Abstract: An air-fuel ratio control system for an internal combustion engine is provided which is capable of appropriately and promptly correcting variation in the air-fuel ratio of a mixture between cylinders and realizing a very robust air-fuel ratio control, even with a complicated exhaust system layout. The ECU of the system for control of the air-fuel ratio of a mixture supplied to first to fourth cylinders determines a feedback correction coefficient, calculates a cylinder-by-cylinder variation coefficient indicative of variation in air-fuel ratio between the cylinders, based on a model parameter of a model having the input of the feedback correction coefficient thereto and the output of the detected air-fuel ratio, identifies the model parameter, corrects a basic fuel injection amount such that the cylinder-by-cylinder variation parameter converges to a moving average value thereof, thereby calculating a cylinder-by-cylinder final fuel injection amount.

Abstract: The individual cylinder air to fuel ratio of an internal combustion engine varies due to the fact that the intake manifold cannot distribute airflow into the individual cylinders evenly. This feature of the present invention utilizes minimum timing for best torque MBT timing criterion provided by the ionization signals or by the in-cylinder pressure signals to balance the air to fuel ratios of the individual cylinders. The control method of the present invention comprises: calculating a mean timing coefficient, calculating a timing coefficient error, integrating the minimum timing for best torque timing coefficient error, calculating a raw fuel trim coefficient, resealing the raw fuel trim coefficient, updating a feedforward look-up table based upon the current engine operating conditions, and calculating a final fueling command.

Abstract: An air-fuel ratio detected by an air-fuel ratio sensor is estimated based on an estimation value of air-fuel ratio of an air-fuel mixture formed inside a cylinder, and based on an air-fuel ratio estimated as being detected by this air-fuel ratio sensor and the air-fuel ratio detected based on an output signal of the air-fuel ratio sensor, the estimation value of the cylinder air-fuel ratio is corrected and a fuel injection quantity is corrected based on the corrected cylinder air-fuel ratio.

Abstract: The invention relates to a method as well as an arrangement for determining cylinder-individual differences of a control variable in a multi-cylinder internal combustion engine. It is provided that a determination of cylinder-individual charge differences is carried out.

Abstract: A fuel supply system for use in an internal combustion engine, comprising: an intake passage; a downstream fuel injection valve near the port of each cylinder of the engine and downstream of the intake passage; and a controller, wherein the intake passage includes a fuel injection/evaporation device which has an upstream fuel injection valve; a heater for evaporating injected fuel; and an air passage for supplying the injected fuel with air. The controller is adapted to control the amount of fuel injected from the downstream fuel injection valve and the upstream fuel injection valve, thereby controlling the fuel-air ratio of the injected fuel.

Abstract: A method is presented for determining the fuel/air ratio in the individual cylinders (single cylinder lambda) of an internal combustion engine having a plurality of cylinders, whose exhaust gases mix together in a common exhaust gas pipe system, from the signal of an exhaust gas probe, whose mounting location lies in the common exhaust gas pipe system, with the aid of an invertible model for the intermixing of the exhaust gases at the mounting location of the exhaust gas probe. The method is distinguished in that, in the determination of the single cylinder lambda from the signal of the one exhaust gas probe evaluated with the aid of the inverted model, the rotational angle position of the exhaust gas probe at its mounting position is taken into consideration.

Abstract: The invention concerns a method for operating an internal combustion engine (1, 18) having a plurality of combustion chambers (4), in the case of which the combustion chambers (4) are charged with fuel and air or with a fuel/air mixture. In order to prevent torque jumps from occurring when cylinders (3) of the internal combustion engine (1, 18) are shut down and when switching the operating mode of direct-injection internal combustion engines (18), it is proposed that the charging of the combustion chambers (4) with fuel and air or with a fuel/air mixture be controlled individually via open-loop or closed-loop control for each combustion chamber (4). In the case of a direct-injection internal combustion engine (18), a certain number of combustion chambers (4) can be operated with homogenous-charge operation, and the remaining combustion chambers (4) can be operated with stratified-charge operation in accordance with the level of torque required.

