Nested Planetary e-Axle Gearbox for Tight Cross-Car Packaging
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Solution Overview
Problem
Existing vehicle subframe architectures face challenges in achieving tight cross-car packaging for multi-speed gearboxes integrated with electric motors and differentials, particularly in two-speed e-synchronous shifting architectures.
Innovation Solution
An electric drive axle design featuring a gearbox with a higher and lower range planetary gear set coupled via a clutch, allowing mechanical power to be directed through either or both gear sets based on the clutch position, enabling compact and efficient operation in different modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a two-speed e-synchronous shifting architecture is used to integrate multi-speed gearbox with electric motor and differential, then the vehicle can operate in different speed ranges, but the cross-car packaging becomes constrained and difficult to achieve tight integration
Solution Approach 1:
The patent implements a nested planetary gear architecture where a first planetary gear set and a second planetary gear set are concentrically arranged around a common sun gear. The second planetary gear set is positioned inside the first planetary gear set, allowing both gear sets to share the same central space. This nested configuration enables multi-speed operation while maintaining a compact cross-car footprint that satisfies tight packaging constraints.
Solution Approach 2:
The patent employs a single electric motor that can operate across multiple speed ranges by coupling it to both the first and second planetary gear sets. The motor serves multiple functions: it can drive the vehicle in high-range mode through the first planetary gear set, in low-range mode through the second planetary gear set, and in e-synchronous mode where both gear sets operate simultaneously. This multi-functional approach eliminates the need for separate motors for different speed ranges, reducing overall system complexity and packaging requirements.
2Volume of moving object
If multiple planetary gear sets are integrated in a compact architecture, then space efficiency is improved, but the device complexity increases
Solution Approach 1:
The patent implements a nested planetary gear architecture where a first planetary gear set and a second planetary gear set are concentrically arranged around a common sun gear. The second planetary gear set is positioned inside the first planetary gear set, allowing both gear sets to share the same central space. This nested configuration enables multi-speed operation while maintaining a compact cross-car footprint that satisfies tight packaging constraints.
Solution Approach 2:
The patent merges multiple planetary gear sets into a single integrated assembly that shares common components. Both the first and second planetary gear sets share a common sun gear and are concentrically arranged around the same central axis. The carrier of the second planetary gear set is coupled to the ring gear of the first planetary gear set, creating a unified structure that reduces the number of separate components and simplifies the overall architecture despite the multi-speed capability.
Data Source
AI summary
An electric drive axle with a two-speed gearbox and shifting system is described herein that advantageously reduces a size and volume of the electric drive axle for tight cross-car packaging in a constrained environment for integration of the gearbox with an electric machine, inverter, and differential. The gearbox includes higher and lower range planetary gear sets that are arranged coaxially with the electric machine. The higher and lower range planetary gear sets can be operated in a higher range mode, where mechanical power from an electric machine bypasses the lower range planetary gear set, and in a lower range mode, where mechanical power from the electric machine travels through the lower range planetary gear set and the higher range planetary gear set. The described configuration expands a functionality of the gearbox and increases the axle's capability with regard to operating range and driving environment.