Abstract: An internal combustion engine comprises an exhaust purification catalyst and an air-fuel ratio sensor arranged at a downstream side of the exhaust purification catalyst, stops or decreases a feed of fuel as fuel cut control, and controls an air-fuel ratio of exhaust gas to a rich air-fuel ratio after the end of the fuel cut control as post reset rich control. A first characteristic of change of air-fuel ratio at the time the output air-fuel ratio first passes a first air-fuel ratio region and a second characteristic of change of air-fuel ratio at the time when the output air-fuel ratio first passes a second air-fuel ratio region different from the first air-fuel ratio region are calculated.

Abstract: An abnormality diagnosis system of limit current type air-fuel ratio sensors comprises a current detecting part and a sensor temperature control device. The abnormality diagnosis system uses the current detecting part to detect the output current of the air-fuel ratio sensor when the air-fuel ratio is made the rich air-fuel ratio in the state where temperature of the air-fuel ratio is made the first temperature and when the air-fuel ratio is made the rich air-fuel ratio in the state where the temperature of the air-fuel ratio is made a second temperature higher than the first temperature. It is judged that the air-fuel ratio sensor is abnormal if the output current when the temperature of the air-fuel ratio sensor is the first temperature is larger than the output current when it is the second temperature by a predetermined value or more.

Abstract: When individually controlling a plurality of supply valves is not available, an object of the invention is to determine which of the plurality of supply valves is abnormal with high accuracy, while suppressing a cost increase. A first supply valve, a first selective reduction NOx catalyst, a second supply valve, a second selective reduction NOx catalyst and a NOx sensor are sequentially provided in an exhaust conduit. With a view to identifying which of abnormality of the first supply valve and abnormality of the second supply valve, an instruction is given to the first supply valve and the second supply valve to increase a supply amount of a reducing agent. This identification is based on a NOx concentration detected by the NOx sensor after elapse of a first specified time duration since an instruction time point that is a time point when this instruction is given.

Abstract: In cases where an NOx selective reduction catalyst is provided at a location downstream of an NOx storage reduction catalyst, NOx purification performance in an exhaust gas purification apparatus as a whole is maintained, irrespective of deterioration of the NOx storage reduction catalyst. For this purpose, the reduction of NOx in the NOx storage reduction catalyst is promoted more when the degree of deterioration of the NOx storage reduction catalyst or the NOx selective reduction catalyst is low than when it is high, and the reduction of NOx in the NOx selective reduction catalyst is promoted more when the degree of deterioration of the NOx storage reduction catalyst or the NOx selective reduction catalyst is high than when it is low.

Abstract: An air-fuel ratio sensor is provided in an exhaust passage of an internal combustion engine which can perform fuel cut control, and detects an air-fuel ratio of exhaust gas. The system calculates the response time of the air-fuel ratio sensor based on a changing output value of the air-fuel ratio sensor while performing or after fuel cut control, and compares the calculated response time and a threshold value to diagnose an abnormality. The abnormality diagnosis system is configured to correct the response time so that the response of the air-fuel ratio sensor is treated as becoming faster, the smaller the lean degree of the air-fuel ratio corresponding to the converged value of the air-fuel ratio sensor during fuel cut control; and diagnose an abnormality in the response of the air-fuel ratio sensor based on the corrected calculated response time and threshold value.

Abstract: In the engine including an MPL-EGR system having an HPL-EGR mechanism 6 and an LPL-EGR mechanism 7, a pressure difference between upstream side pressure and downstream side pressure of a low pressure EGR cooler 73 provided in the LPL-EGR mechanism 7 is detected by a pressure difference sensor 89. When an actual pressure difference value detected is higher than a reference pressure difference value in a state where no blocking occurs in the LPL-EGR mechanism 7, and the deviation amount therebetween reaches a predetermined amount, it is determined that the blocking occurs in the inside of the low pressure EGR cooler 73. In contrast, when the actual pressure difference value detected is lower than the reference pressure difference value, and the deviation amount therebetween reaches a predetermined amount, it is determined that the blocking occurs in the inside of the pipe members 74 and 75 except the low pressure EGR cooler 73.

Abstract: In a failure determination system that performs failure determination of an exhaust gas purification apparatus having a NOx selective catalytic reduction catalyst (NOx catalyst) that is disposed in an exhaust passage of an internal combustion engine and uses ammonia as a reducing agent, the failure determination of the exhaust gas purification apparatus is performed by a failure determination unit, based on a detected value of a NOx sensor that detects NOx in exhaust gas. Then, based on an adsorption amount difference at assumed failure that is the difference between an ammonia equilibrium adsorption amount in the NOx catalyst in an equilibrium state of ammonia adsorption, assuming that the exhaust gas purification apparatus is in a predefined failure state, and an actual ammonia adsorption amount in the NOx catalyst, the failure determination itself by the failure determination unit is inhibited or the use of the NOx sensor in the failure determination is restricted.

