JPH0693931A - Exhaust gas purifying device for internal combustion engine - Google Patents

Abstract

PURPOSE:To control an EGR valve opening degree to a proper real EGR rate in relation to a demanded EGR rate by controlling an EGR valve opening degree suitably on the basis of a judging signal from a purge judging means. CONSTITUTION:A rotational sensor 14 for detecting the number of engine revolutions and a load sensor 15 for detecting the load of an engine are provided as an engine operating condition detecting means. A means for detecting the control signal of a purge valve 10 is provided in a control unit 13 serving as a purge judging means. When it is judged by the control means in the control unit 13 on the basis of a detecting signal outputted from engine operating condition detecting means 14, 15 and a judging signal outputted from purge judging means 10, 13 that it is not in purge condition, an EGR valve opening degree is controlled to an exhaust reflux control (EGR) valve opening degree. On the other hand, when it is judged that it is in purge condition, the EGR valve opening degree is controlled to a degree reduced a prescribed value. It is thus possible to make an EGR rate correspond to a demand value so as to reduce HC and so on.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, and more particularly to an exhaust gas recirculation device for recirculating a part of exhaust gas to an intake system, and an unburned gas adsorbent is arranged in the exhaust system. Exhaust gas purification device

[0002]

2. Description of the Related Art Conventionally, as an exhaust gas purification device for an internal combustion engine,
It is widely known that a catalyst is arranged in the exhaust passage, and the chemical adsorption of the catalyst promotes the oxidation reaction of unburned gas in the exhaust to purify the exhaust. However, in such an exhaust gas purification device, when the exhaust gas temperature is low such as when the engine is started, the catalyst does not rise to the activation temperature and the exhaust gas purification action is significantly reduced, so the exhaust gas is sufficiently purified. I can't.

For this reason, in a specific operation region where the exhaust gas purification capability of the catalyst is insufficient, unburned gas of the exhaust gas, for example, unburned HC is adsorbed by the adsorbent arranged in the exhaust system, and the operating state is A technique has been proposed in which exhaust gas is satisfactorily purified irrespective of the above. Specifically, such a technique is such that an adsorbent is interposed in an exhaust branch passage that branches from the exhaust passage and joins again, and the exhaust branch passage is opened in a specific operating state such as when the engine temperature is low when the exhaust temperature is low. The control valve is provided.

[0004] Conventionally, there is known a technique in which unburned HC is adsorbed on an adsorbent and, after warming up of the engine, the adsorbed unburned HC is purged by exhaust gas and recirculated to an intake system. (See JP-A-62-162715).

[0005]

By the way, in an engine equipped with the above-mentioned unburned HC purging system, an exhaust gas recirculation device (hereinafter referred to as "E") for recirculating a part of exhaust gas to the intake system.
(Referred to as a GR device), the unburned HC is purged by exhaust gas and recirculated to the intake system to generate EG.
The R rate changes, and the variation in the EGR rate causes a problem of an increase in exhaust emission.

That is, since the purge gas is the exhaust gas, it itself becomes EGR, and the EGR amount by the purge gas is supplied to the intake system in addition to the EGR amount from the normal EGR system. The actual EGR rate increases, causing deterioration of HC and drivability. Therefore, it is conceivable to use an air pump or the like and introduce fresh air as the purge gas, but there are many problems to be solved such as weight increase and cost increase by providing the air pump and the like, and as a solution to the problem, I'm not satisfied.

Therefore, in view of the above-mentioned conventional problems, the present invention makes an EGR rate correspond to a required value in an exhaust gas purifying apparatus that purges unburned gas in exhaust gas with exhaust gas and recirculates it to an intake system. , HC is reduced and drivability is improved.

[0008]

Therefore, according to the first invention, an exhaust gas recirculation passage for recirculating a part of exhaust gas to the intake system,
The exhaust gas recirculation passage is provided with an exhaust gas recirculation control valve for controlling the exhaust gas recirculation amount, while the exhaust passage has an adsorbent material for adsorbing unburned gas in the exhaust gas, and a part of the exhaust gas. An exhaust gas purifying apparatus for an internal combustion engine, which is provided with a purge gas introduction passage for guiding the adsorbent to the adsorbent as a purge gas of the unburned gas adsorbed on the adsorbent, and a purge gas recirculation passage for returning the purge gas accompanied by the unburned gas to the intake system In the engine operating state detecting means, a purge determining means for determining whether or not purging is in progress, a storage means for storing an opening degree of the exhaust gas recirculation control valve which is set in advance according to the engine operating state, and the engine. Based on the detection signal output from the operating state detection means and the determination signal output from the purge determination means, when it is determined that the purging is not in progress, the storage means is stored according to the engine operating state. The exhaust gas recirculation control valve opening degree is controlled to the stored opening degree, and when it is determined that the purging is being performed, the exhaust gas recirculation control valve opening degree stored in the storage means is controlled to a value reduced by a predetermined value according to the engine operating state. And a control means for performing the operation.

