliding plate 204 is attached to one side portion 201b of the rail 201 and extends in the driving direction Dd. In the moving body 200, the vibration of the piezoelectric actuator 100 is transmitted to the rail 201 via the sliding plate 204, and the rail 201 is driven in the driving direction Dd together with the sliding plate 204.

[0024] (Piezoelectric element) With reference to FIGS. 4 to 10, the piezoelectric element 1 will be described. As shown in FIG. 4, the piezoelectric element 1 includes a piezoelectric body 2 and a plurality of external electrodes 4, 5, 6, 7, 8, 9. The piezoelectric body 2 has a rectangular parallelepiped shape. The rectangular parallelepiped shape includes a shape of a rectangular parallelepiped with chamfered corners and edges, and a shape of a rectangular parallelepiped with rounded corners and edges. The piezoelectric body 2 has a pair of end faces 2a, 2b facing each other, a pair of side faces 2c, 2d facing each other, and a pair of main faces 2e, 2f facing each other.

[0025] The direction D1 in which the end faces 2a, 2b face each other, the direction D2 in which the side faces 2c, 2d face each other, and the direction D3 in which the main faces 2e, 2f face each other intersect with each other. In the present embodiment, the direction D1, the direction D2, and the direction D3 are orthogonal to each other. The direction D1 is the length direction of the piezoelectric body 2. The direction D2 is the width direction of the piezoelectric body 2. The direction D3 is the thickness direction of the piezoelectric body 2. The main faces 2e, 2f have a rectangular shape. The long side direction of the main faces 2e, 2f coincides with the direction D1. The short side direction of the main faces 2e, 2f coincides with the direction D2.

[0026] Each of the end faces 2a, 2b extends in the direction D2 so as to connect between the side faces 2c, 2d. Each of the end faces 2a, 2b also extends in the direction D3 so as to connect between the main faces 2e, 2f. Each of the side faces 2c, 2d extends in the direction D1 so as to connect between the end faces 2a, 2b. Each of the side faces 2c, 2d also extends in the direction D3 so as to connect between the main faces 2e, 2f. Each of the main faces 2e, 2f extends in the direction D1 so as to connect between the end faces 2a, 2b. Each of the main faces 2e, 2f also extends in the direction D2 so as to connect between the side faces 2c, 2d.

[0027] The width of the piezoelectric body 2 (the length in the direction D2) is, for example, 2.5 mm. The length of the piezoelectric body 2 (the length in the direction D1) is, for example, 9 mm. The thickness of the piezoelectric body 2 (the length in the direction D3) is, for example, 1 mm. The width of the piezoelectric body 2 is longer than the thickness of the piezoelectric body 2 and shorter than the length of the piezoelectric body 2.

[0028] Each surface 2a, 2b, 2c, 2d, 2e, 2f of the piezoelectric element 2 is, for example, a polished surface polished by barrel polishing. Among the surfaces 2a, 2b, 2c, 2d, 2e, 2f, each ridge line portion 2g located between two adjacent surfaces has a rounded chamfered shape. Each ridge line portion 2g is composed of a curved surface. Among the surfaces 2a, 2b, 2c, 2d, 2e, 2f, each corner portion 2h located between three adjacent surfaces has a rounded chamfered shape. Each corner portion 2h is composed of a curved surface.

[0029] The external electrodes 4, 5, 6 are arranged on the side surface 2c of the piezoelectric element 2. The external electrodes 4, 5, 6 are spaced apart from each other. The external electrodes 4, 5, 6 are arranged side by side in the direction D1. The external electrode 4 is arranged on the end surface 2a side. The external electrode 4 is spaced apart from the end surface 2a. The external electrode 5 is arranged on the end surface 2b side. The external electrode 5 is spaced apart from the end surface 2b. The external electrode 6 is arranged between the external electrode 4 and the external electrode 5. The external electrode 6 is spaced apart from each of the external electrode 4 and the external electrode 5.

[0030] The external electrodes 4, 5, 6 have the same shape as each other. The external electrodes 4, 5, 6 have a rectangular shape when viewed from the direction D2. Each of the external electrodes 4, 5, 6 extends in the direction D3 so as to connect the main surface 2e and the main surface 2f. Each of the external electrodes 4, 5, 6 is formed over the entire side surface 2c in the direction D3. Each of the external electrodes 4, 5, 6 is also provided at each of the ridge line portion 2g between the side surface 2c and the main surface 2e and the ridge line portion 2g between the side surface 2c and the main surface 2f.

[0031] The external electrodes 7, 8, 9 are arranged on the side surface 2d of the piezoelectric element 2. The external electrodes 7, 8, 9 are spaced apart from each other. The external electrodes 7, 8, 9 are arranged side by side in the direction D1. The external electrode 7 is arranged on the end surface 2a side. The external electrode 7 is spaced apart from the end surface 2a. The external electrode 8 is arranged on the end surface 2b side. The external electrode 8 is spaced apart from the end surface 2b. The external electrode 9 is arranged between the external electrode 7 and the external electrode 8. The external electrode 9 is spaced apart from each of the external electrode 7 and the external electrode 8.

[0032] The external electrodes 7, 8, and 9 have the same shape as each other. The external electrodes 7, 8, and 9 are rectangular when viewed from the direction D2. Each of the external electrodes 7, 8, and 9 extends in the direction D3 so as to connect the main surface 2e and the main surface 2f. Each of the external electrodes 7, 8, and 9 is formed over the entire direction D3 of the side surface 2d. Each of the external electrodes 7, 8, and 9 is also provided at each of the ridge line portion 2g between the side surface 2d and the main surface 2e and the ridge line portion 2g between the side surface 2d and the main surface 2f.

[0033] The external electrode 4 and the external electrode 7 face each other in the direction D2. The external electrode 4 and the external electrode 7 are provided so as to overlap each other when viewed from the direction D2. The external electrode 5 and the external electrode 8 face each other in the direction D2. The external electrode 5 and the external electrode 8 are provided so as to overlap each other when viewed from the direction D2. The external electrode 6 and the external electrode 9 face each other in the direction D2. The external electrode 6 and the external electrode 9 are provided so as to overlap each other when viewed from the direction D2.

[0034] The external electrodes 4, 5, 6, 7, 8, and 9 are formed on the side surfaces 2c and 2d by, for example, a sputtering method. The external electrodes 4, 5, 6, 7, 8, and 9 may be formed by a vapor deposition method. Examples of the film structure constituting the external electrodes 4, 5, 6, 7, 8, and 9 include Cr / Ni, NiCu / Ag, SnAg, or Au. The thickness of the external electrodes 4, 5, 6, 7, 8, and 9 is, for example, 0.5 μm or more and 2.5 μm or less. The length of the external electrodes 4, 5, 6, 7, 8, and 9 in the direction D1 is, for example, 1 mm or more and 1.5 mm or less.

