Electric Axle Planetary Transmission With Nested Compact Gear Stages
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Solution Overview
Problem
Existing electrically driven axles in motor vehicles require multi-stage transmissions to manage high rotational speeds, necessitating a compact design to optimize installation space, while maintaining efficient torque distribution to the wheels.
Innovation Solution
A drive device featuring a series connection of first and second planetary gear sets with external toothing, where the ring gear of the first planetary gear set is doubly supported by bearings to stabilize against radial forces, and shift elements allow for interlocking and detaching to achieve gear ratios, enabling a compact and shiftable transmission design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If multi-stage transmissions are used to manage high rotational speeds, then the transmission can achieve optimal efficiency, but the installation space requirement increases
Solution Approach 1:
The patent employs nested planetary gear sets where the second planetary gear set is positioned within the first planetary gear set. The sun gear of the first planetary gear set serves as the carrier for the second planetary gear set, creating a compact nested arrangement that reduces overall transmission size while maintaining multi-stage gear reduction capability for managing high rotational speeds efficiently.
Solution Approach 2:
The patent utilizes the radial dimension by arranging planetary gear sets concentrically around a common axis. The ring gear of the first planetary gear set provides an external toothing that engages with the sun gear of the second planetary gear set in the radial direction, allowing compact three-dimensional packaging of multiple gear stages without increasing axial length.
2Area of stationary object
If compact transmission design is implemented to optimize installation space, then the device complexity increases
Solution Approach 1:
The ring gear of the first planetary gear set serves multiple functions: it acts as a gear element for the first planetary stage, provides external toothing for engagement with the second planetary gear set, and serves as a structural support element. The sun gear of the first planetary gear set simultaneously functions as a gear element and as the carrier for the second planetary gear set, reducing the need for separate components.
Solution Approach 2:
The patent merges the carrier function of the first planetary gear set with the structural support function by making the sun gear of the first stage serve as the carrier for the second stage. This consolidation of functions reduces the number of separate components and simplifies the overall transmission structure while maintaining compact dimensions.
3Volume of moving object
If external toothing of ring gear is used, then the gear set can be compactly arranged, but radial forces increase causing deformation
Solution Approach 1:
The patent introduces counterbalancing support elements that oppose the radial forces generated by the external toothing of the ring gear. These support structures are strategically positioned to provide counteracting forces that prevent oval deformation of the ring gear under load, maintaining structural integrity while preserving the compact external toothing design.
Data Source
AI summary
A drive device for an electrically driven axle of a motor vehicle may include at least one electric machine, a shiftable transmission connected downstream from the at least one electric machine, and a differential coupled to the transmission for distributing drive torque to the axle. The transmission has first and second planetary gear sets connected in series. The at least one electric machine engages with an external toothing of a ring gear of the first planetary gear set. A carrier of the first planetary gear set is rotationally fixed to a sun gear of the second planetary gear set. A sun gear of the first planetary gear set is detachably couplable to a housing. A ring gear of the second planetary gear set is coupled to the housing. A carrier of the second planetary gear set is an output of the transmission. The first planetary gear set is interlockable.