Engine Misfire Diagnosis Threshold Adjustment for Catalyst Overheating
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Solution Overview
Problem
Existing abnormality diagnosis apparatuses for internal combustion engines fail to accurately diagnose catalyst abnormalities due to the stop process, which causes overheating and erroneous misfire detection, leading to incorrect diagnoses and damage accumulation in the exhaust gas control apparatus.
Innovation Solution
The apparatus performs a catalyst abnormality diagnosis by correcting the misfire counter values and adjusting thresholds based on the number of fuel supply stops, accounting for the damage from overheating and excluding stopped cylinders from misfire detection, while also conducting misfire abnormality diagnosis with corrected thresholds to avoid erroneous detections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the stop process is performed to supply oxygen to the exhaust gas control apparatus, then the catalyst warm-up is promoted, but the temperature of the exhaust gas control apparatus rises excessively causing damage accumulation
Solution Approach 1:
The system performs preliminary detection of misfire events and identifies patterns before they cause excessive catalyst temperature rise. By detecting misfires in advance and recognizing their relationship with stop process timing, the system can prevent harmful overheating while maintaining catalyst warm-up functionality
Solution Approach 2:
The system continuously monitors engine rotational speed fluctuations to detect misfire events and feeds this information back to the control device. This feedback mechanism enables real-time adjustment of stop process timing and duration to prevent excessive catalyst temperature rise while maintaining effective warm-up
2Measurement precision
If misfire detection is performed in all cylinders during stop process, then complete monitoring is achieved, but false positive misfire detections occur due to air introduction through stopped cylinders
Solution Approach 1:
The system segments the misfire detection process by identifying which cylinders are currently stopped versus actively combusting. Misfire detection is selectively applied only to cylinders that should be producing combustion, excluding cylinders intentionally stopped for oxygen supply. This segmentation eliminates false positives while maintaining monitoring coverage for relevant cylinders
Solution Approach 2:
The system dynamically adjusts misfire detection parameters based on the current stop process state. By recognizing the timing and duration of stop process execution, the system adapts its detection thresholds and target cylinders in real-time, ensuring accurate differentiation between intentional air introduction and actual misfire events
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for accurate diagnosis of catalyst abnormalities and misfire events, reducing false positives and reflecting actual damage from overheating, thereby improving the reliability of engine diagnostics.
Implementation Method 1
An oxidation reaction in the catalyst is then promoted to raise the temperature of the catalyst
Implementation Method 2
an oxidation reaction is triggered to raise the temperature of the exhaust gas control apparatus excessively
Data Source
AI summary
An abnormality diagnosis apparatus performs a stop process for stopping the supply of fuel to at least one of a plurality of cylinders and supplying fuel to the other cylinders or cylinder. The abnormality diagnosis apparatus performs a catalyst abnormality diagnosis process for diagnosing that there is an abnormality in an exhaust gas control apparatus, based on the value of a first misfire counter indicating the number of times of detection of a misfire during the operation of an internal combustion engine by a prescribed amount. In the catalyst abnormality diagnosis process, the abnormality diagnosis apparatus diagnoses that there is an abnormality in the exhaust gas control apparatus with the value of the first misfire counter being smaller when the stop process is performed than when the stop process is not performed during the operation of the internal combustion engine by the prescribed amount.