JP2020070787A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of suppressing an excessive increase in the amount of fuel adhering to an intake system due to intake asynchronous injection in a rich combustion cylinder.
When a temperature increase request for a three-way catalyst occurs, an injection amount correction request value α is set to a value larger than “0”, and one of cylinders # 1 to # 4 has a cylinder #w (w = 1). To 4) are rich combustion cylinders that are richer than the theoretical air-fuel ratio, and the remaining cylinders #x, #y, #z (x, y, z = 1 to 4) are leaner than the theoretical air-fuel ratio. Executes dither control for lean burn cylinders. When the dither control process is executed, the split ratio calculation process M16 changes the split ratio K from "0" to a value greater than "0" and less than "1", so that intake synchronous injection and intake asynchronous are performed in one combustion cycle. Perform injection.
[Selection diagram] Figure 2

Description

  The present invention relates to a control device for an internal combustion engine that controls an internal combustion engine that includes a port injection valve that injects fuel into an intake passage and an exhaust gas purification device that purifies exhaust gas discharged from a plurality of cylinders.

For example, Patent Document 1 below describes an internal combustion engine that injects fuel using a port injection valve.
Further, for example, in Patent Document 2 below, when there is a request for warm-up of a catalyst device (exhaust gas purification device), some cylinders are made into rich combustion cylinders whose air-fuel ratio is richer than the theoretical air-fuel ratio, and the remaining cylinders are made. , A control device that executes a dither control process for a lean-burn cylinder in which the air-fuel ratio is leaner than the stoichiometric air-fuel ratio.

JP, 2007-263047, A JP, 2007-332867, A

  By the way, when there is a demand for warming up the exhaust purification device, the temperature of the intake system such as the intake passage and the intake valve is low, the amount of fuel adhering to the intake system is large, and the air-fuel mixture to be burned in the combustion chamber is The controllability of the air-fuel ratio tends to decrease. Therefore, when the dither control is executed when the temperature of the intake system is low, the amount of fuel injected from the port injection valve that supplies fuel to the rich combustion cylinders increases, so the amount of fuel that adheres to the intake system increases. There is a possibility that the amount of the air-fuel ratio increases and eventually the controllability of the air-fuel ratio deteriorates.

  1. An internal combustion engine including a port injection valve that injects fuel into the intake passage and an exhaust gas purification device that purifies exhaust gas discharged from a plurality of cylinders is a control target, and one combustion is performed to control the air-fuel ratio to a target air-fuel ratio. A required fuel injection amount calculation process for calculating a required fuel injection amount that is a required fuel injection amount in a cycle, and an air-fuel ratio of some of the plurality of cylinders is corrected by increasing the required fuel injection amount. Is a rich combustion cylinder that is richer than the stoichiometric air-fuel ratio, and a cylinder different from the some of the plurality of cylinders, the air-fuel ratio is less than the stoichiometric air-fuel ratio by reducing the required injection amount. In order to obtain a lean combustion cylinder that is also lean, the fuel is injected in synchronization with the dither control process for operating the port injection valve and the fuel injection that can be executed in one combustion cycle, that is, the opening period of the intake valve. Injection amount allocated to the intake synchronous injection when the requested injection amount of fuel is allocated to the intake synchronous injection and the intake asynchronous injection that injects fuel at a timing advanced from the intake synchronous injection. The control device for an internal combustion engine executes an increasing process for increasing the division ratio, which is the ratio of 1), when the dither control process is executed.

  In the above configuration, by increasing the division ratio when executing the dither control process, the injection amount of the intake asynchronous injection having a strong positive correlation with the fuel amount adhering to the intake system, as compared with the case where it is not increased, It can be reduced during the dither control process. Therefore, it is possible to suppress an excessive increase in the amount of fuel adhering to the intake system due to the asynchronous intake injection in the rich combustion cylinder due to the dither control.

  2. The division ratio is set to “0” when the dither control process is not executed, and the increase process sets the division ratio to “1” larger than “0” to “1” when the dither control process is executed. The control device for an internal combustion engine according to the above 1, which is a process of increasing the value to a value smaller than ".

  In the above-described configuration, when the dither control process is executed, instead of the injection consisting of only the intake asynchronous injection, the multi injection process of the intake asynchronous injection and the intake synchronous injection is switched. Therefore, the injection amount of the intake asynchronous injection in the rich combustion cylinder can be reduced as compared with the case where the switching is not performed.

  3. The synchronous side priority process is executed to increase the amount of correction correction of the required injection amount divided into the intake asynchronous injection and the intake synchronous injection in the rich combustion cylinder, in the intake synchronous injection, as compared with the intake asynchronous injection. It is the control device for an internal combustion engine described in 1 or 2 above.

  In the above-described configuration, by executing the synchronous side priority process, the asynchronous injection amount of the rich combustion cylinder can be reduced and the amount of fuel adhering to the intake system can be reduced as compared with the case where it is not executed. ..

  4. When the dither control process is being executed, a determination process is performed to determine whether the ignitability of the air-fuel mixture in the combustion chamber of the internal combustion engine is reduced, and the determination process determines that the ignitability is reduced. The control device for an internal combustion engine according to any one of 1 to 3 above, which executes a reduction process of reducing the division ratio.

