JP2007332867A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine capable of early warming up a catalyst, while effectively restraining an output torque variation. <P>SOLUTION: This control device of the internal combustion engine performs control for early warming up the catalyst to the internal combustion engine supplied with fuel from at least one of a port injection valve and a cylinder injection valve. Actually, a dither control means performs dither control for changing a fuel injection quantity so as to alternately switch lean combustion and rich combustion. An injection control means performs cylinder injection to a cylinder for performing the rich combustion, and also performs port injection in an intake stroke, when performing the dither control. Thus, output torque generated in the rich combustion can be restrained. Thus, the control device of the internal combustion engine can early warm up the catalyst while restraining the output torque variation generable in the dither control. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine that performs control for warming up a catalyst early.

  Conventionally, catalyst warm-up control for raising the temperature of an exhaust gas purifying catalyst to an activation temperature after an internal combustion engine is started has been performed. For example, Patent Literature 1 describes catalyst warm-up control (injection dither control) that supplies oxygen by lean combustion and combustible component (CO (carbon monoxide)) by rich combustion. By executing such control, the oxidation reaction of CO in the catalyst is increased, and the catalyst is heated by the heat generated by the oxidation reaction, thereby promoting warming up of the catalyst.

Patent Document 2 describes a technique for performing catalyst warm-up control by supplying CO to the catalyst by performing intake stroke injection and compression stroke injection (that is, forming a weak stratification in the cylinder). ing. Further, Patent Document 3 describes a technique for simultaneously supplying CO and O ₂ by compression stroke injection and expansion stroke injection. In addition, Patent Documents 4 and 5 describe techniques related to the present invention.

JP-A-9-88663 JP 11-324765 A JP 2001-304016 A JP 2001-107790 A JP-A-9-273415

  However, in the technique described in Patent Document 1 described above, an output torque difference is generated between the output torque at the time of lean combustion and the output torque at the time of rich fuel, and output torque fluctuations are performed when catalyst warm-up control is executed. May occur. Further, even with the techniques described in Patent Documents 2 to 5, it is difficult to appropriately perform catalyst warm-up control while suppressing such output torque fluctuations.

  The present invention has been made to solve the above-described problems, and provides an internal combustion engine control apparatus capable of warming up a catalyst early while effectively suppressing fluctuations in output torque. With the goal.

  In one aspect of the present invention, an internal combustion engine control apparatus warms up a catalyst provided on an exhaust passage for an internal combustion engine to which fuel is supplied from at least one of a port injection valve and a cylinder injection valve. The control device for the internal combustion engine that performs control for performing dither control for changing the fuel injection amount so that lean combustion and rich combustion are switched alternately, and when the dither control is executed, Injection control means for performing in-cylinder injection by controlling the in-cylinder injection valve for the cylinder performing combustion, and performing port injection in the intake stroke by controlling the port injection valve. Features.

  The control device for an internal combustion engine performs control for warming up the catalyst provided on the exhaust passage with respect to the internal combustion engine to which fuel is supplied from at least one of the port injection valve and the in-cylinder injection valve. It is. Specifically, the dither control means warms up the catalyst by performing dither control that changes the fuel injection amount so that lean combustion and rich combustion are alternately switched. Further, the injection control means performs the in-cylinder injection by controlling the in-cylinder injection valve and the intake stroke by controlling the port injection valve for the cylinder that performs rich combustion when performing the dither control. At port injection. The injection control means performs only in-cylinder injection for the cylinder that performs rich combustion. When fuel is injected in this way, in a cylinder that performs rich combustion, the fuel that is port-injected in the intake stroke does not substantially contribute to combustion, and only the fuel that is injected in-cylinder contributes to combustion. Therefore, generation of output torque during rich combustion can be suppressed. Therefore, according to the control apparatus for an internal combustion engine described above, it is possible to warm up the catalyst early while suppressing output torque fluctuation that may occur during dither control.

  In one aspect of the control apparatus for an internal combustion engine, the injection control unit causes the cylinder performing the rich combustion to in-cylinder an amount of fuel to be injected during the lean combustion and injects during the rich combustion. The fuel injection amount corresponding to the difference between the fuel injection amount to be injected and the fuel injection amount to be injected for the lean combustion is port-injected.

  In this aspect, the injection control means in-cylinder injects the fuel injection amount to be injected at the time of lean combustion into the cylinder performing the rich combustion, and the fuel injection amount to be injected at the time of rich combustion and the fuel to be injected to the lean combustion. The fuel injection amount corresponding to the difference from the injection amount is port-injected. In this case, in the cylinder that is richly burned, the fuel injection amount that is injected into the cylinder that contributes to combustion that generates output torque is the fuel injection amount that is injected into the cylinder when performing lean combustion. It is almost the same. Therefore, the output torque at the time of rich combustion and the output torque at the time of lean combustion are substantially the same. Therefore, according to the control device for an internal combustion engine described above, it is possible to effectively suppress output torque fluctuation that may occur during dither control.

  In another aspect of the control device for an internal combustion engine, when the required ignition retardation amount is equal to or less than a predetermined value, the injection control means sets the port injection valve to the cylinder that performs the rich combustion. Port injection is performed by controlling, and in-cylinder injection is performed in the exhaust stroke by controlling the in-cylinder injection valve.

