Gas Sensor Housing Weld Geometry to Prevent Weld Pinholes
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Solution Overview
Problem
Conventional gas sensors experience pinhole formation due to volatile gases generated from residual oil components during welding, leading to potential corrosion and sealing defects, especially in harsh environments or prolonged use.
Innovation Solution
The gas sensor design includes a housing and outer cylinder configuration where the contact distance between the outer peripheral surface of the housing and the inner peripheral surface of the outer cylinder is limited to a reference distance calculated by the formula Lr = k × Da / (Tb × Tc), ensuring volatile gases can escape, thereby preventing pinhole formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the housing and outer cylinder are welded together, then the structural strength and sealing performance are improved, but pinholes may form on the welded portion surface due to volatile gases from residual oil components
Solution Approach 1:
The patent applies preliminary action by designing a specific contact distance structure before welding occurs. The contact distance between the housing outer peripheral surface and outer cylinder inner peripheral surface is predetermined to be equal to or less than the reference distance, which allows volatile gases to escape before they can be trapped in the weld metal, thereby preventing pinhole formation while maintaining structural integrity
Solution Approach 2:
The contact distance structure acts as an intermediary mechanism between the housing and outer cylinder. This intermediate space serves as a gas escape route, mediating the conflict between achieving strong welding and preventing pinholes by providing a controlled pathway for volatile gases to exit during the welding process
2Manufacturing precision
If extensive cleaning processes are applied to remove residual oil components, then pinhole formation is prevented, but manufacturing time and costs increase
Solution Approach 1:
The patent applies parameter changes by shifting the control parameter from surface cleanliness to contact distance geometry. Instead of controlling the amount of residual oil through cleaning processes, the invention controls the contact distance parameter to ensure it is equal to or less than the reference distance, thereby changing the approach from chemical/cleaning-based control to geometric/structural control
Solution Approach 2:
The invention converts the harmful effect of residual oil components into a beneficial outcome. By designing the contact distance to allow volatile gases to escape, the patent transforms what would normally be a defect-causing element (trapped gases) into a controlled process feature, eliminating the need for extensive cleaning while still preventing pinholes
3Manufacturing precision
If the contact distance is reduced to allow gas escape, then pinhole formation is suppressed, but the assembly precision requirements increase
Solution Approach 1:
The patent applies self-service by designing the contact distance structure to automatically provide the gas escape function without requiring additional components or complex assembly procedures. The geometric relationship between the housing and outer cylinder inherently creates the gas escape pathway, making the system self-regulating and reducing the need for external control mechanisms
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 effectively suppresses pinhole generation, reducing the risk of corrosion and sealing defects, and eliminates the need for extensive cleaning processes, thus minimizing manufacturing time and costs.
Implementation Method 1
an outer cylinder made of metal and mounted on an outer peripheral surface of the housing by press-fitting a part of a rear end side of the housing in the axial direction
Implementation Method 2
performing welding in a circumferential direction at an overlapping portion with the press-fitted housing
Implementation Method 3
the residual oil component or the like may become a volatile gas by heat during welding
Data Source
AI summary
Provided is a gas sensor including a housing made of metal through which a sensor element is inserted and an outer cylinder made of metal welded to an outer periphery of the housing, in which generation of pinholes on a surface of a welded portion is suppressed. In a gas sensor according to one aspect of the present invention, a contact distance Lg, which is a length in an axial direction of an outer peripheral surface of a housing in contact with an inner peripheral surface of an outer cylinder on a rear end side with respect to a molten portion of the outer cylinder formed by welding, is equal to or less than a reference distance Lr.