Keystone Second Ring Groove in Pistons for Carbon-Driven Ring Sticking
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Solution Overview
Problem
High-temperature internal combustion engine pistons face issues with carbon deposits causing piston rings to stick due to conventional rectangular ring grooves, which are costly to replace with keystone grooves for higher temperature applications.
Innovation Solution
Designing pistons with a rectangular first ring groove and a keystone second ring groove, where the first ring groove has perpendicular side flanks and the second ring groove has side flanks angled greater than 90 degrees, preventing carbon deposition and ring sticking at high temperatures, while maintaining low manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the first ring groove is formed with a keystone cross-section to prevent ring sticking, then ring sticking is prevented, but manufacturing cost increases significantly
Solution Approach 1:
The patent applies different cross-sectional shapes to different ring grooves based on their specific operational requirements. The first ring groove uses a rectangular cross-section while the second ring groove uses a keystone cross-section. This localized differentiation allows the keystone geometry to be applied only where it is most needed for preventing ring sticking, rather than uniformly across all grooves, thereby reducing manufacturing complexity and cost while maintaining reliability where critical.
2Reliability
If the second ring groove is formed with a keystone cross-section to prevent carbon deposition, then ring sticking is prevented, but manufacturing complexity increases
Solution Approach 1:
The patent implements local quality by assigning different geometric characteristics to specific ring grooves. The second ring groove, which operates in a temperature range prone to carbon deposition (200°C to 280°C), is given the keystone cross-section with angled side flanks. This localized geometric complexity is confined only to where it provides the necessary functional benefit, keeping the overall device complexity manageable.
3Ease of manufacture
If all ring grooves are formed with rectangular cross-section to simplify manufacturing, then manufacturing cost is reduced, but ring sticking occurs at high temperatures
Solution Approach 1:
The patent resolves this contradiction by applying local quality - using rectangular cross-sections for the first ring groove where manufacturing simplicity is advantageous, and keystone cross-sections for the second ring groove where reliability against ring sticking is critical. This selective approach optimizes the balance between manufacturing ease and operational reliability.
Solution Approach 2:
The patent segments the ring groove system into different functional zones. The first ring groove handles high-temperature combustion gases with a rectangular cross-section, while the second ring groove handles the intermediate temperature zone prone to carbon deposition with a keystone cross-section. This segmentation allows each groove to be optimized for its specific operational conditions.
Data Source
AI summary
A piston for a high temperature internal combustion engine is provided. The piston includes an upper wall, base wall, outer rib, and inner rib defining a cooling chamber therebetween, and a plurality of ring grooves formed in the outer rib. Only the second ring groove is formed with the keystone cross-section, and all of the other ring grooves are formed with the conventional rectangular cross-section. Thus, the piston can be formed with low manufacturing costs and can also provide exceptional performance when used in high temperature combustion engines, wherein the temperature at the first ring groove is greater than 280° C., and thus prevents carbon from depositing or burns off any carbon deposits, but the temperature at the second ring groove is between 200° C. and 280° C., in which case carbon deposits can form and cause the piston ring to stick.