Fuel injector

Details Fuel injector Fuel injector

1999-07-01

2001-04-17

Douglas, Lisa Ann (Department: 3752)

Fluid sprinkling, spraying, and diffusing

Fluid pressure responsive discharge modifier* or flow...

Fuel injector or burner

C239S584000, C251S129060

Reexamination Certificate

active

06216964

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to an injector for use in supplying fuel to a combustion space of an internal combustion engine. The invention relates, in particular, to an injector of the outwardly opening type suitable for use in supplying fuel to an engine of the compression ignition type.
Part of a typical injector of the outwardly opening type is illustrated in FIG.
1
. As shown in
FIG. 1
, the injector comprises a needle
1
slidable within a bore
2
formed in a nozzle body
3
. The bore
2
defines a seating with which the needle
1
is engageable to control the supply of fuel to a chamber
4
. The position of the needle
1
also determines how many of a plurality of outlet openings
5
communicate with the chamber
4
.
Part of the needle
1
downstream of the seating is of diameter substantially equal to the adjacent part of the bore
2
and engagement therebetween guides movement of the needle
1
. It has been found, however, that fuel may leak between this part of the needle
1
and the bore resulting in inefficient combustion of fuel and high levels of emissions. Where the injector is used with a fuel system of the direct injection type, the level of leakage may be increased due to dilation of the bore
2
.
SUMMARY OF THE INVENTION
The disadvantage described hereinbefore can be reduced by increasing the axial length of the region of the needle which engages the bore to guide the movement of the needle, and this can be achieved by providing the needle with a fuel supply passage which communicates with one or more outlet openings provided in the needle rather than in the nozzle body. However, by providing the outlet openings in the needle rather than the nozzle body, angular movement of the needle, in use, may result in the delivery of fuel being incorrectly orientated where the fuel injector is not mounted vertically.
According to a first aspect of the invention there is provided an injector comprising a valve needle slidable within a bore formed in a nozzle body, the valve needle including an axially extending fuel supply passage which communicates with at least one outlet opening provided in the needle, wherein the end of the supply passage adjacent the outlet opening is closed by a plug, the plug having an inner end region which is arranged to be located, in use, adjacent the, or at least one of the, outlet openings and shaped to modify the flow characteristics of the fuel flow upstream of at least one of the said outlet openings.
The plug may, for example, be shaped to define a recess, for example of conical or part spherical form, or may include a projection of, for example, cylindrical or conical form. The inner end region of the plug may be shaped to generate cavitation upstream the outlet openings, or may increase or decrease other hydraulic disturbances upstream of the outlet openings.
The fuel injector may further comprise lock means arranged to restrict angular movement of the needle about the axis of the needle relative to the nozzle body.
The lock means conveniently comprises a lock member extending within formations provided in the valve needle and the nozzle body. The lock member may take the form of a pin, and the formations may define a groove or slot in the upper end surface of the valve needle and a groove or recess formed in the upper surface of the nozzle body.
The injector in accordance with this embodiment of the invention is advantageous in that as angular movement of the needle is restricted, if the needle includes one or more outlet openings, the orientation of fuel sprays formed at the outlet openings, in use, remain fixed.
The valve needle may carry an annular abutment member which is engageable with the seating to control the flow of fuel past the seating.
The abutment member may be an interference fit or may be secured to the valve needle by, for example, welding or brazing.
The use of an abutment member carried by the valve needle simplifies manufacture of the valve needle.
According to a second aspect of the invention there is provided a fuel injector comprising a valve needle slidable within a bore formed in a nozzle body, and lock means arranged to restrict angular movement of the needle about the axis of the needle relative to the nozzle body.
According to a third aspect of the invention there is provided a fuel injector of the outwardly opening type comprising a valve needle slidable within a bore provided in a nozzle body, the bore defining a valve seating, the valve needle carrying an annular abutment member which is engageable with the seating to control the flow of fuel past the seating.
According to another aspect of the invention there is provided a fuel injector comprising a valve needle slidable within a bore formed in a nozzle body, wherein the diameters of the needle, the bore and the outer periphery of the nozzle body are chosen to optimize stress levels within the nozzle body and the needle, thereby restricting the leakage of fuel between the needle and the nozzle body to an acceptable level.


REFERENCES:
patent: 2096581 (1937-10-01), Goldberg
patent: 4382553 (1983-05-01), Thoma et al.
patent: 5755385 (1998-05-01), Potz et al.
patent: 5899385 (1999-05-01), Hofmann et al.
patent: 6085726 (2000-07-01), Lei et al.
patent: 2314119 (1997-12-01), None

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