Motor Shaft Grounding Structure for Reliable Shaft Current Discharge
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Solution Overview
Problem
Existing methods for preventing shaft current in new energy vehicle motors, such as using insulating bearings, conductive grease, and shaft grounding brushes, are costly and do not fully prevent electrical corrosion due to residual potential differences between the motor shaft and housing.
Innovation Solution
A motor design incorporating a conductive part, elastic body, and fastener that conduct shaft current to the motor end cover through a top hole in the motor shaft, utilizing a conductive part and elastic body to maintain contact during rotation and axial movement, reducing the need for expensive materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If insulating bearings are used to block shaft current, then the shaft current is prevented from passing through, but the cost increases and residual potential difference still causes corrosion
Solution Approach 1:
The patent extracts the shaft current grounding function from the bearing system by providing a separate grounding brush assembly that contacts the motor shaft directly. This separates the current conduction path from the bearing, allowing standard bearings to be used while still preventing shaft current damage, thereby reducing cost while maintaining reliability.
Solution Approach 2:
The grounding brush acts as an intermediary component between the motor shaft and the housing ground. It provides a dedicated low-resistance path for shaft current to flow to ground, preventing current from passing through the bearing oil film, thus protecting the bearing without requiring expensive insulating bearings.
2Reliability
If conductive grease or shaft grounding brushes are used to conduct shaft current out, then electrical corrosion is prevented, but the cost increases
Solution Approach 1:
The patent employs a simple carbon brush assembly that is inexpensive to manufacture and replace. This grounding brush provides effective shaft current conduction at a fraction of the cost of insulating bearings, accepting that the brush may wear and need replacement but offering a much lower initial cost solution.
Solution Approach 2:
The patent changes the approach from modifying bearing properties (insulating bearings) or adding expensive conductive materials (conductive grease) to using a simple carbon brush with appropriate electrical conductivity. This parameter change in the conduction path material achieves corrosion prevention at lower cost.
3Device complexity
If a fixed conductive connection is used for shaft grounding, then the structure is simple, but reliability decreases during axial movement
Solution Approach 1:
The patent introduces a spring-loaded mechanism in the grounding brush assembly that allows dynamic adjustment of the contact pressure between the brush and motor shaft. This dynamic structure maintains reliable electrical contact during axial movement and thermal expansion while keeping the overall grounding structure simple and self-adjusting.
Solution Approach 2:
The spring in the grounding brush assembly provides beforehand cushioning by pre-loading the contact surface. This ensures that even during axial movement or vibration, the brush maintains continuous contact with the motor shaft, preventing loss of grounding connection without requiring complex active control mechanisms.
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 eliminates shaft current with high reliability and low cost by maintaining continuous contact through elastic means, reducing the risk of electrical corrosion and simplifying maintenance.
Implementation Method 1
an elastic body that is installed in the passage, and an end of the elastic body abuts against the other end of the conductive part
Data Source
AI summary
A motor and an electric drive system are proposed. The motor comprises a motor shaft, a motor end cover, a conductive part, an elastic body and a fastener. A top hole is provided at an end of the motor shaft. A passage is provided in the motor end cover, and the passage faces the top hole. The conductive part is installed in the passage and abuts against an inner ring of the top hole. The elastic body is installed in the passage and abuts against the conductive part. The fastener abuts against the elastic body and is connected to the passage, and is used to conduct out a shaft current induced by the motor shaft to the motor end cover through the conductive part, the elastic body and the fastener in sequence. According to the utility model, the shaft current can be conducted out by means of the conductive part and the inner ring of the top hole, and the motor shaft can also achieve a certain area of contact during the rotation, and the effect of eliminating the shaft current is good. The utility model also proposes an electric drive system.