JPH08172782A - Ultrasonic motor - Google Patents

Abstract

PURPOSE: To obtain high torque with a light weight by imparting torsional vibration to an elastic body and displacing the elastic body so that the driving surface of the elastic body comes into contact with a relatively moving member. CONSTITUTION: When a piezoelectric element 2 for bending is deformed so that elements 2-1 and 2-4 are made to elongate (arrows A) and elements 2-2 and 2-3 are made to shrink (arrows B), an elastic body 1 is bent so that the right end is protruding upward and the left end is protruding downward. At this time, a piezoelectric element 3 for torsion undergoes thickness sliding deformation so that the outside is on the left side (arrows D) and the inside is on the right side (arrows C). The elastic body 1 is twisted in the clockwise direction (arrow E) viewed from the right side and twisted in the counterclockwise direction (arrow F) viewed from the left side, so the elastic body 1 is symmetrically bent and deformed with respect to a central axis CL. As a result, the reaction from guide rails 4-1 and 4-4 caused by the torsional motion of the elastic body 1 becomes the advancing force only in the forward direction (arrow G) having the directivity, and the elastic body 1 itself is made to advance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor utilizing torsional vibration.

[0002]

2. Description of the Related Art FIG. 10 is a perspective view showing a conventional example of an ultrasonic motor utilizing torsional vibration. Conventionally, in this type of ultrasonic motor, the stator 101 includes a piezoelectric element 10 for torsional vibration between two cylindrical vibrators 102 and 103.
4, the piezoelectric element 105 for longitudinal vibration is arranged above the vibrator 103. Piezoelectric element 1 for torsional vibration
Reference numeral 04 denotes a piezoelectric element 105 for longitudinal vibration that is polarized in the circumferential direction.
Are polarized in the thickness direction. Further, the rotor 106
Are arranged above the piezoelectric element 105 for longitudinal vibration.

A vibrator 102 constituting the stator 101,
103 and the piezoelectric elements 104 and 105 are the shaft 107
Is fixed (screwed to the threaded portion of the shaft 107),
The rotor 106 is rotatably provided on the shaft 107 via a ball bearing 108. Shaft 1
A nut 110 is screwed onto the tip of 07 via a spring 109 to bring the rotor 106 into pressure contact with the stator 101.

The piezoelectric element 104 for torsional vibration and the piezoelectric element 105 for longitudinal vibration are driven by controlling the phase of a voltage of the same frequency oscillated from an oscillator 111 by a phase shifter 112. The piezoelectric element 104 for torsional vibration is used for the rotor 10
6 gives a mechanical displacement for rotation, and the piezoelectric element 105 for longitudinal vibration cyclically changes the frictional force acting between the stator 101 and the rotor 106 in synchronization with the cycle of torsional vibration by the piezoelectric element 104. By doing so, it plays a role of converting vibration into movement in one direction.

FIG. 11 is an exploded perspective view showing a stator of an ultrasonic motor according to a conventional example. Since the piezoelectric element 104 for torsional vibration needs to be polarized in the circumferential direction, the piezoelectric material is once divided into about 6 to 8 fan-shaped small pieces as shown in FIG. 11, and after each small piece is polarized. , Again combined in a ring. In addition, 104a is an electrode.

[0006]

However, in the above-mentioned conventional ultrasonic motor, the piezoelectric element 104 that generates thickness shear vibration is subdivided into a plurality of pieces so as to cause rotational slip, and is arranged and bonded and fixed in an annular shape. It had to be done and it was very difficult to process.

The ultrasonic motor shown in FIG. 10 uses vertical vibration as the vibration of the clutch component. Since this vibration is performed without resonance using the laminated piezoelectric element, the amplitude cannot be increased. When the preload is increased while the vibration of the clutch component remains small, the vibration of the clutch component accurately distinguishes the normal rotation and the reverse rotation of the twist that appears during one cycle, and the rotation moves cyclically. There is a problem that efficiency is reduced because it is difficult to convey to the body. Also, since this ultrasonic motor combines torsional vibration and longitudinal vibration, in order to obtain a high torque driving force,
There is a problem that the diameter of the stator 101 has to be increased and the weight increases. Furthermore, the stator 101
Since there is a shaft at the center of the piezoelectric element, the size and shape of the piezoelectric element are limited, and a large driving force cannot be obtained. on the other hand,
The conventional ultrasonic motor uses torsional vibration,
There was nothing to move in a straight line.

