Fuel Injector Bellows Assembly for Fluid-Tight Lubricant Compensation
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Solution Overview
Problem
The assembly of crimping bellows in fuel injectors is technically complex due to the need for screwing and welding connections, which complicates the design and requires high torsion forces, especially when dealing with fuels lacking lubrication properties.
Innovation Solution
A fuel injector design that allows for simple assembly of the crimping bellows by forming a lubricant-filled compensating chamber with a tubular crimping bellows connected via a first and second connecting part, utilizing a screwing surface or positive-locking mechanisms to apply torsion forces without mechanically loading the bellows, and ensuring a fluid-tight connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the crimping bellows is connected to connecting parts by welding to create a fluid-tight connection, then the seal against fuel is ensured, but the assembly becomes technically complex and requires high torsion forces for screwing
Solution Approach 1:
The connecting part is divided into two separate components: a first connecting part that is welded to the crimping bellows, and a second connecting part that is screwed into the housing. This segmentation allows the welding operation to be performed on a smaller, more manageable component, reducing assembly complexity while maintaining fluid-tight connection reliability.
Solution Approach 2:
The first connecting part acts as an intermediary between the crimping bellows and the housing. It provides a welded connection to the bellows while offering external threading for the second connecting part, thereby mediating between the requirements for fluid-tight sealing and ease of assembly.
2Ease of manufacture
If the crimping bellows is screwed into the housing directly, then the assembly process is simplified, but the bellows is subjected to mechanical stress and torsion forces
Solution Approach 1:
The connection system is segmented into a first connecting part (welded to bellows) and a second connecting part (screwed to housing). This allows the screwing operation to be applied to the rigid second connecting part rather than the flexible bellows, simplifying assembly while protecting the bellows from mechanical stress.
Solution Approach 2:
The screwing function is extracted from the crimping bellows and transferred to a separate second connecting part. This extraction allows the bellows to be connected via welding without bearing the mechanical loads of screwing, thereby simplifying the overall assembly process while preserving bellows integrity.
3Ease of operation
If a separate lubricant supply system is implemented for the valve element guides, then the mobility of the valve element is maintained, but the device complexity increases
Solution Approach 1:
The lubricant supply system is merged with the existing fuel injector structure by utilizing the compensating chamber and integrating lubricant delivery through available passages. This combines the lubrication function with existing components rather than adding entirely separate systems, thereby maintaining valve element mobility while minimizing device complexity.
Solution Approach 2:
The compensating chamber serves multiple functions: it compensates for volume changes during valve operation and simultaneously serves as a reservoir for lubricant supply to the valve element guides. This multi-functionality maintains ease of operation while avoiding the complexity of separate dedicated lubrication systems.
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
Facilitates easy and cost-effective assembly of the crimping bellows, eliminating the need for complex screwing and welding processes, and maintaining a fluid-tight seal without mechanical stress on the bellows.
Implementation Method 1
the volume of the compensating chamber bounded by the crimping bellows changes. To compensate for this, the compensating chamber is connected via recesses or bores to a compensating chamber, also bounded by a crimping bellows, which reduces its volume when the valve element moves accordingly
Implementation Method 2
The bellows is connected at its ends directly to the valve element or to connecting parts by welding to obtain a media-tight connection
Implementation Method 3
A torsion force can be exerted on the first connecting part via the screwing surface by means of a force- or positive-locking connection with a tool or with another component of the fuel injector in order to screw it into a fastening thread
Data Source
AI summary
A fuel injector for metered delivery of a gaseous or liquid fuel having a housing (1) in which a compensating chamber (3) bounded by a tubular crimping bellows (5) and fillable with a lubricant is formed, wherein the crimping bellows (5) is connected at one end with a first connecting part (7) and at the other end with a second connecting part (8) by a fluid-tight connection. A thread (12) and a screwing surface (15; 17; 20; 32) accessible from the interior of the crimping bellows (5) are formed on the first connecting part (7), wherein a screwing force can be applied to the first connecting part (7) on the screwing surface (15; 17; 20; 32) by means of a force- or positive-locking connection with a tool (18) or with another component (8) of the fuel injector, in order to screw it into a fastening thread (13) in the housing (1).