| 摘要 |
PROBLEM TO BE SOLVED: To provide a wheel bearing device having improved repetitive fatigue strength by relaxing stress concentration which occurs in a recessed portion of the flange base of a hub ring between a raceway surface and a large collar face. SOLUTION: In the wheel bearing device in the form of a hub unit and a double row tapered roller bearing, an inner ring 3 is fitted to an inner ring fitting face 2a provided at one end of the hub ring 2 and the inner ring 3 and the hub ring 2 are provided with inner ring raceway surfaces 2b, 3b in rows, respectively. The hub ring 2 is formed of carbon steel, and a hardening layer 20 with heat treatment is provided at a portion on the surface of the hub ring 2 ranging from at least a raceway surface 2a to the flange base. The recessed portion 2e consisting of a peripheral groove is provided along a corner portion of the hardening layer 20 of the hub ring 2 between the inner ring raceway surface 2b and the large collar face 2d located adjacent to the inner ring raceway surface 2b in contact with the end face of a roller 5. The recessed portion 2e is formed with grinding work and its inner face is ground after forming the hardening layer 20. With the work after forming the hardening layer 20, compression residual stress is imparted to the surface of the hardening layer 20. COPYRIGHT: (C)2007,JPO&INPIT
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