Selective Nitriding of Piston Rings for Flexible Oil Scraping
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Solution Overview
Problem
Piston rings with reduced elasticity for low friction power consumption face challenges in maintaining effective oil scraping capability without becoming brittle and fragile due to nitrogen treatment, which affects oil consumption control.
Innovation Solution
A piston ring design where the area close to the outer circumferential lower edge is not provided with a nitride layer, and a protective layer such as chrome or nickel is used to prevent nitridation, allowing for a smaller, flexible chamfer that is not subjected to nitrogen treatment, thereby maintaining flexibility and preventing brittleness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If nitrogen treatment is applied to the piston ring to improve high temperature and wear resistance, then the piston ring becomes more resistant to high temperature and wear, but the piston ring becomes brittle and fragile
Solution Approach 1:
The patent applies selective nitridation where only specific areas of the piston ring (the outer circumferential lower edge and chamfer regions) are subjected to nitrogen treatment, while other areas remain untreated. This is achieved by using a mask structure during the nitriding process to control the distribution of the nitride layer, thereby obtaining different surface properties in different regions of the same component.
2Ease of operation
If a large chamfer is provided on the piston ring to improve oil scraping capability, then the oil scraping capability is improved, but the chamfer becomes brittle and easily damaged after nitrogen treatment
Solution Approach 1:
The patent applies selective nitridation where only specific areas of the piston ring (the outer circumferential lower edge and chamfer regions) are subjected to nitrogen treatment, while other areas remain untreated. This is achieved by using a mask structure during the nitriding process to control the distribution of the nitride layer, thereby obtaining different surface properties in different regions of the same component.
3Loss of energy
If the elasticity of the piston ring is reduced to achieve low friction power consumption, then friction power consumption is reduced, but the sealing performance deteriorates and oil consumption increases
Solution Approach 1:
The patent modifies the chemical composition and physical properties of the piston ring surface by controlling the nitridation process parameters, including temperature (500-550°C), time (2-5 hours), and atmosphere composition. These parameter changes create a hardened surface layer that maintains sealing effectiveness while allowing the bulk material to retain lower elasticity for reduced friction.
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 solution enhances the piston ring's oil scraping capability while reducing the risk of increased oil consumption by maintaining flexibility and preventing brittleness, thus addressing the trade-off between low friction and effective sealing.
Implementation Method 1
providing a protective layer that prevents the piston ring body from nitridation
Implementation Method 2
Each of the upper and lower surfaces 5, 4, the working surface 3, and the inner surface (inner circumferential surface) 6 of the piston ring is subjected to nitrogen treatment so that the piston ring is resistant to high temperature and wear
Data Source
AI summary
A piston ring for an engine may include a piston ring body. The piston ring body may include a working surface, a lower surface, an upper surface, and an inner surface. An area of the working surface and/or the lower surface which is close to an outer circumferential lower edge of the piston ring body is not provided with a nitride layer, the outer circumferential lower edge is formed with a chamfer, the chamfer does not have a nitride layer, and an additional area of the piston ring has a nitride layer.