機械的な摩擦を介さない非接触形の超音波モータに関する研究

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We have studied the non-contact type ultrasonic motors which are constructed of the stator and the rotor set with a small gap about zero point several mm between them. It is considered that the driving force of this type ultrasonic motors is given by the radiation pressure of the sound wave radiated from the stator vibrator. The stator vibrator is made of the piezoelectric ceramic disk and vibrating in the direction vertical to the disk surface. The vibration mode is the B_<03> mode which is one of the flexural vibrations of the disk.In the disk, there exist two degenerated B_<03> modes whose mode patterns are perpendicular to each other. Hence, when the two input signals with 90ﾟC phase difference are applied to the different two electrodes which are prepared for driving each B_<03> mode, the vibration mode rotors in the circumferential direction. As a result, the rotor set with a small gap on the stator vibrator rotates in the same direction as the vibration mode rotation. The revolution speed achieved about 3,000r.p.m. under 80V_<p-p> input voltage. The size of this ultrasonic motor was rather large ; that is, the diameter was 20mm and the thickness was 2mm.Then, two small non-contact type ultrasonic motors have been investigated. The size of one of the small-sized non-contact ultrasonic motors is 10mm in diameter and 1mm in thickness. Another ultrasonic motor was miniaturized similarly to the size of 5mm in diameter and 0.5mm in thickness. The ultrasonic motor of 10mm diameter rotated in about 1,500r.p.m.revolution speed under 8V_<p-p> input AC(68KHz) signal.The revolution speed of 5mm diameter ultrasonic motor was about 4,000r.p.m. under 30V_<p-p> input AC(136KHz) signal. Moreover, much smaller non-contact ultrasonic motors of 2mm in diameter ahs been rotated int hespeedofabout 700r.p.m.