Electrically Variable Transmission with Planetary Gear Segmentation
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Solution Overview
Problem
Conventional vehicle transmission systems, particularly in hybrid electric vehicles, face inefficiencies in fuel consumption and emissions due to the wide variation in engine demands, and existing electrically variable transmissions are heavy and costly due to the need for extensive electric machinery for power conversion.
Innovation Solution
The development of an electrically variable transmission system utilizing three or four planetary gear sets, two motor/generators, and up to four torque transmitting devices, allowing for selective operation in power-split variable speed ratios and fixed speed ratios, which reduces the reliance on electric machinery by using mechanical power transmission points and regenerative braking for improved efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a series hybrid electric drive system is used to allow continuous variation in torque and speed ratio, then the engine can operate independently for improved emissions and efficiency, but the weight and cost of electric machinery increases significantly
Solution Approach 1:
The transmission system is divided into multiple planetary gear sets (first, second, third, and optional fourth) that process power in parallel paths. This segmentation allows the electric machinery to handle only a fraction of the total power, reducing the size and weight of motors and generators while maintaining the ability to control engine operation independently for emissions reduction.
Solution Approach 2:
Instead of using electric machinery to transform all engine power (excessive action), the system uses differential gearing to send only a fraction of power through electric motor/generators. The remainder flows through a mechanical path, achieving the desired continuous variation in torque and speed ratio with reduced electric machinery requirements.
2Adaptability or versatility
If extensive electric machinery is used for power conversion in hybrid vehicles, then continuous variation in torque and speed ratio is achieved, but the cost of the system increases
Solution Approach 1:
The power flow is segmented into multiple parallel paths through planetary gear sets, with only a portion requiring electric conversion. This reduces the quantity of expensive electric machinery needed while preserving the capability for continuous torque and speed ratio variation.
Solution Approach 2:
The planetary gear sets serve multiple functions: they provide mechanical power transmission, enable differential power splitting between mechanical and electrical paths, and facilitate continuous variation in torque and speed ratio. This multi-functionality reduces reliance on specialized expensive electric components.
3Weight of moving object
If multiple planetary gear sets are used to reduce reliance on electric machinery, then the size and cost of electric motor/generators is minimized, but the device complexity increases
Solution Approach 1:
The planetary gear sets are arranged in a nested configuration where the output of one gear set feeds into another, with interconnecting members linking corresponding elements (sun gears, ring gears, carriers) across multiple stages. This nested architecture achieves compact power splitting while managing complexity through systematic repetition of modular gear set units.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances vehicle acceleration, improves fuel economy through regenerative braking and electric-only idling, and reduces emissions, while also minimizing the size and cost of electric motor/generators required, achieving optimal energy efficiency and emissions control.
Implementation Method 1
A power-split transmission can use what is commonly understood to be 'differential gearing' to achieve a continuously variable torque and speed ratio between input and output
Implementation Method 2
An electric generator can transform mechanical power from the engine into electrical power, and an electric motor can transform that electric power back into mechanical power at different torques and speeds
Implementation Method 3
An electric storage battery used as a source of power for propulsion may be added to this arrangement
Implementation Method 4
Transmission gear selection typically allows power from the engine to be delivered to the rest of the drive system with a ratio of torque multiplication and speed reduction
Data Source
AI summary
The electrically variable transmission family of the present invention provides low-content, low-cost electrically variable transmission mechanisms including first, second, third and optional fourth differential gear sets, a battery, two electric machines serving interchangeably as motors or generators, up to four selectable torque-transfer devices. The selectable torque transmitting devices are engaged to yield an EVT with a continuously variable range of speeds (including reverse) and up to three mechanically fixed speed ratios. The torque transmitting devices and the first and second motor/generators are operable to provide five operating modes in the electrically variable transmission, including battery reverse mode, EVT reverse mode, reverse and forward launch modes, continuously variable transmission range mode, and fixed ratio mode.