Fixed-type constant velocity universal joint

A fixed type constant velocity universal joint, comprising:

• an outer joint member including a spherical inner peripheral surface having eight curved track grooves extending in an axial direction, the outer joint member having an opening side and a deep side being separate from each other in the axial direction;
• an inner joint member including a spherical outer peripheral surface having eight curved track grooves extending in the axial direction;
• eight balls each arranged between one of the curved track grooves of the outer joint member and a corresponding one of the curved track grooves of the inner joint member;
• a cage, which has eight pockets configured to receive the balls in a one-by-one manner, and includes a spherical outer peripheral surface and a spherical inner peripheral surface that are held in slide contact with the spherical inner peripheral surface of the outer joint member and the spherical outer peripheral surface of the inner joint member, respectively;
• a shaft coupled to the inner joint member to be able to transmit power;
• and
• a ball retaining mechanism,
• wherein a curvature center of the curved track grooves of the outer joint member and a curvature center of the curved track grooves of the inner joint member are offset to opposite sides in the axial direction with respect to a joint center by an equal distance, wherein a ratio W1o/DBALL of an axial length (W1o) from the joint center to an opening-side end surface of the outer joint member to a diameter (DBALL) of each of the balls is set to fall within a range of from 0.35 to 0.52,
• wherein a ratio WC/DBALL of a width (WC) of the cage to the diameter (DBALL) of each of the balls is set to fall within a range of from 1.63 to 1.80,
• wherein an inclination allowing space for the cage, which is configured to ensure a ball incorporation angle, is defined by a deep-side bottom portion of the outer joint member,
• wherein the ball retaining mechanism comprises a cylindrical shaft portion formed at an end portion of the shaft and an angle restriction stopper surface at an inner periphery of a recessed portion formed in the deep-side bottom portion, and the cylindrical shaft portion and the angle restriction stopper surface interfere with each other at an angle smaller than the ball incorporation angle, and
• wherein an end surface corner portion of the cylindrical shaft portion of the shaft is positioned within a range surrounded by a circle (CC) containing the spherical outer peripheral surface of the cage and a circle (CT) containing groove bottoms of the curved track grooves of the outer joint member on the deep side of the outer joint member in a longitudinal cross section containing a joint axis under a state in which an operating angle is 0°.