| 摘要 |
A digital closed loop fuel control system for an internal combustion engine having a zirconia sensor which provides a signal changing abruptly between first and second values as the air/fuel ratio varies through a stoichiometric ratio. The output of the zirconia sensor is sampled at constant frequency sampling intervals and an up/down counter is set in one of its counting modes as a function of whether the air/fuel ratio is less than or greater than the stoichiometric ratio. During each sampling interval, a first number of clock pulses from a clock pulse generator are coupled to the up/down counter when the air/fuel ratio is greater than a stoichiometric ratio and a second number of the clock pulses are coupled to the up/down counter when the air/fuel ratio is less than the stoichiometric ratio. The air/fuel ratio of the fuel mixture supplied to the internal combustion engine is varied in accord with the net count in the up/down counter so that the average air/fuel ratio is offset from the stoichiometric air/fuel ratio by a value determined by the difference in the first and second numbers of clock pulses supplied to the up/down counter. |
