Abstract: A reduction method for a catalytic converter in an exhaust system of an internal combustion engine for reducing the oxygen content in the catalytic converter, in particular after an overrun fuel cutoff mode of the internal combustion engine, the method including first injection of fuel into a first cylinder, the first injection taking place after an ignition point in time of a compression stroke of a first working cycle of the cylinder and including an introduction of the injected fuel from the cylinder into the catalytic converter during an exhaust stroke of the first cylinder.

Abstract: An engine includes a cylinder, a piston reciprocable within the cylinder in response to the combustion of a mixture of air and fuel, and a venturi having a throat. The venturi is positioned to draw in air and direct the air and fuel to the cylinder. A fuel inlet is positioned to direct gaseous fuel into the throat, a valve is coupled to the fuel inlet, and an engine control module operable to control the valve and the fuel flow into the throat.

Abstract: A gas sensor element includes a main body having a solid electrolyte body on which a measurement gas-side electrode and a reference gas-side electrode are provided, a trap layer covering an outer peripheral surface of the main body to trap poisoning substances contained in a measurement gas, and a waterproof protective layer covering an outer peripheral surface of the trap layer. In the protective layer, there is formed at least one measurement gas introduction port for introducing the measurement gas to the measurement gas-side electrode via the trap layer.

Abstract: A controller of an air-fuel ratio sensor includes, in a digital processor, an adjuster and a control unit, among which the adjuster adjusts a second input digital value for a control of an output voltage of a second voltage application circuit to a preset voltage, and the control unit controls, based on a calculation result of a digital value of a sensor current, a first input digital value for a control of an output voltage of an output terminal of a first OP amplifier of a first voltage application circuit to a voltage Vu based on the equation, Vu=Vout±(Vtar+Is×Rs), so that an application voltage applied to the air-fuel ratio sensor is quickly adjusted to a target voltage.

Abstract: A control apparatus using a feedback control algorithm including an integral term, which is capable of controlling a controlled object having a response lag characteristic while suppressing influences of aging and sudden changes in an operating state, and thereby improving control accuracy. The control apparatus that controls a supercharger includes an ECU. The ECU calculates a reference FB target pressure using a first-order lag equation, an allowable upper limit value based on a value obtained by adding a predetermined allowable range value to the reference FB target pressure, an FB target pressure such that an actual boost pressure does not exceed the allowable upper limit value, and a feedback correction term using a PI control algorithm such that the actual boost pressure becomes equal to the FB target pressure, and controls the actual boost pressure using a driver demand boost pressure and the feedback correction term.

Abstract: An induction cleaning analyzing system includes a pressure sensor, an ignition event detector, and a control module. The pressure sensor measures airflow pressures of intake air and/or exhaust from cylinders in a common airflow pathway of a vehicle. The ignition event detector determines ignition events of the cylinders. The control module obtains pressure waveforms representative of the airflow pressures and divides the pressure waveforms into waveform segments. The control module associates different subsets of the waveform segments with different ones of the cylinders using the ignition events. The control module also identifies cyclic variations in the airflow pressures flowing in the common airflow pathway and caused by at least one of the cylinders by examining the waveform segments associated with the at least one of the cylinders.

Abstract: Methods and systems are provided for adjusting a rate of change in a reference voltage of an oxygen sensor. In one example, a method may include gradually increasing a reference voltage of an oxygen sensor from a lower first voltage to a higher second voltage at a ramp rate. The ramp rate may be based on engine operating conditions.

Abstract: The internal combustion engine (1) has a throttle (23) for controlling an intake air amount and performs start-up through cranking. The starter switch (36) detects cranking initiation, and the crank angle sensor (33, 34) detects the number of revolutions of the engine. The controller (31) drives the throttle (23) in a closed position along with the cranking initiation. The controller (31) can obtain both the intake negative pressure for promoting vaporization of fuel and the intake air amount necessary to maintain the idle rotation speed by counting the number of strokes or the number of revolutions of the internal combustion engine (1) from the cranking initiation and opening the throttle (23) from the closed position as the count number reaches a predetermined number.

