Coaxial Electric Drive Assembly for Compact Axle Integration
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Solution Overview
Problem
Existing electric drives for motor vehicles require large space due to the separation of electric machines, transmission gearings, and differential drives, which complicates their integration into compact axle designs, especially in hybrid vehicles where high-speed electric motors produce low torque necessitating complex transmission systems.
Innovation Solution
A compact electric drive assembly featuring a hollow motor shaft with a coaxial arrangement of an electric machine, transmission gearing, and differential drive, utilizing a crown gear and driven gear connected in a rotationally fixed manner to reduce the transmission ratio and space requirements, allowing for efficient torque transmission to vehicle wheels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If electric motors are configured for high speeds up to 12,000 r.p.m. to provide power, then power output is improved, but torque values remain low at about 50 Nm requiring complex transmission gearings
Solution Approach 1:
The patent combines the electric motor, transmission gearing, and differential drive into a single integrated unit with a common housing. The motor shaft is directly coupled to the drive gear, eliminating the need for separate mounting and complex coupling mechanisms, thereby reducing overall system complexity while maintaining high power output capability
Solution Approach 2:
The motor shaft serves multiple functions simultaneously: it acts as the rotor shaft for the electric motor, the drive shaft for the transmission gearing, and the input shaft for the differential drive. This multi-functionality reduces the number of separate components needed and simplifies the overall transmission system
2Force
If transmission gearings are used to translate high speed into low speed, then torque is increased, but space requirements increase due to separation of components
Solution Approach 1:
The transmission gearing and differential drive are merged into a single integrated unit where the drive gear is directly connected to the motor shaft and the crown gear is directly connected to the differential carrier. This eliminates the need for separate mounting spaces and reduces the overall volume required for the power transmission system
Solution Approach 2:
The patent employs a nested arrangement where the motor shaft is positioned centrally and the drive gear is mounted on it, with the crown gear and differential carrier arranged around and around them respectively. This concentric nesting minimizes the radial and axial space requirements of the transmission system
3Ease of manufacture
If electric machine, transmission gearing, and differential drive are arranged separately, then each component can be optimized independently, but the overall assembly requires large space
Solution Approach 1:
The electric machine, transmission gearing, and differential drive are combined into a single integrated assembly with a common housing and shared mounting structure. The motor shaft is directly coupled to the drive gear, and the crown gear is directly connected to the differential carrier, eliminating the need for separate mounting brackets and coupling mechanisms, thereby reducing overall assembly space
Solution Approach 2:
The patent transitions from a linear or distributed arrangement of components to a three-dimensional concentric arrangement. The motor shaft, drive gear, crown gear, and differential carrier are arranged in nested concentric layers around a central axis, efficiently utilizing radial and axial space while maintaining independent component optimization
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 compact design enables efficient energy conversion and storage, reduces space requirements, and allows for flexible integration into various vehicle axles, enhancing the performance and versatility of electric drives in hybrid vehicles by minimizing the need for extensive transmission gearing.
Implementation Method 1
an electric machine (3), a transmission gearing (5) and a differential drive (6)
Implementation Method 2
the transmission gearing (5) is configured to translate a high speed into a low speed
Implementation Method 3
the differential drive (6) divides the introduced torque to two sideshafts for driving the vehicle wheels
Data Source
AI summary
An electric drive for driving a motor vehicle comprises an electric machine, a transmission gearing and a differential drive; wherein the electric machine comprises a motor shaft that is rotatably driveable around a first rotational axis A1; wherein the transmission gearing comprises a drive gear connected to the motor shaft, at least one intermediate gear rotatingly drivable by the drive gear around a second rotational axis A2, a crown gear rotatingly drivable by the intermediate gear around a third rotational axis A3, and a driven gear connected to the crown gear; wherein the driven gear and the crown gear are arranged coaxially relative to one another and are connected to one another in a rotationally fixed way so that they rotate jointly around the third rotational axis A3, wherein the third rotational axis A3 crosses the first rotationally axis A1. A driveline assembly can have such an electric drive.