[0035] The external electrodes 4, 5, 6, 7, 8, and 9 may be a baked electrode layer formed by baking a conductive paste. As the conductive paste, a conductive paste containing a conductive material mainly composed of Ag can be used. The external electrodes 4, 5, 6, 7, 8, and 9 may further have a plating layer formed by electroplating. Examples of the plating layer include a Ni / Au plating layer.

[0036] As shown in FIG. 7, the piezoelectric element 2 is a laminate and has piezoelectric layers 10 to 19 laminated in the direction D3. The piezoelectric element 2 is configured by laminating the piezoelectric layers 10 to 19 in the direction D3. The lamination direction of the piezoelectric layers 10 to 19 coincides with the opposing direction of the main surfaces 2e and 2f. The piezoelectric layers 10 to 19 have a rectangular plate shape.

[0037] The piezoelectric layers 10 and 19 are disposed at both ends in the lamination direction (direction D3). The outer surface of the piezoelectric layer 10 constitutes the main surface 2e. The outer surface of the piezoelectric layer 19 constitutes the main surface 2f. The piezoelectric layers 11 to 18 are disposed between the piezoelectric layers 10 and 19 in the lamination direction. The thickness (length in the direction D3) of each of the piezoelectric layers 10 and 19 disposed at both ends in the lamination direction is thinner than the thickness (length in the direction D3) of each of the piezoelectric layers 11 to 18 disposed between the piezoelectric layers 10 and 19.

[0038] The thickness of the piezoelectric layers 10 and 19 is, for example, 0.02 mm or more and 0.03 mm or less. In the lamination direction, the thickness of the piezoelectric layers 11 to 18 is, for example, 0.12 mm or more and 0.2 mm or less. In this embodiment, the piezoelectric layers 10 and 19 have the same thickness as each other, but they may be different from each other. The plurality of piezoelectric layers 11 to 18 have the same thickness as each other, but they may be different from each other.

[0039] Each of the piezoelectric layers 10 to 19 is made of a piezoelectric ceramic material. Examples of the piezoelectric ceramic material include PZT [Pb(Zr,Ti)O 3 , PT (PbTiO 3 ), PLZT [(Pb,La)(Zr,Ti)O 3 , or barium titanate (BaTiO 3 ). Each of the piezoelectric layers 10 to 19 is a sintered body of a ceramic green sheet containing a piezoelectric ceramic material. In the actual piezoelectric element 2, each of the piezoelectric layers 10 to 19 is integrated to such an extent that the boundaries between the piezoelectric layers 10 to 19 are not visible.

[0040] The piezoelectric element 1 is disposed within the piezoelectric body 2 and includes a plurality of internal electrodes 20, 30A, 30B for generating a plurality of active regions in the piezoelectric body 2. In the piezoelectric element 1, the internal electrodes 30A, 30B as the first internal electrodes and the internal electrode 20 as the second internal electrode are alternately arranged via each piezoelectric layer 10 to 19. The first internal electrode may be either of the internal electrodes 30A, 30B. However, the piezoelectric element 1 needs to have at least one layer of the internal electrodes 30A, 30B. The plurality of internal electrodes 20, 30A, 30B are laminated such that a pair of internal electrodes 20 are positioned at both ends in the stacking direction (direction D3).

[0041] In the present embodiment, the piezoelectric element 1 includes a plurality of internal electrodes 20, a plurality of internal electrodes 30A, and a plurality of internal electrodes 30B. Specifically, the piezoelectric element 1 includes five internal electrodes 20 respectively disposed on the piezoelectric layers 10, 12, 14, 16, 18, two internal electrodes 30A respectively disposed on the piezoelectric layers 11, 15, and two internal electrodes 30B respectively disposed on the piezoelectric layers 13, 17.

[0042] The plurality of internal electrodes 20 are respectively disposed between the piezoelectric layer 10 and the piezoelectric layer 11, between the piezoelectric layer 12 and the piezoelectric layer 13, between the piezoelectric layer 14 and the piezoelectric layer 15, between the piezoelectric layer 16 and the piezoelectric layer 17, and between the piezoelectric layer 18 and the piezoelectric layer 19. The plurality of internal electrodes 30A are respectively disposed between the piezoelectric layer 11 and the piezoelectric layer 12, and between the piezoelectric layer 15 and the piezoelectric layer 16. The plurality of internal electrodes 30B are respectively disposed between the piezoelectric layer 13 and the piezoelectric layer 14, and between the piezoelectric layer 17 and the piezoelectric layer 18.

[0043] The internal electrode 30A disposed on the piezoelectric layer 11 faces the internal electrode 20 through the piezoelectric layer 11 and also faces the internal electrode 20 through the piezoelectric layer 12. The internal electrode 30B disposed on the piezoelectric layer 13 faces the internal electrode 20 through the piezoelectric layer 13 and also faces the internal electrode 20 through the piezoelectric layer 14. The internal electrode 30A disposed on the piezoelectric layer 15 faces the internal electrode 20 through the piezoelectric layer 15 and also faces the internal electrode 20 through the piezoelectric layer 16. The internal electrode 30B disposed on the piezoelectric layer 17 faces the internal electrode 20 through the piezoelectric layer 17 and also faces the internal electrode 20 through the piezoelectric layer 18.

[0044] Each of the internal electrodes 20, 30A, and 30B is made of a conductive material (e.g., Ag / Pd, Pt, Pd, or Cu, etc.). Each of the internal electrodes 20, 30A, and 30B is configured as a sintered body of a conductive paste containing the above conductive material.

[0045] FIG. 8 is a plan view showing the internal electrode 20 disposed on the piezoelectric layer 10. As shown in FIG. 8, the internal electrode 20 has a main electrode portion 20a and connection portions 20b and 20c. The main electrode portion 20a has a rectangular shape with the longitudinal direction of the piezoelectric element 2 being the longitudinal direction of the main electrode portion 20a. The main electrode portion 20a is provided spaced apart from the end faces 2a, 2b and the side faces 2c, 2d.

[0046] As also shown in FIG. 5, the connection portion 20b extends from one side face along the longitudinal direction (direction D1) of the main electrode portion 20a to the side face 2c side of the piezoelectric element 2 and is exposed at the ridge line portion 2g between the side face 2c and the main face 2e of the piezoelectric element 2. The connection portion 20b is located at the center in the longitudinal direction (direction D1) of the piezoelectric element 2. The connection portion 20c extends from the other side face along the longitudinal direction of the main electrode portion 20a to the side face 2d side of the piezoelectric element 2 and is exposed at the ridge line portion 2g between the side face 2d and the main face 2e of the piezoelectric element 2. The connection portion 20c is located at the center in the longitudinal direction of the piezoelectric element 2.

