High-Temperature Sensor Covering Member with Glass-Ceramic Composite
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Solution Overview
Problem
Conventional temperature sensors used in exhaust systems of internal combustion engines face issues with separation of output lines from pads at high temperatures, leading to performance deterioration due to inadequate thermal shock resistance and softening of covering members.
Innovation Solution
A temperature sensitive element with a ceramic substrate, metallic resistor layer, conductive pads, and output lines covered by a glass-ceramic covering member with a volume ratio of 3 vol %/97 vol % to 50 vol %/50 vol % ceramic to glass, where the glass has a softening point of 900° C. or higher, and the ceramic maintains the covering member's shape at high temperatures, preventing separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the covering member is formed of glass only, then the manufacturing process is simple, but the covering member softens at high temperature and cannot maintain its shape, leading to separation of output lines from pads
Solution Approach 1:
The covering member is formed as a composite material consisting of both glass and ceramic components. The glass provides ease of manufacturing and bonding properties, while the ceramic component maintains structural integrity at high temperatures. This composite structure resolves the contradiction by combining materials with complementary properties to achieve both manufacturability and high-temperature reliability.
2Ease of manufacture
If the softening point of the glass is lowered to improve manufacturing, then the glass becomes easier to process, but the covering member cannot withstand high temperature environments (850°C or higher)
Solution Approach 1:
The invention changes the physical parameters of the glass by controlling its chemical composition to achieve a softening point of 900°C or higher. Specific compositional adjustments (such as modifying oxide ratios) allow the glass to maintain both manufacturability and high-temperature resistance, resolving the contradiction between ease of processing and temperature withstand capability.
3Stability of the object's composition
If the ceramic content in the covering member is increased to improve high-temperature stability, then the shape maintenance improves, but the manufacturing complexity increases
Solution Approach 1:
The invention optimizes the compositional parameters by defining a specific ceramic-to-glass ratio range (3-50 vol% ceramic). This parameter optimization ensures that the covering member achieves sufficient shape stability at high temperatures while maintaining reasonable manufacturing complexity. The balanced composition resolves the contradiction between stability and manufacturing simplicity.
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 the possibility of separation between output lines and pads, enhancing the temperature sensor's high-temperature endurance and maintaining accurate temperature detection by suppressing the softening of the covering member and controlling thermal expansion coefficients.
Implementation Method 1
The softening point or melting point of the glass in the covering member is 900° C. or higher
Implementation Method 2
the presence of the ceramic allows the covering member to maintain its shape, when the ceramic does not soften at this temperature
Implementation Method 3
This temperature sensor detects the temperature of a measurement object (e.g., a measurement gas) by utilizing a change in the electric resistance of the metallic resistor due to a change in temperature
Data Source
AI summary
A temperature sensitive element in a temperature sensor includes a covering member formed from alumina and aluminosilicate glass, and the volume ratio of the alumina to the aluminosilicate glass (the alumina/the aluminosilicate glass) in the covering member is 30 vol %/70 vol %. The aluminosilicate glass contained in the covering member is high heat-resistant glass having a softening point of 900° C. or higher. The covering member can hold output lines and pads and can restrain separation of the output lines from the pads and separation of the pads from a ceramic substrate even in an environment of higher temperature as compared with the case where the covering member is formed of the aluminosilicate glass only.