Patent ID: 7793862

Claim:
A control servo valve for the controlling a fuel injector, comprising: a valve body having a tubular portion extending along a longitudinal axis and radially delimiting a control chamber communicating with an inlet of high pressure fuel, said valve body being set in a fixed position and comprising a stem extending along said longitudinal axis opposite said tubular portion; an outlet passage provided internally to said valve body and communicating permanently with said control chamber, said outlet passage comprising at least two radial channels giving out into an annular outlet chamber through an outer lateral surface of said stem; an open/close tubular element coupled to said outer lateral surface substantially in a fluid-tight way and axially movable with respect to said stem, said tubular element being normally held by elastic means on an end-of-travel closing position, in which it closes said annular outlet chamber so as to be subject to a zero axial resultant force by the pressure of said high pressure fuel; and electro actuating means operable to axially move said tubular element against the urge of said elastic means from said end-of-travel closing position to an end-of-travel opening position, in which it leaves said annular outlet chamber open; wherein said radial channels each comprise respective first tubular portions having calibrated lengths and diameters, and respective second tubular portions having diameters larger than the diameter of the corresponding first portions, the respective first and second tubular portions of each radial channel extending linearly and being coaxial with each other and wherein the second tubular portions always give out into the annular outlet chamber.