Abstract: An air-fuel ratio control system includes an air-fuel ratio sensor (23, 24) disposed upstream or downstream of an exhaust purification catalyst, and performs feedback control of the fuel supply amount such that an output value of the air-fuel ratio sensor is controlled to the target air-fuel ratio. The feedback control is performed by calculating a correction amount by summing up the value of a proportional and the value of an integral calculated based on the deviation between the output value of the air-fuel ratio sensor and the target air-fuel ratio, and correcting the fuel supply amount based on the obtained correction amount. At cold startup of the internal combustion engine, the value of the integral is set to be a smaller value from the startup of the internal combustion engine until a predetermined period elapses.

Abstract: An air-fuel ratio control system maintaining constant an oxygen storage amount or oxygen release amount per unit time with respect to an exhaust purification catalyst having an oxygen storage capacity even if the intake air amount changes is provided.

Abstract: An exhaust purification device includes a front catalyst arranged in an exhaust system of the internal combustion engine that is longitudinally mounted in a vehicle, a rear catalyst arranged in the exhaust system downstream of the front catalyst, and a bypass pipe that communicates with the exhaust passage of the exhaust system upstream of the front catalyst, communicates with the exhaust passage between the front catalyst and the rear catalyst, and is arranged at a position that is spaced apart in a direction perpendicular to the vibration direction of the exhaust system.

Abstract: An air-fuel ratio control system maintaining constant an oxygen storage amount or oxygen release amount per unit time with respect to an exhaust purification catalyst having an oxygen storage capacity even if the intake air amount changes is provided.

Abstract: An acceleration request is detected in accordance with an accelerator opening PA (time t3 in FIG. 5B). If the detected acceleration request is a moderate acceleration request, an idle opening TA0 is set as an actual throttle opening TA (FIG. 5E), and a request for retarding an intake valve timing VVT is issued (FIG. 5D). Recovery from fuel cut-off is achieved at time t4 at which a misfire limit value (combustion assurance VVT value L) is reached by an actual VVT value (FIG. 5A).

Abstract: An acceleration request is detected in accordance with an accelerator opening PA (time t3 in FIG. 5B). If the detected acceleration request is a moderate acceleration request, an idle opening TA0 is set as an actual throttle opening TA (FIG. 5E), and a request for retarding an intake valve timing VVT is issued (FIG. 5D). Recovery from fuel cut-off is achieved at time t4 at which a misfire limit value (combustion assurance VVT value L) is reached by an actual VVT value (FIG. 5A).

Abstract: The output from an air-fuel ratio sensor is corrected using an integral term that is calculated by integrating values of deviation of the output from an oxygen sensor with respect to a reference output that would be obtained when the combustion air-fuel ratio is stoichiometric, when an engine operates with a target combustion air-fuel ratio set to the stoichiometric air-fuel ratio. A fuel-cutoff prohibition period in which fuel supply cutoff is prohibited is set so that the engine continues to operate with the target combustion air-fuel ratio set to the stoichiometric air-fuel ratio, until the integral term is updated at least once. The integral term may be updated when a predetermined updating condition is satisfied.

Abstract: An air-fuel ratio control apparatus of an internal combustion engine includes first and second catalysts 10 and 12, first air-fuel ratio acquiring means 8 provided up-stream of the first catalyst, for acquiring an air-fuel ratio of exhaust gas; second air-fuel ratio acquiring means 11 for acquiring an air-fuel ratio of the exhaust gas flowing into the second catalyst, and air-fuel ratio controlling means 13 for controlling an air-fuel ratio according to the air-fuel ratios acquired by the first and second air-fuel ratio acquiring means, and the air-fuel ratio controlling means is provided with lean control means 13 for controlling an air-fuel ratio until the second catalyst becomes lean after completion of a fuel quantity increasing operation of the engine, and intermediate lean control means 13 for performing control to change the air-fuel ratio to a lean air-fuel ratio within the range enough to make the first catalyst lean and not enough to make the second catalyst lean, between the fuel quantity increasin

Abstract: A first integration value is obtained by performing time integration on a feedback control signal during the time interval between the instant at which the deviation between a reference signal and the output signal of an oxygen sensor reverses from a negative value to a positive value and the instant at which the deviation reverses back to the negative value. A second integration value is obtained by performing time integration on a feedback control signal during the time interval between the instant at which the deviation between a reference signal and the output signal of the oxygen sensor reverses from a positive value to a negative value and the instant at which the deviation reverses back to the positive value. When the deviation between the absolute values of the first and second integration values is smaller than a predetermined threshold value, it is concluded that a feedback learning value is completely learned.

