Fuel Injection Valve Threaded Connection High-Pressure Sealing
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Solution Overview
Problem
Existing fuel injection valves face challenges in maintaining a tight seal under high fuel injection pressures, particularly in the threaded connection region, which is subjected to pressures over 1500 bar, leading to stringent requirements for improved sealing efficiency.
Innovation Solution
The fuel injection valve incorporates a threaded connection with at least two toothing regions of different dimensions, featuring a thread-free intermediate section, where the second toothing region has a smaller thread diameter and twice the number of teeth compared to the first, allowing for enhanced sealing and easier mounting, while the increased wall thickness in the second region effectively absorbs pressure stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single threaded connection is used, then the structure is simple, but the sealing performance under high pressure is insufficient
Solution Approach 1:
The threaded connection is divided into two distinct toothing regions with different thread dimensions. The first toothing region (coarser pitch) provides structural support and ease of mounting, while the second toothing region (finer pitch) provides enhanced sealing performance under high pressure. This segmentation allows each region to be optimized for its specific function.
Solution Approach 2:
Different regions of the threaded connection are given different thread characteristics. The first toothing region has coarser threads suitable for initial engagement and mounting, while the second toothing region has finer threads optimized for sealing under pressure. This local differentiation of quality enables simultaneous optimization of mounting ease and sealing reliability.
2Reliability
If the clamping nut wall thickness is increased to absorb pressure stresses, then the sealing improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The pressure absorption function is distributed to the two toothing regions rather than requiring a uniformly thick clamping nut. The first toothing region handles initial engagement with standard wall thickness, while the second toothing region provides enhanced pressure distribution under high fuel pressure, reducing the need for excessive wall thickness throughout the entire clamping nut.
3Reliability
If the threaded connection is optimized for sealing, then the seal tightness improves, but the mounting complexity increases
Solution Approach 1:
The mounting process is segmented into two phases corresponding to the two toothing regions. The first toothing region with its coarser pitch facilitates initial engagement and mounting operations, while the second toothing region with finer pitch engages subsequently to provide the tight seal. This sequential engagement maintains ease of mounting while achieving superior sealing.
Solution Approach 2:
The first toothing region performs the preliminary action of initial engagement and mounting, preparing the connection for the second phase. This preliminary engagement with coarser threads makes the mounting process easier before the finer second toothing region engages to provide the final tight seal.
Data Source
AI summary
A fuel injection valve (100) for internal combustion engines, having a housing (10) in which a nozzle body (11) is at least indirectly axially clamped against a holding body (15) by means of a clamping nut (18), wherein the clamping nut (18) radially surrounds the nozzle body (11), and wherein a threaded connection (20) between the holding body (15) and the clamping nut (18) is formed between the clamping nut (18) and the holding body (15) in a region which is axially spaced apart from the nozzle body (11). The threaded connection (20) comprises at least two toothing regions (21, 22) which have different threaded dimensions and are arranged axially one behind the other in the longitudinal direction of the housing (10).