Abstract: An exhaust gas purification device comprises a NOx catalyst for purifying NOx contained in exhaust gas by using ammonia as a reducing agent, an ammonia supply device for supplying ammonia to the NOx catalyst, a catalyst temperature sensor for detecting the internal temperature of the NOx catalyst, and a control unit that stops the ammonia supply from the ammonia supply device when the stop condition is satisfied that the internal temperature of the NOx catalyst becomes equal to or higher than first prescribed temperature in the process where ammonia is supplied from the ammonia supply device to the NOx catalyst.

Abstract: An exhaust gas purifying system reliably detects an amount of accumulated particulates, lengthens forced regeneration intervals, and improves fuel efficiency. The exhaust gas purifying system comprises: a particulate filter 22 disposed in an exhaust system of an internal combustion engine 2 and collecting particulates from exhaust gas, and an NO2 generating unit 21 upstream of or in the particulate filter 22; a discharged particulate amount calculating unit A1 calculates an amount Me of discharged particulates on the basis of an excess air ratio ?; a burnt particulate amount calculating unit A2 calculates an amount Mb of burnt particulates on the basis of the temperature of exhaust gas in front of the particulate filter or the temperature of the particulate filter; and a particulate accumulation amount calculating unit calculates an amount Ma of accumulated particulates on the basis of the amount Me of discharged particulates or the amount Mb of burnt particulates.

Abstract: An exhaust gas purification device comprises a NOx catalyst for purifying NOx contained in exhaust gas by using ammonia as a reducing agent, an ammonia supply device for supplying ammonia to the NOx catalyst, a catalyst temperature sensor for detecting the internal temperature of the NOx catalyst, and a control unit that stops the ammonia supply from the ammonia supply device when the stop condition is satisfied that the internal temperature of the NOx catalyst becomes equal to or higher than first prescribed temperature in the process where ammonia is supplied from the ammonia supply device to the NOx catalyst.

Abstract: An exhaust gas purifying system reliably detects an amount of accumulated particulates, lengthens forced regeneration intervals, and improves fuel efficiency. The exhaust gas purifying system comprises: a particulate filter 22 disposed in an exhaust system of an internal combustion engine 2 and collecting particulates from exhaust gas, and an NO2 generating unit 21 upstream of or in the particulate filter 22; a discharged particulate amount calculating unit A1 calculates an amount Me of discharged particulates on the basis of an excess air ratio ?; a burnt particulate amount calculating unit A2 calculates an amount Mb of burnt particulates on the basis of the temperature of exhaust gas in front of the particulate filter or the temperature of the particulate filter; and a particulate accumulation amount calculating unit calculates an amount Ma of accumulated particulates on the basis of the amount Me of discharged particulates or the amount Mb of burnt particulates.

Abstract: An engine control system comprises a NOx catalyst selectively reducing NOx from exhaust gases, a reducing agent supply providing the reducing agent to an exhaust system and positioned upstream of the NOx catalyst, NOx sensors detecting an amount of NOx in exhaust gases emitted by an internal combustion engine, a fuel injection system injecting fuel to the internal combustion engine in a main injection mode or a pilot-and-main injection mode, and a control unit activating the fuel injection system in the pilot-and-main injection mode when a NOx purifying efficiency determined on the basis of data of emitted NOx is equal to or below a preset purifying efficiency.

Abstract: An engine control system comprises a NOx catalyst selectively reducing NOx from exhaust gases, a reducing agent supply providing the reducing agent to an exhaust system and positioned upstream of the NOx catalyst, NOx sensors detecting an amount of NOx in exhaust gases emitted by an internal combustion engine, a fuel injection system injecting fuel to the internal combustion engine in a main injection mode or a pilot-and-main injection mode, and a control unit activating the fuel injection system in the pilot-and-main injection mode when a NOx purifying efficiency determined on the basis of data of emitted NOx is equal to or below a preset purifying efficiency.

Abstract: An NOx catalyst 17 for selectively reducing NOx in exhaust gas by adsorbing ammonia is provided at an exhaust system of an engine 1, ammonia or urea water is supplied to the NOx catalyst by reducing agent supplying means 29, a consumption amount of ammonia adsorbed to the NOx catalyst is derived by consumption amount deriving means 43 based on an exhaust amount of NOx exhausted from the engine detected or estimated by NOx exhaust amount deriving means 41 and an actual NOx cleaning rate by the NOx catalyst derived by actual NOx cleaning rate deriving means 42, an actual adsorption amount of ammonia adsorbed to the NOx catalyst is derived in accordance with an addition amount of ammonia and the consumption amount of ammonia by adsorption amount deriving means 45 and the reducing agent supplying means is controlled by controlling means 46 in accordance with the actual adsorption amount.