Patent ID: 8320063

Claim:
An actuator comprising: an electromechanical transducer configured to cause mechanical displacement in accordance with a voltage applied thereto; a driving shaft which is axially displaced and inclined, respectively, by the mechanical displacement of the electromechanical transducer; a movable member configured to frictionally engage the driving shaft; and a driving circuit configured to superimpose (a) an alternating driving voltage configured to cause axial vibrations of the driving shaft so as to cause sliding displacement of the movable member relative to the driving shaft, and (b) a direct-current variable driving voltage configured to cause an inclination of the driving shaft at a desired angle, the variable driving voltage having a low rate of change so as to prevent the sliding displacement of the movable member relative to the driving shaft, and the driving circuit configured to apply the superposed voltages to the electromechanical transducer.