Abstract: A piston is formed with a rib which is formed on a base portion and is formed with through holes which is formed in such manner that the core is in contact with a projection portions of a holding die.

Abstract: A light metal alloy cast piston comprises a thermal strut provided in the shoulder portion of the piston skirt. The thermal strut is composed of a fiber reinforced metal portion containing high tensile strength fibers integrally molded in the matrix metal. The piston is shaped in such a manner that the inner periphery of the thermal strut is exposed toward the inside of the piston skirt, except for the regions at the piston pin bosses, to avoid the presence of non-reinforced metal a the inside of the thermal strut. This arrangement prevents the formation of cracks along the inner periphery of the thermal strut.

Abstract: A light metal alloy cast piston including a thermal strut (32, 48, 52) arranged in a shoulder portion of the piston skirt. The thermal strut is composed of an annular fiber-reinforced metal portion in which high-tensile-strength reinforcing fibers are integrally molded. The reinforcing fibers include first fibers (34), such as carbon fibers, having a coefficient of linear expansion substantially smaller than that of the matrix metal alloy, and second fibers (36), such as silicon carbide fibers and alumina fibers, having a flexural or bending strength larger than that of the first fibers. The first fibers primarily serve to restrain thermal expansion of the piston skirt and the second fibers, having a larger bending strength, act to protect the first fibers from excessive bending forces. In a preferred embodiment, the first fibers are located in the inner region of the thermal strut and the second fibers are arranged in the outer region.