Shaft member for dynamic pressure bearing device

Abstract

Provided is a bearing member for a dynamic pressure bearing device, which is excellent in wear resistance and which can exhibit a high dynamic pressure action. A shaft material (11) is rolled to form a recess (7) for causing the dynamic action of a lubricant in a radial bearing clearance (6). Then, a surface layer portion (14) of the recess (7) to be formed on the outer circumference (11a) of the shaft material (11) is rolled to form a first hardened layer (14a). At the same time, a surface layer portion (15) of a surrounding area (8) of the recess (7) is also rolled to form a first hardened layer (15a) at its partial area. After the recess (7) was rolled, that shaft material (11) is barreled. As a result, the outermost surface layer of the surface layer portion (15) is barreled to form a second hardened layer (15b). The hardness of the second hardened layer (15b) formed in the surrounding area (8) is higher by 50 Hv to 200 Hv than that of the first hardened layer (14a) formed in the recess (7).

Description

technical field [0001] The present invention relates to a shaft member for a dynamic pressure bearing device. Background technique [0002] The dynamic pressure bearing device is a device that supports the shaft member in a relatively rotatable manner through the dynamic pressure of the fluid generated in the bearing gap. Recently, it is suitable for use as an information bearing due to its superior rotation accuracy, high-speed rotation, and quietness. Bearing devices for electric motors mounted on various electronic devices including machines. Specifically, it is used as a bearing device for spindle motors mounted on information equipment such as magnetic disk devices such as HDD, optical disk devices such as CD-ROM, CD-R / RW, and DVD-ROM / RAM, and optical disk devices such as MD and MO. , used as a multifunctional scanner motor for a laser beam printer (LBP), a color wheel motor for a projector, or a bearing device for motors such as fan motors. [0003] For example, in a...

AI Technical Summary

Problems solved by technology

[0010]However, usually, since the above-mentioned heat treatment is performed at a high temperature, deformation of the shaft itself is unavoidable, and there is a possibility that the accuracy of the outer peripheral surface may decrease

In particular, when the dynamic pressure groove is formed with a small size and high precision, the deformation of the shaft during heat treatment is likely to adversely affect the shape accuracy of the dynamic pressure groove.

As a result, for example, the depth or shape of the dynamic pressure groove varies, and there is a possibility that a sufficient dynamic pressure effect cannot be exerted.

The means disclosed in the above documents are only aimed at improving the surface hardness of the shaft member, and do not consider the decrease in the accuracy of the outer peripheral surface caused by deformation during heat treatment.

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