JP3468139B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine having a regenerating means for regenerating a reduction in the purifying ability of a NOx catalyst provided in an exhaust passage.

[0002]

2. Description of the Related Art In recent years, a lean-burn internal combustion engine has been put into practical use in which the internal combustion engine is operated at a lean air-fuel ratio to improve fuel efficiency. In this lean burn internal combustion engine, when operating at a lean air-fuel ratio, there is a problem that the three-way catalyst cannot sufficiently purify NOx (nitrogen oxide) in the exhaust gas due to its purification characteristics. Recently, when operating at a lean air-fuel ratio. In particular, an occlusion type NOx catalyst has been adopted which occludes NOx in exhaust gas and releases and reduces NOx occluded during operation at a stoichio or rich air-fuel ratio.

This storage-type NOx catalyst converts NOx in exhaust gas into a nitrate (X-NO ₃ ) in the excess oxygen state of an internal combustion engine.
Is a catalyst having the characteristic of simultaneously occluding and releasing the occluded NOx in the excess state of carbon monoxide (CO) to reduce it to nitrogen (N ₂ ) (at the same time, carbonate X-CO ₃ is produced). However, the fuel contains a sulfur (S) component, and this S component reacts with oxygen to produce a sulfur oxide (SO).
x), and SOx is stored as a sulfate instead of NOx in the storage type NOx catalyst instead of nitrate, and there is a problem that the purification efficiency of the catalyst is reduced. However, it has been known that the SOx stored in the catalyst is removed (S purge) by setting the air-fuel ratio to a rich state to bring the catalyst to a high temperature state. For example, in JP-A-7-217474, when the storage amount of SOx exceeds an allowable amount and the catalyst temperature is higher than a predetermined temperature, the air-fuel ratio is temporarily made rich and the temperature of the catalyst is raised to increase the SOx. Is released to restore the purification efficiency of the storage type NOx catalyst.

[0004]

However, in the above-mentioned publication, the storage type NOx catalyst which releases SOx by making the air-fuel ratio rich regardless of the operating state of the internal combustion engine is conditioned on the storage amount of SOx and the catalyst temperature. Playback control is being executed.

Therefore, for example, if the regeneration control is executed while the vehicle is in an operating state where acceleration / deceleration is repeated in a place such as an urban area, the occlusion type NOx catalyst is unlikely to reach the high temperature state necessary for releasing SOx, and the occlusion It takes a long time to regenerate the type NOx catalyst. Then, S of the occlusion type NOx catalyst
Although the Ox storage amount exceeds the allowable amount, it is not possible to properly execute the regeneration of the storage type NOx catalyst, and unnecessary fuel is injected to make the air-fuel ratio rich so that the fuel consumption is reduced. There is a problem that it worsens.

The present invention solves such a problem, and reliably suppresses NOx storage while suppressing deterioration of fuel consumption.
It is an object of the present invention to provide an exhaust gas purification device for an internal combustion engine, in which a catalyst can be regenerated.

[0007]

In the exhaust gas purifying apparatus for an internal combustion engine according to the first aspect of the present invention for achieving the above object, when the exhaust air-fuel ratio is an oxidizing atmosphere in the exhaust passage of the internal combustion engine, the exhaust gas A storage type NOx catalyst that stores NOx and releases or reduces the stored NOx in a reducing atmosphere is provided, and the degree of reduction in the purifying ability of the storage type NOx catalyst due to the sulfur component contained in the exhaust gas is detected or estimated. The purifying ability detecting means, the regenerating means for regenerating the catalytic purifying ability by raising the temperature of the occlusion type NOx catalyst and making the surroundings a reducing atmosphere, and the execution conditions of the regenerating means are changed according to the degree of decrease in the catalytic purifying ability. an execution condition changing means is provided, by operating the reproducing means when the control means execution condition of the execution condition changing means according to the catalyst purification capability reduced degree is satisfied, in this case, Line conditions change means, touch occlusion-type NOx
Vehicle speed as an execution condition according to the degree of deterioration of the purification capacity of the medium
The driving conditions based on the degree are changed . Also,
In the exhaust gas purifying apparatus for an internal combustion engine according to the invention of claim 2,
The condition change means was detected or estimated by the purification capacity detection means.
Execution conditions according to the degree of reduction in purification capacity of the storage type NOx catalyst
Based on the operating conditions of a vehicle equipped with an internal combustion engine
I am trying to change the operating conditions. According to the invention of claim 3,
In an exhaust gas purification device for an internal combustion engine, the execution condition changing means is
The internal combustion engine is installed as an execution condition according to the degree of deterioration
The operating conditions of the mounted vehicles include high-speed stable operation and steady operation.
Rolling, decelerating operation, slow acceleration operation, acceleration operation, or idle
Try to change any one of driving conditions
It In the exhaust gas purifying apparatus for an internal combustion engine according to the invention of claim 4,
The mode selecting means is an internal combustion engine when the control means is operating.
Intake stroke injection depending on engine load or engine speed
To select injection mode or compression stroke injection mode.
ing. In the exhaust gas purification device for an internal combustion engine according to the invention of claim 5,
Is the mode selection means during execution of the operation of the control means.
Secondary injection depending on the load of the internal combustion engine or the engine speed
I am trying to select the firing or ignition timing retard.
In the exhaust gas purification device for an internal combustion engine according to the invention of claim 6,
The stage is a regeneration means based on the catalyst temperature of the storage type NOx catalyst.
Feedback control hand for feedback controlling the operation
It has steps. Exhaust gas purification of an internal combustion engine according to the invention of claim 7
In the device, the feedback control means operates the regeneration means.
After a predetermined time, and the catalyst temperature is higher than the predetermined temperature
When you have feedback control.

