Drive Unit Ground Line Routing for Common Mode Noise Reduction
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Solution Overview
Problem
Conventional electric motor designs in vehicles are prone to noise, which is transmitted as common mode noise and can interfere with in-vehicle radio systems, and existing solutions either reduce noise affecting the controller but increase noise leakage or lack understanding of noise paths.
Innovation Solution
A drive unit configuration that includes a rotating electric machine with a stator and rotor, a controller holding member, and a power supply connector that routes stray capacitance noise back to the power supply ground line, converting common mode noise into normal mode noise, thereby simplifying noise reduction and reducing radio interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the motor case and heat sink are connected to the vehicle body frame to reduce noise affecting the controller, then the noise affecting the controller is reduced, but the noise leaking out from the motor increases
Solution Approach 1:
The ground connection is segmented into two separate paths: one path connects the motor case and heat sink to the vehicle body frame for reducing controller noise, while another path provides a dedicated ground line from the power supply to the controller holding member for managing motor noise. This segmentation allows independent optimization of each noise path.
Solution Approach 2:
A ground line is introduced as an intermediary element that provides a controlled path for noise current. The ground line connects the power supply ground terminal to the controller holding member, serving as a mediator that directs noise current away from the motor case and heat sink, thereby reducing external noise leakage while maintaining controller noise protection.
2Object-generated harmful factors
If the ground line is coupled to the power supply ground terminal via the substrate and power supply connector, then the noise returns to the power supply as normal mode noise, but the configuration complexity increases
Solution Approach 1:
The ground line serves multiple functions simultaneously: it provides the return path for noise current, establishes a reference potential for the controller, and connects the power supply ground terminal to the controller holding member. By making the ground line multi-functional, the patent avoids adding separate dedicated noise management components, thereby reducing overall system complexity.
Solution Approach 2:
The existing substrate and power supply connector are utilized to create the ground line path, rather than requiring separate dedicated components. The substrate's ground traces and the power supply connector's ground terminals are made to serve the additional function of noise current return path, allowing the system to manage noise using already-present structural elements.
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 configuration effectively reduces common mode noise and minimizes radio noise leakage, enhancing noise reduction without increasing the motor's size or complexity.
Implementation Method 1
a heat generation element mounted on a heat generation element mounting surface, which is a controller holding member side surface of the substrate that enables heat dissipation from the heat generation element to the controller holding member
Implementation Method 2
a ground line coupled to a ground terminal of the power supply providing a conductive connection to the controller holding member via the substrate and the power supply connector
Data Source
AI summary
A drive unit that includes a rotating electric machine having a stator with winding wound on the stator and with a shaft rotating within the stator, and a rotor rotatable relative to the stator. The drive unit also includes a controller holding member disposed on one end of the rotating electric machine, and a controller having a substrate fixed to the controller holding member, a heat generation element mounted on a heat generation element mounting surface. The drive unit further includes a power supply connector connecting the substrate and a power supply, and a ground line coupled to a ground terminal of the power supply providing a conductive connection to the controller holding member via the substrate and the power supply connector. With this structure, the drive unit's common mode noise may be reduced.