JP2008240675A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimize air fuel ratio for prevention of a drop of turbocharger rotation speed and rich spike control during rich control of a NOx emission control catalyst in an internal combustion engine having an exhaust gas passage passing through a turbocharger and an exhaust passage not passing through the exhaust passage. <P>SOLUTION: A control device for an internal combustion engine performs rich spike control for temporally enriching air fuel ratio for reducing NOx stored in the NOx storage catalyst. Each cylinder of the internal combustion engine includes a first exhaust valve communicating to an exhaust passage passing through the turbocharger and a second exhaust valve communicating to the exhaust passage not passing through the turbocharger. Internal EGR quantity fluctuates due to difference of back pressure between a first and a second exhaust passages, NOx quantity entering the NOx emission control catalyst fluctuates, and slippage of controlled variable of rich spike is generated. Internal EGR quantity is estimated, and controlled variable is corrected and optimized based on that. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to exhaust purification control of an internal combustion engine having a turbocharger.

  There is known a turbocharged engine in which one of a plurality of exhaust valves provided in a cylinder is connected to an exhaust passage through a turbocharger and the other is connected to the exhaust passage without going through a turbocharger. As an engine of this type, for example, the engine described in Patent Document 1 closes an exhaust valve that communicates with the turbocharger in the second half of the exhaust stroke, and closes an exhaust valve that does not communicate with the turbocharger in the first half of the exhaust stroke. Patent Document 2 describes a technique for stopping one exhaust valve in each cylinder in a closed state using an electromagnetically driven valve.

  On the other hand, in a configuration in which a NOx occlusion reduction type catalyst is provided in the exhaust system in a supercharged lean burn engine or the like, rich control that temporarily makes the air-fuel ratio rich in order to reduce the stored NOx (also called “rich spike control”) .) Is known to do. However, in an engine having a configuration such as Patent Document 1, the exhaust gas amount to the turbocharger side may decrease during rich control, and the turbocharger rotational speed may drop, resulting in reduced performance. Further, during rich control, the internal EGR amount may change due to blow-through that occurs in the exhaust passage on the side that does not pass through the turbocharger or the change in back pressure of the turbocharger, resulting in a deviation in the air-fuel ratio during rich control.

JP-A-10-89106 JP 2000-73790 A

  The present invention has been made in view of the above points. An internal combustion engine having an exhaust valve connected to an exhaust passage connected to a turbocharger and an exhaust valve connected to the exhaust passage without passing through the turbocharger in each cylinder. An object of the present invention is to prevent the turbocharger speed from decreasing and optimize the air-fuel ratio for rich spike control during rich control of the NOx storage reduction catalyst.

  In one aspect of the present invention, a plurality of first exhaust valves connected to a first exhaust passage communicating with a turbine of a turbocharger and a second exhaust valve connected to a second exhaust passage not passing through the turbine. An internal combustion engine control device comprising: a cylinder; a third exhaust passage formed by joining the first and second exhaust passages; and a NOx purification catalyst provided in the third exhaust passage. Rich spike control means for performing rich spike for temporarily enriching the air-fuel ratio for NOx reduction in the purification catalyst, internal EGR amount estimation means for estimating the internal EGR amount in the cylinder, and the estimated internal EGR amount Correction means for correcting the control amount of the rich spike.

  The control apparatus for an internal combustion engine performs rich spike control for temporarily enriching the air-fuel ratio in order to reduce NOx stored in the NOx purification catalyst. Each cylinder of the internal combustion engine has a first exhaust valve that communicates with an exhaust passage that passes through the turbocharger, and a second exhaust valve that communicates with an exhaust passage that does not pass through the turbocharger. Therefore, the internal EGR amount fluctuates due to a difference in the back pressure between the first and second exhaust passages, and as a result, the amount of NOx entering the NOx purification catalyst fluctuates, resulting in a deviation in the rich spike control amount. . Therefore, the internal EGR amount is estimated, and the rich spike control amount is corrected and optimized based on the estimated internal EGR amount.

  In a preferred aspect, the correction means corrects the control amount so that the NOx reduction amount increases as the estimated internal EGR amount decreases. In a preferred example, the control amount includes at least one of the time and interval of fuel injection by rich spike.

