Particulate Matter Detection Element Shielding Layer
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Solution Overview
Problem
Conventional particulate matter detection sensors for internal combustion engine exhaust gas purification systems face issues with non-uniform electric field distribution, leading to inconsistent PM accumulation and reduced reliability due to local accumulation on areas with high electric field intensity, resulting in incorrect output and reduced regeneration timing accuracy.
Innovation Solution
A particulate matter detection element with a shielding layer made of heat-insulating material is used to cover areas with non-uniform electric field intensity, ensuring a uniform electric field distribution on the detection area, preventing PM accumulation on these areas and promoting consistent PM accumulation on the detection electrodes, thereby stabilizing the dead time period and output reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional PM detection sensor without shielding layer is used, then the device complexity is reduced, but the reliability deteriorates due to non-uniform electric field distribution causing local PM accumulation
Solution Approach 1:
The shielding layer is selectively applied only to specific areas of the detection electrode where non-uniform electric field distribution occurs, rather than covering the entire electrode. This localized approach addresses the reliability issue at critical locations while minimizing the increase in device complexity.
Solution Approach 2:
The shielding layer acts as an intermediary element between the detection electrode and the exhaust gas flow. It modifies the electric field distribution by blocking field lines in non-uniform regions, thereby preventing PM accumulation without interfering with the overall detection function.
2Productivity
If the electric field intensity is increased to improve PM accumulation speed, then the productivity is improved, but the reliability deteriorates due to enhanced local accumulation on high electric field areas
Solution Approach 1:
The shielding layer creates local differences in electric field exposure by protecting specific areas from the exhaust gas flow. This allows high electric field intensity to be maintained in the detection region for improved PM accumulation speed, while preventing local accumulation in shielded areas that would compromise detection accuracy.
Solution Approach 2:
The detection electrode area is effectively segmented into shielded and unshielded regions. This segmentation allows different parts of the electrode to serve different functions: unshielded areas maintain high electric field intensity for rapid PM accumulation, while shielded areas prevent local accumulation and ensure uniform detection characteristics.
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 solution achieves a stable dead time period and high reliability in detecting particulate matter by preventing local accumulation on non-uniform electric field areas and ensuring consistent PM detection, improving the accuracy of regeneration timing and reducing the probability of incorrect outputs.
Implementation Method 1
The heating unit generates heat energy when receiving electric power. The heat energy increases a temperature of the PM detection part to a desired temperature (for example, a temperature within a range of 400° C. to 600° C.), and burns the smoke accumulated on the area between the conductive electrodes.
Implementation Method 2
The shielding layer is made of heat insulating material. The shielding layer covers a predetermined area on the detection part so that an area having a uniform electric field intensity generated when a voltage is supplied between the detection electrodes is exposed to the target detection gas.
Data Source
AI summary
A shielding part is formed on a detection part in a particulate matter detection element. The detection part has a pair of detection electrodes formed in a comb structure. A shielding layer is made of heat insulating material and formed on the detection part in order to shield a predetermined area having non-uniform electric field intensity. An area having uniform electric field intensity on the detection part is exposed only to exhaust gas as target detection gas when a predetermined voltage is supplied between the detection electrodes in order to detect electric characteristics of the detection part. This structure prevents the area other than the area having the uniform electric field intensity on the detection part from being exposed to the exhaust gas.