JPH06343275A - Electrode arrangement of piezoelectric element - Google Patents

Abstract

PURPOSE:To enhance an efficiency by equalizing vibrating states of A-and B-phases in an ultrasonic motor in which nodes of a synthesized wave and vibration are used. CONSTITUTION:A piezoelectric element comprises a thin type piezoelectric element having one side fixed to a stator, and electrodes disposed so that A- phase.B-phase of opposite side to a common electrode of the stator side are deviated by 1/4 wavelength in such a manner that electrodes of the phases are alternately reversely polarized, wherein the electrode dispositions of the A- and B-phases and polarizing directions are laterally symmetrical.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode arrangement of a thin piezoelectric element which constitutes a stator of an ultrasonic motor.

[0002]

2. Description of the Related Art In a conventional piezoelectric element of a stator, an A-phase electrode 1 and a B-phase electrode 2 are formed as shown in FIG.

[0003]

Therefore, when each phase is excited independently, there is a difference in amplitude, resonance frequency, vibration node position, and the like between the phases. This caused a decrease in efficiency and a problem in ultrasonic waves using the composite wave of each phase and the position of the node. Therefore, the present invention solves such a problem, and its purpose is to provide a phase A and a phase B.
This is to make the vibration states of the phases equal.

[0004]

In order to solve the above problems, the present invention provides a thin piezoelectric element having one surface fixed to a stator,
A piezoelectric element in which the A-phase and B-phase on the opposite side to the common electrode on the stator side are positionally shifted by ¼ wavelength, and the electrodes in each phase are alternately polarized in opposite directions. In the above, the arrangement of the electrodes of the A phase and the B phase and the polarization directions are symmetrical.

[0005]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a first embodiment of the present invention,
FIG. 3 is an electrode layout diagram of a ring-shaped piezoelectric element that constitutes a stator of an ultrasonic motor. In FIG. 1, the back surface of the piezoelectric element is conductively adhered to a metal stator to serve as a common electrode for excitation. The surface is roughly divided into an A-phase electrode 1 and a B-phase electrode 2, and the remaining electrode 3 is for monitoring the resonance state of each phase. The electrodes in each phase are in a positional relationship of being displaced by a quarter wavelength, and in the excited state, there are three wavelengths along the circumferential direction. FIG. 4 is a diagram showing the excitation state of the electrodes of each phase and the stator. In the figure, the state of waveform 6 is obtained when the phase A is independently excited, and the state of waveform 7 is obtained when the phase B is independently excited. In each phase, two adjacent electrodes polarized in opposite directions form one wavelength of vibration. The symbol + • 1 shown in each figure indicates the direction of the polarization treatment at the electrode. In FIG. 1, the electrode angle is 60 degrees, and the A phase and the B phase have three waves on the circumference. The feedback electrode 3 is set at 15 degrees, but it is not necessary if it is not necessary. In any case, as shown in FIG. 1, the electrode arrangement and the polarization directions of the A phase and the B phase are symmetrical.

FIG. 2 is a diagram showing a second embodiment in which there are four waves excited in the circumferential direction. In this case, the electrode has an angle of 45 degrees. FIG. 3 is a diagram showing the third embodiment, in which five waves exist and the electrodes are at 36 degrees. Further, in the drawings showing each embodiment, the electrode 4 is an electrode excited by both the A phase and the B phase, and it is not necessary to make the angles (60 °, 45 °, 36 °) according to the number of waves described above. . It is considered that this is because if only the position of the node of vibration is determined, the resonance will occur regardless of the electrode area.

[0007]

As described above, the A-phase and B-phase electrode arrangement and the polarization directions of the piezoelectric element are bilaterally symmetrical, so that the A-phase and B-phase vibration states can be made as equal as possible. This is useful for increasing the efficiency of an ultrasonic motor that uses a synthetic wave or vibration node.

[Brief description of drawings]

FIG. 1A is a surface view showing a first embodiment of the present invention,
(B) Rear view.

FIG. 2A is a front view and FIG. 2B is a rear view showing a second embodiment.

FIG. 3A is a front view and FIG. 3B is a rear view showing a third embodiment.

FIG. 4 is a diagram showing an excited state.

FIG. 5A is a front view and FIG. 5B is a rear view of an electrode layout of a piezoelectric element according to a conventional technique.

[Explanation of symbols]

 1 ... A phase electrode 2 ... B phase electrode

Claims (1)

[Claims] 1. A thin piezoelectric element having one surface fixed to a stator and having an A phase on the opposite surface side to a common electrode on the stator side.
In a piezoelectric element in which the B phase has an electrode arrangement that is positionally deviated by a quarter wavelength, and the electrodes in each phase are alternately polarized in opposite directions, the A phase and B phase electrode arrangement and the polarization direction are The electrode arrangement of the piezoelectric element, which is symmetrical.