Method for producing a hollow engine valve

摘要

The present invention provides a method for producing a hollow engine valve, with which the production process can be simplified and the processing precision can be improved. To this end, the present invention provides a method for producing a hollow engine valve (1) which is provided with a valve main body (10) in which a hollow hole (10c) is formed along a valve umbrella part (10a) and a hollow shaft part (10b), wherein a solid round bar (11) forming the material of the valve main body (10) is molded to a semi-finished article (12) by means of a single hot-forging process, the semi-finished article (12) is subjected to rotary swaging whereby the semi-finished article (12) is molded into a semi-finished article (13), the semi-finished article (13) is subjected to necking whereby the semi-finished article (13) is molded into the valve main body (10), and a shaft end sealing member (20) is joined to the end part of the hollow shaft part (10b) of the valve main body (10).

主权项

1. A method for producing a hollow engine valve including a valve body in which a hollow hole extending through a valve umbrella portion and a hollow stem portion connected to the valve umbrella portion is formed, characterized in that the method comprises:
shaping a solid round bar which is a raw material of the valve body into a valve body semi-finished product in which a semi-finished product hollow hole is formed, by performing hot forging once without forming a step in a semi-finished product hollow hole by insertion of a core, the semi-finished product hollow hole corresponding to the hollow hole and formed to extend through a semi-finished product valve umbrella portion corresponding to the valve umbrella portion and a semi-finished product hollow stem portion corresponding to the hollow stem portion; subjecting the valve body semi-finished product to a rotary swaging process in which an outer peripheral surface of the semi-finished product hollow stem portion is pressed while the valve body semi-finished product is rotated, and thereby reducing a diameter of the semi-finished product hollow stem portion and increasing a stem length of the semi-finished product hollow stem portion; subjecting the valve body semi-finished product subjected to the rotary swaging process to a necking process in which the semi-finished product hollow stem portion and a semi-finished product neck portion being a connection portion between the semi-finished product valve umbrella portion and the semi-finished product hollow stem portion are drawn stepwise, and thereby reducing the diameter of the semi-finished product hollow stem portion and increasing the stem length of the semi-finished product hollow stem portion to shape the valve body semi-finished product into the valve body; and joining a stem end sealing member to an end portion of the hollow stem portion in the valve body to seal the hollow hole.