JP4826503B2 - Exhaust control device for internal combustion engine - Google Patents

Description

  The present invention relates to exhaust control of an internal combustion engine including an exhaust gas recirculation passage that recirculates exhaust gas from an exhaust passage to an intake passage.

  2. Description of the Related Art Conventionally, there is known an exhaust purification system for an internal combustion engine that is provided with a fuel addition valve for adding fuel to an exhaust passage and adds fuel for regeneration of an exhaust purification device such as a catalyst or a filter. For example, when a nitrogen oxide (NOx) occlusion reduction type catalyst is provided as an exhaust purification device, NOx is reduced by adding fuel as a reducing agent from a fuel addition valve to make exhaust rich. In addition, when a filter such as DPF (Diesel Particulate Filter) is provided as an exhaust purification device, fuel is added to regenerate particulate matter (PM) accumulated on the filter.

  On the other hand, an exhaust gas recirculation (EGR) device is known in which a part of exhaust gas discharged from an internal combustion engine to the exhaust passage is recirculated to the intake side to lower the combustion temperature and suppress the generation of NOx. In Patent Document 1, in addition to an EGR device that recirculates exhaust gas from a position upstream of the catalyst in the exhaust passage to the intake side, an exhaust gas that includes an EGR device that recirculates exhaust gas from a position downstream of the catalyst to the intake side. A purification system is described.

  Patent Document 2 describes a method of stopping the recirculation of exhaust gas by the EGR device when fuel is added to the exhaust gas for catalyst regeneration.

JP-A-2005-76456 JP 2005-282477 A

In the case of an exhaust gas purification system including an EGR device that recirculates exhaust gas from the downstream side to the intake side from the fuel addition valve as in Patent Document 1, carbon dioxide generated in the catalyst and DPF by fuel addition for catalyst regeneration control Since (CO ₂ ) goes around to the intake side and the combustion state of the internal combustion engine fluctuates and the torque fluctuates, it becomes difficult to achieve both regeneration control by fuel addition and NOx reduction by EGR. In particular, in a transient state of the internal combustion engine such as during acceleration, the intake air amount changes, and a large amount of CO ₂ is recirculated to the intake side, which may cause a malfunction such as misfire because the EGR amount exceeds the upper limit value.

  The present invention has been made in view of the above points, and in the case of including an exhaust gas recirculation device that recirculates exhaust gas downstream from a fuel addition valve provided in an exhaust passage, the catalyst regeneration control is in progress and the internal combustion engine is in a transient state. The purpose is to control the EGR amount so as not to exceed the upper limit.

In one aspect of the present invention, an exhaust control device for an internal combustion engine includes an exhaust purification device provided in an exhaust passage of the internal combustion engine, and fuel addition means provided in an upstream position of the exhaust purification device in the exhaust passage. A first exhaust gas recirculation device that recirculates exhaust gas from an upstream position of the exhaust gas purification device in the exhaust passage to an intake air side of the internal combustion engine, and an internal combustion engine from a downstream position of the exhaust gas purification device in the exhaust passage. When the regeneration control of the second exhaust gas recirculation device for recirculating exhaust gas to the intake side of the exhaust gas and the exhaust gas purification device using the fuel addition means is being performed and the internal combustion engine is in a transient state, when the total exhaust gas recirculation amount by the second exhaust gas recirculation device exceeds a predetermined upper limit value, while maintaining the exhaust gas recirculation amount of the second exhaust gas recirculation system, reducing the exhaust gas recirculation amount of the first exhaust gas recirculation system Comprising a make control means.

  In the exhaust control device for an internal combustion engine described above, an exhaust purification device such as a DPF and a NOx storage reduction catalyst is provided on the exhaust passage. Fuel addition means such as a fuel addition valve is provided upstream of the exhaust purification device. The fuel addition means can add fuel to the exhaust passage for catalyst regeneration such as PM regeneration for the DPF, NOx reduction for the NOx storage reduction catalyst, and sulfur poisoning recovery. In addition, a first exhaust gas recirculation device that recirculates exhaust gas from the upstream side of the exhaust gas purification device to the intake side and a second exhaust gas recirculation device that recirculates exhaust gas from the downstream side of the exhaust gas purification device to the intake side are provided.

