Abstract: The fill metered hydraulically actuated fuel injection system of the present invention utilizes an actuation fluid, preferably lubricating oil, as its actuation medium that is separate and different from the fuel fluid which is actually injected into the engine. Injectors according to the present invention are hydraulically actuated and include a conventional VOP type needle check, and fuel is pressurized by a plunger driven by an intensifier piston. The end of each injection event is achieved when the plunger and piston reach the end of their strokes, which provides for an abrupt end to each injection event. An abrupt end to injection is further accomplished by providing a pressure relief passage in the plunger that relieves pressure acting on the needle check at the end of injection in order to both quickly dissipate residual fuel pressure and allow the needle check to close more rapidly.

Abstract: A hydraulically actuated fuel injector includes an intensifier piston with a tapered or conical protuberance and an injector body with a conical seat. During the pre-injection stage, the piston is spring loaded to seat its conical protuberance against the conical seat of the injector body. To start the injection, actuation fluid is admitted to the injector. The injector actuation volume is pressurized and the pressure acts initially only on the top of the conical protuberance of the piston. The displacement of the piston is temporarily retarded during the first stage of injection due to a throttling effect in allowing the high pressure fluid to act on the remaining top surface of the piston. The throttling effect is provided by the relatively narrow flow area between the conical protuberance and the conically shaped seat.

Abstract: A fuel injector nozzle assembly has a housing defining a blind bore and at least one injection orifice at the bottom portion thereof and a fuel injection passage fluidly connecting the bottom portion of the blind bore and a source of pressurized fluid. A primary check is disposed in the blind bore. A spring between the housing and the check establishes a first valve opening pressure. A secondary check is slidably disposed in the fuel injection passage, defining an aperture therethrough. A secondary check spring is disposed between the secondary check and the housing, establishing a second valve opening pressure.