Reduced Friction Piston Ring

A two-piece liquid lubricated gas seal assembly for internal combustion engines, gas pumps and gas compressors for use in a piston;

• wherein the two pieces are axially stacked diametrically expandable rings, and together comprise an outside diameter, an inside diameter, and upper and lower faces substantially perpendicular to the piston ring axis;
• the piston has an annular ring groove comprising an upper flank, a lower flank and a bottom, and the piston is axially reciprocated in a bore;
• the piston ring assembly is disposed in the ring groove such that the outside diameters of the two rings comprising the gas seal assembly are in liquid lubricated axial sliding contact with the cylinder bore surface, the inside diameters spaced away from the groove bottom, and the gas seal assembly upper and lower faces are adjacent the upper and lower groove flanks respectively;
• the annular space between the gas seal assembly inner diameter and the groove bottom is in fluid communication with the gas above the ring such that its pressure is substantially equal to the gas pressure above the gas seal assembly;
• at least one of the two rings comprising the gas seal assembly incorporates geometric features that axially separate the outside diameters of the two rings such that an annular fluid passage is defined by a gap between the upper and lower rings and the cylinder bore surface, wherein said annular fluid passage is in fluid communication with the gas above the gas seal such that its pressure is substantially equal to the gas pressure above the gas seal;
• the generally cylindrical lower ring serving a gas sealing function and the generally cylindrical upper ring serving a slider bearing function;
• accommodating means are provided to maintain the lower ring gas sealing function and the upper ring slider bearing function as the piston tilts relative to the bore;
• and,
• the two rings incorporate means to mechanically interlock with each other such that outward radial load on the gas seal ring is transferred to the slider bearing ring.