Particulate Matter Sensor with Through-Hole Segmentation
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Solution Overview
Problem
Conventional PM sensors face accuracy issues in the initial state due to particulate matter (PM) entering and accumulating in the porous filter, which affects capacitance measurements, leading to unreliable detection results when little or no PM is present.
Innovation Solution
The PM sensor design includes an accumulation section with a pair of electrodes and through holes that allow PM to pass through, minimizing accumulation and ensuring accurate detection by preventing PM from adhering to the electrodes, thus maintaining stable accuracy even in the initial state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a porous filter is used to accumulate PM on its surface for detection, then PM can be detected by capacitance measurement, but PM may enter and stay in the porous filter, reducing detection accuracy in the initial state
Solution Approach 1:
The accumulation section is divided into a detection region (where electrodes are located) and a through-hole region (where PM passes through). This segmentation allows PM to be detected on the upstream surface while preventing it from entering and staying in the filter structure, thereby maintaining detection accuracy in the initial state.
Solution Approach 2:
Through holes are introduced as intermediary structures that allow PM to pass through the accumulation section without accumulating inside. These through holes act as a mediator between the upstream surface (where detection occurs) and the downstream side, preventing PM from entering the filter interior while still allowing the capacitance-based detection mechanism to function.
2Quantity of substance
If PM accumulates in the porous filter, then capacitance changes can be measured, but the detection accuracy deteriorates when there is no or small amount of PM accumulated
Solution Approach 1:
The harmful function of the porous filter (PM entering and staying inside) is extracted and eliminated by introducing through holes. This allows the filter to retain only the useful function of accumulating PM on the upstream surface for detection, while removing the capability to trap PM inside, thereby maintaining accurate detection even with small amounts of PM.
3Reliability
If the accumulation section blocks the exhaust gas passage to accumulate PM, then PM detection is enabled, but PM enters and stays in the accumulation section, affecting initial state detection
Solution Approach 1:
Different regions of the accumulation section are given different properties: the upstream surface has PM accumulation capability for detection, while the through-hole regions have PM passage capability. This local differentiation allows the accumulation section to block the passage sufficiently for detection while providing escape routes that prevent PM from staying inside, maintaining initial state detection 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
This design enhances the accuracy of PM detection by preventing PM from accumulating in the sensor, ensuring reliable measurements even when little or no PM is present, thereby stabilizing the detection results.
Implementation Method 1
The PM sensor derives the amount of PM accumulated in the porous filter according to the capacitance of a capacitor consisting of at least a pair of electrodes
Data Source
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Figure 3A
AI summary
This particulate matter (PM) sensor is provided with: a deposition part that is disposed so as to obstruct a passage for exhaust gas including particulate matter, has a surface on the upstream side of the passage on which particulate matter is deposited, and has at least one through hole formed therein; and at least a pair of electrodes that oppose each other so as to sandwich the deposition part. The at least one through hole penetrates from the surface of the deposition unit on the upstream-side of the flow of the exhaust gas to the surface on the downstream side.