During regeneration control of the exhaust purification device by adding fuel, CO ₂ is generated by the added fuel combusting with the catalyst, and this is recirculated to the intake side by the second exhaust recirculation device. In the steady state of the engine, there is no problem because the upper limit value of the exhaust gas recirculation amount (EGR amount) is set and the exhaust gas recirculation amount is controlled in consideration of the CO ₂ wraparound. However, when the engine is in a transitional state due to an acceleration request, etc., if the amount of sneak in CO ₂ increases due to changes in the intake air amount and the engine speed, etc., the EGR amount exceeds the EGR upper limit value and misfires occur. May occur. Therefore, when it is determined that the exhaust gas recirculation amount exceeds the upper limit when the engine is in a transient state during the regeneration control, the first quick response is made while maintaining the exhaust gas recirculation amount of the second exhaust gas recirculation device . By reducing the exhaust gas recirculation amount of the exhaust gas recirculation apparatus, the occurrence of misfires is prevented.

In another aspect of the present invention, an exhaust control device for an internal combustion engine includes an exhaust purification device provided in an exhaust passage of the internal combustion engine, and a fuel addition means provided in an upstream position of the exhaust purification device in the exhaust passage. A first exhaust gas recirculation device that recirculates exhaust gas from an upstream position of the exhaust gas purification device in the exhaust passage to an intake air side of the internal combustion engine, and an internal combustion engine from a downstream position of the exhaust gas purification device in the exhaust passage. When the regeneration control of the second exhaust gas recirculation device for recirculating exhaust gas to the intake side of the exhaust gas and the exhaust gas purification device using the fuel addition means is being performed and the internal combustion engine is in a transient state, When the total exhaust gas recirculation amount by the second exhaust gas recirculation device exceeds a predetermined upper limit, the exhaust gas return of the first exhaust gas recirculation device is maintained while maintaining the total exhaust gas recirculation rate of the first and second exhaust gas recirculation devices. With increasing rate, and a control means for relatively reducing an exhaust gas recirculation rate of the second exhaust gas recirculation system. In this exhaust control device, the ratio of the second exhaust gas recirculation device in the total exhaust gas recirculation amount is relatively lowered, so that the influence of CO ₂ wraparound generated by the second exhaust gas recirculation device is reduced, and the exhaust gas return is reduced. Prevents the flow rate from exceeding the upper limit. In a preferred example in this case, the exhaust control device for an internal combustion engine includes a variable turbocharger, and the control means controls the variable turbocharger to the closed side.

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

[Device configuration]
FIG. 1 is a block diagram showing a schematic configuration of an exhaust control device for an internal combustion engine according to an embodiment of the present invention. In FIG. 1, solid arrows indicate the flow of intake and exhaust, and broken arrows indicate control signals.

  In FIG. 1, an exhaust control device 100 for an internal combustion engine includes an inline 4-cylinder internal combustion engine (hereinafter referred to as “engine”) 10 having first to fourth (# 1 to # 4) cylinders. Each cylinder of the engine 10 is connected to an intake manifold 11 and an exhaust manifold 12. The engine 10 includes a fuel injection valve 15 provided in each cylinder and a common rail 14 that supplies high-pressure fuel to each fuel injection valve 15, and the fuel is in a high-pressure state on the common rail 14 by a fuel pump (not shown). Supplied in. The fuel injection amount and injection timing from the fuel injection valve 15 are controlled by a control signal S4 supplied from the ECU 7.

  In the intake passage 20 connected to the intake manifold 11, there are an air flow meter 21 that measures the amount of air flowing into the engine 10, a throttle valve 22, a compressor 23 a of the turbocharger 23, and an intercooler 24 that cools the intake air. Is provided. The detection signal S1 from the air flow meter 21 is supplied to the ECU 7. The opening degree of the throttle valve 22 is controlled by a control signal S2 supplied from the ECU 7. The turbocharger 23 is a variable nozzle type, and the opening degree is controlled based on a control signal S8 from the ECU 7.

  A turbine 23 b of a turbocharger 23 is provided in the exhaust passage 25 connected to the exhaust manifold 12. The upstream position of the turbine 23 b in the exhaust passage 25 and the downstream position from the intercooler 24 in the intake passage 20 are connected by an EGR passage 31. The EGR passage 31 is provided with an EGR valve 33 for controlling the EGR amount. The opening degree of the EGR valve 33 is controlled by a control signal S3 supplied from the ECU 7. The EGR device in which the outlet for EGR gas is located upstream of the turbine of the turbocharger is referred to as a “high pressure loop (HPL) EGR device”.