  In this aspect, when the required ignition retardation amount is equal to or less than the predetermined value, the injection control means performs port injection instead of performing in-cylinder injection and port injection in the intake stroke with respect to the cylinder performing rich combustion. And in-cylinder injection in the exhaust stroke. In this case, since it is not necessary to retard the ignition timing significantly, the injection control is executed based on the port injection in order to give priority to the fuel consumption at the time of low load. When fuel is injected in this way, in a cylinder that performs rich combustion, in-cylinder injected fuel hardly contributes to combustion that generates output torque, but is discharged as it is, and only port-injected fuel has output torque. Contributes to the combustion that occurs. Therefore, according to the control device for an internal combustion engine described above, it is possible to suppress fluctuations in output torque that may occur during dither control while ensuring fuel efficiency during dither control.

  In another aspect of the control apparatus for an internal combustion engine, the injection control unit performs injection when the lean combustion is performed for the cylinder that performs the rich combustion when the required ignition retardation amount is equal to or less than a predetermined value. The fuel injection amount to be injected is port-injected, and the fuel injection amount corresponding to the difference between the fuel injection amount to be injected in the rich combustion and the fuel injection amount to be injected in the lean combustion is injected into the cylinder in the exhaust stroke .

  In this aspect, the injection control means port-injects the fuel injection amount to be injected at the time of lean combustion into the cylinder that performs rich combustion, and the fuel injection amount to be injected at the time of rich combustion and the fuel injection to be injected at the time of lean combustion. The fuel injection amount corresponding to the difference from the amount is injected into the cylinder in the exhaust stroke. In this case, in the richly burned cylinder, the fuel injection amount that is port-injected that contributes to the combustion that generates the output torque is substantially the same as the fuel injection amount that is port-injected when the lean combustion is performed. . Therefore, the output torque during rich combustion and the output torque during lean combustion are substantially the same. Therefore, according to the control device for an internal combustion engine described above, it is possible to effectively suppress output torque fluctuation that may occur during dither control.

  Preferably, the internal combustion engine control apparatus is provided on a bypass passage that bypasses the upstream side and the downstream side of the turbocharger in the exhaust passage when the required ignition retardation amount is equal to or less than a predetermined value. Means for controlling the waste gate valve in the opening direction is further provided. Thereby, at the time of rich combustion, since the raise of the turbine rotation speed of a turbocharger is suppressed, the raise of an output torque can be suppressed. Therefore, according to the control device for an internal combustion engine, it is possible to effectively suppress the output torque fluctuation during the dither control.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

[overall structure]
First, the overall configuration of a system to which the control device for an internal combustion engine according to the present embodiment is applied will be described.

  FIG. 1 is a schematic diagram illustrating a configuration of a vehicle to which a control device for an internal combustion engine according to the present embodiment is applied. In FIG. 1, solid arrows indicate gas flows, and broken arrows indicate input / output of signals.

  The vehicle mainly includes an air cleaner (AC) 2, an intake passage 3, a turbocharger 4, an intercooler (IC) 5, a throttle valve 6, a surge tank 7, an engine (internal combustion engine) 8, , Exhaust passage 18, bypass passage 19, waste gate valve 20, three-way catalyst 21, intake pressure sensor 31, water temperature sensor 32, oxygen sensor 33, accelerator opening sensor 34, ECU (Engine Control) Unit) 50.

  The air cleaner 2 purifies air (intake air) acquired from the outside and supplies it to the intake passage 3. A compressor 4a of the turbocharger 4 is disposed in the intake passage 3, and the intake air is compressed (supercharged) by the rotation of the compressor 4a. Further, an intercooler 5 for cooling the intake air and a throttle valve 6 for adjusting the intake air amount supplied to the engine 8 are provided in the intake passage 3. The throttle valve 6 is controlled by a control signal supplied from the ECU 50.

  The intake air that has passed through the throttle valve 6 is temporarily stored in a surge tank 7 formed on the intake passage 3 and then flows into a plurality of cylinders (not shown) of the engine 8. The engine 8 generates power by burning an air-fuel mixture obtained by mixing the supplied intake air and fuel in the cylinder. The engine 8 is constituted by, for example, a gasoline engine or a diesel engine. Exhaust gas generated by combustion in the engine 8 is discharged to the exhaust passage 18. The ECU 50 controls the fuel ignition timing and the fuel injection amount in the engine 8.

  Here, a specific configuration of the engine 8 will be described with reference to FIG. The engine 8 mainly includes a port injection valve 9, an in-cylinder injection valve 10, a cylinder (cylinder) 11a, a spark plug 12, an intake valve 13a, and an exhaust valve 13b. In FIG. 2, only one cylinder 11a is shown for convenience of explanation, but the engine 8 actually has a plurality of cylinders 11a.

  The port injection valve 9 is an injector that is provided on the intake passage 3 and injects fuel into the intake passage 3. The in-cylinder injection valve 10 is an injector that is provided in the cylinder 11a and injects fuel directly into the combustion chamber 11b of the cylinder 11a. The port injection valve 9 and the in-cylinder injection valve 10 are controlled by a control signal supplied from the ECU 50. That is, fuel injection control is executed by the ECU 50.

  Intake air is supplied from the intake passage 3 to the combustion chamber 11b of the cylinder 11a, and fuel is supplied from at least one of the port injection valve 9 and the in-cylinder injection valve 10 described above. In the combustion chamber 11b, the mixture of the supplied intake air and fuel is combusted by being ignited by ignition of the spark plug 12. In this case, the piston 11c reciprocates due to combustion, and this reciprocating motion is transmitted to the crankshaft (not shown) via the connecting rod 11d to rotate the crankshaft. Note that the spark plug 12 is controlled by a control signal supplied from the ECU 50. In other words, the ignition timing is controlled by the ECU 50.

  Furthermore, an intake valve 13a and an exhaust valve 13b are provided in the combustion chamber 11b. The intake valve 13a opens / closes to control conduction / interruption between the intake passage 3 and the combustion chamber 11b. Further, the exhaust valve 13b controls opening / closing of the exhaust passage 18 and the combustion chamber 11b by opening and closing.

