Piston Ring Chromium Coating for Faster Running-In
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Solution Overview
Problem
Piston rings in internal combustion engines, particularly large ones, experience prolonged running-in times due to high wear resistance of existing hard chromium solid particle layers, leading to engine failure and high oil consumption.
Innovation Solution
A piston ring design featuring a first hard chromium layer with embedded solid particles and a second particle-free hard chromium layer with widened cracks, where the second layer acts as a lubricant reservoir, reducing the running-in time and improving sliding properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard chromium layer with embedded solid particles is applied to improve wear and seizure resistance, then wear resistance is improved, but running-in time becomes excessively long (2000+ hours)
Solution Approach 1:
The hard chromium layer is divided into two distinct segments: a first layer containing embedded solid particles for wear resistance, and a second particle-free layer with a crack network for lubricant storage. This segmentation allows each layer to fulfill its specific function without the negative effects of the other, resolving the contradiction between wear resistance and running-in time.
Solution Approach 2:
Different regions of the coating have different properties: the first hard chromium layer has high wear resistance due to embedded particles, while the second layer has a crack network structure optimized for lubricant storage and running-in behavior. This local differentiation allows the coating to provide both wear protection and acceptable running-in characteristics.
2Reliability
If solid particles are embedded in the hard chromium layer to improve seizure resistance, then seizure resistance is improved, but oil consumption increases during the running-in phase
Solution Approach 1:
The coating is segmented into two functional layers: the first layer with embedded particles provides seizure resistance, while the second particle-free layer with cracks provides lubricant storage to reduce oil consumption during running-in. This segmentation resolves the contradiction by separating the functions of seizure protection and lubricant management.
Solution Approach 2:
The second hard chromium layer contains a crack network that creates a porous structure for lubricant storage. This porous structure allows the coating to retain lubricant during the running-in phase, reducing oil consumption while maintaining seizure resistance through the underlying particle-containing layer.
3Reliability
If a hard chromium layer with high wear resistance is applied, then fire resistance is improved, but sliding properties deteriorate during the running-in phase
Solution Approach 1:
The coating is divided into two layers with different properties: the first layer provides fire resistance through high wear resistance, while the second layer provides improved sliding properties during running-in through its crack network structure that stores and releases lubricant.
Solution Approach 2:
Different regions of the coating have optimized properties for different functions: the inner layer has high wear resistance for fire protection, while the outer layer has a crack network structure optimized for lubricant storage and sliding performance during running-in.
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 shortens the running-in phase, reduces oil consumption, and enhances the piston ring's performance by allowing the particle-free layer to wear off, enabling the solid particle layer to take over as a friction partner.
Implementation Method 1
a first hard chromium layer, which has a crack network, is electrolytically deposited on the outer circumferential surface
Implementation Method 2
the outer circumferential surfaces (running surfaces) of the piston rings are usually provided with wear protection coatings, for example in the form of electrolytically deposited hard chromium layers
Implementation Method 3
the direction of electric current is reversed, wherein cracks that have formed widen and the solid particles are deposited in the cracks
Data Source
AI summary
A piston ring includes a base body having an inner circumferential surface, first and second flank surfaces and an outer circumferential surface, wherein a first hard chromium layer with a crack network is applied to the outer circumferential surface and has a crack density of 10-250 cracks per mm and solid particles having an average particle size of 0.01-10 μm embedded in cracks of the first hard chromium layer, a second hard chromium layer having a crack network applied to the first hard chromium layer and having a crack density of the crack network of 10-250 cracks per mm, no solid particles being embedded in the cracks thereof, where the cracks have an average width of 1-15 μm, the cracks are electrolytically expanded and the surface proportion of the cracks are 3-25% based on a total surface of the second hard chromium layer.