It is an object of the present invention to provide an ultrasonic motor which is easy to process, is light in weight, can obtain a high torque driving force, and can be moved linearly.

[0009]

In order to solve the above-mentioned problems, an ultrasonic motor according to a first aspect of the present invention is provided with an elastic body having an end portion on the outer periphery of a cylinder as a drive surface, and a relative member contacting the drive surface of the elastic body. When the moving member, the first electromechanical conversion element that applies torsional vibration to the elastic body, and the elastic body are twisted, the driving surface of the elastic body is displaced so as to come into contact with the relative moving member. A second electromechanical conversion element is included.

According to a second aspect of the present invention, in the ultrasonic motor according to the first aspect, a pressing member for pressing the elastic body and the relative moving member into contact with each other is provided.

The invention of claim 3 is the invention of claim 1 or claim 2.
In the ultrasonic motor according to the item (1), there is provided a central support member that supports the elastic body in the vicinity of the center of the central axis and in a direction orthogonal to the central axis.

According to a fourth aspect of the present invention, in the ultrasonic motor according to any one of the first to third aspects, the elastic body has a shape in which a column is roughly divided into two in the axial direction. The first electromechanical conversion element is arranged on a dividing surface of the elastic body.

According to a fifth aspect of the present invention, in the ultrasonic motor according to the fourth aspect, the second electromechanical conversion element is an element for flexural deformation, which is arranged on a divided surface of the elastic body. Is characterized by.

According to a sixth aspect of the present invention, in the ultrasonic motor according to the fourth aspect, the second electromechanical conversion element is an element for extensional deformation arranged at an end of the elastic body. Is characterized by.

According to a seventh aspect of the invention, in the ultrasonic motor according to the fourth aspect, the second electromechanical conversion element is an element for thickness-sliding deformation arranged at an end of the elastic body. It is characterized by that.

According to an eighth aspect of the present invention, in the ultrasonic motor according to any one of the first to seventh aspects, the relative moving member is a guide rail that comes into contact with the drive surface of the elastic body, The elastic body is displaced so as to come into contact with the guide rail when the driving surface thereof is torsionally vibrated,
The feature is that the reaction force obtains a progressive force.

According to a ninth aspect of the present invention, in the ultrasonic motor according to the eighth aspect, the elastic body is a portion whose driving surface is chamfered at the end edge of a cylinder, and the guide rail has the elastic body. The feature is that the driving surface of the body is clamped from four corners.

According to a tenth aspect of the present invention, in the ultrasonic motor according to the ninth aspect, the guide rails are arranged such that a pair of diagonally arranged reaction forces pass through the center of the elastic body. It is characterized by having done.

[0019]

According to the first aspect, the first electromechanical conversion element is used to excite the natural vibration mode in the torsional direction in the elastic body,
By bringing the elastic body into contact with the relative moving member by the second electromechanical conversion element, the torsional movement of both ends of the elastic body is transmitted to the relative moving member, and the reaction caused by the torsional movement of the elastic body is used as the moving force. , The driving force can be taken out directly and as a linear moving force. In other words, in order to linearly advance the elastic body (moving body), a reliable traveling force can be obtained by using the torsional rotation movement of the elastic body itself as the driving force instead of the elliptical movement due to the combination of the vertical and horizontal displacements. To be

According to the second aspect, since the elastic member and the relative moving member are brought into pressure contact with each other by the pressing member, the driving force can be efficiently transmitted. According to the third aspect, since the central support member supports the vicinity of the center of the elastic body, stable movement can be performed. According to the fourth aspect, since the first electromechanical conversion element is arranged on the dividing surface of the elastic body having a shape in which the cylinder is roughly divided into two in the axial direction, it is possible to extremely easily manufacture the element such as polarization and assembly. Moreover, a large element can be used.

