JP2017139937A - Piezoelectric drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric drive device in which a piezo electric element is downsized, and the piezo electric element and a weight member are easily coupled and wired while having an excellent mechanical strength, and reducing a loss of deviation of the piezo electric element.SOLUTION: A piezoelectric drive device 10 moves a movement member 14 movably engaged to a shaft 16 along an axial direction by driving a lamination piezo electric element 20. A first outer part electrode 26 includes a first outer part connection part 26a which is formed to a Z axial bottom end surface. On an opposite surface of a weight member 30 facing to the bottom end surface of an element 20, a weight side metal surface 36 is formed. A weight side circuit pattern 36 is metal-connected to a first outer part connection part 26a. A metal surface 18 is formed on the bottom end surface of the shaft 16 facing to a Z axial direction top end surface, and is metal-coupled to a second outer part connection part 27a.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a piezoelectric driving device for vibrating a laminated piezoelectric element and moving a moving body such as a lens frame engaged with a shaft in an axial direction.

  As a piezoelectric driving device for driving a lens frame in the axial direction using a laminated piezoelectric element, for example, the one shown in Patent Document 1 is known. In the piezoelectric drive device disclosed in Patent Document 1, a connection terminal is attached to a non-expandable portion of the piezoelectric element, and a wiring member is connected to the connection terminal to supply power to the piezoelectric element.

  In the invention shown in Patent Document 1, the non-stretchable portion of the piezoelectric element is made to function as a weight portion. However, in order for the non-expandable portion of the piezoelectric element to function as a weight portion, it is necessary to make the non-expandable portion relatively large along with the miniaturization of the piezoelectric element, which is against the demand for downsizing of the piezoelectric element. .

  Therefore, apart from the piezoelectric element, it is necessary to connect a weight member having a specific gravity larger than that of the piezoelectric element. In that case, conventionally, the work of connecting the wiring member to the connection terminal of the piezoelectric element and the work of connecting the piezoelectric element and the weight member are required. It was desired.

JP 2007-274777 A

  The present invention has been made in view of such a situation, and the object thereof is that the piezoelectric element can be miniaturized, the piezoelectric element and the weight member can be easily connected and wired, and excellent in mechanical strength. It is an object of the present invention to provide a piezoelectric driving device with little loss of displacement of a piezoelectric element.

In order to achieve the above object, a piezoelectric drive device according to the present invention includes:
A laminated piezoelectric element having an internal electrode laminated with a piezoelectric layer interposed therebetween, and a pair of first external electrode and second external electrode electrically connected to the internal electrode;
A weight member attached to one first end face in the stacking direction of the stacked piezoelectric element;
A shaft attached to the other second end face in the stacking direction of the stacked piezoelectric element,
A piezoelectric driving device that moves along the axial direction a moving member that is movably engaged with the shaft in the axial direction by driving the laminated piezoelectric element,
The first external electrode has a first external connection formed on the first end face;
The second external electrode has a second external connection portion formed on the second end face;
A weight-side metal surface is formed on the opposite surface of the weight member facing the first end surface, and the weight-side metal surface is metal-bonded to the first external connection portion,
A shaft-side metal surface is formed on an opposing surface of the shaft facing the second end surface, and the shaft-side metal surface is metal-bonded to the second external connection portion.

  In the piezoelectric driving device according to the present invention, lead wires, metal terminals, and the like are not connected to the multilayer piezoelectric element via solder or the like. The power supply to the multilayer piezoelectric element according to the present invention includes the metal coupling between the weight side metal surface of the weight member and the first external connection portion of the multilayer piezoelectric element, and the shaft side metal surface of the shaft and the first of the multilayer piezoelectric element. 2 It is performed by metal bonding with an external connection part. The portion where these metal bonds are performed is a portion to which a reverse polarity voltage for driving the multilayer piezoelectric element is applied, and at the same time, the connection between the multilayer piezoelectric element and the weight member, the multilayer piezoelectric element, Also serves as a connection with the shaft.

