Abstract: There is provided a control apparatus for an internal combustion engine, which can favorably reduce a load necessary for cranking at the time of the next start, while preventing the fresh air inflow to a catalyst at the time of the stop of the internal combustion engine. A valve stop command is issued to an electrically-driven actuator so that the operational states of intake and exhaust valves becomes a valve closed/stopped state when fuel supply is stopped in response to an establishment of a predetermined stop condition of the internal combustion engine. Then, to return the operational states of the intake and exhaust valves to a valve operating state after the completion of the stopping operation of the internal combustion engine, a valve return command is issued to the actuator, and a crankshaft is rotationally driven by a predetermined angle required to return the operational states of the intake and exhaust valves to the valve operating state.

Abstract: An engine includes variable valve mechanisms capable of causing an intake valve and an exhaust valve to stop. An ECU estimates poisoning states of catalysts, and executes and prohibits stopping of the valves based on the poisoning states. When stopping of the valves is prohibited during a fuel-cut operation, the ECU drives a crankshaft of the engine by means of a motor to idle the engine. Thus, even in a hybrid vehicle in which the engine is stopped during a fuel-cut operation, a sufficient amount of oxygen can be rapidly supplied to the catalysts by utilizing a pumping action of pistons, and the catalysts can be caused to recover from rich poisoning efficiently.

Abstract: An air-fuel ratio control device includes an air-fuel ratio sensor provided upstream from a three-way catalyst, and an oxygen sensor provided downstream from the three-way catalyst. The air-fuel ratio control device controls the fuel supply amount based on the output from the air-fuel ratio sensor, and compensates for errors in the air-fuel ratio sensor by correcting the fuel supply amount based on the output from the oxygen sensor. The fuel supply correction amount is calculated based on an integral term that integrates the deviation between the output from the downstream air-fuel ratio sensor and the target air-fuel ratio. When a fuel supply adjustment control is executed, the value of the integral term in the sub-feedback control is not updated for a predetermined period after the fuel supply adjustment control ends. The actual air-fuel ratio is thus brought to the target air-fuel ratio in an appropriate manner.

Abstract: Internal combustion engine air-fuel ratio control apparatus and method in which the target air-fuel ratio of exhaust gas flowing into an exhaust-gas purification catalyst unit is controlled through at least proportional-integral control such that the correction amount per unit time of the oxygen amount in said catalyst unit is maintained constant. When the intake air amount is smaller than a predetermined amount and the air-fuel ratio detected by an oxygen sensor provided downstream of the catalyst unit is rich, the target air-fuel ratio is controlled to suppress an increase in the air-fuel ratio in the exhaust-gas purification catalyst unit. Accordingly, even if rapid acceleration operation is performed in a state where the intake air amount is extremely small and the air-fuel ratio detected by the oxygen sensor is rich, NOx in exhaust gas can be sufficiently removed through reduction reactions at the exhaust-gas purification catalyst unit.

Abstract: Valve stopping control is performed that changes an operating state of an intake valve and an exhaust valve to a closed-valve stopped state when executing a fuel-cut operation. A device is provided that sets an in-cylinder return-time target air-fuel ratio for an initial two return cycles when returning from a fuel-cut operation. The return-time target air-fuel ratio is set so that respective air-fuel ratios of air-fuel mixtures of fuel and air injected into the same cylinder for respective cycles during the initial return cycles each become values that fall within a combustible range, and so that even if a total amount of fuel injected into the same cylinder for the initial return cycles is supplied into the cylinder during an arbitrary single cycle, the air-fuel ratio of the air-fuel mixture of the total amount of fuel and air becomes a value that falls within the combustible range.

