JPS6477484A - Ultrasonic motor and method for driving same - Google Patents

Abstract

PURPOSE:To improve the efficiency of driving a motor by radially polarizing a ring- shaped piezoelectric ceramic board, properly arranging electrodes and exciting in-plane flexural oscillations by using a piezoelectric longitudinal effect. CONSTITUTION:Band-shaped electrodes 12 are set up along an outer circumference on the surface of a ring-shaped piezoelectric ceramic board 11, and the electrodes 12 are divided into sections such as four ones. Band-shaped electrodes 13 are also mounted onto the surface along an inner circumference, and divided into four sections similarly. DC high tension is applied among the opposed four electrodes by employing the opposed four electrodes, and the ceramic board 11 is polarized in the direction of the arrow. Consequently, the piezoelectric ceramic board electrodes are connected electrically as shown in the figure, and two pairs of electrode terminals 14, 15 are led out to the outside. AC voltage corresponding to the resonance frequency of in-plane flexural oscillations is applied to two pairs of the electrode terminals, the phase of AC voltage is made to differ at 90 deg. mutually, and elliptical vibrations are excited in the outer circumferential side face of the piezoelectric ceramic board. When the piezoelectric ceramic board 11 is used as a stator and the ring-shaped elastic bodies are pressure-welded onto the outer circumferential section, the elastic bodies are operated as a rotor, thus acquiring a rotary motion having excellent efficiency.