WO2012133650A1

WO2012133650A1 - Ultrasonic motor

Info

Publication number: WO2012133650A1
Application number: PCT/JP2012/058356
Authority: WO
Inventors: 瀧澤宏行
Original assignee: オリンパス株式会社
Priority date: 2011-03-31
Filing date: 2012-03-29
Publication date: 2012-10-04
Also published as: JP2012217237A

Abstract

Provided is an ultrasonic motor capable of efficiently producing a torsional resonant vibration by actively using the bending vibration of a piezoelectric element. An ultrasonic motor provided with at least an oscillator having a length ratio set in a manner such that a cross section perpendicular to the center axis is rectangular, and a rotor that is in contact with an elliptical-vibration-generating surface of the oscillator, and is rotationally driven with a center axis perpendicular to the elliptical-vibration-generating surface of the oscillator as the rotational axis, wherein: elliptical vibrations are formed by synthesizing a vertical primary resonant vibration that expands/contracts in the direction of the rotational axis of the oscillator, and a torsional secondary resonant vibration or torsional tertiary resonant vibration in which the rotational axis is set as the torsional axis thereof; and the length ratio of the rectangular shape of the oscillator is set in a manner such that the resonant frequencies of the vertical primary resonant vibration that expands/contracts in the direction of the rotational axis of the oscillator, and the torsional secondary resonant vibration or torsional tertiary resonant vibration in which the rotational axis is set as the torsional axis thereof almost match one another. Therein, the oscillator is provided with two polarization axes positioned along each of the two polarization directions, and each forming an acute angle in relation to the rotational axis.

Description

Ultrasonic motor

The present invention relates to an ultrasonic motor.

For example, Patent Document 1 listed below proposes an ultrasonic motor that generates elliptical vibration by synthesizing longitudinal vibration and torsional vibration of a vibrator and rotates a rotor. FIG. 1 of Patent Document 1 below shows an exploded perspective view of the vibrator, in which a plurality of piezoelectric elements are inserted between elastic bodies cut obliquely with respect to the vibrator axis direction. It has become. In addition, the positive electrode of the piezoelectric element is divided into two parts, which are referred to herein as A phase and B phase, respectively.

Here, by applying an alternating voltage having the same phase to the A phase and the B phase, longitudinal vibration can be generated in the rod-shaped vibrator. Further, torsional vibration can be generated in the rod-shaped vibrator by applying alternating voltages having opposite phases to the A phase and the B phase. The groove position of the vibrator is adjusted so that the resonance frequency of the longitudinal vibration and the resonance frequency of the torsional vibration are substantially matched. When alternating voltages having different π / 2 phases are applied to the A phase and the B phase, longitudinal vibration and torsional vibration are generated simultaneously, and elliptical vibration can be generated on the upper surface of the rod-shaped elastic body. By pressing the rotor against the upper surface of the rod-shaped elastic body, the rotor can be rotated clockwise (CW direction) or counterclockwise (CCW direction).

JP-A-9-117168

However, as shown in FIG. 1, the ultrasonic motor described in Patent Document 1 requires a piezoelectric element and an elastic body, the elastic body must be cut obliquely, longitudinal vibration and torsional vibration. In order to adjust the frequency, there are problems such as providing a groove in a part of the elastic body, a complicated structure, and difficulty in assembling. Therefore, the configuration of the vibrator as a whole becomes very complicated, and there is a problem that the generation efficiency of torsional resonance vibration is low.

Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide an ultrasonic motor capable of efficiently generating torsional resonance vibration by actively using bending vibration of a piezoelectric element. There is. In addition, the present invention comprises a single member, has a simple structure, does not require a groove, etc., can easily excite longitudinal vibration and torsional vibration, and synthesizes longitudinal vibration and torsional vibration. An object of the present invention is to provide an ultrasonic motor that forms elliptical vibration and rotates a rotor by elliptical vibration.

In order to solve the above-described problems and achieve the object, an ultrasonic motor according to the present invention includes a vibrator having a rectangular length ratio in a cross section perpendicular to the central axis, and an elliptic vibration generation surface of the vibrator. An ultrasonic motor comprising at least a rotor that is in contact with and is driven to rotate about a central axis that is orthogonal to the elliptical vibration generation surface of the vibrator as a rotational axis, and longitudinal longitudinal resonance vibration that expands and contracts in the direction of the rotational axis of the vibrator. And a torsional secondary resonance vibration or a torsional tertiary resonance vibration having a rotation axis as a torsion axis to form an elliptical vibration, and a longitudinal primary resonance vibration that expands and contracts in the direction of the rotation axis of the vibrator. The rectangular length ratio of the vibrator is set so that the resonance frequency of the torsional secondary resonance vibration or torsional tertiary resonance vibration with the rotation axis as the torsion axis is substantially the same. Two polarizations, each with an acute angle to Is characterized in that in comprises two polarization axes along respectively.

In the ultrasonic motor according to the present invention, it is preferable to set the relationship between the two polarization directions and the drive electrodes so that the vibrator expands and contracts in opposite directions along the two polarization directions.

In the ultrasonic motor according to the present invention, the vibrator is preferably made of, for example, a single plate or a laminate of single plates.

In the ultrasonic motor according to the present invention, the elliptical vibration is formed by combining the longitudinal primary resonance vibration and the torsional tertiary resonance vibration, and the drive electrode is arranged so as to correspond to the antinode position of the torsional tertiary resonance vibration. It is preferable.

In the ultrasonic motor according to the present invention, the elliptical vibration is formed by combining the longitudinal primary resonance vibration and the torsional secondary resonance vibration, and the drive electrode is arranged so as to correspond to the antinode position of the torsional secondary resonance vibration. It is preferable.

The ultrasonic motor according to the present invention has an effect that the torsional resonance vibration can be efficiently generated by positively using the bending vibration of the piezoelectric element. In addition, the ultrasonic motor of the present invention is composed of a single member, has a simple structure, does not require a groove, and can easily excite longitudinal vibration and torsional vibration. Are combined to produce elliptical vibration, and the rotor can be rotated by elliptical vibration.

