Nec Tokin Corporation

Tokin Corporation

Toru Kumagai

Makoto Teshima

Koji Uchida

Yutaka Suzuki

In a vibration actuator using a magnetic circuit device ( ), a supporting arrangement ( ) elastically supports the magnetic circuit device. A coil ( ) is inserted into a magnetic gap ( ) of the magnetic circuit device and is supported by a vibration plate ( ). The vibration actuator has a first operation mode in which the magnetic circuit device mainly vibrates to transmit vibration through the vibration plate to the outside, a second vibration mode in which the coil mainly vibrates to produce a buzzer sound through the vibration plate, and a third vibration mode in which the magnetic circuit device and the coil mainly vibrate to produce a sound corresponding to a speech through the vibration plate.

Vibration actuator having three vibration modes

A vibration actuator includes an electromechanical transducer having a magnetic circuit ( - ) and a driving coil ( ), a support frame ( ), and a damper ( ) 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 ( ). The damper ( ) comprises inner and outer ring portions ( ) and a plurality of spiral spring portions ( ) determined by a plurality of spiral slits ( ) 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 (&thgr;) 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 angular degree or more. In a preferable example, the effective spring length is determined by a product (r&middot;&thgr;) of an average radius (r) value by the unit of &ldquo;mm&rdquo; and the effective angle (&thgr;) 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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Shiroishi, Japan

Toru Kumagai