Abstract: A catalyst degradation determining method includes the steps of: controlling an upstream-of-catalyst air-fuel ratio occurring upstream of a first catalyst to an air-fuel ratio that is rich of a stoichiometric air-fuel ratio so that first and second catalysts store oxygen up to a maximum storage amount of oxygen. The method then includes the steps of controlling the upstream-of-catalyst air-fuel ratio to a first lean air-fuel ratio until an output of a downstream-of-first-catalyst sensor indicates a lean air-fuel ratio, and then to a second lean air-fuel ratio and that has a value that is determined in accordance with an oxidizing-reducing capability index value, until a time point when an output of a downstream-of-second-catalyst air-fuel ratio sensor indicates an air-fuel ratio that is lean.

Abstract: A catalyst degradation determining method includes the steps of: controlling an upstream-of-catalyst air-fuel ratio occurring upstream of a first catalyst to an air-fuel ratio that is rich of a stoichiometric air-fuel ratio so that first and second catalysts store oxygen up to a maximum storage amount of oxygen. The method then includes the steps of controlling the upstream-of-catalyst air-fuel ratio to a first lean air-fuel ratio until an output of a downstream-of-first-catalyst sensor indicates a lean air-fuel ratio, and then to a second lean air-fuel ratio and that has a value that is determined in accordance with an oxidizing-reducing capability index value, until a time point when an output of a downstream-of-second-catalyst air-fuel ratio sensor indicates an air-fuel ratio that is lean.

Abstract: A catalyst degradation determining method includes the steps of: controlling an upstream-of-catalyst air-fuel ratio occurring upstream of a first catalyst to an air-fuel ratio that is rich of a stoichiometric air-fuel ratio so that first and second catalysts store oxygen up to a maximum storage amount of oxygen. The method then includes the steps of controlling the upstream-of-catalyst air-fuel ratio to a first lean air-fuel ratio until an output of a downstream-of-first-catalyst sensor indicates a lean air-fuel ratio, and then to a second lean air-fuel ratio and that has a value that is determined in accordance with an oxidizing-reducing capability index value, until a time point when an output of a downstream-of-second-catalyst air-fuel ratio sensor indicates an air-fuel ratio that is lean.

Abstract: A catalyst degradation determining method includes the steps of: controlling an upstream-of-catalyst air-fuel ratio occurring upstream of a first catalyst to an air-fuel ratio that is rich of a stoichiometric air-fuel ratio so that first and second catalysts store oxygen up to a maximum storage amount of oxygen. The method then includes the steps of controlling the upstream-of-catalyst air-fuel ratio to a first lean air-fuel ratio until an output of a downstream-of-first-catalyst sensor indicates a lean air-fuel ratio, and then to a second lean air-fuel ratio and that has a value that is determined in accordance with an oxidizing-reducing capability index value, until a time point when an output of a downstream-of-second-catalyst air-fuel ratio sensor indicates an air-fuel ratio that is lean.

Abstract: A catalyst degradation determining method includes the steps of: controlling an upstream-of-catalyst air-fuel ratio occurring upstream of a first catalyst to an air-fuel ratio that is rich of a stoichiometric air-fuel ratio so that first and second catalysts store oxygen up to a maximum storage amount of oxygen. The method then includes the steps of controlling the upstream-of-catalyst air-fuel ratio to a first lean air-fuel ratio until an output of a downstream-of-first-catalyst sensor indicates a lean air-fuel ratio, and then to a second lean air-fuel ratio and that has a value that is determined in accordance with an oxidizing-reducing capability index value, until a time point when an output of a downstream-of-second-catalyst air-fuel ratio sensor indicates an air-fuel ratio that is lean.

Abstract: A catalyst degradation determining method includes the steps of: controlling an upstream-of-catalyst air-fuel ratio occurring upstream of a first catalyst to an air-fuel ratio that is rich of a stoichiometric air-fuel ratio so that first and second catalysts store oxygen up to a maximum storage amount of oxygen. The method then includes the steps of controlling the upstream-of-catalyst air-fuel ratio to a first lean air-fuel ratio until an output of a downstream-of-first-catalyst sensor indicates a lean air-fuel ratio, and then to a second lean air-fuel ratio and that has a value that is determined in accordance with an oxidizing-reducing capability index value, until a time point when an output of a downstream-of-second-catalyst air-fuel ratio sensor indicates an air-fuel ratio that is lean.

