Piston ring having a non-uniform radial pressure distribution

摘要

A piston ring has a gap defined by ring gap faces oriented toward one another and a nominal outer radius assumed by the piston ring in a closed position in which the piston ring is in an installed state in an engine cylinder having a radius equalling the nominal outer radius of the piston ring. The piston ring has first length portions extending from both ring gap faces and having a central angle of at least 15 DEG and less than 25 DEG and second length portions immediately adjoining each respective first length portion and having a central angle of approximately 10 DEG . In the installed state the first length portions have a radius of curvature equalling the nominal outer radius and the radius of curvature of the second length portions is smaller than the nominal outer radius. By virtue of such a ring configuration, a radial pressure distribution of the piston ring in the installed state is substantially zero at the ring gap and increases in opposite directions from the ring gap to a maximum value in the second length portions. The maximum value is in excess of 200% of an average circumferential radial pressure distribution of the piston ring in the installed state.