| 摘要 |
An ultrasonic motor (10) that is capable of stable driving by preventing uneven rotation of a driven body and maintaining the drive efficiency is provided. The ultrasonic motor includes a plurality of ultrasonic transducers (1,2) including alternately stacked first piezoelectric elements and second piezoelectric elements, and a control unit for applying the same two-phase driving AC voltages to the plurality of ultrasonic transducers. The ultrasonic motor simultaneously generates longitudinal vibration and flexural vibration at the ultrasonic transducers to generate substantially elliptic vibration at output ends of the ultrasonic transducers and relatively moves the ultrasonic transducers and a driven body in contact with the ultrasonic transducers. The control unit (60) includes a vibration detection circuit (66) that detects the vibrations of the ultrasonic transducers and outputs an average-vibration detection signal, a phase comparator circuit (68) that detects a phase difference between one of the two-phase driving AC voltages applied to the ultrasonic transducers and the average-vibration detection signal, and a frequency control circuit (70) that controls the frequency of the driving AC voltages such that the phase difference detected by the phase comparing part is a predetermined value.
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