Electric Powertrain Dry Sump Lubrication Splash Loss Reduction
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Solution Overview
Problem
Existing powertrain assemblies for electric and hybrid vehicles face high 'splash losses' due to the use of 'wet sump' lubrication systems, which require complex and costly oil tight seals and separate lubrication systems for the gearbox and axle, and struggle with compactness due to the need for additional oil storage areas, especially when trying to reduce power losses associated with high-speed electric motor operation.
Innovation Solution
A powertrain assembly with a dry sump lubrication system where the gearbox oil storage area is separate from the gearbox oil sump and formed within the axle oil sump, utilizing a scavenge pump to retrieve oil from the gearbox sump and convey it to a storage area, and a main pump to distribute it to the gearbox gears, reducing oil levels and splash losses without the need for additional reservoirs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wet sump lubrication system is used in the gearbox, then the gears are effectively lubricated, but splash losses increase and energy efficiency decreases
Solution Approach 1:
The lubrication system is segmented into two separate circuits: a wet sump circuit for the axle (providing effective lubrication through oil immersion) and a dry sump circuit for the gearbox (reducing splash losses through controlled oil distribution). The gearbox uses a pump to deliver oil to gear surfaces rather than allowing gears to churn through oil, while the axle retains traditional wet sump lubrication for optimal performance.
Solution Approach 2:
Different lubrication approaches are applied to different parts of the powertrain based on their specific requirements. The gearbox, operating at high speeds with sensitive gears, receives controlled oil delivery via pump and spray nozzles (dry sump). The axle, with its different operational characteristics, uses traditional wet sump immersion lubrication. This local differentiation optimizes both energy efficiency and lubrication effectiveness.
2Reliability
If separate lubrication systems are used for gearbox and axle, then each component is optimized, but device complexity and cost increase due to oil tight seals required
Solution Approach 1:
A common oil reservoir serves as an intermediary structure that houses both the wet sump lubrication system for the axle and the dry sump lubrication system for the gearbox. This shared reservoir eliminates the need for complex oil tight seals between separate systems, while still allowing independent lubrication circuits with separate pumps, filters, and control mechanisms for each component.
3Force
If a wide gear reduction ratio is implemented through multiple reduction stages, then torque demand is fulfilled, but the gearbox size increases and available space for other parts decreases
Solution Approach 1:
The powertrain integrates the electric motor, gearbox with wide gear reduction, and axle into a closely coupled architecture where the motor is positioned near the axle and the gearbox connects them directly. This merging of components into a compact powertrain package achieves the required torque multiplication through multiple reduction stages while minimizing the overall volume occupied by these subsystems.
4Device complexity
If electric motor and gearbox are positioned in the vicinity of the drive wheel axle, then compact design is achieved, but space for batteries and suspension assemblies is reduced
Solution Approach 1:
The powertrain components are arranged in a three-dimensional configuration around the drive wheel axle, utilizing vertical and radial spaces rather than only linear extensions. The electric motor, gearbox, and axle are positioned in a compact volumetric arrangement that optimizes space utilization in multiple dimensions, reducing the footprint while maintaining functional requirements.
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
This configuration reduces splash losses and improves efficiency by eliminating the need for complex oil seals and additional storage, allowing for a more compact design while maintaining effective lubrication, and synergistically reduces losses at both the gearbox and axle levels.
Implementation Method 1
a scavenge pump and a first duct configured to retrieve oil from the gear box oil sump and to convey the retrieved oil up to the oil storage area
Implementation Method 2
a main pump and a second duct configured to convey oil from the storage oil area to lubricate the gears of the gearbox
Implementation Method 3
A powertrain assembly with a dry sump lubrication system where the gearbox oil storage area is separate from the gearbox oil sump and formed within the axle oil sump, utilizing a scavenge pump to retrieve oil from the gearbox sump and convey it to a storage area, and a main pump to distribute it to the gearbox gears, reducing oil levels and splash losses
Data Source
AI summary
A powertrain assembly includes one or several electric motors, a gearbox comprising a gearbox housing, an axle comprising: an axle housing, movable parts inside axle housing, comprising a shaft for a wheel, a lubricating system comprising an axle lubricating device comprising an axle oil sump and a gearbox lubricating device comprising a gearbox oil sump inside the gearbox housing which is a dry sump having an oil storage area which is separate from said gearbox oil sump, a scavenge pump and a first duct configured to retrieve oil from gear box oil sump and to convey the retrieved oil up to the oil storage area, and a main pump and a second duct configured to convey oil from the storage oil area to lubricate the gears of the gearbox.