[0047] Internal electrodes 20 having the same shape as those on the piezoelectric layer 10 are also disposed on the piezoelectric layers 12, 14, 16, 18. Each internal electrode 20 faces a plurality of electrode portions 31, 32, 33, 34 (see FIGS. 9 and 10) included in the internal electrodes 30A and 30B via the piezoelectric layers 11 to 18 and functions as a common electrode.

[0048] In the internal electrode 20 disposed on the piezoelectric layers 12, 14, 16, the connection portion 20b is exposed on the side surface 2c of the piezoelectric element 2, and the connection portion 20c is exposed on the side surface 2d of the piezoelectric element 2. In the internal electrode 20 disposed on the piezoelectric layer 18, the connection portion 20b is exposed on the ridge line portion 2g between the side surface 2c and the main surface 2f of the piezoelectric element 2, and the connection portion 20c is exposed on the ridge line portion 2g between the side surface 2d and the main surface 2f of the piezoelectric element 2. The connection portion 20b of each internal electrode 20 is connected to the external electrode 6. The connection portion 20c of each internal electrode 20 is connected to the external electrode 9. The internal electrodes 20 disposed on the piezoelectric layers 10 and 18 are connected to the corresponding external electrodes 6 and 9 at the ridge line portion 2g. The internal electrodes 20 disposed on the piezoelectric layers 12, 14, 16 are connected to the external electrodes 6 and 9 at the side surfaces 2c and 2d.

[0049] FIG. 9 is a plan view showing the internal electrode 30A disposed on the piezoelectric layer 11. As shown in FIG. 9, the internal electrode 30A includes electrode portions 31, 32, 33, 34, and a connection portion 35. An internal electrode 30A having the same shape as that on the piezoelectric layer 11 is also disposed on the piezoelectric layer 15.

[0050] The electrode portions 31, 32, 33, 34 are arranged in a matrix with two rows each in the directions D1 and D2. The electrode portions 31, 33 are arranged side by side along the direction D1 on the side surface 2c side. The electrode portions 32, 34 are arranged side by side along the direction D1 on the side surface 2d side. The electrode portions 31, 34 are arranged side by side along the direction D2 on the end surface 2a side. The electrode portions 32, 33 are arranged side by side along the direction D2 on the end surface 2b side.

[0051] The electrode portions 31, 32, 33, and 34 are respectively arranged one by one in four divided regions formed by dividing the piezoelectric layer 11 into two parts in the direction D1 and the direction D2. The electrode portions 31 and 32 are located diagonally to each other. The electrode portions 33 and 34 are located diagonally to each other. The electrode portions 31 and 32 are arranged spaced apart from each other on the piezoelectric layer 11. The electrode portions 33 and 34 are connected to each other by a connection portion 36 on the piezoelectric layer 11.

[0052] The electrode portion 31 is arranged on the piezoelectric layer 11 on the corner side formed by the end face 2a and the side face 2c of the piezoelectric element 2. The electrode portion 31 has a main electrode portion 31a and a connection portion 31b. The main electrode portion 31a and the connection portion 31b are integrally formed. The main electrode portion 31a has a substantially rectangular shape and is spaced apart from each of the end faces 2a, 2b and the side faces 2c, 2d. The connection portion 31b extends from the main electrode portion 31a toward the side face 2c and is exposed on the side face 2c.

[0053] The electrode portion 32 is arranged on the piezoelectric layer 11 on the corner side that is diagonal to the corner where the electrode portion 31 is arranged, that is, on the corner side formed by the end face 2b and the side face 2d of the piezoelectric element 2. The electrode portion 32 has a main electrode portion 32a and a connection portion 32b. The main electrode portion 32a and the connection portion 32b are integrally formed. The main electrode portion 32a has a substantially rectangular shape and is spaced apart from each of the end faces 2a, 2b and the side faces 2c, 2d. The connection portion 32b extends from the main electrode portion 32a toward the side face 2d and is exposed on the side face 2d.

[0054] The electrode portion 33 is arranged on the piezoelectric layer 11 on the corner side formed by the end face 2b and the side face 2c of the piezoelectric element 2. The electrode portion 33 has a main electrode portion 33a and a connection portion 33b. The main electrode portion 33a and the connection portion 33b are integrally formed. The main electrode portion 33a has a substantially rectangular shape and is spaced apart from each of the end faces 2a, 2b and the side faces 2c, 2d. The connection portion 33b extends from the main electrode portion 33a toward the side face 2c and is exposed on the side face 2c.

[0055] The electrode portion 34 is disposed on the piezoelectric layer 11 at a corner diagonal to the corner where the electrode portion 33 is disposed, that is, on the corner side formed by the end face 2a and the side face 2d of the piezoelectric element 2. The electrode portion 34 has a main electrode portion 34a and a connection portion 34b. The main electrode portion 34a and the connection portion 34b are integrally formed. The main electrode portion 34a has a substantially rectangular shape and is spaced apart from each of the end faces 2a, 2b and each of the side faces 2c, 2d. The connection portion 34b extends from the main electrode portion 34a toward the side face 2d side and is exposed on the side face 2d.

[0056] The connection portion 35 electrically connects the electrode portion 33 and the electrode portion 34. Specifically, the connection portion 35 electrically connects the main electrode portion 33a of the electrode portion 33 and the main electrode portion 34a of the electrode portion 34. The connection portion 35 is disposed at the center in the directions D1 and D2 on the piezoelectric layer 11. The connection portion 35 is disposed between the electrode portions 31 and 32 that are diagonally disposed with a predetermined interval therebetween. The connection portion 35 is spaced apart from the electrode portions 31 and 32. The connection portion 35 extends in a direction inclined with respect to the directions D1 and D2 when viewed from the direction D3.

[0057] The lengths of the connection portions 20b, 20c, 31b, 32b, 33b, 34b in the direction D1 are, for example, equal to each other and are 0.9 mm or more and 1.4 mm or less. The lengths of the connection portions 20b, 20c, 31b, 32b, 33b, 34b in the direction D1 are equal to or less than the lengths of the external electrodes 4, 5, 6, 7, 8, 9 in the direction D1. Thereby, since the exposed portions of the internal electrodes are protected by the external electrodes, it is possible to prevent the solder used when connecting a flexible printed circuit board (FPC) or the like to the external electrodes from penetrating to the internal electrode side (solder erosion of the internal electrodes).

