Non-Circular Piston Pin Assembly for Two-Stroke Lubrication
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Two-stroke internal combustion engines face challenges in lubricating the piston pin due to constant positive pressure, leading to potential scuffing or seizure, as traditional lubrication methods fail to effectively supply fluid to the highly loaded pin joint.
Innovation Solution
A piston assembly with a non-circular piston pin and a piston pin bearing cage, featuring a bi-axial geometry that creates mechanical gaps to allow lubrication fluid to enter the pin joint, ensuring adequate lubrication by transitioning load between inner and outer bearing zones, and utilizing a 'cam lobe' effect to lift the piston for fluid entry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional circular piston pin is used in a two-stroke engine, then the structure is simple and manufacturing is easy, but the pin joint cannot be adequately lubricated due to constant positive pressure causing scuffing or seizure
Solution Approach 1:
The patent applies asymmetry by changing the piston pin cross-section from a circular shape to an asymmetric shape with flattened portions. This asymmetric geometry creates variable clearance gaps between the piston pin and the piston pin bore, allowing lubrication fluid to enter the pin joint during operation. The flattened portions create larger gaps that facilitate fluid entry, resolving the lubrication problem while maintaining a relatively simple cylindrical pin structure with modified cross-section.
Solution Approach 2:
The patent applies dynamics by designing the piston pin with an asymmetric cross-section that dynamically varies the clearance gap as the pin rotates or moves within the piston. This dynamic geometry allows the gap between the piston pin and bore to open and close during operation, creating pressure-driven lubrication flow paths. The dynamic clearance variation enables continuous lubrication delivery to the pin joint under the constant positive pressure conditions of two-stroke engines.
2Reliability
If the piston pin is designed with a non-circular cross-section to create lubrication gaps, then lubrication effectiveness improves, but manufacturing precision requirements increase
Solution Approach 1:
The asymmetric cross-section with flattened portions is designed to create sufficient clearance gaps for lubrication without requiring extremely tight tolerances. The flattening creates intentional larger gaps that are more tolerant of manufacturing variations, while still maintaining adequate load-bearing surface area. This approach achieves effective lubrication while keeping manufacturing precision requirements at practical levels.
Solution Approach 2:
The patent modifies the geometric parameters of the piston pin cross-section by introducing flattened portions with specific dimensions and orientations. These parameter changes create the necessary clearance gaps for lubrication fluid entry while maintaining overall pin strength and load-carrying capability. The specific flattening depth and orientation can be optimized to balance lubrication effectiveness with manufacturing feasibility.
3Strength
If a non-circular piston pin with bi-axial geometry is used, then load-carrying capability and lubrication are enhanced, but the device complexity increases
Solution Approach 1:
The bi-axial asymmetric geometry creates distinct inner and outer bearing zones with different load-carrying characteristics. The asymmetric cross-section with flattened portions distributes loads more effectively across these zones while maintaining structural integrity. This geometry provides enhanced load-carrying capability through the bi-axial configuration without requiring completely complex structural features, as the modification remains a cross-sectional change to the cylindrical pin.
Solution Approach 2:
The bi-axial geometry effectively segments the load-bearing function into distinct inner and outer bearing zones along the piston pin. This segmentation allows different portions of the pin to handle different load components, improving overall load-carrying capability. The flattened portions create natural segmentation of the cross-section into load-bearing and clearance-providing areas, achieving functional segmentation without adding separate components.
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 bi-axial piston pin arrangement effectively prevents scuffing and seizure by ensuring continuous lubrication, enhancing the load-carrying capability and maintaining engine performance even during overspeed conditions.
Implementation Method 1
gaps for receiving fluid are created between the piston pin and the upper portion of the piston in response to the piston moving reciprocally in the cylinder bore
Implementation Method 2
ensuring adequate lubrication by transitioning load between inner and outer bearing zones
Implementation Method 3
utilizing a 'cam lobe' effect to lift the piston for fluid entry
Implementation Method 4
The at least one inlet port is configured to direct cooling fluid flowing into the piston from a first trajectory to a second trajectory
Data Source
AI summary
Pistons and piston assemblies for an internal combustion engine is provided. The piston assembly includes a piston coupled to a connecting rod with a piston pin. The piston pin includes a non-circular outer cross-sectional shape.