Controlled homogeneous-charge, compression-ignition engine

A method of operating a diesel-cycle engine including a plurality of combustion cylinders and a first piston reciprocally mounted within each of the combustion cylinders and presenting a first piston face defining one boundary of a combustion chamber within a combustion cylinder;

• a head covering the combustion cylinders and having exhaust ports and a plurality of cylindrical recesses, each of the cylindrical recesses opening into a respective combustion cylinder;
• a second piston reciprocally mounted in each of the recesses;
• and an engine exhaust valve for opening and closing each exhaust port, the second piston presenting a second piston face defining a second boundary of the combustion chamber, said method comprising:
• introducing a fuel-air mixture into the combustion chamber;
• compressing the fuel-air mixture by a compression stroke of the first piston;
• and
• moving said second piston outward from a retracted position to an extended position within a cylindrical recess within the head after the first piston has reached top dead center at the beginning of the expansion stroke of said first piston, to reduce the volume of the combustion chamber and to increase the compression ratio to a level causing auto-ignition of the fuel-air mixture.

A diesel-cycle engine comprising:

• a plurality of combustion cylinders;
• a first piston reciprocally mounted within each of said combustion cylinders, said piston presenting a first piston face defining one boundary of a combustion chamber within said combustion cylinder;
• a head covering said combustion cylinders and having a plurality of cylindrical recesses, each opening into a respective combustion cylinder;
• a second piston reciprocally mounted in each of said recesses, said second piston being a double-faced piston presenting a second piston face defining a second boundary of the combustion chamber and a third piston face defining a control chamber in cooperation with a cylindrical recess in said head;
• repositioning means for returning said second piston to its retracted position between successive compression strokes of said first piston, said repositioning means comprising an exhaust duct in communication with said control chamber and a control valve in said exhaust duct;
• means for introducing a fuel-air mixture into the combustion chamber;
• and
• means for moving said second piston from a retracted position outward in said cylindrical recess, to an extended position, after said first piston has reached top dead center, during the beginning of the expansion stroke of said first piston, to reduce the volume of the combustion chamber and increase the compression ratio to a level causing auto-ignition of the fuel-air mixture.

A method of operating a diesel-cycle engine including a plurality of combustion cylinders and a first piston reciprocally mounted within each of the combustion cylinders and presenting a first piston face defining one boundary of a combustion chamber within a combustion cylinder;

• a head covering the combustion cylinders and having exhaust ports and a plurality of cylindrical recesses, each of the cylindrical recesses opening into a respective combustion cylinder;
• a double-faced second piston reciprocally mounted in each of the recesses;
• and an engine exhaust valve for opening and closing each exhaust port, the second piston presenting a second piston face defining a second boundary of the combustion chamber and a third piston face defining a control chamber in cooperation with the cylindrical recess in the head, said method comprising:
• introducing a fuel-air mixture into the combustion chamber;
• compressing the fuel-air mixture by a compression stroke of the first piston;
• and
• introducing a fluid at high pressure into the control chamber to drive said second piston outward from a retracted position to an extended position within a cylindrical recess within the head after the first piston has reached top dead center at the beginning of the expansion stroke of said first piston, to reduce the volume of the combustion chamber and to increase the compression ratio to a level causing auto-ignition of the fuel-air mixture.