| 摘要 |
PURPOSE:To achieve the enhancement in the primary compression ratio and the cooling efficiency of piston by constituting a piston made of A1 alloy and the like with a plural number of divided parts, and hermetically filling a high heat conductivity substance such as sodium in the internal space part thereof. CONSTITUTION:A piston 1 is formed by welding a lower half part 2 and an upper half part 3 being made of Al alloy, and the lower half part 2 forms a recess part 7 between the central part 4 having a piston-pin housing recess part 5a and a con'rod small end part housing recess part 5b, and the piston side wall part 6 on the outside thereof. Above the central part 4, a projection 9 having a through hole 10 in the transverse direction is integrally formed. While a space S is formed by the above recess part 7, through hole 10 and the inner surface of the upper half part 3, in this space S a substance which is excellent in the heat conductivity such as metallic sodium and the like is hermetically filled. Further, on the inner surface of the lower half part 2 and the upper half part 3 forming the space S, Ni-plated layers are formed to prevent the corrosion of the piston. |
