초록 ▼

There is disclosed a method of controlling the air-fuel ratio in which the fuel injection rate is controlled by the learning correction coefficient for obstruction of the air flow motor so as to compensate the aging of the air flow meter, and there are a plurality of learning correction coefficients

There is disclosed a method of controlling the air-fuel ratio in which the fuel injection rate is controlled by the learning correction coefficient for obstruction of the air flow motor so as to compensate the aging of the air flow meter, and there are a plurality of learning correction coefficients allotted to the predetermined intake air flow rate regions Q 1 -Q n . The intake air flow rate is measured and the judgement is made as to which region the measured flow rate belongs to. When the measured intake air flowrate is judged to be in any flowrate region other than the flowrate Q 1 corresponding to the full closing of a throttle valve, the obstruction compensating learning correction coefficients FGQ 2 -FGQ n allotted to all of the flowrate regions excluding the obstruction compensating learning correction coefficient FGQ 1 allotted to the flow-rate region Q 1 are simultaneously learned.

대표청구항 ▼

1. A method of controlling air-fuel ratio wherein a basic fuel injection time duration is determined in accordance with an intake air flow rate measured by means for measuring the intake air flow rate and an engine rotational speed, then the basic fuel injection time duration is corrected such that

1. A method of controlling air-fuel ratio wherein a basic fuel injection time duration is determined in accordance with an intake air flow rate measured by means for measuring the intake air flow rate and an engine rotational speed, then the basic fuel injection time duration is corrected such that the air-fuel ratio becomes the stoichiometric air-fuel ratio, and an aging of said intake air flow rate measuring means is compensated by learning correction coefficients FGQ 1 -FGQ n for obstruction of said intake air flow rate measuring means, said method comprising the steps of: judging the intake air flow rate as to which flow rate regions Q 1 -Q n the intake air flow rate belongs to; renewing, in accordance with the measured air-fuel ratio, the learning correction coefficient FGQ 1 for the flow rate regions Q 1 when judging is made that the intake air flow rate Q belongs to the flow rate regions Q 1 corresponding to an idle condition and the learning correction coefficient FGQ 2 -FGQ n for respective flow rate regions Q 2 -Q n, respectively, when judging is made that the intake air flow rate Q belongs to one of the flow rate regions Q 2 -Q n, respectively. 2. A method of controlling air-fuel ratio as set forth in claim 1, wherein each of the learning correction coefficients FGQ 1 -FGQ n is increased in response to the air-fuel ratio being rich side of the stoichiometric air-fuel ratio and is decreased in response to the air-fuel ratio being lean side of the stoichiometric air-fuel ratio. 3. A method of controlling air-fuel ratio as set forth in claim 1, wherein a feedback correction coefficient FAF is calculated in accordance with the measured air-fuel ratio so as to increase in response to the air-fuel ratio being lean side of the stoichiometric air-fuel ratio and decrease in response to the air-fuel ratio being rich side of the stoichiometric air-fuel ratio, and the learning correction coefficient FGQ 1 -FGQ n is increased when a mean value of the feedback correction coefficient FAF is less than a reference value and decreased when the mean value of the feedback correction coefficient FAF is reference value or more. 4. A method of controlling air-fuel ratio wherein a basic fuel injection time duration is determined in accordance with an intake air flow rate measured by means for measuring the intake air flow rate and an engine rotational speed, then the basic fuel injection time duration is corrected such that the air-fuel ratio becomes the stoichiometric air-fuel ratio, an aging of said intake air flow rate measuring means is compensated by learning correction coefficients FGQ 1 -FGQ n for obstruction of said intake air flow rate measuring means and an influence of altitude on the air-fuel ratio is prevented by learning correction coefficient FHAC for altitude of highlands, said method comprising the steps of: judging the intake air flow rate as to which one of flow rate regions Q 1 -Q n the intake air flow rate belongs to; renewing the learning correction coefficients FGQ 1 -FGQ n for the judged flow rate regions Q 1 -Q n, respectively, in accordance with the measured air-fuel ratio; decreasing the learning correction coefficients FGQ 1 -FGQ n and increasing the learning correction coefficient FHAC when all learning correction coefficients FGQ 1 -FGQ n are positive, and increasing the learning correction coefficients FGQ 1 -FGQ n and decreasing the learning correction coefficient FHAC when all learning correction coefficients are negative; and renewing the learning correction coefficient FHAC when each of the flow rate regions Q 1 -Q n is judged. 