Abstract: An electronic controller integrates a rate of progress dK of thermal degradation of exhaust purifying catalyst at every predetermined time period, to calculate degree of thermal degradation K of the exhaust purifying catalyst, when the state of thermal degradation of the exhaust purifying catalyst is to be detected. By comparing the degree of thermal degradation K with a defect determining value S, whether the exhaust purifying catalyst is defective because of thermal degradation or not is determined. In calculating the degree of thermal degradation K, the electronic controller calculates the rate of progress dK of thermal degradation in the predetermined time period based on the integrated value of rate of progress dK of thermal degradation up to the last time (degree of thermal degradation K) and on the temperature T of exhaust purifying catalyst at that time, and adds the same to the integrated value up to the last time.

Abstract: The exhaust gas purifier includes a fuel addition valve, an NOx catalytic converter, and a catalyst loaded PM filter. The catalyst temperature of catalyst loaded PM filter is increased to a target temperature by adding fuel to the exhaust gas from fuel addition valve, whereby PM trapped on the filter is purified. When the NOx catalytic converter is deteriorated, the target catalyst temperature of catalyst loaded PM filter is changed to a value larger than the target catalyst temperature when the NOx catalytic converter is in a normal state.

Abstract: Whether discharge of high-concentration, unburned fuel is indicated or not is determined based on air-fuel ratio AF, calculated air-fuel ratio AFc and exhaust temperature thco (S110, S112, S114). If it is determined that high-concentration, unburned fuel would be discharged (“no” in any of S110, S112, S114), amount of fuel addition per one addition is decreased in PM regeneration control (S116). Therefore, in a state where high concentration HC is to be discharged to the downstream of an exhaust purifying filter, the amount of fuel addition at one time is immediately decreased, so that discharge of high-concentration HC to the outside can be prevented, and generation of white smoke can reliably be prevented.

Abstract: During sulfur release control in an internal combustion engine, a rich period and a lean period are alternately repeated. The air-fuel ratio of exhaust gas is controlled toward a target air-fuel ratio (14.3) by adding fuel from a fuel adding valve in the rich period. An ECU determines whether the actual air-fuel ratio of exhaust gas detected by an air-fuel ratio sensor has reached a stoichiometric air-fuel ratio each time the rich period ends at which addition of fuel from the fuel adding valve is stopped. A counter counts the number of times the ECU has determined that the actual air-fuel ratio of exhaust gas has not reached the stoichiometric air-fuel ratio. When the value of the counter becomes greater than or equal to a permissible value, the ECU determines that there is an abnormality in the sulfur release control.

Abstract: If the amount of fuel added to exhaust gas becomes excessive as a result of an abnormality of an addition agent supply unit (60), the air-fuel ratio of exhaust as decreases. If an exhaust gas air-fuel ratio obtained from a value output from an A/F sensor (4) remains equal to or smaller than a predetermined value for a predetermined period, an ECU (2) determines that an addition agent supply unit (60) is abnormal. Upon detection of an abnormality of the addition agent supply unit (60), the ECU (2) incrteases an amount of EGR gas recirculated to the intake side by an EGR unit (40), reduces an amount of fuel injection from injectors (11), and restricts an operational state of an engine body (10) to a low-speed/low-load state. Also, the ECU (2) turns a warning lamp (7) on, warns a driver of the abnormality of the addition agent supply unit (60), and makes it possible to pull a vehicle over safely.

Abstract: The exhaust gas purifier includes a fuel addition valve, an NOx catalytic converter, and a catalyst loaded PM filter. The catalyst temperature of catalyst loaded PM filter is increased to a target temperature by adding fuel to the exhaust gas from fuel addition valve, whereby PM trapped on the filter is purified. When the NOx catalytic converter is deteriorated, the target catalyst temperature of catalyst loaded PM filter is changed to a value larger than the target catalyst temperature when the NOx catalytic converter is in a normal state.

Abstract: Whether discharge of high-concentration, unburned fuel is indicated or not is determined based on air-fuel ratio AF, calculated air-fuel ratio AFc and exhaust temperature thco (S110, S112, S114). If it is determined that high-concentration, unburned fuel would be discharged (“no” in any of S110, S112, S114), amount of fuel addition per one addition is decreased in PM regeneration control (S116). Therefore, in a state where high concentration HC is to be discharged to the downstream of an exhaust purifying filter, the amount of fuel addition at one time is immediately decreased, so that discharge of high-concentration HC to the outside can be prevented, and generation of white smoke can reliably be prevented.

Abstract: An electronic controller integrates a rate of progress dK of thermal degradation of exhaust purifying catalyst at every predetermined time period, to calculate degree of thermal degradation K of the exhaust purifying catalyst, when the state of thermal degradation of the exhaust purifying catalyst is to be detected. By comparing the degree of thermal degradation K with a defect determining value S, whether the exhaust purifying catalyst is defective because of thermal degradation or not is determined. In calculating the degree of thermal degradation K, the electronic controller calculates the rate of progress dK of thermal degradation in the predetermined time period based on the integrated value of rate of progress dK of thermal degradation up to the last time (degree of thermal degradation K) and on the temperature T of exhaust purifying catalyst at that time, and adds the same to the integrated value up to the last time.