  Here, the difference in operation and effect between fuel injection by the port injection valve 9 (port injection) and fuel injection by the in-cylinder injection valve 10 (in-cylinder injection) will be briefly described. According to the port injection, since the fuel is injected to a position away from the combustion chamber 11b to some extent, the fuel in the cylinder can be made homogeneous. Therefore, it can be said that the port injection is excellent in combustibility and excellent in fuel efficiency at a low load. On the other hand, according to the in-cylinder injection (in-cylinder stratified injection), since the fuel is directly injected into the combustion chamber 11b, the fuel can be collected and ignited in the vicinity of the spark plug 12. Therefore, it can be said that in-cylinder injection is advantageous in the lean limit and the retard limit. That is, when in-cylinder injection is performed, the ignition timing can be delayed more than when port injection is performed.

  Returning to FIG. 1, other components of the vehicle will be described.

  The exhaust gas discharged from the engine 8 rotates the turbine 4 b of the turbocharger 4 provided in the exhaust passage 18. The rotational torque of the turbine 4b is transmitted to the compressor 4a in the supercharger 4 and rotated, whereby the intake air passing through the turbocharger 4 is compressed (supercharged).

  A bypass passage 19 that bypasses the upstream side and the downstream side of the turbocharger 4 is connected to the exhaust passage 18. A waste gate valve 20 is provided on the bypass passage 19. When the wastegate valve 20 is closed, the exhaust gas flows into the supercharger 4 and does not flow into the bypass passage 19. Conversely, when the wastegate valve 20 is open, the exhaust gas also flows into the bypass passage 19 as indicated by the arrow 105 in FIG. Therefore, an increase in the rotational speed of the compressor 4a is suppressed. That is, supercharging by the turbocharger 4 is suppressed. Such control of the opening degree of the waste gate valve 20 is performed by the ECU 50.

A three-way catalyst 21 having a function of purifying exhaust gas is provided on the exhaust passage 18. Specifically, the three-way catalyst 21 is a catalyst having a noble metal such as platinum or rhodium as an active component, and nitrogen oxide (NO _x ), carbon monoxide (CO), hydrocarbon (HC) in exhaust gas. And the like. Further, the exhaust gas purification capacity of the three-way catalyst 21 changes according to its temperature. Specifically, when the three-way catalyst 21 is at a temperature near the activation temperature, the exhaust gas purification capability is increased. Therefore, it is necessary to raise the temperature of the three-way catalyst 21 to the activation temperature at the time of cold start. Hereinafter, the three-way catalyst 21 is also simply referred to as “catalyst”.

  The intake pressure sensor 31 is provided in the surge tank 7 and detects the intake air amount. The water temperature sensor 32 detects the temperature of the cooling water that cools the engine 8, and the oxygen sensor 33 is provided on the exhaust passage 18 and detects the oxygen concentration in the exhaust gas. The accelerator opening sensor 34 detects the accelerator opening by the driver. Detection values detected by these sensors are supplied to the ECU 50 as detection signals.

  The ECU 50 includes a CPU, a ROM, a RAM, an A / D converter, and the like (not shown). The ECU 50 performs in-vehicle control based on outputs supplied from various sensors in the vehicle. In the present embodiment, the ECU 50 performs control for warming up the three-way catalyst 21 early. Specifically, the ECU 50 executes control (hereinafter referred to as “dither control”) for changing the fuel injection amount so that the air-fuel ratio is alternately switched between rich and lean. In other words, the ECU 50 alternately executes rich injection and lean injection by increasing or decreasing the fuel injection amount in a zigzag manner. Such control is executed by increasing the CO oxidation reaction in the three-way catalyst 21 and heating the three-way catalyst 21 with heat generated by the oxidation reaction, thereby promoting warm-up of the three-way catalyst 21. This is to make it happen.

  Furthermore, in the present embodiment, the ECU 50 performs control for suppressing the output torque difference between the output torque at the time of lean combustion and the output torque at the time of rich fuel when performing the above-described dither control. Execute. Specifically, the ECU 50 controls port injection and in-cylinder injection during dither control, thereby suppressing output torque fluctuation caused by dither control. Thus, the ECU 50 functions as a control device for the internal combustion engine in the present invention. Specifically, the ECU 50 operates as a dither control unit and an injection control unit.

[Dither control]
Next, the basic concept of dither control according to this embodiment will be described.

  In the present embodiment, dither control is executed in order to warm up the three-way catalyst 21 at the time of cold start. Specifically, control is performed so that the rich injection and the lean injection are alternately switched. Further, in the present embodiment, when the dither control is executed, control is executed to suppress the output torque difference generated between the output torque at the time of lean combustion and the output torque at the time of rich fuel. Such an output torque difference is considered to be basically caused by a difference between a combustion injection amount injected during rich combustion and a fuel injection amount injected during lean combustion. In the present embodiment, when the dither control is executed, the injection control for controlling the port injection and the in-cylinder injection without changing the combustion injection amount to be injected during the rich combustion and the fuel injection amount to be injected during the lean combustion. By executing this, the output torque fluctuation as described above is suppressed.

  Further, in the present embodiment, when performing the above-described dither control, an amount (hereinafter referred to as “required ignition delay amount”) by which the ignition timing should be retarded in order to warm up the three-way catalyst 21 early. Different injection control is executed when it is larger than the predetermined value and when the required ignition retard amount is equal to or smaller than the predetermined value. Specifically, when the required ignition retardation amount is larger than a predetermined value, dither control based on in-cylinder injection that is likely to retard ignition (hereinafter referred to as “in-cylinder injection dither control”) is performed. . On the other hand, when the required ignition retard amount is equal to or less than a predetermined value, dither control based on port injection (hereinafter referred to as “port injection dither control”) is performed in order to give priority to fuel consumption at a low load. )I do. The details of the in-cylinder injection dither control and the port injection dither control will be described later.

