JP2008095699A - Control apparatus for multi-cylinder internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control apparatus for a multi-cylinder internal combustion engine, capable of reducing the variation in torque between cylinders as well as the variation in air-fuel ratios between cylinders. <P>SOLUTION: The control apparatus calculates an exhaust gas air-fuel ratio of cylinders #1-#4, in which the operation angle of an intake valve 2 is set to a predetermined operation angle, e.g., a maximum operation angle, based on an output value from an air-fuel ratio sensor 57 so as to minimize a variation in a fuel injection quantity between the cylinders by that exhaust gas air-fuel ratio. That is, the exhaust gas air-fuel ratio of the cylinders #1-#4, in which the valve opening characteristics of the intake valve 2 and an exhaust valve 3 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 56, for example, and not limited by the valve opening characteristics of the intake valve 2 or the exhaust valve 3 is calculated, and the variation in the fuel injection quantity among the cylinders is then reduced by that exhaust gas air-fuel ratio. Then, the variation in valve opening characteristics among the cylinders is reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for a multi-cylinder internal combustion engine.

  2. Description of the Related Art Conventionally, a control apparatus for a multi-cylinder internal combustion engine that suppresses variation among cylinders is known. An example of a control device for this type of multi-cylinder internal combustion engine is disclosed in Patent Document 1, for example. In the control device for a multi-cylinder internal combustion engine described in the patent document, the air-fuel ratio of which cylinder among a plurality of cylinders is calculated based on the output value of the air-fuel ratio sensor, and the valve lift amount of each cylinder is calculated. By controlling, variation in the air-fuel ratio between the cylinders is suppressed.

Japanese Patent Laid-Open No. 6-213044

  However, as in the control device for a multi-cylinder internal combustion engine described in Patent Document 1, based on the output value of the air-fuel ratio sensor, it is calculated which one of the plurality of cylinders has an air-fuel ratio. When the valve lift amount is controlled, the variation in the air-fuel ratio between the cylinders is suppressed. However, if there is a variation in the fuel injection amount between the cylinders, the variation in torque between the cylinders will occur, causing pulsation. There was a risk of it. On the other hand, in the control apparatus for a multi-cylinder internal combustion engine described in Patent Document 1, it is not considered that even if the variation in air-fuel ratio between cylinders is suppressed, the variation in torque between cylinders may occur. Therefore, depending on the control device for the multi-cylinder internal combustion engine described in Patent Document 1, there is a possibility that the situation in which the variation in the torque between the cylinders cannot be avoided although the variation in the air-fuel ratio between the cylinders is suppressed. there were.

  Furthermore, in the control device for a multi-cylinder internal combustion engine described in Patent Document 1, variation in air-fuel ratio between cylinders is suppressed by controlling the valve lift amount. However, Patent Document 1 discloses an intake valve and an exhaust valve. It is not disclosed how to suppress the variation in the air-fuel ratio between the cylinders when the valve overlap amount can be changed. Further, Patent Document 1 does not disclose how to suppress the variation in the air-fuel ratio between the cylinders when the operating angle of the intake valve can be changed. Therefore, depending on the control device of the multi-cylinder internal combustion engine described in Patent Document 1, when the valve overlap amount of the intake valve and the exhaust valve can be changed, or when the operating angle of the intake valve can be changed, There is a possibility that the variation in the air-fuel ratio cannot be suppressed appropriately.

  In view of the above problems, an object of the present invention is to provide a control device for a multi-cylinder internal combustion engine that can suppress variation in air-fuel ratio between cylinders and suppress variation in torque between cylinders.

  Another object of the present invention is to provide a control device for a multi-cylinder internal combustion engine that can appropriately suppress variation in air-fuel ratio between cylinders. More specifically, the present invention can appropriately suppress variation in air-fuel ratio between cylinders when the valve overlap amount of the intake valve and the exhaust valve can be changed or when the operating angle of the intake valve can be changed. An object of the present invention is to provide a control device for a cylinder internal combustion engine.

  Furthermore, according to the present invention, the value of the target air-fuel ratio can be made more appropriate than when the target air-fuel ratio is not corrected based on the operating angle of the intake valve. That is, a multi-cylinder capable of executing appropriate air-fuel ratio feedback control even when the sensor gas hit is poor, that is, even when the target air-fuel ratio calculated from the sensor output value does not reach an appropriate target air-fuel ratio. An object of the present invention is to provide a control device for an internal combustion engine.

  According to the first aspect of the present invention, in the control apparatus for a multi-cylinder internal combustion engine that suppresses variation among cylinders, the intake air amount sucked into the cylinder is based on the valve opening characteristics of the intake valve or the exhaust valve. Calculating the exhaust gas air-fuel ratio of the cylinder in which the valve opening characteristics of the intake valve and the exhaust valve are set so as not to be restricted, and suppressing variation in the fuel injection amount between the cylinders based on the exhaust gas air-fuel ratio A control apparatus for a multi-cylinder internal combustion engine is provided.

  According to the second aspect of the present invention, the intake air amount sucked into the cylinder is not limited based on the valve opening characteristics of the intake valve or the exhaust valve, but is limited based on the throttle valve opening. The exhaust gas air-fuel ratio of a cylinder in which valve opening characteristics of the intake valve and the exhaust valve are set is calculated, and variation in the fuel injection amount between the cylinders is suppressed based on the exhaust gas air-fuel ratio. A control apparatus for a multi-cylinder internal combustion engine according to claim 1 is provided.

  In the control apparatus for a multi-cylinder internal combustion engine according to claim 1 or 2, the intake air and exhaust valves are controlled so that the amount of intake air sucked into the cylinder is not limited based on the valve opening characteristics of the intake or exhaust valves. The exhaust gas air-fuel ratio of the cylinder for which the valve opening characteristic is set is calculated. Preferably, the intake air valve and the exhaust valve are not limited based on the valve opening characteristics of the intake valve or the exhaust valve but limited based on the throttle valve opening. The exhaust gas air-fuel ratio of the cylinder for which the open characteristic is set is calculated. In other words, when calculating the exhaust gas air-fuel ratio of a cylinder, the amount of intake air drawn into the cylinder is not limited based on the valve opening characteristics of the intake valve or exhaust valve, but limited based on the throttle valve opening. Thus, the valve opening characteristics of the intake valve and the exhaust valve are set. In other words, by setting the throttle valve opening for calculating the exhaust gas air-fuel ratio of a certain cylinder and the throttle valve opening for calculating the exhaust gas air-fuel ratio of another cylinder to be substantially equal, The amount of intake air taken into the cylinder when calculating the gas air-fuel ratio can be made equal to the amount of intake air taken into the cylinder when calculating the exhaust gas air-fuel ratio of other cylinders. Furthermore, in the control apparatus for a multi-cylinder internal combustion engine according to claim 1 or 2, when calculating the exhaust gas air-fuel ratio of a certain cylinder, the amount of intake air sucked into the cylinder and the exhaust gas air-fuel ratio of other cylinders are calculated. While making the amount of intake air sucked into the cylinder equal when calculating, variation in the fuel injection amount between the cylinders is suppressed based on the exhaust gas air-fuel ratio. That is, the fuel injection amount is corrected so that the exhaust gas air-fuel ratios of all the cylinders become equal after the intake air amounts of all the cylinders are made equal. Therefore, although the variation in the air-fuel ratio between the cylinders is suppressed as in the control device for the multi-cylinder internal combustion engine described in Patent Document 1, the torque between the cylinders is reduced when there is a variation in the fuel injection amount between the cylinders. It is possible to avoid the occurrence of variability and pulsation. That is, variation in air-fuel ratio between cylinders can be suppressed and variation in torque between cylinders can be suppressed.

  According to the third aspect of the present invention, in the control apparatus for a multi-cylinder internal combustion engine that suppresses variation among cylinders, the exhaust gas air-fuel ratio of the cylinder in which the operating angle of the intake valve is set to a predetermined operating angle is set. There is provided a control apparatus for a multi-cylinder internal combustion engine, characterized in that it calculates and suppresses variation in fuel injection amount between cylinders based on the exhaust gas air-fuel ratio.

  According to the fourth aspect of the present invention, the exhaust gas air-fuel ratio of the cylinder in which the operating angle of the intake valve is set so that the intake air amount sucked into the cylinder is not limited based on the operating angle of the intake valve. The control apparatus for a multi-cylinder internal combustion engine according to claim 3 is provided, wherein variation in fuel injection amount between cylinders is suppressed based on the exhaust gas air-fuel ratio.

  According to the fifth aspect of the present invention, the action of the intake valve is such that the amount of intake air drawn into the cylinder is not limited based on the operating angle of the intake valve, but is limited based on the throttle valve opening. 5. The multi-cylinder internal combustion engine according to claim 4, wherein an exhaust gas air-fuel ratio of a cylinder in which an angle is set is calculated, and variation in fuel injection amount between the cylinders is suppressed based on the exhaust gas air-fuel ratio. A control device is provided.

  According to the sixth aspect of the present invention, the exhaust gas air-fuel ratio of the cylinder in which the operating angle of the intake valve is set to the maximum operating angle is calculated, and the fuel injection amount between the cylinders is calculated based on the exhaust gas air-fuel ratio. The control apparatus for a multi-cylinder internal combustion engine according to claim 3, wherein variation is suppressed.

  In the control apparatus for a multi-cylinder internal combustion engine according to any one of claims 3 to 6, the exhaust gas air-fuel ratio of a cylinder in which the operating angle of the intake valve is set to a predetermined operating angle is calculated. Specifically, the exhaust gas air-fuel ratio of the cylinder in which the operating angle of the intake valve is set is calculated so that the amount of intake air taken into the cylinder is not limited based on the operating angle of the intake valve. Preferably, the cylinder in which the operating angle of the intake valve is set so that the amount of intake air sucked into the cylinder is not limited based on the operating angle of the intake valve but limited based on the throttle valve opening. The exhaust gas air-fuel ratio is calculated. Optimally, the exhaust gas air-fuel ratio of the cylinder in which the operating angle of the intake valve is set to the maximum operating angle is calculated. That is, when calculating the exhaust gas air-fuel ratio of a certain cylinder, the amount of intake air sucked into the cylinder is not limited based on the operating angle of the intake valve, but limited based on the throttle valve opening. The operating angle of the intake valve is set to the maximum operating angle. In other words, by setting the throttle valve opening for calculating the exhaust gas air-fuel ratio of a certain cylinder and the throttle valve opening for calculating the exhaust gas air-fuel ratio of another cylinder to be substantially equal, The amount of intake air taken into the cylinder when calculating the gas air-fuel ratio can be made equal to the amount of intake air taken into the cylinder when calculating the exhaust gas air-fuel ratio of other cylinders. Furthermore, in the control apparatus for a multi-cylinder internal combustion engine according to claims 3 to 6, when calculating the exhaust gas air-fuel ratio of a certain cylinder, the amount of intake air sucked into that cylinder and the exhaust gas air-fuel ratio of other cylinders are calculated. When calculating, the intake air amount taken into the cylinder is made equal, and the variation in the fuel injection amount between the cylinders is suppressed based on the exhaust gas air-fuel ratio. That is, the fuel injection amount is corrected so that the exhaust gas air-fuel ratios of all the cylinders become equal after the intake air amounts of all the cylinders are made equal. Therefore, although the variation in the air-fuel ratio between the cylinders is suppressed as in the control device for the multi-cylinder internal combustion engine described in Patent Document 1, the torque between the cylinders is reduced when there is a variation in the fuel injection amount between the cylinders. It is possible to avoid the occurrence of variability and pulsation. That is, variation in air-fuel ratio between cylinders can be suppressed and variation in torque between cylinders can be suppressed.

  According to the seventh aspect of the present invention, in a control apparatus for a multi-cylinder internal combustion engine that suppresses variations among cylinders, exhaust of a cylinder in which the valve overlap amount of the intake valve and the exhaust valve is set to a predetermined amount. There is provided a control apparatus for a multi-cylinder internal combustion engine that calculates a gas air-fuel ratio and suppresses variation in fuel injection amount between cylinders based on the exhaust gas air-fuel ratio.

  According to the eighth aspect of the present invention, the valve overlap amount of the intake valve and the exhaust valve is set so that the intake air amount sucked into the cylinder is not limited based on the valve overlap amount of the intake valve and the exhaust valve. 8. The control of a multi-cylinder internal combustion engine according to claim 7, wherein an exhaust gas air-fuel ratio of the set cylinder is calculated, and variation in fuel injection amount between the cylinders is suppressed based on the exhaust gas air-fuel ratio. An apparatus is provided.

  According to the ninth aspect of the present invention, the intake air amount sucked into the cylinder is not limited based on the valve overlap amount of the intake valve and the exhaust valve, but is limited based on the throttle valve opening. The exhaust gas air-fuel ratio of a cylinder for which the valve overlap amount of the intake valve and the exhaust valve is set is calculated, and variation in the fuel injection amount between the cylinders is suppressed based on the exhaust gas air-fuel ratio. A control device for a multi-cylinder internal combustion engine according to claim 8 is provided.

  According to the invention described in claim 10, the exhaust gas air-fuel ratio of the cylinder in which the valve overlap amount of the intake valve and the exhaust valve is set to the minimum valve overlap amount is calculated, and based on the exhaust gas air-fuel ratio. The control apparatus for a multi-cylinder internal combustion engine according to claim 7, wherein variation in fuel injection amount between cylinders is suppressed.

