| 摘要 |
A bearing device suitable for a spindle motor, which comprises a base, a spindle stood on a central portion of the base, a radial cylindrical member (4) fixed on the spindle, a pair of thrust plates (3) secured to both end surfaces of the radial cylindrical member, and a radial sleeve (6) rotatably supported by the thrust plates (3) and the radial sleeve (6), wherein a radial hydrodynamic bearing is formed by the radial cylindrical member (4) and the radial sleeve (6), thrust hydrodynamic bearings are formed by both end portions of the radial sleeve (6) and the thrust plates (3), a gas is employed as a fluid for generating dynamic pressure in the thrust hydrodynamic bearings, the radial bearing has a minute clearance, a chamfer portion is provided on the outer periphery of each end of the radial cylindrical member (4), and another chamfer portion is provided on the inner periphery of each end of the radial sleeve (6), thereby providing an air gap (13) at each axial end of the radial hydrodynamic bearing, which is surrounded by these chamfer portions and one thrust plate (3), a lubricating liquid is employed as a fluid for generating dynamic pressure in the radial hydrodynamic bearing, small holes (8) for collecting the lubricating liquid are formed in the outer peripheral surface of the radial cylindrical member (4), and lubricating liquid is sealed in the bearing clearance of the radial hydrodynamic bearing by virtue of the presence of the air gaps (13).
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