Fuel Rail End Seal Structure for Gasoline Direct Injection
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Solution Overview
Problem
Conventional fuel rail end seal structures for gasoline direct injection engines face challenges in meeting higher pressure requirements due to the weakness of brazed portions under radial deformation and potential breakage from stress concentration, requiring thicker rail bodies and compromising seal stability.
Innovation Solution
The end seal structure features a collar brazed to the outer circumference of the pipe with an end cap having a cap-nut shape, where the end cap is screwed and tightened to create axial pressure contact, avoiding radial force on the brazed portion and ensuring it does not contact the fuel, thus enhancing resistance to fatigue failure and maintaining seal reliability without needing a thicker rail body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If end caps are joined to the body pipe by brazing, then the end seal structure is simple, but the brazed portions become the weakest portions under radial deformation and may break due to stress concentration
Solution Approach 1:
The end seal structure is divided into three separate components: the body pipe, the collar (joined by brazing), and the end cap (screwed onto the collar). This segmentation ensures that the brazed joint only connects the collar to the body pipe, while the end cap connection is mechanically screwed, distributing stresses more effectively and preventing the brazed portion from being the weakest link.
Solution Approach 2:
The collar acts as an intermediary component between the body pipe and the end cap. It is joined to the body pipe by brazing but provides a threaded interface for the end cap, thereby protecting the brazed joint from direct exposure to fuel and radial deformation stresses that would otherwise concentrate on the brazed end cap connection.
2Strength
If the rail body is made thicker to strengthen the end seal structure, then the strength increases, but the manufacturing complexity and cost increase
Solution Approach 1:
Instead of making the entire rail body thicker, the invention segments the end seal structure into separate components (collar and end cap) that can be added to the existing rail body design. This allows strengthening the end seal without increasing the overall rail body thickness, maintaining ease of manufacture while improving strength.
3Strength
If threading is performed on the body pipe to directly fix the end caps, then the end cap attachment is strong, but the body pipe needs to be made thicker
Solution Approach 1:
The collar serves as an intermediary component that is brazed to the body pipe and provides the threaded interface for the end cap. This eliminates the need to thread the body pipe directly, avoiding the requirement to make the body pipe thicker while still achieving strong end cap attachment.
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 configuration effectively resists higher pressures, prevents breakage from stress concentration, ensures stable and reliable sealing, and allows for minimal rail body thickness, facilitating better brazing quality and component integration.
Implementation Method 1
a collar 2 is joined by brazing to an outer circumference of an end of a pipe 1 of a rail body
Implementation Method 2
an end cap 3 having a cap-nut shape is screwed and fixed to the collar 2
Implementation Method 3
the end cap 3 brings into pressure contact with an end of an opening at the end of the pipe 1 by an axial force created by tightening of the end cap 3
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Provided is an end seal structure of a fuel rail for a gasoline direct injection engine, the fuel rail being constructed and arranged such that an end or both ends of a rail body composed of a tubular body such as a pipe is/are closed by an end cap or end caps, the end seal structure having a simple structure that does not need to provide a thicker fuel rail, making it possible for the end cap portion to meet higher pressure requirements. The end seal structure is characterized in that: a collar is joined by brazing to an outer circumference of an end of a pipe of the rail body including a pipe; the end cap having a cap-nut shape and including a sealing projection on an surface thereof facing the opening at the end of the pipe of the rail body, is screwed and fixed to the collar; and the sealing projection of the end cap brings into pressure contact with the end of the opening of the rail body by an axial force created by tightening of the end cap having the cap-nut shape to seal the end of the opening of the rail body.