  In the control apparatus for a multi-cylinder internal combustion engine according to claims 7 to 10, the exhaust gas air-fuel ratio of a cylinder in which the valve overlap amounts of the intake valve and the exhaust valve are set to a predetermined amount is calculated. More specifically, the exhaust of the cylinder in which the valve overlap amount of the intake valve and the exhaust valve is set so that the intake air amount sucked into the cylinder is not limited based on the valve overlap amount of the intake valve and the exhaust valve. A gas air-fuel ratio is calculated. Preferably, the intake air amount sucked into the cylinder is not limited based on the valve overlap amount of the intake valve and the exhaust valve, but is limited based on the throttle valve opening. The exhaust gas air-fuel ratio of the cylinder for which the valve overlap amount is set is calculated. Optimally, the exhaust gas air-fuel ratio of the cylinder in which the valve overlap amount of the intake valve and the exhaust valve is set to the minimum valve overlap amount is calculated. That is, when calculating the exhaust gas air-fuel ratio of a certain cylinder, the intake air amount sucked into the cylinder is not limited based on the valve overlap amount of the intake valve and the exhaust valve, but based on the throttle valve opening degree. The valve overlap amount of the intake valve and the exhaust valve is set to the minimum valve overlap amount so as to be limited. In other words, by setting the throttle valve opening for calculating the exhaust gas air-fuel ratio of a certain cylinder and the throttle valve opening for calculating the exhaust gas air-fuel ratio of another cylinder to be substantially equal, The amount of intake air taken into the cylinder when calculating the gas air-fuel ratio can be made equal to the amount of intake air taken into the cylinder when calculating the exhaust gas air-fuel ratio of other cylinders. Furthermore, in the control apparatus for a multi-cylinder internal combustion engine according to any one of claims 7 to 10, when calculating the exhaust gas air-fuel ratio of a certain cylinder, the amount of intake air sucked into that cylinder and the exhaust gas air-fuel ratio of other cylinders are calculated. When calculating, the intake air amount taken into the cylinder is made equal, and the variation in the fuel injection amount between the cylinders is suppressed based on the exhaust gas air-fuel ratio. That is, the fuel injection amount is corrected so that the exhaust gas air-fuel ratios of all the cylinders become equal after the intake air amounts of all the cylinders are made equal. Therefore, although the variation in the air-fuel ratio between the cylinders is suppressed as in the control device for the multi-cylinder internal combustion engine described in Patent Document 1, the torque between the cylinders is reduced when there is a variation in the fuel injection amount between the cylinders. It is possible to avoid the occurrence of variability and pulsation. That is, variation in air-fuel ratio between cylinders can be suppressed and variation in torque between cylinders can be suppressed.

  According to the eleventh aspect of the present invention, after suppressing variation in the fuel injection amount between the cylinders, the intake air amount sucked into the cylinder is limited based on the valve opening characteristics of the intake valve or the exhaust valve. The exhaust gas air-fuel ratio is calculated for a cylinder for which the valve opening characteristics of the intake valve and the exhaust valve are set, and variations in the valve opening characteristics of the intake valve and the exhaust valve between the cylinders are suppressed based on the exhaust gas air-fuel ratio. A control device for a multi-cylinder internal combustion engine according to any one of claims 1 to 10 is provided.

  According to the twelfth aspect of the present invention, after suppressing variation in the fuel injection amount between the cylinders, the intake air amount sucked into the cylinder is not limited based on the throttle valve opening, and the intake valve or the exhaust valve The exhaust gas air-fuel ratio of the cylinder in which the valve opening characteristics of the intake valve and the exhaust valve are set so as to be limited based on the valve opening characteristic of the valve is calculated, and the intake valve between the cylinders is calculated based on the exhaust gas air-fuel ratio And a control device for a multi-cylinder internal combustion engine according to claim 11, wherein variations in valve opening characteristics of the exhaust valve are suppressed.

In the control device for a multi-cylinder internal combustion engine according to claim 11 and 12, after suppressing variation in the fuel injection amount between the cylinders, the intake air amount sucked into the cylinder becomes the valve opening characteristic of the intake valve or the exhaust valve. The exhaust gas air-fuel ratio of the cylinders for which the valve opening characteristics of the intake valve and the exhaust valve are set to be limited based on the exhaust gas air-fuel ratio is calculated, and the valve opening of the intake valve and the exhaust valve between the cylinders is calculated based on the exhaust gas air-fuel ratio. Variation in characteristics is suppressed. Preferably, after suppressing variation in the fuel injection amount between the cylinders, the intake air amount sucked into the cylinder is not limited based on the throttle valve opening, but based on the valve opening characteristics of the intake valve or the exhaust valve. The exhaust gas air-fuel ratio of the cylinders for which the valve opening characteristics of the intake valve and the exhaust valve are set so as to be limited are calculated, and the valve opening characteristics of the intake valve and the exhaust valve between the cylinders are calculated based on the exhaust gas air-fuel ratio The variation of is suppressed. That is, the valve opening characteristics of the intake valve and the exhaust valve of each cylinder so that the exhaust gas air-fuel ratio of one cylinder and the exhaust gas air-fuel ratio of the other cylinder become equal while suppressing the variation in the fuel injection amount between the cylinders. Will be changed.
Therefore, even when there is a variation in the fuel injection amount between the cylinders, the variation in the valve opening characteristics of the intake valve and the exhaust valve between the cylinders can be suppressed without causing a variation in the torque between the cylinders. .

  According to the thirteenth aspect of the present invention, the exhaust gas air-fuel ratio of the cylinder in which the operating angle of the intake valve is set to be smaller than the predetermined operating angle after suppressing the variation in the fuel injection amount between the cylinders. And a control device for a multi-cylinder internal combustion engine according to any one of claims 3 to 6, wherein variation in intake air amount between cylinders is suppressed based on the exhaust gas air-fuel ratio. Is done.

  In the control device for a multi-cylinder internal combustion engine according to claim 13, after suppressing the variation in the fuel injection amount between the cylinders, the operating angle of the intake valve is set to be smaller than the predetermined operating angle. The exhaust gas air-fuel ratio is calculated, and the variation in the intake air amount between the cylinders is suppressed based on the exhaust gas air-fuel ratio. In other words, the working angle of the intake valve of each cylinder can be changed so that the exhaust gas air-fuel ratio of one cylinder is equal to the exhaust gas air-fuel ratio of the other cylinder while suppressing variation in the fuel injection amount between the cylinders. . Therefore, even when there is a variation in the fuel injection amount between the cylinders, the variation in the intake air amount between the cylinders can be suppressed without causing a variation in the torque between the cylinders.

  According to the fourteenth aspect of the present invention, the exhaust gas air-fuel ratio of the cylinder in which the operating angle of the intake valve is set to be smaller than the predetermined operating angle after suppressing the variation in the fuel injection amount between the cylinders. The control device for a multi-cylinder internal combustion engine according to any one of claims 3 to 6, wherein a variation in the operating angle of the intake valve between the cylinders is suppressed based on the exhaust gas air-fuel ratio. Is provided.

  In the control device for a multi-cylinder internal combustion engine according to claim 14, after suppressing the variation in the fuel injection amount between the cylinders, the operating angle of the intake valve is set to be smaller than the predetermined operating angle. The exhaust gas air-fuel ratio is calculated, and variation in the operating angle of the intake valve between the cylinders is suppressed based on the exhaust gas air-fuel ratio. In other words, the working angle of the intake valve of each cylinder can be changed so that the exhaust gas air-fuel ratio of one cylinder is equal to the exhaust gas air-fuel ratio of the other cylinder while suppressing variation in the fuel injection amount between the cylinders. . Therefore, even if there is a variation in the fuel injection amount between the cylinders, it is possible to suppress a variation in the operating angle of the intake valve between the cylinders without causing a variation in torque between the cylinders.

  According to the fifteenth aspect of the present invention, there is provided the control device for a multi-cylinder internal combustion engine according to any one of the first to fourteenth aspects, wherein variation between cylinders is suppressed using a neural network. Is done.

  In the control device for a multi-cylinder internal combustion engine according to the fifteenth aspect, variation between cylinders is suppressed by using a neural network. Therefore, variation between cylinders can be more effectively suppressed than when no neural network is used.

  According to the sixteenth aspect of the present invention, in the control device for a multi-cylinder internal combustion engine that suppresses the variation between cylinders, the variation between the cylinders is suppressed based on the valve overlap amount of the intake valve and the exhaust valve. A control apparatus for a multi-cylinder internal combustion engine is provided.

  According to the invention described in claim 17, the multi-cylinder internal combustion engine according to claim 16, wherein variation in the fuel injection amount between the cylinders is suppressed based on the valve overlap amount of the intake valve and the exhaust valve. A control device is provided.

  In the control device for a multi-cylinder internal combustion engine according to the sixteenth and seventeenth aspects, variation among cylinders is suppressed based on valve overlap amounts of the intake valve and the exhaust valve. Specifically, variation in the fuel injection amount between the cylinders is suppressed based on the valve overlap amount of the intake valve and the exhaust valve. Therefore, when the valve overlap amount of the intake valve and the exhaust valve can be changed, the variation among the cylinders is not suppressed based on the valve overlap amount of the intake valve and the exhaust valve. The variation in the air-fuel ratio between the cylinders can be suppressed more appropriately than the control device. That is, the variation in the air-fuel ratio between the cylinders can be appropriately suppressed.

According to the invention of claim 18, in the control device for a multi-cylinder internal combustion engine in which the number of sensors for detecting the air-fuel ratio or the oxygen concentration is less than the number of cylinders, the air-fuel ratio is determined based on the operating angle of the intake valve. A control apparatus for a multi-cylinder internal combustion engine is provided that corrects a predetermined coefficient related to feedback control.
According to the nineteenth aspect of the present invention, the predetermined coefficient related to the air-fuel ratio feedback control is corrected so that the target air-fuel ratio correction amount increases as the operating angle of the intake valve decreases. A control device for a multi-cylinder internal combustion engine according to claim 18 is provided.

According to the twentieth aspect of the present invention, in the control device for a multi-cylinder internal combustion engine in which the number of sensors for detecting the air-fuel ratio or the oxygen concentration is less than the number of cylinders, the target air-fuel ratio is determined based on the operating angle of the intake valve. A control apparatus for a multi-cylinder internal combustion engine is provided.
According to the invention of claim 21, the correction of the target air-fuel ratio is such that the correction amount of the target air-fuel ratio increases as the operating angle of the intake valve decreases. A control apparatus for a multi-cylinder internal combustion engine is provided.

  According to the twenty-second aspect of the present invention, when a variation in the air-fuel ratio between cylinders is detected, the target air-fuel ratio is calculated, and the target air-fuel ratio is calculated based on the target air-fuel ratio and the operating angle of the intake valve at that time. When the relationship between the air-fuel ratio and the intake valve operating angle is calculated and the intake valve operating angle is changed, the target airflow after the intake valve operating angle change is changed based on the changed intake valve operating angle and the relationship. The control apparatus for a multi-cylinder internal combustion engine according to any one of claims 18 to 21, wherein an air-fuel ratio is calculated.

  In the control device for a multi-cylinder internal combustion engine according to claims 18 to 22, the predetermined coefficient relating to the air-fuel ratio feedback control is corrected based on the operating angle of the intake valve. Specifically, the target air-fuel ratio is corrected based on the operating angle of the intake valve. For example, if the target air-fuel ratio is not set appropriately due to poor gas contact with the sensor, and as a result the overall air-fuel ratio is shifted to the rich side, the entire air-fuel ratio is shifted to the lean side. The target air / fuel ratio is corrected. Further, when the actual operating angle of the intake valve deviates from the target operating angle of the intake valve, the target air / fuel ratio set based on the output value of the sensor is more appropriate as the operating angle of the intake valve is smaller. In view of the fact that the operating angle of the intake valve decreases, for example, the correction amount of the target air-fuel ratio increases. Therefore, the value of the target air-fuel ratio can be set to a more appropriate value than when the target air-fuel ratio is not corrected based on the operating angle of the intake valve. That is, appropriate air-fuel ratio feedback control can be executed even when the gas contact of the sensor is poor, that is, even when the target air-fuel ratio calculated from the sensor output value does not reach an appropriate target air-fuel ratio. Specifically, when a variation in air-fuel ratio between cylinders is detected, the target air-fuel ratio is calculated (corrected to an appropriate target air-fuel ratio), and based on the target air-fuel ratio and the operating angle of the intake valve at that time When the relationship between the target air-fuel ratio and the intake valve operating angle is calculated and the intake valve operating angle is changed, the intake valve operating angle is changed based on the changed intake valve operating angle and the relationship. An appropriate target air-fuel ratio is calculated. For example, a relational expression or a map can be used to indicate the relationship between the target air-fuel ratio and the operating angle of the intake valve.

  According to the twenty-third aspect of the present invention, when the calculated correction amount of the fuel injection amount is small, the variation in the air-fuel ratio between the cylinders is suppressed by correcting the fuel injection amount separately for each cylinder, and the calculation is performed. When the corrected fuel injection amount is large, the fuel injection amount correction amount is guarded with a predetermined value, the target air-fuel ratio is corrected, and the fuel injection amounts of all cylinders are uniformly set based on the target air-fuel ratio. The control device for a multi-cylinder internal combustion engine according to any one of claims 18 to 22, wherein correction is performed.

  In the control device for a multi-cylinder internal combustion engine according to claim 23, in view of the possibility that torque fluctuation may occur if the fuel injection amount correction amount is large, each of the calculated fuel injection amount correction amounts is small. By separately correcting the fuel injection amount for each cylinder, variation in the air-fuel ratio among the cylinders is suppressed, and when the calculated fuel injection amount correction amount is large, the fuel injection amount correction amount is guarded at a predetermined value. The target air-fuel ratio is corrected, and the fuel injection amounts of all cylinders are uniformly corrected based on the target air-fuel ratio. Therefore, it is possible to appropriately control the air-fuel ratio while suppressing torque fluctuation.

  According to the first to tenth aspects of the present invention, the throttle valve opening when calculating the exhaust gas air-fuel ratio of a certain cylinder and the throttle valve opening when calculating the exhaust gas air-fuel ratio of another cylinder are approximately equal. By making them equal, when calculating the exhaust gas air-fuel ratio of a certain cylinder, the amount of intake air sucked into that cylinder and when calculating the exhaust gas air-fuel ratio of other cylinders are sucked into that cylinder. The amount of intake air can be made equal. Further, when the variation in the air-fuel ratio between the cylinders is suppressed as in the control device for a multi-cylinder internal combustion engine described in Japanese Patent Application Laid-Open No. 6-213044, the cylinder is used when there is a variation in the fuel injection amount between the cylinders. It is possible to avoid the occurrence of pulsation due to variations in torque between the two. That is, variation in air-fuel ratio between cylinders can be suppressed and variation in torque between cylinders can be suppressed.

