Gas Sensor Inner Pump Electrode NOx Detection Accuracy
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Solution Overview
Problem
Gas sensors used for detecting NOx concentrations face accuracy issues due to the presence of Au in the inner pump electrode, which leads to NOx reduction and decreased detection accuracy over time, and the challenge of maintaining accurate gas concentration detection in low-oxygen atmospheres.
Innovation Solution
The gas sensor design includes a preliminary pump cell that pumps oxygen into the measurement-object gas flow section to prevent low-oxygen atmospheres near the inner pump electrodes, eliminating the need for Au and maintaining accurate NOx detection by adjusting oxygen concentrations using main and auxiliary pump cells, ensuring that the inner pump electrodes do not reduce NOx, even without Au.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Au is included in the inner pump electrode to prevent NOx reduction, then NOx detection accuracy is maintained initially, but Au evaporates and adheres to the measurement electrode over time, causing detection accuracy to decrease
Solution Approach 1:
The patent removes Au from the inner pump electrode composition entirely, extracting the problematic element that causes evaporation and adhesion to the measurement electrode. The inner pump electrode is configured to operate without Au while still preventing NOx reduction through controlled oxygen concentration management.
Solution Approach 2:
The patent changes the operational parameters of the pump cell to maintain high oxygen concentration in the measurement-object gas flow section. By adjusting the oxygen concentration parameter rather than relying on Au, the system prevents NOx reduction without the harmful side effects of Au evaporation.
2Duration of action of stationary object
If the inner pump electrode contains no Au to prevent evaporation, then detection accuracy is maintained over time, but the electrode reduces NOx in low-oxygen atmospheres, decreasing detection accuracy
Solution Approach 1:
The patent applies preliminary action by configuring the pump cell to proactively maintain high oxygen concentration in the measurement-object gas flow section before NOx reduction can occur. The inner preliminary pump electrode pumps oxygen into the measurement-object gas flow section upstream, preventing low-oxygen conditions from developing in the first place.
Solution Approach 2:
The patent introduces oxygen concentration control as an intermediary mechanism between the inner pump electrode and NOx. By mediating the oxygen concentration in the measurement-object gas flow section, the system prevents direct interaction between the electrode and NOx that would lead to reduction, without requiring Au.
3Measurement precision
If oxygen concentration in the measurement-object gas flow section is increased to prevent NOx reduction, then NOx detection accuracy is maintained, but additional pump cells and complexity are required
Solution Approach 1:
The patent segments the pump function into two distinct parts: the inner preliminary pump electrode that pumps oxygen into the measurement-object gas flow section, and the main pump cell that performs the primary pumping function. This segmentation allows each component to have a specialized role, simplifying the overall control strategy.
Solution Approach 2:
The inner preliminary pump electrode serves multiple functions: it prevents low-oxygen atmospheres from forming, prevents NOx reduction, and maintains detection accuracy. By making this component multi-functional, the patent reduces the need for additional specialized components to handle each individual problem.
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 configuration maintains specific gas concentration detection accuracy over a long period by preventing NOx reduction and suppressing noble metal evaporation, allowing for accurate NOx detection without the need for Au in the inner pump electrodes, even in low-oxygen conditions.
Implementation Method 1
The preliminary pump cell pumps oxygen into a preliminary chamber to prevent the measurement-object gas from reaching the first internal space in a state in which the measurement-object gas is a low-oxygen atmosphere
Implementation Method 2
The main pump cell pumps oxygen from a first internal space to adjust an oxygen concentration of the first internal space
Implementation Method 3
The auxiliary pump cell pumps oxygen from a second internal space to adjust an oxygen concentration of the second internal space
Implementation Method 4
the concentration of NOx in the measurement-object gas is detected based on a current that flows at an electrode (measurement electrode) within the sensor element in accordance with the oxygen concentration after the reduction
Implementation Method 5
an element body, a main pump cell, an auxiliary pump cell, a preliminary pump cell, a measurement electrode, a reference electrode
Data Source
AI summary
A gas sensor includes an element body, an inner main pump electrode, an inner auxiliary pump electrode, an inner preliminary pump electrode, a measurement electrode, a reference electrode, a measurement voltage detection device, a specific gas concentration detection device. The inner preliminary pump electrode, the inner main pump electrode, the inner auxiliary pump electrode and the measurement electrode include each contain a noble metal having catalytic activity. At least one of the inner preliminary pump electrode and the inner main pump electrode contains no noble metal having a catalytic activity suppression ability, the catalytic activity suppression ability being an ability to suppress the catalytic activity of the noble metal having the catalytic activity from being exhibited to the specific gas. The inner auxiliary pump electrode contains a noble metal having the catalytic activity suppression ability.