Fluid sprinkling – spraying – and diffusing – Fluid pressure responsive discharge modifier* or flow... – Fuel injector or burner
Reexamination Certificate
1997-12-10
2001-03-13
Kashnikow, Andres (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Fluid pressure responsive discharge modifier* or flow...
Fuel injector or burner
C239S585100, C251S129160, C251S129190
Reexamination Certificate
active
06199774
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a perfected electromagnetic metering valve for a fuel injector, in particular for internal combustion engines.
The metering valves of fuel injectors normally comprise a control chamber with a discharge conduit, which is normally closed by a shutter by means of a main spring, and which is opened by energizing an electromagnet to so move the armature as to overcome the force exerted by the spring. In known valves, the armature is normally rigidly connected to a stem sliding inside a fixed guide.
When closing the discharge conduit, the kinetic energy of the armature and the stem is dissipate in the impact of the shutter against the valve; and, when opening the discharge conduit, the kinetic energy of the return stroke of the armature and the stem is dissipated in the impact of the stem against a stop.
Such impact generates considerable force proportional to the mass and speed of the armature and stem and inversely proportional to the duration of impact, which is very short; and, on account of the hardness of the stem, ball and body of the valve, results in considerable rebound, both when opening and closing the valve, so that the movement of the armature fails to provide for steady operation of the injector.
One proposal to reduce rebound of the mass arrested in both the opening and closing stroke is to disconnect the armature from the stem, and provide a second spring weaker than the main spring and for pushing the armature against an element of the stem. In yet another known valve, the stem is provided with a flange housed inside a chamber in which fuel is circulated, and in which the movement of the flange creates a certain amount of turbulence to further reduce rebound.
Such known valves, however, present the drawback of not allowing a small interval between two consecutive movements of the armature, as requested, for example, by high-speed injection engines. In particular, such valves are unsuitable for engines requiring a preinjection of fuel shortly before the main injection. In which case, in fact, the overtravel of the armature with respect to the travel of the stem prevents the armature from returning to the idle position prior to the main injection.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a straightforward, reliable metering valve of the above type, designed to overcome the aforementioned drawbacks typically associated with known valves, and which provides for ensuring rapid return/arrest of the armature in the idle/stop position.
According to the present invention, there is provided a metering valve comprising a shutter for a discharge conduit of a control chamber; an electromagnet for activating an armature to control said shutter via an intermediate element; and a first spring acting on said intermediate element to keep said shutter in a closed position; said armature being disconnected from said intermediate element, and being held in an idle position resting against the intermediate element by a second spring; characterized in that stop means are provided for arresting the movement of said armature produced by said first spring; said stop means being independent of said shutter, and being so arranged as to reduce the overtravel of said armature with respect to the travel of said intermediate element, permit rapid return of said armature to the idle position, and damp the rebound of said armature produced by said first spring and said second spring.
More specifically, in a metering valve wherein the armature is substantially in the form of a disk forming one piece with a sleeve, and the intermediate element is in the form of a stem coaxial with the disk and on which the sleeve slides, said stop means comprise at least a bush of calibrated thickness and sliding freely on said stem between the armature and a fixed stop.
REFERENCES:
patent: 4142683 (1979-03-01), Casey et al.
patent: 4749892 (1988-06-01), Mesenich
patent: 5114077 (1992-05-01), Cerny
patent: 5381999 (1995-01-01), Ricco
patent: 5820101 (1998-10-01), Ricco
patent: 0404336 (1990-12-01), None
patent: 0753658 (1997-01-01), None
Patent Abstract of Japan vol. 010, No. 342 (M-536), 19 Nov. 1986 & JP 61 142358 A (Hitachi LTD), 30 Jun. 1986.
Elasis Sistema Ricerca Fiat Nel Mezzogiorno Societa Consortile p
Kashnikow Andres
Ladas & Parry
Nguyen Dinh Q
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