  According to the eleventh and twelfth aspects of the present invention, even if there is a variation in the fuel injection amount between the cylinders, the intake valve and the exhaust valve between the cylinders do not cause a variation in the torque between the cylinders. Variations in valve opening characteristics can be suppressed.

  According to the thirteenth aspect of the present invention, even when there is a variation in the fuel injection amount between the cylinders, the variation in the intake air amount between the cylinders is suppressed without causing a variation in the torque between the cylinders. be able to.

  According to the fourteenth aspect of the present invention, even if there is a variation in the fuel injection amount between the cylinders, the variation in the operating angle of the intake valve between the cylinders can be reduced without causing a variation in the torque between the cylinders. Can be suppressed.

  According to the fifteenth aspect of the present invention, variations among cylinders can be more effectively suppressed than when no neural network is used.

  According to the sixteenth and seventeenth aspects, when the valve overlap amount of the intake valve and the exhaust valve can be changed, the variation between the cylinders is not suppressed based on the valve overlap amount of the intake valve and the exhaust valve. The variation in the air-fuel ratio among the cylinders can be suppressed more appropriately than the control device for a multi-cylinder internal combustion engine described in Japanese Laid-Open Patent Publication No. 6-213044. That is, the variation in the air-fuel ratio between the cylinders can be appropriately suppressed.

  According to the invention described in claims 18 to 22, the value of the target air-fuel ratio can be set to an appropriate value as compared with the case where the target air-fuel ratio is not corrected based on the operating angle of the intake valve. That is, appropriate air-fuel ratio feedback control can be executed even when the gas contact of the sensor is poor, that is, even when the target air-fuel ratio calculated from the sensor output value does not reach an appropriate target air-fuel ratio.

  According to the twenty-third aspect of the present invention, the air-fuel ratio can be appropriately controlled while suppressing torque fluctuation.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  1 is a schematic configuration diagram of a first embodiment of an internal combustion engine control device according to the present invention, FIG. 2 is a detailed view of an intake system of the internal combustion engine control device shown in FIG. 1, and FIG. 3 is shown in FIG. 2 is a plan view of an intake system and the like of the control device for the internal combustion engine. FIG. 1-3, 1 is an internal combustion engine, 2 is an intake valve, 3 is an exhaust valve, 4 is a cam for opening and closing the intake valve, 5 is a cam for opening and closing the exhaust valve, and 6 is a cam for intake valve A camshaft carrying 4 and a camshaft carrying an exhaust valve cam 5 are shown. FIG. 4 is a detailed view of the intake valve cam and camshaft shown in FIG. As shown in FIG. 4, the cam profile of the cam 4 of this embodiment changes in the direction of the camshaft central axis. That is, in the cam 4 of this embodiment, the nose height at the left end in FIG. 4 is larger than the nose height at the right end. That is, the valve lift amount of the intake valve 2 of the present embodiment is smaller when the valve lifter is in contact with the right end of the cam 4 than when the valve lifter is in contact with the left end of the cam 4.

Returning to the description of FIGS. 1 to 3, 8 is a combustion chamber formed in the cylinder, and 9 is for moving the cam 4 in the direction of the camshaft central axis with respect to the intake valve 2 in order to change the valve lift amount. This is a valve lift amount changing device. That is, by operating the valve lift changing device 9, the cam 4 and the valve lifter are brought into contact with each other at the left end (FIG. 4) of the cam 4, or the cam 4 and the valve lifter are brought into contact with each other at the right end (FIG. 4). Can be. When the valve lift amount of the intake valve 2 is changed by the valve lift amount changing device 9, the opening area of the intake valve 2 is changed accordingly. In the intake valve 2 of the present embodiment, the opening area of the intake valve 2 increases as the valve lift amount increases. Reference numeral 10 denotes a driver for driving the valve lift amount changing device 9, and 11 denotes an opening / closing timing shift device for shifting the opening / closing timing of the intake valve without changing the valve opening period of the intake valve 2. That is, by operating the opening / closing timing shift device 11, the opening / closing timing of the intake valve 2 can be shifted to the advance side or shifted to the retard side. An oil control valve 12 controls oil pressure for operating the opening / closing timing shift device 11.
Note that the variable valve mechanism in the present embodiment includes both the valve lift amount changing device 9 and the opening / closing timing shift device 11.

  13 is a crankshaft, 14 is an oil pan, 15 is a fuel injection valve, 16 is a sensor for detecting the valve lift amount and opening / closing timing shift amount of the intake valve 2, and 17 is a sensor for detecting the engine speed. . 18 is an intake pipe pressure sensor for detecting the pressure in the intake pipe for supplying intake air into the cylinder, 19 is an air flow meter, 20 is a cooling water temperature sensor for detecting the temperature of the cooling water of the internal combustion engine, and 21 is in the cylinder. An intake air temperature sensor 22 for detecting the temperature of intake air supplied to the inside of the intake pipe, and 22 is an ECU (electronic control unit). 50 is a cylinder, 51 and 52 are intake pipes, 53 is a surge tank, 54 is an exhaust pipe, 55 is a spark plug, 56 is a throttle valve whose opening degree can be changed regardless of the accelerator pedal opening degree, and 57 is an exhaust gas empty An air-fuel ratio sensor for detecting the fuel ratio.

  FIG. 5 is a detailed view of the valve lift amount changing device and the like shown in FIG. In FIG. 5, 30 is a magnetic body connected to the intake valve camshaft 6, 31 is a coil for biasing the magnetic body 30 to the left, and 32 is a compression spring for biasing the magnetic body 30 to the right. is there. As the energization amount to the coil 31 is increased, the amount of movement of the cam 4 and the camshaft 6 to the left side is increased, and the valve lift amount of the intake valve 2 is decreased.

  FIG. 6 is a diagram showing how the valve lift amount of the intake valve changes as the valve lift amount changing device is operated. As shown in FIG. 6, the valve lift amount of the intake valve 2 is increased as the energization amount to the coil 31 is decreased (solid line → broken line → dashed line). Further, in the present embodiment, the valve opening period of the intake valve 2 is also changed as the valve lift amount changing device 9 is operated. That is, the operating angle of the intake valve 2 can be changed. Specifically, as the valve lift amount of the intake valve 2 is increased, the operating angle of the intake valve 2 is increased (solid line → broken line → dashed line). Furthermore, in this embodiment, the timing at which the valve lift amount of the intake valve 2 peaks is also changed as the valve lift amount changing device 9 is operated. More specifically, as the valve lift amount of the intake valve 2 is increased, the timing at which the valve lift amount of the intake valve 2 peaks is retarded (solid line → broken line → dashed line).

  FIG. 7 is a detailed view of the opening / closing timing shift device and the like shown in FIG. In FIG. 7, 40 is an advance side oil passage for shifting the opening / closing timing of the intake valve 2 to the advance side, 41 is a retard angle side oil passage for shifting the opening / closing timing of the intake valve 2 to the retard side, 42 is an oil pump. As the hydraulic pressure in the advance side oil passage 40 increases, the opening / closing timing of the intake valve 2 is shifted to the advance side. That is, the rotational phase of the camshaft 6 relative to the crankshaft 13 is advanced. On the other hand, the opening / closing timing of the intake valve 2 is shifted to the retard side as the oil pressure in the retard side oil passage 41 is increased. That is, the rotational phase of the camshaft 6 with respect to the crankshaft 13 is retarded.

  FIG. 8 is a diagram showing how the opening / closing timing of the intake valve shifts as the opening / closing timing shift device is operated. As shown in FIG. 8, the opening / closing timing of the intake valve 2 is shifted to the advance side as the hydraulic pressure in the advance side oil passage 40 increases (solid line → broken line → dashed line). At this time, the valve opening period of the intake valve 2 is not changed, that is, the length of the period during which the intake valve 2 is opened is not changed.

  FIG. 9 is a detailed view of an intake system and the like of the control device for the internal combustion engine of the second embodiment. 9, the same reference numerals as those shown in FIGS. 1 to 8 indicate the same parts or portions as the parts or parts shown in FIGS. In the present embodiment, the exhaust valve drive cam is configured in substantially the same manner as the intake valve drive cam 4 shown in FIG. Reference numeral 9 ′ denotes a valve lift amount changing device for moving the exhaust valve driving cam in the direction of the camshaft central axis with respect to the exhaust valve 3 in order to change the valve lift amount of the exhaust valve 3. The valve lift amount changing device 9 ′ is configured in substantially the same manner as the valve lift amount changing device 9. Reference numeral 11 ′ denotes an opening / closing timing shift device for shifting the opening / closing timing of the exhaust valve without changing the valve opening period of the exhaust valve 3. This opening / closing timing shift device 11 ′ is configured in substantially the same manner as the opening / closing timing shift device 11.

  FIG. 10 is a detailed view of the intake system and the like of the control device for the internal combustion engine of the third embodiment. 10, the same reference numerals as those shown in FIGS. 1 to 8 indicate the same parts or portions as the parts or parts shown in FIGS. 58 is, for example, an electromagnetically driven intake valve driving device capable of independently driving each intake valve 2 (see FIG. 3). 58 'is, for example, an electromagnetically driven exhaust valve driving device capable of independently driving each exhaust valve 3 (see FIG. 3).

  In the modification of the first to third embodiments described above, the throttle valve 56 can be eliminated.

  In the first to third embodiments and the modifications thereof described above, the air-fuel ratio of which cylinder among the plurality of cylinders # 1 to # 4 is calculated based on the output value of the air-fuel ratio sensor 57. By controlling the valve lift amount of the intake valve 2 and / or the exhaust valve 3 of each cylinder, it is possible to suppress variations in the air-fuel ratio between the cylinders. However, if there is a variation in the fuel injection amount between the cylinders, even if the variation in the air-fuel ratio between the cylinders is suppressed, the variation in torque between the cylinders will occur, causing pulsation (torque fluctuation). End up. Therefore, in the first to third embodiments and their modifications, control described later is performed in order to suppress variation in air-fuel ratio between cylinders and to suppress variation in torque between cylinders.

  FIG. 11 is a flowchart showing the fuel injection amount variation learning method of the first to third embodiments and their modifications. This routine is executed at predetermined time intervals. As shown in FIG. 11, when this routine is started, first, at step 100, it is determined whether or not the operating angle of the intake valve 2 is maximized as indicated by a one-dot chain line in FIG. When YES, the amount of intake air taken into the cylinder 50 is determined based on the opening of the throttle valve 56 or the cross-sectional area of the most throttled portions in the intake pipes 51 and 52, and the intake valve 2 between the cylinders Even if there is a variation in the operating angle, it is determined that the intake air amount does not vary between the cylinders in accordance therewith, and the routine proceeds to step 101. On the other hand, when NO, that is, when the operating angle of the intake valve 2 is relatively small and the opening area of the intake valve 2 is relatively small, the intake air amount sucked into the cylinder 50 is based on the opening area of the intake valve 2. If there is a variation in the operating angle of the intake valve 2 between the cylinders, it is determined that the intake air amount varies between the cylinders and the variation learning of the fuel injection amount cannot be performed. finish.

  In step 101, it is determined whether or not it is time to calculate the exhaust gas air-fuel ratio of a specific cylinder (N-th cylinder) among the plurality of cylinders # 1 to # 4. When YES, the routine proceeds to step 102, and when NO, this routine is terminated. In step 102, the exhaust gas air-fuel ratio of the Nth cylinder is detected for several cycles, and the average air-fuel ratio thereof is calculated. This average air-fuel ratio is calculated for all the cylinders # 1 to # 4. Next, at step 103, based on the idea that the intake air amounts sucked into the cylinders # 1 to # 4 are equal, the air-fuel ratios of the cylinders # 1 to # 4 calculated at step 102 are calculated between the cylinders. The fuel injection amount variation ΔQn is calculated.

  Next, at step 104, the fuel injection amount variation rate Qrate-n is calculated based on the fuel injection amount variation ΔQn between the cylinders calculated at step 103. Next, at step 105, the fuel injection amounts of the cylinders # 1 to # 4 are corrected so that there is no variation in the fuel injection amounts among the cylinders.

  According to the first to third embodiments, when it is determined in step 100 that the operating angle of the intake valve 2 is set to the maximum operating angle, in step 102, the exhaust gas air-fuel ratio of the cylinder is calculated. Is done. That is, when it is determined in step 100 that the operating angle of the intake valve 2 is set so that the amount of intake air sucked into the cylinder is not limited based on the operating angle of the intake valve 2, Then, the exhaust gas air-fuel ratio of the cylinder is calculated. More specifically, the operating angle of the intake valve 2 is not limited based on the operating angle of the intake valve 2 but limited based on the opening of the throttle valve 56. When it is determined in step 100 that it is set, in step 102, the exhaust gas air-fuel ratio of the cylinder is calculated. That is, when calculating the exhaust gas air-fuel ratio of a cylinder in step 102, the amount of intake air sucked into the cylinder is not limited based on the operating angle of the intake valve 2 in a step (not shown). The operating angle of the intake valve 2 is set to the maximum operating angle so as to be limited based on the opening of the throttle valve 56. That is, the opening degree of the throttle valve 56 when calculating the exhaust gas air-fuel ratio of the first cylinder # 1 and the opening degree of the throttle valve 56 when calculating the exhaust gas air-fuel ratios of the other cylinders # 2 to # 4. By substantially equalizing, when calculating the exhaust gas air-fuel ratio of the first cylinder # 1, the intake air amount sucked into the cylinder # 1 and the exhaust gas air-fuel ratios of the other cylinders # 2 to # 4 are set. When calculating, the intake air amount sucked into the cylinders # 2 to # 4 can be made equal.