[0058] FIG. 10 is a plan view showing the internal electrode 30B disposed on the piezoelectric layer 13. As shown in FIG. 10, the internal electrode 30B is different from the internal electrode 30A in that it includes a connection portion 36 instead of the connection portion 35 (see FIG. 9). The connection portion 36 electrically connects the electrode portion 31 and the electrode portion 32. Specifically, the connection portion 36 electrically connects the main electrode portion 31a of the electrode portion 31 and the main electrode portion 32a of the electrode portion 32. The connection portion 36 is disposed at the center in the directions D1 and D2 on the piezoelectric layer 13. The connection portion 36 is disposed between the electrode portion 33 and the electrode portion 34 which are diagonally disposed with a predetermined interval therebetween. The connection portion 36 is separated from the electrode portion 33 and the electrode portion 34. The connection portion 36 extends in a direction inclined with respect to the directions D1 and D2 when viewed from the direction D3. An internal electrode 30B having the same shape as that on the piezoelectric layer 13 is also disposed on the piezoelectric layer 17.

[0059] In each of the internal electrodes 30A and 30B, the plurality of connection portions 31b are respectively connected to the external electrode 4 on the side surface 2c. The plurality of electrode portions 31 are electrically connected to each other via the external electrode 4. The plurality of connection portions 32b are respectively connected to the external electrode 8 on the side surface 2d. The plurality of electrode portions 32 are electrically connected to each other via the external electrode 8. The plurality of connection portions 33b are respectively connected to the external electrode 5 on the side surface 2c. The plurality of electrode portions 33 are electrically connected to each other via the external electrode 5. The plurality of connection portions 34b are respectively connected to the external electrode 7 on the side surface 2d. The plurality of electrode portions 34 are electrically connected to each other via the external electrode 7.

[0060] As described above, in the internal electrode 30A, the electrode portions 33 and 34 are connected to each other via the connection portion 35. In the internal electrode 30B, the electrode portions 31 and 32 are connected to each other via the connection portion 36. Therefore, all the electrode portions 31 and 32 are electrically connected to each other through the connection portion 36, the external electrode 4, and the external electrode 8. All the electrode portions 33 and 34 are electrically connected to each other through the connection portion 35, the external electrode 5, and the external electrode 7.

[0061] In the piezoelectric element 1 configured as described above, different potentials can be applied to the external electrodes 4, 5, and 6 by the wiring member 40. As an example, the external electrode 6 is connected to the ground, and different potentials are applied to the external electrodes 4 and 5. Thereby, a plurality of active regions that are piezoelectrically active are generated in the piezoelectric body 2. The plurality of active regions are formed corresponding to the electrode portions 31, 32, 33, and 34.

[0062] Specifically, among the piezoelectric layers 11 to 18, the regions overlapping the electrode portions 31, 32, 33, and 34 when viewed from the direction D3 become the active regions. Among the piezoelectric layers 11 to 18, between the main electrode portion 31a of the electrode portion 31 and the main electrode portion 20a of the internal electrode 20, between the main electrode portion 32a of the electrode portion 32 and the main electrode portion 20a of the internal electrode 20, between the main electrode portion 33a of the electrode portion 33 and the main electrode portion 20a of the internal electrode 20, and between the main electrode portion 34a of the electrode portion 34 and the main electrode portion 20a of the internal electrode 20, the sandwiched regions become the active regions.

[0063] The piezoelectric element 1 has two resonance modes during driving. The piezoelectric element 1 vibrates by the superposition of a longitudinal vibration mode vibrating in the direction D1 and a bending vibration mode in the direction D2. In the piezoelectric element 1, for example, among the active regions corresponding to the electrode portions 31 and 32 and the active regions corresponding to the electrode portions 33 and 34, one of the active regions is expanded and contracted along the direction D1, and the other active region is not displaced. Thereby, when viewed from the direction D3, the piezoelectric element 1 bends and vibrates in an S shape.

[0064] (Wiring member) As shown in FIGS. 1 to 3, the wiring member 40 is electrically and physically connected to the piezoelectric element 1. The wiring member 40 is, for example, a flexible printed circuit board (FPC) or a flexible flat cable (FFC). The wiring member 40 has a base 41 and a plurality of conductors 42, 43, 44. The base 41 is made of a resin such as a polyimide resin, for example. The conductors 42, 43, 44 are arranged on one surface of the base 41 so as to be spaced apart from each other in this order. The conductors 42, 43, 44 are joined to one surface of the base 41 by an adhesive layer (not shown). The conductors 42, 43, 44 are made of, for example, Cu. The conductors 42, 43, 44 may have a configuration in which a Ni plating layer and an Au plating layer are provided in this order on a Cu layer, for example.

[0065] Although not shown, a cover made of a resin such as a polyimide resin is provided on one surface of the base 41. The ends of the conductors 42, 43, 44 are exposed from the cover. The wiring member 40 is arranged such that one surface of the base 41 faces the side surface 2c of the piezoelectric element 1. The end of the conductor 42 is connected to the external electrode 4 of the piezoelectric element 1 by solder 45. The end of the conductor 43 is connected to the external electrode 6 of the piezoelectric element 1 by solder 45. The end of the conductor 44 is connected to the external electrode 5 of the piezoelectric element 1 by solder 45. The wiring member 40 is connected to a drive circuit (not shown) disposed outside the housing 80.

[0066] (Contact) The contact 46 is disposed on the end face 2a of the piezoelectric element 1. The contact 46 is attached to the end face 2a by adhesion, for example. The contact 46 has a prismatic shape, for example. The contact 46 is made of zirconia, alumina, or the like. The contact 46 is pressed against the sliding plate 204 of the moving body 200.

[0067] (Supporting member) As shown in FIGS. 1 to 3 and FIG. 11, the first support member 50 faces the moving body 200 in the direction D1 via the piezoelectric element 1 and supports the end face 2b. In FIG. 11, the external electrodes 4 to 9 are not shown. The first support member 50 is made of, for example, resin. The first support member 50 is made of, for example, plastics such as PPS (polyphenylene sulfide) and LCP (liquid crystal polymer). According to the resin-made first support member 50, the piezoelectric element 1 is hardly damaged. The first support member 50 is biased toward the end face 2b by the first biasing member 71. The first support member 50 is provided so as to be movable in a direction orthogonal to the direction D3 in accordance with the deformation of the end face 2b. The first support member 50 is formed to have the same thickness as the piezoelectric element 1. That is, the length of the first support member 50 in the direction D3 is equal to the length of the piezoelectric element 1 in the direction D3.

[0068] The first support member 50 has a support portion 51, a facing portion 52, a protruding portion 53, and a positioning portion 54. The support portion 51 has a first surface 51a and a second surface 51b that face each other in the direction D1. The first surface 51a abuts against the end face 2b and supports the end face 2b. The first surface 51a has a rectangular shape and has substantially the same shape as the end face 2b. The first biasing member 71 is in contact with the second surface 51b. In the present embodiment, the second surface 51b has the same shape as the first surface 51a.

