EVT Lockup Clutch Eliminates Motor Reaction Torque
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Solution Overview
Problem
Existing electrically variable transmissions (EVTs) require high motor power and torque ratings, leading to increased costs and inefficiencies, particularly due to the need for multiple clutches and complex gear arrangements to achieve a wide range of speed ratios, which results in power flow opposition between electro-mechanical and mechanical paths at various speed ratios.
Innovation Solution
A single-range electrically variable transmission with a lockup clutch that allows direct transmission of engine torque to the output member without requiring reaction torque from the first motor/generator, establishing a fixed mechanical speed ratio and eliminating the need for power flow through motor/generators, thereby reducing motor power requirements and enabling smaller, less expensive motor/generators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple clutches and complex gear arrangements are used to achieve a wide range of speed ratios, then the transmission range is improved, but the device complexity and motor power requirements increase
Solution Approach 1:
The patent extracts the torque multiplication function from the complex multi-clutch system and concentrates it in a single lockup clutch positioned at the output of the differential gear set. This simplifies the clutch arrangement from multiple clutches to one, while maintaining the ability to achieve wide transmission ratios through the differential set's inherent mechanical points and electro-mechanical operation.
Solution Approach 2:
The differential gear set is designed to serve multiple functions: it provides continuous variable ratio transmission through electro-mechanical operation, establishes fixed mechanical points without clutches, and enables torque multiplication through the lockup clutch. This multi-functional design eliminates the need for separate clutch mechanisms that would otherwise be required to achieve the same effects.
2Adaptability or versatility
If multiple clutches are used to effect alternative power flows, then the transmission ratio range is improved, but the motor power and torque ratings must be increased
Solution Approach 1:
The lockup clutch acts as an intermediary element that directly couples the differential gear set output to the transmission output shaft, bypassing the need for motor/generator reaction torque. This intermediary mechanism allows torque to be transmitted mechanically without requiring the motor/generators to handle the full torque multiplication, thereby reducing their power and torque ratings.
Solution Approach 2:
The patent replaces the electro-mechanical torque multiplication path (through motor/generators) with a direct mechanical path through the lockup clutch. This substitution eliminates the need for high motor power ratings by using a purely mechanical torque transmission route when the lockup clutch is engaged, particularly at the mechanical point where the differential set provides fixed ratios.
3Adaptability or versatility
If a wide range of speed ratios is achieved through electro-mechanical paths, then the transmission versatility is improved, but power flow opposition occurs between electro-mechanical and mechanical paths
Solution Approach 1:
The system dynamically switches between electro-mechanical operation and direct mechanical coupling through the lockup clutch based on operating conditions. At mechanical points where the differential set provides fixed ratios, the lockup clutch is engaged to eliminate power flow opposition. During variable ratio transitions, the system operates in electro-mechanical mode. This dynamic adaptation minimizes energy losses from power flow opposition while maintaining wide transmission ratio capability.
Data Source
AI summary
A single range, electrically variable transmission (EVT) is provided with a lockup clutch that reduces motor power requirements. When applied, the lockup clutch allows engine torque to be transmitted directly to the output without the necessity of a motor/generator supplying reaction torque. With the lockup clutch applied, the transmission operates with zero electro-mechanical power flow at a fixed mechanical ratio, thus mitigating the power peak which occurs through the motor/generators. Input-split, output-split, and compound-split transmissions are disclosed. A method of operating an EVT with a lockup clutch is also provided.