JPH02179281A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To enable a control to be attained at both high and low speeds using a simplified structure by providing a vibrator to each of a stator and a rotor and supplying a progressive wave generating signal to each vibrator. CONSTITUTION:An ultrasonic motor is constituted of a cover 20, stator 22 sticking a vibrator 24, rotor 32, output shaft 26, etc. This rotor 32 spreads providing in its circumferential part 32a of elastic material a vibrator 36 supplied with power by a conductive brush 38 and a conductive disk 40. Then a progressive wave generating signal is supplied to the vibrators 24, 36 generating a progressive wave, and the rotor 32 is driven rotating in accordance with its both side progressive waves.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic motor, and particularly to an ultrasonic motor suitable for high-speed rotation and low-speed rotation.

[Conventional technology]

In a conventional ultrasonic motor of this kind, as shown in Fig. 1G, a rotor 8 is pressed against a stator 2 made of an elastic body to which a vibrator 4 is attached, through a packing 12 by the elastic force of a spring 12. As a result, the rotor 8 rotates using the traveling waves generated in the stator 2, and this rotation is transmitted to the output shaft 6. Also, JP-A-62-207180
The publication discloses an ultrasonic device having a ring-shaped vibrator that generates a traveling wave by a vibration source that generates ultrasonic vibration, and a rotor that is pressed against the vibrator and rotates by the traveling wave to rotate a rotating shaft. In the sonic vibration motor, an ultrasonic motor is disclosed which is provided with a press-contact state adjusting means, that is, an electromagnetic clutch mechanism, which can release the press-contact state of the rotor to the vibrator.

[Problem that the invention seeks to solve]

As mentioned above, the rotation of the output shaft of an ultrasonic motor uses traveling waves generated in the stator.

It was difficult to control the output shaft at high or low speeds.

The present invention aims to eliminate the above problems.

[Means to solve problems]

In order to achieve the above object, the present invention includes a ring-shaped elastic stator 22 fixed to a cover 20 and having a vibrator 24 stretched on one surface, and an output rotatably supported by the cover 20. It is equipped with a shaft 26 and a ring-shaped rotor 32 attached to the output shaft 26 so as to be interlocked with the rotation direction, and a circumferential portion 32a of the rotor 32 formed of an elastic body is connected to the traveling wave forming surface of the stator 22. The vibrator 36 is placed in contact with the circumferential portion 32a.

[Effect]

In the above configuration, when a traveling wave generation signal is supplied to the vibrator 24 from the drive circuit, a traveling wave traveling in the circumferential direction is formed in the stator 22. On the other hand, when a traveling wave generation signal traveling in the opposite direction to the traveling wave is supplied to the vibrator 36, a traveling wave is generated in the circumferential portion 32a of the rotor 32 that faces the traveling wave forming surface of the stator 22, and the rotor 32 Stator 22
The rotor 3
2 is driven at high speed in the rotational direction. When the vibrator 36 generates a traveling wave in the same direction, the rotor 32 rotates at a low speed, or stands still when the traveling speeds of the rotor 32 and stator 22 are the same.

〔Example〕

First, the principle of the ultrasonic motor will be explained with reference to FIGS. 4 to 9.

Mechanism of generation of standing waves When piezoelectric ceramics are polarized by alternately reversing their direction and a voltage is applied, they ``stretch'' as shown in Figure 4a.
"shrink" and distortion occurs alternately.

By reversing the polarity of the voltage applied to piezoelectric ceramics,
As shown in Figure 4, the strain direction is also reversed. When this piezoelectric ceramic is attached to an elastic body as shown in Figure 4a, and a voltage is applied to the piezoelectric ceramic to generate strain, the elastic body will have a stretched side of the piezoelectric ceramic as shown in Figure 5. becomes a valley, and the contracted side becomes a peak.

When the polarity of the voltage applied to the piezoelectric ceramic is reversed, the deflection of the elastic body is also reversed, as shown in FIG. 5C. As shown in FIG. 5d, when an alternating current voltage is applied to the piezoelectric ceramic, standing waves are generated in the elastic body. What is a standing wave? Figure 5 e
It is a wave that moves up and down repeatedly in the same place as shown in the figure.

Mechanism for generating traveling waves Next, a mechanism for generating traveling waves by combining these standing waves will be explained. As shown in Figure 6a, the elastic body has two
Pieces of piezoelectric ceramics are pasted with 174 wavelengths shifted from each other, that is, 1 mechanically shifted by 90", and alternating current voltages temporally shifted by 90 degrees in phase are applied to each piezoelectric ceramic, as shown in FIG. 6. The two pieces of piezoelectric ceramics A and B each vibrate with a standing wave as shown in Figure 6, Q'8, and the wave A and B that is the sum of these two standing waves.
That is, the vibration of one elastic body becomes a traveling wave that advances with time as shown in FIG. 6(f).