5. A method of controlling air-fuel ratio as set forth in claim 4, wherein each of the learning correction coefficients FGQ 1 -FGQ n and the learning correction coefficient FHAC are increased in response to the air-fuel ratio being rich side of the stoichiometric air-fuel ratio, respectively, and are decreased in response to the air-fuel ratio being lean side of the stoichiometric air-fuel ratio, respectively. 6. A method of controlling air-fuel ratio as set forth in claim 1, wherein a feedback correction coefficient FAF is calculated in accordance with the measured air-fuel ratio so as to increase in response to the air-fuel ratio being lean side of the stoichiometric air-fuel ratio and decrease in response to the air-fuel ratio being rich side of the stoichiometric air-fuel ratio, and the learning correction coefficient FGQ 1 -FGQ n and the learning correction coefficient FHAC are increased when a mean value of the feedback correction coefficient FAF is less than a reference value, respectively, and decreased when the mean value of the feedback correction coefficient FAF is reference value or more, respectively. 7. A method of controlling an air-fuel ratio as set forth in claim 4, wherein: a lower limit for learning correction coefficient FHAC is set on the basis of the altitude compensating learning correction coefficient FHAC computed when the throttle valve is fully closed; in the flowrate region Q n other than the flow rate region Q 1, if the altitude compensating learning correction coefficient FHAC is less than the lower limit for learning correction coefficient FHAC, the altitude compensating learning correction coefficient FHAC is regarded as the lower limit thereof. 8. A method of controlling air-fuel ratio wherein a basic fuel injection time duration is determined in accordance with an intake air flow rate measured by means for measuring the intake air flow rate and an engine rotational speed, then the basic fuel injection time duration is corrected such that the air-fuel ratio becomes the stoiohiometric air-fuel ratio, and an aging of said intake air flow rate measuring means is compensated by learning correction coefficients FGQ 1 -FGQ n for obstruction of said intake air flow rate measuring means, said method comprising the steps of: judging the intake air flow rate as to which flow rate regions Q 1 -Q n the intake air flow rate belongs to; renewing, in accordance with the measured air-fuel ratio, the learning correction coefficients FGQ 1 -FGQ n for respective flow rate regions Q 1 -Q n in accordance with the judged one of flow rate Q 1 -Q n . determining a lower limit for the learning correction coefficient FGQ corresponding to the flow rate adjacent to the flow rate region Q 1 by a line connecting a point P 1 indicative of the learning correction coefficient FGQ 1 to a point P 2 indicative of zero of the learning correction coefficient FGQ at a predetermined flow rate within a predetermined flow rate region. 9. A method of controlling air-fuel ratio as set forth in claim 8, wherein each of the learning correction coefficients FGQ 1 -FGQ n is increased in response to the air-fuel ratio being rich side of the stoichiometric air-fuel ratio and is decreased in response to the air-fuel ratio being lean side of the stoiohiometric air-fuel ratio. 10. A method of controlling air-fuel ratio as set forth in claim 8, wherein a feedback correction coefficient FAF is calculated in accordance with the measured air-fuel ratio so as to increase in response to the air-fuel ratio being lean side of the stoichiometric air-fuel ratio and decrease in response to the air-fuel ratio being rich side of the stoichiometric air-fuel ratio, and the learning correction coefficient FGQ 1 -FGQ n is increased when a mean value of the feedback correction coefficient FAF is less than a reference value and decreased when the mean value of the feedback correction coefficient FAF is reference value or more.