Patent ID: 9573418
Date: 2017-02-21
CPC Classifications: B60B,F16C,F16D

Claim:
1. A bearing device for a wheel, comprising: an outer member having double-row outer raceways, an inner member having double-row inner raceways, an outer joint member having a shaft section formed therein, and an extruded portion, the inner member has a hub wheel having a hole portion and a flange for attachment to a wheel, the shaft section of the outer joint member being inserted in a fitting manner into the hole portion of the hub wheel is coupled to the hub wheel, wherein an axially extending projection provided on an outer surface of the shaft section of the outer joint member is press-fitted along an axial direction into a small recessed portion provided on an inner surface of the hole portion of the hub wheel, a recess is formed in the hole portion of the hub wheel by the press-fitting of the projection, and the extruded portion is generated by the forming of the recess, to thereby form a recess-projection fitting structure in which the projection and the recess are held in close contact with each other over an entire region of fitting contact regions therebetween, wherein a surface of the recess is a cut face formed by cutting the small recessed portion by the press-fitting of the projection, and wherein hardness of at least a press-fitting start end portion of the projection is set to be higher than hardness of a region of the hub wheel in which the recess is formed, and a hardness difference therebetween is set to be equal to or larger than 20 points in HRC.