  In another aspect of the present invention, a plurality of first exhaust valves connected to a first exhaust passage communicating with a turbine of the turbocharger and a second exhaust valve connected to a second exhaust passage not passing through the turbine. An internal combustion engine control device comprising: a cylinder; a third exhaust passage formed by joining the first and second exhaust passages; and a NOx purification catalyst provided in the third exhaust passage. Rich spike control means for performing a rich spike for temporarily enriching the air-fuel ratio for NOx reduction in the purification catalyst, and closing the second exhaust valve while the rich spike control means is executing the rich spike And an exhaust valve control means for controlling to the side.

  The control apparatus for an internal combustion engine performs rich spike control for temporarily enriching the air-fuel ratio in order to reduce NOx stored in the NOx purification catalyst. Here, when the throttle valve is controlled to the closed side in order to prevent torque fluctuation due to air-fuel ratio enrichment during a rich spike, the intake air amount decreases and the turbocharger rotational speed decreases. Therefore, during rich spike execution, the second exhaust valve on the exhaust passage side that does not pass through the turbocharger is controlled to the closed side to secure the amount of exhaust gas on the exhaust passage side that passes through the turbocharger, and the rotation of the turbocharger. Prevents a drop in numbers.

  In one aspect of the control apparatus for an internal combustion engine, the exhaust valve control means includes a throttle valve control means for controlling a throttle valve to a closed side while the rich spike control means is executing a rich spike. The second exhaust valve is controlled to the closed side a predetermined time before the throttle valve control means controls the throttle valve to the closed side. As a result, the influence of the exhaust valve control delay and the exhaust transport delay can be reduced, and a reduction in the turbocharger speed can be effectively prevented.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

[overall structure]
FIG. 1 shows a schematic configuration of a control device 100 for an internal combustion engine to which the present invention is applied. The control apparatus 100 for an internal combustion engine mainly includes an internal combustion engine (hereinafter referred to as “engine”) 1, an ECU (Engine Control Unit) 10, a turbocharger 13, a start catalyst 21, and a NOx storage reduction catalyst ( (Hereinafter also referred to as “NSR catalyst”).

  The engine 1 is an example of a supercharged lean burn engine capable of lean combustion, and is a four-cylinder direct injection engine. Each cylinder 2 has a fuel injection valve 9, two intake valves 3, and two exhaust valves 4a and 4b. The fuel injection valve 9 injects fuel based on a control signal S2 supplied from the ECU 10.

  The intake valve 3 of each cylinder 2 is connected to the intake passage 5 via a surge tank 15. An air cleaner 11, a throttle valve 12, a compressor 13 c of a turbocharger 13, and an intercooler 14 are provided in the intake passage 5. The opening degree of the throttle valve 12 is controlled by a control signal S1 supplied from the ECU 10.

  The exhaust valve 4a of each cylinder 2 passes through the exhaust passage 6 through the turbocharger turbine 13t and then communicates with the exhaust passage 8. On the other hand, the exhaust valve 4b of each cylinder 2 communicates with the exhaust passage 8 through the exhaust passage 7 without passing through the turbine 13t. That is, the exhaust passage 6 connected to the exhaust valve 4a of each cylinder 2 merges with the exhaust passage 7 connected to the exhaust valve 4b of each cylinder 2 after passing through the turbine 13t to form an exhaust passage 8. Yes.

  An air-fuel ratio sensor (hereinafter referred to as “A / F sensor”) 25 is provided in the exhaust passage 6 at an upstream position of the turbine 13 t. Further, an A / F sensor 26 is provided in the exhaust passage 7 upstream of the joining position with the exhaust passage 8. Output signals S3 and S4 of the A / F sensors 25 and 26 are supplied to the ECU 10.

A start catalyst 21 and an NSR catalyst 22 are provided in the exhaust passage 8 in this order from the upstream side. Further, an oxygen (O ₂ ) sensor 23 is provided in the exhaust passage 8 downstream of the NSR catalyst 22. An output signal S5 of the oxygen sensor 23 is supplied to the ECU 10.

  The start catalyst 21 is composed of, for example, a three-way catalyst, and purifies exhaust gas particularly when starting the engine.

  The NSR catalyst 22 stores NOx in the exhaust gas when the air-fuel ratio is lean, and reduces the stored NOx when the air-fuel ratio is rich or stoichiometric. When the NOx occlusion amount of the NSR catalyst 22 exceeds a predetermined amount, the ECU 10 adds fuel as a reducing agent from the fuel injection valve 9 to temporarily set the air-fuel ratio to a forced rich state, thereby making the NSR catalyst 22 NOx stored in is reduced and purified. This control is called “rich spike (control)”. Specifically, the ECU 10 is based on the air-fuel ratio detected by the A / F sensors 25 and 26 provided upstream of the start catalyst 21, the oxygen concentration detected by the oxygen sensor provided downstream of the NSR catalyst 22, and the like. The air-fuel ratio of the exhaust gas is determined and rich spike control is performed.

