EV Drivetrain Recirculation Shaft Layout for High Reduction Torque
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Solution Overview
Problem
Heavy-duty electric vehicles face challenges with high reduction ratios in their drivetrains, leading to heavy and bulky gears that increase weight and reduce ground clearance due to the need for highly loaded gears.
Innovation Solution
A compact and lightweight drivetrain design featuring a clutch system that switches between two gear configurations, distributing load between the main shaft and recirculation shaft, and using a dog clutch for efficient torque transmission, allowing for a higher reduction ratio while reducing gear and pinion load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a high reduction ratio is used to achieve high vehicle loading capacity, then the torque necessary to start the vehicle is provided, but the gears become heavy and bulky, increasing weight and reducing ground clearance
Solution Approach 1:
The drivetrain is segmented into two independent power transmission paths: a direct path (main shaft → main pinion → first gearwheel → output shaft) and a recirculating path (main shaft → second pinion → second gearwheel → recirculation shaft → first gearwheel → output shaft). This segmentation allows the load to be distributed across multiple gear stages, reducing the burden on individual gears and enabling lighter gear design while maintaining high reduction ratio for torque multiplication.
2Force
If a high reduction ratio is used to achieve high vehicle loading capacity, then the torque necessary to start the vehicle is provided, but the gears become bulky, increasing drivetrain volume and reducing ground clearance
Solution Approach 1:
The recirculation shaft is arranged parallel to the output shaft, creating a three-dimensional power transmission layout that efficiently utilizes available space. This spatial arrangement allows the recirculating path to coexist with the direct path without significantly increasing the overall drivetrain envelope, thereby reducing ground clearance impact while achieving high reduction ratio for torque multiplication.
3Weight of moving object
If the load is distributed between main shaft and recirculation shaft through dual pinion-gearwheel meshing, then gear and pinion load is reduced enabling lighter design, but the device complexity increases
Solution Approach 1:
The first gearwheel serves multiple functions: it is driven by the main pinion in the direct path, drives the output shaft, and is also driven by the recirculation pinion in the recirculating path. Similarly, the second gearwheel and recirculation shaft form an integrated recirculating loop. This multi-functionality reduces the need for separate dedicated components, managing complexity while achieving load distribution for lighter gear design.
Data Source
AI summary
A drivetrain includes a main shaft, driven by an electric motor, and a wheel output shaft. Two gearwheels, mounted around the output shaft to rotate freely, are meshing with respective main pinions integral with the main shaft. A clutch system car engage either one of the gearwheel with the output shaft. To reduce the load applied to the gearwheels, the drivetrain includes a recirculation shaft, freely rotating relative to a housing of the drivetrain, and two recirculation pinion, integral with the recirculation shaft, each meshing with a respective gearwheel. When the clutch system engages one of the gearwheel with the output shaft, the recirculation shaft is driven by the main shaft through the other gearwheel meshing with the respective main and recirculation pinions, and the output shaft is driven both by the main and recirculation shafts, through the engaged gearwheel meshing with the respective main and recirculation pinions.