Abstract: A method of metering fuel with a fuel injector, in particular a fuel injector for fuel injection systems in internal combustion engines is described, having a piezoelectric or magnetostrictive actuator and a valve closing body which is operable by the actuator with a valve lift, cooperating with a valve seat face provided on a valve seat body to form a sealing seat. The valve lift may be adjusted variably as a function of a variable control signal triggering an actuator to produce a variable fuel flow at the sealing seat. To produce afitted curve, the fuel flow of the fuel jet sprayed by the fuel injector is measured as a function of the control signal to produce a fitted curve, and a predetermined fuel flow is set with the control signal by using the fitted curve.

Abstract: A device and a method are described for controlling an internal combustion engine, in which a control deviation and a governor are allocated to each cylinder of the internal combustion engine, each governor preselecting a cylinder-specific triggering signal on the basis of the allocated control deviation. Cylinder-specific actual values are ascertained on the basis of a signal from a sensor arranged in the exhaust train and are compared to a setpoint value. Triggering signals for the cylinder-individual control of the fuel quantity and/or air quantity are preselected on the basis of the comparison.

Abstract: An air-fuel ratio control apparatus for controlling an air-fuel ratio of an air-fuel mixture to be supplied to an internal combustion engine having a plurality of cylinders so that the air-fuel ratio coincides with a target air-fuel ratio. An air-fuel ratio is detected by an air-fuel ratio sensor provided at a position downstream of a joining portion of an exhaust manifold connected to the plurality of cylinders. Model parameters of a controlled object model defined by a relation between an air-fuel ratio detected by the air-fuel ratio sensor and a fuel supply amount parameter that specifies a fuel supply amount to each cylinder of the engine. A degree of differences between air-fuel ratios of air-fuel mixtures to be supplied to the plurality of cylinders is determined according to the identified model parameters.

Abstract: A generic technique for the detection of air-fuel ratio or torque imbalances in a three-cylinder engine equipped with either a current production oxygen sensor or a wide-range A/F sensor, or a crankshaft torque sensor, is disclosed. The method is based on a frequency-domain characterization of pattern of imbalances and its geometric decomposition into two basic templates. Once the contribution of each basic template to the overall imbalances is computed, templates of same magnitude of imbalances but of opposite direction are imposed to restore air-fuel ratio (or torque) balance among cylinders. At any desired operating condition, elimination of imbalances is achieved within few engine cycles. The method is applicable to current and future engine technologies with variable valve-actuation, fuel injectors and/or individual spark control.

Abstract: An internal combustion engine having cylinders with injection valves and air mass-setting actuators, an air/fuel ratio sensor detecting the ratio in the individual cylinders, and a sensor detecting a torque generated in the individual cylinders or differences in the torques generated in the cylinders includes individually determining the air/fuel ratio for each cylinder, individually correcting an activation of the fuel injection valve for each cylinder as a function of the detected air/fuel ratio and of a desired value of the air/fuel ratio, determining the variable characterizing the torque or the differences in the torque for each cylinder, individually correcting an activation of the air mass-setting actuator for each cylinder as a function of the detected value of the variable characterizing the torque or of the variable characterizing the difference in the torque specifically with the effect of assimilating the torques generated by the individual cylinders.

Abstract: An exhaust treatment system for an internal combustion engine includes a catalytic emission control device. When transitioning the engine between a lean operating condition and a stoichiometric operating condition, as when scheduling a purge of the downstream device to thereby release an amount of a selected exhaust gas constituent, such as NOx, that has been stored in the downstream device during the lean operating condition, the air-fuel ratio of the air-fuel mixture supplied to each cylinder is sequentially stepped from an air-fuel ratio of at least about 18 to the stoichiometric air-fuel ratio. The purge event is preferably commenced when all but one cylinders has been stepped to stoichiometric operation, with the air-fuel mixture supplied to the last cylinder being stepped immediately to an air-fuel ratio rich of a stoichiometric air-fuel ratio.

Abstract: In an engine control apparatus for a multicylinder engine including an injection pulse width-setting unit for setting an injection pulse width for an injection valve situated in each cylinder based on signals output from an engine operational condition-detection system situated in a vehicle; the injection pulse width-setting unit includes an engine starting injection pulse-setting unit for setting an injection pulse width for each cylinder in the engine starting operation, and the engine starting injection pulse-setting unit includes an injection pulse width-correction unit for determining a correction coefficient to a basic injection pulse width, for each cylinder at each cycle.

