A fuel injector for use in delivering fuel to an internal combustion engine includes 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 nozzle needle is controlled by fuel pressure within a control chamber. A nozzle control valve controls fuel flow into and out of the control chamber to pressurize and depressurize the control chamber, respectively. The fuel injector also includes a variable flow passage in communication with the control chamber through which fuel flows out of the control chamber at a variable rate throughout the range of movement of the valve needle so that movement of the valve needle is damped to a greater extent as it approaches the fully-open position.
1. 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; and
a nozzle control valve for controlling fuel flow into and out of the control chamber to pressurise and depressurise the control chamber, respectively,
the fuel injector further comprising 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, wherein the injector further comprises an additional flow passage in communication with the control chamber through which fuel flows out of the control chamber;
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.
2. A fuel injector as claimed in claim 1 , wherein the additional flow passage presents a fixed restriction to the fuel flow out of the control chamber.
3. A fuel injector as claimed claim 1 , 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.
4. A fuel injector as claimed in claim 1 , 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.
5. A fuel injector as claimed in claim 4 , wherein an entry port to the flow passage into the control chamber is uncovered by the valve needle or the part carried thereby to a lesser degree when the valve needle is in the fully-open position compared to the extent of uncovering when the valve needle is in the fully-closed position.
6. A fuel injector as claimed in claim 5 , wherein the entry port to the flow passage is fully covered by the valve needle or the part carried thereby when the valve needle is in the fully-open position.
7. A fuel injector as claimed in claim 5 , wherein the entry port to the flow passage is at least partially uncovered by the valve needle or the part carried thereby when the valve needle is in the fully-closed position.
8. A fuel injector as claimed in claim 7 , wherein the entry port to the flow passage is fully uncovered when the valve needle is in the fully-closed position.
9. A fuel injector as claimed in claim 8 , wherein the entry port to the flow passage remains fully uncovered for a portion of the range of movement of the valve needle immediately following initial movement away from the fully-closed position.
10. A fuel injector as claimed in claim 1 , wherein the nozzle control valve is a three-way control valve.
11. A fuel injector as claimed in claim 1 , wherein the control chamber is defined in an upper surface of an injector body within which the valve needle or a part carried thereby is guided and wherein a shim plate closes the open end of the control chamber.
12. A fuel injector as claimed in claim 11 , wherein the shim plate is located between the injector body and a control valve housing for the nozzle control valve, the nozzle control valve having first and second valve seats defined by the injector body and the nozzle control valve, respectively.
13. A fuel injector as claimed in claim 12 , wherein the shim plate is provided with a shim plate chamber which extends through the shim plate and receives a portion of a valve pin of the control valve.
14. 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.
15. 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.
16. A fuel injector as claimed in claim 1 wherein fuel flows into the control chamber through the variable flow passage arrangement and the additional flow passage in order to move the valve needle to the fully-closed position.
17. A fuel injector as claimed in claim 14 wherein fuel flows into the control chamber through the variable flow passage arrangement and the additional flow passage in order to move the valve needle to the fully-closed position.
18. A fuel injector as claimed in claim 15 wherein fuel flows into the control chamber through the variable flow passage arrangement and the additional flow passage in order to move the valve needle to the fully-closed position.