Abstract: Art is provided for an exhaust purification system for an internal combustion engine, which decreases an amount of exhaust flowing to a storage-reduction type NOx catalyst and supplies a reducer to the NOx catalyst so as to reduce NOx stored in the NOx catalyst, wherein the manner in which the reducer is dispersed in the NOx catalyst can be controlled to achieve more reliable execution of a NOx reduction treatment. Air-fuel ratio detecting unit is disposed upstream and downstream of the storage-reduction type NOx catalyst. During a predetermined period subsequent to decreasing an amount of exhaust flowing to the NOx catalyst and adding the reducer to the exhaust, a reducer-adding timing is changed such that a difference between an air-fuel ratio detected by the air-fuel ratio detecting unit disposed upstream of the NOx catalyst and an air-fuel ratio detected by the air-fuel ratio detecting unit disposed downstream of the NOx catalyst becomes a predetermined target value.

Abstract: An object of the invention is to estimate the quantity of N2O produced in an ammonia oxidation catalyst in a case where the ammonia oxidation catalyst is provided in an exhaust passage of an internal combustion engine. In a case where an ammonia oxidation catalyst having the function of oxidizing ammonia is provided in an exhaust passage of an internal combustion engine, the quantity of N2O produced in the ammonia oxidation catalyst is estimated based on the difference between a measurement value of an upstream NOx sensor provided in the exhaust passage upstream of the ammonia oxidation catalyst and a measurement value of a downstream NOx sensor provided in the exhaust passage downstream of the ammonia oxidation catalyst.

Abstract: In an exhaust emission control system of an internal combustion engine, a NOx selective reduction catalyst is disposed in an engine exhaust passage, and an aqueous solution of urea stored in an aqueous-urea tank is supplied to the NOx selective reduction catalyst so as to selectively reduce NOx. A NOx sensor is provided in the engine exhaust passage downstream of the NOx selective reduction catalyst for detecting the NOx conversion efficiency of the NOx selective reduction catalyst, and the concentration of aqueous urea in the aqueous-urea tank is estimated from the detected NOx conversion efficiency. The exhaust emission control system and method make it possible to detect the concentration of aqueous urea at reduced cost.

Abstract: The invention has an object of exerting favorable NOx reducing effects even at an exhaust temperature lower than in the prior art without trouble, e.g., at startup after long-term engine rest and is directed to an exhaust emission control device wherein a selective reduction catalyst 5 capable of selectively reacting NOx with ammonia even in the presence of oxygen is incorporated in an exhaust pipe 4, urea water 6 as reducing agent being added in the pipe 4 upstream of the reduction catalyst 5 to depurate NOx through reduction.

Abstract: A device for purifying exhaust gas of an internal combustion engine comprising a NOx catalyst device, fuel feeding means for feeding additional fuel into combusted gas flowing into the NOx catalyst device during the regeneration treatment, and a NOx concentration sensor arranged on the exhaust downstream of the NOx catalyst device, wherein when the NOx concentration detected by the NOx concentration sensor is lower than a preset concentration during the regeneration treatment of this time, the amount of NOx absorbed by the NOx catalyst device during a preset period until the regeneration treatment of the next time is estimated by utilizing the NOx concentration sensor, and when the absorbed amount of NOx is smaller than a preset amount, it is decided that the amount of additional fuel fed during the regeneration processing of this time had been abnormally decreased.

Abstract: An internal combustion engine wherein when an aqueous urea solution should be fed from an aqueous urea solution feed valve (8), a feed pump (9) is operated forward and aqueous urea solution in an aqueous urea solution tank (4) is fed through an aqueous urea solution feed passage (10) into the aqueous urea solution feed valve (8). When ceasing the feed of aqueous urea solution from the aqueous urea solution feed valve (8), the feed pump (9) is operated in reverse whereby the ammonia gas generated in the aqueous urea solution tank (4) is drawn through a ammonia gas feed pipe (11) into the aqueous urea solution feed passage (10). Next, when the feed pump (9) is operated forward, the ammonia gas drawn into the aqueous urea solution feed path (10) is ejected from the aqueous urea solution feed valve (8).

Abstract: An object of the present invention is to suppress, in a system in which an NOx selective catalytic reduction catalyst and a particulate filter are provided in an exhaust passage of an internal combustion engine, discharge of ammonia from the NOx selective catalytic reduction catalyst. In the exhaust gas purification system for an internal combustion engine according to the present invention, when a condition for executing a filter temperature raising control is satisfied, the supply of urea to the NOx selective catalytic reduction catalyst by urea supply means is stopped, and the filter temperature raising control is executed by filter temperature raising means after a specific time has elapsed since the time of stoppage of the supply of urea to the NOx selective catalytic reduction catalyst.

