Multi-ratio Transmission with Nested Planetary Gear Sets
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The development of power transmissions with seven or more forward speed ratios and one reverse speed ratio is hindered by complexity, size, and cost, limiting their adoption in passenger vehicles despite offering improved acceleration and fuel economy.
Innovation Solution
A family of power transmissions utilizing three planetary gear sets with seven torque-transmitting devices, including brakes and clutches, to achieve at least seven forward speed ratios and one reverse speed ratio, allowing for various speed ratios and ratio spreads through tooth ratio selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of forward speed ratios is increased to seven or more, then vehicle acceleration and fuel economy are improved, but transmission complexity, size, and cost increase
Solution Approach 1:
The transmission is divided into three separate planetary gear sets (first, second, and third planetary gear sets), each capable of providing gear ratios independently. This segmentation allows the system to achieve seven or more forward speed ratios through various combinations of the planetary sets rather than requiring a single complex gear train, thereby improving acceleration and fuel economy while managing complexity through modular design
Solution Approach 2:
The planetary gear sets are designed with multi-functionality where each set can operate in multiple modes and combinations. The first, second, and third planetary gear sets can be engaged in various sequences and combinations to provide different gear ratios, allowing the same hardware to serve multiple functions and achieve seven or more forward speed ratios without proportionally increasing component count
2Productivity
If the number of forward speed ratios is increased to seven or more, then vehicle acceleration and fuel economy are improved, but transmission size increases
Solution Approach 1:
The three planetary gear sets are arranged in a nested or compact configuration where components share common mounting structures and spatial relationships. The planetary sets are positioned to minimize overall transmission footprint while maintaining the necessary gear ratio capabilities, allowing seven or more forward speed ratios to be achieved within a compact size that does not linearly scale with the number of ratios
3Productivity
If the number of forward speed ratios is increased to seven or more, then vehicle acceleration and fuel economy are improved, but transmission cost increases
Solution Approach 1:
Multiple planetary gear sets share common components including torque transmitting devices, planetary carriers, and housing structures. The first, second, and third planetary gear sets are integrated into a single transmission assembly with shared manufacturing processes and common parts, reducing the overall cost of producing a seven-speed or higher transmission compared to using separate gear sets or more traditional gear train designs
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 six or seven torque-transmitting mechanisms and three 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 six or seven torque-transmitting mechanisms provide interconnections between various gear members and with the transmission housing, and are operated in combinations of two to establish at least seven forward speed ratios and at least one reverse speed ratio.