Piston cooling configurations utilizing lubricating oil from a bearing reservoir in an opposed-piston engine
Pressurized lubricating oil is accumulated in the bearings of opposed pistons and accumulated oil is dispensed therefrom for bearing lubrication and also for cooling the undercrowns of the pistons by jets of oil emitted from the bearings.
1. A piston cooling configuration for an opposed-piston engine, comprising:
a piston with a crown having an end surface shaped to form a combustion chamber with an end surface of an opposing piston;
the crown including an undercrown;
a bearing mounted in the piston between the undercrown and a small end of a connecting rod;
the bearing including a wristpin and a bearing surface;
an oil reservoir in the wristpin in fluid communication with one or more wristpin oil outlet passages positioned to pass oil through the wristpin into a lubrication interface between the wristpin and the bearing surface;
at least one oiling groove in the bearing surface which is in fluid communication with a wristpin oil outlet passage of the oil reservoir;
a wristpin oil inlet passage in fluid communication with the reservoir; and,
at least one cooling jet outlet in a part of the bearing that does not move relative to the undercrown;
in which the cooling jet outlet is in fluid communication with the oil reservoir via the at least one oiling groove and is aimed toward an undercrown portion, further in which the oil reservoir is an annular recess with opposing ends and has an axis that corresponds to an axis on which the wristpin oscillates.
2. The piston cooling configuration of claim 1 , in which the wristpin is received on the small end of the connecting rod.
3. The piston cooling configuration of claim 2 , in which:
the part of the bearing that does not move relative to the undercrown includes a bearing member supporting the wristpin for rotatable oscillation with respect to the undercrown in response to movement of the piston; and,
the cooling jet outlet includes an oil outlet passage in the bearing member.
4. The piston cooling configuration of claim 3 , in which:
the connecting rod includes an oil passage in fluid communication with the wristpin oil inlet passage; and,
the oil outlet passage in the bearing member receives pressurized oil from the at least one oiling groove.
5. The piston cooling configuration of claim 4 , in which the wristpin and the bearing surface form a biaxial bearing.
6. An opposed-piston engine including at least one cylinder with longitudinally-separated exhaust and intake ports, a pair of pistons disposed in opposition to one another in a bore of the cylinder, and a pair of connecting rods, in which each piston is coupled to a respective connecting rod by a bearing, and at least one piston includes a piston cooling configuration according to any one of the preceding claims.