Olympus Optical Company, Ltd.

Shouichi Saito

Hiromichi Sakano

A rotor is formed by a rotary frame 3 composed of a nonmagnetic material, a field magnet 5, a yoke 4 and an auxiliary yoke 7. A disk 12 is mounted on the rotary frame 3. An opening 4b is formed in the yoke 4 to thereby cause attractive magnetic flux from the field magnet 5 to effectively act on a clamping yoke 13 of the disk, so that the disk 12 can be firmly clamped. The yoke 4 covers the circumferential part of the field magnet 5 on its disk 12 side to thereby cut off magnetic flux leakage toward the disk 12, so that its adverse effect on the recording surface of the disk 12 can be avoided. The auxiliary yoke 7 so arranged that a stator coil 6 is interposed between the auxiliary yoke 7 and the field magnet 5 is secured to the rotary frame 3 to thereby increase effective rotating magnetic flux so that output torque is increased.

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Hachioji, Japan

Shouichi Saito