Bearing Raceway Microconcave Pits for Fretting and Friction Reduction
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Solution Overview
Problem
Rolling contact bearings in wheel hubs face issues with fretting and friction due to poor lubrication, which existing technologies have not adequately addressed.
Innovation Solution
The implementation of microconcave pits in raceway surfaces with specific roughness (Ra) and skewness (Rsk) parameters, ranging from 0.1 to 0.25 microns and −3.5 to −1.0, respectively, to reduce local pressures and enhance lubrication, thereby minimizing fretting and friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If microconcave pits are created in raceway surfaces to improve lubrication, then fretting performance is enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by creating microconcave pits only in specific regions of the raceway surface where contact stresses are highest, rather than uniformly across the entire surface. This localized modification targets the critical areas for fretting prevention while minimizing overall manufacturing complexity. The pits are strategically positioned to capture and retain lubricant exactly where it is most needed for reducing fretting between rolling elements and raceways.
2Reliability
If surface roughness is increased to reduce fretting, then lubrication is improved, but friction increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the roughness parameters Ra (0.1-0.25 microns) and Rsk (-3.5 to -1.0) of the microconcave pit surfaces. By optimizing these specific parameters, the invention achieves a balance where the surface is rough enough to trap lubricant and prevent fretting, but not so rough that it generates excessive friction. The negative skewness parameter ensures the presence of deep valleys for lubricant storage while limiting peak heights that would increase friction.
3Reliability
If deep microconcave valleys are created for grease reservoirs, then lubrication is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies precise parameter ranges for the microconcave pits: Ra between 0.1-0.25 microns and Rsk between -3.5 to -1.0. These parameter definitions provide clear manufacturing targets that balance lubrication effectiveness with manufacturability. The negative skewness parameter specifically ensures deep valleys for grease storage while the controlled Ra value prevents excessive surface irregularities that would be difficult to manufacture.
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 configuration reduces fretting damage and friction by creating a topography with deep valleys as grease reservoirs and lower plateaus, achieving a 10% loaded ballset friction reduction at medium speeds while maintaining grease effectiveness.
Implementation Method 1
the raceway surfaces of the inner or the outer member are microroughened surfaces, meaning they are formed with an innumerable number of randomly formed microconcave, or alternatively microconcave-like, pits for surface-microroughening that are also composed of a succession of plateaus and valleys, wherein plateaus, as it will be disclosed hereinafter, reduce local pressures within the contact between rolling elements and rings, while deep valleys serve as grease reservoirs
Implementation Method 2
plateaus, as it will be disclosed hereinafter, reduce local pressures within the contact between rolling elements and rings
Data Source
AI summary
A rolling contact bearing, wherein the surface of the raceways of an outer member and/or an inner member are randomly formed with an innumerable number of microconcavelike pits, the surfaces are provided with said pits having a surface roughness value smaller than 0.25 microns and a skewness Rsk value such that −3.5<Rsk<−1.0.