JP2009090213A - Oscillatory wave driving apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce difference in the frequency of two resonance modes of a bolt-fastened Langevin type oscillator, increase the output power per unit volume, and economically stabilize motor capability. <P>SOLUTION: The oscillatory wave driving apparatus comprises an elastic body having a through hole having a step part, a fastening member, an electric-mechanical energy conversion device installed in the elastic body and the fastening member and having a through hole, a shaft which has a screw part to be fitted with the fastening member by screwing and a step part for regulating the position of the thrust direction of the elastic body and is to be inserted into the through holes of the elastic body and the electric-mechanical energy conversion device, and an oscillating body which fixes the elastic body sandwiched between the step part and the fastening member and the electric-mechanical energy conversion device by fastening the fastening member in the shaft and the normal line direction of a contact face of the shaft step and the step part of the elastic body faces nearer to the axial center direction as it is in more outer circumferential side. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vibrator used in a vibration wave driving device used for a camera lens, OA equipment, or the like. In particular, the present invention relates to the structure of a vibrator of a small rotary vibration wave driving device.

  The vibration wave driving device has been applied to products such as camera lens driving applications, and there are an annular type and a rod type.

As a rod-type vibration wave driving device, for example, an ultrasonic motor, there is, for example, Japanese Patent Laid-Open No. 4-91671, and the driving principle is described therein. In the vibrator disclosed herein, an electro-mechanical energy conversion element is sandwiched and fixed from both sides by an elastic member, and a vibrating body is constituted by the electro-mechanical energy conversion element and the elastic member. Further, the vibrator disclosed in Japanese Patent Application Laid-Open No. 2004-112924 relates to a structure for sandwiching a vibrator, and is configured to have an outer peripheral high pressure structure in order to improve the characteristics of the vibrator. In addition, the vibrator disclosed in Japanese Patent Application Laid-Open No. 11-122955 has been attempted to improve the characteristics of the vibrator by integrating the elastic body and the shaft by plastic flow.
Japanese Patent Laid-Open No. 4-91671 JP 2004-112924 A Japanese Patent Laid-Open No. 11-122955

  However, in order to reduce the size of the vibration wave drive device in the longitudinal direction and achieve high output per unit volume, the contact structure of various parts has a greater effect on the characteristics of the vibrator than before. It has been found that further strength is required.

  A conventional bar-shaped ultrasonic motor integrates both parts by press-fitting an elastic body and a shaft or by plastic deformation. However, as a demand in the world, there is a desire to make such a rod-type vibrating body motor more inexpensive and increase its output.

  The conventional press-fitting method requires fairly strict dimensional tolerances, which inevitably increases costs. In addition, the initial characteristic Δf of the vibrator (difference in the resonance frequency of two different bending vibrations orthogonal to each other) is determined by pressing the elastic body and the shaft into the contact state in the circumferential direction (coupled state). Since unevenness occurs, it becomes large. In addition to reducing the motor performance, it is necessary to put the correction process into the assembly work process, which makes it impossible to fully automate the assembly of the vibrator, which is one of the factors that do not reduce the cost.

  Rather than integrating by press fitting, the vibration characteristics are better when the contact area is made as small as possible and the surface pressure is locally increased to cause vibration without causing relative sliding friction between the elastic body and the shaft. can get. Even if minute sliding friction occurs, vibration loss (internal loss) of the vibrating body caused by it can be suppressed to the minimum, so that even better vibration characteristics and motor performance than when press-fitted are obtained. It has recently been found that it can. The challenge is how to achieve such a configuration without costing small components.

  In addition, since the stress generated in each component increases when the output is increased, it is a problem to increase the strength of each component without incurring costs.

  An object of the present invention is to solve the above-described problems, and to realize a vibration wave driving device and a vibrator that can obtain high output at low cost and have small individual differences.

  In order to solve the above problems, the invention according to claim 1 of the present application is an elastic body in which a through-hole having a step portion is formed, a fastening member, and the elastic body and the fastening member. The elastic body and the electro-mechanical energy conversion element are formed with the electro-mechanical energy conversion element formed with a screw part screwed into the fastening member and a step part for regulating the position of the elastic body in the thrust direction. The elastic body sandwiched between the stepped portion and the fastening member by fastening the fastening member to the shaft, and the electro-mechanical energy conversion element. The vibrating body to be fixed is a vibration wave driving device in which the normal direction of the contact surface between the shaft step portion and the elastic step portion is directed toward the axial direction toward the outer peripheral side.

  The invention according to claim 2 of the present application is a vibration wave driving device in which the elastic step portion has at least an R portion.

  The invention according to claim 3 of the present application is a vibration wave driving device in which the elastic step portion is subjected to nitriding treatment.

  The invention according to claim 4 of the present application is a vibration wave drive device in which the rigidity of the shaft step portion is partially different in hardness or shape.

  According to the present invention, since the normal direction of the contact surface between the shaft step portion and the elastic step portion is directed toward the axial direction toward the outer peripheral side, both parts can be centered with a simple structure. For this reason, Δf generated at the initial stage of assembly, which has been generated due to pressure unevenness or the like of the portion that has been press-fitted in the past, is not generated, and the initial characteristics can be stabilized.

  In addition, relative slip between the elastic body and the shaft due to vibration can be maintained in a stable state because the force acting in the axial direction is stronger toward the outer peripheral side, and displacement in the radial direction can be prevented. Since the places where the surface pressure is increased are concentrated on the outer peripheral side, minute slips hardly occur and the internal loss of the vibrator can be reduced.

  Further, in order to increase the strength of the elastic body, the strength of the stainless steel member can be increased by providing a nitride layer up to the step portion of the elastic body, and the fatigue fracture limit has been improved.

