DLC-Coated Piston Ring for Wear Resistance Without Bore Attack
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Solution Overview
Problem
DLC coatings on piston rings for internal combustion engines face challenges in maintaining wear resistance and low attacking properties against cylinder bore surfaces, especially in environments with engine lubricating oil deposits that cause abrasive wear.
Innovation Solution
A piston ring with a DLC coating having a specific sp2 component ratio of 0.5 to 0.85, coating hardness of 12 GPa to 26 GPa, Young's modulus of 250 GPa or less, and controlled macroparticle density, along with an underlayer containing Ti, Cr, or Si, to enhance adhesion and reduce wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DLC coating with high sp2 component ratio is used to improve wear resistance, then wear resistance is improved, but attacking property against cylinder bore increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the sp2 component ratio within the range of 0.5 to 0.85, coating hardness between 12-26 GPa, and Young's modulus at 250 GPa or less. This optimization of physical and chemical parameters enables the DLC coating to achieve both improved wear resistance and reduced attacking property against the cylinder bore, resolving the technical contradiction between these two opposing requirements.
Solution Approach 2:
The patent employs composite material structure by creating a DLC coating with controlled sp2-sp3 hybridization that combines the wear resistance benefits of higher sp2 content with the lower attacking property characteristics of optimized sp3 content. The composite nature of the coating, with its specific ratio of sp2 and sp3 bonded carbon, allows simultaneous achievement of durability and compatibility with cylinder bore surfaces.
2Reliability
If DLC coating hardness is increased to improve wear resistance, then wear resistance is improved, but coating becomes more brittle and peeling resistance decreases
Solution Approach 1:
The patent resolves this contradiction by optimizing the coating hardness parameter within the specific range of 12-26 GPa and controlling Young's modulus to be 250 GPa or less. This parameter optimization ensures the coating is hard enough to resist wear from deposits and abrasive particles, while maintaining sufficient ductility and adhesion to prevent peeling under thermal and mechanical stress during engine operation.
Solution Approach 2:
The patent applies local quality by creating a DLC coating with specific sp2 component distribution that provides varying properties through the coating thickness. The coating structure is designed to have appropriate hardness at the surface for wear resistance while maintaining flexibility and adhesion at the substrate interface, thus preventing peeling while resisting wear.
3Force
If engine lubricating oil is used to reduce friction, then friction is reduced, but deposit generation increases causing abrasive wear
Solution Approach 1:
The patent applies the blessing in disguise principle by designing a DLC coating specifically capable of withstanding the abrasive effects of deposits generated during engine operation. The coating's optimized sp2 component ratio (0.5 to 0.85) and hardness (12-26 GPa) provide resistance to abrasive wear from deposits, while still maintaining low friction characteristics. This converts the harmful effect of deposit generation into a manageable condition where the coating protects the piston ring.
Solution Approach 2:
The patent addresses this contradiction by optimizing the DLC coating parameters including sp2 component ratio (0.5 to 0.85), hardness (12-26 GPa), and Young's modulus (≤250 GPa). These parameter changes create a coating that maintains low friction coefficients for reduced sliding resistance while simultaneously providing sufficient hardness and toughness to resist abrasive wear from engine deposits, thus resolving the contradiction between friction reduction and abrasive wear protection.
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 DLC coating provides excellent wear resistance and low attacking properties on cylinder bore surfaces, reducing abrasive wear and improving durability in engine lubricating oil environments.
Implementation Method 1
The outer peripheral sliding surface of a piston ring used on a piston for an internal combustion engine may be covered with a DLC (diamond-like carbon) coating
Implementation Method 2
An object of the present invention is to provide a piston ring covered with a DLC coating which has excellent wear resistance with a sufficient effect also against the above-described abrasive wear
Data Source
Figure 1(A)~1(B)
Figure 2(A)~2(B)
Figure 3
AI summary
The present invention addresses the problem of providing a piston ring covered with a DLC coating that has excellent wear resistance and shows a low attacking property on a cylinder bore sliding surface. The problem is solved by a piston ring which is used in the presence of an engine lubricating oil and includes a DLC coating on an outer peripheral sliding surface. The DLC coating has an sp2 component ratio of 0.5 to 0.85 as determined from a TEM-EELS spectrum obtained by a combination of a transmission electron microscope (TEM) and electron energy loss spectroscopy (EELS), as well as a coating hardness of 12 GPa to 26 GPa and a Young's modulus of 250 GPa or less as measured by a nanoindentation method.