Fluid dynamic pressure bearing device, spindle motor provided with the fluid dynamic pressure bearing device, and recording disk drive device

Abstract

A fluid dynamic pressure bearing device includes a shaft member () and a bearing member (), at least one of the shaft member or the bearing member being rotatable with respect to the other. A shaft member-side annular member () is fixed with respect to the shaft member. The shaft member-side annular member includes a large-diameter rim portion and a small-diameter outer circumferential surface portion. A bearing member-side annular member () is fixed with respect to the bearing member. The bearing member-side annular member includes an inner circumferential large-diameter step portion, and a small-diameter inner circumferential surface portion. A plurality of convex surface portions are 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. A reflux groove () surrounds the convex surface portions.