US 5,209,206 A · Air-fuel ratio control system

Abstract

An air-fuel ratio control system compares an air-fuel ratio indicated by air-fuel ratio information from an air-fuel ratio sensor and a target air-fuel ratio determined depending on operating conditions of a motor vehicle which incorporates the air-fuel ratio control system, for reliably determining at least a failure of the air-fuel ratio sensor. When a failure of the air-fuel ratio sensor is detected, an air-fuel ratio feedback control process is stopped or the air-fuel ratio sensor is disabled, preventing the air-fuel ratio from being corrected in error based on an output signal from the air-fuel ratio sensor which has failed. Therefore, the air-fuel ratio control system prevents problems such as poor exhaust gas purification, reduced drivability, and unstable engine idling from taking place.

Claims11

Dependent claims

An air-fuel ratio control system for an internal combustion engine on a motor vehicle, comprising:

an air-fuel ratio sensor for producing an air-fuel ratio signal indicative of the concentration of oxygen in an exhaust gas produced by a burned air-fuel mixture in the internal combustion engine;
first means comprising failure determining means responsive to an output signal from said air-fuel ratio sensor and a target air-fuel ratio determined depending on operating conditions of the motor vehicle, for determining at least an irreparable failure of said air-fuel ratio sensor through comparison between said output signal and said target air-fuel ratio;
air-fuel ratio feedback control means for correcting an air-fuel ratio correction according to at least said air-fuel ratio signal so that an actual air-fuel ratio of the internal combustion engine is equal to said target air-fuel ratio;
and
second means comprising failure processing means for disabling said air-fuel ratio feedback control means and said air-fuel ratio sensor in response to an output signal from said failure determining means which indicates an irreparable failure of said air-fuel ratio sensor.

2 more elements

A method for controlling air-fuel ratio for an internal combustion engine on a motor vehicle, comprising the steps of:

(a) producing an air-fuel ratio signal by an air-fuel ratio sensor indicative of the concentration of oxygen in an exhaust gas produced by a burned air-fuel mixture in the internal combustion engine;
(b) comparing an output signal from said air-fuel ratio sensor and a target air-fuel ratio determined by operating conditions of the motor vehicle;
(c) determining at least an irreparable failure of said air-fuel ratio sensor through the comparison at said step (b);
(d) correcting an air-fuel ratio correction according to at least said air-fuel ratio signal so that an actual air-fuel ratio of the internal combustion engine is equal to said target air-fuel ratio;
and
(e) disabling said air-fuel ratio correction at said step (d) and said air-fuel ratio sensor in response to an output signal from said step (c) which indicates an irreparable failure of said air-fuel ratio sensor.

3 more elements

A method for controlling air-fuel ratio for an internal combustion engine on a motor vehicle, comprising the steps of:

(a) producing an air-fuel ratio signal by an air-fuel ratio sensor in proportion to a concentration of oxygen in an exhaust gas produced by a burned air-fuel mixture in the internal combustion engine;
(b) producing an output electric signal by a sensor cell depending on a difference between a concentration of oxygen in a reference gas having an oxygen excess ratio which is larger than 1;
(c) detecting said output signal produced at said step (b) from said sensor cell;
(d) producing an electric control signal by control means to cause said output electric signal to have a predetermined value;
(e) moving oxygen ions by a pump cell in response to said electric control signal produced at said step (d);
(f) producing an air-fuel ratio signal depending on an electric current flowing between said control means and said pump cell;
(g) producing a stoichiometric air-fuel ratio signal corresponding to a voltage developed across said pump cell;
and
(h) determining at least an irreparable failure of said air-fuel ratio sensor through a comparison between an output signal from said air-fuel ratio sensor and a target air-fuel ratio determined depending on operating conditions of the motor vehicle, the comparison including the step of comparing at least one said air-fuel ratio signal and said stoichiometric air-fuel ratio signal with said target air-fuel ratio.

6 more elements

Dependencies are inferred from the claim text.

Air-fuel ratio control system

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Air-fuel ratio control system

Life of this patent

Abstract

Claims11