Fine Particle Detection System Shielding for Exhaust Gas Accuracy
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Solution Overview
Problem
Existing fine particle detection systems face challenges in accurately measuring the amount of fine particles in exhaust gas due to low signal current intensity and interference from leakage currents and electromagnetic noises, making it difficult to detect filter deterioration or defects in real-time.
Innovation Solution
A fine particle detection system with a sensor and drive control device that includes an ion source unit, particle charging unit, and shielding mechanisms to generate and trap ions, and a double-shield cable to prevent leakage and electromagnetic interference, allowing for accurate detection of signal current and determination of fine particle amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If aerial discharge is used to generate ions for charging fine particles, then the fine particle detection capability is enabled, but leakage current and electromagnetic noises interfere with the low signal current measurement
Solution Approach 1:
The patent introduces an intermediary grounding structure (grounding wire connected to the exhaust pipe) that acts as a mediator between the high-voltage ion generation region and the signal measurement region. This grounding structure provides a reference potential that isolates the measurement circuit from electromagnetic disturbances and leakage currents, enabling accurate detection of the微弱 signal current without interference from the aerial discharge process.
Solution Approach 2:
The patent extracts and separates the harmful factors (leakage current and electromagnetic noises) from the signal measurement path by using a dedicated grounding wire connected to the exhaust pipe. This extraction allows the signal current detection to be performed independently from the ion generation process, removing the interfering elements while preserving the detection function.
2Measurement precision
If the signal current is kept at very low intensity to accurately reflect fine particle amounts, then measurement precision is improved, but the system becomes more vulnerable to leakage current and electromagnetic interference
Solution Approach 1:
The grounding wire serves as an intermediary element that stabilizes the electrical potential in the measurement region. By providing a stable reference potential connected to the exhaust pipe, it shields the low-level signal current measurement from fluctuations caused by leakage current and electromagnetic noises, thereby maintaining both precision and reliability simultaneously.
Solution Approach 2:
The patent establishes equipotentiality by connecting the grounding wire to the exhaust pipe, creating a common reference potential for both the ion generation process and the signal measurement. This equipotential reference eliminates potential differences that would otherwise cause leakage current and electromagnetic interference, allowing accurate measurement of the微弱 signal current.
3Reliability
If shielding structures are added to prevent electromagnetic interference, then reliability is improved, but device complexity increases
Solution Approach 1:
Instead of adding complex shielding structures, the patent extracts and removes the harmful electromagnetic interference by using a simple grounding wire connected to the exhaust pipe. This approach eliminates the need for elaborate shielding mechanisms while achieving reliable protection against electromagnetic noises and leakage currents.
Solution Approach 2:
The patent uses a simple, inexpensive grounding wire as a disposable-like element that provides effective shielding without adding permanent structural complexity. This simple grounding structure achieves the same protective function as complex shielding systems but with minimal device complexity and cost.
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 system effectively detects fine particle amounts in exhaust gas with improved accuracy, reducing errors from leakage currents and electromagnetic noises, enabling timely detection of filter issues and ensuring reliable exhaust gas purification.
Implementation Method 1
a first electrode set to a first floating potential; and a second electrode set to a second floating potential that is a positive or negative potential having an effective potential value higher than that of the first floating potential, to generate ions by aerial discharge between the first and second electrodes
Implementation Method 2
a mixing space for mixing the introduced exhaust gas with the ions generated from the ion source unit so as to form charged fine particles by charging the fine particles in the introduced exhaust gas with some of the ions
Implementation Method 3
a trapping electrode being electrically continuous with the first electrode and adapted to trap a remainder of the ions that remain as stray ions without being used for charging of the fine particles
Implementation Method 4
the lead being a double-shield cable having: a power supply wiring line connected to the second electrode; an inner shield line being electrically continuous with the inner sensor casing, while being electrically insulated from the power supply wiring line, and circumferentially surrounding the power supply wiring line; and an outer shield line being electrically continuous with the outer sensor casing, while being electrically insulated from the inner shield line, and circumferentially surrounding and electromagnetically shield the inner shield line
Data Source
AI summary
There is provided a fine particle detection system with a fine particle sensor, a cable and a sensor drive control device. The fine particle sensor has an ion source unit with first and second electrodes, a particle charging unit and inner and outer sensor casings. The cable has a power supply wiring line connected to the second electrode, an inner shield line electrically continuous with the inner sensor casing and an outer shield line electrically continuous with the outer sensor casing. The sensor drive control device has an ion-source power supply circuit, a signal current detection circuit, an inner circuit casing electrically continuous with a first output terminal of the ion-source power supply circuit and surrounding the ion-source power supply circuit and an outer circuit casing connected to the ground potential and shielding the ion-source power supply circuit, the signal current detection circuit and the inner circuit casing.