Particulate Matter Sensor with Filamentous Structure Detection
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Solution Overview
Problem
Existing in-situ particulate matter sensors for internal combustion engines face limitations such as slow response times, reliability issues, and difficulty in detecting low current signals due to soot accumulation, which affects their performance and accuracy in measuring exhaust particulate matter.
Innovation Solution
A particulate matter sensor that uses an electrode with a high voltage to create an electric field, allowing soot particles to form filamentous structures which break off and carry charge, generating detectable current pulses, thereby increasing the measured current and reducing the need for special insulation and remedies for soot accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contact charge sensors use high voltage electrodes to detect particulate matter, then measurement precision is improved, but device complexity increases due to insulation requirements
Solution Approach 1:
The patent extracts the high voltage generation function to an external power supply unit, separating it from the sensor body. This eliminates the need for complex high voltage insulation within the sensor housing, while still enabling contact charge detection. The sensor only requires simple electrical connections for signal output, not for high voltage supply.
Solution Approach 2:
The patent introduces an intermediary external power supply unit that provides high voltage to the sensor electrode through controlled connections. This mediator handles the complex insulation and high voltage management outside the sensor, allowing the sensor itself to remain simple while maintaining measurement precision.
2Device complexity
If accumulative sensors allow soot to accumulate on surfaces for measurement, then device simplicity is improved, but response speed deteriorates
Solution Approach 1:
The patent implements periodic burn-off cycles where accumulated soot is periodically ignited and removed from the sensor surface. This periodic action resets the sensor, enabling it to maintain simplicity while achieving real-time response capability. The cycle alternates between accumulation phase (measurement) and burn-off phase (reset).
Solution Approach 2:
The patent discards accumulated soot through periodic combustion and recovers the sensor surface for continued use. This process eliminates the permanent accumulation problem of traditional accumulative sensors, allowing repeated measurement cycles without degradation of response speed.
3Speed
If ionizing induced charge sensors use high voltage corona discharge to charge particles, then response speed is improved, but device complexity increases
Solution Approach 1:
The patent extracts the ionizing function to an external power supply, leaving only a simple electrode in the sensor. This eliminates the need for complex high voltage generation components within the sensor housing, reducing apparatus size while maintaining the ability to create charged particles through contact charge mechanism.
Solution Approach 2:
The patent replaces the mechanical corona discharge system with a simpler contact charge mechanism. Instead of using high voltage to create ions that attach to particles, the system uses direct contact between charged electrode and particles, simplifying the mechanical structure while achieving similar functional results.
4Measurement precision
If contact charge sensors measure very small currents from particle charge transfer, then measurement precision is improved, but reliability deteriorates due to current leakage
Solution Approach 1:
The patent extracts the high voltage supply function externally, allowing the sensor to operate with simple low voltage signal connections. This eliminates leakage paths associated with high voltage connections within the sensor, improving reliability while maintaining the ability to detect charge transfer signals through differential measurement techniques.
Solution Approach 2:
The patent uses differential measurement techniques that compare potentials across the electrode, effectively canceling out common-mode leakage currents. By measuring the potential difference rather than absolute potential, the system achieves reliable detection of small charge transfer signals despite the presence of leakage paths.
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 solution enables a sensor with a faster response time than traditional contact charge sensors but slower than real-time sensors, allowing for accurate particulate matter measurement with higher current signals, reducing the demand on electrical insulation and signal amplification, and maintaining performance in harsh engine environments.
Implementation Method 1
the electrode generates an electric field to facilitate formation of particulate matter into at least one filamentous structure on the surface of the electrode
Implementation Method 2
the filamentous structure having a particulate matter structure surface charge substantially equal to the electrode surface charge
Data Source
Figure 1
Figure 2A~2B
Figure 2C~3
AI summary
A sensor assembly to measure particulate matter is described. The sensor assembly includes a voltage source, a sensor electrode, a grounded assembly, an integration capacitor, and a current meter. The sensor electrode is coupled to the voltage source to receive a voltage. The sensor electrode is disposed within a directed and controlled exhaust flow within the sensor assembly to facilitate particle agglomeration into particulate matter structures at a surface of the sensor electrode. The grounded assembly is coupled to a ground reference and disposed at a distance from the sensor electrode. The integration capacitor is coupled to a negative side of the voltage source. The integration capacitor is configured to integrate in time current pulses from charge transfers from the sensor electrode of the particulate matter structures.