Gas Sensor Element Heat Insulating Space Water Resistance
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Solution Overview
Problem
Conventional gas sensors with porous protective layers suffer from inadequate water resistance, leading to water-induced cracking, especially when exposed to large amounts of water, due to insufficient adhesion and delamination of the protective layers.
Innovation Solution
A gas sensor element with an elongated planar ceramic body featuring internal chambers, electrochemical pump cells, and a heater, along with a porous protective layer configuration that includes a heat insulating space between the protective layer and the element base, and a second protective layer with higher porosity on the side surfaces, to enhance water resistance and prevent delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous protective layer is formed directly on the element base to prevent water-induced cracking, then water resistance is improved, but adhesion strength deteriorates leading to delamination and detachment
Solution Approach 1:
A dense protective layer is introduced as an intermediary between the porous protective layer and the element base. This dense layer serves as a bonding interface that provides strong adhesion to the element base while the porous layer above it maintains water resistance. The dense layer prevents direct contact between the porous layer and the element base, eliminating the adhesion problem while preserving the water protection function.
Solution Approach 2:
The protective structure is designed as a composite of two distinct layers: a dense protective layer providing adhesion and mechanical strength, and a porous protective layer providing water resistance. This composite structure combines the advantages of both materials - the dense layer bonds strongly to the element base while the porous layer above it prevents water-induced cracking through its water-repelling properties.
2Temperature
If a porous protective layer is formed at the leading end portion to reduce thermal conduction, then thermal management is improved, but water resistance deteriorates due to insufficient coverage in high-temperature regions
Solution Approach 1:
The protective layers are strategically positioned based on local temperature conditions. The dense and porous protective layers are formed specifically in the leading end portion where high temperature causes water-induced cracking, while the rest of the element base remains without these layers. This localized application provides thermal management where needed while maintaining water resistance in the critical high-temperature region.
3Use of energy by moving object
If the porous protective layer is made thinner to reduce power consumption, then energy efficiency is improved, but water resistance deteriorates due to insufficient protection against water exposure
Solution Approach 1:
The protective function is achieved through a composite structure where the dense layer provides mechanical support and adhesion, while the porous layer provides water resistance. This composite approach allows for optimized thicknesses that balance power consumption with adequate water protection, as the dense layer compensates for any thickness reduction in the porous layer by providing structural integrity.
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 configuration significantly improves water resistance and prevents delamination and detachment of the protective layers, effectively mitigating water-induced cracking by maintaining a heat insulating space and ensuring stable adhesion, even under high-temperature conditions.
Implementation Method 1
a single heat insulating space is interposed between the first leading-end protective layer and a portion of the element base
Implementation Method 2
a first leading-end protective layer (2) which is porous
Implementation Method 3
a heater (150) buried in a predetermined range on a side of the one end portion of the ceramic body
Implementation Method 4
an elongated planar ceramic body (101) made of an oxygen-ion conductive solid electrolyte
Data Source
AI summary
A sensor element includes: an element base including: a ceramic body made of an oxygen-ion conductive solid electrolyte, and having a gas inlet at one end portion thereof; at least two internal chambers located inside the ceramic body, and communicating with the gas inlet under predetermined diffusion resistance; an electrochemical pump cell including an electrode located on an outer surface of the ceramic body, an electrode facing the internal chambers, and solid electrolytes located therebetween; and a heater buried in the ceramic body; and a porous leading-end protective layer surrounding a first range at least including a part from a leading end surface to two internal chambers close to the gas inlet of the element base. A single heat insulating space is interposed between the leading-end protective layer and a portion of the element base in which the two internal chambers are located.