超音波モータを用いた振動アラーム付AQの開発 Development of Ultrasonic Motor-Equipped Vibration Alarm Analog Quartz Watch
This study aimed at substantiating possibilities of next-generation microactuators for use in watches. To do this, we have developed an ultrasonic motor that is one of promising elements as a new principle-based actuator. Measuring 10 mm in diameter and 4.5 mm in thickness, this motor records the world's smallest one for practical use. It is powered by a single lithium coin battery and is expected to be applied to a wide range of small-sized portable information devices including watches. Its simple structure makes it possible to reduce the size and also to lower driving frequency. As the primary application, we have incorporated a vibration alarm using this motor into an analog quartz watch. Different from conventional electronic alarm, this watch indicates the alarm time through gentle vibration, Namely, a rotor with an eccentric weight rotates at high speed and centrifugal force generates vibration intermittently. Our experimental study covered establishment of design parameters, such as rotor pressurization, and also of specifications for vibrator capable of rotating at high-speed. In this connection, the basic motor performance was made clear. Development of this motor allowed us to apply a vibration alarm to watches for the first time. Such application has not been achieved so far by conventional electromagnetic motor.
日本時計学会誌 141(0), 37-54, 1992