Conductive Sleeve for Motor Shaft Grounding Brush Wear
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Solution Overview
Problem
In electrical rotary machines, the resistance of a shaft surface increases over time due to oxidation, leading to higher contact resistance and potential damage to bearings from electrical discharges, as conventional coatings are not durable enough to withstand the sliding action of grounding brushes.
Innovation Solution
A conductive sleeve with a metallic or polymer base covered by a conductive layer, such as gold or nickel, is used to create a durable sliding surface for the grounding brush, reducing contact resistance and preventing surface changes over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional coating is applied on the shaft surface to maintain conductivity, then the initial contact resistance is reduced, but the coating is damaged or removed by sliding of the grounding brush over time
Solution Approach 1:
The patent applies a composite material solution by combining a polymer base material with a conductive metallic layer (gold, nickel, or copper). The polymer provides mechanical durability and wear resistance, while the metallic layer provides electrical conductivity. This composite structure resolves the contradiction by ensuring the coating withstands brush sliding while maintaining low contact resistance throughout the service life.
2Ease of manufacture
If the shaft surface is left unprotected to avoid coating application, then manufacturing complexity is reduced, but oxidation occurs leading to increased contact resistance and bearing damage
Solution Approach 1:
The patent applies the local quality principle by providing a conductive coating only on the specific area where the grounding brush contacts the shaft, rather than protecting the entire shaft. The coating is applied to the outer cylindrical surface in the brush contact region, maintaining electrical conductivity where needed while avoiding unnecessary coating application elsewhere, thus balancing manufacturing ease with reliability.
3Duration of action of stationary object
If a thick conductive coating is applied to ensure durability, then wear resistance is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent employs a thin film conductive coating rather than a thick coating. The metallic layer is applied as a thin film sufficient to provide electrical conductivity and wear resistance. This approach achieves the required durability without the need for thick coatings, thereby reducing manufacturing complexity and cost while maintaining adequate protection against wear and electrical discharge.
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 conductive sleeve maintains low contact resistance and prevents surface degradation, ensuring consistent performance and reducing the risk of bearing damage during the service life of the motor.
Implementation Method 1
a conductive layer covering at least partially an outer surface of the base facing a sliding surface of the grounding brush
Implementation Method 2
the resistance of a shaft surface increases over time due to oxidation
Data Source
AI summary
An electrical machine having a non-rotating part, a rotating part, at least one bearing supporting said rotating part and having a rotating ring and a non-rotating ring, a fiber grounding brush fixed to said non-rotating part and having a support secured to the non-rotating part and a plurality of conductive fibers having a first end secured to said support and a second free end, opposite to said first end, extending towards the rotating part, and a conductive sleeve having a base fastened to the rotating part or to the rotating ring of the bearing and a conductive layer covering at a portion of a surface of the base, the second free end of the conductive fibers of the fiber grounding brush being in contact with said conductive layer.