JP2009228641A - Control system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To more suitably control a combustion state in each cylinder during transient operation when an EGR device is provided on an internal combustion engine including a plurality of cylinders. <P>SOLUTION: Combustion parameters of each cylinder are controlled based on a distance from an EGR valve to each cylinder on a circulation route of EGR gas when an operation condition of the internal combustion engine is a transient operation during which an engine load and an EGR gas quantity are varied. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an internal combustion engine control system having a plurality of cylinders, and more particularly to an internal combustion engine control system including an EGR device that introduces a part of exhaust gas into an intake system of the internal combustion engine as EGR gas.

  Conventionally, an EGR passage having one end connected to the exhaust system and the other end connected to the intake system and an EGR valve provided in the EGR passage are introduced into the intake system as EGR gas through the EGR passage. EGR devices are known. In such an EGR device, the amount of EGR gas introduced into the intake system via the EGR passage is controlled by changing the opening of the EGR valve, and as a result, the amount of EGR gas flowing into the internal combustion engine. Is controlled.

  In Patent Document 1, when EGR gas is recirculated by an EGR device to an internal combustion engine having a plurality of cylinders, the cylinder-by-cylinder intake air amount and the cylinder-by-cylinder EGR gas recirculation amount are estimated and calculated. A technique for calculating the air-fuel ratio for each cylinder based on the value is described. Further, in Patent Document 1, the fuel injection amount for each cylinder is controlled based on the calculated air-fuel ratio for each cylinder.

  In Patent Document 1, an intake air amount is measured by an air flow sensor, a rotational speed is measured by a rotational speed sensor, an intake pressure is measured by an intake pressure sensor, an exhaust pressure is measured by an exhaust pressure sensor, and an exhaust temperature sensor is used. Measure the exhaust temperature. Then, the intake air amount for each cylinder is estimated and calculated from the intake air amount, the intake pressure, the rotational speed, the layout of each intake port with respect to the intake passage, and the passage shape of each intake port. Further, the exhaust gas recirculation amount for each cylinder is estimated and calculated from the intake pressure, the exhaust pressure, the exhaust temperature, the rotational speed, the installation layout of the EGR passage with respect to the intake passage, the layout of each intake port with respect to the intake passage, and the passage shape of each intake port. .

  According to the technique described in Patent Document 1, the air-fuel ratio of each cylinder when the operation state of the internal combustion engine is a steady operation can be made uniform.

In Patent Document 2, a target EGR amount is calculated from the target EGR rate and the intake air amount, and further, the EGR gas transport delay corresponding to the intake system capacity from the EGR valve to the cylinder with respect to the target EGR amount is calculated. Describes a technique for calculating a compensated target EGR amount by performing advance processing for compensating for the difference between the EGR amount controlled by the EGR valve and the EGR amount sucked into the cylinder.
Japanese Patent No. 3854544 Japanese Patent No. 3783738 JP 2000-161145 A JP 2000-110627 A JP-A-11-257162

When an EGR device is provided in an internal combustion engine having a plurality of cylinders, the distance from the EGR valve provided in the EGR passage to each cylinder may be different. In this case, when the amount of EGR gas flowing into the internal combustion engine is increased or decreased by changing the opening of the EGR valve, the EGR in the cylinder having a relatively short distance from the EGR valve on the EGR gas flow path. The amount of gas changes earlier than the amount of EGR gas in the cylinder with the relatively long distance.

  Therefore, when the operating state of the internal combustion engine is a transient operation in which the engine load and the EGR gas amount are increased or decreased, the amount of EGR gas for each cylinder may be uneven. If the amount of EGR gas for each cylinder becomes non-uniform, the combustion state deteriorates due to this, and misfire, knocking, and torque fluctuation may occur.

  The present invention has been made in view of the above problems, and more suitably controls the combustion state in each cylinder during transient operation when an internal combustion engine having a plurality of cylinders is provided with an EGR device. The purpose is to provide a technology that can do this.

  The present invention provides a combustion parameter for each cylinder based on the distance from the EGR valve to each cylinder on the EGR gas flow path when the operating state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas change. Is to control.

More specifically, the control system for an internal combustion engine according to the present invention is:
A control system for an internal combustion engine having a plurality of cylinders,
An EGR passage having one end connected to the exhaust system and the other end connected to the intake system and an EGR valve provided in the EGR passage are introduced into the intake system as EGR gas through the EGR passage. An EGR device;
When the operation state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas change, the combustion parameter is controlled for each cylinder based on the distance from the EGR valve to each cylinder on the EGR gas flow path. And a combustion parameter control means.

  During transient operation, the combustion parameter is controlled for each cylinder based on the distance from the EGR valve to each cylinder on the EGR gas flow path, so that the combustion parameter corresponding to the actual amount of EGR gas in each cylinder Can be controlled. Therefore, according to the present invention, even when the operating state of the internal combustion engine is a transient operation, the combustion state in each cylinder can be more suitably controlled.

  In the present invention, the combustion parameter control means may control the ignition timing in each cylinder. In this case, when the operating state of the internal combustion engine becomes a transient operation in which the engine load and the amount of EGR gas decrease, the ignition timing in each cylinder may be advanced once by the combustion parameter control means. In each cylinder, the timing at which the ignition timing is advanced and the timing at which the ignition timing is retarded is set to be longer in a cylinder having a relatively long distance from the EGR valve on the EGR gas flow path than in a cylinder having a relatively short distance. May be late.

  When the operating state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas decrease, the timing at which the amount of EGR gas actually decreases in each cylinder is later than the timing at which the amount of intake air decreases. At this time, it is possible to suppress the occurrence of misfire or torque reduction in each cylinder by once advancing the ignition timing in each cylinder.

  Furthermore, the timing at which the amount of EGR gas actually decreases in each cylinder is earlier in a cylinder having a relatively short distance than in a cylinder having a relatively long distance from the EGR valve on the EGR gas flow path. Therefore, the timing for retarding the ignition timing after the ignition timing has been advanced in each cylinder is greater than the cylinder having a relatively short distance in a cylinder having a relatively long distance from the EGR valve on the EGR gas flow path. Slow down. As a result, in each cylinder, the advanced ignition timing can be retarded in accordance with the timing at which the amount of EGR gas actually decreases.

  Thus, according to the above, even when the operating state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas decrease, the ignition timing in each cylinder is set to the actual EGR gas in each cylinder. It can be time according to the amount. As a result, misfire, torque fluctuation, and knocking during transient operation can be suppressed.

  Further, when the operating state of the internal combustion engine becomes a transient operation in which the engine load and the amount of EGR gas increase, the ignition timing in each cylinder may be once retarded by the combustion parameter control means. In the same manner as described above, the timing for advancing the ignition timing after retarding the ignition timing in each cylinder is the same for cylinders with a relatively long distance from the EGR valve on the EGR gas flow path. It may be slower than a relatively short cylinder.

  When the operation state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas increase, the timing at which the amount of EGR gas actually increases in each cylinder is later than the timing at which the intake air amount increases. At this time, knocking in each cylinder can be suppressed by once retarding the ignition timing in each cylinder.

  Furthermore, the timing at which the amount of EGR gas in each cylinder actually increases is earlier in a cylinder having a relatively short distance than in a cylinder having a relatively long distance from the EGR valve on the EGR gas flow path. Therefore, after delaying the ignition timing in each cylinder, the timing for advancing the ignition timing is set to be longer in a cylinder having a relatively long distance from the EGR valve on the EGR gas flow path than in a cylinder having a relatively short distance. Slow down. Thereby, in each cylinder, the retarded ignition timing can be advanced in accordance with the timing at which the amount of EGR gas actually increases.

