Patent ID: 7740187

Claim:
A fuel injector for an internal combustion engine; the injector having a nozzle for injecting fuel into a relative cylinder of the engine, and comprising: a hollow injector body extending in an axial direction; a control rod movable axially with respect to said injector body to open and close said nozzle; a control servo valve housed in said injector body and comprising: a) an electro-actuator; b) a control chamber, which is bounded axially at one side by said control rod, communicates with a fuel inlet, and has a discharge passage comprising a calibrated portion; and c) a sleeve movable axially, under the control of said electro-actuator, between a closed position, in which it closes said discharge passage, and an open position, in which it opens said discharge passage to vary the pressure in said control chamber and so produce axial movement of said control rod; wherein said control servo valve also comprises an axial rod fixed with respect to said injector body and an outer lateral surface on the axial rod through which said discharge passage comes out; said sleeve being fitted to said outer lateral surface to slide axially in substantially fluidtight manner, and, in said closed position, being effective to close said discharge passage so as to be subjected to substantially zero resultant axial pressure by the fuel; and wherein said calibrated portion is formed in the axial rod close to the outlet of said discharge passage to produce swirl or cavitation in the fuel outflow near to the closing area between said sleeve and said axial rod.