Nitrogen Oxide Sensor Voltage Thresholds for SCR Regeneration
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Solution Overview
Problem
Current nitrogen oxide sensors face challenges in precisely measuring NOx and NH3 emissions during the nitrogen oxide trap regeneration phase, with existing methods being less accurate and requiring additional lambda sensors for precise switch-over determination.
Innovation Solution
A method and device for operating a nitrogen oxide sensor that determines a first measurement signal between a reference and external electrode, compares it with predefined threshold values, and assigns the second measurement signal to either NOx or NH3 emissions, allowing for precise measurement without the need for lambda sensors, using specific threshold values of 450 mV and 10 ppm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional nitrogen oxide sensor operation is used, then the sensor can measure exhaust gas composition, but the measurement precision of NOx and NH3 emissions is insufficient during nitrogen oxide trap regeneration phase
Solution Approach 1:
The patent changes the evaluation parameter from solely relying on lambda sensor switch-over determination to using voltage measurement between reference and external electrodes as the primary criterion. By monitoring voltage thresholds (e.g., 450 mV) in the nitrogen oxide sensor, the system can directly determine when NH3 desorption begins, enabling precise measurement of both NOx and NH3 emissions during regeneration without depending on lambda sensor signals.
2Measurement precision
If lambda sensors are used for switch-over determination, then the system can identify regeneration phases, but the device complexity increases and measurement accuracy is reduced
Solution Approach 1:
The patent makes the nitrogen oxide sensor multi-functional by using it both for its primary function of measuring nitrogen oxide content and for determining the switch-over point during regeneration through voltage measurement between its reference and external electrodes. This eliminates the need for separate lambda sensors for switch-over detection, reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The patent combines the functions of NOx measurement and regeneration phase detection into a single nitrogen oxide sensor system. By evaluating the voltage between the reference electrode and external electrode within the same sensor device, the system merges what would traditionally require separate sensors, thereby reducing overall system complexity and improving integration.
3Measurement precision
If additional lambda sensors are installed for precise switch-over determination, then the switch-over point can be identified, but the manufacturing cost and device complexity increase
Solution Approach 1:
The nitrogen oxide sensor performs self-service by using its own internal voltage signal (between reference and external electrodes) to determine the switch-over point during regeneration. This self-diagnostic capability eliminates the need for additional lambda sensors, reducing manufacturing cost and system complexity while maintaining precise switch-over detection.
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
Enables very precise measurement of NOx and NH3 emissions during the nitrogen oxide trap regeneration phase, particularly important for SCR control, by accurately determining the switch-over point and reducing the reliance on lambda sensors, thereby improving emission monitoring accuracy.
Implementation Method 1
a first measurement signal of the nitrogen oxide sensor (10) which is representative of a detected voltage between a reference electrode (20) and an external electrode (17) is determined
Implementation Method 2
The nitrogen oxide contained in the exhaust gas is decomposed in the second chamber by applying a further current
Data Source
AI summary
A method for operating a nitrogen oxide sensor comprising: sensing a first measurement signal of the nitrogen oxide sensor, the first measurement signal representing a detected voltage between a reference electrode and an external electrode; sensing a second measurement signal representing a measured gas content in a measuring chamber of the nitrogen oxide sensor; comparing the first measurement signal with a predefined first threshold value; and if the first threshold value is exceeded, assigning the second measurement signal to an emission of NH3.