Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side and downstream-side air-fuel ratio sensors including an air-fuel ratio correction amount. Also, a learning correction amount is calculated so that a mean value of the air-fuel ratio correction amount is brought close to a reference value. The actual air-fuel ratio is further adjusted in accordance with the learning correction amount.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side and downstream-side air-fuel ratio sensors. Also, when the output of the upstream-side air-fuel ratio sensor is in an abnormal state, an alarm is generated.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an air-fuel ratio correction amount is calculated in accordance with the outputs of the upstream-side and downstrean-side air-fuel ratio sensors, thereby obtaining an actual air-fuel ratio. When a time period of reversions of the output of the downstreamn-side air-fuel ratio sensor is larger than a predetermined value, the calculation of the air-fuel ratio correction amount by the output of the downstream-side air-fuel ratio sensor is prohibited.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side and downstream-side air-fuel ratio sensors including an air-fuel ratio correction amount. Also, a learning correction amount is calculated so that an integration amount of the air-fuel ratio correction amount is brought close to a reference value. The actual air-fuel ratio is further adjusted in accordance with the learning correction amount.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side and downstream-side air-fuel ratio sensors. A center value of an air-fuel ratio correction amount or an air-fuel ratio feedback control parameter calculated based upon the output of the downstream-side air-fuel ratio sensor is calculated by a learning control, and an air-fuel ratio feedback control is initiated by using the center value when the engine enters into an air-fuel ratio feedback control state.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side and downstream-side air-fuel ratio sensors. Also, when the output of the upstream-side air-fuel ratio sensor is in an abnormal state, an alarm is generated.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side air-fuel ratio sensor and the downstream-side air-fuel ratio sensor. The adjustment of the air-fuel ratio by the downstream-side air-fuel ratio sensor is stopped when the engine is in a predetermined state.

Abstract: In a double air-fuel ratio sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust passage, the actual air-fuel ratio is adjusted in accordance with an air-fuel ratio correction amount calculated by using the output of the upstream-side air-fuel ratio sensor and an air-fuel ratio feedback control parameter such as delay time periods, skip amounts, or integration amounts calculated by using the output of the downstream-side air-fuel ratio sensor, and the calculation of the air-fuel ratio feedback control parameter is prohibited when the downstream-side air-fuel ratio sensor is in an abnormal state.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, a delay operation is performed upon the output of the downstream-side air-fuel ratio sensor, so that the actual air-fuel ratio is adjusted in accordance with the output of the upstream-side air-fuel ratio sensor and the delayed output of the downstream-side air-fuel ratio sensor.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side and downstream-side air-fuel ratio sensors including an air-fuel ratio correction amount. Accordingly, only when the change of the intake air density is large, is a learning correction amount calculated so that a means value of the air-fuel ratio correction amount is brought close to a reference value. The actual air-fuel ratio is further adjusted in accordance with the learning correction amount.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, the actual air-fuel ratio is adjusted in accordance with the output of the upstream-side and downstream-side air-fuel ratio sensors. For a predetermined time period after the engine enters an air-fuel ratio feedback control for the downstream-side air-fuel ratio sensor, the control speed by the downstream-side air-fuel ratio sensor is increased.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side and downstream-side air-fuel ratio sensors including an air-fuel ratio correction amount. When a change of an air-fuel ratio correction amount or a change of an air-fuel ratio feedback control parameter calculated in accordance with the output of the downstream-side air-fuel ratio sensor is small, a learning correction amount is calculated so that a mean value of the air-fuel ratio correction amount is brought close to a reference value. The actual air-fuel ratio is further adjusted in accordance with the learning correction amount.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side air-fuel ratio sensor and the downstream-side air-fuel ratio sensor. The adjustment of the actual air-fuel ratio by the downstream-side air-fuel ratio sensor is prohibited in accordance with a coolant temperature of the engine.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an air-fuel ratio correction amount is gradually changed in accordance with the output of the upstream-side air-fuel ratio sensor, and the actual air-fuel ratio is adjusted in accordance with the air-fuel ratio correction amount. The gradual-change speed of the air-fuel ratio correction amount is changed in accordance with the output of the downstream-side air-fuel ratio sensor.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an air-fuel ratio correction amount is remarkably changed when the output of the upstream-side air-fuel ratio sensor is switched from the lean side to the rich side or vice versa, and the actual air-fuel ratio is adjusted in accordance with the air-fuel ratio correction amount. The remarkable-change speed of the air-fuel ratio correction amount is changed in accordance with the output of the downstream-side air-fuel ratio sensor.

Abstract: A fuel injection control method for an internal combustion engine in which asynchronous fuel injection can be carried out in accordance with the change in the number of engine rotations and throttle valve opening and asynchronously with the rotations of a crank shaft within a predetermined range of the number of engine rotations while inhibiting the asynchronous fuel injection when the number of engine rotations is not within the range, whereby the lean and over rich conditions of the air/fuel ratio which often occurred in the conventional method for controlling fuel injection can be prevented and acceleration with a good response can be realized.

Abstract: In an internal combustion engine mounted on a four wheel drive (4WD) vehicle, the fuel cut-off engine speed (N.sub.c) and the fuel cut-off recovery engine speed (N.sub.R) are calculated in accordance with the coolant temperature of the engine. When the vehicle is in a 4WD mode, predetermined minimum values are set in the calculated fuel cut-off engine speed and the calculated fuel cut-off engine speed. When the throttle valve is completely closed and it is determined that the current engine speed is higher than the calculated fuel cut-off engine speed (N.sub.c) or the calculated fuel cut-off recovery engine speed (N.sub.R), which is selected in accordance with whether or not the fuel cut-off operation was being carried out, the fuel cut-off operation is carried out.

Abstract: A fuel-air mixture supply system comprising a Venturi portion formed on the inner surface of a cylindrical suction system having a throttle valve therein, at least one fuel injection port provided in the Venturi portion and open into the suction system, an atomizing chamber located adjacently to the fuel injection port in a co-axial manner to the fuel injection port and having a nozzle to make the atomizing chamber communicate with the fuel injection port, a fuel injection valve connected to the cylindrical suction system to inject the fuel into the atomizing chamber at a predetermined pressure and an air bleed passage making the portion above the throttle valve in the suction system communicate with the atomizing chamber. The fuel injected into the atomizing chamber from the fuel injection valve is atomized by the air drawn into the chamber from the suction system through the air bleed passage.

Abstract: An arrangement for controlling the air-fuel ratio of an air-fuel mixture to be supplied to an internal combustion engine is disclosed. In the arrangement a fluidic element or fluidic elements, performing high frequency on-off control action, are arranged in feedback control circuits for regulating the amount of flow of air or fuel to be supplied into an engine carburetor, thereby adjusting the air-fuel ratio to the level of the stoichiometric air-fuel ratio.

Abstract: A device for controlling the air-fuel ratio of the mixture supplied to an internal combustion engine having a Venturi-type carburetor is disclosed. The device comprises a sensor for detecting the concentration of oxygen contained in the exhaust gas, an electromagnetic valve arranged in an air bleed passage of said carburetor, which passage is controlled so as to be either of opened or closed by said valve in accordance with a signal from said sensor, and another valve comprising an air valve arranged in said air bleed passage and controlling the quantity of air bleed by changing the opening area of said air bleed passage in accordance with the quantity of the suction air introduced to a combustion chamber.