JP2018101094A - Vibration type actuator, lens driving device, optical instrument, and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To drive a lens group at an equal speed irrespective of the direction of movement without changing driving conditions for a vibration type actuator according to the direction of movement of the lens group.SOLUTION: In a vibration type actuator 1 comprising a vibrator 11 and a driven body 12, the vibrator 11 includes a plate-like elastic body 112, projection parts 112a and 112b provided on one face of the elastic body 112 and in contact with the driven body 12, and a piezoelectric element 111 adhered to the other face of the elastic body 112. Driving vibration includes a vibration mode having a nodal line substantially parallel to a direction orthogonal to both the thickness direction of the elastic body 112 and a relative direction of movement between the vibrator 11 and driven body 12; the projection parts 112a and 112b are provided at positions shifted in the direction of movement by a predetermined distance from the position of the nodal line when the driving vibration is excited.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a vibration type actuator, a lens driving device, an optical device, and an electronic device, and more particularly to a technique for moving a driving object such as a lens using a vibration type actuator.

  Vibrating actuators that are small and light, have a large driving force, have a wide speed range, and can be driven silently, are used for lens driving in optical equipment (imaging devices) such as digital cameras. ing. Various types of vibration actuators are known. For example, Patent Document 1 includes a vibrating body having a structure in which a protrusion is provided on one surface of a plate-like elastic body and a piezoelectric element is bonded to the other surface, and the tip of the protrusion is a driven body. A vibration type actuator having a structure in pressure contact is described. In this vibration type actuator, an alternating voltage is applied to the piezoelectric element to generate an elliptical motion at the tip of the protrusion, and the protrusion gives a thrust (frictional force) to the driven body. Can be moved relatively.

  By the way, in Patent Document 2, a lens group, a feed rod for moving the lens group, a lens moving frame supported by the feed rod, and a biasing spring are used to urge the lens group in the optical axis direction. A lens barrel provided with a mechanism for shifting is described.

Japanese Patent Laid-Open No. 2004-304877 JP-A-4-342211

  Consider a configuration in which the vibration type actuator described in Patent Document 1 is applied to the lens barrel described in Patent Document 2 to drive the lens group in the optical axis direction. In the lens barrel described in Patent Document 2, the driving load when moving the lens group in the optical axis direction differs between the direction in which the biasing spring biases the lens group and the opposite direction. Therefore, in order to make the moving speed of the lens group the same in the direction in which the biasing spring biases the lens group and in the opposite direction, it is necessary to change the driving conditions according to the moving direction of the lens group. In other words, when the driving condition of the vibration type actuator is constant regardless of the moving direction of the lens group, there arises a problem that the moving speed varies depending on the moving direction of the lens group.

  In the present invention, when the driven object is urged in one of the moving directions, the driven object can be driven at the same speed regardless of the moving direction without changing the driving condition of the vibration type actuator. An object of the present invention is to provide a simple vibration type actuator.

  The vibration-type actuator according to the present invention is a vibration-type actuator in which the vibration body and the friction member move relative to each other when the drive vibration is excited by the vibration body that is press-contacted with the friction member. The vibrating body includes a flat elastic body, a protrusion provided on one surface of the elastic body so as to protrude in the thickness direction of the elastic body, a protrusion that contacts the friction member, and the other surface of the elastic body An electro-mechanical energy conversion element bonded to the substrate, and having a nodal line substantially parallel to the thickness direction of the elastic body and a direction orthogonal to both directions of relative movement directions of the vibration body and the friction member The protrusion is provided at a position shifted by a predetermined distance in the moving direction from the position of the nodal line when the driving vibration including a vibration mode is excited.

  According to the present invention, when the driven object is biased in one direction of movement, the driven object is moved at the same speed regardless of the moving direction without changing the driving condition of the vibration type actuator. Can be driven.

