Abstract: A three-way valve is mounted in the middle of a bypass passage bypassing the upstream and downstream of a compressor, and a purge passage is connected to the three-way valve. When the negative throttle pressure is equal to or above a predetermined value (close to vacuum), the recirculation of the supercharged pressure is performed through the bypass passage. On the other hand, when the negative throttle pressure is below the predetermined value, the purging of the canister is performed on the upstream side of the compressor through the bypass passage.

Abstract: When conditions for purging fuel vapor from a canister, and conditions for learning an idle rotation speed materialize together, then purge concentration is computed. If the purge concentration is low, purge is prohibited, and learning is carried out, while if the purge concentration is high, learning is prohibited and purge is carried out. In this way, erroneous learning due to carrying out purge during learning can be avoided, and the opportunity for purging can be maintained.

Abstract: An object of the present invention is to carry out air-fuel ratio learning to a high accuracy even in a region such as the idling region wherein the number of acquisitions of air-fuel ratio feedback correction values within a predetermined period is small. Average values A for one fluctuation period of an air-fuel ratio feedback correction coefficient .alpha. are computed and stored in order of computation in a RAM, and an arithmetical mean value B obtained. A weighted average value C of a previous learning correction coefficient .sub.KL and the arithmetical mean value B is then obtained (C=X.multidot.B+(1-X).multidot.K.sub.L). The weighting proportion X is set larger the larger the number of acquisitions of the average value A. C is updated/set as a new learning correction coefficient K.sub.L. In this way, since the updating/setting treatment of the learning correction coefficient K.sub.L is carried out in accordance with the acquisition conditions of .alpha.

Abstract: An air-fuel ratio feedback correction coefficient is controlled proportionally and integrally based on the oxygen density of the exhaust gas as detected by an oxygen sensor. The oxygen sensor has decreased response characteristics at low temperatures. When the ignition switch is switched on, a heater in the oxygen sensor is turned on and an initial value KLMDo of a correction value is set based on engine water temperature Tw. The initial value is in turn gradually increased over time and converges to 1.0. Excessive control amplitudes during cold engine starting are thus avoided by compensation for the oxygen sensor temperature condition.

Abstract: A basic discharge QK Of a fuel pump is determined based on an engine load and an engine rotational speed, and further a correction amount QG for correcting the basic discharge QK based on comparison of an actual fuel pressure PT with a target pressure Po is learnt for every driving conditions. Then, the basic discharge QK is corrected with the correction amount QG, whereas in a transient condition, the basic discharge QK is corrected with a transient correction amount QT set on the basis of a variation rate .DELTA.PT Of the fuel pressure PT. Thus, it is possible to ensure that an amount of fuel required by an engine is surely supplied without excess fuel supply from the fuel pump.

Abstract: In an air-fuel ratio control system for an internal combustion engine, a proportional part for determining a feedback correction factor is corrected by a value proportional to an intake air flow corresponding value, whereas an integral part for determining the feedback correction factor is corrected by a value proportional to a square of the intake air flow corresponding value.

Abstract: In an internal combustion engine, an air/fuel ratio senator containing a heater for promoting activation of a sensor element is constituted such that turning-on and heating by the heater is started only after a deviation of an output of the air/fuel ratio sensor becomes more than a predetermined value after starting of the engine. Therefore, forced heating by the heater begins only after moisture in the exhaust adhering to the sensor element is made to fully evaporate by exhaust heat, thereby preventing damage on the sensor element. The damage would be caused by thermal shock due to a difference in the temperature between the inner and the outer surfaces of the sensor element due to forced heating of the moisture.

Abstract: An air/fuel ratio control method and system for an internal combustion engine employing first and second air/fuel ratio sensors, respectively upstream and downstream of a catalytic converter, sets and stores learnt correction values, by learning through an averaging process, for an air/fuel ratio correction value by a second air/fuel ratio sensor, stores a degree of progress of learning with respect to each learning, and modifies the learnt correction value with a modification ratio depending upon the degree of progress of learning. Accordingly, both a promotion of the learning and an enhancement of the accuracy of the learning can be achieved, and thus the emission control performance can be improved by progressively reducing an offset at the transition from an inactive state to an active state of the air/fuel ratio feedback control or at the transition of an engine driving range.

Abstract: In a device for feedback control of an air/fuel ratio using an oxygen sensor for detecting oxygen concentration in exhaust gas, two different reference levels for diagnosis are set according to a detection signal level of the above oxygen sensor. And a response time with which the detection signal of the oxygen sensor crosses the above reference levels for diagnosis is measured so as to diagnose deterioration of the oxygen sensor based on comparison between the above measured response time and a predetermined response time.

