Abstract: To obtain an exhaust gas purification method for an internal combustion engine for detecting timing at which an inflow NOx amount flowing into an NOx absorption catalyst exceeds an NOx amount processable by the NOx absorption catalyst, and enriches the air/fuel ratio to prevent deterioration of the exhaust gas and maintain good fuel consumption. Based on an NOx amount absorbed in the NOx absorption catalyst and a maximum NOx absorption amount NOx of the absorption catalyst, a processable NOx amount processable by the NOx absorption catalyst per unit time is calculated and compared with the inflow NOx amount entering the NOx absorption catalyst per unit time, and when it is determined that the inflow NOx amount is greater, the air/fuel ratio is switched to rich.

Abstract: An air-fuel ratio of exhaust gas flowing into a NOx absorber catalyst is compulsorily changed from a lean side to a rich side to release NOx absorbed by the NOx absorber catalyst. The Nox is reduced at the same time. If temperature of the NOx absorber catalyst is lower than a first predetermined temperature T1, temporaral change of the air-fuel ratio of the exhaust gas to the rich side for the purpose of releasing and reducing NOx is inhibited, and if temperature of the NOx absorber catalyst is higher than the first predetermined temperature T1 and lower than a second predetermined temperature T2, at the time of changing temporarily the air-fuel ratio of the exhaust gas to the rich side for the purpose of releasing and reducing NOx, timing of changing the air-fuel ratio and the set air-fuel ratio are changed depending on the temperature of the NOx absorber catalyst.

Abstract: To obtain an exhaust gas purification method for an internal combustion engine for detecting timing at which an inflow NOx amount flowing into an NOx absorption catalyst exceeds an NOx amount processable by the NOx absorption catalyst, and enriches the air/fuel ratio to prevent deterioration of the exhaust gas and maintain good fuel consumption. Based on an NOx amount absorbed in the NOx absorption catalyst and a maximum NOx absorption amount NOx of the absorption catalyst, a processable NOx amount processable by the NOx absorption catalyst per unit time is calculated and compared with the inflow NOx amount entering the NOx absorption catalyst per unit time, and when it is determined that the inflow NOx amount is greater, the air/fuel ratio is switched to rich.

Abstract: An air-fuel ratio of exhaust gas flowing into a NOx absorber catalyst is compulsorily changed from a lean side to a rich side to release NOx absorbed by the NOx absorber catalyst. The Nox is reduced at the same time. If temperature of the NOx absorber catalyst is lower than a first predetermined temperature T1, temporaral change of the air-fuel ratio of the exhaust gas to the rich side for the purpose of releasing and reducing NOx is inhibited, and if temperature of the NOx absorber catalyst is higher than the first predetermined temperature T1 and lower than a second predetermined temperature T2, at the time of changing temporarily the air-fuel ratio of the exhaust gas to the rich side for the purpose of releasing and reducing NOx, timing of changing the air-fuel ratio and the set air-fuel ratio are changed depending on the temperature of the NOx absorber catalyst.

Abstract: An air/fuel ratio correction cylinder determining section 25 specifies, based on the peak phase, a cylinder for which an air/fuel ratio is to be corrected. A cylinder-specific air/fuel ratio correcting section in the form of respective cylinder correcting sections 31 through 34 corrects an amount of fuel to be supplied to a cylinder which becomes an air/fuel ratio correction target. A cylinder for which an air/fuel ratio deviates from the remaining cylinders is specified as a fuel amount correction target based on a change in the output value of the air/fuel ratio sensor.

Abstract: An air/fuel ratio control apparatus for an internal combustion engine is capable of making the air/fuel ratios of respective cylinders uniform with high accuracy without causing an increase in the load of arithmetic operations of a CPU, while avoiding the influence of a change in an engine operating state, etc. An air/fuel ratio detection period setting section 22 sets an air/fuel ratio detection period T in which all the exhaust strokes of respective cylinders of the engine are included. A peak phase detecting section 21 takes in an output value &lgr; of an air/fuel ratio sensor 8 for an air/fuel ratio detection period, and detects a peak phase P&lgr; which becomes a maximum on a rich side or a lean side owing to a change in the air/fuel ratio. An air/fuel ratio correction cylinder determining section 25 specifies, based on the peak phase, a cylinder for which an air/fuel ratio is to be corrected.

Abstract: A device for controlling the fuel pressure in a direct cylinder fuel injection engine, which suppresses the over-shooting or under-shooting of fuel pressure under a condition in which the fuel pressure is changing, in order to improve the response and stability. A control means 20A controls the fuel pressure by feedback so that a real fuel pressure PF comes into agreement with a target fuel pressure PFo, and includes a means 204 for operating the fuel pressure correction amount for variably setting a control gain for controlling the fuel pressure by feedback, the means for operating the fuel pressure correction amount so working as to change the control gain when the target fuel pressure has changed by more than a predetermined amount from a first control gain for when the fuel pressure remains steady over to a second control gain for when the fuel pressure changes.

Abstract: A fuel injection control assembly for a cylinder-injected engine includes a mean fuel pressure calculating element for calculating mean fuel pressure, a fuel pressure regulator for adjusting the fuel pressure, an injection pulse calculating element for calculating an injection pulse duration for an injector based on the mean fuel pressure, and a cycle modifying element for modifying the calculation cycle for the mean fuel pressure in response to the running speed of the engine or of a high-pressure pump, the cycle modifying element setting the calculation cycle to a length greater than or equal to a running cycle of the high-pressure pump to ensure that the number of times that fuel pressure is detected within each calculation cycle of the mean fuel pressure calculating element is greater than or equal to a predetermined number of times.