For example, the execution condition of the regenerating means for regenerating the catalyst purifying ability according to the degree of reduction in the purifying ability of the storage type NOx catalyst is changed, that is, the regeneration is performed when the degree of reduction in the purifying ability of the storage type NOx catalyst due to the sulfur component is small. While the execution conditions of the means are made strict, the execution conditions of the regeneration means are relaxed when the degree of reduction in the purification capacity is large, and regardless of the operating state of the internal combustion engine, the occlusion type NOx catalyst stores while suppressing the deterioration of fuel efficiency. The stored NOx catalyst can be regenerated by reliably releasing the stored sulfur component.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic configuration of an exhaust gas purification apparatus for an internal combustion engine according to an embodiment of the present invention, FIG. 2 is a flowchart of S purge control by the exhaust gas purification apparatus of the present embodiment, and FIGS. FIG. 5 shows a flowchart of the deterioration determination control of the storage type NOx catalyst by the exhaust purification device of FIG. 5, and FIG. 5 is a time chart showing the time change of the poisoning S amount when the S purge is performed.

The internal combustion engine (hereinafter, referred to as an engine) of this embodiment has, for example, a fuel injection mode (operating mode).
Is a in-cylinder injection spark ignition in-line 4-cylinder gasoline engine capable of performing fuel injection in the intake stroke (intake stroke injection mode) or fuel injection in the compression stroke (compression stroke injection mode) by switching between. The in-cylinder injection type engine 11 can be easily operated at the stoichiometric air-fuel ratio (stoichio) and at the rich air-fuel ratio (rich air-fuel ratio operation), as well as at the lean air-fuel ratio (lean air-fuel ratio). (Operation) can be realized, and particularly in the compression stroke injection mode, operation with a super lean air-fuel ratio is possible.

In this embodiment, as shown in FIG.
An electromagnetic fuel injection valve 14 is attached to a cylinder head 12 of the engine 11 for each cylinder together with an ignition plug 13, and the fuel injection valve 14 can directly inject fuel into a combustion chamber 15. . This fuel injection valve 14
Is connected to a fuel supply device (fuel pump) having a fuel tank via a fuel pipe (not shown). The fuel in the fuel tank is supplied at a high fuel pressure, and this fuel is supplied from the fuel injection valve 14 to the combustion chamber 15 Inject at a desired fuel pressure inward. At this time, the fuel injection amount is determined from the fuel discharge pressure of the fuel pump and the valve opening time (fuel injection time) of the fuel injection valve 14.

An intake port is formed in the cylinder head 12 in a substantially upright direction for each cylinder, and one end of an intake manifold 16 is connected so as to communicate with each intake port. A drive-by-wire (DBW) type electric throttle valve 17 is connected to the other end of the intake manifold 16.
Is a throttle sensor 1 that detects the throttle opening θth
8 are provided. Further, the cylinder head 12 has
An exhaust port is formed in a substantially horizontal direction for each cylinder,
Exhaust manifold 1 communicating with each exhaust port
One ends of 9 are connected to each other.

The engine 11 is provided with a crank angle sensor 20 for detecting the crank angle, and the crank angle sensor 20 can detect the engine rotation speed Ne. The in-cylinder injection type engine 1 described above
No. 1 is already known, and its detailed description is omitted here.

Further, the exhaust manifold 1 of the engine 11
An exhaust pipe (exhaust passage) 21 is connected to the exhaust pipe 9, and a muffler (not shown) is connected to the exhaust pipe 21 via a small three-way catalyst 22 adjacent to the engine 11 and an exhaust purification catalyst device 23. . Then, a portion of the exhaust pipe 21 between the three-way catalyst 22 and the exhaust purification catalyst device 23 is located immediately upstream of the exhaust purification catalyst device 23, that is, immediately upstream of an occlusion type NOx catalyst 25 described later. A high temperature sensor 24 for detecting the exhaust gas temperature is provided.

