Zoned Cylinder Bore Finishes for Opposed-Piston Ring Lubrication
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Solution Overview
Problem
In opposed-piston internal combustion engines, there is a challenge in managing the friction and lubrication between piston rings and the cylinder bore surface, as a rough surface finish is needed to retain sufficient lubricating oil for reduced friction and durability, but excessive oil can lead to increased emissions and combustion issues, requiring a balanced surface finish that minimizes oil consumption while maintaining adequate lubrication.
Innovation Solution
The cylinder bore surface is divided into zones with different surface finishes, with a rougher finish in the inner zone for inner piston rings and a smoother finish in the outer zones for outer piston rings, tailored to specific lubrication objectives in high-friction regions, including additional finishing in top ring reversal zones to mitigate dry lubrication effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rough surface finish is provided in the inner zone to retain sufficient lubricating oil for reduced friction and durability, then lubrication is improved, but oil consumption increases leading to increased emissions and combustion issues
Solution Approach 1:
The patent applies different surface finish roughness values to different zones of the cylinder bore. The inner zone (where combustion occurs) has a rougher surface finish to retain lubricating oil and reduce friction, while the outer zones have a smoother surface finish to minimize oil retention and reduce oil consumption. This local differentiation resolves the contradiction by providing enhanced lubrication exactly where it is needed for reliability while limiting oil consumption and emissions in other areas.
2Object-generated harmful factors
If a smooth surface finish is provided in outer zones to minimize oil retention and reduce emissions, then emissions are reduced, but friction and scuffing increase in those zones
Solution Approach 1:
The patent differentiates surface finish roughness by zone: outer zones have smoother finishes to minimize oil retention and reduce emissions, while the inner zone has a rougher finish to provide adequate lubrication. This local quality approach allows the system to tolerate higher friction in outer zones (where oil is scraped away anyway) while ensuring low friction in the inner zone where combustion occurs and lubrication is critical for reliability.
3Reliability
If a uniform rough surface finish is provided throughout the bore to ensure adequate lubrication, then friction is reduced, but oil consumption increases excessively
Solution Approach 1:
The patent implements a non-uniform surface finish with different roughness values in different zones. The inner zone has higher roughness to retain oil and reduce friction, while outer zones have lower roughness to minimize oil retention. This spatial variation in surface quality allows the system to achieve adequate friction reduction where it matters most while significantly reducing overall oil consumption compared to a uniformly rough surface.
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 approach effectively minimizes friction and scuffing, maintains adequate lubrication, and reduces oil consumption, thereby enhancing engine efficiency and durability while controlling emissions.
Implementation Method 1
Oil is retained in the bore by means of a surface finish that imparts a texture in the bore surface. As oil is transported inwardly from the outer ends to the inner zone, the lubricating oil forms a film that is supported on the bore surface by the surface finish. The film lubricates the piston ring/cylinder bore interface during engine operation, thereby reducing friction
Data Source
AI summary
A cylinder for an internal combustion opposed-piston engine includes a bore, either as part of the cylinder directly or of a liner. The bore has a surface for guiding a pair of pistons disposed for opposing movement in the cylinder. The cylinder bore has three zones of surface finishes: an inner zone extending between and including exhaust and intake ports, where only piston compression rings travel on the bore surface; two instances of an outer zone where only piston oil control rings travel on the bore surface; and two instances of a port zone where both types of rings travel on overlapping paths in the same bore surface portion. Each zone may have a particular surface finish that is tailored to specific requirements including oil control, ring wear, and scuff resistance relevant to the zone.