Method for controlling engine exhaust gas system
First Claim
1. 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.
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Accused Products
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.
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Citations
13 Claims
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1. A method for controlling an engine exhaust gas system, comprising the steps of:
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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. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for controlling engine exhaust gas systems, comprising the steps of:
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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. - View Dependent Claims (8, 9)
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10. A method for controlling engine exhaust gas systems, comprising the steps of:
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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. - View Dependent Claims (11, 12, 13)
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Specification