The exhaust purification catalyst device 23 is a storage type NO
The three-way catalyst 26 has two catalysts, the x-catalyst 25 and the three-way catalyst 26, and the three-way catalyst 26 is the storage type NOx catalyst 25.
It is arranged on the downstream side. When the occlusion type NOx catalyst 25 has the function of a three-way catalyst, only the occlusion type NOx catalyst 25 may be used. This occlusion type N
The Ox catalyst 25 once occludes NOx in an oxidizing atmosphere, and N 2 in a reducing atmosphere containing mainly CO.
It has a function of releasing Ox and reducing it to N ₂ (nitrogen) or the like. Specifically, the occlusion-type NOx catalyst 25 is configured as a catalyst having platinum (Pt), rhodium (Rh), etc. as a noble metal, and barium (B) as an occlusion material.
Alkali metals and alkaline earth metals such as a) are adopted. NOx is provided downstream of the occlusion type NOx catalyst 25.
A NOx sensor 27 that detects the concentration is provided.

Further, an input / output device and a storage device (ROM, R
AM, non-volatile RAM, etc.), central processing unit (CPU),
An ECU (electronic control unit) 28 having a timer counter and the like is provided, and the ECU 28 performs comprehensive control of the exhaust purification system of the present embodiment including the engine 11. That is, on the input side of the ECU 28,
Various sensors such as the high temperature sensor 24 and the NOx sensor 27 described above are connected, and the detection information from these sensors is input. On the other hand, on the output side of the ECU 28, the above-mentioned spark plug 13 and fuel injection valve 14 are connected via an ignition coil.
Etc. are connected, these ignition coil, fuel injection valve 1
The optimum values such as the fuel injection amount and the ignition timing calculated based on the detection information from various sensors are output to 4 and the like. As a result, a proper amount of fuel is injected from the fuel injection valve 14 at proper timing, and the ignition plug 13 ignites at proper timing.

Actually, the ECU 28 uses the throttle opening information θth from the throttle sensor 18 and the engine rotation speed information Ne from the crank angle sensor 20 as the target in-cylinder pressure corresponding to the engine load, that is, the target average effective pressure Pe. Further, the fuel injection mode is set from a map (not shown) according to the target average effective pressure Pe and the engine speed information Ne. For example, when the target average effective pressure Pe and the engine rotation speed Ne are both small, the fuel injection mode is set to the compression stroke injection mode, and the fuel is injected in the compression stroke, while the target average effective pressure Pe increases, or When the rotation speed Ne increases, the fuel injection mode is changed to the intake stroke injection mode, and the fuel is injected in the intake stroke.

Then, from the target average effective pressure Pe and the engine speed Ne, the target air-fuel ratio (target A /
F) is set, and an appropriate amount of fuel injection is set to this target A / F.
It is decided based on. Further, the catalyst temperature Tcat is estimated from the exhaust gas temperature information detected by the high temperature sensor 24. Specifically, the high temperature sensor 24 and the occlusion type NOx catalyst 25
In order to correct an error caused by the fact that the and are arranged at a distance from each other, a temperature difference map is set in advance by an experiment or the like according to the target average effective pressure Pe and the engine rotation speed information Ne. The catalyst temperature Tcat is uniquely estimated when the target average effective pressure Pe and the engine rotation speed information Ne are determined.

The operation of the exhaust gas purifying apparatus for an internal combustion engine of this embodiment having the above-mentioned structure will be described below.

In the occlusion type NOx catalyst 25 of the exhaust purification catalyst device 23, nitrate is produced from NOx in the exhaust gas in an atmosphere with excess oxygen concentration as in the super lean combustion operation in the lean mode, so that NOx is occlusion. Exhaust gas is purified. On the other hand, in the three-way catalyst 26, the nitrate stored in the storage NOx catalyst 25 reacts with the CO in the exhaust gas in an atmosphere in which the oxygen concentration is lowered to generate a carbonate and release NOx. Therefore, the storage type NOx catalyst 25
When the storage of NOx in the NOx catalyst advances, the oxygen concentration is lowered by enriching the air-fuel ratio or performing additional fuel injection, and NOx is released from the storage-type NOx catalyst 25 to maintain the function.

By the way, the sulfur component contained in the fuel or the lubricating oil is also present in the exhaust gas, and the storage type NOx catalyst 25 stores SOx as well as NOx in the oxygen concentration excess atmosphere. That is, the sulfur component is oxidized into SOx, and a part of this SOx reacts with the NOx storage agent 25 on the storage-type NOx catalyst 25 to form a sulfate to store in the storage-type NOx catalyst 25. To do.

Further, the occlusion type NOx catalyst 25 has a function of releasing the attached SOx when the oxygen concentration decreases. That is, in an atmosphere with a reduced oxygen concentration, the occlusion type N
Part of the sulfate stored in the Ox catalyst 25 reacts with CO in the exhaust gas to generate a carbonate, and SOx is released. However, since the sulfate has a higher stability as a salt than the nitrate and is only partially decomposed in an atmosphere with a reduced oxygen concentration, the amount of the sulfate remaining in the occlusion type NOx catalyst 25 increases with time. To do. As a result, the NOx storage capacity of the storage-type NOx catalyst 25 decreases with time, and the performance of the storage-type NOx catalyst 25 deteriorates (S poisoning).

