Antiblow-by piston and seal construction for high temperature applications
Reference Number: N 01-02
Inventors: Rao, V. Durga N.; Kabat, Daniel M.
The invention is a piston and ring assembly operative within a cylindrical bore wall to retain fluid to one side of the assembly. The assembly comprises (a) a piston having at least one annular stepped groove in the side wall of the piston, the groove being stepped into uppermost and lowermost spaces with the uppermost space having the greatest depth; (b) at least two split compression rings in the one groove, effective to each substantially annularly engage the bore wall, the rings having mating surfaces superimposed one upon another and having their split ends out of superimposed alignment, each ring residing essentially in a different one of the spaces with the uppermost ring engageable with both the groove step and the next lowermost of the rings and (c) a solid lubricant that coats essentially all of the groove and constitutes the non-mating surfaces of the superimposed rings, whereby pressure of said retained fluid forces the rings together to act in unison and seal jointly against both the step and a side of the groove opposite the retained fluid. Such assembly substantially reduces blow-by of pressurized fluids, reduces the crevice volume, eliminates pumping of oil into the chamber above the piston while reducing flutter of the compression rings, and substantially reduces premature ring failure. The solid film lubricant assists in eliminating freezing of the rings against the groove sides, increasing ring fatigue life, enhancing ring tension and reducing engine emissions.