Importance

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Abstract

An Air/Fuel mixture control system for an internal combustion engine which uses a closed loop controller for varying an air/fuel mixture in response to the voltage output of the engine's exhaust gas oxygen sensor. The oxygen sensor will produce a voltage output which is classified in a range extending from very rich, net rich, net lean or very lean depending upon the sensed voltage output in milli-volts. The controller responds to an onset of a lean or rich exhaust signal, representative of either too much or too little oxygen, by instructing the fuel injectors to either increase or decrease the fuel delivery rate to a predetermined rich step value or lean step value. The delivery rate at the rich or lean step value is maintained until the onset of either a rich or lean exhaust indication or until a predetermined rich or lean step duration expires. The controller then responds to the expiration of the rich or lean step duration by selectively increasing or decreasing the fuel delivery rate in a progressive manner from the predetermined rich or lean step values until a rich or lean exhaust indication is produced. The controller than responds to the onset of each rich or lean exhaust indication by abruptly decreasing or increasing the fuel delivery rate to a predetermined lean or rich step value as well as contemporaneously calculating a corrected rich or lean step value which is greater than the initial rich or lean step value. The fuel delivery rate is then maintained at the corrected rich or lean value until the onset of either a lean or rich exhaust indication, at which point the process is repeated. The method of the fuel control system functions to minimize the fluctuations and magnitude of the rich and lean step values and to thereby accomplish more precise adjustments of fuel delivery so as to achieve stoichemetry in the fuel/air mixture.

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First Claim