Hydraulically-actuated fuel injector with direct control needle valve

Abstract

A hydraulically actuated fuel injector includes an injector body having an actuation fluid inlet, an actuation fluid cavity, a nozzle chamber open to a nozzle outlet and a needle control chamber. A hydraulic means within the injector pressurizes fuel in the nozzle chamber. The hydraulic means includes an actuation fluid control valve having a solenoid and is moveable between a first position in which the actuation fluid inlet is open to the actuation fluid cavity and a second position in which the actuation fluid inlet is closed to the actuation fluid cavity. A needle valve member 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 member includes a closing hydraulic surface exposed to pressure in the needle control chamber. A needle control valve that also utilizes the same solenoid is attached to the injector body and 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. The slower response time of the actuation fluid control valve allows for direct control of the fast responding needle valve.