  Thus, according to the above, even when the operation state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas increase, the ignition timing in each cylinder is set to the actual EGR gas in each cylinder. It can be time according to the amount. Thereby, it is possible to suppress the occurrence of misfire and torque fluctuation during transient operation.

Further, as described above, when the ignition timing in each cylinder is controlled based on the distance from the EGR valve to each cylinder on the EGR gas flow path, the detected value of the air-fuel ratio sensor, the O ₂ sensor, or the like is used. Based on this, it is possible to control the respective ignition timings without acquiring the actual amount of EGR gas in each cylinder. Therefore, it is possible to feed-forward control the ignition timing in each cylinder to a more suitable timing even during transient operation.

  In the present invention, the combustion parameter control means may control the fuel injection amount in each cylinder. In this case, when the operation state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas are decreased, the rate of decrease is reduced while the fuel injection amount in each cylinder is gradually decreased by the combustion parameter control means. May be reduced. In the course of gradually decreasing the fuel injection amount, the timing at which the rate of decrease is reduced is longer in a cylinder having a relatively long distance from the EGR valve on the EGR gas flow path than in a cylinder having a relatively short distance. May be late.

  When the operation state of the internal combustion engine is a transient operation in which the engine load decreases, the fuel injection amount in each cylinder is gradually decreased. Here, the decrease rate of the fuel injection amount is a decrease amount of the fuel injection amount per unit time.

When the operating state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas decrease, the timing at which the amount of EGR gas in each cylinder actually decreases starts to decrease the fuel injection amount in each cylinder. Slower than timing. If the amount of EGR gas actually decreases while the fuel injection amount is being decreased, the air-fuel ratio of the gas in the cylinder increases compared to before the amount of EGR gas decreases. That is, the air-fuel ratio of the gas in the cylinder fluctuates during transient operation.

  Therefore, in each cylinder, while decreasing the fuel injection amount, the rate of decrease of the fuel injection amount is reduced, and the timing of reducing the decrease rate is compared with the distance from the EGR valve on the EGR gas flow path. In a long cylinder, the distance is slower than in a relatively short cylinder.

  According to this, in each cylinder, the fuel injection amount reduction rate can be reduced at the timing when the amount of EGR gas actually decreases while the fuel injection amount is being reduced. Therefore, it is possible to suppress an increase in the air-fuel ratio of the gas in each cylinder due to the actual decrease in the amount of EGR gas.

  Therefore, according to the above, even when the operation state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas are reduced, the fluctuation of the air-fuel ratio of the gas in each cylinder during the transient operation is suppressed. I can do it. Thereby, it is possible to suppress the occurrence of misfire and torque fluctuation during transient operation.

  Further, when the operation state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas increase, the rate of increase is increased while the fuel injection amount in each cylinder is gradually increased by the combustion parameter control means. It may be lowered. When the fuel injection amount is gradually increased, the rate at which the rate of increase is reduced is less for a cylinder with a relatively long distance from the EGR valve on the EGR gas flow path than for a cylinder with a relatively short distance. May be late.

  When the operating state of the internal combustion engine is a transient operation in which the engine load increases, the fuel injection amount in each cylinder is gradually increased. Here, the increase rate of the fuel injection amount is an increase amount of the fuel injection amount per unit time.

  When the operating state of the internal combustion engine becomes a transient operation in which the engine load and the amount of EGR gas increase, the timing at which the amount of EGR gas in each cylinder actually increases starts to increase the fuel injection amount in each cylinder. Slower than timing. When the amount of EGR gas actually increases while the fuel injection amount is being increased, the air-fuel ratio of the gas in the cylinder is lowered as compared to before the amount of EGR gas is increased. That is, the air-fuel ratio of the gas in the cylinder fluctuates during transient operation.

  Therefore, in each cylinder, the rate of increase of the fuel injection amount is reduced while the fuel injection amount is being increased, and the distance from the EGR valve on the EGR gas flow path is compared when the increase rate is reduced. In a long cylinder, the distance is slower than in a relatively short cylinder.

  According to this, in each cylinder, the increase rate of the fuel injection amount can be reduced at the timing when the amount of EGR gas actually increases while the fuel injection amount is being increased. Thereby, the fall of the air fuel ratio of the gas in each cylinder by the amount of EGR gas increasing can be suppressed.

  Therefore, according to the above, even when the operation state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas increase, the air-fuel ratio of the gas in each cylinder varies during the transient operation. Can be suppressed. Thereby, it is possible to suppress the occurrence of misfire and torque fluctuation during transient operation.

  When controlling the timing of reducing the decrease rate or the increase rate of the fuel injection amount in each cylinder based on the distance from the EGR valve to each cylinder on the EGR gas flow path as described above, a sensor such as an air-fuel ratio sensor Based on the detected value, it is possible to control the timing at which the decrease rate or increase rate of each fuel injection amount is reduced without acquiring the actual air-fuel ratio in each cylinder. Therefore, it is possible to feed-forward control the air-fuel ratio of the gas in each cylinder to a more suitable value even during transient operation.

  In some cases, the amount of EGR gas flowing into the internal combustion engine is controlled in accordance with the operating state of the internal combustion engine so that the torque of the internal combustion engine becomes a maximum value. In this case, during transient operation, as described above, each cylinder is controlled by controlling the timing at which the rate of decrease or increase in the fuel injection amount in each cylinder is reduced based on the distance from the EGR valve on the EGR gas flow path. Even if the variation in the air-fuel ratio is suppressed, if there is a difference in the actual amount of EGR gas between the cylinders, there is a risk that a difference will occur in the torque generated by the combustion of fuel between the cylinders. is there.

  Therefore, in the above case, EGR gas amount control means is further provided for controlling the amount of EGR gas flowing into the internal combustion engine in accordance with the operating state of the internal combustion engine so that the torque of the internal combustion engine becomes a maximum value. When the internal combustion engine is in a transient operation in which the engine load and the amount of EGR gas change, the ignition timing in the cylinder having a relatively short distance from the EGR valve on the EGR gas flow path is retarded. And / or by advancing the ignition timing in a cylinder having a relatively long distance, a difference in torque between the cylinders may be suppressed.

  During the transient operation, the ignition timing in each cylinder is controlled as described above to reduce the torque generated in the cylinder in which the amount of EGR gas changes relatively quickly and / or the amount of EGR gas is relatively low. The torque generated in the slowly changing cylinder can be increased. Therefore, the difference in torque between the cylinders can be suppressed.

  In the above case, when the operation state of the internal combustion engine is a transient operation, in the cylinder having a relatively long distance from the EGR valve on the EGR gas flow path, the ignition timing at that time has the maximum torque. Or when it is determined that knocking will occur when the ignition timing is advanced, the fuel injection amount in the cylinder may be increased. By correcting the fuel injection amount to be increased, the torque generated in the cylinder can be increased as in the case where the ignition timing is advanced.

In the present invention, the in-cylinder intake air amount calculation means for calculating the in-cylinder intake air amount that is the intake air amount flowing into one cylinder based on the value of the parameter relating to the operating state of the internal combustion engine,
A total EGR gas amount calculating means for calculating a total EGR gas amount that is an amount of EGR gas passing through the EGR valve based on a parameter value relating to an operating state of the internal combustion engine;
When the operation state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas change, the amount of EGR gas that passes through the EGR valve changes until the amount of EGR gas in the cylinder changes. Response delay time calculating means for calculating the response delay time for each cylinder based on the value of the parameter relating to the operating state of the internal combustion engine and the distance from the EGR valve to each cylinder on the EGR gas flow path;
Cylinder calculated by the total EGR gas amount calculated by the total EGR gas amount calculating means and the response delay time calculating means when the operating state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas change In-cylinder EGR gas amount calculating means for calculating an in-cylinder EGR gas amount, which is an amount of EGR gas in the cylinder, for each cylinder based on the response delay time for each cylinder;
When the operating state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas change, the cylinder calculated by the in-cylinder EGR gas amount calculating means from the in-cylinder intake amount calculated by the in-cylinder intake amount calculating means In-cylinder air amount calculating means for calculating the air amount in the cylinder for each cylinder by subtracting the internal EGR gas amount may be further provided.

