Temperature Sensor Void Sheath Thermal Stress
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Solution Overview
Problem
Temperature sensors experience disconnection of joint portions due to thermal stress when subjected to high-temperature and low-temperature cycles, as the metal tube and sheath shrink at different rates, causing stress on the element electrode wires and metal conductors.
Innovation Solution
A temperature sensor design featuring a void space forward of the temperature sensitive body within the surrounding portion, which absorbs thermal stress by allowing the holding member to be pushed rearward, reducing the stress on the joint portions between the element electrode wire and sheath conductor, and improving heat conduction for faster response times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cement is charged to reach the forward end of the metal tube to hold the temperature sensitive element, then the temperature sensitive element is securely held, but thermal stress causes disconnection of joint portions during temperature cycles
Solution Approach 1:
A void space is intentionally created between the cement and the forward end of the metal tube to serve as a cushioning zone. This void absorbs thermal expansion and contraction forces before they can be transmitted to the joint portions, preventing disconnection during temperature cycles while maintaining secure holding of the temperature sensitive element.
Solution Approach 2:
The void space acts as an intermediary buffer between the cement and the metal tube forward end. It mediates the thermal stress by providing a compressible space that absorbs expansion forces, preventing direct transmission of stress to the vulnerable joint portions during temperature fluctuations.
2Adaptability or versatility
If the metal tube and sheath are subjected to temperature cycles, then the sensor operates in realistic conditions, but differential thermal contraction causes stress on element electrode wires
Solution Approach 1:
The void space is pre-formed to anticipate and absorb the differential thermal contraction that occurs during temperature cycles. By providing this cushioning zone beforehand, the design prevents stress concentration at the joint portions when the metal tube and sheath contract at different rates, maintaining joint strength under realistic operating conditions.
3Productivity
If cement is used to hold the temperature sensitive element, then the element is securely positioned, but heat conduction to the element is insufficient for fast response
Solution Approach 1:
The void space serves as a thermal pathway intermediary, allowing heat to reach the temperature sensitive element more efficiently. By removing cement from the forward end region, heat can conduct directly to the element through the void space or alternative pathways, improving response speed while the cement remains in position to provide secure holding.
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 void space effectively suppresses the disconnection of joint portions by absorbing thermal stress, enhancing the reliability of the temperature sensor under temperature fluctuations.
Implementation Method 1
when the temperature sensor placed under high-temperature conditions is transferred to low-temperature conditions, the temperature of the periphery of the temperature sensitive element may sharply decrease from high temperature to low temperature. In this case, the temperature of the metal tube forming an outer wall decreases first, and this decrease in temperature causes the metal tube to shrink.
Implementation Method 2
improving heat conduction for faster response times
Data Source
AI summary
A temperature sensor includes a temperature sensitive element, a sheath portion, a surrounding portion, and a holding member. This temperature sensor has a void formed forward of a temperature sensitive body. When the void is projected in an axial direction of the surrounding portion from a forward end side of the surrounding portion, the void contains at least a forward end surface of the temperature sensitive body.