Low profile fluid dynamic bearing

Abstract

The design comprises a shaft and sleeve supported for relative rotation by a journal type fluid dynamic bearing utilizing grooves on one of the shaft or sleeve surfaces. A grooved pattern of a design similar to that usually found on a thrust plate is defined on an axial end surface of the shaft or the counterplate facing the axial end of the shaft, so that thrust is created to maintain separation of the end of the shaft and the facing thrust plate during relative rotation. In one embodiment, to establish and maintain the gap between the shaft end and the facing counterplate, the journal bearing has an asymmetry to pump toward the shaft end having the bearing. In a further refinement, to maintain the shaft and gap within an optimum spacing, a magnet is mounted to provide an axially directed magnetic force on the shaft which works against the axial force created by shaft end thrust bearing. To prevent separation of the shaft and sleeve or hub, the hub which is integrated with a rotating shaft, further incorporates a shoulder which extends axially beneath a cooperating shoulder on the sleeve surrounding the shaft to prevent any more than a limited axially displacement of the hub and shaft relative to the sleeve.