Fuel pump-injector unitary assembly for internal combustion engine

A fuel pump-injector unitary assembly for an internal combustion engine, comprising an injector body having an axial bore with the bottom traversed by at least one fuel spray nozzle, at least one fuel inlet duct opening in said axial bore near the bottom thereof, a plunger or needle slidable in said bore between a first position wherein said plunger is spaced from the bore bottom, and a second position corresponding to the position of the end of injection, where the tapered lower end of the plunger obturates the spray nozzles, said pump-injector unitary assembly comprising means for metering the fuel quantity injected through said spray nozzle, said metering means comprising a transfer passageway provided in the plunger and communicating at a first end with a fuel discharge duct when the plunger is in its first position, with said fuel discharge duct opening through the wall of said axial bore, a metering ring surrounding said plunger and located in an annular chamber of the injector body, with said bore and said discharge duct opening in said annular chamber, and said metering ring having an upper edge of which at least a portion co-operates with the first end of said transfer passageway to effect fuel metering, and means for regulating the position of the ring in the injector body, said transfer passageway having its second end opening at the free or lower end of the plunger and said portion of the upper edge of the metering ring defining the beginning of the injection by obturating said first end of said longitudinal passageway.