It is a figure which shows schematic structure of the vibration type actuator which concerns on embodiment of this invention. It is a figure explaining schematic structure of the vibrating body with which the vibration type actuator of FIG. 1 is provided. It is a figure explaining the aspect of the drive vibration excited by the vibrating body which concerns on a prior art example. It is a figure explaining the aspect of the drive vibration excited by the vibrating body in this embodiment. It is a figure explaining the vibration displacement which arises in the front-end | tip of the projection part of the vibrating body which concerns on a prior art example. It is a figure explaining the vibration displacement which arises at the front-end | tip of the projection part of the vibrating body in this embodiment. It is a figure explaining the effect | action of the thrust which the vibrating body which concerns on a prior art example gives to a friction member. It is a figure explaining the effect | action of the thrust which the vibrating body in this embodiment gives to a friction member. It is a figure which compares and compares the speed-thrust diagram of a vibration type actuator with a prior art example and an Example. It is a schematic sectional drawing of the lens drive device concerning this embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1A is an exploded perspective view of a vibration type actuator 1 according to an embodiment of the present invention. In addition, as shown to Fig.1 (a), the x-axis direction, y-axis direction, and z-axis direction which mutually orthogonally cross are prescribed | regulated. FIG. 1B is a cross-sectional view (zx cross-sectional view) taken along the cross-section A shown in FIG. As will be described later, the x-axis direction is a relative movement direction of the vibrating body 11 and the driven body 12 constituting the vibration type actuator 1. The z-axis direction is the thickness direction of the elastic body 112 constituting the vibrating body 11, and is the protruding direction of the protrusions 112a and 112b provided on the elastic body 112. The y-axis direction is a direction orthogonal to both the x-axis direction and the z-axis direction, and is also the width direction of the elastic body 112.

  The vibration type actuator 1 includes a vibration body 11, a driven body 12, a screw 13, a vibration body holding member 14, a pressure unit 15, a rolling member 16, a cover plate 17, and a screw 18. The vibrating body 11 includes a piezoelectric element 111 and an elastic body 112. The piezoelectric element 111 which is an electro-mechanical energy conversion element has a structure in which a predetermined shape of electrode film is formed on the front and back surfaces of a rectangular and flat piezoelectric ceramic, for example. For example, lead zirconate titanate (PZT) is used as the piezoelectric ceramic, and the piezoelectric ceramic is polarized in the z-axis direction which is the thickness direction. The piezoelectric element 111 is bonded to one surface of a rectangular and flat elastic body 112 using an adhesive. The elastic body 112 is made of, for example, stainless steel (stainless steel plate). On the surface of the elastic body 112 opposite to the surface to which the piezoelectric element 111 is bonded, projections 112a and 112b are formed at two locations at predetermined intervals in the longitudinal direction (x-axis direction). Further, bonded portions 112 c and 112 d for bonding the vibrating body 11 to the vibrating body holding member 14 are formed at the longitudinal ends of the elastic body 112, respectively. The drive vibration excited on the vibrating body 11 will be described later.

  The driven body 12 includes a friction member 121 and a friction member fixing portion 122. Although the friction member 121 is fixed to the friction member fixing portion 122 using the screw 13, the fixing method is not limited. The protrusions 112 a and 112 b of the vibrating body 11 are in contact with the friction member 121 by the pressure applied from the pressurizing unit 15. Although details will be described later, the vibrating body 11 is excited by applying elliptical motion in the zx plane to the tips of the protrusions 112a and 112b and applying a thrust (friction force) to the friction member 121 from the protrusions 112a and 112b. And the driven body 12 can be relatively moved in the x-axis direction. From the viewpoint of smoothly moving the vibrating body 11 and the driven body 12 and obtaining sufficient durability, the sliding surface of the friction member 121 that is in pressure contact with the protrusions 112a and 112b is smooth and has high hardness. It is desirable that Therefore, in the present embodiment, for example, a stainless steel plate is used for the friction member 121. For example, a resin molded body can be used for the friction member fixing portion 122.

  The vibrating body holding member 14 is made of resin, for example. Holes are formed in the bonded portions 112c and 112d of the elastic body 112, and convex portions are formed in the vibrating body holding member 14 so as to be fitted with the holes formed in the bonded portions 112c and 112d. . The vibrating body 11 is fixed to the vibrating body holding member 14 by fitting the holes of the joined portions 112c and 112d and the convex portions of the vibrating body holding member 14 and bonding them with an adhesive or the like.

  The pressure unit 15 includes a pressure plate 151 and a pressure member 152. The pressure plate 151 is made of an elastic member such as felt. The pressure plate 151 uniformly applies the pressing force (biasing force) from the pressure member 152 to the piezoelectric element 111 and applies drive vibration to the pressure member 152 excited by the vibrating body 11. Suppress transmission. The pressure member 152 is, for example, a coil spring, and is incorporated between the pressure plate 151 and the vibrating body holding member 14 in a state of being compressed and deformed. Therefore, the force at which the pressure member 152 tries to extend is transmitted to the vibrating body 11 via the pressure plate 151, so that the tips of the protrusions 112 a and 112 b are in pressure contact with the sliding surface of the friction member 121. A guide groove 14a in which the rolling member 16 is disposed is provided on the surface of the vibration body holding member 14 opposite to the surface on which the vibration body 11 is disposed.

