JPS6455082A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To increase motor efficiency, by designing the length of the projection of a vibration transmitting member in the vicinity of 1/4 of the wave length of the driving frequency of a motor. CONSTITUTION:Eight pieces of electrode 1a, divided into the areas of 45 deg. for example, are provided on the surface of a disc type first piezo-electric vibrating piece 1 in the stator of an ultrasonic motor. The electrodes are polarized so that the polarized directions in the direction of the thickness of the electrodes are different in every neighboring electrodes of the vibrating piece 1. A disc type second piezo-electric vibrating piece 2 is constituted in the same manner as the first piezo-electric vibrating piece 1. The first and second piezo-electric vibrating pieces 1, 2 are attached to an elastic body 3 so as to be superposed while vibration transmitting members or the projections 4 are formed at a position at about 1/2 of a diameter and a shaft 5 is formed at the center of the elastic body 3. The resonance frequency of said projections 4 is designed so as to be larger than the frequency of the driving of the motor while the length of said wave is neighbored to 1/4 of said wave length. According to this method, generation of heat may be prevented and the efficiency of the motor may be improved.