Downstream Air-Fuel Ratio Sensor Abnormality Detection
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Solution Overview
Problem
Existing air-fuel ratio control systems for internal combustion engines struggle to reliably detect abnormalities in downstream oxygen sensors, leading to inaccurate fuel injection adjustments and potential engine performance issues due to variations in air-fuel ratios across cylinders and non-uniform exhaust gas exposure.
Innovation Solution
A method involving alternately switching the target air-fuel ratio between rich and lean settings, detecting deviations, and performing feedback control to adjust the learning value, allowing for the detection of sensor abnormalities based on repeated decreases and increases in the learning value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If feedback control is performed based on the output signal of the upstream side air-fuel ratio sensor, then the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst is controlled to be the stoichiometric air-fuel ratio, but the air-fuel ratio detected by the downstream side oxygen sensor continues to deviate to the lean side or rich side due to cylinder variations and non-uniform exhaust gas contact
Solution Approach 1:
The patent applies feedback control by using the output signal of the downstream side oxygen sensor to correct the feedback correction coefficient. This creates a closed-loop system where the sensor output directly influences fuel injection adjustments, allowing the system to compensate for deviations and maintain accurate air-fuel ratio control despite cylinder variations and exhaust gas flow inconsistencies.
Solution Approach 2:
The patent changes the parameter of the feedback correction coefficient by obtaining a correction value based on the downstream side oxygen sensor output. This correction value is then used to adjust the feedback correction coefficient, thereby adapting the control system to actual operating conditions and eliminating false abnormality detections.
2Productivity
If the air-fuel ratio is feedback controlled to the stoichiometric air-fuel ratio based on the upstream side air-fuel ratio sensor, then fuel injection amount is adjusted, but the downstream side oxygen sensor may continuously detect lean or rich deviations even when normal due to exhaust gas flow distribution
Solution Approach 1:
The system uses feedback from the downstream side oxygen sensor to continuously monitor and adjust fuel injection. The sensor output is used to obtain correction values that modify the feedback correction coefficient, creating a self-regulating mechanism that distinguishes between temporary deviations and actual sensor abnormalities, thereby improving detection reliability.
Solution Approach 2:
The patent performs preliminary correction of the feedback correction coefficient using the downstream side oxygen sensor output before final fuel injection control. This preliminary action anticipates and compensates for potential deviations, preventing false abnormality detections and ensuring reliable sensor monitoring.
3Measurement precision
If learning value is continuously updated based on downstream side oxygen sensor output, then air-fuel ratio control is refined, but repeated decreases and increases in learning value indicate sensor abnormalities that need reliable detection
Solution Approach 1:
The learning value is continuously updated based on feedback from the downstream side oxygen sensor output. This feedback mechanism allows the system to refine air-fuel ratio control by adapting to actual operating conditions. The systematic approach to updating the learning value provides a clear pattern for detecting sensor abnormalities through repeated decreases and increases.
Solution Approach 2:
The learning value is dynamically adjusted based on real-time sensor output and operating conditions. This dynamic updating allows the system to adapt to changing engine conditions while providing a clear signal when abnormalities occur. The dynamic nature of the learning value creates distinguishable patterns between normal operation and sensor failures.
Data Source
AI summary
Downstream side air-fuel ratio sensor signal based adaptive air-fuel ratio control. When the air-fuel ratio detected by the downstream side air-fuel ratio sensor is maintained lean unduly, a stuck learning control is performed to decrease a learning value to lower the air-fuel ratio. Adaptive learning value update control is performed based on the downstream side air-fuel ratio sensor signal to increase the learning value when an upstream air-fuel ratio deviates to the rich side and to decrease the learning value when the upstream air-fuel ratio deviates to the lean side. It is judged that the downstream side air-fuel ratio sensor is abnormal when a certain value or more of decrease of the learning value and a certain value or more of increase of the learning value are repeated.