INVESTIGATION OF ULTRASONIC MOTORS USING THIN PIEZO-CERAMICS AND A METAL COMPOSITE-PLATE FOR WATCHES

The authors have developed a 0.4-mm-thick longitudinal bar-type ultrasonic motor for use in watches, using a thin plate stator and a rotor equipped within the same plane. The stator is driven to vibrate length wise by piezo-ceramics oscillated in the first longitudinal mode. The stator then uses a slant projection tooth to pick at the rotor, and drive it. The motor is simply constructed and is easily driven at low voltages. This paper shows that the ultrasonic motor possesses the requisite size and operating characteristics for use in driving the date wheel of a watch.