Fuel injection system for a diesel engine

Claim 1

A fuel injection system for a Diesel engine comprising a common high pressure fuel supply conduit (Common Rail), a high pressure fuel pump supplying fuel under pressure to said fuel supply conduit, a number of valve-controlled injectors in communication with said fuel supply conduit so as to receive fuel under pressure therefrom, each injector including a body with a control needle movably disposed therein and having a valve seat and a spring engaging the control needle so as to be normally seated on said valve seat and a needle actuator for lifting said needle of its seated position under the control of an electronic control unit, said needle including a piston-like tip with slot-shaped orifices formed in the outer surface thereof which orifices are fully covered when said control needle is seated but are exposed as said control needle is unseated by said needle actuator, said control needle including a pressure compensation piston disposed in a cylinder formed in said injector body and defining in said injector body with said piston-like needle tip a pressure chamber in communication with said fuel supply conduit for compensating the fuel pressure effective on said control needle so that the effective cross-section of the orifice opening of said injector is controlled solely by said needle actuator.