Ultrasonic Motor Using a Large-Diameter Torsional Vibrator with Slant Slits

This paper deals with a large-diameter rod-type ultrasonic motor, in which only the torsional vibration is excited piezoelectrically. This new motor is designed to improve the performance of a relatively high-torque motor by increasing the diameter of the stator vibrator. The characteristic feature of the motor construction is that many slits are cut aslant on the vibrator end-face in contact with a rotor in order to form small slanted cantilever beams; that is, these cantilever beams operate in the bending vibration due to coupling with the main torsional vibration of the stator and lift the rotor in the inclined direction to rotate it. Therefore, this motor operates fundamentally one-way, and thus its advantage is that it is easily driven with a single power source. The first part of this paper concerns the simulated results of an aslant slit torsional vibrator, especially on its slanted cantilever beam, and the second part describes the experimental investigation of the prototype motor.