Two-cycle, opposed-piston internal combustion engine

1. An internal combustion engine, comprising:

an engine frame;

first and second side-mounted crankshafts rotatably supported on the frame;

a cylinder with a bore supported on the engine frame;

first and second opposed pistons for reciprocating in the bore so as to protrude from the bore during at least a portion of an operating cycle of the engine;

rods connecting each piston to both crankshafts;

each piston including a crown and a skirt with inner and outer surfaces;

a first coolant manifold supported on the engine frame;

a first dispenser extending from the first coolant manifold into the first piston and aimed at the crown of the first piston;

a second coolant manifold supported on the engine frame;

a second dispenser extending from the second coolant manifold into the second piston and aimed at the crown of the second piston; and

a coolant supply system connected to the first and second coolant manifolds for supplying liquid coolant under pressure to the first and second coolant manifolds.

2. The engine of claim 1 , wherein the first and second dispensers are further aimed at the inner surfaces of the piston skirts of the first and second pistons.

3. The engine of claim 1 , wherein the coolant supply system includes:

a source of liquid coolant; and,

a pump connected to the source and to the first and second coolant manifolds.

4. The engine of claim 3 , wherein the source of liquid coolant is a diesel fuel reservoir.

5. The engine of claim 3 , wherein the liquid coolant comprises diesel fuel.

6. The engine of claim 3 , wherein the liquid coolant comprises a lubricant.

7. The engine of claim 3 , wherein the engine is a two-stroke compression-ignition engine and the liquid coolant comprises diesel fuel.

8. The engine of claim 3 , wherein the pistons are ringless pistons.

9. The engine of claim 1 , wherein the pistons are ringless pistons.

10. The engine of claim 1 , wherein the frame supports compressive forces between the crankshafts.

11. The engine of claim 1 , wherein the engine is a two-stroke compression-ignition engine.

12. The engine of claim 1 , wherein the engine is installed in a machine.

13. The engine of claim 1 , wherein the engine is installed in a vehicle.

14. The engine of claim 13 , wherein the vehicle is a water craft.

15. The engine of claim 13 , wherein the vehicle is an aircraft.

16. The engine of claim 13 , wherein the vehicle is a surface vehicle.

17. The engine of claim 1 , wherein the engine is installed in a power tool.

18. The engine of claim 1 , wherein the engine is installed in a generator.

19. A method for operating an internal combustion engine including a pair of side-mounted crankshafts, at least one cylinder with a bore and at least two ports, a pair of opposed pistons disposed in the bore, each piston coupled to both crankshafts and including a skirt terminating in an open end, and a pair of dispensers, each dispenser extending into the interior of a respective piston, the method including:

causing the pistons to be at least partially withdrawn from the at least one cylinder during engine operation; and

applying a liquid coolant to the interior of each piston, including along the inner surface of the skirt to the open end of the piston, through a respective dispenser; and,

collecting the liquid coolant in a sump.

20. The method of claim 19 , further including supplying liquid coolant under pressure to the dispensers.

21. The method of claim 19 , wherein the liquid coolant comprises diesel fuel.

22. The method of claim 19 , wherein the liquid coolant comprises a lubricant.

23. An internal combustion engine, comprising:

a pair of crankshafts;

a cylinder with opposing ends;

the pair of crankshafts disposed with their axes parallel to each other and lying in a common plane that intersects the cylinder near its longitudinal center and that is perpendicular to the axis of the cylinder;

a manifold fixed to each end of the cylinder, the cylinder and manifolds defining a bore;

opposed pistons disposed in the bore for reciprocating between respective bottom and top dead center positions;

each piston including a crown and a skirt;

piston rods linking the pistons to the crankshafts; and,

each bore having a length such that the skirt of each piston is substantially withdrawn from the bore near its bottom dead center position and each piston is substantially enclosed in the bore near its top dead center position.

24. The engine of claim 23 , wherein the pistons each have an axial length and at least 50% of the axial length of each piston is withdrawn from the bore near its bottom dead center position.

25. The engine of claim 23 , wherein the pistons each have an axial length and at least 75% of the axial length of each piston is withdrawn from the bore near its bottom dead center position.

26. A method for operating an internal combustion engine having two crankshafts, a cylinder with a bore, and opposed pistons disposed in the bore for reciprocating between respective bottom and top dead center positions, each piston being coupled to both crankshafts and including a crown and a skirt, the method including:

moving the pistons in the bore between top and bottom dead center positions;

rotating the crankshafts in response to movement of the pistons;

substantially withdrawing each piston from the bore near its bottom dead center position; and

substantially enclosing each piston in the bore near its top dead center position.

27. The method of claim 26 , wherein substantially withdrawing includes withdrawing each piston such that only a portion of the crown of each piston remains in the bore when the piston is near its bottom dead center position.

28. The method of claim 26 , wherein the pistons each have an axial length and substantially withdrawing includes withdrawing at least 50% of the axial length of each piston from the bore near its bottom dead center position.

29. The method of claim 26 , wherein the pistons each have an axial length and substantially withdrawing includes withdrawing at least 75% of the axial length of each piston from the bore near its bottom dead center position.

30. An internal combustion engine, comprising:

a plurality of cylinders with opposing ends and a bore;

opposed pistons disposed in the bore of each cylinder for reciprocating between respective bottom and top dead center positions;

each piston including a crown and a skirt;

each bore having a length such that the skirt of each piston disposed in the bore is substantially withdrawn from the bore near its bottom dead center position and is substantially enclosed in the bore near its top dead center position;

first and second coolant manifolds;

first dispensers extending from the first coolant manifold into the skirts of first pistons of the opposed pistons; and,

second dispensers extending from the second manifold into the skirts of second pistons of the opposed pistons.

31. The engine of claim 30 , wherein:

the first dispensers being aimed at the crowns of the first pistons;

the second dispensers being aimed at the crowns of the second pistons; and

the engine further including a system for supplying liquid coolant under pressure to the first and second manifolds.

32. The engine of claim 31 , wherein the first and second dispensers are further aimed at the inner surfaces of the piston skirts of the first and second pistons.

33. A method for operating an internal combustion engine including at least one cylinder with a bore, a pair of opposed pistons disposed in the bore, and a pair of dispensers, each piston including a skirt terminating in an open end, and each dispenser extending through an open end into the interior of a respective piston, the method including:

causing each piston to be substantially withdrawn from the bore near a bottom dead center position during engine operation; and

applying a liquid coolant to the crown and inner surface of the skirt to the open end of each piston through a respective dispenser throughout engine operation.

34. The method of claim 33 , further including:

collecting liquid coolant applied to the interiors of the pistons; and

cooling the collected liquid coolant.