  Although the amount of fuel adhering to the intake system can be reduced by increasing the split ratio, depending on the operating point of the internal combustion engine, there is concern that the fuel injected by the intake synchronous injection may hit the spark plug directly. .. Therefore, in the above-described configuration, the plug fog can be suppressed by detecting the plug fog and reducing the ignitability, and reducing the division ratio when it is determined that the ignitability is low.

  5. In the dither control process, a part of the plurality of cylinders is set as the rich combustion cylinder, and a cylinder other than the part of the plurality of cylinders is set as the lean combustion cylinder. In the included predetermined period, the sum of the number of appearances of the combustion stroke of the lean combustion cylinder of the reduction ratio with respect to the required injection amount in the lean combustion cylinder, and the rich combustion of the increase ratio with respect to the required injection amount in the rich combustion cylinder It is a process for making the sum of the number of appearances of the combustion stroke of the cylinders equal, and the increasing process is performed so that the injection amount of the intake synchronous injection of the lean combustion cylinder becomes the minimum injection amount of the port injection valve. 3. The control device for an internal combustion engine according to the above item 2, including a process for increasing the division ratio.

  In the above configuration, the split ratio is set so that the injection amount in the intake synchronous injection of the lean combustion cylinder becomes the minimum injection amount of the port injection valve, so that the injection amount in the intake synchronous injection of the lean combustion cylinder is equal to or more than the minimum injection amount. Under such a condition, the division ratio can be minimized. Therefore, the injection amount can be minimized while the intake-synchronized injection is introduced due to the dither control process.

FIG. 1 is a diagram showing a control device for an internal combustion engine and an internal combustion engine according to an embodiment. The block diagram which shows a part of process which the control apparatus concerning the embodiment performs. (A) And (b) is a time chart which shows an injection pattern. 6 is a flowchart showing a procedure of a division ratio calculation process according to the same embodiment. The flowchart which shows the procedure of the division ratio calculation process concerning 2nd Embodiment.

<First Embodiment>
Hereinafter, the first embodiment will be described with reference to the drawings.
In the internal combustion engine 10 shown in FIG. 1, a port injection valve 14 is provided in the intake passage 12. The air sucked from the intake passage 12 and the fuel injected from the port injection valve 14 flow into the combustion chambers 18 of the cylinders # 1 to # 4 as the intake valve 16 opens. The combustion chamber 18 is provided with an ignition device 20 that causes spark discharge. In the combustion chamber 18, the mixture of air and fuel is used for combustion, and the mixture used for combustion is discharged as exhaust gas to the exhaust passage 24 when the exhaust valve 22 is opened. A three-way catalyst 26 having an oxygen storage capacity is provided in the exhaust passage 24.

  The control device 30 sets the internal combustion engine 10 as a control target, and operates the port injection valve 14, the operation unit of the internal combustion engine 10 such as the ignition device 20 in order to control the control amount (torque, exhaust gas component ratio, etc.). .. That is, the control device 30 operates the operation units by outputting the operation signals MS1 and MS2 to the port injection valve 14 and the ignition device 20, respectively. At this time, the control device 30 controls the air-fuel ratio Af detected by the air-fuel ratio sensor 40 on the upstream side of the three-way catalyst 26, the output signal Scr of the crank angle sensor 42, and the intake air amount Ga detected by the air flow meter 44. The temperature of the cooling water of the internal combustion engine 10 (water temperature THW) detected by the water temperature sensor 46 is referred to. The control device 30 includes a CPU 32, a ROM 34, and a peripheral circuit 36, which are connected to each other via a communication line 38. Here, the peripheral circuit 36 includes a circuit that generates a clock signal that defines an internal operation, a power supply circuit, a reset circuit, and the like.

FIG. 2 shows a part of the processing realized by the CPU 32 executing the program stored in the ROM 34.
The base injection amount calculation process M10 is a process of calculating the base injection amount Qb, which is the base value of the fuel amount for making the air-fuel ratio of the air-fuel mixture in the combustion chamber 18 the target air-fuel ratio, based on the charging efficiency η. Specifically, in the base injection amount calculation process M10, for example, when the filling efficiency η is expressed as a percentage, the filling efficiency η is set to the fuel amount QTH per 1% of the filling efficiency η for making the air-fuel ratio the target air-fuel ratio. The base injection amount Qb may be calculated by multiplication. The base injection amount Qb is a fuel amount calculated for controlling the air-fuel ratio to the target air-fuel ratio based on the amount of air filled in the combustion chamber 18. Incidentally, the target air-fuel ratio may be the theoretical air-fuel ratio, for example. The charging efficiency η is a parameter indicating the amount of air filled in the combustion chamber 18, and is calculated by the CPU 32 based on the intake air amount Ga and the rotation speed NE. The rotation speed NE is calculated by the CPU 32 based on the output signal Scr of the crank angle sensor 42.