It is a perspective view showing the composition of the ultrasonic motor concerning the embodiment of the present invention. It is a disassembled perspective view which shows the structure of the ultrasonic motor which concerns on embodiment of this invention. (A) is a perspective view showing a schematic configuration of a vibrator according to an embodiment of the present invention, (b) is a perspective view showing a vibration state in a torsional primary vibration mode by a broken line, and (c) is a longitudinal 1 A perspective view showing a vibration state in the secondary vibration mode by a broken line, (d) is a perspective view showing a vibration state in the torsional secondary vibration mode by a broken line, and (e) is a broken line showing a vibration state in the torsional tertiary vibration mode. It is the perspective view shown by. It is a graph showing the resonance frequency of each mode when the height of the vibrator is constant and the horizontal axis is the length of the short side / the length of the long side. It is a figure which shows the structure of the piezoelectric element for longitudinal vibration, Comprising: (a) is a perspective view, (b) is the side view seen from the VB direction of (a). (A) is a perspective view showing a state in which the longitudinal vibration piezoelectric element is extended when a drive signal is applied to the longitudinal vibration piezoelectric element of FIG. 5, and (b) is a side view seen from the VIB direction of (a). is there. 5A is a perspective view showing a state in which the longitudinal vibration piezoelectric element is contracted when a drive signal is applied to the longitudinal vibration piezoelectric element in FIG. 5, and FIG. 5B is a side view seen from the VIIB direction of FIG. is there. 5A is a perspective view showing a state in which the longitudinal vibration piezoelectric element expands and contracts when a drive signal is applied to the longitudinal vibration piezoelectric element in FIG. 5, and FIG. 5B is a side view seen from the VIIIB direction in FIG. is there. It is a figure which shows the structure of the piezoelectric element for diagonal vibration, Comprising: (a) is a perspective view, (b) is the side view seen from the IXB direction of (a). 9A is a perspective view showing a state in which the oblique vibration piezoelectric element is extended when a drive signal is applied to the oblique vibration piezoelectric element in FIG. 9, and FIG. 9B is a front view seen from the XB direction of FIG. is there. 9A is a perspective view showing a state in which the oblique vibration piezoelectric element is contracted when a drive signal is applied to the oblique vibration piezoelectric element of FIG. 9, and FIG. 9B is a front view seen from the XIB direction of FIG. is there. 9A is a perspective view showing a state in which the oblique vibration piezoelectric element is expanded and contracted when a drive signal is applied to the oblique vibration piezoelectric element in FIG. 9, and FIG. 9B is a front view seen from the XIIB direction in FIG. is there. (A) is a perspective view showing the configuration of a single plate type piezoelectric element for oblique torsional vibration, (b) is a side view seen from the XIIIB direction of (a), and (c) is seen from the XIIIC direction of (a). It is a side view. (A) is a perspective view showing an oblique torsion state when a drive signal is applied to the oblique torsional vibration piezoelectric element of FIG. 13, (b) is a side view seen from the XIVB direction of (a), and (c) is ( It is the side view seen from the XIVC direction of a). 13A is a perspective view showing oblique torsional vibration when a drive signal is applied to the oblique torsional vibration piezoelectric element of FIG. 13 in the direction opposite to that of FIG. 14, and FIG. 13B is a side view of FIG. 13A viewed from the XVB direction. FIG. 4C is a side view as seen from the XVC direction of FIG. (A) is a perspective view showing a configuration of a single plate type oblique torsional vibration piezoelectric element, (b) is a side view seen from the XVIB direction of (a), and (c) is seen from the XVIC direction of (a). It is a side view. (A) is a perspective view showing an oblique torsion state when a drive signal is applied to the oblique torsional vibration piezoelectric element of FIG. 16, (b) is a side view seen from the XVIIB direction of (a), and (c) is ( It is the side view seen from the XVIIC direction of a). 16A is a perspective view showing an oblique twist state when a drive signal is applied to the oblique torsional vibration piezoelectric element of FIG. 16 in the direction opposite to that of FIG. 17, and FIG. 16B is a side view seen from the XVIIIB direction of FIG. FIG. 4C is a side view as seen from the XVIIIC direction of FIG. (A) is a perspective view showing the structure of a bonded type oblique torsional vibration piezoelectric element, (b) is a side view seen from the XIXB direction of (a), and (c) is seen from the XIXC direction of (a). It is a side view. (A) is a perspective view showing an oblique torsion state when a drive signal is applied to the oblique torsional vibration piezoelectric element of FIG. 19, (b) is a side view seen from the XXB direction of (a), and (c) is ( It is the side view seen from the XXC direction of a). 19A is a perspective view showing an oblique torsion state when a drive signal is applied to the oblique torsional vibration piezoelectric element of FIG. 19 in the direction opposite to that of FIG. 20, and FIG. 19B is a side view of the piezoelectric element shown in FIG. (C) is a side view seen from the XXIC direction of (a). It is a perspective view which shows the structure of the vibrator | oscillator based on 1st Example. FIG. 23 is a diagram illustrating a side view seen from the direction XXIII in FIG. 22 and a view seen from the side of the vibration state in the torsional tertiary resonance vibration shown in FIG. It is the front view seen from the XXIV direction of FIG. It is a perspective view which shows the structure of the vibrator | oscillator based on 2nd Example. FIG. 26 is a diagram showing a side view seen from the XXVI direction in FIG. 25 and a view seen from the side of the vibration state in the torsional secondary resonance vibration shown in FIG. It is the front view seen from the XXVII direction of FIG.

Embodiments of an ultrasonic motor according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by the following embodiment.
An ultrasonic motor 100 according to an embodiment of the present invention generates elliptical vibration by synthesizing longitudinal primary resonance vibration and torsional secondary resonance vibration. As shown in FIGS. A rotor 102 is provided.

The vibrator 101 is a substantially rectangular parallelepiped piezoelectric element whose cross section perpendicular to the central axis 100c (rotation axis) has a rectangular length ratio. Of the rectangular cross section of the vibrator 101, two drive electrodes are provided on two short sides 101s facing each other. 1 and 2, only the two

drive electrodes

121 and 122 formed on one side of the two short sides 101s facing each other are illustrated.

