JPH04133675A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To make it possible to provide a normal rotation and reverse rotation by locating two piezoelectric elements between two cylindrical stators and by expansion-controlling an expansion actuator located between the central portion of a rotor and a stator on the operation side in response to a normal/ reverse change in the direction of the torsional vibration of the stator on the operation side. CONSTITUTION:Two sets of ring-shaped piezoelectric elements 4b with electrodes 4a adhered to said elements are placed arranged between two cylindrical stators 1 and 2, and the respective stators are connected and fixed with a bolt 3 near the central axial line of said stators thereby forming a Langevin oscillator. A rotor 5 having a circumferential surface as perimeter is located at the end surface opposite to the piezoelectric element side of the stator 2. In addition, a laminated piezoelectric actuator 7 is located at a recessed place in the rotor 5. A power supply for driving the laminated piezoelectric actuator 7 is formed in such a manner that the sequence of actuator expansion can be convertible to the opposite of the sequence in normal rotation, thereby applying the torsional vibration in reverse direction only to the rotor 5 and reversely rotating said rotor.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an ultrasonic motor using a Langevin type vibrator, and in particular, the present invention relates to an ultrasonic motor using a Langevin type vibrator. The rotor can be rotated forward or backward by acting on the rotor.

[Prior Art] Conventionally, as an ultrasonic motor using a Langevin type ultrasonic transducer, one having a structure shown in Japanese Patent Laid-Open No. 61-49670 is known. This Langevin type vibrator has a plurality of cantilever beams tilted in the circumferential direction attached to the base part on the same circumference, and when the base part is vibrated by a piezoelectric material, the resonance of these cantilevers causes It is designed to create elliptical vibrations in the same direction along the line. The rotor, which is pressed against the cantilever beams, is rotated by the elliptical vibration of the cantilever beams in a fixed direction.

[Problems to be Solved by the Invention] Conventional Langevin-type vibrators can only generate elliptical vibrations in a fixed direction on multiple cantilever beams tilted in the same direction, but cannot reverse the direction of the elliptical vibrations. There isn't. For this reason, conventional Langevin type ultrasonic motors cannot be switched between forward and reverse rotation, which limits the range of use, and requires two motors for forward and reverse rotation. .

Therefore, the present invention does not provide a cantilever beam to the Langevin type vibrator (it is configured to produce torsional vibration that is repeated in the forward and reverse directions at minute time intervals, and the direction of the torsional vibration is constant). The purpose is to act on the rotor so that the rotor can rotate in forward and reverse directions.

[Means to solve the problem 1 The present invention is an ultrasonic motor that achieves the above object.

The cylindrical stator of the Langevin type vibrator is configured to generate torsional vibration in forward and reverse directions. A laminated piezoelectric actuator that presses the rotor onto the stator and pushes up the rotor is provided, and the laminated piezoelectric actuator is configured to expand and contract in response to forward and reverse changes in the direction of torsional vibration of the stator.

[Function] The Langevin type vibrator described above is configured to shift the resonance frequency of longitudinal vibration and the resonance frequency of torsional vibration so that it vibrates at the resonance frequency of torsional vibration. Therefore, in the Langevin type vibrator, the longitudinal vibration is at a minimum and the torsional vibration is at a maximum, and the vibrations generated in the working side stator of the Langevin vibrator are mainly torsional vibrations in the forward and reverse directions.

On the other hand, the laminated piezoelectric actuator is controlled to expand and contract in response to forward and reverse changes in the direction of torsional vibration of the stator on the operating side. It becomes a pressure-welded state,
The rotor is rotated in the forward direction. Note that when torsional vibration occurs in the opposite direction, the laminated piezoelectric actuator expands and pushes up the rotor, so that torsional vibration does not act on the rotor.

Furthermore, when the rotor is rotated in the opposite direction, the expansion and contraction control of the laminated piezoelectric actuator may be performed in the opposite direction. In that case, when the torsional vibration of the stator is in the opposite direction, the rotor is pressed against the stator, and the rotor rotates in the opposite direction.

[Example] Embodiments of the present invention will be described with reference to FIGS. 1 to 3.

