Patent ID: 7568839

Claim:
A fluid dynamic pressure bearing comprising, a shaft having a shaft body and a thrust bearing plate which extends in the radial direction all around the outer peripheral surface of the shaft body, a housing for housing the shaft such that it rotates freely, and a working fluid filling a gap between the shaft and the housing, and there is provided an annular dynamic pressure generating face made by forming a dynamic pressure generating groove, which draws the working fluid toward a midway position in the radial direction from the inside and outside of the thrust bearing plate in the radial direction, or toward a position near an outer peripheral rim from the inside in the radial direction, when the shaft and the housing are rotated relative to each other about the axis, on the thickness direction end face of the thrust bearing plate or on an inner surface of the housing facing the end face via a gap, and an inner groove section, which is located on an inner peripheral side of the dynamic pressure generating face and that is depressed more than the dynamic pressure generating face in the thickness direction, and there is provided a through hole which passes through the thrust bearing plate in the thickness direction so as to open to the dynamic pressure generating face, and there is provided a communicating cavity which connects the opening portion of the through hole and the inner groove section.