Platinum-Strontium Electrode Wire for Vibration-Resistant Temperature Sensor
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Solution Overview
Problem
Temperature sensors used in vibration-exposed environments, such as vehicle exhaust systems, face issues with electrode wire breakage due to strong vibrations and poor weld zone strength caused by the addition of oxides like zirconia or yttria, which do not melt during welding, leading to reduced mechanical strength and increased likelihood of fracture.
Innovation Solution
The use of electrode wires formed by adding strontium to platinum or platinum alloys, which enhances mechanical strength without the need for oxides, allowing for better weldability and improved welding strength between electrode and signal wires, thereby preventing weld zone fractures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If oxide-containing dispersion-strengthened platinum material is used to form electrode wires, then the strength of the electrode wires is enhanced, but the welding strength of the weld zones between electrode wires and signal wires decreases
Solution Approach 1:
The patent changes the material parameter by replacing oxide-containing dispersion-strengthened platinum material with strontium-containing platinum material. This parameter change allows the material to achieve both high electrode wire strength and good weldability, as strontium does not prevent melting during welding like oxides do.
Solution Approach 2:
The patent uses composite materials by combining platinum with strontium to create a new material system. This composite material (platinum-strontium intermetallic compound) provides both the required mechanical strength and welding properties that neither pure platinum nor oxide-containing materials could achieve alone.
2Strength
If zirconia or yttria is added to platinum to form dispersion-strengthened electrode wires, then the mechanical strength of the electrode wires increases, but the weldability deteriorates because the oxides do not melt during welding
Solution Approach 1:
The patent changes the strengthening mechanism parameter from oxide-based dispersion strengthening to strontium-based intermetallic compound formation. This parameter change maintains the dispersion strengthening effect while eliminating the welding problem, as strontium-containing materials can be properly welded without unmelted inclusions.
3Speed
If the temperature sensor is rapidly cooled from high temperature to low temperature, then the measurement response is improved, but a large load is imposed on the weld zones causing potential fracture
Solution Approach 1:
The patent changes the material parameter (electrode wire composition) to strontium-containing platinum material, which provides superior weld zone strength. This parameter change enables the weld zones to withstand the large thermal loads imposed during rapid cooling cycles without fracturing.
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 provides a temperature sensor with enhanced electrode wire strength and excellent weldability, ensuring high reliability even in environments with strong vibrations, by forming platinum-strontium intermetallic compounds that restrain crystal grain coarsening and maintain good welding strength.
Implementation Method 1
forming platinum-strontium intermetallic compounds that restrain crystal grain coarsening
Implementation Method 2
restrain crystal grain coarsening
Implementation Method 3
electrode wires and signal wires are laser-welded to one another
Implementation Method 4
the melting point of platinum is 1,770° C., and that of a platinum alloy is 2,000° C. or lower
Implementation Method 5
a temperature-sensing portion, such as a thermistor portion made of a thermistor material
Data Source
AI summary
In a temperature sensor (1), a pair of electrode wires (25) of a thermistor element (21) are formed of a material prepared by adding strontium to platinum or a platinum alloy and without addition of zirconia or a like oxide. Rear end portions of the electrode wires (25) formed of the above-mentioned material and front end portions of sheath core wires (3) are laser-welded to one another in an overlapping condition.