Valve Lifter Coating with SP3 Bonding Fraction for Low Friction
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Solution Overview
Problem
Existing valve lifters for automotive internal combustion engines face challenges in achieving satisfactory low-friction characteristics without the need for specially designed oils, as conventional coatings like DLC or CrN require additional lubrication to function optimally.
Innovation Solution
A valve lifter with multiple coating layers, including a DLC layer with a SP3 bonding fraction of 60-70% and a metal-containing diamond-like carbon (Me-DLC) layer, formed through carbonitriding and sputtering processes, which provides low-friction characteristics without the need for specialized oils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DLC or CrN coating is applied to reduce friction, then low-friction characteristics are improved, but the requirement for specially designed oil increases
Solution Approach 1:
The invention changes the bonding structure parameter of the DLC layer by controlling the SP3 bonding fraction to be 60-70%, which is lower than conventional DLC coatings. This parameter change allows the coating to achieve low-friction characteristics without requiring specially designed oils, thus resolving the contradiction between friction reduction and oil compatibility
Solution Approach 2:
The invention creates a composite coating structure with multiple layers including a buffer layer, Me-DLC layer, and DLC layer with specific SP3 bonding fraction. This composite structure combines the advantages of different materials to achieve both low-friction characteristics and compatibility with conventional oils
2Manufacturing precision
If mirror surface finishing is applied to the valve lifter surface, then surface smoothness is improved, but satisfactory surface roughness is not achieved
Solution Approach 1:
The invention changes the surface roughness parameter by controlling the base body surface roughness (Ra) to be within 0.01-0.04 μm before coating application. This optimized surface preparation parameter enables the subsequent DLC coating to achieve both smoothness and satisfactory surface roughness characteristics
3Reliability
If conventional DLC coating is applied to reduce friction, then friction characteristics are improved, but wear resistance is insufficient
Solution Approach 1:
The invention applies a composite coating structure consisting of a buffer layer, Me-DLC layer (0.3-0.6 μm), and DLC layer (1.0-1.5 μm) with SP3 bonding fraction of 60-70%. This multi-layer composite structure provides both low-friction characteristics and enhanced wear resistance, resolving the contradiction between friction reduction and wear protection
Solution Approach 2:
The invention applies different coating layers with different properties at different locations/depths: the buffer layer provides adhesion, the Me-DLC layer provides intermediate properties, and the top DLC layer with specific SP3 bonding fraction provides low friction. This local differentiation of coating properties achieves both friction reduction and wear resistance
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 achieves superior low-friction and wear-resistant properties, demonstrated by reduced friction torque and minimal wear scars during durability tests, enhancing engine performance without the requirement for specific oils.
Implementation Method 1
a buffer layer formed by sputtering a metal target on a surface of the base body... formed by sputtering a target selected from the group consisting of W, Cr, Ti, and Mo on the buffer layer
Implementation Method 2
a valve lifter may comprise a plurality of coating layers formed on the surface thereof... wherein a top coating layer among the plurality of coating layers is a DLC layer
Implementation Method 3
a diamond-like carbon layer formed on the Me diamond-like carbon layer, having a thickness of 1 ̃1.5 μm, and having a SP3 bonding fraction of 60 ̃70%
Data Source
AI summary
The present invention provides a valve lifter, including a buffer layer, a Me diamond-like carbon layer having a thickness of 0.3˜0.6 μm, and a diamond-like carbon layer having a thickness of 1˜1.5 μm and a SP3 bonding fraction of 60˜70%, which are sequentially formed on a base body which is subjected to carbonitriding treatment. The valve lifter can exhibit superior low-friction characteristics and wear resistance.