Fuel Tank Pipe End Structure for EVOH-Compatible Welding
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Solution Overview
Problem
Existing methods for welding vehicle fuel tank conduits face challenges such as incompatibility of ethylene vinyl alcohol (EVOH) with welding, requiring additional steps and increased conduit diameter, which complicates the manufacturing process and reduces reproducibility.
Innovation Solution
A method involving cutting the end portion of the conduit parallel or at a non-zero angle to the main axis during molding, forming a male shoulder passively, and using a removable female shoulder insert in the mold to maintain weldability without increasing the external diameter, allowing for a compact and easily producible conduit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a barrier layer of EVOH is added to increase impermeability, then fuel leakage risk is reduced, but welding compatibility is lost
Solution Approach 1:
The conduit is divided into two distinct portions: a first portion with the EVOH barrier layer for impermeability, and a second portion without the barrier layer for welding compatibility. This segmentation allows each portion to fulfill its specific function independently, resolving the contradiction between fuel leakage prevention and welding capability.
Solution Approach 2:
The barrier layer is applied locally only to the first portion of the conduit, while the second portion remains free of the barrier layer. This local quality approach ensures that the barrier function is provided where needed (for fuel containment) while maintaining welding compatibility at the connection point.
2Area of stationary object
If a fin is added to increase welding surface area, then welding interface area is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The solution extracts the barrier layer from the welding portion rather than adding complex structural elements like fins. By removing the barrier layer from the second portion, sufficient welding surface area is provided without increasing manufacturing complexity or requiring additional components.
3Length of stationary object
If the pipe is compressed axially during molding to create a bead, then polymer thickness for welding is improved, but manufacturing reproducibility decreases
Solution Approach 1:
The barrier layer is selectively applied to the first portion before the final molding step, establishing the correct configuration in advance. This preliminary action ensures that the second portion remains free of barrier material, providing consistent polymer thickness for welding without requiring critical axial compression operations that would reduce reproducibility.
4Ease of manufacture
If additional fastening steps are added to the process, then welding preparation is improved, but overall process complexity increases
Solution Approach 1:
The conduit structure itself provides the welding preparation by having a second portion free of barrier layer. This self-service approach means the conduit is inherently ready for welding without requiring additional fastening steps or preparation operations, thereby simplifying the overall manufacturing process.
Data Source
Figure 1~4
Figure 5~7
AI summary
This method for manufacturing a pipe (2) for a vehicle fuel tank involves - moulding a wall, comprising an inner layer (6) made from ethylene vinyl alcohol (EVOH) and an outer layer (8) made from a polymer suitable for welding, in a mould comprising at least one female shoulder that creates at least one male shoulder on an outer surface of an end portion of the wall during moulding, then - cutting off the end portion of the wall.