| 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 subtracted from a reference value Tr by a subtractor 18, and a subtraction result A is outputted to a switch control 23. The switch control part 25 connects switches 14 and 15 to terminals 14c and 15c when the subtraction result A is positive, turns on a switch 20, and at the same time sets non-supply time data to a synchronization switcher 22. The synchronization switcher 22 intermittently turns on the switch 21 for every period of one signal of bi-phase signals outputted from a phase-shifting circuit 13 with time corresponding to the non-supply time data in-between and supplies an AC signal simultaneously and intermittently to a pair of piezoelectric bodies 2a and 2b of the ultrasonic motor 1, thus increasing the temperature of the ultrasonic motor 1. |
