JP2013156296A - Lens driving device and piezoelectric actuator unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens driving device capable of efficiently transmitting driving force from a piezoelectric actuator to a lens holder, and capable of accurately driving the lens holder.SOLUTION: A lens driving device is equipped with a lens holder, a piezoelectric actuator 50, and a back surface member 70. An element 51 of the piezoelectric actuator 50 has node points N1 and N2 in which displacement in an opposite direction of main surfaces 50a and 50b is minimum, and a node point N3 in which displacement in the opposite direction is minimum and displacement in a direction orthogonal to the opposite direction is minimum, and which is positioned between the node points N1 and N2. Protrusions 71-73 of the back surface member 70 are pressed against the main surface 50b at positions respectively corresponding to the node points N1-N3 when viewed from the opposite direction. Resistance generated between the protrusions 71 and 72, and the main surface 50b is lower than resistance generated between the protrusion 73 and the main surface 50b.

Description

  The present invention relates to a lens driving device and a piezoelectric actuator unit for driving a camera lens mounted on, for example, a mobile phone.

  As a kind of piezoelectric actuator, a vibrating body having first and second main surfaces facing each other and having a piezoelectric element, a friction member provided on the first main surface and for applying a driving force to a driven body, And a support member disposed on the second main surface and in the vicinity of a vibration node of the vibrating body is known (see Patent Document 1). In the piezoelectric actuator of Patent Document 1, it is difficult to inhibit the vibration of the vibrating body by disposing the support member near the node where the vibration of the vibrating body is minimized.

JP 2009-106154 A

  However, when the support member is disposed only near the center of the second main surface in the longitudinal direction (see FIG. 1 of Patent Document 1), it is difficult to support the vibrating body in a balanced manner in the longitudinal direction. There is a possibility that the contact of the friction member with the lens holder may be uneven. Further, when the support member is disposed near the node of the bending vibration in the thickness direction of the vibrating body (see FIG. 3 of Patent Document 1), the vibration of the vibrating body in the thickness direction is difficult to inhibit, The vibration of the vibrating body in the direction was obstructed. Therefore, in the conventional piezoelectric actuator, it is difficult to appropriately transmit the driving force to the driven body, and there is a possibility that a loss occurs in the transmission of the driving force from the piezoelectric actuator to the driven body. Further, since the operation of the piezoelectric actuator is not properly transmitted to the driven body, it is difficult to drive the driven body with high accuracy.

  Accordingly, an object of the present invention is to provide a lens driving device and a piezoelectric actuator unit that can efficiently transmit a driving force from a piezoelectric actuator to a driven body and can drive the driven body with high accuracy. .

  A lens driving device according to the present invention has a lens holder for holding a lens and first and second main surfaces facing each other, and the lens holder is moved so as to move the lens holder in the optical axis direction of the lens. A piezoelectric actuator for applying a driving force; and a back member positioned on the second main surface side; the piezoelectric actuator is an element that deforms in the opposing direction of the first and second main surfaces and in a direction perpendicular to the opposing direction; A pair of first and second node points which are located on the first main surface side of the element and have a friction part for applying a driving force to the lens holder, and the element has a minimum displacement in the facing direction. And a third node point located between the first and second node points and having a minimum displacement in the opposite direction and a minimum displacement in the direction orthogonal to the opposite direction. The back member has first to third protrusions protruding toward the second main surface, and the first to third protrusions are first when viewed from the opposing direction. Are pressed against the second main surface at positions corresponding to the third node points, respectively, and the second main surface is between the first to third protrusions and the second main surface. A drag that prevents the movement of the first to third protrusions along each of the first and third protrusions is generated, and a drag generated between the first and second protrusions and the second main surface is generated between the third protrusion and the second protrusion. It is lower than the drag generated between the two main surfaces.

  In the lens driving device according to the present invention, when viewed from the opposite direction, the first to third protrusions of the back member are located at positions corresponding to the first to third node points, respectively. It is pressed against the main surface. The drag generated between the first and second protrusions and the second main surface is lower than the drag generated between the third protrusion and the second main surface. The first and second node points have the smallest displacement in the facing direction, and the drag generated between the first and second protrusions and the second main surface is lower. Even if the piezoelectric actuator vibrates in the direction orthogonal to the facing direction, the vibration is not easily inhibited by the first and second protrusions. In addition, since the displacement in the opposite direction is minimum at the third node point and the displacement in the direction orthogonal to the opposite direction is minimum, the drag generated between the third protrusion and the second main surface is reduced. Even if it is higher, the vibration of the piezoelectric actuator is not easily inhibited by the third protrusion. Moreover, since the first to third protrusions are pressed against the second main surface, the friction portion can be brought into uniform contact with the lens holder that is the driven body. As a result, the driving force can be efficiently transmitted from the piezoelectric actuator to the lens holder, and the lens holder as the driven body can be driven with high accuracy.

  The piezoelectric actuator further includes a flexible printed circuit board that is located between the third protrusion and the element and is electrically connected to the element, and the surface of the flexible printed circuit board that faces the third protrusion is A part of the second main surface may be configured, and the third protrusion may be pressed against the flexible printed circuit board. In this case, since the flexible printed circuit board is between the element and the back member, electrical connection between the flexible printed circuit board and the element is facilitated. Further, the flexible printed board has flexibility and exhibits a buffering action against vibration of the element. Therefore, even if the drag generated between the third protrusion and the second main surface is higher, it is possible to further prevent the vibration of the element from being inhibited.

  The first and second protrusions may be slidable with respect to the second main surface. In this case, even if the piezoelectric actuator vibrates in the direction orthogonal to the facing direction, the vibration is hardly inhibited by the first and second protrusions.

