SURFACE MODIFYING JIG OF ENGINE VALVE AND SURFACE MODIFYING METHOD EMPLOYING IT

摘要

A surface modifying jig (10) of an engine valve comprising a substantially circular ring portion (24) for holding the valve head (14) of an engine valve (12), a head holding portion (28) having a diameter decreasing gradually downward from the inner circumferential side of the ring portion (24), and a stem holding portion (30) formed below the head holding portion (28) with a substantially constant diameter. When plasma nitriding is performed, the valve head (14) comes into annular line contact with the ring portion (24) and being held by the head holding portion (28) while kept in annular plane contact therewith, and a valve stem (16) is held by the stem holding portion (30) while kept in annular plane contact therewith.