Fuel Injector Needle Rotational Positioning via Stop and Bias
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Solution Overview
Problem
Existing fuel injectors for internal combustion engines face issues with fuel leakage due to uncontrolled rotational mating between the needle and the nozzle seat, resulting from the spline-like interface and clearance that allow relative angular movement.
Innovation Solution
A fuel injector design that incorporates mutually cooperating axial guide elements with rotational play, a rotational stop to limit this play, and a force transfer arrangement to bias the needle into a fixed rotational position at the stop, ensuring consistent sealing and reducing fuel leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a spline-like keying feature is used between the needle and nozzle body, then the range of rotation of the needle is limited, but this promotes uneven wear and develops random patterns of convex and concave irregularities on contact surfaces
Solution Approach 1:
The patent removes the spline-like keying feature from the interface between the needle and nozzle body. Instead, it uses a simple cylindrical guide interface that allows controlled rotational play without promoting uneven wear patterns, thereby eliminating the harmful effect while maintaining the necessary rotational limitation.
Solution Approach 2:
The patent introduces a rotational stop that is preliminarily positioned to limit the rotational play before the needle and nozzle seat come into contact. This preliminary constraint ensures that the needle assumes a correct rotational position relative to the nozzle body, preventing the development of uneven wear patterns during operation.
2Ease of operation
If clearance is provided in the spline-like interface to avoid undue friction, then axial movement of the needle is accurately controlled, but this allows relative angular/rotational movement that prevents consistent sealing
Solution Approach 1:
The patent separates the axial guidance function from the rotational constraint function. The cylindrical guide elements provide axial movement control through clearance, while a separate rotational stop mechanism provides rotational limitation. This segmentation allows each mechanism to optimize its specific function without interfering with the other.
Solution Approach 2:
The rotational stop acts as an intermediary element between the needle and nozzle body. It mediates the rotational play by providing a physical limit that ensures the needle assumes a correct rotational position when mating with the nozzle seat, thereby ensuring consistent sealing without restricting axial movement.
3Force
If rotational play is allowed between the needle and nozzle body, then friction is reduced, but this means the formed irregularities in contact surfaces will not always mate well enough to provide a tight seal
Solution Approach 1:
The patent allows partial rotational play to reduce friction during needle movement, but simultaneously provides excessive rotational constraint through the rotational stop to ensure proper sealing. The rotational stop creates a hard limit that prevents excessive rotational deviation, ensuring that the contact surfaces mate correctly despite the presence of friction-reducing clearance.
Data Source
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AI summary
A fuel injector comprises a needle movable within a nozzle body. The fuel injector has a closed state in which the needle is mated with a nozzle seat, and an open state in which the needle is spaced apart from the nozzle seat to allow fuel to be dispensed from the nozzle body. The needle and the nozzle body have mutually cooperating axial guide elements that guide the needle along a geometrical longitudinal axis of the needle. The guide elements present, with respect to said longitudinal axis, a rotational play between the needle and the nozzle body. A rotational stop is provided to limit the rotational play. The fuel injector further comprises a force transfer arrangement configured to provide to the needle a rotational force relative to said longitudinal axis, the rotational force biasing the needle to assume a fixed rotational position at said rotational stop relative to the nozzle body in said closed state of the fuel injector.