Patent ID: 7705516

Claim:
A drive unit, comprising: a piezoelectric element configured to elongate and contract when a voltage is applied to electrodes of the piezoelectric element; a vibrating member having one end thereof fixed to the piezoelectric element and which is configured to be reciprocally displaced in an axial direction by the elongation and contraction of the piezoelectric element; a frictional engagement member which frictionally engages the vibrating member and which is slidingly displaceable relative to the vibrating member by reciprocal displacements of the vibrating member; and a drive circuit connected to power supply, which applies a voltage of the power supply to the piezoelectric element with a specified driving period, wherein the drive circuit comprises: a bridge circuit which includes a charge switching element configured to connect the electrodes of the piezoelectric element to the power supply; a discharge switching element configured to connect the electrodes of the piezoelectric element to ground; and a switch circuit configured to insert a limiting resistor in at least either one of a current path between the power supply and the bridge circuit and a current path between the bridge circuit and the ground; the switch circuit comprising a limited current path including the limiting resistor, and a bypass current path including a bypass switch for opening the bypass current path in parallel with the limited current path; and wherein the piezoelectric element is elongated and contracted by applying a voltage thereto with the limiting resistor inserted in the current path, so that the frictional engagement member is slowly displaced.