Sensor Assembly Thermal Bushing Design
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Solution Overview
Problem
Existing sensor assemblies face challenges in achieving rapid temperature response times while maintaining a hermetic seal, especially in high-pressure systems, where the design must balance thermal conductivity and mechanical sealing requirements.
Innovation Solution
The sensor assembly design incorporates a thermally conductive bushing with high thermal conductivity materials like copper or silver, coupled with an insulating coupling made from low thermal conductivity materials like plastic, and a compressed gasket to ensure direct heat transfer to the sensor while isolating it from the housing, thereby enhancing temperature response speed and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sensor is hermetically sealed to the housing, then the sealing reliability is improved, but the temperature response time deteriorates
Solution Approach 1:
The housing is segmented into two functional zones: a hermetic sealing zone (housing body) and a thermal conduction zone (bushing). The bushing acts as a separate thermal pathway that extends into the medium while the housing maintains the hermetic seal, allowing the sensor to be thermally connected to the medium without compromising the seal integrity.
Solution Approach 2:
The bushing serves as an intermediary element between the sensor and the medium. It provides a direct thermal conduction path from the medium to the sensor while being thermally isolated from the housing by the insulating coupling, thus enabling rapid temperature response without requiring the housing itself to be thermally conductive.
2Loss of time
If the housing is made from thermally conductive material, then the temperature response time is improved, but the thermal isolation from the housing deteriorates
Solution Approach 1:
The thermal conduction function is extracted from the housing structure and assigned to a separate bushing component. This allows the housing to maintain its primary function of hermetic sealing while the bushing provides dedicated thermal conduction to the sensor, preventing thermal interference from the housing material.
Solution Approach 2:
Thermal conductivity is localized to specific regions: the bushing has high thermal conductivity (≥375 W/m-K) to conduct heat from the medium to the sensor, while the coupling has low thermal conductivity (≤25 W/m-K) to provide thermal isolation. This spatial differentiation of thermal properties enables both rapid response and thermal isolation.
3Loss of time
If a direct heat flow path is created from the medium to the sensor, then the temperature response time is improved, but the hermetic sealing becomes more difficult
Solution Approach 1:
The system is segmented into a hermetic sealing subsystem (housing with sensor package) and a thermal conduction subsystem (bushing with coupling). The bushing can extend through or beyond the housing without compromising the seal, as it provides a separate thermal pathway that does not require breaking the hermetic barrier.
Solution Approach 2:
The bushing acts as an intermediary that bridges the thermal gap between the medium and sensor without requiring direct penetration of the hermetic seal. The insulating coupling further mediates between the bushing and housing, allowing the bushing to extend into the medium while the housing maintains its sealed environment.
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
This design significantly improves the temperature response time of thermal sensors by providing a direct heat flow path and thermal isolation, allowing for more accurate and rapid sensing of temperature changes compared to conventional designs, as demonstrated by the graph in FIG. 5.
Implementation Method 1
the bushing is made from a material with a thermal conductivity greater than or equal to 375 W/m-K wherein the top surface of the bushing is coupled to the bottom surface of the sensor package such that the through hole is aligned with the sensor port and the bottom of the bushing extends down into the tubular section towards the port
Implementation Method 2
the coupling is made from a material with a thermal conductivity less than or equal to 25 W/m-K wherein the coupling is assembled to the sensor between the bushing and the housing such that the second outside surface is adjacent to the housing and an inside surface of the second through hole is adjacent to the outside surface
Implementation Method 3
a gasket assembled between the second top surface and a bottom surface of the flange
Data Source
AI summary
A sensor assembly is provided that allows for a more rapid sensing of thermal changes. In preferred embodiments, the sensor assembly includes a housing, sensor package, bushing, coupling and gasket. The bushing is made from a conductive material like copper or silver and provides a conductive path from the bottom of the sensor package directly into the medium whose temperature is to be sensed or close thereto. A coupling is provided between the conductive bushing the metal housing to prevent heat exchange between the metal housing and the bushing. The gasket is placed in compression and provides a constant force holding the conductive bushing against the bottom of the sensor package.