Exhaust purifying method and apparatus of an internal combustion engine

A method for purifying an exhaust gas of an internal combustion engine, comprising:

• temporarily trapping a plurality of particulates contained in an exhaust gas discharged from a combustion chamber with a filter, and removing the particulates by oxidation;
• alternately switching a valve between a first flow passage to feed the exhaust gas to the first side of the filter and a second flow passage to feed the exhaust gas to the second side of the filter, the valve has a bypass mode in which the exhaust gas bypasses the filter;
• and
• inhibiting the valve from being positioned in the bypass mode while the exhaust gas has a relatively small air-fuel ratio flowing into the filter, and
• allowing the valve to be positioned in the bypass mode while the exhaust gas has a relatively large air-fuel ratio flowing into the filter.

An exhaust purifying apparatus of an internal combustion engine, comprising:

• a filter that temporarily traps a plurality of particulates contained in an exhaust gas discharged from a combustion chamber, the filter removes the particulates by oxidation, the filter has a NOx absorbent that absorbs NOx in a lean range and discharges NOx in a stoichiometric air-fuel ratio range or a rich air-fuel ratio range;
• a valve that alternately switches between a first flow passage to feed the exhaust gas from a first side of the filter, and a second flow passage to feed the exhaust gas from a second side of the filter, the valve has a bypass mode in which the exhaust gas bypasses the filter;
• and
• a controller that:
• normally positions the valve in the bypass mode when particulate oxidation of the filter is lower than a predetermined level, and
• inhibits the valve from being positioned in the bypass mode when NOx is discharged from the NOx absorbent, even if the particulate oxidation of the particulate filter is lower than the predetermined level.

A method for purifying an exhaust gas of an internal combustion engine, comprising:

• temporarily trapping a plurality of particulates contained in an exhaust gas discharged from a combustion chamber with a filter;
• removing the particulates by oxidation, the filter has a NOx absorbent that absorbs NOx in a lean range and discharges NOx in a stoichiometric air-fuel ratio range or a rich air-fuel ratio range;
• agitating the particulates by alternately switching between a first flow passage to feed the exhaust gas to a first side of the filter and a second flow passage to feed the exhaust gas to a second side of the filter, the valve has a bypass mode in which the exhaust gas bypasses the filter during the switching;
• positioning the valve in the bypass mode when particulate oxidation of the filter is lower than a predetermined level;
• and
• inhibiting the valve from being positioned in the bypass mode when NOx is discharged from the NOx absorbent, even if the particulate oxidation of the particulate filter is lower than the predetermined level.