Variable flow rate valve for mechnically actuated fuel injector

A mechanically actuated electronically controlled fuel injector (MEUI) includes a first electrical actuator that controls the position of a spill valve, and a second electrical actuator to control pressure on a closing hydraulic surface associated with a directly operated needle valve. The fuel injector is actuated via rotation of a cam to move a plunger to displace fuel from a fuel pumping chamber either to a spill passage, or at high pressure out of a nozzle outlet of the fuel injector for an injection event. The minimum controllable fuel injection quantity, especially as it relates to small closely coupled post injections following a large main injection, is accomplished by the inclusion of a variable flow rate valve that restricts fluid flow from a needle control chamber toward a drain, but is relatively unrestricted to high pressure fluid flow toward the needle control chamber. The inclusion of the variable flow rate valve slows the rate at which pressure drops in the needle control chamber to commence an injection event, but permits a fast rate at which pressure may build in the needle control chamber to end an injection event. The result is a smaller post injection quantity and more controllability over the dwell time between injection events.