High-Temperature Hardening Filler for Exhaust Gas Temperature Sensors
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Solution Overview
Problem
Temperature sensors installed in exhaust gas systems of internal combustion engines face issues with vibration damage and instability due to thermal expansion differences between the cover case and filler materials, leading to gaps and unreliable signal outputs at high temperatures.
Innovation Solution
A temperature sensor design with a filler material that hardens at a temperature higher than the operational environment, ensuring no gap forms between the cover case and filler, and using a porous insulation filler with a specific pore ratio to maintain stability and responsiveness under high temperature and vibration conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cement material filler with hardening temperature of approximately 150°C is used to fix the temperature sensitive element, then the temperature sensitive element is protected from vibration influence, but a gap opens between the cover case and filler at exhaust gas temperatures of 600-700°C due to thermal expansion coefficient difference
Solution Approach 1:
The patent changes the key parameter of the filler material from conventional cement-based material (hardening at 150°C) to high-temperature hardening material (hardening at 800-1000°C). This parameter change ensures the filler maintains its structural integrity and bonding strength at exhaust gas temperatures of 600-700°C, preventing gap formation between the cover case and filler while continuing to provide vibration protection.
Solution Approach 2:
The patent employs composite material composition for the filler, combining high-temperature hardening cementitious materials with specific aggregate components. This composite structure provides both the required high-temperature stability to prevent gap opening and the mechanical properties to protect against vibration damage to the temperature sensitive element.
2Ease of manufacture
If the filler material hardens at low temperature (150°C), then the manufacturing process is simpler, but the filler cannot maintain structural integrity at high operating temperatures (600-700°C)
Solution Approach 1:
The patent modifies the hardening temperature parameter of the filler material from 150°C to 800-1000°C by selecting specialized high-temperature cementitious binders. Although this requires higher processing temperatures, it ensures the filler maintains its mechanical strength and dimensional stability throughout the entire operating temperature range of the exhaust gas sensor (600-700°C), preventing softening or degradation.
3Adaptability or versatility
If the cover case and filler have different thermal expansion coefficients, then material selection is more flexible, but a gap opens between them at high temperatures
Solution Approach 1:
The patent addresses the thermal expansion mismatch by changing the material composition parameters of the filler to include components with thermal expansion characteristics better matched to the stainless steel cover case. This parameter optimization reduces the differential thermal expansion between cover case and filler, preventing gap formation during temperature cycling while still allowing flexibility in material selection.
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 prevents vibration-induced damage and maintains stable signal output by ensuring a tight fit between the filler and cover case, and enhances the sensor's durability and responsiveness by controlling thermal expansion and oxygen partial pressure fluctuations.
Implementation Method 1
there is a possibility of causing a gap to open between the cover case and the filler by a difference in thermal expansion coefficient between the cover case made of a stainless steel and the filler made of a cement material
Data Source
AI summary
In a temperature sensor having a temperature sensitive element, a sheath pin connected to the temperature sensitive element, and a cover case. The cover case, filled with a filler, accommodates the temperature sensitive element and the sheath pin. A hardening temperature of the filler is not less than an actual usage environment of the temperature sensor. Another temperature sensor has a temperature sensitive element exposed at a high temperature of not less than 750° C., a thermistor element, a sheath pin, an anti-vibration filler, and a metal cover case fixed to an end part of the sheath pin. The metal cover case accommodates the sheath pin and the thermistor element. The filler is made of a porous insulation material having a pore ratio within a range of 30 to 70% and filled around the thermistor element in the metal cover case.