Abstract: A catalyst (17) of a NOx absorbing-and-reducing type is disposed in an exhaust passage (10) of an engine (1). The catalyst (17) absorbs a NOx component in an exhaust gas under an over-oxygen atmosphere and reductively emits the absorbed NOx component according to reduction of oxygen concentration. A control unit (20) of the engine (1) estimates a momentary amount of the absorbed NOx component, and further estimates an integrated amount of the absorbed NOx component according to the integration of the momentary amounts. Then the control unit (20) lets the catalyst (17) to emit the NOx component when the integrated amount is equal to or greater than a predetermined absorption amount. In addition, the control unit (20) corrects the momentary amount to a smaller value in adverse proportion to the increase in the integrated amount.

Abstract: An exhaust gas purifying apparatus comprises a control unit (29) operative to estimate an amount of NOx absorbed by a NOx trap material (17) disposed in an exhaust passage (10) and to make an air-fuel ratio richer so as thereby to cause the NOx trap material to release sulfur when the estimated amount of NOx absorption exceeds a specified amount. Further, the control unit (29) operative to estimate an amount of sulfur absorbed by the NOx trap material (17) and to make an air-fuel ratio richer and rising a temperature of exhaust gas so as thereby to cause the NOx trap material to release sulfur when the estimated amount of sulfur absorption exceeds a specified amount. The control unit restricts an air-fuel ratio from being made richer when the NOx trap material is not expected to absorb NOx due to progress of sulfur absorption resulting from conditionally the sulfur releasing.

Abstract: An engine control system for a direct injection-spark ignition type of engine which is equipped with a fuel injector for spraying fuel directly into a combustion chamber and an exhaust system having a lean NOx conversion catalyst for lowering an emission level of nitrogen oxides (NOx) in exhaust gas at an air-fuel ratio of &lgr;>1 controls divides a given amount of fuel into two parts which are intermittently delivered through early and late split injection respectively in a intake stroke and controls a fuel injector such that a midpoint between points at which the early and late split injection are timed respectively to start is before a midpoint of a intake stroke while the engine is in a lean fuel charge zone.

Abstract: An exhaust gas purifying apparatus comprises a control unit (29) operative to estimate an amount of NOx absorbed by a NOx trap material (17) disposed in an exhaust passage (10) and to make an air-fuel ratio richer so as thereby to cause the NOx trap material to release sulfur when the estimated amount of NOx absorption exceeds a specified amount. Further, the control unit (29) operative to estimate an amount of sulfur absorbed by the NOx trap material (17) and to make an air-fuel ratio richer and rising a temperature of exhaust gas so as thereby to cause the NOx trap material to release sulfur when the estimated amount of sulfur absorption exceeds a specified amount. The control means restricts an air-fuel ratio from being made richer when the NOx trap material is not expected to absorb NOx due to progress of sulfur absorption resulting from conditionally the sulfur releasing.

Abstract: In steps S25 to S42, in order to activate an inactive catalyst earlier, the air-fuel ratio in a combustion chamber is set to be &lgr;≈1 during a period T1 after engine start until catalyst light-off at around 50% HC purifying ratio immediately after the HC purifying ratio begins to rapidly rise, before the catalyst warms up, divisional injection is made at least during the period T1 required until light-off is reached, and a swirl is weakened during the period T1 compared to a latter period which follows this period T1. The divisional injection is made and the swirl is strengthened even during the latter period.

Abstract: In a direct injection engine including an injector (22) for directly injecting fuel into a combustion chamber (15) and a lean NOx catalyst (36), an ECU (50) changes the air-fuel ratio from that higher than the stoichiometric air-fuel ratio to that substantially equal to or lower than the stoichiometric air-fuel ratio. When the air-fuel ratio has changed from a air-fuel ratio higher than the stoichiometric air-fuel ratio to an air-fuel ratio substantially equal to or lower than the stoichiometric air-fuel ratio, the ECU controls to divisionally execute fuel injection from the injector (22) in at least two injections, i.e., leading injection that starts within the intake stroke period and trailing injection that starts within the compression stroke period.

