BUILT-UP CAM SHAFT WITH INDUCTION-HARDENED CAM AND INDUCTION-HARDENING METHOD OF CAM

摘要

PURPOSE: To elongate the life of a camshaft or a cam disc by inductively hardening a surface layer on an outer periphery of a cam disc on a camshaft by the alternating magnetic field, and increasing the internal compression stress produced on the hardened surface zone by the hardening. CONSTITUTION: This camshaft 1 comprises an approximately annular cam disc 3 fixed on a tubular shaft body 2. Relative to this cam disc 3, the surface layer hardening is executed by the induction of an outer periphery, before its fixing. The hardening produces high internal compression stress of at least -450 N/mm<2> on a surface zone of about 0.5 mm depth near the surface. Whereby the internal tensile stress of at least -150 N/mm<2> exists even after the cam disc 3 is mounted on the shaft body 2. After the hardening, the cam disc 3 is preheated at least at 250 deg.C (but below transformation temperature) by applying a medium-frequency magnetic field to the cam disc 3, then the alternating magnetic field of different intensity or frequency is applied, and only the surface zone is heated by the transformation temperature, and then quenched.