  The cover plate 17 is fixed to the friction member fixing portion 122 using screws 18 (or screws or the like). At this time, the ball as the rolling member 16 is inserted between the guide groove 14 a provided in the vibrating body holding member 14 and the cover plate 17. Thereby, the vibrating body 11, the vibrating body holding member 14, and the pressure unit 15 are integrally guided by the guide groove 14 a and can move relative to the driven body 12 in the x-axis direction. Yes.

  The configuration shown in FIG. 1 is an example of the configuration of the vibration type actuator according to the embodiment of the present invention, and the configuration of the vibration type actuator according to the embodiment of the present invention is not limited to the configuration shown in FIG. For example, the configuration in which the vibrating body 11 is brought into pressure contact with the friction member 121 is not a configuration in which the pressure plate 151 is pushed by the force that the pressure member 152 tries to extend, but the pressure plate that is pressed by the force that the pressure member 152 tries to contract. The structure which pulls 151 may be sufficient. Moreover, the structure which the friction member 121 moves may be sufficient instead of the structure to which the vibrating body 11 moves.

  Next, the positions of the protrusions 112a and 112b in the vibrating body 11 and the driving vibration excited on the vibrating body 11 will be described. FIG. 2A is a side view of the vibrating body 11. FIG. 2B is a front view of the vibrating body 11. FIG. 2C is a bottom view of the vibrating body 11. Protrusions 112a0 and 112b0 indicated by broken lines in FIGS. 2A and 2C respectively indicate the projecting parts of the vibrator according to the conventional example (the above-mentioned Patent Document 1). FIG. 3 is a diagram illustrating a mode of driving vibration excited by the vibrating body 11 ′ by simplifying the vibrating body 11 ′ according to the conventional example. 3A is a view (side view) of the vibrating body 11 ′ viewed from the y-axis direction, and FIG. 3B is a view (front view) of the vibrating body 11 ′ viewed from the x-axis direction. is there. FIG. 4 is a diagram illustrating a mode of driving vibration excited by the vibrating body 11 by simplifying the vibrating body 11 in the present embodiment. 4A is a view (side view) of the vibrating body 11 viewed from the y-axis direction, and FIG. 4B is a view (front view) of the vibrating body 11 viewed from the x-axis direction.

  The drive vibration excited by the vibrator according to the conventional example and the movement of the protrusions 112a0 and 112b0 are compared with the drive vibration excited by the vibrator 11 and the movement of the protrusions 112a and 112b in the present embodiment. To do. 2, 3, and 4, positions M and P represent positions in the x-axis direction of the centers of the protrusions 112 a 0 and 112 b 0 included in the vibrating body 11 ′. The position O represents the center of the vibrating bodies 11 and 11 ′ in the x-axis direction and is common to the vibrating bodies 11 and 11 ′. The position L represents the center in the y-axis direction of the vibrating bodies 11 and 11 ′, is the position in the y-axis direction of the center of the protrusions 112a0 and 112b0, and is the y-axis direction of the center of the protrusions 112a and 112b. It is also the position at. 2 and 4, positions N and Q represent positions in the x-axis direction of the centers of the protrusions 112 a and 112 b included in the vibrating body 11. The distance between the position M and the position N in the x-axis direction and the distance between the position P and the position Q are both a predetermined distance δ.

  The same drive vibration is excited in the vibrating bodies 11 and 11 ′. The drive vibration can be generated by exciting the vibrations in the two vibration modes simultaneously to the vibrators 11 and 11 ′. As shown in FIGS. 3A and 4A, one vibration mode is a natural vibration mode (mode 1 (primary out-of-plane bending) having three nodal lines substantially parallel to the y-axis in the x-axis direction. Vibration mode)). As shown in FIGS. 3B and 4B, another vibration mode is a natural vibration mode (mode 2 (2) having two nodal lines substantially parallel to the x-axis in the y-axis direction. The next out-of-plane bending vibration mode)). 3 and 4 exaggerately show how the vibrating bodies 11 and 11 'are deformed in each vibration mode.

  The protrusions 112a0 and 112b0 vibrate in the x-axis direction due to mode 1 vibration, and vibrate in the y-axis direction due to mode 2 vibration. Therefore, by simultaneously exciting each vibration of mode 1 and mode 2 with a predetermined phase difference, the driving vibration in which the tip of the protrusions 112a0 and 112b0 draws an elliptical locus in the zx plane (elliptical movement) is generated as a vibrating body. 11 '. Similarly, elliptical motion can also be generated at the tips of the protrusions 112a and 112b by simultaneously exciting the vibrations of mode 1 and mode 2 with a predetermined phase difference.