  ECU10 is comprised including CPU, ROM, RAM, etc. which are not shown in figure, and controls an engine based on the output signal from the various sensors in a vehicle. In the present embodiment, the ECU 10 executes a rich spike that temporarily injects fuel to reduce the NOx stored in the NSR catalyst 22 to make the air-fuel ratio rich. At this time, the ECU 10 controls the opening degree of the throttle valve 12, the fuel injection amount from the fuel injection valve 9, the opening degree of the exhaust valves 4a and 4b of each cylinder 2, and the like.

  In the above configuration, the exhaust valve 4a corresponds to the first exhaust valve in the present invention, the exhaust passage 6 corresponds to the first exhaust passage, the exhaust valve 4b corresponds to the second exhaust valve, The passage 7 corresponds to a second exhaust passage. The exhaust passage 8 corresponds to a third exhaust passage, and the NSR catalyst 22 corresponds to a NOx purification catalyst. Further, the ECU 10 functions as rich spike control means, internal EGR amount estimation means, correction means, exhaust valve control means, and throttle valve control means.

[First Embodiment]
The first embodiment estimates the residual gas amount in each cylinder 2 (hereinafter referred to as “external gas recirculation (EGR) amount”) when performing the rich spike control described above. The rich spike control is optimized based on the EGR amount. In general, the internal EGR means that the gas after combustion in the previous cycle remains in the cylinder without being discharged to the exhaust port, or is once discharged but returned to the cylinder at the time of valve overlap.

  In the configuration shown in FIG. 1, there is an exhaust passage that passes through the turbocharger and an exhaust passage that does not pass through the turbocharger. Therefore, a difference occurs in the back pressure between the cylinder group that communicates with the turbocharger and the cylinder group that does not communicate with the turbocharger. . For example, in a high engine speed range, the back pressure is much higher than the boost pressure in the cylinder group leading to the turbocharger, and the internal EGR increases. When the internal EGR amount increases, the amount of exhaust gas containing NOx sent to the NSR catalyst decreases accordingly, and the NOx amount stored in the NSR catalyst also decreases. Therefore, although the NSR catalyst stores only a small amount of NOx, a rich spike is executed, which may lead to unnecessary fuel consumption deterioration. As described above, the optimum control amount in the rich spike control, that is, the fuel injection time, the fuel injection interval, the target air-fuel ratio, and the like change according to the internal EGR amount. From this point of view, in the present embodiment, the internal EGR amount is estimated when the rich spike control is executed, and the control amount in the rich spike control is corrected based on the estimation result.

  Specifically, the control amount to be corrected includes the time and interval of rich spike by rich spike control, the rich degree of air-fuel ratio (target air-fuel ratio), and the like. The “time” of the rich spike is a time during which one fuel injection is continued, and the “interval” is a time interval (interval) when performing a plurality of fuel injections. Further, “the richness of the air-fuel ratio” means how much the air-fuel ratio is set by rich spike control, and the time and interval of fuel injection are set according to this value.

  As a control amount correction method, the amount of NOx sent to the NSR catalyst (hereinafter, also referred to as “entered NOx amount”) decreases as the internal EGR amount increases. Each control amount is corrected so that the richness of the air-fuel ratio decreases so that the interval becomes longer so as to shorten. Conversely, the smaller the internal EGR amount, the greater the amount of NOx that enters the NSR catalyst. Therefore, each control is performed so that the richness of the air-fuel ratio increases so that the interval between the rich spike time becomes longer and the interval becomes shorter. The amount is corrected.

  Next, a method for estimating the internal EGR amount will be described. The internal EGR amount changes according to the operating state of the engine, specifically, the engine speed, load, valve timing, and the like. Further, the internal EGR amount also changes depending on the operating state of the turbocharger, for example, the rotational speed of the turbocharger. Therefore, the ECU 10 detects these to estimate the internal EGR amount. Specifically, the higher the engine speed, the greater the engine load, the shorter the valve overlap period, and the higher the turbocharger speed, the greater the internal EGR amount. Therefore, the relationship between these parameters and the correction coefficient of the internal EGR amount is prepared in advance by a map or the like, and the internal EGR amount is estimated by referring to the map according to the operating state of the engine and the turbocharger. Note that the above parameters are exemplary, and even if not all of them are used, the internal EGR amount may be estimated using some of them.

