Gas Sensor Inner Space Aspect Ratio for NOx Measurement Stability
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Solution Overview
Problem
Conventional gas sensors measuring NOx concentration face fluctuations in measured values due to temperature distribution and oxygen concentration variations within the sensor element, leading to instability in the measured current.
Innovation Solution
The gas sensor design incorporates a solid electrolyte body with a specific arrangement of inner spaces, where the first electrode is on the surface and the second electrode is in a separate space, with a predetermined aspect ratio of 0.05 to 0.25, and a distance from the surface of 10% or more of the sensor element's short-side length, reducing the impact of temperature and flow velocity variations on measured values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the inner space of the sensor element is designed with conventional dimensions, then the sensor structure is simple, but the temperature distribution and oxygen concentration variations cause fluctuation in measured values
Solution Approach 1:
The patent applies parameter changes by optimizing the aspect ratio of the inner space to a specific range (0.05 to 0.25) and positioning it at a specific distance (10% or more of the short-side length) from the sensor element surface. These parameter optimizations reduce temperature distribution and oxygen concentration variations, thereby stabilizing measured values without fundamentally changing the sensor structure.
2Reliability
If the pump cell pumping capability is increased to control oxygen concentration, then oxygen distribution improves, but the offset current fluctuation increases due to remaining oxygen near the measuring electrode
Solution Approach 1:
The patent applies local quality by creating a specific spatial configuration where the inner space is positioned at a predetermined distance from the sensor element surface. This local structural arrangement optimizes oxygen distribution within the inner space while reducing offset current fluctuations, achieving both reliable oxygen concentration control and stable measured current.
3Adaptability or versatility
If the sensor element surface temperature decreases due to measurement gas effects, then the sensor responds to gas composition, but the impedance of the pump cell varies causing measured current fluctuation
Solution Approach 1:
The patent applies parameter changes by optimizing the inner space aspect ratio to a specific range (0.05 to 0.25) and positioning it at a specific distance (10% or more of the short-side length) from the sensor element surface. These parameter optimizations reduce temperature distribution and oxygen concentration variations, thereby stabilizing measured values without fundamentally changing the sensor structure.
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 stabilizes the measured values by minimizing the effect of temperature and oxygen concentration distributions, resulting in a more accurate NOx concentration measurement.
Implementation Method 1
a solid electrolyte body formed mainly of an oxygen ion conductive solid electrolyte
Implementation Method 2
a pump cell having a first electrode and a second electrode, for pumping oxygen out of the inner space by applying a predetermined voltage between the first electrode and the second electrode
Data Source
AI summary
A gas sensor having a sensor element that includes an inner space for introducing a measurement gas therein from an external space and a pump cell which has a first electrode formed on a surface of the inner space and a second electrode formed in a space different from the inner space and is provided to pump oxygen out of the inner space by applying a predetermined voltage between the first electrode and the second electrode. Assuming that the length of the inner space in a short-side direction of the sensor element as viewed from the front end portion side thereof is x1 and the length of the inner space in a longitudinal direction of the sensor element as viewed from the front end portion side thereof is x2, the following inequality is satisfied: 0.05≦x1/x2≦0.25.