| 摘要 |
A method for producing a hollow head poppet valve for an internal combustion engine comprises: providing a blank 20 with core material 2 such as sodium, tin or aluminium, and mantle material 3, such as a steel alloy, with melting point higher than the core; shaping the blank into a poppet having; cutting the tip of the poppet stem to expose the core material; heating to a temperature above the core material melting point and below that of the mantle material; removing the core material via the cut tip providing a hollow poppet; filling the hollow poppet with a material having a thermal conductivity higher than the mantle material; closing the cut valve tip. The blank may be cylindrical and have a diameter equal to that of the finished poppet stem, and the head may be further formed by upsetting a blank end (Figures 2a-c). Alternatively the blank may be extrusion forged to produce the stem (Figures 1a-c). In both embodiments the head may be further shaped in a die (7, 8). The heating step may form part of a precipitation or solution heat treating step. In use the sodium liquefies and the shaker effect occurs. |