Abstract: In an internal combustion engine, an NOx selective reduction catalyst (14) is arranged in an engine exhaust passage, and an NOx storage catalyst (12) is arranged in the engine exhaust passage upstream of the NOx selective reduction catalyst (14). When the amount of NOx stored in the NOx storage catalyst (12) exceeds a predetermined allowable value, the NOx storage catalyst (12) is raised in temperature to make the NOx storage catalyst (12) release the NOx. The amount of urea feed is decreased by exactly the amount of reduction of the calculated stored NOx amount with respect to the amount of urea feed determined from the engine operating state, and the amount of urea feed is increased by exactly the amount of reduction of the calculated released NOx amount with respect to the amount of urea feed determined from the engine operating state.

Abstract: A NOx storing catalyst (11) comprising a precious metal catalyst (46) and NOx absorbent (47) is arranged in an exhaust passage. When the air-fuel ratio of the exhaust gas is lean, the storing catalyst cold stores the NO2 contained in the exhaust in the absorbent when the catalyst is inactive and hot stores the cold stored NO2 in the absorbent when the catalyst is made active. The NO2 contained in the exhaust is cold stored in the absorbent when the catalyst is not activated, and when a predetermined NOx storing catalyst restoring condition (107) is met, a NOx storing catalyst restoring control (109, 115) including raising the NOx storing catalyst temperature to a predetermined temperature to active it (109) is executed so as to restore the cold storing capability of the NOx absorbent.

Abstract: In an internal combustion engine, an NOx selective reduction catalyst (15) is arranged in the engine exhaust passage, and the amount of deposition of the HC deposited at the NOx selective reduction catalyst (15) is estimated. When the estimated HC deposition amount exceeds a predetermined allowable deposition amount, the NOx selective reduction catalyst (15) is raised in temperature to make the deposited HC desorb from the NOx selective reduction catalyst (15), and thereby the NOx selective reduction catalyst (15) from HC poisoning is restored.

Abstract: A catalyst suitable for reducing NOx in exhaust gas by ammonia in the presence of excess oxygen is arranged in an engine exhaust passage. The catalyst is fed an aqueous urea solution from an addition control valve, part of the urea fed to the catalyst is stored in the catalyst, and the ammonia produced from the urea stored in the catalyst is used to reduce the NOx in the exhaust gas. It is judged whether the storage capacity of the catalyst is larger than a preset allowable upper limit capacity. When it is judged that the storage capacity of the catalyst is larger than the allowable upper limit capacity, the feed of the aqueous urea solution is prohibited.

Abstract: In an internal combustion engine, an NOX selective reducing catalyst is arranged in an engine exhaust passage. Urea is fed in the NOX selective reducing catalyst, ammonia generated from this urea is adsorbed at the NOX selective reducing catalyst, and the NOX contained in the exhaust gas is selectively reduced mainly by the adsorbed ammonia. An NOX sensor able to detect NOX and ammonia contained in the exhaust gas is arranged in the engine exhaust passage downstream of the NOX selective reducing catalyst. It is judged that the amount of adsorption of ammonia at the NOX selective reducing catalyst is saturated based on the detection value of the NOX sensor when the feed of fuel to the engine is stopped during the deceleration operation.

Abstract: In an internal combustion engine, an NOx selective reducing catalyst (15) is arranged in an engine exhaust passage and an oxidation catalyst (12) is arranged in the engine exhaust passage upstream of the NOx selective reducing catalyst (15). At the time of engine startup, HC is fed from a HC feed valve (28) to the oxidation catalyst (12), thereby raising the temperature of the NOx selective reducing catalyst(15) by the heat of the oxidation reaction of HC. At this time, the temperature of the NOx selective reducing catalyst (15) is raised to a HC desorption range where HC is desorbed from the NOx selective reducing catalyst (15).

Abstract: In an internal combustion engine, an NOx selective reduction catalyst (15) is arranged in the engine exhaust passage and a urea aqueous solution stored in a urea aqueous solution tank (20) is fed to the NOx selective reduction catalyst (15) where the NOx is selectively reduced. Opening and closing of the urea aqueous solution refill port (40) of the urea aqueous solution tank (20) are detected and it is judged if the urea aqueous solution is refilled in the urea aqueous solution tank (20). When it is judged that the NOx purification rate has fallen to an allowable level or less at the time of engine operation right after the urea aqueous solution is refilled in the urea aqueous solution tank (20), it is judged that the refilled urea aqueous solution is abnormal.