According to the fifth to seventh aspects, the second electromechanical conversion element displaces the elastic body by utilizing deformation such as bending deformation, extension deformation, and thickness sliding deformation. The timing of contacting the relative moving member can be easily set. According to the eighth aspect, the screw motions of the rotations in different directions generated at both ends of the moving body are brought into contact with each other by the guide rails to be extracted as a traveling force in one direction to obtain a linear driving force. Further, since the guide rails are arranged at the four corners, the driving force can be taken out even in a half cycle in which the torsional movement direction of the elastic body is reversed, and driving with high energy efficiency can be performed. According to the ninth aspect, since the area of the contact surface between the elastic body and the relative moving member is increased, the driving efficiency is improved. According to the tenth aspect, since the reaction force of the guide rails arranged diagonally passes through the center of the elastic body, it is possible to suppress the generation of the rotational moment of the elastic body which is unrelated to the traveling force.

[0022]

【Example】

(First Embodiment) The present invention will be described in detail below with reference to the drawings and the like. FIG. 1 is a sectional view showing a first embodiment of an ultrasonic motor according to the present invention. The elastic body 1 is a columnar elastically deformable member such as metal or plastic. As shown in FIG. 2 described later, the elastic body 1 has a plurality of piezoelectric elements 2, 3 on the division surface obtained by dividing the cylinder in the axial direction. Is sandwiched between. In addition, the piezoelectric elements 2 and 3 are attached to the elastic body 1
It is an element that generates the following bending natural vibration and first-order torsional natural vibration.

The elastic body 1 plays a role as a moving body which advances in the longitudinal direction of the guide rail 4. The guide rails (relative moving members) 4 are bar members each having a rectangular cross section with a large chamfered corner.
Are arranged such that the chamfered portions thereof contact both ends of the cylinder of the elastic body (moving body) 1. These guide rails 4 are in pressure contact with the elastic body 1 by springs 5 supported by a frame-shaped fixed portion. Elastic body 1
In order to improve the contact efficiency with the guide rail 4,
It is preferable that both end edges of the cylinder are chamfered in a curved or linear shape. The elastic body 1 is supported by a central guide rail (central support member) 6 using a bearing in a direction substantially orthogonal to the center of the central axis of the cylinder and orthogonal to the central axis.

FIG. 2 is a diagram showing the arrangement of piezoelectric elements of the ultrasonic motor according to the first embodiment, and FIGS. 3 and 4 are bending vibrations of the elastic body of the ultrasonic motor according to the first embodiment. It is a schematic diagram which shows. The piezoelectric element 2 is an element (second electromechanical conversion element) for converting electric energy into mechanical energy and giving bending vibration to the elastic body 1, and has a piezoelectric strain constant d _31.
Those with a high value are preferably used. The piezoelectric element 3 is an element (first electromechanical conversion element) for converting electric energy into mechanical energy and giving torsional vibration to the elastic body 1, and one having a high piezoelectric strain constant d ₁₅ is preferably used. .

As shown in FIG. 2, the elastic body 1 is composed of semi-columns 1a and 1b obtained by dividing a columnar shape into two in the longitudinal direction. As shown in FIG. 2B, a plurality of piezoelectric elements 2 and 3 are sandwiched and bonded to the dividing surfaces of the semi-columns 1a and 1b of the elastic body 1. In this embodiment, two piezoelectric elements 2 and 3 are arranged in two rows so as to be point-symmetric with respect to the central axis of the elastic body 1. Frequency voltages that generate bending vibration and torsional vibration are applied to the piezoelectric elements 2 and 3, respectively. As shown in FIG. 3, two bending piezoelectric elements 2 each having a length half the length of the elastic body 1 are arranged.

In FIG. 3, in the bending piezoelectric element 2, the element 2-1 on the upper right side extends (arrow A), and the element 2-on the upper left side
2 is contracted (arrow B), the element 2-3 on the lower right side is contracted (arrow B), and the element 2-4 on the lower left side is extended (arrow A). It will bend so that the left end is convex downward. At this time, the piezoelectric elements 3 for twisting undergo thickness-slip deformation so that the outside is on the right (arrow D) and the inside is on the left (arrow C), so that the elastic body 1 is viewed clockwise from the right side. Twisted to (arrow E),
It is twisted counterclockwise (arrow F) when viewed from the left side.

