Multi-Speed Transmission with Front and Rear Planetary Gearsets
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Solution Overview
Problem
Existing multi-speed transmissions are limited in the number of gears they can achieve despite having a large number of components, and they lack a structurally simple design.
Innovation Solution
A multi-speed transmission design with six shift elements, including three clutches and three brakes, utilizing three 3-carrier 5-shaft front-mounted gear sets and two 2-carrier 4-shaft rear-mounted gear sets, allowing for at least 12 forward gears and one reverse gear, with a focus on reducing complexity and installation space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a large number of shift elements (seven clutches and brakes) are used to achieve multiple gears, then the number of gears is limited to 11 forward gears and one reverse gear, but the structural complexity increases significantly
Solution Approach 1:
The patent combines multiple gear sets (front-mounted and rear-mounted) into a unified transmission system where gear ratios are achieved through coordinated engagement of clutches and brakes across different gear sets. This merging allows achieving 12 forward gears and reverse gear with only 6 shift elements, resolving the contradiction between gear variety and structural complexity
Solution Approach 2:
Each shift element (clutch or brake) is designed to serve multiple functions across different gear ratios. For example, the same clutch may be engaged in combination with different brakes to achieve multiple forward gears, and the same brake may work with different clutches for various reverse gear configurations. This multi-functionality reduces the total number of shift elements needed while maintaining high gear adaptability
2Adaptability or versatility
If traditional multi-speed transmission designs are used with multiple gear sets, then at least 12 forward gears and one reverse gear can be achieved, but the installation space and manufacturing complexity increase
Solution Approach 1:
The transmission system is segmented into distinct front-mounted gear sets and rear-mounted gear sets, each with specific functions. The front-mounted gear sets handle certain gear ratios while the rear-mounted gear sets handle others, allowing independent optimization and simplification of each segment's design and manufacturing
Solution Approach 2:
The patent employs a nested arrangement where planetary gear sets are contained within compact housings, and multiple gear sets are arranged in a space-efficient configuration. The front-mounted and rear-mounted gear sets are positioned to minimize overall transmission length while maintaining proper mechanical connections, reducing installation space and manufacturing complexity
3Adaptability or versatility
If the maximum number of gears is achieved with traditional designs, then 11 forward gears and one reverse gear are obtained, but the number of shift elements increases to seven
Solution Approach 1:
The transmission system uses dynamic engagement and disengagement of clutches and brakes to achieve different gear ratios. Instead of requiring a separate fixed mechanism for each gear, the system dynamically reconfigures the power flow path by selectively engaging shift elements, allowing 12 forward gears and reverse gear with only 6 shift elements
Solution Approach 2:
The system changes the operational parameters of the shift elements (which clutch or brake is engaged, and in what combination) to achieve different gear ratios. By varying the engagement state of the 6 shift elements across different operating conditions, the system achieves multiple gear ratios without requiring a proportional increase in the number of shift elements
Data Source
AI summary
A multi-speed transmission having drive and output shafts, front-mounted planetary gearsets, rear-mounted planetary gearsets and six shift elements. Selective engagement of shift elements selectively renders a drive shaft speed and speeds generated in the front gearsets for achieving a reverse gear and twelve forward gears via the rear gearsets transmissible as an output speed to the output shaft. Four shift elements are assigned to the front gearsets and two are assigned to the rear gearsets. At least one front gearset is rigidly connected to an element of the rear gearsets, resulting in six different output speeds of the front gearsets being transmissible to the rear gearsets. If normalized to the drive shaft input speed, one output speed is smaller than 0, three output speeds are between 0 and 1, one output speed is equal to 1 and one output speed is greater than 1.