  FIG. 3 is a flowchart showing dither control according to the present embodiment. This process is repeatedly executed by the ECU 50 at a predetermined cycle.

  First, in step S101, the ECU 50 determines whether there is a dither control request. Specifically, the ECU 50 determines whether or not the three-way catalyst 21 is warmed up. If there is a dither control request (step S101; Yes), the process proceeds to step S102. If there is no dither control request (step S101; No), the process exits the flow.

  In step S102, when the dither control is performed, a swing width (hereinafter referred to as “dither injection amplitude amount”) when the air-fuel ratio is varied between rich and lean is set. Specifically, the ECU 50 refers to a map or the like and sets the dither injection amplitude amount based on the catalyst temperature. FIG. 4 shows an example of a map used when setting the dither injection amplitude amount. FIG. 4 shows the catalyst temperature on the horizontal axis and the dither injection amplitude amount on the vertical axis. According to the map, the dither injection amplitude amount having a larger value is determined as the catalyst temperature is lower, and the dither injection amplitude amount having a smaller value is determined as the catalyst temperature is higher.

  Returning to FIG. When the process of step S102 described above ends, the process proceeds to step S103.

  In step S103, the ECU 50 determines whether or not there is an ignition retard warm-up request during idling during cold start. In other words, the ECU 50 determines whether or not the required ignition retard amount is greater than a predetermined value during idling during cold start. Here, how to obtain the required ignition retard amount will be described with reference to FIG. FIG. 5A shows an example of the relationship between the ignition timing (horizontal axis) and the exhaust gas temperature (vertical axis). FIG. 5B shows the required ignition retard amount (from the catalyst temperature (horizontal axis)). An example of a map used for obtaining (vertical axis) is shown. FIG. 5A shows that the exhaust gas temperature increases as the ignition timing is retarded. When the exhaust gas temperature rises in this way, it is considered that the catalyst temperature also rises. Therefore, when such a relationship between the ignition timing and the catalyst temperature is taken into consideration, a map as shown in FIG. 5B is created. According to the map shown in FIG. 5 (b), a larger required ignition retard amount is obtained as the catalyst temperature is lower, and a smaller required ignition retard amount is obtained as the catalyst temperature is higher.

  Returning to FIG. When the required ignition retardation amount is larger than the predetermined value (step S103; Yes), the process proceeds to step S104. In this case, it is considered that the catalyst temperature is at a low temperature. Therefore, since it is necessary to raise the catalyst temperature greatly, it is desirable to retard the ignition timing relatively large. Therefore, in step S104, the ECU 50 executes dither control (in-cylinder injection dither control) based on the in-cylinder injection that easily retards ignition. In other words, when in-cylinder injection is performed, the ignition timing can be greatly retarded compared to when port injection is performed. Therefore, when the required ignition retard amount is larger than a predetermined value, the in-cylinder injection dither control based on the in-cylinder injection is executed. Details of the in-cylinder dither control will be described later. Then, the process exits the flow.

  On the other hand, when the required ignition retard amount is equal to or less than the predetermined value (step S103; No), the process proceeds to step S105. In this case, it is considered that the catalyst temperature is relatively high (assuming that the activation temperature has not been reached). Therefore, it is not necessary to greatly increase the catalyst temperature, and therefore it is not necessary to retard the ignition timing so much. Accordingly, in step S105, the ECU 50 executes dither control (dither control during port injection) based on port injection instead of in-cylinder injection in order to give priority to fuel consumption at low loads. The details of the port injection dither control will be described later. Then, the process exits the flow.

[Dither control during in-cylinder injection]
Next, the in-cylinder injection dither control according to the present embodiment will be described.

  As described with reference to FIG. 3, when there is an ignition retard warm-up request during idling during cold start, that is, when the required ignition retard amount is greater than a predetermined value, the in-cylinder injection dither control is performed. Execute. That is, the dither control based on the in-cylinder injection that is unlikely to cause misfire even when the ignition is retarded is executed.

  Specifically, in the present embodiment, in-cylinder injection is performed by controlling the in-cylinder injection valve 10 and the port injection valve 9 is controlled with respect to the cylinder 11a that performs rich combustion when performing dither control. By doing so, port injection is performed in the intake stroke. On the other hand, only in-cylinder injection is performed on the cylinder 11a that performs lean combustion when the dither control is performed. When the fuel is injected in this way, in the cylinder 11a that performs rich combustion, the fuel that is port-injected in the intake stroke is hardly used for the combustion that generates the output torque, and only the fuel that is injected in the cylinder generates the output torque. It is considered to be used for combustion. That is, it can be said that the output torque generated when the in-cylinder dither control is performed is caused by the combustion of the fuel injected in the cylinder. Therefore, according to the in-cylinder injection dither control according to the present embodiment, it is possible to suppress the generation of output torque during rich combustion while ensuring a rich air-fuel ratio in the cylinder. Therefore, it is possible to suppress output torque fluctuation that may occur when dither control is performed.