Abstract: An exhaust-gas cleaning device comprises an absorption quantity detector (22) for determining the first and second amounts of NOx and oxygen absorbed by a NOx-absorbing material and an oxygen-absorbing material during first and second reference times based on sensing signals fed from an oxygen concentration detector (11), a NOx quantity estimator (23) for obtaining first and second estimated values of the amount of NOx absorbed by the NOx-absorbing material during the first and second reference times in accordance with engine operating condition, and a deterioration detector (24) for making a judgment on deterioration of the NOx-absorbing material based on the first and second amounts of absorption of NOx and oxygen determined by the absorption quantity detector (22) and the first and second estimated values of the amount of NOx obtained by the NOx quantity estimator (23).

Abstract: In a direct injection engine which comprises an injector (22) for directly injecting fuel into a combustion chamber (15) and a lean NOx catalyst (36), an ECU (50) changes the air-fuel ratio from that higher than the stoichiometric air-fuel ratio to that substantially equal to or lower than the stoichiometric air-fuel ratio. When the air-fuel ratio has changed from a air-fuel ratio higher than the stoichiometric air-fuel ratio to an air-fuel ratio substantially equal to or lower than the stoichiometric air-fuel ratio, the ECU controls to divisionally execute fuel injection from the injector (22) in at least two injections, i.e., leading injection that starts within the intake stroke period and trailing injection that starts within the compression stroke period.

Abstract: A catalyst light-off device for a direct injection engine comprises a temperature state identifier (31) for judging the temperature state of a catalyst (22) for converting exhaust gases, a fuel injection controller (33) for controlling fuel injection from an injector (11), and an ignition timing controller (35). When the catalyst is in its unheated state in which its temperature is lower than its activation temperature, the fuel injection controller (33) causes the injector (11) to make split injection during a period from an intake stroke to an ignition point including a later injection cycle which produces a mixture having local unevenness and an earlier injection cycle which produces a uniform and lean mixture, and the ignition timing controller (35) retards the ignition point.

Abstract: A catalyst (17) of a NOx absorbing-and-reducing type is disposed in an exhaust passage (10) of an engine (1). The catalyst (17) absorbs a NOx component in an exhaust gas under an over-oxygen atmosphere and reductively emits the absorbed NOx component according to reduction of oxygen concentration. A control unit (20) of the engine (1) estimates a momentary amount of the absorbed NOx component, and further estimates an integrated amount of the absorbed NOx component according to the integration of the momentary amounts. Then the control unit (20) lets the catalyst (17) to emit the NOx component when the integrated amount is equal to or greater than a predetermined absorption amount. In addition, the control unit (20) corrects the momentary amount to a smaller value in adverse proportion to the increase in the integrated amount.

Abstract: To reduce the amounts of HC, NOx and other emissions from a direct injection engine when a catalyst is still in its unheated state, and to promote catalyst quick light-off operation by increasing the temperature of exhaust gases, a control device comprises a temperature state identifier (31) for judging the temperature state of a catalyst (22) and a fuel injection controller (33) for controlling fuel injection from an injector (11).

Abstract: A control device for a direct injection engine includes an identifier for judging whether a catalyst is in its unheated state in which its temperature is lower than its activation temperature, an engine temperature state detector for sensing the temperature state of the engine, and a fuel injection controller for controlling fuel injection from the injector. The fuel injection controller controls an injector in such a way that it makes at least two-step split injection including an earlier injection cycle performed during an intake stroke and a later injection cycle performed in a middle portion of a compression stroke or later when the catalyst is in its unheated state, and the later injection cycle is retarded when the catalyst is still in its unheated state but the engine temperature has become higher than a specified temperature compared to a case where the temperature of the engine is equal to or lower than the specified temperature.

Abstract: In steps S25 to S42, in order to activate an inactive catalyst earlier, the air-fuel ratio in a combustion chamber is set to be &lgr;≈1 during a period T1 after engine start until catalyst light-off at around 50% HC purifying ratio immediately after the HC purifying ratio begins to rapidly rise, before the catalyst warms up, divisional injection is made at least during the period T1 required until light-off is reached, and a swirl is weakened during the period T1 compared to a latter period which follows this period T1. The divisional injection is made and the swirl is strengthened even during the latter period.