[0069] The facing portion 52 has a first surface 52a and a second surface 52b that face each other in the direction D1. The first surface 52a faces the second support member 60 in the direction D1. The first surface 52a is continuous with the first surface 51a and constitutes the same plane as the first surface 51a. The second surface 52b is continuous with the second surface 51b and constitutes the same plane as the second surface 51b.

[0070] The protruding portion 53 protrudes in the direction D1 from the first surface 52a of the opposing portion 52. The protruding portion 53 includes a top portion 53a that abuts against the second support member 60. The top portion 53a is the abutting portion of the protruding portion 53 with the second support member 60. The first support member 50 and the second support member 60 are in point contact with each other when viewed from the direction D3. Since the top portion 53a extends in the direction D3, the first support member 50 and the second support member 60 are in line contact with each other.

[0071] The distance W2 by which the abutting portion of the protruding portion 53 with the second support member 60, that is, the top portion 53a, is spaced apart from the piezoelectric element 1 in the direction D2 is 0.3 times or more and 0.7 times or less the length W1 of the piezoelectric element 1 (piezoelectric body 2) in the direction D2. In the present embodiment, the protruding portion 53 is provided on the entire first surface 52a of the opposing portion 52. The protruding portion 53 has a tapered shape in which the width in the direction D2 gradually narrows as it moves away from the first surface 52a in the direction D1. The protruding portion 53 has a triangular prism shape with the direction D3 as the axial direction. The protruding portion 53 has a triangular shape when viewed from the direction D3. For example, the protruding portion 53 has an isosceles triangular shape with the first surface 52a as the base when viewed from the direction D3.

[0072] The positioning portion 54 defines the position of the piezoelectric element 1 in the direction D2. The positioning portion 54 is constituted by a step portion between the first surface 51a of the support portion 51 or the first surface 52a of the opposing portion 52 and the protruding portion 53. In the present embodiment, the protruding portion 53 is provided on the entire first surface 52a of the opposing portion 52, and the protruding portion 53 is adjacent to the first surface 51a of the support portion 51. Therefore, the positioning portion 54 is constituted by a step portion between the first surface 51a of the support portion 51 and the protruding portion 53. The positioning portion 54 abuts against the ridge line portion 2g between the end face 2b and the side face 2d, preventing the piezoelectric element 1 from moving to the side of the protruding portion 53 beyond the positioning portion 54 in the direction D2.

[0073] The second support member 60 faces the wiring member 40 and the later-described placement surface 82s in the direction D2 via the piezoelectric element 1 and supports the side surface 2d. The second support member 60 is a member separate from the first support member 50. The second support member 60 is made of, for example, the same material as the first support member 50. The second support member 60 is made of, for example, resin. The second support member 60 is made of, for example, plastics such as PPS (polyphenylene sulfide) and LCP (liquid crystal polymer). According to the resin-made second support member 60, it is difficult for the piezoelectric element 1 to be damaged. The second support member 60 is biased toward the side surface 2d by the second biasing member 72. The second support member 60 is provided so as to be movable in a direction orthogonal to the direction D3 in accordance with the deformation of the side surface 2d. The second support member 60 is formed with the same thickness as the piezoelectric element 1. That is, the length of the second support member 60 in the direction D3 is equivalent to the length of the piezoelectric element 1 in the direction D3.

[0074] The second support member 60 has a first surface 60a and a second surface 60b that face each other in the direction D2, a third surface 60c that faces the first support member 50 in the direction D1, and a pair of support portions 61. The first surface 60a faces the side surface 2d in the direction D2. The first surface 60a has a rectangular shape and substantially the same shape as the side surface 2d. The second biasing member 72 is in contact with the second surface 60b. In the present embodiment, the second surface 60b has the same shape as the first surface 60a. The third surface 60c faces the opposing portion 52 and the protruding portion 53 of the first support member 50 in the direction D1 and is in contact with the top 53a of the protruding portion 53.

[0075] The pair of support portions 61 are spaced apart from each other in the direction D1. The pair of support portions 61 protrude from the first surface 60a in the direction D2. The pair of support portions 61 are in contact with the piezoelectric element 1 and support the side surface 2d. That is, the second support member 60 supports the piezoelectric element 1 at two locations. One support portion 61 is disposed at one end of the first surface 60a in the direction D2 and is in contact with the external electrode 7. The other support portion 61 is disposed at the other end of the first surface 60a in the direction D2 and is in contact with the external electrode 8. The length of the support portion 61 in the direction D1 is shorter than the lengths of the external electrodes 7 and 8 in the direction D1. The protruding height (the length in the direction D2) of the support portion 61 is set in accordance with the amplitude of the piezoelectric element 1 so that the side surface 2d does not contact the first surface 60a even when the piezoelectric element 1 vibrates.

[0076] (Biasing member) The first biasing member 71 biases the first support member 50 in the direction D1 and causes it to contact the end surface 2b. The first biasing member 71 is an elastic member such as a coil spring. One end of the first biasing member 71 is in contact with the second surface 51b of the support portion 51 of the first support member 50. The first biasing member 71 is disposed so as to overlap the support portion 51 and the piezoelectric element 1 when viewed from the direction D1. Since the first biasing member 71 is not in contact with the piezoelectric element 1, it is difficult for the piezoelectric element 1 to be damaged.

[0077] The second biasing member 72 biases the second support member 60 in the direction D2 and causes it to contact the piezoelectric element 1. The second biasing member 72 is an elastic member such as a coil spring. One end of the second biasing member 72 is in contact with the second surface 60b of the second support member 60. One end of the second biasing member 72 is in contact with the central portion of the second surface 60b in the direction D1. The second biasing member 72 is located between the pair of support portions 61 in the direction D1. The second biasing member 72 is disposed at a position where it does not overlap with either of the pair of support portions 61 when viewed from the direction D2. Since the second biasing member 72 is not in contact with the piezoelectric element 1, it is difficult for the piezoelectric element 1 to be damaged.

[0078] (Housing) As shown in FIGS. 1 to 3, the housing 80 houses the piezoelectric element 1, the end portion of the wiring member 40, the first support member 50, the second support member 60, the first biasing member 71, and the second biasing member 72. The housing 80 has a bottom wall 81 and side walls 82, 83, 84, 85. The bottom wall 81 and the side walls 82, 83, 84, 85 are integrally formed. The above-described respective members such as the piezoelectric element 1 are arranged on the bottom wall 81. The bottom wall 81 faces the above-described respective members such as the piezoelectric element 1 in the direction D3.

