Double Disconnect Transmission Reverser Windage Reduction
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Solution Overview
Problem
Prior transmission designs experience high windage and gyroscopic flutter in the reverse clutch due to high-speed operation, leading to thermal failure and pauses in acceleration when switching between forward and reverse modes.
Innovation Solution
A transmission reverser system with an output shaft, idler shaft, counter shaft, forward and reverse clutches, and a disconnect device that allows for smooth shifting between forward and reverse modes by engaging and disengaging specific gears and clutches, reducing rotational speeds and windage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a countershaft reverser rotates at high speeds when the vehicle is operating at high forward speeds, then the reverser can change direction effectively, but high windage and gyroscopic flutter occur in the reverse clutch causing thermal failure
Solution Approach 1:
The reverser is divided into two independent shafts: a countershaft that remains stationary during forward operation and an output shaft that rotates with the transmission output. This segmentation allows the reverser to avoid high-speed rotation of the entire countershaft while still achieving direction reversal when needed.
Solution Approach 2:
The system dynamically switches between two operational states: in forward mode, the countershaft is braked and stationary while the output shaft rotates; in reverse mode, the brakes are released and the countershaft rotates with the output shaft. This dynamic adaptation eliminates unnecessary high-speed rotation that causes windage and gyroscopic effects.
2Ease of operation
If a synchronized reverser goes to neutral when switching between forward and reverse, then gear engagement is smooth, but acceleration pauses occur
Solution Approach 1:
The synchronization function is extracted from the main power transmission path and placed in a separate synchronization mechanism. This allows the reverser to synchronize gears without requiring the output shaft to go to neutral, thereby maintaining continuous acceleration and eliminating pauses.
Solution Approach 2:
A synchronization mechanism acts as an intermediary between the gear selection and power transmission. It prepares the gear engagement conditions independently without interrupting the output shaft rotation, allowing smooth shifting without acceleration pauses.
Data Source
AI summary
In accordance with an example embodiment, a transmission reverser may include a forward mode and a reverse mode. In the forward mode, a forward clutch is in the engaged condition causing an output gear to rotate with an output shaft. In the reverse mode, a reverse clutch and a disconnect clutch are in engaged conditions causing a counter shaft to rotate relative to the output shaft based upon the ratios of a first reverse gear to an idler gear and the idler gear to a second reverse gear and further causing the output gear to rotate relative to the counter shaft based upon the ratio of a third reverse gear to the output gear.