Abstract: A diesel engine exhaust treatment system has both a NOx reduction device and a diesel particulate filter. The system is designed to ensure that the NOx reduction device operates within its optimal temperature conditions. Using exhaust flow control valves, the exhaust flow can be directed into either the NOx reduction device first or into the diesel particulate filter first, and then into the other device, before exiting out the tailpipe.

Abstract: An apparatus for controlling air-fuel ratio of an internal combustion engine having: a three-way catalytic converter; an oxygen sensor, which is installed at the upstream side of said catalytic converter in respect to exhaust gas flow direction, for generating a switching signal showing rich/lean relative to a certain air-fuel ratio; and an air-fuel ratio sensor, which is installed at the downstream side of said catalytic converter, for generating a linear output signal corresponding to the air-fuel ratio, wherein the apparatus includes a deviation calculation unit for calculating deviation between air-fuel ratio measured by the air-fuel ratio sensor, and target air-fuel ratio; and a feedback control unit of the air-fuel ratio for carrying out feedback control of air-fuel ratio based on the deviation calculated by a deviation calculation unit, and the output signal of the oxygen sensor.

Abstract: An exhaust gas purifying apparatus for a diesel engine has a filter provided in an exhaust pipe of the engine for trapping diesel particulates contained in exhaust gas. The filter is re-generated when an accumulated amount of the diesel particulates exceeds a predetermined value. An electronic control unit estimates the accumulated amount of the diesel particulates from a pressure loss at the filter, based on an accumulation characteristic in which the pressure loss is related to the accumulated amount of the diesel particulates, and corrects the accumulation characteristic depending on flow velocity of the exhaust gas.

Abstract: A method of regulating an amount of NH3 stored in a catalyst of an exhaust after-treatment system includes determining a mass of NH3 into the catalyst based on a dosing rate of a dosing agent that is injected into an exhaust stream upstream of the catalyst and determining a mass of NH3 out of the catalyst. An accumulated mass of NH3 within the catalyst is calculated based on the mass of NH3 into the catalyst and the mass of NH3 out of the catalyst. The dosing rate is regulated based on the accumulated mass of NH3 within the catalyst.