초록 ▼

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 seati

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.

대표청구항 ▼

1. A fuel injector having a fuel outlet comprising:a valve needle, moveable within a first bore and engageable with a seating to control fuel flow through the outlet, the valve needle having a thrust surface having a first effective surface area and oriented such that the application of fuel under p

1. A fuel injector having a fuel outlet comprising:a valve needle, moveable within a first bore and engageable with a seating to control fuel flow through the outlet, the valve needle having a thrust surface having a first effective surface area and 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, and wherein the valve needle includes an upper guide region including a first surface, at an end remote from the fuel outlet, which is arranged to cooperate with an adjacent region of the first bore so as to guide movement of the valve needle within the first bore; a valve member for controlling fuel pressure within a control chamber; a housing defining a second bore comprising a first bore portion and a second bore portion, the first bore portion having a first diameter and the second bore portion having a second diameter which is greater than the first diameter of the first bore portion; a piston member consisting of no more than one cylinder including a substantially constant diameter and a frusto-conical end and being slidable within the first bore portion and the second bore portion and configured to at least partially define the control chamber within the second bore portion, the piston member being exposed to fuel pressure within the control chamber and being arranged to transmit a force applied by the fuel pressure to the valve needle, wherein the piston member has a second effective surface area exposed to the fuel pressure which is greater than the first effective surface area of the thrust surface so as to urge the valve needle towards the seating; and a thrust pin member engaged between the piston member and the valve needle, such that the thrust pin member is in engagement with a second surface of the upper guide region of the valve needle, the thrust pin member being configured to transmit the force applied to the piston member by the fuel pressure to the valve needle, wherein the thrust pin member has an axial length which is sufficiently short to ensure flexing of the thrust pin member is limited following reduction in fuel pressure within the control chamber.