Hitachi, Ltd.

Akira Tamura

Fumio Tajima

Kunio Miyashita

Hiroshi Katayama

Teizo Tamura

Kouichi Saito

Kenichi Hironaka

Saburo Kazama

Yosimi Sekita

Takuro Kawano

A rotary head apparatus includes magnetic heads on its outer peripheral portion and rotatably supported in a hollow space defined by fixed hollow upper and lower cylindrical drums, a brushless motor stator coil attached to one or the other of the fixed drums, and a brushless motor magnet and yoke, or a first and a second magnets, arranged on the rotary head apparatus on both sides of the stator coil with a gap therebetween.

Rotary head apparatus with motor magnet and yoke surrounding motor

A permanent magnet electric machine such as, for example, a motor or generator, including a permanent magnet field member, an armature having salient magnetic poles and armature windings. A greatest common division of the number of magnetic poles of the field member and the salient magnetic poles having the armature windings differs from the number of magnetic poles. A group of grooves is formed between the salient magnetic poles having an interval of 2/3M.pi., with M being an integer which is not a multiple of three. To reduce the occurrence of cogging torque, auxiliary grooves are provided on the surface of the salient poles at positions which are spaced apart from positions of the grooves by (.pi./3)K+(.pi./6), in terms of electrical angle, with K being an integer.

Permanent magnet electrical machine with reduced cogging

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Toukai, Japan

Akira Tamura