  Further, according to the first to third embodiments, when calculating the exhaust gas air-fuel ratio of a certain cylinder # 1, the amount of intake air taken into that cylinder # 1 and the exhaust of the other cylinders # 2 to # 4 are calculated. When it is determined in step 100 that the amount of intake air sucked into the cylinders # 2 to # 4 becomes equal when calculating the gas air-fuel ratio, in step 105, between the cylinders based on the exhaust gas air-fuel ratio. Variations in the fuel injection amount are suppressed. That is, the fuel injection amount is corrected so that the exhaust gas air-fuel ratios of all the cylinders become equal after the intake air amounts of all the cylinders are made equal. Therefore, variation in air-fuel ratio between cylinders can be suppressed and variation in torque between cylinders can be suppressed.

  In other words, according to the first to third embodiments, the amount of intake air sucked into the cylinder is not limited based on the valve opening characteristic of the intake valve 2 but limited based on the opening degree of the throttle valve 56. When it is determined in step 100 that the valve opening characteristic of the intake valve 2 is set as described above, in step 102, the exhaust gas air-fuel ratio of the cylinder is calculated. That is, when calculating the exhaust gas air-fuel ratio of a cylinder in step 102, the amount of intake air sucked into the cylinder is not limited based on the valve opening characteristics of the intake valve 2 in a step (not shown). The valve opening characteristic of the intake valve 2 is set so as to be limited based on the opening degree of the throttle valve 56.

  Further, according to the modifications of the first to third embodiments in which the throttle valve 56 is not provided, the operating angle of the intake valve 2 is set to the maximum operating angle, as in the first to third embodiments. If it is determined in step 100, the exhaust gas air-fuel ratio of the cylinder is calculated in step 102. That is, when it is determined in step 100 that the operating angle of the intake valve 2 is set so that the amount of intake air sucked into the cylinder is not limited based on the operating angle of the intake valve 2, Then, the exhaust gas air-fuel ratio of the cylinder is calculated. More specifically, the amount of intake air sucked into the cylinder is not limited based on the operating angle of the intake valve 2, but is limited based on the cross-sectional area of the most narrowed portions in the intake pipes 51 and 52. Thus, when it is determined in step 100 that the operating angle of the intake valve 2 is set, in step 102, the exhaust gas air-fuel ratio of the cylinder is calculated. That is, when calculating the exhaust gas air-fuel ratio of a cylinder in step 102, the amount of intake air sucked into the cylinder is not limited based on the operating angle of the intake valve 2 in the step (not shown). The operating angle of the intake valve 2 is set to the maximum operating angle so as to be limited based on the cross-sectional area of the most narrowed portions in the intake pipes 51 and 52.

  In other words, according to the modifications of the first to third embodiments, the amount of intake air sucked into the cylinder is not limited based on the valve opening characteristics of the intake valve 2, and the intake air in the intake pipes 51 and 52 is not limited. When it is determined in step 100 that the valve opening characteristic of the intake valve 2 is set so as to be limited based on the cross-sectional area of the most narrowed portion, in step 102, the exhaust gas air-fuel ratio of that cylinder is determined. Is calculated. That is, when calculating the exhaust gas air-fuel ratio of a cylinder in step 102, the amount of intake air sucked into the cylinder is not limited based on the valve opening characteristics of the intake valve 2 in a step (not shown). The valve opening characteristic of the intake valve 2 is set so as to be limited based on the cross-sectional area of the most narrowed portion in the intake pipes 51 and 52.

  Further, according to the first to third embodiments and the modifications thereof, the variation among the cylinders is suppressed based on the operating angle of the intake valve. Specifically, the variation in the fuel injection amount between the cylinders is suppressed based on the operating angle of the intake valve. More specifically, when it is determined in step 100 of FIG. 11 that the operating angle of the intake valve 2 is the maximum, in step 105, variation in the fuel injection amount between the cylinders is suppressed. Therefore, when the operating angle of the intake valve can be changed, the variation in the air-fuel ratio between the cylinders can be more appropriately suppressed than when the variation between the cylinders is not suppressed based on the operating angle of the intake valve. That is, the variation in the air-fuel ratio between the cylinders can be appropriately suppressed.

  FIG. 12 is a flowchart showing the intake valve operating angle variation learning method of the third embodiment and its modification. This routine is executed at predetermined time intervals in the same manner as the routine shown in FIG. As shown in FIG. 12, when this routine is started, it is first determined in step 150 whether or not the execution of step 105 shown in FIG. 11 has been completed. When correction of the fuel injection amount for all cylinders has been completed, the routine proceeds to step 151. When it has not been completed, it is determined that variation in the operating angle of the intake valve 2 among the cylinders cannot be suppressed, and this routine is terminated. To do. In step 151, it is determined whether or not the operating angle of the intake valve 2 is equal to or less than a predetermined threshold value. That is, the operating angle of the intake valve 2 is relatively limited so that the intake air amount sucked into the cylinder is not limited based on the opening of the throttle valve 56 but limited based on the operating angle of the intake valve 2. It is determined whether or not a small value is set. When YES, the routine proceeds to step 152, and when NO, this routine is terminated.

  In step 152, it is determined whether or not it is time to calculate the exhaust gas air-fuel ratio of a specific cylinder (N-th cylinder) among the plurality of cylinders # 1 to # 4. When the determination is YES, the routine proceeds to step 153, and when the determination is NO, this routine is terminated. In step 153, the exhaust gas air-fuel ratio of the Nth cylinder is detected for several cycles, and the average air-fuel ratio thereof is calculated. This average air-fuel ratio is calculated for all the cylinders # 1 to # 4. Next, at step 154, based on the idea that the fuel injection amounts of the cylinders # 1 to # 4 are equal, the intake air amount between the cylinders is calculated from the air-fuel ratio of the cylinders # 1 to # 4 calculated at step 153. Variation ΔQ is calculated.

  Next, at step 155, based on the intake air amount variation ΔQ between the cylinders calculated at step 154, the operating angle variation ΔAng of the intake valve 2 of the specific cylinder (Nth cylinder) is calculated. The calculation of the operating angle variation ΔAng of the intake valve 2 is performed for all the cylinders # 1 to # 4. Next, at step 156, each of the cylinders # 1 to # 4 is controlled by the intake valve drive device 58 so that the variation in the operating angle of the intake valve 2 between the cylinders is eliminated, that is, the variation in the intake air amount between the cylinders is eliminated. The operating angle of the intake valve 2 is corrected.

  According to the third embodiment, after suppressing variation in the fuel injection amount between the cylinders in step 105 of FIG. 11, the intake air amount sucked into the cylinders is limited based on the opening degree of the throttle valve 56. First, when it is determined in step 151 that the valve opening characteristic of the intake valve 2 is set so as to be limited based on the valve opening characteristic of the intake valve 2, in step 153, the exhaust gas air-fuel ratio of the cylinder is determined. Then, in step 156, variation in the valve opening characteristics of the intake valve 2 between the cylinders is suppressed based on the exhaust gas air-fuel ratio. That is, while suppressing variations in the fuel injection amount among the cylinders, each cylinder # 1 to # 1 is set so that the exhaust gas air-fuel ratio of a certain cylinder # 1 is equal to the exhaust gas air-fuel ratio of the other cylinders # 2 to # 4. The valve opening characteristic of the intake valve 2 of # 4 is changed. Therefore, even if there is a variation in the fuel injection amount between the cylinders, the variation in the valve opening characteristics of the intake valve 2 between the cylinders can be suppressed without causing a variation in the torque between the cylinders. .

  Further, according to the modification of the third embodiment, after suppressing the variation in the fuel injection amount between the cylinders in step 105 of FIG. In step 151, it is determined that the valve opening characteristic of the intake valve 2 is set not to be limited based on the cross-sectional area of the most narrowed portion but to be limited based on the valve opening characteristic of the intake valve 2. In step 153, the exhaust gas air-fuel ratio of the cylinder is calculated. Then, in step 156, variation in the valve opening characteristics of the intake valve 2 between the cylinders is suppressed based on the exhaust gas air-fuel ratio. That is, while suppressing variations in the fuel injection amount among the cylinders, each cylinder # 1 to # 1 is set so that the exhaust gas air-fuel ratio of a certain cylinder # 1 is equal to the exhaust gas air-fuel ratio of the other cylinders # 2 to # 4. The valve opening characteristic of the intake valve 2 of # 4 is changed. Therefore, even if there is a variation in the fuel injection amount between the cylinders, the variation in the valve opening characteristics of the intake valve 2 between the cylinders can be suppressed without causing a variation in the torque between the cylinders. .

  Specifically, according to the third embodiment and its modification, after suppressing the variation in the fuel injection amount between the cylinders in step 105 of FIG. 11, the operating angle of the intake valve 2 is greater than the maximum operating angle in step 151. Is determined to be set to a small predetermined operating angle, the exhaust gas air-fuel ratio is calculated in step 153, and then in step 156, the operating angle of the intake valve 2 between the cylinders is calculated based on the exhaust gas air-fuel ratio. Variation is suppressed. That is, while suppressing variations in the fuel injection amount among the cylinders, each cylinder # 1 to # 1 is set so that the exhaust gas air-fuel ratio of a certain cylinder # 1 is equal to the exhaust gas air-fuel ratio of the other cylinders # 2 to # 4. The working angle of the intake valve 2 of # 4 is changed. Therefore, even if there is a variation in the fuel injection amount between the cylinders, it is possible to suppress a variation in the operating angle of the intake valve 2 between the cylinders without causing a variation in torque between the cylinders.

  In other words, according to the third embodiment and its modification, after suppressing the variation in the fuel injection amount between the cylinders in step 105 of FIG. 11, the operating angle of the intake valve 2 is greater than the maximum operating angle in step 151. When it is determined that the predetermined working angle is set to a small predetermined operating angle, the exhaust gas air-fuel ratio is calculated in step 153, and then in step 156, variation in the intake air amount between the cylinders is suppressed based on the exhaust gas air-fuel ratio. The That is, while suppressing variations in the fuel injection amount among the cylinders, each cylinder # 1 to # 1 is set so that the exhaust gas air-fuel ratio of a certain cylinder # 1 is equal to the exhaust gas air-fuel ratio of the other cylinders # 2 to # 4. The working angle of the intake valve 2 of # 4 is changed. Therefore, even if there is a variation in the fuel injection amount between the cylinders, it is possible to suppress the variation in the intake air amount between the cylinders without causing a variation in the torque between the cylinders.

  Further, according to the first to third embodiments and the modifications thereof, the variation among the cylinders is suppressed based on the operating angle of the intake valve. Specifically, when it is determined in step 151 of FIG. 12 that the operating angle of the intake valve 2 is equal to or smaller than a predetermined threshold value, the variation in the operating angle of the intake valve 2 between the cylinders is suppressed in step 156. . Therefore, when the operating angle of the intake valve can be changed, the variation in the air-fuel ratio between the cylinders is suppressed more appropriately than the case where the variation in the operating angle of the intake valve 2 between the cylinders is suppressed regardless of the above-described threshold. can do. That is, the variation in the air-fuel ratio between the cylinders can be appropriately suppressed.

  FIG. 13 is a flowchart showing the intake valve operating angle variation learning method of the first and second embodiments and their modifications. This routine is executed at predetermined time intervals in the same manner as the routine shown in FIG. As shown in FIG. 13, when this routine is started, it is first determined in step 150 whether or not the execution of step 105 shown in FIG. 11 has been completed, as in the case shown in FIG. When correction of the fuel injection amount for all cylinders has been completed, the routine proceeds to step 151. When it has not been completed, it is determined that variation in the operating angle of the intake valve 2 among the cylinders cannot be suppressed, and this routine is terminated. To do. In step 151, as in the case shown in FIG. 12, it is determined whether or not the operating angle of the intake valve 2 is equal to or smaller than a predetermined threshold value. When YES, the routine proceeds to step 152, and when NO, this routine is terminated.

  In step 152, as in the case shown in FIG. 12, it is determined whether it is time to calculate the exhaust gas air-fuel ratio of a specific cylinder (N-th cylinder) among the plurality of cylinders # 1 to # 4. When the determination is YES, the routine proceeds to step 153, and when the determination is NO, this routine is terminated. In step 153, as in the case shown in FIG. 12, the exhaust gas air-fuel ratio of the Nth cylinder is detected for several cycles, and the average air-fuel ratio thereof is calculated. Next, at step 154, as in the case shown in FIG. 12, the cylinders # 1 to # 4 calculated at step 153 are based on the idea that the fuel injection amounts of the cylinders # 1 to # 4 are equal. The variation ΔQ of the intake air amount between the cylinders is calculated from the air-fuel ratio.

  Next, at step 250, based on the variation ΔQ in the intake air amount between the cylinders calculated at step 154, the fuel injection amount of each cylinder is corrected so that the torques of all the cylinders # 1 to # 4 are equal. Next, at step 251, the ignition timing of each cylinder is corrected so that the torques of all cylinders # 1 to # 4 are equal based on the variation ΔQ of the intake air amount between the cylinders calculated at step 154. For example, during engine high load operation where knocking is likely to occur, the ignition timing of a cylinder having a relatively large intake air amount is retarded.

  According to the first and second embodiments, after suppressing the variation in the fuel injection amount between the cylinders in step 105 of FIG. 11, the intake air amount sucked into the cylinder is based on the opening degree of the throttle valve 56. When it is determined in step 151 of FIG. 13 that the valve opening characteristic of the intake valve 2 is set so as to be restricted based on the valve opening characteristic of the intake valve 2, the cylinder is determined in step 153. Then, in step 250 and step 251, the fuel injection amount and the ignition timing are corrected, and the variation in torque between the cylinders is suppressed.

  Moreover, according to the modification of 1st and 2nd embodiment, after suppressing the dispersion | variation in the fuel injection quantity between cylinders in step 105 of FIG. 11, the intake air amount suck | inhaled in a cylinder is the intake pipe 51, If the valve opening characteristic of the intake valve 2 is set so as to be limited based on the valve opening characteristic of the intake valve 2 without being restricted based on the cross-sectional area of the most narrowed portion in FIG. When the determination is made at step 151, the exhaust gas air-fuel ratio of the cylinder is calculated at step 153, and then the fuel injection amount and ignition timing are corrected at step 250 and step 251, thereby suppressing the variation in torque between the cylinders. Is done.

