Capacitance-Based PM Sensor for Real-Time Filter Efficiency Monitoring
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Solution Overview
Problem
Existing exhaust purification devices for internal combustion engines fail to monitor particulate matter (PM) collecting efficiency in real time, making it difficult to detect filter degradation before failure, which can lead to unexpected breakdowns.
Innovation Solution
The implementation of an exhaust purification device with upstream and downstream sensors, each comprising a filter with porous partition walls and electrodes forming capacitors, allowing for real-time measurement of PM collecting efficiency through electrostatic capacitance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resistance-type PM sensors are arranged upstream and downstream of the filter to determine filter failure, then it is possible to detect filter failure, but it is not possible to recognize the tendency of collecting efficiency to degrade before failure
Solution Approach 1:
The patent changes the measurement parameter from resistance (in prior art) to electrostatic capacitance. The capacitance value changes in response to PM accumulation on the sensor filter, enabling real-time monitoring of collecting efficiency trends before filter failure occurs. This parameter change allows detection of degradation tendencies that resistance measurements cannot capture.
Solution Approach 2:
The patent replaces the resistance-type sensing mechanism with an electrostatic capacitance-based sensing mechanism. The capacitance sensor uses electrostatic fields to detect PM accumulation, substituting the electrical resistance measurement approach. This substitution enables more sensitive detection of PM collecting efficiency changes, allowing early warning of filter degradation trends.
2Reliability
If real-time acquisition of PM collecting efficiency is implemented, then it is possible to recognize degradation tendency before failure, but the device complexity increases with additional sensors and capacitance measurement systems
Solution Approach 1:
The capacitance sensor structure serves multiple functions: it acts as both a PM collection filter (through the porous partition walls) and a sensing element (through the electrode pairs measuring capacitance). This multi-functionality reduces the need for separate sensing components, thereby limiting the increase in device complexity while enabling real-time efficiency monitoring.
Solution Approach 2:
The patent merges the filter structure and sensor structure into a single integrated component. The sensor filter combines the porous partition walls for PM collection with the electrode pairs for capacitance measurement, eliminating the need for separate filter and sensor assemblies. This merging reduces overall system complexity while achieving real-time monitoring capability.
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
Enables real-time monitoring of PM collecting efficiency, allowing for timely filter maintenance and preventing failures by detecting efficiency degradation before it becomes critical.
Implementation Method 1
at least one pair of first electrodes arranged to face each other with the first cell interposed therebetween so as to form a capacitor
Implementation Method 2
a first electrostatic capacitance between the pair of first electrodes and a second electrostatic capacitance between the pair of second electrodes
Data Source
AI summary
There is provided a first PM sensor provided upstream of a filter and including a first sensor filter having a plurality of first cells collecting PM in the exhaust gas to be introduced into the filter, and a first pair of electrodes arranged to face each other with the first cell interposed therebetween, a second PM sensor provided downstream of the filter and including a second sensor filter having a plurality of second cells collecting PM in the exhaust gas discharged from the filter, and a second pair of electrodes arranged to face each other with the second cell interposed therebetween, and a filter state determination unit for acquiring an efficiency of collecting the PM in the filter, based on a first electrostatic capacitance between the first pair of electrodes and a second electrostatic capacitance between the second pair of electrodes.