Capacitance Sensor Segmentation for In-Motion Self-Diagnosis
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Solution Overview
Problem
Capacitance type physical quantity sensors face issues with malfunction detection due to stiction between electrodes, leading to delayed abnormality determination, especially when the vehicle is in motion, as existing methods only perform abnormality checks when the vehicle is stopped.
Innovation Solution
A physical quantity sensor design incorporating a first and second capacitance element section with distinct saturation values, a drive circuit, multiplexer, and determination circuit, allowing for time-sharing signal output and self-diagnosis without relying on external requests, enabling prompt detection of abnormalities even when the vehicle is in motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If abnormality determination is performed only when the vehicle is in a stopped state, then false detections due to acceleration are reduced, but the abnormality detection is delayed for a relatively long period of time
Solution Approach 1:
The physical quantity detection element is divided into a first element section with a first capacitance and a second element section with a second capacitance. The first capacitance has a first saturation capacitance value at which the first capacitance is saturated by a first physical quantity, and the second capacitance has a second saturation capacitance value at which the second capacitance is saturated by a second physical quantity smaller in absolute value than the first physical quantity. This segmentation allows the second element section to serve as a monitoring component that can detect abnormalities during vehicle operation without being affected by normal acceleration conditions.
Solution Approach 2:
The second element section is configured to saturate at a lower physical quantity threshold than the first element section, creating a preliminary warning mechanism. When the second capacitance reaches its saturation capacitance value, it triggers a determination that the first element section may be abnormal, prompting proactive monitoring before actual malfunction occurs during normal operation.
2Loss of time
If continuous monitoring is performed to enable prompt abnormality detection, then response time is reduced, but false detections may occur during vehicle operation
Solution Approach 1:
The first and second element sections have different local characteristics - the second element section is designed with a lower saturation threshold specifically for monitoring purposes, while the first element section maintains its full measurement capability. This allows continuous monitoring through the second section without compromising the accuracy of the primary detection section.
Solution Approach 2:
The second element section acts as an intermediary monitoring component that indirectly indicates the status of the first element section. By monitoring the saturation state of the second capacitance, the system can infer potential abnormalities in the first element section without directly measuring the same physical quantity, thus avoiding false detections during normal operation.
3Device complexity
If a single capacitance element is used, then device complexity is reduced, but the ability to perform self-diagnosis and detect abnormalities is insufficient
Solution Approach 1:
Both the first and second element sections can function as physical quantity detection elements, but in the normal operation mode, the first element section serves as the primary detector while the second element section serves as a monitoring element. This multi-functionality allows the system to perform both accurate physical quantity measurement and self-diagnosis using the same sensor structure.
Solution Approach 2:
The patent merges the detection function and the monitoring function into a single sensor device with two capacitance elements. The determination circuit combines information from both the first and second element sections to make abnormality determinations, integrating multiple functions without requiring separate independent systems.
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 proactive self-diagnosis and reduced chances of vain self-diagnosis, improving the reliability of physical quantity detection and reducing errors in external device control, particularly in vehicles.
Implementation Method 1
a capacitance type physical quantity sensor which detects a physical quantity using the phenomenon that the capacitance value of the capacitance generated between electrodes opposed to each other and provided to a physical quantity detection element changes in accordance with the magnitude and the direction of the physical quantity
Data Source
AI summary
A physical quantity sensor includes a first element section in which first capacitances varying in accordance with a physical quantity have first saturation capacitance values at which the first capacitances are saturated by a first physical quantity, a second element section in which a second capacitances varying in accordance with the physical quantity have second saturation capacitance values at which the second capacitances are saturated by a second physical quantity smaller in absolute value than the first physical quantity, a multiplexer for outputting the first signals from the first element section and the second signals from the second element section, and a determination circuit that determines whether or not the level of the second signal input via the multiplexer reaches a threshold value which is a level of the second signal when the second physical quantity acts.