US 4,561,400 A · Method of controlling air-fuel ratio

Abstract

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.sub.1 -Q.sub.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.sub.1 corresponding to the full closing of a throttle valve, the obstruction compensating learning correction coefficients FGQ.sub.2 -FGQ.sub.n allotted to all of the flowrate regions excluding the obstruction compensating learning correction coefficient FGQ.sub.1 allotted to the flow-rate region Q.sub.1 are simultaneously learned.

Claims10

Dependent claims

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.sub.1 -FGQ.sub.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.sub.1 -Q.sub.n the intake air flow rate belongs to;
renewing, in accordance with the measured air-fuel ratio, the learning correction coefficient FGQ.sub.1 for the flow rate regions Q.sub.1 when judging is made that the intake air flow rate Q belongs to the flow rate regions Q.sub.1 corresponding to an idle condition and the learning correction coefficient FGQ.sub.2 -FGQ.sub.n for respective flow rate regions Q.sub.2 -Q.sub.n, respectively, when judging is made that the intake air flow rate Q belongs to one of the flow rate regions Q.sub.2 -Q.sub.n, respectively.

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.sub.1 -FGQ.sub.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.sub.1 -Q.sub.n the intake air flow rate belongs to;
renewing the learning correction coefficients FGQ.sub.1 -FGQ.sub.n for the judged flow rate regions Q.sub.1 -Q.sub.n, respectively, in accordance with the measured air-fuel ratio;
decreasing the learning correction coefficients FGQ.sub.1 -FGQ.sub.n and increasing the learning correction coefficient FHAC when all learning correction coefficients FGQ.sub.1 -FGQ.sub.n are positive, and increasing the learning correction coefficients FGQ.sub.1 -FGQ.sub.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.sub.1 -Q.sub.n is judged.

2 more elements

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.sub.1 -FGQ.sub.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.sub.1 -Q.sub.n the intake air flow rate belongs to;
renewing, in accordance with the measured air-fuel ratio, the learning correction coefficients FGQ.sub.1 -FGQ.sub.n for respective flow rate regions Q.sub.1 -Q.sub.n in accordance with the judged one of flow rate Q.sub.1 -Q.sub.n.
determining a lower limit for the learning correction coefficient FGQ corresponding to the flow rate adjacent to the flow rate region Q.sub.1 by a line connecting a point P.sub.1 indicative of the learning correction coefficient FGQ.sub.1 to a point P.sub.2 indicative of zero of the learning correction coefficient FGQ at a predetermined flow rate within a predetermined flow rate region.

Dependencies are inferred from the claim text.

Method of controlling air-fuel ratio

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Method of controlling air-fuel ratio

Life of this patent

Abstract

Claims10