Closed gallery monobloc piston having oil drainage groove

摘要

A monobloc piston has a piston head with a combustion bowl formed in its upper surface and a plurality of ring grooves formed in an outer surface of a ring belt. An oil cooling gallery is formed in the piston head which is defined in part by a wall of the combustion bowl and ring belt. The piston has a unitized, immovable piston skirt which is formed as one piece with the pin bosses and fixed at its upper end to the ring belt. Piston rings are disposed in each of the ring grooves, and the piston head is further formed with an oil drainage groove which is located below the lowest of the ring grooves. The oil drainage groove is closed in the vicinity between adjacent pin bores but is open across outer side faces of the pin bores such that oil collected in the oil drainage is drained to the crank case across the open side faces to better manage the flow of oil scraped from the walls of the piston cylinder during operation of the piston to reduce oil consumption and hydrocarbon emissions.