Gas Sensor Oxygen Pumping Cell Design for NOx Detection Accuracy
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Solution Overview
Problem
Downsizing gas sensors reduces the amount of gas flowing into detection chambers, leading to lower detection accuracy due to increased errors, particularly in detecting specific gas components like nitrogen oxide (NOx).
Innovation Solution
A gas sensor design with a first detection chamber having a cross-sectional area of 0.03 mm2 to 0.22 mm2 and an oxygen-concentration sensing cell with a sensing electrode positioned downstream of the inner electrode, where the distance between the electrode center and the inner electrode's end is at least ten times the height of the space, enhances oxygen-pumping efficiency and reduces temperature differences, thereby improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the detection chamber is downsized, then oxygen-pumping efficiency is enhanced and power consumption is reduced, but the gas amount flowing into the detection chamber is reduced leading to lower detection accuracy
Solution Approach 1:
The detection system is divided into two separate detection chambers: a first detection chamber for oxygen concentration measurement and a second detection chamber for specific gas component detection. This segmentation allows each chamber to be optimized for its specific function, with the first chamber downsized for low power consumption while the second chamber maintains sufficient size for accurate specific gas detection.
Solution Approach 2:
The first detection chamber acts as an intermediary that processes the gas sample by measuring oxygen concentration and controlling oxygen partial pressure before the gas reaches the second detection chamber. This intermediary processing enables the second chamber to focus on specific gas component detection with improved accuracy.
2Volume of moving object
If the detection chamber is downsized, then the gas sensor element size is reduced, but the amount of specific gas component to be detected is reduced
Solution Approach 1:
The gas sensor element is segmented into two functional parts: a compact first detection chamber for oxygen sensing and a second detection chamber for specific gas component analysis. This segmentation enables overall downsizing of the sensor element while maintaining sufficient detection capacity for specific gases through the dedicated second chamber.
Solution Approach 2:
The patent utilizes a layered/laminated structure where the first and second detection chambers are arranged in different spatial dimensions. This dimensional arrangement allows compact integration of both detection functions within a small overall volume, achieving downsizing without sacrificing detection accuracy.
3Temperature
If the detection chamber is downsized, then temperature difference between different locations is reduced, but detection error increases due to reduced gas amount
Solution Approach 1:
By segmenting the detection function into two chambers, the first chamber can be optimized for uniform temperature distribution (reducing temperature differences) while the second chamber receives pre-conditioned gas with sufficient concentration of specific components for accurate detection despite the overall downsizing.
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 enhances the oxygen-pumping efficiency, reduces power consumption, and maintains detection accuracy by minimizing detection errors, allowing for both downsized gas sensors and improved NOx detection precision.
Implementation Method 1
a first oxygen pumping cell including a first solid electrolyte body and a pair of first electrodes formed on the first solid electrolyte body, wherein the pair of first electrodes include a first inner electrode disposed within the first detection chamber, wherein the first oxygen pumping cell is configured to pump oxygen from/into the gas which has been introduced into the first detection chamber
Implementation Method 2
an oxygen-concentration sensing cell including a third solid electrolyte body and a pair of third electrodes disposed on the third solid electrolyte body, wherein the pair of third electrodes include a sensing electrode disposed within the first detection chamber, wherein the oxygen-concentration sensing cell is configured to generate a voltage between the third electrodes in accordance with an oxygen concentration within the first detection chamber
Implementation Method 3
a second oxygen pumping cell including a second solid electrolyte body and a pair of second electrodes formed on the second solid electrolyte body, wherein the pair of second electrodes include an inside second pumping electrode disposed within the second detection chamber, wherein the second oxygen pumping cell is configured to pass an electric current according to a concentration of specific gas component within the second detection chamber
Implementation Method 4
a first detection chamber into which a gas to be detected is introduced through a first diffusion resisting portion
Data Source
AI summary
A gas sensor includes a gas sensor element. The gas sensor element includes a first detection chamber; a first oxygen pumping cell including a first solid electrolyte body and a pair of first electrodes; a second detection chamber; a second oxygen pumping cell including a second solid electrolyte body and a pair of second electrodes; and an oxygen-concentration sensing cell including a third solid electrolyte body and a pair of third electrodes. A sensing electrode of the third electrodes is disposed downstream beyond a first inner electrode of the first electrodes relative to a gas flow direction. A cross-sectional area of a space of the first detection chamber which faces the first inner electrode falls within a range from 0.03 mm2 to 0.22 mm2. A center of the sensing electrode is located downstream beyond a downstream end of the first inner electrode to cause a distance between the center of the sensing electrode and the downstream end of the first inner electrode to be greater than or equal to ten times magnitude of a height of the space.