  Next, details of the present invention will be described in accordance with the description of the embodiments.

  FIG. 1 shows a first embodiment.

  In FIG. 1 (a), b is a first elastic body having a step portion made of a material with low vibration damping such as metal, and c has a step portion for regulating the thrust direction of the first elastic body. It is a shaft which has a screw part screwed together with a fastening member. d is a piezoelectric element that is an electro-mechanical energy conversion element, e is a second elastic body, and f is a fastening member that is screwed with a screw portion formed on the shaft c.

  The shaft c is inserted into a through-hole provided in the central part of the first elastic body b, the piezoelectric element d, and the second elastic body e. A step is provided in the middle of the shaft c, and this step hits a step provided on the inner wall of the first elastic body b. A screw part is formed at the tip of the shaft c, and a first elastic body b, a piezoelectric element d, and a second elastic body are formed by screwing and tightening a fastening member f that is a fastening member to the screw part. e can be fixed and functions as the vibrator a.

  FIG. 1 (b) shows the state of the contact surface at the step portion of the first elastic body b and the shaft c. (Circle portion in FIG. 1 (a)) The edge portion of the step portion of the shaft c is in contact with the R portion of the step portion of the first elastic body b. By adopting such a configuration, it is possible to provide a centering action between the two parts with a simple structure, so that the side surface of the first elastic body b and the shaft c does not contact each other, and a stable gap g is formed. Can be formed. Since the gap g is uniformly on the circumference, it is possible to suppress the occurrence of the initial Δf (the difference between the resonance frequencies of two different bending vibrations orthogonal to each other of the vibrator).

  h is a flexible substrate, which is used to supply electric energy to the vibrator a to generate vibrations or to extract charges to the outside for detection of vibrations generated by the vibrator a. The upper end of the shaft c is fixed and supports the vibrator c.

At the time of driving, the electrodes of the piezoelectric element d are grouped into two electrode groups. When an alternating electric field having a different phase is applied to each electrode group from a power source (not shown), the transducers are orthogonal to each other. Two bending vibrations are excited. By adjusting the phase of the applied voltage, a 90-degree temporal phase difference can be given between the two vibrations. As a result, the bending vibration of the rod-shaped vibrator rotates around the axis of the vibrator. i is a contact body that comes into contact with the upper end of the vibrator a, and is rotationally driven by the combined vibration of the vibrator a. j is a contact spring that is in direct contact with the vibrator a, k is a gear for taking out an output, has a flange 1 and a sliding bearing structure, and makes the contact body i rotatable with respect to the shaft c. m is a coil spring as a spring member that presses the contact body i against the vibrator a, and enables frictional contact between the vibrator a and the contact body i.

  FIG. 2 shows a second embodiment.

  The step portion of the first elastic body b is composed of only the R portion. In order to increase the radial direction regulating force, it is desirable that the arc has a large curvature. By configuring the step part with only the R part, it is possible to create a structure that maximizes the radial restriction force by making the maximum use of the limited narrow space. It is possible to suppress the phenomenon that the child characteristics change.

  In addition, we thought that surface contact was good in the past, but by bringing it closer to line contact as much as possible, we can suppress the increase in internal loss caused by minute deviation due to vibration, and there is less vibration loss than before A vibrator can be provided.

  FIG. 3 shows a third embodiment.

  The surface of the step portion of the first elastic body b is nitrided to show a nitride layer n. The first elastic body b is a stainless steel member, and the surface hardness after nitriding is about 1200 [Hv]. Fatigue fracture strength can be increased by providing a nitride layer on the inner and outer diameters of the stainless steel member.

  FIG. 4 shows a fourth embodiment.

  Of the stepped portion of the shaft c, only the portion in contact with the first elastic body b is configured to reduce the hardness. By doing so, the shape of the shaft c is deformed along the R portion of the first elastic body b, and they are positioned at positions where they are stable. Therefore, the alignment effect for reducing the initial Δf can be stably obtained. In addition, by making the rigidity of the shaft c softer by one part in shape, it is possible to obtain an alignment effect that positions the shafts c at stable positions.

1 is a cross-sectional view of a vibration wave driving device as a first embodiment. Sectional drawing of the vibration wave drive device as 2nd Embodiment. Sectional drawing of the vibration wave drive device as 3rd Embodiment. Sectional drawing of the vibration wave drive device as 4th Embodiment.

Explanation of symbols

a vibrator
b First elastic body
c shaft
d Piezoelectric element
e Second elastic body
f Tightening member
g Clearance
h Flexible substrate
i Contact
j Contact spring
k gear
l Flange
m Coil spring
n Nitride layer

Claims (4)

  An elastic body in which a through hole having a step portion is formed, a fastening member, an electromechanical energy conversion element having a through hole formed between the elastic body and the fastening member, and the fastening member and the screw A screw part to be joined and a step part for regulating the position of the elastic body in the thrust direction are formed, the elastic body and a shaft inserted into a through hole of the electromechanical energy conversion element, and the fastening member A vibration body that fixes the elastic body and the electromechanical energy conversion element sandwiched between the stepped portion and the tightening member by tightening the shaft; and the shaft stepped portion and the elastic stepped portion A vibration wave driving device characterized in that the normal direction of the contact surface is oriented in the axial direction toward the outer peripheral side.   2. The vibration wave driving device according to claim 1, wherein the elastic body step portion has at least an R portion.   The vibration wave driving device according to claim 1, wherein the elastic step portion is subjected to nitriding treatment.   The vibration wave driving device according to any one of claims 1 to 3, wherein the rigidity of the shaft step portion is partially different in hardness or shape.

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