A second aspect of the invention comprises an exhaust gas recirculation passage for recirculating a part of exhaust gas to an intake system, and an exhaust gas recirculation control valve interposed in the exhaust gas recirculation passage for controlling the amount of exhaust gas recirculation, while the exhaust passage is provided. A passage through which an adsorbent for adsorbing the unburned gas in the exhaust gas is inserted, a purge gas introduction passage for guiding a part of the exhaust gas to the adsorbent as a purge gas for the unburned gas adsorbed by the adsorbent, and the unburned gas In an exhaust gas purifying apparatus for an internal combustion engine, which is provided with a purge gas recirculation passage for recirculating the purge gas to the intake system, the purge gas recirculation passage is joined to the exhaust gas recirculation passage upstream of the exhaust gas recirculation control valve.

[0010]

In the first aspect of the present invention, it is determined whether or not purging is being performed. If the purging is not being performed, the EGR valve opening is read from a normal EGR map provided as a storage means, and this EGR valve opening is determined. Control, execute the normal EGR control, and if purging is in progress, for example,
As a function of the control means, the EGR valve opening is read from the EGR map for purging in which the opening is set to be smaller than the normal EGR valve opening in consideration of the purge gas recirculation, and the EGR valve opening is controlled. Since the normal EGR control is executed, the E from the normal EGR system is
Even if the EGR amount by the purge gas is supplied to the intake system in addition to the GR amount, the actual EG appropriate for the required EGR rate is obtained.
The R rate can be controlled, and HC can be reduced and drivability can be improved.

In the second invention, the purge gas flow rate and E
Since the total recirculation gas flow rate including the GR flow rate is controlled by the exhaust gas recirculation control valve, it is possible to control the actual EGR rate to the proper EGR rate with respect to the required EGR rate.
Can be reduced and drivability can be improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. In FIG. 1 showing the system configuration of an embodiment of the first invention, an exhaust manifold 2 and an intake manifold 3 of an internal combustion engine (hereinafter referred to as engine) 1 are shown.
And are communicated with each other via the EGR passage 4 that recirculates a part of the exhaust gas to the intake system. In the middle of this EGR passage 4, EG
A control valve (hereinafter referred to as an EGR valve) 5 that controls the R amount is provided.

On the other hand, there is provided an exhaust branch passage 7 that branches from a part of the exhaust passage 6 connected to the exhaust manifold 2 and then joins again, and the branch passage 7 contains unburned HC and the like in the exhaust. An adsorbent 8 such as activated carbon for adsorbing the unburned gas is inserted. Branch passage 7 on the upstream side of the adsorbent 8
The intake manifold 3 is communicated with the intake manifold 3 through a purge gas recirculation passage 9. This purge gas recirculation passage 9
A purge valve 10 for opening and closing the passage 9 is provided in the middle of the process.

A switching valve 11 for selectively opening and closing the exhaust passage 6 and the branch passage 7 is provided at a branch portion of the branch passage 7 of the exhaust passage 6. Here, a water temperature sensor 12 for detecting the engine cooling water temperature is provided as an operation state detecting means for detecting a cold operation and a warm up operation of the engine 1, and a detection signal output from the water temperature sensor 12 is a control signal. Input to the unit 13. The control unit 13 controls switching of the switching valve 11 and opening / closing of the purge valve 10 based on a detection signal output from the water temperature sensor 12 to control whether unburned gas is adsorbed or purged. The purge control means for controlling is installed by software.