Abstract: Various embodiments relating to air-fuel ratio control are described herein. In one embodiment a method includes adjusting fuel injection to an engine responsive to air-fuel ratio sensor feedback with a first control structure, and in response to an air-fuel ratio sensor asymmetric degradation, adjusting fuel injection to the engine responsive to air-fuel ratio sensor feedback with a second, different, control structure.

Abstract: A system according to the principles of the present disclosure includes a gain determination module, a desired torque determination module, and an engine operation control module. The gain determination module determines a gain based on a desired speed of an engine and a change rate of an actual speed of the engine. The desired torque determination module determines a desired torque based on the gain and a difference between the actual speed and the desired speed. The engine operation control module controls at least one of a throttle area, a spark timing, and a fueling rate based on the desired torque.

Abstract: In a feedback control system in which a base gain having a constant value or a variable gain is set as a feedback gain in accordance with the state of the system and an input value is calculated based on a function having, as variables, a proportional term and an integral term, the integral term is recalculated when a discriminant value obtained by substituting a base proportional term calculated using the base gain for the proportional term and a normal integral term calculated using the feedback gain for the integral term in the function is larger than an upper limit value. The integral term is recalculated in such a way that a value obtained by substituting the base proportional term for the proportional term and the recalculated integral term for the integral term in the function becomes equal to or smaller than the upper limit value.

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 engine control system includes a saturation determination module, an adjustment factor generation module, and a fuel control module. The saturation determination module determines when a first exhaust gas oxygen (EGO) sensor is saturated, wherein the first EGO sensor is located upstream from a catalyst. The adjustment factor generation module generates an adjustment factor for an integral gain of a fuel control module when the first EGO sensor is saturated. The fuel control module adjusts a fuel command for an engine based on differences between expected and measured amounts of oxygen in exhaust gas produced by the engine, a proportional gain, the integral gain, and the integral gain adjustment factor.

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: An engine control system includes a proportional correction module and a variable proportional gain determination module. The proportional correction module generates a proportional correction for a fuel command to an engine based on a variable proportional gain and a difference between expected and measured amounts of oxygen in exhaust gas produced by the engine. The variable proportional gain determination module determines the variable proportional gain based on a nominal gain and an amount of time since a polarity of the difference has changed, wherein the nominal gain is based on engine operating parameters.

Abstract: The invention relates to a method for regulating the lambda value of an internal combustion engine with a catalytic converter for subsequently treating the exhaust gases of the internal combustion engine, with a binary lambda probe, which is mounted upstream from the catalytic converter and which senses the composition of the exhaust gases. According to the invention, the lambda set value is superimposed with a lean/rich amplitude. This lean/rich amplitude has an integral component and a discontinuous component leading back to the lambda set value. When a change that differs from the change in the exhaust gas composition caused by the lean/rich amplitude is detected, the coefficient of the integral component is modified and/or a discontinuous component is added to the integral component or subtracted therefrom.

Abstract: A passive control device is interposable between an oxygen sensor and an electric control unit of a motor vehicle to modify a reference voltage used by the electric control unit so that a richer fuel mixture is provided to an internal combustion engine of the motor vehicle than would otherwise be provided in absence of the passive control device. The passive control device directly passes the voltage signal from the oxygen sensor to the electronic control unit without modification. The passive control device works with the electronic control unit to provide a richer fuel mixture without reprogramming the electronic control unit.

Abstract: An interface device for a gas sensor includes a detection resistor having first and second ends to generate voltages by a current output of the gas sensor, a differential amplifier having first and second input terminals to receive the voltages of the first and second resistor ends and an output terminal to output a voltage according to a difference between the voltages of the first and second resistor ends, a first switching element to transmit the voltage of the first resistor end to the first input terminal of the differential amplifier in a transmission state and interrupt transmission of the voltage of the first resistor end to the first input terminal of the differential amplifier in an interruption state and a second switching element turned on to establish continuity between the first and second input terminals of the differential amplifier when the first switching element is in the interruption state.

Abstract: A method and system is disclosed which relates to controlling a stationary gaseous-fueled internal combustion engine. The method may include measuring an air to fuel ratio of the engine, calculating a difference between the measured air to fuel ratio and a desired air to fuel ratio for the engine, and automatically controlling an air to fuel mixture supplied to the engine in accordance with the calculated difference to enable the engine to run at substantially the desired air to fuel ratio.

