Talc Filler Airtightness in Gas Sensors Under Thermal Shock
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Solution Overview
Problem
Conventional gas sensors experience decreased airtightness due to thermal expansion and contraction cycles, leading to inaccurate readings, as the filler portion composed of granulated talc fails to adequately follow thermal shock cycles and becomes compromised by voids and gaps.
Innovation Solution
A gas sensor design with a filler portion filled with talc powder having a c-axis orientation between 60% to 85% and porosity not exceeding 10%, which allows it to adapt to thermal expansion and contraction cycles, maintaining airtightness even under applied forces perpendicular to the axial direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If granulated talc powder is used as filler material, then airtightness is initially provided, but airtightness deteriorates after thermal shock cycles
Solution Approach 1:
The patent changes the physical and chemical parameters of the filler material by using sintered talc instead of granulated talc powder. The sintering process creates a hardened, porous structure with controlled pore size distribution that maintains stability under thermal shock cycles while preserving airtightness functionality.
Solution Approach 2:
The patent creates a composite filler structure by sintering talc particles together, forming a composite material that combines the benefits of porous structure (for airtightness) with sintered bonding (for thermal stability). This composite approach resolves the contradiction between initial airtightness and long-term stability.
2Temperature
If talc grains are highly oriented, then coefficient of thermal expansion is reduced, but airtightness deteriorates due to void formation
Solution Approach 1:
The patent utilizes porous sintered talc material that maintains controlled porosity for airtightness while the sintering process creates a structure that accommodates thermal expansion. The porous structure allows the material to expand and contract without forming voids that would compromise airtightness.
3Reliability
If filler portion is compressed to fill space, then airtightness is improved, but thermal shock resistance decreases
Solution Approach 1:
The sintering process fundamentally changes the physical parameters of the filler material, creating a hardened structure with controlled porosity that can withstand thermal shock cycles while maintaining airtightness. The sintered structure is less compliant but more stable under thermal stress.
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 improved gas sensor effectively prevents deterioration of airtightness between the housing case and sensor elements, ensuring accurate gas concentration detection by maintaining airtightness and handling thermal shock cycles effectively.
Implementation Method 1
the conventional gas sensor having the filler portion 9 cannot adequately follow the repetition of thermal shock cycle test of expansion and contraction of each of the housing case, the gas sensor element, the insulator, etc.
Implementation Method 2
the conventional gas sensor having the filler portion 9 cannot adequately follow the repetition of thermal shock cycle test of expansion and contraction of each of the housing case, the gas sensor element, the insulator, etc.
Implementation Method 3
the thin-leaf shaped grains of talc 901 slide relative to each other
Data Source
AI summary
A gas sensor has a cylindrical housing case, a gas sensor element as a sensor component, and a filler portion. The filler portion is formed between the inner surface of the cylindrical housing case and the outer surface of the gas sensor element. The filler portion is filled with filler powder composed of talc as a layered compound. Talc is a principal ingredient of the filler powder. The space formed between the cylindrical housing case and the gas sensor element is sealed with the filler powder in the filler portion. The filler powder in the filler portion has a degree of c-axis orientation within a range of 60% to 85%, The filler powder in the filler portion has a porosity of not more than 10%.