  Further, according to the first to third embodiments and the modifications thereof, the variation among the cylinders is suppressed based on the operating angle of the intake valve. Specifically, when it is determined in step 151 of FIG. 13 that the operating angle of the intake valve 2 is equal to or smaller than a predetermined threshold value, in step 250, variation in the air-fuel ratio between the cylinders is suppressed. Therefore, when the operating angle of the intake valve can be changed, the variation in the air-fuel ratio between the cylinders can be suppressed more appropriately than the case where the variation in the air-fuel ratio between the cylinders is suppressed regardless of the above-described threshold. . That is, the variation in the air-fuel ratio between the cylinders can be appropriately suppressed.

  Hereinafter, fourth to sixth embodiments of the control device for an internal combustion engine of the present invention will be described. The configurations of the fourth to sixth embodiments are substantially the same as the configurations of the first to third embodiments described above. The configuration of the modification examples of the fourth to sixth embodiments is almost the same as the configuration of the modification examples of the first to third embodiments described above.

  FIG. 14 is a flowchart showing fuel injection amount variation learning methods of the fourth to sixth embodiments and their modifications. This routine is executed at predetermined time intervals similarly to the case shown in FIG. As shown in FIG. 14, when this routine is started, it is first determined in step 300 whether or not the valve overlap amounts of the intake valve 2 and the exhaust valve 3 are minimized. When YES, since the amount of blown back gas from the cylinder 50 to the intake pipe 51 is small, the intake air quantity sucked into the cylinder 50 is throttled most in the opening of the throttle valve 56 or in the intake pipes 51 and 52. Even if there is a variation in the valve overlap amount between the intake valve 2 and the exhaust valve 3 between the cylinders, it is determined that the intake air amount does not vary between the cylinders. Go to step 101. On the other hand, when NO, that is, when the valve overlap amount of the intake valve 2 and the exhaust valve 3 is relatively large, the intake air amount sucked into the cylinder 50 becomes the valve overlap amount of the intake valve 2 and the exhaust valve 3. If there is a variation in the valve overlap amount between the cylinders, it is determined that the intake air amount varies between the cylinders and the variation learning of the fuel injection amount cannot be learned. finish.

  In step 101, as in the case shown in FIG. 11, it is determined whether it is time to calculate the exhaust gas air-fuel ratio of a specific cylinder (N-th cylinder) among the plurality of cylinders # 1 to # 4. When YES, the routine proceeds to step 102, and when NO, this routine is terminated. In step 102, as in the case shown in FIG. 11, the exhaust gas air-fuel ratio of the Nth cylinder is detected for several cycles, and the average air-fuel ratio thereof is calculated. Next, at step 103, similarly to the case shown in FIG. 11, the variation ΔQn of the fuel injection amount between the cylinders is calculated from the air-fuel ratio of each cylinder # 1 to # 4 calculated at step 102.

  Next, at step 104, similarly to the case shown in FIG. 11, the variation rate Qrate-n of the fuel injection amount is calculated based on the variation ΔQn of the fuel injection amount between the cylinders calculated at step 103. Next, at step 105, as in the case shown in FIG. 11, the fuel injection amounts of the cylinders # 1 to # 4 are corrected so that there is no variation in the fuel injection amounts between the cylinders.

  According to the fourth to sixth embodiments, when it is determined in step 300 that the valve overlap amount of the intake valve 2 and the exhaust valve 3 is set to the minimum valve overlap amount, An exhaust gas air-fuel ratio of the cylinder is calculated. That is, when the valve overlap amount of the intake valve 2 and the exhaust valve 3 is set so that the intake air amount sucked into the cylinder is not limited based on the valve overlap amount of the intake valve 2 and the exhaust valve 3. When determined in step 300, in step 102, the exhaust gas air-fuel ratio of the cylinder is calculated. More specifically, the intake air amount sucked into the cylinder is not limited based on the valve overlap amount of the intake valve 2 and the exhaust valve 3, but is limited based on the opening degree of the throttle valve 56. When it is determined in step 300 that the valve overlap amounts of the valve 2 and the exhaust valve 3 are set, in step 102, the exhaust gas air-fuel ratio of the cylinder is calculated. That is, when the exhaust gas air-fuel ratio of a cylinder is calculated in step 102, the intake air amount sucked into the cylinder is based on the valve overlap amounts of the intake valve 2 and the exhaust valve 3 in a step (not shown). However, the valve overlap amounts of the intake valve 2 and the exhaust valve 3 are set to the minimum valve overlap amount so as to be limited based on the opening degree of the throttle valve 56. That is, the opening degree of the throttle valve 56 when calculating the exhaust gas air-fuel ratio of the first cylinder # 1 and the opening degree of the throttle valve 56 when calculating the exhaust gas air-fuel ratios of the other cylinders # 2 to # 4. By substantially equalizing, when calculating the exhaust gas air-fuel ratio of the first cylinder # 1, the intake air amount sucked into the cylinder # 1 and the exhaust gas air-fuel ratios of the other cylinders # 2 to # 4 are set. When calculating, the intake air amount sucked into the cylinders # 2 to # 4 can be made equal.

  Furthermore, according to the fourth to sixth embodiments, when calculating the exhaust gas air-fuel ratio of a certain cylinder # 1, the amount of intake air taken into that cylinder # 1 and the exhaust of other cylinders # 2 to # 4 are calculated. When it is determined in step 300 that the amount of intake air sucked into the cylinders # 2 to # 4 becomes equal when calculating the gas air-fuel ratio, in step 105, between the cylinders based on the exhaust gas air-fuel ratio. Variations in the fuel injection amount are suppressed. That is, the fuel injection amount is corrected so that the exhaust gas air-fuel ratios of all the cylinders become equal after the intake air amounts of all the cylinders are made equal. Therefore, variation in air-fuel ratio between cylinders can be suppressed and variation in torque between cylinders can be suppressed.

  In other words, according to the fourth to sixth embodiments, the intake air amount sucked into the cylinder is not limited based on the valve opening characteristics of the intake valve 2 and the exhaust valve 3, and the opening degree of the throttle valve 56 is not limited. When it is determined in step 300 that the valve opening characteristics of the intake valve 2 and the exhaust valve 3 are set so as to be limited based on the above, in step 102, the exhaust gas air-fuel ratio of the cylinder is calculated. That is, when calculating the exhaust gas air-fuel ratio of a cylinder in step 102, the amount of intake air taken into the cylinder in the step (not shown) is based on the valve opening characteristics of the intake valve 2 and the exhaust valve 3. The valve opening characteristics of the intake valve 2 and the exhaust valve 3 are set so as to be limited based on the opening degree of the throttle valve 56.

  Further, according to the modifications of the fourth to sixth embodiments in which the throttle valve 56 is not provided, the valve overlap amounts of the intake valve 2 and the exhaust valve 3 are the same as in the fourth to sixth embodiments. When it is determined in step 300 that the minimum valve overlap amount is set, in step 102, the exhaust gas air-fuel ratio of the cylinder is calculated. That is, when the valve overlap amount of the intake valve 2 and the exhaust valve 3 is set so that the intake air amount sucked into the cylinder is not limited based on the valve overlap amount of the intake valve 2 and the exhaust valve 3. When determined in step 300, in step 102, the exhaust gas air-fuel ratio of the cylinder is calculated. More specifically, the intake air amount sucked into the cylinder is not limited based on the valve overlap amount of the intake valve 2 and the exhaust valve 3, and the most restrictive portion of the intake pipes 51 and 52 is disconnected. When it is determined in step 300 that the valve overlap amounts of the intake valve 2 and the exhaust valve 3 are set so as to be limited based on the area, in step 102, the exhaust gas air-fuel ratio of the cylinder is calculated. The That is, when calculating the exhaust gas air-fuel ratio of a cylinder in step 102, the intake air amount sucked into the cylinder is based on the valve overlap amounts of the intake valve 2 and the exhaust valve 3 in a step (not shown). The valve overlap amount of the intake valve 2 and the exhaust valve 3 is set to the minimum valve overlap amount so as to be limited based on the cross-sectional area of the most narrowed portions in the intake pipes 51 and 52. Is done.

  In other words, according to the modifications of the fourth to sixth embodiments, the intake air amount sucked into the cylinder is not limited based on the valve opening characteristics of the intake valve 2 and the exhaust valve 3, and the intake pipe 51 , 52, when it is determined in step 300 that the valve opening characteristics of the intake valve 2 and the exhaust valve 3 are set so as to be limited based on the cross-sectional area of the most narrowed portion, in step 102 Then, the exhaust gas air-fuel ratio of the cylinder is calculated. That is, when calculating the exhaust gas air-fuel ratio of a cylinder in step 102, the amount of intake air taken into the cylinder in the step (not shown) is based on the valve opening characteristics of the intake valve 2 and the exhaust valve 3. The valve opening characteristics of the intake valve 2 and the exhaust valve 3 are set so as to be limited based on the cross-sectional area of the most narrowed portions in the intake pipes 51 and 52.

  In addition, according to the fourth to sixth embodiments and their modifications, variations among cylinders are suppressed based on the valve overlap amounts of the intake valve and the exhaust valve. Specifically, variation in the fuel injection amount between the cylinders is suppressed based on the valve overlap amount of the intake valve and the exhaust valve. More specifically, when it is determined in step 300 of FIG. 14 that the valve overlap amount of the intake valve 2 and the exhaust valve 3 is minimum, in step 105, the variation in the fuel injection amount between the cylinders is suppressed. For this reason, when the valve overlap amount of the intake valve and the exhaust valve can be changed, the variation in the air-fuel ratio between the cylinders more appropriately than when the variation between the cylinders is not suppressed based on the valve overlap amount of the intake valve and the exhaust valve. Can be suppressed. That is, the variation in the air-fuel ratio between the cylinders can be appropriately suppressed.

  FIG. 15 is a flowchart showing a valve overlap amount variation learning method of the sixth embodiment and its modification. This routine is executed at predetermined time intervals in the same manner as the routine shown in FIG. As shown in FIG. 15, when this routine is started, it is first determined in step 150 whether or not the execution of step 105 shown in FIG. 14 has been completed, as in the case shown in FIG. When correction of the fuel injection amount of all cylinders is completed, the process proceeds to step 450, and when it is not yet completed, it is determined that variation in the valve overlap amount of the intake valve 2 and the exhaust valve 3 between the cylinders cannot be suppressed. This routine is then terminated. In step 450, it is determined whether or not the valve overlap amounts of the intake valve 2 and the exhaust valve 3 are equal to or greater than a predetermined threshold value. That is, the intake valve 2 is not limited based on the opening degree of the throttle valve 56 but limited based on the valve overlap amount of the intake valve 2 and the exhaust valve 3. It is then determined whether or not the valve overlap amount of the exhaust valve 3 is set to a relatively large value. When YES, the routine proceeds to step 152, and when NO, this routine is terminated.

  In step 152, as in the case shown in FIG. 12, it is determined whether it is time to calculate the exhaust gas air-fuel ratio of a specific cylinder (N-th cylinder) among the plurality of cylinders # 1 to # 4. When the determination is YES, the routine proceeds to step 153, and when the determination is NO, this routine is terminated. In step 153, as in the case shown in FIG. 12, the exhaust gas air-fuel ratio of the Nth cylinder is detected for several cycles, and the average air-fuel ratio thereof is calculated. Next, at step 154, as in the case shown in FIG. 12, the cylinders # 1 to # 4 calculated at step 153 are based on the idea that the fuel injection amounts of the cylinders # 1 to # 4 are equal. The variation ΔQ of the intake air amount between the cylinders is calculated from the air-fuel ratio.

  Next, at step 451, based on the variation ΔQ of the intake air amount between the cylinders calculated at step 154, the variation ΔVO of the valve overlap amount of the intake valve 2 and the exhaust valve 3 of the specific cylinder (Nth cylinder) is calculated. . The calculation of the variation ΔVO of the valve overlap amount of the intake valve 2 and the exhaust valve 3 is performed for all the cylinders # 1 to # 4. Next, at step 452, each cylinder is controlled by the intake valve drive device 58 so that the variation in the valve overlap amount between the intake valve 2 and the exhaust valve 3 between the cylinders is eliminated, that is, the variation in the intake air amount between the cylinders is eliminated. The opening timings of the intake valves 2 of # 1 to # 4 are corrected, and the closing timings of the exhaust valves 3 of the cylinders # 1 to # 4 are corrected by the exhaust valve driving device 58 ′.

  According to the sixth embodiment, after suppressing the variation in the fuel injection amount between the cylinders in step 105 of FIG. 14, the intake air amount sucked into the cylinders is limited based on the opening degree of the throttle valve 56. When it is determined in step 450 of FIG. 15 that the valve opening characteristics of the intake valve 2 and the exhaust valve 3 are set so as to be limited based on the valve opening characteristics of the intake valve 2 and the exhaust valve 3, In 153, the exhaust gas air-fuel ratio of the cylinder is calculated. Then, in step 452, variations in the valve opening characteristics of the intake valve 2 and the exhaust valve 3 between the cylinders are suppressed based on the exhaust gas air-fuel ratio. That is, while suppressing the variation in the fuel injection amount between the cylinders, the cylinders # 1 to # 1 are set so that the exhaust gas air-fuel ratio of a certain cylinder # 1 is equal to the exhaust gas air-fuel ratios of the other cylinders # 2 to # 4. The valve opening characteristics of the intake valve 2 and the exhaust valve 3 of # 4 are changed. Therefore, even when there is a variation in the fuel injection amount between the cylinders, the variation in the valve opening characteristics of the intake valve 2 and the exhaust valve 3 between the cylinders is suppressed without causing a variation in the torque between the cylinders. can do.

