A constant-velocity universal joint including a generally cup-shaped outer joint member and an inner joint member that define first and second groove portions. A pinch angle by which a ball is pinched in the first groove portion is open toward an opening of the outer joint member. A pinch angle by which the ball is pinched in the second groove is open toward a bottom of the outer joint member. An absolute value of the pinch angle in a larger-pinch-angle groove portion that is one of the first and second groove portions, is larger than an absolute value of the pinch angle in a smaller-pinch-angle groove portion that is the other of the first and second groove portions in a reference state. A radial clearance in the smaller-pinch-angle groove portion is larger than a radial clearance in the larger-pinch-angle groove portion when torque is not transmitted in the reference state.

A constant-velocity universal joint including a generally cup-shaped outer joint member and an inner joint member that define first and second groove portions. A pinch angle by which a ball is pinched in the first groove portion is open toward an opening of the outer joint member. A pinch angle by which the ball is pinched in the second groove is open toward a bottom of the outer joint member. An absolute value of the pinch angle in a larger-pinch-angle groove portion that is one of the first and second groove portions, is larger than an absolute value of the pinch angle in a smaller-pinch-angle groove portion that is the other of the first and second groove portions in a reference state. A radial clearance in the smaller-pinch-angle groove portion is larger than a radial clearance in the larger-pinch-angle groove portion when torque is not transmitted in the reference state.

Constant-velocity ball joint, having at least a joint outer part with an axis of rotation and with outer ball tracks and with outer center lines, a joint inner part with inner ball tracks and inner center lines, and a large number of torque-transmitting balls which are each guided in mutually associated outer ball tracks and inner ball tracks.

A constant-speed universal joint includes: an outer ring; an inner ring; a plurality of balls that engages with the outer-ring ball grooves and the inner-ring ball grooves; and a holder that is interposed between an inner spherical surface of the outer ring and an outer spherical surface of the inner ring and in which a holding window for holding the plurality of balls is formed. A chamfered portion is formed in the inner ring. The chamfered portion includes a linear section portion that is formed in a linear shape in a section perpendicular to a moving locus of the center of the corresponding ball and an arc section portion that is formed in a protruding arc shape in the section perpendicular to the moving locus of the center of the corresponding ball.

A constant-speed universal joint includes: an outer ring; an inner ring; a plurality of balls that engages with the outer-ring ball grooves and the inner-ring ball grooves; and a holder that is interposed between an inner spherical surface of the outer ring and an outer spherical surface of the inner ring and in which a holding window for holding the plurality of balls is formed. A chamfered portion is formed in the inner ring. The chamfered portion includes a linear section portion that is formed in a linear shape in a section perpendicular to a moving locus of the center of the corresponding ball and an arc section portion that is formed in a protruding arc shape in the section perpendicular to the moving locus of the center of the corresponding ball.

In a constant velocity joint, a center locus of a first ball rolling on a first outer central portion is inclined such that a distance from a central axis of an outer joint member decreases toward a bottom side of the outer joint member. A center locus of a second ball rolling on a second outer central portion is formed in a linear shape and inclined such that a distance from the central axis of the outer joint member increases toward the bottom side of the outer joint member. A center locus of the second ball rolling on the second outer bottom side portion is formed in an arc shape and disposed in the outer joint member at a position radially inwardly from a tangent at a connecting position between the second outer central portion and the second outer bottom side portion.

In a constant velocity joint, a center locus of a first ball rolling on a first outer central portion is inclined such that a distance from a central axis of an outer joint member decreases toward a bottom side of the outer joint member. A center locus of a second ball rolling on a second outer central portion is formed in a linear shape and inclined such that a distance from the central axis of the outer joint member increases toward the bottom side of the outer joint member. A center locus of the second ball rolling on the second outer bottom side portion is formed in an arc shape and disposed in the outer joint member at a position radially inwardly from a tangent at a connecting position between the second outer central portion and the second outer bottom side portion.

A fixed type constant velocity universal joint has outer joint member track grooves each with a raceway center line that includes an arc-shaped portion having a curvature center that has no offset with respect to a joint center in an axial direction. The track grooves are formed such that adjacent track grooves are inclined in opposite directions. The joint also has inner joint member track grooves that are each formed to be mirror-symmetric with a corresponding one of the outer joint member track grooves with a plane including the joint center and being orthogonal to the axis of the joint at an operating angle of 0°. When at a large operating angle, an operating angle at which a torque transmission ball loses contact with the inner joint member track groove is larger than that at which the torque transmission ball loses contact with the outer joint member track groove.

Provided is a cage (5, 65, 95) for a constant velocity universal joint, which is formed into a ring shape with a substantially uniform thickness, including a plurality of pockets (20, 80, 110) formed in a circumferential direction of the cage (5, 65, 95), for receiving torque transmitting balls, respectively, the cage (5, 65, 95) being formed of carbon steel including 0.41 to 0.51 mass % of C, 0.10 to 0.35 mass % of Si, 0.60 to 0.90 mass % of Mn, 0.005 to 0.030 mass % of P, and 0.002 to 0.035 mass % of S, with the balance being Fe and an element inevitably remaining at the time of steelmaking and refining, the cage (5, 65, 95) being subjected to carburizing, quenching, and tempering as heat treatment, each of the plurality of pockets (20, 80, 110) having a side surface (23, 83, 113) finished after the heat treatment.

A joint-center-fixed constant velocity joint configured to be provided in a vehicle includes an outer joint member, an inner joint member, a first ball, a second ball, and a cage. While a center of the first ball is moving to a position of the maximum use angle on an opening side from a joint center, a first open angle faces the opening side. While a center of the second ball is moving to a position of the maximum use angle on a bottom side from the joint center, a second open angle is not reversed from a state where the second open angle faces the bottom side to a state where the second open angle faces the opening side.