Particulate Matter Sensor Capacitance Stability
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Solution Overview
Problem
Capacitance type particulate matter sensors face challenges in maintaining constant capacitance at high temperatures due to sharp changes in dielectric constants, limiting their usage and requiring excessive expensive materials like platinum, which increases production costs.
Innovation Solution
A particulate matter sensor design featuring externally formed capacitor components and a heater unit within the insulating substrate, allowing for separate control of sensing electrodes and capacitors, reducing the need for internal capacitors and minimizing platinum usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitor parts are formed adjacent to sensing parts on the insulating substrate, then the sensor can measure capacitance to detect PM, but the capacitance becomes unstable at high temperatures due to dielectric constant changes
Solution Approach 1:
The patent divides the capacitor structure into two separate locations: capacitor parts formed on the insulating substrate (away from high temperature exposure) and sensing parts exposed to exhaust gases. This segmentation allows the capacitor function to operate in a stable temperature environment while the sensing function operates in the high temperature exhaust environment, resolving the contradiction between capacitance measurement stability and high temperature performance.
Solution Approach 2:
The patent introduces conductive particles (PM) as an intermediary medium that bridges the sensing parts and capacitor parts. The PM particles deposited on the sensing parts create a conductive path to the capacitor parts, enabling capacitance measurement without requiring the capacitor parts to be directly exposed to high temperatures. This intermediary approach allows the system to measure PM-related capacitance changes while keeping the capacitor components in a thermally stable environment.
2Quantity of substance
If the insulating substrate uses alumina with low dielectric constant (10-20), then the capacitor parts can be formed, but excessive expensive materials like platinum are needed to achieve desired capacitance
Solution Approach 1:
The patent utilizes the third dimension (vertical stacking) by forming capacitor parts with multiple layers on the insulating substrate. Instead of relying solely on increasing the lateral area of capacitor parts (which would require more platinum), the invention creates multi-layer capacitor structures that increase capacitance through vertical stacking. This dimensional approach allows achieving desired capacitance values with reduced platinum material quantity.
3Measurement precision
If capacitor parts are formed with large area to achieve desired capacitance, then capacitance value is sufficient, but production cost increases due to excessive expensive materials
Solution Approach 1:
The patent employs composite material structures for the capacitor parts, combining conductive materials (such as platinum) with other materials to create multi-layer capacitor structures. This composite approach allows achieving sufficient capacitance values through optimized material combinations and layer configurations, reducing the total amount of expensive platinum material needed while maintaining the required capacitance 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
Enables constant capacitance measurement across varying temperatures without affecting the sensor's performance and significantly reduces the use of expensive materials, thereby lowering production costs and enhancing design flexibility.
Implementation Method 1
a heater unit disposed inside the insulating substrate and configured to provide heat for removing the particulate matter deposited on the sensing electrodes
Implementation Method 2
measure a capacitance between the external electrodes and the internal electrodes using an area of PM deposited between the external electrodes and a distance between the external electrodes and the internal electrodes
Implementation Method 3
a sharp change in dielectric constant occurs due to properties of a material thereof in a high temperature environment
Data Source
AI summary
A particulate matter sensor is provided that can include: an insulating substrate; a plurality of sensing electrodes which are disposed on one surface of the insulating substrate and spaced a predetermined interval from each other so as not to be electrically connected to each other; a connection electrode disposed to be coplanar with the plurality of sensing electrodes and connected to a connection terminal formed on the one surface of the insulating substrate to be connected to some or all of the plurality of sensing electrodes through deposited particulate matter; a plurality of terminals formed on the one surface of the insulating substrate and connected one-to-one with the plurality of sensing electrodes and the connection electrode; and a heater unit disposed inside the insulating substrate and configured to provide heat for removing the particulate matter deposited on the sensing electrodes.