Capacitive Particulate Matter Sensor for Exhaust Gas
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Solution Overview
Problem
Resistor-type particulate matter sensors have a slow response speed and are prone to malfunction due to the deposition of electrically conductive foreign matter, which causes signal distortion.
Innovation Solution
A particulate matter sensor design featuring a first and second electrode unit separated by insulation layers, with a heater unit to maintain temperature and a temperature sensing unit, allowing capacitance between the electrodes to be measured as particulate matter deposits, thereby preventing sensor damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resistor-type PM sensor is used to diagnose DPF malfunctioning, then the sensor can detect particulate matter deposition, but the response speed is very slow at the initial stage and signal distortion occurs when electrically conductive foreign matter is deposited
Solution Approach 1:
The patent replaces the resistor-type sensing mechanism with a capacitive sensing mechanism. Instead of measuring electrical resistance changes through current flow (which causes signal distortion with conductive foreign matter), the invention measures capacitance changes between electrodes. This substitution eliminates the response delay and signal distortion issues because capacitance measurement does not require current flow through the deposited particles, thereby improving both response speed and measurement reliability simultaneously
Solution Approach 2:
The patent changes the measurement parameter from electrical resistance to capacitance. By measuring the capacitance between the first and second electrodes instead of resistance, the system avoids the problems of slow response and signal distortion. The capacitance change reflects particulate matter deposition without being affected by the electrical conductivity of foreign matter, thus improving both response speed and measurement accuracy
2Reliability
If a resistor-type PM sensor is used, then particulate matter can be detected through current generation, but electrically conductive foreign matter causes signal distortion and sensor malfunctioning
Solution Approach 1:
The patent substitutes the resistive measurement system with a capacitive measurement system. The capacitive sensor measures the change in capacitance between electrodes caused by particulate matter deposition, rather than measuring current flow as in resistive sensors. This substitution eliminates the harmful effect of electrically conductive foreign matter causing signal distortion, as capacitance measurement is not dependent on the electrical conductivity of the deposited material, thereby protecting sensor functionality
Solution Approach 2:
The patent introduces capacitance as an intermediary measurement parameter that indirectly detects particulate matter deposition without requiring direct electrical contact or current flow through the particles. This intermediary approach allows the sensor to detect PM accumulation while being immune to the harmful effects of conductive foreign matter, as the measurement is based on the dielectric properties rather than electrical conductivity of the deposited material
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 sensor effectively measures capacitance changes caused by deposited particulate matter, preventing signal distortion and maintaining functionality even with electrically conductive foreign matter.
Implementation Method 1
The first electrodes and the second electrodes are arranged respectively corresponding to each other. The first electrodes are configured to be electrically connected to each other by particulates deposited therebetween to allow capacitance between the first electrodes and the second electrodes to be changed.
Implementation Method 2
a heater unit formed on a first side of a fourth insulation layer located on a second side of the third insulation layer, the heater unit configured to heat the first and second electrode units
Implementation Method 3
a temperature sensing unit formed on a first side of a third insulation layer located on a second side of the second insulation layer
Data Source
AI summary
A particulate matter sensor and an exhaust gas purification system using the same are provided. A particular matter sensor according to some embodiments of the present invention includes a first insulation layer including a first electrode unit exposed on a first side thereof, which includes a plurality of first electrodes not electrically connected to each other, a second insulation layer arranged in parallel to the first insulation layer with a space therebetween, including a second electrode unit on a first side thereof, which includes a plurality of second electrodes electrically connected to each other, a temperature sensing unit formed on a first side of a third insulation layer located on a second side of the second insulation layer, and a heater unit formed on a first side of a fourth insulation layer located on a second side of the third insulation layer, the heater unit configured to heat the first and second electrode units. One of the first electrodes is configured to be electrically connected to a first electrical contact terminal. The second electrodes are electrically connected to a second electrical contact terminal. The first electrodes and the second electrodes are arranged respectively corresponding to each other. The first electrodes are configured to be electrically connected to each other by particulates deposited therebetween to allow capacitance between the first electrode and the second electrode to be changed.