  Here, the in-cylinder intake amount is the sum of the intake air amount flowing into one cylinder and the amount of EGR gas.

  Based on the above, it is possible to calculate the air amount in each cylinder when the operating state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas change. In addition, even during transient operation, in addition to the distance from the EGR valve to each cylinder on the EGR gas flow path, the combustion parameter in each cylinder is controlled based on the air amount for each cylinder thus calculated. Thus, the combustion state in each cylinder during transient operation can be controlled more suitably.

  According to the present invention, even when an EGR device is provided in an internal combustion engine having a plurality of cylinders, the combustion state in each cylinder during transient operation can be more suitably controlled.

  Hereinafter, specific embodiments of a control system for an internal combustion engine according to the present invention will be described with reference to the drawings.

<Example 1>
(Schematic configuration of internal combustion engine and its intake and exhaust system)
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and its intake / exhaust system according to the present embodiment. The internal combustion engine 1 is a gasoline engine for driving a vehicle having four cylinders 2 (hereinafter, # 1 to 4 in FIG. 1 are referred to as cylinders 1 to 4 respectively). A fuel injection valve (not shown) is provided at the intake port of each cylinder 2. Each cylinder 2 is provided with a spark plug 3 that ignites the air-fuel mixture supplied into the cylinder 2.

  An intake manifold 5 and an exhaust manifold 7 are connected to the internal combustion engine 1. One end of an intake passage 4 is connected to the intake manifold 5. One end of an exhaust passage 6 is connected to the exhaust manifold 7.

  A compressor housing 8 a of a turbocharger 8 is installed in the intake passage 4. A turbine housing 8 b of a turbocharger 8 is installed in the exhaust passage 6.

  A throttle valve 9 is provided in the intake passage 4 on the downstream side of the compressor housing 8a. A three-way catalyst 10 is provided in the exhaust passage 6 on the downstream side of the turbine housing 8b.

  An air flow meter 11 is provided in the intake passage 4 upstream of the compressor housing 8a. The intake manifold 5 is provided with a pressure sensor 12 for detecting intake pressure. An air-fuel ratio sensor 13 is provided upstream of the turbine housing 8b in the exhaust passage 6.

  The internal combustion engine 1 according to this embodiment includes an EGR device 14 that introduces a part of exhaust gas into the intake system as EGR gas. The EGR device 14 has an EGR passage 15 and an EGR valve 16. The EGR passage 15 has one end connected to the exhaust manifold 7 and the other end connected to the intake manifold 5. The EGR valve 16 is provided in the EGR passage 15. With such a configuration, EGR gas is introduced from the exhaust manifold 7 to the intake manifold 5 via the EGR passage 15. Further, the amount of EGR gas introduced into the intake manifold 5 is controlled by changing the opening degree of the EGR valve 16.

  The internal combustion engine 1 is provided with an electronic control unit (ECU) 20. The ECU 20 is a unit that controls the operating state of the internal combustion engine 1 and the like. An air flow meter 11, a pressure sensor 12, an air-fuel ratio sensor 13, a crank position sensor 21, and an accelerator opening sensor 22 are electrically connected to the ECU 20. The crank position sensor 21 detects the crank angle of the internal combustion engine 1. The accelerator opening sensor 22 detects the accelerator opening of a vehicle on which the internal combustion engine 1 is mounted. Output signals from the sensors are input to the ECU 20.

  The ECU 20 derives the engine speed of the internal combustion engine 1 based on the detected value of the crank position sensor 21. Further, the ECU 20 derives the engine load of the internal combustion engine 1 based on the detection value of the accelerator opening sensor 22.

  Further, the ECU 20 is electrically connected to the fuel injection valve of each cylinder 2, each spark plug 3, the throttle valve 9 and the EGR valve 16. These are controlled by the ECU 20.

(Control during transient operation)
In the present embodiment, the EGR gas is introduced into the intake manifold 5 by the EGR device, whereby the EGR gas is supplied to the internal combustion engine 1 together with the intake air. Thereby, the amount of NOx discharged from the internal combustion engine 1 is suppressed.

  The amount of EGR gas supplied to the internal combustion engine 1 is controlled by changing the opening of the EGR valve 16 based on the operating state of the internal combustion engine 1. That is, when the engine load of the internal combustion engine 1 increases, the EGR valve 16 is controlled in the valve opening direction, and the amount of EGR gas flowing into the internal combustion engine 1 increases. On the other hand, when the engine load of the internal combustion engine 1 decreases, the EGR valve 16 is controlled in the valve closing direction, and the amount of EGR gas flowing into the internal combustion engine 1 decreases.

  Here, in the configuration of the present embodiment, the distance from the EGR valve 16 to each cylinder 2 is different on the EGR gas flow path. Specifically, the distance from the EGR valve 16 is the shortest in the fourth cylinder and is longer in the order of the third to first cylinders. In such a case, when the opening degree of the EGR valve 16 is changed so as to change the amount of EGR gas, the timing at which the actual amount of EGR gas in each cylinder 2 changes is different for each cylinder 2. . That is, the amount of EGR gas in the fourth cylinder changes the fastest, and the amount of EGR gas in the first cylinder changes the latest.

  Therefore, if the operating state of the internal combustion engine 1 is a transient operation in which the engine load and the amount of EGR gas flowing into the internal combustion engine 1 increase or decrease, the amount of EGR gas for each cylinder 2 may become non-uniform. If the amount of EGR gas for each cylinder 2 is uneven and the ignition timing in one combustion cycle in each cylinder 2 is the same, misfire, torque fluctuation, and knocking may occur.

  Therefore, in this embodiment, when the operation state of the internal combustion engine 1 is a transient operation in which the engine load and the amount of EGR gas flowing into the internal combustion engine 1 increase or decrease, the EGR valve on the EGR gas flow path The ignition timing in one combustion cycle in each cylinder 2 is individually controlled by the ECU 20 according to the distance from 16 to each cylinder 2.

  Hereinafter, in the present embodiment, regarding the control of the ignition timing in each cylinder 2 when the operation state of the internal combustion engine 1 is a transient operation in which the engine load and the amount of EGR gas flowing into the internal combustion engine 1 increase or decrease. This will be described based on the time charts shown in FIGS. Here, the ignition timing in the first cylinder having the longest distance from the EGR valve 16 on the EGR gas flow path and the fourth cylinder having the shortest distance from the EGR valve 16 on the EGR gas flow path is taken as an example. I will explain.

(During transient operation when engine load and EGR gas amount are reduced)
FIG. 2 shows the accelerator opening, the opening of the EGR valve 16, the internal combustion engine 1 when the operating state of the internal combustion engine 1 is a transient operation in which the engine load and the amount of EGR gas flowing into the internal combustion engine 1 are reduced. Time chart showing the total intake air amount (sum of the air amount flowing into all cylinders 2), the amount of EGR gas in the first and fourth cylinders, and the transition of the ignition timing in the first and fourth cylinders It is.