  As another method, the internal EGR amount may be estimated based on the amount of blow-through (also referred to as “scavenging” or “scavenging”) of the cylinder. As an example, in FIG. 1, after closing the exhaust valve 4a communicating with the turbine 13t, the exhaust valve 4b not communicating with the turbine is opened. Then, the air-fuel ratios of the exhaust passage 6 on the exhaust valve 4a side and the exhaust passage 7 on the exhaust valve 4b side are detected by the A / F sensors 25 and 26, and the blow-by amount is estimated based on the difference between the air-fuel ratios. As the blow-through amount is larger, the inside of the cylinder is scavenged, so the internal EGR amount is smaller. Therefore, if a correction coefficient for the internal EGR amount with respect to the blow-through amount is prepared with a map or the like, the internal EGR amount can be estimated based on the blow-through amount using the output signals of the A / F sensors 25 and 26.

  Next, the rich spike control according to the present embodiment will be described in detail. FIG. 2 is a flowchart of the rich spike control according to the first embodiment. This control is mainly executed by the ECU 10 based on the outputs of various sensors.

  First, the ECU 10 reads the operating state of the engine 1 and the operating state of the turbocharger 13 (step S101), and determines whether or not the engine 1 is in a lean operation (step S102). When the lean operation is not being performed (step S102; No), the process ends.

  On the other hand, when the lean operation is being performed (step S102; Yes), the ECU 10 calculates the amount of NOx entering the NSR catalyst 22 based on the operation state of the engine 1 (step S103). Specifically, a basic map showing the relationship between parameters indicating the engine operating state such as engine speed and engine load and the amount of NOx entering the NSR catalyst 22 is prepared in advance, and the ECU 10 determines the current engine speed. Then, referring to the basic map from the engine load or the like, the amount of entering NOx is calculated. This entering NOx amount is the basic entering NOx amount before correction.

  Next, the ECU 10 calculates a rich spike control amount based on the obtained incoming NOx amount (step S104). Here, the rich spike control amount includes the time and interval of fuel injection by the rich spike as described above. The rich spike control amount with respect to the entering NOx amount can be prepared by a map or the like, for example.

  Next, the ECU 10 executes an internal EGR amount estimation process (step S105). A flowchart of the internal EGR amount estimation processing is shown in FIG. First, the ECU 10 calculates an internal EGR amount correction coefficient k1 based on the rotational speed of the engine 1 (step S201), and calculates an internal EGR amount correction coefficient k2 based on the load of the engine 1 (step S202). Next, the ECU 10 calculates a correction coefficient k3 for the internal EGR amount based on the valve overlap period (step S203), and calculates a correction coefficient k4 for the internal EGR amount based on the rotational speed of the turbocharger 13 (step S204). ). Then, the ECU 10 estimates the internal EGR amount by correcting the basic amount of the internal EGR amount using the correction coefficients k1 to k4 (step S205).

  When the internal EGR amount is estimated, the process returns to FIG. 2, and the ECU 10 corrects the basic entering NOx amount obtained in step S103 using the estimated internal EGR amount (step S106). As the amount of internal EGR obtained by estimation increases, the amount of new intake air to the engine 1 decreases and the combustion temperature decreases. Since NOx generation is an endothermic reaction, the amount of NOx generated correspondingly decreases, and the amount of NOx entering the NSR catalyst 22 decreases.

  Next, the ECU 10 corrects the rich spike control amount based on the corrected input NOx amount (step S107). As a result, the rich spike control amount adapted to the input NOx amount corrected based on the internal EGR amount, specifically, the rich spike time and interval are set.

  When the rich spike control amount is obtained in this way, the ECU 10 executes rich spike processing (step S108). The details of the rich spike processing are shown in the flowchart of FIG. In the rich spike process, first, the ECU 10 determines whether or not the engine 1 is in a lean operation (step S301). If the lean operation is not being performed, the process ends.

  On the other hand, when the lean operation is being performed, the ECU 10 determines whether or not the rich spike execution condition is satisfied (step S302). As an execution condition of the rich spike, for example, the lean operation has continued for a predetermined time. When the rich spike execution condition is satisfied (step S302; Yes), the ECU 10 executes the rich spike (step S303).

