Conductive Bearing Retainers for EMI Suppression
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Solution Overview
Problem
Turret systems with rotating gimbal interfaces face significant challenges in suppressing electromagnetic interference (EMI) due to high electrical resistance at dynamic bearing interfaces, which allows EMI to radiate and complicates operational performance, especially with stringent customer requirements for reduced resistance values.
Innovation Solution
The implementation of electrically conductive bearing retainers with an array of contact members that create a conductive path between the static and dynamic sides of a rotating joint, effectively closing the open Faraday cage volume and reducing EMI radiation by enhancing electrical conductivity across the interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional bearing retainers are used, then the bearing interface allows rotation, but the electrical resistance is high causing EMI radiation
Solution Approach 1:
The bearing retainer is constructed as a composite structure combining electrically conductive material (such as copper or copper alloy) with bearing functional elements. This composite design provides both the mechanical function of supporting ball bearings and the electrical function of conducting current to ground, thereby reducing EMI radiation while maintaining rotational capability
Solution Approach 2:
The invention merges the electrical conduction function with the mechanical bearing support function into a single integrated retainer component. The conductive material forms both the structural retainer that holds bearings and the electrical pathway to ground, eliminating the need for separate electrical connection components and ensuring low electrical resistance across the rotating interface
2Object-affected harmful factors
If the electrical resistance is reduced to meet customer requirements, then EMI radiation is suppressed, but the bearing interface complexity increases
Solution Approach 1:
The bearing retainer is designed as a multi-functional component that simultaneously performs mechanical support for ball bearings and electrical conduction to ground. This universal design reduces the overall system complexity by eliminating separate electrical connection components while meeting the stringent electrical resistance requirements for EMI suppression
3Reliability
If conductive material is added to reduce EMI, then electrical conductivity improves, but the bearing retainer weight increases
Solution Approach 1:
The retainer uses composite material construction combining conductive materials (such as copper or copper alloys) with bearing functional elements. This approach achieves the required electrical conductivity for EMI suppression while managing weight through material selection and structural optimization of the composite retainer design
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 solution significantly reduces EMI radiation emissions by creating a conductive path between the static and dynamic sides of the rotating joint, meeting the stringent resistance requirements and enhancing the operational reliability of turret systems.
Implementation Method 1
an array of contact members (116) for creating an electrical path between the static and dynamic sides of a dynamic bearing interface
Implementation Method 2
A Faraday cage, often simply referred to as a shield, is an enclosure formed of a conductive material and designed to exclude electromagnetic fields in an application of Gauss' law
Implementation Method 3
The motors are often powered with high frequency voltages that can generate extremely strong electromagnetic interference radiation (EMI) emissions
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
Electrically conductive bearing retainers create an electrical path between the static and dynamic sides of a rotating joint to block EMI radiation from entering or leaving a system. Concentric annular inner and outer bearing retainers with an array of conductive contact members therebetween are installed in contact with the inner and outer races of a dynamic bearing interface. Each contact member includes a base and tips. The outer bearing retainer ring has a recess for mounting a contact member and a notch for positioning the contact member tips to make contact with the inner bearing retainer ring. The inner bearing retainer ring includes a conductive contact surface. The contact member tips contact the conductive contact surface to create a dynamic shield between an inner bearing race and an outer bearing race.