Planetary Gear Train for 12-Speed Automatic Transmission
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Solution Overview
Problem
Automatic transmissions with multiple planetary gear sets and control elements face challenges in achieving efficient power transmission and fuel efficiency due to increased complexity, length, and production costs, limiting their ability to implement higher shift levels without compromising mountability and shift quality.
Innovation Solution
A planetary gear train configuration utilizing four planetary gear sets with seven control elements, including clutches and brakes, to achieve forward 11 shifts and reverse 1 shift, optimizing power transmission and fuel efficiency by operating within a low rpm engine region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of planetary gear sets is increased to achieve higher shift levels, then the transmission level increases, but the length of the transmission increases and mountability deteriorates
Solution Approach 1:
The patent applies nesting by arranging planetary gear sets in a compact configuration where gear sets share common components and spatial arrangements. The planetary gear sets are nested within a confined transmission housing space, allowing multiple gear sets to coexist without proportionally increasing the overall transmission length, thereby achieving high shift levels while maintaining mountability.
Solution Approach 2:
The patent merges control elements and shafts across multiple planetary gear sets, allowing a single shaft to serve multiple gear sets and reducing the total number of discrete components. This consolidation reduces the overall transmission length while maintaining the required 11 forward shift levels.
2Adaptability or versatility
If the number of planetary gear sets is increased to achieve higher shift levels, then the transmission level increases, but the number of internal components increases and production cost increases
Solution Approach 1:
The patent implements multi-functionality by designing control elements and shafts that serve multiple planetary gear sets simultaneously. A single shaft can engage with multiple gear sets through selectively connectable arrangements, and control elements are configured to control multiple gear sets, thereby reducing the total component count while achieving 11 forward shift levels.
Solution Approach 2:
The patent combines multiple functions into fewer components by merging control elements and shafts that can operate across different planetary gear sets. This consolidation reduces the number of discrete internal components required while maintaining the complexity needed for high shift level operation.
3Adaptability or versatility
If the number of planetary gear sets is increased to achieve higher shift levels, then the transmission level increases, but the weight increases and power transmission efficiency deteriorates
Solution Approach 1:
The patent uses nesting to arrange planetary gear sets in a space-efficient configuration that minimizes the overall transmission weight. By nesting gear sets within a compact housing and allowing shared components, the weight increase is minimized relative to the achieved shift level.
Solution Approach 2:
The patent merges multiple gear sets and control elements into a unified structure that reduces total weight. Shared shafts and control elements eliminate redundant components, reducing the overall weight while maintaining the capability for 11 forward shift levels.
4Adaptability or versatility
If more control elements are used to achieve higher shift levels, then the transmission level increases, but the number of friction elements increases and shift quality deteriorates
Solution Approach 1:
The patent applies multi-functionality by configuring control elements to manage multiple planetary gear sets simultaneously. Each control element is designed to control specific gear sets based on the desired shift level, reducing the total number of control elements required while achieving 11 forward shift levels and maintaining shift quality.
Data Source
AI summary
A planetary gear train may include first to fourth planetary gear sets having first to twelfth rotation elements; a first shaft connected with the first rotation element; a second shaft connecting the second and sixth rotation elements; a third shaft connecting the third, seventh, and tenth rotation elements; a fourth shaft connected with the fourth rotation element and a transmission housing; a fifth shaft connected with the fifth rotation element and selectively connectable with the third shaft; a sixth shaft connected with the eighth rotation element and the output shaft; a seventh shaft connected with the ninth rotation element; an eighth shaft connected with the eleventh rotation element, selectively connectable with the first shaft and the second shaft, respectively, and connected with the input shaft; and a ninth shaft connected with the twelfth rotation element and selectively connectable with the sixth shaft.