  In the above example, the internal EGR amount is estimated from the engine speed, load, etc. as shown in FIG. 3, but instead of or in addition, the internal EGR amount is estimated based on the blow-by amount of the cylinder as described above. The amount of EGR may be estimated.

  As described above, in the present embodiment, when rich spike control is performed, the internal EGR amount is estimated, the NOx amount entering the NSR catalyst 22 is corrected accordingly, and the rich spike control amount is further optimized. Therefore, the internal EGR amount fluctuates due to the back pressure difference between the exhaust passage 6 passing through the turbine 13t of the turbocharger 13 and the exhaust passage 7 not passing through, the blow-through in the cylinder, etc., and the NOx amount entering the NSR catalyst 22 Even if changes, rich spike can be executed with an appropriate control amount.

[Second Embodiment]
Next, a second embodiment will be described. In the configuration shown in FIG. 1, during the rich spike control of the NSR catalyst, fuel as a reducing agent is added, so the output torque of the engine temporarily increases, and drivability may be adversely affected. In order to prevent this problem, there is a method of preventing torque fluctuation by reducing the intake air amount by controlling the throttle valve to the closed side during the rich spike control.

  However, when the throttle valve is controlled to the closed side and the intake air amount decreases, the amount of exhaust gas sent to the turbocharger also decreases, and the rotational speed of the turbocharger decreases. Since it takes time to increase the rotational speed of the turbocharger once lowered, this may lead to deterioration of drivability.

  Therefore, in the second embodiment, when rich spike control is performed, the exhaust valve 4b connected to the exhaust passage 7 that does not pass through the turbine 13t of the turbocharger 13 is controlled to the closed side, so that the turbine 13t is correspondingly reduced. The amount of exhaust gas flowing to the exhaust passage 6 is increased. This suppresses a decrease in the rotational speed of the turbocharger and prevents torque fluctuation.

  FIG. 5 shows a timing chart of the rich spike control according to the second embodiment. The ECU 10 monitors the rich spike execution condition, and issues a rich spike request at time t1 when the execution condition is satisfied. At the same time, the ECU 10 enriches the air-fuel ratio by fuel injection from the fuel injection valve 9 and controls the throttle valve 12 to the closed side. Thus, torque fluctuations due to air-fuel ratio enrichment by rich spike control are suppressed by a reduction in intake air amount by throttle valve 12 being throttled.

  Here, the ECU 10 maintains the exhaust valve 4a on the turbine 13t side of the turbocharger 13 in the open state, and controls the exhaust valve 4b on the side not passing through the turbine 13t to the closed side. Thereby, the rotation speed of the turbocharger 13 is maintained high.

  If the exhaust valve 4b on the side not passing through the turbine 13t is not controlled to be closed, as shown in the graph 31, the rotational speed of the turbocharger 13 decreases during execution of the rich spike.

  Thus, in this embodiment, at the time of rich spike control, the exhaust valve 4b on the side that does not pass through the turbine 13t of the turbocharger 13 is controlled to the closed side, thereby preventing a decrease in the rotational speed of the turbocharger 13.

  In this case, considering the control delay when the exhaust valve 4b is driven to the closed side and the transport delay of the exhaust, the timing for controlling the exhaust valve 4b to the closed side is closed according to the rich spike request. It is preferable to precede the timing of control to the side. In the example of FIG. 5, the ECU 10 controls the exhaust valve 4b to the closing side at a timing earlier than the time t1 at which the throttle valve 12 is controlled to the closing side. In actuality, the ECU 10 controls the exhaust valve 4b to the closed side a little before the rich spike execution condition is satisfied, executes the rich spike after a predetermined time ΔT1 has elapsed, and the throttle. This is realized by controlling the valve 12 to the closed side.

  Also, when the rich spike is ended, the ECU 10 preferably returns the exhaust valve 4b to the open state before returning the throttle valve 12 to the open state. This is also to eliminate the influence of the control delay of the exhaust valve 4b and the exhaust transport delay.

  In the above control, the amount of closing the exhaust valve 4b is set to an extent necessary to suppress a decrease in the rotational speed of the turbocharger, and does not necessarily need to be fully closed.

  FIG. 6 shows a flowchart of the rich spike control according to the second embodiment. First, the ECU 10 detects the operating state of the engine 1 (step S401), and then determines whether or not the engine 1 is in a lean operation (step S402). If the lean operation is not being performed, the process ends.

