Shaft member for fluid dynamic bearing device

Abstract

Provided is a shaft member for a fluid dynamic bearing device, which is excellent in wear resistance and which can exert a high dynamic pressure effect. A shaft material (11) is rolled to form a recess (7) for causing a dynamic pressure effect of a lubricating oil in a radial bearing clearance (6). In this case, in a surface layer portion (14) of the recess (7) to be formed in an outer peripheral surface (11a) of the shaft material (11), a first hardened layer (14a) is formed by rolling. At the same time, also in a surface layer portion (15) of a surrounding region (8) of the recess (7), a first hardened layer (15a) is formed by rolling at a partial region thereof. After the recess (7) is formed by the rolling, barreling is applied to the shaft material (11). As a result, an outermost surface layer portion of the surface layer portion (15) is formed with a second hardened layer (15b) by the barreling. A hardness of the second hardened layer (15b) formed in the surrounding region (8) is higher by 50 Hv or more and 200 Hv or less than that of the first hardened layer (14a) formed in the recess (7).

Dependencies are inferred from the claim text.