JP2669013B2 - Electrode structure of ultrasonic motor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor, and more particularly to an electrode structure provided on a piezoelectric body for generating vibration.

2. Description of the Related Art Ultrasonic vibration is indispensable for driving an ultrasonic motor. The configuration of this ultrasonic motor is shown in FIG. In the figure, 6 is a piezoelectric body that generates vibration, 7 is an elastic body, 8 is a lining material, 9 is a rotating body, and the piezoelectric body 6 and the elastic body 7 constitute a stator 10a. The body 9 constitutes the rotor 10b. Then, the stator 10a, which is the drive source of the motor, and the rotor 10b are brought into pressure contact with each other, and the output of the motor is taken out by the frictional force and vibration.

It is desirable that the stator and the rotor are in close contact with each other over as wide an area as possible. However, in the configuration of the conventional ultrasonic motor, the excitation of the vibration is not uniformly generated in the plane of the stator, but is generated on one side of the drive electrode. The reason is that the electrode structure provided on the piezoelectric body is not a structure that uniformly generates vibration in a plane. The conventional electrode structure has a structure in which two sets of standing waves are generated to generate a traveling wave, and the two sets are combined to generate a traveling wave.

The conventional electrode structure for driving the ultrasonic motor and the generation state of the traveling wave thereof will be described below with reference to FIGS. 4 (a) and 4 (b).

As a conventional method of generating a standing wave, the surface of the piezoelectric body 11 is divided into an electrode group 12 and an electrode group 13, and each half has an electrode structure that generates a standing wave. These electrode structures have two sets of electrodes on the inner and outer circumferences (electrode group 12 and electrode group).
13) and an electrode structure (FIG. 4 (a)) in which two sets of standing liquid are generated, and a two-piece (electrode group 12 and electrode group 13) divided in the circumferential direction (electrode group 13). 4 (b)).

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the conventional ultrasonic motor, it is difficult to generate two sets of uniform standing liquid in the plane of the piezoelectric body in the plane as described above. There are drawbacks such as reduction and generation of unnecessary vibration not used for driving.

An object of the present invention is to solve the conventional problem, and an object of the present invention is to provide an electrode structure of an ultrasonic motor capable of generating uniform vibration in a plane and suppressing unnecessary vibration.

Means for Solving the Problems In order to solve the conventional problems, the present invention has a structure in which two sets of driving electrodes for standing wave generation provided on a piezoelectric body are uniformly distributed on the piezoelectric body. Is.

Function The present invention can uniformly generate the vibration amplitude on the surface of the piezoelectric body. Therefore, generation of audible sound can be prevented.

According to the present invention, a plurality of electrodes are arranged symmetrically as much as possible on the piezoelectric body on the stator, which is a vibrating body, and two-phase voltages are applied respectively. As an example, if the wave number of the drive electrode per phase is set to 4 sets on one side, the wave numbers of the 4 sets are arranged at symmetrical positions, that is, the electrodes may be arranged at an angle of 90 degrees. . Along with this, the electrode arrangement of the first layer of the other phases is also changed to the electrode arrangement configuration of being shifted by 90 degrees (arrangement shifted by 1/4 wavelength) by the phase angle.

If the number of waves is 5 wavelengths now, electrodes will be provided at intervals of 360 ° / 5 = 72 °. With such an electrode configuration, it is possible to prevent generation of an audible sound due to generation of an unnecessary vibration mode symmetrical twice or three times, which has occurred in the conventional electrode configuration, and also prevent deterioration of characteristics of the ultrasonic motor.

EXAMPLE FIG. 1 shows an electrode arrangement structure on a piezoelectric body of a ring type ultrasonic motor according to the present invention. In FIG. 1, 1 is a piezoelectric substrate, 2 is a first drive electrode, 3 is a second drive electrode, and each drive electrode is formed of two electrodes.

FIG. 2 shows the piezoelectric electrode arrangement structure on the back surface of FIG. 1, 4 is a first common electrode corresponding to the first drive electrode, and 5 is a common electrode.
Indicates a second common electrode corresponding to the second drive electrode. FIGS. 3A and 3B show an embodiment of a desk type ultrasonic motor as a second embodiment. (A) shows the piezoelectric electrode arrangement structure on the front surface, and (b) shows the piezoelectric electrode arrangement structure on the back surface of FIG.

In FIG. 1, FIG. 2, and FIG. 3, the polarization direction of the piezoelectric body is respectively polarized in a direction perpendicular to the surface of the piezoelectric body. There are two cases of polarization from top to bottom, or
Symbols or-symbols are used to illustrate each.

In order to generate two sets of standing waves, the first drive electrode 2, the first set including the first common electrode 4, the second drive electrode 3, and the second common electrode 5 2 in the second set
Apply phase voltage.

When the driving state of the electrode structure of the ultrasonic motor according to the present invention is compared with that of the conventional electrode arrangement structure, in the characteristics of the ultrasonic motor, almost the same results are obtained in terms of efficiency and output, and further unnecessary. With respect to vibration, excellent results were obtained as compared with the conventional one. Explaining the unnecessary vibration, a large rotation speed was obtained for the same load. In other words, unnecessary vibration did not occur up to a large output. Also,
In the desk-type ultrasonic motor, conventionally, two piezoelectric bodies were used as the drive source, but it is possible to excite the traveling wave with only one piezoelectric body.

EFFECTS OF THE INVENTION As is apparent from the above description, according to the present invention, two sets of drive electrodes are evenly distributed and arranged on the piezoelectric body, respectively.
Since the two-phase voltages are applied to the two sets of drive electrodes and the corresponding common electrodes, it is possible to prevent the generation of unnecessary vibration and prevent the characteristic deterioration of the ultrasonic motor.

[Brief description of the drawings]

FIG. 1 is a structural view of an electrode arrangement provided on a driving piezoelectric body, FIG. 2 is a structural view of an electrode arrangement on the back surface of the piezoelectric body corresponding to FIG. 1, and FIG.
FIG. 4 is a diagram showing an electrode arrangement structure of a desk-type ultrasonic motor according to a second embodiment, FIG. 4 is a diagram showing an electrode arrangement structure of a conventional example, and FIG. 5 is a perspective view of the ultrasonic motor. 1 ... Piezoelectric substrate, 2 ... First drive electrode, 3 ... Second
Drive electrodes, 4 ... First common electrode, 5 ... Second common electrode.

Claims (1)

(57) [Claims] 1. An ultrasonic motor driven by using elastic vibration generated in a piezoelectric body, comprising a plurality of electrodes on a piezoelectric body serving as a driving source of the motor, wherein the electrodes are polarized by the same standing wave. An electrode structure of an ultrasonic motor in which two pairs of standing wave generating drive electrodes are alternately and evenly distributed on a piezoelectric body, with a pair of electrodes having different poles.