Abstract: A catalyst degradation determining method includes the steps of: controlling an upstream-of-catalyst air-fuel ratio occurring upstream of a first catalyst to an air-fuel ratio that is rich of a stoichiometric air-fuel ratio so that first and second catalysts store oxygen up to a maximum storage amount of oxygen. The method then includes the steps of controlling the upstream-of-catalyst air-fuel ratio to a first lean air-fuel ratio until an output of a downstream-of-first-catalyst sensor indicates a lean air-fuel ratio, and then to a second lean air-fuel ratio and that has a value that is determined in accordance with an oxidizing-reducing capability index value, until a time point when an output of a downstream-of-second-catalyst air-fuel ratio sensor indicates an air-fuel ratio that is lean.

Abstract: A catalyst degradation determining method is for use with an emission control apparatus of an internal combustion engine that includes a catalyst disposed in an exhaust passage of the internal combustion engine, and a downstream-of-catalyst air-fuel ratio sensor disposed in the exhaust passage downstream of the catalyst. The method includes the steps of: acquiring an oxidizing-reducing capability index value that changes in accordance with a degree of an oxidizing-reducing capability of the catalyst; controlling an upstream-of-catalyst air-fuel ratio occurring upstream of the catalyst to an air-fuel ratio that is lean of a stoichiometric air-fuel ratio so that the catalyst stores oxygen in the catalyst up to a maximum storage amount of oxygen.

Abstract: In a control device, in a control device of an internal combustion engine provided with an internal combustion engine main body mounted to a vehicle and a heater operating on the basis of an output from a specific sensor given as a trigger at least before the internal combustion engine main body starts, whether or not the heater is operated before the start is stored, and it is judged that the sensor has failed when operation of the heater is not stored.

Abstract: An idle speed control system of an internal combustion engine controls a speed of the internal combustion engine during idling. In its attempt to shift the idle speed control after the internal combustion engine has been started from an open-loop control to a feedback control, the system brings an actual engine speed in the open-loop control to a target speed of the feedback control in a step-by-step manner. It can thus damp shock that occurs when the open-loop control is shifted to the feedback control after the internal combustion engine has been started.

Abstract: An air-fuel ratio control apparatus of an internal combustion engine according to the present invention is provided with an oxygen storage amount estimator for estimating an oxygen storage amount of an exhaust purifying catalyst and air-fuel ratio control means for controlling an air-fuel ratio, based on the oxygen storage amount. An upper threshold and a lower threshold are set for the oxygen storage amount, and the air-fuel ratio controller performs such control that, when the oxygen storage amount is larger than the upper threshold, the controller controls the air-fuel ratio to a rich region and that, when the oxygen storage amount is smaller than the lower threshold, the controller controls the air-fuel ratio to a lean region.

Abstract: An air-fuel ratio control system for an internal combustion engine estimates an oxygen storage amount of a catalyst based on a record of an oxygen storage amount, and controls an air-fuel ratio based on the estimated oxygen storage amount. The catalyst is divided into multiple sections in a flow direction of an exhaust gas, the oxygen storage amount in a specified section is estimated according to a behavior of an exhaust gas on upstream and downstream sides of the respective specified sections, and the air-fuel ratio is controlled based on the estimated oxygen storage amount in the specified section.

Abstract: An air-fuel ratio control system for an internal combustion engine estimates an oxygen storage amount of a catalyst based on a record of an oxygen storage amount, and controls an air-fuel ratio based on the estimated oxygen storage amount. The catalyst is divided into multiple sections in a flow direction of an exhaust gas, the oxygen storage amount in a specified section is estimated according to a behavior of an exhaust gas on upstream and downstream sides of the respective specified sections, and the air-fuel ratio is controlled based on the estimated oxygen storage amount in the specified section.

Abstract: In a control device, in a control device of an internal combustion engine provided with an internal combustion engine main body mounted to a vehicle and a heater operating on the basis of an output from a specific sensor given as a trigger at least before the internal combustion engine main body starts, whether or not the heater is operated before the start is stored, and it is judged that the sensor has failed when operation of the heater is not stored.

Abstract: An air-fuel ratio control apparatus of an internal combustion engine according to the present invention is provided with oxygen storage amount estimating means for estimating an oxygen storage amount of an exhaust purifying catalyst and air-fuel ratio control means for controlling an air-fuel ratio, based on the oxygen storage amount. An upper threshold and a lower threshold are set for the oxygen storage amount, and the air-fuel ratio control means performs such control that, when the oxygen storage amount is larger than the upper threshold, the control means controls the air-fuel ratio to a rich region and that, when the oxygen storage amount is smaller than the lower threshold, the control means controls the air-fuel ratio to a lean region.

Abstract: An idle speed control system of an internal combustion engine controls a speed of the internal combustion engine during idling. In its attempt to shift the idle speed control after the internal combustion engine has been started from an open-loop control to a feedback control, the system brings an actual engine speed in the open-loop control to a target speed of the feedback control in a step-by-step manner. It can thus damp shock that occurs when the open-loop control is shifted to the feedback control after the internal combustion engine has been started.