JPS6474360A - Piston made of tough cast iron - Google Patents

Abstract

PURPOSE:To reduce casting defects due to the deflection of a core and prevent the cooling performance of a piston from being deteriorated, by forming a cooling vacant space from the inside upper part to the lower part on the inside of a piston ring groove part and forming a recessed part into a nearly U-shape along a boss from the outer peripheral surface of the piston on the boss upper side. CONSTITUTION:When a piston 11 is cast, a core for forming an inner peripheral surface 16 and a core for shaping a cooling vacant space 15 are arranged in a main mold for forming an outer shape, and the molten metal of spheroidal graphite cast iron is poured. Since, in this case, a recessed part 14 is formed in a nearly U-shaped recessed part on the outer peripheral surface of the piston 11, the need for using a core for molding the recessed part 14 is avoided. Therefore, the quantity of the core for shaping the recessed part 14 can be reduced by one, and the generation rate of the casting defect due to the deflection of the core can be reduced. Further, since the piston 11 has a sufficiently large cooling void space 15, the cooling performance of the piston 11 is not deteriorated.