Dual Hard Chromium Piston Ring Coating for Faster Run-In
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Piston rings in internal combustion engines face long running-in times due to high wear resistance of hard chromium solid particle layers, leading to potential engine failure and excessive oil consumption, particularly in large engines.
Innovation Solution
A piston ring design featuring a base body with a first hard chrome layer containing embedded solid particles and a second particle-free hard chrome layer with an expanded crack network, which acts as a lubricant reservoir, reducing running-in time and oil consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard chrome solid particle layer is applied to the piston ring surface, then wear resistance is improved, but running-in time increases significantly
Solution Approach 1:
The hard chrome layer is segmented into two distinct layers: a first layer containing solid particles for wear resistance, and a second particle-free layer for improved running-in behavior. This segmentation allows each layer to perform its specific function optimally without the negative effects of the other.
Solution Approach 2:
Different regions of the coating have different properties: the first hard chrome layer near the substrate contains solid particles for high wear resistance, while the second outer layer is particle-free to provide better running-in characteristics. This local differentiation resolves the contradiction between wear resistance and running-in time.
2Strength
If a hard chrome solid particle layer is applied to the piston ring surface, then wear resistance is improved, but oil consumption increases
Solution Approach 1:
The coating is divided into two functional layers where the second particle-free layer reduces friction and oil consumption during the running-in phase, while the first particle-containing layer maintains wear resistance. This segmentation allows the system to achieve both low oil consumption and high wear resistance.
Solution Approach 2:
The outer surface has different properties from the inner layer: the particle-free second layer provides lower friction and reduced oil consumption, while the particle-containing first layer provides wear resistance. This local quality differentiation resolves the contradiction between wear resistance and oil consumption.
3Quantity of substance
If the crack network surface proportion is increased, then lubricant reservoir capacity is improved, but surface hardness may be reduced
Solution Approach 1:
The crack network is concentrated in the second particle-free hard chrome layer, which has lower hardness requirements. This segmentation allows the first particle-containing layer to maintain high surface hardness and wear resistance, while the second layer provides lubricant reservoir capacity through its crack network.
Solution Approach 2:
Different layers have different mechanical properties: the first layer maintains high hardness with minimal cracks, while the second layer has a developed crack network for lubricant storage. This local quality differentiation allows the system to achieve both high surface hardness and adequate lubricant reservoir capacity.
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 design significantly improves running-in behavior by utilizing the particle-free hard chrome layer to shorten the initial operation period, reducing oil consumption and ensuring the solid particle layer takes over as a friction partner after running-in, while maintaining high wear resistance.
Implementation Method 1
the outer circumferential surfaces (running surfaces) of the piston rings are typically coated with wear-resistant layers, for example, in the form of electrolytically deposited hard chrome coatings
Implementation Method 2
a first hard chromium layer with a crack network is electrolytically deposited on the outer circumferential surface
Implementation Method 3
the current direction is reversed, whereby any cracks formed widen and the solid particles are embedded in the cracks
Data Source
Figure 1
AI summary
The invention relates to a piston ring having a main body. The main body has an inner peripheral surface, a first flank surface, a second flank surface and an outer peripheral surface. A first hard chromium layer having a network of cracks is applied to the outer peripheral surface. The network of cracks of the first hard chromium layer has a crack density of 10-250 cracks per mm, and solid particles having an average particle size of 0.01-10 µm are embedded into the cracks of the first hard chromium layer. A second hard chromium layer having a network of cracks is applied to the first hard chromium layer. The crack density of the network of cracks of the second hard chromium layer is 10-250 cracks per mm, and no solid particles are embedded into the cracks of the second hard chromium layer. The cracks at the surface of the second hard chromium layer have an average width of 1-15 µm, the cracks at the surface of the second hard chromium layer are electrolytically expanded, and the surface proportion of the cracks at the surface of the second hard chromium layer is 3-25%, with respect to the entire surface of the second hard chromium layer.