Noncontacting surface areas are provided between the top wall of an oil control ring and the top surface of its groove to avoid entrapment of oil between adjacent surfaces of the two members during downward motion of a piston in a reciprocating, internal combustion engine. The noncontacting surface areas may be provided by circular grooves formed in the top surface of the groove or the ring. Alternatively, either the top surface of the groove or the top wall of the oil control ring may be formed so that it slopes away from the surface of its mating member and forms a tapered annular cavity that diverges away from the outer cylindrical surface of the piston. All of the described arrangements reduce the contact area between the top of the ring and the top of the groove during downward movement of the piston, thereby permitting the oil control ring to seal against the upper surface of its groove. The present invention effectively controls the flow of oil toward the compression ring during intake and expansion strokes of the engine.
Susumu Ariga