  Therefore, it is possible to simultaneously ensure a strong connection between the multilayer piezoelectric element and the weight member, a strong connection between the multilayer piezoelectric element and the shaft, and a wiring for electrical connection to the multilayer piezoelectric element. . Therefore, even if the size of the multilayer piezoelectric element is reduced, the connection between the multilayer piezoelectric element and the weight member is facilitated, the connection between the multilayer piezoelectric element and the shaft is facilitated, and the power to the multilayer piezoelectric element is further increased. Wiring for supply becomes easy. Also, these automatic operations are facilitated.

  Furthermore, since the wiring members such as lead wires and metal terminals are not connected to the multilayer piezoelectric element separately from the weight and the shaft, no sudden force acts on the wiring member, and the connecting portion with the wiring member There is no disconnection. Further, since at least a part (or all) of the shaft and at least a part (or all) of the weight member also serve as wiring, it contributes to a reduction in the number of parts.

  Furthermore, since the laminated piezoelectric element and the weight member are connected by metal bonding, and the laminated piezoelectric element and the shaft are connected by metal bonding, their bonding strength is improved. Further, compared to the case where the multilayer piezoelectric element and the shaft or the multilayer piezoelectric element and the weight member are connected with an adhesive, there is no displacement absorption at the adhesive portion, and the displacement force of the multilayer piezoelectric element is directly Is transmitted to the weight and the shaft, and the driving force is improved (there is little loss of displacement).

  Preferably, the weight member is made of metal. By configuring the weight member with metal, the density of the weight member is increased, which contributes to the miniaturization of the piezoelectric driving device. In addition, by configuring the weight member with metal, the outer surface of the weight member forms the weight-side metal surface itself, and it is not necessary to form a metal surface separately from the weight member. When the weight member is made of a material other than metal, the weight side metal surface for metal bonding with the laminated piezoelectric element may be formed of a circuit pattern such as a metal film.

  Preferably, a shaft press is in contact with the shaft, and electric power can be supplied to the shaft-side metal surface through the shaft and the shaft press. For example, in a lens driving device or the like, the shaft retainer is a necessary component, and power can be supplied to the stacked piezoelectric element via the shaft-side metal surface without increasing the number of components.

  When the shaft is made of metal, the shaft-side metal surface can be easily formed using the outer surface of the shaft itself. In that case, the shaft itself becomes an electrical conduction path. The same applies when the shaft is a conductive member other than metal. However, in order to form the metal surface, a circuit pattern may be formed with a metal film or the like at a predetermined position of the shaft. This is the same when the shaft is an insulator.

FIG. 1 is a schematic cross-sectional view of a lens driving device according to an embodiment of the present invention. FIG. 2 is an exploded perspective view of the lens driving device shown in FIG.

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

  As shown in FIG. 1, a piezoelectric driving device 10 according to an embodiment of the present invention includes a lens frame (moving body) 14 that holds a lens 12 attached to, for example, a camera, an axial direction of a shaft 16 (Z-axis direction). ) Along the lens drive device. The lens frame 14 is attached to a predetermined position in the axial direction of the shaft 16 by friction so as to be movable in the axial direction.

  The shaft 16 vibrates when the laminated piezoelectric element 20 expands and contracts in the Z-axis direction, and the vibration causes the lens frame 14 to move to one or the other in the Z-axis direction with respect to the shaft 16. The amount of movement in which direction is determined by the shape of the voltage waveform applied to the laminated piezoelectric element 20 and the application time.

  The piezoelectric driving device 10 includes a shaft 16, a stacked piezoelectric element 20, and a weight member 30. The shaft 16 generally has a cylindrical shape, and is made of, for example, a carbon reinforced plastic, a steel material such as stainless steel, or a non-ferrous metal such as aluminum. The shaft 16 is inserted into and engaged with a through hole 14a formed in the lens frame 14, and holds the lens frame 14 so as to be movable in the Z-axis direction.

