Constant-speed universal joint

A constant-velocity universal joint of a joint center fixed type, the constant-velocity universal Joint comprising:

• an outer ring in which a plurality of outer-ring ball grooves extending in an axial direction is formed in an inner circumferential surface;
• an inner ring in which a plurality of inner-ring ball grooves extending in the axial direction is formed in an outer circumferential surface;
• 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,
• wherein the plurality of inner-ring ball grooves includes a first inner-ring ball groove and a second inner-ring ball roove having different shapes,
• wherein a chamfered portion is formed in the inner ring between each of the inner-ring ball grooves and the outer spherical surface, and
• wherein the chamfered portion includes a linear section portion and an arc section portion, the linear section portion is located in the chamfered portion close to the outer spherical surface and is formed in a linear shape in a section perpendicular to a moving locus of a center of the corresponding ball, and the arc section portion is located in the chamfered portion close to the corresponding:
• inner-ring ball groove and is formed in a protruding arc shape in the section perpendicular to the moving locus of the center of the corresponding ball.