Air-Fuel Ratio Sensor Abnormality Detection Using Output Change Period
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Solution Overview
Problem
Existing abnormality determining devices for air-fuel ratio sensors struggle to accurately detect sensor abnormalities, particularly when the air-fuel ratio sensor output changes gradually due to deterioration, leading to incorrect assessments.
Innovation Solution
An abnormality determining apparatus that includes an air-fuel ratio controller, an output change period parameter calculator, and an output change amount extremum calculator, which calculates and analyzes the output change period and extremum to determine sensor abnormalities based on the relationship between these parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the air-fuel ratio sensor output changes gradually due to deterioration, then the sensor continues to operate, but the abnormality detection accuracy deteriorates
Solution Approach 1:
The patent changes the detection parameters from simply monitoring output change amount to analyzing both output change amount and output change period. By introducing time-domain analysis of the sensor response characteristics, the system can detect abnormalities even when output changes are gradual, thereby maintaining detection accuracy throughout the sensor's extended operational life.
2Ease of operation
If the output change maximum value is used for abnormality determination, then the detection method is simple, but false positives occur when output changes gradually
Solution Approach 1:
The patent transitions from one-dimensional detection (only output change amount) to two-dimensional detection by adding output change period as a new dimension. This dimensional expansion allows the system to distinguish between normal gradual changes and actual abnormalities, reducing false positives while maintaining operational simplicity through automated parameter comparison.
3Productivity
If only output change amount is monitored, then the detection process is fast, but diagnostic precision is insufficient for gradual changes
Solution Approach 1:
The patent performs preliminary calculation of both output change amount and output change period parameters during normal operation. By pre-computing these parameters and establishing their relationship patterns, the system maintains fast detection speed while improving diagnostic precision, as the additional period parameter is calculated using the same operational data without requiring separate measurement steps.
Data Source
AI summary
An abnormality determining apparatus includes an air-fuel ratio controller, an output change period parameter calculator, an output change amount extremum calculator, and an abnormality determining device. The abnormality determining device is configured to determine an abnormality of an air-fuel ratio sensor based on a relationship between an output change period parameter and an output change amount extremum.