  More specifically, a fuel injection amount to be injected during lean combustion (hereinafter referred to as “lean injection amount”) is injected into the cylinder 11a that performs rich combustion, and fuel injection to be injected during rich combustion. The fuel injection amount corresponding to the difference between the amount (hereinafter referred to as “rich injection amount”) and the lean injection amount is port-injected in the intake stroke (hereinafter, this injection amount is referred to as “port injection amount”). That is, the fuel injection amount injected into the cylinder is the same during the rich combustion and the lean combustion, and during the rich combustion, the fuel injection amount that makes the air-fuel ratio rich is the port injection amount. As described above, the port-injected fuel in the intake stroke hardly contributes to the combustion that generates the output torque, and only the fuel injected in the cylinder contributes to the combustion that generates the output torque. Therefore, according to the above-described injection control, the fuel injection amount injected in the cylinder during the rich combustion and the lean combustion in the dither control is the same, so the output torque during the rich combustion is the same as the output torque during the lean combustion. It is almost the same. Therefore, according to the in-cylinder injection dither control according to the present embodiment, it is possible to effectively suppress the output torque fluctuation that may occur during the dither control.

  Next, the in-cylinder injection dither control will be specifically described with reference to FIGS.

  FIG. 6 is a view for explaining the ignition timing set during the in-cylinder injection dither control. FIG. 6 shows the air-fuel ratio (A / F) on the horizontal axis and the ignition timing on the vertical axis. A straight line 56 indicates the in-cylinder injection limit, and a straight line 57 indicates the port injection limit. From this, it can be seen that the in-cylinder injection limit is located on the more retarded side than the port injection limit. That is, it can be said that when in-cylinder injection is performed, misfire due to ignition delay is less likely to occur than when port injection is performed. During in-cylinder dither control, in-cylinder injection is performed, so that the ignition timing is set in consideration of the in-cylinder injection limit. For example, at the time of in-cylinder injection dither control, the ignition timing indicated by reference numeral 55 is set. In this case, the ignition timing is set so as to be retarded so as not to reach the in-cylinder injection limit. Note that the air-fuel ratio indicated by reference numeral 55 indicates the average air-fuel ratio during rich fuel and lean combustion. Therefore, the air-fuel ratio is almost stoichiometric.

  FIG. 7 is a diagram showing the fuel injection amount and output torque (engine torque) during the dither control during in-cylinder injection. In FIG. 7A, the graph indicated by reference numeral 60 indicates the fuel injection amount that is injected when performing lean combustion in which only in-cylinder injection is performed, and the graph indicated by reference numeral 61 indicates only in-cylinder injection. The fuel injection amount injected when executing the rich combustion to be performed (hereinafter, the case where such injection control is performed is also referred to as “first comparative example”) is shown. On the other hand, the graph denoted by reference numeral 62 indicates the fuel injection amount (injection control according to the present embodiment) that is injected when performing rich combustion in which in-cylinder injection and port injection are performed. In this case, the fuel injection amount indicated by reference numeral 62a indicates a rich injection amount, the fuel injection amount indicated by reference numeral 62b indicates a lean injection amount, and the fuel injection amount indicated by reference numeral 62c indicates a port injection amount. . As described above, in this embodiment, the lean injection amount 62b is injected into the cylinder and the port injection amount 63c is port injected. The rich injection amount 62a is the same as the fuel injection amount in the injection control according to the first comparative example, and the lean injection amount 62b is the same as the fuel injection amount injected during lean combustion.

  FIG. 7B shows the output torque when the injection control is executed with the fuel injection amount described above. Specifically, the output torque indicated by reference numeral 63 is the output torque obtained when the lean combustion that performs only in-cylinder injection is executed, and the output torque indicated by reference numeral 64 performs the rich combustion that performs only in-cylinder injection. The output torque indicated by reference numeral 65 is the output torque obtained when rich combustion in which in-cylinder injection and port injection are performed is executed. From FIG. 7B, when the lean combustion is executed and the rich combustion that performs only in-cylinder injection is executed (when the injection control according to the first comparative example is executed), the output torque is compared. It can be seen that there is a relatively large difference. This is due to the difference in the fuel injection amount injected in the cylinder. Therefore, when the dither control that alternately switches between the above-described lean combustion and rich combustion that performs only in-cylinder injection is performed, output torque fluctuations occur.

  On the other hand, when the rich combustion that performs in-cylinder injection and port injection is executed (when the injection control according to this embodiment is executed) and when the lean combustion is executed, the output torque is almost equal. You can see that it does n’t change. Therefore, it can be said that the output torque fluctuation hardly occurs when the above-described lean combustion and the dither control for alternately switching the rich combustion in which the in-cylinder injection and the port injection are performed. This is because the in-cylinder fuel injection amount is made the same during rich combustion and lean combustion.

  FIG. 8 is a diagram for explaining the output torque fluctuation. FIG. 8 shows the air-fuel ratio (A / F) on the horizontal axis and the output torque on the vertical axis. A curve 69 shows the relationship between the output torque and the air-fuel ratio when only in-cylinder injection is executed. This shows that the output torque increases as the air-fuel ratio becomes richer. Further, points 66 and 67 located on the curve 69 indicate the output torque at the time of lean combustion and the output torque at the time of executing rich combustion that performs only in-cylinder injection, respectively. Further, the point indicated by reference numeral 68 that is not located on the curve 69 represents the output torque when rich combustion is performed in which both in-cylinder injection and port injection are performed. From this, it can be seen that a comparatively large output torque difference is generated when comparing the case where lean combustion is executed and the case where rich combustion which performs only in-cylinder injection is executed. On the other hand, when rich combustion in which in-cylinder injection and port injection are performed is compared with a case in which lean combustion is performed, it can be seen that there is almost no difference in output torque.

  FIG. 9 is a flowchart showing the in-cylinder injection dither control according to the present embodiment. This process is executed in the process of step S104 shown in FIG. Further, this process is executed by the ECU 50.