  The piezoelectric actuator further includes first and second protrusions that protrude outward from the second main surface, the first protrusion is in contact with the first protrusion, and the second protrusion is the first protrusion. The surface of the first projection that faces the first projection and that faces the first projection constitutes a part of the second main surface, and the surface of the second projection that faces the second projection is the second. A part of the main surface may be constituted. In this case, the balance of the load applied to the piezoelectric actuator from the first and second protrusions contacting the first and second protrusions is adjusted by setting the first and second protrusions to a desired height. can do. Therefore, the friction part can be made to contact the lens holder more uniformly.

  The piezoelectric actuator unit according to the present invention has first and second main surfaces facing each other, a piezoelectric actuator that applies a driving force to the driven body so as to move in a predetermined direction, and a second main surface side. A piezoelectric member is disposed on the first main surface side of the element and the lens holder, and the piezoelectric actuator is disposed in the opposing direction of the first and second main surfaces and in a direction orthogonal to the opposing direction. The element has a friction portion for applying a driving force to the element, and the element includes a pair of first and second node points having a minimum displacement in the facing direction of the first and second main surfaces, and a displacement in the facing direction. And a third node point located between the first and second node points, and the back member has a second main point. First to third protrusions projecting toward the first, and the first to third protrusions are second at positions corresponding to the first to third node points when viewed from the opposing direction. Between the first and third protrusions and the second main surface, there is a drag that prevents the movement of the first to third protrusions along the second main surface. The drag generated between the first and second protrusions and the second main surface is lower than the drag generated between the third protrusion and the second main surface.

  In the piezoelectric actuator unit according to the present invention, when viewed from the facing direction, the first to third protrusions of the back member are in positions corresponding to the first to third node points, respectively. It is pressed against the main surface. The drag generated between the first and second protrusions and the second main surface is lower than the drag generated between the third protrusion and the second main surface. The first and second node points have the smallest displacement in the facing direction, and the drag generated between the first and second protrusions and the second main surface is lower. Even if the piezoelectric actuator vibrates in the direction orthogonal to the facing direction, the vibration is not easily inhibited by the first and second protrusions. In addition, since the displacement in the opposite direction is minimum at the third node point and the displacement in the direction orthogonal to the opposite direction is minimum, the drag generated between the third protrusion and the second main surface is reduced. Even if it is higher, the vibration of the piezoelectric actuator is not easily inhibited by the third protrusion. Moreover, since the first to third protrusions are pressed against the second main surface, the friction part can be brought into uniform contact with the lens holder. As a result, the driving force can be efficiently transmitted from the piezoelectric actuator to the driven body, and the driven body can be driven with high accuracy.

  According to the present invention, it is possible to provide a lens driving device and a piezoelectric actuator unit capable of efficiently transmitting a driving force from a piezoelectric actuator to a driven body and driving the driven body with high accuracy.

FIG. 1 is a plan view showing a lens driving device according to this embodiment. FIG. 2 is an exploded perspective view showing a part of the lens driving device according to the present embodiment. FIG. 3A is a top view showing the piezoelectric actuator body, and FIG. 3B is a side view showing the piezoelectric actuator. FIG. 4 is a side view showing the piezoelectric actuator and the back member. FIG. 5 is a perspective view showing the back member. FIG. 6 is a perspective view showing another example of the urging unit. FIG. 7 is a perspective view showing another example of the back member.

  Preferred embodiments of the present invention will be described with reference to the drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and a duplicate description is omitted.

[Configuration of lens driving device]
As shown in FIG. 1, the lens driving device 1 includes a housing 10 including a base and a cover, a lens holder 20, a piezoelectric actuator unit 30, and an urging unit 40. The lens driving device 1 is a device that drives a camera lens mounted on, for example, a mobile phone. The lens driving device 1 is set to have a planar shape of, for example, 8.5 mm × 8.5 mm.

  The housing 10 accommodates the lens holder 20, the piezoelectric actuator unit 30, and the biasing unit 40 therein. The base of the housing 10 has a bottom part in which a perfect circular opening 11a is formed and a side wall part 13 standing from the bottom part. The base (bottom) has a rectangular shape in plan view. Therefore, the base has four corners 10a to 10d as shown in FIG. When viewed from the optical axis direction OA of the lens, the corner 10a is adjacent to the corners 10b and 10d, the corner 10b is adjacent to the corners 10a and 10c, and the corner 10c is adjacent to the corners 10b and 10d. The portion 10d is adjacent to the corner portions 10a and 10c.

  The side wall part 13 is provided over the four sides of the bottom part, and is formed integrally with the bottom part. The bottom portion and the side wall portion 13 define a space for accommodating the lens holder 20. The base is formed of a liquid crystal polymer containing a filler such as glass fiber or inorganic material. The rectangular shape includes not only a shape whose corner is a right angle but also a shape whose corner is chamfered.

  The cover of the housing 10 has a hollow rectangular parallelepiped shape that is open on one side. The cover has a surface portion facing the bottom portion and side portions extending from the four sides of the surface portion. On the surface portion, a perfect circular opening 11b is formed at a position facing the opening 11a. An opening (not shown) is formed in the side surface, and this opening fits into an engaging protrusion (not shown) formed on the outer surface of the side wall portion 13 of the base, so that the cover is attached to the base. It is attached. The cover is formed of, for example, SPCC (cold rolled steel).

