Gas Sensor Glass Coat Prevents Soot Adherence
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Solution Overview
Problem
Conductive substances like soot adhere to solid electrolyte bodies in gas sensors, causing leak currents and deteriorating gas concentration detection performance, and existing alumina paste applications are inefficient with high likelihood of pinhole formation.
Innovation Solution
A gas sensor design featuring a glass coat with a transition point over 700 degrees C. covers side faces of the detection element, preventing soot adherence and leak currents, and using glass slurry applied after firing ensures a dense, pore-free layer with improved productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alumina paste is applied to the solid electrolyte body by printing method, then the insulating layer is formed to prevent soot adherence, but pinholes are likely to be generated requiring multiple applications which reduces productivity
Solution Approach 1:
The invention changes the material parameter from alumina paste to glass paste with specific glass transition temperature (600-700°C), enabling single-application dense coating without pinholes while maintaining insulating functionality
Solution Approach 2:
The invention uses glass paste as a composite material that combines insulating properties with flow characteristics during firing, creating a dense pinhole-free layer in single application
2Object-affected harmful factors
If the detection electrode temperature is increased to burn off soot, then soot adherence is prevented, but the glass coat may be damaged or deformed
Solution Approach 1:
The invention carefully selects and controls the glass transition temperature parameter of the glass paste (600-700°C) to be higher than detection electrode temperature, preventing glass coat damage while maintaining soot burn-off capability
Solution Approach 2:
The glass coat is applied selectively to specific regions of the solid electrolyte body where soot adherence occurs, providing localized protection without requiring overall temperature increase that would damage the glass
3Object-affected harmful factors
If the glass transition point of the glass coat is increased to prevent soot adherence, then soot resistance is improved, but thermal expansion distortions may increase
Solution Approach 1:
The invention optimizes the glass transition temperature parameter to a specific range (600-700°C) that provides sufficient soot resistance while minimizing thermal expansion distortions during operation
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 glass coat effectively prevents soot adherence and leak currents, maintaining gas concentration detection performance while reducing thermal expansion-related distortions and improving the sensor's durability and productivity.
Implementation Method 1
a region from a front end of the inner member to at least a part of the detection electrode along the longitudinal direction of the detection element is covered with a glass coat having a glass transition point of over 700 degrees C.
Implementation Method 2
a heater laminated on the detection element and having therein an heat-generating portion that is disposed at a position corresponding to at least the detection electrode
Implementation Method 3
generating oxygen ion conductivity of the solid electrolyte body (e.g., 200 to 600 degrees C.)
Implementation Method 4
a glass coat having a glass transition point of over 700 degrees C.
Data Source
AI summary
A gas sensor including a gas sensor element, and an inner member surrounding the gas sensor element. The gas sensor element has a detection element having therein a space to which a gas to be measured is introduced, and a heater laminated on the detection element. The detection element includes a first oxygen pumping cell for pumping oxygen into or out of the space, an oxygen concentration detection cell, a detection electrode and a reference electrode. In side faces of the detection element along a laminating direction, a region from a front end of the inner member to a part of the detection electrode along a longitudinal direction is covered with a glass coat having a glass transition point of over 700° C. Further the detection electrode is controlled at a temperature range from 600° C. or more to not more than the glass transition point of the glass coat.