| 摘要 |
PURPOSE:To make it possible to prepare a cam shaft perfectly prevented from peeling generation and excellent in reliability, by a method wherein the cam shaft of an internal-combustion engine is constituted by the integral casting of a cam and a rotary shaft each of which is made of carbon steel and the surface of the cam is subjected to mechanical processing and thereafter to phosphate treatment. CONSTITUTION:In bringing the contact of a rocker arm 5 supported by the cam 7 and the rocker shaft 4 of the cam shaft 6 in the moving valve system structure in an internal-combustion engine to rolling contact in place of slide contact, a defect generating peeling on the surface of a roller 9 is generated by the repeated rolling contact of the roller 19 and the cam 7. In order to prevent this phenomenon, the cam 7 and a rotary shaft 8 are integrally cast from carbon steel containing 0.45-0.51% C, 0.15-0.35% Si, 0.60-0.90% Mn, P<0.03% and S<0.035% and surface mechanical processing is applied to the cam 7. In the next step, the cam 7 is subjected to surface hardening treatment and, thereafter, a phosphate film with a thickness of 5-10mum is formed to the treated surface thereof to adjust surface roughness to 8mum Rz or less. |
