Exhaust NOx Catalyst Diagnosis via Conditional Integration
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Solution Overview
Problem
Existing exhaust gas purification systems face challenges in accurately diagnosing reduced NOx purification efficiency due to factors like catalyst deterioration, abnormal control system conditions, and reducing agent quality, leading to unreliable diagnosis results.
Innovation Solution
A trouble diagnosis device and method that compare integrated NOx amounts at the upstream and downstream sides of the NOx catalyst only when specific conditions for normal reduction are met, using flow rate calculations and threshold comparisons to determine system abnormalities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If NOx amounts are compared continuously without condition checking, then diagnosis frequency is high, but diagnosis reliability decreases due to inefficient reduction conditions
Solution Approach 1:
The patent applies dynamics by making the diagnosis process adaptive to operating conditions. The control unit dynamically determines whether to perform diagnosis based on real-time assessment of reduction efficiency conditions (temperature, NOx concentration, air-fuel ratio). This allows the system to switch between continuous monitoring and conditional diagnosis, optimizing both reliability and frequency according to actual system state.
Solution Approach 2:
The patent changes the parameter of diagnosis execution from constant (always on) to variable (condition-dependent). By introducing conditional parameters (temperature threshold, concentration threshold, air-fuel ratio threshold), the system only performs comparison when these parameters indicate efficient reduction conditions, thereby improving reliability without completely sacrificing diagnostic coverage.
2Measurement precision
If multiple sensors are deployed for continuous monitoring, then measurement accuracy improves, but system cost and complexity increase
Solution Approach 1:
The patent extracts the essential diagnostic function from a multi-sensor continuous monitoring system. Instead of requiring multiple sensors for constant monitoring, it extracts the core comparison function and applies it selectively based on operating conditions. This reduces sensor requirements while maintaining diagnostic capability through intelligent condition-based execution.
Solution Approach 2:
The system uses existing sensor data (temperature, NOx concentration, air-fuel ratio) to self-determine when diagnosis should be performed. Rather than requiring additional sensors or external control, the system leverages its own operational parameters to gate the diagnostic process, reducing overall system complexity.
3Adaptability or versatility
If diagnosis is performed during unstable engine operations, then comprehensive coverage is achieved, but diagnosis accuracy decreases
Solution Approach 1:
The patent applies local quality by creating different diagnostic modes for different operating conditions. Stable operating conditions receive full diagnostic scrutiny with comparison-based analysis, while unstable conditions are either excluded from comparison or receive simplified monitoring. This localized approach to diagnostic intensity maintains accuracy where possible while preserving system adaptability.
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 reliability of diagnosing exhaust gas purification system issues by excluding inefficient reduction conditions and efficiently performing diagnostics without starting from scratch, even during unstable engine operations, while reducing the need for multiple sensors and lowering costs.
Implementation Method 1
exhaust gas purification system for passing exhaust gas discharged from an internal combustion engine through NOx catalyst to reduce NOx contained in the exhaust gas
Data Source
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AI summary
There are provided a trouble diagnosis device and a trouble diagnosis method for an exhaust gas purification system in which the presence or absence of a trouble of the exhaust gas purification system such as abnormality of a control system for the exhaust gas purification system, catalyst deterioration or the like can be determined with high precision, and the reliability of the exhaust gas purification system can be enhanced. The device includes upstream-side NOx flow rate calculating means, downstream-side NOx flow rate calculating means, reduction condition determining means for determining whether at least one condition for performing normal reduction of NOx is satisfied, upstream-side NOx flow amount calculating means for integrating the upstream-side NOx flow amount to calculate the amount of NOx passing through the upstream side of the catalyst within a predetermined time when the condition concerned is determined to be satisfied, downstream-side NOx amount calculating means for integrating the downstream-side NOx flow amount to calculate the amount of NOx passing through the downstream side of the catalyst within a predetermined time when the condition concerned is determined to be satisfied, and trouble determining means for comparing the upstream-side NOx amount and the downstream-side NOx amount to determine whether the exhaust gas purification system operates normally.