Abstract: An apparatus supplies assist air toward an injection nozzle of a fuel injection valve of an internal combustion engine, to atomize an injected fuel. The apparatus starts and stops supplying the assist air according to engine operating conditions while correcting ignition timing or an engine intake air quantity, to thereby suppress fluctuations in engine output.

Abstract: An air-fuel ratio controlling apparatus carries out air-fuel ratio feedback control with the use of air-fuel ratio sensors disposed on the upsteam and downstream sides of a three-way catalytic converter. An air-fuel ratio feedback correction coefficient calculated based on an output value of the upstream air-fuel ratio sensor is corrected according to a correction quantity obtained based on an output value of the downstream air-fuel ratio sensor. This correction quantity is calculated according to a learned collective correction quantity uniformly applicable for a whole operation region, and learned regional correction quantites applicable for divided operation regions, respectively. When the learned collective correction quantity is corrected through addition, a portion added to the learned collective correction quantity is subtracted from each of the learned regional correction quantities.

Abstract: An internal combustion engine coupled with a supercharger includes an air flow meter positioned upstream of the compressor of the supercharger. The engine also has an intercooler disposed between the compressor and a throttle valve. Variation in an amount of air in a boost chamber between the compressor and the throttle valve are derived on the basis of the volume of the boost chamber and variations of the boost pressure detected between the intercooler and the throttle valve. The intake air flow rate detected by the air flow meter is corrected by the thus calculated variations in the amount of air.

Abstract: First and second air-fuel ratio sensors are disposed upstream and downstream of a catalytic converter respectively, and these sensors provide detection signals used to set first and second air-fuel ratio correction quantities, respectively, whereby an averaged air-fuel ratio corection quantity is calculated. During a steady operation in which a change in the averaged air-fuel correction quantity is below a predetermined value, a final air-fuel ratio correction quantity is calculated according to the first and second air-fuel ratio correction quantities. During a transient operation in which a change in the averaged first air-fuel ratio correction quantity exceeds the predetermined value, the second air-fuel ratio correction quantity is fixed from when the change exceeds the predetermined value until a predetermined time has elapsed after the change drops below the predetermined value.

Abstract: An apparatus for controllably sucking intake air into each cylinder of an internal combustion engine and method for controlling the intake air quantity of the internal combustion engine are disclosed in which, in an intake air passage, a first throttle valve associated with an acceleration element (accelerator pedal) is installed in a portion of the intake air passage located upstream of an intake manifold and a plurality of second throttle valves are installed in intake ports branched from the intake manifold whose opening angle is controlled by means of an actuator in response to a control signal input thereto. In addition, a bypass passage is connected between the intake air passage upstream of the first throttle valve and exits of the intake ports downstream of the second throttle valves to provide a swirl stream of the intake air sucked into each combustion chamber and a bypass intake air quantity control valve is installed in the bypass passage.

Abstract: In an internal combustion engine coupled with a supercharger, a basic fuel supply amount is calculated on the basis of an intake air flow rate measured by a hot wire type air flow meter and an engine speed. During an engine decelerating condition, the maximum value (limit value) of the basic fuel supply amount is set on the basis of an open area of an induction system, which is based on a degree of opening of a throttle valve, and the engine speed. The basic fuel supply amount based on the measured value of the air flow meter is limited and can not exceed a value.

Abstract: When the engine throttle valve is closed or very nearly closed, the induction vacuum assumes a level whereat the flow of exhaust gas through the EGR conduit can be induced to assume a sonic level and maximize. Under these conditions, by opening the EGR control valve and checking the change in induction pressure, the amount of recirculation can be monitored in a manner which enables partial EGR conduit blockage and/or similar types of malfunctions to be detected.

Abstract: A method for detecting an intake pressure in an internal combustion engine which comprises detecting the intake pressure in the engine and at least one engine driving condition, variably setting a sampling period of the intake pressure to a sampling period, according to the engine driving condition, which is substantially different from a pulsation period of the intake pressure, sampling processing the intake pressure according to the sampling period set to set the value obtained by the sampling processing as a final detected value of the intake pressure, whereby the reliable sampling of the intake pressure is performed even if the intake pressure is pulsated.

Abstract: An air/fuel ratio control system is designed for detecting small deceleration and subsequently detecting small magnitude acceleration. When small magnitude acceleration is detected, a LAMBDA control correction value which is utilized for deriving fuel injection amount, is fixed at a predetermined value for a predetermined period. The air/fuel ratio utilized during the aforementioned period is set at a value greater than the instantaneous value at a timing at which a demand for small magnitude acceleration is detected.