Serviceable Bearing Assembly for Grounding Motor Shaft Currents
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Solution Overview
Problem
Existing rolling bearings in electric motors fail prematurely due to high frequency grounding currents causing electrical discharges, leading to surface damage, noise, and reduced service life, with existing solutions like grounding brushes being ineffective in dirty environments and sacrificial bearings requiring complex maintenance.
Innovation Solution
A rolling bearing assembly with a mounting and dismounting device that allows easy replacement and grounding, featuring a conductive sleeve and axial preload element, ensuring secure fit and electrical conductivity, and an elastic member for thermal tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sacrificial bearing is used to protect main bearings from electrical discharges, then the main bearings are protected, but the bearing replacement requires complex disassembly of the rotor from the stator
Solution Approach 1:
The bearing assembly is segmented into a modular unit comprising the bearing, retaining ring, and mounting device that can be independently installed and removed from the rotor shaft, separating the maintenance operation from the stator and main bearing assembly
Solution Approach 2:
A mounting device with a sleeve acts as an intermediary mechanism between the bearing assembly and the rotor shaft, enabling tool-free installation and removal without requiring disassembly of the rotor-stator assembly
2Reliability
If grounding brushes with conductive fibers are used to ground high frequency currents, then current grounding is achieved, but the brushes become ineffective in dirty environments with oil or dirt creating additional resistance
Solution Approach 1:
The sacrificial bearing is designed as a disposable component that absorbs electrical discharges and is easily replaced when degraded, eliminating the need for maintenance of grounding brushes in contaminated environments
Solution Approach 2:
The grounding function is extracted from the main bearing system and transferred to the sacrificial bearing assembly, which can be independently maintained without affecting the main bearings or requiring complex grounding mechanisms
3Strength
If lubricant films are used to separate rolling elements from raceways, then mechanical separation is achieved, but electrical current flows through the bearing causing premature failure
Solution Approach 1:
The sacrificial bearing intentionally accepts electrical discharges that would otherwise damage main bearings, converting a harmful effect into a controlled degradation of a replaceable component
Solution Approach 2:
The sacrificial bearing is designed as a consumable component with lower cost and easier replaceability compared to main bearings, allowing it to absorb electrical damage without compromising the overall system reliability
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 solution extends the service life of main bearings by effectively grounding high frequency currents, reducing noise and vibration, and enabling easy maintenance without disassembling the rotor from the stator.
Implementation Method 1
an axial preload element axially disposed between the supporting shaft and the sleeve to exert a permanent axial force therebetween in order to ensure an efficient contact between the rolling elements and the first and second rings
Implementation Method 2
an elastic member for thermal tolerance
Implementation Method 3
featuring a conductive sleeve and axial preload element, ensuring secure fit and electrical conductivity
Data Source
AI summary
A rolling assembly having a rolling bearing provided with a first ring and with a second ring capable of rotating concentrically relative to one another, and with a plurality of rolling elements disposed between the first and second rings. The assembly further includes a bearing mounting and dismounting device having a supporting shaft to which the first ring of the rolling bearing is mounted, and a sleeve slidably mounted on the supporting shaft between a remote position from the rolling bearing and a close position in which the sleeve is in axial contact with the second ring of the rolling bearing.