| 摘要 |
PURPOSE:To drive an ultrasonic motor stably by setting the resonance frequency of first oscillation mode in the direction of the relative motion of a rotor equal to or higher than the resonance frequency of second oscillation mode in the perpendicular direction. CONSTITUTION:The ultrasonic motor comprises a resilient body 1A having the parts 13, 14 for taking out the driving force, and piezoelectric elements 11, 12, 15, 16 bonded to the surface of the resilient body. When high frequency voltages having phase difference of pi/2 are applied to the piezoelectric elements 11, 12, bending oscillation and longitudinal oscillation take place in the resilient body 1A to cause elliptical motion of the driving force take-out parts 13, 14 which come into contact with a rotor. Since the resilient body 1A is shaped such that the resonance frequency of primary longitudinal oscillation will be equal to or higher than the resonance frequency of quartic elliptical motion, the ultrasonic motor can be driven stably by setting the frequency of high frequency voltage being applied to the piezoelectric elements 11, 12 equal to or higher than the resonance frequency of primary longitudinal oscillation. |
