| 摘要 |
PURPOSE:To enable the manufacture of a hollow cam shaft a low cost by forc ing a plastic deformation of a steel pipe through a cold extrusion process using a die and a core bar. CONSTITUTION:A drawn portion 11 is formed on one end of a steel drawn hollow pipe 1. After inserting into the pipe 1 a core bar 2 of a cylindrical shape composing of four stage outside diameters, the pipe 1 is set in a cold extrusion forming machine composed of a die 3a and a press P of a thick plate as its main component. The pipe 1 and the core bar 2 are inserted into and drawn through the die 3a in one until by having it extruded with the press P from the rear and, next, the pipe 1 and the core bar 2 are inserted into and drawn through a die 3b having a larger hole diameter than the die 3a. The core bar 2 is drawn out from the pipe 1 and the drawn portion 1 cut off. With this constitution, the shaft 1 is formed with two stages of the outside circumferential surface composing of a small diameter portion 14 having four V shape grooves 4 in the shaft direction along the hole shape of the die 3a and a large diameter portion 13 along the hole shape of the die 3b, and with the inside circumferential surface along the external shape of the core bar 2. |
