A forging method for an outer joint member of a constant velocity universal joint,
- the constant velocity universal joint comprising:
- an outer joint member having a spherical inner peripheral surface in which a plurality of track grooves are formed;
- an inner joint member having a spherical outer peripheral surface in which a plurality of track grooves are formed so as to be paired with the track grooves of the outer joint member;
- a plurality of balls, which are interposed between the track grooves of the outer joint member and the track grooves of the inner joint member, and are configured to transmit torque;
- and
- a cage, which is interposed between the spherical inner peripheral surface of the outer joint member and the spherical outer peripheral surface of the inner joint member, and is configured to hold the balls,
- the track grooves of the outer joint member and the track grooves of the inner joint member each having an arc-shaped ball raceway center line having a curvature center that is prevented from being offset in an axial direction with respect to a joint center,
- a plane including the ball raceway center line and the joint center being inclined in a circumferential direction with respect to a joint axial line,
- each of the track grooves of the outer joint member and each of the track grooves of the inner joint member, which are paired with each other, being inclined in mutually opposite directions,
- the forging method comprising:
- aligning, before a pre-processing material is fitted into a punch set, phases of grooves formed in an inner peripheral surface of a cylindrical portion of the pre-processing material and phases of track groove portion forming surfaces of the punch set with each other with use of a phase alignment mechanism;
- and
- performing ironing by fitting the punch set that is radially expandable and contractible into the cylindrical portion of the pre-processing material of the outer joint member comprising the cylindrical portion under a state in which the phases are aligned with each other, and press-fitting the cylindrical portion into a hole of a die, and
- the phase alignment mechanism comprising a phase alignment jig comprising a pair of convex portions, which are to be fitted into two grooves of the pre-processing material which are adjacent to each other in the circumferential direction under a state in which the phases of the grooves in the inner peripheral surface of the pre-processing material and the phases of the track groove portion forming surfaces of the punch set are aligned with each other, and are restricted from being fitted thereto under a state in which the phases of the grooves in the inner peripheral surface of the pre-processing material and the phases of the track groove portion forming surfaces of the punch set are not aligned with each other.