摘要 |
PURPOSE:To prevent temperature drop while the drive of an ultrasonic motor is at halt in a state where a still torque can be obtained. CONSTITUTION:A temperature sensor 17 detects the temperature around an ultrasonic motor 1, the detection signal T is compared with a reference value Tr by temperature comparison 18, and the comparison result is outputted to a switch control 25. The switch control part 25 connects switches 14 and 15 to terminals 14c and 15c when T is smaller than Tr and at the same time turns on a switch 20. A synchronization switcher 22 alternately switches a switch 21 for every one period of one signal of bi-phase signals outputted from a phase-shifting circuit 13 and supplies an AC signal alternately to a pair of piezoelectric bodies 2a and 2b of the ultrasonic motor 1, thus increasing the temperature of the ultrasonic motor 1. |