Bearing Conductive Shunt Ring for Electrical Current Diversion
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Solution Overview
Problem
In applications where bearings are exposed to electrical current and lubricants, such as in hybrid vehicles, existing technologies fail to safely divert electrical current while allowing free flow of lubricants, leading to potential damage from electric discharge machining and impaired bearing operation.
Innovation Solution
A conductive shunt ring with radially extending fingers and carbon fiber elements is integrated into the bearing, ensuring electrical current is safely grounded around the raceways and rolling elements, while the inner diameter design allows for unobstructed lubricant flow by exceeding the pitch diameter, thus preventing damage and maintaining bearing functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive shunt ring is added to divert electrical current, then bearing reliability is improved, but device complexity increases
Solution Approach 1:
The conductive shunt ring is nested within the bearing structure, specifically positioned inside the inner ring with its outer diameter less than the inner ring's inner diameter. This nesting allows the shunt ring to be integrated into the existing bearing components without requiring separate housing or additional external structures, thereby improving reliability while minimizing increases in device complexity.
Solution Approach 2:
The shunt ring combines multiple functions into a single component: it provides electrical conductivity to divert current, maintains structural integrity within the bearing, and allows lubricant flow through its design. By merging these functions into one integrated component rather than separate elements, the solution improves reliability while controlling device complexity.
2Reliability
If the shunt ring inner diameter is reduced to improve electrical contact, then electrical conductivity is improved, but lubricant flow is blocked
Solution Approach 1:
The shunt ring employs local quality by having different functional zones: the outer diameter surface provides continuous contact with the inner ring for electrical conductivity, while the inner diameter is specifically sized to be less than the inner ring's inner diameter but still allow lubricant passage. This localized differentiation of properties allows simultaneous optimization of electrical contact and lubricant flow.
Solution Approach 2:
The solution changes the critical parameter of the shunt ring inner diameter to be less than the inner ring inner diameter, creating an optimized gap that balances two competing requirements: close enough to the rolling elements to effectively divert electrical current, yet large enough to allow free lubricant flow. This parameter optimization resolves the contradiction between electrical conductivity and lubricant flow.
3Reliability
If the shunt ring contacts the rolling elements, then electrical current diversion is improved, but free-flow of lubricant is impeded
Solution Approach 1:
The design extracts the shunt ring from direct contact with the rolling elements by positioning its inner diameter less than the inner ring's inner diameter, creating a clearance that prevents interference with rolling element movement and lubricant flow. Instead of relying on contact with rolling elements for current diversion, the shunt ring achieves its function through contact with the inner ring and proximity to the electrical discharge path, thereby maintaining current diversion effectiveness while eliminating lubricant flow restriction.
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 effectively grounds electrical current without interfering with lubricant flow, preventing damage to the bearing and ensuring continuous operation in non-sealed, wet environments.
Implementation Method 1
A plurality of carbon fiber elements extend from each finger and contact the inner ring to conduct electrical current between the inner ring and outer ring
Data Source
AI summary
A rolling element bearing includes an inner ring and an outer ring, with rolling elements therebetween. The plurality of rolling elements collectively define a pitch diameter. An electrically-conductive shunt ring has an outer diameter surface and an inner diameter surface, one of which contacting either the outer ring or the inner ring, and the other not directly contacting the rings. A plurality of fingers extend from the contacting diameter surface. A plurality of carbon fiber elements extend from each finger and contact the other of the rings, to conduct electrical current between the inner ring and outer ring. The non-contacting diameter surface of the shunt ring defines a diameter that exceeds the pitch diameter to enable free-flow of lubricant through the bearing.