Further, according to the modification of the sixth embodiment, after suppressing the variation in the fuel injection amount between the cylinders in step 105 of FIG. 14, the intake air amount sucked into the cylinders is increased in the intake pipes 51 and 52. The valve opening characteristics of the intake valve 2 and the exhaust valve 3 are set so as to be limited based on the valve opening characteristics of the intake valve 2 and the exhaust valve 3 without being limited based on the cross-sectional area of the most narrowed portion. If it is determined in step 450 in FIG. 15, the exhaust gas air-fuel ratio of the cylinder is calculated in step 153, and then in step 452, the intake valve 2 and the exhaust gas between the cylinders based on the exhaust gas air-fuel ratio are calculated. Variations in the valve opening characteristics of the valve 3 are suppressed.
That is, while suppressing the variation in the fuel injection amount between the cylinders, the cylinders # 1 to # 1 are set so that the exhaust gas air-fuel ratio of a certain cylinder # 1 is equal to the exhaust gas air-fuel ratios of the other cylinders # 2 to # 4. The valve opening characteristics of the intake valve 2 and the exhaust valve 3 of # 4 are changed. Therefore, even when there is a variation in the fuel injection amount between the cylinders, the variation in the valve opening characteristics of the intake valve 2 and the exhaust valve 3 between the cylinders is suppressed without causing a variation in the torque between the cylinders. can do.

  Specifically, according to the sixth embodiment and its modification, after suppressing the variation in the fuel injection amount between the cylinders in step 105 in FIG. 14, the intake valve 2 and the exhaust valve 3 in step 450 in FIG. When it is determined that the valve overlap amount is set to a predetermined valve overlap amount larger than the minimum valve overlap amount, the exhaust gas air-fuel ratio is calculated in step 153, and then in step 452, the exhaust gas air-fuel ratio is calculated. Based on this, variation in the valve overlap amount of the intake valve 2 and the exhaust valve 3 between the cylinders is suppressed. That is, while suppressing the variation in the fuel injection amount between the cylinders, the cylinders # 1 to # 1 are set so that the exhaust gas air-fuel ratio of a certain cylinder # 1 is equal to the exhaust gas air-fuel ratios of the other cylinders # 2 to # 4. The valve overlap amount of the intake valve 2 and the exhaust valve 3 of # 4 is changed. Therefore, even when there is a variation in the fuel injection amount between the cylinders, the variation in the valve overlap amount of the intake valve 2 and the exhaust valve 3 between the cylinders is prevented without causing a variation in the torque between the cylinders. Can be suppressed.

  In other words, according to the sixth embodiment and its modification, after suppressing the variation in the fuel injection amount between the cylinders in step 105 of FIG. 14, the valves of the intake valve 2 and the exhaust valve 3 in step 450 of FIG. When it is determined that the overlap amount is set to a predetermined valve overlap amount larger than the minimum valve overlap amount, the exhaust gas air-fuel ratio is calculated in step 153, and then in step 452, the exhaust gas air-fuel ratio is set to the exhaust gas air-fuel ratio. Based on this, variation in intake air amount between cylinders is suppressed. That is, while suppressing the variation in the fuel injection amount between the cylinders, the cylinders # 1 to # 1 are set so that the exhaust gas air-fuel ratio of a certain cylinder # 1 is equal to the exhaust gas air-fuel ratios of the other cylinders # 2 to # 4. The valve overlap amount of the intake valve 2 and the exhaust valve 3 of # 4 is changed. Therefore, even if there is a variation in the fuel injection amount between the cylinders, it is possible to suppress the variation in the intake air amount between the cylinders without causing a variation in the torque between the cylinders.

  Further, according to the sixth embodiment and its modification, variation between cylinders is suppressed based on the valve overlap amounts of the intake valve and the exhaust valve. Specifically, when it is determined in step 450 of FIG. 15 that the valve overlap amount of the intake valve 2 and the exhaust valve 3 is greater than or equal to a predetermined threshold value, the intake valve 2 and the exhaust valve between the cylinders are determined in step 452. The variation in the valve overlap amount of 3 is suppressed. Therefore, when the valve overlap amount of the intake valve and the exhaust valve can be changed, the variation in the valve overlap amount of the intake valve 2 and the exhaust valve 3 between the cylinders is suppressed regardless of the threshold value described above. The variation in the air-fuel ratio between the cylinders can be appropriately suppressed. That is, the variation in the air-fuel ratio between the cylinders can be appropriately suppressed.

  FIG. 16 is a flowchart showing valve overlap amount variation learning methods of the fourth and fifth embodiments and their modifications. This routine is executed at predetermined time intervals in the same manner as the routine shown in FIG. As shown in FIG. 16, when this routine is started, first, in step 150, it is determined whether or not the execution of step 105 shown in FIG. 14 is completed as in the case shown in FIG. When correction of the fuel injection amount of all cylinders is completed, the process proceeds to step 450, and when it is not yet completed, it is determined that variation in the valve overlap amount of the intake valve 2 and the exhaust valve 3 between the cylinders cannot be suppressed. This routine is then terminated. In step 450, as in the case shown in FIG. 15, it is determined whether or not the valve overlap amounts of the intake valve 2 and the exhaust valve 3 are equal to or greater than a predetermined threshold value. When YES, the routine proceeds to step 152, and when NO, this routine is terminated.

  In step 152, as in the case shown in FIG. 15, it is determined whether it is time to calculate the exhaust gas air-fuel ratio of the specific cylinder (N-th cylinder) among the plurality of cylinders # 1 to # 4. When the determination is YES, the routine proceeds to step 153, and when the determination is NO, this routine is terminated. In step 153, as in the case shown in FIG. 15, the exhaust gas air-fuel ratio of the Nth cylinder is detected for several cycles, and the average air-fuel ratio thereof is calculated. Next, at step 154, similarly to the case shown in FIG. 15, the cylinders # 1 to # 4 calculated at step 153 are based on the idea that the fuel injection amounts of the cylinders # 1 to # 4 are equal. The variation ΔQ of the intake air amount between the cylinders is calculated from the air-fuel ratio.

  Next, at step 250, similarly to the case shown in FIG. 13, based on the variation ΔQ of the intake air amount between the cylinders calculated at step 154, the torques of all the cylinders # 1 to # 4 are made equal. The fuel injection amount is corrected. Next, at step 251, similarly to the case shown in FIG. 13, based on the variation ΔQ of the intake air amount between the cylinders calculated at step 154, the torques of all cylinders # 1 to # 4 are made equal to each other. The ignition timing is corrected. For example, during engine high load operation where knocking is likely to occur, the ignition timing of a cylinder having a relatively large intake air amount is retarded.

  According to the fourth and fifth embodiments, after suppressing variation in the fuel injection amount between cylinders in step 105 of FIG. 14, the intake air amount sucked into the cylinder is based on the opening degree of the throttle valve 56. 16 is determined in step 450 of FIG. 16 that the valve opening characteristics of the intake valve 2 and the exhaust valve 3 are set so as to be limited based on the valve opening characteristics of the intake valve 2 and the exhaust valve 3. Sometimes, at step 153, the exhaust gas air-fuel ratio of the cylinder is calculated, and then at step 250 and step 251, the fuel injection amount and the ignition timing are corrected to suppress the variation in torque between the cylinders.

  Further, according to the modification of the fourth and fifth embodiments, after suppressing the variation in the fuel injection amount between the cylinders in step 105 of FIG. 14, the intake air amount sucked into the cylinders becomes the intake pipe 51, The valve opening characteristics of the intake valve 2 and the exhaust valve 3 are not limited based on the cross-sectional area of the most narrowed portion in the valve 52 but are limited based on the valve opening characteristics of the intake valve 2 and the exhaust valve 3. 16 is determined in step 450 of FIG. 16, the exhaust gas air-fuel ratio of the cylinder is calculated in step 153, and then the fuel injection amount and the ignition timing are corrected in step 250 and step 251. Variation in torque between cylinders is suppressed.

  In addition, according to the fourth and fifth embodiments and their modifications, variations among cylinders are suppressed based on the valve overlap amounts of the intake valve and the exhaust valve. Specifically, when it is determined in step 450 of FIG. 16 that the valve overlap amount of the intake valve 2 and the exhaust valve 3 is equal to or greater than a predetermined threshold value, the variation in air-fuel ratio between cylinders is suppressed in step 250. Is done. Therefore, when the valve overlap amount of the intake valve and the exhaust valve can be changed, the variation of the air-fuel ratio between the cylinders is more appropriately improved than the case where the variation of the air-fuel ratio between the cylinders is suppressed regardless of the threshold value described above. Can be suppressed. That is, the variation in the air-fuel ratio between the cylinders can be appropriately suppressed.

  Hereinafter, a seventh embodiment of the control device for an internal combustion engine of the present invention will be described. The configuration of this embodiment is a combination of any of the configurations of the first to sixth embodiments and their modifications described above and the configuration described later. FIG. 17 is a schematic configuration diagram of a control device for an internal combustion engine according to the seventh embodiment. 17, the same reference numerals as those shown in FIGS. 1 to 10 indicate the same parts or portions as the parts or parts shown in FIGS. Reference numeral 22 'denotes an intake air amount calculation unit constituting a part of the ECU 22, 22 "denotes a delay system calculation unit using a neural network constituting another part of the ECU 22, and 60 denotes a neural network. The configuration is almost the same as a known neural network described in Japanese Utility Model Publication No. 9-88685.

  In the present embodiment, a neural network is used to compensate for the delays of the valve lift amount changing devices 9, 9 ′, the opening / closing timing shift devices 11, 11 ′, the intake valve driving device 58, and the exhaust valve driving device 58 ′ during engine transient operation. 60 is used to suppress variations among cylinders. Specifically, when calculating the intake air amount during engine transient operation, the output value of the air flow meter 19, the opening degree of the throttle valve 56, the rate of change of the throttle valve opening degree, the opening timing of the intake valve 2, the intake valve 2 The intake air amount is estimated based on the valve closing timing, the engine speed, the water temperature, the oil temperature, the hydraulic pressure, and the output value of the intake air temperature sensor 21, and calculated based on the intake air amount and the output value of the air-fuel ratio sensor 57. The delay due to the neural network is learned from the difference from the air amount. As a result, the actual air-fuel ratio can be accurately matched with the target air-fuel ratio under any conditions.

  That is, a neural network is applied to the intake air amount delay calculation unit, and the intake air amount is calculated based on the above-described data. An error is detected from the fuel injection amount calculated based on the intake air amount and the actual exhaust gas air-fuel ratio in the cycle. By repeating this in every pattern and correcting the sensitivity coefficient of each parameter, the actual air-fuel ratio can be accurately matched with the target air-fuel ratio under any engine operating conditions.

  Hereinafter, an eighth embodiment of the control apparatus for an internal combustion engine of the present invention will be described. The configuration of the eighth embodiment is substantially the same as the configuration of any of the first and second embodiments described above and their modifications. Alternatively, although not shown, the eighth embodiment can be configured such that a plurality of intake valve cams having different cam profiles can be provided and used by switching them to change the valve opening characteristics of the intake valve. It is.

  FIG. 18 is a flowchart showing the inter-cylinder variation suppression control method of the eighth embodiment. This routine is executed at predetermined time intervals. As shown in FIG. 18, when this routine is started, first, at step 500, it is determined whether or not a map to be described later has already been created. If YES, the process proceeds to step 505. If NO, the process proceeds to step 501. In step 501, for example, a method described in Japanese Patent Application Laid-Open No. 59-101562 or Japanese Patent Application Laid-Open No. 5-180040 is used, based on the output value of the air-fuel ratio sensor 57, in a steady state such as during engine idle operation. The air-fuel ratio of each cylinder # 1 to # 4 is calculated.

  Next, at step 502, it is determined whether there is a variation in the air-fuel ratio between the cylinders. When the variation in air-fuel ratio between the cylinders is greater than or equal to a predetermined value, the routine proceeds to step 503, and when the variation in air-fuel ratio between the cylinders is less than the predetermined value, this routine is terminated. In step 503, the fuel injection amount correction coefficient for each cylinder # 1 to # 4 is calculated based on the calculated air-fuel ratio for each cylinder # 1 to # 4. For example, when the actual air-fuel ratio of a cylinder varies to the rich side with respect to the target air-fuel ratio, a relatively small value of the fuel injection amount correction coefficient is calculated in order to reduce the fuel injection amount of that cylinder. On the other hand, when the actual air-fuel ratio of a certain cylinder varies on the lean side with respect to the target air-fuel ratio, a relatively large value of the fuel injection amount correction coefficient is calculated in order to increase the fuel injection amount of that cylinder.

  Next, at step 504, based on the fuel injection amount correction coefficient calculated at step 503 and the operating angle of the intake valve 2 at that time, the fuel injection amount indicating the relationship between the fuel injection amount correction coefficient and the operating angle of the intake valve 2. A correction coefficient map is created. FIG. 19 is a diagram showing the relationship between the fuel injection amount correction coefficient and the operating angle of the intake valve. As shown in FIG. 19, when the point P1 is calculated in step 503, in step 504, a curve L1 indicating the relationship between the fuel injection amount correction coefficient and the operating angle of the intake valve is calculated from the point P1, and the curve L1 Based on this, a fuel injection amount correction coefficient map is created. In the modification of the eighth embodiment, in step 504, instead of creating a map, a relational expression obtained by simplifying the curve L1 can be calculated. In another modification of the eighth embodiment, not only the point P1 but also the point P1 ′ is calculated in the same step as the step 503, and a curve similar to the curve L1 is calculated based on the points P1 and P1 ′. It is also possible to create a fuel injection amount correction coefficient map based on the curve.

  In step 505, the fuel injection amount is corrected for each cylinder # 1 to # 4. That is, when the map shown in FIG. 19 is not created and it is determined NO in step 500, a fuel injection amount correction coefficient for correcting the fuel injection amount is calculated in step 503, and in step 505, The fuel injection amount is corrected based on the fuel injection amount correction coefficient. On the other hand, if the map shown in FIG. 19 has already been created and it is determined YES in step 500, step 503 is performed even if the operating angle of intake valve 2 has been changed from the time the map was created. In step 505, the fuel injection amount is corrected based on the already created map.

