To prevent swing and improve rotation precision by chamfering an outer peripheral fringe of a flange part of a dynamic bearing in which the flange part is eccentric for a shaft part so that an end face of the flange part becomes concentric with the shaft part.
Lubricant for generating dynamic pressure is filled between a housing 1 and a shaft 2, and the shaft 2 is constituted by a shaft part 5 and a flange part 6 which is eccentric for it. Moreover, a dynamic pressure generation groove for radial direction support is formed on an outer peripheral face of the shaft part 5, a dynamic pressure generation groove for axial direction support is formed on end faces 6a, 6b of the flange part 6, and a chamfered part C is formed at an outer peripheral fringe of the flange part 6 so that the end faces 6a, 6b become concentric with the shaft part 5. Consequently, radii in each part in the peripheral direction of the end faces 6a, 6b become the same, and support forces due to dynamic pressure at any place in the peripheral direction of the end faces 6a, 6b become equal. As a result, the center of rotation of the housing 1 does not swing for a shaft core of the shaft 2, and rotation precision is improved.
HIRAOKA TAIJI
TAKAMURA YASUO