Here, when the engine 1 is cold such as when starting, the switching valve 11 closes the exhaust passage 6 to open the branch passage 7, while closing the purge valve 10. In this state, all the exhaust gas containing a large amount of unburned HC and the like flows to the adsorbent 8 through the branch passage 7, and the unburned HC and the like in the exhaust gas is adsorbed on the adsorbent 8
Trapped in the atmosphere and prevented from being released into the atmosphere. As the engine 1 warms up gradually, the switching valve 11 closes the branch passage 7, opens the exhaust passage 6, and opens the purge valve 10. In this state, the exhaust gas is discharged through the exhaust passage 6, and at the same time, a part of the exhaust gas flows in from the downstream side of the adsorbent 8 and flows backward through the adsorbent 8 into the branch passage 7 and is trapped in the adsorbent 8. The unburned gas is separated, flows through the purge gas recirculation passage 9 together with the unburned gas, and is introduced into the intake manifold 3.

On the other hand, a rotation sensor 14 for detecting the engine speed and a load sensor 15 for detecting the engine load are provided as the engine operating state detecting means.
The detection signals output from 4 and 15 are input to the control unit 13. Further, a means for detecting a control signal of the purge valve 10 is provided in the control unit 13 as a purge determining means for determining whether or not purging is being performed.

Then, the storage means for storing the opening of the EGR valve 5 which is set in advance according to the engine operating state, the detection signals output from the rotation sensor 14 and the load sensor 15, and the purge valve control signal detection means are output. When it is determined that purging is not in progress based on the detected signal, the EGR valve opening degree stored in the storage means is controlled according to the engine speed and load, and when it is determined that purging is in progress, the engine is opened. The control unit 13 is equipped with a control means for controlling the opening degree of the EGR valve stored in the storage means by a predetermined value in accordance with the rotation speed and the load in a software manner.

That is, the EGR valve 5 opening degree is stored in advance as an EGR valve depending on the engine speed and the load.
The control unit 13 is equipped with a normal EGR map (see FIG. 2) in which the range of the opening value of the valve 5 is assigned by software. Further, the control unit 13 is equipped with a purging EGR map (see FIG. 3) in which a region of the opening degree value of the EGR valve 5 is assigned in advance by software in accordance with the engine speed and the load.

The opening degree value of the EGR valve 5 assigned to the purge EGR map shown in FIG. 3 is set smaller than the opening degree value of the EGR valve assigned to the normal EGR map shown in FIG. Therefore, the control means, based on the detection signal output from the rotation sensor 14 and the load sensor 15 and the detection signal output from the purge valve control signal detection means, determines that the engine speed and the load are not in the purging state. The opening value of the EGR valve 5 is read out by referring to the normal EGR map, and the EGR valve 5 is adjusted so as to have the read opening value of the EGR valve 5.
When the purge is determined to be in progress, the opening value of the EGR valve according to the engine speed and the load is read by referring to the purge EGR map, and the read EGR valve 5 is opened. A control signal is output to the EGR valve 5 so as to obtain a frequency value.

The operation of the control means will be described with reference to the flowchart of FIG. In the flowchart,
In step 1 (indicated as S1 in the figure; hereinafter the same), the control signal of the purge valve 10 is detected, and in step 2,
Based on the control signal of the purge valve 10, the purge valve 1
It is determined whether 0 is open or closed, that is, whether purging or not purging. If it is determined that the purge valve 10 is closed and purging is not in progress, the routine proceeds to step 3, where the normal EGR map is referred to and the opening value of the EGR valve 5 according to the engine speed and load at that time is read. Read out. If it is determined that the purge valve 10 is open and purging is in progress, the process proceeds to step 4 and the purge EG
With reference to the R map, the opening value of the EGR valve 5 corresponding to the engine speed and the load at that time is read.

In step 5, a control signal is output to the EGR valve 5 so that the opening value of the EGR valve 5 read in step 3 or 4 is reached, and the EGR valve 5 is operated. According to such an embodiment, the purge valve 1
A control signal of 0 is detected to determine whether or not purging is in progress. If purging is not in progress, EG is determined from the normal EGR map.
The R valve opening is read out, the EGR valve opening is controlled to this value, and normal EGR control is executed. When purging is in progress, the flow rate of purge gas is taken into consideration to reduce the EGR valve opening from the normal EGR valve opening. EGR for purge set to different opening
Since the EGR valve opening is read from the map and the EGR valve opening is controlled to execute the normal EGR control, the EGR amount from the purge gas is added to the intake system in addition to the EGR amount from the normal EGR system. Even if supplied, the required EGR rate can be controlled to a proper actual EGR rate, and HC can be reduced and drivability can be improved.

