Patent ID: 7380989
Filing Date: 2008-06-03
Classification: F16C,G11B,H02K

Abstract:
1. A dynamic pressure bearing device comprising: a substantially columnar shaft centered on and extending along a central axis; a sleeve in which the shaft is received, the sleeve being coaxial with the shaft such that an inner surface of the sleeve opposes, in a radial direction perpendicular to the center axis, an outer surface of the shaft; and fluid retained between the sleeve and the shaft in the radial direction, wherein the shaft is rotatable relative to the sleeve in a circumferential direction of the sleeve with the fluid interposed therebetween, the sleeve has a plurality of first grooves in the inner surface thereof, the first grooves having opposite ends in the axial direction of the sleeve, and each of the first grooves having opposite sides in the circumferential direction of the inner surface of the sleeve, the sleeve also has a respective bank disposed adjacent each of at least one of the ends of the first grooves in the axial direction of the sleeve, each said bank being raised relative to the first grooves inwardly in the radial direction so as to prevent fluid from escaping axially from the first grooves, the first grooves being arrayed circumferentially along the inner surface of the sleeve, and the depth of each of the first grooves decreases in the circumferential direction in which the shaft rotates relative to the sleeve, whereby the pressure of fluid retained in the first grooves increases when the shaft rotates relative to the sleeve in said circumferential direction.