Solenoid operated unit injector having distinct timing, metering and

Abstract

A cam-operated, electronically controlled, unit fuel injector (2) including an injector body (4) containing a fluid timing circuit (20) and a fluid metering circuit (22) communicating with an injector cavity (14) within which is mounted a reciprocating plunger (16,76,78) operated by an injector cam (12) which causes the plunger (16,76,78) to experience first and second dwells during each injector cycle wherein fluid may flow in the timing circuit (20) but may not flow in the metering circuit (22) during the first dwell and may flow in the metering circuit (22) but may not flow in the timing circuit (20) during the second dwell and wherein a solenoid valve (44) is opened during the first dwell to control timing and is closed during the second dwell to control metering. Injector plunger (16) includes an inner plunger section (76) and an outer plunger section (78) mounted for independent reciprocal movement within the injector cavity (14) to define an injector chamber (80) adjacent the inner end of the injector cavity (14) and a variable volume timing chamber (90) between the inner and outer plunger sections. The timing chamber is filled with fuel during the first dwell to subsequent form a hydraulic link of variable effective length dependent upon the time of solenoid valve opening during the first dwell.