  The lens holder 20 has a cylindrical body portion 21 and is disposed in an accommodation space defined by the bottom portion and the side wall portion 13. The inner peripheral surface and the outer peripheral surface of the trunk portion 21 have a perfect cross-sectional shape. A lens barrel (not shown) that houses a lens is attached to the inside of the body portion 21. The lens holder 20 holds a lens by attaching a lens barrel. The lens held in the lens barrel is exposed through the base opening 11a and the cover opening 11b. The lens holder 20 is made of, for example, a liquid crystal polymer containing carbon fiber or nylon.

  As shown in FIGS. 1 and 2, the lens holder 20 has a wide protruding portion 22 that protrudes outward from the outer peripheral surface of the body portion 21 in a first direction X orthogonal to the optical axis direction OA of the lens. Have The first direction X in which the wide protruding portion 22 protrudes coincides with the radial direction of the trunk portion 21 in the present embodiment. The wide protrusion 22 extends along the optical axis direction OA of the lens and the second direction Y orthogonal to the first direction X (the tangential direction of the body 21 when viewed from the optical axis direction OA of the lens). Yes. In the present embodiment, the width of the wide protrusion 22 in the second direction Y is set to be larger than the radius of the trunk portion 21 but smaller than the diameter.

  The wide protrusion 22 is located between the corner 10a and the corner 10b of the base when the lens holder 20 is mounted on the base of the housing 10. As shown in FIGS. 1 and 2, the wide protrusion 22 has a side wall surface 22a located at the corner 10a of the base and a side wall surface 22b located at the corner 10b of the base. The side wall surfaces 22 a and 22 b protrude outward from the body portion 21 along the first direction X. The side wall surface 22a and the side wall surface 22b are opposed to each other in the second direction Y.

  A pair of groove portions 23a and 23b extending along the optical axis direction OA of the lens is formed on the side wall surface 22b. The groove portions 23a and 23b are adjacent to each other in the first direction X. The grooves 23a and 23b have a V-shape that becomes narrower toward the back as viewed from the optical axis direction OA of the lens. Therefore, a later-described ball member 41a that engages with the groove 23a contacts the groove 23a at two points, and a later-described ball member 41b that engages with the groove 23b contacts with the groove 23b at two points.

  The lens holder 20 has a flat substrate 24 on which friction portions 52a and 52b of a piezoelectric actuator 50 to be described later abut. The substrate 24 is fixed to the side wall surface 22 a of the wide protrusion 22. Thus, the substrate 24 substantially functions as a side surface of the wide protrusion 22 (side surface of the lens holder 20). The substrate 24 is made of, for example, SiC or zirconia. The substrate 24 may be formed integrally with the lens holder 20.

  As shown in FIGS. 1 and 2, the piezoelectric actuator unit 30 includes a piezoelectric actuator 50 and a back member 70. The piezoelectric actuator unit 30 is located at the corner 10a of the base.

  In the present embodiment, the piezoelectric actuator 50 includes a rectangular parallelepiped element 51 (see FIG. 3) and a flexible printed circuit board 60, and is disposed close to the circuit board 24. The piezoelectric actuator 50 has a pair of opposing first and second main surfaces 50a and 50b. The element 51 is a so-called multilayer piezoelectric element. The length of the element 51 is set to about 2.5 mm, for example. The thickness of the element 51 is set to about 0.5 mm, for example. The width of the element 51 is set to about 1.8 mm, for example. As shown in FIG. 3B, the element 51 has a plurality (four in this embodiment) of active parts A1 to A4 that expand and contract in accordance with the applied voltage value.

  On the first main surface 50a side of the element 51, a plurality of (two in this embodiment) friction portions 52a and 52b are positioned along the arrangement direction of the active portions A1 to A4. When viewed from the first and second main surfaces 50a and 50b, the second main surface 50b has an external electrode 53 and a pair of protrusions 54a corresponding to the position (node point) at which expansion and contraction is minimized. , 54b.

  Each of the friction portions 52a and 52b has a semi-cylindrical shape, is spaced apart in the optical axis direction OA of the lens (the arrangement direction of the active portions A1 to A4), and the first direction X (the arrangement of the active portions A1 to A4). Direction and a direction orthogonal to the opposing direction of the first and second main surfaces 51a and 51b). The friction portions 52 a and 52 b are in contact with the outer peripheral surface of the lens holder 20 (the side wall surface 22 a of the wide protrusion 22) indirectly by contacting the substrate 24. The height of each of the friction portions 52a and 52b is set to about 50 μm, for example. The surfaces of the friction portions 52 a and 52 b constitute a part of the first main surface 50 a of the piezoelectric actuator 50. That is, in the present embodiment, the first main surface 50a is an uneven surface constituted by a combination of the surface of the element 51 and the surfaces of the friction portions 52a and 52b.

  The element 51 has two resonance modes during driving. Specifically, the element 51 includes a longitudinal vibration mode (first vibration mode) that vibrates in the longitudinal direction of the element 51 (the arrangement direction of the active portions A1 to A4), and a thickness direction (first main surface) of the element 51. It vibrates by overlapping with a bending vibration mode (second vibration mode) in the direction in which 51a and the second main surface 51b face each other.

  When the active part A1 composed of the first internal electrode, the ground internal electrode and the piezoelectric layer and the active part A4 composed of the fourth internal electrode, the ground internal electrode and the piezoelectric layer are driven, the active part Since A1 and A4 are expanded and the active portions A2 and A3 are contracted, the friction portion 52a is separated from the substrate 24, and the friction portion 52b is in contact with the substrate 24, so that friction is generated between the friction portion 52b and the substrate 24. Power is generated. The substrate 24 moves in the optical axis direction OA of the lens by the frictional force generated between the friction part 52b and the substrate 24.