In FIG. 4, in the bending piezoelectric element 2, the element 2-1 on the upper right side contracts (arrow B), and the element 2-on the upper left side
When the elastic body 1 is deformed so that 2 extends (arrow A), the element 2-3 on the lower right side extends (arrow A), and the element 2-4 on the lower left side contracts (arrow B), the right end of the elastic body 1 moves downward. It will bend so that the left end is convex. At this time, the piezoelectric element 3 for twisting undergoes thickness-slip deformation so that the inside is on the right (arrow C) and the outside is on the left (arrow D).
Is twisted counterclockwise (arrow F) when viewed from the right side and clockwise (arrow E) when viewed from the left side.

FIG. 5 is a block diagram showing a drive circuit of the ultrasonic motor according to the first embodiment. The oscillator 21 is for oscillating a frequency voltage, the output of which is branched, one of which is phase-shifted by the phase shifter 28 and then amplified by the amplifier 22 (sin ωt), and a piezoelectric element for twisting. Connected to 3. The phase shifter 28 is for performing speed adjustment and forward / reverse control. The other branched output of the oscillator 21 is further branched so that one is connected to the amplifier 23 and the other is connected to the 180 ° phaser 24. The 180 ° phase shifter 24 is for shifting the frequency signal (sin ωt) from the oscillator 21 by 180 °, and its output is connected to the amplifier 25.

The output (sin ωt) of the amplifier 23 is transmitted through the changeover switch 26 to the two pairs of piezoelectric elements 2-2 and 2-3.
Connected to the output of the amplifier 25 (-sinωt)
Via the changeover switch 27, two pairs of piezoelectric elements 2-
1 and 4 are connected. This changeover switch 26,
27 is a piezoelectric element 2 for selectively outputting the outputs of the amplifiers 23 and 25.
(2-2, 2-3 or 2-1, 2-4) is a switch for switching the moving direction of the elastic body 1.

FIGS. 6 and 7 are diagrams for explaining the operation of the ultrasonic motor according to the first embodiment. As shown in FIG. 6, during a half cycle in which the elastic body (moving body) 1 performs torsional vibration in the clockwise direction (counterclockwise direction when viewed from the left side) when viewed from the right side, the elastic body 1 simultaneously undergoes the secondary vibration. Due to the bending vibration of, the bending deformation symmetrical with respect to the central axis CL is performed. At this time,
The elastic body 1 is in contact with the guide rails 4-1 and 4-4 only at two positions that are point-symmetric with respect to the central axis CL. As a result, the guide rail 4-by the torsional movement of the elastic body 1
The reaction from 1, 4-4 becomes a traveling force only in the forward direction (arrow G) having directivity, and advances the elastic body 1 itself.

Further, as shown in FIG. 7, the elastic body (moving body) 1 is subjected to a torsional vibration in a counterclockwise direction (clockwise when viewed from the left side) when viewed from the right side, and during the half cycle, the elastic body 1 is moved. Is 2
The next flexural vibration causes flexural deformation in the direction opposite to that of the other guide rails 4-2 and 4-3, which is opposite to the above. As a result, the reaction from the guide rails 4-2 and 4-3 due to the torsional movement of the elastic body 1 becomes a traveling force only in the forward direction (arrow G) having directivity, and the elastic body 1
Move yourself forward.

The traveling direction of the elastic body 1 described above is maintained even during one cycle in which the twisting direction of the torsional vibration is reversed.
It is always kept in one direction (forward direction). Also, the elastic body 1
When the reverse travel is performed, the applied frequency phase may be shifted by the switches 26 and 27 shown in FIG. 5 so that the flexural vibration cycle is delayed (advanced) by a half cycle with respect to the torsional vibration cycle. According to the first embodiment, since the vibration of the clutch component uses the resonance mode of bending vibration, a large amplitude can be obtained. For this reason, the vibration of the clutch component can accurately distinguish between normal rotation and reverse rotation of the twist appearing in one cycle, and transmit the rotation to the moving body periodically, which has the advantage of improving the driving efficiency. is there.