The rotor 102 has a substantially disk shape, and its lower surface is in contact with the

frictional contact members

103a and 103b provided on the elliptical vibration generating surface 101a of the vibrator 101, and a central axis 100c orthogonal to the elliptical vibration generating surface 101a of the vibrator 101. Is driven to rotate about the rotation axis.

A structure for attaching the rotor 102 to the vibrator 101 will be described.
A holder 110 is fixed in the vicinity of a node of the vibrator 101 (piezoelectric element). Between the elliptical vibration generating surface 101a of the vibrator 101 and the holder 110, a shaft 105, a rotor 102, a bearing 107, a pressing spring 108, and a spring pressing ring 109 are arranged in this order. This arrangement is performed concentrically with respect to the central axis 100c.

A bearing 107 is coupled to the central recess 102a of the rotor 102, and a shaft 105 is inserted into the rotor 102 and the bearing 107 along the central axis 100c. The lower part of the shaft 105 is disposed in contact with the elliptical vibration generating surface 101 a of the vibrator 101.

The upper end of the shaft 105 inserted through the rotor 102 and the bearing 107 is inserted through the pressing spring 108 and the spring holding ring 109 in this order, and is further disposed above the holder 110 through the through hole 110a in the upper part of the holder 110. The shaft fixing ring 111 is screwed. Thereby, the shaft 105 is fixed to the holder 110.

The spring retainer ring 109 and the shaft 105 are screwed together by a thread groove, and by rotating the spring retainer ring 109 and changing its position relative to the shaft 105, the force of the pressing spring 108 is adjusted and the frictional contact of the rotor 102 is achieved. The amount of pressing force applied to the

members

103a and 103b can be adjusted.

Next, with reference to FIG. 3 and FIG. 4, the coincidence of the resonance frequencies of the vibrator 101 (piezoelectric element) used in the ultrasonic motor 10 will be described. FIG. 4 shows the change of the resonance frequency with respect to “the length of the short side / the length of the long side (a / b)”. The curve A1 shows the case of the torsional primary vibration, and the curve A2 shows the torsional secondary vibration. The curve A3 shows the case of torsional tertiary vibration, and the straight line B shows the case of longitudinal primary vibration.

As shown in FIG. 3A, the vibrator 101 has a substantially rectangular parallelepiped shape. The length of the short side 101s of the rectangular cross section orthogonal to the central axis 100c is a, the length of the long side 101f is b, The height along the central axis 100c is c. In the following description, the height direction is the direction of vibration in the primary vibration mode and the axial direction of torsion of torsional vibration. The magnitude relationship between a, b, and c is a <b <c.

In the vibrator 101, by setting the dimensions a, b, and c to appropriate values, the resonance frequency of the longitudinal primary vibration mode and the resonance frequency of the torsional secondary vibration mode or the torsional tertiary vibration mode are approximately set. Match.

Here, FIGS. 3B to 3E show the torsional vibration directions p1 and p2, the longitudinal vibration direction q, and the vibration node N. FIG. One node N exists at the center position in the height direction in the torsional primary vibration (FIG. 3B) and the longitudinal primary vibration (FIG. 3C), and the torsional secondary vibration (FIG. 3D). ) At two positions in the height direction, and at three positions in the height direction in the torsional tertiary vibration (FIG. 3 (e)).

Further, in FIGS. 3B to 3E, the solid line indicates the shape of the vibrator 101 before vibration, and the broken line indicates the shape of the vibrator 101 after vibration.

As can be seen from FIG. 4, when a / b is changed, the resonance frequency of the longitudinal primary vibration mode does not depend on a / b and takes a substantially constant value, but the resonance frequency of torsional vibration is It increases as the a / b value increases.

Also, the resonance frequency of the torsional primary vibration mode is not matched with the resonance frequency of the longitudinal primary vibration mode regardless of the value of a / b. In contrast, the resonance frequency of the torsional secondary vibration mode coincides with the resonance frequency of the longitudinal primary vibration mode in the vicinity where the a / b value is 0.6. The resonance frequency of the torsional tertiary vibration mode coincides with the resonance frequency of the longitudinal primary vibration mode where the a / b value is in the vicinity of 0.3. Therefore, in the vibrator 101, a / b is 0.25 to 0.35 in the longitudinal primary torsional tertiary vibration, and a / b is 0.5 to 0.6 in the longitudinal primary torsional secondary vibration. The lengths a and b are set as follows.

In the ultrasonic motor 100, a longitudinal primary resonance vibration that expands and contracts along the direction of the central axis 100c (rotation axis) of the vibrator 101 and a torsional secondary resonance vibration or a torsional tertiary resonance vibration having the center axis 100c as a torsion axis. Are combined to form an elliptical vibration. The ratio (ratio) of the lengths a and b is the longitudinal primary resonance vibration that expands and contracts in the direction of the central axis 100c of the vibrator 101 and the torsional secondary resonance vibration or the torsional tertiary resonance vibration that uses the central axis 100c as the torsion axis. The resonance frequencies of and are set so as to substantially match.

Next, a longitudinal vibration piezoelectric element, an oblique vibration piezoelectric element, and a torsional vibration piezoelectric element, which are the basis of the piezoelectric element used in the vibrator 101 of the above embodiment, will be described in order with reference to FIGS. To do.
First, the longitudinal vibration piezoelectric element will be described with reference to FIGS. 5A and 5B are diagrams showing a configuration of the longitudinal vibration piezoelectric element, in which FIG. 5A is a perspective view, and FIG. 5B is a side view seen from the VB direction of FIG. 6A is a perspective view showing a state in which the longitudinal vibration piezoelectric element is extended when a drive signal is applied to the longitudinal vibration piezoelectric element of FIG. 5, and FIG. 6B is a VIB direction of FIG. 6A. It is the side view seen from. 7A is a perspective view showing a state in which the longitudinal vibration piezoelectric element is contracted when a drive signal is applied to the longitudinal vibration piezoelectric element of FIG. 5, and FIG. 7B is a VIIB direction of FIG. 7A. It is the side view seen from. 8A is a perspective view showing a state in which the longitudinal vibration piezoelectric element expands and contracts when a drive signal is applied to the longitudinal vibration piezoelectric element of FIG. 5, and FIG. 8B is a VIIIB direction of FIG. 8A. It is the side view seen from.

