Patent ID: 8267802

Claim:
A fixed type constant velocity universal joint, comprising: an outer joint member having an inner surface in which a plurality of guide grooves are formed; an inner joint member having an outer surface in which a plurality of guide grooves are formed; a plurality of balls interposed between the plurality of guide grooves of the outer joint member and the plurality of guide grooves of the inner joint member, for transmitting torque; and a retainer for retaining the plurality of balls, wherein a center of curvature of each of the plurality of guide grooves of the outer joint member and a center of curvature of each of the plurality of guide grooves of the inner joint member are offset to opposite sides of a joint center along a central axis of the fixed type constant velocity universal joint by equal distances, the center of curvature of each of the plurality of guide grooves of the outer joint member being offset from and on a same side of the joint center as a spherical surface center of an outer surface of the retainer, and the center of curvature of each of the plurality of guide grooves of the inner joint member being offset from and on a same side of the joint center as a spherical surface center of an inner surface of the retainer, wherein R 1 representing F/PCR falls within a range of 0.045≦R 1 ≦0.065, F being a track offset amount that is a distance between the center of curvature of each of the plurality of guide grooves of the outer joint member and the spherical surface center of the outer surface of the retainer or between the center of curvature of each of the plurality of guide grooves of the inner joint member and the spherical surface center of the inner surface of the retainer, and PCR being a length of a line connecting the center of curvature of each of the plurality of guide grooves of the outer joint member or the center of curvature of each of the plurality of guide grooves of the inner joint member and a center of each of the plurality of balls to each other, and wherein As representing αt/α falls within a range of 0.45≦As≦0.65, αt being an angle formed between: a line connecting the spherical surface center of the outer surface of the retainer or the spherical surface center of the inner surface of the retainer and the center of each of the plurality of balls to each other; and the line connecting the center of curvature of each of the plurality of guide grooves of the outer joint member or the center of curvature of each of the plurality of guide grooves of the inner joint member and the center of each of the plurality of balls to each other, respectively, αc being an angle formed between: the line connecting the spherical surface center of the outer surface of the retainer or the spherical surface center of the inner surface of the retainer and the center of each of the plurality of balls to each other; and a line connecting the joint center and the center of each of the plurality of balls to each other, and a sum of αt and αc being α.