  In FIG. 2, the accelerator opening decreases at the time point (a). Accordingly, at the time of (a), the opening degree of the EGR valve 16 and the throttle valve 9 decreases. At this time, the response delay time is longer when the actual amount of EGR gas in each cylinder 2 of the internal combustion engine 1 is decreased than when the actual intake air amount of the internal combustion engine 1 is decreased. Due to this, if the actual amount of EGR gas with respect to the amount of air in each cylinder 2 becomes excessively large, there is a possibility that misfire or torque decrease may occur.

  Therefore, in this embodiment, the ignition timing by the spark plug 3 in each cylinder 2 is gradually advanced according to the actual change in the intake air amount from the time point (a). Thereby, generation | occurrence | production of misfire and the fall of a torque can be suppressed.

  Then, after the amount of intake air starts to decrease, the actual amount of EGR gas in each cylinder 2 also starts decreasing after that. When the actual amount of EGR gas in each cylinder 2 decreases, it is necessary to retard and return the ignition timing by the spark plug 3 advanced in each cylinder 2.

  At this time, the actual amount of EGR gas first begins to decrease in the fourth cylinder. Thereafter, the actual amount of EGR gas begins to decrease with a delay in the order of the third to first cylinders. In FIG. 2, the amount of EGR gas in the fourth cylinder starts to decrease at a time point (b) later than the time point (a), and the first cylinder at a time point (c) later than the time point (b). The amount of EGR gas inside begins to decrease.

  Therefore, if the ignition timing by the spark plug 3 in each cylinder 2 is retarded at the same timing, the ignition timing in one combustion cycle is excessively early or excessively late with respect to the actual amount of EGR gas in a certain cylinder. There is a risk of time.

  Therefore, in the present embodiment, after the time point (a), first, the ignition timing by the spark plug 3 in the fourth cylinder closest to the EGR valve 16 on the EGR gas flow path is retarded. Thereafter, the ignition timing by the spark plug 3 is retarded with a delay in the order of the third to third cylinders.

  Further, as the flow rate of the intake air flowing into the internal combustion engine 1 (the sum of the intake air amount and the EGR gas amount) increases, the response delay time for the actual decrease in the EGR gas amount in each cylinder 2 becomes shorter. Accordingly, the timing for retarding the ignition timing in each cylinder 2 is determined based on the operating state of the internal combustion engine 1 in addition to the distance from the EGR valve 16 to each cylinder 2 on the EGR gas flow path. That is, as the flow rate of the intake air flowing into the internal combustion engine 1 increases, the timing for retarding the ignition timing in each cylinder 2 is advanced.

  According to the control as described above, as shown in FIG. 2, the timing for retarding the ignition timing by the spark plug 3 in the fourth cylinder can be set to the point (b), and the ignition in the first cylinder is performed. The timing at which the ignition timing by the plug 3 is retarded can be the time point (c). That is, in each cylinder 2, it is possible to retard the advanced ignition timing in accordance with the timing at which the amount of EGR gas actually decreases.

(During transient operation where engine load and EGR gas amount increase)
FIG. 3 shows the accelerator opening, the opening of the EGR valve 16, the total intake of the internal combustion engine 1 during the transient operation in which the operating state of the internal combustion engine 1 increases the engine load and the amount of EGR gas flowing into the internal combustion engine 1. It is a time chart which shows transition of the amount of air, the quantity of EGR gas in the 1st and 4th cylinders, and the ignition timing in the 1st and 4th cylinders.

  In FIG. 3, the accelerator opening increases at the point (a). Accordingly, at the time of (a), the opening degree of the EGR valve 16 and the throttle valve 9 increases. At this time, as described above, the increase in the actual amount of EGR gas in each cylinder 2 of the internal combustion engine 1 has a longer response delay time than the increase in the actual intake air amount of the internal combustion engine 1. As a result, knocking may occur when the actual amount of EGR gas with respect to the amount of air in each cylinder 2 becomes too small.

  Therefore, in this embodiment, the ignition timing by the spark plug 3 in each cylinder 2 is gradually retarded in accordance with the actual change in intake air amount from the time point (a). Thereby, the occurrence of knocking can be suppressed.

  Then, after the intake air amount starts to increase, the actual amount of EGR gas in each cylinder 2 also starts increasing after that. When the actual amount of EGR gas in each cylinder 2 increases, it is necessary to advance and return the ignition timing by the spark plug 3 retarded in each cylinder 2.

  At this time, the actual amount of EGR gas first starts to increase in the fourth cylinder. Thereafter, the actual amount of EGR gas begins to increase with a delay in the order of the third to first cylinders. In FIG. 3, the amount of EGR gas in the fourth cylinder begins to increase at a time point (b) later than the time point (a), and the first cylinder at a time point (c) later than the time point (b). The amount of EGR gas inside begins to increase.

  Therefore, if the ignition timing by the spark plug 3 in each cylinder 2 is advanced at the same timing, the ignition timing in one combustion cycle is excessively early with respect to the actual amount of EGR gas in a certain cylinder as described above. Or there is a risk that it will be an excessively late time.

  Therefore, in this embodiment, first, the ignition timing by the spark plug 3 in the fourth cylinder closest to the EGR valve 16 on the EGR gas flow path is advanced. Thereafter, the ignition timing by the spark plug 3 is advanced with a delay in the order of the third to first cylinders.

  For the same reason as described above, the timing for advancing the ignition timing by the spark plug 3 in each cylinder 2 is added to the distance from the EGR valve 16 to each cylinder 2 on the EGR gas flow path, and the internal combustion engine 1 is determined based on the operation state. That is, as the flow rate of the intake air flowing into the internal combustion engine 1 increases, the timing at which the ignition timing by the spark plug 3 in each cylinder 2 is advanced is advanced.

  According to the control as described above, as shown in FIG. 3, the timing for advancing the ignition timing by the spark plug 3 in the fourth cylinder can be set to the time point (b), and the ignition in the first cylinder is performed. The timing at which the ignition timing by the plug 3 is advanced can be the time point (c). That is, in each cylinder 2, the retarded ignition timing can be advanced in accordance with the timing at which the amount of EGR gas actually increases.

  As described above, according to this embodiment, even when the operating state of the internal combustion engine 1 is a transient operation in which the engine load and the amount of EGR gas decrease or increase, the ignition timing in each cylinder 2 is set to each cylinder. 2 can be set to a time according to the actual amount of EGR gas. Therefore, misfire, torque reduction, and knocking during transient operation can be suppressed.

In this embodiment, the ignition timing in each cylinder 2 is controlled based on the distance from the EGR valve 16 to each cylinder 2 on the EGR gas flow path. Therefore, it is possible to control each ignition timing without acquiring the actual amount of EGR gas in each cylinder 2 based on the detection value of a sensor such as an air-fuel ratio sensor or an O ₂ sensor. Therefore, it is possible to feed-forward control the ignition timing in each cylinder 2 to a more suitable timing even during transient operation.

  In the present embodiment, the ignition timing in one combustion cycle corresponds to the combustion parameter according to the present invention. Further, the ECU 20 that controls the ignition timing in one combustion cycle in each cylinder 2 corresponds to the combustion parameter control means according to the present invention.

<Example 2>
The schematic configuration of the internal combustion engine and its intake / exhaust system according to this embodiment is the same as that of the first embodiment.

(Control during transient operation)
When the operating state of the internal combustion engine 1 is a transient operation in which the engine load and the amount of EGR gas flowing into the internal combustion engine 1 increase or decrease, the fuel injection valve in each cylinder 2 responds to the increase or decrease of the intake air amount. The fuel injection amount is gradually increased or decreased.

