| 摘要 |
A HC adsorption type three-way catalytic converter (13) is arranged in an exhaust gas passage of a diesel engine (1) at a position upstream of an exhaust gas purifying device (15,14) constituted of at least one of a diesel particulate filter (15) and a NOx trapping catalytic converter (14). Upon need of reactivation of the diesel particulate filter (15) or NOx trapping catalytic converter (14) under cold operation of the engine, a control unit (20) carries out lowering an excess air ratio of the exhaust gas of the engine when the temperature of the catalyst bed of the three-way catalytic converter (13) is lower than or equal to a first predetermined temperature (#TBED1) (viz.,oxidization activation temperature); raising the excess air ratio of the exhaust gas when the temperature of the catalyst bed of the three-way catalytic converter (13) is higher than the first predetermined temperature (#TBED1) but lower than or equal to a second predetermined temperature (#TBED2) (viz.,three-way catalyst activation temperature); and lowering the excess air ratio of the exhaust gas until the temperature of the exhaust gas purifying device (15,14) becomes to a third predetermined temperature (#TBED3) (viz.,reactivation assuring temperature) when the temperature of the catalyst bed of the three-way catalytic converter (13) is higher than the second predetermined temperature (#TBED2). <IMAGE>A HC adsorption type three-way catalytic converter (13) is arranged in an exhaust gas passage of a diesel engine (1) at a position upstream of an exhaust gas purifying device (15,14) constituted of at least one of a diesel particulate filter (15) and a NOx trapping catalytic converter (14). Upon need of reactivation of the diesel particulate filter (15) or NOx trapping catalytic converter (14) under cold operation of the engine, a control unit (20) carries out lowering an excess air ratio of the exhaust gas of the engine when the temperature of the catalyst bed of the three-way catalytic converter (13) is lower than or equal to a first predetermined temperature (#TBED1) (viz.,oxidization activation temperature); raising the excess air ratio of the exhaust gas when the temperature of the catalyst bed of the three-way catalytic converter (13) is higher than the first predetermined temperature (#TBED1) but lower than or equal to a second predetermined temperature (#TBED2) (viz.,three-way catalyst activation temperature); and lowering the excess air ratio of the exhaust gas until the temperature of the exhaust gas purifying device (15,14) becomes to a third predetermined temperature (#TBED3) (viz.,reactivation assuring temperature) when the temperature of the catalyst bed of the three-way catalytic converter (13) is higher than the second predetermined temperature (#TBED2). <IMAGE> |
