Abstract: A rich control for temporarily declining an air-fuel ratio of exhaust gas discharged from an engine combustion chamber is performed by an additional fuel being injected into a cylinder in an expansion stroke or an exhaust stroke in a state where a throttle opening degree is switched from a base throttle opening degree to a throttle opening degree for the rich control and an EGR rate is switched from a base EGR rate to an EGR rate for the rich control. The rich control is terminated by returning the throttle opening degree (VTH) to the base throttle opening degree (VTHB), stopping the injection of the additional fuel (Qa), and temporarily increasing the amount of a main fuel (Qm). Then, an EGR control valve opening degree (VEGR) is controlled such that the EGR rate (REGR) is returned to the base EGR rate (REGRB).

Abstract: Rich control is performed to hold an air-fuel ratio of an exhaust gas discharged from an engine combustion chamber temporarily richer than the stoichiometric air-fuel ratio by injecting additional fuel into a cylinder in an expansion stroke or exhaust stroke while an exhaust gas recirculation rate is made lower than a base exhaust gas recirculation rate. A variable valve timing mechanism able to change an overlap period is provided. When ending rich control (ta2), the injection of additional fuel is stopped and the overlap period (OL) is increased from a base overlap period (OLB) and held there while an EGR rate (REGR) is kept lower than a base EGR rate (REGRB) and when a delay time (dt) elapses, the EGR rate and the overlap period are reset to the base EGR rate and the base overlap period.

Abstract: A rich control for temporarily declining an air-fuel ratio of exhaust gas discharged from an engine combustion chamber is performed by an additional fuel being injected into a cylinder in an expansion stroke or an exhaust stroke in a state where a throttle opening degree is switched from a base throttle opening degree to a throttle opening degree for the rich control and an EGR rate is switched from a base EGR rate to an EGR rate for the rich control. The rich control is initiated by switching a low pressure side EGR control valve opening degree (VEGRL) to a low pressure side EGR control valve opening degree for the rich control (VEGRLR), then switching a high pressure side EGR control valve opening degree (VEGRH) to a high pressure side EGR control valve opening degree for the rich control (VEGRHR), then controlling the throttle opening degree (VTH), and then initiating the injection of the additional fuel (Qa).

Abstract: In an internal combustion engine, an exhaust purification catalyst and a hydrocarbon feed valve are arranged in an exhaust passage. When a temperature of the exhaust purification catalyst falls in a first catalyst temperature region (I), a first NOX purification method is performed, while when a temperature of the exhaust purification catalyst falls in a second catalyst temperature region (II), a second NOX purification method is performed. When the temperature of the exhaust purification catalyst falls in a region (IIP) in the second catalyst temperature region close to the first catalyst temperature region, the temperature of the exhaust purification catalyst is made to increase to shift the region in which the temperature of the exhaust purification catalyst falls to the first catalyst temperature region to thereby switch the NOX purification method used from the second NOX purification method to the first NOX purification method.

Abstract: In an internal combustion engine, an exhaust purification catalyst and a hydrocarbon feed valve are arranged in an exhaust passage. When the air-fuel ratio of the exhaust gas which flows into the exhaust purification catalyst should be made rich, rich control, which makes the air-fuel ratio of the exhaust gas which is exhausted from the combustion chamber rich, is performed. In order to prevent clogging of the hydrocarbon feed valve, clogging preventing injection which injects hydrocarbons from the hydrocarbon feed valve by an injection interval ?tCB is performed. The exhaust purification catalyst has an oxygen storage ability. At the initial period of rich control, clogging preventing injection is performed by a shorter injection interval ?tCS.

Abstract: A rich control for temporarily declining an air-fuel ratio of exhaust gas discharged from an engine combustion chamber is performed by an additional fuel being injected into a cylinder in an expansion stroke or an exhaust stroke in a state where a throttle opening degree is switched from a base throttle opening degree to a throttle opening degree for the rich control and an EGR rate is switched from a base EGR rate to an EGR rate for the rich control. The rich control is initiated by switching a low pressure side EGR control valve opening degree (VEGRL) to a low pressure side EGR control valve opening degree for the rich control (VEGRLR), then switching a high pressure side EGR control valve opening degree (VEGRH) to a high pressure side EGR control valve opening degree for the rich control (VEGRHR) then controlling the throttle opening degree (VTH), and then initiating the injection of the additional fuel (Qa).

