Abstract: A particulate deposit amount Spm on a particulate filter disposed in an exhaust passage is estimated during a usual period different from a regeneration period of the particulate filter and during the regeneration period thereof respectively. An increase value Dpm per unit time of the Spm during the usual period is estimated based upon an engine operating condition and a total amount of the Spm is determined by integration thereof (S15, 16).

Abstract: An exhaust gas purifying method for an internal combustion engine, including determining an amount of particulates in an exhaust gas which is accumulated in a particulate filter disposed within an exhaust passage of the engine, determining whether the particulate filter is at an adequate state for regeneration, and executing regeneration of the particulate filter by controlling oxygen concentration in the exhaust gas depending on the amount of the trapped particulates when it is determined that the particulate filter is at the adequate state and the amount of the accumulated particulates exceeds a first preset value. An exhaust gas purifying apparatus including a plurality of sensors detecting parameters relative to an engine operating condition, a particulate filter operative to accumulate particulates present in exhaust gas flowing thereinto and a controller programmed to implement the determinations and the execution of regeneration of the method.

Abstract: An exhaust gas purification apparatus for an internal combustion engine comprises a NOx trap catalyst disposed in an exhaust passage of the internal combustion engine and a control unit. At a purification timing, the control unit determines a space velocity of exhaust gas and selectively switches between a first air-fuel ratio control mode for controlling the air-fuel ratio of the exhaust gas to a rich air-fuel ratio with no need to decrease a concentration of oxygen in the exhaust gas when the determined space velocity is lower than or equal to a threshold value, and selects a second air-fuel ratio control mode for not only controlling the air-fuel ratio of the exhaust gas to a rich air-fuel ratio but also making the concentration of oxygen in the exhaust gas lower than that of the first air-fuel ratio control mode when the determined space velocity is higher than the threshold value.

Abstract: In order to improve performance of NOx reduction, an additional fuel injection immediately after a main fuel injection is performed. By such additional fuel injection, hydrogen (H2) is supplied to a NOx trap catalyst. And in order to prevent engine output torque from varying by the additional fuel injection, the main fuel injection is controlled by whether the additional fuel injection is performed.

Abstract: A nitrogen oxide absorbing material (38) which absorbs nitrogen oxide when the reduction component concentration of exhaust gas in the exhaust passage (31) of an engine (1) is lower than a predetermined concentration, and discharges nitrogen oxide when the reduction component concentration of exhaust gas in the exhaust passage (31) of the engine (1) is higher than the predetermined concentration, and a catalyst (38) which promotes reduction of the discharged nitrogen oxides by a reduction component are provided. A controller (40) first reduces the reduction component concentration of the exhaust gas over a first predetermined time period by, for example, advancing the fuel injection timing. The controller (40) then increases the reduction component concentration of the exhaust gas over a second predetermined time period by, for example, retarding the fuel injection timing.