摘要 |
PURPOSE: To reduce the static electricity generated at sliding time while ensuring stable performance by forming a dynamic pressure bearing of sintered material with specified Young's modulus and a volumetric specific resistance value, to increase rigidity and to reduce deformation. CONSTITUTION: A bearing device comprises a shaft 1, dynamic pressure thrust bearing 2 and a sleeve 3, to rotate the sleeve 3 with the shaft 1 serving as the fixed axis. A herringbone-shaped groove 4a is formed in a surface of the shaft 1 mutually opposed to an internal periphery of the sleeve 3. The dynamic pressure thrust bearing 2 is formed of sintered material having 300GPa or higher Young's modulus and a 10<6> Ω.cm or less volumetric specific resistance value, to use a metal of stainless steel or the like in the shaft 1. Further, the sintered material is preferable mainly composed of Al2 O3 , to use Al2 O3 -TiC system ceramics containing 20wt.% or more TiC. In this way, a stable dynamic pressure characteristic is obtained by decreasing deflection, in a dynamic pressure bearing, and further since static electricity can be released, reliability can be improved. |