  The feedback process M12 is a process of calculating the feedback correction coefficient KAF by adding “1” to the correction ratio δ which is the operation amount for feedback-controlling the air-fuel ratio Af which is the feedback control amount to the target value Af *. The feedback correction coefficient KAF is a correction coefficient for the base injection amount Qb. Here, when the correction ratio δ is “0”, the correction ratio of the base injection amount Qb is zero. When the correction ratio δ is larger than “0”, the base injection amount Qb is increased and corrected, and when the correction ratio δ is smaller than “0”, the base injection amount Qb is decreased and corrected. In the present embodiment, the output value of the integration element that outputs the integrated value of the sum of the output values of the proportional element and the differential element that receive the difference between the target value Af * and the air-fuel ratio Af and the same difference as the output value The sum of the above is defined as the correction ratio δ.

The required injection amount calculation process M14 is a process of correcting the base injection amount Qb by multiplying the base injection amount Qb by the feedback correction coefficient KAF to calculate the required injection amount Qd.
The split ratio calculation process M16 is a process of calculating the split ratio K, which is the ratio of the intake synchronous injection amount when the requested injection amount Qd of fuel is injected by the intake asynchronous injection and the intake synchronous injection.

  In FIG. 3A, there are two types of intake synchronous injection that injects fuel in synchronization with the opening period of the intake valve 16 and intake asynchronous injection that injects fuel at a timing that is more advanced than the intake synchronous injection. The multi-injection process which performs a fuel injection is shown. Specifically, the intake synchronous injection is to inject fuel so that the period during which the fuel injected from the port injection valve 14 reaches the position before the opening of the intake valve 16 falls within the opening period of the intake valve 16. .. Here, the position before opening the valve means the downstream end of the intake port, in other words, the inlet portion to the combustion chamber 18. Further, the start point of the “arrival period” is the timing at which the fuel injected at the earliest timing of the fuel injected from the port injection valve 14 reaches the position before valve opening, and the end point is the port injection valve. This is the timing at which the fuel injected at the latest timing of the fuel injected from 14 reaches the position before valve opening. On the other hand, in the intake asynchronous injection, the fuel injected from the port injection valve 14 is injected so that the fuel reaches the intake valve 16 before the intake valve 16 opens. In other words, the intake asynchronous injection is an injection in which the fuel injected from the port injection valve 14 stays in the intake passage 12 until the intake valve 16 opens, and then flows into the combustion chamber 18 after opening. is there. In the intake asynchronous injection in the present embodiment, the fuel is injected such that the period in which the fuel injected from the port injection valve 14 reaches the position before the opening of the intake valve 16 falls within the closing period of the intake valve 16. I shall.

In the present embodiment, basically, the split ratio K is set to "0", and as shown in FIG. 3B, the single injection process for executing only the intake asynchronous injection is executed.
Returning to FIG. 2, the post-division first injection amount calculation process M18 is a process of calculating the first injection amount (post-division first injection amount) by multiplying the required injection amount Qd by "1-K". is there. The post-split second injection amount calculation process M20 is a process of calculating the second injection amount (second split second injection amount) by multiplying the required injection amount Qd by the split ratio K. The first injection amount after division is always the injection amount command value (asynchronous injection amount command value Qns *) of the intake asynchronous injection of the cylinders # 1 to # 4.

  In the required value output process M30, the target air-fuel ratio is set to the air-fuel ratio when the air-fuel mixture in each of the cylinders # 1 to # 4, which is the air-fuel mixture to be combusted, is collected into one during the period in which the crankshaft makes two revolutions. Also, this is a process of calculating and outputting the injection amount correction request value α of the dither control that makes the air-fuel ratio of the air-fuel mixture to be burned different between the cylinders. Here, in the dither control according to the present embodiment, one of the first cylinder # 1 to the fourth cylinder # 4 is a rich combustion cylinder that makes the air-fuel ratio of the air-fuel mixture richer than the stoichiometric air-fuel ratio. And the remaining three cylinders are lean-burn cylinders in which the air-fuel ratio of the air-fuel mixture is leaner than the stoichiometric air-fuel ratio. Then, the injection amount in the rich combustion cylinder is set to "1 + α" times the required injection amount Qd, and the injection amount in the lean combustion cylinder is set to "1- (α / 3)" times the required injection amount Qd. As a result, the following two values (a) and (a) become equal.

  Value (a): The number of appearances of the combustion stroke of the rich combustion cylinder (here, once) of the increase ratio (here, “α”) to the required injection amount Qd in the rich combustion cylinder during the period in which the crankshaft makes two revolutions. Sum of minutes (here, “α” itself).

  Value (a): The number of appearances of the combustion stroke of the lean combustion cylinder (here, 3) of the reduction ratio (here, “α / 3”) with respect to the required injection amount Qd in the lean combustion cylinder during the period in which the crankshaft makes two revolutions. Sum of times) (here, “α” itself).

  By making the value (a) and the value (a) equal, if the amount of air filled in each of the cylinders # 1 to # 4 is the same during the period in which the crankshaft makes two revolutions, the cylinder # of the internal combustion engine 10 In each of 1 to # 4, the air-fuel ratio when collecting the air-fuel mixture to be combusted into one can be made equal to the target air-fuel ratio.

