Patent ID: 9010296
Filing Date: 2015-04-21
Classification: F02B,F02F,F16J,Y02T

Abstract:
1. A piston for a spark-ignition engine, comprising: a land part, an upper surface of which has a crown part forming a combustion chamber; a pair of skirt parts extending downward from a peripheral part of the land part and facing each other in a radial direction thereof; a pair of sidewall parts coupling side end parts of the pair of skirt parts to each other; a pin boss part that is formed in each of the sidewall parts; and a thinned part formed in the land part, wherein the crown part has a flat base surface and a bulging part bulging upward above the base surface, the thinned part is formed into a concave shape that is opened in a region outside a predetermined region held between the sidewall parts in a lower surface of the land part, an upper end part of the thinned part is located within the bulging part above the base surface of the crown part, in a planar view the predetermined region is a region that extends in an intake/exhaust direction of the combustion chamber, the pin boss part, in the planar view, is formed such that a shaft center thereof runs in a direction perpendicular to the intake/exhaust direction of the combustion chamber and passes through a shaft center of the land part, an opening section of the thinned part is partially disposed in a position that intersects with the shaft center of the pin boss part, in the planar view, and the bulging part is formed to have a mountain-shaped cross section extending in a direction of the shaft center of the pin boss part, and is disposed on the shaft center of the pin boss part in the planar view.