As shown in FIGS. 5A and 5B, the longitudinal vibration piezoelectric element 150 is a substantially rectangular parallelepiped piezoelectric body. The longitudinal vibration piezoelectric element 150 is provided with a first drive electrode 150a on the top surface and a second drive electrode 150b on the bottom surface. The first drive electrode 150a and the second drive electrode 150b are each connected to an external power source (not shown). For connection, for example, FPC is used, and one end of the FPC is fixed to each electrode. Accordingly, a drive signal is applied to the longitudinal vibration piezoelectric element 150 via the first drive electrode 150a and the second drive electrode 150b. Therefore, the direction in which the drive signal is applied to the drive electrode is a direction from the first drive electrode 150a to the second drive electrode 150b or from the second drive electrode 150b to the first drive electrode 150a depending on the electrical polarity of the signal. It becomes.

The polarization direction P1 of the longitudinal vibration piezoelectric element 150 shown in FIGS. 5 to 8 is a direction from the second drive electrode 150b toward the first drive electrode 150a, and is along the direction in which the drive signal is applied.
The longitudinal vibration piezoelectric element 150 having such a configuration vertically vibrates in the vertical direction as shown in FIGS. 6 to 8 when a drive signal is applied. Specifically, when one of the positive and negative electrodes of the external power source is connected to the first drive electrode 150a and the other is connected to the second drive electrode 150b, the longitudinal vibration piezoelectric element 150 extends in the vertical direction (see FIG. 6) When the connection to the first drive electrode 150a and the second drive electrode 150b is exchanged, the longitudinal vibration piezoelectric element 150 contracts in the vertical direction (FIG. 7). Further, when alternating current is applied between the first drive electrode 150a and the

second drive electrode

150b, 150 expands and contracts along the vertical direction, that is, the polarization direction P1 (FIG. 8).
Therefore, the longitudinal vibration piezoelectric element 150 can be vibrated longitudinally in accordance with signals applied to the first drive electrode 150a and the second drive electrode 150b.

Next, the piezoelectric element for oblique vibration will be described with reference to FIGS. FIGS. 9A and 9B are diagrams showing the configuration of the piezoelectric element for oblique vibration, where FIG. 9A is a perspective view and FIG. 9B is a side view as seen from the IXB direction of FIG. 10A is a perspective view showing a state in which the oblique vibration piezoelectric element is extended when a drive signal is applied to the oblique vibration piezoelectric element in FIG. 9, and FIG. 10B is an XB direction of FIG. 10A. It is the front view seen from. 11A is a perspective view showing a state where the oblique vibration piezoelectric element is contracted when a drive signal is applied to the oblique vibration piezoelectric element of FIG. 9, and FIG. 11B is a XIB direction of FIG. 11A. It is the front view seen from. 12A is a perspective view showing a state in which the oblique vibration piezoelectric element expands and contracts when a drive signal is applied to the oblique vibration piezoelectric element of FIG. 9, and FIG. 12B is a XIIB direction of FIG. 12A. It is the front view seen from.

As shown in FIGS. 9A and 9B, the oblique vibration piezoelectric element 160 is a substantially rectangular parallelepiped piezoelectric element similar to the longitudinal vibration piezoelectric element 150. The oblique vibration piezoelectric element 160 is provided with a first drive electrode 160 a on the upper side of the side surface 161 and a second drive electrode 160 b on the lower side of the side surface 162 facing the side surface 161. The first drive electrode 160a and the second drive electrode 160b are each connected to an external power source (not shown). For connection, for example, FPC is used, and one end of the FPC is fixed to each electrode. As a result, a drive signal is applied to the oblique vibration piezoelectric element 160 via the first drive electrode 160a and the second drive electrode 160b. Therefore, the direction in which the drive signal is applied to the drive electrode is a direction from the first drive electrode 160a to the second drive electrode 160b or from the second drive electrode 160b to the first drive electrode 160a depending on the electrical polarity of the signal. It becomes.

The polarization direction P2 of the oblique vibration piezoelectric element 160 shown in FIG. 9 to FIG. 12 is a direction from the second drive electrode 160b toward the first drive electrode 160a, along the direction in which the drive signal is applied.
The oblique vibration piezoelectric element 160 having such a configuration has an upper left corner when the oblique vibration piezoelectric element 160 is viewed from the front as shown in FIGS. 10 to 12 by applying a drive signal. It vibrates in an oblique direction substantially along a diagonal line connecting the lower right corner. Specifically, when one of the positive and negative electrodes of the external power source is connected to the first drive electrode 160a and the other is connected to the second drive electrode 160b, the oblique vibration piezoelectric element 160 extends in an oblique direction (see FIG. 10) When the connection to the first drive electrode 160a and the second drive electrode 160b is switched, the oblique vibration piezoelectric element 160 contracts in an oblique direction (FIG. 11). Furthermore, when alternating current is applied between the first drive electrode 160a and the second drive electrode 160b, the 160 expands and contracts in an oblique direction, that is, a polarization direction (FIG. 12).
Therefore, the piezoelectric element for oblique vibration 160 can be vibrated obliquely in accordance with signals applied to the first drive electrode 160a and the second drive electrode 160b.

Next, the oblique torsional vibration piezoelectric element will be described with reference to FIGS. This oblique torsional vibration piezoelectric element is provided with two polarization axes along two polarization directions, respectively, and by setting these two polarization directions and drive electrodes in a predetermined relationship, oblique torsional vibration is generated. .

First, a case where two polarization directions are opposite to each other in a single plate type in which a piezoelectric element for oblique torsional vibration is constituted by one piezoelectric element will be described with reference to FIGS.
13A is a perspective view showing a configuration of a single-plate type oblique torsional vibration piezoelectric element, FIG. 13B is a side view seen from the XIIIB direction of FIG. 13A, and FIG. 13C is a XIIIC direction of FIG. It is the side view seen from. 14A is a perspective view showing an oblique twisted state when a drive signal is applied to the oblique torsional vibration piezoelectric element of FIG. 13, FIG. 14B is a side view seen from the XIVB direction of FIG. ) Is a side view seen from the XIVC direction of (a). 15A is a perspective view showing an oblique twist state when a drive signal is applied to the oblique torsional vibration piezoelectric element of FIG. 13 in the direction opposite to that of FIG. 14, and FIG. 15B is an XVB direction of FIG. The side view seen, (c) is the side view seen from the XVC direction of (a).

