Conductive Shaft Seal Structure for Stable Motor Grounding
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Solution Overview
Problem
Conventional sealing devices for electric motors experience unstable electrical continuity due to a small and variable contact area between the seal and the shaft, leading to noise issues in devices like AM radio receivers caused by induced currents.
Innovation Solution
A sealing device comprising an annular reinforcing ring, an electrically conductive elastic member with a lip that protrudes and is slidable, and at least one spring to press the lip against the shaft, ensuring stable electrical contact between the housing and the shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional seal is used to seal the gap between housing and shaft, then the structure is simple, but the electrical continuity is unstable due to small and variable contact area
Solution Approach 1:
The sealing device is divided into multiple functional components: an elastic member for sealing, a reinforcing ring for structural support, and a spring for maintaining contact pressure. This segmentation allows each component to optimize its specific function while collectively ensuring stable electrical continuity through the lip-shaft contact interface.
Solution Approach 2:
The sealing device combines multiple materials with different properties: an electrically conductive elastic material for the main body, a rigid reinforcing ring material, and a spring material. This composite approach enables simultaneous achievement of electrical conductivity, elastic sealing, and mechanical strength, resolving the contradiction between reliability and complexity.
2Reliability
If the contact area between seal and shaft is small, then the sealing device is compact, but the electrical continuity becomes unstable and prone to variation
Solution Approach 1:
The spring component provides dynamic contact pressure that automatically adjusts to variations in shaft position and seal deformation. This dynamic mechanism ensures stable electrical continuity by maintaining optimal contact pressure between the lip and shaft, even when the contact area is limited, preventing electrical discontinuity without requiring excessive contact area.
3Reliability
If an electrically conductive elastic material is used, then electrical continuity is improved, but the material selection and manufacturing become more complex
Solution Approach 1:
The patent specifies key parameters for the electrically conductive elastic material, including electrical conductivity requirements and elastic properties. By defining these parameters clearly, the invention guides material selection without requiring complex or exotic materials, maintaining ease of manufacture while ensuring reliable electrical continuity through the sealing device.
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 provides stable electrical continuity, reducing noise and potential differences between the housing and shaft, thereby minimizing damage to bearings and improving the reliability of the sealing device.
Implementation Method 1
at least one annular spring that presses the lip against the outer peripheral surface of the shaft
Implementation Method 2
The elastic member is made of an electrically conductive elastic material
Data Source
AI summary
A sealing device includes an annular reinforcing ring fixed to a housing, an annular elastic member that includes a fixing portion fixed to the reinforcing ring, and a lip that protrudes from the fixed portion and is in slidable contact with an outer peripheral surface of a shaft, and at least one annular spring that presses the lip against the outer peripheral surface of the shaft, the lip being between the at least one spring and the outer peripheral surface of the shaft. The elastic member is made of an electrically conductive elastic material. A contact surface, which is a part of the lip and is in contact with the outer peripheral surface of the shaft, is straight when viewed in a cross section defined by a plane that includes a central axis of the elastic member. A width of the at least one annular spring is greater than its thickness.