For this reason, the storage type NOx catalyst 25 adsorbs a certain amount or more of the sulfur component (SOx) and the NOx catalyst 2
When it is determined that No. 5 has deteriorated, the temperature of the catalyst is raised,
Moreover, the stored SOx is released (regeneration means) by setting the air-fuel ratio to a reducing atmosphere (S purge operation).

That is, in the S purge control, as shown in FIG. 2, first, in step S11, it is determined whether or not the NOx catalyst 25 is deteriorated by S (sulfur), that is, this storage type NOx.
It is determined whether or not the amount of SOx stored in the catalyst 25 (poisoned S amount Qs) has reached a predetermined S purge determination reference value. Here, the poisoning S amount Qs is a value obtained by estimation,
Hereinafter, a method for estimating the poisoning S amount Qs (purification ability detecting means) will be briefly described.

The poisoning S amount Qs is basically set based on the fuel injection integrated amount Qf, and is calculated by the following equation for each execution cycle of the fuel injection control routine (not shown). Qs = Qs (n−1) + ΔQf · K−Rs (1) Here, Qs (n−1) is the previous value of the poisoning S amount, and Δ
Qf indicates the fuel injection integrated amount per execution cycle, K indicates the correction coefficient, and Rs indicates the regeneration S amount per execution cycle.

That is, the present poisoning S amount Qs is corrected by adding the correction amount K to the fuel injection integrated amount ΔQf per execution cycle, and the regenerated S amount Rs per execution cycle is subtracted from this integrated value. Required by that. This correction coefficient K
Is the S poisoning coefficient K1 according to the air-fuel ratio A / F, the S poisoning coefficient K2 according to the S content in the fuel, and the S depending on the catalyst temperature Tcat, for example, as shown in the following equation (2). Poisoning coefficient K3
It consists of the product of three correction factors. K = K1, K2, K3 (2)

Further, the reproduction S amount Rs per execution cycle is calculated from the following equation (3). Rs = α · R1 · R2 · dT (3) where α is the regeneration rate (set value) per unit time, dT is the execution cycle of the fuel injection control routine, and R1 and R2 Indicates the regeneration capacity coefficient corresponding to the catalyst temperature Tcat and the regeneration capacity coefficient corresponding to the air-fuel ratio A / F, respectively.

Then, in step S11, it is determined whether or not the poisoning S amount Qs of the storage type NOx catalyst 25 has reached the S purge determination reference value. In the present embodiment, the storage type NOx is determined. The degree of purification capacity reduction is estimated by comparing the poisoning S amount Qs of the catalyst 25 with a plurality of S purge determination reference values, and the condition for regenerating the catalyst purification capacity (S purge) is changed according to the degree of purification capacity reduction. (Execution condition changing means)
The ECU 28 (control means) executes the S purge when the execution condition is satisfied.

Here, the deterioration determination control of the occlusion type NOx catalyst 25 will be described. In this deterioration determination control, a large number of S purge determination reference values A1, A21, A22, A3, A
4, A5, A6, A7, A8, and the relationship of each S purge determination reference value is A1 <A21 <A22 <A3 <A4 <A
5 <A6 <A7 <A8.

In the deterioration determination control of the occlusion type NOx catalyst 25, as shown in FIGS. 3 and 4, in step S31, the poisoning S amount Qs of the occlusion type NOx catalyst 25 obtained as described above is the S purge determination. It is determined whether the reference value A1 or more. When it is determined that the poisoning S amount Qs has not reached the determination reference value A1, the routine is exited without doing anything. On the other hand, when it is determined that the poisoning S amount Qs has reached the determination reference value A1, the process proceeds to step S32, and it is determined whether the poisoning S amount Qs is the S purge determination reference value A21 or more. When it is determined in step S32 that the poisoning S amount Qs has not reached the determination reference value A22, the process proceeds to step S48 and is estimated from the exhaust temperature information detected by the high temperature sensor 24. It is determined whether the catalyst temperature Tcat is equal to or higher than a predetermined high temperature TcatH (for example, 650 ° C.) at which S purge is possible (execution condition).
Here, the catalyst temperature Tcat is S purgeable catalyst temperature TcatH
If so, the process proceeds to step S12 (see FIG. 2) and the control mode is switched to the S purge mode. That is, in this case, since the occlusion-type NOx catalyst 25 is originally at a high temperature at which S purge can be performed, the overall A / F is made rich without actually performing the control for increasing the catalyst temperature, which will be described later. S purging can be performed by simply performing the S purging, and the deterioration of fuel due to the S purging can be minimized. If the temperature is lower than the S purgeable catalyst temperature TcatH, this routine is exited.

