Particulate Matter Sensor Temperature Correction
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Solution Overview
Problem
Existing particulate matter (PM) sensors in internal combustion engines face challenges in accurately detecting PM levels due to influences from temperature variations, exhaust flow rates, and electrical resistance changes, leading to inconsistent detection values.
Innovation Solution
A detection apparatus is designed with a particulate matter detection unit, temperature detection unit, and correction unit that corrects PM detection values based on exhaust temperature, insulator temperature, and exhaust flow rate, mitigating the effects of thermal migration and electrical resistance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a PM sensor is used to detect PM amount in exhaust gas, then PM detection capability is provided, but detection accuracy deteriorates due to temperature variations and thermal migration
Solution Approach 1:
A temperature sensor is introduced as an intermediary device to detect the temperature of the insulator. This temperature information is then used as a correction parameter to compensate for the harmful effects of temperature variations on the PM sensor output, thereby maintaining measurement precision despite the presence of thermal migration and temperature fluctuations.
Solution Approach 2:
The system changes the operating parameters by introducing temperature correction based on detected insulator temperature. By adjusting the PM detection values according to temperature parameters, the system compensates for thermal migration effects and maintains accurate PM measurement across varying temperature conditions.
2Reliability
If PM is deposited on the insulator to enable current flow between electrodes, then PM detection function is achieved, but detection reliability deteriorates due to thermal migration causing PM to move away from the insulator
Solution Approach 1:
The temperature sensor provides continuous feedback on the insulator temperature, which is then used to correct the PM detection values. This feedback mechanism compensates for the harmful thermal migration effect that causes PM to move away from the insulator, ensuring reliable PM detection despite the dynamic movement of particulate matter.
3Productivity
If the exhaust flow rate is increased to improve emission control, then exhaust purification performance is improved, but PM detection accuracy deteriorates due to reduced PM deposition on the insulator
Solution Approach 1:
The system introduces exhaust flow rate as an additional correction parameter. By detecting the exhaust flow rate and using it to adjust the PM detection values, the system compensates for the reduced PM deposition that occurs at higher flow rates, thereby maintaining measurement precision while allowing improved exhaust purification performance.
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 apparatus achieves high-accuracy PM detection in exhaust paths by accounting for temperature and flow rate influences, providing reliable PM measurement independent of thermal migration and electrical resistance variations.
Implementation Method 1
PM is electrically conductive, accumulation of PM between the electrodes 51 and 52 to the extent of connecting therebetween will create an electrically conductive state across the electrodes. Accordingly, when voltage is applied across the electrodes 51 and 52 by the power supply 54, current passes across the electrodes 51 and 52.
Implementation Method 2
In a condition where different temperature regions adjacently exist, so-called thermal migration is induced by which particulates in a higher-temperature region migrate toward a lower-temperature region.
Data Source
AI summary
A detection apparatus includes a particulate matter (PM) detection unit, a temperature detection unit, and a correction unit. The PM detection unit includes an insulator, a pair of electrodes, and a detector. The insulator is disposed in an exhaust path of an internal combustion engine through which an exhaust gas flows. The pair of electrodes are arranged in contact with at least a part of the insulator. The detector detects a PM detection value which is a value correlated to an amount of PM in the exhaust gas. The temperature detection unit detects at least one of an exhaust temperature of the exhaust gas passing through the PM detection unit and an insulator temperature of the insulator. The correction unit corrects the PM detection value detected by the PM detection unit based on at least one of the exhaust temperature and the insulator temperature.