Abstract: An internal combustion engine that utilizes a control system for improving operation of the engine under a variety of conditions. The control system includes a sensor that directly senses a combustion condition. The output of the sensor is utilized in adjusting the air-fuel mixture delivered to each cylinder to optimize engine operation.

Abstract: A system for regulating the fuel-air mixture in a multi-cylinder internal combustion engine. The system utilizes binary sensors to detect relative deviations from stoichiometric combustion, including individual combustion events, and allows for regulation to achieve optimal and similar combustion to take place in all the cylinders.

Abstract: A fuel injection control device of an engine having a plurality of cylinders, that prevents sudden change in combustion condition. The control device calculates a basic amount of fuel to be injected into cylinders. The controller then decides an amount of adjustment ultimately made to the basic amount of fuel based on an engine revolution speed difference between the cylinders. The adjustment is stepwise made to the basic amount of fuel so that a total amount of fuel gradually increases or decreases. Since a steep change does not occur in the total amount of fuel, the combustion condition does not change suddenly and the engine does not vibrate.

Abstract: An air/fuel ratio correction cylinder determining section 25 specifies, based on the peak phase, a cylinder for which an air/fuel ratio is to be corrected. A cylinder-specific air/fuel ratio correcting section in the form of respective cylinder correcting sections 31 through 34 corrects an amount of fuel to be supplied to a cylinder which becomes an air/fuel ratio correction target. A cylinder for which an air/fuel ratio deviates from the remaining cylinders is specified as a fuel amount correction target based on a change in the output value of the air/fuel ratio sensor.

Abstract: A control system of an internal combustion engine is comprised of an operation angle adjustment mechanism which continuously varies an operation angle of intake valves of the engine, an air-fuel ratio detector which detects an exhaust parameter indicative of air-fuel ratio information, and a control unit which are coupled to the operation angle adjustment mechanism and the air-fuel ratio detector. The control unit feedback-controls an air-fuel ratio of the engine on the basis of the exhaust parameter and corrects the operation angle on the basis of the exhaust parameter.

Abstract: The switching characteristic of zirconia solid electrolyte type oxygen sensors is shaped to generate a limited proportional range around the stoichiometric A/F through a modified operation of the port injection or direct fuel injection control system. The linear response is obtained by imposing fuel-injection offsets, of particular patterns and magnitudes, on the average fuel quantity determined by the closed-loop fuel controller. The linear range of the sensor is then used for precise stoichiometric A/F control for tailpipe emission improvements. Also, further reductions in HC and CO emissions during cold-start (with leaner air-fuel ratio operation) and reduction in NOx (slightly rich air-fuel ratio operation) under warm-up and hot conditions are made possible using production O2 sensors.

Abstract: There is disclosed an apparatus in which changes of linear A/F sensor or engine response characteristics can be detected with high precision in a broad range during operation of an engine. The apparatus includes a controller 50 for controlling an air/fuel ratio of each cylinder of a multiple cylinder engine, and a linear A/F sensor 28 for emitting an output which is proportional to the air/fuel ratio of an exhaust tube assembly. The air/fuel ratio of a specific cylinder is changed by a predetermined amount, a vibration component amplitude or a frequency component based on an engine rotation number is extracted from a signal obtained from the linear A/F sensor 28, and the response characteristics of an air/fuel ratio detector or the engine are detected from the amplitude or a power of the frequency component.

Abstract: An internal combustion engine having cylinders with injection valves and air mass-setting actuators, an air/fuel ratio sensor detecting the ratio in the individual cylinders, and a sensor detecting a torque generated in the individual cylinders or differences in the torques generated in the cylinders includes individually determining the air/fuel ratio for each cylinder, individually correcting an activation of the fuel injection valve for each cylinder as a function of the detected air/fuel ratio and of a desired value of the air/fuel ratio, determining the variable characterizing the torque or the differences in the torque for each cylinder, individually correcting an activation of the air mass-setting actuator for each cylinder as a function of the detected value of the variable characterizing the torque or of the variable characterizing the difference in the torque specifically with the effect of assimilating the torques generated by the individual cylinders.

