Thin Ultrasonic Spindle-Motor Using Non-Axisymmetric ((1,1))-Mode of a Ring Vibrator

Several thin ultrasonic motors using a nonaxisymmetric ((1, 1)) vibration mode of a ring vibrator have been developed for disc drives or micro-fan. A stator vibrator has a single vibrating piece or double ones at the inner side of the ring vibrator. The vibrating pieces drive a rotating shaft. A preload was applied between the shaft and vibrating pieces in in-plane or virtical directions to the stator vibrator. The thickness and diameter of this type of an ultrasonic motor were 0.6mm and 12.7mm, respectively. This paper describes some kinds of ultrasonic spindle-motor constructions proposed by authors and their experimental results. As one of experimental results, the high revolution speed of 6,300rpm and input power of 0.91 W at 170.9kHz and 30Vp-p were obtained.