Multi-ratio Transmission Using Nested Planetary Gear Sets
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Solution Overview
Problem
Current power transmissions with three planetary gear sets face challenges in achieving seven forward speed ratios and one reverse speed ratio due to complexity, size, and cost, limiting their adoption in passenger vehicles.
Innovation Solution
A family of power transmissions utilizing three planetary gear sets with seven torque-transmitting devices, including clutches and brakes, to selectively engage members of the gear sets and achieve the desired speed ratios through specific combinations, allowing for a variety of speed ratios and ratio spreads by adjusting tooth ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If seven-, eight- and nine-speed transmissions are developed to improve acceleration and fuel economy, then vehicle performance improves, but complexity, size and cost increase
Solution Approach 1:
The transmission is divided into three separate planetary gear sets, each capable of independent operation. This segmentation allows the complex function of providing multiple speed ratios to be distributed across simpler modular units, making the overall system more manageable and potentially reducing complexity despite the high number of speed ratios
Solution Approach 2:
Each planetary gear set is designed to perform multiple functions - they can operate independently or in combination with other gear sets to produce different speed ratios. This multi-functionality allows the transmission to achieve seven forward and one reverse speed ratio using a standardized modular architecture, reducing overall system complexity
2Productivity
If seven-, eight- and nine-speed transmissions are developed to improve acceleration and fuel economy, then vehicle performance improves, but size increases
Solution Approach 1:
The planetary gear sets are arranged in a nested or compact configuration where components of one gear set can share space with components of other gear sets. This nesting approach allows three complete planetary gear sets to be packaged in a smaller overall volume than would be required if they were arranged separately, making the transmission size more acceptable for passenger vehicles
3Productivity
If seven-, eight- and nine-speed transmissions are developed to improve acceleration and fuel economy, then vehicle performance improves, but cost increases
Solution Approach 1:
Common components such as the torque converter, input shaft, and output shaft are shared across all three planetary gear sets. This merging of components reduces the total number of parts that need to be manufactured and assembled, thereby reducing manufacturing cost despite the complex functionality provided by seven forward and one reverse speed ratio
Data Source
AI summary
The transmission has a plurality of members that can be utilized in powertrains to provide at least seven forward speed ratios and one reverse speed ratio. The transmission includes three planetary gear sets having seven torque-transmitting mechanisms and two fixed interconnections. The powertrain includes an engine and torque converter that is continuously connected to at least one of the planetary gear members and an output member that is continuously connected with another one of the planetary gear members. The seven torque-transmitting mechanisms provide interconnections between various gear members and with the transmission housing, and are operated in combinations of three to establish at least seven forward speed ratios and at least one reverse speed ratio.