Fuel injection timing control system of fuel-injection pump for diesel engines

A fuel injection timing control system for a diesel fuel injection pump (1) with an electromagnetic solenoid valve (26) in which an injection timing of fuel supplied from the diesel fuel injection pump (1) to a diesel fuel injector (16) is controllable by a duty cycle (DTCV) of the electromagnetic solenoid valve (26), said system comprising:

• a target injection timing setting circuit (step S1) for setting a target injection timing based on an engine operating condition;
• an actual injection timing detection circuit (step S2) for detecting an actual injection timing;
• a duty-cycle setting circuit (steps S3, S4, S5, S6, S7) for setting a duty cycle (DTCVP) of the electromagnetic solenoid valve (26) by comparing said target injection timing with said actual injection timing;
• an entry-into-dead-zone detection circuit (step S15) for detecting entry of said duty cycle (DTCVP) into a predetermined dead-zone;
• a duty-cycle limiting permission circuit (steps S16, S17, S18) for generating an enable signal of duty-cycle limitation processing with a predetermined delay time (TM1) from detection of the entry of said duty cycle into said predetermined dead-zone;
• and
• a duty-cycle limitation processing circuit (steps S19, S20, S21, S32, S34) being responsive to said enable signal from said duty-cycle limiting permission circuit for limiting said duty cycle (DTCV) to a predetermined duty cycle limiting value (LIM) so that said duty cycle comes out of said predetermined dead-zone.

A fuel injection timing control system for a diesel fuel injection pump (1), comprising:

• a pressure-differential operated timer piston (8), each piston end cooperating with a pump casing to define a high-pressure chamber (21) and a low-pressure chamber (23), said timer piston (8) mechanically linked to a pump plunger (6) for changing a set position of said pump plunger (6) through an axial movement of said timer piston (8) based on a pressure differential between said high-pressure and low-pressure chambers;
• a duty-cycle controlled electromagnetic solenoid valve (26) fluidly disposed in a communication passage (25-1, 25-2) intercommunicating said high-pressure and low-pressure chambers (21, 23) for causing a change in the set position of said pump plunger (6) by varying the pressure differential in response to a duty cycle (DTCV) of said electromagnetic solenoid valve (26), and for regulating an injection timing of fuel supplied from the diesel fuel injection pump (1) to a diesel fuel injector (16) with the change in the set position of said pump plunger (6);
• a target injection timing setting circuit (step S1) for setting a target injection timing based on an engine operating condition;
• an actual injection timing detection circuit (step S2) for detecting an actual injection timing;
• a duty-cycle setting circuit (steps S3, S4, S5, S6, S7) for setting a duty cycle (DTCVP) of said electromagnetic solenoid valve (26) by comparing said target injection timing with said actual injection timing;
• an entry-into-dead-zone detection circuit (step S15) for detecting entry of said duty cycle (DTCVP) into a predetermined lower dead-zone;
• a duty-cycle limiting permission circuit (steps S16, S17, S18) for generating an enable signal of duty-cycle limitation processing with a predetermined delay time (TM1) from detection of the entry of said duty cycle into said predetermined lower dead-zone;
• and
• a duty-cycle limitation processing circuit (steps S19, S20, S21, S32, S34) being responsive to said enable signal from said duty-cycle limiting permission circuit for limiting said duty cycle (DTCV) to a predetermined duty cycle lower limiting value (LIM) so that said duty cycle comes out of said predetermined lower dead-zone.