Abstract: An exhaust-gas cleaning device comprises an absorption quantity detector (22) for determining the first and second amounts of NOx and oxygen absorbed by a NOx-absorbing material and an oxygen-absorbing material during first and second reference times based on sensing signals fed from an oxygen concentration detector (11), a NOx quantity estimator (23) for obtaining first and second estimated values of the amount of NOx absorbed by the NOx-absorbing material during the first and second reference times in accordance with engine operating condition, and a deterioration detector (24) for making a judgment on deterioration of the NOx-absorbing material based on the first and second amounts of absorption of NOx and oxygen determined by the absorption quantity detector (22) and the first and second estimated values of the amount of NOx obtained by the NOx quantity estimator (23).

Abstract: An engine control device, which is adapted for an engine provided with an NOx-absorbing material arranged in an exhaust passage for absorbing NOx in an oxygen-rich atmosphere, and releasing NOx and absorbing sulfur content when the oxygen concentration drops, includes a discriminator for judging whether the amount of sulfur absorbed by the NOx-absorbing material has reached a prescribed quantity, and a reductant concentration controller which increases the temperature of the NOx-absorbing material by decreasing a quantity related to EGR ratio for desulfurizing the NOx-absorbing material based on the result of judgment made by the discriminator. When the quantity related to the EGR ratio is decreased, the temperature of exhaust gas increases. Consequently, the temperature of the NOx-absorbing material increases and the sulfur in the NOx-absorbing material is freed and released.

Abstract: An engine control system for a direct injection-spark ignition type of engine which is equipped with a fuel injector for spraying fuel directly into a combustion chamber, an exhaust system having a lean NOx conversion catalyst for lowering an emission level of nitrogen oxides (NOx) in exhaust gas and an exhaust gas recirculation system divides a given amount of fuel into two parts which are intermittently delivered through early and late split injection respectively in a intake stroke and controls a fuel injector such that a midpoint between points at which the early and late split injection are timed respectively to start is before a midpoint of a intake stroke and the exhaust gas recirculation system admits exhaust gas partly into an intake air stream while the engine is in a lean homogeneous charge zone.

Abstract: An exhaust gas purifying system includes an exhaust gas purifying catalyst having a nitrogen oxide absorbing material which is installed in an exhaust line of an engine and performs split fuel injection to inject fuel directly into each combustion chamber partly during a suction stroke and partly during a compression stroke to provide and supply an increased amount of carbon monoxide to the nitrogen oxide absorbing material so as thereby to desorb sulfur oxides from the nitrogen oxide absorbing material.

Abstract: An engine control system for a direct injection-spark ignition type of engine which is equipped with an exhaust system having a lean NOx conversion catalyst for lowering a NOx level of exhaust gas while the engine operates in a lean fuel charge zone controls the engine to make stratified charge combustion in a zone of partial engine loadings and homogeneous charge combustion in a zone other than said partial engine loading zone and, while the engine operates in a zone where enriched homogeneous charge combustion is made, divides a given amount of fuel into two parts and sprays them through early and late split injection in a intake stroke and admits exhaust gas partly into an intake air stream introduced into the intake system from the exhaust system while the early and late split injection are made. The split injection are caused such that a midpoint between points at which the early and late split injection are timed to start before a midpoint of a intake stroke.

Abstract: An engine control system for a direct injection-spark ignition type of engine which is equipped with a fuel injector for spraying fuel directly into a combustion chamber and an exhaust system having a lean NOx conversion catalyst for lowering an emission level of nitrogen oxides (NOx) in exhaust gas at an air-fuel ratio of .lambda.>1 controls divides a given amount of fuel into two parts which are intermittently delivered through early and late split injection respectively in a intake stroke and controls a fuel injector such that a midpoint between points at which the early and late split injection are timed respectively to start is before a midpoint of a intake stroke while the engine is in a cold condition in an enriched fuel charge zone.

Abstract: An engine control system for a direct injection-spark ignition type of engine which is equipped with a fuel injector for spraying fuel directly into a combustion chamber and an exhaust system having a lean NOx conversion catalyst for lowering an emission level of nitrogen oxides (NOx) in exhaust gas at an air-fuel ratio of .lambda.>1 controls divides a given amount of fuel into two parts which are intermittently delivered through early and late split injection respectively in a intake stroke and controls a fuel injector such that a midpoint between points at which the early and late split injection are timed respectively to start is before a midpoint of a intake stroke while the engine is in a lean fuel charge zone.