Method for production of valve head portion of hollow engine valve and hollow engine valve

摘要

Forming of a valve head portion (1) of a hollow engine valve (V) comprising a material particularly satisfactory in heat resistance is performed by cold forging. The material with excellent heat resistance is worked to form a valve head portion semifinished product (11) having a hollow hole (S11) whose inner diameter (φ11) is equal to the maximum inner diameter (φ11) of a hollow hole (S1) of a finished product of the valve head portion (1), and having a diameter-increased section (111) whose maximum outer diameter (φ12) is equal to the maximum outer diameter (φ12) of a diameter-increased section (1a) of the finished product. Parts of the valve head portion semifinished product other than a central part to a lower part of the diameter-increased section (111) are necked down by cold forging performed a plurality of times to obtain the finished product of the valve head portion (1).

主权项

1. A hollow engine valve, comprising:
a hollow shaft portion sealed at one end; and a valve head portion of a single-piece material attached to another end of the hollow shaft portion; the single-piece material being a material having heat resistance comparable to or better than the heat resistance of a material for the hollow shaft portion; the valve head portion comprising a cylindrical barrel section and a diameter-increased section at one end of the barrel section, the diameter-increased section including a bottom section; a valve head portion hollow hole opening at a side attached to the hollow shaft portion, the valve head portion hollow hole having a first inner surface, at the diameter-increased section, having an inner diameter that increases as the first inner surface extends toward the bottom section, and a second inner surface at the bottom of the valve head portion hollow hole; and the maximum diameter of the valve head portion hollow hole being larger than a maximum outer diameter of the hollow shaft portion; and the first inner surface and the second inner surface forming a single continuous curved surface.