  When a request for warming up the three-way catalyst 26 occurs, the request value output process M30 sets the injection amount correction request value α to a value greater than zero. Here, the warm-up request for the three-way catalyst 26 is determined by the condition (c1) that the integrated value InGa of the intake air amount Ga from the start of the internal combustion engine 10 is equal to or more than the first specified value Inth1 and the integrated value InGa. 2 It is assumed that the logical product is true when the logical product is equal to or less than the specified value Inth2 (> Inth1) and the condition (c2) that the water temperature THW is equal to or lower than the predetermined temperature THWth. The condition (c1) is a condition for determining that the temperature of the upstream end of the three-way catalyst 26 is the activation temperature. The condition (c2) is a condition under which it is determined that the entire three-way catalyst 26 has not been activated yet.

  Specifically, the request value output process M30 includes a process of variably setting the injection amount correction request value α based on the rotation speed NE and the charging efficiency η. Specifically, the ROM 34 stores map data that defines the relationship between the rotational speed NE and the charging efficiency η as an input variable and the injection amount correction request value α as an output variable, and the CPU 32 uses the map data. A map calculation of the injection amount correction request value α may be performed.

  The map data is set data of discrete values of input variables and output variable values corresponding to the respective input variable values. In addition, for example, when the value of the input variable matches any one of the values of the input variable of the map data, the map operation uses the value of the output variable of the corresponding map data as the operation result. The value obtained by interpolating the values of a plurality of output variables may be used as the calculation result.

  The rich-side dither correction amount calculation process M32 is a process for calculating the injection amount correction amount “Qd · α” of the cylinder #w, which is a rich combustion cylinder, by multiplying the required injection amount Qd by the injection amount correction request value α. Is. Here, “w” means any of “1” to “4”. The rich side dither correction process M34 adds the divided second injection amount “K · Qd” to the output value of the rich side dither correction amount calculation process M32, thereby performing the intake-synchronized injection for the cylinder #w which is the rich combustion cylinder. The injection amount command value (synchronous injection amount command value Qs * (# w)) is calculated.

  The multiplication process M36 is a process of multiplying the injection amount correction request value α by “−1/3”, and the lean-side dither correction amount calculation process M38 multiplies the required injection amount Qd by the output value of the multiplication process M36. , A process for calculating the injection amount correction amount “Qd · (−α / 3)” of the cylinders #x, #y, #z, which are the lean-burn cylinders. Here, “x”, “y”, and “z” are any of “1” to “4”, and “w”, “x”, “y”, and “z” are mutually Be different. The lean-side dither correction processing M40 adds the post-split second injection amount “K · Qd” to the output value of the lean-side dither correction amount calculation processing M38, thereby making the cylinders #x, #y, which are lean combustion cylinders. This is a process of calculating the synchronous injection amount command value Qs * (# x, #y, #z) for #z.

Incidentally, which of the cylinders # 1 to # 4 is the rich combustion cylinder is preferably changed in a cycle longer than the period in which the crankshaft makes two revolutions.
The injection valve operation processing M42 outputs the operation signal MS1 to the port injection valve 14 at the injection timing of the intake asynchronous injection, so that the fuel amount injected from the port injection valve 14 becomes the asynchronous injection amount command value Qns *. This is a process of operating the valve 14. Further, the injection valve operation process M42 outputs the operation signal MS1 to the port injection valve 14 at the injection timing of the intake synchronous injection of the cylinder #w which is the rich combustion cylinder, and the fuel amount injected from the port injection valve 14 is synchronized. This is a process of operating the port injection valve 14 so that the amount is in accordance with the injection amount command value Qs * (# w). Further, the injection valve operation processing M42 outputs the operation signal MS1 to the port injection valve 14 at the injection timing of the intake synchronous injection of the cylinders #x, #y, #z which are the lean combustion cylinders, and the injection from the port injection valve 14 is performed. This is a process of operating the port injection valve 14 so that the amount of fuel to be injected becomes an amount according to the synchronous injection amount command value Qs * (# x, #y, #z).

  FIG. 4 shows the procedure of the division ratio calculation process M16. The process shown in FIG. 4 is realized by the CPU 32 repeatedly executing the program stored in the ROM 34, for example, in a predetermined cycle. In the following, a step number of each process is expressed by a number with “S” added to the beginning.

  In the series of processes shown in FIG. 4, the CPU 32 first determines whether or not the injection amount correction request value α is larger than zero (S10). This process is a process of determining whether or not it is time to execute the dither control process. Then, when determining that the injection amount correction request value α is zero (S10: NO), the CPU 32 substitutes zero into the division ratio K because it is the case where the dither control process is not executed (S12). As a result, as shown in FIG. 3B, all the fuel of the required injection amount Qd is injected by the intake asynchronous injection.