  The positions M, O, and P correspond to the position of the mode 1 vibration node line (hereinafter referred to as “node position”), and the position L corresponds to the antinode position of mode 2 vibration. The positions of the centers of the protrusions 112a0 and 112b0 according to the conventional example in the x-axis direction match the positions M and P, and the position in the y-axis direction matches the position L. On the other hand, the positions of the centers of the protrusions 112a and 112b in the present embodiment in the x-axis direction coincide with the positions N and Q that are uniformly displaced in the x-axis direction by the distance δ from the positions M and P, and the y-axis The position in the direction matches the position L. Here, the distance d between the two protrusions 112a and 112b is set to an approximately integral multiple of the wavelength of mode 1 (except for zero). Note that the protrusions 112a and 112b and the protrusions 112a0 and 112b0 have different positions in the X-axis direction on the vibrating bodies 11 and 11 ′, and thus the trajectory of the elliptical motion generated at the respective tips is different. The details will be described later.

  Next, the operation of the vibrating body 11 in the present embodiment will be described in comparison with the operation of the vibrating body 11 ′ according to the conventional example. FIG. 5A shows the protrusions 112a0 when the phase difference between the vibrations of modes 1 and 2 is set to approximately π / 2 (approximately 90 °) to excite the drive vibration in the vibration body 11 ′ according to the conventional example. It is a figure explaining the vibration displacement of the front-end | tip of 112b0. FIG. 5B shows the locus of vibration displacement at the tips of the protrusions 112a0 and 112b0 when the vibration of modes 1 and 2 is set to a phase difference of approximately π / 2 to excite the drive vibration in the vibrating body 11 ′. It is a figure explaining.

  In the vibrating body 11 ′ according to the conventional example, as described above, the centers of the protrusions 112a0 and 112b0 are at the mode 1 vibration node positions and at the mode 2 vibration antinode positions. As shown in FIG. 3, when mode 1 vibration is excited in the vibrating body 11 ′, the tips of the protrusions 112 a 0 and 112 b 0 have displacements in the x-axis direction as main components and displacements in the y-axis direction and the z-axis direction. A sufficiently small vibration displacement occurs. In addition, when mode 2 vibration is excited in the vibrating body 11 ′, vibration displacements are generated in the protrusions 112 a 0 and 112 b 0 with the displacement in the z-axis direction and the displacement in the x-axis direction and the y-axis direction being sufficiently small. . Therefore, when the phase difference between the vibrations of modes 1 and 2 is set to approximately π / 2, as shown in FIG. 5A, the vibration phase φ ′ of the vibration displacement in the x-axis direction and the vibration displacement in the z-axis direction is also It becomes approximately π / 2. As a result, as shown in FIG. 5B, elliptical motion can be generated in the zx plane at the tips of the protrusions 112a0 and 112b0, and the elliptical locus at this time passes through the center of the ellipse parallel to the z axis. The shape is substantially line symmetrical about the axis. It should be noted that the rotational direction of the elliptical motion is reversed when the phase difference between modes 1 and 2 is + π / 2 and when −π / 2.

  FIG. 6A shows the vibrations at the tips of the protrusions 112a and 112b when the vibration difference of modes 1 and 2 is set to approximately π / 2 to excite the drive vibration in the vibration body 11 in this embodiment. It is a figure explaining a displacement. FIG. 6B illustrates the locus of vibration displacement at the tips of the protrusions 112a and 112b when the vibrations of modes 1 and 2 are set to a phase difference of π / 2 to excite the drive vibration in the vibrating body 11. FIG.

  In the vibrating body 11, the centers of the protrusions 112 a and 112 b are at the antinode position for the mode 2 vibration, but at the position shifted by the distance δ from the node position for the mode 1 vibration. As shown in FIG. 4, when mode 2 vibration is excited in the vibrating body 11, as in the vibrating body 11 ′ according to the conventional example, the protrusions 112 a and 112 b have displacement in the z-axis direction as a main component. As a result, vibration displacement occurs in which the displacement in the x-axis direction and the y-axis direction is sufficiently small. The vibration displacement in this case is indicated by a solid line in the upper part of FIG. On the other hand, when mode 1 vibration is excited in the vibrating body 11, the displacement in the y-axis direction is sufficiently small at the tips of the protrusions 112a and 112b, but vibration displacement having displacement in the x-axis direction and the z-axis direction is generated. .

