Fuel Injector
A dual-mode fuel injector has an internal part containing a variable volume chamber space which fills with fuel at common rail pressure and a plunger which is operable to force fuel out of the variable volume chamber space and to be injected out of the nozzle through the injection orifices at amplified pressure greater than common rail pressure. The plunger and the internal part have respective surfaces which come into mutual abutment during filling of the variable volume chamber space with fuel at common rail pressure and which, when in mutual abutment, create a seal which seals fuel in the variable volume chamber space against escape from the variable volume chamber space past the seal.
1 . A fuel injector which is selectively operable to a common rail injection mode and an amplified pressure injection mode, the fuel injector having a longitudinal axis and comprising:
a body having a fuel inlet port through which liquid fuel is introduced into the body at a common rail pressure;
a nozzle assembly disposed at an axial end of the body, the nozzle assembly comprising a nozzle having injection orifices at a tip end of the nozzle and a needle which is disposed within the nozzle and is biased axially against a seat to close the injection orifices to fuel in the body;
an electric injection control actuator which when energized while the fuel injector is in common rail injection mode, is effective to cause the needle to be unseated from the seat and fuel to be injected out of the nozzle through the injection orifices at common rail pressure;
a pressure-amplifying mechanism which is internal to the body and comprises an internal part containing a variable volume chamber space which, when the electric injection control actuator is not being energized, fills with fuel at common rail pressure from the fuel inlet port, and a plunger which when the electric injection control actuator is energized to unseat the needle from the seat with the fuel injector in the amplified pressure injection mode, is operable to force fuel out of the variable volume chamber space and to be injected out of the nozzle through the injection orifices at amplified pressure greater than common rail pressure; and
the plunger and the internal part comprising respective surfaces which come into mutual abutment during filling of the variable volume chamber space with fuel at common rail pressure and which, when in mutual abutment, create a seal which seals fuel in the variable volume chamber space against escape from the variable volume chamber space past the seal.
2 . The fuel injector as set forth in claim 1 in which the respective surfaces which come into mutual abutment during filling of the variable volume chamber space with fuel at common rail pressure comprise respective frustoconical surfaces having different cone angles.
3 . The fuel injector as set forth in claim 1 in which the respective surfaces which come into mutual abutment during filling of the variable volume chamber space with fuel at common rail pressure comprise respective flat surfaces which are perpendicular to the longitudinal axis.
4 . The fuel injector as set forth in claim 3 in which one of the respective flat surfaces comprises a surface of a circular washer secured in place on the internal part.
5 . The fuel injector as set forth in claim 3 in which one of the respective flat surfaces comprises a surface of a part assembled to the plunger by a fastener.