Patent ID: 7118182

Claim:
An axle unit for a drive wheel, comprising: an outer ring including an outer raceway in an inner peripheral surface of said outer ring, said outer ring being unrotatable even when said axle unit is in use; a hub including a mounting flange formed in an outer-end portion of an outer peripheral surface of said hub for supporting the drive wheel, a first inner raceway formed directly or through an outboard-side inner ring in a middle portion of said outer peripheral surface of said hub, a second inner raceway formed in a direction of an inner-end portion of said outer peripheral surface, and a spline hole formed in a central portion of said hub; a drive shaft member including a spline shaft disposed on an outer-end portion of said drive shaft so as to be engageable with said spline hole, said drive shaft having an inner-end portion formed as a housing portion to serve as an outer ring of a constant velocity joint; and, a plurality of rolling elements rollably interposed between said outer raceway and said inner raceway, said axle unit further comprising: an inside engaging portion formed so as to extend around the outer periphery of said spline shaft; an outside engaging portion formed so as to extend around the inner periphery of said hub, said outside engaging portion being disposed in a position that corresponds to said inside engaging portion; and a retaining ring made of elastic material, wherein said retaining ring is bridgingly interposed between said inside and outside engaging portions to thereby prevent the spline shaft from slipping out of said spline hole, an inboard-side inner ring with said second inner raceway formed in an outer peripheral surface of said inboard-side inner ring, said inboard-side inner ring being fixed to said hub in such a manner that an inner-end face of said inboard-side inner ring is held by a caulk portion formed in the-inner end portion of said hub, which inner-end portion of said hub projects beyond said inner-end face of said inboard-side inner ring, by caulking and spreading the inner-end portion of said hub outwardly in a diameter direction of said hub, a portion of said caulk portion, that is opposed to an outer-end face of said housing portion, is formed as a flat surface parallel to said outer-end face of said housing portion, wherein said flat surface and said outer-end face of housing portion are butted against each other, wherein the retaining ring urges the flat surface of the caulked portion against the outer end face of the housing portion.