Shift-By-Wire Neutral Indication After Clutch Disengagement
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Solution Overview
Problem
In shift-by-wire systems for automatic transmissions, if the engagement element fails to disengage during a shifting operation from a running range to a neutral range, the vehicle may move despite a neutral indicator display, causing a mismatch between driver recognition and vehicle behavior.
Innovation Solution
A control device and method that changes the indicator display to neutral only after successful disengagement determination of the engagement element, and implements torque limitation control to prevent unintended vehicle movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the indicator immediately displays neutral when a shifting operation from running range to neutral range is performed, then the response speed of the indicator is improved, but the reliability of the vehicle state indication deteriorates because the vehicle may move despite the neutral display
Solution Approach 1:
The system performs preliminary determination of engagement element disengagement status before changing the indicator display to neutral. The control unit checks whether the engagement element has actually disengaged by monitoring transmission output shaft rotation speed or other parameters, and only then updates the indicator to neutral display. This preliminary verification ensures the indicator accurately reflects the actual vehicle state before display change.
2Ease of operation
If the indicator displays neutral before confirming disengagement of the engagement element, then the ease of operation is improved, but the safety of the vehicle deteriorates due to potential unintended movement
Solution Approach 1:
The system implements feedback control by continuously monitoring the actual transmission state (through rotation speed sensors, clutch position sensors, or other detection means) and comparing it with the desired neutral state. The indicator display is updated only when the feedback confirms that the engagement element has successfully disengaged and the transmission is truly in neutral. This closed-loop feedback ensures safety while maintaining operational ease.
3Reliability
If the system waits for disengagement determination before changing indicator display, then the reliability of vehicle state indication is improved, but the loss of time increases during shifting operation
Solution Approach 1:
The system monitors multiple parameters simultaneously to determine disengagement status, including transmission output shaft rotation speed, engine rotation speed, and potentially clutch hydraulic pressure. By evaluating changes in these parameters over time, the system can quickly determine when disengagement has occurred without excessive delay. The indicator display is updated as soon as the parameter changes confirm neutral state, balancing reliability with minimal time loss.
Data Source
AI summary
A Controller constitutes a control device for a vehicle having an automatic transmission on which a shift-by-wire system is mounted. The controller changes display of an range indicator to N-range display after disengagement determination of an power transmission clutch is made when a shifting operation from a D range to a N range is performed.