AMT Shift Spindle Control for Dog Teeth Engagement
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Solution Overview
Problem
Conventional automated manual transmissions (AMT) experience uncomfortable driving force non-transmission periods during shifts, particularly in shift-down directions, due to prolonged clutch disengagement, which can lead to shallow engagement of dog teeth and increased risk of 'dog abutment', resulting in inefficient gear changes and potential for shifting errors.
Innovation Solution
A speed change apparatus with a controller-driven shift spindle mechanism that disengages the clutch at a specific angle, allowing for immediate cancellation of shallow engagement without operating the change mechanism, thereby reducing the disengagement time and preventing unintended gear shifts, and uses a learning process to determine the optimal clutch-disengaging shift spindle angle based on rotational angles of the shift drum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the clutch disengagement time is shortened to reduce driving force non-transmission period, then driver comfort is improved, but shallow engagement of dog teeth occurs
Solution Approach 1:
The clutch disengagement process is segmented into multiple phases: initial disengagement phase, shallow engagement cancellation phase, and final engagement phase. This segmentation allows the system to briefly disengage the clutch to cancel shallow engagement without maintaining disengagement for an extended period, thus reducing overall driving force non-transmission while ensuring proper dog teeth engagement.
Solution Approach 2:
The system performs preliminary action by rotating the clutch lifter cam plate in the shift-up direction before final clutch engagement to cancel shallow engagement of dog teeth. This preliminary rotation ensures that dog teeth are properly meshed before driving force is transmitted, preventing engagement issues while minimizing clutch disengagement time.
2Reliability
If the clutch disengagement time is extended to allow proper gear change operations, then shallow engagement is prevented, but driver comfort deteriorates due to prolonged driving force non-transmission
Solution Approach 1:
The clutch lifter cam plate performs periodic rotational movements: first in the shift-down direction to engage gears, then in the shift-up direction to cancel shallow engagement, and finally returns to the engaged position. This periodic action sequence ensures proper dog teeth engagement while minimizing the total duration of clutch disengagement, thereby maintaining driver comfort.
Solution Approach 2:
The system changes the rotational parameter of the clutch lifter cam plate dynamically during the shifting process. By rotating the cam plate in the shift-up direction temporarily to cancel shallow engagement and then returning it to the engaged position, the system optimizes both engagement quality and disengagement time without requiring extended clutch disengagement.
3Reliability
If the shift spindle rotates further to cancel shallow engagement, then shallow engagement is removed, but unintended shift-down operation occurs
Solution Approach 1:
The control unit monitors the rotational position of the shift spindle and the state of the change mechanism during the shifting process. When shallow engagement is detected, the control unit provides feedback to rotate the clutch lifter cam plate in the shift-up direction to cancel it, while simultaneously monitoring to prevent excessive rotation that would trigger unintended shift-down operations, ensuring precise control of the shifting process.
Solution Approach 2:
The clutch lifter cam plate acts as an intermediary mechanism between the shift spindle and the dog clutch. By rotating the cam plate in the shift-up direction, the system can cancel shallow engagement of dog teeth without directly rotating the shift spindle further, thus preventing unintended shift-down operations while still achieving proper engagement cancellation.
Data Source
AI summary
In a speed change apparatus for a vehicle, a controller stores as a clutch-disengaging shift spindle angle θ1 a position at which a clutch is disengaged when a shift spindle is rotated in a first direction. The controller controls the shift spindle by a first step W1 of rotating the shift spindle in the first direction until a disengaging-side target angle Ta1 is reached; a second step W2 of returning the shift spindle in a second direction opposite to the first direction; and a third step W3 of rotating the shift spindle in the first direction up to the clutch-disengaging shift spindle angle θ1 and thereafter rotating the shift spindle in the second direction to return the shift spindle, upon detection of an output from a drum angle sensor, the output corresponding to shallow engagement of dog teeth.