Abstract: A catalyst is positioned in an exhaust path of an internal-combustion engine. A main air-fuel ratio sensor and sub-oxygen sensor are respectively positioned upstream and downstream of the catalyst. A main feedback operation is performed so that the output of the main air-fuel ratio sensor is fed back and reflected in the fuel injection quantity until the control A/F prevailing upstream of the catalyst coincides with the target A/F. A sub-feedback operation is performed so that the output of the sub-oxygen sensor is fed back and reflected in the fuel injection quantity until the air-fuel ratio of an exhaust gas flowing out of the catalyst agrees with a theoretical air-fuel ratio. Since a catalyst window varies in accordance with the intake air quantity, the fuel injection quantity is corrected so that the larger the intake air quantity becomes, the richer the control A/F is.

Abstract: A first integration value is obtained by performing time integration on a feedback control signal during the time interval between the instant at which the deviation between a reference signal and the output signal of an oxygen sensor reverses from a negative value to a positive value and the instant at which the deviation reverses back to the negative value. A second integration value is obtained by performing time integration on a feedback control signal during the time interval between the instant at which the deviation between a reference signal and the output signal of the oxygen sensor reverses from a positive value to a negative value and the instant at which the deviation reverses back to the positive value. When the deviation between the absolute values of the first and second integration values is smaller than a predetermined threshold value, it is concluded that a feedback learning value is completely learned.

Abstract: An upstream-side catalyst is arranged in an exhaust passage and a downstream-side catalyst is arranged in the exhaust passage downstream of the upstream-side catalyst. An air-fuel ratio sensor is attached for detecting the air-fuel ratio in the exhaust passage between the upstream-side catalyst and downstream-side catalyst. A representative upstream-side stored oxygen value OXU is calculated based on whether the control state of the engine is the “slight rich” control, “slight lean” control, fuel increase correction, or engine fuel cut and a representative downstream-side stored oxygen value OXD is calculated based on the engine control state and the output of the air-fuel ratio sensor.

Abstract: An upstream-side catalyst is arranged in an exhaust passage and a downstream-side catalyst is arranged in the exhaust passage downstream of the upstream-side catalyst. An air-fuel ratio sensor is attached for detecting the air-fuel ratio in the exhaust passage between the upstream-side catalyst and downstream-side catalyst. A representative upstream-side stored oxygen value OXU is calculated based on whether the control state of the engine is the “slight rich” control, “slight lean” control, fuel increase correction, or engine fuel cut and a representative downstream-side stored oxygen value OXD is calculated based on the engine control state and the output of the air-fuel ratio sensor.

Abstract: A catalyst is positioned in an exhaust path of an internal-combustion engine. A main air-fuel ratio sensor and sub-oxygen sensor are respectively positioned upstream and downstream of the catalyst. A main feedback operation is performed so that the output of the main air-fuel ratio sensor is fed back and reflected in the fuel injection quantity until the control A/F prevailing upstream of the catalyst coincides with the target A/F. A sub-feedback operation is performed so that the output of the sub-oxygen sensor is fed back and reflected in the fuel injection quantity until the air-fuel ratio of an exhaust gas flowing out of the catalyst agrees with a theoretical air-fuel ratio. Since a catalyst window varies in accordance with the intake air quantity, the fuel injection quantity is corrected so that the larger the intake air quantity becomes, the richer the control A/F is.

