SHAFT MEMBER FOR DYNAMIC PRESSURE BEARING DEVICE AND METHOD OF PRODUCING THE SAME

摘要

Provided are a shaft member for a dynamic pressure bearing device, dimensional accuracy of which is increased at low cost, and method of producing the shaft member. Also provided are a shaft member for a dynamic pressure bearing device, in which dynamic-pressure grooves are highly accurately processed without involving steep rise in processing cost, and a method of producing the shaft member. A shaft blank (10) integrally having a shaft section (11) and a flange section (12) is formed by forging, and the cylindricality of a part of or the entire part of an outer peripheral surface (11a) of the shaft section (11) is corrected. A shaft end surface (11b) of the shaft blank (10) and an end surface (12b), on the opposite side of the shaft, of the flange section (12) are turned with the surface (13) having been subjected to the correction set as the standard. This way a shaft member (2) is produced. The cylindricality of radial bearing surfaces (23a, 23b) formed on the outer periphery of a shaft section (21) of the shaft member (2) is not more than 3 mum. Further, in a common forging process, a shaft blank (110) integrally having a shaft section (111) and a flange section (112) is formed at the same time when thrust dynamic pressure groove regions (112a, 112b) are formed in both end surfaces of the flange (112). After the forging process, in a common form rolling process, radial dynamic pressure groove regions (113a, 113b) are formed in an outer peripheral surface (111a) of the shaft section (111). The radial dynamic pressure groove regions (113a, 113b) and the thrust dynamic pressure groove regions (112a, 112b) are turned in a turning process after the form rolling process.