[0079] The side walls 82, 83, 84, 85 are provided on the bottom wall 81 so as to surround the above-described respective members such as the piezoelectric element 1 when viewed from the direction D3. The side wall 82 and the side wall 83 face each other in the direction D2. The side walls 82, 83 extend in the direction D1. The side walls 84, 85 face each other in the direction D1. The side walls 84, 85 extend in the direction D2. The side wall 84 connects one end of the side wall 82 in the direction D1 and one end of the side wall 82 in the direction D1. The side wall 85 is connected to the other end of the side wall 83 in the direction D1. The side wall 85 is arranged at a distance from the side wall 82. An end portion on the end face 2a side of the piezoelectric element 1 is arranged between the side wall 85 and the side wall 82. The end face 2a is exposed from the housing 80. The contact 46 is arranged outside the housing 80.

[0080] The wiring member 40 is drawn out along the direction D3 outside the housing 80. The housing 80 may further have a lid portion that faces the bottom wall 81 in the direction D3 and covers the above-described respective members such as the piezoelectric element 1. In this case, a hole for drawing out the wiring member 40 may be provided in the lid portion.

[0081] The side wall 82 has an arrangement surface 82s on which the piezoelectric element 1 is arranged via the end portion of the wiring member 40. The arrangement surface 82s is orthogonal to the direction D2. The arrangement surface 82s faces the first support member 50 in the direction D2 with a gap (space) therebetween. Thus, it is suppressed that the side wall 82 interferes with the first support member 50. The arrangement surface 82s includes a pair of first regions R1 that come into contact with the wiring member 40 and a second region R2 that does not come into contact with the wiring member 40. The wiring member 40 is not joined to the arrangement surface 82s.

[0082] One first region R1 is provided corresponding to the conductor 42 and the external electrode 4. The other first region R1 is provided corresponding to the conductor 44 and the external electrode 5. The second region R2 is disposed between the pair of first regions R1 in the direction D1. The second region R2 is provided corresponding to the conductor 43 and the external electrode 6. When viewed from the direction (i.e., the direction D2) orthogonal to the arrangement surface 82s, the second region R2 has a size that covers the entire conductor 43 and the external electrode 6. The length of the second region R2 in the direction D1 is longer than the length of the conductor 43 in the direction D1 and the length of the external electrode 6 in the direction D1.

[0083] On the side wall 82, a notch portion 82a for exposing the bottom wall 81 is provided from the arrangement surface 82s toward the outside of the housing 80. The notch portion 82a is provided as a recess that does not penetrate the side wall 83, but may be a through hole. The depth of the recess (the length in the direction D2) is set according to the amplitude of the piezoelectric element 1 so that the wiring member 40 does not contact the bottom surface of the recess even when the piezoelectric element 1 vibrates. The second region R2 is constituted by the notch portion 82a. When viewed from the direction D1, the conductor 43 and the external electrode 6 are disposed within the notch portion 82a. The space constituted by the notch portion 82a and the bottom wall 81 is connected to the internal space of the housing 80.

[0084] The side wall 83 faces the first support member 50 and the second support member 60 in the direction D2 with a gap (space) therebetween. Therefore, it is suppressed that the side wall 83 interferes with the first support member 50 and the second support member 60 respectively. The side wall 84 faces the first support member 50 in the direction D1 with a gap (space) therebetween. Therefore, it is suppressed that the side wall 84 interferes with the first support member 50. The side wall 85 faces the second support member 60 in the direction D1 with a gap (space) therebetween. Therefore, it is suppressed that the side wall 85 interferes with the second support member 60. The side wall 85 faces the side surface 2d of the piezoelectric element 1 in the direction D2 with a gap (space) therebetween. Therefore, it is suppressed that the side wall 85 interferes with the piezoelectric element 1.

[0085] The side wall 84 is provided with a notch 84a for exposing the bottom wall 81. The notch 84a is provided as a recess that does not penetrate the side wall 84. The notch 84a and the bottom wall 81 constitute a housing portion 86 for housing the first biasing member 71. The internal space of the housing portion 86 is connected to the internal space of the housing 80. The side wall 83 is provided with a notch 83a for exposing the bottom wall 81. The notch 83a is provided as a recess that does not penetrate the side wall 83. The notch 83a and the bottom wall 81 constitute a housing portion 87 for housing the second biasing member 72. The internal space of the housing portion 87 is connected to the internal space of the housing 80.

[0086] (Operation of the piezoelectric actuator) Referring to FIG. 12, the operation of the piezoelectric actuator 100 will be described. In FIG. 12, the illustration of the wiring member 40, the first biasing member 71, the second biasing member 72, the housing 80, and the external electrodes 4 to 9 is omitted. FIG. 12(a) shows a state where no voltage (potential) is applied to the external electrodes 4, 5, 6 (see FIG. 4). FIG. 12(b) shows a state where the external electrode 6 is connected to the ground, a positive voltage is applied to the external electrode 5, and a zero voltage is applied to the external electrode 4. At this time, the active regions corresponding to the electrode portions 31, 32 (see FIGS. 9 and 10) are deformed so as to contract in the direction D1. As a result, when viewed from the main surface 2f side, the piezoelectric element 1 is deformed in an S shape. FIG. 12(c) shows a state where the external electrode 6 is connected to the ground, a negative voltage is applied to the external electrode 5, and a zero voltage is applied to the external electrode 4. At this time, the active regions corresponding to the electrode portions 33, 34 are deformed so as to extend in the direction D1. As a result, when viewed from the main surface 2f side, the piezoelectric element 1 is deformed in an inverted S shape.

[0087] A sinusoidal voltage with a positive and negative amplitude is applied to the piezoelectric element 1, and the states shown in FIGS. 12(b) and 12(c) are continuously repeated, so that the piezoelectric actuator 100 operates continuously. As a result, a force is transmitted from the contact 46 to the moving body 200 (see FIG. 1) and is converted into the movement of the moving body 200. Since the first biasing member 71 (see FIG. 1) applies a biasing force (pressing force) F1 in the direction D1 to the first support member 50, the first support member 50 moves in response to the deformation of the end face 2b, and the support portion 51 continues to contact the end face 2b. Since the second biasing member 72 (see FIG. 1) applies a biasing force (pressing force) F2 in the direction D2 to the second support member 60, the second support member 60 moves in response to the deformation of the side face 2d, and the pair of support portions 61 continue to contact the external electrodes 7 and 8.

[0088] The pair of support portions 61 are in contact with a node of the vibration of the piezoelectric element 1 (a position where no amplitude is generated in the vibration) or in the vicinity thereof. The pair of support portions 61 are not in contact with the antinode of the vibration of the piezoelectric element 1 (a position where the amplitude is maximum in the vibration). Therefore, the pair of support portions 61 can support the piezoelectric element 1 without inhibiting the vibration of the piezoelectric element 1.

