Automatic Transmission Gear Train Merging Planetary Sets
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Solution Overview
Problem
Current automatic transmissions with fewer speeds, such as four or five-speed transmissions, are inefficient in optimizing speed ratios, leading to suboptimal fuel mileage and performance, and the design of gear trains with multiple planetary gear sets is complex, affecting durability and power transmission efficiency.
Innovation Solution
A gear train configuration for automatic transmissions that includes a first simple planetary gear set and a second compound planetary gear set, combined with three clutches and two brakes, allowing for six forward speeds and one reverse speed by selectively connecting rotational elements through friction members, optimizing torque transmission and shifting mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a transmission realizes a greater number of shift speeds, then fuel mileage and performance are improved, but device complexity increases
Solution Approach 1:
The patent combines two simple planetary gear sets into a single compound planetary gear set by sharing a common sun gear and planet carrier. This merging approach enables the transmission to achieve six forward speeds and one reverse speed while reducing the overall number of discrete gear sets needed, thereby improving fuel efficiency without proportionally increasing device complexity
2Productivity
If a transmission realizes a greater number of shift speeds, then performance is improved, but durability decreases
Solution Approach 1:
By merging two planetary gear sets into a compound configuration with shared components, the patent reduces the total number of friction members (clutches and brakes) required to control the gear train. This consolidation fewer engagement points and potential failure modes, thereby maintaining high performance across six forward speeds while improving durability through a more robust, simplified structure
3Productivity
If a transmission realizes a greater number of shift speeds, then speed ratio optimization is improved, but power transmission efficiency decreases
Solution Approach 1:
The compound planetary gear set merges multiple gear trains into a unified structure where power flows through shared sun gears and planet carriers. This consolidation reduces the number of separate power transmission paths and friction members required, minimizing energy losses while enabling optimized speed ratios across six forward gears for improved fuel economy and performance
4Device complexity
If the number of friction members is minimized, then hydraulic line construction is simplified, but the ability to control multiple speeds is reduced
Solution Approach 1:
The patent merges the functionality of multiple friction members into a coordinated system controlling the compound planetary gear set. By strategically positioning three clutches and two brakes within the unified gear structure, the system achieves six forward speeds and one reverse speed with minimized hydraulic complexity, as the shared components allow multiple speed ratios to be controlled through fewer engagement points
Solution Approach 2:
The friction members are designed with variable connectivity, allowing their functional relationships to change dynamically across different gear ranges. This dynamic configuration enables the same set of friction members to control multiple speed ratios by changing which rotational elements they connect, maintaining versatile speed control while minimizing the total number of friction members and hydraulic lines required
Data Source
AI summary
A gear train of an automatic transmission for a vehicle according to an exemplary embodiment of the present invention includes a first planetary gear set, a second planetary gear set composed of two simple planetary gear sets, three clutches, and two brakes, and thus the gear train of an automatic transmission may realize six forward speeds and one reverse speed.