Gas Sensor Element Non-Uniform Protective Layer Design
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Solution Overview
Problem
Conventional gas sensor elements with a curved bottom portion suffer from low water resistance and strength due to thermal stress and water accumulation, and increasing the protective layer thickness to improve water resistance increases manufacturing costs and reduces responsiveness.
Innovation Solution
A gas sensor element with a protective layer having a thicker film thickness and higher porosity at the bottom portion compared to the leg portion, with a film thickness ratio of 1.2 to 2 and porosity ratio of 1.1 to 10, to enhance water resistance and responsiveness while preventing cracking during thermal spraying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the film thickness of the protective layer is increased to improve water resistance, then water resistance is improved, but manufacturing cost increases and responsiveness decreases
Solution Approach 1:
The protective layer is designed with non-uniform film thickness, where the bottom portion has a larger film thickness (100-1000 μm) for enhanced water resistance, while the leg portion has a smaller film thickness (100-500 μm) for maintained responsiveness. This local differentiation allows each region to have optimized properties for its specific functional requirements.
Solution Approach 2:
The protective layer is segmented into two distinct regions: the bottom portion and the leg portion, each with different film thickness characteristics. This segmentation enables independent optimization of water resistance in the bottom portion while preserving gas diffusion capability in the leg portion.
2Reliability
If the film thickness of the protective layer is increased to improve water resistance, then water resistance is improved, but manufacturing time increases
Solution Approach 1:
Instead of uniformly increasing the protective layer thickness throughout the entire structure, the invention applies increased thickness only locally to the bottom portion where water resistance is most critical. This localized approach reduces overall manufacturing time and material usage while achieving the required water protection.
3Reliability
If the film thickness of the protective layer is increased to improve water resistance, then water resistance is improved, but material cost increases
Solution Approach 1:
The protective layer material is distributed non-uniformly, with higher concentration in the bottom portion and lower concentration in the leg portion. This local quality differentiation reduces total material consumption and manufacturing cost while maintaining adequate water resistance where most needed.
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 a gas sensor element with improved water resistance and responsiveness, maintaining low manufacturing costs and preventing cracking, ensuring stable sensor outputs and durability.
Implementation Method 1
a protective layer which covers the outer side surface of the solid electrolytic substance together with the measuring electrode and allows gas to be measured to pass through the protective layer
Implementation Method 2
a solid electrolytic substance having a bottomed cylindrical shape and oxygen ion conductivity
Data Source
AI summary
The present invention provides, as one aspect, a gas sensor element including a solid electrolytic substance having a bottomed cylindrical shape and oxygen ion conductivity, a reference electrode arranged on an inner side surface of the solid electrolytic substance, a measuring electrode arranged on an outer side surface of the solid electrolytic substance, and a protective layer which covers the outer side surface of the solid electrolytic substance together with the measuring electrode and which allows gas to be measured to pass through the protective layer, wherein an end side of the gas sensor element is formed of a leg portion whose profile line is straight on an axial cross section and a bottom portion whose profile line is curved, and the film thickness of the protective layer of the bottom portion is larger than the film thickness of the protective layer of the leg portion.