  The multilayer piezoelectric element 20 includes an element body 21, a first external electrode 26, and a second external electrode 27 that have a substantially prismatic shape (a quadrangular prism in this embodiment). Inside the element main body 21, first and second internal electrodes 24 and 25 are alternately stacked with the piezoelectric layer 22 interposed therebetween. The portions of the piezoelectric layer 26 in which the first internal electrodes 24 and the second internal electrodes 25b are alternately stacked serve as active portions that expand and contract in the Z-axis direction, and are formed at both ends of these stacked portions in the Z-axis direction. The portion of the piezoelectric layer only becomes an inactive portion. The external shape of the element body 21 is not limited to a prismatic shape, and may be a cylindrical shape, an elliptical columnar shape, or other shapes.

  The first external electrode 26 formed on the outer surface of the element body 21 includes a first external connection portion 26a and a first side electrode portion 26b, which are integrally formed. The second external electrode 27 insulated from the first external electrode 26 and formed on the outer surface of the element body 21 includes a second external connection portion 27a and a second side electrode portion 27b, which are integrally formed. It is formed.

  The first side electrode part 26b is formed on one of the pair of side surfaces facing the X-axis direction of the element body 21, and is connected only to the first internal electrode 24 of the element body 21, and the second internal It is not connected to the electrode 25. The first side electrode 26 b extends to the lower end in the Z-axis direction on the side surface of the element body 21, and is formed on the lower end surface (first end face) in the Z-axis direction of the element body 21. Connected continuously.

  The second side surface electrode portion 27b is formed on the other of the pair of side surfaces facing the X-axis direction of the element body 21 and is connected only to the second internal electrode 25 of the element body 21. It is not connected to the electrode 24. The second side surface electrode 27 b extends to the upper end in the Z-axis direction on the side surface of the element body 21, and the second external connection portion 27 a formed on the upper end surface (second end surface) in the Z-axis direction of the element body 21. Connected continuously. The first external connection portion 26a and the second external connection portion 27a are formed to face each other at both ends in the Z-axis direction of the multilayer piezoelectric element 20.

  As shown in FIG. 2, in this embodiment, the external electrodes 26 and 27 are not formed on the pair of side surfaces facing the Y-axis direction of the element body 21, but insulation between the external electrodes 26 and 27 is ensured. For example, these side surfaces may be formed continuously. In the drawing, the X axis, the Y axis, and the Z axis are perpendicular to each other, and the Z axis coincides with the stacking direction of the internal electrodes 24 and 25 and also coincides with the axial direction of the shaft 16.

  A resin layer for preventing migration may be formed on the side surface of the element body 21 shown in FIG. 2 where the external electrodes 26 and 27 are not formed (side surface facing the Y-axis direction). . The resin layer may cover the side electrode portions 26b and / or 27b.

  Examples of the conductive material constituting the first internal electrode 24 and the second internal electrode 25 include noble metals such as Ag, Pd, Au, and Pt and alloys thereof (Ag—Pd, etc.), or base metals such as Cu and Ni. Although these alloys etc. are mentioned, it is not specifically limited.

  The conductive material constituting the first external electrode 26 and the second external electrode 27 is not particularly limited, and the same material as the conductive material constituting the internal electrode can be used. The first external electrode 26 and the second external electrode 27 are formed on the outer surface of the element body 21 by, for example, baking a conductive paste, and the various metal plating layers and sputter layers are formed on the surface. May be. The thickness of the external electrodes 26 and 27 is not particularly limited, but is preferably 0.5 to 50 μm.

  The material of the piezoelectric layer 22 is not particularly limited as long as the material exhibits a piezoelectric effect or a reverse piezoelectric effect, and examples thereof include PbZrx Ti1-x O3 and BaTiO3. Moreover, the component for characteristic improvement etc. may contain, The content should just determine suitably according to a desired characteristic.