  First, in step S401, the ECU 50 sets a fuel injection amount (lean injection amount) to be injected during lean combustion. In this case, the ECU 50 sets the lean injection amount in consideration of the dither injection amplitude amount set in the process of step S102 shown in FIG. The ECU 50 controls the cylinder 11a that performs lean combustion to in-cylinder the fuel injection amount set as described above. Then, the process proceeds to step S402.

  In step S402, the ECU 50 sets a fuel injection amount (rich injection amount) to be injected during rich combustion. In this case, the ECU 50 sets the rich injection amount in consideration of the lean injection amount set in step S401 and the dither injection amplitude amount set in the process of step S102 shown in FIG. In this case, the rich injection amount is a fuel injection amount obtained by adding the lean injection amount (fuel injection amount determined in step S401) to be injected into the cylinder and the port injection amount to be port-injected. When the fuel injection amount is set in this way, the ECU 50 injects the lean injection amount into the cylinder and the port injection amount into the port 11 for the cylinder 11a that performs rich combustion. When the above process ends, the process exits the flow.

  According to the above-described in-cylinder injection dither control, when the required ignition retardation amount is larger than a predetermined value, the three-way catalyst 21 is warmed up early while effectively suppressing the output torque fluctuation that may occur during the dither control. It becomes possible to do.

[Dither control during port injection]
Next, the port injection dither control according to the present embodiment will be described.

  As described above (see FIG. 3), when there is no ignition retard warm-up request at the time of cold start, that is, when the required ignition retard amount is equal to or less than a predetermined value, Instead of performing dither control during injection, dither control during port injection is executed. That is, the dither control is executed based on the port injection in order to give priority to the fuel consumption at the time of low load.

  Specifically, when performing dither control, the cylinder 11a that performs rich combustion performs port injection by controlling the port injection valve 9, and also controls the in-cylinder injection valve 10 to perform the exhaust stroke. In-cylinder injection (hereinafter, also referred to as “in-cylinder exhaust stroke injection”) is performed. In this case, the fuel injected in the in-cylinder exhaust stroke is not used for combustion that generates output torque, but is directly discharged into the exhaust passage 18. On the other hand, when the dither control is executed, only the port injection is performed on the cylinder 11a that performs lean combustion. When the fuel is injected in this way, in the cylinder 11a that performs rich combustion, the fuel injected in the cylinder exhaust stroke hardly contributes to the combustion that generates the output torque, and the combustion in which only the fuel injected by the port generates the output torque. Contribute to. Therefore, according to the port injection dither control according to the present embodiment, it is possible to suppress the generation of output torque during rich combustion while ensuring a rich air-fuel ratio in the cylinder. Therefore, it is possible to suppress output torque fluctuation that may occur when dither control is performed.

  More specifically, for the cylinder 11a that performs rich combustion, a lean injection amount that is injected during lean combustion is port-injected, and a fuel injection amount that corresponds to the difference between the rich injection amount and the lean injection amount (hereinafter, this injection amount). Is called “in-cylinder exhaust stroke injection amount”). That is, the fuel injection amount for port injection is made the same during rich combustion and lean combustion, and during rich combustion, the fuel injection amount that makes the air-fuel ratio rich is made the in-cylinder injection amount in the exhaust stroke. As described above, the fuel injected in the cylinder exhaust stroke hardly contributes to the combustion generating the output torque, and only the fuel injected into the port contributes to the combustion generating the output torque. Therefore, according to the above-described injection control, the fuel injection amount injected into the port during the rich combustion and the lean combustion in the dither control is the same, so the output torque during the rich combustion is approximately the same as the output torque during the lean combustion. It will be the same. Therefore, according to the dither control during port injection according to the present embodiment, it is possible to effectively suppress the output torque fluctuation that can occur during the dither control.

  Next, the in-cylinder injection dither control will be specifically described with reference to FIGS. 10 to 13.

  FIG. 10 is a diagram for explaining the basic concept of the port injection dither control. FIG. 10 shows a timing chart of opening and closing of the intake valve 13a (graph indicated by reference numeral 70), opening and closing of the exhaust valve 13b (graph indicated by reference numeral 71), and four cycles (graph indicated by reference numeral 72). In this case, the intake valve 13a is opened during the intake stroke, and the exhaust valve 13b is opened during the exhaust stroke. Further, port injection is executed at time t11 immediately before the intake stroke, and fuel is ignited at time t12 in the compression stroke. In the port injection dither control according to the present embodiment, in-cylinder injection is executed at time t13 in the initial stage of the exhaust stroke, that is, in-cylinder exhaust stroke injection is executed. In this case, since the exhaust valve 13b is opened in the exhaust stroke, the fuel injected in the cylinder exhaust stroke is discharged from the exhaust passage 18 as it is.

  FIG. 11 is a diagram showing the fuel injection amount and output torque (engine torque) during the port injection dither control. In FIG. 11A, the graph indicated by reference numeral 80 indicates the fuel injection amount to be injected when performing lean combustion that performs only port injection, and the graph indicated by reference numeral 81 indicates a rich that performs only port injection. A fuel injection amount that is injected when combustion is performed (hereinafter, the case where such injection control is performed is also referred to as a “second comparative example”) is shown. On the other hand, the graph indicated by reference numeral 82 indicates the fuel injection amount (injection control according to the present embodiment) that is injected when performing rich combustion in which port injection and in-cylinder exhaust stroke injection are performed. In this case, the fuel injection amount indicated by reference numeral 82a indicates the rich injection amount, the fuel injection amount indicated by reference numeral 82b indicates the lean injection amount, and the fuel injection amount indicated by reference numeral 82c indicates the in-cylinder exhaust stroke injection amount. Show. As described above, in this embodiment, the lean injection amount 82b is port-injected, and the in-cylinder exhaust stroke injection amount 83c is injected into the in-cylinder exhaust stroke. The rich injection amount 82a is the same as the fuel injection amount in the injection control according to the second comparative example, and the lean injection amount 82b is substantially the same as the fuel injection amount injected during lean combustion.

