Apparatus and method for controlling air-fuel ratio of an internal combustion engine
AssigneeUnisia Jecs Corporation
InventorAkira Uchikawa
Life of this patent
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Abstract
An air-fuel ratio feedback correction coefficient for correcting a fuel supply quantity to an engine is proportional-plus-integral controlled based on an output from an oxygen sensor for detecting oxygen concentration in the exhaust gases. When the oxygen sensor is in an inactive condition, deviation of an air-fuel ratio control point in the air-fuel ratio feedback control is detected, and an operating quantity in the proportional-plus-integral control is corrected so as to reduce the detected deviation.
Claims20
An apparatus for controlling an air-fuel ratio of an internal combustion engine, said apparatus comprising:
- an air-fuel ratio sensor provided in an engine exhaust passage, being responsive to the concentration of specific constituents of the exhaust gas which change with an air-fuel ratio of the engine intake mixture, thus causing a change in the output value;
- air-fuel ratio feedback control means for feedback controlling a fuel supply quantity to the engine so that the air-fuel ratio of the engine intake mixture approaches a target air-fuel ratio, based on an output value from said air-fuel ratio sensor;
- inactive condition detection means for detecting an inactive condition of said air-fuel ratio sensor;
- air-fuel ratio deviation detection means for detecting deviation from the target air-fuel ratio of an air-fuel ratio control point in said air-fuel ratio feedback control means, when the inactive condition of said air-fuel ratio sensor is detected by said inactive condition detection means;
- and
- control characteristics correction means for correcting the characteristics of said air-fuel ratio feedback control means in a direction to reduce the deviation of the air-fuel ratio control point detected by said air-fuel ratio deviation detection means.
A method of controlling an air-fuel ratio of an internal combustion engine wherein an air-fuel ratio sensor is provided in an engine exhaust passage, said sensor being responsive to the concentration of specific constituents of the exhaust gas which change with an air-fuel ratio of the engine intake mixture, thus causing a change in the output value, said method including:
- feedback controlling a fuel supply quantity to the engine so that the air-fuel ratio of the engine intake mixture approaches a target air-fuel ratio, based on an output value from said air-fuel ratio sensor;
- detecting an inactive condition of said air-fuel ratio sensor;
- detecting a deviation from the target air-fuel ratio of an air-fuel ratio control point in said air-fuel ratio feedback control under said inactive condition;
- and correcting the characteristics of said air-fuel ratio feedback control in a direction so as to reduce the deviation of said air-fuel ratio control point.
Dependencies are inferred from the claim text.