[0089] The top portion 53a of the protruding portion 53 of the first support member 50 is in contact with the second support member 60 at least in the state shown in FIG. 12(a). As shown in FIGS. 12(b) and 12(c), even when the first support member 50 moves, the position of the top portion 53a hardly changes. Also, the position on the second support member 60 where the top portion 53a contacts hardly changes. Since the top portion 53a is disposed in a position where it is in contact with or slightly separated from the second support member 60, it does not interfere with the second support member 60. Therefore, in the piezoelectric actuator 100, smooth movement of the piezoelectric element 1 is realized.

[0090] As shown in FIG. 13, the piezoelectric actuator 110 according to the comparative example has a first support member 150 instead of the first support member 50. The first support member 150 is different from the first support member 50 in that the top 53a of the protruding portion 53 is in contact with the piezoelectric element 1 and is not separated from the piezoelectric element 1. In FIG. 13(a), as in FIG. 12(a), a state where no voltage (potential) is applied to the external electrodes 4, 5, 6 (see FIG. 4) is shown. In FIG. 13(b), as in FIG. 12(b), the external electrode 6 is connected to the ground, and a positive voltage is applied to the external electrode 5 and a zero voltage is applied to the external electrode 4. In FIG. 13(c), as in FIG. 12(c), the external electrode 6 is connected to the ground, and a negative voltage is applied to the external electrode 5 and a zero voltage is applied to the external electrode 4.

[0091] Also in the piezoelectric actuator 110, the top 53a of the protruding portion 53 of the first support member 50 is in contact with the second support member 60 at least in the state of FIG. 13(a). As shown in FIGS. 13(b) and 13(c), when the first support member 50 moves, the position of the top 53a changes. In particular, in the state of FIG. 13(b), the top 53a overlaps the second support member 60. This indicates that the top 53a interferes with the second support member 60.

[0092] FIG. 14 shows the relationship between the frequency of the voltage applied to the piezoelectric element 1 and the moving speed of the moving body 200 for an embodiment in which the top 53a does not interfere with the second support member 60 and a comparative example in which the top 53a interferes with the second support member 60. In the design of the comparative example with interference, the movement of the piezoelectric element 1 is inhibited, so the shape of the graph is distorted and the peak is relatively low. On the other hand, in the design of the embodiment without interference, the movement of the piezoelectric element 1 is not inhibited, so the shape of the graph is smooth and the peak is relatively high.

[0093] (Operation and Effect) As described above, in the piezoelectric actuator 100, the first support member 50 is provided to be movable in accordance with the deformation of the end face 2b of the piezoelectric element 1. The second support member 60 is provided to be movable in accordance with the deformation of the side face 2d of the piezoelectric element 1. In this way, since the first support member 50 and the second support member 60 are provided to be movable separately, the vibration of the piezoelectric element 1 is hardly inhibited. The first support member 50 includes a top portion 53a that abuts against the second support member 60. Therefore, when the piezoelectric actuator 100 is assembled, the position of the second support member 60 is easily determined uniquely with respect to the first support member 50. Thus, the piezoelectric actuator 100 can be easily assembled.

[0094] The distance W2 between the piezoelectric element 1 and the top portion 53a of the protruding portion 53 in the direction D2 is not less than 0.3 times and not more than 0.7 times the length W1 of the piezoelectric element 1 in the direction D2. Therefore, even when the first support member 50 and the second support member 60 move in accordance with the vibration of the piezoelectric element 1, interference between the first support member 50 and the second support member 60 is suppressed. Thus, inhibition of the vibration of the piezoelectric element 1 is suppressed.

[0095] The first biasing member 71 biases the first support member 50 in the direction D1 and causes it to abut against the end face 2b. Therefore, a configuration in which the first support member 50 is movable in accordance with the deformation of the end face 2b is easily realized. Since the first surface 51a of the first support member 50 is not joined to the end face 2b, inhibition of the vibration of the piezoelectric element 1 is suppressed.

[0096] The second biasing member 72 biases the second support member 60 in the direction D2 and causes it to abut against the external electrodes 7 and 8. Therefore, a configuration in which the second support member 60 is movable in accordance with the deformation of the side face 2d is easily realized. Since each support portion 61 of the second support member 60 is not joined to the piezoelectric element 1, inhibition of the vibration of the piezoelectric element 1 is suppressed.

[0097] Since the second support member 60 supports the side surface 2d by the pair of support portions 61, the side surface 2d can be reliably supported. The second biasing member 72 is positioned between the pair of support portions 61 in the direction D2. Therefore, the second biasing member 72 can impart a biasing force to the pair of support portions 61 in a well-balanced manner. Since the two-point support of the side surface 2d can be realized by one second biasing member 72, it is efficient.

[0098] The first support member 50 has a positioning portion 54 that defines the position of the piezoelectric element 1 in the direction D2. Therefore, the piezoelectric element 1 can be suppressed from moving in the direction D2 on the first support member 50.

[0099] When viewed from the direction D2 orthogonal to the placement surface 82s, the second region R2 has a size that covers the entire external electrode 6. Therefore, it is reliably suppressed that the external electrode 6 interferes with the placement surface 82s via the wiring member 40. Thus, vibration can be reliably transmitted to the moving body 200.

[0100] The pair of first regions R1 are provided corresponding to the external electrodes 4 and 5. Therefore, since the wiring member 40 and the placement surface 82s are in a state close to point contact, the position where the piezoelectric element 1 is pressed is accurately determined and the vibration is stabilized.

[0101] The second region R2 is arranged between the pair of first regions R1. The external electrodes 4 and 5 protrude from the side surface 2c of the piezoelectric body 2 by the thickness thereof. Therefore, the piezoelectric element 1 is supported by the placement surface 82s in the pair of first regions R1 via the wiring member 40. By being supported at two locations in this way, the piezoelectric element 1 is stably arranged on the placement surface 82s without tilting or rattling.

[0102] The second region R2 is constituted by a notch portion 82a which is a recess or a through hole provided in the placement surface 82s. Therefore, a configuration in which the second region R2 does not contact the wiring member 40 can be easily realized.

[0103] [Second Embodiment] As shown in FIG. 15, the piezoelectric actuator 100A according to the second embodiment is different from the piezoelectric actuator 100 in that it includes a first support member 50A and a second support member 60A. The top 53a of the protruding portion 53 in the first support member 50A has a rounded curved surface (R surface or C surface), and abuts against the second support member 60A with the curved surface. Thereby, breakage of the protruding portion 53 is suppressed. Also, breakage of the third surface 60c of the second support member 60A that abuts against the top 53a is suppressed. Each of the pair of support portions 61 of the second support member 60A has a rounded curved surface (R surface or C surface), and abuts against the external electrodes 7 and 8 with the curved surface. Thereby, breakage of the pair of support portions 61 is suppressed. Also, breakage of the external electrodes 7 and 8 that abut against the pair of support portions 61 is suppressed.

