NOx Trap Catalyst Diagnosis via Lean Temperature Raise
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Solution Overview
Problem
Existing methods for diagnosing the abnormality of NOx trap catalysts in lean-burn internal combustion engines face challenges in detecting small degrees of deterioration, as the decrease in NOx storage amount is also small, making it difficult to accurately diagnose catalyst abnormalities.
Innovation Solution
An abnormality diagnosis system that performs a lean temperature raise process to increase the temperature of the NOx trap catalyst above a predetermined level while maintaining a lean air-fuel ratio, allowing for diagnosis based on NOx storage efficiency, which differentiates between normal and deteriorated catalysts by exploiting changes in efficiency post-process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional diagnosis methods based on NOx storage amount are used, then the diagnosis system is simple to operate, but the measurement precision deteriorates when the degree of deterioration is small
Solution Approach 1:
The system performs a lean temperature raise process before diagnosis to prepare the catalyst in a standardized state. This preliminary action ensures that the catalyst temperature is elevated and NOx storage amount is reduced, creating consistent initial conditions for accurate diagnosis of small deterioration degrees.
Solution Approach 2:
The system changes the operating parameters by performing a lean temperature raise process that elevates catalyst temperature and reduces NOx storage amount before diagnosis. This parameter change enhances the sensitivity of the diagnosis system, enabling detection of small deterioration degrees that would be imperceptible under normal operating conditions.
2Reliability
If the NOx storage amount in the NOx trap catalyst is small, then the catalyst is in good condition, but the ability to detect deterioration deteriorates
Solution Approach 1:
The system performs a lean temperature raise process before diagnosis to reduce the NOx storage amount in the catalyst. By clearing accumulated NOx beforehand, the system establishes a baseline state where even small amounts of deterioration can be detected, rather than being masked by large existing NOx storage amounts.
Solution Approach 2:
The system changes the NOx storage amount parameter by performing a lean temperature raise process that reduces NOx content in the catalyst before diagnosis. This parameter change increases the sensitivity of detection, allowing reliable identification of small deterioration degrees that would be undetectable when large amounts of NOx are stored.
3Measurement precision
If a lean temperature raise process is performed before diagnosis, then the diagnostic precision is improved, but the diagnosis time increases
Solution Approach 1:
The system performs a lean temperature raise process as a preliminary step before diagnosis to elevate catalyst temperature and reduce NOx storage amount. This preliminary action ensures that subsequent diagnosis measurements are taken under optimized conditions, improving precision while the process is integrated efficiently into the overall diagnosis workflow.
Solution Approach 2:
The system changes temperature and NOx storage amount parameters through a lean temperature raise process before diagnosis. These parameter changes enhance measurement precision by creating optimal diagnostic conditions, and the process duration is managed as part of the integrated diagnosis cycle.
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
Enables accurate abnormality diagnosis of NOx trap catalysts even at small degrees of deterioration by highlighting differences in NOx storage efficiency post-lean temperature raise, improving diagnostic precision and reliability.
Implementation Method 1
The NOx trap catalyst has the function of storing NOx in the exhaust gas when the air-fuel ratio of the exhaust gas is a lean air fuel ratio
Implementation Method 2
The NSR catalyst has the function of storing NOx in the exhaust gas when the exhaust gas has a lean air-fuel ratio and reducing NOx stored therein when the exhaust gas has an air-fuel ratio equal to or lower than the theoretical air-fuel ratio and a reducing agent is present
Implementation Method 3
a lean temperature raise performing unit that performs a lean temperature raise process, which is the process of raising the temperature of the NOx trap catalyst to or above a predetermined temperature while keeping the air-fuel ratio of exhaust gas flowing into the NOx trap catalyst at a lean air-fuel ratio
Data Source
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AI summary
An object of the invention is to provide a technology that enables abnormality diagnosis of an NOx trap catalyst to make the diagnosis that the NOx trap catalyst is abnormal even if the degree of deterioration of the NOx trap catalyst is relatively small yet. When performing abnormality diagnosis of an NOx trap catalyst, a system according to the invention performs a lean temperature raising process, which is the process of raising the temperature of the NOx trap catalyst to or above a predetermined temperature while keeping the air-fuel ratio of the exhaust gas flowing into the NOx trap catalyst at a lean air-fuel ratio higher than the theoretical air-fuel ratio. The system diagnoses abnormality of the NOx trap catalyst on the basis of the NOx storage efficiency of the NOx trap catalyst or a parameter correlating with that NOx storage efficiency after the completion of the lean temperature raise process.