  As shown in FIG. 2, in the piezoelectric driving device 10, the upper surface of the weight member 30 in the Z-axis direction is disposed so as to face the lower end surface of the element body 21 in the Z-axis direction. The weight member 30 has a rectangular parallelepiped shape as a whole, but the shape is not particularly limited.

  The weight member 30 preferably includes a metal material having a relatively large specific gravity such as tungsten so as to suitably function as an inertial body for giving displacement to the shaft 16, but is not particularly limited. For example, iron, steel, You may comprise with conductors, such as a noble metal and aluminum. When the weight main body 32 is made of metal, the outer surface of the weight main body 32 is a metal surface.

  In particular, a weight-side metal surface 36 to which the first external connection portion 26 a is metal-bonded is formed on the facing surface of the weight member 30 corresponding to the lower surface in the Z-axis direction of the multilayer piezoelectric element 20. Further, the lower surface of the weight member 30 in the Z-axis direction is also a metal surface, and is metal-bonded to the frame-side circuit pattern 46 formed on the surface 42 of the frame 40.

  The weight member 30 may be made of an insulating material such as plastic or ceramic. In that case, it is necessary to form the weight side metal surface 36 to which the first external connection portion 26a is metal-bonded on the facing surface of the weight member 30 corresponding to the lower surface of the multilayer piezoelectric element 20 in the Z-axis direction. In addition, the lower surface of the weight member 30 in the Z-axis direction is also a metal surface, and it is necessary to electrically connect them. Therefore, a circuit pattern made of a metal film or the like may be formed on the surface of the insulating weight member 30.

  Further, when the weight member 30 is made of metal, the outer surface other than the weight side metal surface 36 and the weight mounting surface 38 which are metal surfaces may be covered with an insulating film.

  In the present embodiment, the method for metal bonding is not particularly limited, and solid-phase bonding techniques such as ultrasonic bonding, solid-phase diffusion bonding, and friction bonding, welding bonding using laser, pulse heat, and the like are used.

  The frame 40 may be a fixing member to which a case surrounding the lens holding frame 14 shown in FIG. On the surface of the frame 40, a frame side circuit pattern 46 and a lead pattern 46a integrally connected thereto are formed. As shown in FIG. 1, the drive circuit 50 is connected to the lead pattern 46 a of the frame side circuit pattern 46. The lead pattern 46a is connected to the drive circuit 50 shown in FIG. These patterns 46 and 46a can be formed on the surface of the frame 42 made of an insulating material by a metal paste baking method, a plating method, a sputtering method, or the like.

  In the present embodiment, as shown in FIG. 1, the laminated piezoelectric element 20 and the shaft 16 are joined to the shaft-side metal surface 18 formed on the lower surface in the Z-axis direction of the shaft 16 and the laminated piezoelectric element 20. This is performed by metal bonding with the second external connection portion 27a formed on the upper surface in the Z-axis direction. Metal bonding is performed by the method described above. The metal bonding at each site may be performed separately or at the same time. In addition, when the shaft 16 is made of metal, the shaft-side metal surface 18 is the lower surface of the shaft 16 in the Z-axis direction. A metal film is formed so that the metal surface 18 is formed on the lower surface.

  A shaft presser 47 is in contact with the shaft 16 in the middle of the shaft 16 in the Z-axis direction at a position that does not interfere with the movement of the lens frame 14 in the Z-axis direction. The shaft retainer 47 has functions such as support of the shaft 16 and positioning of the shaft 16, and is generally attached to the lens driving device. In the present embodiment, the shaft holder 47 itself is made of a conductive member, or the shaft 47 itself is made of an insulating member, and a circuit pattern or a pattern is formed so that a conductive path is formed at the contact portion with the shaft 16. A conductive member is provided.

  When the shaft presser 47 is made of a conductive member, for example, a wire 47a is connected to the shaft presser 47. The wiring 47 a is connected to the drive circuit 50. At least a part of the wiring 47a may be constituted by a lead wire, but it is preferably constituted by a circuit pattern formed on the surface of the frame 40, for example. When the shaft presser 47 is made of an insulating member, the wiring 47 a is connected to a circuit pattern formed on the surface of the shaft presser 47. The circuit pattern formed on the surface of the shaft retainer 47 is electrically connected to the surface of the shaft 16.

