Fuel Rail End Seal Using Threaded Cap and Brazed Collar
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Solution Overview
Problem
Conventional fuel rail end seal structures for gasoline direct injection engines, which rely on brazing for closure, are weakened by radial deformation forces at high pressures and prone to breakage due to stress concentration at brazed parts in contact with the fuel.
Innovation Solution
A thread fastening method using a collar and gasket is employed, where the collar is brazed to the fuel rail body, and a convex end cap is screwed onto the thread fastening part, with a metal gasket sealing between the end cap and the rail body, distributing compressive stress to the brazed part and avoiding direct contact with the fuel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If end caps are joined to the body pipe by brazing, then the structure is simple, but the brazed parts become the weakest points under high internal pressure and radial deformation forces
Solution Approach 1:
The end cap assembly is segmented into multiple functional components: a collar brazed to the body pipe, a separate gasket for sealing, and a threaded end cap for closure. This segmentation allows each component to perform its specific function optimally while distributing stress away from the brazed joint.
Solution Approach 2:
A collar is introduced as an intermediary component between the body pipe and the end cap. The collar is brazed to the body pipe and provides a threaded interface for the end cap, thereby protecting the brazed joint from direct contact with fuel and radial deformation forces.
Solution Approach 3:
Different parts of the end seal structure have different material properties and functions: the collar and body pipe are made of materials suitable for brazing and pressure resistance, the gasket is made of elastomeric material for sealing, and the end cap is made of materials resistant to fuel and pressure. This local optimization of material properties enhances overall strength.
2Reliability
If brazed parts are in direct contact with fuel, then the sealing is direct, but unevenness in the brazed parts causes stress concentration and breakage
Solution Approach 1:
A gasket is introduced as an intermediary sealing element between the end cap and the body pipe/collar assembly. This gasket performs the sealing function while being isolated from the brazed joints, eliminating stress concentration issues at the brazed parts.
Solution Approach 2:
The sealing function is extracted from the brazed joint and assigned to a dedicated gasket component. This separation allows the brazed joint to focus on structural connection while the gasket handles sealing, improving both reliability and durability.
3Power
If higher pressure requirements are met, then the fuel injection system performance improves, but the end cap structure becomes more vulnerable to radial deformation and breakage
Solution Approach 1:
The end cap assembly is segmented into components that can independently handle different aspects of high pressure: the collar and body pipe handle radial deformation through brazed connection, the gasket handles sealing under pressure, and the threaded end cap handles closure forces. This segmentation allows the system to meet higher pressure requirements without compromising reliability.
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 enhances fatigue resistance and meets higher pressure requirements, reduces the risk of breakage from unevenness, and ensures a stable and reliable seal, while also improving corrosion and pressure resistance with stainless steel and surface-treated materials.
Implementation Method 1
a collar (2) brazed at an outer circumference of an opening end of the fuel rail body (1)
Implementation Method 2
a gasket (5) that is made of metal and interposed between the convex end cap (4) and the fuel rail body (1). The gasket (5) is tightened by an axial force generated due to tightening of the convex end cap (4) so as to seal the opening end of the fuel rail body (1)
Data Source
AI summary
Provided is an end seal structure of a fuel rail for a gasoline direct injection engine that has a simple structure and allows an end cap part to meet higher pressure requirements in a fuel rail having the structure in which one end or both ends of a rail body composed of a tubular member, such as a pipe, is/are closed by an end cap or end caps. The end seal structure employs a thread fastening method using the end cap and a collar brazed at the opening end of the fuel rail body and a gasket sealing method as a sealing method, wherein a gasket interposed between the end cap and the fuel rail body is tightened by an axial force generated due to tightening of the end cap that is screwed and fastened to the fuel rail body so as to be sealed.