Air Flowmeter Anomaly Diagnosis Using Exhaust Temperature
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Solution Overview
Problem
Existing anomaly diagnosing methods for air flowmeters in internal combustion engines face challenges in accurately distinguishing between anomalies in the air flowmeter and stuck-open anomalies of the addition valve, leading to erroneous determinations due to temperature differences and noise factors.
Innovation Solution
The proposed anomaly diagnosing apparatus calculates an estimated air amount based on the air-fuel ratio and fuel injection amount, and determines anomalies by considering the difference between the detected air flowmeter value and the estimated air amount, while also accounting for the exhaust temperature and its reference value, to differentiate between actual anomalies and stuck-open valve issues, thereby improving diagnostic accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the air flowmeter detected value is compared directly with the estimated air amount to determine anomalies, then the anomaly detection process is simple, but erroneous determination occurs when the addition valve is stuck open due to temperature differences
Solution Approach 1:
The patent introduces exhaust temperature as an intermediary parameter to mediate between the air flowmeter detected value and the estimated air amount. By comparing the detected exhaust temperature with a reference temperature, the system determines whether to apply a temperature correction to the estimated air amount before comparison, thereby preventing erroneous anomaly detection when the addition valve is stuck open
Solution Approach 2:
The patent dynamically adjusts the estimated air amount based on exhaust temperature conditions. When the exhaust temperature exceeds the reference temperature by a predetermined threshold, the system applies a temperature correction to the estimated air amount. This parameter change approach allows the detection threshold to adapt to different operating conditions, improving detection accuracy while maintaining a relatively simple detection framework
2Device complexity
If the estimated air amount is calculated based on air-fuel ratio and fuel injection amount, then the estimation is simplified, but it cannot account for fuel added by the addition valve leading to estimation errors
Solution Approach 1:
The patent performs preliminary detection of exhaust temperature before finalizing the air amount estimation. By checking whether the exhaust temperature exceeds the reference temperature beforehand, the system can proactively apply temperature correction to the estimated air amount, ensuring that the estimation accounts for potential fuel addition by the addition valve without requiring direct measurement of the addition valve's fuel contribution
Solution Approach 2:
The patent replaces direct mechanical measurement of all fuel sources with an indirect thermal field-based estimation approach. Instead of mechanically measuring the fuel addition from the addition valve, the system uses exhaust temperature as a proxy indicator to infer fuel addition and accordingly adjusts the air amount estimation, simplifying the estimation process while improving accuracy
3Speed
If anomaly determination is performed continuously without considering temperature conditions, then the response speed is fast, but noise factors lead to false anomaly detections
Solution Approach 1:
The patent performs preliminary evaluation of exhaust temperature conditions before executing the anomaly determination logic. By checking whether the temperature difference exceeds the predetermined threshold in advance, the system prepares the appropriate comparison baseline, enabling fast anomaly detection without being triggered by normal temperature variations that would constitute noise
Solution Approach 2:
The patent implements periodic monitoring of exhaust temperature and performs anomaly determination at discrete intervals when temperature conditions are evaluated. This periodic approach with conditional execution maintains fast response to actual anomalies while filtering out continuous noise, as the system only activates anomaly detection logic when temperature conditions warrant it
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 enhances the accuracy of anomaly detection in air flowmeters by minimizing erroneous determinations and noise factors, ensuring precise identification of upward displacement anomalies and reducing the influence of temperature differences and valve operation states.
Implementation Method 1
the fuel added by the addition valve is oxidized by the catalyst and raises the exhaust temperature downstream of the catalyst
Data Source
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AI summary
An air flowmeter (50) is arranged in an intake passage (12). An air-fuel ratio sensor (56) is arranged downstream of an addition valve (26) in an exhaust passage (20). An exhaust temperature sensor (52) is arranged downstream of a catalyst (22). An air amount estimating process calculates an estimated air amount (Gae) based on the air-fuel ratio (Af) detected by the air-fuel ratio sensor (56) and the fuel amount (Q) injected by a fuel injection valve (18). An upward displacement anomaly determining process determines that there is an anomaly in which a detected value (Ga) of the air flowmeter (50) is greater than an actual value if a logical conjunction is true of the condition that the detected value (Ga) of the air flowmeter (50) is greater than the estimated air amount (Gae) by a margin greater than or equal to a specified amount (ΔGa1) and the condition that an amount by which a detected value (Tex) of the exhaust temperature sensor (52) exceeds a reference value (Texe) is smaller than or equal to a predetermined amount (ΔTe).