Wheel driving unit and method of manufacturing the same

A wheel-driving unit comprising a wheel-supporting bearing unit and a constant velocity joint unit connected together through a retaining ring,

• said wheel-supporting bearing unit comprising:
• an outer ring including a double row of outer raceways formed in the inner peripheral surface thereof and unrotatable even when it is in use;
• a hub including a flange for supporting wheels in the near-to-outer-end portion of the outer peripheral surface thereof, and a first inner raceway formed directly or through a separately disposed inner ring in the middle portion thereof, with the inner ring including a second inner raceway formed in the outer peripheral surface thereof being fitted with and fixed to the outer surface of the near-to-inner-end portion of the outer peripheral surface of said hub;
• rolling elements rollably interposed between one of said outer raceways and said first inner raceway as well as between the other of said outer raceways and said second inner raceway respectively by twos or more;
• and,
• a first spline portion formed in said hub or in a portion of the peripheral surface of a member connected to and fixed to said hub,
• said constant velocity joint unit comprising a differential-side constant velocity joint and a wheel-side constant velocity joint respectively connected to the both end portions of a drive shaft, said constant velocity joint unit further comprising a drive member including, in the outer end portion thereof, a second spline portion to be spline engaged with said first spline portion and also having an inner end portion formed as an outer ring for a constant velocity joint constituting said wheel-side constant velocity joint,
• said retaining ring being formed so as to have an incomplete ring shape as a whole and enlargeable and reducible in diameter;
• and also, in a state where said first and second spline portions are spline engaged with each other, said retaining ring being bridgingly interposable between a first engaging portion formed in said hub or in a portion of the peripheral surface of a member connected and fixed to said hub and a second engaging portion formed in a portion of the peripheral surface of the outer end portion of said drive member to thereby prevent removal of the engagement between said first and second spline portions,
• wherein the circumferential-direction widths of at least part of a plurality of teeth constituting at least one of said first and second spline portions are varied gradually in the axial direction of said spline portion, whereby, as said second spline portion is inserted into said first spline portion, said teeth are able to bite into the groove portions of its mating spline portion in a wedge-like manner.