  On the other hand, when the CPU 32 determines that it is greater than zero (S10: YES), the split ratio K is set to “{Qmin + (α / 3) · Qd} / Qd” according to the minimum injection amount Qmin of the port injection valve 14. Substitute (S14). Here, the minimum injection amount Qmin is determined by the structure of the port injection valve 14. That is, due to the structure of the port injection valve 14, when the injection amount is excessively small, the control accuracy of the injection amount decreases, so that the port injection valve 14 has a minimum so that the error of the injection amount falls within the allowable range. The injection amount Qmin is set.

  This processing is performed under the condition that the synchronous injection amount command value Qs * (# x, #y, #z) in the cylinders #x, #y, #z which are the lean combustion cylinders is equal to or more than the minimum injection amount Qmin. This is a setting for making K as small as possible.

That is, the synchronous injection amount command value Qs * (# x, #y, #z) is expressed by the following equation (c1).
Qs * (# x, #y, #z) = K * Qd-([alpha] / 3) * Qd ... (c1)
Therefore, the condition that the synchronous injection amount command value Qs * (# x, #y, #z) is greater than or equal to the minimum injection amount Qmin is the following expression (c2).

K ・ Qd- (α / 3) ・ Qd ≧ Qmin ... (c2)
According to the above equation (c2), the condition that the division ratio K should satisfy is the following equation (c3).
K ≧ {Qmin + (α / 3) · Qd} / Qd ... (c3)
Therefore, by setting the division ratio K to “{Qmin + (α / 3) · Qd} / Qd”, the synchronous injection amount command value Qs * (# for the lean combustion cylinders #x, #y, #z. The division ratio K can be minimized under the condition that (x, #y, #z) is equal to or greater than the minimum injection amount Qmin.

When the processes of S12 and S14 are completed, the CPU 32 once ends the series of processes shown in FIG.
Here, the operation and effect of the present embodiment will be described.

  In principle, the CPU 32 injects all of the required injection amount Qd of fuel by intake asynchronous injection. On the other hand, when executing the dither control process, the CPU 32 injects the fuel of the required injection amount Qd by the multi-injection process including the intake asynchronous injection and the intake synchronous injection. As a result, the asynchronous injection amount command value Qns * can be made smaller as compared with the case where all of the fuel of the required injection amount Qd is injected by the intake asynchronous injection, and eventually the intake passage 12 and the intake valve 16 are attached to the intake system. The amount of fuel consumed can be reduced. In the present embodiment, since the dither control process is executed to warm up the three-way catalyst 26, the temperature of the intake system tends to be low when the dither control process is executed, and the amount of fuel adhering to the intake system Is likely to increase. Therefore, reducing the asynchronous injection amount command value Qns * is particularly effective in suppressing a decrease in controllability of the air-fuel ratio of the air-fuel mixture to be burned in the combustion chamber 18.

  Further, in the present embodiment, the condition that the synchronous injection amount command value Qs * (# x, #y, #z) in the cylinders #x, #y, #z, which are lean combustion cylinders, is equal to or greater than the minimum injection amount Qmin. , The division ratio K is set to the minimum. Therefore, while introducing the intake-synchronized injection due to the execution of the dither control process, the injection amount can be minimized, and consequently, the intake asynchronous injection amount can be changed compared to the case where the dither control process is not executed. It can be made as small as possible.

<Second Embodiment>
Hereinafter, the second embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment.

  In the above-described embodiment, the division is performed under the condition that the synchronous injection amount command value Qs * (# x, #y, #z) in the cylinders #x, #y, #z, which are lean combustion cylinders, is equal to or more than the minimum injection amount Qmin. The ratio K was set to the minimum. On the other hand, in the present embodiment, when executing the dither control process, the division ratio K is further increased.

  FIG. 5 shows the procedure of the division ratio calculation process M16 according to this embodiment. The process shown in FIG. 5 is realized by the CPU 32 repeatedly executing the program stored in the ROM 34, for example, in a predetermined cycle.

  In the series of processes shown in FIG. 5, the CPU 32 first determines whether or not the injection amount correction request value α has switched from “0” to a value larger than “0” (S20). This process is a process of determining whether it is the start time of the dither control process. When the CPU 32 determines that it has been switched (S20: YES), it substitutes the initial value K0 for the division ratio K (S22). The initial value K0 is set to a value at which the synchronous injection amount command value Qs * of the lean combustion cylinder is larger than the minimum injection amount Qmin, regardless of the possible values of the injection amount correction request value α and the request injection amount Qd.

  On the other hand, when the CPU 32 determines that it is not the time of switching (S20: NO), it determines whether the injection amount correction request value α is “0” (S24). When determining that the CPU 32 is “0” (S24: YES), the CPU 32 substitutes “0” into the division ratio K (S26).

  On the other hand, when the process of S22 is completed or when the determination of S24 is negative, the CPU 32 calculates the crankshaft rotation fluctuation amount Δω (S28). Here, the rotational fluctuation amount Δω is the rotational speed at a predetermined angular interval including only one compression top dead center, and the compression top dead center is set to the compression top of the pair of cylinders whose compression top dead centers appear adjacent in time series. It is the absolute value of the value obtained by subtracting the value in the cylinder in which compression top dead center appears later from the value in the cylinder in which dead center appears.

