Gas Sensor Element with Insulating Exposed Spaces
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Solution Overview
Problem
Gas sensors with sensor elements exposed to high temperatures, such as 800°C, face cracking issues due to rapid cooling when moisture adheres to their surfaces, which existing protective layers fail to adequately prevent.
Innovation Solution
A sensor element design featuring a protective layer with exposed spaces that block heat conduction, allowing for controlled cooling and improved moisture resistance, including pillar portions and varying space arrangements to maintain strength and insulation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer is formed on the sensor element surface by printing or plasma spraying, then cracking due to moisture adherence is suppressed, but heat conduction is not sufficiently blocked and rapid cooling still occurs
Solution Approach 1:
The protective layer is designed with a porous structure containing multiple voids that act as heat insulation barriers. These pores block heat conduction from the sensor element to the external environment, preventing rapid cooling when moisture adheres to the surface, while still allowing the protective layer to suppress cracking.
Solution Approach 2:
The protective layer has non-uniform thickness distribution, being thicker at the center portion and thinner at edge portions. This local quality variation optimizes heat insulation at the center where the sensor element is most vulnerable to cooling, while maintaining adequate protection at edges.
2Temperature
If the protective layer is made thicker to improve heat insulation, then moisture resistance is improved, but manufacturing complexity and material usage increase
Solution Approach 1:
Instead of uniformly increasing protective layer thickness, the invention applies variable thickness locally - thicker at the center where heat insulation is most needed, and thinner at edges. This reduces overall material usage and manufacturing complexity while achieving the required heat insulation performance.
Solution Approach 2:
The protective layer thickness is dynamically adjusted based on positional requirements, creating an optimized gradient structure that balances heat insulation needs with manufacturing feasibility and material efficiency.
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 effectively suppresses cracking and enhances moisture resistance by regulating temperature gradients and stress distribution across the sensor element's surface, ensuring reliable operation in high-temperature environments.
Implementation Method 1
since heat conduction in a direction of thickness of the protective layer can be blocked off by the exposed spaces, cooling of the element body is suppressed when moisture adheres to the surface of the protective layer
Implementation Method 2
the protective layer includes one or more exposed spaces to which the first surface is exposed... heat-insulating the middle of a region of the first surface, the region being covered with the protective layer, by the exposed space
Data Source
AI summary
A sensor element includes an element body having an elongate rectangular parallelepiped shape and including solid electrolyte layers with oxygen ion conductivity, an outer pump electrode disposed on a first surface of the element body, and a protective layer covering at least a part of the first surface of the element body and including one or more exposed spaces (an upper space) to which the first surface is exposed.