Abstract: In an internal combustion engine, a urea adsorption type selective reduction catalyst is arranged in an engine exhaust passage. By feeding urea from a urea feed valve into the exhaust gas flowing into this selective reduction catalyst, the NOx included in the exhaust gas is reduced in the selective reduction catalyst. TO suppress the generation of hydrogen cyanide, an HC adsorption catalyst for adsorption of the HC in the exhaust gas is arranged in the engine exhaust passage upstream of the selective reduction catalyst.

Abstract: An internal combustion engine, in which an NOx selective reducing catalyst (15) is arranged inside an engine exhaust passage, and aqueous urea stored in an aqueous urea tank (20) is fed to the NOx selective reducing catalyst (15) to selectively reduce the NOx. The aqueous urea tank (20) comprises a main tank (20a) and a sub tank (20b) arranged inside the main tank (20a). The aqueous urea in the sub tank (20b) is sent to an aqueous urea feed valve (17). When the aqueous urea tank (20) should be refilled with aqueous urea, the sub tank (20b) is refilled with aqueous urea. It is detected by a level sensor (40) if the aqueous urea in the aqueous urea tank (20) is refilled. When it is judged that the NOx purification rate falls below an allowable level at the time of engine operation right after the aqueous urea in the aqueous urea tank (20) has been refilled, it is judged that the refilled aqueous urea is abnormal.

Abstract: In an internal combustion engine, an NOX selective reduction catalyst (15) is arranged in the engine exhaust passage, and a urea aqueous solution feed valve (17) is arranged in the engine exhaust passage upstream of the NOX selective reduction catalyst (15). Based on the detections results of an NOX purification rate detecting means for detecting the NOX purification rate by the NOX selective reduction catalyst (15), a urea aqueous solution feed amount detecting means for detecting the amount of feed of the urea aqueous solution, and a urea aqueous solution concentration detecting means for detecting the concentration of the urea aqueous solution, abnormalities in the NOX selective reduction catalyst (15), urea aqueous solution feed system, and urea aqueous solution are judged.

Abstract: There are provided a fuel addition means which adds fuel into the exhaust, a NOx storage reduction catalyst by which NOx which has been stored is reduced by fuel which is added by the fuel addition means, and a control means which, based upon the intake air amount of the internal combustion engine, the fuel supply amount to the internal combustion engine, the target air/fuel ratio during NOx reduction, and the rich continuation period over which this target air/fuel ratio should be continued, calculates an added fuel amount to be added during this rich continuation period, and controls the fuel addition means so that fuel is added by dispersing this calculated added fuel amount over this rich continuation period.

Abstract: The task for the present invention is to reduce more of an oxide that is stored in a NOx storage reduction catalyst, even in a case where a clogging has occurred in a reducing agent adding valve that is provided in an exhaust passage of an internal combustion engine. The present invention is provided with rich spike control performing means that, when an oxide that is stored in the NOx storage reduction catalyst is reduced, performs a rich spike control and that, when lowering the air-fuel ratio in the exhaust gas, performs addition of a reducing agent by the reducing agent adding valve multiple times, which is performed when a crank angle of the internal combustion engine is in a specified range. When the clogging has occurred in the reducing agent adding valve, the number of times the air-fuel ratio in the exhaust gas is lowered while the rich spike control is being performed by the rich spike control performing means is increased.

Abstract: An NOx adsorbent is arranged in an exhaust passage of an internal combustion engine, a fuel addition valve (28) is arranged in the exhaust passage upstream of the NOx adsorbent, and, when the NOx adsorbent should be made to release the NOx, the fuel addition valve (28) adds fuel to the NOx adsorbent in the required fuel addition amount to make the air-fuel ratio of the exhaust gas flowing into the NOx adsorbent temporarily rich. In this case, the required fuel addition amount is added divided into a plurality of operations. The fuel addition rate of the fuel addition valve (28) is detected and the overall addition time from the start of the initial divided addition to the end of the final divided addition is corrected in accordance with the fuel addition rate. Further, the divided addition time, interval, or number of divided additions is corrected so that the amount of fuel actually added from the fuel addition valve (28) is maintained at the required fuel addition amount.