Particulate Matter Detection Element with Rough Insulating Member
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Solution Overview
Problem
The existing particulate matter detection sensors in exhaust gas purification systems face issues with particulate matter detachment due to weak retentive forces, leading to reduced detection accuracy and output, especially under varying exhaust gas conditions.
Innovation Solution
A particulate matter detection element with laminated detection electrodes and insulating members, where the insulating members have a surface roughness between 0.8 μm and 8.0 μm, enhancing the retentive force of particulate matter and preventing detachment, and a cylindrical cover member surrounds the detection element to maintain the deposition part's orientation relative to exhaust gas flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the deposition part surface is polished smoothly to expose electrode layer end surfaces, then the detection sensor structure is formed, but the retentive force of deposited particulate matter becomes weak causing easy detachment
Solution Approach 1:
The patent applies local quality by differentiating the surface roughness of different regions: the insulating member surface is made rough (Ra 0.8-8.0 μm) to enhance particulate matter retention, while the electrode layer end surfaces are kept smooth for proper electrical contact and signal detection. This localized differentiation resolves the contradiction between smooth surface requirements for electrode exposure and rough surface requirements for particulate retention.
2Quantity of substance
If the particulate matter accumulates on the deposition part, then the detection output increases, but the weight increase causes particulate matter to detach due to weak retentive force
Solution Approach 1:
The patent changes the surface roughness parameter of the insulating member to Ra 0.8-8.0 μm, which creates minute unevenness that enhances the retentive force through increased surface area and mechanical interlocking. This parameter change allows particulate matter to accumulate effectively while preventing detachment even as weight increases, resolving the contradiction between accumulation and stability.
3Speed
If the exhaust gas velocity increases or the weight of particulate matter increases, then the flow dynamics change, but the particulate matter detaches due to insufficient retentive force
Solution Approach 1:
The patent utilizes a porous or uneven surface structure on the insulating member with controlled roughness (Ra 0.8-8.0 μm), creating a network of minute cavities and irregularities that mechanically trap particulate matter. This porous-like structure provides enhanced retention against varying exhaust gas velocities and particulate weights, resolving the contradiction between flow dynamics and retention stability.
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 configuration increases detection accuracy and prevents output decreases by ensuring particulate matter remains deposited, even under conditions of increased exhaust gas velocity or weight, allowing for easier assembly and maintaining detection sensitivity.
Implementation Method 1
a surface roughness of at least the insulating member disposed between the paired detection electrodes being between 0.8 μm and 8.0 μm in 10-point average roughness... the retentive force of the particulate matter on the surface of the insulating member increases
Data Source
AI summary
A particulate matter detection element 1 includes paired detection electrodes 12 for detecting particulate matter contained in exhaust gas discharged from an internal combustion engine, and insulating member 13 made of electrically insulating material. In the particulate matter detection element 1, at least part of the paired detection electrodes 12 is exposed from the insulating member 13 in the direction perpendicular to the lamination direction of the paired detection electrodes 1, to cause part of the particulate matter to deposit thereon. The surface roughness of at least the insulating member disposed between the paired detection electrodes is between 0.8 μm and 8.0 μm in 10-point average roughness.