Fuel injector

A fuel injector for use in delivering fuel to an internal combustion engine, the fuel injector comprising:

• a nozzle having a valve needle which is moveable with respect to a valve needle seating through a range of movement between a fully-closed position and a fully-open position to control fuel delivery through at least one nozzle outlet, whereby movement of the valve needle is controlled by fuel pressure within a control chamber;
• a nozzle control valve for controlling fuel flow into and out of the control chamber to pressurise and depressurise the control chamber, respectively;
• a variable flow passage arrangement in communication with the control chamber for varying the rate of flow of fuel out of the control chamber throughout the range of movement of the valve needle such that movement of the valve needle is damped to a greater extent as it approaches the fully-open position compared to initial movement away from the fully-closed position;
• and
• an additional flow passage in communication with the control chamber through which fuel flows out of the control chamber;
• wherein the variable flow passage arrangement is provided by cooperation between the valve needle or a part carried thereby and a flow passage into the control chamber, whereby the valve needle or the part carried thereby cooperates with the flow passage to a variable degree throughout the range of movement of the valve needle to provide a variable rate of flow of fuel through the variable flow passage arrangement;
• whereby fuel flows into the control chamber through at least one of the variable flow passage arrangement and the additional flow passage in order to move the valve needle to the fully-closed position.

A fuel injector for use in delivering fuel to an internal combustion engine, the fuel injector comprising:

• a nozzle having a valve needle which is moveable with respect to a valve needle seating through a range of movement between a fully-closed position and a fully-open position to control fuel delivery through at least one nozzle outlet, whereby movement of the valve needle is controlled by fuel pressure within a control chamber;
• a nozzle control valve for controlling fuel flow into and out of the control chamber to pressurise and depressurise the control chamber, respectively,
• a variable flow passage arrangement in communication with the control chamber for varying the rate of flow of fuel out of the control chamber throughout the range of movement of the valve needle such that movement of the valve needle is damped to a greater extent as it approaches the fully-open position compared to initial movement away from the fully-closed position;
• and
• an additional flow passage in communication with the control chamber through which fuel flows out of the control chamber;
• wherein the valve needle or a part carried thereby includes a formation at its end remote from the valve needle seating which cooperates with the additional flow passage to provide a further localised damping effect for the valve needle just prior to it reaching its fully-open position;
• whereby fuel flows into the control chamber through at least one of the variable flow passage arrangement and the additional flow passage in order to move the valve needle to the fully-closed position.