Abstract: The exhaust cleaner for internal combustion engine is equipped with NOx storage reduction catalyst (161, 162) which is disposed in exhaust passage of an internal combustion engine and which absorb and reduce the NOx contained in exhaust gas. The NOx storage reduction catalyst (161, 162) each include a coating layer that has been formed on the inner wall of cells through which the exhaust passage, the coating layer having the catalytic function. The coating layers have been formed so that the thickness of the coating layer of the NOx storage reduction catalyst (161) located upstream in the flow of the exhaust gas is smaller than the thickness of the coating layer of the NOx storage reduction catalyst (162) located downstream. Due to this configuration, the NOx storage reduction catalyst (161, 162) are inhibit from being poisoned by sulfur and high NOx removal percentage is maintained.

Abstract: An object of the present invention is to increase the accuracy of a deterioration determination in a deterioration determination system of an exhaust emission control device having a selective reduction type NOx catalyst, by suppressing false determinations when the deterioration determination is made. The deterioration determination system includes a catalyst having an oxidative capacity downstream of a NOx catalyst using ammonia as a reducing agent. When an amount of ammonia adsorbed by the NOx catalyst is larger than an equilibrium adsorption amount, out of the amount of ammonia flowing into the catalyst having the oxidative capacity, at least one of the amount of ammonia flowing out from the catalyst having the oxidative capacity and the amount of ammonia converted to NOx in the catalyst having the oxidative capacity or a total value of both is calculated.

Abstract: The invention provides a technique for more accurately executing failure diagnosis for an exhaust gas control apparatus having both a selective reduction function and a filter function. To this end, a failure diagnosis apparatus according to the invention for the exhaust gas control apparatus having both the selective reduction function and the filter function computes a NOx purification rate pertaining to a case where the exhaust gas control apparatus is normal based on an estimated value of the amount of particulate matter (PM) collected or accumulated in the exhaust gas control apparatus and an estimated value of the NO2 ratio of exhaust gas flowing into the exhaust gas control apparatus, and determines that the exhaust gas control apparatus fails when the difference between the result of the calculation and an actual NOx purification rate exceeds a threshold.

Abstract: The present invention has its object to provide a technique which can eliminate HC poisoning of an exhaust gas purification catalyst in a suitable manner in a fuel injection control system of an internal combustion engine which can use a liquid fuel and a gas fuel. In order to achieve this object, the present invention is constructed such that in the fuel injection control system of an internal combustion engine capable of using a liquid fuel and a gas fuel, when HC poisoning of the exhaust gas purification catalyst has occurred, HC poisoning is intended to be eliminated by causing the internal combustion engine to operate by the use of the gas fuel if the temperature of the exhaust gas purification catalyst is less than a specified value, whereas the elimination of HC poisoning is intended by causing the internal combustion engine to operate by the use of the liquid fuel if the temperature of an exhaust gas purification device is not less than the specified value.

Abstract: In a failure determination system that performs failure determination of an exhaust gas purification apparatus having a NOx selective catalytic reduction catalyst (NOx catalyst) that is disposed in an exhaust passage of an internal combustion engine and uses ammonia as a reducing agent, the failure determination of the exhaust gas purification apparatus is performed by a failure determination unit, based on a detected value of a NOx sensor that detects NOx in exhaust gas. Then, based on an adsorption amount difference at assumed failure that is the difference between an ammonia equilibrium adsorption amount in the NOx catalyst in an equilibrium state of ammonia adsorption, assuming that the exhaust gas purification apparatus is in a predefined failure state, and an actual ammonia adsorption amount in the NOx catalyst, the failure determination itself by the failure determination unit is inhibited or the use of the NOx sensor in the failure determination is restricted.

Abstract: An object of the present invention is to detect an abnormality in an exhaust gas purification apparatus having an NSR catalyst and an SCR catalyst disposed on a downstream side of the NSR catalyst more favorably. Air-fuel ratio reduction control is executed to reduce NOx occluded to the NSR catalyst when an integrated value of an amount of NOx flowing into the NSR catalyst reaches an upper limit value of an amount of NOx that can be occluded to the NSR catalyst in a normal condition. It is determined whether or not the exhaust gas purification apparatus is in an abnormal state on the basis of a NOx purification ratio of the exhaust gas purification apparatus calculated at this time.