  FIG. 11B shows the output torque when the injection control is executed with the fuel injection amount described above. Specifically, the output torque indicated by reference numeral 83 is an output torque obtained when lean combustion that performs only port injection is performed, and the output torque indicated by reference numeral 84 indicates when rich combustion that performs only port injection is performed. The output torque indicated by reference numeral 85 is the output torque obtained when the rich combustion in which the port injection and the in-cylinder exhaust stroke injection are performed is executed. From FIG. 11 (b), it is compared with the output torque when the lean combustion is executed and the rich combustion in which only the port injection is executed (when the injection control according to the second comparative example is executed) is compared. It can be seen that there is a significant difference. This is due to the difference in the amount of fuel injected by port injection. Therefore, when dither control is performed in which the above-described lean combustion and rich combustion in which only port injection is performed are alternately performed, output torque fluctuation occurs.

  In contrast, when the rich combustion in which the port injection and the in-cylinder exhaust stroke injection are performed (when the injection control according to the present embodiment is executed) is compared with the case in which the lean combustion is executed, the output torque It can be seen that there is almost no change. Therefore, it can be said that there is almost no output torque fluctuation when the dither control in which the above-described lean combustion and rich combustion in which the port injection and the in-cylinder exhaust stroke injection are performed alternately is performed. This is because the fuel injection amount for port injection is made the same during rich combustion and lean combustion.

  FIG. 12 is a diagram for explaining the output torque fluctuation. FIG. 12 shows the air-fuel ratio (A / F) on the horizontal axis and the output torque on the vertical axis. A curve 89 shows the relationship between the output torque and the air-fuel ratio when only port injection is executed. This shows that the output torque increases as the air-fuel ratio becomes richer. Also, points 86 and 87 located on the curve 89 indicate the output torque at the time of lean combustion and the output torque at the time of executing rich combustion in which only port injection is performed. Further, a point indicated by reference numeral 88 that is not located on the curve 89 indicates an output torque when rich combustion is performed in which both port injection and in-cylinder exhaust stroke injection are performed. From this, it can be seen that a comparatively large output torque difference is produced when comparing the case where lean combustion is executed with the case where rich combustion which performs only port injection is executed. In contrast, when rich combustion in which port injection and in-cylinder exhaust stroke injection are performed is compared with a case in which lean combustion is performed, it can be seen that there is almost no output torque difference.

  FIG. 13 is a flowchart showing port injection dither control according to the present embodiment. This process is executed in the process of step S105 shown in FIG. Further, this process is executed by the ECU 50.

  First, in step S501, the ECU 50 sets a fuel injection amount (lean injection amount) to be injected during lean combustion. In this case, the ECU 50 sets the lean injection amount in consideration of the dither injection amplitude amount set in the process of step S102 shown in FIG. The ECU 50 controls the cylinder 11a that performs lean combustion to perform port injection of the fuel injection amount set as described above. Then, the process proceeds to step S502.

  In step S502, the ECU 50 sets a fuel injection amount (rich injection amount) to be injected during rich combustion. In this case, the ECU 50 sets the rich injection amount taking into account the lean injection amount set in step S501 and the dither injection amplitude amount set in step S102 shown in FIG. In this case, the rich injection amount is a fuel injection amount obtained by adding the lean injection amount (the fuel injection amount determined in step S501) for port injection and the in-cylinder exhaust stroke injection amount for in-cylinder exhaust stroke injection. When the fuel injection amount is set in this way, the ECU 50 performs the port injection of the lean injection amount and the in-cylinder exhaust stroke injection amount to the cylinder 11a that performs rich combustion, and the in-cylinder exhaust stroke injection amount. When the above process ends, the process exits the flow.

  According to the above-described port injection dither control, when the required ignition retardation amount is equal to or less than the predetermined value, the three-way catalyst 21 is warmed up early while effectively suppressing the output torque fluctuation that may occur during the dither control. It becomes possible to do. In addition, since the port injection dither control basically executes the port injection, it is possible to ensure fuel consumption during the dither control.

[Modification]
Next, control according to a modification of the present invention will be described. In the modification, when the required ignition retardation amount is equal to or less than a predetermined value, the above-described port injection dither control is executed and the waste gate valve 20 is controlled to open. This is to suppress an increase in output torque by suppressing an increase in the rotational speed of the turbine 4b of the turbocharger 4 (hereinafter referred to as "turbine rotational speed") during rich combustion. . That is, the control according to the modified example is performed in order to suppress the output torque fluctuation during the dither control by suppressing the increase in the output torque due to the increase in the turbine rotation speed during the rich combustion.

  Here, a basic concept of control according to the modification will be described with reference to FIG.

  FIG. 14A is a diagram showing the relationship between the in-cylinder exhaust stroke injection amount (horizontal axis) and the exhaust temperature (vertical axis). From this, it is understood that the exhaust gas temperature increases when the in-cylinder exhaust stroke injection amount is increased. FIG. 14B is a diagram showing the relationship between the exhaust temperature (horizontal axis) and the turbine speed (vertical axis). From this, it can be seen that when the exhaust gas temperature rises, the turbine speed increases. 14 (a) and 14 (b), it is understood that when the in-cylinder exhaust stroke injection amount is increased, the exhaust gas temperature increases and the turbine speed increases. When the turbine rotational speed increases in this way, the intake air amount also increases, so the output torque of the engine 8 tends to increase.