  Therefore, when the phase difference between the vibrations of modes 1 and 2 is set to approximately π / 2, the z-axis direction component of the vibration displacement is the z-axis direction of the vibration displacement of mode 1 as shown in the lower part of FIG. The vibration displacement (one-dot chain line) is obtained by superimposing the component (solid line) and the z-axis direction component (broken line) of the vibration displacement in mode 2. As a result, the vibration phase φ between the vibration displacement in the x-axis direction and the vibration displacement in the z-axis direction becomes less than π / 2, and the elliptical locus drawn by the tips of the protrusions 112a and 112b in the zx plane is shown in FIG. As shown in FIG. 4, the asymmetric shape is not line symmetric with respect to an axis parallel to the z axis and passing through the center of the ellipse. Note that the distance d in the x-axis direction between the protrusions 112a and 112b is set to be approximately an integer multiple of the wavelength of mode 1 as described above, so that the shape of the elliptical locus drawn by the tip of the protrusion 112a and the protrusion 112b The shape of the elliptical locus drawn by the tip is substantially the same as the shape shown in FIG.

  In the vibration type actuator 1, the vibrating body 11 is pressurized toward the friction member 121 by the pressure unit 15, and the protrusions 112 a and 112 b are in pressure contact with the friction member 121. Therefore, when an elliptical motion is excited at the tips of the protrusions 112a and 112b as described above, thrust is applied from the protrusions 112a and 112b to the friction member 121. In this way, the integrated vibrating body 11, the vibrating body holding member 14, and the pressure unit 15, and the integrated driven body 12 and cover plate 17 can be relatively moved in the x-axis direction. At that time, the action of the thrust that the vibrating body 11 gives to the friction member 121 will be described below in comparison with the action of the thrust that the vibrating body 11 ′ according to the conventional example gives to the friction member 121.

  FIG. 7 is a diagram for explaining the action of thrust applied to the friction member 121 by the vibrating body 11 ′ according to the conventional example. 7A and 7B, the rotation directions of the elliptical motions of the protrusions 112a0 and 112b0 are reversed. FIG. 8 is a diagram for explaining the action of thrust applied to the friction member 121 by the vibrating body 11 in the present embodiment. 8A and 8B, the rotation directions of the elliptical motions of the protrusions 112a and 112b are reversed. In FIGS. 7 and 8, the structures of the vibrating bodies 11 ′ and 11 are simplified, and the deformation of the vibrating bodies 11 ′ and 11 is exaggerated.

  In FIG. 7A, since the rotation direction of the protrusions 112a0 and 112b0 is the negative direction in the x-axis direction with respect to the sliding surface of the friction member 121, it is assumed that the friction member 121 is fixed. The vibrating body 11 ′ moves in the positive direction of the x-axis direction. The no-load speed at this time is denoted by va ′. In FIG. 7B, since it is assumed that the friction member 121 is fixed because the rotation direction of the projections 112a0 and 112b0 is the positive direction in the x-axis direction with respect to the sliding surface of the friction member 121. The vibrating body 11 ′ moves in the negative direction of the x-axis direction. The no-load speed at this time is assumed to be vb ′. Similarly, in FIG. 8A, since the rotation direction of the protrusions 112a and 112b is the negative direction in the x-axis direction with respect to the sliding surface of the friction member 121, it is assumed that the friction member 121 is fixed. In this case, the vibrating body 11 moves in the positive direction of the x-axis direction. The no-load speed at this time is assumed to be va. In FIG. 8B, when the rotation direction of the protrusions 112a and 112b is the positive direction in the x-axis direction with respect to the sliding surface of the friction member 121, it is assumed that the friction member 121 is fixed. The vibrating body 11 moves in the negative direction of the x-axis direction. The no-load speed at this time is assumed to be vb.

  As shown in FIG. 7A, the direction of the force when the protrusions 112a0 and 112b0 of the vibrating body 11 ′ according to the conventional example contact the friction member 121 is set to fa ′. At this time, the sliding of the friction member 121 The force in the x-axis direction of the thrust acting on the surface is referred to as fax ′. Further, as shown in FIG. 7B, the direction of the force when the protrusions 112a0 and 112b0 contact the friction member 121 is fb ′, and the x-axis direction acting on the sliding surface of the friction member 121 at this time Is the force fbx ′. Then, the force fax ′ is directed in the negative direction of the x axis, the force fbx ′ is directed in the positive direction of the x axis, and the directions of the forces fax ′ and fbx ′ are opposite to each other. At this time, as shown in FIG. 5B, the elliptical trajectory drawn by the tips of the protrusions 112a0 and 112b0 has a shape substantially axisymmetric with respect to an axis parallel to the z axis and passing through the center of the ellipse. And the magnitude of the force fbx ′ substantially coincide with each other. Therefore, the no-load speed va ′ and the no-load speed vb ′ are substantially the same.

