High-Temperature Sensor Thermal Expansion Management
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Solution Overview
Problem
Existing high-temperature sensors for combustion engine exhaust ducts face challenges in withstanding high mechanical and chemical stress, maintaining reliability, and extending life cycle, especially when exposed to temperatures between 600° C. to 900° C., as current solutions either partially address mechanical, electrical, or metrological issues without comprehensive protection.
Innovation Solution
A high-temperature sensor design featuring a metallic protective tube with a measuring resistance and internal conductors enclosed in a ceramic housing filled with oxygen-providing ceramic powder, including admixtures like manganese (IV) oxide, and an auxiliary component with a higher thermal expansion coefficient to manage thermal stress and prevent reductive atmospheres, ensuring strain relief and oxidation protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metallic protective tube is used to enclose the measuring resistance and internal conductors, then mechanical strength and structural stability are improved, but the measuring resistance is vulnerable to oxidation and chemical corrosion from the exhaust gas environment
Solution Approach 1:
The patent employs a composite structure combining a metallic protective tube with a ceramic housing and ceramic powder filling. The metallic tube provides mechanical strength while the ceramic components provide oxidation and chemical corrosion protection to the measuring resistance, creating a multi-material protective system that addresses both mechanical and chemical protection requirements
Solution Approach 2:
The patent creates an inert protective atmosphere by filling the protective tube with ceramic powder that releases oxygen to prevent reductive conditions. This oxygen-providing environment protects the platinum measuring resistance from oxidation while maintaining the mechanical protection of the metallic tube structure
2Strength
If the protective tube is made metallic to provide structural integrity, then mechanical protection is improved, but thermal expansion stress during temperature cycling causes deformation and compromised protection
Solution Approach 1:
The patent addresses thermal expansion by introducing an auxiliary component with a higher coefficient of thermal expansion than the metallic protective tube. This auxiliary component compensates for the thermal expansion differences during temperature cycling, preventing deformation and maintaining the protective structure's integrity across temperature variations
Solution Approach 2:
The patent creates a composite protective system where the auxiliary component with higher thermal expansion coefficient works in conjunction with the metallic protective tube and ceramic housing. This multi-material arrangement balances mechanical strength with thermal expansion compensation, maintaining structural integrity during thermal cycling
3Reliability
If connections are made tight and strain-relieved to improve electrical connection reliability, then electrical stability is improved, but mechanical stress from thermal cycling and vibration causes connection failure
Solution Approach 1:
The patent applies strain relief measures beforehand by incorporating flexible connection wires and auxiliary components that can accommodate mechanical stress from thermal cycling and vibration. These strain-relief features are built into the connection structure in advance, cushioning against mechanical stress while maintaining tight electrical connections
Solution Approach 2:
The patent uses flexible connection wires and strain-relief structures to connect the measuring resistance to the external circuit. These flexible elements accommodate mechanical stress and vibration while maintaining reliable electrical connections, preventing connection failure under mechanical stress
4Object-affected harmful factors
If openings are made in the protective tube to allow oxygen influx for oxidation protection, then oxidation resistance is improved, but mechanical strength and sealing are compromised
Solution Approach 1:
The patent creates an inert protective atmosphere by filling the tube with ceramic powder that releases oxygen to prevent reductive conditions. This eliminates the need for physical openings while still providing oxidation protection to the measuring resistance, maintaining both mechanical integrity and chemical protection
Solution Approach 2:
The patent uses oxygen-providing oxide compounds in the ceramic powder to create a strongly oxidizing environment that protects the platinum measuring resistance from oxidation. This chemical protection mechanism eliminates the need for physical openings, maintaining mechanical strength while providing oxidation resistance
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 enhances the sensor's mechanical and chemical resistance, improves reliability, and extends the life cycle by managing thermal expansion and preventing reductive conditions, thus providing comprehensive protection against high-temperature and corrosive environments.
Implementation Method 1
At least one auxiliary component (21), having a higher coefficient of thermal expansion than the protective tube (8), is arranged proximate connection of the connecting cable (14) to the protective tube (8)
Implementation Method 2
The ceramic powder contains admixtures of oxygen-providing oxide compounds
Data Source
AI summary
The invention relates to a high-temperature sensor, which can be used at temperatures of at least 600° C. and comprises a metallic protective tube and a measuring resistance that is surrounded by a ceramic powder. The measuring resistance is connected to the electric cable by means of stress-relieved measuring resistance connecting wires and internal conductors. The latter are provided with a solid and/or flexible insulation consisting of a ceramic material. The measuring resistance and the internal conductors are arranged in a metallic protective tube, which narrows in the vicinity of the measuring resistance. The ceramic powder contains admixtures of oxygen-giving oxide compounds.