Piston Ring Carbon Coating Matched to Cylinder Hardness
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Solution Overview
Problem
Conventional DLC coatings on piston rings exhibit increased wear when slid against cylinder surfaces made of materials other than aluminum alloys, such as those with iron-based thermal spray coatings, despite their high hardness, which is undesirable for wear resistance.
Innovation Solution
A hydrogen-free amorphous carbon coating with a Vickers hardness sum of 2500 HV or less and a Raman spectrum peak intensity ratio ID/IG between 0.60 and 1.33 is applied to the piston ring, reducing wear by enhancing plastic deformation and crystal grain fineness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high hardness DLC coating (3000-4000 HV) is applied to the piston ring outer peripheral surface, then wear resistance is improved, but the coating wears more when sliding on cylinder surfaces made of materials other than aluminum alloys
Solution Approach 1:
The patent changes the key parameter of DLC coating hardness from the conventional high range (3000-4000 HV) to a lower range (1500-2500 HV). This parameter change resolves the contradiction by reducing the coating's tendency to wear against hard cylinder surfaces while maintaining sufficient wear resistance through the optimized hardness value that balances durability and compatibility with iron-based cylinder coatings
Solution Approach 2:
The patent employs a composite material system consisting of the DLC coating on the piston ring combined with specific cylinder materials (aluminum alloys or iron-based thermal spray coatings). The composite approach optimizes the interaction between the coating and cylinder surface, where the lower hardness DLC coating works synergistically with the cylinder material properties to reduce wear while maintaining reliability
2Reliability
If the DLC coating hardness is increased to improve wear resistance, then the coating becomes more resistant to wear on aluminum alloy cylinders, but the coating experiences increased wear on iron-based thermal spray coated cylinders
Solution Approach 1:
The patent creates a universal DLC coating solution that functions effectively with multiple cylinder material types (aluminum alloys and iron-based thermal spray coatings). By optimizing the coating hardness to 1500-2500 HV, the coating achieves multi-functionality, providing adequate wear resistance across different cylinder materials without requiring material-specific customization, thus resolving the adaptability contradiction
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
This configuration significantly reduces the wear of the DLC coating on the piston ring, independent of the cylinder material, by mitigating damage from foreign matter and improving lubrication, thereby extending the coating's lifespan.
Implementation Method 1
enhancing plastic deformation and crystal grain fineness
Data Source
Figure 1A~1B
AI summary
A combination of a cylinder and a piston ring with which the amount of wear of a hard carbon coating forming an outer peripheral surface of the piston ring is reduced according to the hardness of an inner peripheral surface of the cylinder, regardless of a material to be applied to the inner peripheral surface of the cylinder, is provided. The present disclosure is a combination of a cylinder and a piston ring, the combination including a cylinder of an internal combustion engine and a piston ring sliding on an inner peripheral surface of the cylinder. The piston ring has an outer peripheral surface sliding on the inner peripheral surface of the cylinder, and the outer peripheral surface is formed of a substantially hydrogen-free amorphous carbon coating. The Vickers hardness Hd of the amorphous carbon coating and the Vickers hardness Hb of the inner peripheral surface of the cylinder satisfy Hd + Hb ≤ 2500 HV. The ratio ID/IG of the peak intensity of the D band to the peak intensity of the G band in a Raman spectrum obtained by measuring the amorphous carbon coating by Raman spectroscopy is 0.60 or more and 1.33 or less.