Hydraulically-actuated fuel injector with idle stability port

摘要

A hydraulically-actuated fuel injector includes an injector body having a nozzle chamber that opens to a nozzle outlet and a plunger bore, and further has a prime spill port and an idle stability port that open to the plunger bore. A hydraulic means for pressurizing fuel in the nozzle chamber includes a plunger mounted to reciprocate in the plunger bore between a retracted position and an advanced position. A portion of the plunger bore and plunger define a fuel pressurization chamber. A needle valve member is mounted 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. A portion of the plunger blocks the prime spill port when the plunger is in its retracted position. A different portion of the plunger blocks the idle stability port when the plunger is in its retracted position. The prime spill port opens to the fuel pressurization chamber over part of the plunger stroke between its retracted position and its advanced position. The idle stability port opens to the fuel pressurization chamber over a different part of the plunger stroke between its retracted position and its advanced position. The prime spill port has a relatively unrestricted flow area, whereas the idle stability port has a relatively restricted flow area about equal to that of the nozzle outlet.