Abstract: An ECU calculates a cylinder flowing air amount based on an intake tube pressure, using an air intake valve model simulating a behavior of air flowing into a combustion chamber via an air intake valve. The ECU calculates an air intake amount based on a detection result of an air amount detection sensor, and determines whether the air intake amount matches an actual amount of air flowing into the combustion chamber. When the air intake amount is determined to match the actual amount, the ECU calculates a learnt value based on comparison of the cylinder flowing air amount with the air intake amount.

Abstract: A cylinder-inflow EGR gas amount is estimated, a misfire limit EGR gas amount is calculated on the basis of an engine operation state, and the misfire limit EGR gas amount is compared with the cylinder-inflow EGR gas amount to predict whether a misfire occurs. When the misfire is predicted, a misfire avoidance control is executed. Further, an actual misfire countermeasure effect amount in a case of the execution of the misfire avoidance control is calculated, and the actual misfire countermeasure effect amount is compared with a required misfire countermeasure effect amount to determine whether the misfire is avoidable when the misfire avoidance control is executed. If the misfire is unavoidable even if the misfire avoidance control is executed, a delay restriction value of an ignition timing to avoid the misfire is calculated, and the amount of a delay in the ignition timing is restricted using the delay restriction value.

Abstract: In an EGR system, a quantity of exhaust gas passing through an EGR valve is computed by an EGR valve model simulating a behavior of the recirculated exhaust gas passing through the EGR valve. An exhaust gas quantity flowing into a cylinder is computed by an EGR-gas-delay model simulating a behavior of the exhaust gas passing through the EGR valve and the throttle valve and then flows into a cylinder. The EGR-gas-delay model includes a confluent-delay model simulating a behavior of EGR gas passing thorough the EGR valve and flowing into the intake passage upstream of the throttle valve; an intake-pipe-delay model simulating a behavior of EGR gas flowing in the intake passage and passing through the throttle valve; and an intake-manifold-delay model simulating a behavior of EGR gas which passes through the throttle valve and then flows into the intake passage downstream of the throttle valve.

Abstract: An ECU calculates a cylinder flowing air amount based on an intake tube pressure, using an air intake valve model simulating a behavior of air flowing into a combustion chamber via an air intake valve. The ECU calculates an air intake amount based on a detection result of an air amount detection sensor, and determines whether the air intake amount matches an actual amount of air flowing into the combustion chamber. When the air intake amount is determined to match the actual amount, the ECU calculates a learnt value based on comparison of the cylinder flowing air amount with the air intake amount.

Abstract: EGR gas quantity information, which indicates a quantity of the EGR gas flowing into a cylinder of an internal combustion engine, is obtained by an ECU. A combustion stop delay control operation, which delays execution of a combustion stop control operation, is executed by the ECU when the quantity of the EGR gas flowing into the cylinder is larger than a normal combustion determination threshold value. When the quantity of the EGR gas flowing into the cylinder becomes equal to or smaller than the normal combustion determination threshold value, the combustion stop control operation is enabled by the ECU.

Abstract: While an engine is an idling state and an EGR opening degree is increased stepwise from a specified opening degree, a variation in engine speed (a standard deviation in engine speed) is repeatedly computed. After that, a specified step amount is successively reduced from the EGR opening degree and the variation in engine speed is successively computed until the EGR opening degree becomes less than or equal to a specified value. Then, a maximum value of the EGR opening degrees where the variation in engine speed becomes minimum is learned as the full-close position.

Abstract: A cylinder-inflow EGR gas quantity determining arrangement estimates or senses a value of a cylinder-inflow EGR gas quantity, which is a quantity of EGR gas that flows into a cylinder of an internal combustion engine. A misfire predicting arrangement predicts whether misfire occurs based on the value of the cylinder-inflow EGR gas quantity and an operational state of the internal combustion engine. A misfire-avoidance control arrangement executes at least one misfire-avoidance control operation to avoid the misfire when the misfire predicting arrangement predicts that the misfire occurs.

Abstract: When a constant driving voltage is applied to a motor driving an EGR valve so that the EGR opening degree is varied, an angular speed of the EGR valve becomes minimal at a position where the driving torque of the EGR valve becomes maximal. In view of this, while an opening degree of the EGR valve is varied with a constant driving voltage applied to the motor, the EGR opening degree where the angular speed becomes minimal is learned as a full-close position.

Abstract: An intake air quantity information determining arrangement senses or computes one of an intake air quantity and a torque of an internal combustion engine as intake air quantity information. A misfire-avoidance control arrangement executes a misfire-avoidance control operation, which avoids misfire by controlling a throttle opening degree of a throttle valve such that a value of the intake air quantity information does not decrease below a normal combustion threshold value.

Abstract: By means of an air model, an estimated quantity of an exhaust gas flowing into a cylinder and a target quantity of the exhaust gas are computed. A deviation between the estimated quantity and the target quantity is multiplied by a feedback gain to obtain a feedback correction quantity. A reference opening degree of an EGR valve is defined according to an engine driving condition and the feedback correction quantity is added to the reference opening degree to obtain a command opening degree of the EGR valve. According to the engine driving condition and the deviation between the estimated quantity and the target quantity, a feedback gain is established so that control accuracy and control stability of a feedback control can be ensured.