  A catalyst 36 is provided at a position downstream of the turbine 23 b in the exhaust passage 25. The catalyst 36 can be, for example, a NOx storage reduction catalyst, DPF, or the like. An exhaust throttle valve 41 is provided at a position downstream of the catalyst 36 in the exhaust passage 25. The opening degree of the exhaust throttle valve 41 is controlled by a control signal S7 supplied from the ECU 7.

  Further, an EGR passage 35 that connects a position of the exhaust passage 25 downstream of the turbine 23b and a position of the intake passage 20 upstream of the compressor 23a is provided. More specifically, the EGR passage 35 is configured to extract exhaust gas (EGR gas) from a position downstream of the catalyst 36 provided in the exhaust passage 25. The EGR passage 35 is provided with an EGR valve 37 for controlling the amount of EGR gas and an EGR cooler 39, and the opening degree of the EGR valve 37 is controlled by a control signal S6 from the ECU 7. An EGR device having an EGR gas outlet on the downstream side of the turbine of the turbocharger is referred to as a “low pressure loop (LPL) EGR device”.

  In addition to the fuel injection valve 15 provided for each cylinder, a fuel addition valve 17 for injecting fuel is provided at a position downstream of the turbine 23b in the exhaust passage 25. The amount of fuel added from the fuel addition valve 17 is controlled by a control signal S5 supplied from the ECU 7. The fuel addition valve 17 adds fuel into the exhaust gas mainly for regeneration of the catalyst 36 provided in the exhaust passage. Instead of providing the fuel addition valve at the above position, for example, the fuel addition valve may be provided at a position upstream of the turbine 23b or at the exhaust manifold 12. However, when the exhaust manifold 12 is provided, it is necessary to dispose the fuel addition valve at a position where the fuel added from the fuel addition valve is not recirculated to the intake side by the high-pressure loop EGR device.

  The ECU 7 includes a CPU, a ROM, a RAM, and the like (not shown), and comprehensively controls each element of the exhaust control device 100 for the internal combustion engine as described above.

  In the above configuration, the catalyst 36 corresponds to the exhaust gas purification device in the present invention, and the high-pressure loop EGR device configured by the EGR passage 31 and the like corresponds to the first exhaust gas recirculation device, and the low-pressure configured by the EGR passage 35 and the like. The loop EGR device corresponds to a second exhaust gas recirculation device. The fuel addition valve 17 corresponds to fuel addition means, and the ECU 7 corresponds to control means.

  FIG. 2 is an example of a map showing the operation region of the EGR device, and specifically shows the relationship between the engine speed and load and the operation regions of the high-pressure loop EGR device and the low-pressure loop EGR device.

  As shown in the figure, the ECU 7 operates only the high-pressure loop EGR device in a region where the engine speed is low and the engine load is small. On the other hand, in the region where the engine speed is high and the required load is high, the ECU 7 operates only the low-pressure loop EGR device. When the engine speed and the required load are between the operating range of the high pressure loop EGR device and the operating range of the low pressure loop EGR device, the ECU 7 operates both the high pressure loop EGR device and the low pressure loop EGR device. A region where both the high-pressure loop EGR device and the low-pressure loop EGR device are operated simultaneously is referred to as an “MPL (Mixed Pressure Loop) region”. Specifically, the ECU 7 obtains the engine speed using a crank angle sensor (not shown) or the like, and calculates the engine load based on the output of the accelerator opening sensor, the fuel injection amount, and the like. Then, control signals S3 and S6 are supplied to the EGR valves 33 and 37 to control the operations of the high pressure loop EGR device and the low pressure loop EGR device.

[First Embodiment]
Next, a first embodiment of the present invention will be described. In the first embodiment, the EGR amount reaches the upper limit value while the fuel addition is being performed from the fuel addition valve 17 for catalyst regeneration and when the internal combustion engine is in a transient state such as during acceleration. It is controlled not to exceed. In the present embodiment, it is assumed that both the HPL-EGR device and the LPL-EGR device are operating.

First, the first control according to the present embodiment will be described. In the MPL region where both the HPL-EGR device and the LPL-EGR device are operated, the sum of the EGR gas amount of the HPL-EGR device and the EGR gas amount of the LPL-EGR device (hereinafter referred to as “total EGR gas amount”). ) Does not exceed a predetermined EGR upper limit value, the EGR amount of each EGR device is controlled. However, when fuel for catalyst regeneration is added in the MPL region, CO ₂ produced by the catalyst is returned to the intake side by the low-pressure loop EGR device. For this reason, the EGR amount periodically increases by the amount of CO _{2 in} the cycle in which fuel addition is performed, and as a result, the total EGR amount may exceed a predetermined EGR upper limit value.

