Automatic Transmission Gear Train with Compound Planetary Set
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current automatic transmission gear trains for vehicles typically limit the number of shift speeds, which can result in suboptimal fuel efficiency and performance, and the design of combining structures for planetary gear sets affects durability and power transmission efficiency.
Innovation Solution
A gear train configuration combining two simple planetary gear sets and one compound planetary gear set using four clutches and two brakes to achieve eight forward speeds and one reverse speed, enhancing power delivery and fuel consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of shift speeds is increased, then fuel efficiency and vehicle performance are improved, but the complexity of the gear train structure increases
Solution Approach 1:
The patent combines two simple planetary gear sets and one compound planetary gear set into a single integrated gear train structure. This merging approach enables eight forward speeds and one reverse speed to be achieved through a unified configuration, resolving the contradiction by achieving high speed variety without proportionally increasing overall structural complexity
Solution Approach 2:
The planetary gear sets are designed with multiple functional paths where the same structural components serve different speed ratio functions. The compound planetary gear set particularly demonstrates multi-functionality by providing multiple intermediate speed ratios through different engagement combinations, allowing the gear train to achieve eight forward speeds without requiring separate dedicated mechanisms for each speed
2Productivity
If more planetary gear sets are combined to achieve more shift speeds, then the number of speeds increases, but the size of the transmission increases
Solution Approach 1:
The patent employs a nested arrangement where planetary gear sets are positioned concentrically and share common rotational axes. The compound planetary gear set nests additional gear elements within the existing planetary structure, allowing multiple speed ratios to be generated within a compact radial envelope, thereby increasing shift speeds without proportionally increasing transmission size
3Power
If the gear train structure is optimized for more speeds, then power delivery performance is enhanced, but the durability may be compromised
Solution Approach 1:
The patent applies different structural characteristics to different parts of the gear train. The compound planetary gear set uses a specialized configuration with multiple pinions and ring gears optimized for high torque transmission, while the simple planetary gear sets use more straightforward configurations. This local optimization allows each section to be tuned for its specific function, maintaining durability while achieving enhanced overall power delivery performance across eight forward speeds
Data Source
AI summary
A gear train of an automatic transmission for a vehicle includes: a first planetary gear set that receives an input speed from an input shaft and outputs a reduced speed; a second planetary gear set that receives the reduced speed of the first planetary gear set and selectively outputs a same speed or a reversed speed; and a third planetary gear set that receives the reduced speed of the first planetary gear set, the input speed from the input shaft, and the output speed of the second planetary gear set, and then outputs a shifted output speed.