Integrated Transmission and Differential Gearing for Compact EV Drivetrains
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Solution Overview
Problem
Conventional transmission and differential gearings in electric vehicles require excessive installation space, generate noise due to large tolerances, and have assembly challenges, especially with the integration of a parking lock.
Innovation Solution
A transmission and differential gearing system with a housing, input shaft, and two coaxial output shafts, featuring a transmission section with two planetary stages and a spur gear differential configured as a planetary gear set, which includes a through-going coupling shaft and a parking lock device, allowing for compact design and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional transmission and differential gearings are used in electric vehicles, then the functionalities of transmission and differential are separated, but the installation space required becomes excessive
Solution Approach 1:
The patent combines the transmission section and differential section into a single integrated gearing unit with a common housing. The transmission section includes planetary stages that share components with the differential section, particularly the carrier and ring gear, eliminating the need for separate transmission and differential housings and reducing overall installation space.
Solution Approach 2:
The patent employs nested planetary stages where the carrier of one planetary stage serves as the input for the next stage. The inner planetary stage is positioned within the outer planetary stage, with the inner carrier being the input shaft for the inner sun gear, creating a compact nested arrangement that reduces volume.
2Ease of operation
If stepped planets are used in the transmission section, then coaxial mounting is achieved, but positioning during assembly becomes problematic
Solution Approach 1:
The patent divides the transmission section into distinct planetary stages with clear separation of functions. Each stage has its own carrier, sun gear, and ring gear, allowing for modular assembly. The input shaft and output shaft are clearly defined as separate components that can be positioned independently, simplifying the assembly process compared to integrated stepped planet designs.
3Volume of moving object
If the transmission section is configured with large gearing tolerances, then installation space is reduced, but noise generation increases
Solution Approach 1:
The patent specifies tight gearing tolerances for the planetary stages and differential components to minimize noise generation. The tooth profiles, pitch circle diameters, and center distances are precisely controlled within narrow tolerance ranges, ensuring quiet operation even in the compact integrated design.
4Volume of moving object
If the carrier is directly connected to the differential cage, then compact design is achieved, but integration of parking lock becomes difficult
Solution Approach 1:
The patent introduces an intermediary extension shaft that connects the carrier to the differential cage. This extension shaft provides an accessible mounting point for the parking lock mechanism, allowing the parking lock to be integrated into the compact design without requiring direct connection between the carrier and differential cage.
Data Source
AI summary
A transmission and differential gearing includes a transmission section and a differential section. The transmission section has an input stage and a load stage. The sun gear of the input stage is connected or coupleable to an input shaft. The ring gear of the bad stage is fixed relative to the housing. The sun gear of the bad stage is connected to the carrier of the input stage. The carrier of the load stage is connected to the ring gear of the input stage. The differential section is a spur gear differential configured as a planetary gear set. The ring gear of the planetary gear set is connected to the carrier of the load stage. The carrier of the planetary gear set and the sun gear of the planetary gear set are connected to a respective one of two output shafts. A motor and gearing unit is also provided.