Kabushiki Kaisha Toshiba

Hiroki Tonai

Michiyasu Komatsu

Hiroshi Komorita

Minoru Takao

Isao Ikeda

Yoshiyuki Fukuda

Hisao Yabe

Yukihiro Takenami

The present invention provides a silicon nitride wear resistant member composed of silicon nitride sintered body containing 1-10 mass % of rare earth element in terms of oxide thereof as sintering agent, wherein a total oxygen content of the silicon nitride sintered body is 6 mass % or less, a porosity of the silicon nitride sintered body is 0.5 vol. % or less, and a maximum size of pore existing in grain boundary phase of the silicon nitride sintered body is 0.3 &mgr;m or less. According to the above structure of the present invention, there can be provided a silicon nitride wear resistant member and a method of manufacturing the member having a high strength and a toughness property, and particularly excellent in sliding characteristics.

Silicon nitride wear resistant member and method of manufacturing the member

In material for ceramic ball that has a spherical portion of approximate sphere at both ends thereof and a belt-like portion at a center thereof over an entire circumferential direction, a difference between a diagonal diameter of the belt-like portion and a polar diameter of the spherical portion is 100 &mgr;m or less. A height of the belt-like portion from the spherical portion is preferable to be 1 mm or less. A width of the belt-like portion is preferable to be 5 mm or less. The material for ceramic ball can be used for material for bearing balls for instance. When applying in such a usage, the material for ceramic ball essentially consists of silicon nitride, Vickers hardness thereof being preferable to be 1400 or more. In the material for ceramic ball of the present invention, a difference between a diagonal diameter of a belt-like portion and a polar diameter of a spherical portion is set at 100 &mgr;m or less. As a result, the material is formed in a shape where the belt-like portion does not project from the spherical portion. Thereby, the belt-like portion of the material for ceramic ball and polar diameter of the spherical portion come into average contact with abrasives or the like. Accordingly, different from the case of the existing material, the belt-like portion can be suppressed from wearing and damaging the abrasives due to the contact.

Material for ceramic ball and method of manufacturing ceramic ball

Wear resistant member for electronic equipment comprises a zirconium oxide sintered body of which specific resistance is in the range from 1 to 10 &OHgr;&middot;m. A conductivity enhancer of which specific resistance is 10 &OHgr;&middot;m or less is compounded to a zirconium oxide sintered body to materialize specific resistance from 1 to 10 &OHgr;&middot;m. For a conductivity enhancer, carbides and nitrides of various kinds of metals can be used. Wear resistant member can be used as a bearing ball, being applied in a rotational driver of electronic equipment such as a magnetic recording device and an optical disk device. Deficiency due to static electricity of electronic equipment is cancelled due to specific resistance that a zirconium oxide sintered body has.

Wear resistant member for electronic equipment and bearing and spindle motor therewith

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Yokohama, Japan

Hiroki Tonai