| 摘要 |
PROBLEM TO BE SOLVED: To reduce cost by simply, easily and highly accurately molding a semifinished product of an engine valve in an excellent surface state by forging.SOLUTION: A cup-shaped metallic intermediate member B is fitted to and held by a molding pin 19 in an inner position of a shaft hole 16a of a die 16, and a molding space of the semifinished product of the engine valve determined by closing a front face of the die 16 by a punch 28, is formed under its holding state, and then, a closing state of these die 16 and punch 28 is maintained by closing maintaining means 21, and afterwards, the die 16 and the punch 28 are pressed together to the molding pin 19 side existing in a fixed state, and thereby, a valve umbrella part is molded by diametrically expanding a bottom part of the intermediate member B as a shape of the molding space under a state of maintaining an incomplete blocking-up state of leaving only a clearance between the shaft hole 16a of the die 16 and the molding pin 19, and a shaft part having a bottomed hole is also molded so as to continue with this valve umbrella part and to reach the inside of the valve umbrella part. |
