Hydrodynamic bearing assembly with single sided grooved counterplate

摘要

An improved spindle motor is disclosed which includes a rotating hub for supporting one or more discs (19) in a disc drive. Also disclosed is a hydrodynamic bearing system for supporting a hub for rotation, the bearing system includes a sleeve (54) and a shaft (50) fitted into an axial bore of the sleeve. The shaft and the sleeve rotate freely relative to one another, and together, define a journal bearing. The shaft supports an annular thrust plate (52). The thrust plate extends into a recess formed by an axial face stepped into the sleeve and a counterplate (58) parallel to the axial face and the thrust plate and attached to the sleeve. A first surface (72) of the thrust plate faces the axial face of the sleeve which has a groove pattern formed on it. A surface (68) of the counterplate faces an opposed, second surface of the thrust plate which has a groove pattern formed on it, to form an effective fluid pumping system in the hydrodynamic bearing.