On the other hand, in step S32, the poisoning S amount Qs
When it is determined that the value reaches the determination reference value A21, the process proceeds to step S33, and it is determined whether the poisoning S amount Qs is equal to or more than the S purge determination reference value A22. When it is determined in step S33 that the poisoning S amount Qs has not reached the determination reference value A22, the process proceeds to step S47, and the average vehicle speed V in the past predetermined time is the predetermined vehicle speed V ₂₁ (eg, , 80 km / h) or more for steady operation (execution condition). Here, if the average vehicle speed V is the steady operation of the predetermined vehicle speed V ₂₁ or more, the process proceeds to step S12, and the control mode is switched to the S purge mode, and if not, the step S12.
At 48, it is determined whether the catalyst temperature Tcat is equal to or higher than the start catalyst temperature Tcat1.

Then, in step S33, the poisoning S amount Q
When it is determined that s has reached the determination reference value A22,
In step S34, it is determined whether the poisoning S amount Qs is equal to or more than the S purge determination reference value A3. Then, in step S34, if it is determined that poisoning S amount Qs is not reached the criterion value A3, the process proceeds to step S46, the low speed average speed V of the past predetermined time than a predetermined vehicle speed V ₂₁ It is determined whether the vehicle is in a steady operation at a predetermined vehicle speed V ₂₂ (for example, 50 km / h) or more (execution condition). Here, if the average vehicle speed V is the steady operation at or above the predetermined vehicle speed V ₂₂ , the control mode is set to S.
Switch to purge mode, otherwise step S4
Move to 7.

On the other hand, in step S34, the poisoning S amount Qs
When it is determined that has reached the determination reference value A3, the process proceeds to step S35. In this way, in the following steps S35 to 39, the poisoning S amount Qs and the judgment reference values A4, A
5, A6, A7, A8 comparison determination (step S35,
36, 37, 38, 39). And A4> Qs
If ≧ A3, it is switched to the S purge mode on condition that it is steady operation regardless of the average vehicle speed V (step 45), and if A5> Qs ≧ A4, it is condition that it is deceleration operation (step 44). Is switched to the S purge mode (however, in this case, most or all of the fuel is injected in the expansion stroke so that torque is not generated as much as possible during deceleration), and if A6> Qs ≧ A5, slow acceleration operation is performed. If there is a condition (step 43), switch to the S purge mode,
If A7> Qs ≧ A6, it is switched to the S purge mode on the condition that the acceleration operation is performed (step 42), and A8>
If Qs ≧ A7, it is switched to the S purge mode on the condition that the engine is idling (step 41), and Qs ≧
If it is A8, it is switched to the S purge mode in the entire operation.

In this way, the poisoning S of the storage type NOx catalyst 25
By comparing the amount Qs with a plurality of S purge determination reference values A1 to A8 in order, the degree of reduction in purification capacity is estimated, and the conditions for executing S purge according to the degree of reduction in purification capacity are the catalyst temperature Tcat and the average predetermined vehicle speed. The operation range is changed to V ₂₁ , V ₂₂ , acceleration / deceleration operation, etc. in order, and the S purge is executed when this execution condition is satisfied at each degree of reduction in the purification capacity. Therefore, even if all the operating states, for example, the operating state of repeating acceleration / deceleration continues and the S purge mode execution condition is not satisfied, and the poisoning S amount Qs of the storage type NOx catalyst 25 increases, the poisoning S amount Qs increases. Since the condition for executing the S purge according to the S amount Qs is relaxed, the S purge mode is reliably executed, and the poisoning S amount Qs excessively increases and the storage capacity of the storage type NOx catalyst 25 decreases. It is possible to prevent deterioration of exhaust gas characteristics due to the above. Further, since the S purge execution conditions are set in the order in which the temperature of the catalyst is easily raised, it is possible to appropriately switch to the S purge mode in which the SOx stored in the storage type NOx catalyst 25 is released while suppressing deterioration of fuel efficiency. .

Then, returning to FIG. 2, in step S11, as described above, the poisoning S amount Qs is determined by the judgment reference values A1 to A1.
When each execution condition is satisfied as compared with A8, the process proceeds to step S12, and the control mode is switched to the S purge mode. As a result, removal of SOx stored in the storage-type NOx catalyst 25, that is, S purge is started.

When this S purge is started, step S
13, the target average effective pressure Pe is a predetermined value Pe1 (Ne
Is smaller than the Pe main injection mode selection map). Then, in this step S13,
When the target average effective pressure Pe is smaller than the predetermined value Pe1, that is, when the engine load and the engine speed are small, such as when idling or running at low speed, step S14.
Move to.