Abstract: This invention is a method and system for a hybrid electric vehicle adaptive fuel strategy to quickly mature an adaptive fuel table. The strategy adaptively alters the amount of fuel delivered to an internal combustion engine to optimize engine efficiency and emissions using engine sensors. Before the adaptive fuel strategy is permitted, an engine “on” idle arbitration logic requires the HEV to be in idle conditions, with normal battery state of charge, normal vacuum in the climate control and brake system reservoir; and, the vapor canister not needing purging. The strategy orders the engine throttle to sweep different airflow regions of the engine to adapt cells within the adaptive fuel table. In the preferred configuration, a generator attached to the vehicle drive train, adds and subtracts torque to maintain constant engine speed during the throttle sweeps.

Abstract: A control apparatus calculates a exhaust gas air-fuel ratio of a plurality of cylinders, in which the operation angle of an intake valve is set to a predetermined operation angle, e.g., a maximum operation angle, based on a value output from an air-fuel ratio sensor so as to minimize a variation in an fuel injection quantity between the plurality of cylinders by that exhaust gas air-fuel ratio. That is, the exhaust gas air-fuel ratio of the plurality of cylinders, in which the valve opening characteristics of the intake valve and an exhaust valve are set such that the intake air amount to be introduced into the plurality of cylinders is limited by the opening amount of a throttle valve, for example, and not limited by the valve opening characteristics of the intake valve or the exhaust valve is calculated, and the variation in the fuel injection quantity among the plurality of cylinders is then reduced by that exhaust gas air-fuel ratio.

Abstract: A device and a method are described for controlling an internal combustion engine, in which a control deviation and a governor are allocated to each cylinder of the internal combustion engine, each governor preselecting a cylinder-specific triggering signal on the basis of the allocated control deviation. Cylinder-specific actual values are ascertained on the basis of a signal from a sensor arranged in the exhaust train and are compared to a setpoint value. Triggering signals for the cylinder-individual control of the fuel quantity and/or air quantity are preselected on the basis of the comparison.

Abstract: An air/fuel ratio control apparatus for an internal combustion engine is capable of making the air/fuel ratios of respective cylinders uniform with high accuracy without causing an increase in the load of arithmetic operations of a CPU, while avoiding the influence of a change in an engine operating state, etc. An air/fuel ratio detection period setting section 22 sets an air/fuel ratio detection period T in which all the exhaust strokes of respective cylinders of the engine are included. A peak phase detecting section 21 takes in an output value &lgr; of an air/fuel ratio sensor 8 for an air/fuel ratio detection period, and detects a peak phase P&lgr; which becomes a maximum on a rich side or a lean side owing to a change in the air/fuel ratio. An air/fuel ratio correction cylinder determining section 25 specifies, based on the peak phase, a cylinder for which an air/fuel ratio is to be corrected.

Abstract: A fuel injection control system for a direct injection-spark ignition type of engine forcibly turns off appliances as an external engine load while the engine operates in a stratified charge combustion mode after warming-up so as thereby to fix a quantity of intake air approximately constant and concurrently feedback controls a quantity of fuel injection according to an engine speed so as to bring the engine speed into a specified idling speed. An actual quantitative variation of fuel injection is learned on the basis of a feedback correction value of the quantity of fuel injection for each of predetermined fuel injection timings which are changed from a timing for minimum advance for best torque (MBT) so as to correspond to injection pulse widths within a region adopted for a micro-flow characteristic of the fuel injector.

Abstract: A method for controlling the titre of the air-fuel mixture in an internal combustion engine provided with at least two cylinders, in which the exhaust gas present in a common exhaust manifold is analyzed in order to measure at least two successive values of the overall air-fuel ratio of the cylinders; a value of the air-fuel ratio of a final combusted cylinder being estimated by carrying out a linear composition of the two successive values of the overall air-fuel ratio of the cylinders and the value of the air-fuel ratio of the final combusted cylinder being attributed to a first of the cylinders and being used to correct a titer of the air-fuel mixture introduced into the first cylinder.

Abstract: An improved internal combustion engine fuel control wherein a single oxygen sensor responsive to the combined exhaust gas flow of several engine cylinders is used both to control the overall or average air/fuel ratio, and to trim the air/fuel ratio in the individual engine cylinders. The oxygen sensor output is sampled in synchronism with the engine firing events, but at twice (or higher) the frequency, and filtered by an engine speed dependent high-pass filter to form a measure of the air/fuel ratio imbalance with respect to time. The imbalance signal, in turn, is parsed into an array of imbalance values that are associated with individual engine cylinders based on engine operating conditions, and the imbalance values are then used to develop correction factors for the respective engine cylinders that reduce the imbalance while preserving the overall or average air/fuel ratio of the engine.

