Electric Sliding Contact Shielding for Motor EMI Containment
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Solution Overview
Problem
Existing electric drive units with integrated electronic circuit boards suffer from electromagnetic interference (EMI) radiation, which can disrupt other electronic functions in motor vehicles, and the brush contact in the intermediate frame also contributes to interference radiation.
Innovation Solution
The electric machine incorporates a conductive sliding contact between the rotor shaft and the stator housing's ground contact, forming a Faraday cage with the stator housing and shielding plate to shield EMI radiation. This design optimally shields carbon brushes and anti-interference components, effectively reducing EMI across a wide frequency range, including up to 3 GHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an electronic circuit board is arranged radially outside the pole housing, then different electronic variants can be realized and the plug connector can be adapted according to space conditions, but the electronic circuit board and brush contact radiate electromagnetic interference radiation that disrupts other electronic functions
Solution Approach 1:
A shielding plate is introduced as an intermediary component between the electronic circuit board and the external environment. This shielding plate, connected to the rotor shaft via a sliding contact, acts as a mediator that blocks electromagnetic radiation from the electronic components and brush contacts, preventing EMI while allowing the adaptable electronic housing design to continue
Solution Approach 2:
The rotor shaft, which naturally rotates and provides a path for EMI radiation, is converted into a beneficial element by using it as the mounting structure for the shielding plate. The sliding contact between the shielding plate and rotor shaft transforms the rotating shaft from a potential EMI antenna into the support structure for the EMC shield, utilizing the existing rotational mechanism for protective purposes
2Object-generated harmful factors
If a sliding contact is formed between the rotor shaft and ground contact of the stator housing, then the rotor shaft is prevented from acting as an antenna for EMC radiation, but additional components and assembly steps are required
Solution Approach 1:
The sliding contact is designed to serve multiple functions simultaneously: it provides the electrical connection for the shielding plate to ground, maintains mechanical contact with the rotating rotor shaft, and enables the shielding plate to rotate with the shaft. This multi-functionality reduces the need for additional separate components, offsetting the added complexity with consolidated design benefits
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 prevents the rotor shaft from acting as an EMI antenna, creating a robust EMC shield that minimizes disruptive radiation, thereby enhancing the reliability and performance of the electric machine in motor vehicles.
Implementation Method 1
The stator housing together with the shielding plate and the rotor shaft forms a closed Faraday cage, which, as an EMC shield, shields the arising electromagnetic interference radiation outward
Implementation Method 2
forming an electrically conductive sliding contact between the rotor shaft and an electrical connection to the ground contact of the stator housing
Data Source
AI summary
Electric machine (10), in particular for adjusting movable parts in a motor vehicle, having a stator housing (22) which accommodates a stator (12) and a rotor (14), wherein the rotor (14) has a rotor shaft (16), and the stator housing (22) has an axial opening (24) through which the rotor shaft (16) projects out of the stator housing (22), wherein an electrically conductive shielding plate (29) is arranged transverse to the rotor shaft (16) and substantially covers the entire opening (24), and an electrically conductive sliding contact (77), which is electrically conductively connected to the shielding plate (29), is formed on the rotor shaft (16).