Patent ID: 6910970

Claim:
A constant velocity universal joint having track grooves formed on both an outer circumference surface of an inner ring, and on an inner circumference surface of an outer ring, and extending in an axial direction, and accommodating balls embedded between both of the track grooves in pockets of a cage interposed between the outer circumference of the inner ring and the inner circumference surface of the outer ring, wherein a cross-section shape of at least the track groove of the inner ring among said track grooves of the inner and outer rings is constituted by a Gothic arch portion that angular contacts with the ball, and an undercut portion formed between a location exceeding a contact point of the Gothic arch portion and the ball and a shoulder portion formed at opposing circumferential ends of the track groove, and retreating from a surface of the radius of curvature of the Gothic arch portion, wherein a chamfer is formed at the shoulder portion of said track groove.