  If there is a risk of hunting when step 505 described above is executed, a fuel injection amount correction coefficient is smoothed in a step (not shown), and then in a step instead of step 505, based on the smoothed fuel injection amount correction coefficient. It is also possible to correct the fuel injection amount. (In this case, the fuel injection amount is corrected by using the value obtained by correcting the fuel injection amount correction coefficient, and the fuel injection amount correction coefficient is converged by repeatedly calculating the fuel injection amount correction coefficient again. Correct the amount.)

According to the eighth embodiment or the modification thereof, the variation among the cylinders is suppressed based on the operating angle of the intake valve 2. Specifically, as shown in FIG. 19, the fuel injection amount correction coefficients of the cylinders # 1 to # 4 are calculated based on the operating angle of the intake valve 2, and in step 505, the fuel injection amount correction coefficients are calculated based on the fuel injection amount correction coefficients. By correcting the fuel injection amounts of the cylinders # 1 to # 4, variations in the fuel injection amounts among the cylinders are suppressed. Therefore, when the working angle of the intake valve can be changed, the variation in the air-fuel ratio between the cylinders can be suppressed more appropriately than in the case where the variation between the cylinders is not suppressed based on the working angle of the intake valve.
Further, according to the eighth embodiment or the modification thereof, since the variation between the cylinders is suppressed based on the operating angle of the intake valve, for example, the gas contact of the sensor 57 is poor and the sensor 57 is calculated from the output value of the sensor 57. Even when the target air-fuel ratio does not reach an appropriate target air-fuel ratio, it is possible to appropriately suppress the variation among cylinders.

Further, according to the eighth embodiment or its modification, the variation in the air-fuel ratio between the cylinders is suppressed by correcting the fuel injection amount based on the operating angle of the intake valve 2 in step 505.
For example, when the air-fuel ratio of a cylinder varies to the rich side, the variation in the air-fuel ratio among the cylinders is suppressed by correcting the amount of fuel injection for that cylinder to be reduced. Further, in view of the fact that the variation in the air-fuel ratio between the cylinders increases when the actual operating angle deviates from the target operating angle as the operating angle of the intake valve decreases, as shown in FIG. As the value becomes smaller, the difference between the fuel injection amount correction coefficient and 1.0 is increased, and as a result, the variation in the fuel injection amount is increased, thereby suppressing variations in the air-fuel ratio among the cylinders. Therefore, the variation in the air-fuel ratio between the cylinders can be suppressed more appropriately than when the fuel injection amount is not corrected based on the operating angle of the intake valve.

  Specifically, when a variation in air-fuel ratio between cylinders is detected in step 501 and step 502, a fuel injection amount correction coefficient for reducing the variation is calculated in step 503, and in step 504, the fuel injection amount correction is corrected. Based on the coefficient and the operating angle of the intake valve at that time, a relationship L1 between the fuel injection amount correction coefficient and the operating angle of the intake valve is calculated, and when the operating angle of the intake valve is changed, A fuel injection amount correction coefficient after changing the intake valve operating angle is calculated based on the operating angle and its relationship L1.

  Hereinafter, a ninth embodiment of the control device for an internal combustion engine of the present invention will be described. The configuration of the ninth embodiment is substantially the same as the configuration of the eighth embodiment described above.

  FIG. 20 is a flowchart showing a target air-fuel ratio correction control method according to the ninth embodiment. This routine is executed at predetermined time intervals. As shown in FIG. 20, when this routine is started, first, at step 600, it is determined whether or not a map to be described later has already been created. If yes, then continue with step 604, otherwise continue with step 501. In step 501, the air-fuel ratios of the cylinders # 1 to # 4 in a steady state such as during engine idle operation are calculated based on the output value of the air-fuel ratio sensor 57, as in the eighth embodiment.

Next, at step 502, as in the eighth embodiment, it is determined whether there is a variation in the air-fuel ratio between the cylinders. When the variation in the air-fuel ratio between the cylinders is greater than or equal to the predetermined value, the routine proceeds to step 601, and when the variation in the air-fuel ratio between the cylinders is less than the predetermined value, this routine is terminated. In step 601, the average air-fuel ratio of all cylinders # 1 to # 4 is calculated. The average air-fuel ratio of all the cylinders # 1 to # 4 is calculated, for example, by adding the air-fuel ratios of the cylinders # 1 to # 4 and dividing it by 4. Next, at step 602, a new air / fuel ratio based on the output value of the sensor 57 (hereinafter referred to as “sensor target air / fuel ratio”), a stoichiometric air / fuel ratio, and the average air / fuel ratio calculated at step 601, for example, are added. A target air-fuel ratio (hereinafter referred to as “corrected target air-fuel ratio”) is calculated. That is, the sensor target air-fuel ratio is corrected, and the corrected target air-fuel ratio is calculated.
Correction target air-fuel ratio = sensor target air-fuel ratio × stoichiometric air-fuel ratio / average air-fuel ratio (1)

If there is a risk of hunting depending on the above equation (1), or if the accuracy of the average air-fuel ratio calculated in step 601 is low, the corrected target air-fuel ratio is set as shown in equation (2). It is also possible to calculate. (In this case, the target air-fuel ratio is corrected using the corrected target air-fuel ratio, and the corrected target air-fuel ratio is converged by repeating the determination of the corrected target air-fuel ratio in step 603. Create a fuel ratio map.)
Corrected target air-fuel ratio = (stoichiometric air-fuel ratio-average air-fuel ratio) / k + sensor target air-fuel ratio (2)
k is a positive integer

  Next, at step 603, based on the corrected target air-fuel ratio calculated at step 602 and the operating angle of the intake valve 2 at that time, a target air-fuel ratio map showing the relationship between the corrected target air-fuel ratio and the operating angle of the intake valve 2 is obtained. Created. FIG. 21 is a diagram showing the relationship between the corrected target air-fuel ratio and the operating angle of the intake valve. As shown in FIG. 21, when the point P2 is calculated in step 602, a curve L2 indicating the relationship between the corrected target air-fuel ratio and the operating angle of the intake valve is calculated from the point P2 in step 603, and the curve L2 Based on this, a target air-fuel ratio map is created. In the modification of the ninth embodiment, in step 603, instead of creating a map, a relational expression obtained by simplifying the curve L2 can be calculated. In another modification of the ninth embodiment, not only point P2 but also point P2 ′ is calculated in the same step as step 602, and a curve similar to curve L2 is calculated based on point P2 and point P2 ′. It is also possible to create a fuel injection amount correction coefficient map based on the curve.

  In step 604, air-fuel ratio feedback control is executed. That is, the fuel injection amounts of all the cylinders # 1 to # 4 are uniformly corrected based on the corrected target air-fuel ratio on the map created in step 603. That is, when the map shown in FIG. 21 is not created and it is determined NO in step 600, the corrected target air-fuel ratio for executing the air-fuel ratio feedback control is calculated in step 602, and in step 604, Air-fuel ratio feedback control is executed based on the corrected target air-fuel ratio. On the other hand, if the map shown in FIG. 21 has already been created and YES is determined in step 600, step 602 is performed even if the operating angle of intake valve 2 has been changed since the map was created. In step 604, air-fuel ratio feedback control is executed based on the corrected target air-fuel ratio on the map that has already been created.

In the ninth embodiment, the fuel injection amount is calculated based on the following equations (3) and (4).
Fuel injection amount = basic injection amount + feedback correction amount (3)
Feedback correction amount = a × f + b × g (4)
a, b are gains, f, g are functions of the corrected target air-fuel ratio and the sensor target air-fuel ratio.

  That is, for example, when the corrected target air-fuel ratio shifts to the lean side, the feedback correction amount decreases and the fuel injection amount is corrected to decrease. On the other hand, for example, when the corrected target air-fuel ratio shifts to the rich side, the feedback correction amount increases and the fuel injection amount is corrected to increase.

  As described above, in the ninth embodiment, the target air-fuel ratio is corrected based on the operating angle of the intake valve 2, that is, the corrected target air-fuel ratio is changed based on the operating angle of the intake valve 2 ( In the modified example of the ninth embodiment, any or all of the coefficients related to the air-fuel ratio feedback control can be corrected based on the operating angle of the intake valve 2 instead. These coefficients include gains a and b, sensor target air-fuel ratio, and the like in addition to the above-described corrected target air-fuel ratio.

In another modification of the ninth embodiment, the fuel injection amount is calculated based on the following formulas (5) and (6) instead.
Fuel injection amount = Basic injection amount + Increase correction amount + Feedback correction amount (5)
Feedback correction amount = A × P + ΣA × I + (dA / dt) × D (6)
A is the deviation between the corrected target air-fuel ratio and the sensor target air-fuel ratio, and P, I, and D are the gain increasing system correction amounts. The correction amount when the engine cooling water temperature is low and the correction amount for suppressing the rise in the exhaust temperature are included.

  In the modification of the ninth embodiment, any or all of the coefficients related to the air-fuel ratio feedback control can be corrected based on the operating angle of the intake valve 2. These coefficients include gains P, I, D, deviation A between the corrected target air-fuel ratio and the sensor target air-fuel ratio, in addition to the above-described corrected target air-fuel ratio.

  According to the ninth embodiment or its modification, the predetermined coefficient relating to the air-fuel ratio feedback control is corrected based on the operating angle of the intake valve 2. Specifically, as shown in FIG. 21, the corrected target air-fuel ratio is calculated based on the operating angle of the intake valve 2. For example, the sensor target air-fuel ratio is not set appropriately because the gas contact of the sensor 57 is poor, and as a result, when the entire air-fuel ratio is shifted to the rich side, the entire air-fuel ratio is shifted to the lean side. Thus, the corrected target air-fuel ratio is calculated.

  Further, according to the ninth embodiment or its modification, when the actual operating angle of the intake valve 2 deviates from the target operating angle of the intake valve 2, the sensor target sky set based on the output value of the sensor 57. In view of the tendency that the smaller the operating angle of the intake valve 2 tends to deviate from the appropriate target air-fuel ratio, for example, as shown in FIG. The correction amount of the fuel ratio is increased, that is, the deviation between the corrected target air-fuel ratio and the stoichiometric air-fuel ratio is increased. Therefore, the value of the target air-fuel ratio can be set to a more appropriate value than when the target air-fuel ratio is not corrected based on the operating angle of the intake valve 2. That is, even when the sensor 57 is in poor gas contact, that is, when the sensor target air-fuel ratio calculated from the output value of the sensor 57 does not reach an appropriate target air-fuel ratio, appropriate air-fuel ratio feedback control can be executed. it can.

  Specifically, when a variation in air-fuel ratio between cylinders is detected in step 501 and step 502, the target air-fuel ratio is calculated (corrected to an appropriate target air-fuel ratio) in step 602, and in step 603, the target air-fuel ratio is calculated. And a relationship L2 between the target air-fuel ratio and the intake valve operating angle is calculated based on the operating angle of the intake valve 2 at that time, and when the operating angle of the intake valve 2 is changed, An appropriate corrected target air-fuel ratio after changing the intake valve operating angle is calculated based on the operating angle and its relationship L2.

  Hereinafter, a tenth embodiment of the control device for an internal combustion engine of the present invention will be described. The configuration of the tenth embodiment is substantially the same as the configuration of the eighth and ninth embodiments described above. Therefore, substantially the same effect as the eighth and ninth embodiments can be obtained.

  FIG. 22 is a flowchart showing the inter-cylinder variation suppression control method of the tenth embodiment. This routine is executed at predetermined time intervals. As shown in FIG. 22, when this routine is started, first, in step 501, as in the eighth and ninth embodiments, based on the output value of the air-fuel ratio sensor 57, for example, during engine idle operation, as shown in FIG. The air-fuel ratio of each cylinder # 1 to # 4 in the steady state is calculated. Next, at step 502, as in the eighth and ninth embodiments, it is determined whether there is a variation in the air-fuel ratio between the cylinders. When the variation in air-fuel ratio between the cylinders is greater than or equal to a predetermined value, the routine proceeds to step 503, and when the variation in air-fuel ratio between the cylinders is less than the predetermined value, this routine is terminated.

  In step 503, the fuel injection amount correction coefficient for each cylinder # 1 to # 4 is calculated based on the calculated air-fuel ratio of each cylinder # 1 to # 4, as in the eighth embodiment. For example, when the actual air-fuel ratio varies to the rich side with respect to the target air-fuel ratio, a relatively small value of the fuel injection amount correction coefficient is calculated in order to reduce the fuel injection amount. On the other hand, when the actual air-fuel ratio varies on the lean side with respect to the target air-fuel ratio, a relatively large value of the fuel injection amount correction coefficient is calculated in order to increase the fuel injection amount. Next, at step 700, it is determined whether or not the fuel injection amount correction coefficient calculated at step 503 is within a predetermined value range. That is, when the fuel injection amount correction coefficient is too small, the process proceeds to step 701. Further, the process proceeds to step 701 also when the fuel injection amount correction coefficient is too large. On the other hand, when the fuel injection amount correction coefficient is within the predetermined value range, the routine proceeds to step 500.

In step 500, it is determined whether or not a fuel injection amount correction coefficient map has been created. If YES, the process proceeds to step 504, and if NO, the process proceeds to step 505.
In step 504, as in the eighth embodiment, based on the fuel injection amount correction coefficient calculated in step 503 and the operating angle of the intake valve 2 at that time, the fuel injection amount correction coefficient as shown in FIG. And a fuel injection amount correction coefficient map showing the relationship between the intake valve 2 and the operating angle of the intake valve 2. In step 505, as in the eighth embodiment, the fuel injection amount is corrected for each cylinder # 1 to # 4. That is, when the map shown in FIG. 19 is not created and it is determined NO in step 500, the fuel injection amount is corrected based on the fuel injection amount correction coefficient calculated in step 503. On the other hand, when the map shown in FIG. 19 has already been created and it is determined YES in step 500, the fuel injection amount is corrected based on the already created map.

