Rate shaping fuel injector with limited throttling

摘要

A closed needle injector assembly is provided which effectively permits low fueling quantity control in short duration injections and pilot quantity control in longer duration events without compromising energy efficiency, maximum fuel delivery rates nor requiring increased operating pressures. The closed needle injector assembly includes first and second needle valve elements and a throttle passage formed in the second needle valve element to restrict fuel flow through an injector orifice. The second needle valve element is telescopingly received within the first needle valve element. Respective control volumes and one or more injection control valves are used to control the movement of the needle valve elements. Operation of the assembly results in movement of the first needle valve element to an open position for throttling fuel flow through the throttle passage followed by subsequent lifting of the second needle valve element for longer duration injections.