Fuel injection system for an internal-combustion engine

Claim 1

A fuel-injection system for an internal-combustion engine, comprising a dual-fluid nozzle mounted on the engine, a high-pressure pump for supplying liquid fuel fluid to said dual-fluid nozzle, a feed pump for supplying an additional liquid fluid, to said dual-fluid nozzle, said dual-fluid nozzle having a body including a nozzle needle which is spring-biased into a closing position in which one end of said needle is seated on a valve seat, an annular space formed around said valve needle adjacent said one end of said valve needle, a fuel supply passage extending from said annular space through said nozzle body and being in communication with said high-pressure fuel pump, said fuel supply passage having a branch passage leading to a control chamber formed in said nozzle body at the other end of said valve needle, said branch passage including a solenoid valve for applying fluid pressure to the other end of said nozzle needle and for relieving said fluid pressure whereby closing and opening of said nozzle needle is achieved, an additional fluid line extending from said feed pump to said annular space for supplying said additional fluid thereto under a pressure substantially lower than the fuel pressure generated by said high-pressure pump, said additional fluid line including a check valve for preventing return flow of said additional fluid out of said annular space, a pressure relief line in communication with said fuel supply passage via a three-way control valve arranged therein, and a control device for operating said solenoid valve for timed relief of fluid pressure from said control chamber for unseating said nozzle needle and for application of fluid pressure to said control chamber for seating said valve needle and also for operating said control valve for either supplying pressurized fuel to said annular chamber or for blocking the pressurized fuel supply and placing said annular chamber in communication with said pressure relief line, while said nozzle needle is seated to permit feeding of said additional fluid into said annular space for the time period during which said control valve establishes said communication.