  When the active part A2 composed of the second internal electrode, the ground internal electrode and the piezoelectric layer and the active part A3 composed of the third internal electrode, the ground internal electrode and the piezoelectric layer are driven, the active part As A2 and A3 expand and the active portions A1 and A4 contract, the friction portion 52b moves away from the substrate 24, and the friction portion 52a comes into contact with the substrate 24, causing friction between the friction portion 52a and the substrate 24. Power is generated. Due to the frictional force generated between the friction portion 52a and the substrate 24, the substrate 24 moves in the optical axis direction OA of the lens and in the direction opposite to the moving direction by the friction portion 52b.

  When the element 51 is driven by applying a voltage whose phase is shifted by 90 degrees to the external electrode 53 connected to the first internal electrode and the external electrode 53 connected to the second internal electrode, the friction parts 52a and 52b Elliptical motions that are 180 degrees out of phase occur, and a frictional force acts alternately between the substrate 24 and the substrate 24 (lens holder 30) moves. That is, the friction parts 52a and 52b drive the lens holder 30 along the optical axis direction OA of the lens. As a result, the piezoelectric actuator 50 applies a driving force toward the side wall surface 22 a of the wide protrusion 22 via the substrate 24.

  In the example shown in FIG. 3B, the element 51 has three node points N1 to N3. The node point N1 is a boundary portion between the active parts A1 and A3, and from the end of the element 51 when the length of the element 51 in the longitudinal direction of the element 51 (the arrangement direction of the active parts A1 to A4) is L. It exists at a position on the inner side of about L / 6. The node point N2 exists at a boundary portion between the active portions A2 and A4 and at a position that is approximately L / 6 inside from the end portion of the element 51. The node point N3 exists in the central portion in the longitudinal direction of the element 51 and in the central portion in the thickness direction. Therefore, the node point N3 is located between the node point N1 and the node point N2. The node points N1 and N2 are points that are displaced in the longitudinal direction of the element 51 but have a minimum displacement in the thickness direction. The node point N3 is a point at which the displacement of the element 51 in both the longitudinal direction and the thickness direction is minimized.

  A plurality (three in this embodiment) of external electrodes 53 are positioned above the second main surface 50b of the element 51, and each has a rectangular shape. Each external electrode 53 extends along the first direction X (the direction perpendicular to the arrangement direction of the active portions A1 to A4 and the opposing direction of the first and second main surfaces 50a and 50b), They are arranged in series while being separated from each other in the direction X. The external electrode 53 is located on the second major surface 50b so as to overlap the node point N3 when viewed from the direction facing the first and second major surfaces 50a, 50b. The thickness of the external electrode 53 is set to about 2 μm, for example.

  Both the protrusions 54a and 54b have a semi-cylindrical shape and protrude outward from the second main surface 50b. Both the protrusions 54a and 54b extend along the first direction X (the direction orthogonal to the arrangement direction of the active portions A1 to A4 and the opposing direction of the first and second main surfaces 50a and 50b). The protrusions 54a and 54b are located on the second main surface 50b side of the element 51 so that the external electrodes 53 are interposed therebetween. The surfaces of the protrusions 54 a and 54 b constitute a part of the second main surface 50 b of the piezoelectric actuator 50.

  The protrusion 54a is located on the second main surface 50b so as to overlap the node point N1 when viewed from the opposing direction of the first and second main surfaces 50a, 50b. The protrusion 54b is located on the second main surface 50b so as to overlap the node point N2 when viewed from the opposing direction of the first and second main surfaces 50a, 50b. Both the protrusions 54a and 54b preferably have a certain degree of hardness and a smooth surface. For example, the protrusions 54a and 54b can be formed by a printing method using a silicone resin as a material. When a printing method is used as a method for manufacturing the protrusions 54a and 54b, variation in height can be reduced. In the present embodiment, the heights of the protrusions 54a and 54b are set higher than the height of the external electrode 53, and are set to about 30 μm, for example.

  Returning to FIG. 2, the flexible printed circuit board 60 includes a film-like insulator and a wiring portion disposed on the insulator. The wiring portion includes a wiring connected to each external electrode 53 by soldering or the like. The flexible printed circuit board 60 is disposed along one side of the base (side wall part 13). In the present embodiment, the flexible printed circuit board 60 is disposed so as to cross between the corner portion 10a and the corner portion 10d.

  One end of the flexible printed circuit board 60 on the corner 10 a side is mounted on the element 51. The other end (not shown) of the flexible printed circuit board 60 on the corner 10d side is fixed to the side wall 13 by adhesion or the like, and is positioned with respect to the base, the lens holder 30, and the like. The end portion is drawn to the outside of the lens driving device 1 through a gap formed between the base and the cover.

  The back surface of the surface on which the element 51 is mounted at one end of the flexible printed circuit board 60 constitutes a part of the second main surface 50b of the piezoelectric actuator 50 in this embodiment. That is, in the present embodiment, the second main surface 50b is an uneven surface formed by a combination of the surface of the element 51, the surfaces of the protrusions 54a and 54b, and the back surface at one end of the flexible printed board 60. ing.

  As shown in FIGS. 2 and 4, a back member 70 is disposed on the back surface at one end of the flexible printed circuit board 60. That is, the back member 70 is located on the second main surface 50b side. The back member 70 is preferably configured using a material that is difficult to deform, such as metal or ceramics. When the back member 70 is made of metal, the back member 70 is formed into a predetermined shape by etching or the like. When the back member 70 is made of ceramic, the back member 70 is formed into a predetermined shape by processing using a dicer or the like.

