| 摘要 |
A HC adsorption type three-way catalytic converter is arranged in an exhaust gas passage of a diesel engine at a position upstream of a diesel particulate filter or a NOx trapping catalytic converter. Upon need of reactivation of the diesel particulate filter or NOx trapping catalytic converter under cold operation of the engine, a control unit 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 is lower than or equal to a first predetermined temperature (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 is higher than the first predetermined temperature but lower than or equal to a second predetermined temperature (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 becomes to a third predetermined temperature (viz., reactivation assuring temperature) when the temperature of the catalyst bed of the three-way catalytic converter is higher than the second predetermined temperature. |