  At this time, as described in the first embodiment, the timing at which the amount of EGR gas in each cylinder 2 actually changes is later than the timing at which the intake air amount changes. Therefore, in each cylinder 2, the amount of EGR gas in each cylinder 2 begins to change while the fuel injection amount gradually increases or decreases in accordance with the intake air amount. Thereby, the air-fuel ratio of the gas in each cylinder 2 fluctuates during transient operation. If the air-fuel ratio of the gas in each cylinder 2 fluctuates, misfire or torque fluctuation may occur.

  Therefore, in this embodiment, when the operation state of the internal combustion engine 1 is a transient operation in which the engine load and the amount of EGR gas flowing into the internal combustion engine 1 increase or decrease, the fuel injection amount is increased or decreased. In the middle, the ECU 20 reduces the increase rate or decrease rate of the fuel injection amount in each cylinder 2 in order to suppress fluctuations in the air-fuel ratio of the gas in each cylinder 2.

  Further, as described in the first embodiment, in the case of the configuration of the present embodiment, during transient operation, when the opening of the EGR valve 16 is changed to change the amount of EGR gas, The timing at which the actual amount of EGR gas changes differs for each cylinder 2. That is, the amount of EGR gas in the fourth cylinder changes the fastest, and the amount of EGR gas in the first cylinder changes the latest.

  Therefore, in this embodiment, the timing at which the increase rate or decrease rate of the fuel injection amount is decreased while the fuel injection amount is being increased or decreased is determined from the EGR valve 16 on the EGR gas flow path to each cylinder 2. Depending on the distance up to, different times are set for each cylinder 2.

  Hereinafter, in the present embodiment, the control of the fuel injection amount in each cylinder 2 when the operation state of the internal combustion engine 1 is a transient operation in which the engine load and the amount of EGR gas flowing into the internal combustion engine 1 increase or decrease. Will be described based on the time charts shown in FIGS. Here, the fuel injection amount in the first cylinder with the longest distance from the EGR valve 16 on the EGR gas flow path and the fourth cylinder with the shortest distance from the EGR valve 16 on the EGR gas flow path is taken as an example. I will give you a description.

(Transient operation with reduced engine load and EGR gas volume)
FIG. 4 shows the accelerator opening, the opening of the EGR valve 16, the internal combustion engine 1 when the operating state of the internal combustion engine 1 is a transient operation in which the engine load and the amount of EGR gas flowing into the internal combustion engine 1 are reduced. 6 is a time chart showing changes in the total intake air amount, the amount of EGR gas in the first and fourth cylinders, and the fuel injection amount in the first and fourth cylinders.

  In FIG. 4, the accelerator opening decreases at the time point (a). Accordingly, at the time of (a), the opening degree of the EGR valve 16 and the throttle valve 9 decreases. Further, the fuel injection amount from the fuel injection valve in each cylinder 2 starts to gradually decrease in accordance with the decrease in the intake air amount from the time point (a).

  Further, as in the first embodiment, after the intake air amount starts to decrease, the actual amount of EGR gas in each cylinder 2 also starts decreasing after that. When the amount of EGR gas in the cylinder 2 starts to decrease, the air-fuel ratio of the gas in the cylinder 2 increases when the fuel injection amount is decreased at the same decrease rate as before that point.

  Further, the actual amount of EGR gas starts to decrease first in the fourth cylinder. Thereafter, the actual amount of EGR gas begins to decrease with a delay in the order of the third to first cylinders. In FIG. 4, the amount of EGR gas in the fourth cylinder starts to decrease at a time point (b) later than the time point (a), and the first cylinder at a time point (c) later than the time point (b). The amount of EGR gas inside begins to decrease.

  Therefore, in this embodiment, after the time point (a), first, the reduction rate of the fuel injection amount in the fourth cylinder that is closest to the EGR valve 16 on the EGR gas flow path is reduced. Thereafter, the fuel injection amount decrease rate is lowered with a delay in the order of the third to first cylinders.

  As described above, the greater the flow rate of the intake air flowing into the internal combustion engine 1, the shorter the response delay time for the actual decrease in the amount of EGR gas in each cylinder 2. Therefore, the timing for reducing the rate of decrease in the fuel injection amount in each cylinder 2 is determined based on the operating state of the internal combustion engine 1 in addition to the distance from the EGR valve 16 to each cylinder 2 on the EGR gas flow path. To do. That is, as the flow rate of the intake air flowing into the internal combustion engine 1 increases, the timing for reducing the rate of decrease in the fuel injection amount in each cylinder 2 is advanced.

  According to the control as described above, as shown in FIG. 4, the timing for reducing the rate of decrease in the fuel injection amount in the fourth cylinder can be set to the time point (b), and the fuel injection in the first cylinder is performed. The timing at which the rate of decrease of the amount is reduced can be the time point (c). That is, in each cylinder 2, it is possible to reduce the fuel injection amount decrease rate in accordance with the timing at which the amount of EGR gas actually decreases.

(During transient operation where engine load and EGR gas amount increase)
FIG. 5 shows the accelerator opening, the opening of the EGR valve 16, the internal combustion engine 1 when the operating state of the internal combustion engine 1 is a transient operation in which the engine load and the amount of EGR gas flowing into the internal combustion engine 1 increase. 6 is a time chart showing changes in the total intake air amount, the amount of EGR gas in the first and fourth cylinders, and the fuel injection amount in the first and fourth cylinders.

  In FIG. 5, the accelerator opening increases at the point (a). Accordingly, at the time of (a), the opening degree of the EGR valve 16 and the throttle valve 9 increases. Further, the fuel injection amount from the fuel injection valve in each cylinder 2 starts to gradually increase in accordance with the increase in the intake air amount from the time point (a).

  Further, as in the first embodiment, after the intake air amount starts to increase, the actual amount of EGR gas in each cylinder 2 also starts increasing after that. When the amount of EGR gas in the cylinder 2 starts to increase, the air-fuel ratio of the gas in the cylinder 2 decreases when the fuel injection amount is increased at the same increase rate as before that point.

Further, the actual amount of EGR gas starts to increase in the fourth cylinder. Thereafter, the actual amount of EGR gas begins to increase with a delay in the order of the third to first cylinders. In FIG. 5, the amount of EGR gas in the fourth cylinder starts to increase at a time point (b) later than the time point (a), and the first cylinder at a time point (c) later than the time point (b). The amount of EGR gas inside begins to increase.

  Therefore, in the present embodiment, after the time point (a), first, the increase rate of the fuel injection amount in the fourth cylinder having the closest distance from the EGR valve 16 on the EGR gas flow path is reduced. Thereafter, the rate of increase of the fuel injection amount is lowered with a delay in the order of the third to first cylinders.

  Further, for the same reason as described above, the timing for reducing the rate of increase of the fuel injection amount in each cylinder 2 is added to the distance from the EGR valve 16 to each cylinder 2 on the EGR gas flow path, and the internal combustion engine 1 It is determined based on the driving state. That is, as the flow rate of the intake air flowing into the internal combustion engine 1 increases, the timing at which the increase rate of the fuel injection amount in each cylinder 2 is reduced is advanced.

  According to the control as described above, as shown in FIG. 5, the timing for reducing the increase rate of the fuel injection amount in the fourth cylinder can be set to the point (b), and the fuel injection in the first cylinder is performed. The timing at which the rate of increase in the amount is reduced can be the time point (c). That is, in each cylinder 2, it is possible to reduce the rate of increase of the fuel injection amount in accordance with the timing at which the amount of EGR gas actually increases.

  As described above, according to the present embodiment, even when the operating state of the internal combustion engine 1 is a transient operation in which the engine load and the amount of EGR gas decrease or increase, Fluctuation of the air / fuel ratio of the gas can be suppressed. As a result, it is possible to suppress the occurrence of misfire and torque fluctuation during transient operation.

