Processor based fuel injection control system

Abstract

An electrical control unit having a microprocessor and a network of counters for governing the electrical operation of a fuel control valve of a fuel injection pump. Four subtraction counters are preset by the processor; one is used as a time counter indexed by time pulses and three are used as pump angle counters indexed by pump clock pulses generated for each predetermined increment of pump rotation. Two of the pump angle counters are employed to precisely open and close the valve for regulating the fuel injection timing and quantity--the total quantity in a normal mode of operation and a pilot quantity in a pilot injection mode. In the pilot mode, the third pump angle counter regulates the main injection quantity and the time counter regulates the time delay between the pilot and main injections. Two addition counters are indexed by the pump clock pulses to determine a count of the pump angle between pump and engine reference points (ERA count) and a count of the pump angle of the valve closure response time (VRA count). The ERA and VRA counts are used by the processor in determining the preset counts for the subtraction counters. Two fixed angle counters are operated by engine clock pulses generated for each predetermined increment of engine rotation, to start and stop a speed counter indexed by the time pulses to determine the instantaneous engine speed between power strokes for fuel balancing at engine idle.