Elliptical locus and rotation principle Traveling waves are excited in the elastic body, and the waves are as shown in Figure 7 a, beQ, d.
, e, if we focus on one point on the surface of the elastic body, that point moves as a - b - c - d - a, and when we synthesize this movement, we get a traveling wave as shown in Figure 7 f. It can be seen that it draws an elliptical trajectory in the opposite direction to the direction in which it travels.

When a moving body is placed on top of an elastic body on which a traveling wave is excited, as shown in Figure 8, the force of this elliptical motion causes the moving body to move in the opposite direction to the direction in which the traveling wave travels. . Further, as shown in FIG. 9, when the elastic body is formed into a ring shape and the traveling wave is rotated counterclockwise, the rotating body above it is rotated in the clockwise direction opposite to the direction of the traveling wave. Further, by switching the rotation direction of the traveling wave, the rotation direction of the rotating body can be switched.

The above is the rotation principle of the traveling wave type ultrasonic motor.

The configuration of the present invention will be explained in detail below with reference to the embodiment shown in FIG.

20'' is a cover that also serves as a mounting base, and a ring-shaped stator 22 made of an elastic body is fixed to this cover.A vibrator 24 made of piezoelectric ceramic is attached to the outer surface of the stator 22.

The side of the stator 22 opposite to the side where the vibrator 24 is disposed constitutes a traveling wave forming surface. Reference numeral 26 denotes a projecting shaft, which is rotatably supported by the cover 20 by ball bearings 28 and 30. Reference numeral 32 denotes a rotor made of a ring-shaped elastic body, and a tube 34 is fixed to the inner diameter of the rotor, and the tube 34 is connected to the output shaft 26 through a keyed structure and a screw fixing mechanism. Fixed. In this state, one side of the circumferential portion 32a of the rotor 32 is in pressure contact with the traveling wave forming surface of the stator 22.

A vibrator 36 made of piezoelectric ceramic is stretched on the side of the circumferential portion 32a of the rotor 32 opposite to the side facing the traveling wave forming surface, and the vibrator 36 is connected to a conductive brush 38 and a conductive plate 40. It is connected to the traveling wave generation signal generating means of the controller by a sliding device consisting of:

Next, the operation of this embodiment will be explained.

When a traveling wave generation signal is supplied to the vibrator 24 from a drive circuit (not shown), a traveling wave is generated on the traveling wave forming surface of the stator 22 . On the other hand, when a traveling wave generation signal is supplied to the vibrator 36, a traveling wave is formed on the side facing the rotor 32, and when the directions of the traveling waves of the rotor 32 and the stator 22 are opposite, both traveling waves are Accordingly, the rotor 32 rotates at high speed. If the traveling directions of the oscillators 24 and 36 are the same and their frequencies are different, the rotor 32 will rotate at a low speed. Stand still.

〔effect〕

Since the present invention is configured as described above, it has the advantage of being able to achieve higher and lower speeds of the ultrasonic motor with a simple structure.

[Brief explanation of the drawing]

Fig. 1 is a sectional view, Fig. 2 is an explanatory drawing, Fig. 3 is an explanatory drawing, Fig. 4 is an explanatory drawing, Fig. 5 is an explanatory drawing, Fig. 6 is an explanatory drawing, Fig. 7 is an explanatory drawing.
The figure is an explanatory diagram, Fig. 8 is an explanatory diagram, Fig. 9 is an explanatory diagram, and Fig. 10 is an explanatory diagram.
The figure is a sectional view of the prior art. 20... Cover 22... Stator, 24... Vibrator, 26... Output shaft, 28. 30... Ball bearing, 32... Rotor, 34... Mounted on pipe, 3
6... Vibrator, 38... Conductive brush, 40... Conductive board Figure 3 Figure 5 Mechanism of generating standing waves Oval locus

Claims (1)

[Claims] (1) A ring-shaped elastic stator 22 fixed to the cover 20 and having a vibrator 24 stretched on one surface, an output shaft 26 rotatably supported by the cover 20, and the output shaft 26 and a ring-shaped rotor 32 attached to the rotor 32 so as to be interlocked in the rotational direction. An ultrasonic motor characterized in that the vibrator 36 is stretched around the circumferential portion 32a.