  Next, the CPU 32 determines whether the rotation fluctuation amount Δω is equal to or larger than the specified amount Δth (S30). This process is a process for determining whether or not there is a plug covering in which the fuel directly hits the plug of the ignition device 20 due to the intake synchronous injection. That is, when the plug is covered, the normal ignition cannot be performed, the combustion of the air-fuel mixture is not normal, and the rotation fluctuation of the crankshaft becomes large.

  When determining that the amount is equal to or greater than the specified amount Δth (S30: YES), the CPU 32 sets the division ratio K to the predetermined amount Δ under the condition that the synchronous injection amount command value Qs * of the lean combustion cylinder is equal to or more than the minimum injection amount Qmin. Only the correction is performed (S32). This process aims at suppressing the occurrence of plug overload by reducing the synchronous injection amount command value Qs *.

Note that the CPU 32 once ends the series of processes shown in FIG. 5 when the processes of S26 and S32 are completed or when the negative determination is made in the process of S30.
As described above, according to the present embodiment, while the split ratio K is made larger than that of the first embodiment, when the plug is covered, the split ratio K is decreased to reduce carbon in the plug. It is possible to suppress the occurrence of so-called plug smoldering that adheres.

<Correspondence>
The correspondence relationship between the matters in the above-described embodiment and the matters described in the above-mentioned "Means for solving the problem" is as follows. Below, the correspondence is shown for each number of the solving means described in the "Means for solving the problem" column. The [1,2,5] exhaust purification device corresponds to the three-way catalyst 26. The dither control process is performed when the injection amount correction request value α is larger than “0”, the request value output process M30, the rich side dither correction amount calculation process M32, the rich side dither correction process M34, the multiplication process M36, the lean side dither. It corresponds to the correction amount calculation process M38, the lean side dither correction process M40, and the injection valve operation process M42. The increase process corresponds to the process of S14 of FIG. 4 and the process of S22 of FIG. [3] In the synchronization-side priority process, the second injection amount after division “K · Qd” is corrected by the injection amount correction request value α, while the first injection amount after division “(1-K) · Qd” is This corresponds to the fact that the injection amount correction request value α has not been corrected. [4] The determination process corresponds to the process of S30, and the decrease process corresponds to the process of S32.

<Other embodiments>
The present embodiment can be modified and implemented as follows. The present embodiment and the following modifications can be implemented in combination with each other within a technically consistent range.

・ About increase processing
In the processing of FIG. 4, the division ratio K is set to the synchronous injection amount command value Qs * (# x, #y, #z) in the cylinders #x, #y, #z which are lean combustion cylinders, and the minimum injection amount Qmin or more. However, the present invention is not limited to this, although the division ratio K is calculated to be the minimum value. For example, the division ratio K may be variably set according to the rotational speed NE and the charging efficiency η that define the operating point of the internal combustion engine 10.

  In the process of S22 of FIG. 5, the division ratio K is set to the initial value K0, but the present invention is not limited to this. For example, the division ratio K is changed according to the rotation speed NE and the charging efficiency η that define the operating point of the internal combustion engine 10. You may set it. In that case, each time a positive determination is made in the process of S30, the division ratio K at that time may be reduced and corrected.

  In the above-described embodiment, when the dither control process is not executed, only the intake asynchronous injection is executed, and when the dither control process is executed, the multi-injection process is executed. The increasing process for increasing the number is not limited to this. For example, when the dither control process is not executed, the division ratio K is variably set according to the rotational speed NE and the charging efficiency η that define the operating point of the internal combustion engine 10, and when the dither control process is executed, it is executed. The processing may be performed such that the actual division ratio K is increased over the division ratio K when not performing.

  It should be noted that it is not essential to increase the division ratio K when executing the dither control process. For example, as described in the following section "Exhaust temperature raising request", the dither control process causes a temperature raising request. When increasing the number of opportunities to perform, the division ratio K may be increased only when the dither control process is executed and the temperature of the intake system is equal to or lower than the specified temperature. When at least one of the injection amounts of the intake synchronous injection and the intake asynchronous injection is less than the minimum injection amount Qmin, the division ratio K is set to "0" even when the dither control process is executed.

・ About priority processing on the synchronization side
In the above embodiment, the increase correction amount of the rich combustion cylinder with respect to the divided first injection amount “(1-K) · Qd” which is the divided required injection amount is set to “0”, and the divided second injection amount “K” is set. The increase correction amount of the rich combustion cylinder with respect to “Qd” is set to “α · Qd”, but is not limited to this. For example, for the predetermined amount of "0" or more and less than "1/2" of the increase correction amount "α.Qd" with respect to the required injection amount Qd in the rich combustion cylinder, the first injection amount after division "(1-K)" The increase correction amount of the asynchronous injection amount command value Qns * (# w) of the rich combustion cylinder with respect to “Qd” may be used.

  However, the increase correction amount of the rich combustion cylinder for the post-split second injection amount “K · Qd” is better than the increase correction amount of the rich combustion cylinder for the post-split first injection amount “(1-K) · Qd”. Increasing the size is not essential. For example, each of the post-split first injection amount “K · Qd” and the post-split second injection amount “(1-K) · Qd” multiplied by the injection amount correction request value α is used as the respective increase correction amount. Good.

