An ultrasonic motor using bending cylindrical transducer based on PZT thin film

Abstract

Ultrasonic motors have a distinguished performance of high torque. Especially, it seems that cylinder type ultrasonic motors are superior to disk or ring type ultrasonic motors in sense of high torque application. For miniaturization of a motor size, simple construction of an ultrasonic transducer become effective. In this work, we propose an ultrasonic motor using bending cylindrical transducer based on PZT thin film on side wall of a small tube. The transducer of the ultrasonic motor is composed of short cylindrical titanium pipe, PZT thin film and electrodes. The titanium pipe is introduced for a base material to deposit PZT thin film by hydrothermal method. The thickness of film is about from 7 to 9 pm. The electrodes are divided into 4 parts in circumferential direction to excite degenerated bending vibration mode with two RF driving electrical sources. A rotor loaded on the transducer turned around in the intended direction.The maximum revolution speed was 295 rpm.