Patent ID: 6860190
Filing Date: 2005-03-01
Classification: F02F,F05C,F16J

Abstract:
1. An engine piston comprising a unitary metal body comprising: head of substantially circular cross-section centered on a longitudinal piston axis defined by an upper crown face, a lower support face and, extending between the faces, a perimeter wall of the head defining a belt of ring grooves; a pair of gudgeon pin bosses, extending axially form the support face, spaced from the perimeter of the head and from each other along a pin axis; a circumferentailly incomplete, axially extending bearing skirt portion defining at the perimeter a thrust bearing region and a non-thrust bearing region spaced apart at opposite sides of the pin axis, each said bearing region extending circumferentially between region ends and being centered on a thrust axis perpendicular to the pin axis, the thrust bearing region being of greater circumferential extent than that of the non-thrust bearing region; bearing skirt reinforcement ribs associated individually with said ends of the thrust and non-thust beaing regions, each said reinforcement ribs extending axially from the head and connecting its associated region end to a said gudgeon pin boss, the reinforcement ribs associated with the ends of the thrust bearing region each having a curvilinear section comprising a substantially smooth transition from the end of the associated region into an outwardly convex section converging toward the associated gudgeon pin boss and merging therewith displaced in a direction along the pin axis toward the perimeter with respect to the reinforcement ribs extending from the ends of the non-thrust bearing region, and in the support face a pair of recesses associated one with each gudgeon pin boss, each said recess being disposed between the pin boss and the perimeter wall and asymmetrical about the pin axis, the recess to one side of the pin axis being defined by the unskirted perimeter, the boss and the reinforcement rib connecting the thrust bearing region and the boss, and to the other side of the pin axis being defined by the unskirted perimeter, the boss and the reinforcement rib connecting the no-thrust region to the boss, and wherein the center of mass and gudgeon pin axis are displaced from the longitudinal axis in the same direction by substantially the same distance.