Abstract: The invention provides an engine controller, which can determine a deterioration mode (gain deterioration or response deterioration) of an air/fuel (A/F) ratio sensor, can detect a degree of the deterioration with high accuracy, and can optimize A/F ratio feedback control in accordance with the diagnosis result. The controller includes a unit for computing frequency response characteristics in a range from an A/F ratio adjusting unit to the A/F ratio sensor, and it diagnoses the A/F ratio sensor based on a gain characteristic and a response characteristic given by the computed frequency response characteristics. In accordance with the diagnosis result, parameters (P- and I-component gains) used in A/F ratio feedback control (PI control) are optimized.

Abstract: Disclosed is an internal combustion engine comprising at least one cylinder and an exhaust manifold in which a catalytic converter, a first exhaust gas probe, and a second exhaust gas probe are disposed. The first exhaust probe is located upstream from the catalytic converter while the second exhaust gas probe is arranged downstream therefrom. A lambda Controller is provided which is configured so as to determine a lambda correction factor in accordance with a first test signal that is assigned to the first exhaust gas probe. A trim controller is provided to which a setpoint value and an actual value of a second test signal allocated to the second exhaust gas probe are fed as a control difference. The trim controller is configured so as to determine a proportionate corrective factor.

Abstract: The invention relates to a method in which at least one component of a technical plant is controlled by means of a PI controller. The actual value of the regulating parameter is continuously determined during operation of the plant and the amplification factor of the PI controller is altered depending on the time relationship of the actual value, until the actual value remains with a tolerance band relative to the set value. The invention further relates to a controller for carrying out said method.

Abstract: A method is specified for controlling a combustion engine in a motor vehicle, namely for optimally adjusting an air/fuel ratio which is distinguished in that the air/fuel ratio is the result of a regulation process. Individual aspects of the invention further address a regulation method particularly suitable for such regulation in consideration of the available input values and readings. For the purposes of supporting regulation, an adaptation method is specified which can also be used independently of the regulation method or with other regulation methods and which enables the regulation to be continuously adapted to the respective operating conditions, such as, for example, the engine operational performance, and signs of wear and tear and disruptions due to deposits etc. which accompany it.

Abstract: The invention relates to a device for controlling an internal combustion engine, comprising a first regulator, whose regulating difference is the difference of an actual value and an estimated value of individual cylinder deviation of the air/fuel ratio from a preset air/fuel ratio. The first regulator also has an integral regulating parameter, its manipulated variable being a first estimated value. A second regulator is also provided, the regulating difference of which is the first estimated value. Said regulator has a proportional regulating parameter whose manipulated variable is an individual cylinder lambda regulating factor. A PT1 filter is additionally provided, by means of which a second estimated value is determined through PT1 filtering of the individual cylinder lambda regulating factor.

Abstract: A technique of controlling an air-fuel ration for an engine, in which an air-fuel ratio feedback correction coefficient ? to correct an amount of fuel injection into the engine is computed based on an output from an air-fuel ratio sensor disposed on an upstream side of a catalytic converter. A gain of the air-fuel ratio feedback correction coefficient ? in respect to a detection result of the air-fuel ratio sensor is decreased as a delay in a transient response of the air-fuel ratio sensor occurs. Thus, an excessive increase in the amount of fuel injection immediately after fuel cuts is prevented.

Abstract: An air-fuel ratio feedback control range is enlarged to improve exhaust purification performance and output stability. In one aspect, an air-fuel ratio control apparatus of an internal combustion engine comprises an air-fuel ratio sensor capable of detecting an air-fuel ratio across both lean and rich ranges with a theoretical air-fuel ratio interposed therebetween. Feedback control is performed so as to bring an actual air-fuel into a target air-fuel ratio at least in a predetermined operational range on the basis of a detected value of the air-fuel ratio sensor. Even in a range where the air-fuel ratio is made richer than the theoretical air-fuel ratio, the target air-fuel ratio is set to be richer, and the air-fuel ratio feedback control may still be executed.