FIG. 3A shows this state. In FIG. 3A, the horizontal axis indicates time, and the vertical axis indicates the amount of EGR gas. Graph 50 shows the amount of HPL-EGR gas, and graph 60 shows the amount of LPL-EGR gas. As shown in the graph 60, the LPL-EGR gas amount periodically increases as indicated by reference numeral 55 due to the above-described CO ₂ wraparound. That is, the amount of LPL-EGR gas fluctuates due to the wraparound of CO ₂ through the LPL-EGR device.

  The total of the HPL-EGR gas amount and the LPL-EGR gas amount is the total EGR gas amount indicated by the broken line graph 70. A graph 80 shows the EGR upper limit value. The EGR upper limit value is an upper limit value of the allowable instantaneous value of the EGR gas amount. If the total EGR gas amount exceeds this value, misfire or the like may occur.

As can be understood from FIG. 3A, the total EGR gas amount does not exceed the EGR upper limit value unless CO ₂ wraps around. However, when the CO ₂ wraparound occurs, the total EGR gas amount exceeds the EGR upper limit value at that moment, and there is a possibility that misfire or the like may occur.

Therefore, in the present embodiment, when the total EGR amount instantaneously exceeds the EGR upper limit due to CO ₂ wraparound, the HPL-EGR gas amount is forcibly decreased. Thereby, it is prevented that the total EGR gas amount exceeds the EGR upper limit value, and the occurrence of misfire or the like is prevented. Here, the reason for reducing the HPL-EGR gas amount, not the LPL-EGR gas amount, is that the LPL-EGR device has a long path length, so the gas transportation delay is large and the response is slow. This is because the EGR device has a shorter path length and quick response than the LPL-EGR device.

FIG. 3B shows the amount of EGR gas when this control is performed. As can be seen from comparison with FIG. 3A, the LPL-EGR gas amount shown in the graph 60 is hardly changed, but the HPL-EGR gas amount shown in the graph 50 is decreased. The EGR gas amount does not exceed the EGR upper limit 80 even at the timing when the CO ₂ wraparound occurs.

  As a specific control example, the ECU 7 monitors the total EGR rate by the HPL-EGR device and the LPL-EGR device. Here, the total EGR rate is given by the following equation.

Total EGR rate = (Ghp + Glp) / Gcyl (1)
Here, “Gcyl” is the amount of intake air to the engine 10 and is given by the following equation (see FIG. 1).

Gcyl = Ga + Ghp + Glp (2)
“Ga” is the amount of fresh air passing through the air flow meter 21, “Ghp” is the amount of HPL-EGR gas, and “Glp” is the amount of LPL-EGR gas.

As understood from the equation (1), when the instantaneous value of the LPL-EGR gas amount increases due to the wraparound of CO ₂ , the total EGR rate also increases. Therefore, when the total EGR rate exceeds a predetermined EGR rate (referred to as “A%”) corresponding to the EGR upper limit value 80 shown in FIGS. 3 (A) and 3 (B), the ECU 7 performs HPL-EGR. The amount of HPL-EGR gas is forcibly decreased by controlling the opening of the EGR valve 33 of the apparatus to the closed side.

Next, the second control according to the present embodiment will be described. Even if the instantaneous value of the total EGR amount does not exceed the EGR upper limit value 80 by the above control, if the total EGR gas amount in a predetermined time increases, a problem such as misfire may still occur. This is shown in FIG. Fuel addition for catalyst regeneration is basically performed in synchronization with the crank angle. When the engine is in a transient state and the engine speed is increased, the fuel addition cycle is shortened, and the interval of CO ₂ wrap-around is shortened. In the example of FIG. 4A, when the engine transitions to a transitional state around time t0, the engine speed increases, and CO ₂ wraparound occurs multiple times during one engine cycle (= 720CA). . Thus, in the transient state, even if the instantaneous value of the total EGR gas amount does not exceed the EGR upper limit value, if the integrated value of the total EGR gas amount exceeds a certain integrated upper limit value, there is a possibility of misfire.

  Therefore, in the present embodiment, for example, the total EGR gas amount in a predetermined period such as one cycle of the engine is monitored, and when this exceeds a predetermined integrated upper limit value, the HPL-EGR gas amount is set in the same manner as in the first control. Forcibly reduce to prevent misfire.

