Cylinder and piston assemblies for opposed piston engines

1. A piston for an opposed piston engine, comprising:

a cylindrical skirt with a crown and an open end opposite the crown;

a piston rod with a bore, a first, disc-shaped end attached to a back surface of the crown, and a second end extending through the open end of the skirt;

a radial array of liquid coolant flow passages in communication with the bore and disposed between the disc-shaped end and the back surface of the crown; and,

a single wristpin retained on the second end of the piston rod and positioned externally to the piston.

2. The piston of claim 1 , in which the liquid coolant flow passages are defined by a radial array of ribs abutting the back surface of the crown.

3. The piston of claim 1 , further including at least one connecting rod received on the wrist pin.

4. The piston of claim 1 , further including a first connecting rod with a forked end received on the wrist pin, and second connecting rods mounted to the wristpin, outboard of the first connecting rod.

5. The piston of claim 4 , each second connecting rod mounted between a respective end of the wristpin and one arm of the forked end.

6. The piston of claim 1 , further including a liquid coolant reservoir positioned outboard of the open end of the skirt with an elongate nozzle extending into the bore through the second end of the piston rod.

7. The piston of claim 6 , further including a first connecting rod with a forked end received on the wrist pin, and second connecting rods mounted to the wristpin, outboard of the first connecting rod.

8. The piston of claim 7 , each second connecting rod mounted between a respective end of the wristpin and one arm of the forked end.

9. A cylinder and piston combination for an opposed piston engine, comprising a cylinder and two pistons, in which

the cylinder includes:

a liner with a bore, an outside surface, and opposing ends;

an exhaust port near an exhaust end of the liner;

an inlet port near an inlet end of the liner;

at least one fuel injector opening in a central portion of the liner;

first liquid coolant grooves in the outside surface and extending from the central portion toward the exhaust end, the first liquid coolant grooves having a first cooling capacity; and,

second liquid coolant grooves in the outside surface and extending from the central portion toward the inlet end, the second liquid coolant grooves having a second cooling capacity less than the first cooling capacity;

each piston includes:

a cylindrical skirt with a crown and an open end opposite the crown;

a piston rod with a bore, a first, disc-shaped end attached to a back surface of the crown, and a second end extending through the open end of the skirt;

a radial array of liquid coolant flow passages in communication with the bore and disposed between the disc-shaped end and the back surface of the crown; and,

a single wristpin retained on the second end of the piston rod and positioned externally to the piston;

and, the pistons are disposed crown-to-crown in the bore of the cylinder liner.

10. The cylinder and piston combination of claim 9 , each piston further including at least one connecting rod received on the wrist pin.

11. The cylinder and piston combination of claim 9 , each piston further including a first connecting rod with a forked end received on the wrist pin, and second connecting rods mounted to the wristpin, outboard of the first connecting rod.

12. The cylinder and piston combination of claim 11 , each second connecting rod mounted between a respective end of the wristpin and one arm of the forked end.

13. The cylinder and piston combination of claim 9 , further including a liquid coolant reservoir for each piston, the liquid coolant reservoir positioned outboard of the open end of the skirt of the piston with an elongate nozzle extending into the bore through the second end of the piston rod.

14. The cylinder and piston combination of claim 13 , further including a first connecting rod with a forked end received on the wrist pin, and second connecting rods mounted to the wristpin, outboard of the first connecting rod.

15. The cylinder and piston combination of claim 14 , each second connecting rod mounted between a respective end of the wristpin and one arm of the forked end.

16. A method of operating an internal-combustion engine with a cylinder and a pair of opposed pistons disposed in a bore of the cylinder, each piston including a crown, the method comprising:

applying a first amount of liquid coolant to a first portion of the cylinder extending from a central portion of the cylinder to an exhaust port of the cylinder;

applying a second amount of liquid coolant to a second portion of the cylinder extending from the central portion to an inlet port of the cylinder;

in which the first amount is greater than the second amount;

applying radially symmetric streams of liquid coolant to a back surface of each piston crown; and,

elastically deforming a compliant piston boot in response to a side force acting between the piston and the cylinder.

17. The method of claim 16 , in which the cylinder includes exhaust and inlet ends and the first amount of liquid coolant flows out of the exhaust end, the second amount of liquid coolant flows out of the inlet end, and liquid coolant flows out of an open end of each piston.

18. The method of claim 17 , in which more liquid coolant contacts a first cylinder liner portion extending from a central portion of the liner to the exhaust port than a second cylinder liner portion extending from the central portion to the inlet port.

19. The method of claim 17 , further comprising applying liquid coolant in a circumferential direction around the central portion of the cylinder.

20. The method of claim 16 , further comprising applying liquid coolant in a circumferential direction around the central portion of the cylinder.