  On the other hand, when the lean operation is being performed, the ECU 10 reads the rich spike control amount from a map or the like based on the operation state of the engine 1, specifically, the engine speed and the engine load (step S403). As described above, the rich spike control amount is the fuel injection time or interval of the rich spike.

  Next, the ECU 10 reads the duration of the lean state of the engine 1 (step S404), and determines that the rich spike execution condition is satisfied when the duration reaches a predetermined time (step S405; Yes). The ECU 10 first controls the exhaust valve 4b on the side not passing through the turbocharger to the closed side (step S406), and waits for the elapse of a predetermined time ΔT1. When the predetermined time ΔT1 has elapsed (step S407; Yes), the ECU 10 controls the throttle valve 12 to the closed side (step S408) and executes a rich spike (step S409).

  Next, the ECU 10 reads the rich spike duration (step S410), and determines whether or not the rich spike end time has been reached (step S411). When the end time is reached, the ECU 10 first returns the exhaust valve 4b on the side not passing through the turbocharger 13 to the open side (step S412), and waits for the elapse of a predetermined time ΔT2. When the predetermined time ΔT2 has elapsed (step S413; Yes), the throttle valve 12 is returned to the open side (step S414), and the rich spike is terminated (step S415).

  As described above, in the second embodiment, during the rich spike control, when the ECU 10 controls the throttle valve 12 to the closed side, the ECU 10 controls the exhaust valve 4b on the side not passing through the turbocharger 13 to the closed side. Suppresses the decrease in the rotation speed. Further, the timing of controlling the exhaust valve 4b is preceded by the timing of controlling the throttle valve 12, thereby preventing the influence of control delay and transport delay and more effectively suppressing the decrease in the turbocharger rotational speed. Can do.

It is a block diagram which shows schematic structure of the control apparatus of the internal combustion engine by this invention. It is a flowchart of the rich spike control by 1st Embodiment. 3 is a flowchart of an internal EGR amount estimation process shown in FIG. 2. It is a flowchart of the rich spike process shown in FIG. It is a timing chart of rich spike control by a 2nd embodiment. It is a flowchart of the rich spike control by 2nd Embodiment.

Explanation of symbols

1 Internal combustion engine
2 cylinder 3 intake valve 4a, 4b exhaust valve 5 intake passage 6, 7, 8 exhaust passage 9 fuel injection valve 10 ECU
13 Turbocharger 22 NOx Storage Reduction Catalyst 23 Oxygen Sensor 25, 26 A / F Sensor

Claims (5)

A plurality of cylinders including a first exhaust valve connected to a first exhaust passage communicating with a turbine of a turbocharger, and a second exhaust valve connected to a second exhaust passage not passing through the turbine; A control device for an internal combustion engine, comprising: a third exhaust passage formed by joining two exhaust passages; and a NOx purification catalyst provided in the third exhaust passage,
Rich spike control means for performing a rich spike for temporarily enriching the air-fuel ratio for NOx reduction in the NOx purification catalyst;
An internal EGR amount estimating means for estimating an internal EGR amount in the cylinder;
A control device for an internal combustion engine, comprising: correction means for correcting the control amount of the rich spike based on the estimated internal EGR amount.   2. The control device for an internal combustion engine according to claim 1, wherein the correction unit corrects the control amount such that the NOx reduction amount increases as the estimated internal EGR amount decreases.   3. The control apparatus for an internal combustion engine according to claim 1, wherein the control amount includes at least one of a time and an interval of fuel injection by a rich spike. A plurality of cylinders including a first exhaust valve connected to a first exhaust passage communicating with a turbine of a turbocharger, and a second exhaust valve connected to a second exhaust passage not passing through the turbine; A control device for an internal combustion engine, comprising: a third exhaust passage formed by joining two exhaust passages; and a NOx purification catalyst provided in the third exhaust passage,
Rich spike control means for performing a rich spike for temporarily enriching the air-fuel ratio for NOx reduction in the NOx purification catalyst;
An exhaust valve control means for controlling the second exhaust valve to the closed side while the rich spike control means is executing a rich spike, and a control device for an internal combustion engine. Throttle valve control means for controlling the throttle valve to the closed side while the rich spike control means is executing rich spike,
The exhaust valve control means controls the second exhaust valve to the closed side a predetermined time before the throttle valve control means controls the throttle valve to the closed side. Control device for internal combustion engine.

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