US 6,012,282 A · Method for controlling engine exhaust gas system

Abstract

A method for controlling an engine exhaust gas system includes the steps of detecting an air-fuel ratio of exhaust gas discharged from an internal engine by an oxygen sensor, controlling the exhaust gas to near the stoichiometric air-fuel ratio by a closed-loop control referring to a resultant signal, and leading the exhaust gas to a three-way catalyst to treat nitrogen oxide, hydrocarbon and carbon monoxide. A nitrogen oxide sensor is provided downstream of the three-way catalyst, and a control value of air-fuel ratio by a closed loop control by the oxygen sensor is corrected to set the nitrogen oxide concentration to a predetermined value in accordance with an output of the nitrogen oxide sensor. The deterioration of the three-way catalyst and/or oxygen sensor is detected by comparing a change in control corrected value for the air-fuel ratio of closed loop control referring to an output of the nitrogen oxide sensor with a predetermined value.

Claims13

Dependent claims

A method for controlling an engine exhaust gas system, comprising the steps of:

detecting an air-fuel ratio of exhaust gas discharged from an internal engine by an oxygen sensor;
controlling said exhaust gas to near the stoichiometric air-fuel ratio by a closed-loop control referring to a resultant signal;
and
leading said exhaust gas to a three-way catalyst to treat nitrogen oxide, hydrocarbon and carbon monoxide;
measuring a nitrogen oxide concentration by a nitrogen oxide sensor provided downstream of said three-way catalyst;
providing a comparison signal based on the result obtained by comparing the measured nitrogen oxide concentration with a predetermined value of nitrogen oxide;
and
correcting the air-fuel ratio by a closed loop control based on said comparison signal so as to keep the nitrogen oxide concentration at said predetermined value.

5 more elements

A method for controlling engine exhaust gas systems, comprising the steps of:

detecting the air-fuel ratio of exhaust gas discharged from an internal engine by an oxygen sensor;
controlling said exhaust gas to near the stoichiometric air-fuel ratio by a closed-loop control using the resultant signal;
and
leading said exhaust gas to a three-way catalyst to treat nitrogen oxides, hydrocarbon and carbon monoxide;
wherein a nitrogen oxide sensor is provided downstream of said three-way catalyst;
and
the nitrogen oxide concentration is set to a predetermined value by correcting a control value for air-fuel ratio by a closed loop control referring to a signal of said oxygen sensor in accordance with an output of said nitrogen oxide sensor, when in accordance with the extent of correction for the control value of an air-fuel ratio, the deterioration of at least one of said three-way catalyst and said oxygen sensor is detected.

4 more elements

A method for controlling engine exhaust gas systems, comprising the steps of:

detecting the air-fuel ratio of exhaust gas discharged from an internal engine by an oxygen sensor;
controlling said exhaust gas to near the stoichiometric air-fuel ratio by a closed loop control using the resultant signal;
and
leading said exhaust gas to a three-way catalyst to treat nitrogen oxides, hydrocarbon and carbon monoxide;
wherein a nitrogen oxide sensor is provided downstream of said three-way catalyst;
and
the nitrogen oxide concentration is set to a predetermined value by correcting a control value for air-fuel ratio by a closed loop control referring to a signal of said oxygen sensor in accordance with an output of said nitrogen oxide sensor, when in accordance with the extent of correction for a change width of the control value of an air-fuel ratio, the deterioration of at least one of said three-way catalyst and said oxygen sensor is detected.

4 more elements

Dependencies are inferred from the claim text.

Method for controlling engine exhaust gas system

Life of this patent

Method for controlling engine exhaust gas system

Life of this patent

Abstract

Claims13