Abstract: The apparatus for estimating the richness of the mixture admitted into each of the n combustion chambers of an engine having injectors comprises a sensor (26) supplying an output signal that varies in substantially linear manner with richness and that is placed at the junction point between the exhausts from the chambers, and also comprises calculation means. These means store a model of the behavior of the exhaust at the junction point based on the assumption that the richness at the junction point is a weighted sum of contributions from the exhausts from the individual chambers, with the weighting coefficient being smaller with increasing age of the combustion in the chamber, and serving on each pass through top dead center to estimate the air/fuel ratio on the basis of the measured values and of the model.

Abstract: There is disclosed an apparatus in which changes of linear A/F sensor or engine response characteristics can be detected with high precision in a broad range during operation of an engine. The apparatus includes a controller 50 for controlling an air/fuel ratio of each cylinder of a multiple cylinder engine, and a linear A/F sensor 28 for emitting an output which is proportional to the air/fuel ratio of an exhaust tube assembly. The air/fuel ratio of a specific cylinder is changed by a predetermined amount, a vibration component amplitude or a frequency component based on an engine rotation number is extracted from a signal obtained from the linear A/F sensor 28, and the response characteristics of an air/fuel ratio detector or the engine are detected from the amplitude or a power of the frequency component.

Abstract: The invention relates to a method for the cylinder-selective control of an air/fuel mixture to be burnt in a multi-cylinder internal combustion engine, in which the lambda values for different cylinders or groups of cylinders are separately sensed and controlled, and also relates to a multi-cylinder internal engine suitable for carrying out the method. In accordance with the invention, the lambda values of the individual cylinders or groups of cylinders are simultaneously controlled to different required values using an integrating I-control proportion with variable integrator slope and/or a differentiating D-control proportion.

Abstract: An improved individual cylinder fuel control method based on sampled readings of a single oxygen sensor responsive to the combined exhaust gas flow of several engine cylinders. A model-based observer is used to reproduce the imbalances of the different cylinders and a proportional-plus-integral controller is used for their elimination. Both the observer and the controller are formulated in terms of a periodic system. The observer input signal is preprocessed such that it reflects at each point of time the deviation from the current A/F-ratio mean value calculated over two engine cycles. Therefore, transient engine operating conditions do not harm the reconstruction of the cylinder imbalances dramatically. The control algorithm features process/controller synchronization based on table lookup and a mechanism to automatically adjust the mapping between the observer estimates and the corresponding cylinders if unstable control operation is detected.

Abstract: A method for controlling the titer of the air-fuel mixture in an internal combustion engine provided with at least two cylinders, in which the exhaust gas present in a common exhaust manifold is analyzed in order to measure at least two successive values of the overall air-fuel ratio of the cylinders; a value of the air-fuel ratio of a final combusted cylinder being estimated by carrying out a linear composition of the two successive values of the overall air-fuel ratio of the cylinders and the value of the air-fuel ratio of the final combusted cylinder being attributed to a first of the cylinders and being used to correct a titer of the air-fuel mixture introduced into the first cylinder.

Abstract: Cylinder-selective control of the air-fuel ratio in a multi-cylinder internal-combustion engine is provided, wherein a lambda probe arranged in the exhaust pipe system generates a voltage signal corresponding to an air-fuel ratio. The voltage signal is supplied to a computing unit which determines the air-fuel ratio for each individual cylinder. A fuel metering unit determines a fuel injection quantity at least as a function of a basic fuel injection value and the determined air-fuel ratios of the individual cylinders, and a fuel supply unit supplies the fuel injection quantity determined by the fuel metering unit to the cylinders of the internal-combustion engine. The computing unit crank-angle-synchronously detects the voltage signal and assigns it to a certain cylinder. A voltage deviation and corresponding injection quantity correction is determined for each cylinder in relation to the voltage signals of the adjacent cylinders.

