Compact Electric Drive Unit With Differential Torque Split
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Solution Overview
Problem
The need for compact and cost-effective drive units in vehicles, particularly those driven by electric motors, is not adequately addressed by existing technologies, especially in all-wheel-drive hybrid vehicles where independent power sources are required for each axle, leading to inefficiencies and increased weight.
Innovation Solution
A compact electric drive unit design that employs a single electric motor to drive a pair of opposite side wheels using an input differential to split torque into two paths, each path having a pinion gear and transfer shaft assemblies that transfer torque to final drive gears, with a locking device to selectively connect or disconnect the input differential, allowing for efficient torque distribution and reduced radial loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a single electric motor is used to drive opposite side wheels, then weight is reduced and cost is decreased, but torque distribution to multiple axles becomes more complex
Solution Approach 1:
The drive unit is segmented into multiple independent torque paths, each with its own pinion gear and transfer shaft assembly. The single motor's torque is divided by a differential into two separate paths, with each path containing a pinion gear that drives two transfer shafts (front and rear). This segmentation allows one motor to efficiently power multiple wheels while maintaining manageable complexity in each individual path.
Solution Approach 2:
Multiple torque paths are merged into a single integrated drive unit architecture. The differential combines the motor's output torque and distributes it to two pinion gears, which then share the torque distribution function with their respective transfer shaft assemblies. This merging achieves compactness and weight reduction while the modular path design controls complexity.
2Loss of energy
If torque is distributed through multiple paths with pinion gears, then efficiency is improved and radial loads are reduced, but device complexity increases
Solution Approach 1:
Each torque path is designed with specific local optimizations: pinion gears are positioned and sized to minimize radial loads on their respective shafts, and transfer shafts are configured with appropriate support bearings. The differential is designed to distribute torque evenly between paths. These local quality improvements reduce energy losses in each path while keeping the overall complexity manageable through repetition of optimized modules.
3Volume of moving object
If a compact drive unit architecture is implemented, then vehicle size is reduced and weight is decreased, but manufacturing precision requirements increase
Solution Approach 1:
The compact drive unit is segmented into standardized torque paths that can be manufactured and assembled as modules. Each path contains a pinion gear and transfer shaft assembly that can be precision-manufactured independently using standard gear cutting processes. This modular segmentation allows for controlled manufacturing precision in each module while achieving overall compactness through their integration around a central differential.
Data Source
AI summary
Compact electric drive units and vehicles with such drive units are provided. An exemplary electric drive unit includes an electric motor configured to provide an electric motor torque; an input differential configured to split the electric motor torque into a first path and a second path; a final drive gear on each path; a pinion gear on each path; and a rear transfer shaft assembly and a front transfer shaft assembly on each path. Further, each pinion gear is configured to transfer torque to a respective rear transfer shaft assembly and a respective front transfer shaft assembly, and the respective rear transfer and front transfer shaft assemblies are configured to transfer torque to the respective final drive gear.