| 摘要 |
A vibration actuator includes an electromechanical transducer having a magnetic circuit (1-4) and a driving coil (5), a support frame (9), and a damper (270) elastically supporting the magnetic circuit onto the support frame to flexibly damp the vibration of the magnetic circuit when a driving AC current is supplied to the coil (5). The damper (270) comprises inner and outer ring portions (271, 272) and a plurality of spiral spring portions (273) determined by a plurality of spiral slits (274, 275) formed in the damper. In order to reduce the spiral spring portion determined by the adjacent two spiral slits in its compliance, each of the spiral spring portions has an effective spring length determined by an effective angle (theta) which is determined as an angle (by angular degree) from an inner end of the inner spiral slit to an outer end of the outer spiral slit defining each respective spiral spring portion around a center of the damper. The effective angle is 55 angular degree or more. In a preferable example, the effective spring length is determined by a product (r.theta) of an average radius (r) value by the unit of "mm" and the effective angle (theta) value by unit of the angular degree. The effective spring length is selected to 320 or more, and preferably 400 or more.
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