(Second Embodiment) FIG. 8 is a diagram showing a second embodiment of the ultrasonic motor according to the present invention. In addition, the same reference numerals are given to the portions having the same functions as those in the first embodiment described above, and the overlapping description will be appropriately omitted.

In the ultrasonic motor of the second embodiment, as shown in FIG. 8, the guide rails 4-1, 4-4 and 4-2, 4-3 are arranged in such a positional relationship that Fyz cancel each other out. It is arranged. By doing so, the linear moving force, which is provided by the guide rail 4 that periodically contacts the elastic body (moving body) 1 at positions symmetrical to each other, is irrelevant,
It is possible to suppress the generation of a rotation moment around the center of the central guide rail 6 of the elastic body 1 as much as possible.

(Third Embodiment) FIG. 9 is a sectional view showing a part of an elastic body of a third embodiment of the ultrasonic motor according to the present invention. In the above-described embodiment, the piezoelectric element 2 that generates bending vibration has a structure sandwiched between the elastic bodies 1.
In the third embodiment, as shown in FIG.
A piezoelectric element 7 for extension and deformation was attached to the end portion of, and contacted with a guide rail (not shown) via a contact member 9. Further, as shown in FIG. 9B, a contact member 9 may be attached to the end surface of the elastic body 1 with the piezoelectric element 8 for thickness sliding deformation being sandwiched between the contact member 9 and a guide rail (not shown). Even in this case, it is possible to move as in the first embodiment. According to the present embodiment, the vibration as the clutch component does not depend on the resonance frequency of the bending vibration mode determined by the shape of the elastic body 1 but is non-resonant due to the piezoelectric elements 7 and 8 that perform extension deformation and thickness sliding deformation. It is forced to vibrate. Therefore, the shape of the elastic body 1 can be determined in consideration of only the torsional vibration mode, which has the advantage of increasing the degree of freedom in design.

(Other Embodiments) The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also included in the present invention. For example, although the electromechanical conversion element has been described as an example of a piezoelectric element, an electrostrictive element, a magnetostrictive element, or the like can be used. Alternatively, the elastic body may be fixed and the long relative movement member may be moved.

Further, the model is not limited to the model described in the above-mentioned embodiment, and by using the mode of the elastic body which generates the torsional natural vibration and devising the guide rail to make contact with it, a linear All the mechanisms for obtaining the driving force are included in the present invention.

[0038]

According to the first aspect of the present invention, the first electromechanical conversion element is used to excite the natural vibration mode in the torsional direction in the elastic body, and the second electromechanical conversion element causes the elastic body to act as a relative moving member. By making contact, the torsional movements of both ends of the elastic body are transmitted to the relative moving member, and the reaction caused by the torsional movement of the elastic body is used as the moving force. Therefore, the driving force can be directly extracted as a linear moving force. it can.

According to the second aspect, since the elastic member and the relative moving member are brought into pressure contact with each other by the pressing member, the driving force can be efficiently transmitted. According to the third aspect, since the central support member supports the vicinity of the center of the elastic body, stable movement can be performed. According to the fourth aspect, since the first electromechanical conversion element is arranged on the dividing surface of the elastic body having a shape in which the cylinder is roughly divided into two in the axial direction, it is possible to extremely easily manufacture the element such as polarization and assembly. Moreover, a large element can be used.

According to the fifth to seventh aspects, the second electromechanical conversion element displaces the elastic body by utilizing deformation such as bending deformation, elongation deformation, and thickness sliding deformation. The timing of contacting the relative moving member can be easily set. According to the eighth aspect, the screw motions of the rotations in different directions generated at both ends of the moving body are brought into contact with each other by the guide rails to be extracted as a traveling force in one direction to obtain a linear driving force. Further, since the guide rails are arranged at the four corners, the driving force can be taken out even in a half cycle in which the torsional movement direction of the elastic body is reversed, and driving with high energy efficiency can be performed. According to the ninth aspect, since the area of the contact surface between the elastic body and the relative moving member is increased, the driving efficiency is improved. According to the tenth aspect, since the reaction force of the guide rails arranged diagonally passes through the center of the elastic body, it is possible to suppress the generation of the rotational moment of the elastic body which is unrelated to the traveling force.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of an ultrasonic motor according to the present invention.