Abstract: Provided is a control apparatus for an internal combustion engine that can favorably achieve compatibility between suppressing deterioration of a catalyst and suppressing progression of rich poisoning thereof when the internal combustion engine has a configuration that performs valve stopping control during a fuel-cut operation. Variable valve operating apparatuses are provided having valve stop mechanisms that can respectively change an operating state of an intake valve and an exhaust valve between a valve operating state and a closed-valve stopped state. When an integrated fuel injection amount is equal to or greater than a predetermined value ? when executing a fuel-cut operation, it is determined that rich poisoning of an upstream catalyst is in a progressed state. In that case, valve stopping control of the intake and exhaust valves is prohibited to thereby supply oxygen to the upstream catalyst.

Abstract: A control apparatus for an internal combustion engine is provided, which is capable of suppressing deterioration of exhaust emission due to an unburned fuel contained in oil which enters a combustion chamber during valve stop control while preventing inflow of fresh air to a catalyst, at a time of valve return following return from fuel cut. Variable valve operating apparatuses having valve stop mechanisms capable of changing operation states of an intake valve and an exhaust valve between valve operation states and valve closed and stopped states are included. Valve stop control that changes the operation states of the intake valve and the exhaust valve to the valve closed and stopped states is performed, at a time of execution of the fuel cut. When a return request from the fuel cut with the valve stop control is detected, a fuel is supplied to a combustion chamber before the operation state of the exhaust valve is returned to the valve operation state.

Abstract: The present invention relates to an air-fuel ratio control device for an internal combustion engine, and makes it possible to maintain high purification performance by suppressing a decrease in the oxygen occlusion capability of a catalyst. When an O2 sensor output oxs is greater than a reference value oxsref, which corresponds to a stoichiometric air-fuel ratio, and smaller than an upper threshold value oxsrefR, a sub-FB reflection coefficient is fixed at a predetermined value vdox2 for providing a lean air-fuel ratio. When, on the other hand, the O2 sensor output oxs is smaller than the reference value oxsref and greater than a lower threshold value oxsrefL, the sub-FB reflection coefficient is fixed at a predetermined value vdox2 for providing a rich air-fuel ratio. The sub-FB reflection coefficient reflects the O2 sensor output oxs in the calculation of a fuel injection amount and increases or decreases to have a consequence on the air-fuel ratio of an exhaust gas.

Abstract: A control apparatus which is capable of determining an abnormality of a stopping operation of an exhaust valve without using a dedicated sensor for detecting the abnormality in an internal combustion engine including a valve stop mechanism capable of maintaining the exhaust valve and an intake valve in a valve closed state is provided. It is discriminated whether or not there is a change to a rich side of a air fuel ratio of gas detected by a main A/F sensor at the time of a fuel cut for all the cylinders associated with a valve stop request for the exhaust valves and intake valves of all the cylinders. Then, when it is discriminated that there is the change to the rich side of the air fuel ratio of the gas, it is determined that the stopping operation of the exhaust valve is not performed in a normal manner in at least one cylinder.

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 of a multi-cylinder internal combustion engine provided with a throttle valve and opening characteristic control means, which system performs feedback control of an air-fuel ratio based on an output of a sensor detecting an air-fuel ratio of exhaust gas and is capable of performing more accurate air-fuel ratio control, is provided. In the feedback control, the relationship of the output of the sensor and a feedback value is corrected based on a feedback learning correction value learned and determined based on the output of the sensor during the feedback control, and, when newly learning the feedback learning correction value, the intake air amount is controlled by only the throttle valve.

Abstract: A control apparatus for an internal combustion engine is provided, the control apparatus being capable of effectively suppressing the inflow of fresh air into a catalyst due to an operational delay of the valve stop mechanism when an execution request for fuel cut is issued. There is provided a valve stop mechanism capable of changing the operational states of intake valves and exhaust valves between a valve operating state and a valve closed/stopped state.

Abstract: There is provided a control apparatus for an internal combustion engine, which can favorably reduce a load necessary for cranking at the time of the next start, while preventing the fresh air inflow to a catalyst at the time of the stop of the internal combustion engine. A valve stop command is issued to an electrically-driven actuator so that the operational states of intake and exhaust valves becomes a valve closed/stopped state when fuel supply is stopped in response to an establishment of a predetermined stop condition of the internal combustion engine. Then, to return the operational states of the intake and exhaust valves to a valve operating state after the completion of the stopping operation of the internal combustion engine, a valve return command is issued to the actuator, and a crankshaft is rotationally driven by a predetermined angle required to return the operational states of the intake and exhaust valves to the valve operating state.