  On the other hand, as shown in FIG. 8A, the force when the projections 112a and 112b of the vibrating body 11 contact the friction member 121 is fa, and the sliding surface of the friction member 121 at this time Let the force in the x-axis direction acting on be Further, as shown in FIG. 8B, the force when the protrusions 112 a and 112 b come into contact with the friction member 121 is fb, and the x-axis direction acting on the sliding surface of the friction member 121 at this time is defined as fb. Let the force be fbx. The force fax is directed in the negative direction of the x-axis, and the negative direction of the x-axis is the direction in which the protrusions 112a and 112b move on the sliding surface of the friction member 121. It acts to promote the movement of the in the positive direction. On the other hand, the force fbx is directed in the negative direction of the x-axis, and the negative direction of the x-axis is opposite to the direction in which the protrusions 112a and 112b move on the sliding surface of the friction member 121. The force fbx acts to suppress the movement of the vibrating body 11 in the negative direction of the x axis. As a result, the no-load speed vb becomes slower than the no-load speed va, and in this respect, the driving characteristics of the vibrating body 11 are different from the driving characteristics of the vibrating body 11 ′ according to the conventional example. In addition, since the shapes of the elliptical trajectories drawn by the protrusions 112a and 112b are substantially the same, the forces sent out by the protrusions 112a and 112b do not interfere (cancel), and thus are due to the elliptical motion of the tips of the protrusions 112a and 112b. The force can be efficiently transmitted to the friction member 121.

  FIG. 9A is a velocity-thrust diagram of a vibration type actuator including a vibrating body 11 ′ according to a conventional example. FIG. 9B is a velocity-thrust diagram of the vibration type actuator 1 including the vibrating body 11 in the present embodiment. In the following description, it is assumed that the friction member 121 is fixed and the vibrating bodies 11 and 11 ′ move in the x-axis direction as described with reference to FIGS. 7 and 8. In FIG. 9B, the relationship between the speed and the thrust when the vibrating body 11 moves in the positive direction of the x axis is represented by a solid line, and the speed when the vibrating body 11 moves in the negative direction of the x axis and The relationship of thrust is represented by a broken line.

  As shown in FIG. 9A, when the load on the vibrating body 11 ′ is no load (T = 0), the no-load speed va ′ and the negative direction when the vibrating body 11 ′ moves in the positive direction of the x-axis. The no-load speed vb ′ when moving to is substantially the same speed v. On the other hand, as shown in FIG. 9B, when the load on the vibrating body 11 is no load, the no-load speed va when the vibrating body 11 moves in the positive direction of the x axis is negative in the x axis. It is larger than the no-load speed vb when moving in the direction. On the other hand, since the static frictional force of the protrusions 112a and 112b against the friction member 121 is the same, the stop torque Ts matches regardless of the moving direction of the vibrating body 11.

  As shown in FIG. 9, the load on each of the vibrating bodies 11 and 11 ′ is different between the positive direction and the negative direction of the x-axis. As shown in FIG. 9, the driving load is T1 in one direction (positive direction) and the other direction (negative) In the direction), it is assumed that the driving load is T2, and the relationship of T1> T2 is established. In this case, in the vibrating body 11 ′ according to the conventional example, the moving speed in the direction in which the drive load T1 is applied is v1 ′, and the moving speed in the direction in which the drive load T2 is applied is v2 ′. A large difference occurs in the moving speed depending on the moving direction. In contrast, in the vibrating body 11 according to the present embodiment, the direction in which the no-load speed is va (> vb) is matched with the direction in which the drive load is T1, and the direction in which the no-load speed is vb is the drive load. Is made to coincide with the direction in which T2 becomes T2. Thereby, the difference between the moving speed v1 in the direction in which the drive load T1 is applied and the moving speed v2 in the direction in which the drive load T2 is applied can be reduced. That is, in the vibration type actuator 1 according to this embodiment, when the driving load is different in each moving direction in which the vibrating body 11 and the driven body 12 are relatively moved, the AC voltage for driving the vibrating body 11 is controlled. Without performing, the difference in the moving speed in each moving direction can be reduced.

