| 摘要 |
PURPOSE:To interrupt power supply to a driving circuit by receiving monitor signals from a monitor electrode and the like mounted on the piezoelectric element of stator and operating an overload interrupting circuit upon elapse of a predetermined time after detection of an overload state. CONSTITUTION:Piezoelectric element for an ultrasonic motor 1 is provided with a monitor electrode 3b for stopping overload having an output terminal connected with a voltage regulating circuit 6 which has an output terminal connected with a shaping circuit 7. A judgment is made that an overload state has occurred if a predetermined time elapses before any pulse signal is provided from the shaping circuit 7 and a switching element S2 in a time controlled monostable multivibrator 8 produces an operational signal. The operational signal causes to function a drive ON/OFF circuit 10 comprising a relay RY2 for interrupting the power supply to an ultrasonic wave motor driving circuit 2 and the like through an overload interrupting circuit 9. Consequently, power supply to the driving circuit is interrupted when overload state of motor sustains for a predetermined time. |