Abstract: An apparatus for preventing a filter for purifying exhaust gas emitted by a vehicle diesel engine from overheating is provided. The filter filters particulate matter in exhaust gas. Particulate matter that is accumulated in the filter through filtering is burned and purified by executing a temperature increase process in which the filter is heated. The apparatus includes an electronic control unit as overheat prevention means. During the temperature increase process, the overheat prevention means executes an increase process for increasing the flow rate of exhaust gas when the filter is likely to overheat. As a result, the filter is effectively prevented from overheating.

Abstract: During sulfur release control in an internal combustion engine, a rich period and a lean period are alternately repeated. The air-fuel ratio of exhaust gas is controlled toward a target air-fuel ratio (14.3) by adding fuel from a fuel adding valve in the rich period. An ECU determines whether the actual air-fuel ratio of exhaust gas detected by an air-fuel ratio sensor has reached a stoichiometric air-fuel ratio each time the rich period ends at which addition of fuel from the fuel adding valve is stopped. A counter counts the number of times the ECU has determined that the actual air-fuel ratio of exhaust gas has not reached the stoichiometric air-fuel ratio. When the value of the counter becomes greater than or equal to a permissible value, the ECU determines that there is an abnormality in the sulfur release control.

Abstract: If the amount of fuel added to exhaust gas becomes excessive as a result of an abnormality of an addition agent supply unit (60), the air-fuel ratio of exhaust as decreases. If an exhaust gas air-fuel ratio obtained from a value output from an A/F sensor (4) remains equal to or smaller than a predetermined value for a predetermined period, an ECU (2) determines that an addition agent supply unit (60) is abnormal. Upon detection of an abnormality of the addition agent supply unit (60), the ECU (2) incrteases an amount of EGR gas recirculated to the intake side by an EGR unit (40), reduces an amount of fuel injection from injectors (11), and restricts an operational state of an engine body (10) to a low-speed/low-load state. Also, the ECU (2) turns a warning lamp (7) on, warns a driver of the abnormality of the addition agent supply unit (60), and makes it possible to pull a vehicle over safely.

Abstract: An internal combustion is capable of switching, during engine operation, between a low-temperature combustion state in which an intake air with a high EGR rate is burned to operate the engine, and a normal combustion state in which an intake air with a low EGR rate is burned to operate the engine. In the internal combustion engine, a pilot injection is executed in addition to a main fuel injection, and furthermore the execution of the pilot injection is restricted during the engine operation with a combustion state switched to the low-temperature combustion state.

Abstract: A pump control valve contained in a high-pressure fuel pump is closed when an engine is stopped, so that the pressure of a common rail is prevented from becoming too high when the engine speed NE is not less than a predetermined value &agr;. The pump control valve is opened when the engine speed NE is decreased to a predetermined value &agr;. Consequently, a predetermined amount of fuel is stored in the pump because the high-pressure fuel pump sucks fuel but does not deliver the fuel to the common rail. Therefore, a lack of fuel being delivered at early stage of startup is prevented because the fuel stored in the pump can be delivered to the common rail in a subsequent startup of the engine. Thus, the pressure of fuel necessary to start the engine can be obtained in a short time, and the time for startup can be decreased.

Abstract: A pump control valve contained in a high-pressure fuel pump is closed when an engine is stopped, so that the pressure of a common rail is prevented from becoming too high when the engine speed NE is not less than a predetermined value &agr;. The pump control valve is opened when the engine speed NE is decreased to a predetermined value &agr;. Consequently, a predetermined amount of fuel is stored in the pump because the high-pressure fuel pump sucks fuel but does not deliver the fuel to the common rail. Therefore, a lack of fuel being delivered at early stage of startup is prevented because the fuel stored in the pump can be delivered to the common rail in a subsequent startup of the engine. Thus, the pressure of fuel necessary to start the engine can be obtained in a short time, and the time for startup can be decreased.

Abstract: An internal combustion is capable of switching, during engine operation, between a low-temperature combustion state in which an intake air with a high EGR rate is burned to operate the engine, and a normal combustion state in which an intake air with a low EGR rate is burned to operate the engine. In the internal combustion engine, a pilot injection is executed in addition to a main fuel injection, and furthermore the execution of the pilot injection is restricted during the engine operation with a combustion state switched to the low-temperature combustion state.

Abstract: In a diagnostic apparatus for an evaporative fuel purge system having a canister receiving fuel from a fuel tank via a vapor passage, the fuel being supplied to an intake air passage of an internal combustion engine via a purge passage from the canister, a pressure detecting unit detects a pressure in the evaporative fuel purge system. A decision making unit determines whether or not a failure has occurred in the evaporative fuel purge system on the basis of a relationship between the pressure detected by the pressure detecting unit and a decision value. A correction unit corrects the relationship on the basis of a value of a parameter having an influence on the pressure detected by the pressure detecting unit.

Abstract: A malfunction detecting apparatus for an evaporated fuel purge system includes a first control valve for controlling a flow of fuel vapor in a purge passage between a canister and an intake passage, a second control valve for controlling a flow of air from the atmosphere to the canister via an air inlet opening of the canister, a first control part for turning OFF the second control valve and for turning ON the first control valve during a first time period, so as to subject the purge passage, the canister, and a vapor passage to a negative pressure of the intake passage during the first time period, and a first discriminator for detecting whether or not a malfunction has occurred in the system, in accordance with a pressure change rate derived from pressures of the system sensed at a start of the first time period and at an end thereof.