As a specific control example, the ECU 7 monitors the intake air amount Gcyl to the engine 10 given by the above equation (2). As understood from the equation (2), when the wraparound of CO ₂ frequently occurs and the LPL-EGR amount Glp increases, the intake air amount Gcyl also increases. Therefore, the ECU 7 determines that the integrated value of the total EGR gas amount exceeds the integrated upper limit value when the change amount of the intake air amount Gcyl exceeds a predetermined ratio (“B%”), and the HPL -Controlling the opening of the EGR valve 33 of the EGR device to the closed side to forcibly reduce the amount of HPL-EGR gas.

  FIG. 5 shows a flowchart of the exhaust control according to the first embodiment. This process is periodically executed by the ECU 7.

  First, the ECU 7 determines whether or not fuel addition is being performed for the catalyst regeneration process (step S101). If fuel addition is not in progress, the process ends.

  When the fuel is being added, the ECU 7 further determines whether or not the engine is in a transient state (step S102). This determination is made based on a change in engine speed, a change in fuel injection amount, a change in accelerator opening, and the like. If the engine is not in a transient state, the process ends.

  When the engine is in a transient state, the ECU 7 calculates the total EGR rate based on the above equation (1), and determines whether or not the calculated total EGR rate exceeds the EGR rate A% (step S103). When the EGR rate A% is exceeded, the ECU 7 determines that the total EGR gas amount has exceeded the EGR upper limit as shown in FIG. 3A, and controls the EGR valve 33 to forcibly set the HPL-EGR rate. (Step S105). Note that the processing in steps S103 and S105 corresponds to the first control described above.

  On the other hand, when the total EGR rate does not exceed the EGR rate A% (step S103; No), the ECU 7 determines whether or not the change in the intake air amount Gcyl exceeds a predetermined rate B% (step S104). When the predetermined ratio B% is exceeded, the ECU 7 determines that the integrated value of the total EGR gas amount exceeds the integrated upper limit value of the EGR amount, and controls the EGR valve 33 to forcibly decrease the HPL-EGR rate. (Step S105). Note that the processing in steps S104 and S105 corresponds to the second control described above.

  As described above, in the first embodiment, when the engine is in a transient state while adding fuel for catalyst regeneration, it is determined that the instantaneous value of the EGR amount or the integrated value for a predetermined time exceeds the upper limit value. Sometimes, the EGR rate of the HPL-EGR device that responds quickly is forcibly reduced to prevent the occurrence of misfire.

[Second Embodiment]
In the first embodiment, when the engine is in a transient state while adding fuel for catalyst regeneration, when it is determined that the instantaneous value of the EGR amount or the integrated value for a predetermined time exceeds the upper limit value, the response is quick. The EGR rate of the HPL-EGR device is forcibly reduced. On the other hand, in 2nd Embodiment, the opening degree of the variable turbocharger 23 is controlled to the close side instead of decreasing the EGR rate of the HPL-EGR device. In this embodiment, it is assumed that both the HPL-EGR device and the LPL-EGR device are operating.

When the opening degree of the turbocharger 23 is controlled to the closed side, the intake air amount increases. In the turbocharger 23, the back pressure on the LPL-EGR device side decreases, and the back pressure on the HPL-EGR device side increases. As a result, the ratio of the LPL-EGR gas amount can be lowered while keeping the total EGR rate the same, and the influence of the wraparound of CO ₂ by the LPL-EGR device can be reduced.

  FIG. 6 schematically shows changes in the EGR amount and the intake air amount in this case. The left side in the figure shows a state before the control of the opening degree of the variable turbocharger, and the right side in the figure shows a state after the control. By controlling the opening of the variable turbocharger to the closed side, the intake air amount Gcyl increases. The total EGR amount also increases, but the EGR rate (= total EGR amount / intake air amount Gcyl) does not change. On the other hand, since the back pressure on the HPL-EGR device side increases and the back pressure on the LPL-EGR device side decreases, the proportion of the HPL-EGR gas amount in the total EGR gas amount increases, and the LPL-EGR gas amount The proportion of occupancy decreases.

  FIG. 7A shows the EGR rate before the control, and FIG. 7B shows the EGR rate after the control. 7A and 7B, graph 51 shows the HPL-EGR rate, graph 61 shows the LPL-EGR rate, graph 71 shows the total EGR rate, and graph 81 shows the upper limit value of the EGR rate. .