Abstract: An intake air quantity information determining arrangement senses or computes one of an intake air quantity and a torque of an internal combustion engine as intake air quantity information. A misfire-avoidance control arrangement executes a misfire-avoidance control operation, which avoids misfire by controlling a throttle opening degree of a throttle valve such that a value of the intake air quantity information does not decrease below a normal combustion threshold value.

Abstract: A cylinder-inflow EGR gas amount is estimated, a misfire limit EGR gas amount is calculated on the basis of an engine operation state, and the misfire limit EGR gas amount is compared with the cylinder-inflow EGR gas amount to predict whether a misfire occurs. When the misfire is predicted, a misfire avoidance control is executed. Further, an actual misfire countermeasure effect amount in a case of the execution of the misfire avoidance control is calculated, and the actual misfire countermeasure effect amount is compared with a required misfire countermeasure effect amount to determine whether the misfire is avoidable when the misfire avoidance control is executed. If the misfire is unavoidable even if the misfire avoidance control is executed, a delay restriction value of an ignition timing to avoid the misfire is calculated, and the amount of a delay in the ignition timing is restricted using the delay restriction value.

Abstract: While an EGR valve is closed, a total gas flow rate is computed based on an intake air pressure. An error of the total gas flow rate is learned and corrected. When the EGR valve is opened, the total gas flow rate is computed based on the intake air pressure. An actual EGR-gas flow rate is computed based on the total gas flow rate and a fresh-air flow rate. By using of the EGR valve model, an estimated EGR-gas flow rate is computed based on the fresh-air flow rate and an opening degree of the EGR valve. An error of the estimated EGR-gas flow rate is learned and corrected based on the actual EGR-gas flow rate and the estimated EGR-gas flow rate. Based on a volume fraction of the corrected estimated EGR-gas flow rate and the fresh-air flow rate, an EGR ratio is computed.

Abstract: An apparatus estimates a quantity of recirculated exhaust gas. The apparatus includes a first unit computing a total quantity of gas, a second unit computing a quantity of exhaust gas passing through an EGR vale by means of an EGR valve model, a third unit computing a temporal quantity of the exhaust gas by means of an EGR diffusion model which simulates a behavior of the exhaust gas, a fourth unit obtaining an intake air quantity by subtracting the temporal exhaust gas quantity from the total gas quantity, a fifth unit correcting the computed intake air quantity by means of intake air quantity measured by the airflow meter, a sixth unit computing an intake air pressure based on the corrected quantity of the intake air, and a seventh unit computing a quantity of the recirculated exhaust gas based on at least the intake air pressure.

Abstract: When a constant driving voltage is applied to a motor driving an EGR valve so that the EGR opening degree is varied, an angular speed of the EGR valve becomes minimal at a position where the driving torque of the EGR valve becomes maximal. In view of this, while an opening degree of the EGR valve is varied with a constant driving voltage applied to the motor, the EGR opening degree where the angular speed becomes minimal is learned as a full-close position.

Abstract: While an engine is an idling state and an EGR opening degree is increased stepwise from a specified opening degree, a variation in engine speed (a standard deviation in engine speed) is repeatedly computed. After that, a specified step amount is successively reduced from the EGR opening degree and the variation in engine speed is successively computed until the EGR opening degree becomes less than or equal to a specified value. Then, a maximum value of the EGR opening degrees where the variation in engine speed becomes minimum is learned as the full-close position.

Abstract: A cylinder-inflow EGR gas quantity determining arrangement estimates or senses a value of a cylinder-inflow EGR gas quantity, which is a quantity of EGR gas that flows into a cylinder of an internal combustion engine. A misfire predicting arrangement predicts whether misfire occurs based on the value of the cylinder-inflow EGR gas quantity and an operational state of the internal combustion engine. A misfire-avoidance control arrangement executes at least one misfire-avoidance control operation to avoid the misfire when the misfire predicting arrangement predicts that the misfire occurs.

Abstract: An intake air quantity information determining arrangement senses or computes one of an intake air quantity and a torque of an internal combustion engine as intake air quantity information. A misfire-avoidance control arrangement executes a misfire-avoidance control operation, which avoids misfire by controlling a throttle opening degree of a throttle valve such that a value of the intake air quantity information does not decrease below a normal combustion threshold value.

Abstract: EGR gas quantity information, which indicates a quantity of the EGR gas flowing into a cylinder of an internal combustion engine, is obtained by an ECU. A combustion stop delay control operation, which delays execution of a combustion stop control operation, is executed by the ECU when the quantity of the EGR gas flowing into the cylinder is larger than a normal combustion determination threshold value. When the quantity of the EGR gas flowing into the cylinder becomes equal to or smaller than the normal combustion determination threshold value, the combustion stop control operation is enabled by the ECU.

Abstract: In an EGR system, a quantity of exhaust gas passing through an EGR valve is computed by an EGR valve model simulating a behavior of the recirculated exhaust gas passing through the EGR valve. An exhaust gas quantity flowing into a cylinder is computed by an EGR-gas-delay model simulating a behavior of the exhaust gas passing through the EGR valve and the throttle valve and then flows into a cylinder. The EGR-gas-delay model includes a confluent-delay model simulating a behavior of EGR gas passing thorough the EGR valve and flowing into the intake passage upstream of the throttle valve; an intake-pipe-delay model simulating a behavior of EGR gas flowing in the intake passage and passing through the throttle valve; and an intake-manifold-delay model simulating a behavior of EGR gas which passes through the throttle valve and then flows into the intake passage downstream of the throttle valve.