・ About judgment processing
In the above embodiment, whether or not the ignitability of the air-fuel mixture in the combustion chamber 18 is decreased is determined based on the rotation fluctuation amount Δω, but the present invention is not limited to this. For example, an in-cylinder pressure sensor that detects the pressure in the combustion chamber 18 may be provided, and whether or not the ignitability has decreased may be determined based on the detection value of the in-cylinder pressure sensor.

・ About reduction processing
In the above embodiment, when it is determined that the ignitability is deteriorated, the division ratio K is gradually decreased until the injection amount of the lean combustion cylinder reaches the minimum injection amount, but the present invention is not limited to this. For example, the division ratio K may be decreased stepwise only once.

・ About the required injection amount calculation process
The required injection amount calculation process is not limited to the process including the base injection amount calculation process M10 for calculating the base injection amount Qb as the open loop operation amount and the feedback process M12 for calculating the feedback operation amount. For example, it may be configured only by the base injection amount calculation process M10.

・ About dither control processing
The injection amount correction request value α may be variably set based on the water temperature THW in addition to the rotation speed NE and the charging efficiency η. Alternatively, for example, the rotational speed NE and the water temperature THW, or the charging efficiency η and the water temperature THW may be variably set based on only two parameters, or, for example, the variable based on only one of the above three parameters. You may set it. Further, instead of using the rotational speed NE and the charging efficiency η as parameters that define the operating point of the internal combustion engine 10, for example, the accelerator operating amount as a load may be used instead of the charging efficiency η as a load. Further, instead of the rotational speed NE and the load, it may be variably set based on the intake air amount Ga.

It is not essential to variably set the injection amount correction request value α based on the above parameters.
In the above embodiment, the number of lean-burn cylinders is larger than the number of rich-burn cylinders, but the number of lean-burn cylinders is not limited to this. For example, the number of rich combustion cylinders and the number of lean combustion cylinders may be the same. Further, for example, all the cylinders # 1 to # 4 are not limited to lean combustion cylinders or rich combustion cylinders, and the air-fuel ratio of one cylinder may be set as the target air-fuel ratio. Further, if the amount of air charged in each of the cylinders # 1 to # 4 is the same in the period in which the crankshaft makes two revolutions, the air-fuel mixture to be burned in each of the cylinders # 1 to # 4 of the internal combustion engine 10 is It is not essential that the air-fuel ratio when collected together is the same as the target air-fuel ratio. For example, in the case where the amount of air filled in each of the cylinders having the combustion stroke within 5 strokes is the same, the mixture to be burned in each of the cylinders having the combustion stroke within 5 strokes is collected into one. The control may be such that the air-fuel ratio becomes the same as the target air-fuel ratio. Further, for example, if the air amounts filled in the cylinders having the combustion stroke in three strokes are the same, the mixture to be burned is collected into one of the three cylinders having the combustion stroke in the three strokes. The air-fuel ratio may be the same as the target air-fuel ratio. However, it is desirable that the period in which both the combustion stroke of the rich combustion cylinder and the combustion stroke of the lean combustion cylinder appear at least once in the period in which the crankshaft makes four revolutions. In other words, if the cylinders that are in the combustion stroke in the predetermined period have the same amount of air, the air-fuel ratio when collecting the air-fuel mixture to be burned in each of the cylinders is the same as the target air-fuel ratio. In such a control, it is desirable that the predetermined period be equal to or less than the period in which the crankshaft makes four revolutions. Here, for example, when the combustion stroke of the rich combustion cylinder appears only once during four revolutions of the crankshaft, the combustion stroke of the rich combustion cylinder and the combustion stroke of the lean combustion cylinder appear. The order is, for example, “R, L, L, L, L, L, L, L”, where R is the rich combustion cylinder and L is the lean combustion cylinder. In this case, a period of "R, L, L, L", which is a period in which the crankshaft makes two revolutions shorter than the predetermined period, is provided, and some of the cylinders # 1 to # 4 are rich-burned. It is a cylinder, and another cylinder is a lean-burn cylinder.

・ "Request for raising exhaust temperature"
The temperature increase request by the dither control process is not limited to the one exemplified in the above embodiment. For example, as described in the section “About exhaust gas purification device”, when the GPF is provided, it may be a request to raise the temperature of the GPF. Further, for example, in order to raise the temperature of the exhaust passage 24 in order to suppress the adhesion of condensed water to the exhaust passage 24, a request for raising the temperature of the exhaust gas by dither control may be generated. However, in the case of increasing the chances of generating the temperature rise request by the dither control process, it is not essential to increase the division ratio K, such as performing the multi-injection process each time the dither control process is performed. For example, the division ratio K may be increased only when the dither control process is executed and the temperature of the intake system is equal to or lower than the specified temperature.

