Abstract: A fuel injector comprising a valve needle, engagable with the seating to control fuel flow through a fuel outlet, the valve needle having a thrust surface oriented such that the application of fuel under pressure thereto applies a force to the valve needle urging the valve needle away from the seating. The fuel injector also comprises a valve member for controlling fuel pressure within a control chamber and a piston member slidable within a bore and defining, with the bore, the control chamber. The piston member is exposed to fuel pressure within the control chamber and is arranged to transmit a force applied by the fuel pressure to the valve needle. The piston member has an effective surface area exposed to the fuel pressure which is greater than that of the thrust surface so as to urge the valve needle towards the seating.

Abstract: A fuel injector comprising a valve needle, engagable with the seating to control fuel flow through a fuel outlet, the valve needle having a thrust surface oriented such that the application of fuel under pressure thereto applies a force to the valve needle urging the valve needle away from the seating. The fuel injector also comprises a valve member for controlling fuel pressure within a control chamber and a piston member slidable within a bore and defining, with the bore, the control chamber. The piston member is exposed to fuel pressure within the control chamber and is arranged to transmit a force applied by the fuel pressure to the valve needle. The piston member has an effective surface area exposed to the fuel pressure which is greater than that of the thrust surface so as to urge the valve needle towards the seating.