13 to 15, the oblique torsional vibration piezoelectric element 200 is a substantially rectangular parallelepiped piezoelectric body. In the oblique torsional vibration piezoelectric element 200, the first drive electrode 201 and the second drive electrode 202 are arranged along the thickness direction of the oblique torsional vibration piezoelectric element 200 on the upper side of the side surface 221, and face the side surface 221. A third drive electrode 211 and a fourth drive electrode 212 are provided below the side surface 222 along the thickness direction of the oblique torsional vibration piezoelectric element 200. The first drive electrode 201 and the third drive electrode 211 are provided on the back surface 223 side, and the second drive electrode 202 and the fourth drive electrode 212 are provided on the front surface 224 side.

The first drive electrode 201, the second drive electrode 202, the third drive electrode 211, and the fourth drive electrode 212 are each connected to an external power source (not shown). For connection, for example, FPC is used, and one end of the FPC is fixed to each electrode. Accordingly, a drive signal is applied to the oblique torsional vibration piezoelectric element 200 via the first drive electrode 201, the second drive electrode 202, the third drive electrode 211, and the fourth drive electrode 212.

The application of the drive signal is performed between the first drive electrode 201 and the third drive electrode 211 and between the second drive electrode 202 and the fourth drive electrode 212, respectively. The direction in which the drive signal is applied between the first drive electrode 201 and the third drive electrode 211 is changed from the first drive electrode 201 to the third drive electrode 211 or from the third drive electrode 211 depending on the electric polarity of the signal. The direction is toward the first drive electrode 201. The direction in which the drive signal is applied between the second drive electrode 202 and the fourth drive electrode 212 is changed from the second drive electrode 202 to the fourth drive electrode 212 or from the fourth drive electrode 212 depending on the electrical polarity of the signal. The direction is toward the second drive electrode 202.

The oblique torsional vibration piezoelectric element 200 has a polarization direction P3 from the first drive electrode 201 to the third drive electrode 211 on the back surface 223 side, and a polarization direction from the fourth drive electrode 212 to the second drive electrode 202 on the front surface 224 side. P4 and two polarization directions. The polarization direction P3 and the polarization direction P4 are opposite to each other, and are directions along the direction in which the drive signal is applied.
The oblique torsional vibration piezoelectric element 200 having such a configuration undergoes oblique torsional vibration as shown in FIGS. 14 and 15 when a drive signal is applied.

The specific oblique torsional vibration is as follows.
In the case shown in FIG. 14, in the external power supply, the energization direction between the first drive electrode 201 and the third drive electrode 211 and the energization direction between the second drive electrode 202 and the fourth drive electrode 212 are the same. Energized in the direction. The twist direction can be changed by controlling the application of power. For example, when applied so as to extend along the polarization direction P4 as shown in FIG. 14A and contract along the polarization direction P3, these movements are combined and as shown by the broken line in FIG. Twist while stretching.

On the other hand, in the case shown in FIG. 15, the energization direction between the first drive electrode 201 and the third drive electrode 211 and the energization direction between the second drive electrode 202 and the fourth drive electrode 212 are respectively shown. This is the reverse of the case shown in FIG. In this case, it is applied so as to shrink along the polarization direction P4 and to extend along the polarization direction P3, and these movements are combined and twisted while extending as shown by a broken line in FIG.
Accordingly, the oblique torsional vibration piezoelectric element 200 can be caused to obliquely vibrate according to signals applied to the first drive electrode 201, the second drive electrode 202, the third drive electrode 211, and the fourth drive electrode 212.

Next, with reference to FIGS. 16 to 18, a case where the two polarization directions are the same in the single plate type oblique torsional vibration piezoelectric element 200 shown in FIGS. 13 to 15 will be described.
16A is a perspective view showing the configuration of a single-plate type piezoelectric element for oblique torsional vibration, FIG. 16B is a side view seen from the XVIB direction of FIG. 16A, and FIG. 16C is the XVIC direction of FIG. It is the side view seen from. FIG. 17A is a perspective view showing an oblique twist state when a drive signal is applied to the oblique torsional vibration piezoelectric element of FIG. 16, FIG. 17B is a side view seen from the XVIIB direction of FIG. ) Is a side view seen from the XVIIC direction of (a). 18A is a perspective view showing an oblique twist state when a drive signal is applied to the oblique torsional vibration piezoelectric element of FIG. 16 in the opposite direction to FIG. 17, and FIG. 18B is a perspective view from the XVIIIB direction of FIG. The side view seen, (c) is the side view seen from the XVIIIC direction of (a).

The application of the drive signal is performed between the first drive electrode 201 and the third drive electrode 211 and between the second drive electrode 202 and the fourth drive electrode 212, respectively. The application direction of the drive signal between the second drive electrode 202 and the fourth drive electrode 212 is opposite to the drive signal application direction between the first drive electrode 201 and the third drive electrode 211.

16 to 18, the oblique torsional vibration piezoelectric element 200 has a polarization direction P5 from the first drive electrode 201 to the third drive electrode 211 on the back surface 223 side, and a fourth to fourth drive electrode 202 on the front surface 224 side. There are two polarization directions, ie, a polarization direction P6 toward the drive electrode 212. The polarization direction P5 and the polarization direction P6 are in the same direction.
The oblique torsional vibration piezoelectric element 200 having such a configuration is subjected to oblique torsional vibration as shown in FIGS. 17 and 18 when a drive signal is applied.

The specific oblique torsional vibration is as follows.
In the case shown in FIG. 17, in the external power supply, the energization direction between the first drive electrode 201 and the third drive electrode 211 and the energization direction between the second drive electrode 202 and the fourth drive electrode 212 are opposite to each other. It is energized to be in the direction of. At this time, similar to the case shown in FIG. 14, if applied so as to extend along the polarization direction P <b> 6 and contract along the polarization direction P <b> 5, these movements are combined and shown by a broken line in FIG. 17. Twist while stretching.

