DRIVER USING ELECTROMECHANICAL CONVERSION ELEMENT

PROBLEM TO BE SOLVED: To substantially eliminate a decrease in a movement speed of an engagement member caused by a repetition of a reciprocating drive over time, and also to substantially eliminate a decrease in an upper limit of the movement speed of the engagement member in a low-temperature environment. SOLUTION: A driver is provided with: an electromechanical conversion element 15; a driving friction member 17 fixed to one end of the electromechanical conversion element 15 in the extending and contracting directions; and the engagement member 11 engaged with the driving friction member by a friction force, and the driver relatively moves the driving friction member 17 and the engagement member 11. A voltage is applied to the electromechanical conversion element 15 at a frequency of 10-300 kHz. A grease having a base oil kinematic viscosity of 300 mm2/s or less at a temperature of 0°C is applied to an engagement section between driving friction member 17 and the engagement member 11. COPYRIGHT: (C)2007,JPO&INPIT