Diesel engine with blowby scavenging

In a diesel engine of the type having acylinder with closed and open ends, a piston reciprocable in the cylinder and defining therewith a variable volume combustion chamber at the cylinder closed end, means at the cylinder closed end for admitting charging fluids to and exhausting residual products from the combustion chamber, a lubricant chamber at the open end of the cylinder, the piston having a skirt bearing on the cylinder under side thrust loading, and at least two spaced sealing rings on the piston and engaging the cylinder to limit the passage of combustion blowby products and lubricant from their respective chambers to the other, at least the top one of said sealing rings being located between the skirt and the combustion chamber end of the piston, and the improvement comprising

• an annular recess around the piston between the skirt and said top sealing ring, said recess comprising a blowby storage space of volume sufficient to collect a substantial amount of the blowby gases which escape from the combustion chamber past the top one of said sealing rings during each cycle of piston reciprocating motion, and
• blowby scavenging means intermittently communicating with said recess to carry away blowby gases collected therein and thereby reduce contamination of the lubricant with particulates from the combustion products, said blowby scavenging means including an air supply passage in the cylinder and positioned to communicate with the piston recess near the bottom position of piston motion and to be closed by the piston skirt during other portions of the piston motion, at least the bottom one of said sealing rings being an oil control ring located on the piston skirt below the position of said air supply passage at the top position motion to avoid passing scavenging air through the oil ring groove and any resultant oil carryover.