In step 701, the fuel injection amount correction coefficient calculated in step 503 is guarded by a predetermined upper limit value and lower limit value. Next, at step 600, as in the ninth embodiment, it is determined whether a target air-fuel ratio map has already been created. If yes, then continue with step 604, otherwise continue with step 601. In step 601, the average air-fuel ratio of all the cylinders # 1 to # 4 is calculated as in the ninth embodiment. Next, at step 602, as in the ninth embodiment, the corrected target air-fuel ratio is calculated based on the sensor target air-fuel ratio, for example, the stoichiometric air-fuel ratio, and the average air-fuel ratio calculated at step 601.
Next, in step 603, as in the ninth embodiment, based on the corrected target air-fuel ratio calculated in step 602 and the operating angle of the intake valve 2 at that time, the corrected target air-fuel ratio and the operating angle of the intake valve 2 are calculated. A target air-fuel ratio map showing the relationship is created.

  In step 604, as in the ninth embodiment, air-fuel ratio feedback control is executed in step 604. As described above, since the fuel injection amount correction coefficient is guarded in step 701, the correction amount of the fuel injection amount is not so large.

  As described above, in the tenth embodiment, the target air-fuel ratio is corrected based on the operating angle of the intake valve 2, that is, the corrected target air-fuel ratio is changed based on the operating angle of the intake valve 2 ( In the modification of the tenth embodiment, instead of any or all of the coefficients relating to the air-fuel ratio feedback control based on the working angle of the intake valve 2, instead of the modification of the tenth embodiment, as in the modification of the ninth embodiment. It is also possible to correct.

  In another modification of the tenth embodiment, the fuel injection amount is calculated based on the above-described equations (5) and (6), as in the other modifications of the ninth embodiment. Further, in the modified example of the tenth embodiment, as in the modified example of the ninth embodiment, any or all of the coefficients regarding the air-fuel ratio feedback control can be corrected based on the operating angle of the intake valve 2. is there.

  According to the tenth embodiment, the same effects as in the eighth and ninth embodiments can be obtained. Furthermore, according to the tenth embodiment, when the correction amount of the fuel injection amount is large, torque fluctuation may occur, and when the calculated correction amount of the fuel injection amount is small and when it is determined in step 700 When the fuel injection amount is separately corrected for each of the cylinders # 1 to # 4 in step 505, the variation in the air-fuel ratio between the cylinders is suppressed, while when the calculated correction amount of the fuel injection amount is large and the step When the determination is made at 700, the correction amount of the fuel injection amount is guarded at a predetermined value at step 701, the corrected target air-fuel ratio is calculated at step 602 and step 603, and all of the correction target air-fuel ratios are calculated based on the corrected target air-fuel ratio at step 604. The fuel injection amounts of the cylinders # 1 to # 4 are corrected uniformly. That is, air-fuel ratio feedback control is executed. Therefore, the air-fuel ratio can be appropriately controlled while suppressing torque fluctuation.

  Naturally, the eighth to tenth embodiments described above are set not only when the valve lift amount of the intake valve 2 is set as shown by the solid line in FIG. 6, but also as shown by the alternate long and short dash line in FIG. The present invention is also applicable to the case where the intake valve 2 is closed, or to the case where the closing timing of the intake valve 2 is retarded.

It is a schematic block diagram of 1st embodiment of the control apparatus of the internal combustion engine of this invention. FIG. 2 is a detailed view of an intake system and the like of the control device for the internal combustion engine shown in FIG. 1. FIG. 3 is a plan view of an intake system and the like of the control device for the internal combustion engine shown in FIG. 2. FIG. 2 is a detailed view of an intake valve cam and a camshaft shown in FIG. 1. It is detail drawing of the valve lift amount changing apparatus etc. which were shown in FIG. It is the figure which showed a mode that the valve lift amount of an intake valve changed with the valve lift amount changing apparatus being operated. FIG. 2 is a detailed view of an opening / closing timing shift device and the like shown in FIG. It is the figure which showed a mode that the opening-and-closing timing of an intake valve shifted with the opening-and-closing timing shift apparatus being operated. It is detail drawing of the intake system etc. of the control apparatus of the internal combustion engine of 2nd embodiment. It is detail drawing of the intake system etc. of the control apparatus of the internal combustion engine of 3rd embodiment. It is the flowchart which showed the fuel injection amount dispersion | variation learning method of 1st to 3rd embodiment and those modifications. It is the flowchart which showed the intake valve action angle variation learning method of 3rd embodiment and its modification. It is the flowchart which showed the intake valve action angle dispersion | variation learning method of 1st and 2nd embodiment and those modifications. It is the flowchart which showed the fuel injection amount dispersion | variation learning method of 4th-6th embodiment and those modifications. It is the flowchart which showed the valve overlap amount variation learning method of 6th Embodiment and its modification. It is the flowchart which showed the valve overlap amount variation | variation learning method of 4th and 5th embodiment and those modifications. It is a schematic block diagram of the control apparatus of the internal combustion engine of 7th embodiment. It is the flowchart which showed the variation suppression control method between cylinders of 8th embodiment. It is a figure which shows the relationship between a fuel injection amount correction coefficient and the operating angle of an intake valve. It is the flowchart which showed the target air fuel ratio correction control method of 9th execution form. It is a figure which shows the relationship between a target air fuel ratio and the operating angle of an intake valve. It is the flowchart which showed the variation suppression control method between cylinders of 10th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Intake valve 3 Exhaust valve 4,5 Cam 6,7 Camshaft 8 Combustion chamber in cylinder 9 Valve lift amount changing device 11 Opening / closing timing shift device 56 Throttle valve 57 Air-fuel ratio sensor 58 Intake valve drive device 58 'Exhaust Valve drive device

Claims (23)

  In a control apparatus for a multi-cylinder internal combustion engine that suppresses variation among cylinders, an intake valve and an exhaust valve are configured so that an intake air amount sucked into the cylinder is not limited based on a valve opening characteristic of the intake valve or the exhaust valve. A control apparatus for a multi-cylinder internal combustion engine that calculates an exhaust gas air-fuel ratio of a cylinder for which a valve opening characteristic is set and suppresses variation in fuel injection amount between the cylinders based on the exhaust gas air-fuel ratio .   The valve opening characteristics of the intake and exhaust valves are set so that the amount of intake air drawn into the cylinder is not limited based on the valve opening characteristics of the intake valve or exhaust valve, but is limited based on the throttle valve opening. 2. The control device for a multi-cylinder internal combustion engine according to claim 1, wherein an exhaust gas air-fuel ratio of a cylinder is calculated, and variation in fuel injection amount between the cylinders is suppressed based on the exhaust gas air-fuel ratio. .   In a control apparatus for a multi-cylinder internal combustion engine that suppresses variation between cylinders, an exhaust gas air-fuel ratio of a cylinder in which an operating angle of an intake valve is set to a predetermined operating angle is calculated, and based on the exhaust gas air-fuel ratio A control apparatus for a multi-cylinder internal combustion engine, characterized by suppressing variations in fuel injection amount between cylinders.   The exhaust gas air-fuel ratio of the cylinder in which the operating angle of the intake valve is set is calculated so that the amount of intake air sucked into the cylinder is not limited based on the operating angle of the intake valve, and based on the exhaust gas air-fuel ratio 4. The control apparatus for a multi-cylinder internal combustion engine according to claim 3, wherein variation in fuel injection amount between cylinders is suppressed.   The amount of intake air sucked into the cylinder is not limited based on the operating angle of the intake valve, but is exhausted from the exhaust gas in the cylinder in which the operating angle of the intake valve is set so as to be limited based on the throttle valve opening. 5. The control apparatus for a multi-cylinder internal combustion engine according to claim 4, wherein the control device for the multi-cylinder internal combustion engine according to claim 4, wherein the control unit calculates a fuel ratio and suppresses variation in fuel injection amount between cylinders based on the exhaust gas air-fuel ratio.   The exhaust gas air-fuel ratio of a cylinder in which the operating angle of the intake valve is set to the maximum operating angle is calculated, and variation in the fuel injection amount between the cylinders is suppressed based on the exhaust gas air-fuel ratio. 4. The control device for a multi-cylinder internal combustion engine according to 3.   In a control device for a multi-cylinder internal combustion engine that suppresses variation between cylinders, an exhaust gas air-fuel ratio is calculated for a cylinder in which the valve overlap amount of the intake valve and the exhaust valve is set to a predetermined amount, and the exhaust gas empty A control device for a multi-cylinder internal combustion engine, characterized in that variation in fuel injection amount between cylinders is suppressed based on an fuel ratio.   The exhaust gas air-fuel ratio of the cylinder in which the valve overlap amount of the intake valve and the exhaust valve is set so that the intake air amount sucked into the cylinder is not limited based on the valve overlap amount of the intake valve and the exhaust valve. 8. The control apparatus for a multi-cylinder internal combustion engine according to claim 7, wherein the control device calculates and controls the variation in the fuel injection amount between the cylinders based on the exhaust gas air-fuel ratio.   The valve overlap amount of the intake valve and the exhaust valve is not limited based on the valve overlap amount of the intake valve and the exhaust valve, but limited based on the throttle valve opening degree. 9. The multi-cylinder internal combustion engine according to claim 8, wherein an exhaust gas air-fuel ratio of a cylinder in which the engine is set is calculated, and variation in fuel injection amount between the cylinders is suppressed based on the exhaust gas air-fuel ratio. Control device.   Calculate the exhaust gas air-fuel ratio of the cylinder in which the valve overlap amount of the intake valve and the exhaust valve is set to the minimum valve overlap amount, and suppress variation in the fuel injection amount between the cylinders based on the exhaust gas air-fuel ratio The control apparatus for a multi-cylinder internal combustion engine according to claim 7.   After suppressing the variation in the fuel injection amount between the cylinders, the valve opening characteristics of the intake valve and the exhaust valve are controlled so that the intake air amount sucked into the cylinder is limited based on the valve opening characteristics of the intake valve or the exhaust valve. 11. The exhaust gas air-fuel ratio of a set cylinder is calculated, and variation in valve opening characteristics of the intake valve and the exhaust valve between the cylinders is suppressed based on the exhaust gas air-fuel ratio. The control apparatus of the multi-cylinder internal combustion engine as described in any one of Claims.   After suppressing the variation in the fuel injection amount between the cylinders, the intake air amount sucked into the cylinder is not limited based on the throttle valve opening, but is limited based on the valve opening characteristics of the intake valve or the exhaust valve. In this way, the exhaust gas air-fuel ratio of the cylinder with the valve opening characteristics of the intake valve and the exhaust valve is calculated, and variation in the valve opening characteristics of the intake valve and the exhaust valve between the cylinders is suppressed based on the exhaust gas air-fuel ratio. The control apparatus for a multi-cylinder internal combustion engine according to claim 11, wherein   After suppressing the variation in the fuel injection amount between the cylinders, the exhaust gas air-fuel ratio is calculated for a cylinder in which the operating angle of the intake valve is set to be smaller than the predetermined operating angle, and based on the exhaust gas air-fuel ratio The control device for a multi-cylinder internal combustion engine according to any one of claims 3 to 6, wherein variation in intake air amount among the cylinders is suppressed.   After suppressing the variation in the fuel injection amount between the cylinders, the exhaust gas air-fuel ratio is calculated for a cylinder in which the operating angle of the intake valve is set to be smaller than the predetermined operating angle, and based on the exhaust gas air-fuel ratio The control device for a multi-cylinder internal combustion engine according to any one of claims 3 to 6, wherein variation in operating angle of the intake valve between the cylinders is suppressed.   The control apparatus for a multi-cylinder internal combustion engine according to any one of claims 1 to 14, wherein variation between cylinders is suppressed using a neural network.   A control apparatus for a multi-cylinder internal combustion engine that suppresses variations among cylinders based on valve overlap amounts of an intake valve and an exhaust valve in a control apparatus for a multi-cylinder internal combustion engine that suppresses variations between cylinders.   The control device for a multi-cylinder internal combustion engine according to claim 16, wherein variation in fuel injection amount between cylinders is suppressed based on valve overlap amounts of the intake valve and the exhaust valve.   In a control apparatus for a multi-cylinder internal combustion engine in which the number of sensors for detecting air-fuel ratio or oxygen concentration is less than the number of cylinders, a predetermined coefficient related to air-fuel ratio feedback control is corrected based on the operating angle of the intake valve. A control apparatus for a multi-cylinder internal combustion engine.   The correction of the predetermined coefficient relating to the air-fuel ratio feedback control is characterized in that the predetermined coefficient is corrected so that the correction amount of the target air-fuel ratio increases as the operating angle of the intake valve decreases. Item 19. The control apparatus for a multi-cylinder internal combustion engine according to Item 18.   In a control apparatus for a multi-cylinder internal combustion engine in which the number of sensors for detecting air-fuel ratio or oxygen concentration is less than the number of cylinders, the multi-cylinder internal combustion engine corrects the target air-fuel ratio based on the operating angle of the intake valve Engine control device.   21. The control device for a multi-cylinder internal combustion engine according to claim 20, wherein the correction of the target air-fuel ratio is such that the correction amount of the target air-fuel ratio increases as the operating angle of the intake valve decreases.   When a variation in air-fuel ratio between cylinders is detected, the target air-fuel ratio is calculated, and the relationship between the target air-fuel ratio and the intake valve operating angle based on the target air-fuel ratio and the operating angle of the intake valve at that time When the operating angle of the intake valve is changed, the target air-fuel ratio after the change of the intake valve operating angle is calculated based on the changed operating angle of the intake valve and the relationship thereof. The control device for a multi-cylinder internal combustion engine according to any one of 18 to 21.   When the calculated correction amount of the fuel injection amount is small, the variation of the air-fuel ratio between the cylinders is suppressed by separately correcting the fuel injection amount for each cylinder. When the calculated correction amount of the fuel injection amount is large The fuel injection amount correction amount is guarded with a predetermined value, the target air-fuel ratio is corrected, and the fuel injection amounts of all cylinders are uniformly corrected based on the target air-fuel ratio. The control apparatus for a multi-cylinder internal combustion engine according to any one of claims 22 to 22.

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