  Further, in this embodiment, when controlling the timing of reducing the decrease rate or increase rate of the fuel injection amount in each cylinder 2 based on the distance from the EGR valve 16 to each cylinder 2 on the EGR gas flow path, Based on the detection value of a sensor such as an air-fuel ratio sensor, it is possible to control the timing at which the decrease rate or increase rate of each fuel injection amount is reduced without acquiring the actual air-fuel ratio in each cylinder 2. Therefore, it is possible to feed-forward control the air-fuel ratio of the gas in each cylinder 2 to a more suitable value even during transient operation.

  In this embodiment, the fuel injection amount corresponds to the combustion parameter according to the present invention. The ECU 20 that controls the fuel injection amount in each cylinder 2 corresponds to the combustion parameter control means according to the present invention.

<Example 3>
The schematic configuration of the internal combustion engine and its intake / exhaust system according to this embodiment is the same as that of the first embodiment.

(Control of EGR gas amount)
The amount of EGR gas flowing into the internal combustion engine 1 is controlled by adjusting the opening of the EGR valve 16 by the ECU 20. In the present embodiment, the amount of EGR gas flowing into the internal combustion engine 1 is controlled so that the torque of the internal combustion engine 1 becomes the maximum value. Hereinafter, the amount of EGR gas that maximizes the torque of the internal combustion engine 1 is referred to as the maximum torque EGR gas amount.

  The maximum torque EGR gas amount changes according to the operating state of the internal combustion engine 1. Therefore, the amount of EGR gas flowing into the internal combustion engine 1 is controlled according to the operating state of the internal combustion engine 1 so that the amount becomes the maximum torque EGR gas amount. In this embodiment, the ECU 20 that controls the amount of EGR gas to the maximum torque EGR gas amount by adjusting the opening of the EGR valve 16 corresponds to the EGR gas amount control means according to the present invention.

(Control during transient operation)
In the present embodiment, the fuel injection amount in each cylinder 2 at the time of transient operation is controlled in the same manner as in the second embodiment. That is, during the transient operation, the increase rate or decrease rate of the fuel injection amount in each cylinder 2 is lowered while increasing or decreasing the fuel injection amount. Furthermore, the timing at which the increase rate or decrease rate of the fuel injection amount is decreased is advanced as the cylinder has a shorter distance from the EGR valve 16 on the EGR gas flow path. This suppresses fluctuations in the air-fuel ratio of the gas in each cylinder 2 during transient operation.

  However, during transient operation, even if the variation in the air-fuel ratio of the gas in each cylinder 2 is suppressed as described above, there may be a difference in the actual amount of EGR gas between the cylinders 2. In this case, in the present embodiment, there is a possibility that a difference occurs in the torque generated by the combustion of fuel between the cylinders 2.

  Specifically, the third and fourth cylinders have a shorter distance from the EGR valve 16 on the EGR gas flow path than the first and second cylinders. In other words, the first and second cylinders have a longer distance from the EGR valve 16 on the EGR gas flow path than the third and fourth cylinders. Therefore, during transient operation, the amount of EGR gas in the third and fourth cylinders changes at an earlier timing than the amount of EGR gas in the first and second cylinders (response delay time is short).

  Here, in the present embodiment, as described above, the amount of EGR gas flowing into the internal combustion engine 1 is controlled with the maximum torque EGR gas amount as a target in accordance with the operating state of the internal combustion engine 1. Therefore, during transient operation, the torque generated by combustion in the cylinder 2 tends to be larger in the third and fourth cylinders where the amount of EGR gas changes relatively quickly than in the first and second cylinders. .

  Therefore, in this embodiment, when the operating state of the internal combustion engine 1 is a transient operation in which the engine load and the amount of EGR gas change, the ignition timing in the third and fourth cylinders is retarded, and / or By advancing the ignition timing in the first and second cylinders, the torque difference between the cylinders 2 is suppressed.

  By retarding the ignition timing in the third and fourth cylinders, the torque generated by the combustion in these cylinders can be reduced. Further, by advancing the ignition timing in the first and second cylinders, the torque generated by combustion in these cylinders can be increased. Therefore, by controlling the ignition timing in each cylinder 2 as described above, the torque difference between the cylinders 2 can be suppressed.

If the ignition timing in the first and second cylinders is MBT (Minimum advance for best torque) when the operating state of the internal combustion engine 1 becomes a transient operation, the ignition timing may be advanced further. It is difficult to increase the torque. Further, if the ignition timing in the first and second cylinders is the trace knock ignition timing when the operating state of the internal combustion engine 1 becomes a transient operation, knocking may occur if the ignition timing is further advanced. .

  Therefore, when the ignition timing in the first and second cylinders is MBT or the trace knock ignition timing, the operating state of the internal combustion engine 1 becomes a transient operation, and the combustion is performed in the first and second cylinders. When increasing the torque generated, the fuel injection amount in these cylinders is corrected to increase.

  FIG. 6 is a flowchart illustrating a control routine according to this embodiment when the operation state of the internal combustion engine 1 is a transient operation in which the engine load and the amount of EGR gas flowing into the internal combustion engine 1 increase or decrease. This will be explained based on. This routine is stored in advance in the ECU 20 and is repeatedly executed at predetermined intervals during the operation of the internal combustion engine 1.

  In the present embodiment, as described above, during the transient operation, the fuel injection amount control similar to that in the second embodiment is performed in order to suppress the fluctuation of the air-fuel ratio of the gas in each cylinder 2. However, the control of the fuel injection amount is realized by executing a routine different from this routine. Therefore, the description is omitted here.

  In this routine, first, in step S101, the ECU 20 determines whether or not the operating state of the internal combustion engine 1 is a transient operation. If an affirmative determination is made in step S101, the ECU 20 proceeds to step S102, and if a negative determination is made, the ECU 20 once ends the execution of this routine.

  In step S102, the ECU 20 determines whether or not the current ignition timing tig1 in the first cylinder and the ignition timing tig2 in the second cylinder are MBT or trace knock ignition timing TK. If an affirmative determination is made in step S102, the ECU 20 proceeds to step S103, and if a negative determination is made, the ECU 20 proceeds to step S104.

  In step S103, the ECU 20 advances the ignition timing tig3 in the third cylinder and the ignition timing tig4 in the fourth cylinder in order to suppress the difference in torque between the cylinders 2, and / or in the first cylinder. The fuel injection amount Qf1 and the fuel injection amount Qf2 in the second cylinder are increased. Thereafter, the ECU 20 once terminates execution of this routine.

  In step S103, any one of the advance control of the ignition timings tig3 and tig4 in the third and fourth cylinders and the increase control of the fuel injection amounts Qf1 and Qf2 in the first and second cylinders is executed. Whether to perform the control or to execute both controls is determined based on the operating state of the internal combustion engine 1 before and after the transient operation. Further, the amount of advance when the ignition timings tig3 and tig4 in the third and fourth cylinders are advanced and the amount of increase when the fuel injection amounts Qf1 and Qf2 in the first and second cylinders are increased are also transient operation. It is determined based on the operating state of the front and rear internal combustion engines 1 and the like. Further, the advance amounts of the ignition timings tig3 and tig4 in the third and fourth cylinders need not be the same. Further, the increase amounts when the fuel injection amounts Qf1 and Qf2 in the first and second cylinders are increased do not have to be the same.

  In step S104, the ECU 20 advances the ignition timing tig3 in the third cylinder and the ignition timing tig4 in the fourth cylinder in order to suppress the difference in torque between the cylinders 2, and / or in the first cylinder. Ignition timing tig1 and ignition timing tig2 in the second cylinder are retarded. Thereafter, the ECU 20 once terminates execution of this routine.