On the other hand, in the case shown in FIG. 18, the energization direction between the first drive electrode 201 and the third drive electrode 211 and the energization direction between the second drive electrode 202 and the fourth drive electrode 212 are respectively shown. This is the reverse of the case shown in FIG. In this case, as in the case shown in FIG. 15, the application is performed so as to shrink along the polarization direction P6 and to extend along the polarization direction P5, and these movements are combined to create a broken line in FIG. It twists while stretching as shown by.
Accordingly, the oblique torsional vibration piezoelectric element 200 can be caused to obliquely vibrate according to signals applied to the first drive electrode 201, the second drive electrode 202, the third drive electrode 211, and the fourth drive electrode 212.

Next, with reference to FIG. 19 to FIG. 21, the case of a bonded type oblique torsional vibration piezoelectric element in which two piezoelectric elements are bonded together will be described.
FIG. 19A is a perspective view showing the configuration of a bonded-type oblique torsional vibration piezoelectric element, FIG. 19B is a side view seen from the XIXB direction of FIG. 19A, and FIG. 19C is the XIXC direction of FIG. It is the side view seen from. 20A is a perspective view showing an oblique twisted state when a drive signal is applied to the oblique torsional vibration piezoelectric element of FIG. 19, FIG. 20B is a side view seen from the XXB direction of FIG. ) Is a side view seen from the XXC direction of (a). 21A is a perspective view showing an oblique twist state when a drive signal is applied to the oblique torsional vibration piezoelectric element of FIG. 19 in the direction opposite to that of FIG. 20, and FIG. 21B is a perspective view from the XXIB direction of FIG. The side view seen, (c) is the side view seen from the XXIC direction of (a).

As shown in FIGS. 19 to 21, the oblique torsional vibration piezoelectric element 300 has a substantially rectangular parallelepiped shape by bonding the first piezoelectric element 300a and the second piezoelectric element 300b having the same shape to each other.
In the oblique torsional vibration piezoelectric element 300, the first drive electrode 301 is provided on the upper side surface 321a of the first piezoelectric element 300a, and the oblique torsional vibration piezoelectric element 300 is disposed on the upper side surface 321b of the second piezoelectric element 300b. A second drive electrode 302 is provided so as to be aligned with the first drive electrode 301 along the thickness direction. A third drive electrode 311 is provided below the side surface 322a facing the side surface 321a of the first piezoelectric element 300a, and an oblique torsional vibration is disposed below the side surface 322b facing the side surface 321b of the second piezoelectric element 300b. A fourth drive electrode 312 is provided so as to be aligned with the third drive electrode 311 along the thickness direction of the piezoelectric element 300.

The first drive electrode 301, the second drive electrode 302, the third drive electrode 311, and the fourth drive electrode 312 are each connected to an external power source (not shown). For connection, for example, FPC is used, and one end of the FPC is fixed to each electrode. As a result, a drive signal is applied to the oblique torsional vibration piezoelectric element 300 via the first drive electrode 301, the second drive electrode 302, the third drive electrode 311, and the fourth drive electrode 312.

Application of the drive signal is performed between the first drive electrode 301 and the third drive electrode 311 and between the second drive electrode 302 and the fourth drive electrode 312, respectively. The direction in which the drive signal is applied between the first drive electrode 301 and the third drive electrode 311 is changed from the first drive electrode 301 to the third drive electrode 311 or from the third drive electrode 311 depending on the electric polarity of the signal. The direction is toward the first drive electrode 301. The direction in which the drive signal is applied between the second drive electrode 302 and the fourth drive electrode 312 is changed from the second drive electrode 302 to the fourth drive electrode 312 or from the fourth drive electrode 312 depending on the electrical polarity of the signal. The direction is toward the second drive electrode 302.

The oblique torsional vibration piezoelectric element 300 has a polarization direction P7 from the first drive electrode 301 to the third drive electrode 311 on the back surface 323 side, and a polarization direction from the fourth drive electrode 312 to the second drive electrode 302 on the front surface 324 side. P8 and two polarization directions. The polarization direction P7 and the polarization direction P8 are opposite to each other, and are directions along the drive signal application direction.
The oblique torsional vibration piezoelectric element 300 having such a configuration is subjected to oblique torsional vibration as shown in FIGS. 20 and 21 when a drive signal is applied.

The specific oblique torsional vibration is as follows.
In the case shown in FIG. 20, as in the case shown in FIG. 14, the external power supply supplies the energization direction between the first drive electrode 301 and the third drive electrode 311, the second drive electrode 302 and the fourth drive electrode 312. Energization is performed so that the energization direction is in the same direction. At this time, as in the case shown in FIG. 14, the application is performed so as to extend along the polarization direction P8 and contract along the polarization direction P7. Twists while stretching as shown.

On the other hand, in the case shown in FIG. 21, the energization direction between the first drive electrode 301 and the third drive electrode 311 and the energization direction between the second drive electrode 312 and the fourth drive electrode 312 are respectively shown. This is the reverse of the case shown in FIG. At this time, as in the case shown in FIG. 15, the application is performed so as to shrink along the polarization direction P8 and to extend along the polarization direction P7. Twists while stretching as shown.
Accordingly, the oblique torsional vibration piezoelectric element 300 can be subjected to oblique torsional vibration in accordance with signals applied to the first drive electrode 301, the second drive electrode 302, the third drive electrode 311, and the fourth drive electrode 312.

In the type in which two piezoelectric elements are bonded together, the two polarization directions P7 and P8 may be opposite to each other as shown in FIGS. it can. When the two polarization directions of the bonded-type oblique torsional vibration piezoelectric element are the same as each other, the same oblique twist is applied by applying a drive signal similar to that of the single plate type shown in FIGS. Since the vibration can occur, detailed description thereof is omitted.

