Patent ID: 7492548

Claim:
A hydrodynamic bearing device comprising: a sleeve having a bearing bore into which a shaft is rotatably inserted; a cover plate which is provided such that a reservoir for storing lubricant or air is defined in the vicinity of one end portion of the bearing bore; a substantially dislike flange which is secured to one end portion of the shaft and has one face confronting one end face of the sleeve in the vicinity of the other end portion of the bearing bore; a thrust plate which is provided so as to confront the other face of the flange and seal a region including the one end face of the sleeve; and at least one communication path extending from the reservoir of the cover plate toward an outer surface of the flange; wherein first and second dynamic pressure generating grooves of a herringbone pattern are arranged in a direction along an axis of the shaft on at least one of an inner peripheral surface of the bearing bore of the sleeve and an outer peripheral surface of the shaft; wherein a third dynamic pressure generating groove of a herringbone pattern is provided on at least one of opposed faces of the flange and the thrust plate and a fourth dynamic pressure generating groove of a herringbone pattern is provided on at least one of the one face of the flange and the one end face of the sleeve; wherein clearances between the shaft and the sleeve and between the flange and the thrust plate including the first, second, third and fourth dynamic pressure generating grooves are filled with lubricant; wherein one of the sleeve and the shaft is mounted on a stationary base and the other of the sleeve and the shaft is mounted on a rotary member; wherein when “S 1 ” denotes a dimension of a radial clearance between the shaft and the sleeve at the time the axis of the shaft is held in alignment with a central axis of the bearing bore, “S 2 ” denotes a dimension of a clearance between the shaft and an inner periphery of the cover plate and “S 3 ” denotes a dimension of clearance between an inner peripheral portion of the cover plate and the other end face of the sleeve, and wherein the dimension S 1 is made smaller than the dimensions S 2 and S 3 .