In step S14, the fuel injection mode of the main injection is set to the compression stroke injection mode regardless of the normal setting described above, and the sub injection is performed in the expansion stroke. That is, when performing the S purge, the two-stage injection is performed by the compression stroke injection and the expansion stroke injection. And goal A /
F, that is, the target A / F as a whole including the main injection and the sub-injection, that is, the whole A / F is set to a predetermined rich air-fuel ratio (a value suitable for S purge, for example, a value 12). At the same time, the target air-fuel ratio (main A / F) of the main injection is determined according to the target average effective pressure Pe and the engine speed Ne based on the main injection mode selection map described above. At this time, the overall A / F is a predetermined rich air-fuel ratio (for example, a value of 1
The main A / F is set while being held in 2). That is, the respective fuel injection ratios of the main injection amount and the sub injection amount are appropriately determined with the overall A / F maintained constant and the reducing atmosphere being formed well.

Generally, if the target average effective pressure Pe or the engine speed Ne is small, it can be determined that the occlusion type NOx catalyst 25 is in a low temperature state, the catalyst temperature Tcat is low, and the temperature increase of the occlusion type NOx catalyst 25 is not easy. Therefore, in this case, it is preferable to increase the auxiliary injection amount while reducing the main injection amount as much as possible while maintaining the overall A / F at the predetermined rich air-fuel ratio as described above.

However, the air-fuel ratio that can be realized in the intake stroke injection mode has an upper limit value (for example, 22), and in this intake stroke injection mode, combustion does not occur at an air-fuel ratio larger than the upper limit value. Therefore, when the main A / F becomes larger than the upper limit value in the intake stroke injection mode, the main injection is performed in the compression stroke in which the combustion is achieved at the air-fuel ratio larger than the upper limit value. Of.

As the engine load or engine speed decreases, the temperature of the storage type NOx catalyst 25, that is,
The catalyst temperature Tcat can be regarded as low. Therefore,
The main A / F has a larger value as the target average effective pressure Pe or the engine rotation speed Ne is smaller, and has a leaner air-fuel ratio side air-fuel ratio. That is, the lower the catalyst temperature Tcat, the smaller the main injection amount and the larger the sub injection amount.

Further, when the S purge is performed, the two-stage injection is performed by the compression stroke injection and the expansion stroke injection, and the overall target A / F
Main A / F (main injection amount) while maintaining a constant value
The sub-A / F (sub-injection amount) ratio is properly determined, but the throttle valve 17 is changed according to the change of the main A / F.
Is operated to adjust the throttle opening θth, and the intake air amount is manipulated, whereby the torque is controlled to be substantially constant. That is, when the main A / F is corrected to the rich air-fuel ratio side, the torque becomes large if it is left as it is, so the throttle opening θ of the throttle valve 17 is increased.
When the main A / F is corrected to the lean air-fuel ratio side, the torque becomes smaller because the correction to reduce th is made.
Correction is performed to increase the throttle opening θth of the throttle valve 17. In this case, it may be set by the selection map of the throttle opening θth for the corrected main A / F.

When the two-stage injection is performed and the fuel is injected in the expansion stroke by the sub-injection as described above, most of this fuel remains unburned, that is, unburned fuel component (unburned H
C) and the like are discharged into the exhaust pipe 21, a part of them reacts (burns) in the exhaust pipe, and the rest flows into the three-way catalyst 22. However, the unburned fuel component flowing into the three-way catalyst 22 causes an oxidation reaction (combustion) in the three-way catalyst 22 by the action of the catalyst when the three-way catalyst 22 is activated. That is, most of the fuel supplied by the sub-injection is burned before reaching the storage type NOx catalyst 25, and the exhaust gas flowing into the storage type NOx catalyst 25 is sufficiently heated. As a result, even if the catalyst temperature Tcat is low, the temperature of the exhaust gas is raised, and the occlusion-type NOx catalyst 25 can be purged by a predetermined high temperature catalyst temperature TcatH (for example, 650).
(.Degree. C.) is rapidly heated, and the S purge can be performed satisfactorily.

On the other hand, when it is determined in step S13 that the target average effective pressure Pe is equal to or higher than the predetermined value Pe1, that is, when the engine load and the engine rotation speed are relatively large as in the case of medium speed running, Control goes to step S15.

In step S15, the fuel injection mode of the main injection is set to the intake stroke injection mode regardless of the normal setting described above, and the sub injection is performed in the expansion stroke. That is, when the S purge is performed, the two-stage injection is performed by the intake stroke injection and the expansion stroke injection. Then, as described above, the overall A / F is set to a predetermined rich air-fuel ratio, and the main injection target air-fuel ratio (main A / F) is maintained while keeping the overall A / F at the predetermined rich air-fuel ratio. Is determined, and the respective fuel injection ratios of the main injection amount and the sub injection amount are appropriately determined.

Normally, if the engine load and the engine speed are relatively large, the occlusion type NOx catalyst 25 is heated to a high temperature to some extent, and it can be judged that the occlusion type NOx catalyst 25 can be easily heated. So in this case,
It is preferable to increase the main injection amount in order to keep the overall A / F at a predetermined rich air-fuel ratio while reducing the sub injection amount.

