| 摘要 |
The present invention relates to a control device for use in internal-combustion engines in which an NSR catalyst and an SCR catalyst are disposed in an exhaust gas passage, and addresses the problem of reducing the amount of NH3 adsorbed onto the SCR catalyst, while mitigating deteriorations in the fuel consumption rate. To this end, the present invention provides a control device for use in internal-combustion engines in which an NSR catalyst and an SCR catalyst are disposed in an exhaust gas passage, wherein, when it is necessary to reduce the amount of NH3 adsorbed onto the SCR catalyst, if the temperature of the SCR catalyst is at least equal to a lower limit temperature at which oxidation of NH3 is possible, the air-fuel ratio of the air-fuel mixture to be combusted in the internal-combustion engine is controlled to a predetermined lean air-fuel ratio that is higher than the stoichiometric air-fuel ratio, and if the temperature of the SCR catalyst is less than the lower limit temperature, the air-fuel ratio of the air-fuel mixture to be combusted in the internal-combustion engine is controlled to a predetermined slightly lean air-fuel ratio that is lower than the predetermined lean air-fuel ratio and is higher than the stoichiometric air-fuel ratio. |
