Conductive Sensor Bridge for High-Temperature Thermal Stress
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Solution Overview
Problem
Conventional sensor assemblies face limitations in high-temperature applications due to differential thermal expansion between metal and ceramic components, leading to stress fractures, mechanical failure, and susceptibility to moisture penetration, which restrict their operating lifetime and temperature range.
Innovation Solution
A sensor assembly design featuring electrically conductive electrode and shield bridges in compression contact with interface layers, made from materials like nickel-chromium alloys and SiC-based coatings, which eliminate differential thermal expansion and provide a hermetic seal, allowing operation up to 1500°C without brazing, thus enhancing durability and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional brazing processes are used to assemble sensor components, then the sensor assembly can be manufactured with metal and ceramic components, but the differential thermal expansion between materials causes stress fractures and mechanical failure at high temperatures
Solution Approach 1:
The patent introduces an intermediate compliant coating layer between the metal housing and ceramic sensor body. This intermediary layer accommodates differential thermal expansion between the two materials, preventing stress fractures while maintaining structural integrity at high temperatures up to 1500°C.
Solution Approach 2:
The sensor assembly uses a composite structure combining metal housing, compliant coating layer, and ceramic sensor body. This composite design leverages the high-temperature stability of ceramic and the thermal expansion compliance of the coating layer to achieve both manufacturing feasibility and structural reliability.
2Stability of the object's composition
If low expansion alloys are used for the housing, then thermal stress between components is minimized, but oxidation occurs at temperatures approaching 500°C
Solution Approach 1:
The compliant coating layer serves as an intermediary barrier between the metal housing and the high-temperature environment. This coating prevents direct exposure of the metal to oxidizing conditions while allowing thermal expansion compliance, enabling operation at temperatures above 500°C without oxidation.
Solution Approach 2:
The compliant coating layer creates a protective environment around the metal housing, preventing oxygen from reaching the metal surface at high temperatures. This effectively creates an inert barrier that prevents oxidation while allowing the metal to maintain its thermal expansion properties.
3Stability of the object's composition
If compliant coatings are used to accommodate thermal expansion, then thermal stress is reduced, but the coatings oxidize at temperatures below 500°C
Solution Approach 1:
The patent uses a composite coating system consisting of multiple layers with different properties. The inner layer provides compliance for thermal expansion, while the outer layer provides oxidation resistance. This composite structure maintains both thermal expansion compliance and oxidation resistance at temperatures above 500°C.
Solution Approach 2:
The coating system is designed with specific material parameters - the inner layer has high compliance for thermal expansion while the outer layer has high oxidation resistance. This parameter optimization allows the coating to function simultaneously as a thermal expansion accommodator and an oxidation barrier at high temperatures.
4Object-affected harmful factors
If hermetic seals are added to prevent oxidation, then oxidation resistance improves, but the complexity of the assembly increases
Solution Approach 1:
The patent merges the thermal expansion compliance function and oxidation protection function into a single integrated compliant coating layer. This eliminates the need for separate hermetic seal components, reducing assembly complexity while maintaining both oxidation resistance and thermal expansion accommodation.
Solution Approach 2:
The compliant coating layer performs multiple functions simultaneously: it accommodates thermal expansion, prevents oxidation, and maintains hermetic sealing. This multi-functional design reduces the overall number of components needed in the sensor assembly.
5Temperature
If the sensor assembly is designed for high temperature operation, then operating temperature range increases, but the lifetime of the assembly decreases due to thermal stress
Solution Approach 1:
The compliant coating layer acts as a mediator that allows the sensor assembly to operate at high temperatures without suffering from thermal stress. By accommodating differential expansion between metal and ceramic components, the coating prevents stress fractures that would otherwise limit the operating lifetime.
Solution Approach 2:
The patent optimizes the material parameters of the coating layer to maintain compliance and oxidation resistance at high temperatures. This parameter optimization enables the sensor assembly to achieve both high operating temperature capability and extended lifetime by preventing thermal stress damage.
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 design extends the operating lifetime and temperature range of sensor assemblies by eliminating thermal stress and oxidation issues, ensuring reliable performance in high-temperature environments while maintaining electrical integrity and mechanical stability.
Implementation Method 1
the housing, bush and sensor body all expand at similar rates to minimise the thermal stress between the individual components
Implementation Method 2
Conductive layers can define electrodes or other sensing elements or shield layers
Implementation Method 3
Non-conductive layers can define insulating spacers that are positioned between conductive layers
Data Source
AI summary
A sensor assembly includes an electrically conductive electrode bridge (26) and a multi-layer, integral sensor body (1). The sensor body (1) includes a core layer (2), an outer insulating layer (4) that substantially surrounds the core layer (2), and an electrically conductive electrode layer (6) between the core layer (2) and the outer insulating layer (4). The sensor body (1) also includes an electrically conductive electrode interface layer (14) at a rear part (12) of the sensor body (1) and in electrical contact with the electrode layer (6). The electrode bridge (26) is held in compression electrical contact with the electrode interface layer (14) during use.