| 摘要 |
PROBLEM TO BE SOLVED: To prevent a bevel part from being supercooled, by filling an adequate amount of low-melting point alloy in a hollow hole extending from the bevel part to the shank part thereof. SOLUTION: A hollow valve element used as an intake valve or an exhaust valve has a valve element 1 composed of a shank part 2 and a bevel part 3 connected to the lower end of the shank part 2 and made of heat-resistant steel, the shank part 2 being composed of a hollow shank part 2a and a bevel part side solid shaft part 2b joined to the upper end of the former. Further, a hollow hole 4 is formed in the hollow shaft part 2a, extending from a position near to the lower end of the bevel part 3 to its one end where the shank part 2a and the solid shank part 2b are joined. A rod 5 made of low melting point alloy serving as a cooling medium is inserted in the hollow hole 4, the rod 5 being melted so as to have a volume which is 1/3 to 1/4 of the volume of the hollow hole 4. The low-melting point alloy 5 has a melting point in a range from 120 to 200deg.C, such as Sn-Bi group or Sn-Bi-Zn group alloy. Thereby it is possible to prevent the bevel part 3 from being supercooled. |