  Next, an application example of the vibration type actuator 1 will be described by taking up a lens driving device provided inside a lens barrel included in an imaging device such as a digital camera. FIG. 10 is a cross-sectional view showing a schematic configuration of the lens driving device 40 provided in the lens barrel. The lens driving device 40 includes the vibration type actuator 1, a driven portion 91, an urging member 92, and a guide member 93. In addition, in FIG. 10, the structure of the vibration type actuator 1 is represented simply. The vibration type actuator 1 has a lens so that the relative moving direction (x-axis direction) of the vibrating body 11 and the driven body 12 coincides with the optical axis direction (the x-axis and the optical axis are substantially parallel). It is arranged in the lens barrel. The driven body 12 is fixed to a frame (not shown) of the lens barrel, and when the vibration type actuator 1 is driven, the vibrating body holding member 14 that holds the vibrating body 11 with respect to the driven body 12. Is movable in the x-axis direction (optical axis direction).

  The driven unit 91 includes a lens 911 and a lens holding member 912. The lens 911 is, for example, a focus lens or a zoom lens. By moving the focus lens in the optical axis direction, a desired subject can be focused (focused). In addition, the shooting angle of view can be changed by moving the zoom lens in the optical axis direction. Here, a configuration including one lens 911 as the driven portion 91 is shown, but the driven portion 91 has a configuration in which a lens group composed of a plurality of lenses is held by a lens holding member 912. May be.

  Each of the two guide members 93 is, for example, a cylindrical rod-shaped member, and is disposed on a frame (not shown) or the like so that the thrust direction (axial direction) is parallel to the optical axis direction of the lens 911. A lens holding member 912 that holds the lens 911 is connected to the vibrating body holding member 14 and is fitted to the two guide members 93 so as to be movable in the optical axis direction. Therefore, the driven portion 91 can be moved in the optical axis direction by driving the vibration type actuator 1 and moving the vibrating body 11 relative to the driven body 12.

  The configuration of the vibration type actuator 1 mounted on the lens driving device 40 is the same as the configuration shown in FIGS. That is, the positions of the protrusions 112a and 112b of the vibrating body 11 in the x-axis direction are uniformly shifted from the nodal position of the mode 1 vibration by the distance δ in the positive direction (second direction) in the x-axis direction. Is provided. In other words, the protrusions 112a and 112b of the vibrating body 11 are provided at positions shifted from the node position of the mode 1 vibration by the distance δ in the direction opposite to the urging direction by the urging member 92. The distance δ is set to less than ¼ of the wavelength of mode 1 vibration. Other configurations are the same as those described with reference to FIG.

  Here, the lens holding member 912 is always moved in the negative direction (first direction) in the x-axis direction by the urging member 92 so that a fitting gap does not occur at the connecting portion between the lens holding member 912 and the vibrating body holding member 14. It is energized. That is, the biasing member 92 always has a force to shrink. In the present embodiment, a coil spring is used as the urging member 92, but the present invention is not limited to this. One of the two guide members 93 is inserted into a coil spring that is a biasing member 92, one end of the coil spring is fixed to the lens holding member 912, and the other end is fixed to a frame (not shown) of the lens barrel. The

  Since the lens holding member 912 is constantly urged in the negative x-axis direction by the urging member 92, the vibrating body 11 is moved positive in the x-axis direction in order to move the lens holding member 912 in the positive x-axis direction. When moving in the direction, a force against the urging force of the urging member 92 is required. Therefore, the driving load for moving the vibrating body 11 in the positive direction of the x-axis direction is larger than the driving load for moving the vibrating body 11 in the negative direction of the x-axis direction.

  Therefore, when the vibrating body 11 is moved in the positive direction of the x-axis direction, as shown in FIG. 8A, the tips of the protrusions 112a and 112b draw a clockwise elliptical locus in the zx plane. To drive. Thereby, the speed-thrust diagram when moving the vibrating body 11 in the positive direction of the x-axis direction can be set to the characteristic indicated by the solid line in FIG. 9B. Further, when the vibrating body 11 is moved in the negative x-axis direction, the tips of the protrusions 112a and 112b draw an anticlockwise elliptical locus in the zx plane as shown in FIG. 8B. To drive. Thereby, the speed-thrust diagram when moving the vibrating body 11 in the negative direction of the x-axis direction can be set to the characteristics indicated by the broken line in FIG. Therefore, when the moving direction of the vibrating body 11 is switched between the positive direction and the negative direction in the x-axis direction in order to advance and retract the lens holding member 912 in the optical axis direction, the AC voltage for driving the vibrating body 11 is controlled. The difference in the moving speed in each moving direction can be reduced.