  In step S104, any one of the advance control of the ignition timings tig3 and tig4 in the third and fourth cylinders and the retard control of the ignition timings tig1 and tig2 in the first and second cylinders is executed. Whether to perform the control or to execute both controls is determined based on the operating state of the internal combustion engine 1 before and after the transient operation. Further, the advance amount when the ignition timings tig3 and tig4 in the third and fourth cylinders are advanced, and the retard amount when the ignition timings tig1 and tig2 in the first and second cylinders are retarded, It is determined based on the operating state of the internal combustion engine 1 before and after the transient operation. Further, the advance amounts of the ignition timings tig3 and tig4 in the third and fourth cylinders need not be the same. Further, the retard amounts when the ignition timings tig1 and tig2 in the first and second cylinders are retarded do not have to be the same.

<Example 4>
The schematic configuration of the internal combustion engine and its intake / exhaust system according to this embodiment is the same as that of the first embodiment.

(Calculation method of air amount in cylinder during transient operation)
In this embodiment, when the operating state of the internal combustion engine 1 is a transient operation in which the engine load and the amount of EGR gas change, the air amount in the cylinder 2 during the transient operation is calculated for each cylinder 2. Hereinafter, a method of calculating the air amount in the cylinder 2 during the transient operation according to the present embodiment will be described based on the flowchart shown in FIG. This routine is stored in advance in the ECU 20 and is repeatedly executed at predetermined intervals during the operation of the internal combustion engine 1.

  In this routine, first, in step S201, the ECU 20 determines whether or not the operating state of the internal combustion engine 1 is a transient operation. If an affirmative determination is made in step S201, the ECU 20 proceeds to step S202, and if a negative determination is made, the ECU 20 once ends the execution of this routine.

  In S202, the ECU 20 determines the engine speed Ne of the internal combustion engine 1, the total intake air amount of the internal combustion engine 1 (detected value of the air flow meter 11) KL, the pressure in the intake manifold 5 (detected value of the pressure sensor 12) Pm, and EGR. The opening degree Degr of the valve 16 is read.

  In this embodiment, the engine speed Ne of the internal combustion engine 1, the total intake air amount KL of the internal combustion engine 1, the pressure Pm in the intake manifold 5 and the opening degree Degr of the EGR valve 16 are determined according to the present invention. It corresponds to the parameter regarding the operation state. However, the parameters relating to the operating state of the internal combustion engine according to the present invention are not limited to these values.

  Next, the ECU 20 proceeds to step S203, and is the intake air amount (intake air amount + EGR gas amount) flowing into one cylinder 2 based on the engine speed Ne of the internal combustion engine 1 and the pressure Pm in the intake manifold 5. An in-cylinder intake air amount Qgas is calculated. In this embodiment, the ECU 20 that executes step S203 corresponds to the in-cylinder intake air amount calculation means according to the present invention.

  If the internal combustion engine 1 is provided with a variable valve mechanism that makes the valve characteristic of the intake valve variable, in step S203, the in-cylinder intake air amount Qgas is calculated in consideration of the valve characteristic at that time.

  Next, the ECU 20 proceeds to step S204, where the amount of EGR gas passing through the EGR valve 16 is determined based on the engine speed Ne of the internal combustion engine 1, the pressure Pm in the intake manifold 5 and the opening degree Degr of the EGR valve 16. A certain total EGR gas amount Qegall is calculated. In the present embodiment, the ECU 20 that executes step S204 corresponds to the total EGR gas amount calculating means according to the present invention.

  Next, the ECU 20 proceeds to step S205, and after the amount of EGR gas passing through the EGR valve 16 changes based on the engine speed Ne of the internal combustion engine 1 and the total intake air amount KL of the internal combustion engine 1, the cylinder 2 A reference response delay time Δtdegrbase, which is a reference value of the response delay time until the amount of the EGR gas changes, is calculated.

  The response delay time from the change in the amount of EGR gas passing through the EGR valve 16 to the change in the amount of EGR gas in the cylinder 2 is different for each cylinder. Here, the reference response delay time Δtdegrbase is calculated as an average value of the response delay times corresponding to each cylinder 2. The reference response delay time Δtdegrbase may be calculated as the response delay time in a specific cylinder among the first to fourth cylinders.

Next, the ECU 20 proceeds to step S206, and the engine speed Ne of the internal combustion engine 1, the total intake air amount KL of the internal combustion engine 1, and the distance Ln (n from the EGR valve 16 to each cylinder 2 on the EGR gas flow path). = 1 to 4: L1 to L4 are correction coefficients for correcting the reference response delay time Δtdegrbase to the response delay time corresponding to each cylinder 2 based on the distance from the EGR valve 16 to the first to fourth cylinders, respectively. cn (n = 1 to 4: c1 to c4 are correction coefficients for calculating response delay times corresponding to the first to fourth cylinders) is calculated for each cylinder 2.

  Here, the correction coefficient cn decreases as the engine speed Ne of the internal combustion engine 1 and the total intake air amount KL of the internal combustion engine 1 increase. The correction coefficient cn increases as the distance Ln from the EGR valve 16 to the cylinder 2 on the EGR gas flow path increases.

  Next, the ECU 20 proceeds to step S207, and the amount of EGR gas in the cylinder 2 changes after the amount of EGR gas passing through the EGR valve 16 changes based on the reference response delay time Δtdegrbase and the correction coefficient cn. Response delay time Δtdegrn (n = 1 to 4: Δtdegr1 to Δtdegr4 are response delay times corresponding to the first to fourth cylinders) for each cylinder 2. In the present embodiment, the ECU 20 that executes step S207 corresponds to the response delay time calculating means according to the present invention.

  Next, the ECU 20 proceeds to step S208, and based on the total EGR gas amount Qegall and the response delay time Δtdegrn, the in-cylinder EGR gas amount Qegrn (n = 1 to 4: Qegr1 to Qegr1), which is the amount of EGR gas in the cylinder 2. Qegr 4 calculates the amount of EGR gas in each of the first to fourth cylinders) for each cylinder 2. In the present embodiment, the ECU 20 that executes step S208 corresponds to the in-cylinder EGR gas amount calculating means according to the present invention.

  Next, the ECU 20 proceeds to step S209, and subtracts the in-cylinder EGR gas amount Qegrn for each cylinder 2 calculated in step S207 from the in-cylinder intake amount Qgas calculated in step S203, so that the inside of the cylinder 2 The air amount Qairn (n = 1 to 4: Qair1 to Qair4 are the air amounts in the first to fourth cylinders) is calculated for each cylinder 2. In the present embodiment, the ECU 20 that executes step S209 corresponds to the in-cylinder air amount calculating means according to the present invention.

  After step S209, the ECU 20 once ends the execution of this routine.

  According to the routine described above, the amount of air in the cylinder 2 can be calculated for each cylinder 2 even during transient operation.

  In this embodiment, the ignition timing in each cylinder 2 is controlled in the same manner as in the first embodiment during transient operation. At this time, the ignition timing in each cylinder 2 is determined based on the air amount in each cylinder 2 calculated by the above method in addition to the distance from the EGR valve 16 to each cylinder 2 on the EGR gas flow path.

  According to this, the ignition timing in each cylinder 2 during the transient operation can be controlled to a more suitable timing. Therefore, the combustion state in each cylinder during transient operation can be made more suitable.

(Modification)
In the present embodiment, the control of the fuel injection amount in each cylinder 2 as in the second embodiment may be performed during the transient operation. In this case, in addition to the distance from the EGR valve 16 to each cylinder 2 on the EGR gas flow path, the fuel injection amount increase rate or decrease rate is calculated based on the air amount in each cylinder 2 calculated by the above method. You may determine the timing to reduce.

