Abstract: An NH3 supply amount controller reduces and adjusts a supply amount of NH3 to an SCR catalyst by an NH3 supplier, when an exhaust gas flowing into an NOx catalyst has a rich air-fuel ratio and NOx occluded by the NOx catalyst is reduced to N2. A reduction amount of the supply amount of the NH3 controlled by the NH3 supply amount controller is set larger when s flow amount of the exhaust gas detected or estimated by an exhaust-gas flow amount detector is larger.

Abstract: An NH3 supply amount controller reduces and adjusts a supply amount of NH3 to an SCR catalyst by an NH3 supplier, when an exhaust gas flowing into an NOX catalyst has a rich air-fuel ratio and NOX occluded by the NOX catalyst is reduced to N2. A reduction amount of the supply amount of the NH3 controlled by the NH3 supply amount controller is set smaller when a temperature of the NOX catalyst detected or estimated by an NOX catalyst temperature detector is higher.

Abstract: An NH3 supply amount controller reduces and adjusts a supply amount of NH3 to an SCR catalyst by an NH3 supplier, when an exhaust gas flowing into an NOX catalyst has a rich air-fuel ratio and NOX occluded by the NOX catalyst is reduced to N2. A reduction amount of the supply amount of the NH3 controlled by the NH3 supply amount controller is set larger when an amount of reducing agent detected or estimated by a reducing agent amount detector is larger.

Abstract: An engine control device is provided, which includes an oxidation catalyst provided in an exhaust passage to oxidize unburned fuel within exhaust gas, a NOx catalyst provided integrally with or downstream of the oxidation catalyst, a PM filter provided in the exhaust passage downstream of the oxidation catalyst to capture fine particulate matter within the exhaust gas, a fuel injector, and a controller. When the particulate matter is accumulated by a given amount, the controller starts a PM filter regeneration control to remove the particulate matter, and after this control is started and when the accumulation amount decreases by a given amount, the controller starts a NOx catalyst regeneration control to switch between a first state in which an air-fuel ratio of the exhaust gas is a stoichiometric air-fuel ratio or less and a second state in which the air-fuel ratio is higher than the stoichiometric air-fuel ratio.

Abstract: An engine includes: an NOx catalyst and an SCR catalyst in an exhaust passage; an excess air ratio change device that changes an excess air ratio of an exhaust gas; and a reducing agent supply device that supplies a reducing agent for SCR including a material for NH3 or NH3 to a portion between the NOx catalyst and the SCR catalyst in the exhaust passages. The engine controls the reducing agent supply device in such a manner that a quantity of the reducing agent for SCR to be supplied from the reducing agent supply device to the exhaust passage 40 becomes small when the excess air ratio of the exhaust gas during regeneration control to regenerate the NOx catalyst is small, as compared to when the excess air ratio ? of the exhaust gas during regeneration control to regenerate the NOx catalyst is large.

Abstract: An NH3 supply amount controller reduces and adjusts a supply amount of NH3 to an SCR catalyst by an NH3 supplier, when an exhaust gas flowing into an NOx catalyst has a rich air-fuel ratio and NOx occluded by the NOx catalyst is reduced to N2. A reduction amount of the supply amount of the NH3 controlled by the NH3 supply amount controller is set larger when an amount of reducing agent detected or estimated by a reducing agent amount detector is larger.

Abstract: An NH3 supply amount controller reduces and adjusts a supply amount of NH3 to an SCR catalyst by an NH3 supplier, when an exhaust gas flowing into an NOX catalyst has a rich air-fuel ratio and NOX occluded by the NOX catalyst is reduced to N2. A reduction amount of the supply amount of the NH3 controlled by the NH3 supply amount controller is set smaller when a temperature of the NOX catalyst detected or estimated by an NOX catalyst temperature detector is higher.

Abstract: An NH3 supply amount controller reduces and adjusts a supply amount of NH3 to an SCR catalyst by an NH3 supplier, when an exhaust gas flowing into an NOx catalyst has a rich air-fuel ratio and NOx occluded by the NOx catalyst is reduced to N2. A reduction amount of the supply amount of the NH3 controlled by the NH3 supply amount controller is set larger when s flow amount of the exhaust gas detected or estimated by an exhaust-gas flow amount detector is larger.

Abstract: An engine control device is provided, which includes an oxidation catalyst provided in an exhaust passage to oxidize unburned fuel within exhaust gas, a NOx catalyst provided integrally with or downstream of the oxidation catalyst, a PM filter provided in the exhaust passage downstream of the oxidation catalyst to capture fine particulate matter within the exhaust gas, a fuel injector, and a controller. When the particulate matter is accumulated by a given amount, the controller starts a PM filter regeneration control to remove the particulate matter, and after this control is started and when the accumulation amount decreases by a given amount, the controller starts a NOx catalyst regeneration control to switch between a first state in which an air-fuel ratio of the exhaust gas is a stoichiometric air-fuel ratio or less and a second state in which the air-fuel ratio is higher than the stoichiometric air-fuel ratio.

Abstract: An engine includes: an NOx catalyst and an SCR catalyst in an exhaust passage; an excess air ratio change device that changes an excess air ratio of an exhaust gas; and a reducing agent supply device that supplies a reducing agent for SCR including a material for NH3 or NH3 to a portion between the NOx catalyst and the SCR catalyst in the exhaust passages. The engine controls the reducing agent supply device in such a manner that a quantity of the reducing agent for SCR to be supplied from the reducing agent supply device to the exhaust passage 40 becomes small when the excess air ratio of the exhaust gas during regeneration control to regenerate the NOx catalyst is small, as compared to when the excess air ratio X of the exhaust gas during regeneration control to regenerate the NOx catalyst is large.