Fuel Injector Sealing Structure for Coaxial Back-Up Ring Alignment
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Solution Overview
Problem
The existing sealing structures between fuel injection valves and delivery pipes face issues with coaxial arrangement and sealing performance due to the inclination of the back-up ring, leading to potential gaps and deterioration of sealing efficiency, especially under varying fuel pressure conditions.
Innovation Solution
A sealing structure that includes an O-ring and a back-up ring, where the back-up ring is designed with a cylindrical shape and specific geometric features such as a pressure-receiving surface and a seating surface, with a gradually increasing inner diameter and a slit, allowing for coaxial arrangement and effective deformation under fuel pressure to fill gaps between the back-up ring and the fuel injection valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the back-up ring is press-fitted into the fuel delivery pipe, then the back-up ring can be installed in the delivery pipe, but the back-up ring may become inclined relative to the central axis, causing misalignment with the fuel injection valve and generating gaps that deteriorate sealing performance
Solution Approach 1:
The back-up ring is designed with non-uniform thickness, having a thicker first portion and a thinner second portion. This local quality variation allows the back-up ring to be press-fitted into the delivery pipe while the thicker first portion provides structural support and prevents excessive deformation, maintaining coaxial alignment with the fuel injection valve despite the pressing operation
Solution Approach 2:
The non-uniform thickness design acts as a pre-engineered cushioning mechanism. The thicker first portion anticipates and absorbs the deformation stress during press-fitting, preventing the back-up ring from becoming inclined or misaligned before it is actually installed and begins its sealing function
2Reliability
If the O-ring has a small amount of deformation, then the O-ring can maintain its shape and reduce wear, but fuel pressure transmitted to the back-up ring varies in the circumferential direction, making it difficult to cancel the inclination of the back-up ring and increasing the risk of gap generation
Solution Approach 1:
The back-up ring's non-uniform thickness creates local quality differences that compensate for circumferential pressure variations. The thicker first portion provides a stable foundation that resists deformation from varying fuel pressure, while the thinner second portion allows controlled deformation to maintain contact with the fuel injection valve, ensuring stable sealing under different pressure conditions
3Device complexity
If the back-up ring is made with uniform thickness, then the structure is simple and easy to manufacture, but it is more prone to becoming inclined during press-fitting and failing to align coaxially with the fuel injection valve
Solution Approach 1:
Instead of uniform thickness, the back-up ring employs non-uniform thickness with a distinct first portion and second portion. This design increases structural complexity slightly but dramatically improves coaxial alignment precision by providing differential support during press-fitting, preventing inclination and ensuring proper alignment with the fuel injection valve
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
The solution ensures reliable coaxial arrangement and improved sealing performance by facilitating surface contact and deformation of the back-up ring, effectively suppressing the generation of gaps and maintaining sealing efficiency even under varying fuel pressure conditions.
Implementation Method 1
an O-ring is pressed against the fuel injection valve due to fuel pressure, the O-ring is then deformed, and a gap between the fuel injection valve and the fuel delivery pipe is thereby filled
Implementation Method 2
even when fuel pressure is applied via the O-ring to the back-up ring, the back-up ring and the fuel injection valve might fail to be coaxially arranged
Data Source
AI summary
A sealing structure includes an O-ring and a back-up ring. An outer diameter of the back-up ring is smaller than an inner diameter of a mounting portion of a delivery pipe. An inner diameter of the back-up ring is gradually increased from a pressure-receiving surface toward a seating surface, and is greater than an outer diameter of a fuel introducing portion of a fuel injection valve. In a section of the back-up ring, an edge angle defined between the pressure-receiving surface and an inner circumferential surface is smaller than a gap angle defined between the pressure-receiving surface and a tapered outer surface of a tapered portion in the fuel introducing portion. A dimension of the seating surface in the back-up ring is shorter than a dimension in an end surface.