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 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 exhaust emission control system of an engine is provided, which includes a NOx catalyst disposed in an exhaust passage for storing NOx within exhaust gas when an air-fuel ratio of the exhaust gas is lean, and reducing the stored NOx when the air-fuel ratio is approximately stoichiometric or rich. A processor executes a NOx reduction controlling module for performing, when the NOx stored amount exceeds a given amount, a NOx reduction control in which a fuel injector performs a post injection of fuel to continuously control the air-fuel ratio to a target ratio so that the stored NOx is reduced to be below a given amount, the target air-fuel ratio being a ratio at which the stored NOx is reducible, the post injection causing the injected fuel to combust inside a cylinder, the execution of the control permitted when an engine load is within a medium load range.

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.

Abstract: An exhaust emission control system of an engine is provided, which includes a NOx catalyst disposed in an exhaust passage for storing NOx within exhaust gas when an air-fuel ratio of the exhaust gas is lean, and reducing the stored NOx when the air-fuel ratio is approximately stoichiometric or rich. A processor executes a NOx reduction controlling module for performing, when the NOx stored amount exceeds a given amount, a NOx reduction control in which a fuel injector performs a post injection of fuel to continuously control the air-fuel ratio to a target ratio so that the stored NOx is reduced to be below a given amount, the target air-fuel ratio being a ratio at which the stored NOx is reducible, the post injection causing the injected fuel to combust inside a cylinder, the execution of the control permitted when an engine load is within a medium load range.

Abstract: An exhaust gas recirculation control device of an engine includes an exhaust turbocharger having a turbine disposed in an exhaust passage and a compressor disposed in an intake passage, low-pressure and high-pressure EGR passages connecting the exhaust passage downstream of the turbine to the intake passage upstream of the compressor and connecting the exhaust passage upstream of the turbine with the intake passage downstream of the compressor, respectively, low-pressure and high-pressure EGR valves disposed in the low-pressure and high-pressure EGR passages and for changing cross-sectional areas thereof, respectively, a valve control device for controlling openings of the low-pressure and high-pressure EGR valves, a total intake gas amount detector for detecting a total intake gas amount, a fresh air amount detector for detecting a fresh air amount, and a pressure difference detector for detecting a pressure difference between the exhaust and intake passage sides of the high-pressure EGR valve.

Abstract: Abnormality diagnosis device for a variable valve mechanism configured to open an exhaust valve even during an intake stroke and capable of selecting a first mode wherein the exhaust valve only opens during an exhaust stroke, or a second mode wherein the exhaust valve opens during both an exhaust stroke and an intake stroke. The abnormality diagnosis by the device determines the mechanism is abnormal when a difference between an exhaust gas returning amount calculated to recirculate from an exhaust passage into a cylinder in the second mode based on intake air amounts in the first and second modes, and an exhaust gas returning amount estimated to recirculate from an exhaust passage in the second mode based on an exhaust gas pressure, exceeds a diagnosis threshold value. The higher an exhaust gas pressure is, the larger an exhaust gas returning amount is estimated to be.

Abstract: Abnormality diagnosis device for a variable valve mechanism configured to open an exhaust valve even during an intake stroke and capable of selecting a first mode wherein the exhaust valve only opens during an exhaust stroke, or a second mode wherein the exhaust valve opens during both an exhaust stroke and an intake stroke. The abnormality diagnosis by the device determines the mechanism is abnormal when a difference between an exhaust gas returning amount calculated to recirculate from an exhaust passage into a cylinder in the second mode based on intake air amounts in the first and second modes, and an exhaust gas returning amount estimated to recirculate from an exhaust passage in the second mode based on an exhaust gas pressure, exceeds a diagnosis threshold value. The higher an exhaust gas pressure is, the larger an exhaust gas returning amount is estimated to be.

Abstract: An exhaust gas recirculation control device of an engine includes an exhaust turbocharger having a turbine disposed in an exhaust passage and a compressor disposed in an intake passage, low-pressure and high-pressure EGR passages connecting the exhaust passage downstream of the turbine to the intake passage upstream of the compressor and connecting the exhaust passage upstream of the turbine with the intake passage downstream of the compressor, respectively, low-pressure and high-pressure EGR valves disposed in the low-pressure and high-pressure EGR passages and for changing cross-sectional areas thereof, respectively, a valve control device for controlling openings of the low-pressure and high-pressure EGR valves, a total intake gas amount detector for detecting a total intake gas amount, a fresh air amount detector for detecting a fresh air amount, and a pressure difference detector for detecting a pressure difference between the exhaust and intake passage sides of the high-pressure EGR valve.