NOx Sensor Functional Check via Oxygen Pump Flow
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Solution Overview
Problem
Existing methods for monitoring nitrogen oxide (NOx) sensors in internal combustion engines are inadequate for differentiating between functional and non-functional sensors, especially in applications behind NOx reduction catalytic converters, due to insufficient excitation and imprecise modeling of NOx emissions.
Innovation Solution
A diagnostic method for nitrogen oxide sensors involves setting the oxygen concentration level in the first chamber to an increased value, detecting the resulting change in pump flow in the second pump cell, and comparing it with a range of permitted values to assess the sensor's functionality, allowing differentiation between functional and non-functional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If comparison with a model calculated from engine parameters is used to monitor NOx signal dynamics, then monitoring can be performed, but reliable differentiation between functional and non-functional sensors is not achieved
Solution Approach 1:
The patent changes the operational parameters of the sensor by setting the oxygen concentration level in the first chamber to an increased value during diagnostic mode. This parameter change creates a distinct test condition that elicits a measurable response (change in pump flow in the second pump cell), enabling reliable differentiation between functional and non-functional sensors without relying on imprecise engine parameter models.
2Object-generated harmful factors
If NOx reduction catalytic converters (NSC or SCR) are installed, then nitrogen oxide emissions are reduced, but sufficient excitation for sensor monitoring is no longer present
Solution Approach 1:
The patent performs a preliminary diagnostic action by temporarily setting the oxygen concentration level to an increased value before normal operation. This preliminary action creates sufficient excitation to elicit a measurable pump flow response, allowing sensor functionality to be verified even in systems with NOx reduction catalytic converters where normal operating conditions provide insufficient excitation.
3Quantity of substance
If the oxygen concentration level in the first chamber is increased, then more oxygen flows into the second chamber via the second diffusion barrier, but the pump flow change becomes difficult to interpret without a reference
Solution Approach 1:
The patent employs feedback by detecting the change in pump flow in the second pump cell that results from the increased oxygen concentration level in the first chamber. This feedback mechanism provides a measurable response that can be compared against expected ranges to interpret whether the sensor is functioning correctly, resolving the difficulty of interpreting pump flow changes without a reference.
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 method provides a reliable means to differentiate between functional and non-functional NOx sensors by analyzing the change in pump flow, enabling more accurate monitoring and reducing false positives or negatives in NOx signal dynamics.
Implementation Method 1
The first chamber has a first oxygen pump cell which is electrically connected to a control unit. In a normal operating mode of the nitrogen oxide sensor, an oxide concentration level in the first chamber is reduced to a predetermined first value with the first pump cell.
Implementation Method 2
An oxygen concentration level which occurs in the second chamber is reduced to a second value with the second pump cell by releasing oxygen from the nitrogen oxides
Implementation Method 3
The pump flow which occurs here in the solid electrolyte of the second pump cell and therefore in the second pump cell is essentially carried by oxygen ions which result from the decomposition of nitrogen oxides.
Implementation Method 4
A diffusion barrier is here, for example, a porous structure which impedes a diffusion of gas particles without, however, completely blocking them.
Data Source
AI summary
A method is presented for checking the functional capability of a nitrogen oxide sensor (10) which has a first chamber (12) and a second chamber (14), wherein the first chamber has a first oxygen pump cell (20) and the second chamber has a second pump cell (34), in a normal operating mode of the nitrogen oxide sensor (10), an oxygen concentration level in the first chamber is reduced to a predetermined first value with the first pump cell, and an oxygen concentration level in the second chamber is reduced to a second value with the second pump cell, said second value being lower than the first value.