Abstract: An apparatus for detecting an abnormal air-fuel ratio variation, includes an abnormality detecting unit that detects an abnormal variation in each of a plurality of fuel injection valves on the basis of an injection ratio between the plurality of fuel injection valves, a fluctuation in the output before the injection ratio is changed and the fluctuation in the output after the injection ratio is changed; and a setting unit that corrects the abnormality determination threshold for each of the plurality of fuel injection valves on the basis of the injection ratio.

Abstract: In an abnormality detection apparatus and an abnormality detection method for a construction in which each of cylinders is provided with a plurality of fuel injection valves, if it is discerned that a cause of the inter-cylinder variation abnormality exists in one of the fuel injection valves, an air/fuel ratio fluctuation parameter as an index value that represents the degree of the abnormality is calculated by normalizing the air/fuel ratio fluctuation parameter regarding that fuel injection valve on the basis of the injection proportion used when the parameter is measured.

Abstract: An apparatus for detecting an abnormal air-fuel ratio variation, includes an abnormality detecting unit that detects an abnormal variation in each of a plurality of fuel injection valves on the basis of an injection ratio between the plurality of fuel injection valves, a fluctuation in the output before the injection ratio is changed and the fluctuation in the output after the injection ratio is changed; and a setting unit that corrects the abnormality determination threshold for each of the plurality of fuel injection valves on the basis of the injection ratio.

Abstract: In an abnormality detection apparatus and an abnormality detection method for a construction in which each of cylinders is provided with a plurality of fuel injection valves, if it is discerned that a cause of the inter-cylinder variation abnormality exists in one of the fuel injection valves, an air/fuel ratio fluctuation parameter as an index value that represents the degree of the abnormality is calculated by normalizing the air/fuel ratio fluctuation parameter regarding that fuel injection valve on the basis of the injection proportion used when the parameter is measured.

Abstract: An internal combustion engine is provided in which fuel pressure is changed and fuel injection is controlled in accordance with engine operating conditions. The internal combustion engine comprises a cylinder, a direct injection injector, a detection unit, and a control unit. The control unit includes two maps describing two factors of a fuel injection characteristic coefficient and an invalid injection period with respect to the fuel pressure of the direct injection injector. A first calculating section calculates a required fuel injection quantity. A second calculating section calculates a required fuel injection period in accordance with the required fuel injection quantity and the two factors of the fuel injection characteristic coefficient and the invalid injection period with respect to the fuel pressure. A controlling section controls the fuel injection such that the fuel is injected for the required fuel injection period.

Abstract: There is provided an internal combustion engine, in which a fuel pressure is changed and a fuel injection quantity is controlled in accordance with an engine operating condition when fuel is injected. The internal combustion engine comprises a cylinder, a direct injection injector arranged so as to supply the fuel to the cylinder, a detection unit for detecting an operating condition of the internal combustion engine, and a control unit for controlling the fuel injection.

Abstract: An electronic control unit corrects ignition timing according to changes in an internal EGR amount accompanying actuation of a variable valve actuation mechanism used in an internal combustion engine. The electronic control unit computes a base correction amount AVVTb based on an engine speed NE and an engine load ratio KL. The control unit multiplies the base correction amount AVVTb by the ratio of a square number of an actual valve overlap amount realOL to a square number of a target valve overlap amount tOL, thereby computing a VVT correction amount AVVT of ignition timing. As result, the engine is easily and properly controlled based on the relationship between the state of the variable valve actuation mechanism and changes in the internal EGR amount.

Abstract: An electronic control unit of an internal combustion engine computes a remaining combusted gas amount Megr1, which exists in a cylinder immediately before an intake valve is opened, based on an intake pipe pressure Pm, an engine speed NE, and an intake valve opening timing Topen. At the same time, the control unit computes a backflow combusted gas amount Megr2, which is the amount of combusted gas that flows back into the cylinder from an exhaust pipe after the intake valve is opened, based on the intake pipe pressure Pm, the engine speed NE and a valve overlap amount OL. The control unit computes the sum of the remaining combusted gas amount Megr1 and the backflow combusted gas amount Megr2, and sets the sum as an estimated internal EGR amount MegrALL. As a result, the internal EGR amount is readily and accurately estimated.

Abstract: An electronic control unit corrects ignition timing according to changes in an internal EGR amount accompanying actuation of a variable valve actuation mechanism used in an internal combustion engine. The electronic control unit computes a base correction amount AVVTb based on an engine speed NE and an engine load ratio KL. The control unit multiplies the base correction amount AVVTb by the ratio of a square number of an actual valve overlap amount realOL to a square number of a target valve overlap amount tOL, thereby computing a VVT correction amount AVVT of ignition timing. As result, the engine is easily and properly controlled based on the relationship between the state of the variable valve actuation mechanism and changes in the internal EGR amount.

Abstract: An electronic control unit of an internal combustion engine computes a remaining combusted gas amount Megr1, which exists in a cylinder immediately before an intake valve is opened, based on an intake pipe pressure Pm, an engine speed NE, and an intake valve opening timing Topen. At the same time, the control unit computes a backflow combusted gas amount Megr2, which is the amount of combusted gas that flows back into the cylinder from an exhaust pipe after the intake valve is opened, based on the intake pipe pressure Pm, the engine speed NE and a valve overlap amount OL. The control unit computes the sum of the remaining combusted gas amount Megr1 and the backflow combusted gas amount Megr2, and sets the sum as an estimated internal EGR amount MegrALL. As a result, the internal EGR amount is readily and accurately estimated.