Electric Axle Drive Torque Vectoring and Shifting
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Solution Overview
Problem
Existing electric axle drives for motor vehicles face inefficiencies in torque transmission and lack effective solutions for differential torque management between output shafts, particularly in shifting gears under load and during traction and overrun operations.
Innovation Solution
The electric axle drive incorporates two spur gear stages and a planetary gear mechanism with shifting elements, including a clutch and a freewheel, allowing for torque transmission optimization and differential torque management through a torque-vectoring unit or transverse lock, enabling efficient operation in two gears across a wide speed range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the planetary gear mechanism is shifted as a block in one gear and the transmission ratio is shifted in the other gear, then gear shifting under load is enabled, but the torque transmission efficiency is reduced due to the complex shifting mechanism
Solution Approach 1:
The planetary gear mechanism is designed to dynamically change its operating mode between two states: (1) shifted as a block where all planetary gears move together, and (2) shifted transmission ratio where the planetary carrier is stationary and only sun gear and ring gear rotate. This dynamic switching enables gear shifting under load while maintaining torque transmission efficiency through optimized power flow paths in each mode.
Solution Approach 2:
The shifting mechanism is segmented into two independent functions: the planetary carrier that can be independently controlled to either rotate with the planetary gears or remain stationary, and the sun gear that can be independently controlled. This segmentation allows the system to achieve both gear shifting capability and efficient torque transmission by selectively activating different components based on operating conditions.
2Adaptability or versatility
If a clutch is used to connect ring gear and sun gear or planetary carrier, then differential torque management is enabled, but the device complexity increases
Solution Approach 1:
The clutch is designed as a multi-functional component that serves multiple purposes: (1) connecting the ring gear to the sun gear for differential torque management, (2) connecting the ring gear to the planetary carrier for torque transmission, and (3) enabling the planetary carrier to be selectively engaged or disengaged. This universal component reduces overall system complexity by consolidating multiple shifting functions into a single device rather than requiring separate mechanisms for each function.
3Adaptability or versatility
If two spur gear stages are used with planetary gear mechanism, then wide speed range operation is enabled, but the manufacturing precision requirements increase
Solution Approach 1:
The system achieves wide speed range operation by changing the operational parameters of the planetary gear mechanism rather than relying solely on precise manufacturing of multiple gear stages. By varying the engagement state of the planetary carrier (rotating vs. stationary) and using the clutch to connect or disconnect different gear elements, the system can achieve multiple effective gear ratios with standard manufacturing tolerances, reducing the stringency of manufacturing precision requirements while maintaining adaptability across a wide speed range.
Data Source
AI summary
An electric axle drive has a transmission arrangement with two gears, with an electric machine for driving two output shafts of the axle of the motor vehicle, a first spur gear stage which can be driven by the electric machine for driving an intermediate shaft and a planetary carrier of a planetary gear mechanism, which planetary carrier is connected fixedly to the intermediate shaft and receives planetary gears, and with an internal gear of the planetary gear mechanism for driving a second spur gear stage, a sun gear of the planetary gear mechanism and shifting elements for shifting the two gears. A first shifting element is configured as a clutch, by way of which the internal gear and the sun gear or the internal gear and the planetary carrier or the sun gear and the planetary carrier can be connected in a torque-transmitting manner.