Particulate Matter Sensor Thermal Stress Reduction via Periodic Heating
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Solution Overview
Problem
Conventional particulate matter sensors face issues with increased thermal stress and accumulation of poisoning matter on the element unit, leading to reduced durability and functionality.
Innovation Solution
A particulate matter detecting device with a heater and control unit that operates for a predetermined period, setting the temperature higher than exhaust gas but lower than the thermal degradation point, to reduce thermal stress and utilize thermophoretic forces to move poisoning matter away from the element unit, thereby minimizing accumulation and maintaining sensor accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the heater maintains the element unit temperature in the predetermined temperature range for burning PM after PM is detected, then the accumulation of PM on the element unit is reduced, but the thermal stress placed on the element unit increases and durability is lowered
Solution Approach 1:
The heater is operated periodically rather than continuously. Specifically, the heater is activated for a predetermined period after the internal combustion engine is stopped, which corresponds to the period when PM is not being deposited on the element unit. This periodic operation allows the element unit temperature to be raised for PM removal while avoiding continuous thermal stress that would degrade durability.
Solution Approach 2:
The temperature parameter of the element unit is dynamically adjusted based on the operational state. The heater control raises the element unit temperature to a level higher than exhaust gas temperature but lower than the thermal degradation threshold, and maintains this temperature only during specific periods when PM deposition is not occurring. This parameter change approach balances PM removal effectiveness with thermal stress reduction.
2Reliability
If the heater operates continuously to remove PM, then the accumulation of poisoning matter is reduced, but the thermal stress on the element unit increases
Solution Approach 1:
The heater operation is scheduled periodically based on the detection of PM accumulation and the operational state of the internal combustion engine. The heater is activated for a predetermined period after engine stop, which is sufficient to remove accumulated PM and poisoning matter without requiring continuous operation. This periodic activation reduces thermal stress while maintaining sensor functionality.
Solution Approach 2:
The system uses the natural cooling period after engine shutdown to perform PM removal without interfering with active PM detection. The heater automatically activates based on predetermined conditions (engine stop and elapsed time), making the system self-regulating and eliminating the need for continuous monitoring and adjustment during operation.
3Object-affected harmful factors
If the temperature of the element unit is raised high to remove poisoning matter, then the accumulation of poisoning matter is reduced, but the element unit may be thermally degraded
Solution Approach 1:
The element unit temperature is precisely controlled within a specific range during heater operation. The temperature is raised above exhaust gas temperature to create the thermophoretic force necessary for removing poisoning matter, but is maintained below the thermal degradation threshold. This controlled parameter change achieves poisoning matter removal while preserving element unit integrity.
Solution Approach 2:
The patent replaces mechanical or chemical cleaning methods with a thermal field approach using controlled heating. By creating a temperature gradient between the element unit and exhaust gas, thermophoresis naturally moves poisoning matter away from the element unit surface, eliminating the need for physical contact or chemical treatments that might damage the element unit.
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 solution effectively reduces thermal stress and accumulation of poisoning matter on the element unit, enhancing the durability and accuracy of particulate matter detection without the need for continuous temperature monitoring.
Implementation Method 1
the predetermined amount of control is set in advance such that the temperature of the element unit is higher than the temperature of the exhaust gas and lower than a predetermined temperature at which the element unit is thermally degraded... the thermophoretic force can be exerted on poisoning matter and PM in a direction away from the element unit
Data Source
AI summary
A particulate matter detecting device includes: an element unit on which particulate matter contained in exhaust gas from an internal combustion engine is deposited; a heater that heats the element unit; a detecting unit that detects the amount of particulate matter on the basis of electrical characteristics of the element unit; and a control unit that controls the operation of the heater. For a predetermined period that does not include a period in which the particulate matter is deposited on the element unit, the control unit operates the heater using a predetermined amount of control set in advance such that the temperature of the element unit is higher than the temperature of the exhaust gas and lower than a predetermined temperature at which the element unit is thermally degraded.