Further, since it is not necessary to provide an air pump or the like, there is no problem to be solved such as increase in weight and increase in cost.
It is a satisfactory solution to the problem. still,
In the above embodiment, a means for detecting the control signal of the purge valve 10 is provided as the purge determination means for determining whether or not the purge valve 1 is used.
0 may be provided with a means for detecting the opening.

Alternatively, as shown in FIG. 5, a flow meter 16 for measuring the flow rate of the purge gas is provided in the purge gas recirculation passage 9, and a flow rate detection signal output from this flow meter 16 is input to the control unit 13. The operation of the exhaust gas recirculation amount control means in the control unit 13 is as shown in the flow chart of FIG. 6, and in step 11, the normal EGR map is referred to and the engine speed and load at that time are determined. The opening value of the EGR valve 5 is read out, and in step 12, the flow rate signal from the flow meter is detected. In step 13, it is determined whether the detected flow rate value is 0,
If the detected flow rate value is 0, that is, if it is determined that purging is not in progress, the process proceeds to step 14, and a control signal is output to the EGR valve 5 so that the opening value of the EGR valve 5 read in step 11 is reached. Then, the EGR valve 5 is operated. Further, when the detected flow rate value is not 0, that is, when it is determined that the purge is being performed, the process proceeds to step 15 and the EGR valve 5 opening value read in step 11 is reduced and corrected according to the flow rate at that time. Then, in step 14, a control signal is output to the EGR valve 5 so that the corrected opening value of the EGR valve is obtained, and the EGR valve 5 is operated.

Next, an embodiment of the second invention will be described with reference to FIG. 7 showing the system configuration. That is, in the figure
The exhaust manifold 22 and the intake manifold 23 of the engine 21 are communicated with each other via an EGR passage 24, and an EGR valve 25 is provided in the middle of the EGR passage 24. On the other hand, as the purge gas introduction passage,
An exhaust branch passage 27 is provided that branches from the middle of the exhaust passage 26 and then joins again. The exhaust branch passage 27 has an adsorbent 28 such as activated carbon that adsorbs unburned gas such as unburned HC in the exhaust. Is installed.

Exhaust branch passage 27 upstream of the adsorbent 28
A purge gas recirculation passage 29 is provided that branches from the above and joins the EGR passage 24 on the upstream side of the EGR valve 25. At the connection between the EGR passage 24 and the purge gas recirculation passage 29, a passage opening only the EGR passage 24, and E
A flow passage switching valve 30 is provided for switching to a flow passage that opens both the GR passage 24 and the purge gas recirculation passage 29. As the switching valve 30, for example, as shown in FIG. 8, two valve bodies 30a and 30b which are provided in the EGR passage 24 and the purge gas recirculation passage 29 and are interlocked with each other.
It suffices to use one having a configuration having.

An exhaust branch passage 27 of the exhaust passage 26 is also provided.
A flow passage switching valve 31 that selectively switches between a flow passage that opens the exhaust passage 26 and a flow passage that opens the branch passage 27 is interposed in the branch portion of the. Next, the operation of this embodiment will be described with reference to FIG. When the engine 21 is cold, such as when the engine 21 is started, the switching valve 30 switches to a flow path that opens only the EGR passage 24 (see FIG. 8A), and at the same time, the switching valve 31 switches to a flow passage that opens the branch passage 27. .

Therefore, the exhaust gas flows into the EGR passage 24 and the branch passage 27. Unburned H in the exhaust flowing through the branch passage 27
C is trapped by the adsorbent 28 and is prevented from being released into the atmosphere. The exhaust gas that has flowed through the EGR passage 24 is returned to the intake manifold 23 and is used for combustion.

The above exhaust flow is the adsorption process. On the other hand, when the engine 21 gradually warms up, the switching valve 31 first switches the exhaust passage 26 to the open passage. After that, the EGR passage 24 is opened by the switching valve 30.
Both of the purge gas recirculation passage 27 and the purge gas recirculation passage 27 are switched to open channels (see FIG. 8B).

Therefore, the exhaust gas flows into the EGR passage 24 and the exhaust passage 26. The exhaust gas flowing through the exhaust passage 26 is discharged as it is, and a part of the exhaust gas flowing through the exhaust passage 26 is branched from the branch passage 27 and flows to the adsorbent 28.
The unburned HC adsorbed on the exhaust gas is desorbed (purged) and flows into the EGR passage 24, and the exhaust gas containing the unburned HC flowing through the EGR passage 24 is recirculated to the intake manifold 23 for combustion.

