Mixed-Potential Gas Sensor with Segmented Oxygen Pumping
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Solution Overview
Problem
Existing gas sensors face challenges in accurately determining hydrocarbon concentrations in exhaust gases from diesel engines due to variations in oxygen concentrations and poor control responsiveness, especially in lean-burn conditions, and errors in reference oxygen concentration and temperature management.
Innovation Solution
A mixed-potential gas sensor with an oxygen-ion conductive solid electrolyte structure, featuring a sensing electrode and a reference electrode, an oxygen pumping cell, and controlled diffusion paths to maintain a constant oxygen concentration of 1 vol % or more in the measurement gas, allowing for accurate hydrocarbon concentration determination by minimizing the impact of oxygen concentration variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If oxygen pumping is used to adjust oxygen concentration in the first processing chamber, then measurement accuracy is improved, but control responsiveness deteriorates
Solution Approach 1:
The sensor is divided into two processing chambers: a first processing chamber for oxygen concentration adjustment and a second processing chamber for hydrocarbon measurement. This segmentation allows the oxygen pumping operation to be isolated from the measurement chamber, improving control responsiveness while maintaining measurement accuracy.
Solution Approach 2:
A diffusion control part is introduced as an intermediary between the first and second processing chambers. This intermediary component controls the oxygen concentration that reaches the measurement chamber, allowing accurate measurement without direct oxygen pumping interference in the measurement chamber.
2Measurement precision
If a two-chamber structure with diffusion control parts is used, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The oxygen pumping cell, first processing chamber, and diffusion control parts are merged into an integrated sensor element structure. This combining approach achieves accurate measurement while avoiding the complexity of completely separate systems.
Solution Approach 2:
The first processing chamber serves multiple functions: oxygen concentration adjustment, interference component removal, and preparation of measurement gas. This multi-functionality reduces the need for additional separate components, simplifying the overall device.
3Power
If oxygen concentration is varied to increase electromotive force output, then sensitivity is improved, but measurement reliability deteriorates
Solution Approach 1:
Oxygen concentration adjustment is performed preliminarily in the first processing chamber before gas enters the measurement chamber. This preliminary action ensures that the measurement chamber operates under stable conditions, improving measurement reliability while maintaining sufficient electromotive force output.
Solution Approach 2:
The oxygen concentration parameter is controlled within a specific range (10^-12 to 10^-6 atm) in the first processing chamber to optimize both electromotive force output and measurement reliability, avoiding extreme values that would compromise reliability.
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
The solution provides excellent detection sensitivity and responsiveness to hydrocarbon concentrations in exhaust gases, maintaining accuracy across varying oxygen concentrations and ensuring reliable hydrocarbon detection in diesel engine exhausts.
Implementation Method 1
a gas sensor that includes a sensor element formed of an oxygen-ion conductive solid electrolyte
Implementation Method 2
a first internal space communicating with the first gas inlet via a predetermined diffusion control part; a second internal space communicating with the first internal space via another predetermined diffusion control part
Implementation Method 3
an oxygen pumping cell including an inside pump electrode facing the first internal space, an outside pump electrode located on an outside surface of the sensor element, and the solid electrolyte located between the inside pump electrode and the outside pump electrode
Data Source
AI summary
Provided is a gas sensor having excellent detection sensitivity and responsiveness. In a sensor element, 3.5≤D2/D1≤6 is satisfied, where D1 is a value of a diffusion resistance of a measurement gas via a main gas distribution part extending from an outside edge position of a first gas inlet to the second internal space, and D2 is a value of a diffusion resistance of a measurement gas flowing via a second gas inlet that causes the outside and the second internal space to communicate with each other. The concentration of a predetermined gas component contained in the measurement gas through the second gas inlet is determined on the basis of a potential difference between the sensing electrode and a reference electrode, while pumping oxygen in or out for the measurement gas via the main gas distribution part such that the oxygen concentration of the second internal space is maintained at 1 vol % or more.