Plain Bearing Electrodynamic Finishing for Faster EHD Film Formation
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Solution Overview
Problem
Plain bearings with form errors or surface imperfections delay the formation of the elasto-hydrodynamic layer, leading to increased wear and reduced reliability due to friction during startup, shutdown, and low-speed rotation.
Innovation Solution
The method involves electrodynamically finishing plain bearing surfaces by applying a voltage differential across the bearing housing and journal shaft with a lubricant in between, using electrical discharge to erode asperities and smooth the surface, which can be done mechanically before electrical separation and controlled based on lubricant properties, load, temperature, and rotational speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mechanical finishing is used to smooth bearing surfaces, then surface roughness is reduced, but the minimum lubricant-film gap cannot be sufficiently reduced and form errors remain
Solution Approach 1:
The patent replaces traditional mechanical finishing methods with an electrodynamic system that uses electrical discharge through the lubricant film. This substitution enables removal of material (asperities) without mechanical contact, achieving both smoother surfaces and reduced minimum gap distances that mechanical methods cannot accomplish.
Solution Approach 2:
The patent changes the physical state and properties of the lubricant by applying high voltage electrical fields across it. This transforms the lubricant from a passive lubricating medium to an active tool for material removal through dielectric breakdown and electrical discharge, enabling precise control of surface finish and gap reduction.
2Ease of manufacture
If bearing surfaces have form errors or asperities, then manufacturing is easier, but EHD layer formation is delayed causing increased wear
Solution Approach 1:
The patent applies electrodynamic finishing during the manufacturing process to preliminarily correct form errors and remove asperities from bearing surfaces before final assembly. This preliminary action ensures that when the bearing enters service, the surfaces are already optimized for immediate EHD layer formation, eliminating the wear-prone startup period.
Solution Approach 2:
The patent uses electrical discharge mechanisms instead of mechanical machining to achieve superior surface quality. This substitution allows for more precise control of surface geometry and eliminates the form errors that typically result from mechanical manufacturing processes.
3Productivity
If voltage differential is applied continuously, then asperities are eroded faster, but energy consumption increases and lubricant degradation accelerates
Solution Approach 1:
The patent employs periodic or pulsed voltage application rather than continuous voltage. This periodic action creates intervals of electrical discharge for asperity removal followed by intervals without voltage to allow lubricant recovery and cooling, thereby maintaining high productivity while reducing overall energy consumption and lubricant degradation.
Solution Approach 2:
The patent uses high-voltage pulses that rapidly erode asperities in brief intense bursts, then skips to the next asperity or waits for cooling. This rushing-through approach achieves fast surface finishing without sustained energy input, minimizing total energy consumption and lubricant exposure to degrading conditions.
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 reduces the minimum lubricant-film gap, minimizes wear, and enhances the reliability and load-carrying capacity of plain bearings by achieving smoother surfaces and faster EHD layer formation, even at low speeds.
Implementation Method 1
A voltage differential applied across the bearing housing and the journal shaft. A bearing surface asperity is eroded with electric discharge between the journal shaft and the bearing housing
Implementation Method 2
KR 20170009072 relates to a thrust bearing produced with an electrical discharge machining process
Implementation Method 3
During rotation the lubricant forms an elasto-hydrodynamic layer (EHD) within the interface between the rotatable element and the bearing surface. The EHD layer communicates the supported load between the rotatable structure and the bearing surface
Implementation Method 4
Carbide or metallic asperities disposed on the bearing surface can be vaporized
Data Source
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Figure 3A~3H
AI summary
A method of electrodynamically finishing a plain bearing includes electrically separating a bearing housing (104) from a journal shaft (106) with a lubricant (108) disposed on a bearing surface of the bearing housing (104). The bearing housing (104) or the journal shaft (106) is rotated relative to the other and a voltage differential applied across the bearing housing (104) and the journal shaft (106). One or more asperities (164) disposed on the bearing surface are eroded with electric discharge events between the journal shaft and the bearing housing. Electrodynamically finished bearing assemblies and reaction/momentum wheel arrangements having such bearing assemblies are also described.