Convex Piston Ring Geometry for Low-Friction Oil Sealing
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Solution Overview
Problem
Existing piston ring combinations in internal combustion engines face challenges in reducing friction loss while maintaining effective oil seal performance, with tapered shapes improving oil sealing but increasing friction.
Innovation Solution
A piston ring combination featuring a top ring, a second ring, and an oil ring with convex-shaped outer peripheral surfaces, where the second ring and oil ring have protruding surfaces curved outward in a radial direction, reducing friction and enhancing oil seal performance by adjusting the barrel width and peak positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tapered shape is used for the second ring outer peripheral surface, then oil seal performance is improved, but friction loss increases
Solution Approach 1:
The patent applies curvature to the outer peripheral surface of the second ring by forming a protruding surface that curves outward in the radial direction. This convex curved shape reduces the contact pressure between the piston ring and cylinder wall compared to a tapered shape, thereby reducing friction loss while maintaining effective oil sealing through the strategically positioned peak of the protruding surface.
2Loss of energy
If a convex-shaped outer peripheral surface is used for the second ring, then friction loss is reduced, but oil seal performance may deteriorate
Solution Approach 1:
The patent applies local quality by creating a protruding surface with a specific convex shape on the second ring's outer peripheral surface. The peak of this protruding surface is strategically positioned to ensure that the curved surface provides both reduced friction through lower contact pressure and maintained oil sealing by creating an effective scraping edge against the cylinder wall.
3Loss of energy
If a convex-shaped outer peripheral surface is used for the oil ring segment, then friction loss is reduced, but oil seal performance may deteriorate
Solution Approach 1:
The patent applies asymmetry to the oil ring segment by forming a protruding surface where the peak is positioned closer to the crankcase side than to the combustion chamber side. This asymmetric convex shape creates different barrel widths on each side, with the crankcase side having a smaller barrel width that enhances oil scraping effectiveness while the overall curved shape reduces friction loss.
Data Source
AI summary
In this piston ring combination, a second outer peripheral surface, which is the outer peripheral surface of a second ring, has a second protruding surface curved into a convex shape, and a pair of third outer peripheral surfaces, which are the outer peripheral surfaces of a pair of segments, each have a third outer peripheral area in which a third protruding surface is formed, the third protruding surfaces being curved into convex shapes. In at least one of the pair of third outer peripheral surfaces, the peripheral edge on a crank-chamber side is positioned farther outward in the diametrical direction than the peripheral edge on a combustion-chamber side, and a peak of the third protruding surface is positioned nearer to the crank chamber than the center of the third outer peripheral surface.