A control valve for controlling the movement of a needle of a fuel injector includes a coil which is attached to a housing of the injector, which housing engages with an armature which can be moved between an open position and a closed position. The armature includes a magnetic plate, through the center of which a rod, which forms a valve piston, extends perpendicularly to the plate to a remote end. The piston slides into a bore in the injector housing, the movements of the armature and of the piston opening or closing channels in which pressurized fuel flows. The armature is provided with a device for quickly discharging the fuel which is captive between the coil and the plate.
1. A control valve which controls movements of a needle of a fuel injector, the control valve comprising:
a coil fixed to an injector body of the fuel injector and cooperating with an armature which moves between an open position close to the coil when the coil is energized and a closed position remote from the coil when the coil is not energized, the armature comprising a magnetic plate, which is located within a cavity, and a valve rod which extends perpendicularly from the magnetic plate in an opposite direction from the coil to a distal end, said valve rod sliding into a bore in the injector body such that a chamber is formed between the bore and the valve rod and such that movements of the armature and of the valve rod allow fluid communication between the chamber and the cavity when the armature is in the open position and prevent fluid communication between the chamber and the cavity when the armature is in the closed position, wherein the valve rod is provided with a rapid discharge device of fuel which is captive between the coil and the magnetic plate such that the rapid discharge device does not provide a path from the chamber to the cavity.
2. The control valve as claimed in claim 1 , wherein the rapid discharge device comprises a discharge channel opening into a first face of the magnetic plate, arranged facing the coil, the discharge channel extending as far as an outlet through which the fuel can spread towards a low-pressure circuit.
3. The control valve as claimed in claim 2 , wherein the discharge channel opens in the center of the first face of the magnetic plate and extends axially in the valve rod.
4. The control valve as claimed in claim 3 , wherein the length of the discharge channel extends scarcely beyond the thickness of the magnetic plate and at least one auxiliary channel extends radially in the valve rod from said discharge channel up to the outlet situated at the periphery of the valve rod, proximate to a second face of the magnetic plate, opposite the first face.
5. The control valve as claimed in claim 2 , wherein the discharge channel extends axially from one end to the other end of the valve rod, from the center of the first face of the magnetic plate to the distal end of the valve rod.
6. The control valve as claimed in claim 5 , wherein the discharge channel comprises a section with a smaller cross section forming a restriction, such that pressure waves spreading in the fuel are damped.
7. The control valve as claimed in claim 6 , wherein the restriction is arranged in an intermediate position in the discharge channel, at a distance from the first face of the magnetic plate and the distal end of the valve rod.
8. The control valve as claimed in claim 6 , wherein the restriction is arranged in the vicinity of one of the ends of the discharge channel.
9. A fuel injector comprising the control valve as claimed in claim 1 .
10. The control valve as claimed in claim 1 , wherein the rapid discharge device is not in fluid communication with the chamber when the armature is in the closed position.