Patent ID: 7618196

Claim:
A wheel bearing apparatus comprising; an outer member formed with double row tapered outer raceway surfaces, each opened axially outwardly on its inner circumference; an inner member includes a wheel hub with a wheel mounting flange formed integrally at one end, a cylindrical portion axially extends from the wheel mounting flange, at least one inner ring is fit onto the cylindrical portion of the wheel hub via a predetermined interference, each inner ring is formed with one of a tapered double row inner raceway surfaces on its outer circumference and is arranged opposite to one of the double row outer raceway surfaces, and a larger outer diameter side of said inner ring having a larger flange portion for guiding tapered rollers; double row tapered rollers are rollably arranged between the outer and inner raceway surfaces via cages; and the at least one inner ring is secured on the wheel hub by a caulked portion, said caulked portion is formed by plastically deforming the end of the cylindrical portion radially outward; a predetermined hardened layer is formed by high frequency induction hardening over a range from the base of the wheel mounting flange to the cylindrical portion; a position of the inner side end of the hardened layer is set within a range from an edge of a chamfered portion at the caulked side of the inner ring to a position corresponding to a root of the larger flange portion; and an annular recess is formed on the end of the cylindrical portion, the depth of the annular recess is set at a length of 5 mm or less from the larger end face of the inner ring at its caulked side, and a depth of the chamfered portion, from the edge of the chamfered portion to the larger end face of the inner ring, is less than the depth of the annular recess so that the hoop stress generated in the outer circumference of the inner ring is reduced.