Patent ID: 7661882

Claim:
A fluid dynamic pressure bearing device, comprising: a shaft member; a bearing member, at least one of the shaft member or the bearing member being rotatable with respect to the other, a micro gap being formed between the shaft member and the bearing member; a shaft member-side annular member fixed with respect to the shaft member, the shaft member-side annular member having an axially inward end portion and an axially outward end portion, the shaft member-side annular member including: a large-diameter rim portion protruding outwardly in a radial direction, and a small-diameter outer circumferential surface portion, continuing from the large-diameter rim portion toward the axially outward end portion; a bearing member-side annular member fixed with respect to the bearing member, the bearing member-side annular member having an axially inward end portion and an axially outward end portion, the bearing member-side annular member including: an inner circumferential large-diameter step portion, and a small-diameter inner circumferential surface portion continuing from the inner circumferential large-diameter step portion toward the axially outward end portion; a plurality of convex surface portions circumferentially formed either on a surface of the inner circumferential large-diameter step portion facing the large-diameter rim portion of the shaft member-side annular member, or on a surface of the large-diameter rim portion of the shaft member-side annular member facing a surface of the inner circumferential large-diameter step portion; at least one concave portion separating the plurality of convex surface portions; a reflux groove surrounding the convex surface portions, the reflux groove allowing flow of lubricant; at least one first dynamic pressure groove formed in either an outer circumferential surface of the shaft member or an inner circumferential surface of the bearing member, the at least one first dynamic pressure groove generating a dynamic pressure receiving a load in a radial direction; and at least one second dynamic pressure groove formed in either the lower surface of the large-diameter rim portion of the shaft member-side annular member or one end surface of the bearing member facing the lower surface of the large-diameter rim portion, the at least one second dynamic pressure groove generating a dynamic pressure receiving a load in a thrust direction.