Multi-Speed Electric Drive Axle With Nested Layshaft Packaging
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Solution Overview
Problem
Existing electric drive axles with multi-speed transmissions face challenges in packaging without impacting cabin space or vehicle clearance.
Innovation Solution
A multi-speed electric drive axle design incorporating a housing assembly, electric motor, differential assembly, and transmission with a multi-speed reduction mechanism using a combination of reduction gearsets, coupling sleeves, and axially movable input shafts to achieve compact packaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a multi-speed transmission is incorporated into an electric drive axle, then the transmission ratio range is improved, but the packaging difficulty increases due to impact on cabin space and vehicle clearance
Solution Approach 1:
The transmission components are arranged in a nested configuration where the input shaft, intermediate shafts, and output shaft are concentrically aligned along a common axis. The gearsets are positioned radially outward from the shafts, allowing multiple transmission stages to be compacted within a small radial envelope. This nested arrangement enables the multi-speed transmission to achieve a wide transmission ratio range while maintaining a compact overall size that does not impact cabin space or vehicle clearance.
Solution Approach 2:
The transmission design transitions from a traditional longitudinal or transverse arrangement to a compact axial arrangement where power is transmitted along a common axis. By stacking gearsets and shafts in the radial direction rather than extending them linearly, the design compresses the transmission volume in the axial dimension while maintaining the necessary transmission ratio range, effectively utilizing three-dimensional space efficiency.
2Adaptability or versatility
If multiple reduction gearsets and intermediate shafts are used to achieve multi-speed transmission, then the transmission ratio range is improved, but the device complexity increases
Solution Approach 1:
The common input shaft and intermediate shafts serve multiple functions simultaneously. Each shaft can engage with different gearsets to provide multiple speed ratios, meaning a single shaft structure performs the work of what would traditionally require multiple separate shafts. The coupling mechanism allows the same physical components to be reconfigured for different transmission ratios, reducing the number of unique parts needed and simplifying the overall device complexity while maintaining a wide transmission ratio range.
Solution Approach 2:
The transmission employs a dynamic coupling mechanism where the input shaft can be selectively connected to different intermediate shafts or gearsets based on the desired speed ratio. This dynamic reconfiguration capability allows the transmission to achieve multiple speed ratios using the same physical components, rather than requiring fixed, dedicated shafts and gearsets for each ratio, thereby reducing structural complexity while maintaining versatility.
Data Source
AI summary
An electric drive axle with an electric motor having a motor shaft that is rotatable about an axis, a differential, and a transmission. The transmission transmits rotary power between the motor shaft and the differential. The multi-speed reduction has an input shaft and at least three on-axis gears. The input shaft is rotatably coupled to the motor shaft. Each of the at least three on-axis gears is co-axial with the input shaft and is rotatable relative to the input shaft in at least one of a first speed ratio and a second speed ratio. The input shaft is axially movable along the axis between a first position, in which a first one of the at least three on-axis gears is rotationally coupled to the input shaft, and a second position in which a second one of the at least three on-axis gears is rotationally coupled to the input shaft.