Automatic Transmission with Four Planetary Gear Sets
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Solution Overview
Problem
Existing automatic transmissions with 8-forward-speed configurations face limitations in providing additional gear ratios without increasing friction loss and complexity, which affects fuel efficiency and transmission controllability.
Innovation Solution
The automatic transmission employs four planetary gear sets with single-pinion configurations and seven engagement mechanisms, including clutches and brakes, to establish nine or more forward gear ratios and a reverse gear, minimizing the number of engagement mechanisms in release mode to reduce friction loss and enhance controllability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the number of gear ratios is increased to improve fuel efficiency, then more engagement mechanisms are required, but this increases friction loss and device complexity
Solution Approach 1:
The transmission system is divided into four independent planetary gear sets (first, second, third, and fourth), each capable of providing different gear ratios. This segmentation allows the system to achieve 10 forward gear ratios and 1 reverse gear ratio through various combinations of engagement mechanisms, thereby improving fuel efficiency without requiring a single complex gear train that would increase friction loss
Solution Approach 2:
The system dynamically engages and disengages seven engagement mechanisms (first to seventh engagement mechanisms) to achieve different gear ratios. By minimizing the number of engagement mechanisms in release mode during operation, the system reduces friction loss while maintaining the capability to provide multiple gear ratios for improved fuel efficiency
2Use of energy by moving object
If more planetary gear sets are added to increase gear ratios, then fuel efficiency improves, but device complexity increases
Solution Approach 1:
Multiple planetary gear sets (first, second, third, and fourth planetary gear sets) are merged into a single integrated transmission system. The gear sets are configured to share common elements and engagement mechanisms, allowing the system to achieve 10 forward gear ratios and 1 reverse gear ratio through coordinated operation of the merged components, thereby reducing overall device complexity compared to separate gear train systems
Solution Approach 2:
Each planetary gear set is designed with multi-functionality, where the same gear set can contribute to multiple different gear ratios depending on which engagement mechanisms are activated. For example, the first planetary gear set can be involved in generating different gear ratios when different combinations of the seven engagement mechanisms are engaged, reducing the need for dedicated gear sets for each ratio and thereby simplifying the overall transmission complexity
Data Source
AI summary
An automatic transmission includes an input shaft, a first planetary gear set, a second planetary gear set, a third planetary gear set, a fourth planetary gear set, and an engagement mechanism. The engagement mechanism includes first to seventh engagement devices. Nine or more forward transmission gear ratios are established by setting each of at least three engagement devices among the first to seventh engagement devices in an engagement mode.