Hereinafter, an example of a vibrator used as the vibrator 101 in the ultrasonic motor 100 according to the embodiment will be described.
Example 1
FIG. 22 is a perspective view showing the configuration of the vibrator 400 according to the first embodiment. 23 is a diagram showing a side view seen from the direction XXIII in FIG. 22 and a view seen from the side of the vibration state in the torsional tertiary resonance vibration shown in FIG. 3E. 24 is a front view seen from the direction XXIV of FIG.
As shown in FIGS. 22 and 23, the vibrator 400 has a substantially rectangular parallelepiped shape in which the first piezoelectric element 400a and the second piezoelectric element 400b having the same shape are bonded to each other.
In the vibrator 400, the first drive electrode 401 is provided on the side surface 421a of the first piezoelectric element 400a, and the first drive electrode 401 and the side surface 421b of the second piezoelectric element 400b are arranged along the thickness direction of the vibrator 400. Second drive electrodes 402 are provided so as to be aligned. The third drive electrode 411 is provided on the side surface 422a facing the side surface 421a of the first piezoelectric element 400a, and the side surface 422b facing the side surface 421b of the second piezoelectric element 400b is along the thickness direction of the vibrator 400. The fourth drive electrode 412 is provided so as to be aligned with the third drive electrode 411. The first drive electrode 401 and the second drive electrode 402 correspond to the two

drive electrodes

121 and 122 of the vibrator 101, respectively.

In the vibrator 400, the short side and the long side of the cross section perpendicular to the central axis 100c are configured so as to satisfy the condition for generating the torsional tertiary resonance vibration shown in FIG. Thereby, the torsional tertiary resonance vibration having the nodes N41, N42 and N43 shown on the right side of FIG. 23 is generated. The vibration state of the torsional tertiary resonance vibration is indicated by a wavy line 450 on the right side of FIG.

The first drive electrode 401, the second drive electrode 402, the third drive electrode 411, and the fourth drive electrode 412 are arranged so as to correspond to the positions of the nodes and antinodes in the vibration state indicated by the wavy line 450. Specifically, as shown in FIG. 23, the first drive electrode 401, the second drive electrode 402, the third drive electrode 411, and the first drive electrode 401 correspond to the antinode position of the torsional tertiary resonance vibration indicated by the wavy line 450. The four drive electrodes 412 are arranged, and the upper ends of the first drive electrode 401 and the second drive electrode 402 are arranged so as to correspond to the node N41, and the third drive electrode 411 and the fourth drive are arranged so as to correspond to the node N42. The lower end of the electrode 412 is disposed.
With such a configuration, the position where the torsional stress becomes maximum becomes a torsion node, and the torsional tertiary resonance vibration is efficiently excited.

The vibrator 400 has a polarization direction P9 from the first drive electrode 401 toward the third drive electrode 411 on the back surface 423 side, and a polarization direction P10 from the fourth drive electrode 412 toward the second drive electrode 402 on the front surface 424 side. It has two polarization directions. The polarization direction P9 and the polarization direction P10 are opposite to each other, and are directions along the drive signal application direction.
In the vibrator 400, the external power supply is such that the energization direction between the first drive electrode 401 and the third drive electrode 411 and the energization direction between the second drive electrode 402 and the fourth drive electrode 412 are in the same direction. It is energized to become. By applying a drive signal to these drive electrodes, a torsional tertiary resonance vibration (FIG. 3E) having the center axis 100c as a torsion axis and a longitudinal primary resonance vibration expanding and contracting in the direction of the center axis 100c are generated. Oval vibration that occurs at the same time and is synthesized occurs. Therefore, elliptical vibration is generated on both end surfaces of the vibrator 400 as the vibrator 101 in the height direction, and thus the elliptical vibration is transmitted to the rotor 102 via the

frictional contact members

103a and 103b.

Furthermore, as shown in FIG. 24, the angle θ4 formed by the polarization axis P40 along the polarization direction P10 and the central axis 100c is an acute angle. Here, since the polarization direction P9 is parallel to the polarization direction P10, the angle between the polarization axis along the polarization direction P9 and the central axis 100c is θ4, which is an acute angle.
In the vibrator 400, elliptical vibration can be easily excited with the simple configuration as described above, so that the vibrator 101 that does not require a groove or the like can be obtained, the number of parts is reduced, and manufacturing is easy. Therefore, an ultrasonic motor with a low cost can be supplied. Furthermore, the torsional tertiary resonance vibration and the longitudinal primary resonance vibration can be controlled independently. Further, the electrode used for polarization can be used as a drive electrode as it is.

(Example 2)
FIG. 25 is a perspective view showing the configuration of the vibrator 500 according to the second embodiment. 26 is a diagram showing a side view seen from the XXVI direction in FIG. 25 and a view seen from the side of the vibration state in the torsional secondary resonance vibration shown in FIG. 3D. 27 is a front view seen from the direction XXVII in FIG.
As shown in FIGS. 25 and 26, the vibrator 500 has a substantially rectangular parallelepiped shape in which the first piezoelectric element 500a and the second piezoelectric element 500b having the same shape are bonded to each other.
In the vibrator 500, the first drive electrode 501 is provided on the side surface 521a of the first piezoelectric element 500a, and the first drive electrode 501 is provided on the side face 521b of the second piezoelectric element 500b along the thickness direction of the vibrator 500. A second drive electrode 502 is provided so as to be aligned. The third drive electrode 511 is provided on the side surface 522a facing the side surface 521a of the first piezoelectric element 500a, and the side surface 522b facing the side surface 521b of the second piezoelectric element 500b is along the thickness direction of the vibrator 500. A fourth drive electrode 512 is provided so as to be aligned with the third drive electrode 511. The first drive electrode 501 and the second drive electrode 502 correspond to the two

drive electrodes

121 and 122 of the vibrator 101, respectively.

In the vibrator 500, the short side and the long side of the cross section perpendicular to the central axis 100c are configured so as to satisfy the condition for generating the torsional secondary resonance vibration shown in FIG. Thereby, the torsional secondary resonance vibration having the nodes N51 and N52 shown on the right side of FIG. 26 is generated. The vibration state of the torsional secondary resonance vibration is indicated by a broken line 550 on the right side of FIG.

The first drive electrode 501, the second drive electrode 502, the third drive electrode 511, and the fourth drive electrode 512 are arranged so as to correspond to the nodes and antinodes of the vibration state indicated by the wavy line 550. Specifically, as shown in FIG. 26, the first drive electrode 501, the second drive electrode 502, the third drive electrode 511, and the first drive electrode 501 correspond to the antinode position of the torsional secondary resonance vibration indicated by the broken line 550. The four drive electrodes 512 are arranged, and the upper ends of the first drive electrode 501 and the second drive electrode 502 are arranged so as to correspond to the node N51, and the third drive electrode 511 and the fourth drive are arranged so as to correspond to the node N52. The lower end of the electrode 512 is disposed.
With such a configuration, the position where the torsional stress becomes maximum becomes a torsion node, and the torsional secondary resonance vibration is efficiently excited.