Abstract: An exhaust gas purification catalyst is recovered from the sulfur poisoning more appropriately.

Abstract: A reduction in the accuracy of a failure determination of a filter due to a reduction in the detection accuracy of a PM sensor is suppressed. In order to achieve this, provision is made for a filter that is arranged in an exhaust passage of an internal combustion engine for trapping particulate matter contained in an exhaust gas, an NOx selective reduction catalyst that is arranged at the downstream side of the filter and reduces NOx by means of a reducing agent which is supplied thereto, a supply device that supplies the reducing agent to the NOx selective reduction catalyst from the upstream side of the NOx selective reduction catalyst, a PM sensor that detects an amount of the particulate matter in the exhaust gas at the downstream side of the NOx selective reduction catalyst, and a prohibition part that prohibits the use of a detected value of the PM sensor in cases where the reducing agent supplied from said supply device passes through the NOx selective reduction catalyst.

Abstract: An exhaust gas purification apparatus for an internal combustion engine is designed to prevent a decrease in the accuracy of measurement by a PM sensor (17). The apparatus includes an NOx catalyst (7) provided in an exhaust passage (3) of an internal combustion engine (1) to reduce NOx by reducing agent supplied to it, a supplying device (6) that supplies urea to the NOx catalyst (7) from the upstream of the NOx catalyst (7), the PM sensor (17) that detects the amount of particulate matter in the exhaust gas in the downstream of the NOx catalyst (7), and a restriction part (10) that restricts supply of urea by the supplying device (6) when the amount of particulate matter adhering to the NOx catalyst (7) is equal to or larger than a threshold.

Abstract: A NOx amount capable of being absorbed by a criteria catalyst as a boundary between degradation and normality is supplied to a NOx storage reduction catalyst and thereafter, a reducer amount corresponding to the NOx amount is supplied by a rich spike operation. Degradation of the NOx catalyst is determined based upon the output of the NOx sensor at this time. Since the degradation of the NOx catalyst is determined only by a magnitude of the NOx sensor output, the degradation diagnosis can be performed with high precision. While the catalyst is normal, the excessive reducers are not supplied and therefore, deterioration of the fuel consumption can be prevented.

Abstract: In cases where at the upstream side of an NOx selective reduction catalyst there is provided another catalyst, sulfur poisoning of both the catalysts is recovered in an appropriate manner. To this end, provision is made for an NH3 generation catalyst arranged in an exhaust passage of an internal combustion engine for generating NH3, the NOx selective reduction catalyst arranged in the exhaust passage at a location downstream of the NH3 generation catalyst for reducing NOx in a selective manner, an upstream side recovery unit to recover sulfur poisoning of the NH3 generation catalyst, and a downstream side recovery unit to recover sulfur poisoning of the NOx selective reduction catalyst after the sulfur poisoning of the NH3 generation catalyst has been recovered by the upstream side recovery unit.

Abstract: The deterioration judgment for an absorption reduction type NOx catalyst (1) is performed quickly and correctly. A catalyst deterioration judging system comprises a supply unit (5) which supplies a reducing agent, a measuring unit (8) which measures a NOx concentration in an exhaust gas at a position downstream from the catalyst (1), a control unit (10) which regulates an amount of the reducing agent so that an air-fuel ratio of the exhaust gas is a lean air-fuel ratio when the reducing agent is supplied from the supply unit (5), and a judging unit (10) which judges deterioration of the catalyst (1) on the basis of the NOx concentration measured by the measuring unit (8) when the amount of the reducing agent is regulated so that the air-fuel ratio of the exhaust gas is the lean air-fuel ratio when NOx is absorbed by the catalyst (1).

Abstract: An air-fuel ratio imbalance among cylinders determining apparatus according to the present invention obtains an output Vabyfs of an air-fuel ratio sensor disposed at a portion downstream of an exhaust gas aggregated portion of an exhaust gas passage, and obtains a second-order differential value d2AF (a change rate of a change rate of a detected air-fuel ratio abyfs) of a detected air-fuel ratio abyfs represented by the air-fuel ratio sensor output Vabyfs. The imbalance determining apparatus determines that an air-fuel ratio imbalance state among cylinders is occurring when a detected air-fuel ratio second-order differential corresponding value (for example, a second-order differential value d2AF per se) obtained in accordance with the second-order differential value d2AF is larger than a first threshold value.