As shown in FIG. 7A, in the state before the control, when the wraparound of CO ₂ occurs, the total EGR rate exceeds the upper limit value of the EGR rate. In contrast, as shown in FIG. 7 (B), when controlled to the closing side turbo opening degree, although HPL-EGR rate increases, the LPL-EGR rate is reduced, the EGR rate by diffraction of CO ₂ The fluctuation is suppressed. More specifically, the magnitude of the CO ₂ wraparound in FIG. 7A (that is, the height of the mountain portion in the graph of the LPL-EGR rate and the total EGR rate) “X1”, FIG. 7B Since the amount of CO ₂ wraparound “X2” becomes smaller, the total EGR rate does not exceed the upper limit as a result. Thereby, generation | occurrence | production of misfire etc. is prevented.

  FIG. 8 is a flowchart of exhaust control according to the second embodiment. This process is also periodically executed by the ECU 7. Note that steps S201 to S204 in FIG. 8 are the same as steps S101 to S104 in the flowchart of the exhaust control of the first embodiment shown in FIG.

When the total EGR rate exceeds the EGR rate A% at step S203 and when the intake air amount Gcyl exceeds the predetermined rate B% at step S204, the ECU 7 sets the opening of the variable turbocharger 23 by the control signal S8. Control to the closing side (step S205). As a result, the amount of intake air increases, the proportion of the LPL-EGR gas amount decreases while maintaining the total EGR rate, and the influence of CO ₂ wraparound is reduced. As a result, the total EGR rate is prevented from exceeding the upper limit value and causing misfires and the like.

1 is a schematic block diagram of an exhaust control device for an internal combustion engine according to an embodiment. The map of an EGR area | region is shown. The change of the amount of EGR by the 1st control of a 1st embodiment is shown. The change of the EGR amount by 2nd control of 1st Embodiment is shown. It is a flowchart of the exhaust control by 1st Embodiment. The change of the amount of intake air and the EGR rate by the control of the second embodiment is shown. The change of the EGR rate by control of 2nd Embodiment is shown. It is a flowchart of the exhaust control by 2nd Embodiment.

Explanation of symbols

7 ECU
DESCRIPTION OF SYMBOLS 10 Engine 15 Fuel injection valve 17 Fuel addition valve 20 Intake passage 23 Turbocharger 25 Exhaust passage 31, 35 EGR passage 36 Catalyst 33, 37 EGR valve

Claims (3)

An exhaust control device for an internal combustion engine,
An exhaust purification device provided in an exhaust passage of the internal combustion engine;
Fuel addition means provided at an upstream position of the exhaust purification device in the exhaust passage;
A first exhaust gas recirculation device for recirculating exhaust gas from an upstream position of the exhaust gas purification device in the exhaust passage to the intake side of the internal combustion engine;
A second exhaust gas recirculation device that recirculates exhaust gas from the downstream side position of the exhaust gas purification device in the exhaust passage to the intake side of the internal combustion engine;
When the regeneration control of the exhaust purification device using the fuel addition means is in progress and the internal combustion engine is in a transient state, the total exhaust gas recirculation amount by the first and second exhaust gas recirculation devices is a predetermined upper limit value. Control means for reducing the exhaust gas recirculation amount of the first exhaust gas recirculation device while maintaining the exhaust gas recirculation amount of the second exhaust gas recirculation device. apparatus. An exhaust control device for an internal combustion engine,
An exhaust purification device provided in an exhaust passage of the internal combustion engine;
Fuel addition means provided at an upstream position of the exhaust purification device in the exhaust passage;
A first exhaust gas recirculation device for recirculating exhaust gas from an upstream position of the exhaust gas purification device in the exhaust passage to the intake side of the internal combustion engine;
A second exhaust gas recirculation device that recirculates exhaust gas from the downstream side position of the exhaust gas purification device in the exhaust passage to the intake side of the internal combustion engine;
When the regeneration control of the exhaust purification device using the fuel addition means is in progress and the internal combustion engine is in a transient state, the total exhaust gas recirculation amount by the first and second exhaust gas recirculation devices is a predetermined upper limit value. Is exceeded, the exhaust gas recirculation rate of the first exhaust gas recirculation device is increased while maintaining the total exhaust gas recirculation rate of the first and second exhaust gas recirculation devices, and the exhaust gas recirculation of the second exhaust gas recirculation device is increased. An exhaust control device for an internal combustion engine, comprising: control means for relatively reducing the rate . The exhaust control device for an internal combustion engine according to claim 2 , further comprising a variable turbocharger, wherein the control means controls the variable turbocharger to a closed side.

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