  Although the present invention has been described in detail based on preferred embodiments thereof, the present invention is not limited to these specific embodiments, and various forms within the scope of the present invention are also included in the present invention. included. For example, although the vibration body 11 has been described as having two protrusions 112a and 112b, it may be provided with a plurality of three or more protrusions, or conversely, only one protrusion is provided. It may be a thing. Even when there is one protrusion, the protrusion is located at a position shifted by a distance δ in the positive direction of the x-axis from the node position (position M, O, P) of mode 1 vibration in the x-axis direction, and in mode 2 It may be provided at the antinode position of the vibration. Further, in the above-described embodiment, the linear drive type vibration type actuator in which the vibrating body moves linearly relative to the friction member is taken up. However, the present invention can be applied only to the linear drive type vibration type actuator. It is not a thing. For example, even in the case of a vibration type actuator configured to rotationally drive an annular or disk-shaped friction member, when the driving load of the driven body varies depending on the rotation direction, the above-described implementation is possible. The same effect as the form can be obtained. The lens driving device 40 described with reference to FIG. 10 is not limited to the lens barrel of the imaging device, and can be used as a lens driving source for, for example, a microscope, a telescope, and other various optical devices. Further, the driven object driven by the vibration type actuator may be other than the lens holding member, and the present invention is applicable to electronic devices other than optical devices.

DESCRIPTION OF SYMBOLS 1 Vibration type actuator 11 Vibrating body 12 Driven body 15 Pressure unit 40 Lens drive device 92 Energizing member 93 Guide member 111 Piezoelectric element 112 Elastic body 112a, 112b Protrusion part 121 Friction member 911 Lens 912 Lens holding member

Claims (9)

A vibration type actuator in which the vibration body and the friction member move relative to each other when a driving vibration is excited in the vibration body pressed into contact with the friction member,
The vibrator is
A flat elastic body;
A protrusion provided on one surface of the elastic body so as to protrude in the thickness direction of the elastic body, and abutting against the friction member;
An electro-mechanical energy conversion element bonded to the other surface of the elastic body,
The nodal line when the driving vibration including a vibration mode having a nodal line substantially parallel to a direction perpendicular to both the thickness direction of the elastic body and the relative moving direction of the vibrating body and the friction member is excited. The vibration type actuator is characterized in that the protrusion is provided at a position shifted from the position by a predetermined distance in the moving direction.   The vibration type actuator according to claim 1, wherein the predetermined distance is less than ¼ of the wavelength of the vibration mode.   The vibration type actuator according to claim 1, wherein the plurality of protrusions are provided at positions that are uniformly deviated from the position of the nodal line in the moving direction.   The vibration type actuator according to claim 3, wherein an interval between the plurality of protrusions in the moving direction is substantially an integer multiple of a wavelength of the vibration mode. A vibration type actuator in which the vibration body and the friction member move relative to each other when a driving vibration is excited in the vibration body pressed into contact with the friction member,
The vibrator is
An elastic body,
A protrusion provided on one surface of the elastic body so as to protrude in the thickness direction of the elastic body, and abutting against the friction member;
An electro-mechanical energy conversion element bonded to the other surface of the elastic body,
The protrusion is driven to vibrate the vibrating body so that the tip of the protrusion performs an elliptical motion in a plane including both the thickness direction of the elastic body and the relative movement direction of the vibrating body and the friction member. The elliptical locus at the tip of the protrusion in the plane is provided at a position that is not line-symmetric with respect to an axis that passes through the center of the elliptical locus and is parallel to the thickness direction. Vibration type actuator. The vibration type actuator according to any one of claims 1 to 4,
A lens holding member that holds the lens and is driven in the optical axis direction by the vibration actuator;
A biasing member that biases the lens holding member in a first direction in the optical axis direction;
A guide member for guiding the lens holding member in the optical axis direction,
In the vibration type actuator, the protrusion is provided at a position shifted from the position of the nodal line by a predetermined distance in a second direction which is a direction opposite to the first direction. Lens drive device. The vibration type actuator according to claim 5,
A lens holding member that holds the lens and is driven in the optical axis direction by the vibration actuator;
A biasing member that biases the lens holding member in a first direction in the optical axis direction;
A guide member for guiding the lens holding member in the optical axis direction,
In the vibration-type actuator, the component of the moving direction of the force when the tip of the protruding portion makes an elliptical motion and contacts the friction member has the first direction regardless of the rotational direction of the elliptical motion. A lens driving device characterized by facing. A lens driving device according to claim 6 or 7,
The optical device, wherein the guide member and the friction member of the vibration type actuator are fixed, and the lens holding member and a vibration body holding member that holds the vibration body in the vibration type actuator are connected. . The vibration type actuator according to any one of claims 1 to 5,
An electronic device comprising: a driving object driven by the vibration actuator.

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