Planetary Gear Train for Automatic Transmission Length Reduction
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Solution Overview
Problem
Current automatic transmissions with increased shift stages face challenges in installability and power flow efficiency due to the number of parts, weight, and production costs, while also requiring improvement in gear ratio span for better fuel consumption.
Innovation Solution
A planetary gear train configuration with four planetary gear sets, two external gears, and six control elements, arranged in a way that reduces length and improves installability, achieving at least nine forward speeds and one reverse speed, with a wide range of gear teeth for optimal gear ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the number of planetary gear sets and control elements is increased to achieve more shift stages, then the fuel consumption and drivability are improved, but the device complexity, length, and installability are deteriorated
Solution Approach 1:
The patent merges multiple planetary gear sets into a single integrated structure where the first, second, and third planetary gear sets share a common input shaft, and the fourth planetary gear set shares an output shaft. This consolidation reduces the number of separate components while maintaining nine forward speeds and one reverse speed, directly addressing the contradiction between achieving multiple shift stages and reducing device complexity
Solution Approach 2:
The planetary gear sets are designed with multi-functional capability where the same gear sets can achieve both forward motion at different speeds and reverse motion. The control elements (clutches and brakes) are configured to enable multiple functions from a limited number of components, allowing nine forward speeds and one reverse speed to be achieved with only six control elements, thereby reducing overall device complexity while maintaining fuel efficiency
2Use of energy by moving object
If the number of planetary gear sets and control elements is increased to achieve more shift stages, then the fuel consumption and drivability are improved, but the length and installability are deteriorated
Solution Approach 1:
The patent employs a nested arrangement where planetary gear sets are positioned concentrically around the input and output shafts. The first, second, and third planetary gear sets are arranged in a nested configuration around the common input shaft, and the fourth planetary gear set is nested around the output shaft. This nesting strategy significantly reduces the axial length of the transmission while maintaining all nine forward speeds and one reverse speed, directly resolving the contradiction between achieving multiple shift stages and reducing transmission length
3Use of energy by moving object
If the number of planetary gear sets and control elements is increased to achieve more shift stages, then the fuel consumption and drivability are improved, but the production cost is increased
Solution Approach 1:
The patent merges multiple planetary gear sets into a single integrated structure where the first, second, and third planetary gear sets share a common input shaft, and the fourth planetary gear set shares an output shaft. This consolidation reduces the number of separate components while maintaining nine forward speeds and one reverse speed, directly addressing the contradiction between achieving multiple shift stages and reducing device complexity
Solution Approach 2:
The planetary gear sets are designed with multi-functional capability where the same gear sets can achieve both forward motion at different speeds and reverse motion. The control elements (clutches and brakes) are configured to enable multiple functions from a limited number of components, allowing nine forward speeds and one reverse speed to be achieved with only six control elements, thereby reducing overall device complexity while maintaining fuel efficiency
4Length of moving object
If the gear ratio span is reduced to shorten the transmission length, then the installability is improved, but the fuel consumption performance is deteriorated
Solution Approach 1:
The patent employs a dynamic gear ratio design where the gear ratios are optimized to provide a wide span (6.5 to 7.5) across nine forward speeds, enabling the transmission to adapt to different driving conditions. This dynamic gear ratio configuration maximizes fuel efficiency by allowing the engine to operate in optimal ranges while maintaining a compact transmission length through the nested planetary gear arrangement
Data Source
AI summary
A planetary gear train of an automatic transmission for a vehicle may include a first planetary gear set, a second planetary gear set, a third planetary gear set, a fourth planetary gear set, an input shaft mounted with the first, second, and third planetary gear sets at an external circumference of the input shaft, an output shaft disposed in parallel with the input shaft and mounted with the fourth planetary gear set on external circumference of the output shaft, a first shaft, a second shaft directly connected with the input shaft, a third shaft, a fourth shaft gear-meshed with the output shaft, a fifth shaft, a sixth shaft, a seventh shaft, an eighth shaft, a ninth shaft directly connected with the output shaft, a tenth shaft, and transfer gears, each gear-meshed with at least one of the shafts.