Method of making and using a piston ring assembly

Abstract

Method of making a piston ring assembly by providing a metallic (i.e. cast aluminum) piston with a crown and an annular depending side wall; machining a stepped annular groove in the side wall having a total height of at least 4 mm (preferably having a combined total height equal to the groove height less 60 microns or less); fabricating a pair of metallic (i.e. aluminum based) split annular compression rings nestable within said groove and effective to operate together as a superimposed unit to seal against both said step and groove; coating said groove and the non-mating surfaces of said rings with solid film lubricants (i.e. graphite, BN and MoS.sub.2); and inserting said pair of coated rings into said coated groove with their split ends out of superimposed alignment. Also a method of reducing piston ring blow-by for a piston ring assembly in a cylinder bore wall of an internal combustion engine, the wall being bathed with oil drawn from a reservoir comprising providing a machined piston and split compression rings as above and reciprocatingly operating the assembly in the bore wall for carrying out engine operation whereby the rings act in unison due to friction at their mating surfaces and are free to radially adjust as a unit with little or no inhibiting friction while maintaining sealing engagement with the step of the groove, a side of the groove, and the oil film on the bore wall.

Dependencies are inferred from the claim text.