Electrically Variable Transmission with Three Planetary Gear Sets
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Solution Overview
Problem
Conventional vehicle transmission systems, particularly those using internal combustion engines, face inefficiencies in fuel consumption and emissions due to varying demands on the engine, and existing hybrid electric systems suffer from weight and cost issues related to electric machinery and energy losses in conversions.
Innovation Solution
An electrically variable transmission system with three planetary gear sets, two motor/generators, and up to five torque transfer devices, allowing for selective operation in power-split variable speed ratios and fixed speed ratios, utilizing planetary gear sets and motor/generators to optimize energy efficiency and reduce emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a series hybrid electric drive system is used to allow engine independence from vehicle torque and speed requirements, then emissions and efficiency are improved, but weight and cost increase due to sufficient electric machinery size
Solution Approach 1:
The transmission system divides power flow into multiple paths: a first path through a first planetary gear set and first motor/generator, and a second path through a second planetary gear set and second motor/generator. This segmentation allows each electric machine to be smaller and less expensive while collectively providing the necessary power and control functions.
Solution Approach 2:
The patent combines multiple planetary gear sets and motor/generators into a unified transmission system where the components work together to achieve both emission reduction and weight management. The interconnected gear sets share common elements (sun gears, ring gears, carriers) to reduce overall system mass while maintaining functionality.
2Use of energy by moving object
If electric machinery is sized to transform all engine power mechanically to electrically and back, then full power conversion is achieved, but useful energy is lost in the conversions
Solution Approach 1:
The transmission system dynamically routes power flow between mechanical and electrical paths based on operating conditions. The control system selectively engages different planetary gear sets and motor/generators to minimize conversion losses while maintaining the ability to perform full power conversion when necessary.
Solution Approach 2:
The system changes operational parameters by switching between different gear set configurations and motor/generator engagement states. This allows optimization of energy conversion efficiency across different operating ranges while preserving full power conversion capability when required.
3Adaptability or versatility
If conventional mechanical transmissions are used with five or six different drive ratios, then some freedom in engine operation is allowed, but fuel consumption and emissions increase due to wide variation in engine demands
Solution Approach 1:
The transmission system transitions from fixed discrete ratios to dynamically variable speed ratios through the coordinated operation of multiple planetary gear sets and motor/generators. This dynamic capability allows continuous optimization of engine operating points, reducing fuel consumption and emissions while maintaining engine operation freedom.
Solution Approach 2:
The transmission system performs multiple functions simultaneously: it provides variable speed ratio adjustment, engine braking, regenerative braking, and start-stop capability. This multi-functionality allows the system to optimize fuel consumption and emissions across a wide range of operating conditions while maintaining versatility in engine operation.
4Speed
If planetary gear sets are used to achieve continuously variable torque and speed ratio, then compactness and different torque/speed ratios are obtained, but device complexity increases with multiple gear sets and interconnections
Solution Approach 1:
The transmission system nests planetary gear sets within each other, sharing common sun gears, ring gears, and carrier members. This nested configuration achieves continuously variable speed ratios while reducing the number of independent components and simplifying the overall device structure.
Solution Approach 2:
The patent merges multiple planetary gear sets into a unified structure where common elements serve multiple functions. The interconnected gear sets share components and coordinate their operation to achieve continuous variable speed ratios without requiring fully separate, complex subsystems.
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
The system improves vehicle acceleration, fuel economy, and emissions by enabling regenerative braking and electric-only idling, while reducing the size and cost of electric motor/generators through optimal energy management and efficient power distribution.
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. One form of differential gearing, as is well known to those skilled in this art, may constitute a planetary gear set.
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 for the remainder of the vehicle drive system.
Implementation Method 3
An electric storage battery used as a source of power for propulsion may be added to this arrangement, forming a series hybrid electric drive system.
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 and third differential gear sets, a battery, two electric machines serving interchangeably as motors or generators, up to five selectable torque-transfer devices and possibly a dog clutch. The selectable torque transfer devices are engaged to yield an EVT with a continuously variable range of speeds (including reverse) and up to four mechanically fixed forward speed ratios. The torque transfer 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.