Second Compression Piston Ring Profile for Radial Liftoff Control
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Solution Overview
Problem
In highly supercharged engines, the second compression piston ring faces instability due to high pressure, leading to radial liftoff from the cylinder wall, as existing taper faced or napier rings are inadequate in controlling oil and sealing effectively.
Innovation Solution
A piston ring design with a divided outer running face into upper, middle, and lower regions, featuring a scraping line and a crest line, where the middle region has alternating convex and concave sections to enhance oil control and reduce radial liftoff, ensuring a smooth transition without edges and providing a larger area for oil distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If taper faced rings or napier rings are used as the second compression ring, then oil scraping capability is improved, but radial liftoff from the cylinder wall occurs due to high pressure on the running face
Solution Approach 1:
The running face of the piston ring is segmented into three distinct regions: an upper running face region, a middle running face region, and a lower running face region. This segmentation allows each region to have different geometric characteristics optimized for specific functions - the upper region for sealing, the middle region with alternating convex and concave sections for hydrodynamic oil control, and the lower region for oil scraping, thereby preventing radial liftoff while maintaining oil control capability
Solution Approach 2:
Different regions of the running face are given different local geometric qualities. The middle running face region specifically features alternating convex and concave sections, creating local variations in surface geometry that generate hydrodynamic pressure zones. This local quality differentiation enables the ring to maintain stable contact with the cylinder wall under high pressure while still providing effective oil scraping through the lower running face region
2Ease of manufacture
If large quantities of oil are thrown back by the piston towards the cylinder wall to fulfill scraping function, then oil scraping is improved, but the oil ring cannot transport these quantities towards the crankcase due to small connecting pieces
Solution Approach 1:
The second compression ring is designed to perform multiple functions simultaneously: it provides compression sealing through the upper running face region, hydrodynamic oil control through the middle region with alternating convex and concave sections, and oil scraping through the lower running face region. This multi-functionality eliminates the need for separate oil ring components with limited transport capacity, as the single ring handles both compression and oil control tasks effectively
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design effectively prevents radial liftoff and improves sealing by distributing oil hydrodynamically, maintaining contact with the cylinder wall and reducing gas pressure-induced displacement, thus enhancing the piston ring's oil control capacity.
Implementation Method 1
The middle running face region has, alternating in the circumferential direction, convex sections which are curved convexly outwards as viewed in axial cross-section, and concave sections which are at least partially curved concavely inwards as viewed in axial cross-section... distributing oil hydrodynamically
Data Source
AI summary
A compression piston ring is provided, in particular a piston ring suitable as a second piston ring in a three-ring piston ring set, which piston ring has convex sections and concave sections alternating in the circumferential direction in a middle running face region in relation to the axial height, wherein the concave sections form profile recesses in the convexly crowned running face.