Abstract: An exhaust purification system includes: an NOx reduction type catalyst, which is provided in an exhaust system; a temperature acquisition unit, which acquires a catalyst temperature of the NOx reduction type catalyst; and a regeneration treatment unit, which executes a catalyst regeneration to recover an NOx purification capacity, wherein the regeneration treatment unit alternately executes a rich control, in which an exhaust air fuel ratio is set to a rich state to raise a temperature of the NOx reduction type catalyst to a predetermined target temperature, and a lean control, in which the exhaust air fuel ratio is set to a lean state to lower the temperature of the NOx reduction type catalyst, and sets an execution period of the lean control based on a deviation between the catalyst temperature acquired by the temperature acquisition unit during the previous rich control and the target temperature.

Abstract: An exhaust purification system includes: an NOx reduction type catalyst, which is provided in an exhaust system of an internal combustion engine and reduces and purifies NOx in an exhaust gas; and a regeneration treatment unit, which recovers an NOx purification capacity of the NOx reduction type catalyst by lowering an excess-air-ratio of the exhaust gas to a predetermined target excess-air-ratio, wherein the regeneration treatment unit includes: a target setting unit, which sets a target intake air amount that is required for setting the exhaust gas to the target excess-air-ratio, based on a fuel injection amount of the internal combustion engine; and an air-system controller, which controls at least one of an intake air amount and an exhaust recirculating amount of the internal combustion engine, in response to the target intake air amount input from the target setting unit.

Abstract: This NOx reduction control method is for an exhaust gas aftertreatment device having an oxidation catalyst and an LNT catalyst which are disposed in an exhaust pipe and repeating an adsorption or occlusion of NOx which is executed when an air-fuel ratio is in a lean state and a reduction of NOx which is executed when the air-fuel ratio is in a rich state, the method including executing a post-injection or an exhaust pipe injection and causing HC to be adsorbed in the oxidation catalyst when an exhaust gas temperature is low, and causing the HC which is adsorbed in the oxidation catalyst to be desorbed and reducing an adsorbed NOx in the LNT catalyst by raising the exhaust gas temperature during the rich state.

Abstract: An exhaust gas purification system which can suppress a decrease in engine torque during a desulfurization process applied to a NOx storage reduction catalyst. The system includes a NOx storage reduction catalyst in an exhaust pipe of an engine, and a desulfurization process control unit that controls an amount of intake air introduced to the engine to enrich the exhaust gas, and performs a desulfurization process to the NOx storage reduction catalyst. The desulfurization process control unit is configured to gradually reduce an amount of intake air when the desulfurization process is commenced.

Abstract: An exhaust gas cleaning system for an internal combustion engine is provided with, in an exhaust passage of an internal combustion engine and in order from an upstream side: a hydrocarbon supply unit; an upstream side catalyst unit of an oxidation catalyst, a NOx reduction catalyst, or the like; and a catalyst-equipped fine particle collection filter having a hydrocarbon adsorption function, wherein when a vehicle on which the engine is mounted accelerates after driving for a preset set time period at a temperature of exhaust gas equal to or less than a preset set exhaust gas temperature, the supply of hydrocarbon into the exhaust gas is started when an exhaust gas temperature becomes equal to or more than a preset first set temperature, and the supply of hydrocarbon is terminated when a preset termination condition is satisfied.

Abstract: When particulate matter (PM) has accumulated on a diesel particulate filter (DPF), multiple-injection, post injection, and exhaust pipe injection are performed such that a reduction gas is burned in a diesel oxidation catalyst (DOC) to raise the exhaust gas temperature, burn the PM accumulated on the DPF, and regenerate the DPF. A light-off performance map is prepared, in advance, by determining burning efficiency relative to the DOC temperature during the post injection and the exhaust pipe injection, both when the catalyst is fresh and when the catalyst has deteriorated. The DOC temperature suitable for the exhaust pipe injection is set from a degree of the catalyst deterioration on the basis of the light-off performance map. The multiple-injection and/or the post injection is performed when the DOC temperature is less than the set temperature, and the exhaust pipe injection is performed when the DOC temperature is equal to or greater than the set temperature.

Abstract: An exhaust gas purification system with a diesel particulate filter in an exhaust passage of an internal combustion engine. A surface filtration cake layer formation enhancement control or a particulate matter generation amount reduction control is temporarily performed immediately after a forced regeneration treatment on the diesel particulate filter. The system and a method are directed to a particulate matter slip-through phenomenon in which the particulate matter slip-through amount temporarily increases immediately after particulate matter re-combustion in a forced regeneration treatment on the diesel particulate filter. The diesel particulate filter is disposed in the exhaust passage of the internal combustion engine and reduces the total amount of particulate matter emitted to the atmosphere immediately after the particulate matter re-combustion in the forced regeneration treatment on the diesel particulate filter.

