| 摘要 |
A closed forging method for a universal joint trunnion (7, 57) wherein a plurality of shanks (10, 60) are formed radially on a boss (8, 58), the closed forging method being characterized in that a forging mold is configured from an openable/closeable die (16, 17) that has formed therein a cavity (20) that approximately corresponds to the trunnion (7, 57), a pair of upper/lower punches (18, 19) that are arranged on a central axis of the die (16, 17) so as to be reciprocally movable and that press a billet (15a, 15a', 15b, 15b'), and a filling punch (30) that is arranged on the central axis of shank-forming mold parts (16a, 17a) of the cavity (20) and that can advance in the radial direction. The closed forging method is also characterized in that the billet (15a, 15b) is inserted into the die (16, 17), and, when the filling punch (30) is advanced inside the cavity (20) of the closed die (16, 17) and is positioned inside the cavity (20), the shanks (10, 60) and a recessed part (25, 75) on the insides thereof are formed as a result of the billet (15a, 15a', 15b, 15b') being pressed by the upper/lower punches (18, 19). |
