Wheel bearing apparatus for a vehicle

摘要

A vehicle wheel bearing apparatus has an outer member; an inner member and double row balls freely rollably contained between outer raceway surfaces and inner raceway surfaces. An inner ring is axially secured relative to a wheel hub by a caulked portion. The caulked portion is formed by plastically deforming the cylindrical portion radially outward. The wheel hub is formed from medium-high carbon steel including carbon of 0.40-0.80% by weight and with a ferrite grain size number selected larger than #3.

主权项

1. A vehicle wheel bearing apparatus comprising:
an outer member formed with double row outer raceway surfaces on its inner circumference; an inner member including a wheel hub and at least one inner ring, the wheel hub is integrally formed with a wheel mounting flange on one of its ends, the wheel hub has an outer circumference with an inner raceway surface and an axially extending cylindrical portion, the at least one inner ring is press-fit onto the cylindrical portion of the wheel hub, an outer circumference of the at least one inner ring includes an inner raceway surface that opposes one of the double row outer raceway surfaces of the outer member; double row balls are freely rollably contained between the outer raceway surfaces and inner raceway surfaces, respectively, of the outer member and the inner member; the at least one inner ring is axially secured relative to the wheel hub by a caulked portion, the caulked portion is formed by deforming the cylindrical portion radially outward; the wheel hub is formed of medium-high carbon steel including carbon of 0.40-0.80% by weight and with a ferrite grain size number that is selected larger than #3; and a draft (La−Lb)/La of a caulking work is set at 0.55 or less, “La” is a length amount of a projection from a larger end of the at least one inner ring to a tip of the projection, a recess is formed with a bottom at a base of the projection, the bottom is substantially coplanar with a larger end face of the at least one inner ring, the projection has a substantially constant thickness extending beyond the bottom of the recess and the larger end face of the at least one inner ring before the caulking of the cylindrical portion and “Lb” is a height of the caulked portion which is the thickness of the caulked portion from the bottom of the recess and the larger end face of the at least one inner ring after the caulking and an entire portion extending beyond the bottom of the recess of the cylindrical portion is caulked, wherein the vehicle wheel bearing apparatus prevents the generation of cracks in the caulked portion during the caulking work.