PM Sensor Sensitivity Correction via Combustion Control
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Solution Overview
Problem
The existing electric resistance type PM sensors for internal combustion engines face issues with varying zero-point output and sensitivity due to individual differences and environmental factors, leading to deteriorating detection accuracy and unstable failure diagnosis of particulate filters.
Innovation Solution
A controller system that includes a PM sensor with a heater for combustion of particulate matter, sensitivity correcting means to adjust output sensitivity based on measured parameters like power supply and elapsed time, and abnormality determining means to detect sensor failures, ensuring accurate detection and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an electric resistance type PM sensor is used for failure diagnosis of the particulate filter, then the sensor can detect PM amount in the exhaust gas, but the detection accuracy deteriorates due to characteristic variation of the sensor
Solution Approach 1:
The system measures the actual output of the PM sensor by combusting captured PM with the heater and comparing it against expected values. This feedback mechanism allows the controller to detect sensor characteristic variations and adjust diagnoses accordingly, resolving the contradiction between detection accuracy and sensor reliability.
Solution Approach 2:
The system changes the operational state of the PM sensor by activating the heater to combust captured PM, thereby changing the resistance value parameter. This allows measurement of the sensor's actual response under controlled conditions, enabling detection of characteristic variations and improvement of both accuracy and reliability.
2Productivity
If the PM sensor operates in a fixed state for continuous monitoring, then the system can continuously detect PM levels, but the sensor characteristic variation makes failure diagnosis unstable
Solution Approach 1:
The system periodically activates the heater to combust captured PM and measure the sensor output, while maintaining continuous monitoring during normal operation. This periodic action allows characterization of sensor response under controlled conditions without interrupting continuous PM level monitoring, thus maintaining both productivity and diagnosis stability.
Solution Approach 2:
The system performs preliminary measurement of the PM sensor's actual output by combusting captured PM before using the sensor for failure diagnosis. This preliminary action characterizes the sensor's current state and allows for adjusted diagnosis thresholds, ensuring stable and accurate failure detection while maintaining continuous 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
The system effectively corrects sensitivity variations and improves detection accuracy by using the PM combustion control to measure and adjust sensitivity, allowing for reliable failure detection and handling of sensor abnormalities without additional diagnosis circuits.
Implementation Method 1
a heater for heating the detection portion; and PM combusting means for combusting and removing the particulate matters by electrical conduction to the heater
Implementation Method 2
an electric resistance type PM sensor is used to make failure diagnosis of the particulate filter
Data Source
AI summary
This invention has an object to appropriately correct characteristic variation of a PM sensor and to improve detection accuracy of the sensor.The PM sensor has a pair of electrodes for capturing the PM in an exhaust gas, and a sensor output changes in accordance with a captured amount of the PM. If the sensor output gets close to a saturated state, the PM combustion control for combusting and removing the PM between the electrodes by a heater is executed.