Conductive Labyrinth Seal for EV Motor Shaft Current Drainage
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Solution Overview
Problem
Electric machines in hybrid and electric vehicles face issues with electrical currents induced in shafts causing mechanical and electromagnetic interference, which can damage components and degrade lubricating greases, leading to increased drag and component damage.
Innovation Solution
A labyrinth seal with interleaved conductive regions and conductive grease is used between the rotor shaft and housing to direct electrical currents away from bearings, forming an electrically conductive pathway that mitigates interference and reduces damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional seal is used between the shaft and housing, then the structure is simple, but electrical currents induced in the shaft cause mechanical and electromagnetic interference that damages components and degrades lubricating grease
Solution Approach 1:
The seal is divided into multiple segments including a first seal ring, second seal ring, and intermediate ring with distinct functions. Each ring contains lubricating grease in its labyrinthine channel, creating segmented zones that collectively manage electrical currents while maintaining structural simplicity
Solution Approach 2:
The labyrinthine seal structure with conductive lubricating grease acts as an intermediary between the shaft and housing, providing a controlled pathway for electrical currents to dissipate safely without directly contacting and damaging sensitive components like bearings
2Productivity
If the shaft is allowed to rotate freely, then the operational efficiency is high, but electrical currents induced in the shaft cause increased drag and component damage
Solution Approach 1:
The seal converts harmful electrical currents induced in the rotating shaft into a beneficial effect by providing a controlled dissipation pathway. The conductive lubricating grease in the labyrinthine channel safely channels electrical currents away from sensitive components, transforming a harmful byproduct of shaft rotation into a manageable phenomenon
Solution Approach 2:
The seal modifies the electrical conductivity parameters in the gap between shaft and housing by introducing conductive lubricating grease. This changes the electrical field distribution and current flow characteristics, reducing electromagnetic interference and drag while allowing continuous shaft rotation
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 directs electrical currents away from sensitive components, reducing mechanical and electromagnetic interference, thereby minimizing damage and drag, and enhancing the operational efficiency of electric machines in vehicles.
Implementation Method 1
A conductive grease is disposed within the tortuous channel. The inner ring, outer ring, and conductive grease are configured to direct electrical currents induced in the shaft to the housing.
Implementation Method 2
The inner and outer rings have interleaved protrusions defining a tortuous channel extending axially between first and second ends of the labyrinth seal.
Data Source
AI summary
A vehicle includes an electric machine. The electric machine is configured to propel the vehicle. The electric machine has a stator, a rotor, and a labyrinth seal. The stator is secured to a housing. The rotor is secured to a shaft and is configured to transfer rotational power generated by the electric machine to at least one drive wheel via the shaft. The labyrinth seal is disposed between the shaft and the housing. The labyrinth seal comprises inner and outer rings secured to the shaft and housing, respectively. The inner and outer rings have interleaved protrusions defining a tortuous channel extending axially between first and second ends of the labyrinth seal. A conductive grease is disposed within the tortuous channel. The inner ring, outer ring, and conductive grease are configured to direct electrical currents induced in the shaft to the housing.