The Langevin type vibrator consists of two sets of ring-shaped piezoelectric elements 4b with electrodes 4a bonded between two cylindrical stators 1.2.
The structure is such that the parts corresponding to the central axis of each stator are connected and fixed by, for example, ports 3. In order to make the stator 2 on the working side of the Langevin type vibrator torsionally vibrate,
As is well known, the Langevin oscillator is constructed so that the resonance frequency of longitudinal vibration and the resonance frequency of torsional vibration are shifted, and by operating the two sets of piezoelectric elements 4b, it is possible to generate vibration at the resonance frequency of torsional vibration. ing.

That is, in the Langevin type vibrator, the resonant frequency of longitudinal vibration and the resonant frequency of torsional vibration are shifted, so that it vibrates mainly at the resonant frequency of torsional vibration. Therefore, in the Langevin type vibrator, the longitudinal vibration is at a minimum and the torsional vibration is at a maximum, and the vibrations generated in the working side stator of the Langevin vibrator are mainly torsional vibrations in the forward and reverse directions. Further, the torsional vibration (lateral vibration) generated in the stator 2 on the operating side is a reciprocating vibration in the lateral direction, and changes in the forward and reverse directions at minute time intervals.

A rotor 5 having a circumferential outer periphery is arranged on the end face of the stator 2 on the opposite side to the piezoelectric element side. The rotor 5 has a recessed center portion on the stator side, and its outer circumferential portion abuts against the outer circumferential portion of the stator 2 . The rotor 5 is pressed against the stator 2 by a spring member (not shown), and is rotated by torsional vibration of the stator 2. Note that an output shaft 6 is protruded to the outside of the rotor 5 in the rotation axis direction.

In order to arrange the laminated piezoelectric actuator 7 in the recess of the rotor 5, in this embodiment, the base of the laminated piezoelectric actuator tuff is fixed to the center of the stator 2 on the operating side, and the tip of the laminated piezoelectric actuator tuff is fixed to the end of the rotor 5. It was placed close to the inner surface of the wall 5a. The laminated piezoelectric actuator 7 is controlled to expand and contract by a drive power source (not shown), and the expansion and contraction control is performed by the stator 2.
This corresponds to changes in the direction of torsional vibrations that occur in When the laminated piezoelectric actuator tough is extended, the end wall 5 of the rotor 5
a is pushed up so that the torsional vibration of the stator 2 does not act on the rotor 5, and the rotor 5 is rotated so that only the torsional vibration in a certain direction acts on the rotor 5. Further, in order to reverse the rotor 5, the drive power source for the laminated piezoelectric actuator 7 is configured to be convertible so that the order of expansion and contraction of the actuator is reversed. Then, by applying only torsional vibration in the direction opposite to that described above to the rotor 5, the rotor can be rotated in the reverse direction.

In the embodiment described above, the rotor 5 was pushed up by the laminated piezoelectric actuator tough, but it is also possible to push up the rotor using other actuators that can control expansion and contraction.

[Effects of the Invention] In the ultrasonic motor of the present invention, torsional vibration that is repeated in the forward and reverse directions is generated in the stator, and the laminated piezoelectric actuator is expanded and contracted in response to changes in the forward and reverse directions of the torsional vibration in the stator. , it is possible to selectively apply only torsional vibration in a certain direction to the rotor. Therefore, a Langevin type ultrasonic motor capable of rotating the rotor forward or backward can be obtained with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of an ultrasonic motor of the present invention, FIG. 2 is a sectional view of a main part of the ultrasonic motor, and FIG. 3 is an exploded perspective view of a Langevin type vibrator. ■, 2: Stator 4b: Piezoelectric element 5: Rotor
6. Output shaft 7: Laminated piezoelectric actuator Applicant Asumo Co., Ltd. Agent Patent attorney Katsu Maki Figure 1 Figure 3 Figure 2

Claims (2)

[Claims] (1) Two piezoelectric elements are interposed between two cylindrical stators, and the parts corresponding to their central axes are connected and fixed with bolts, etc. to construct a Langevin-type vibrator that can generate torsional vibration in forward and reverse directions. The outer periphery of the rotor is pressed against the end face of the stator on the operating side, and a telescopic actuator for pushing up the rotor is placed between the center of the rotor and the stator on the operating side. An ultrasonic motor characterized by being configured so that expansion and contraction can be controlled in response to forward and reverse changes in the direction of torsional vibration of a stator. (2) Forming a recess in the center part of the rotor on the stator side,
2. The ultrasonic motor according to claim 1, wherein a laminated piezoelectric actuator is disposed in the recess, and the laminated piezoelectric actuator is fixed to the center of the stator on the operating side.