・ About the exhaust gas purification device
The exhaust gas purification device is not limited to the one including only the three-way catalyst 26. For example, a gasoline particulate filter (GPF) may be provided downstream of the three-way catalyst 26. Further, for example, a three-way catalyst may be provided downstream of the GPF. Further, for example, only the GPF may be provided. However, when a catalyst having an oxygen storage capacity is not provided upstream of the GPF, it is desirable to provide the GPF with an oxygen storage capacity in order to increase the temperature raising capacity by dither control.

・ About control device
The control device is not limited to one that includes the CPU 32 and the ROM 34 and executes software processing. For example, a dedicated hardware circuit (for example, ASIC) for performing hardware processing on at least a part of the software processed in the above embodiment may be provided. That is, the control device may have any of the following configurations (a) to (c). (A) A processing device that executes all of the above processes according to a program, and a program storage device such as a ROM that stores the program. (B) A processing device and a program storage device that execute a part of the above processes according to a program, and a dedicated hardware circuit that executes the remaining processes. (C) A dedicated hardware circuit for executing all of the above processes is provided. Here, a plurality of software processing circuits including a processing device and a program storage device or dedicated hardware circuits may be provided. That is, the above processing may be executed by a processing circuit including at least one of one or a plurality of software processing circuits and one or a plurality of dedicated hardware circuits.

・ About internal combustion engine
The internal combustion engine is not limited to the 4-cylinder internal combustion engine. For example, an in-line 6-cylinder internal combustion engine may be used. Further, for example, a V-type internal combustion engine or the like may be provided with the first exhaust gas purification device and the second exhaust gas purification device, and the cylinders for purifying the exhaust gas may be different. Further, it may be provided with a supercharger. By the way, in the case of an internal combustion engine equipped with a supercharger, it is particularly difficult to use dither control because the temperature of the exhaust gas purification device located downstream of the internal combustion engine is less likely to rise due to the heat in the exhaust being taken away by the supercharger. It is valid.

  10 ... Internal combustion engine, 12 ... Intake passage, 14 ... Port injection valve, 16 ... Intake valve, 18 ... Combustion chamber, 20 ... Ignition device, 22 ... Exhaust valve, 24 ... Exhaust passage, 26 ... Three-way catalyst, 30 ... Control Device, 32 ... CPU, 34 ... ROM, 36 ... Peripheral circuit, 38 ... Communication line, 40 ... Air-fuel ratio sensor, 42 ... Crank angle sensor, 44 ... Air flow meter, 46 ... Water temperature sensor.

Claims (5)

A control target is an internal combustion engine that includes a port injection valve that injects fuel into an intake passage and an exhaust gas purification device that purifies exhaust gas discharged from a plurality of cylinders.
A required injection amount calculation process for calculating a fuel of a required injection amount which is an injection amount required in one combustion cycle to control the air-fuel ratio to the target air-fuel ratio,
A part of the plurality of cylinders is a rich combustion cylinder in which the air-fuel ratio is richer than the theoretical air-fuel ratio by increasing and correcting the required injection amount, and the part of the plurality of cylinders is A dither control process for operating the port injection valve, in order to make the cylinder different from the cylinder a lean combustion cylinder in which the air-fuel ratio is leaner than the stoichiometric air-fuel ratio by correcting the required injection amount by reducing,
Intake synchronous injection, which is fuel injection that can be executed in one combustion cycle, that injects fuel in synchronism with the opening period of the intake valve, and asynchronous intake that injects fuel at a timing that is more advanced than the intake synchronous injection. An increase process for increasing the division ratio, which is the ratio of the injection amount allocated to the intake synchronous injection when the required injection amount of fuel is allocated to the injection, when executing the dither control process. Control device for internal combustion engine. When the dither control process is not executed, the division ratio is set to “0”,
The internal combustion engine according to claim 1, wherein the increasing process is a process of increasing the division ratio from “0” to a value larger than “0” and smaller than “1” when the dither control process is executed. Control device.   The synchronous side priority process is executed to increase the amount of correction correction of the required injection amount divided into the intake asynchronous injection and the intake synchronous injection in the rich combustion cylinder, in the intake synchronous injection, as compared with the intake asynchronous injection. The control device for an internal combustion engine according to claim 1. A determination process for determining whether or not the ignitability of the air-fuel mixture in the combustion chamber of the internal combustion engine is decreased when the dither control process is being executed,
The control device for an internal combustion engine according to any one of claims 1 to 3, wherein when the determination process determines that the ignitability is reduced, a reduction process for reducing the division ratio is executed. In the dither control process, a part of the plurality of cylinders is set as the rich combustion cylinder, and a cylinder other than the part of the plurality of cylinders is set as the lean combustion cylinder. In the included predetermined period, the sum of the number of appearances of the combustion stroke of the lean combustion cylinder of the reduction ratio with respect to the required injection amount in the lean combustion cylinder, and the rich combustion of the increase ratio with respect to the required injection amount in the rich combustion cylinder It is a process to make the sum of the number of appearances of the combustion stroke of the cylinders equal,
The control device for an internal combustion engine according to claim 2, wherein the increasing process includes a process of increasing the division ratio so that an injection amount of the intake synchronous injection of the lean combustion cylinder becomes a minimum injection amount of the port injection valve.