Fuel injector and method for controlling the same

A method of controlling a fuel injector comprising a nozzle having a valve needle movable between a closed position and an open position in response to fuel pressure within a control chamber;

• the method comprising selectively operating first and second nozzle control valves to control fuel flow into and out of the control chamber;
• wherein the first nozzle control valve is selectively operated to open a first fluid pathway to a first drain line to reduce fuel pressure within the control chamber;
• the first nozzle control valve is also selectively operated to open a second fluid pathway to a high pressure supply line to increase fuel pressure within the control chamber;
• the second nozzle control valve being selectively operated to open a third fluid pathway to a second drain line to reduce fuel pressure within the control chamber;
• and
• the second nozzle control valve is also operated to place the control chamber in fluid communication with the high pressure supply line to increase fuel pressure within the control chamber.

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 closed position and an 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 within a nozzle chamber, wherein the nozzle chamber is in constant fluid communication with a high pressure supply line, wherein fuel pressure within the control chamber urges the valve needle toward the closed position, and wherein fuel pressure within the nozzle chamber urges the valve needle toward the open position;
• and
• first and second nozzle control valves for controlling fuel flow into and out of the control chamber to pressurise and depressurise the control chamber;
• wherein said first nozzle control valve is operable selectively to place the control chamber in fluid communication with a first fuel drain;
• said first nozzle control valve also is operable selectively to place the control chamber in fluid communication with the high pressure supply line and the nozzle chamber;
• said second nozzle control valve is operable selectively to place the control chamber in fluid communication with a second fuel drain;
• and
• said second nozzle control valve is operable to place the control chamber in fluid communication with the high pressure supply line
• said first nozzle control valve is operable to prevent fluid communication between said nozzle chamber and said control chamber when fluid communication is provided between said control chamber and said first fuel drain.