| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain a helical gear having good precise tooth lead without developing shrinkage hole at the addendum part of the helical gear formed at the initial stage in a punching process of a pressing machine by extruding a blank while rotating at the larger extruding angle than the desired torsion angle and successively, the same extruding angle as the desired tortion angle. SOLUTION: On the outer peripheral surface of a die attached with a a projection in the faced dies, an outer spline 10 having larger torsion angle than the desired torsion angle of the helical gear, is arranged. The die 2 attached with the projection is integrally lowered with the punch 1 and a helical guide 3, and the helical guide 3 is brought into contact with a stopper 6 and stopped, and the die 2 attached with the projection is lowered while rotating together with the punch 1 along an outer spline 10 arranged on the outer peripheral surface of the die 2 to execute a notching with cutting to the blank 7. By this method, the development of the shrinkage hole at the addendum part of the gear is prevented. Successively, only the punch 1 is lowered while rotating along the tooth having the same torsion angle as the desired torsion angle of the helical gear to keep the tooth lead precision.</p> |
