Three-Shaft EV Transmission Layout for More Gears in Less Length
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Solution Overview
Problem
Existing multi-speed transmissions in electric vehicles face challenges such as power flow constraints due to shaft and gear arrangements, and the inability to provide a desired gear drop for certain vehicle platforms.
Innovation Solution
A compact transmission design that uses three parallel shafts with clutches positioned on the input and output shafts to selectively engage and disengage gears, allowing for at least three discrete operating gears and efficient power flow through aligned or crossed gear meshes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a multi-speed transmission is designed with multiple shafts and gears to provide multiple operating gears, then the number of available gears increases, but the transmission length and complexity increase
Solution Approach 1:
The patent uses three parallel shafts (input shaft, layshaft, output shaft) arranged in a compact configuration. By utilizing the spatial arrangement of multiple parallel shafts with gears positioned at different locations along each shaft, the transmission achieves three or more operating gears while maintaining a short overall length. The clutches positioned on the input and output shafts enable selective engagement of different gear pairs without requiring additional shaft length.
Solution Approach 2:
The transmission is divided into distinct functional segments: the input shaft with first pair of gears and first clutch, the layshaft with second pair of gears, and the output shaft with third pair of gears and second clutch. This segmentation allows independent control of gear engagement through the clutches, enabling multiple operating gears to be achieved through selective coupling of gear pairs across the three shafts without increasing transmission length.
2Adaptability or versatility
If traditional shaft and gear arrangements are used to couple the engine to the output, then power flow constraints occur, but the design becomes more flexible
Solution Approach 1:
The layshaft acts as an intermediary between the input shaft and output shaft. The second pair of gears on the layshaft meshes with both the first pair of gears on the input shaft and the third pair of gears on the output shaft, providing a flexible intermediate stage for power transmission. This intermediary arrangement allows multiple power flow paths and gear ratio combinations without creating direct constraints between the input and output shafts.
Solution Approach 2:
The clutches positioned on the input and output shafts enable dynamic engagement and disengagement of different gear pairs. This dynamic control allows the transmission to adapt power flow paths based on operating conditions, selecting different gear combinations (first gear pair with second gear pair, or first gear pair with third gear pair) to optimize performance and avoid power flow constraints.
Data Source
AI summary
Methods and systems for a transmission are provided. In one example, the transmission includes an input shaft with a first pair of gears that reside thereon, a first clutch positioned between the first pair of gears and designed to selectively rotationally couple a selected gear in the first pair of gears to the input shaft, and a layshaft with a second pair of gears fixedly coupled thereto. The transmission further includes an output shaft with a third pair of gears that reside thereon and a second clutch positioned between the third pair of gears and designed to selectively rotationally couple a selected gear in the third pair of gears to the output shaft.