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 wide variations in demand, and series hybrid electric drive systems suffer from weight and cost issues related to electric machinery and energy losses in conversions.
Innovation Solution
The development of an electrically variable transmission system with three planetary gear sets, two motor/generators, and four or five torque transfer devices, allowing for selective operation in power-split variable speed ratios and fixed speed ratios, utilizing planetary gear sets or alternative gearing configurations to optimize energy efficiency and reduce emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a series hybrid electric drive system is used to improve fuel consumption and emissions, then the engine can operate with improved efficiency and emissions, but the system suffers from weight and cost of sufficient electric machinery and useful energy lost in conversions
Solution Approach 1:
The transmission system is divided into multiple planetary gear sets (first, second, and third planetary gear sets) with differentials, allowing the power to be split into multiple paths. This segmentation enables more efficient power distribution and reduces the burden on any single electric machine, thereby reducing overall weight while maintaining fuel efficiency benefits.
Solution Approach 2:
The patent combines multiple planetary gear sets with differentials into a single integrated transmission system. This merging allows for more compact packaging of electric machinery components, reducing overall weight while maintaining the fuel efficiency advantages of hybrid operation.
2Adaptability or versatility
If electric machinery is used to transform mechanical power to electrical power and back to achieve continuous variation in torque and speed ratio, then continuous variation in ratio is achieved, but useful energy is lost in these conversions
Solution Approach 1:
The transmission system maintains continuous power flow through multiple planetary gear sets and differentials, ensuring that power is continuously transmitted through mechanical paths rather than being repeatedly converted between mechanical and electrical forms. This continuity reduces energy losses while maintaining adaptability.
Solution Approach 2:
The planetary gear sets and differentials act as intermediaries between the engine and the wheels, providing continuous mechanical power transmission paths that reduce the need for repeated electro-mechanical conversions. This intermediary mechanical transmission system minimizes energy losses while maintaining continuous variation capability.
3Volume of moving object
If planetary gear sets are used to achieve differential gearing and continuous variable torque and speed ratio, then compactness and different torque and speed ratios are achieved, but device complexity increases
Solution Approach 1:
The transmission system employs nested planetary gear sets where gear sets are arranged concentrically and interconnected through shared components. This nesting achieves compact packaging while the systematic interconnection reduces operational complexity compared to separate gear sets.
Solution Approach 2:
The planetary gear sets are designed with multi-functionality, where each gear set can operate in multiple modes (direct drive, reduction, overdrive) depending on clutch engagement. This universality reduces the need for additional specialized components, thereby reducing overall device complexity while maintaining compactness.
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 system enhances vehicle acceleration, improves fuel economy through regenerative braking and electric-only idling, and provides a compact, lightweight solution with reduced fuel consumption and emissions, offering improved energy efficiency and emissions performance.
Implementation Method 1
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 2
Planetary gearing is usually the preferred embodiment employed in differentially geared inventions, with the advantages of compactness and different torque and speed ratios among all members of the planetary gear set
Implementation Method 3
This system also allows the electric machine attached to the remainder of the drive train to act as a generator, recovering energy from slowing the vehicle into the battery by regenerative braking
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, four or five selectable torque-transfer devices (two clutches and two or three brakes), 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 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.