Abstract: A purge flow rate to be added (a value to be added or subtracted) DQPGC is calculated based on a deviation between a target purge flow rate QPGCMD (the current value) and the purge flow rate QPGC(k?1) that was calculated in the previous control cycle (step S118), and a purge flow rate QPGC (the current value) is calculated by adding (adding or subtracting) the purge flow rate to be added DQPGC which is so calculated to the previous value QPGC(k?1) of the purge flow rate (steps S130 to S132).

Abstract: A purge flow rate to be added (a value to be added or subtracted) DQPGC is calculated based on a deviation between a target purge flow rate QPGCMD (the current value) and the purge flow rate QPGC(k−1) that was calculated in the previous control cycle (step S118), and a purge flow rate QPGC (the current value) is calculated by adding (adding or subtracting) the purge flow rate to be added DQPGC which is so calculated to the previous value QPGC(k−1) of the purge flow rate (steps S130 to S132).

Abstract: An evaporated fuel controller for an internal-combustion engine comprises a purge system for purging evaporated fuel generated inside a fuel tank to an intake system of the engine. The controller determines a guard value in accordance with driving conditions of the engine. The guard value is an upper limit of the evaporated fuel. The purge control valve is controlled to prevent the amount of the evaporated fuel from exceeding the guard value. Thus, the amount of the evaporated fuel is controlled so that influence on the air-fuel ratio control is minimized. In one embodiment, the controller further determines a transport lag of the evaporated fuel between the purge control valve and the engine. The controller determines an evaporated fuel amount purged a time period earlier, the time period corresponding to the transport lag.

Abstract: An evaporated fuel controller for an internal-combustion engine comprises a purge system for purging evaporated fuel generated inside a fuel tank to an intake system of the engine. The controller determines a guard value in accordance with driving conditions of the engine. The guard value is an upper limit of the evaporated fuel. The purge control valve is controlled to prevent the amount of the evaporated fuel from exceeding the guard value. Thus, the amount of the evaporated fuel is controlled so that influence on the air-fuel ratio control is minimized. In one embodiment, the controller further determines a transport lag of the evaporated fuel between the purge control valve and the engine. The controller determines an evaporated fuel amount purged a time period earlier, the time period corresponding to the transport lag.

Abstract: An air-fuel ratio control system for an internal combustion engine is provided, which includes an oxygen concentration sensor arranged in the exhaust system and having an output characteristic that an output thereof is substantially proportional to concentration of oxygen present in exhaust gases from the engine. An ECU is responsive to the output of the oxygen concentration sensor, for carrying out feedback control of the air-fuel ratio of a mixture supplied to the engine so as to make the air-fuel ratio equal to a desired air-fuel ratio. An activated state of the oxygen concentration sensor is detected. Correction of the air-fuel ratio of the mixture by the feedback control is limited, depending upon the detected activated state of the oxygen concentration sensor.