  In this case, the fuel injection amount in each cylinder 2 during the transient operation can be controlled to a more suitable amount. Therefore, the combustion state in each cylinder 2 during the transient operation can be made more suitable.

  In the present embodiment, during the transient operation, the fuel injection amount and the ignition timing in each cylinder 2 similar to those in the third embodiment may be controlled. In this case, in addition to the distance from the EGR valve 16 to each cylinder 2 on the EGR gas flow path, the fuel injection amount increase rate or decrease rate is calculated based on the air amount in each cylinder 2 calculated by the above method. You may control the timing and ignition timing to reduce.

  In this case, the fuel injection amount and ignition timing in each cylinder 2 during the transient operation can be controlled to a more suitable amount and timing. Therefore, the combustion state in each cylinder 2 during the transient operation can be made more suitable.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows schematic structure of the internal combustion engine which concerns on Example 1, and its intake / exhaust system. When the operation state of the internal combustion engine according to the first embodiment is a transient operation in which the engine load and the amount of EGR gas flowing into the internal combustion engine are reduced, the accelerator opening, the EGR valve opening, 6 is a time chart showing the intake air amount, the amount of EGR gas in the first and fourth cylinders, and the transition of the ignition timing in the first and fourth cylinders. When the operating state of the internal combustion engine according to the first embodiment is a transient operation in which the engine load and the amount of EGR gas flowing into the internal combustion engine increase, the accelerator opening, the EGR valve opening, 6 is a time chart showing the intake air amount, the amount of EGR gas in the first and fourth cylinders, and the transition of the ignition timing in the first and fourth cylinders. When the operating state of the internal combustion engine according to the second embodiment is a transient operation in which the engine load and the amount of EGR gas flowing into the internal combustion engine are reduced, the accelerator opening, the EGR valve opening, The time chart which shows transition of the amount of intake air, the amount of EGR gas in the 1st and 4th cylinders, and the fuel injection amount in the 1st and 4th cylinders. When the operating state of the internal combustion engine according to the second embodiment is a transient operation in which the engine load and the amount of EGR gas flowing into the internal combustion engine increase, the accelerator opening, the EGR valve opening, The time chart which shows transition of the amount of intake air, the amount of EGR gas in the 1st and 4th cylinders, and the fuel injection amount in the 1st and 4th cylinders. 7 is a flowchart illustrating a control routine according to a third embodiment when the operation state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas flowing into the internal combustion engine are increased or decreased. 10 is a flowchart illustrating a routine for calculating an air amount in a cylinder during transient operation according to a fourth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Spark plug 4 ... Intake passage 5 ... Intake manifold 6 ... Exhaust passage 7 ... Exhaust manifold 9 ... Throttle valve 10 ... Three-way catalyst 11 ・ Air flow meter 12 ・ Pressure sensor 14 ・ EGR device 15 ・ EGR passage 16 ・ EGR valve 13 ・ Air-fuel ratio sensor 20 ・ ECU
21 ・ ・ Crank position sensor 22 ・ ・ Accelerator position sensor

Claims (8)

A control system for an internal combustion engine having a plurality of cylinders,
An EGR passage having one end connected to the exhaust system and the other end connected to the intake system and an EGR valve provided in the EGR passage are introduced into the intake system as EGR gas through the EGR passage. An EGR device;
When the operation state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas change, the combustion parameter is controlled for each cylinder based on the distance from the EGR valve to each cylinder on the EGR gas flow path. A control system for an internal combustion engine, comprising: a combustion parameter control means; The combustion parameter control means controls the ignition timing in each cylinder;
When the operating state of the internal combustion engine becomes a transient operation in which the engine load and the amount of EGR gas decrease, the combustion parameter control means advances the ignition timing in each cylinder, and thereafter sets the ignition timing in each cylinder. 2. The internal combustion engine according to claim 1, wherein the timing of retarding is made slower in a cylinder having a relatively long distance from the EGR valve on the EGR gas flow path than in a cylinder having a relatively short distance. Control system. The combustion parameter control means controls the ignition timing in each cylinder;
When the operating state of the internal combustion engine becomes a transient operation in which the engine load and the amount of EGR gas increase, the combustion parameter control means retards the ignition timing in each cylinder, and thereafter sets the ignition timing in each cylinder. 2. The internal combustion engine according to claim 1, wherein the timing of advance is made slower in a cylinder having a relatively long distance from the EGR valve on an EGR gas flow path than in a cylinder having a relatively short distance. Control system. The combustion parameter control means controls the fuel injection amount in each cylinder;
When the operating state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas decrease, the rate of decrease is reduced while the fuel injection amount in each cylinder is being gradually decreased by the combustion parameter control means. And reducing the rate of decrease in a cylinder having a relatively long distance from the EGR valve on the EGR gas flow path, as compared with a cylinder having a relatively short distance. 2. A control system for an internal combustion engine according to 1. The combustion parameter control means controls the fuel injection amount in each cylinder;
When the operating state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas increase, the combustion parameter control means reduces the rate of increase while gradually increasing the fuel injection amount in each cylinder. And a timing at which the rate of increase is decreased in a cylinder having a relatively long distance from the EGR valve on the EGR gas flow path, as compared with a cylinder having a relatively short distance. 2. A control system for an internal combustion engine according to 1. EGR gas amount control means for controlling the amount of EGR gas flowing into the internal combustion engine according to the operating state of the internal combustion engine so that the torque of the internal combustion engine becomes a maximum value;
Retarding the ignition timing in a cylinder having a relatively short distance from the EGR valve on the flow path of the EGR gas when the operation state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas change; and 6. The control system for an internal combustion engine according to claim 4, wherein a torque difference between the cylinders is suppressed by advancing an ignition timing in a cylinder having a relatively long distance. When the operating state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas change, the ignition timing at that time is torque in a cylinder having a relatively long distance from the EGR valve on the EGR gas flow path. 7. The control system for an internal combustion engine according to claim 6, wherein when the engine reaches a maximum value or when it can be determined that knocking occurs when the ignition timing is advanced, the fuel injection amount in the cylinder is increased and corrected. . In-cylinder intake air amount calculating means for calculating an in-cylinder intake air amount that is an intake air amount flowing into one cylinder based on a value of a parameter relating to an operating state of the internal combustion engine;
A total EGR gas amount calculating means for calculating a total EGR gas amount that is an amount of EGR gas passing through the EGR valve based on a parameter value relating to an operating state of the internal combustion engine;
When the operation state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas change, the amount of EGR gas that passes through the EGR valve changes until the amount of EGR gas in the cylinder changes. Response delay time calculating means for calculating the response delay time for each cylinder based on the value of the parameter relating to the operating state of the internal combustion engine and the distance from the EGR valve to each cylinder on the EGR gas flow path;
Cylinder calculated by the total EGR gas amount calculated by the total EGR gas amount calculating means and the response delay time calculating means when the operating state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas change In-cylinder EGR gas amount calculating means for calculating an in-cylinder EGR gas amount, which is an amount of EGR gas in the cylinder, for each cylinder based on the response delay time for each cylinder;
When the operating state of the internal combustion engine is a transient operation in which the engine load and the amount of EGR gas change, the cylinder calculated by the in-cylinder EGR gas amount calculating means from the in-cylinder intake amount calculated by the in-cylinder intake amount calculating means The in-cylinder air amount calculating means for calculating the air amount in the cylinder for each cylinder by subtracting the internal EGR gas amount, further comprising: Control system for internal combustion engine.

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