Ultrasonic motor.

摘要

An ultrasonic motor comprising a vibrator (2) which is vibrated by a piezo-electric element ring (3) having a plurality of angularly spaced apart piezo-electric sub-elements (30a1, 30a2, 30a3, 30b1, 30b2, 30b3); a rotatable member (1) which is in contact with the vibrator (2) and which is arranged to be rotated by the latter; and drive means (Figure 8) for impressing voltages on the sub-elements so as to produce vibration of the vibrator (2) which causes rotation of the rotatable member (1); characterised in that the rotatable member (1) has angularly spaced apart non-contact regions (1b) which are out of contact with the vibrator (2) and which are spaced from each other by half the wavelength of the said vibration.