Fuel Injector Flow Limiter for Fail-Safe Injection Shutoff
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Solution Overview
Problem
Existing fuel injectors face challenges in controlling the nozzle needle due to high injection pressures, leading to potential continuous fuel injection and engine damage during malfunctions.
Innovation Solution
A fuel injector with a flow restrictor featuring a throttle bushing, throttle insert, and spring element that limits fuel flow by creating a reservoir and sealing mechanism to prevent continuous fuel injection during malfunctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solenoid valve is used to directly control the nozzle needle, then the injection can be precisely controlled, but the electromagnetic forces required would be too great for the limited installation space
Solution Approach 1:
The patent introduces a pilot valve (servo valve) as an intermediary component between the solenoid valve and the nozzle needle. The solenoid valve controls a small pilot valve that regulates fuel pressure to a control chamber, which then actuates the much larger nozzle needle. This intermediary mechanism allows precise electronic control while using manageable electromagnetic forces suitable for limited installation space.
2Productivity
If the outlet throttle of the control chamber is continuously open, then fuel can flow freely, but continuous fuel injection would cause serious engine damage during malfunctions
Solution Approach 1:
The patent incorporates a flow limiter device that preemptively restricts the maximum fuel flow capacity of the injector. The flow limiter includes a throttle bushing with a through-hole and a throttle insert that can seal against a sealing section. This preliminary restriction ensures that even if the control system fails, the maximum possible fuel flow is limited, preventing catastrophic engine damage while still allowing sufficient flow for normal injection operations.
Solution Approach 2:
The flow limiter uses a simple, sacrificial mechanical sealing approach rather than complex electronic control. The throttle insert can make contact with the sealing section to seal the through-hole, providing a passive, fail-safe mechanism that requires no energy or complex components. This simple mechanical solution is preferred over sophisticated continuous control systems for the critical safety function.
3Object-affected harmful factors
If a flow limiter with a sealable through-hole is added to prevent continuous fuel flow, then engine protection is improved, but the device complexity increases
Solution Approach 1:
The patent integrates the flow limiter components (throttle bushing, throttle insert, spring element) into the existing injector structure. The throttle bushing with through-hole is positioned within the fuel supply path, and the throttle insert works in conjunction with existing sealing surfaces. This merging approach adds protection functionality while minimizing the increase in overall device complexity by reusing existing structural elements.
Solution Approach 2:
The flow limiter is designed as a modular assembly of discrete components: a throttle bushing with a through-hole, a movable throttle insert, and a spring element. This segmentation allows each component to perform a specific function (flow passage, sealing, actuation) and facilitates easy manufacturing, assembly, and maintenance. The modular design adds functionality without creating a monolithic complex structure.
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
Prevents excessive fuel injection by engaging the shut-off mechanism in case of injector failure, minimizing engine damage.
Implementation Method 1
a spring element (6) mounted in the through-hole (3) that pushes the throttle insert (4) away from the sealing section (5)
Implementation Method 2
The constant high pressure on the side of the throttle insert facing the rail then causes the throttle insert, which slides within the throttle bushing, to move towards the sealing section
Implementation Method 3
the throttle insert (4) has a sealing surface at its end facing the sealing section, which closes the through-hole upon contact with the sealing section
Data Source
Figure 1a~1c
Figure 2a~2d
AI summary
The present invention relates to a flow limiter for a fuel injection system, which flow limiter comprises: a throttle bush, which has a through-hole; a throttle insert, which is movably held in a first portion of the through-hole; a sealing portion in a second portion of the through-hole, which has a reduced cross-section in comparison with the first portion of the through-hole; and a spring element, which is held in the through-hole and pushes the throttle insert away from the sealing portion. The invention is characterized in that the throttle insert has, at its end nearest the sealing portion, a sealing surface, which closes the through-hole when the sealing surface is in contact with the sealing portion.