Exhaust Gas Sensor Abnormality Detection with Scavenging Stability Exclusion
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Solution Overview
Problem
Existing abnormality detection systems for exhaust gas sensors in internal combustion engines often incorrectly determine sensor abnormalities due to unstable exhaust scavenging behavior, leading to erroneous maintenance and increased costs.
Innovation Solution
An abnormality detection device that calculates the responsiveness of the exhaust gas sensor based on the timewise change of its output values and excludes periods of unstable behavior, determining sensor abnormality only when responsiveness falls below a predetermined threshold, thus preventing false positives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If exhaust scavenging behavior is unstable, then the oxygen sensor exhibits unstable behavior with longer response time, but this leads to erroneous determination of sensor abnormality even when the sensor is not deteriorated
Solution Approach 1:
The abnormality determination unit dynamically adjusts the responsiveness threshold based on exhaust scavenging stability. When scavenging is unstable (indicated by inverted differential values), the system temporarily suspends abnormality determination or adjusts thresholds, allowing sensor responsiveness to vary without triggering false abnormality flags. This dynamic adaptation resolves the contradiction by making the measurement system flexible to operational conditions.
Solution Approach 2:
The system continuously monitors the differential value of sensor output to detect scavenging stability and uses this feedback to control whether abnormality determination should proceed. When the differential value indicates unstable scavenging (inversion detected), the system feeds back to suspend determination, preventing erroneous conclusions. This feedback mechanism ensures reliable abnormality detection only under stable operating conditions.
2Device complexity
If a single exhaust gas sensor is used to detect exhaust gas from multiple exhaust pipes, then the number of parts is reduced and structure is simplified, but exhaust scavenging becomes unstable due to mixing state
Solution Approach 1:
The invention extracts the stability assessment function from the sensor reading itself and separates it into a independent differential value analysis. By calculating the differential value between consecutive sensor outputs, the system identifies scavenging stability independently of the actual gas composition, allowing the single sensor to function reliably despite mixed exhaust conditions.
Solution Approach 2:
The differential value calculation acts as an intermediary that mediates between the unstable mixed exhaust conditions and the sensor readings. This intermediate calculation layer filters out the instability caused by exhaust mixing, allowing the abnormality determination to proceed based on genuine sensor performance rather than flow variability.
3Reliability
If abnormality determination is performed continuously based on sensor responsiveness, then timely detection of sensor deterioration is achieved, but false positives increase due to unstable exhaust scavenging periods
Solution Approach 1:
The system performs abnormality determination periodically but conditionally - only when exhaust scavenging stability is confirmed through differential value analysis. This periodic yet conditional approach balances timely detection with accuracy, ensuring that measurements are taken at appropriate intervals without being triggered during unstable scavenging periods that would produce false positives.
Data Source
AI summary
An abnormality detection device determines abnormality in an exhaust gas sensor, disposed in an exhaust passage of an engine to detect a component in exhaust gas. The abnormality detection device includes: a responsiveness determination unit configured to calculate responsiveness of the exhaust gas sensor on the basis of a timewise change of output values of the exhaust gas sensor; and an abnormality determination unit configured to determine that the exhaust gas sensor has abnormality when the responsiveness calculated by the responsiveness determination unit is lower than a predetermined responsiveness threshold. The abnormality determination unit determines if the exhaust gas sensor has abnormality, excluding an excluded period during which a slope of the output values becomes zero or is inversed with respect to a preceding trend of the timewise change while the output values of the exhaust gas sensor timewisely change between a predetermined first and second determination values.