[0104] [Third Embodiment] As shown in FIGS. 16 and 17, the piezoelectric actuator 100B according to the third embodiment is different from the piezoelectric actuator 100 in that it includes a first support member 50B and a second support member 60B. The first support member 50B is rotatably connected to the second support member 60B by a connecting shaft 90 provided on the protruding portion 53. The protruding portion 53 and the end portion on the third surface 60c side of the second support member 60B are arranged so as to overlap each other when viewed from the direction D3. The connecting shaft 90 is inserted through a through hole provided in the protruding portion 53 and is inserted into a hole provided in the end portion on the third surface 60c side of the second support member 60B. In the piezoelectric actuator 100B, since the first support member 50B and the second support member 60B are connected by the connecting shaft 90, the position of the second support member 60B is surely determined with respect to the first support member 50B. Therefore, assembly is easier.

[0105] As described with reference to FIG. 12, in the piezoelectric actuator 100, even when the first support member 50 and the second support member 60 move due to the vibration of the piezoelectric element 1, the contact positions of the first support member 50 and the second support member 60 hardly change. In the piezoelectric actuator 100B, since the connecting shaft 90 is provided at a portion where the positions of the first support member 50B and the second support member 60B hardly change, the vibration of the piezoelectric element 1 is not inhibited.

[0106] The embodiments of the present invention have been described above. However, the present invention is not necessarily limited to the above-described embodiments, and various modifications can be made without departing from the gist thereof.

[0107] [Modification Example] In the above embodiment, an example has been described in which the piezoelectric element 2 is formed by laminating the piezoelectric layers 10 to 19. However, the number of laminated piezoelectric layers is not limited to this, and is appropriately set according to the design. In the above embodiment, a pair of internal electrodes 20 are arranged at the laminated ends, but internal electrodes 30A and 30B may be arranged. The internal electrodes 30A and 30B may be exposed at the ridge line portion 2g. The thicknesses of the piezoelectric layers 10 to 19 may be equal to each other. Each ridge line portion 2g and each corner portion 2h do not necessarily have a rounded chamfered shape.

[0108] The first surface 51a of the first support member 50 may be joined to the end surface 2b. The second biasing member 72 may be arranged at a position overlapping the support portion 61 when viewed from the direction D2. The piezoelectric actuator 100 may include a pair of second biasing members 72. In this case, the pair of second biasing members 72 may be arranged so as to face the pair of support portions 61 in the direction D2. That is, one of the second biasing members 72 may face one of the support portions 61 in the direction D2, and the other second biasing member 72 may face the other support portion 61 in the direction D2.

[0109] The pair of support portions 61 may be in contact with the side surface 2d. That is, the pair of support portions 61 may be in contact with a portion of the side surface 2d where the external electrodes 7 to 9 are not provided. The pair of support portions 61 may be in contact with, for example, a portion located between the external electrodes 7 and 9 on the side surface 2d, and a portion located between the external electrodes 8 and 9.

[0110] The above embodiments and modification examples may be appropriately combined.

Explanation of Reference Numerals

[0111] 1... Piezoelectric element, 2... Piezoelectric body, 2a, 2b... End faces, 2c, 2d... Side faces, 2e, 2f... Main faces, 50, 50A, 50B... First support members, 51... Support portion, 52... Opposing portion, 53... Protrusion, 53a... Top portion, 54... Positioning portion, 60, 60A, 60B... Second support members, 71... First biasing member, 72... Second biasing member, 80... Housing, 82s... Arrangement surface, 90... Connecting shaft, 100, 100A, 100B... Piezoelectric actuator.

Claims

1. A piezoelectric actuator for driving an object to be driven, a piezoelectric element having a piezoelectric body and a first external electrode disposed on the piezoelectric body; A wiring member connected to the first external electrode; a housing having a placement surface on which the piezoelectric element is placed via the wiring member; a support member supporting the piezoelectric element, the arrangement surface includes a first region in contact with the wiring member, and a second region provided in correspondence with the first external electrode and not in contact with the wiring member; Piezoelectric actuator.

2. When viewed from a direction perpendicular to the arrangement surface, the second region has a size sufficient to cover the entire first external electrode.

2. The piezoelectric actuator according to claim 1.

3. The piezoelectric element further includes a second external electrode disposed on the piezoelectric body, The first region is provided to correspond to the second external electrode.

3. The piezoelectric actuator according to claim 1 or 2.

4. The second region is disposed between a pair of the first regions. The piezoelectric actuator according to any one of claims 1 to 3.

5. The second region is configured by a recess or a through hole provided on the arrangement surface. The piezoelectric actuator according to any one of claims 1 to 4.

6. the piezoelectric element has a rectangular shape and includes a pair of main surfaces facing each other, a first end face and a second end face facing each other in a long-side direction of the pair of main surfaces, and a first side face and a second side face facing each other in a short-side direction of the pair of main surfaces, the support member has a first support member that faces the driven object in the long side direction via the piezoelectric element and supports the first end surface, and a second support member that faces a placement surface of a housing on which the piezoelectric element is placed in the short side direction via the piezoelectric element and supports the first side surface, The first support member is provided to be movable in response to deformation of the first end surface, The second support member is provided to be movable in response to deformation of the first side surface. The piezoelectric actuator according to any one of claims 1 to 5.

7. The first support member has a facing portion facing the second support member in the long side direction, and a protruding portion protruding from the facing portion in the long side direction and abutting against the second support member.

7. The piezoelectric actuator according to claim 6.

8. a distance between the contact portion of the protrusion with the second support member and the piezoelectric element in the short side direction is 0.3 to 0.7 times the length of the piezoelectric element in the short side direction; 8. The piezoelectric actuator according to claim 7.

9. a first biasing member that biases the first support member in the long side direction to bring the first support member into contact with the piezoelectric element; A second biasing member biases the second support member in the short side direction to contact the piezoelectric element. The piezoelectric actuator according to any one of claims 6 to 8.

10. a first biasing member that biases the first support member in the long side direction to bring the first support member into contact with the piezoelectric element; a second biasing member that biases the second support member in the short side direction to contact the piezoelectric element, The second support member has a pair of support portions spaced apart from each other in the long side direction and supporting the first side surface, The second biasing member is located between the pair of support portions in the long side direction. The piezoelectric actuator according to any one of claims 6 to 8.

11. The second support member has a pair of support portions spaced apart from each other in the long side direction and supporting the first side surface. The piezoelectric actuator according to any one of claims 6 to 9.

12. The first support member has a positioning portion that determines a position of the piezoelectric element in the short side direction. The piezoelectric actuator according to any one of claims 6 to 11.

Images