Abstract: A high-temperature NOx occlusion reduction type catalyst in which an NOx occlusion material containing an alkali metal is supported, and a low-temperature NOx occlusion reduction type catalyst in which an NOx occlusion material containing an alkaline earth metal is supported, are disposed in series on an upstream side and a downstream side, respectively, of an exhaust gas purification system. An oxidation catalyst is disposed on an upstream side of the high-temperature NOx occlusion reduction type catalyst. The desulfurization of the NOx occlusion reduction type catalysts is facilitated, and the NOx reduction efficiency is improved by the partial oxidation of hydrocarbons in the exhaust gas, while a wide NOx active temperature window is achieved.

Abstract: A diesel oxidation catalyst, a NOx occlusion reduction catalyst, and a diesel particulate filter are connected to an exhaust pipe of an engine, downstream of an exhaust pipe injector provided on the exhaust pipe. NOx in the exhaust gas is occluded by the NOx occlusion reduction catalyst when an air-fuel ratio is lean. The occluded NOx is reduced and purified when the air-fuel ratio is rich. When a prescribed amount of particulate matter has accumulated in the diesel particulate filter, the exhaust gas temperature is raised when performing particulate matter regeneration. The exhaust gas temperature is further raised to perform a sulphur purge. The rich condition is prohibited during the particulate matter regeneration period and the sulphur purge period.

Abstract: When particulate matter (PM) has accumulated on a diesel particulate filter (DPF), multiple-injection, post injection, and exhaust pipe injection are performed such that a reduction gas is burned in a diesel oxidation catalyst (DOC) to raise the exhaust gas temperature, burn the PM accumulated on the DPF, and regenerate the DPF. A light-off performance map is prepared, in advance, by determining burning efficiency relative to the DOC temperature during the post injection and the exhaust pipe injection, both when the catalyst is fresh and when the catalyst has deteriorated. The DOC temperature suitable for the exhaust pipe injection is set from a degree of the catalyst deterioration on the basis of the light-off performance map. The multiple-injection and/or the post injection is performed when the DOC temperature is less than the set temperature, and the exhaust pipe injection is performed when the DOC temperature is equal to or greater than the set temperature.

Abstract: Exhaust gas of an internal combustion engine is made to pass through an exhaust gas purification device after passing through a pre-oxidation catalyst. When a first temperature of the exhaust gas on an upstream side of the device is lower than a first set temperature, multistage temperature rise injection is performed. When the first temperature becomes the first set temperature or more, post injection is performed in addition to the multistage temperature rise injection, and feedback control of the post injection is executed so that a second temperature of the exhaust gas on a downstream side of the exhaust gas purification device becomes a second set temperature.

Abstract: An engine exhaust gas post-treatment device including a mechanism that can vary opening timing of an exhaust valve, and a control method. A unit is configured to raise a temperature of a part or all of the device to not less than a preset temperature by the mechanism opening the exhaust valve in an exhaust stroke at normal combustion within a range of an afterburning period, and the mechanism feeds the device an exhaust gas whose temperature and pressure are high due to combustion of fuel injected into a cylinder. After the exhaust gas is treated by the device, or when the device is regenerated, the unit adds an unburned fuel component to the exhaust gas by an additional injection of an injector in the cylinder or an injection of a hydrocarbon addition nozzle provided at an exhaust port in accordance with the valve opening timing by the unit.

Abstract: When a catalyst temperature of a catalyst device is at or below a lower limit air-fuel ratio richness control is prohibited. When a first timing, where an estimated value of a NOx storage amount has reached an enrichment start threshold value, and a second timing, based on a set interval time in an enrichment interval time map, are both satisfied, the control is started. The second timing is corrected by multiplying the set interval time by an enrichment interval correction coefficient preset based on the catalyst temperature and a storage ratio of the estimated value of the NOx storage amount to an enrichment start threshold value of the NOx storage amount. The frequency of the air-fuel ratio richness control of a catalyst device configured to recover a purification capacity of a catalyst is reduced, and the catalyst temperature is raised while preventing white smoke development and hydrocarbon slip, to thereby achieve improvement in exhaust gas composition and improvement in fuel efficiency.

