Gas Sensor Outer Protective Tube Welding Relocation
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Solution Overview
Problem
Existing gas sensors face challenges with complex and error-prone weld seams for attaching protective tubes to the sensor housing, leading to unsatisfactory stability and durability, especially under high temperatures or temperature gradients.
Innovation Solution
A sensor design with a fastening element featuring an external thread on the outer protective tube, allowing for a weld further away from the gas-side end section, reducing thermal stress and eliminating the need for a widened inner protective tube, thus enhancing thermomechanical robustness and material efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a weld seam is made from the outer protective tube through the inner protective tube into the sensor housing, then the protective tubes are fixed to the sensor housing, but the connection becomes complicated and error-prone, and material costs increase due to the need for a widened inner protective tube
Solution Approach 1:
The invention extracts the welding operation from the inner protective tube and relocates it to the outer protective tube only. The weld seam now starts from the outer protective tube and ends at the sensor housing, bypassing the inner protective tube. This simplifies the welding process by eliminating the need to weld through multiple tubes while maintaining secure fixation of both protective tubes to the housing.
Solution Approach 2:
The welding process is segmented into a single-stage operation rather than a multi-stage process. Instead of welding the inner tube to the housing and then welding the outer tube to the inner tube, the invention performs one welding operation that directly secures the outer tube to the housing, reducing process complexity and potential for error.
2Ease of manufacture
If the inner protective tube has a cross-sectional enlargement on its end section to be plugged onto an annular shoulder, then the protective tubes can be fastened to the sensor housing, but material costs increase and the connection stability decreases under high temperature conditions
Solution Approach 1:
The invention removes the cross-sectional enlargement from the inner protective tube entirely. Instead, the outer protective tube is designed with a corresponding enlargement that directly engages with the annular shoulder of the sensor housing. This eliminates the need for the inner tube to have a widened section while maintaining a secure mechanical connection.
Solution Approach 2:
Rather than having the inner tube with the enlargement, the invention inverts the approach by placing the enlargement on the outer tube. This reversal allows the outer tube to directly engage with the housing annular shoulder, simplifying the overall structure and improving thermal stability by reducing the number of connection points subject to thermal stress.
3Strength
If the weld seam is located close to the gas-side end section of the outer protective tube, then the protective tubes are securely attached, but the connection is exposed to high temperatures and large temperature gradients causing failure
Solution Approach 1:
The invention positions the weld seam in a different spatial location - specifically on the outer protective tube at a distance from the gas-side end section. This dimensional repositioning moves the welding operation away from the high-temperature zone near the exhaust gas contact point, reducing thermal stress on the weld while maintaining structural integrity through the extended weld path along the tube.
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 more robust and durable connection of protective tubes to the sensor housing, improving stability under high temperature conditions and reducing material costs, while maintaining a gas-tight seal.
Implementation Method 1
a weld seam is finally made, which extends from the housing-side end section of the outer protective tube through the underlying end section of the inner protective tube into the sensor housing
Implementation Method 2
the fastening element has at least one external thread
Data Source
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AI summary
The invention relates to a sensor (10) for determining at least one property of a gas to be measured in a chamber (64) for the gas to be measured, in particular the temperature or the concentration of a gas component, in particular in the exhaust gas of an internal combustion engine. The sensor (10) has a sensor element (12), a gas-side sensor portion (14) of which protrudes out of a sensor housing (16), said portion being exposed to the gas to be measured, and a double protective tube (18), which surrounds the sensor portion (14) and which has at least one outer protective tube (20) and at least one inner protective tube (22). The outer protective tube (20) has a housing-side end portion (38) and a gas-side end portion (36). The sensor (10) has at least one fixing element (40) for fixing the sensor (10) to the chamber (64) for the gas to be measured. The housing-side end portion (38) of the outer protective tube (20) is fixed to the sensor housing (16) outside of the chamber (64) for the gas to be measured when the sensor is fixed to the chamber (64) for the gas to be measured.