| 摘要 |
A piston and ring assembly operative within a cylindrical bore wall to retain fluid to one side of the assembly, comprising 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; at least two split compression rings in the 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, and a solid lubricant that coats essentially all of the groove and constitutes the non-mating surfaces of the superimposed rings. Pressure of the 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. 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.
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