Abstract: Rich control is performed to hold an air-fuel ratio of an exhaust gas discharged from an engine combustion chamber temporarily richer than the stoichiometric air-fuel ratio by injecting additional fuel into a cylinder in an expansion stroke or exhaust stroke while an exhaust gas recirculation rate is made lower than a base exhaust gas recirculation rate. A variable valve timing mechanism able to change an overlap period is provided. When ending rich control (ta2), the injection of additional fuel is stopped and the overlap period (OL) is increased from a base overlap period (OLB) and held there while an EGR rate (REGR) is kept lower than a base EGR rate (REGRB) and when a delay time (dt) elapses, the EGR rate and the overlap period are reset to the base EGR rate and the base overlap period.

Abstract: A rich control for temporarily declining an air-fuel ratio of exhaust gas discharged from an engine combustion chamber is performed by an additional fuel being injected into a cylinder in an expansion stroke or an exhaust stroke in a state where a throttle opening degree is switched from a base throttle opening degree to a throttle opening degree for the rich control and an EGR rate is switched from a base EGR rate to an EGR rate for the rich control. The rich control is terminated by returning the throttle opening degree (VTH) to the base throttle opening degree (VTHB), stopping the injection of the additional fuel (Qa), and temporarily increasing the amount of a main fuel (Qm). Then, an EGR control valve opening degree (VEGR) is controlled such that the EGR rate (REGR) is returned to the base EGR rate (REGRB).

Abstract: In an internal combustion engine, an exhaust purification catalyst and a hydrocarbon feed valve are arranged in an exhaust passage. When a temperature of the exhaust purification catalyst falls in a first catalyst temperature region (I), a first NOX purification method is performed, while when a temperature of the exhaust purification catalyst falls in a second catalyst temperature region (II), a second NOX purification method is performed. When the temperature of the exhaust purification catalyst falls in a region (IIP) in the second catalyst temperature region close to the first catalyst temperature region, the temperature of the exhaust purification catalyst is made to increase to shift the region in which the temperature of the exhaust purification catalyst falls to the first catalyst temperature region to thereby switch the NOX purification method used from the second NOX purification method to the first NOX purification method.

Abstract: In an internal combustion engine, an exhaust purification catalyst and a hydrocarbon feed valve are arranged in an exhaust passage. When the air-fuel ratio of the exhaust gas which flows into the exhaust purification catalyst should be made rich, rich control, which makes the air-fuel ratio of the exhaust gas which is exhausted from the combustion chamber rich, is performed. In order to prevent clogging of the hydrocarbon feed valve, clogging preventing injection which injects hydrocarbons from the hydrocarbon feed valve by an injection interval ?tCB is performed. The exhaust purification catalyst has an oxygen storage ability. At the initial period of rich control, clogging preventing injection is performed by a shorter injection interval ?tCS.

Abstract: A decrease in determination accuracy on filter trouble due to a decrease in detection accuracy of a PM sensor is restricted. A filter, a selective reduction type NOx catalyst provided on a downstream of the filter, the PM sensor detecting an amount of PM on a downstream of the selective reduction type NOx catalyst, and a removal section conducting a process for removing a reducing agent attached to the PM sensor in a case where at least one of conditions is satisfied that a temperature of the selective reduction type NOx catalyst is equal to or lower than a threshold, that a temperature of the exhaust is equal to or lower than a threshold, that a flow rate of the exhaust is equal to or higher than a threshold, and that an adsorption amount of the reducing agent in the selective reduction type NOx catalyst is equal to or larger than a threshold are included.

Abstract: A decrease in determination accuracy on filter trouble due to a decrease in detection accuracy of a PM sensor is restricted. A filter, a selective reduction type NOx catalyst provided on a downstream of the filter, the PM sensor detecting an amount of PM on a downstream of the selective reduction type NOx catalyst, and a removal section conducting a process for removing a reducing agent attached to the PM sensor in a case where at least one of conditions is satisfied that a temperature of the selective reduction type NOx catalyst is equal to or lower than a threshold, that a temperature of the exhaust is equal to or lower than a threshold, that a flow rate of the exhaust is equal to or higher than a threshold, and that an adsorption amount of the reducing agent in the selective reduction type NOx catalyst is equal to or larger than a threshold are included.

Abstract: A control device for an internal combustion engine switches an air-fuel ratio of an air-fuel mixture in a cylinder from a first air-fuel ratio leaner than stoichiometry for normal operation to a second air-fuel ratio richer than the stoichiometry. During a switching period from beginning to end of the switching, the control device carries out intake throttling to control the air-fuel ratio of the air-fuel mixture in the cylinder to a third air-fuel ratio richer than the first air-fuel ratio and leaner than the stoichiometry, while learning a correction value for a fuel injection amount. During the switching period, before the intake throttling is completed, the control device carries out such a post-injection as prevents injected fuel from being combusted and learns the correction value. After the intake throttling is completed, the control device carries out such an after-injection as allows the injected fuel to be incompletely combusted and learns the correction value.