However, the air-fuel ratio that can be realized in the compression stroke injection mode has a lower limit value (for example, the value 24), and in this compression stroke injection mode, conversely to the above case, combustion occurs at an air-fuel ratio below the lower limit value. Does not hold. Therefore, when the air-fuel ratio of the main injection is less than or equal to the lower limit value, the main injection is performed in the intake stroke in which combustion is established at the air-fuel ratio below the lower limit value.

Also in this case, similarly to the above,
The unburned fuel component flowing into the three-way catalyst 22 is
Oxidation reaction (combustion) is caused by the action of the catalyst inside. That is, most of the fuel supplied by the sub-injection is burned before reaching the storage type NOx catalyst 25, and the exhaust gas flowing into the storage type NOx catalyst 25 is sufficiently heated. As a result, the storage type NOx catalyst 25 can be S-purged at a predetermined high temperature catalyst temperature TcatH (for example, at the time of traveling at medium speed) with the entire A / F kept constant and the reducing atmosphere is well formed. , 650 ° C.), and S purge can be satisfactorily carried out.

By the way, when the vehicle is traveling at a high speed and the engine speed Ne and the target average effective pressure Pe are large, the two-stage injection is difficult due to the restrictions of the injector driver and the like. It can be judged that it is possible to heat the occlusion type NOx catalyst 25 to a predetermined high temperature catalyst temperature TcatH capable of S purging only by the retard of the ignition timing because the exhaust gas temperature is relatively high originally. Therefore, in this case, only the main injection is performed in the intake stroke instead of the two-stage injection in step S15, and the temperature rise control is performed by the retard of the ignition timing. Even in this case, the overall A / F is set to the predetermined rich air-fuel ratio (for example, the value 12). Further, when the engine rotation speed Ne and the target average effective pressure Pe are extremely large and the main A / F has a rich air-fuel ratio, the combustion heat is extremely large and the exhaust gas temperature is increased without performing the temperature raising control. It can be determined that S is high enough to allow purging, and in this case, step S15 is skipped.

Thus, in steps S14 and S15,
When the two-stage injection is executed and the temperature of the exhaust gas flowing into the occlusion type NOx catalyst 25 is sufficiently raised by the oxidation reaction in the three-way catalyst 22, in step S16, after the S purge is started by executing step S12. It is determined whether or not a predetermined time t1 (for example, several tens of seconds) has elapsed. Then, if the predetermined time t1 has elapsed, the process proceeds to step S17,
If the predetermined time t1 has not elapsed, the process returns to step S12. In step S17, it is determined whether the catalyst temperature Tcat is higher than the predetermined catalyst temperature TcatM, and if it is higher than the predetermined catalyst temperature TcatM, the process proceeds to step S18.
If the catalyst temperature is lower than the predetermined catalyst temperature TcatM, the process returns to step S12.

When a predetermined time t1 has elapsed after the start of the S purge and the catalyst temperature Tcat becomes higher than the predetermined catalyst temperature TcatM, the temperature is extremely higher on the downstream side than on the catalyst upstream side. The state disappears, the difference between the high temperature sensor 24 installed immediately upstream of the catalyst and the catalyst temperature is small, and it can be determined that the catalyst will not be overheated even if the catalyst temperature feedback control is performed. Therefore, the process proceeds to step S18. Start the temperature feedback control. In this catalyst temperature feedback control, the catalyst temperature Tcat is compared with a predetermined catalyst temperature TcatH, and the main A / F set based on the main injection mode selection map is set to the catalyst temperature Tcat.
Correction is made according to the temperature deviation integration ΣΔTcat of. Furthermore, when the main A / F reaches the upper limit value or the lower limit value,
The ignition timing set based on the main injection mode selection map is corrected according to the temperature deviation integration ΣΔTcat of the catalyst temperature Tcat.

More specifically, the temperature deviation integration ΣΔTcat is calculated from the following equation (4). ΣΔTcat = ΣΔTcat (n-1) + ΔTcat (4) where ΔTcat is a temperature deviation and is a predetermined high temperature TcatH
(Eg, 650 ° C.) and the present catalyst temperature Tcat estimated based on the high temperature sensor 24, and is calculated from the following equation (5). ΔTcat = TcatH−Tcat (5)

Actually, the temperature deviation integration ΣΔTcat and the correction value of the main A / F are mapped beforehand as shown in Table 1 by an experiment or the like, and the main A / F is the main A / F.
It is corrected based on the correction value map of F (integral correction).

[0054]

[Table 1]

Here, among the correction values of the main A / F, the plus sign (+) indicates the lean side correction, and the minus sign (−) indicates the rich side correction. That is, when the occlusion type NOx catalyst 25 is heated by overshooting above a predetermined high temperature TcatH, the temperature deviation integration ΣΔTcat becomes a negative value, and in this case, the main A / F is on the negative side, that is, It is corrected to the rich side, the fuel amount of the secondary injection is reduced, and it is returned to the predetermined high temperature TcatH. After that, if the temperature deviation integration ΣΔTcat becomes a positive value by undershooting,
The main A / F is corrected to the positive side, that is, to the lean side, the fuel amount of the secondary injection is increased, and the catalyst temperature Tcat is again raised to the predetermined high temperature TcatH.

