Fuel Pipe Connection Head Geometry to Prevent Cap-Nut Buckling
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Solution Overview
Problem
The connection head part of fuel pipes in fuel distribution and supply devices experiences stress-induced buckling due to axial forces from cap nuts, particularly in gasoline engines where increasing thickness is costly and not feasible, while diesel engines require thicker materials to withstand high pressures.
Innovation Solution
A fuel pipe design featuring a connection head part with a first and second curved portion and a straight portion, where the straight portion disperses axial force, reducing maximum stress and improving strength without increasing thickness, and can be manufactured with equal plate thickness to the pipe body using plastic working.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the connection head part is increased to prevent buckling, then the strength is improved, but the manufacturing cost increases
Solution Approach 1:
The connection head part incorporates a curved portion with a specific radius of curvature that helps distribute stress and prevent buckling under axial load. The curved geometry transforms the stress distribution pattern, allowing the thin-walled structure to resist buckling without increasing thickness, thereby maintaining manufacturing cost-effectiveness while improving strength.
2Strength
If the thickness of the connection head part is increased to withstand axial force, then the strength is improved, but the plate thickness cannot be kept equal to the pipe body
Solution Approach 1:
The curved portion with optimized radius of curvature provides structural reinforcement that allows the connection head part to maintain equal plate thickness with the pipe body. The curvature geometry inherently resists buckling forces, eliminating the need for localized thickness increase while maintaining strength under axial load from the cap nut.
3Stress or pressure
If a linear flow path is created by increasing connection head part thickness, then the pressure resistance is improved, but the cost increases
Solution Approach 1:
The curved portion with specific radius of curvature reinforces the connection head part structure to withstand high pressure (up to 200 MPa in diesel applications) without requiring increased thickness. This maintains the linear flow path geometry while using cost-effective thin-walled construction, resolving the contradiction between pressure resistance and manufacturing cost.
Data Source
AI summary
Provided is a fuel pipe connected to a fuel distribution pipe distributing and supplying fuel to a plurality of fuel injection devices. The fuel pipe includes a pipe body and a connection head part fastened to the fuel distribution pipe by a cap nut. The connection head part includes a first curved portion curved in a circular shape in a reference cross-section including a central axis A of the fuel pipe and abutting against a seat surface formed on an inner peripheral surface of the fuel distribution pipe, a second curved portion curved in a circular shape in the reference cross-section and locked on a locking surface formed on an inner peripheral surface of the cap nut, and a straight portion extending linearly in the reference cross-section and interconnecting the first curved portion and the second curved portion.