Air-Fuel Ratio Sensor Abnormality Diagnosis via Response Correction
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Solution Overview
Problem
Existing abnormality diagnosis systems for air-fuel ratio sensors struggle to accurately diagnose deterioration due to changes in output gain, which can be caused by manufacturing variations and exhaust gas pressure, leading to incorrect identification of sensor abnormalities.
Innovation Solution
An abnormality diagnosis system that calculates a response parameter during fuel cut control, corrects values based on converged output values, and compares them to thresholds to accurately diagnose sensor abnormalities, accounting for changes in air-fuel ratio lean degrees.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If response time is used as the diagnosis criterion, then sensor deterioration can be detected, but output gain changes cause false abnormality judgments
Solution Approach 1:
The invention changes the reference basis from fixed response time values to relative change rates. By calculating the rate of change of response time and comparing it to the rate of change of output gain, the system distinguishes between actual sensor deterioration and normal output gain variations, thereby resolving the false judgment problem
Solution Approach 2:
The system continuously monitors both response time and output gain, using the output gain information as feedback to correct the response time diagnosis. The diagnosis result is adjusted based on the relationship between response time change and output gain change, preventing false abnormality judgments
2Ease of operation
If fixed threshold values are used for diagnosis, then the system is simple to operate, but it cannot adapt to output gain variations
Solution Approach 1:
The invention transforms the static fixed threshold into a dynamic adaptive threshold. The diagnosis threshold automatically adjusts based on the output gain value, allowing the system to adapt to different operating conditions and sensor characteristics without increasing operational complexity
Solution Approach 2:
The system changes the threshold parameter dynamically based on output gain measurements. When output gain varies, the diagnosis threshold is automatically adjusted to maintain accurate abnormality detection, resolving the contradiction between simplicity and adaptability
3Reliability
If response time is corrected based on average intake air, then downstream sensor diagnosis is improved, but output gain changes still affect diagnosis accuracy
Solution Approach 1:
The system uses output gain information as feedback to further correct the response time diagnosis. Even with intake air-based correction applied, the output gain change rate is used to adjust the final diagnosis result, ensuring accurate detection of actual sensor deterioration
Solution Approach 2:
The invention introduces an additional correction parameter based on output gain changes. This multi-parameter correction approach (intake air + output gain) improves diagnosis accuracy for downstream sensors while compensating for output gain variations
Data Source
AI summary
An air-fuel ratio sensor is provided in an exhaust passage of an internal combustion engine which can perform fuel cut control, and detects an air-fuel ratio of exhaust gas. The system calculates the response time of the air-fuel ratio sensor based on a changing output value of the air-fuel ratio sensor while performing or after fuel cut control, and compares the calculated response time and a threshold value to diagnose an abnormality. The abnormality diagnosis system is configured to correct the response time so that the response of the air-fuel ratio sensor is treated as becoming faster, the smaller the lean degree of the air-fuel ratio corresponding to the converged value of the air-fuel ratio sensor during fuel cut control; and diagnose an abnormality in the response of the air-fuel ratio sensor based on the corrected calculated response time and threshold value.