Abstract: The fuel pump control system includes an electronic control unit (ECU) for controlling the discharge capacity of a plunger type high pressure fuel pump driven by a driving cam connected to the camshaft of an engine. The engine is provided with a variable valve timing device for controlling valve timing of the engine by adjusting the rotation phase of the camshaft relative to the crankshaft. The pump is provided with a suction valve. When the open/close timing of the suction valve changes, the effective discharge stroke of the pump and, thereby the discharge capacity of the pump changes. The ECU estimates the change in the valve timing of the engine during the effective discharge stroke of the pump before the effective discharge stroke starts, and adjusts the open/close timing of the suction valve in accordance with the estimated change in the valve timing so that the discharge capacity of the pump becomes a target discharge capacity regardless of the change in the valve timing of the engine.

Abstract: An air-fuel ratio control device for an engine comprises a three way catalyst arranged in the exhaust passage, an upstream-side air-fuel ratio sensor arranged in the exhaust passage upstream of the three way catalyst, and an downstream-side air-fuel ratio sensor arranged in the exhaust passage downstream of the three way catalyst. A first feedback correction coefficient is calculated on the basis of an output of the upstream-side sensor to make the air-fuel ratio equal to the stoichiometric air-fuel ratio. A smoothed value is calculated on the basis of an output of the downstream-side sensor, the absolute value of a changing rate of the smoothed value being smaller than the absolute value of the changing rate of the output of the downstream-side sensor. A second feedback correction coefficient is calculated on the basis of a deviation of the output of the downstream-side sensor from the smoothed value. The first feedback correction coefficient is corrected using the second feedback correction coefficient.

Abstract: An evaporated fuel treatment device comprising a purge control valve for controlling an amount of fuel vapor fed into the intake passage from a charcoal canister. The fuel vapor concentration is divided into a first fuel vapor concentration changing proportionally to a purge rate of the fuel vapor and a second fuel vapor concentration changing without regard as to the purge rate of the fuel vapor. The first fuel vapor concentration per unit purge rate is reduced following a reduction in the amount of fuel absorbed in the canister. At this time, the second fuel vapor concentration is calculated from the amount of deviation of the air-fuel ratio from the target air-fuel ratio.

Abstract: The present invention provides an apparatus and a method for controlling fuel injection in a multicylinder internal combustion engine to prevent discharge of unburned HC and purify the exhaust gas at the engine start-up. The apparatus controls the opening of fuel injection valves by a drive circuit for a period of time on the basis of a cranking amount TAUST determined corresponding to the engine conditions at the start of the engine and a post-cranking amount TAU determined corresponding to the engine conditions after the engine is started. The apparatus detects completion of fuel injections at the start of the engine by detecting that the cranking amount TAUST has been injected once to each cylinder and switches the fuel injection amount from the cranking amount TAUST to the post-cranking amount TAU after detecting the completion of the above fuel injections.

Abstract: The device for detecting the air-fuel ratio in an internal combustion engine comprising an air-fuel ratio sensor arranged in an exhaust system of the engine and passes an electric current when an electric voltage is applied thereto, an air-fuel ratio sensor circuit that applies the electric voltage to the sensor, detects the current and outputs a signal proportional to the magnitude of the detected current, and a memory for storing a conversion map for calculating the air-fuel ratio in the engine corresponding to the output of the air-fuel ratio sensor circuit by the use of a reference air-fuel ratio sensor and the reference air-fuel ratio sensor circuit.

Abstract: A fuel supply control system for an engine comprises a fuel injector for feeding fuel into the engine, a canister for temporarily storing fuel vapor, and an air-fuel ratio sensor for sensing an air-fuel ratio of the engine. The canister is connected to an intake passage downstream of a throttle valve to purge a purge gas, that is, air containing fuel vapor, into the intake passage. An amount of fuel to be injected from the fuel injector is corrected in accordance with output a signals of the air-fuel ratio sensor to make the air-fuel ratio equal to a target air-fuel ratio. An initial value of a fuel vapor concentration coefficient, which represents a concentration of fuel vapor in air fed into the engine, is calculated in accordance with a deviation caused when the purging operation starts.