NOx Sensor Inspection via Exhaust Temperature and Flow Control
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Solution Overview
Problem
Existing NOx sensor inspection methods lack accuracy in diagnosing deterioration or malfunction due to residual reductant effects, leading to potential misreplacement of NOx sensors, which can reduce vehicle operating efficiency.
Innovation Solution
A NOx sensor inspection program that involves high-temperature and high-flow-rate exhaust driving processes to neutralize reductant effects, allowing for accurate comparison of upstream and downstream NOx sensor readings, thereby determining sensor deterioration or malfunction with precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If NOx sensor diagnosis is performed during vehicle traveling by comparing NOx concentrations before and behind reduction catalyst, then the diagnosis can be performed in actual operating conditions, but the diagnosis accuracy deteriorates due to residual reductant effects on the reduction catalyst
Solution Approach 1:
The inspection program performs preliminary actions to eliminate residual reductant effects before conducting the NOx sensor diagnosis. Specifically, it executes high-temperature exhaust driving to desorb adsorbed reductant from the reduction catalyst, and high-flow-rate exhaust driving to flush remaining reductant from the exhaust passage. This preliminary preparation ensures that the subsequent NOx concentration comparison accurately reflects sensor performance rather than catalyst activity, thereby resolving the contradiction between performing diagnosis during actual operation and maintaining high diagnostic accuracy.
2Loss of time
If NOx sensor inspection is performed without eliminating residual reductant effects, then the inspection process is simple and quick, but the determination of sensor deterioration or malfunction becomes inaccurate leading to potential misreplacement
Solution Approach 1:
The inspection program changes operating parameters (temperature and flow rate) to eliminate residual reductant effects. By executing high-temperature exhaust driving to raise exhaust gas temperature and desorb reductant, followed by high-flow-rate exhaust driving to increase exhaust gas flow and flush remaining reductant, the system prepares the exhaust system for accurate sensor inspection. These parameter changes ensure that subsequent NOx concentration measurements reflect true sensor performance, preventing misdiagnosis while maintaining reasonable inspection time through automated control sequences.
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 ensures accurate determination of NOx sensor health, preventing unnecessary replacements and maintaining vehicle efficiency by eliminating residual reductant influences during inspections.
Implementation Method 1
performing high-temperature exhaust driving for setting a temperature of exhaust gas to be higher than or equal to a predetermined high temperature
Implementation Method 2
performing high-flow-rate exhaust driving for setting a speed of internal combustion engine to be more than or equal to a predetermined high speed after a flow rate of the exhaust gas is not reduced
Data Source
AI summary
A process of causing an engine (10) to perform high-temperature exhaust driving (D1) after urea water from an urea water injection valve (33) is not supplied to an SCR catalyst (34), and a process of causing the engine (10) to perform high-flow-rate exhaust driving (D2) after a flow rate of exhaust gas from a cylinder interior (13) is not reduced are performed on an ECU (40). A process of determining deterioration or malfunction of upstream and downstream NOx sensors (47 and 48) based on detected values (Ca and Cb) acquired when the engine speed (Na) reaches a determination speed (Nx) is performed on a vehicle external computer (52).