The above exhaust flow is the purge process.
After the above purging process is completed, the switching valve 30 switches the flow path to open only the EGR passage 24.
In such a configuration, the EGR amount flowing through the EGR passage 24 is controlled by the EGR valve 25 whose opening degree is adjusted based on the operating state of the engine 21.

According to the above configuration, the purge gas flow rate and the E
Since the total recirculation gas flow rate including the GR flow rate can be controlled by the EGR valve 25, the actual EGR rate can be controlled to a proper actual EGR rate with respect to the required EGR rate, and HC is reduced and drivability is improved. be able to. Further, according to such an embodiment, there is an advantage that a simple passage structure having only three valves is required.

FIG. 10 shows another embodiment of the second invention. In the figure, an exhaust branch passage 27 is provided as a purge gas introduction passage, which branches from a part of the exhaust passage 26 and then joins again. The exhaust branch passage 27 has unburned gas such as unburned HC in the exhaust gas. Adsorbent such as activated carbon that adsorbs carbon 2
The structure in which 8 is interposed is the same as that of the embodiment of FIG.

An EGR passage 34 is provided which branches from the branch passage 27 on the upstream side of the adsorbent 28 and merges with the intake manifold 23 of the engine 21, and an EGR valve 25 is interposed in the EGR passage 34. Further, a purge gas recirculation passage 39 is provided which branches from the branch passage 27 on the downstream side of the adsorbent 28 and joins with the EGR passage 34 on the upstream side of the EGR valve 25.

Exhaust passage 26 in parallel with the branch passage 27
An opening / closing valve 32 is interposed in the. Further, the branch passage 27 is provided at the connecting portion between the branch passage 27 and the EGR passage 34.
A flow rate control valve 33 for controlling the flow rate of the exhaust gas flowing through is installed. Further, at a connection portion between the branch passage 27 and the purge gas recirculation passage 39, a passage switching valve capable of switching the passage so that the exhaust gas passing through the adsorbent 28 selectively flows into the exhaust passage 26 and the purge gas recirculation passage 39. 35 is interposed.

Next, the operation of this embodiment will be described with reference to FIG. When the engine 21 is cold, such as when the engine 21 is started, the opening / closing valve 32 first closes the exhaust passage 26 that is in parallel with the branch passage 27. Next, the flow rate control valve 33 is controlled to a predetermined opening, and the switching valve 35 is set to the adsorbent 2.
The exhaust gas that has passed through 8 is switched to flow into the exhaust passage 26.

Therefore, the exhaust gas flows into the EGR passage 34 and the branch passage 27. Unburned H in the exhaust flowing through the branch passage 27
C is trapped by the adsorbent 28 and is prevented from being released into the atmosphere. The exhaust gas that has flowed through the EGR passage 34 is returned to the intake manifold 23 and is used for combustion.

The above exhaust flow is the adsorption process. On the other hand, when the engine 21 is gradually warmed up, first, the exhaust passage 2 which is arranged in parallel with the branch passage 27 by the opening / closing valve 32.
6 is opened, and the switching valve 35 is switched so that the exhaust gas passing through the adsorbent 28 flows into the purge gas recirculation passage 39 (the flow passage to the exhaust passage 26 is closed).

Therefore, the exhaust gas flows into the exhaust passage 26 and is discharged as it is, and a part of the exhaust gas branches into the EGR passage 34 and the branch passage 27. The exhaust gas flowing through the branch passage 27 desorbs (purges) the unburned HC adsorbed by the adsorbent 28, flows into the purge gas recirculation passage 39, joins the exhaust gas flowing through the EGR passage 34, and recirculates to the intake manifold 23. And burned.

The above exhaust flow is the purge process.
After the above purge process is completed, the flow control valve 3
The opening degree in the direction of flowing into the adsorbent 28 of No. 3 is set to 0, and
The switching valve 35 remains in the purge stroke state (closed state with the exhaust passage 26). In this embodiment as well, the total recirculation gas flow rate, which is a combination of the purge gas flow rate and the EGR flow rate, can be controlled by the EGR valve 25, so that the actual EGR rate can be controlled to an appropriate actual EGR rate with respect to the required EGR rate. Can be reduced and drivability can be improved. Further, according to this embodiment, it is necessary to provide four valves, but there is an advantage that the control for keeping the EGR pressure difference constant is easy.

