| 摘要 |
PURPOSE:To make thermal expansion around the circumference of a sleeve during running approximately uniform and to restrict the gap between a piston and the sleeve in order to prevent the short-circuiting of gas and the waste of oil, by using a preheated cast-iron sleeve with large wall thickness in a specific casting stage, and boring the sleeve thereafter. CONSTITUTION:When a large wall-thickness and high-rigidity cast-iron sleeve 3 having the wall-thickness set to >=10% of its inner diam. is used, the influence of casting strain of the cylinder barrels 11-14 of an aluminum alloy on the sleeve 3 becomes small. Further, by preheating the sleeve 3 up to 150-700 deg.C, the heat of molten metal to be removed by the sleeve 3 is less even if the wall thickness of sleeve 3 is large. Accordingly, the metallurgical structure around the sleeve 3 is made almost uniform because the solidifying speed of molten metal around the sleeve 3 is made uniform. Furthermore, the shrinkage of sleeve 3 follows up the shrinkage of molten metal caused by solidifying. In this way, the residual casting stress of sleeve 3 is made almost uniform around its circumference. When an engine is assembled and driven by subjecting boring work to the inner circumferential surface of each sleeve 3 in this state, the amount of thermal expansion around the circumference of each sleeve 3 is made almost uniform.
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