Patent ID: 7451743

Claim:
A unit fuel injector comprising: a pump including a plunger in a pumping chamber; a nozzle that can be opened and closed by a control valve, wherein an injection event will occur when the control valve is actuated and will not occur when the control valve is not actuated; an accumulator fluidly connected between the pump and the nozzle to store pressurized fuel at high pressure for injection events independent of the pump; a fuel supply for supplying fuel to the pump and to the nozzle by way of the accumulator; and an accumulator fill valve assembly mounted between the pump and the nozzle in high pressure fluid communication with the accumulator and operable between an open condition and a closed condition, wherein the accumulator fill valve assembly comprises a spool, one portion of which is in fluid communication with the fuel supply, and another portion of which is in fluid communication with the accumulator, whereby in the open condition, the accumulator is in fluid communication with the pumping chamber and in the closed condition, the accumulator is not in fluid communication with the pumping chamber and when pressure in the accumulator exceeds a set point the spool will be moved against pressure in the fuel supply to the closed condition.