Internal combustion engine electronic ignition control system

Abstract

An electronic ignition control system for internal combustion engine, notably for motor vehicles, which comprises a rotary member revolving at the engine velocity and provided with at least two reference marks of which the positions correspond to the maximum ignition advance angle and to the minimum ignition advance angle, respectively, said reference marks defining at least one area on said rotary member, a sensor disposed in close vicinity of said rotary member so as to detect the moments of passage of said reference marks and at least one up-and-down counter for counting pulses, said rotary member further comprising a third reference mark separate from the first two reference marks aforesaid so as to define two successive areas (A = 12, 13; B = 13, 14) scanned in succession by said sensor, while a first up-and-down counter positively counts the pulses from a first clock system during the passage of said first area (A) and negatively counts, during the passage of the second area (B), the pulses from a second clock system adapted to emit pulses at a frequency programmable according to the desired ignition advance law, the resetting of said up-and-down counter being utilized for producing the ignition spark.