Abstract: A constant velocity universal joint has track shapes which facilitate quality control on a forging die set, securing higher durability through securement of a stable contact state of forging-molded tracks and finishing-processed tracks with respect to balls. At least one of each of track grooves of an outer joint member and each of track grooves of an inner joint member is formed by cold-forging finishing. A track groove bottom side of the at least one of each of the track grooves is formed into a Gothic arch shape in horizontal cross-section, and a track groove opening side of the at least one of each of the track grooves is are each formed into an elliptical shape in horizontal cross-section.

Abstract: A constant velocity universal joint includes an outer joint member in which at least one end portion is open, an inner joint member for transmitting torque together with the outer joint member through balls under a state in which angular displacement is allowed, and a boot for closing an opening portion of the outer joint member. The boot has a small diameter end portion fitted onto a shaft extending from the inner joint member, a lip portion abutting on an outer peripheral surface of the shaft, and a ventilation groove for establishing communication between an inside and an outside of the boot. The lip portion and the ventilation groove are formed in an inner peripheral surface of the small diameter end portion of the boot.

Abstract: Provided is a constant velocity universal joint having track shapes which facilitate quality control on a forging die set and products as in a conventional case while securing higher durability through securement of a stable contact state of forging-molded tracks and finishing-processed tracks with respect to balls. At least one of each of track grooves (22) of an outer joint member (23) and each of track grooves (25) of an inner joint member (26) is formed by cold-forging finishing. A track groove bottom side of the at least one of each of the track grooves (22) and the track grooves (25) is formed into a Gothic arch shape in horizontal cross-section, and track groove opening sides of the at least one of each of the track grooves (22) and the track grooves (25) are each formed into an elliptical shape in horizontal cross-section.

Abstract: Disclosed is a constant velocity universal joint, comprising: an outer joint member (10) in which at least one end portion is open; an inner joint member (20) for transmitting torque together with the outer joint member (10) through balls (30) under a state in which angular displacement is allowed; a boot (70) for closing an opening portion of the outer joint member (10), the boot (70) having a small diameter end portion (72) fitted onto a shaft (50) extending from the inner joint member (20); a lip portion (75) abutting on an outer peripheral surface of the shaft (50); and a ventilation groove (76) for establishing communication between an inside and an outside of the boot (70), the lip portion (75) and the ventilation groove (76) being formed in an inner peripheral surface of the small diameter end portion (72) of the boot (70).