Injector for common-rail system

摘要

The injector comprises a nozzle needle (20) working against a seat (17), and a piston rod (22) acting in the axial direction on the needle, the end face of the latter subjected to the fuel inlet pressure being smaller than one (27) on the rod subjected to this pressure. At the end of the rod furthest from the nozzle needle is a control unit (36) containing a solenoid valve (38) with pilot needle (25) and a component (13) with discharge passage connecting chambers (37,71) at its ends. In the first chamber, the solenoid valve opens and shuts the passage using the pilot needle, while a second chamber (48) is situated at the rear end of the pilot needle. This accommodates a return spring (47), and is hydraulically separated from the first chamber (37). The first or second (48) chambers are supplied by passages (55,56) with pressure.