Patent ID: 6073602
Filing Date: 2000-06-13
Classification: F02F,F05C

Abstract:
A piston for an internal-combustion engine, comprising:a ring land extending to a crown;a pin boss formed in a lower side of the ring land;a piston pin bore formed in the pin boss; anda skirt section extending to the ring land,said skirt section comprising a thrust side skirt which contacts with an inner surface of a cylinder during an expansion stroke and a counter-thrust side skirt and an area of the thrust side skirt is greater than an area of the counter-thrust side skirt;wherein the thrust side skirt comprises first and second lateral regions and a circumferential middle region that is located between the first and second lateral regions along a circumferential direction around a piston center line;wherein each of the first and second lateral regions comprises an upper subregion that is located closer to the ring land, a lower subregion that is located farther from the ring land, and a middle subregion that is located between the upper subregion and the lower subregion;wherein a wall thickness of the middle subregion is greater than that of the upper and lower subregions, and a wall thickness of a portion between the middle subregion and the upper subregion and a wall thickness of a portion between the middle subregion and the lower subregion are varied gradually; andwherein a wall thickness of a center region in the circumferential middle region that is substantially perpendicular to an axis line of the piston pin is substantially constant along the piston center line.