Multi-speed Transmission with Four Planetary Gear Sets
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Solution Overview
Problem
Conventional automatic transmissions face challenges in efficiently managing a wide range of vehicle speeds, as some engines operate optimally within a narrow speed range, requiring transmissions that can adapt power transmission speed ratios effectively for both low-speed acceleration and high-speed cruising.
Innovation Solution
The transmission employs four simple planetary gear sets and six selectively engaging clutches to establish ten forward and one reverse speed ratio, allowing for flexible speed relationships between input and output shafts through fixed and shiftable gearing arrangements, enabling efficient power transmission across various speed conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a transmission uses a narrow range of gear ratios, then the structure is simpler, but the engine cannot operate efficiently across a wide range of vehicle speeds
Solution Approach 1:
The transmission is divided into multiple planetary gear sets (first, second, third, and fourth gear sets) with different reduction ratios, allowing the system to segment the overall speed ratio range into multiple manageable stages. Each gear set handles a specific portion of the speed ratio requirements, enabling the transmission to achieve a wide overall range while keeping individual gear set designs relatively simple and standardized.
Solution Approach 2:
Multiple planetary gear sets are nested within a single transmission housing, with each gear set containing sun gears, planet gears, and ring gears that are interconnected through shared components like the intermediate shaft. This nested configuration allows multiple gear reduction stages to be compactly arranged, achieving a wide speed ratio range without proportionally increasing the transmission's external dimensions or structural complexity.
2Adaptability or versatility
If a transmission uses multiple planetary gear sets, then more speed ratios are achieved, but the number of clutches and control complexity increases
Solution Approach 1:
The intermediate shaft serves multiple functions by being simultaneously connected to the first, second, and third planetary gear sets. This single component acts as a common interface for multiple gear sets, allowing clutches to control multiple gear engagement scenarios. The intermediate shaft's multi-functional role reduces the need for separate control mechanisms for each gear set, thereby reducing overall clutch requirements despite having four planetary gear sets.
Solution Approach 2:
Multiple planetary gear sets are combined within a unified transmission architecture that shares common components such as the intermediate shaft, clutch module, and housing. By merging the gear sets into a single integrated system rather than separate units, the transmission achieves ten forward and one reverse speed ratio through coordinated operation of the combined gear sets, reducing the total number of independent clutch actuators needed compared to having separate transmission units.
3Force
If the transmission optimizes for low-speed acceleration, then torque multiplication is improved, but high-speed cruising efficiency decreases
Solution Approach 1:
The transmission dynamically switches between different planetary gear sets and clutch configurations based on the required operating conditions. At low speeds, the system engages gear sets with higher reduction ratios to maximize torque multiplication for acceleration. At high speeds, the system transitions to gear sets with lower reduction ratios or direct drive configurations, allowing the engine to operate in its optimal fuel-efficient range while maintaining appropriate wheel speed. This dynamic reconfiguration enables the transmission to optimize both torque multiplication and fuel efficiency across different driving conditions.
Data Source
AI summary
A family of transmission gearing arrangements produces up to ten forward and one reverse speed ratios by selective engagement of various combinations of three or four clutches. Each disclosed transmission includes four planetary gear sets and six clutches. Two of the clutches can be brakes.