Compound Split Transmission Fixed Ratio Gear Reduction
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Solution Overview
Problem
Existing electro-mechanical transmissions for vehicles face challenges in providing a wide range of output gear ratios efficiently using reasonable gear sizes, especially when integrating electric devices with internal combustion engines for hybrid powertrains.
Innovation Solution
A compound split transmission system incorporating a first and second planetary gear set, along with a fixed ratio gear reduction system, which directs torque between the electric devices and allows for a wide range of output gear ratios by transmitting rotation at reduced rotational speed and increased torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a wide range of output gear ratios is desired, then the transmission must accommodate varying rotational speed and torque requirements, but using conventional single planetary gear sets limits the achievable gear ratio range with reasonable gear sizes
Solution Approach 1:
The transmission system is divided into two separate planetary gear sets (first and second planetary gear sets), each handling different portions of the gear ratio range. The first planetary gear set handles one range of gear ratios while the second handles another range, allowing the system to achieve a wide overall gear ratio range without requiring excessively large individual gears in a single set
Solution Approach 2:
The patent employs a nested configuration where the second planetary gear set is positioned within or alongside the first planetary gear set. This nesting allows both gear sets to share space efficiently, achieving a wide gear ratio range through combined operation while keeping the overall transmission compact and avoiding excessive gear sizes
2Adaptability or versatility
If electric devices are integrated with internal combustion engines for hybrid powertrains, then flexible power delivery is improved, but managing torque distribution between multiple power sources increases system complexity
Solution Approach 1:
The transmission system is designed to universally handle multiple power sources (internal combustion engine and one or more electric devices) and multiple operating modes (series hybrid, parallel hybrid, fully electric). The same planetary gear sets and torque management mechanisms serve all these functions, providing flexible power delivery without proportionally increasing system complexity
Solution Approach 2:
The planetary gear sets act as intermediary mechanisms that facilitate smooth torque distribution and mixing between the engine and electric devices. Through the compound split configuration and fixed ratio gear reduction system, the transmission mediates the interaction between different power sources, enabling flexible power delivery while simplifying control compared to direct coupling arrangements
3Adaptability or versatility
If a compound split transmission is used to achieve wide gear ratio range, then output gear ratio versatility is improved, but the number of planetary gear sets increases system complexity
Solution Approach 1:
The patent merges the functions of multiple planetary gear sets into a unified compound split transmission system. The first and second planetary gear sets are combined with a fixed ratio gear reduction system to create an integrated architecture that achieves wide gear ratio range while sharing common components and control mechanisms, thereby limiting the increase in overall system complexity
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 transmission system effectively manages torque and rotational speed, enabling efficient power delivery to vehicle wheels, supporting both hybrid and fully electric operation modes with a compact gear configuration suitable for various vehicle applications.
Implementation Method 1
A fixed ratio gear reduction system interconnects the input and the second planetary gear set. The fixed ratio gear reduction system is operable to transmit rotation from the input to the second planetary gear set at a reduced rotational speed and at an increased torque.
Data Source
AI summary
A transmission includes an input member, an output member, a first electric device, and a second electric device. A first planetary gear set is coupled to the first electric device. A second planetary gear set is coupled to the second electric device. The output is coupled to both the first planetary gear set and the second planetary gear set. The input is connected to the first planetary gear set. A fixed ratio gear reduction system couples the input and the second planetary gear set. The fixed ratio gear reduction system is operable to transmit rotation from the input to the second planetary gear set at a reduced rotational speed and at an increased torque.