OPEN NOZZLE FUEL INJECTOR HAVING DRIVE TRAIN WEAR COMPENSATION

摘要

A cam operated open nozzle fuel injector (12) is provided comprising a reciprocating plunger assembly including an outer plunger (32), an inner plunger (36) and a variable volume timing chamber (52) located between the plungers. A hold down force generating means includes a cam having a hold down cam or ramp portion (106) for maintaining the inner plunger in an innermost position against the inner end of the injector body with a sufficient hold down force during each hold down period throughout injector operation independently of injector train wear. The hold down cam portion operates to move the outer plunger inwardly towards the inner plunger throughout a substantial portion of the hold down period. The hold down cam portion functions to compensate for fuel drainage from the timing chambers so as to maintain a predetermined pressure in the timing chamber corresponding to a desired hold down force.