Patent ID: 7911114

Claim:
An impact drive actuator comprising: a fixing member; a vibrator having a first end fixed to the fixing member and a second end configured to expand and contract; a vibrating member fixed to the second end of the vibrator and configured to be movable in the expansion and contraction direction of the vibrator; a movable body disposed on the vibrating member and configured to be movable in a desirable direction relative to the fixing member; a drive circuit configured to supply a drive signal whose value changes at a predetermined cycle to the vibrator for causing the vibrator to be displaced; and a friction adjustment section configured to change a frictional force acting between the movable body and vibrating member, the friction adjustment section including: a first electrode disposed on a surface of the movable body that faces the vibrating member; and a single second electrode disposed on a surface of the vibrating member that faces the first electrode and is electrically isolated from the first electrode, an electrostatic force being caused to act between the first and second electrodes to change an electrostatic force between the vibrating member and movable body at a time of expansion and contraction of the vibrator by which an inertial force is acted on the movable body, and the frictional force acting between the movable body and the vibrating member is changed, thereby relatively moving the movable body in a desirable direction with respect to the fixing member; wherein a third electrode is disposed on a surface of the vibrating member that faces the moving body and a potential difference is applied between the second and third electrodes to generate the electrostatic force between the first and second electrodes.