Abstract: The output from an air-fuel ratio sensor is corrected using an integral term that is calculated by integrating values of deviation of the output from an oxygen sensor with respect to a reference output that would be obtained when the combustion air-fuel ratio is stoichiometric, when an engine operates with a target combustion air-fuel ratio set to the stoichiometric air-fuel ratio. A fuel-cutoff prohibition period in which fuel supply cutoff is prohibited is set so that the engine continues to operate with the target combustion air-fuel ratio set to the stoichiometric air-fuel ratio, until the integral term is updated at least once. The integral term may be updated when a predetermined updating condition is satisfied.

Abstract: To prevent RPM decrease, misfire, and engine stall by refraining from correcting, the amount of fuel to shift an air-fuel ratio toward a lean side to the extent of exceeding a combustion limit when the internal combustion engine operates at a low load, a control apparatus is provided for controlling operation of an internal combustion engine. The apparatus includes an air-fuel ratio state determiner, a characteristic retainer and a fuel correction amount calculator, in which a coolant temperature coefficient of a coolant temperature coefficient characteristic is set to be smaller than a constant value in a region where a coolant temperature is lower than a constant temperature.

Abstract: The invention provides an engine controller, which can determine a deterioration mode (gain deterioration or response deterioration) of an air/fuel (A/F) ratio sensor, can detect a degree of the deterioration with high accuracy, and can optimize A/F ratio feedback control in accordance with the diagnosis result. The controller includes a unit for computing frequency response characteristics in a range from an A/F ratio adjusting unit to the A/F ratio sensor, and it diagnoses the A/F ratio sensor based on a gain characteristic and a response characteristic given by the computed frequency response characteristics. In accordance with the diagnosis result, parameters (P- and I-component gains) used in A/F ratio feedback control (PI control) are optimized.

Abstract: A method of controlling fuel input to an engine of a vehicle. A feedback signal is received from a sensor that senses engine exhaust. A dither signal having the same frequency as the feedback signal is applied to a fuel control signal controlling fuel to the engine. A proportional/integral correction is applied to the fuel control signal based on the frequency.

Abstract: The invention relates to a new method and system for optimizing the efficiency of an automotive catalytic converter. The claimed invention comprises adjusting an air/fuel ratio in the cylinders of an internal combustion engine to maintain a desired level of oxidants in the catalytic converter. At various times, the actual amount of oxidants stored in the catalytic converter is determined. The actual oxidant amount is compared to a target amount of oxidants to be stored in the catalytic converter. The air/fuel ratio in the cylinders is adjusted based on magnitude of the difference between the actual oxidant amount and the target oxidant amount to prevent NOx and hydrocarbon breakthrough.

Abstract: The present invention has an object to provide an air-fuel ratio control apparatus of an internal combustion engine and a method thereof, for estimating with high accuracy an oxygen adsorption amount in an exhaust purification catalyst, and controlling the oxygen adsorption amount in the exhaust purification catalyst at an optimum amount, thereby enabling to maintain high exhaust purification efficiency.

Abstract: When an output signal from an oxygen sensor is within a predetermined range including a value equivalent to a stoichiometric air-fuel ratio, the output signal is converted into air-fuel ratio data, to compute an air-fuel ratio control signal based on a deviation between the air-fuel ratio data and a target air-fuel ratio. When the output signal from the oxygen sensor is outside the predetermined range, it is judged based on the output signal whether an actual air-fuel ratio is richer or leaner than the target air-fuel ratio, to compute the air-fuel ratio control signal based on the judgment result.

Abstract: The invention relates to a new method and system for optimizing the efficiency of an automotive catalytic converter. The invention comprises adjusting an air/fuel ratio in the cylinders of an internal combustion engine to maintain the amount of oxidants stored in the catalyst at or near an oxidant target value. The oxidant target value is either a pre-determined constant value or a dynamically-determined value that is calculated based on engine operating conditions. The air/fuel ratio in the cylinders is adjusted based on the magnitude of the difference between the actual oxidant amount and the target oxidant amount to prevent NOx and hydrocarbon breakthrough.

