Three-Planetary Gear Electrically Variable Transmission
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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 the wide variation in engine demands, and series hybrid electric drive systems suffer from weight and cost issues related to electric machinery and energy conversion losses.
Innovation Solution
An electrically variable transmission system with three planetary gear sets, two motor/generators, and multiple torque transmitting devices allows for selective operation in both power-split variable speed ratios and fixed speed ratios, utilizing a dog clutch to reduce clutch spin losses and enabling efficient regenerative braking and electric-only idling, thereby optimizing energy efficiency and emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a series hybrid electric drive system is used to allow engine independence from vehicle torque and speed requirements, then emissions and fuel consumption are improved, but weight and cost increase due to sufficient electric machinery
Solution Approach 1:
The transmission system is divided into multiple planetary gear sets (first, second, and third planetary gear sets) with different configurations, allowing each segment to handle specific torque and speed requirements. This segmentation enables the electric machinery to be smaller since each motor/generator only needs to handle a portion of the total power transmission rather than the entire engine output.
Solution Approach 2:
The system dynamically switches between different operational modes including electric-only mode, hybrid mode, and mechanical direct connection mode. The control system adjusts the engagement of clutches and the operation of motor/generators based on real-time vehicle requirements, allowing the electric machinery to operate only when needed rather than continuously, reducing the required size.
2Adaptability or versatility
If sufficient electric machinery is used to transform all engine power from mechanical to electrical and back, then continuous variable torque and speed control is achieved, but energy conversion losses increase
Solution Approach 1:
The transmission system dynamically switches between electrically variable modes and mechanically variable modes. When mechanical direct connection is used through the planetary gear sets, power is transmitted without electrical conversion, eliminating conversion losses. The system only uses electrical conversion when variable torque and speed control is required, minimizing energy losses while maintaining adaptability.
Solution Approach 2:
The power transmission is segmented into multiple paths: one through electric motor/generators for variable control and another through mechanical planetary gear sets for direct transmission. This allows the system to choose the most efficient path for each operating condition, reducing overall energy conversion losses.
3Adaptability or versatility
If multiple planetary gear sets and torque transmitting devices are used to provide variable speed ratios, then transmission ratio coverage is improved, but device complexity increases
Solution Approach 1:
Multiple planetary gear sets are merged into a single integrated transmission system where the first, second, and third planetary gear sets work together with shared components. The clutches and motor/generators are integrated across all gear sets, allowing the system to achieve wide transmission ratio coverage while reducing overall complexity compared to separate independent gear sets.
Solution Approach 2:
The planetary gear sets are designed with multi-functionality where each gear set can operate in different modes (direct connection, variable ratio, fixed ratio) and can be engaged or disengaged based on requirements. This universality allows the system to achieve diverse transmission ratios without requiring separate dedicated mechanisms for each function, reducing overall device complexity.
4Ease of operation
If conventional clutches are used for smooth transitions between driving ratios, then transition smoothness is achieved, but clutch spin losses increase
Solution Approach 1:
Electric motor/generators are introduced as intermediary devices between the input and output of the transmission system. During transitions between driving ratios, the motor/generators can fill in torque gaps and smooth out transitions without requiring prolonged clutch engagement, reducing clutch spin losses while maintaining transition smoothness.
Solution Approach 2:
The control system performs preliminary engagement of clutches and motor/generators before actual ratio changes occur. By pre-positioning the torque transmission path and using electric assistance to bridge torque gaps, the system minimizes the duration and intensity of clutch slip, reducing spin losses while ensuring smooth transitions.
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 achieves improved vehicle acceleration, reduced fuel consumption, and lower emissions by optimizing energy efficiency, capacity, package size, and ratio coverage, allowing for smaller and lighter transmission designs with reduced electric motor/generator size and cost.
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
utilizing a dog clutch to reduce clutch spin losses
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 transmitting devices are engaged to yield an EVT with a continuously variable range of speeds (including reverse) and four mechanically fixed forward 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.