Patent ID: 6388362
Filing Date: 2002-05-14
Classification: H02N

Abstract:
An ultrasonic motor comprising:a piezoelectric element; an oscillator bonded to the piezoelectric element for frictionally driving a moving body by means of an oscillation wave generated in the oscillator in response to elongation and contraction movement of the piezoelectric element; an oscillation drive circuit for generating the oscillation wave by self-excited oscillation of the oscillator; and start/stop signal generating means for generating an output signal for controlling the starting and stopping of the ultrasonic motor by bringing the oscillation drive circuit into an active state and a stop state, respectively; wherein the oscillation drive circuit comprises a power amplifier for amplifying an excitation signal, a capacitive circuit for adjusting a frequency of the oscillation signal, and a switching circuit connected in parallel with a capacitive element of the capacitive circuit for short-circuiting terminals of the capacitive element based on the output signal from the start/stop signal generating means; and wherein when the oscillation drive circuit is brought into the stop state based on the output signal from the start/stop signal generating means, the switching circuit is turned ON and the terminals of the capacitive element are thereby brought into a short-circuited state to discharge the capacitive element during the stop state.