Ammonia Sensor Abnormality Detection via Oxygen Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing abnormality detection methods for ammonia sensors in exhaust purification systems have low accuracy due to the lack of consideration for the effects of other elements on the sensors, leading to unreliable determination of sensor abnormalities.
Innovation Solution
An abnormality determination apparatus that calculates ammonia concentration using both the ammonia sensor and oxygen sensor outputs, and the NOX sensor and oxygen sensor outputs, to determine the presence of abnormalities in the ammonia sensor, accounting for oxygen concentration dependence and allowing for accurate detection even when the reductant supply is stopped.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If ammonia sensor output is used directly for abnormality determination, then the determination process is simple, but the detection accuracy is low due to lack of consideration for oxygen concentration effects
Solution Approach 1:
The patent introduces oxygen concentration as an intermediary parameter to mediate between the ammonia sensor output and the abnormality determination. By using the oxygen sensor output to correct the ammonia sensor signal, the system accounts for oxygen's interfering effect on ammonia detection, thereby improving accuracy without requiring complex direct measurement of ammonia concentration
Solution Approach 2:
The system implements feedback by continuously monitoring oxygen concentration and using it to dynamically correct the ammonia sensor output. The correction value is calculated based on the oxygen sensor signal and fed back to adjust the ammonia concentration determination, creating a closed-loop system that compensates for oxygen interference in real-time
2Reliability
If reductant supply is stopped to perform abnormality determination, then the detection can be performed during a stable period, but ammonia supply to the catalyst continues causing ongoing purification effects
Solution Approach 1:
The patent performs preliminary action by stopping the reductant supply before conducting the abnormality determination. This creates a controlled condition where ammonia generation ceases, allowing the system to observe the catalyst's ammonia storage and release characteristics without continued ammonia input, thereby establishing a reliable baseline for sensor abnormality detection
Solution Approach 2:
The system dynamically manages the reductant supply by stopping it at specific moments to create favorable conditions for abnormality determination. The control unit timing the reductant interruption and subsequent ammonia concentration monitoring adapts the purification process to accommodate the diagnostic requirement, balancing operational continuity with reliable sensor assessment
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 abnormality detection by correcting for oxygen concentration dependence and enabling detection during the continuation period after reductant supply cessation, providing a more reliable assessment of ammonia sensor performance.
Implementation Method 1
a selective reduction-type catalyst that is provided in an exhaust passage of an internal combustion engine and purifies nitrogen oxide in exhaust gas using ammonia
Implementation Method 2
an ammonia sensor that is provided on a downstream side of the catalyst and outputs a sensor signal based on an ammonia concentration in the exhaust gas
Implementation Method 3
an NOX sensor that is provided on a downstream side of the catalyst and outputs a sensor signal based on an NOX concentration in the exhaust gas
Implementation Method 4
an oxygen sensor that is provided on a downstream side of the catalyst and outputs a sensor signal based on an oxygen concentration in the exhaust gas
Implementation Method 5
a supply apparatus that supplies a reductant for generating ammonia on an upstream side of the catalyst in the exhaust passage
Data Source
AI summary
An abnormality determination apparatus for an ammonia sensor is usable in an exhaust purification system including a catalyst, a supply apparatus, an ammonia sensor, an NOX sensor, and an oxygen sensor. During a continuation period within which ammonia supply to the catalyst continues after the supply apparatus stops supply of reductant, the abnormality determination apparatus calculates the ammonia concentration on a downstream side of the catalyst as a first concentration value, based on an output of the ammonia sensor and an output of the oxygen sensor. During the continuation period, the abnormality determination apparatus calculates the ammonia concentration on the downstream side of the catalyst as a second concentration value, based on an output of the NOX sensor and the output of the oxygen sensor. The abnormality determination apparatus determines presence or absence of abnormality in the ammonia sensor based on the first concentration value and the second concentration value.