POWER TRANSMISSION SHAFT FOR CAR TRANSMISSION

PURPOSE:To feed a hole inner part with a cooling liquid smoothly in time of hardening as well as to aim at the promotion of sufficient hardening, by forming a through hole along an axial center of a power transmission shaft for a car transmission, while hardening the whole surface ranging from an outer circumferential surface to an inner circumferential surface. CONSTITUTION:A through hole 101 and a radial hole 102 being formed in the specified position so as to connect this through hole 101 to a shaft outer surface both are formed along an axial center of an output shaft 1 of a car automatic transmission. This output shaft 1 is produced in the following process that a cylindrical steel material is cut in the specified length each, and the outer circumferential surface, the through hole, etc., are processed as specified, while the radial hole 102 is formed, then it is heated under high temperature and carburized, and after that it is dipped in a cooling liquid and quenched and hardened. At this quenching process, since the cooling liquid is freely flowable inside the through hole, an ample quenching effect is secured, thus uniform hardening for both inner and outer circumferential surfaces is performable.