  FIG. 14C shows the output torque when the wastegate valve 20 is closed and the output torque when the wastegate valve 20 is opened. Specifically, in FIG. 14C, the horizontal axis indicates time, and the vertical axis indicates output torque. A curve 90 indicated by a solid line indicates the output torque when the waste gate valve 20 is closed, and a curve 91 indicated by a broken line indicates the output torque when the waste gate valve 20 is opened. From this, it can be seen that when the wastegate valve 20 is opened, the output torque is smaller than when the wastegate valve 20 is closed. This is because by opening the waste gate valve 20, the amount of exhaust gas supplied to the turbocharger 4 is reduced, the turbine rotational speed is reduced, and supercharging by the turbocharger 4 is suppressed. Because. As described above, in the control according to the modified example, the waste gate valve 20 is controlled to be opened in order to prevent the turbine rotational speed from being increased by in-cylinder exhaust stroke injection at the time of rich combustion.

  FIG. 15 is a flowchart illustrating control according to the modification. This process is executed in the process of step S105 shown in FIG. 3 instead of the process related to the port injection dither control (see FIG. 13). This process is also executed by the ECU 50.

  Note that the processing in steps S601 and S602 in the control according to the modification is the same as the processing in steps S501 and S502 in the above-described port injection dither control (see FIG. 13), and thus the description thereof is omitted. Here, only the process of step S603 will be described.

  In step S603, the ECU 50 sets the opening degree of the waste gate valve 20 (the waste gate valve opening degree). Specifically, the ECU 50 sets the waste gate valve opening according to the dither injection amplitude amount set in the process of step S102 shown in FIG. For example, the ECU 50 sets the opening degree of the waste gate valve larger as the dither injection amplitude amount is larger. This is because when the dither injection amplitude amount is large, a large value is set as the in-cylinder exhaust stroke injection amount, so that the turbine rotational speed tends to increase. When the above process ends, the process exits the flow.

  According to the control according to the above modification, it is possible to effectively suppress the output torque fluctuation that can occur during the dither control by suppressing the increase in the turbine rotational speed during the rich combustion.

1 is a schematic diagram showing a configuration of a vehicle to which a control device for an internal combustion engine according to an embodiment is applied. It is a figure which shows schematic structure of an engine. It is a flowchart which shows the dither control which concerns on this embodiment. It is a figure which shows the map used when setting a dither injection amplitude amount. It is a figure for demonstrating the method of calculating | requiring the request | requirement ignition retard amount. It is a figure for demonstrating the ignition timing set at the time of the dither control at the time of in-cylinder injection. It is a figure which shows the fuel injection quantity and output torque at the time of the dither control at the time of in-cylinder injection. It is a figure for demonstrating the output torque fluctuation | variation at the time of the dither control at the time of in-cylinder injection. It is a flowchart which shows the dither control at the time of cylinder injection. It is a figure for demonstrating the basic concept of the dither control at the time of port injection. It is a figure which shows the fuel injection quantity and output torque at the time of the dither control at the time of port injection. It is a figure for demonstrating the output torque fluctuation | variation at the time of port injection dither control. It is a flowchart which shows dither control at the time of port injection. It is a figure for demonstrating the basic concept of the control which concerns on a modification. It is a flowchart which shows the control which concerns on a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Intake passage 4 Turbocharger 6 Throttle valve 8 Engine 9 Port injection valve 10 In-cylinder injection valve 11a Cylinder 12 Spark plug 13a Intake valve 13b Exhaust valve 18 Exhaust passage 19 Bypass passage 20 Wastegate valve 21 Three-way catalyst 50 ECU

Claims (5)

A control device for an internal combustion engine that performs control for warming up a catalyst provided on an exhaust passage to an internal combustion engine to which fuel is supplied from at least one of a port injection valve and a cylinder injection valve,
Dither control means for performing dither control to change the fuel injection amount so that lean combustion and rich combustion are alternately switched;
When performing the dither control, in-cylinder injection is performed on the cylinder that performs rich combustion by controlling the in-cylinder injection valve, and in the intake stroke by controlling the port injection valve. An internal combustion engine control device.   The injection control unit causes the cylinder performing the rich combustion to in-cylinder the fuel injection amount to be injected at the time of the lean combustion, and to inject the fuel injection amount to be injected at the time of the rich combustion and the lean combustion. 2. The control device for an internal combustion engine according to claim 1, wherein the fuel injection amount corresponding to the difference from the power injection amount is port-injected.   The injection control means performs port injection by controlling the port injection valve for the cylinder that performs the rich combustion when the required ignition retardation amount is equal to or less than a predetermined value, and the in-cylinder injection. 3. The control apparatus for an internal combustion engine according to claim 1, wherein in-cylinder injection is performed in an exhaust stroke by controlling a valve.   When the required ignition retardation amount is equal to or less than a predetermined value, the injection control means causes the cylinder performing the rich combustion to port-inject the fuel injection amount to be injected at the time of the lean combustion, and the rich combustion 4. The internal combustion engine according to claim 3, wherein a fuel injection amount corresponding to a difference between a fuel injection amount to be injected at a time and a fuel injection amount to be injected at the time of lean combustion is injected in the cylinder in the exhaust stroke. Control device.   When the required ignition retard amount is equal to or less than a predetermined value, the waste gate valve provided on the bypass passage that bypasses the upstream side and the downstream side of the turbocharger in the exhaust passage is controlled to open. The control device for an internal combustion engine according to claim 3 or 4, further comprising means.

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