Abstract: The invention relates to a new method and system for optimizing the efficiency of an automotive catalytic converter by adjusting the engine air/fuel ratio based on estimates of the actual amount of oxidants stored in the catalyst. To do so, the invented system estimates an amount of oxidants stored in the catalyst. The amount of oxidants stored is estimated by determining an amount of oxidants that are available for storage by the catalyst or that are needed to oxidize hydrocarbons being produced by the engine. Based thereon, a change in oxidant storage in the catalyst is calculated. The estimate of the amount of oxidants that are available for storage by the catalyst or that are needed to oxidize hydrocarbons is adjusted based on a feedback parameter.

Abstract: An air-fuel ratio correction coefficient calculating component is provided to an air-fuel ratio controller for an engine having the wide range air-fuel ratio sensor. In order to compensate for a time lag in detection of an air-fuel ratio detected by the wide range air-fuel ratio sensor from the time when a mixed gas of the air-fuel ratio is supplied to the engine, the air-fuel ratio controller includes a component for calculating an air-fuel ratio correction coefficient to control an amount of fuel supplied to the engine based on an output signal of the air-fuel ratio sensor. The air-fuel ratio correction coefficient calculating component calculates the air-fuel ratio correction coefficient based on a nonlinear calculation element. The non-linear calculation element has an ON-OFF characteristic, a neutral zone characteristic, a saturation characteristic or a characteristic combining a plurality of characteristics selected from the above-mentioned characteristics.

Abstract: In order to reduce noxious exhaust gasses and to improve output power of an engine when it is accelerated, by determining whether an I-gain is out of a predetermined range if a vehicle driving condition is changed to acceleration, the I-gain and a P-gain are modified and fuel supply is controlled on the basis of the modified gains if the I-gain is out of the predetermined range. Furthermore, by measuring a duration of inversion of the O2 sensor, an additional amount of fuel supplied is calculated if the measured duration exceeds a predetermined duration.

Abstract: When an output signal from an oxygen sensor is within a predetermined range including a value equivalent to a stoichiometric air-fuel ratio, the output signal is converted into air-fuel ratio data, to compute an air-fuel ratio control signal based on a deviation between the air-fuel ratio data and a target air-fuel ratio. When the output signal from the oxygen sensor is outside the predetermined range, it is judged based on the output signal whether an actual air-fuel ratio is richer or leaner than the target air-fuel ratio, to compute the air-fuel ratio control signal based on the judgment result.

Abstract: A method and an arrangement for detecting combustion misfires in internal combustion engines are presented where a measured ionic current signal is subjected to a floating short-time integration and a feature is formed which corresponds to the maximum value of the floating short-time integrator within the entire measuring window. The window length of the short-time integrator is shorter than the total measuring window and is floatingly displaced over the measuring window.

Abstract: Even when a reaction delay time of an A/F ratio detection device changes, an A/F ratio controller prevents an A/F ratio feedback control from being disturbed. The controller is programmed to calculate an A/F ratio feedback coefficient by proportional term control and integration term control, and to set length of time for said integration term to be carried out in accordance with an operating state of the engine. It is programmed to calculate the integration term based on the set time and to set a proportional term for shifting said A/F ratio feedback coefficient. It is further programmed to detect a deviation between a first A/F ratio feedback coefficient before the integration term is carried out and a second A/F ratio feedback coefficient after the integration term is carried out and the coefficient is shifted by the proportional term set by said means for setting the proportional term. Based on the detected deviation, the length of time for the integration term to be carried out is corrected.

Abstract: The invention relates to a new method and system for optimizing the efficiency of an automotive catalytic converter. The invention comprises adjusting an air/fuel ratio in the cylinders of an internal combustion engine to maintain the amount of oxidants stored in the catalyst at or near an oxidant target value. The oxidant target value is either a pre-determined constant value or a dynamically-determined value that is calculated based on engine operating conditions. The air/fuel ratio in the cylinders is adjusted based on the magnitude of the difference between the actual oxidant amount and the target oxidant amount to prevent NOx and hydrocarbon breakthrough.

