Fluid sprinkling – spraying – and diffusing – Including valve means in flow line – Reciprocating
Reexamination Certificate
2000-09-26
2001-09-11
Douglas, Lisa Ann (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Including valve means in flow line
Reciprocating
C239S585300, C251S129210, C251S210000
Reexamination Certificate
active
06286770
ABSTRACT:
The present invention relates to a fuel injector of an improved type.
In particular, the present invention relates to a fuel injector for internal-combustion engines, to which the following description specifically refers, without detracting from generality.
BACKGROUND OF THE INVENTION
As is known, the fuel injectors for internal-combustion engines which are commercially available at present comprise: a main tubular body, which is provided with a central through pipe, which ends at an axial end of the tubular body, in a spray nozzle, which can project outside the injector a jet of finely sprayed fuel; a shutter unit, which is fitted such as to be axially mobile inside the central pipe, from and towards the position of closure, in which it closes the spray nozzle, such as to prevent discharge of the fuel; and a contrast spring which can maintain the shutter unit in the said position of closure.
Outside the main tubular body, the fuel injectors additionally comprise a coil made of electrically conductive material, which, when an electric current is passed through it, can generate a magnetic field which can overcome the resilient force of the spring, such as to move the shutter unit away temporarily from the position of closure, so as to permit controlled discharge of the fuel.
The shutter unit is obviously made at least partially of ferro-magnetic material, and in some types of injector, it consists of a cup-type body with a cylindrical shape, which is fitted such as to be mobile axially inside the central pipe, with its own base facing towards the spray nozzle, such that in the position of closure, it is disposed with its base abutting a flat surface provided on the spray nozzle.
Owing to the strong mechanical stresses to which it is subjected, the shutter unit, i.e. the cup-type body with a cylindrical shape, normally consists of a cylindrical tubular element made of ferro-magnetic material, and of a highly-resistant sealing disc made of rigid material, which is welded to an axial end of the said cylindrical tubular element. This disc has a considerable thickness, and is provided on its outer flat surface with two concentric annular projections which have the same height, and can provide the hydraulic sealing when they abut the flat surface which delimits the spray nozzle. Finally, in order to permit passage of the fuel, the sealing disc is provided with a plurality of through holes, which can put the interior of the cup-type body into communication with the outer flat surface of the disc, at the area delimited by the two concentric circular projections.
The main disadvantage of the above-described fuel injectors is that in the final part of their vital cycle, they are subject at intervals to undesirable blow-by of fuel, with a substantial increase in the pollutant emissions, which does not enable the internal-combustion engine to comply with the directives concerning pollutant emission.
In fact, in the long term, the repeated impacts of the shutter unit on the flat surface which delimits the spray nozzle give rise to localised resilient deformations, which in some cases do not allow the shutter disc, or rather its two concentric annular projections, to be placed so as to abut correctly the flat surface which delimits the spray nozzle, so as to provide the hydraulic sealing, and thus prevent discharge of the fuel from the spray nozzle.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a fuel injector for internal-combustion engines, which is free from the above-described disadvantages.
According to the present invention, a fuel injector of an improved type is provided, which comprises a main tubular body, provided with at least one through pipe which ends in a spray nozzle which can spray to the exterior the fuel which is present inside the through pipe, and a shutter unit which is mobile inside the said through pipe, from and towards a position of closure, in which it abuts the spray nozzle, shutting the latter such as to prevent discharge of the fuel; the spray nozzle being provided with a sealing surface against which the shutter unit can abut, and the shutter unit being shaped substantially in the form of a cup, such that, in the position of closure, its own base abuts the said sealing surface, in order to prevent the fuel from being discharged; the said fuel injector being characterised in that the base of the said shutter unit is provided with a sealing projection, which can abut the sealing surface of the spray nozzle, in order to form the hydraulic seal, and a stop projection, which can temporarily abut the said sealing surface in order to stop the path of the shutter element itself; the sealing projection having a height which is greater than the height of the stop projection, and the base of the said shutter unit being resiliently deformable, so as to permit impact in succession of the said sealing projection and the said stop projection.
REFERENCES:
patent: 2525796 (1950-10-01), Harding
patent: 3567135 (1971-03-01), Gebert
patent: 5636827 (1997-06-01), Kilgore et al.
patent: 5823446 (1998-10-01), Bennett et al.
patent: 6095186 (2000-08-01), Nagel
patent: 475 475 (1969-07-01), None
patent: 0683315 (1995-11-01), None
Boaro Maurizio
Cristiani Marcello
Neretti Massimo
Baker & Daniels
Douglas Lisa Ann
Magneti Marelli S.p.A.
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