Exhaust Sensor Porous Protective Layer Water Resistance
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Solution Overview
Problem
Existing exhaust sensors lack sufficient water resistance due to inadequate internal observation and improvement of the porous protective layer's properties, which are typically enhanced only externally.
Innovation Solution
The exhaust sensor incorporates a porous protective layer composed of aggregate particles with a controlled number of crystal grain boundary intersections per unit area, ranging from 1 to 10,000/μm², to enhance the layer's strength and water resistance by dispersing stress energy effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous protective layer is provided on the sensor element to protect from water, then water resistance is improved, but the layer lacks sufficient internal strength to withstand thermal shock
Solution Approach 1:
The patent changes the microstructural parameters of the porous protective layer by controlling the number of crystal grain boundary intersections (3-100 intersections per unit area) and the size distribution of aggregate particles. This parameter optimization enhances both water resistance and thermal shock resistance simultaneously, resolving the contradiction between protective function and structural strength.
Solution Approach 2:
The porous protective layer is constructed as a composite material system consisting of aggregate particles (ceramic particles) bound with binder material. This composite structure provides both the porosity needed for water resistance and the mechanical strength required to withstand thermal shock, resolving the contradiction between protective function and structural integrity.
2Strength
If the porous protective layer is made denser to improve strength, then structural integrity is improved, but gas permeability deteriorates
Solution Approach 1:
The patent applies local quality by creating a porous protective layer with localized density characteristics. The layer maintains sufficient porosity in regions critical for gas diffusion while providing enhanced strength where structural integrity is needed, achieving both gas permeability and structural strength through spatially differentiated properties.
Solution Approach 2:
The patent utilizes porous materials science by optimizing the pore structure, aggregate particle size distribution, and crystal grain boundary characteristics of the porous protective layer. This allows the layer to maintain high gas permeability for efficient exhaust gas detection while simultaneously providing the structural strength needed to withstand thermal environments.
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
This approach significantly improves the water resistance of the porous protective layer, allowing it to withstand thermal shock and maintain structural integrity, thereby enhancing the sensor's performance in detecting exhaust gases from internal combustion engines.
Implementation Method 1
the number of crystal grain boundary intersections where three or more of the crystal grains intersect, per unit area, is in the range of 1 to 10,000/μm2
Data Source
AI summary
The sensor element of an exhaust sensor has a solid electrolyte body provided with a detection electrode exposed to a gas to be detected, and provided with a reference electrode. A porous protective layer is provided on the outer surface of the solid electrolyte body including the surface of the detection electrode. The porous protective layer is composed of a plurality of aggregate particles bonded to each other. When a plurality of crystal grains constituting an aggregate particle are observed in cross section, the number of crystal grain boundary intersections where three or more of the crystal grains intersect, per unit area, is in the range of 1 to 10,000/μm2.