Offset Piston Bearing Segmentation for Lubrication
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing piston assemblies with offset connecting rod bearings face inefficiencies in lubrication due to inadequate load distribution and reduced load-bearing area, leading to elevated friction and wear, especially under high engine speeds and firing pressures.
Innovation Solution
The piston assembly features a connecting rod with a running surface having two outer lands and one inner land that alternately support the load, with a bearing disposed within the circular openings to simultaneously support the load at the point of highest stress, and an offset design that optimizes load distribution and lubrication by generating an oil film during the engine's working cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If offset journal bearing designs with segmented bearing surfaces are used, then lubrication is improved by load alternation between segments, but the load bearing area is reduced limiting maximum load transmission
Solution Approach 1:
The bearing is divided into multiple segments (typically three segments: two outer segments and one inner segment) that are radially offset from each other. This segmentation allows different portions of the bearing to alternately support the connecting rod load during engine operation, creating periodic load relief that maintains hydrodynamic lubrication. The segmented structure is a direct application of the segmentation principle to resolve the lubrication-load bearing area contradiction.
Solution Approach 2:
The bearing segments are arranged in an asymmetric, radially offset configuration rather than a symmetric arrangement. The inner segment is offset radially inward relative to the outer segments, creating an asymmetric load distribution pattern. This asymmetric geometry enables the load to be distributed across different segments at different crank angles, optimizing both lubrication and load-bearing capabilities.
2Reliability
If grooved bearing surfaces are used to enhance lubrication distribution, then lubrication is improved, but the load bearing area is further reduced
Solution Approach 1:
The bearing incorporates localized lubrication features such as oil grooves or oil holes in specific strategic locations rather than across the entire bearing surface. These localized features are positioned to deliver lubrication precisely where needed during the load alternation cycle, maintaining effective lubrication while preserving maximum load-bearing area on the remaining bearing surfaces.
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 design enhances lubrication and load-bearing capacity, reducing friction and wear, and maintaining efficiency and durability by ensuring sufficient oil film generation and distribution across the bearing surfaces, even under peak loads.
Implementation Method 1
an insufficient lubrication between the connecting rod and its associated bearing can result in elevated friction and wear
Data Source
AI summary
A piston assembly is disclosed for use with an engine. The piston assembly may include a first and second piston crown and a first and second connecting rod. The first and second connecting rods may each have a first end pivotally connected to the first and second piston crowns, respectively, and a second end with a circular opening configured to receive a throw of a crankshaft. The second connecting rod may have a running surface defining at least two outer lands and at least one inner land disposed between the at least two outer lands that alternately support a load of the second piston crown. The piston assembly may further include a bearing. Both the inner and outer lands may simultaneously support the load of the second piston crown against the bearing at a point of highest load on the second piston crown.