US Patent 7588012 Fuel system having variable injection pressure

A fuel injector for a work machine is disclosed. The fuel injector has nozzle member having at least one orifice and a needle valve element having a tip end. The needle valve element is axially movable to selectively allow and block fuel flow through the at least one orifice with the tip end. The fuel injector also has at least one supply passageway in communication with the tip end of the needle valve and a variable restrictive device disposed within the at least one supply passageway.