Valve timing adjusting device

摘要

A region including an engaging hole is given surface treatment such as partial quench hardening by induction hardening for improving surface hardness of the region. The partial quench hardening by induction hardening provides the region with satisfactory mechanical strength or surface hardness enough for resisting deformation of the engaging hole and wear-out of an edge of opening of the engaging hole caused by putting in and out of the lock pin.