Planetary Gear Train for Automatic Transmission with Nested Gear Sets
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Increasing the number of shift stages in automatic transmissions to enhance fuel efficiency and drivability leads to increased complexity, length, production cost, and weight, compromising installability and power flow efficiency.
Innovation Solution
A planetary gear train with three single pinion gear sets and six control elements that selectively interconnect shafts to achieve at least eight forward speeds and one reverse speed, improving power delivery and fuel efficiency while maintaining a minimal component count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the number of planetary gear sets is increased to achieve more shift stages, then fuel consumption is improved, but device complexity and length increase
Solution Approach 1:
The patent merges multiple planetary gear sets (first, second, and third planetary gear sets) into a single integrated transmission system where gear sets share common components such as the sun gear, planet carrier, and ring gear. This consolidation achieves multiple shift stages (8 forward speeds and 1 reverse speed) while reducing the total number of discrete components compared to traditional multi-gear-set designs, thereby improving fuel consumption without proportionally increasing device complexity
Solution Approach 2:
The patent implements a universal planetary gear structure where a single set of sun gear, planet carrier, and ring gear serves multiple functions across different shift stages. The control elements (clutches and brakes) selectively engage different components of the same planetary gear set to achieve various gear ratios, allowing the same physical components to perform multiple gear reduction functions, thus reducing the need for additional separate planetary gear sets
2Use of energy by moving object
If the number of planetary gear sets is increased to achieve more shift stages, then fuel consumption is improved, but the length of transmission increases
Solution Approach 1:
The patent arranges the planetary gear sets in a nested configuration where the first, second, and third planetary gear sets are positioned concentrically around a common axis. The sun gear, planet carrier, and ring gear of different gear sets are integrated and share the same spatial envelope, allowing multiple gear stages to be packed into a compact axial space, thereby achieving extended gear ratios without proportionally increasing transmission length
Solution Approach 2:
The patent transitions from a linear arrangement of separate planetary gear sets to a concentric radial arrangement where multiple gear sets share a common rotational axis. This dimensional reorganization allows the transmission to achieve multiple shift stages by utilizing radial space rather than extending axially, thus improving fuel consumption through multi-staging while minimizing the increase in transmission length
3Use of energy by moving object
If the number of planetary gear sets is increased to achieve more shift stages, then fuel consumption is improved, but production cost and weight increase
Solution Approach 1:
The patent combines multiple planetary gear sets into a unified structure where components such as the sun gear, planet carrier, and ring gear are shared across different gear stages. This merging eliminates the need for duplicate components that would otherwise be required in separate planetary gear sets, thereby achieving multiple shift stages for improved fuel consumption while reducing the total weight of the transmission system
Solution Approach 2:
The patent designs a universal planetary gear mechanism where the same physical components (sun gear, planet carrier, ring gear) perform multiple gear reduction functions across different shift stages. By making these components multi-functional rather than dedicated to single stages, the patent reduces the total material required and thus the weight, while still achieving the fuel consumption benefits of multiple shift stages
Data Source
AI summary
A planetary gear train of an automatic transmission for a vehicle may include an input shaft for receiving an engine torque, an output shaft for outputting a shifted engine torque, a first planetary gear set, a second planetary gear set, a third planetary gear set, and six control elements for selectively interconnecting the rotation elements, a first shaft connected with the first rotation element, and selectively connectable with the input shaft, a second shaft selectively connectable with the first shaft, a third shaft, a fourth shaft selectively connectable with the input shaft, a fifth shaft directly connected with the transmission housing, a sixth shaft selectively connectable with the first shaft, and a seventh shaft selectively connectable with the third shaft, and directly connected with the output shaft.