Tapered Metallic Shell for Gas Sensor Press-Fit Load Reduction
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Solution Overview
Problem
The existing gas sensor technology faces challenges with excessive press-fitting loads due to manufacturing tolerances, leading to potential breakage of the sleeve or increased costs and reduced productivity, as the current methods either require annealing or crimping to mitigate these loads.
Innovation Solution
A gas sensor design incorporating a tapered portion on the metallic shell's outer surface, which allows the tubular body to be smoothly press-fitted with a reduced load, featuring a diameter-increased and diameter-reduced portion for stable positioning and reduced interference, thereby minimizing the press-fitting load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If press-fitting is performed without a tapered portion, then the assembly process is simple, but the press-fitting load becomes excessive causing sleeve breakage or increased costs
Solution Approach 1:
A tapered portion is formed in advance on the outer surface of the metallic shell at the press-fitting location. This preliminary geometric modification allows the tubular body to be gradually guided during press-fitting, distributing the load and preventing excessive force that would cause breakage or require additional processing steps like annealing.
Solution Approach 2:
The geometry of the metallic shell is changed by introducing a tapered portion with a specific angle. This parameter change transforms the press-fitting process from a high-load abrupt insertion to a gradual, load-distributed process, reducing the maximum press-fitting force required while maintaining assembly simplicity.
2Manufacturing precision
If manufacturing tolerances are tight, then assembly precision is high, but press-fitting load increases due to interference
Solution Approach 1:
The tapered portion acts as a cushioning feature that compensates for manufacturing tolerances. By providing a gradual transition zone, it absorbs the interference caused by tight tolerances, allowing components to be pressed together with reduced force even when dimensional variations exist, thereby preventing excessive load while maintaining precision assembly.
3Reliability
If annealing is performed to reduce press-fitting load, then sleeve breakage is prevented, but productivity decreases and cost increases
Solution Approach 1:
Instead of performing annealing as a preliminary thermal treatment, the tapered portion is formed as a preliminary geometric feature on the metallic shell. This design-based solution prevents sleeve breakage through load distribution during press-fitting, eliminating the need for additional annealing process steps and maintaining high productivity while ensuring reliability.
4Reliability
If crimping is used instead of press-fitting, then sleeve breakage is avoided, but manufacturing complexity and cost increase
Solution Approach 1:
The geometric parameter of the metallic shell is changed by adding a tapered portion, which transforms the press-fitting process into a low-load operation that prevents sleeve breakage. This maintains the simplicity of the press-fitting manufacturing process while achieving the reliability benefits previously requiring more complex methods like crimping.
Data Source
AI summary
A gas sensor includes a gas sensor element having a detection portion, a metallic shell holding the gas sensor element, and a tubular body made of metal, which is welded in a state of being externally fitted to a front side or a rear side of the metallic shell. In the present invention, the tubular body is tightly fitted to a tapered portion that is provided at an outer surface of the metallic shell and is radially narrowed toward the tubular body. The tubular body is welded at the tapered portion.