Gas Sensor Element Protective Layer Layout for Accurate Detection
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Solution Overview
Problem
Multilayer gas sensor elements experience measurement errors due to difficulty in achieving stable high measurement accuracy, primarily caused by oxygen leakage and diffusion through protective layers.
Innovation Solution
A gas sensor element design with a porous protective layer covering the distal end portion, meeting the condition d/L≥1, where L is the thickness of the protective layer and d is the thickness of the solid-state electrolyte, combined with a vent hole facing the chamber to facilitate oxygen discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous protective layer is provided to trap contaminants and improve water resistance, then reliability is improved, but oxygen diffusion through the protective layer causes measurement errors
Solution Approach 1:
The patent applies local quality by creating a thickness gradient in the protective layer: the distal end portion (exposed to measurement gas) has thickness L1, while the proximal end portion (near solid-state electrolyte) has thickness L2 where L2 < L1. This gradient structure allows the distal portion to effectively trap contaminants while the thinner proximal portion minimizes oxygen diffusion path to the solid-state electrolyte, resolving the contradiction between protection and measurement accuracy.
2Reliability
If the protective layer thickness is increased to improve protection, then reliability is improved, but oxygen diffusion distance increases causing larger measurement errors
Solution Approach 1:
The patent implements local quality through spatially varying protective layer thickness: thicker at the distal end for maximum contaminant trapping and water resistance, thinner at the proximal end to minimize oxygen diffusion distance to the solid-state electrolyte. This local differentiation resolves the contradiction by optimizing each region's thickness for its specific function.
Solution Approach 2:
The patent transitions from a uniform one-dimensional thickness to a two-dimensional thickness distribution across the protective layer surface. By varying thickness in the radial direction (distal vs proximal ends), the solution adds a dimensional aspect to the protective layer design, allowing simultaneous optimization of protection and measurement accuracy.
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
Improves measurement accuracy by reducing oxygen intrusion into the chamber, thereby minimizing measurement errors and enhancing the reliability of gas concentration detection.
Implementation Method 1
a distal end portion of the element is covered with a porous protective layer... intended to trap contaminants in the gas to be measured
Implementation Method 2
a solid-state electrolyte having oxygen ion conductivity
Data Source
AI summary
A gas sensor element includes: a solid-state electrolyte having oxygen ion conductivity; a chamber formed on a first surface of the solid-state electrolyte, into which a gas to be measured is introduced; a chamber forming layer that is laminated on the first surface side of the solid-state electrolyte; a duct formed on a second surface of the solid-state electrolyte, into which a reference gas is introduced; and a duct forming layer that is laminated on the second surface side of the solid-state electrolyte. At least a distal end portion of the gas sensor element located distally from a proximal end of the chamber is covered with a porous protective layer. A condition of d/L≥1 is met with L denoting a thickness of the protective layer at a lamination-direction position same as that of the solid-state electrolyte and d denoting a thickness of the solid-state electrolyte.