Multi-Speed Transmission Planetary Gear Arrangement
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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 proposed transmission system employs a combination of simple planetary gear sets and clutches to establish fixed and selective speed relationships among shafts, utilizing brake mechanisms to achieve various speed ratios, including forward and reverse gear configurations, allowing for efficient power transmission across a range of vehicle speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a transmission uses a narrow range of speed 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 independent planetary gear sets (first, second, third, and fourth gear sets) that can be selectively engaged through clutches and brakes. Each gear set provides specific speed ratios, and by segmenting the overall gear transmission into these modular units, the system achieves a wide range of speed ratios while maintaining manageable structural complexity through standardized planetary gear modules.
Solution Approach 2:
The transmission employs dynamic engagement and disengagement of clutches (first through fourth clutches) and brakes (first through fourth brakes) to selectively activate different planetary gear sets based on vehicle speed and engine operating conditions. This dynamic reconfiguration allows the transmission to adaptively provide appropriate speed ratios across a wide range of vehicle speeds, resolving the contradiction between adaptability and structural simplicity.
2Productivity
If a transmission provides multiple speed ratios for wide speed range, then engine efficiency is improved, but the device complexity increases
Solution Approach 1:
Each planetary gear set is designed to serve multiple functions by selectively engaging different clutches and brakes. For example, the first planetary gear set can provide first forward speed ratio through first clutch and first brake, and second forward speed ratio through second clutch and second brake. This multi-functionality reduces the need for completely separate gear sets for each ratio, thereby improving engine efficiency across multiple speed ranges while controlling overall device complexity.
Solution Approach 2:
The transmission employs nested planetary gear sets where gear sets are arranged concentrically around a common input shaft and output shaft. The first, second, third, and fourth planetary gear sets share common rotational axes and can be engaged in combination, allowing multiple speed ratios to be achieved through nested configuration rather than requiring separate transmission paths, thus improving productivity while managing complexity.
3Stability of the object's composition
If the transmission uses fixed speed relationship arrangements, then the structure is more stable, but the ability to adapt to different speed ratios is reduced
Solution Approach 1:
Clutches and brakes serve as intermediary elements between the fixed-speed planetary gear sets and the desired variable speed ratios. The clutches (first through fourth clutches) selectively connect different planetary gear sets to the input shaft, while brakes (first through fourth brakes) selectively hold planetary gear elements stationary. These intermediaries enable the fixed structural components to adaptively provide different speed ratios, maintaining structural stability while achieving versatility.
Data Source
AI summary
A transmission gearing arrangement produces nine forward speed ratios and one reverse speed ratio by selective engagement of three shift elements in various combinations. Some embodiment includes four simple planetary gear sets and six shift elements of which one is a brake. Another embodiment includes two axis transfer gear pairs in place of one of the planetary gear sets.