Common-Rail Injector Flow Limiter Design
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Solution Overview
Problem
Modular common rail fuel injection systems with integrated high-pressure accumulators face challenges in fatigue strength due to press fits and complex bore intersections, particularly under extreme pressure loads, and require different designs for top-feed and side-feed injectors, which increases component variety and complexity.
Innovation Solution
The flow limiter is inserted between the holding body and storage tube, secured by screwing them together, eliminating the need for press fits and retaining rings, with axial fixing pins and conical sealing surfaces ensuring a high-pressure-tight connection and preventing twisting, allowing for a unified design for both injector types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If flow limiters are arranged in front of the storage volume in terms of flow, then the flow limiter can be easily installed, but the fatigue strength is reduced due to press fits and complex bore intersections under extreme pressure loads
Solution Approach 1:
The flow limiter is positioned after the storage volume in terms of flow direction, inverted from the conventional upstream placement. This reversal allows the flow limiter to be integrated into the holding body without requiring press fits or complex bore intersections, thereby maintaining fatigue strength while ensuring easy installation through standard machining operations.
2Adaptability or versatility
If different designs are used for top-feed and side-feed injectors, then each injector type can be optimized, but the component variety and complexity increase
Solution Approach 1:
The flow limiter design integrated into the holding body serves as a universal solution applicable to both top-feed and side-feed injector configurations. The holding body's integrated flow limiter eliminates the need for separate flow limiter assemblies, allowing the same basic design to be used across different injector types without increasing component variety.
3Reliability
If press fits and retaining rings are used to secure the flow limiter, then the flow limiter is firmly fixed, but the fatigue strength is compromised under extreme pressure loads
Solution Approach 1:
The flow limiter is extracted from the conventional design that requires press fits or retaining rings and is instead directly integrated into the holding body structure. This extraction eliminates the need for separate fixation elements that compromise fatigue strength, while the integrated design ensures reliable fixation through the holding body's inherent structural integrity under extreme pressure loads.
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
In the case of an injector (1) of a modular common-rail fuel injection system with a high-pressure accumulator (6) integrated in the injector body, the injector (1) comprises an injection nozzle (2), which has a nozzle needle (15) guided axially displaceably therein and surrounded by a nozzle chamber (19), a high-pressure line (8) which connects the high-pressure accumulator (6) to the nozzle chamber (19), and a holding body (5) which, at the face side, is screwed to the component, in particular accumulator pipe (25), which forms the high-pressure accumulator (6), through which holding body the high-pressure line (8) runs, wherein, downstream of the high-pressure accumulator (6) in terms of flow, there is arranged a throughflow limiter (26) for limiting the fuel flow rate delivered out of the high-pressure accumulator (6) to the injection nozzle (2). The throughflow limiter (26) is formed as a separate component which is placed between the holding body (5) and the accumulator pipe (25) and which is fixed by the screw connection between the holding body (5) and accumulator pipe (25).