AMT Crawler Gear Shift Using Non-Zero Countershaft Speed
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Solution Overview
Problem
Automated mechanical transmissions (AMTs) in heavy-duty vehicles experience unwanted noise and jerk during crawler gear engagement due to tooth-to-tooth contact at zero rotational speed, which current technologies fail to adequately mitigate.
Innovation Solution
Engage the crawler gear before the countershaft is completely stopped and at a predetermined rotational speed, using a clutch to introduce a controlled rotational speed, thereby reducing noise and jerk. This involves a clutch mechanism between the input shaft and power unit, and a gearbox brake to manage rotational speeds, ensuring engagement occurs at a non-zero speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the crawler gear is engaged at zero rotational speed, then the gear engagement is achieved, but unwanted noise and jerk occur due to tooth-to-tooth contact
Solution Approach 1:
The patent changes the rotational speed parameter from zero to a predetermined non-zero value during crawler gear engagement. The transmission control unit is configured to engage the crawler gear when the countershaft rotates at a predetermined rotational speed rather than at zero speed, which eliminates tooth-to-tooth contact and reduces noise and jerk during engagement.
2Manufacturing precision
If the countershaft is completely stopped before engagement, then the gear teeth align properly, but noise and jerk increase due to tooth-to-tooth contact
Solution Approach 1:
The patent modifies the rotational speed parameter from zero to a predetermined non-zero value. By engaging the crawler gear while the countershaft rotates at this predetermined speed rather than being completely stopped, the gear teeth engage smoothly without impact contact, eliminating noise and jerk while maintaining proper alignment.
3Object-affected harmful factors
If a clutch is used to introduce controlled rotational speed, then noise and jerk are reduced, but device complexity increases
Solution Approach 1:
The patent utilizes the existing clutch mechanism in the automated mechanical transmission system to achieve controlled rotational speed for crawler gear engagement. Rather than adding a new device, the invention leverages the self-service capability of the existing clutch to rotate the countershaft at a predetermined speed before engagement, thereby reducing noise and jerk without significantly increasing overall system complexity.
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to an automated mechanical transmission (100) for a vehicle (110), comprising: - a main gearbox assembly (MG) comprising a main shaft (1) and being adapted to be shiftable between at least one engaged state and a neutral state; - a split gearbox assembly (SG) comprising an input shaft (2) and being adapted to be shiftable between a first engaged state, a second engaged state and a neutral state; - a countershaft (3); - a crawler gearbox assembly (CG) comprising a crawler gear engagement member (5) which is adapted to selectively engage and disengage a crawler gear defining a torque path from the input shaft (2) to the main gearbox assembly (MG) via the countershaft (3); - a gearbox brake (6); and - a transmission control unit (7); - wherein the transmission is configured to be settable in an AMT neutral state defined by the main gearbox assembly (MG) being in the neutral state, the split gearbox assembly (SG) being in one of the engaged states and the input shaft (2) being in driving connection with a power unit (120) causing the input shaft (2) to rotate when the transmission is in use; wherein: - when the transmission control unit (7) obtains a request to engage the crawler gear from the AMT neutral state, the transmission control unit (7) is configured to: - apply the gearbox brake (6) so that a rotational speed of the countershaft (3) is reduced to a first predetermined rotational speed which is higher than a zero rotational speed; and - when the first predetermined rotational speed is reached, release the gearbox brake (6), set the split gearbox assembly (SG) to the neutral state and engage the crawler gear by the crawler gear engagement member (5). The invention also relates to a method and to a vehicle (110).