  If the shaft 16 is composed of a conductive member, one voltage from the drive circuit 50 is transmitted to the shaft presser 47 itself or its circuit pattern via the wiring 47 a, and from there through the shaft 16 and the metal surface 18. To the second external electrode 27. When the shaft 16 is made of an insulating member, it is transmitted to the second external electrode 27 through the circuit pattern formed on the surface of the shaft 16 and the metal surface 18. The other voltage from the drive circuit 50 is transmitted to the first external electrode 26 through the lead pattern 46a, the frame side circuit pattern 46, and the weight member 30.

  The drive circuit 50 is a circuit for applying a drive voltage to the multilayer piezoelectric element 20. The drive circuit 50 may be attached to the frame 40 or may be provided separately from the frame 40. The method for forming the patterns 46, 46a or other circuit patterns on the frame 40 is not particularly limited, and for example, a method for forming a circuit pattern on a general circuit board is used.

  The voltage waveform output by the drive circuit 50 is not particularly limited. For example, the drive circuit 50 outputs a voltage waveform having a sawtooth waveform, thereby exceeding the deformation amount of the laminated piezoelectric element 20 and the displacement amount of the shaft 16 associated therewith. The amount of movement can be generated in the lens frame 14 as a moving member.

  In the piezoelectric driving device 10 according to the present embodiment, lead wires, metal terminals, and the like are not connected to the multilayer piezoelectric element 20 via solder or the like. Electric power is supplied to the laminated piezoelectric element 20 by metal bonding between the weight side metal surface 36 and the first external connection portion 26 and metal bonding between the shaft side metal surface 18 and the second external connection portion 27. The portion where these metal bonds are performed is a portion to which a reverse polarity voltage for driving the multilayer piezoelectric element 20 is applied, and at the same time, the connection between the multilayer piezoelectric element 20 and the weight member 30, and the multilayer type It also serves as a connection between the piezoelectric element 20 and the shaft 16.

  Therefore, the strong connection between the multilayer piezoelectric element 20 and the weight member 30, the strong connection between the multilayer piezoelectric element 20 and the shaft 16, and the wiring for electrical connection to the multilayer piezoelectric element 20 are simultaneously performed. Can be secured. Therefore, even if the multilayer piezoelectric element 20 is reduced in size, the multilayer piezoelectric element 20 and the weight member 30 can be easily connected, and the multilayer piezoelectric element 20 and the shaft 16 can be easily connected. Wiring for supplying power to the element 20 is facilitated. Also, these automatic operations are facilitated.

  Furthermore, since a wiring member such as a lead wire or a metal terminal is not connected to the laminated piezoelectric element 20 separately from the weight member, no sudden force is applied to the wiring member, and the connection portion with the wiring member is not affected. There is no disconnection. Further, since at least a part (or all) of the shaft 16 and at least a part (or all) of the weight member 30 also serve as wiring, it contributes to the reduction of the number of parts.

  Furthermore, since the laminated piezoelectric element 20 and the weight member 30 are connected by metal bonding, and the laminated piezoelectric element 20 and the shaft 16 are connected by metal bonding, their bonding strength is improved. Further, compared to the case where these are connected by an adhesive, there is no displacement absorption at the adhesive portion, and the displacement force of the laminated piezoelectric element 20 is directly transmitted to the weight member 30 and the shaft 16 to improve the driving force. (Displacement loss is small).

  In the present embodiment, the weight member 30 is made of metal, so that the density of the weight member 30 is increased, which contributes to the miniaturization of the piezoelectric driving device 10. Further, by configuring the weight member 30 with metal, the outer surface of the weight member 30 forms the weight-side metal surface itself, and it is not necessary to form a metal surface separately from the weight member 30. When the weight member 30 is made of a material other than metal, the weight side metal surface for metal bonding with the stacked piezoelectric element may be formed of a circuit pattern such as a metal film.

