Ultrasonic motor and electronic apparatus equipped with ultrasonic motor

摘要

An ultrasonic motor has a self-excited oscillation circuit comprised of a vibrating body having a piezoelectric element and an amplifier circuit for amplifying an output signal of the piezoelectric element for oscillating the vibrating body in a predetermined natural mode. A moving body is disposed in contact with the vibrating body and is driven in response to oscillation of the vibrating body. A control signal generating circuit outputs to the self-excited oscillation circuit a drive command signal or a stop command signal to bring the self-excited oscillation circuit into a drive state to drive the moving body or a stop state, respectively. The control signal generating circuit is set so that a length of the drive command signal is a time period required for the self-excited oscillation circuit to start oscillating at a frequency corresponding to a given frequency for driving the moving body.