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 fuel injection amount is controlled so that the air-fuel ratio of exhaust gas flowing into a catalyst (6) oscillates around a stoichiometric air-fuel ratio. When it is estimated that the level of oxygen storage capacity of the catalyst (6) is lower than a predetermined reference capacity, the amplitude of the air-fuel ratio of the exhaust gas which oscillates around the stoichiometric air-fuel ratio is reduced by controlling the fuel injection amount. The level of the oxygen storage capacity of the catalyst (6) is estimated based on the amplitude of the output signal from an oxygen sensor (14) disposed downstream of the catalyst (6).

Abstract: Internal combustion engine air-fuel ratio control apparatus and method in which the target air-fuel ratio of exhaust gas flowing into an exhaust-gas purification catalyst unit is controlled through at least proportional-integral control such that the correction amount per unit time of the oxygen amount in said catalyst unit is maintained constant. When the intake air amount is smaller than a predetermined amount and the air-fuel ratio detected by an oxygen sensor provided downstream of the catalyst unit is rich, the target air-fuel ratio is controlled to suppress an increase in the air-fuel ratio in the exhaust-gas purification catalyst unit. Accordingly, even if rapid acceleration operation is performed in a state where the intake air amount is extremely small and the air-fuel ratio detected by the oxygen sensor is rich, NOx in exhaust gas can be sufficiently removed through reduction reactions at the exhaust-gas purification catalyst unit.

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 device includes an air-fuel ratio sensor provided upstream from a three-way catalyst, and an oxygen sensor provided downstream from the three-way catalyst. The air-fuel ratio control device controls the fuel supply amount based on the output from the air-fuel ratio sensor, and compensates for errors in the air-fuel ratio sensor by correcting the fuel supply amount based on the output from the oxygen sensor. The fuel supply correction amount is calculated based on an integral term that integrates the deviation between the output from the downstream air-fuel ratio sensor and the target air-fuel ratio. When a fuel supply adjustment control is executed, the value of the integral term in the sub-feedback control is not updated for a predetermined period after the fuel supply adjustment control ends. The actual air-fuel ratio is thus brought to the target air-fuel ratio in an appropriate manner.

Abstract: An air-fuel ratio control system of a multi-cylinder internal combustion engine provided with a throttle valve and opening characteristic control means, which system performs feedback control of an air-fuel ratio based on an output of a sensor detecting an air-fuel ratio of exhaust gas and is capable of performing more accurate air-fuel ratio control, is provided. In the feedback control, the relationship of the output of the sensor and a feedback value is corrected based on a feedback learning correction value learned and determined based on the output of the sensor during the feedback control, and, when newly learning the feedback learning correction value, the intake air amount is controlled by only the throttle valve.

Abstract: The present invention relates to an air-fuel ratio control device for an internal combustion engine, and makes it possible to maintain high purification performance by suppressing a decrease in the oxygen occlusion capability of a catalyst. When an O2 sensor output oxs is greater than a reference value oxsref, which corresponds to a stoichiometric air-fuel ratio, and smaller than an upper threshold value oxsrefR, a sub-FB reflection coefficient is fixed at a predetermined value vdox2 for providing a lean air-fuel ratio. When, on the other hand, the O2 sensor output oxs is smaller than the reference value oxsref and greater than a lower threshold value oxsrefL, the sub-FB reflection coefficient is fixed at a predetermined value vdox2 for providing a rich air-fuel ratio. The sub-FB reflection coefficient reflects the O2 sensor output oxs in the calculation of a fuel injection amount and increases or decreases to have a consequence on the air-fuel ratio of an exhaust gas.