Shift Control Device Prevents Unintended Movement on Steep Slopes
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Solution Overview
Problem
Conventional shift-by-wire mechanisms in automatic transmissions risk unintentional vehicle movement when the engine is stopped, particularly on steep slopes, due to the inability to prevent shifting out of the parking range without engine power.
Innovation Solution
A shift control device with a selection means, switching control means, gradient detection means, and determination means that maintains the parking range if the engine is not producing power and the slope is steep, preventing unintended shifting and issuing warnings to the driver when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the shift range is switched to another range in the key-on state when the engine is stopped, then the parking state can be released, but the vehicle may unintentionally start to move on steep slopes
Solution Approach 1:
The system performs preliminary checks of engine state and road gradient before allowing shift range switching. By detecting these conditions in advance, the system prevents unintentional vehicle movement on steep slopes while still allowing normal parking release operations under safe conditions.
Solution Approach 2:
The control device acts as an intermediary between the driver's shift range selection and the actual transmission switching. It mediates by blocking the shift command when engine is stopped and gradient exceeds threshold, while allowing the command to pass through when conditions are safe, thus preventing unintended vehicle movement.
2Reliability
If the parking range is maintained when the engine is not producing power and the slope is steep, then unintentional vehicle movement is prevented, but the driver's intended operation may be blocked
Solution Approach 1:
The system continuously monitors engine state and road gradient, providing feedback to the control logic. This feedback mechanism allows the system to dynamically adjust shift range switching permissions based on real-time conditions, preventing unintended movement while allowing intended operations when safe.
Solution Approach 2:
The system dynamically adjusts the availability of shift range switching based on changing conditions. When engine is stopped and gradient is high, switching is blocked; when engine starts or gradient decreases, switching becomes available. This dynamic adaptation resolves the contradiction between safety and operational flexibility.
3Ease of operation
If the shift-by-wire mechanism allows automatic shifting, then convenience is improved, but the risk of unintentional movement increases when power unit cannot produce drive power
Solution Approach 1:
The system applies preliminary anti-action by blocking the automatic shifting function before it can cause harmful effects. By detecting when the engine is stopped and gradient is high, the system preemptively prevents the shift command from being executed, thus countering the potential harmful effect of unintentional vehicle movement before it occurs.
Data Source
AI summary
The SBW-CU that constitutes the shift control device, in the case of selection information for selecting a shift range other than the P range being output by the selection position determination unit when the shift range of the automatic transmission is the P range, maintains the P range without switching the shift range of the automatic transmission in the case of the engine being stopped, and the gradient of the road surface being equal to or greater than a predetermined threshold, and switches the shift range of the automatic transmission based on selection information in the case of the engine not being stopped, or in the case of the road surface gradient being less than the aforementioned predetermined threshold.