Air-Fuel Ratio Sensor Abnormality Detection via Dynamic Thresholds
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Solution Overview
Problem
Conventional abnormality determination devices for air-fuel ratio sensors fail to accurately detect abnormalities due to their reliance on static thresholds and differential values, which do not account for the dynamic changes in air-fuel ratios and can lead to false negatives or false positives, especially during fuel-cut operations.
Innovation Solution
An abnormality determination device that calculates differential values of air-fuel ratio sensor outputs and compares them to predetermined thresholds, using local extremum values and output ranges to determine sensor abnormalities, allowing for comprehensive and accurate detection across various air-fuel ratio regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If static thresholds and differential values are used to determine sensor abnormalities, then the determination process is simple, but the accuracy decreases due to false negatives or false positives during fuel-cut operations
Solution Approach 1:
The patent applies dynamics by transitioning from static thresholds to dynamic threshold determination. The threshold is no longer fixed but is determined based on the air-fuel ratio region (rich region, lean region, or theoretical air-fuel ratio region) and operational state (fuel-cut operation). This allows the threshold to adapt to changing conditions, eliminating false negatives/positives while maintaining a relatively simple determination process through region-based classification.
Solution Approach 2:
The patent changes the parameter of the threshold from a static value to a dynamic value that varies with operating conditions. By determining thresholds based on air-fuel ratio regions and fuel-cut operation status, the system adjusts the comparison criterion to match the current operational state, thereby improving detection accuracy without significantly complicating the overall process.
2Device complexity
If conventional differential value counting methods are used, then the device complexity is low, but the reliability decreases due to inability to detect abnormalities accurately during dynamic operations
Solution Approach 1:
The patent applies local quality by treating different air-fuel ratio regions (rich region, lean region, theoretical air-fuel ratio region) and operational states (fuel-cut operation) as distinct contexts with different threshold criteria. Each region has its own specific threshold determination method, allowing for localized optimization of detection accuracy without requiring a completely complex unified system.
Solution Approach 2:
The system introduces dynamic threshold determination based on operational state (fuel-cut operation detection) and air-fuel ratio region identification. This dynamic approach improves reliability by adapting the determination criteria to current conditions while maintaining manageable complexity through structured region-based classification and clear decision logic.
3Ease of operation
If fixed threshold comparison is used for output values, then the determination process is straightforward, but the adaptability decreases when air-fuel ratio changes dynamically during fuel-cut operations
Solution Approach 1:
The patent implements dynamics by making the threshold adaptive rather than fixed. The threshold is dynamically determined based on the identified air-fuel ratio region and fuel-cut operation status. This allows the system to maintain straightforward comparison logic while achieving high adaptability to dynamic operating conditions through region-based threshold selection.
Solution Approach 2:
The system changes the threshold parameter from a fixed value to a dynamically determined value that reflects current operating conditions. By selecting appropriate thresholds based on air-fuel ratio regions and fuel-cut state, the system achieves both straightforward comparison processing and high adaptability to dynamic changes.
Data Source
AI summary
An abnormality determination device for an air-fuel ratio sensor includes a differential value calculator and an abnormality determiner. The differential value calculator is configured to calculate a differential value of an output value of the air-fuel ratio sensor which is configured to detect an air-fuel ratio of exhaust gas. The abnormality determiner is configured to determine abnormality of the air-fuel ratio sensor based on a result of comparison between a reference output value of the air-fuel ratio sensor and a predetermined threshold. The reference output value is obtained by the air-fuel ratio sensor when the differential value calculated by the differential value calculator becomes a predetermined value.