Abstract: Disclosed is a method to determine a failure status of a cylinder and for controlling an air fuel ratio for each cylinder by a simple method using a wide range oxygen sensor. When the engine in a car is in normal status, output values of the wide range oxygen sensor are determined. These measures detect the density of oxygen in the exhaust gasses during a predetermined cycle at specific crank angles, the ensemble average values are found, and the maximum and minimum values of the computed ensemble average values are detected. If the difference between the maximum and minimum values is greater than a set reference value, it is determined that there is a failure of a cylinder, and the position of the cylinder at the maximum or minimum value is determined.

Abstract: An engine control program is divided into an application layer and a platform layer. The application layer defines a program which is independent of a hardware and is provided under an object-oriented design. The platform layer defines a program which is dependent on the hardware and is provided under the object-oriented design, and divided into three layers, that is, an upper layer, an intermediate layer and a lower layer. The upper layer, intermediate layer and the lower layer includes a sensor/actuator layer, a device driver layer and a virtual MPU layer, respectively.

Abstract: An air-fuel ratio control system for a multi-cylinder internal combustion engine is equipped with an exhaust emission control catalyst disposed in an exhaust passage of the engine, air-fuel ratio control means for controlling an air-fuel ratio of at least one of the plurality of cylinders, and an exhaust gas temperature sensor operating as catalyst temperature detection. During a cold start of the engine, the air-fuel ratio control means achieves one of rich-state and stoichiometric operation in all of the cylinders until the temperature of the exhaust emission control catalyst reaches a predetermined temperature. After the temperature of the exhaust emission control catalyst has reached the predetermined temperature, the air-fuel ratio control means starts lean-state operation in a first portion of the plurality of cylinders while maintaining rich-state operation in a second portion of the plurality of cylinders.

Abstract: An improved individual cylinder fuel control method based on sampled readings of a single oxygen sensor responsive to the combined exhaust gas flow of several engine cylinders. The oxygen sensor output is sampled in synchronism with the engine firing events, a stored non-volatile table of offset values is used to correlate the sampled oxygen sensor values with individual engine cylinders, and a new offset value is determined and stored in place of a current offset value when the current offset value fails to reduce a measure of air/fuel ratio maldistribution among the engine cylinders. In systems having an oxygen sensor of the switching type, the measure of air/fuel ratio maldistribution is determined by filtering and integrating the oxygen sensor signal, and the new offset value is determined by repeatedly incrementing the stored offset value, and fueling the individual cylinders of the engine based on the incremented offset value, until the measure of air-fuel ratio maldistribution decreases.

Abstract: A start-up strategy for engine feedback control that utilizes a combustion condition sensor associated with only one cylinder. On starting and warm-up, only that one cylinder is feedback-controlled at all times. Under these conditions, the amount of corrected fuel supplied to the feedback cylinder is added to a fixed incremental amount of fuel that will be supplied to the remaining cylinders. This promotes smooth warm-up without backfiring or stalling and a quicker transition to all cylinder feedback control.

Abstract: A control system for an outboard motor is disclosed. The control system includes a feedback control which obtains feedback data from a combustion condition sensor. The motor includes an engine positioned in a cowling and having a vertically extending output shaft in driving relation with a water propulsion device of the motor. The engine has at least one combustion chamber and an air/fuel charging system for delivering air and fuel into the combustion chamber for combustion therein. The motor includes an exhaust system for routing exhaust from the engine to a point external to the motor. The exhaust system includes an exhaust passage leading from the chamber to a main exhaust passage which extends vertically downward to an exhaust guide positioned below the engine. A passage leads from the exhaust guide into an expansion chamber and thereon to an exhaust discharge.

Abstract: A fuel metering control system for an internal combustion engine including a feedback loop having an adaptive controller and an adaptation mechanism that estimates controller parameters .theta.. The adaptive controller corrects the quantity of fuel injection to bring a controlled variable obtained at least based on an output of said air/fuel ratio sensor, to a desired value. The adaptation mechanism is input with the controlled variable once per prescribed crank angle such as a TDC of a certain cylinder and estimates the controller parameters. Using the controller parameters, it is discriminated whether system operates stably.

Abstract: An air-fuel ratio control system for an internal combustion engine includes an air-fuel ratio sensor arranged in the exhaust system of the engine. An ECU determines activation of the air-fuel ratio sensor and carries out feedback control of the air-fuel ratio of a mixture supplied to the engine in response to the output from the air-fuel ratio sensor. An intermediate state of the air-fuel ratio sensor corresponding to a transient state of the air-fuel ratio sensor from an inactive state thereof to an active state thereof is determined. The output from the air-fuel ratio sensor for use in execution of the feedback control is corrected when the air-fuel ratio sensor is in the intermediate state.

