Piston Ring DLC Coating Matched to Cylinder Bore Hardness
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Solution Overview
Problem
Conventional DLC coatings on piston rings exhibit increased wear when slid against cylinder surfaces with 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 combination of a cylinder and piston ring where the piston ring's outer peripheral surface is formed with a substantially hydrogen-free amorphous carbon coating, with Vickers hardness and Raman spectrum peak intensity ratios optimized to reduce wear, specifically setting the sum of Vickers hardness of the DLC coating and the cylinder's bore surface to 2500 HV or less and the ID/IG ratio to 0.60 or more and 1.33 or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a DLC coating with high hardness (3000 HV to 4000 HV) is used on the piston ring outer peripheral surface, then wear resistance is improved, but the amount of wear increases when sliding on cylinder surfaces with materials other than aluminum alloys
Solution Approach 1:
The invention changes the hardness parameter of the DLC coating from conventional high hardness (3000-4000 HV) to a controlled range (1500-2500 HV). This parameter modification resolves the contradiction by optimizing the hardness level to achieve appropriate plastic deformation capability that prevents excessive wear when sliding on iron-based thermal spray coatings, while still maintaining sufficient wear resistance
Solution Approach 2:
The invention creates a composite structure by combining the DLC coating with specifically controlled cylinder bore surface materials (aluminum alloys or iron-based thermal spray coatings with controlled hardness). The composite system achieves optimal wear performance through the interaction between the softened DLC coating and the complementary cylinder surface material properties
2Reliability
If the hardness of the DLC coating is increased to improve wear resistance, then the coating becomes more resistant to sliding wear, but the coating loses plastic deformation capability and experiences increased wear on non-aluminum cylinder surfaces
Solution Approach 1:
The invention modifies the hardness parameter of the DLC coating to a lower range (1500-2500 HV) that preserves plastic deformation capability. This parameter change allows the coating to deform plastically under sliding conditions, preventing brittle failure and excessive wear when interacting with iron-based thermal spray coatings, while still providing adequate wear resistance
3Reliability
If a cylinder with iron-based thermal spray coating is used to improve heat transfer and wear resistance, then overall bore temperature is reduced and wear resistance is improved, but the DLC coating on the piston ring experiences increased wear
Solution Approach 1:
The invention changes the hardness parameter of the DLC coating to a lower range (1500-2500 HV) that is compatible with iron-based thermal spray coatings. This modification enables the coating to exhibit appropriate plastic deformation when sliding on the thermal spray surface, preventing the increased wear that occurs with conventional high-hardness DLC coatings
Solution Approach 2:
The invention creates a compatible composite system between the DLC-coated piston ring and the iron-based thermal spray coated cylinder. The controlled hardness of the DLC coating complements the properties of the thermal spray coating, achieving synergistic wear resistance and heat transfer performance without the wear problems associated with high-hardness DLC
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, improving plastic deformation and lubrication, thereby mitigating damage from foreign matter and enhancing wear resistance regardless of the cylinder's material.
Implementation Method 1
The hard carbon coating is made of, for example, amorphous carbon called diamond-like carbon (DLC). The structural essential of DLC is a mixture of diamond bonds (sp3 bonds) and graphite bonds (sp2 bonds) as bonds of carbon.
Implementation Method 2
a piston ring sliding on an inner peripheral surface of the cylinder
Data Source
AI summary
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.