Patent ID: 7094155

Claim:
A constant velocity universal joint, comprising: an outer race having a spherical inner surface, said spherical inner surface having a plurality of track grooves defined therein, each of said track grooves in the outer race having a groove bottom of a longitudinal sectional shape representing a shape of a curve; an inner race having a spherical outer surface and positioned inside the outer race, said spherical outer surface having a plurality of track grooves defined therein in correspondence with the respective track grooves in the outer race, each of said track grooves in the inner race having a groove bottom of a longitudinal sectional shape representing a shape of a curve; a plurality of balls interposed between the outer and inner races and rotatably accommodated between the mating track grooves in the outer and inner races; a retainer having a plurality of pockets accommodating therein the corresponding balls, said retainer having a spherical outer surface, held in surface contact with the spherical inner surface of the outer race, and a spherical inner surface held in surface contact with the spherical outer surface of the inner race; each of said track grooves in the outer race having a center of curvature lying in an axial section of the outer race; and each of said track grooves in the inner race having a center of curvature lying on an axial section of the inner race, said center of curvature of each track groove in the outer race and said center of curvature of each track groove in the inner race being offset an equal distance leftwardly and rightwardly with respect to an angle center of the universal joint; at least one of said spherical inner surface of the outer race or each of the track grooves in the outer race being defined by a post-hardening cut surface, a surface of at least the retainer being formed with a surface treatment layer to reduce a frictional resistance, and a surface treatment layer formed in the inner and outer races is different than the surface treatment layer formed in the surface of the retainer.