Shift Position Sensor Abnormality Detection via Opposite-Direction Signal Check
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Solution Overview
Problem
Existing shift position detecting devices for vehicles face challenges in reliably detecting sensor abnormalities, such as disconnection or short circuits, which can lead to malfunctioning of forward-reverse switching and difficulties in executing a limp-home mode, especially when one of the sensors fails.
Innovation Solution
A shift position detecting device configured with four or more sensors and an electronic control unit that determines the shift position based on signals from normal sensors, detects abnormalities by checking for signals opposite to the travel direction, and switches to a neutral gear as a fail-safe measure to prevent forward-reverse switching malfunctioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If four or more sensors are used to detect shift position, then the system can continue operation in limp-home mode when one sensor fails, but the risk of forward-reverse switching malfunction increases when sensor abnormalities occur
Solution Approach 1:
The system performs preliminary abnormality determination by checking whether sensors output signals corresponding to shift positions for traveling in the direction opposite to the current traveling direction. This preliminary detection prevents forward-reverse switching malfunction before it occurs, allowing the system to switch to neutral gear as a fail-safe measure while maintaining limp-home mode operation with remaining functional sensors
Solution Approach 2:
The system continuously monitors sensor outputs and provides feedback on abnormality detection. When a sensor abnormality is detected through the opposite-direction signal check, the system feeds back this information to switch to neutral gear, preventing malfunction while allowing continued operation in limp-home mode using the remaining normal sensors
2Object-affected harmful factors
If the system executes fail-safe mode by switching to neutral gear when sensor abnormality is detected, then forward-reverse switching malfunction is prevented, but limp-home mode operation becomes difficult
Solution Approach 1:
The abnormality determination is performed preliminarily by checking for signals opposite to the current traveling direction before actual malfunction occurs. This early detection allows the system to prepare for fail-safe action while maintaining awareness of the abnormal state, enabling informed decisions about whether to switch to neutral gear or continue in limp-home mode
Solution Approach 2:
The system dynamically adjusts its response based on the abnormality detection results. When opposite-direction signals are detected, the system can dynamically switch between continuing limp-home mode operation and executing fail-safe neutral gear switching, allowing flexible adaptation to the specific abnormal condition while preventing harmful malfunctions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables reliable limp-home mode operation by avoiding malfunctioning of forward-reverse switching even when one sensor fails, ensuring safe vehicle operation by switching to neutral gear in case of sensor abnormalities.
Implementation Method 1
a magnet is arranged to face three Hall elements that are arranged on a straight line and function as sensors and the shift position of the shift selector is detected based on signals (output voltages) output from the respective Hall elements
Data Source
AI summary
A detecting device includes a shift selector, a magnet disposed in the shift selector, four or more sensors arranged at positions facing the magnet and an ECU. The ECU is configured to (i) determine a shift position based on signals output from the four or more sensors when the magnet is relatively displaced with respect to the four or more sensors in response to an operation of the shift selector, (ii) determine the shift position based on signals output from three or more of the four or more sensors determined to be normal when any one of the four or more sensors is abnormal, and (iii) determine the abnormality based on whether or not the three or more sensors output, during the traveling of the vehicle, a signal to a shift position pertaining to a case of traveling in the direction opposite to a traveling direction of the vehicle.