Ultrasonic motor and electronic apparatus equipped with ultrasonic motor.

摘要

An ultrasonic motor for stepwise driving a rotor 112, in which the stepping amount of the rotor is made smaller than the interval between nodes of a standing wave, or the stepwise movement of the nodes thereof. An ultrasonic vibration generating circuit 107 includes a circuit 106 to generate a travelling wave used to rotate the rotor 112 and a circuit 105 to generate a standing wave used to stop rotation of the rotor. A power source 101 drives an oscillating circuit 102 whose output is divided in a circuit 103 and supplied to a timing pulse generating circuit 104. The output of circuit 104 is to a switching circuit 108 which controls the selection of input from the ultrasonic vibration generating circuit 107 to output to a piezoelectric vibrator drive circuit 109 which energises a piezoelectric vibrator 110. Ultrasonic vibrations are produced at a vibrator member 111, secured to the vibrator 110 and having a plurality of comb-like projection portions. The rotor 112 has a number of poles which is greater than the number of nodes when the standing wave is generated. The rotor 112 is pressed into engagement with the vibrator member 111 and is subject to rotation by the travelling wave and stopping by the standing wave. The rotor is stopped at a force balanced position, depending on the positions of the poles of the rotor, the positions of the nodes of the standing wave, and the positions of the projection portions of the vibrator member. By properly changing the travelling wave and standing wave, a smaller stepping angle of the rotor than the interval between nodes or the stepwise movement of the nodes may be achieved. <IMAGE>