Patent ID: 6907859

Claim:
An internal combustion engine comprising: a cylinder and a piston movable with reciprocating motion within the cylinder, the piston motion providing a succession of four strokes including an induction stroke, a compression stroke, a power stroke and an exhaust stroke, wherein the engine is a gasoline engine or a diesel engine; wherein the compression stroke serves to compress a quantity of gas within the cylinder in preparation for the power stroke, the compression-stroke gas being a mixture of air and fuel in the gasoline engine, or air without fuel in the diesel engine, the compression stroke providing a reduction in volume of the gas characterized by a compression ratio; the power stroke provides for an expansion in volume of a quantity of gas within the cylinder, characterized by an expansion ratio, the gas in the power stroke being a mixture of air, fuel, and products of combustion; the engine further comprises reducing means for reducing the compression ratio to a value less than the expansion ratio; the reducing means comprises a return manifold for coupling a portion of the quantity of the gas from the cylinder during the compression stroke to a source of the compression-stroke gas; and a head of the cylinder includes a return port communicating with an arm of the return manifold, and a return valve operative for closing and opening the return port, and wherein the return manifold includes a central chamber having a volume larger than a volume of the arm, the engine further comprising a discharge valve located in an end portion of the arm adjacent the central chamber of the return manifold, wherein the discharge valve is operative to open and to close a passage between the arm and the central chamber of the return manifold, the arm of the return manifold defining a holding tank between the return valve and the discharge valve.