  As shown in FIGS. 4 and 5, the back member 70 has first to third protrusions 71 to 73 that protrude toward the second main surface 50 b side. That is, the back member 70 has a structure in which the first to third protrusions 71 to 73 protrude from the one surface 74a of the flat plate portion 74 having a rectangular shape. The thickness of the flat plate portion 74 is set to, for example, about 170 μm. The heights of the first and second protrusions 71 and 72 are set to about 130 μm, for example. The height of the third protrusion 73 is set to about 60 μm, for example. Therefore, in the present embodiment, the height of the first and second protrusions 71 and 72 is higher than the height of the third protrusion 73.

  Each of the first to third protrusions 71 to 73 has a rectangular parallelepiped shape and extends along the first direction X. The first and second protrusions 71 and 72 are located on both ends of the one surface 74a in the optical axis direction OA of the lens, respectively, and the third protrusion 73 is the first and second protrusions 71, 72, respectively. 72.

  As shown in FIG. 4, the first protrusion 71 is in contact with the apex of the protrusion 54a. Therefore, the first protrusion 71 overlaps the node point N1 when viewed from the second direction Y (opposite direction of the first and second main surfaces 50a and 50b). The first protrusion 71 is not restrained by the protrusion 54a by adhesion or the like. Therefore, the first protrusion 71 can move in the optical axis direction OA of the lens so as to slide on the surface of the protrusion 54a. That is, the first protrusion 71 is slidable with respect to the second main surface 50b.

  The second protrusion 72 is in contact with the apex of the protrusion 54b. Therefore, the second protrusion 72 overlaps the node point N2 when viewed from the second direction Y (opposite direction of the first and second main surfaces 50a and 50b). The second protrusion 72 is not restrained by the protrusion 54b by adhesion or the like. Therefore, the second protrusion 72 can move in the optical axis direction OA of the lens so as to slide on the surface of the protrusion 54b. That is, the second protrusion 72 is slidable with respect to the second main surface 50b. Accordingly, the first and second protrusions 71 and 72 are prevented from moving along the second main surface 50b between the first and second protrusions 71 and 72 and the second main surface 50b. There is no drag.

  The third protrusion 73 overlaps the external electrode 53 and the node point N3 when viewed from the second direction Y (opposite direction of the first and second main surfaces 50a and 50b). The third protrusion 73 is bonded to the back surface at one end of the flexible printed circuit board 60 with an adhesive 75 such as a silicone resin. Therefore, the third protrusion 73 is restrained by the second main surface 50 b via the flexible printed board 60 and the external electrode 53. Accordingly, a drag force that prevents the movement of the third protrusion 73 along the second main surface 50b is generated between the third protrusion 73 and the second main surface 50b. That is, the drag generated between the first and second protrusions 71 and 72 and the second main surface 50b is lower than the drag generated between the third protrusion 73 and the second main surface 50b. It has become. Therefore, the first and second protrusions 71 and 72 are easier to move between the second main surface 51 b than the third protrusion 73.

  The other surface 74b of the back member 70 is directly or indirectly fixed to the sidewall 13 of the housing with an adhesive or the like.

  The drag E (see FIG. 1) of the back member 70 due to the elastic force F of the urging member 44 (described later) is applied to the piezoelectric actuator 50 via the first to third protrusions 71 to 73 of the back member 70. It is transmitted. Therefore, the first protrusion 71 pushes against the piezoelectric actuator 50 at a position corresponding to the node point N1 when viewed from the second direction Y (opposite direction of the first and second main surfaces 50a and 50b). It has been applied. The second protrusion 72 is pressed against the piezoelectric actuator 50 at a position corresponding to the node point N2 when viewed from the second direction Y (opposite direction of the first and second main surfaces 50a and 50b). ing. The third protrusion 73 is pressed against the piezoelectric actuator 50 at a position corresponding to the node point N3 when viewed from the second direction Y (opposite direction of the first and second main surfaces 50a and 50b). ing.

  The piezoelectric actuator 50 and the back member 70 constitute a piezoelectric actuator unit. Further, as shown in FIG. 4, the flexible printed circuit board 60 is located between the third protrusion 73 and the element 51 in the second direction Y, and the first protrusion in the optical axis direction OA of the lens. It is located between the part 71 and the protrusion 54a and the second protrusion 72 and the protrusion 54b.

  Returning to FIGS. 1 and 2, the urging unit 40 includes a plurality (two in the present embodiment) of ball members 41 a, a plurality (two in the present embodiment) of ball members 41 b, a holding member 42, A plate member 43 and an urging member 44 are provided. The urging unit 40 is located at the corner 10b of the base.

  The two ball members 41a are both engaged with the groove 23a and are arranged along the optical axis direction OA of the lens. The two ball members 41b are both engaged with the groove 23b and are arranged along the optical axis direction OA of the lens. As described above, the ball members 41a and 41b engage with the grooves 23a and 23b, respectively, so that the lens holder 20 can be moved along the optical axis direction OA without being inclined with respect to the optical axis direction OA of the lens. it can. The ball members 41a and 41b have the same diameter, and are made of, for example, stainless steel.

  The holding member 42 is a flat plate member having a rectangular shape. The holding member 42 is formed with a pair of holding holes 42a corresponding to the two ball members 41a and a pair of holding holes 42b corresponding to the two ball members 41b. The holding hole 42a has a square shape and is slightly larger than the diameter of the ball member 41a. Therefore, the holding hole 42a holds the ball member 41a rotatably. The holding hole 42b has a square shape and is slightly larger than the diameter of the ball member 41b. Therefore, the holding hole 42b holds the ball member 41b rotatably. The holding member 42 is made of, for example, stainless steel.

