Electric Drive Axle Gearbox with Single-Clutch Planetary Range Shifting
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Solution Overview
Problem
Existing electric vehicle transmissions, such as those described in US 2016/0003351 A1, require complex structural architectures and control strategies due to the use of multiple clutches for two-speed operation, limiting their efficiency and applicability in various vehicle platforms.
Innovation Solution
An electric drive axle with a gearbox that includes a higher range planetary gear set coupled to a lower range planetary gear set via a clutch, allowing selective power routing through both gear sets to achieve high and low range modes in a space-efficient package, utilizing a controller to switch between modes based on operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple clutches are used to achieve two-speed operation, then the transmission can provide high and low range gear ratios, but the structural architecture and control strategy complexity increases
Solution Approach 1:
The patent combines two planetary gear sets (first and second planetary gear sets) into a single integrated transmission system. The planetary gear sets share common components including the input shaft, carrier, and ring gear, allowing the system to achieve multiple gear ratios without requiring multiple separate clutches. This merging approach reduces structural complexity while maintaining the ability to provide both high and low range gear ratios.
Solution Approach 2:
The single clutch in the patent performs multiple functions by selectively engaging different elements of the planetary gear sets. The clutch can engage the first planetary gear set for high range operation, the second planetary gear set for low range operation, and coordinate between them for intermediate ranges. This multi-functional clutch design eliminates the need for multiple dedicated clutches while achieving the same gear ratio versatility.
2Volume of moving object
If a compact gearbox design is used, then space efficiency is improved, but the ability to provide both high and low range functionality may be limited
Solution Approach 1:
The patent employs a nested arrangement where the first and second planetary gear sets are positioned concentrically around a shared input shaft and carrier. The gear sets are arranged in a compact, space-efficient configuration that allows both high and low range functionality within a reduced volume. The nested structure enables multiple gear ratios to be achieved without increasing the overall gearbox footprint.
3Adaptability or versatility
If traditional multi-clutch transmissions are used, then high and low range modes are achieved, but energy consumption increases
Solution Approach 1:
The patent extracts and eliminates the redundant clutch components from traditional multi-clutch transmission designs. By removing the unnecessary clutches and using a single clutch to control both planetary gear sets, the system reduces the number of moving parts that consume energy. This extraction of excess components directly reduces transmission energy consumption while maintaining full operating range capability.
Data Source
AI summary
Methods and systems for an electric drive axle are provided. An electric drive axle, in one example, includes an electric machine rotationally coupled to a gearbox which includes a higher range planetary gear set coupled to a lower range planetary gear set via a clutch. The clutch is configured to selectively rotationally couple an input gear to a sun gear in each of the higher range planetary gear set and the lower range planetary gear set in different positions or selectively rotationally couple a carrier in the higher range planetary gear set to a carrier and a sun gear in the lower range planetary gear set in different positions.