Exhaust Sensor Capacitance Water Detection
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Solution Overview
Problem
Existing sensors for detecting particulate matter in exhaust gas systems do not reliably detect condensate water or water infiltration, which can lead to sensor failure and system degradation.
Innovation Solution
A sensor system that uses electrostatic capacitance changes to differentiate between particulate matter and water presence, with a control unit to estimate water amount and protect other sensors by prohibiting energization during water detection, integrating water infiltration determination with PM detection in a single sensor configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensor uses electrostatic capacitance change to detect PM, then PM detection capability is improved, but the ability to detect water is insufficient
Solution Approach 1:
The sensor divides the detection function into multiple independent electrode pairs, each capable of detecting different substances. By arranging multiple electrode pairs at different positions, the sensor can separately detect PM and water based on their different effects on electrostatic capacitance, thus resolving the contradiction between PM detection precision and water detection capability.
Solution Approach 2:
The sensor achieves multi-functionality by using the same electrostatic capacitance measurement principle to detect both PM and water. The control unit analyzes capacitance changes from multiple electrode pairs to simultaneously perform PM detection and water detection, making a single sensor system capable of multiple detection functions without requiring separate sensors.
2Device complexity
If a single sensor is used for both PM and water detection, then device complexity is reduced, but detection reliability for both substances may be compromised
Solution Approach 1:
The sensor structure is segmented into multiple electrode pairs (first electrode pair and second electrode pair) positioned differently within the exhaust flow path. This segmentation allows each electrode pair to independently contribute to detection, with the control unit processing signals from each pair to distinguish between PM and water effects, maintaining detection reliability while using a single integrated sensor device.
Solution Approach 2:
The control unit acts as an intermediary that processes electrostatic capacitance signals from multiple electrode pairs. It analyzes the patterns of capacitance changes to differentiate between PM accumulation and water presence, enabling reliable dual detection through a single sensor system without direct physical separation of detection functions.
3Reliability
If water is not detected, then sensor protection is insufficient, but adding dedicated water detection increases system complexity
Solution Approach 1:
The existing PM detection sensor is made universal by enabling it to also detect water through analysis of electrostatic capacitance changes from multiple electrode pairs. The control unit uses the same hardware infrastructure to perform both PM detection and water detection, providing sensor protection capability without adding dedicated water detection hardware, thus avoiding increased system complexity.
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
Enables reliable detection of water in the exhaust system, protecting sensors from water-related failures and simplifying the configuration by using a single sensor for both PM and water detection, thereby preventing sensor damage and maintaining system efficiency.
Implementation Method 1
a sensor unit 30 having a first electrode member 32 and a second electrode member 33 which face each other with a capacitor configuration
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
There is provided a sensor unit 30 arranged in an exhaust system of an internal combustion engine and including a filter member 31 having a plurality of cells divided by porous partition walls and collecting particulate matter in exhaust gas, and at least one pair of electrode members 32, 33 arranged to face each other with the cell interposed therebetween so as to form a capacitor, and a control unit 40 estimating an amount of the particulate matter in the exhaust gas and detecting water present in the exhaust system of the engine, based on an electrostatic capacitance between the pair of electrode members 32, 33.