Abstract: The invention relates to a new method and system for optimizing the efficiency of an automotive catalytic converter by adjusting the engine air/fuel ratio based on estimates of the actual amount of oxidants stored in the catalyst. To do so, the invented system estimates an amount of oxidants stored in the catalyst. The amount of oxidants stored is estimated by determining an amount of oxidants that are available for storage by the catalyst or that are needed to oxidize hydrocarbons being produced by the engine. Based thereon, a change in oxidant storage in the catalyst is calculated. The estimate of the amount of oxidants that are available for storage by the catalyst or that are needed to oxidize hydrocarbons is adjusted based on a feedback parameter.

Abstract: In an air-fuel ratio feedback control of an internal combustion engine aimed to approximate an air-fuel ratio to a target air-fuel ratio set according to operating conditions of the engine, the feedback control is carried out using the feedback control amount which is computed according to a sliding mode control, having a deviation between the target air-fuel ratio and the detected air-fuel ratio detected by the air-fuel ratio sensor set as a switching function. According to the present invention, a simple air-fuel ratio feedback control is carried out according to an accurate sliding mode control with no dispersion for each engine, that is easy to design, and that can be applied generally to any kind of vehicle or engine.

Abstract: In order to reduce noxious exhaust gasses and to improve output power of an engine when it is accelerated, by determining whether an I-gain is out of a predetermined range if a vehicle driving condition is changed to acceleration, the I-gain and a P-gain are modified and fuel supply is controlled on the basis of the modified gains if the I-gain is out of the predetermined range.

Abstract: A method and apparatus for controlling universal exhaust gas oxygen (UEGO) sensors comprises an application specific integrated circuit (ASIC) that includes a sensor control utilizing proportional-integral-derivative control loop, sensor drivers for generating pumping currents that reflect the changes of voltages representative of oxygen levels in the reference and test chambers of the UEGO sensor, a communication circuit for communicating with an engine control module, and output buffers for conditioning replications of the pumping current for delivery to an output circuit. In addition to the ASIC, a sensor interface conditions the sensor signals and an output circuit transforms the pumping circuit replications to compatible inputs for the engine control module. Preferably, all of the circuits are formed on a portion of a circuit board in the engine control module. A trim compensation circuit compensates for sensor deviation from an ideal performance standard.

Abstract: A diagnosis system for a wide-range A/F sensor receives an air-fuel ratio (A/F) of air-fuel mixture supplied to an engine for the A/F sensor. An control unit of the diagnosis system corrects an A/F controlled object of a feedback control on the basis of a detection result of the A/F sensor to adjust the A/F at a target A/F. The control unit diagnoses an abnormality of the A/F sensor from variation of the detection value of the A/F sensor during a time period from the start of the switching of the target A/F. The control unit sets a control gain of an A/F feedback control at a value greater than a normal control gain during the diagnosis.

Abstract: A method of determining a goal voltage for a fuel/air sensor of an engine electronic fuel injection system includes the steps of determining a goal fuel/air sensor voltage, superimposing a wave form forcing function to the fuel/air sensor voltage for providing a goal fuel/air sensor voltage having a wave form pattern and controlling the engine to operate according to the goal fuel/air sensor voltage. The wave form forcing function provides the required fuel/air perturbations that are required to retain proper oxygen storage of the catalyst to maintain high three-way conversion efficiency.

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: A non-linear term UNL is computed as UNL=gain GNL×(air-fuel ratio detection value−target air-fuel ratio)/(|air-fuel ratio detection value−target air-fuel ratio|)+previous value UNL (OLD), and a linear term UL is computed as UL=gain GL×(air-fuel ratio detection value−target air-fuel ratio)/air-fuel ratio detection value. An addition of UNL and UL is set as an air-fuel ratio feedback correction coefficient to correct a fuel injection quantity. The gain GL is set a greater value as |air-fuel ratio detection value−target air-fuel ratio| becomes greater.

Abstract: An air-fuel ratio feedback control of an internal combustion engine is performed, by a sliding mode control, by computing an air-fuel ratio feedback control amount including a linear term and a nonlinear term, and at the time of when switching a target air-fuel ratio or at the time of when switching the operating condition, such as the cutting of purge, where the air-fuel ratio is changed, the nonlinear term is initialized to a predetermined value corresponding to the post-switched operating condition.