Gas Sensor Element Diffusion Geometry to Suppress Pressure Dependence
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Solution Overview
Problem
Conventional gas sensors experience excessive static pressure dependence of the pump current due to large diffusion resistance from the outside to the internal cavity, affecting the accuracy of NOx concentration detection.
Innovation Solution
The sensor element is configured with a diffusion rate-limiting section whose height is calculated using Equation (A) based on specific parameters, ensuring a minimum height of 0.0035 mm or greater, thereby reducing the cross-sectional area and suppressing excessive pressure dependence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the diffusion rate-limiting section has a small cross-sectional area to reduce diffusion resistance, then the diffusion resistance decreases, but the static pressure dependence of the pump current increases excessively
Solution Approach 1:
The patent changes the geometric parameters of the diffusion rate-limiting section, specifically setting the height t to be 0.0035 mm or greater based on Equation (A) that relates height to path length L, width H, limiting current Ip, diffusion coefficient D, gas constant R, temperature T, and oxygen partial pressures Poe and Pod. This parameter optimization resolves the contradiction by finding the optimal height that balances diffusion resistance reduction with static pressure dependence suppression.
2Object-affected harmful factors
If the diffusion rate-limiting section has a large cross-sectional area to reduce static pressure dependence, then the static pressure dependence decreases, but the diffusion resistance becomes excessively large
Solution Approach 1:
The patent optimizes the height parameter t of the diffusion rate-limiting section to be 0.0035 mm or greater, which is derived from Equation (A) considering the relationship between geometric parameters (L, H, t) and operational parameters (Ip, D, R, T, Poe, Pod). This optimized parameter range ensures sufficient diffusion while minimizing static pressure dependence effects.
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 effectively suppresses the excessive increase in static pressure dependence of the pump current, enhancing the accuracy and reliability of NOx concentration measurement.
Implementation Method 1
a diffusion rate-limiting section provided in the measurement gas flow path, the diffusion rate-limiting section being configured to guide the measurement gas from the outside into the oxygen concentration adjustment chamber while imparting diffusion resistance
Implementation Method 2
an element body having an oxygen-ion-conductive solid electrolyte layer
Data Source
AI summary
A sensor element includes an element body, at least one adjustment pump cell having an inner electrode disposed in an oxygen concentration adjustment chamber, a measurement electrode, a diffusion rate-limiting section. A height t [mm] of the diffusion rate-limiting section, obtained based on the following parameters: a path length L [cm] of the diffusion rate-limiting section; a width H [cm] of the diffusion rate-limiting section; a limiting current Ip [A] of the adjustment pump cell; the Faraday constant F [A·sec/mol]; the diffusion coefficient D [cm2/sec] of oxygen; the gas constant R [cm3·atm/mol·K]; a temperature T [K] of the inner electrode; an oxygen partial pressure Poe [atm] in the measurement gas; and an oxygen partial pressure Pod [atm] in the oxygen concentration adjustment chamber, is 0.0035 or greater.