Coaxial Multi-Speed Electric Axle for Compact High-Torque Packaging
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Solution Overview
Problem
Vehicle electrification demands compact electric axles with high torque and efficiency, constrained by spatial limitations from other vehicle systems.
Innovation Solution
A multi-speed electric axle with a coaxial architecture utilizing three planetary gear sets and a differential, featuring a clutch to switch between higher and lower range modes, reducing bearing and gear losses for enhanced efficiency and torque capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a multi-speed electric axle with three planetary gear sets is used, then torque capability and efficiency are improved, but device complexity increases
Solution Approach 1:
The patent implements a nested planetary gear architecture where three planetary gear sets are arranged coaxially, with each gear set containing sun gears, planet gears, and ring gears that are interconnected. The second planetary gear set is nested within the first, and the third planetary gear set is nested within the second, creating a compact multi-speed transmission system that achieves high torque multiplication while maintaining a compact structure.
Solution Approach 2:
The patent employs a clutch mechanism that dynamically engages and disengages to lock or unlock the sun gear and carrier of the second planetary gear set, enabling the system to switch between higher range mode (when clutch is engaged) and lower range mode (when clutch is disengaged). This dynamic control allows the gear train to adapt its complexity based on operating conditions, providing high torque when needed while maintaining simpler operation during normal driving.
2Volume of moving object
If a compact coaxial architecture is used, then spatial constraints are reduced, but manufacturing complexity increases
Solution Approach 1:
The coaxial nested arrangement of three planetary gear sets allows the entire multi-speed transmission system to be packaged in a compact cylindrical volume, with each gear set concentrically positioned around the previous one. This nesting approach minimizes the radial and axial dimensions of the axle assembly, making it suitable for vehicles with tight packaging constraints while the modular nested structure facilitates standardized manufacturing processes.
Solution Approach 2:
The planetary gear sets share common components and mounting structures, with the carrier of one gear set serving as the housing for the next gear set. This multi-functional design reduces the number of separate parts that need to be manufactured and assembled, as each component serves multiple functions within the nested architecture, thereby simplifying the overall manufacturing process despite the compact design.
3Loss of energy
If the clutch locks the sun gear and carrier in higher range mode, then bearing and gear losses are reduced, but torque capability is reduced
Solution Approach 1:
The clutch mechanism provides dynamic control over the engagement of the second planetary gear set, allowing the system to operate in higher range mode with the clutch engaged to reduce losses during efficient cruising conditions, and switching to lower range mode with the clutch disengaged when maximum torque capability is required. This dynamic switching enables the system to optimize between efficiency and torque based on real-time driving conditions.
Solution Approach 2:
The system changes its effective gear ratio parameter by engaging or disengaging the clutch, which locks or unlocks the sun gear and carrier of the second planetary gear set. When locked, the system operates with a higher effective gear ratio that reduces bearing and gear losses for improved efficiency. When unlocked, the system can access lower gear ratios that provide higher torque multiplication, thus changing the operational parameter to match driving requirements.
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 sun gear in a first planetary gear set, a second planetary gear set rotationally coupled to a carrier in the first planetary gear set, a third planetary gear set rotationally coupled to the second planetary gear set, and a differential rotationally coupled to the third planetary gear set. In the multi-speed electric axle, the electric machine, the first planetary gear set, the second planetary gear set, the third planetary gear set, and the differential are coaxially arranged.