PM Sensor Self-Diagnosis via Exhaust Flow Rate Analysis
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Solution Overview
Problem
Existing diagnostic devices for particulate matter (PM) sensors in internal combustion engines are costly due to the need for multiple sensors and may fail to detect functional failures or deterioration early, especially when sensor regeneration frequency is low.
Innovation Solution
A diagnostic device that includes a time-rate-of-change calculation unit and an abnormality determination unit, which calculates the time rate of change of PM amounts detected by a PM sensor during low fuel injection periods and determines sensor abnormalities based on this calculation, eliminating the need for multiple sensors and enabling early detection of functional failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two PM sensors are provided at substantially the same position for diagnostic purposes, then sensor failure detection capability is improved, but device cost increases
Solution Approach 1:
The single PM sensor performs self-diagnosis by monitoring its own output signal characteristics. The diagnostic device determines sensor abnormalities by analyzing whether the particulate matter amount changes exceed predetermined thresholds during specific engine operating conditions, allowing the sensor to detect its own failures without requiring a redundant sensor.
Solution Approach 2:
Instead of using multiple sensors to detect failures by comparison, the invention inverts the approach by using a single sensor and detecting failures through abnormal signal behavior patterns. The diagnostic method looks for unexpected changes in the sensor output that indicate malfunction, rather than comparing outputs from multiple healthy sensors.
2Measurement precision
If sensor regeneration is performed frequently to enable diagnostic comparison, then failure detection accuracy is improved, but loss of time and productivity increase
Solution Approach 1:
The diagnostic device performs continuous monitoring of the sensor output signal during normal sensor operation, rather than waiting for regeneration events. By analyzing the temporal characteristics of PM amount changes during specific engine conditions before failure occurs, the system can detect abnormalities early without requiring frequent regeneration cycles.
Solution Approach 2:
The system continuously monitors the sensor output signal and provides feedback to the diagnostic device, which analyzes whether changes in particulate matter amount exceed predetermined thresholds. This continuous feedback mechanism enables real-time detection of sensor degradation or failure without interrupting normal sensor function or requiring regeneration.
3Productivity
If diagnostic determination is based on PM amount changes during normal operation, then diagnostic frequency is improved, but measurement precision may decrease
Solution Approach 1:
The diagnostic device applies different evaluation criteria based on specific engine operating conditions. It determines abnormalities by checking whether PM amount changes exceed predetermined thresholds during specific conditions (such as idle operation or low load), rather than using a single universal threshold for all operating conditions. This localized approach maintains high detection accuracy across varying operational contexts.
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 reduces costs by eliminating the need for multiple sensors and allows for more frequent abnormality determinations, enabling early detection of PM sensor failures and deteriorations, improving diagnostic efficiency and accuracy.
Implementation Method 1
A PM amount is estimated based on the fact that the electric resistance value changes with the conductive PM (mainly soot ingredients) adhering to the electrodes
Data Source
AI summary
There is provided the diagnostic device for a sensor which is arranged in an exhaust passage of an internal combustion engine and detects a particulate matter amount in exhaust, the diagnostic device including a time-rate-of-change calculation unit which calculates a time rate of change of the particulate matter amount detected by the sensor during a period in which a fuel injection amount of the internal combustion engine is equal to or less than a predetermined injection amount threshold, and an abnormality determination unit which determines an abnormality of the sensor based on the time rate of change of the particulate matter amount calculated by the time-rate-of-change calculation unit.