Patent ID: 6377145
Filing Date: 2002-04-23
Classification: H04R

Abstract:
A vibration actuator comprising:an electro-mechanical transducer including a driving coil and a magnetic circuit comprising a magnet and yoke, a support frame, and a damper supporting the magnetic circuit onto the support frame, said damper comprising an inner ring portion, an outer ring portion, and a plurality of spiral spring portions connecting the inner and outer ring portions, wherein each of the spiral spring portions extends in a spiral shape from the inner ring portion to the outer ring portion and is defined by an inner spiral slit and an outer spiral slit, wherein each of the spiral spring portions has an effective spring length of at least 320 (mmÂ·degrees), said effective spring length being determined by a product (rÂ·&thgr;) of an average radius (r) (in mm) and an effective angle (&thgr;) of each respective spiral spring portion, and said effective angle being determined as an angle (by angular degree) from an inner end of the inner spiral slit defining each respective spiral spring portion to an outer end of the outer spiral slit defining each respective spiral spring portion around a center of the damper, and wherein: each of said spiral slits has a shape determined by a radial inner contour line and a radial outer contour line so that a slit width of each respective spiral slit is increased at the inner and outer end portions, said radial inner contour line comprises a spiral line extending from the outer end toward the inner end of each respective slit and a circular arc in a vicinity of the inner end, the circular arc being concentric with the inner ring portion, and said radial outer contour line comprises a spiral line extending from the inner end toward the outer end of each respective slit and a circular arc in a vicinity of the outer end, the circular arc being concentric with the outer ring portion.