Electrostatic PM Sensor Electrode Diagnostics via Localized Gap
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Solution Overview
Problem
Existing electrostatic particulate matter (PM) sensors in vehicle exhaust systems face challenges in diagnostics, such as detecting electrical faults and ensuring sensor plausibility, due to the lack of soot exposure during normal operation, which complicates on-board diagnostics (OBD) and compliance with regulations like CARB requirements.
Innovation Solution
The implementation of an electrostatic PM sensor design with spaced apart electrodes and a controller that varies voltage to induce electrostatic discharge at a localized gap, allowing for diagnostic tasks like continuity checks, plausibility determination, and installation fault detection by creating a reduced gap region for controlled breakdown and comparing breakdown voltages at different temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant voltage is maintained between electrodes during normal operation, then the sensor can detect soot particles, but diagnostic capabilities are limited and electrical faults cannot be detected
Solution Approach 1:
The patent implements dynamic voltage control where the controller switches between a first voltage level during normal soot detection and a second higher voltage level during diagnostic tests. This dynamic adjustment enables the system to perform both soot measurement and self-diagnostics using the same electrode structure, resolving the contradiction between operational simplicity and diagnostic capability.
Solution Approach 2:
The electrode system is designed to serve multiple functions: detecting soot particles during normal operation and performing diagnostic tests by inducing electrostatic discharge. By making the voltage control system universal, it can adapt to different operational modes without requiring separate diagnostic hardware, thus improving reliability while maintaining acceptable complexity.
2Reliability
If voltage is increased to induce electrostatic discharge for diagnostics, then electrical faults can be detected, but false positives may occur from resistive loads
Solution Approach 1:
The patent employs periodic diagnostic testing where voltage is increased to induce electrostatic discharge only during designated diagnostic intervals, not continuously. This periodic action allows the system to detect electrical faults when resistive loads are less likely to cause false positives, while maintaining accurate soot detection during normal operational intervals when the lower voltage is applied.
Solution Approach 2:
The controller monitors the current response during voltage increases and uses feedback to distinguish between legitimate electrostatic discharge indicating electrical faults and current responses from resistive loads. By analyzing the characteristics of the current response, the system can accurately identify true faults while filtering out false positives, thus maintaining both fault detection accuracy and soot detection precision.
3Use of energy by moving object
If a localized gap is created for controlled discharge, then diagnostics can be performed at lower voltages, but the electrode structure becomes more complex
Solution Approach 1:
The patent introduces a localized gap with reduced spacing between electrodes at a specific position along the electrode length. This local modification creates a preferred discharge location that enables controlled electrostatic discharge at lower voltages. The rest of the electrode structure maintains its original design for soot detection, so the overall complexity increase is minimal while achieving the energy reduction benefit.
Solution Approach 2:
The electrode gap is segmented into a bulk gap region for normal soot detection and a localized reduced-gap region for controlled diagnostic discharge. This segmentation allows each region to serve its specific function optimally: the bulk gap maintains adequate spacing for regular operation, while the localized gap provides a controlled path for diagnostic discharge at lower voltages, thus reducing overall voltage requirements without significantly complicating the electrode structure.
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 approach enables effective diagnostics, ensuring the sensor's functionality and installation integrity, differentiating normal responses from faulty outputs, and accurately detecting soot presence while preventing false positives from resistive loads, thus enhancing regulatory compliance and system reliability.
Implementation Method 1
a controller configured to increase a voltage between the electrodes to induce an electrostatic discharge at the localized gap
Implementation Method 2
the electrostatic force attracting the particles to the opposing electrode exceeds the force holding the dendrite together
Data Source
AI summary
Particulate matter (PM) sensors and diagnostics performed using the PM sensors are disclosed. The PM sensors and diagnostics may be used in exhaust systems, such as vehicle exhaust systems, to detect soot. In at least one embodiment, an electrostatic particulate matter (PM) sensor is provided including first and second spaced apart electrodes forming a bulk gap therebetween having a bulk distance and a localized gap therebetween having a localized distance less than the bulk distance. A controller may be configured to control a voltage between the electrodes to induce an electrostatic discharge at the localized gap at a lower voltage than at the bulk gap. Various diagnostics may be performed using the disclosed PM sensors, including a wiring/continuity diagnostic, a soot detection plausibility diagnostic, and/or an installation diagnostic.