Planetary Multi-Speed Electric Axle for Compact High-Torque Packaging
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Solution Overview
Problem
Vehicle electrification demands high torque and efficient powertrains, especially for towing and payload, while existing systems face spatial and thermal constraints from internal combustion engines, and powershifting is desired in rear wheel drive powertrains to achieve high range and efficiency.
Innovation Solution
A multi-speed electric axle with an electric machine rotationally coupled to an input shaft and a planetary gear set, featuring clutches to selectively engage gears for high and low range operation, compactly packaged to fit various vehicle platforms, including hybrid vehicles with exhaust systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If internal combustion engines are used to power generators for high range and efficiency during towing, then range and efficiency are improved, but spatial constraints and thermal constraints are imposed on electrical components
Solution Approach 1:
The patent merges the electric machine, planetary gear set, differential, and clutch mechanisms into a single integrated electric axle assembly. This consolidation eliminates the need for separate engine-generator components, reducing spatial requirements while maintaining the ability to achieve high range and efficiency through electrical power delivery.
Solution Approach 2:
The electric axle assembly performs multiple functions: it provides torque multiplication through the planetary gear set, distributes power to both wheels via the differential, enables powershifting through clutch mechanisms, and delivers electrical power. This multi-functionality replaces the need for separate engine-generator systems, freeing up spatial space.
2Power
If electric vehicle weight increases due to added mass from traction batteries, then torque and power demands increase, but packaging constraints are worsened
Solution Approach 1:
By combining the electric machine, transmission components, and differential into a single compact axle assembly, the patent reduces the overall volume required to accommodate high torque and power delivery systems. This integrated design allows the vehicle to meet increased torque demands without proportionally increasing packaging volume.
Solution Approach 2:
The planetary gear set is nested within the electric axle housing, with the differential and clutch mechanisms arranged in a compact, space-efficient configuration. This nesting approach allows multiple functional components to occupy overlapping or adjacent spatial volumes, maximizing power density while minimizing packaging constraints.
3Use of energy by moving object
If powershifting is implemented in rear wheel drive powertrains, then range and efficiency are improved, but device complexity increases
Solution Approach 1:
The patent combines the powershifting mechanism with the differential and planetary gear set in a single integrated assembly. The clutch mechanisms are positioned to directly engage with the planetary gear components, eliminating the need for separate powershifting systems and reducing overall device complexity while maintaining the ability to achieve multiple operating gears for improved range and efficiency.
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 multi-speed electric axle achieves increased compactness and efficiency, allowing for higher torque and reduced spatial constraints, enhancing vehicle performance and packaging flexibility.
Implementation Method 1
a planetary gear set including a ring gear meshed with a gear fixedly coupled to the input shaft
Implementation Method 2
a first clutch configured to selectively ground a sun gear in the first planetary gear set
Implementation Method 3
a second clutch configured to selectively rotationally couple a sun gear in the planetary gear set with the shaft
Implementation Method 4
an electric machine rotationally coupled to an input shaft
Data Source
AI summary
A system and method for a multi-speed electric axle. The multi-speed electric axle includes, in one example, an electric machine rotationally coupled to an input shaft, a planetary gear set including a ring gear meshed with a gear fixedly coupled to the input shaft and a carrier that is rotationally coupled to a shaft, a first clutch configured to selectively ground a sun gear in the first planetary gear set, and a second clutch configured to selectively rotationally couple a sun gear in the planetary gear set with the shaft.