Variable volume chamber device for preventing leakage in an open nozzle injector

A common rail, open nozzle fuel injection system for injecting fuel periodically into the combustion chambers of a multi-cylinder internal combustion engine, comprising

• a common rail for supplying fuel from a fuel supply through a common passageway simultaneously to locations, respectively, adjacent the combustion chambers of the multi-cylinder internal combustion engine;
• a plurality of fuel injectors fluidically connected with said common rail at said locations, respectively, for periodically injecting controlled quantities of fuel into corresponding combustion chambers, each said fuel injector having
• an injector body containing a metering chamber for receiving fuel from the common rail and at least one injection orifice for forming an open pathway for fuel to be injected into the corresponding combustion chamber, and
• an injector plunger mounted for reciprocal movement within said injector body to define successive cycles including an injection phase during which fuel is forced at high pressure through said injection orifice into the corresponding combustion chamber and a metering phase during which said common rail is connected fluidically with the corresponding metering chamber to cause fuel to be metered into said metering chamber and during which said injection orifice remains open thereby connecting fluidically said common rail with the corresponding combustion chamber through said metering chamber;
• a shut off valve mounted within said common rail upstream of said fuel injectors to isolate, when closed, said fuel injectors from the source of fuel under pressure to shut off the engine potentially causing at least one said injector plunger to be stopped while in its metering phase thereby creating a leakage path for fuel to flow from said common rail through said metering chamber into the corresponding combustion chamber;
• and
• leakage prevention means for preventing fuel flow into the combustion chamber of any said fuel injector that may be stopped in its metering phase by reducing the fuel pressure within said common rail downstream of said shut off valve, said leakage prevention means including
• an variable volume chamber fluidically connectable with the common rail and having an internal volume which increases a predetermined amount when expanded from a collapsed condition to an fully expanded condition, and
• expansion control means for causing said variable volume to be held in a collapsed condition during engine operation and to expand upon engine shutdown sufficiently to prevent the flow of fuel from any injector into the corresponding combustion chamber.