Abstract: An exhaust gas after-treatment device, including an oxidation catalyst and a diesel particulate filter in order from an upstream side, is provided in an exhaust passage of an internal combustion engine. A target value of an exhaust gas recirculation rate in exhaust gas recirculation control is set to be a second exhaust gas recirculation rate higher than a first exhaust gas recirculation rate at a time of a normal operation of the engine and the control is performed, when a catalyst index temperature that indexes a temperature of the oxidation catalyst falls within a set temperature region between a lower limit set temperature and an upper limit set temperature which are preliminarily set, and where an estimated particulate matter deposition amount of the diesel particulate filter is less than a preliminarily set regeneration start threshold value, after an operation state of the engine transitions from a traveling operation state to idling.

Abstract: An exhaust gas purification system including a catalyst device configured to recover a purification capacity of a catalyst by an air-fuel ratio richness control, based on a richness control permission range where the air-fuel ratio richness control is permitted to be performed, and a richness control prohibition range where the air-fuel ratio richness control is prohibited from being performed. A catalyst temperature of the catalyst device and an air intake amount of an internal combustion engine are parameters for determining the richness control permission range or the richness control prohibition range. The richness control prohibition range is set as a range where the catalyst temperature of the catalyst device is lower than a preset lower limit catalyst temperature and the air intake amount is larger than a preset upper limit air intake amount. The lower limit catalyst temperature is set to a temperature lower than a catalyst activation temperature.

Abstract: An exhaust gas purification system which feeds hydrocarbon by a post-injection under preset conditions to an upstream side of an exhaust gas purification device positioned on the exhaust path of an internal combustion engine, restoring the purifying capacity of the device or purifying the exhaust gas of the device. Under hydrocarbon feed conditions, if a combination of the exhaust gas temperature and exhaust gas flowrate or intake flowrate during control is deemed to be in a misfire region in which hydrocarbon which is fed to the exhaust path no longer combusts in the exhaust gas purification unit, the feed of hydrocarbon is stopped. As a result, it is possible to prevent deposit of hydrocarbon on catalysts or other exhaust gas purification units of the device, making it possible to constantly maintain the temperature of the unit in a controllable state.

Abstract: An occlusion cycle and a rich reduction cycle are repeated alternately in a NOx occlusion reduction catalyst connected to an exhaust pipe of an engine. When a NOx occlusion rate decreases while the occlusion cycle and the rich reduction cycle are being repeated, a sulphur purge is performed. A NOx occlusion map, which indicates the NOx occlusion amount of the NOx occlusion reduction catalyst during the occlusion cycle, as affected by aging degradation, is prepared in advance, and an ideal NOx occlusion amount is determined based on the NOx occlusion map. In the meantime, an actual NOx occlusion amount during the occlusion cycle is calculated from a NOx sensor value. Degradation of the NOx occlusion reduction catalyst due to sulfur poisoning is distinguished from thermal degradation of the NOx occlusion reduction catalyst based on the difference between the ideal NOx occlusion amount and the actual NOx occlusion amount.

Abstract: A diesel oxidation catalyst, a NOx occlusion reduction catalyst, and a diesel particulate filter are connected to an exhaust pipe of an engine, downstream of an exhaust pipe injector provided on the exhaust pipe. NOx in the exhaust gas is occluded by the NOx occlusion reduction catalyst when an air-fuel ratio is lean. The occluded NOx is reduced and purified when the air-fuel ratio is rich. When a prescribed amount of particulate matter has accumulated in the diesel particulate filter, the exhaust gas temperature is raised when performing particulate matter regeneration. The exhaust gas temperature is further raised to perform a sulphur purge. The rich condition is prohibited during the particulate matter regeneration period and the sulphur purge period.

Abstract: An exhaust gas purification system which can suppress a decrease in engine torque during a desulfurization process applied to a NOx storage reduction catalyst. The system includes a NOx storage reduction catalyst in an exhaust pipe of an engine, and a desulfurization process control unit that controls an amount of intake air introduced to the engine to enrich the exhaust gas, and performs a desulfurization process to the NOx storage reduction catalyst. The desulfurization process control unit is configured to gradually reduce an amount of intake air when the desulfurization process is commenced.

Abstract: An exhaust gas purification method of a diesel engine, which purifies exhaust gas while suppressing deterioration in drivability and fuel consumption, including when exhaust gas enters a rich reduction state, opening an EGR valve and closing an intake throttle, if a temperature of an NOx occlusion reduction catalyst is at or above a predetermined temperature, and a vehicle having a diesel engine is decelerating from a speed at or above a predetermined speed, and then closing an exhaust throttle provided downstream of the NOx occlusion reduction catalyst and supplying fuel to the NOx occlusion reduction catalyst as a reductant.