Hitachi, Ltd.

Tomoyuki Saitou

Katsutoshi Nii

Ichiro Hashimoto

Sueo Akashi

Takeshi Nakajima

Nobukatu Sone

Fusanori Ohira

A motor has a stator with a base part and a hollow projection as well as a rotor with a shaft which extends into the hollow projection. A radial bearing is mounted between the shaft and the hollow projection. There may be a further radial bearing in the base part of the stator. The radial bearing, lubricated by magnetic fluid, is sealed between the shaft and the projection by a magnetic seal at the end of the hollow projection remote from the base part. The rotor has an annular part extending around the hollow projection, which supports permanent magnets forming an armature. Those permanent magnets interact with drive coils on the stator to cause rotation of the rotor about the axis of the shaft. There is also a magnetic thrust bearing between the annular part of the rotor and the projection of the stator. This magnetic thrust bearing is axially displaced relative to the magnetic seal towards the base part of the stator, to counteract the effect of the magnetic thrust bearing on the magnetic seal.

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Hitachi, Japan

Tomoyuki Saitou