  The plate member 43 is a flat plate member having a rectangular shape. The plate member 43 is formed with a pair of grooves 43a and 43b extending along the optical axis direction OA of the lens. The groove portions 43a and 43b are adjacent to each other in the first direction X. The grooves 43a and 43b have a V-shape that becomes narrower toward the back as viewed from the optical axis direction OA of the lens. Therefore, the ball member 41a that engages with the groove 43a comes into contact with the groove 43a at two points, and the ball member 41b that engages with the groove 43b comes into contact with the groove 43b at two points. The plate member 43 is made of, for example, a liquid crystal polymer or nylon.

  The urging member 44 is a rectangular elastic plate that is elastically deformed in the present embodiment, and as shown in FIG. 1, the side wall surface 22b of the wide protrusion 22 via the plate member 43 and the ball members 41a and 41b ( An urging force (elastic force) F is applied to the lens holder 20). One surface 44a of the urging member 44 is in contact with the surface of the plate member 43 opposite to the surface on which the groove portions 43a and 43b are formed.

  These surfaces may be bonded by an adhesive or the like, or may simply be in contact with each other. The other surface 44b of the urging member 44 is directly or indirectly fixed to the side wall portion 13 of the housing with an adhesive or the like. The urging member 44 is preferably constructed using various elastic materials made of a resin such as silicone rubber. When such an elastic material is used as the urging member 44, the vibration excited by the element 51 is absorbed and noise is suppressed, and the impact applied to the lens driving device 1 is absorbed and the element 51 is cracked. The suppressing effect can be obtained.

  As shown in FIGS. 1 and 2, in this embodiment, the biasing member 44, the plate member 43, the ball members 41 a and 41 b, and the lens holder 20 are aligned along the direction of the biasing force F generated by the biasing member 44. The wide protrusion 22, the substrate 24, the piezoelectric actuator 50, the flexible printed circuit board 60, and the back member 70 are arranged in this order. Therefore, in the lens holder 20, the position where the urging force F is applied by the urging member 44 and the position where the driving force is applied by the piezoelectric actuator 50 face each other across the wide protrusion 22, and the urging member 44 The urging force F is directed toward the piezoelectric actuator 50.

[Action]
As described above, in the present embodiment, the first to third protrusions 71 to 73 of the back member 70 are connected to the node point N1 when viewed from the opposing direction of the first and second main surfaces 50a and 50b. Are pressed against the second main surface 50b of the piezoelectric actuator 50 at positions corresponding to N3. The drag generated between the first and second protrusions 71 and 72 and the second main surface 50b is greater than the drag generated between the third protrusion 73 and the second main surface 50b. Is also low. At the node points N1 and N2, the displacement in the opposing direction of the first and second main surfaces 50a and 50b is minimal, and between the first and second protrusions 71 and 72 and the second main surface 50b. Even if the piezoelectric actuator 50 vibrates in a direction orthogonal to the opposing direction of the first and second main surfaces 50a and 50b (the optical axis direction OA of the lens), the drag generated in the The vibration is not easily inhibited by the first and second protrusions 71 and 72. Further, at the node point N3, the displacement in the facing direction of the first and second main surfaces 50a and 50b is the smallest and the displacement in the direction orthogonal to the facing direction (the optical axis direction OA of the lens) is the smallest. Even if the drag generated between the third protrusion 73 and the second main surface 50 b is higher, the vibration of the piezoelectric actuator 50 is not easily inhibited by the third protrusion 73. Moreover, since the first to third three projecting portions 71 to 73 are pressed against the second main surface 51b, the frictional portions 52a and 52b are uniformly brought into contact with the lens holder 20 which is a driven body. Can do. As a result, it is possible to efficiently transmit the driving force from the piezoelectric actuator 50 to the lens holder 20 and to drive the piezoelectric actuator 50 with high accuracy.

  In the present embodiment, the piezoelectric actuator 50 includes the flexible printed circuit board 60 that is located between the third protrusion 73 and the second main surface 50 b and is electrically connected to the element 51. . Since the flexible printed board 60 has flexibility, even if the element 51 vibrates, the flexible printed board 60 can move following the vibration. Therefore, the flexible printed circuit board 60 and the element 51 can be easily electrically connected, and the electrical connection between the element 51 and the flexible printed circuit board 60 can be maintained well.

  In the present embodiment, the third protrusion 73 is pressed against the flexible printed circuit board 60 that constitutes a part of the second main surface 50b. The flexible printed board 60 has flexibility and exhibits a buffering action against the vibration of the element 51. Therefore, even if the drag generated between the third protrusion 73 and the second main surface 50b is higher, the vibration of the element 51 is further hardly inhibited.

  In the present embodiment, the first and second protrusions 71 and 72 are slidable with respect to the second main surface 50b. Therefore, even if the element 51 vibrates in a direction orthogonal to the opposing direction of the first and second main surfaces 50a and 50b (the optical axis direction OA of the lens), the vibration is not affected by the first and second protrusions 71, 72 is hardly inhibited.

  In the present embodiment, the piezoelectric actuator 50 includes first and second protrusions 54a and 54b that protrude outward from the second main surface 50b, and the first protrusion 71 is the first protrusion 71. The second protrusion 72 is in contact with the second protrusion 54b while being in contact with the protrusion 54a. The surface of the first protrusion 54a that faces the first protrusion 71 constitutes a part of the second main surface 50b, and the surface of the second protrusion 54b that faces the second protrusion 72 is the first. 2 constitutes a part of the main surface 50b. Therefore, by setting the first and second protrusions 54a and 54b to desired heights, the piezoelectric actuators can move from the first and second protrusions 71 and 72 that are in contact with the first and second protrusions 54a and 54b, respectively. The balance of the load given to 50 can be adjusted. Therefore, the friction portions 52a and 52b can be made to contact the lens holder 20 more uniformly.