  Further, a shaft presser 47 is in contact with the shaft 16, and electric power can be supplied to the shaft side metal surface through the shaft 16 and the shaft presser 47. For example, in a lens driving device or the like, the shaft retainer is a necessary component, and power can be supplied to the laminated piezoelectric element 20 via the shaft-side metal surface 18 without increasing the number of components.

  Furthermore, in this embodiment, when the shaft 16 is a metal, the shaft side metal surface 18 can be easily formed using the outer surface of the shaft 16 itself. In that case, the shaft 16 itself becomes an electrical conduction path. The same applies when the shaft 16 is a conductive member other than metal. However, in order to form the metal surface 18, a circuit pattern may be formed with a metal film or the like at a predetermined position of the shaft 16. The same applies to the case where the shaft 16 is an insulator.

  In the present embodiment, the weight member 30 is coupled to the frame 40, and at the same time, the circuit pattern 46 formed on the frame 40 and the weight member 30 can be electrically connected. These connections can also be made by metal bonding.

  The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.

  For example, in the above-described embodiment, ultrasonic bonding is used as a method for metal bonding, but other methods may be used. Examples of other methods for metal bonding include diffusion bonding, friction bonding, laser, and pulse heat.

  In the above-described embodiment, the driving device that moves the lens frame 14 holding the lens 12 along the shaft is illustrated as the piezoelectric driving device 10. However, the moving body may be a member other than the lens frame. good. Examples of the moving body include a leaf spring called a slider.

  Furthermore, in the present embodiment, the multilayer piezoelectric element 20 and the weight member 30 may be metal-bonded, and the multilayer piezoelectric element 20 and the shaft 16 may be metal-bonded. Other than that. For example, the weight member 30 and the frame 40 may be bonded by a method other than metal bonding, for example, solder bonding or bonding (including a conductive adhesive).

DESCRIPTION OF SYMBOLS 10 ... Piezoelectric drive device 12 ... Lens 14 ... Lens frame 14a ... Through-hole 16 ... Shaft 18 ... Shaft side metal surface 20 ... Laminated piezoelectric element 21 ... Element main body 22 ... Piezoelectric layer 24 ... First internal electrode 25 ... Second internal Electrode 26 ... 1st external electrode 26a ... 1st external connection part 26b ... 1st side electrode part 27 ... 2nd external electrode 27a ... 2nd external connection part 27b ... 2nd side electrode part 30 ... Weight member 36 ... Weight side metal Surface 38 ... Weight mounting surface 40 ... Frame 42 ... Surface 46 ... Frame side circuit pattern 46a ... Lead pattern 47 ... Shaft retainer 50 ... Drive circuit

Claims (3)

A laminated piezoelectric element having an internal electrode laminated with a piezoelectric layer interposed therebetween, and a pair of first external electrode and second external electrode electrically connected to the internal electrode;
A weight member attached to one first end face in the stacking direction of the stacked piezoelectric element;
A shaft attached to the other second end face in the stacking direction of the stacked piezoelectric element,
A piezoelectric driving device that moves along the axial direction a moving member that is movably engaged with the shaft in the axial direction by driving the laminated piezoelectric element,
The first external electrode has a first external connection formed on the first end face;
The second external electrode has a second external connection portion formed on the second end face;
A weight-side metal surface is formed on the opposite surface of the weight member facing the first end surface, and the weight-side metal surface is metal-bonded to the first external connection portion,
A shaft-side metal surface is formed on an opposing surface of the shaft facing the second end surface, and the shaft-side metal surface is metal-bonded to the second external connection portion. apparatus.   The piezoelectric driving device according to claim 1, wherein the weight member is made of metal.   3. The piezoelectric driving device according to claim 1, wherein a shaft press is in contact with the shaft, and electric power can be supplied to a metal surface of the shaft through the shaft and the shaft press.

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