Diagonal Electrode DPF Sensor for Accurate PM Detection
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Solution Overview
Problem
Conventional PM sensors face challenges in accurately detecting the average PM deposit quantity of a diesel particulate filter (DPF) due to capacitance instability and incomplete detection, as they are often connected in parallel with a larger and thermally/mechanically unstable capacitor formed between electrodes and a metal housing, leading to inaccurate readings.
Innovation Solution
The PM sensor design features first and second electrodes inserted into open cells of a DPF, arranged diagonally, with short-circuiting lines to increase facing area and capacitance, allowing for accurate detection of the average PM deposit quantity by forming a parallel plane plate capacitor with a smaller distance between electrodes, reducing the influence of the housing and ensuring a large enough capacitance for detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two electrodes are installed on the outer circumference of the DPF to detect PM deposit quantity, then the PM deposit quantity can be detected, but the capacitance becomes notably larger and thermally/mechanically unstable due to the housing, leading to inaccurate detection
Solution Approach 1:
The invention extracts the detection function from the conventional outer-circumference electrode configuration and relocates it inside the DPF. By inserting electrodes into the honeycomb structure's internal cells, the design eliminates the parasitic capacitance formed between outer electrodes and the metal housing, thereby removing the source of thermal and mechanical instability while preserving the detection function.
Solution Approach 2:
The invention transitions from a two-dimensional surface-mounted electrode configuration (on the outer circumference) to a three-dimensional internal configuration (within the honeycomb cells). This spatial repositioning allows the electrodes to be surrounded by the DPF structure on multiple sides, increasing the effective detection area and improving measurement accuracy while isolating the capacitance from housing interference.
2Quantity of substance
If the distance between electrodes is reduced to increase capacitance, then the capacitance becomes large enough for detection, but the detection area of the DPF is reduced, leading to incomplete PM deposit quantity measurement
Solution Approach 1:
The invention divides the DPF's internal space into multiple detection zones by inserting electrodes into specific honeycomb cells. By strategically selecting which cells contain electrodes and which remain empty, the design creates a segmented detection pattern that collectively covers the entire DPF volume. This segmentation allows the capacitance to be sufficiently large while maintaining comprehensive detection coverage through the distributed electrode arrangement.
3Measurement precision
If electrodes are arranged to cover the entire DPF, then complete PM deposit quantity detection is achieved, but the capacitance becomes too small for reliable detection
Solution Approach 1:
The invention merges multiple capacitance contributions from electrodes inserted into different honeycomb cells to create a cumulative detection signal. By arranging electrodes in specific patterns (e.g., alternating or diagonal configurations), the individual capacitances add up to provide both sufficient magnitude for reliable detection and comprehensive spatial coverage of the entire DPF structure.
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 design enables accurate detection of the average PM deposit quantity across the entire DPF while securing a sufficient capacitance for reliable detection, reducing the risk of damage during regeneration and improving measurement precision.
Implementation Method 1
the capacitance of a capacitor formed by the two electrodes 83 and 84 is changed according to the PM deposit quantity of the entire DPF 82
Implementation Method 2
since the PM as a mixture of a dielectric with a conductor is deposited between electrodes, the capacitance increases linearly with respect to the PM deposit quantity
Data Source
AI summary
A diesel particulate filter (“DPF”) including vertically and horizontally stacked cells in which all of vertical and horizontal sides are surrounded by walls formed of a porous material, and sealing end faces of the cells alternately vertically and horizontally are provided with first and second electrodes. In a particulate matter (“PM”) sensor in which a PM deposit quantity of the DPF is detected by a capacitance of a capacitor formed by the first and second electrodes, among open cells, the first electrodes are inserted into the open cells arranged in a line in a diagonal direction, and the second electrodes are inserted into the open cells arranged in a line in the diagonal direction and including the open cells secondarily adjacent to each of the open cells into which the first electrodes are inserted.