  In the present embodiment, the biasing member 44 applies a biasing force to the lens holder 20 toward the piezoelectric actuator 50 via the ball members 41a and 41b. Therefore, the contact state between the lens holder 20 and the piezoelectric actuator 50 is kept good. Then, the position where the urging force is applied by the urging member 44 and the position where the driving force is applied by the piezoelectric actuator 50 face each other across the wide protrusion 22 of the lens holder 20, and the urging force by the urging member 44 is the piezoelectric actuator. Heading to 50. For this reason, the urging member 44 is not positioned on the driving force transmission path from the piezoelectric actuator 50 to the lens holder 20, and loss of transmission of the driving force from the piezoelectric actuator 50 to the lens holder 20 is unlikely to occur. In addition, since the urging force by the urging member 44 can be applied to the wide projecting portion 22 having high rigidity, the contact state between the lens holder 20 and the piezoelectric actuator 50 becomes better, and the piezoelectric actuator 50 to the lens. The driving force to the holder 20 is easily transmitted. Further, in the present embodiment, the ball members 41a and 41b are engaged with the groove portions 23a and 23b and the groove portions 43a and 43b, respectively, to guide the lens holder 20 in the optical axis direction OA of the lens. Since a shaft that easily generates a frictional force with the through hole is not used for guiding the lens holder 20, loss in transmission of driving force from the piezoelectric actuator 50 to the lens holder 20 is further less likely to occur. As a result, the driving force from the piezoelectric actuator 50 is efficiently transmitted to the lens holder 20.

  In this embodiment, the housing 10 is further provided for housing the lens holder 20, the piezoelectric actuator unit 30, and the biasing unit 40. The piezoelectric actuator 50 is disposed at the corner 10 a of the housing 10, and the biasing member 44 is disposed at the corner 10 b adjacent to the corner 10 a of the housing 10. The wide protrusion 22 has a pair of side wall surfaces 22a and 22b facing each other in the extending direction of the wide protrusion 22 (second direction Y). The side wall surface 22a is located at the corner 10a, and the side wall surface 22b is Located in the corner 10b. A driving force is applied toward the side wall surface 22a by the piezoelectric actuator 50, and an urging force is applied toward the side wall surface 22b by the urging member 44. Therefore, the piezoelectric actuator 50 and the biasing member 44 are disposed at the corner of the housing 10 that becomes a dead space. In addition, the driving force is applied by the piezoelectric actuator 50 in the corner portion 10a, and the biasing force is applied by the biasing member 44 in the corner portion 10b. Therefore, even if the lens holder 20 is enlarged, the region of the member for applying the driving force and the urging force is ensured in the dead space, so that the application of the driving force and the urging force to the lens holder 20 is not hindered. Therefore, both the enlargement of the lens holder 20 and the miniaturization of the lens driving device 1 can be achieved. As a result, when the size of the lens holder 20 is set to the same level as the conventional one, a small lens driving device 1 can be obtained. On the other hand, when the size of the lens driving device 1 is set to the same level as the conventional one, the lens holder 20 can be enlarged, and a lens having a larger diameter can be mounted on the lens holder 20.

[Other Embodiments]
Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments. For example, instead of using the holding member 42, the plate member 43, and the urging member 44, the urging unit 40 having a form in which the function of holding the ball members 41 a and 41 b and the function of generating the urging force are integrated is used. May be.

  Specifically, as shown in FIG. 6, the urging unit 40 includes ball members 41 a and 41 b and a holding base 142. A conical projection 144 that protrudes outward (side wall 13) is formed at the center of one surface of the holding base 142. The holding base 142 and the protrusion 144 can be configured using various elastic materials such as polyacetal. Therefore, the protrusion 144 exhibits a function of generating an urging force instead of the urging member 44. The protrusion 144 can have various shapes such as a cylindrical shape, a pyramid shape, and a prism shape instead of the conical shape. Further, the holding base 142 may be formed with a plurality of protrusions 144, and the plurality of protrusions 144 are preferably disposed so as to uniformly apply an urging force (elastic force) to the lens holder 20. .

  The holding base 142 is formed with four slits 145 that penetrate in the thickness direction and extend in the longitudinal direction. Of these four slits 145, two slits positioned between the projection 144 and one end in the longitudinal direction of the holding base 142 both extend from the vicinity of the center of the holding base 142 to one end. ing. Of these four slits 145, two slits located between the protrusion 144 and the other end in the longitudinal direction of the holding base 142 both extend from the vicinity of the center of the holding base 142 to the other end. ing.

  At the center in the longitudinal direction of each slit 145, a holding hole 146 for holding the ball members 41a and 41b is formed in the thickness direction of the holding base 142 so as to overlap with each slit 145. The inner surface of each holding hole 146 has a spherical shape. The size of each holding hole 146 is slightly larger than the ball members 41a and 41b. Therefore, the ball members 41a and 41b are rotatably held in the respective holding holes 146 without dropping.

  When such an urging unit 40 is used, the holding member 42, the plate member 43, and the urging member 44 are not required, and the number of components is reduced, so that the lens driving device 1 can be reduced in size. Note that the slit 145 is provided to facilitate the fitting of the ball members 41a and 41b into the holding hole 146, and thus the slit 145 may not be formed in the holding base 142. In this case, the ball members 41 a and 41 b can be held in the holding hole 146 by pushing the ball members 41 a and 41 b into the holding hole 146.

