Multi-Speed EV Transmission Using a Dual-Function Intermediate Gear
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Solution Overview
Problem
Existing electric drive axles and transmissions face challenges in balancing available gear range and packaging efficiency, often requiring tradeoffs between the number of gears and compactness, which are exacerbated by large electric vehicle battery packs.
Innovation Solution
A transmission system with an intermediate shaft rotationally coupled to input and output shafts, featuring a first gear and a plurality of clutches that allow power transfer directly or indirectly between gears in different modes, enabling dual-use functionality of the intermediate shaft gear to expand gear ratios without increasing system size or complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of gears is increased to expand gear range, then gear ratio selection is improved, but packaging efficiency deteriorates due to increased system size
Solution Approach 1:
The intermediate shaft gear is designed to perform multiple functions: it acts as a pinion gear in some operating modes and as an idler gear in other modes. This dual functionality allows the same physical component to enable multiple gear ratios without requiring additional gears, thereby expanding gear range while maintaining compact packaging.
Solution Approach 2:
The system uses actively controlled clutches to dynamically reconfigure power flow paths between different gears. By switching between direct power transfer and indirect power transfer through the intermediate shaft, the system can select from multiple gear ratios using the same physical components, achieving gear range expansion without increasing transmission size.
2Loss of energy
If direct power transfer is used between gears, then efficiency is improved, but gear ratio variety is limited
Solution Approach 1:
The intermediate shaft gear acts as a mediator that enables indirect power transfer between input and output shafts. When the clutch system routes power through this intermediate gear, additional gear ratios become available. The system can switch between direct power transfer (for efficiency) and indirect power transfer through the intermediate gear (for gear ratio variety), resolving the contradiction between efficiency and versatility.
Data Source
AI summary
Methods and systems for a vehicle transmission are provided. A transmission system includes, in one example, an intermediate shaft rotationally coupled to an input shaft and an output shaft, wherein the input shaft is configured to receive rotational input from an electric machine. The system further includes a first gear coupled to the intermediate shaft, and a plurality of clutches coupled to the input shaft and the output shaft and configured to in a first mode, transfer power directly between a second gear coupled to the input shaft, the first gear, and a third gear coupled to the output shaft, and in a second mode, transfer power indirectly between the second gear, the first gear, and/or the third gear.