Patent ID: 7249722
Filing Date: 2007-07-31
Classification: F02M

Abstract:
1. A fuel injector comprising: a nozzle holder body defining a needle bore axially extending between a needle guide and a nozzle body defining a nozzle seat, said needle guide axially interrupted into upper and lower needle guide portions by a circumferential fuel inlet control volume having first upper and first lower metering edges, said nozzle holder body defining a fuel inlet passage communicating with said fuel inlet control volume; and an elongated needle valve received in said needle bore for axial reciprocation therein between a closed position and an open position, said needle valve having oppositely disposed tip and head ends axially separated by a needle valve shank, said tip end being disposed adjacent to and configured to engage said nozzle seat when said needle valve is in the closed position, said head end having an outside surface received within said needle guide and axially interrupted into outside surface upper and lower portions by a first control volume having second upper and second lower metering edges, said head end defining a fuel passage communicating between said first control volume and said needle bore axially below a bottom edge of said outside surface lower portion, the needle guide having a greater diameter than the nozzle seat to provide a differential area for hydraulically moving the needle valve away from engagement with said nozzle seat, the fuel inlet control volume being connected to receive periodic high pressure pulses of fuel for opening the needle valve against a closure bias, when the needle valve is in said closed position, said first upper metering edge and said second lower metering edge are axially spaced to define a circumferential fluid flow clearance and said lower needle guide portion axially overlaps with said outside surface lower portion, said axial overlap being greater than or equal to an axial dimension of said fluid flow clearance, whereby initial movement of said needle valve is produced by fuel flowing through said fluid flow clearance and said fuel passage to said needle bore.