Nitrogen Oxide Trap Diagnosis Using Reducer Mass and Regeneration Duration
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Solution Overview
Problem
Current methods for diagnosing the operating state of nitrogen oxide traps in vehicles are imprecise, leading to false detection and non-detection of faulty traps, particularly due to inaccuracies in determining NOx mass during transient engine conditions and sensitivity to temperature variations, especially when oxygen sensors are not optimally positioned.
Innovation Solution
A diagnostic method that calculates a diagnostic criterion based on the mass of reducers consumed during the regeneration phase, incorporating the duration of the regeneration phase and the reduction efficiency of the trap, to accurately determine the trap's state by comparing this criterion with a failure threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diagnostic method based on reducer mass consumption is used, then the trap can be monitored for storage efficiency, but the determination becomes imprecise due to inability to reliably determine NOx flow rates during transient engine conditions
Solution Approach 1:
The patent introduces an intermediary approach by using oxygen sensors to measure oxygen concentration upstream and downstream of the trap, and using exhaust gas flow rate measurements to calculate reducer consumption. This intermediary method allows indirect determination of trap performance without requiring direct NOx flow rate measurements, thereby resolving the precision problem during transient conditions
Solution Approach 2:
The patent replaces the direct chemical measurement approach (attempting to measure NOx flow rates) with a physical measurement approach (measuring oxygen concentration differences and exhaust gas flow rates). This substitution enables reliable diagnostic calculations during transient engine conditions where direct NOx measurements are unreliable
2Device complexity
If oxygen sensors are positioned away from the trap for practical installation reasons, then the device complexity is reduced, but the diagnostic precision deteriorates due to distance from the trap
Solution Approach 1:
The patent introduces exhaust gas flow rate measurement as an intermediary parameter that compensates for the distance between sensors and trap. By measuring the flow rate of exhaust gases passing through the trap, the system can calculate the actual amount of reducers consumed during regeneration, thereby maintaining diagnostic accuracy despite sensor positioning away from the trap
Solution Approach 2:
The patent implements a feedback mechanism where oxygen sensors continuously monitor oxygen concentration upstream and downstream of the trap, and the control unit uses this feedback information along with flow rate measurements to calculate the diagnostic criterion. This feedback loop ensures accurate trap status determination regardless of sensor position
3Device complexity
If a simple diagnostic criterion based only on reducer mass is used, then the diagnostic process is simplified, but false detections increase due to temperature sensitivity
Solution Approach 1:
The patent implements feedback control where the diagnostic criterion calculation incorporates real-time measurements of oxygen concentration differences and exhaust gas flow rates. This feedback mechanism allows the system to adapt to varying temperature conditions and trap efficiency changes, reducing false detections while maintaining a relatively simple diagnostic process
Solution Approach 2:
The patent makes the diagnostic criterion dynamic by continuously updating it based on real-time measurements during the regeneration phase. The criterion adapts to changing operating conditions including temperature variations, thereby improving detection accuracy without requiring an overly complex diagnostic process
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 precision of nitrogen oxide trap diagnostics, reducing false alarms and missed detections by accounting for the duration and efficiency of the regeneration phase, thereby ensuring compliance with stringent emission standards.
Implementation Method 1
the trap retains part of the NOx molecules emitted by the engine on various catalytic storage compartments
Implementation Method 2
reducing agents (unburnt hydrocarbons HC and carbon monoxide CO) coming from the engine pass through the trap and reduce the molecules of NOx into molecules of nitrogen N2 and carbon dioxide CO2
Data Source
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AI summary
A method for diagnosing (44) a nitrogen oxide trap that is able to decompose, during a regeneration phase, the nitrogen oxides stored in the trap by reaction with reducers, comprising: - a step (48) of determining a diagnostic criterion (C) dependent on the mass of reducers (Mred) consumed during the regeneration phase; - a step (49) of comparing the diagnostic criterion (C) to a fault threshold below which the trap is defined as being faulty; and - a step (50) of issuing a signal indicating the fault status of the trap, characterised in that it involves determining the diagnostic criterion (C) on the basis of a set of parameters including at least the mass of reducers (Mred) consumed during the regeneration phase, the duration of the regeneration phase, and a reduction efficiency value of the trap during the regeneration phase.