Gas Sensor Water Penetration Reduction Structure
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Solution Overview
Problem
Gas sensors with porous protection layers are prone to moisture ingress, leading to corrosion and short circuits at connector electrodes due to capillary action in exhaust gases.
Innovation Solution
Incorporating a water-penetration reduction portion with a gap region absent of porous layer and dense bodies with low porosity, positioned to intercept moisture before it reaches the connector electrodes, along with a cylindrical body and compacts to absorb water, effectively reducing capillary movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a porous protection layer is applied to cover the connector electrodes, then the protection against chemical components is improved, but moisture can penetrate through the porous layer via capillarity causing corrosion and short circuits
Solution Approach 1:
The protection structure is divided into multiple segments: a porous protection layer for chemical protection, dense bodies with very low porosity (≤10%) positioned between the porous layer and connector electrodes to block moisture, and hydrophobic coating layers. This segmentation allows each layer to perform its specific function without interfering with others.
Solution Approach 2:
Dense bodies serve as intermediary elements positioned between the porous protection layer and the connector electrodes. These dense bodies with porosity of 10% or less act as mediators that prevent moisture penetrating through the porous layer from reaching the connector electrodes, while still allowing the porous layer to provide chemical protection.
2Reliability
If the porous layer is made more dense to reduce moisture penetration, then moisture resistance is improved, but protection against chemical components and gas permeability deteriorate
Solution Approach 1:
The protection system is segmented into distinct functional layers: a porous protection layer maintaining high porosity for chemical protection and gas permeability, and separate dense bodies with low porosity specifically for moisture blocking. This allows optimization of each layer's porosity independently for its specific function.
Solution Approach 2:
Different regions of the protection structure have different porosity characteristics tailored to local requirements. The porous protection layer has high porosity for chemical protection, while the dense bodies positioned at critical locations have low porosity for moisture resistance, creating local quality variations that optimize overall performance.
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
Significantly reduces the likelihood of moisture reaching the connector electrodes, thereby preventing corrosion and short circuits, while maintaining a compact design with minimal exposed surface area.
Implementation Method 1
the moisture contained in an exhaust gas may move inside the porous layer by capillarity
Implementation Method 2
the dense bodies pressing the compacts in the axial direction... the water-penetration reduction portion reducing the capillarity of water in the longitudinal direction
Data Source
AI summary
A gas sensor includes a sensor element and one or more hollow columnar dense bodies. The sensor element includes an element main body having a side surface, a porous layer and a water-penetration reduction portion that cover at least a front end-side part of the side surface. The water-penetration reduction portion disposed on the side surface so as to divide the porous layer an overlap length W that is the length of a continuous overlap between a range in which the water-penetration reduction portion is present in the longitudinal direction and a range in which inner peripheral surfaces of the one or more dense bodies are present in the longitudinal direction being 0.5 mm or more, the water-penetration reduction portion being a gap region in which the porous layer is absent, the water-penetration reduction portion reduces the capillarity of water.