| 摘要 |
An air-fuel ratio control system for an internal combustion engine having an intake passage, an exhaust passage, air-fuel mixture supply unit, on-off type electro-magnetic valve for correcting the air-fuel ratio of the air-fuel mixture supplied by the air-fuel mixture supply unit, a dither signal generating circuit for producing a periodical dither signal having a waveform, a shift control circuit for shifting the level of the center of the dither signal, a driving circuit for producing a driving output according to the dither signal, and detecting means for detecting the concentration of oxygen in exhaust gases passing through the exhaust passage. The system is provided with a memory circuit unit for memorizing a peak level of output of the detecting circuit and for producing an output according to the memorized peak level, first circuit being applied with outputs of the detector and of the memory circuit for detecting deviation of the dither signal detected by the detector. A decision circuit is responsive to outputs of the first circuit for producing an output representing direction and amount of the deviation of the detected dither signal from the stoichiometric air-fuel ratio, and a second circuit responsive to the decision circuit output for providing dependent thereon a shifting amount for shifting the dither signal via the shift control circuit such that the deviation of the dither signal is corrected to the stoichiometric air-fuel ratio.
|