  Moreover, you may use the back member 70 of a structure different from this embodiment mentioned above. Specifically, the third protrusion 73 of the back member 70 does not extend along the first direction X, and may be a protrusion that protrudes from the vicinity of the center of the one surface 74 a of the flat plate portion 74. Good. FIG. 7 shows an example in which the protrusion is cylindrical. In this case, since the area where the third protrusion 73 is bonded to the flexible printed circuit board 60 is greatly reduced, the restraining force of the third protrusion 73 on the second main surface 50b can be reduced. Therefore, the vibration of the element 51 is less likely to be inhibited.

  Further, the electrical connection of the element 51 may not be performed by the flexible printed circuit board 60. In this case, the third protrusion 73 of the back member 70 is in direct contact with the element 51. Furthermore, the piezoelectric actuator 50 may not have the protrusions 54a and 54b. In this case, the first and second protrusions 71 and 72 of the back member 70 are in direct contact with the element 51. That is, when the first to third protrusions 71 to 73 are viewed from the opposing direction of the first and second main surfaces 51a and 51b, the second main surface at positions corresponding to the node points N1 to N3, respectively. The case where the first to third protrusions 71 to 73 are pressed directly against the element 51, or the case where the first to third protrusions 71 to 73 are pressed against the protrusions 54a and 54b and the flexible printed circuit board 60. included.

  In this embodiment, an elastic plate is used as the urging member 44, but various urging members such as a coil spring and a leaf spring can be used.

  In the present embodiment, the first and second protrusions 71 and 72 are in contact with the protrusions 54a and 54b and are not bonded, but the first and second protrusions 71 and 72 are not protruded. 54a and 54b may be attached by adhesion or the like. In the embodiment in which the piezoelectric actuator 50 does not have the protrusions 54a and 54b, the first and second protrusions 71 and 72 may be attached to the second main surface 50b by bonding or the like. In these cases, however, the drag generated between the first and second protrusions 71 and 72 and the second main surface 50b is generated between the third protrusion 73 and the second main surface 50b. It is lower than the drag to do. Therefore, the first and second protrusions 71 and 72 are easier to move between the second main surface 51 b than the third protrusion 73.

  DESCRIPTION OF SYMBOLS 1 ... Lens drive device, 10 ... Housing, 10a, 10b ... Corner | angular part, 20 ... Lens holder (driven body), 22 ... Wide protrusion part, 22a, 22b ... Side wall surface, 23a, 23b ... Groove part, 30 ... Piezoelectric actuator Unit: 40 ... biasing unit, 41a, 41b ... ball member, 44 ... biasing member, 50 ... piezoelectric actuator, 50a ... first main surface, 50b ... second main surface, 51 ... element, 52a, 52b ... Friction part, 54a, 54b ... projection, 60 ... flexible printed circuit board, 70 ... back member, 71-73 ... first to third projections, 146 ... through hole, N1-N3 ... node point, OA ... lens light Axial direction.

Claims (5)

A lens holder for holding the lens;
A piezoelectric actuator having first and second main surfaces facing each other, and applying a driving force to the lens holder so as to move the lens holder in the optical axis direction of the lens;
A back member located on the second main surface side,
The piezoelectric actuator is
An element that deforms in a facing direction of the first and second main surfaces and a direction orthogonal to the facing direction;
A friction part that is positioned on the first main surface side of the element and that gives the driving force to the lens holder;
The element is
A pair of first and second node points having a minimum displacement in the facing direction;
A displacement in the facing direction is minimal and a displacement in a direction orthogonal to the facing direction is minimal, and a third node point located between the first and second node points,
The back member has first to third protrusions protruding toward the second main surface,
The first to third protrusions are pressed against the second main surface at positions corresponding to the first to third node points when viewed from the facing direction,
Between the first to third protrusions and the second main surface, drag forces that prevent the movement of the first to third protrusions along the second main surface are generated, respectively.
The drag generated between the first and second protrusions and the second main surface is lower than the drag generated between the third protrusion and the second main surface. Drive device. The piezoelectric actuator further includes a flexible printed circuit board that is located between the third protrusion and the element and is electrically connected to the element.
Of the flexible printed circuit board, the surface facing the third protrusion constitutes a part of the second main surface,
The lens driving device according to claim 1, wherein the third protrusion is pressed against the flexible printed circuit board.   The lens driving device according to claim 1, wherein the first and second protrusions are slidable with respect to the second main surface. The piezoelectric actuator further includes first and second protrusions that protrude outward from the second main surface, the first protrusion being in contact with the first protrusion and the second protrusion. The protrusion of the second portion is in contact with the second protrusion,
A surface of the first protrusion that faces the first protrusion constitutes a part of the second main surface,
4. The lens driving device according to claim 1, wherein a surface of the second protrusion facing the second protrusion constitutes a part of the second main surface. 5. A piezoelectric actuator having first and second main surfaces facing each other and applying a driving force to the driven body so as to move in a predetermined direction;
A back member located on the second main surface side,
The piezoelectric actuator is
An element that deforms in a facing direction of the first and second main surfaces and a direction orthogonal to the facing direction;
A friction part that is positioned on the first main surface side of the element and that gives the driving force to the lens holder;
The element is
A pair of first and second node points having a minimum displacement in the opposing direction of the first and second main surfaces;
A displacement in the facing direction is minimal and a displacement in a direction orthogonal to the facing direction is minimal, and a third node point located between the first and second node points,
The back member has first to third protrusions protruding toward the second main surface,
The first to third protrusions are pressed against the second main surface at positions corresponding to the first to third node points when viewed from the facing direction,
Between the first to third protrusions and the second main surface, drag forces that prevent the movement of the first to third protrusions along the second main surface are generated, respectively.
A piezoelectric force generated between the first and second protrusions and the second main surface is lower than a drag force generated between the third protrusion and the second main surface. Actuator unit.

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