Abstract: An air-fuel ratio control system for an internal combustion engine includes an air-fuel ratio sensor arranged in the exhaust system of the engine. An ECU estimates the air-fuel ratio of a mixture supplied to each of the cylinders cylinder by cylinder in response to an output from the air-fuel ratio sensor, by using an observer for observing an internal operative state of the exhaust system, based on a model representative of the behavior of the exhaust system, and calculates cylinder-by-cylinder air-fuel ratio control amounts corresponding respectively to the cylinders for carrying out feedback control of the air-fuel ratio of the mixture supplied to each of the cylinders such that the estimated air-fuel ratio of the mixture supplied to each of the cylinders is converged to a desired value.

Abstract: An air-fuel ratio control system for an internal combustion engine includes an air-fuel ratio sensor for detecting the air-fuel ratio of exhaust gases from the engine. An ECU estimates the air-fuel ratio of a mixture supplied to each of the cylinders cylinder by cylinder in response to an output from the air-fuel ratio sensor, by using an observer based on a model representative of the behavior of the exhaust system. Cylinder-by-cylinder air-fuel ratio control amounts corresponding respectively to the cylinders are calculated for carrying out feedback control of the air-fuel ratio of the mixture such that each of the estimated air-fuel ratio is converged to a desired value.

Abstract: A cylinder-by-cylinder air-fuel ratio-estimating system for an internal combustion engine includes an air-fuel ratio sensor arranged in the exhaust system of the engine. The air-fuel ratio of a mixture supplied to each of the cylinders of the engine is estimated based on an output from the air-fuel ratio sensor, by using an observer for observing the internal operative state of the exhaust system based on a model representative of the behavior of the exhaust system. The estimated air-fuel ratio of the mixture supplied to each of the cylinders is initialized to a value corresponding to the output from the air-fuel ratio sensor, depending upon operating conditions of the engine.

Abstract: An engine feedback control for an internal combustion engine having at least two combustion chambers is disclosed. When a sensor detects a high engine temperature condition of the engine, the feedback control changes the air/fuel ratio of the air and fuel supplied to each combustion chamber in a manner which prevents operation of any combustion chamber in a disabling range.

Abstract: An air-fuel ratio control system for an internal combustion has a plurality of cylinders and an exhaust system. The air-fuel ratio of exhaust gases emitted from the cylinders is detected by an air-fuel ratio sensor arranged in the exhaust system. The air-fuel ratio of a mixture supplied to each of the cylinders is estimated based on an output from the air-fuel ratio sensor by using an observer for observing an internal operative state of the exhaust system by means of a model representative of a behavior of the exhaust system. Feedback control of an amount of fuel to be supplied to the each of the cylinders is carried out in response to the output from the air-fuel ratio sensor by using a controller of a recurrence formula type, such that the air-fuel ratio of the mixture supplied to the each of the cylinders is converged to a desired value.

Abstract: A fuel metering control system for an internal combustion engine having a plurality of cylinders. The system includes an air/fuel ratio sensor and engine operating condition detecting means for detecting engine operating conditions such as engine speed and engine load. The basic quantity of fuel injection is determined by retrieving mapped data according to the detected parameters. A plurality of controllers are provided all using outputs of the air/fuel ratio sensor. The controllers are configured to receive the sensor outputs through filters having different cutout frequency so as to avoid control interference therebetween.

Abstract: A catalytic reaction system for promoting hydrocarbon reduction during periods of fuel rich engine operation of a multicylinder internal combustion engine which operates from signals generated by a microprocessor based engine controller. Each cylinder is fueled by an injection means, signalled by the engine controller. The amount of fuel injected into each cylinder may be different, so that each cylinder can be operated at different fuel/air ratios. The microprocessor senses metered air intake, ambient temperatures, engine speed and exhaust gas oxygen content. The sensed information is used to calculate the amount of oxygen needed by the catalytic converter to efficiently remove hydrocarbons and by adjusting the fuel/air ratios in one or more cylinders, effects the quantity of oxygen fed to the exhaust gas.