Hydraulically-actuated fuel injector with direct control needle valve

摘要

A hydraulically actuated fuel injector includes an injector body having a needle control chamber, a nozzle chamber, and a nozzle outlet that opens to the nozzle chamber. Fuel within the injector is hydraulically pressurized during each injection cycle. A needle valve is positioned to reciprocate in the nozzle chamber between an open position in which the nozzle outlet is open and a closed position in which the nozzle outlet is closed. The needle valve includes a closing hydraulic surface exposed to pressure in the needle control chamber. A needle control valve is mounted within the injector body and is moveable between an off position in which the needle control chamber is opened to a source of high pressure fluid and an on position in which the needle control chamber is opened to a low pressure passage.