| 摘要 |
PURPOSE:To prevent as much as possible concentration of stress at the boundaries of respective polarized portions of a piezoelectric element and improve reliability, driving efficiency and output at the time of driving a motor. CONSTITUTION:An area of both end portions 20b in the circumferencial direction of a plurality of independent electrodes 20 arranged respectively to a couple of regions 3a, 3b at a single side of a circular piezoelectric element for rotating a rotor by generating therein a travelling wave is set smaller than the area of the central region 20a. |
