Development of a self-oscillating ultrasonic micro-motor and its application to a watch

We have developed an ultrasonic micro-motor for use as a micro-actuator in place of an electromagnetic motor. This ultrasonic micro-motor, which can be driven by a single signal and in which the change of the direction of the rotor movement can be made easily by selecting the electrode to apply the driving signal, can easily construct a self-oscillating circuit and simplify the driving circuit. We have also simplified the motor structure, which is easy to miniaturize and mass-produce. We applied a version of this motor with a diameter of 8 mm to a vibration alarm, and one with a diameter of 4.5 mm to a driving source of a calendar mechanism in a watch. This ultrasonic micro-motor is expected to be of use as a new driving source in a broad range of fields.