Electric Drive Unit Fluid Path for Pump-Free Cooling and Lubrication
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Solution Overview
Problem
Existing electric drive units face challenges in efficiently conveying and managing fluid flow for cooling and lubrication, particularly in managing pressure and optimizing fluid flow paths within the drive units.
Innovation Solution
The electric drive unit incorporates a housing with a collar portion, baffles, seals, and conduits that define a fluid flow path, where fluid flow is directed through passages, disrupted by baffles, and channeled through seals and conduits to manage pressure and facilitate lubrication of bearings, all without the need for an auxiliary pump.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a traditional fluid flow path is used in electric drive units, then the structure is simple, but the fluid flow efficiency is poor and pressure drops occur
Solution Approach 1:
The housing is segmented into multiple functional portions: a first holding portion with baffles for fluid distribution, a collar portion for directing fluid onto the rotor shaft, a second holding portion for collecting fluid, and conduits for fluid return. This segmentation allows each portion to optimize fluid flow in its specific zone, improving overall fluid flow efficiency while managing the complexity through modular functional design.
Solution Approach 2:
The fluid flow path transitions from simple linear flow to multi-dimensional flow patterns. Fluid is distributed circumferentially around the rotor shaft through the collar portion, creating radial and circumferential flow components. The baffles in the first holding portion create complex three-dimensional flow patterns that enhance cooling efficiency throughout the motor housing volume.
2Temperature
If fluid flow path is extended to improve cooling coverage, then cooling effectiveness increases, but pressure drops increase
Solution Approach 1:
The first holding portion with baffles performs preliminary fluid distribution before fluid reaches the collar portion. Fluid is pre-distributed circumferentially around the rotor shaft area, ensuring uniform cooling coverage from the start. This preliminary distribution prevents localized pressure drops that would occur if fluid had to travel long distances to reach different cooling zones.
Solution Approach 2:
The collar portion acts as an intermediary element between the first and second holding portions. It receives fluid from the first holding portion, redistributes it onto the rotor shaft and surrounding areas, and channels excess fluid to the second holding portion. This intermediary function maintains fluid pressure by creating multiple short flow paths instead of one long path, reducing overall pressure drop while achieving comprehensive cooling.
3Productivity
If auxiliary pumps are added to maintain fluid pressure, then fluid flow is improved, but device complexity and cost increase
Solution Approach 1:
The housing structure itself provides fluid flow management functions through its internal geometry. The baffles in the first holding portion, the collar portion's shape, and the conduit arrangement create self-regulating fluid distribution and return paths. The system uses the natural circulation created by the electric motor's operation and gravity to maintain fluid flow, eliminating the need for auxiliary pumps while keeping the device simple.
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 enhances fluid flow efficiency, reduces pressure within the flow path, and ensures effective lubrication and cooling of components, improving overall performance and reducing the need for additional pumping systems.
Implementation Method 1
rotation of the rotor shaft encourages circumferential flow of fluid along the first holding portion of the housing
Implementation Method 2
the plurality of baffles are configured to disrupt the circumferential flow of fluid along the first holding portion of the housing
Implementation Method 3
a first seal positioned radially between the outer rotor shaft surface and the first holding portion of the housing
Implementation Method 4
a plurality of conduits extending between the first holding portion and the second holding portion
Implementation Method 5
a bearing positioned radially between the output shaft and the second holding portion of the housing and configured to support and facilitate rotation of the output shaft relative to the housing
Data Source
AI summary
A drive unit for a vehicle includes an electric motor, an output shaft, and a housing. The electric motor includes a rotor shaft having an inner surface with a hollow accessible via an opening at an axial end of the rotor shaft and an outer surface opposite the inner surface. The output shaft extends into the hollow through the opening. The housing houses the electric motor and defines a fluid flow path for fluid. The housing has a collar portion about the output shaft, a first holding portion on a first axial side of the collar portion and having baffles that are circumferentially offset from each other, a second holding portion on a second axial side of the collar portion opposite the first axial side, such that the collar portion is positioned axially between the first and second holding portions, and conduits extending between the first and second holding portions.