The vibrator 500 has a polarization direction P11 from the first drive electrode 501 to the third drive electrode 511 on the back surface 523 side, and a polarization direction P12 from the fourth drive electrode 512 to the second drive electrode 502 on the front surface 524 side. It has two polarization directions. The polarization direction P11 and the polarization direction P12 are opposite to each other, and are directions along the direction in which the drive signal is applied.
In the vibrator 500, the external power supply has the same energization direction between the first drive electrode 501 and the third drive electrode 511 and the energization direction between the second drive electrode 502 and the fourth drive electrode 512. It is energized to become. By applying a drive signal to these drive electrodes, a torsional secondary resonance vibration (FIG. 3D) having the center axis 100c as a torsion axis and a longitudinal primary resonance vibration expanding and contracting in the direction of the center axis 100c are generated. Oval vibration that occurs at the same time and is synthesized occurs. Therefore, elliptical vibration is generated on both end surfaces of the vibrator 500 as the vibrator 101 in the height direction, and thus the elliptical vibration is transmitted to the rotor 102 via the

frictional contact members

103a and 103b.

Further, as shown in FIG. 27, the angle θ5 formed by the polarization axis P50 along the polarization direction P12 and the central axis 100c is an acute angle. Here, since the polarization direction P11 is parallel to the polarization direction P12, the angle formed between the polarization axis along the polarization direction P11 and the central axis 100c is θ5, which is an acute angle.
In the vibrator 500, elliptical vibration can be easily excited with the simple configuration as described above, so that the vibrator 101 that does not require a groove or the like can be obtained, the number of parts is reduced, and manufacturing is easy. Therefore, an ultrasonic motor with a low cost can be supplied. Furthermore, the torsional secondary resonance vibration and the longitudinal primary resonance vibration can be controlled independently. Further, the electrode used for polarization can be used as a drive electrode as it is.

In the first and second embodiments, the two polarization directions are opposite to each other. However, even when the two directions are the same, the short side and the long side of the cross section perpendicular to the central axis 100c satisfy the conditions shown in FIG. By configuring the sides, torsional tertiary resonance vibration or torsional secondary resonance vibration can be generated.
In the first and second embodiments, the two piezoelectric elements are bonded to each other. However, the piezoelectric elements may be formed of a single plate. Also, more than two piezoelectric elements, for example, four, eight,. . . You may comprise by this piezoelectric element.

As described above, the ultrasonic motor according to the present invention is suitable for an ultrasonic motor that forms elliptical vibration by combining vibration and oblique torsional vibration and rotates the rotor by elliptical vibration.

DESCRIPTION OF SYMBOLS 100 Ultrasonic motor 100c Center axis 101 Vibrator 101a Elliptical vibration generating surface 101f Long side 101s Short side 102

Rotor

103a, 103b Friction contact member 105 Shaft 107 Bearing 108 Pressing spring 109 Spring pressing ring 110 Holder 111

Shaft fixing ring

121, 122 Drive Electrode 150 Piezoelectric element for longitudinal vibration 150a First drive electrode 150b Second drive electrode 160 Piezoelectric element for oblique vibration 160a First drive electrode 160b Second drive electrode 200 Piezoelectric element for oblique torsional vibration 201 First drive electrode 202 Second drive electrode 211 Third driving electrode 212 Fourth driving electrode 300 Piezoelectric element for oblique torsional vibration 300a First piezoelectric element 300b Second piezoelectric element 301 First driving electrode 302 Second driving electrode 311 Third driving electrode 3 2 4th drive electrode 400 Vibrator 400a 1st piezoelectric element 400b 2nd piezoelectric element 401 1st drive electrode 402 2nd drive electrode 411 3rd drive electrode 412 4th drive electrode 500 Vibrator 500a 1st piezoelectric element 500b 2nd piezoelectric Element 501 First drive electrode 502 Second drive electrode 511 Third drive electrode 512 Fourth drive electrode P1, P2, P3, P4, P5, P6, P7, P8, P9, P10, P11, P12 Polarization direction P40, P50 Polarization axis

Claims

A vibrator having a rectangular length ratio in a cross section perpendicular to the central axis, and rotating about the central axis in contact with the elliptical vibration generating surface of the vibrator and orthogonal to the elliptical vibration generating surface of the vibrator An ultrasonic motor comprising at least a rotor to be driven,
By combining the longitudinal primary resonance vibration of the vibrator extending and contracting in the direction of the rotation axis and the torsional secondary resonance vibration or the torsional tertiary resonance vibration having the rotation axis as the torsion axis, an elliptical vibration is formed. Become
The longitudinal primary resonance vibration that expands and contracts in the direction of the rotation axis of the vibrator and the resonance frequency of the torsional secondary resonance vibration or the torsional tertiary resonance vibration that uses the rotation axis as a torsion axis are substantially the same. Set the rectangular length ratio of the vibrator,
2. The ultrasonic motor according to claim 1, wherein the vibrator includes two polarization axes respectively along two polarization directions that form acute angles with respect to the rotation axis.
2. The ultrasonic motor according to claim 1, wherein the relationship between the two polarization directions and the drive electrode is set so that the vibrator expands and contracts in opposite directions along the two polarization directions.
The ultrasonic motor according to claim 2, wherein the vibrator is made of a single plate.
The ultrasonic motor according to claim 2, wherein the vibrator is composed of two plates.
The elliptical vibration is formed by combining the longitudinal primary resonance vibration and the torsional tertiary resonance vibration,
The ultrasonic motor according to claim 2, wherein the drive electrode is disposed so as to correspond to an antinode position of the torsional tertiary resonance vibration.
The elliptical vibration is formed by combining the longitudinal primary resonance vibration and the torsional secondary resonance vibration,
The ultrasonic motor according to claim 2, wherein the drive electrode is arranged so as to correspond to an antinode position of the torsional secondary resonance vibration.