Piston with a biaxial bearing for an opposed-piston engine

1. A piston apparatus, comprising:

a cylindrical piston body configured to slide in an opposed-piston, internal combustion engine cylinder having a bore diameter (D 1 ); and,

the piston body including a biaxial bearing structure configured to define a biaxial wrist pin diameter (D 2 );

wherein, D 2 <0.5D 1 .

2. The piston apparatus of claim 1 , in which the biaxial bearing structure comprises a biaxial bearing surface with at least one bearing surface segment defining a first axis and at least a second bearing surface segment defining a second axis parallel to the first axis.

3. The piston apparatus of claim 1 , in which the biaxial bearing structure comprises a biaxial wrist pin with at least one wrist pin journal segment defining a first axis and at least a second wrist pin journal segment defining a second axis parallel to the first axis.

4. The piston apparatus of claim 1 , in which the bore diameter (D 1 ) comprises a cylinder bore diameter, a cylinder liner diameter, or a piston diameter.

5. The piston apparatus of claim 1 , in which the biaxial wrist pin diameter (D 2 ) is measured as a wrist pin bore diameter, a first wrist pin journal segment diameter, a second wrist pin journal segment diameter, a first wrist pin bearing surface segment diameter, or a second wrist pin bearing surface segment diameter.

6. The piston apparatus of claim 1 , wherein 0.3(D 1 )≤(D 2 )≤0.45 (D 1 ).

7. The piston apparatus of claim 6 , in which the biaxial bearing structure comprises a biaxial bearing surface with at least one bearing surface segment defining a first axis and at least a second bearing surface segment defining a second axis parallel to the first axis.

8. The piston apparatus of claim 7 , in which the biaxial bearing structure comprises a biaxial wrist pin with at least one wrist pin surface segment defining a first axis and at least a second wrist pin surface segment defining a second axis parallel to the first axis.

9. The piston apparatus of claim 1 , in which in which the biaxial bearing structure comprises a biaxial wrist pin with a plurality of wrist pin journal segments occupying a biaxial bearing width, in which no journal segment has a width exceeding 40% of the biaxial bearing width.

10. The piston apparatus of claim 9 , in which the biaxial wrist pin with at least one wrist pin journal segment defining a first axis and at least a second wrist pin journal segment defining a second axis parallel to the first axis.

11. The piston apparatus of claim 9 , in which the bore diameter (D 1 ) comprises a cylinder bore diameter, a cylinder liner diameter, or a piston diameter.

12. The piston apparatus of claim 9 , in which the diameter (D 2 ) is measured as a wrist pin bore diameter, a first wrist pin journal segment diameter, a second wrist pin journal segment diameter, a first wrist pin bearing surface segment diameter, or a second wrist pin bearing surface segment diameter.

13. The piston apparatus of claim 9 , wherein 0.3(D 1 )≤(D 2 )≤0.45(D 1 ).

14. A piston apparatus, comprising:

a generally cylindrical piston body configured to slide in an opposed-piston, internal combustion engine cylinder; and,

a biaxial bearing structure comprising a biaxial wrist pin with a plurality of wrist pin journal segments defining a biaxial bearing width, in which no wrist pin journal segment has a width exceeding 40% of the biaxial bearing width.

15. The piston apparatus of claim 14 , in which the biaxial wrist pin comprises at least one wrist pin journal segment defining a first axis and at least a second wrist pin journal segment defining a second axis parallel to the first axis.

16. The piston apparatus of claim 14 , in which the biaxial bearing structure further comprises a biaxial bearing surface with at least one bearing surface segment defining a first axis and at least a second bearing surface segment defining a second axis parallel to the first axis.

17. The piston apparatus of claim 14 , in which in which the wrist pin journal segments are substantially equal in width.

18. A piston apparatus, comprising:

a piston body configured to slide in an opposed-piston, internal combustion engine cylinder;

a biaxial bearing structure comprising a biaxial wrist pin with a plurality of wrist pin journal segments, each journal segment configured with a respective width, a sum of the respective widths defining a biaxial bearing width, in which no wrist pin journal segment has a width exceeding 40% of the biaxial bearing width;

the opposed-piston engine cylinder having a bore diameter (D 1 ); and, the piston body including a biaxial bearing structure configured to define a biaxial wrist pin diameter (D 2 );

wherein, D 2 <0.5D 1 .

19. The piston apparatus of claim 18 , in which the biaxial wrist pin comprises at least one wrist pin journal segment defining a first axis and at least a second wrist pin journal segment defining a second axis parallel to the first axis.

20. The piston apparatus of claim 18 , in which the biaxial bearing structure further comprises a biaxial bearing surface with at least one bearing surface segment defining a first axis and at least a second bearing surface segment defining a second axis parallel to the first axis.

21. The piston apparatus of claim 18 , in which in which the wrist pin journal segments are substantially equal in width.

22. The piston apparatus of claim 18 , in which the bore diameter (D 1 ) comprises a cylinder bore diameter, a cylinder liner diameter, or a piston diameter.

23. The piston apparatus of claim 18 , in which the biaxial wrist pin diameter (D 2 ) is measured as a wrist pin bore diameter, a first wrist pin journal segment diameter, a second wrist pin journal segment diameter, a first wrist pin bearing surface segment diameter, or a second wrist pin bearing surface segment diameter.

24. The piston apparatus of claim 18 , wherein 0.3(D 1 )≤(D 2 )≤0.45(D 1 ).