As described above, the present invention has been described with reference to the specific embodiments, but the present invention is not limited to this, and a person skilled in the art can attach the present invention to the present invention. Without departing from the scope of the appended claims
It should be noted that various changes and modifications are possible.

[0041]

As described above, according to the first aspect of the present invention, when it is determined that purging is not in progress based on the determination signal output from the purge determination means, it is stored according to the engine operating state. The exhaust gas recirculation control valve opening is controlled to a value obtained by subtracting a predetermined value from the stored exhaust gas recirculation control valve opening according to the engine operating state when it is determined that purging is in progress. Even if the EGR amount from the purge gas is supplied to the intake system in addition to the EGR amount from the EGR system, it is possible to control the actual EGR rate to a proper actual EGR rate with respect to the required EGR rate, thereby reducing HC and drivability. It is possible to improve.

According to the second invention, the purge gas flow rate and the E
Since the total recirculation gas flow rate including the GR flow rate is controlled by the exhaust gas recirculation control valve, it is possible to control the actual EGR rate to the proper EGR rate in the same manner, thereby reducing HC and operating. It is possible to improve the sex.

[Brief description of drawings]

FIG. 1 is a system diagram of an embodiment of the first invention.

FIG. 2 is a normal EGR map in the above embodiment.

FIG. 3 is an EGR map for purging in the same embodiment.

FIG. 4 is a flowchart for explaining the operation of the above embodiment.

FIG. 5 is a system diagram of another embodiment.

FIG. 6 is a flowchart explaining the operation of another embodiment of the above.

FIG. 7 is a system diagram of an embodiment of the second invention.

FIG. 8 is a configuration diagram of a switching valve of the above embodiment.

FIG. 9 is a diagram for explaining the operation of the above embodiment.

FIG. 10 is a system diagram of another embodiment.

FIG. 11 is a diagram for explaining the operation of another embodiment of the above.

[Explanation of symbols]

 1 engine 2 exhaust manifold 3 intake manifold 4 EGR passage 5 EGR valve 6 exhaust passage 7 exhaust branch passage 8 adsorbent 9 purge gas recirculation passage 10 purge valve 11 switching valve 13 control unit 14 rotation sensor 15 load sensor 16 flow meter 21 engine 22 exhaust manifold 23 intake manifold 24 EGR passage 25 EGR valve 26 exhaust passage 27 exhaust branch passage 28 adsorbent 29 purge gas recirculation passage 34 EGR passage 39 purge gas recirculation passage

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display area F01N 9/00 Z

Claims (2)

[Claims] 1. An exhaust gas recirculation passage that recirculates a part of exhaust gas to an intake system, and an exhaust gas recirculation control valve that is interposed in the exhaust gas recirculation passage to control the amount of exhaust gas recirculation. A passage having an adsorbent for adsorbing the unburned gas, a purge gas introduction passage for guiding a part of exhaust gas to the adsorbent as a purge gas for the unburned gas adsorbed by the adsorbent, and a purge gas accompanied by the unburned gas In an exhaust gas purification apparatus for an internal combustion engine, which is provided with a purge gas recirculation passage that recirculates air into the intake system, engine operating state detecting means, purge determining means for determining whether purging is in progress, Based on the storage means for storing the opening degree of the exhaust gas recirculation control valve set by the above, the detection signal output from the engine operating state detection means and the determination signal output from the purge determination means, purging is not performed. When it is determined that the exhaust gas recirculation control valve opening is stored in the storage unit according to the engine operating state, it is stored in the storage unit according to the engine operating state when it is determined to be purging. An exhaust emission control device for an internal combustion engine, comprising: a control unit that controls the opening of the exhaust gas recirculation control valve to a value that is reduced by a predetermined value. 2. An exhaust gas recirculation passage that recirculates a part of exhaust gas to an intake system, and an exhaust gas recirculation control valve that is interposed in the exhaust gas recirculation passage to control the amount of exhaust gas recirculation. A passage having an adsorbent for adsorbing the unburned gas, a purge gas introduction passage for guiding a part of exhaust gas to the adsorbent as a purge gas for the unburned gas adsorbed by the adsorbent, and a purge gas accompanied by the unburned gas In an exhaust gas purification apparatus for an internal combustion engine, which is provided with a purge gas recirculation passage for recirculating the exhaust gas to an intake system, the purge gas recirculation passage is joined to an exhaust gas recirculation passage upstream of an exhaust gas recirculation control valve. apparatus.