Gas Sensor Element Porosity Design for Oxygen Control

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Solution Overview

Problem

Existing sensor elements for detecting specific gas concentrations, such as NOx, face manufacturing variations due to high porosity leads, which can lead to increased oxygen concentration in reference gas chambers, affecting detection accuracy.

Innovation Solution

A sensor element design with a higher porosity lead in the second pump circuit to release oxygen from the reference gas chamber, reducing manufacturing variations and maintaining a stable oxygen concentration, while a lower porosity lead in the first pump circuit minimizes resistance value variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If leads with high porosity are used to suppress oxygen concentration increase in the reference gas chamber, then oxygen release is improved, but manufacturing variations in resistance values increase

Engineering Contradiction:

Improveoxygen concentration controlVSAvoidresistance value consistency

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies different porosity levels to different leads based on their specific functions. The first reference electrode lead has higher porosity (5-25%) to optimize oxygen release from the reference gas chamber, while the second reference electrode lead has lower porosity (1-5%) to minimize resistance variations. This localized differentiation of material properties resolves the contradiction by matching porosity to functional requirements.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the porosity parameter of the leads to achieve the desired balance between oxygen release and resistance stability. By controlling the porosity within specific ranges for different leads, the invention optimizes both oxygen concentration control and manufacturing precision, transforming the contradiction into an optimized design.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If multiple leads with gas permeability are used in the reference oxygen chamber, then oxygen concentration is suppressed, but circuit resistance variations increase

Engineering Contradiction:

Improvereference gas chamber stabilityVSAvoidcircuit resistance consistency

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent differentiates the porosity of different leads based on their functional roles. The first reference electrode lead (connected to the reference gas chamber) has higher porosity to facilitate oxygen release, while the second reference electrode lead (connected to the measurement chamber) has lower porosity to maintain stable resistance. This local differentiation resolves the contradiction between reference chamber stability and circuit resistance consistency.

Inventive Principle:

Principle #3Local quality

3Measurement precision

If high porosity leads are used to maintain stable oxygen concentration, then detection accuracy is improved, but manufacturing variations increase

Engineering Contradiction:

Improvegas concentration detection accuracyVSAvoidlead resistance consistency

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The patent applies different porosity characteristics to different leads based on their specific functions in the measurement system. The first reference electrode lead has higher porosity to maintain stable oxygen concentration for accurate detection, while the second reference electrode lead has lower porosity to minimize manufacturing variations in resistance, thereby supporting both detection accuracy and manufacturing precision.

Inventive Principle:

Principle #3Local quality

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 design effectively reduces manufacturing variations and maintains a stable oxygen concentration in the reference gas chamber, enhancing the accuracy of NOx concentration detection.

Implementation Method 1

a first reference electrode lead that connects the first reference electrode terminal and the first reference electrode to each other, and a second reference electrode lead that connects the second reference electrode terminal and the second reference electrode to each other, wherein a resistance value R2 between the second pump electrode terminal and the second reference electrode terminal of the second pump circuit is higher than a resistance value R1 between the first pump electrode terminal and the first reference electrode terminal of the first pump circuit, and a porosity P2 of the second reference electrode lead is higher than a porosity P1 of the first reference electrode lead

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 2

an element body including an oxygen-ion-conductive solid electrolyte layer and having formed therein a measurement-object gas flow section and a reference gas chamber

Methodology Applied

Scientific EffectIon transport through solid electrolyte: Fast Ion Conductor

Data Source

PatentUS11852607B2Sensor element and gas sensor

Publication Date: 2023.12.26 NGK INSULATORS LTD

AI summary

A sensor element includes a first pump cell including a first pump electrode and a first reference electrode, a first pump circuit including the first pump cell and a first reference electrode lead, a second pump cell including a second pump electrode and a second reference electrode and a second pump circuit including the second pump cell and a second pump electrode. A resistance value R2 of the second pump circuit is higher than a resistance value R1 of the first pump circuit, and a porosity P2 of the second reference electrode lead is higher than a porosity P1 of the first reference electrode lead.