초록 ▼

To optimally operate a NOx-occluded type catalytic converter installed in an exhaust passage of an internal combustion engine, there are employed an air/fuel ratio sensor for detecting an exhaust air/fuel ratio of the exhaust gas downstream of the converter; and a control device for controlling an a

To optimally operate a NOx-occluded type catalytic converter installed in an exhaust passage of an internal combustion engine, there are employed an air/fuel ratio sensor for detecting an exhaust air/fuel ratio of the exhaust gas downstream of the converter; and a control device for controlling an air/fuel ratio of a combustible mixture fed to the engine. The control device comprises a first section for causing the converter to effect NOx-reduction treatment by making the air/fuel ratio of the combustible mixture richer and/or stoichiometric; and a second section for learning and correcting the condition of the NOx-reduction treatment, based on the exhaust air/fuel ratio detected by the sensor under the NOx-reduction treatment.

대표청구항 ▼

[ What is claimed is:] [1.] In an internal combustion engine having an air/fuel mixture supply device by which a combustible mixture fed to the engine is provided,an exhaust gas purifying system comprising:a NOx-occluded type catalytic converter installed in an exhaust passage through which an exhau

[ What is claimed is:] [1.] In an internal combustion engine having an air/fuel mixture supply device by which a combustible mixture fed to the engine is provided,an exhaust gas purifying system comprising:a NOx-occluded type catalytic converter installed in an exhaust passage through which an exhaust gas from the engine passes, said converter occluding NOx in the exhaust gas when the exhaust gas shows a leaner air/fuel ratio and releasing and reducing NOx with an aid of HC and CO in the exhaust gas when the exhaust gas shows a richer or stoichiometric air/fuel ratio;an air/fuel ratio sensor disposed downstream of said converter for detecting an exhaust air/fuel ratio of the exhaust gas downstream of said converter; anda control device for controlling an air/fuel ratio of said combustible mixture, said control device including:a first section for making the air/fuel ratio of the combustible mixture richer or stoichiometric to cause said converter to effect a NOx-reduction treatment on the absorbed or adsorbed NOx; anda second section for learning and correcting the condition of the NOx-reduction treatment, based on the exhaust air/fuel ratio detected by said sensor under the NOx-reduction treatment, d second section including:a rich level learning means which learns and corrects a rich level of the combustible mixture under the NOx-reduction treatment, based on a first period for which the air/fuel ratio of the exhaust gas detected by said sensor is kept near stoichiometric; anda rich condition keeping time learning means which learns and corrects a rich condition keeping time for which the air/fuel ratio of said combustible mixture is kept rich under the NOx-reduction treatment, based on a second period for which the air/fuel ratio detected by said sensor is kept rich, said second period appearing after said first period.