FIG. 2 is a diagram showing an arrangement of piezoelectric elements of the ultrasonic motor according to the first embodiment.

FIG. 3 is a schematic diagram showing flexural vibration of an elastic body of the ultrasonic motor according to the first embodiment.

FIG. 4 is a schematic diagram showing flexural vibration of an elastic body of the ultrasonic motor according to the first embodiment.

FIG. 5 is a block diagram showing a drive circuit of the ultrasonic motor according to the first embodiment.

FIG. 6 is a diagram for explaining the operation of the ultrasonic motor according to the first embodiment.

FIG. 7 is a diagram for explaining the operation of the ultrasonic motor according to the first embodiment.

FIG. 8 is a diagram showing a second embodiment of the ultrasonic motor according to the present invention.

FIG. 9 is a diagram showing a third embodiment of the ultrasonic motor according to the present invention.

FIG. 10 is a perspective view showing a conventional example of an ultrasonic motor utilizing torsional vibration.

FIG. 11 is an exploded perspective view showing a stator of an ultrasonic motor according to a conventional example.

[Explanation of symbols]

 1 Elastic body 2 Piezoelectric element (for flexural vibration) 3 Piezoelectric element (for torsional vibration) 4 Guide rail 5 Spring 6 Central guide rail 7 Piezoelectric element (for extensional deformation) 8 Piezoelectric element (for thickness sliding deformation) 9 Contact member

Claims (10)

[Claims] 1. An elastic body having an end portion on the outer periphery of a cylinder as a drive surface, a relative moving member in contact with the drive surface of the elastic body, and a first electromechanical conversion element for imparting torsional vibration to the elastic body, A second displacing a driving surface of the elastic body so as to contact the relative moving member when the elastic body is twisted;
Ultrasonic motor including the electromechanical conversion element of. 2. The ultrasonic motor according to claim 1, further comprising a pressing member that presses the elastic body and the relative moving member into pressure contact with each other. 3. The ultrasonic motor according to claim 1, further comprising a central support member that supports the elastic body in the vicinity of the center of the central axis and in a direction orthogonal to the central axis. Ultrasonic motor characterized by. 4. The ultrasonic motor according to any one of claims 1 to 3, wherein the elastic body has a shape in which a column is roughly divided into two in the axial direction. An ultrasonic motor, wherein the mechanical conversion element is arranged on a divided surface of the elastic body. 5. The ultrasonic motor according to claim 4, wherein the second electromechanical conversion element is an element for flexural deformation arranged on a division surface of the elastic body. Sonic motor. 6. The ultrasonic motor according to claim 4, wherein the second electromechanical conversion element is an element for extensional deformation arranged at an end of the elastic body. Sonic motor. 7. The ultrasonic motor according to claim 4, wherein the second electromechanical conversion element is an element for thickness sliding deformation arranged at an end of the elastic body. Ultrasonic motor. 8. The ultrasonic motor according to claim 1, wherein the relative moving member is a guide rail that contacts a drive surface of the elastic body, and the elastic body is An ultrasonic motor characterized in that when the driving surface is torsionally vibrated, the driving surface is displaced so as to come into contact with the guide rail, and a reaction force is generated to obtain a traveling force. 9. The ultrasonic motor according to claim 8, wherein the elastic body is a portion where a driving surface of the elastic body is chamfered at an end edge portion of a cylinder, and the guide rail includes a driving surface of the elastic body. An ultrasonic motor characterized by being clamped from four corners. 10. The ultrasonic motor according to claim 9, wherein the guide rails are arranged such that a pair of diagonally arranged reaction forces pass through a center of the elastic body. Ultrasonic motor to do.