By the way, by correcting the main A / F in this way, the catalyst temperature Tcat becomes stable at a predetermined high temperature TcatH, that is, the occlusion type NOx catalyst 25 is held at the predetermined high temperature TcatH. When the catalyst temperature Tcat is stabilized in this way, thereafter, it is only necessary to perform the temperature rise control for maintaining the predetermined high temperature TcatH. That is, main A
/ F is set to a small value to increase the main injection amount, while the sub-injection amount is narrowed down.

Further, when fuel is injected in the compression stroke injection mode, there is a restriction on the air-fuel ratio at which combustion is established due to the structure, and the main A / F has a lower limit value (for example, value 24) or an upper limit value (for example, 24). For example, when the value reaches 50), the whole A
A / F is maintained at a predetermined rich air-fuel ratio (for example, a value of 12), and the main A / F correction value is also held, while the ignition timing correction is performed in addition to the two-stage injection so that the temperature increase control is continued. . On the other hand, when the fuel injection is performed in the intake stroke injection mode, the air-fuel ratio is limited by the upper limit value (for example, the value 22) as described above, and at the same time, the predetermined overall A / F is set.
When (for example, the value 12) becomes the lower limit and the main A / F becomes the upper limit value (for example, the value 22), the overall A / F is maintained at a predetermined rich air-fuel ratio (for example, the value 12) and the main A / F is maintained. While maintaining the / F correction value as well, the ignition timing correction is performed in addition to the two-stage injection to continue the temperature increase control.

This ignition timing correction amount is the temperature deviation integration ΣΔ
It is set according to Tcat. Actually, the temperature deviation integration Σ
ΔTcat and the ignition timing correction amount are mapped in advance as shown in Table 2 by an experiment or the like, and the ignition timing is corrected based on the ignition timing correction amount map (integral correction). It should be noted that during normal combustion control, the reference ignition timing is set to the advance side as much as possible so that the torque becomes large, but when performing ignition timing correction, there is a margin when correcting the ignition timing to the advance side. Therefore, the reference ignition timing when performing the correction is set to the neutral position between advance and retard.

[0059]

[Table 2]

Here, in the ignition timing correction amount, the positive sign (+) indicates the correction toward the advance side, and the negative sign (-) indicates the correction toward the retard side. That is, similarly to the above, when the occlusion type NOx catalyst 25 is heated overshooting the predetermined high temperature TcatH, the temperature deviation integration ΣΔTcat becomes a negative value, and in this case, the ignition timing correction amount is positive. Side, that is, the advance side is corrected, and the temperature rise effect is reduced. After that, when the temperature deviation integration ΣΔTcat becomes a positive value by undershooting, the ignition timing correction amount is corrected to the negative side, that is, the retard side, and the temperature raising effect is enhanced, and the catalyst temperature Tcat is increased again. The temperature is raised to a predetermined high temperature TcatH.

As a result, the storage type NOx catalyst 25 is stably maintained at the predetermined high temperature TcatH, and the S purge is favorably continued.

Then, returning to FIG. 2, in a step S19, it is determined whether or not the S purge of the storage type NOx catalyst 25 is completed. That is, it is determined whether or not the storage type NOx catalyst 25 is regenerated and the poisoning S amount Qs becomes equal to or less than the S purge end reference value C (0 or a value near 0). The determination as to whether or not the S purge is completed may be made based on the elapsed time from the start of the S purge mode.
In this case, the elapsed time may be set in advance by experiments or the like as the time that can sufficiently remove SOx when the storage-type NOx catalyst 25 is kept at a predetermined high temperature TcatH in the reducing atmosphere.

In this step S19, if the poisoning S amount Qs of the storage type NOx catalyst 25 is larger than the termination reference value C, S
If it is determined that the purge has not ended, the process returns to step S12 to continue the temperature increase control in the S purge mode. On the other hand, in step S19, the storage type NOx catalyst 25
When it is determined that the S-purging amount of Qs is less than the termination reference value C and the S-purging is finished, it is considered that SOx is sufficiently removed, and this routine is exited to terminate the S-purging control.

As described above, as shown in FIG.
In the exhaust gas purification device for the internal combustion engine of the present embodiment, the storage type NO
It is determined whether or not the poisoning S amount Qs stored in the x catalyst 25 exceeds a predetermined amount. At this time, the poisoning S amount Qs is sequentially compared with a plurality of S purge determination reference values A1 to A8, and the purification capacity is increased. The degree of deterioration is estimated, and S is calculated according to the degree of decrease in the purification capacity.
Conditions catalyst temperature Tcat to perform purging, average predetermined vehicle speed V _21, V _22, and change the operating region in stages as will expand in order such as acceleration and deceleration operation, the execution condition for each decreased reducing ability degree satisfied When this occurs, the S purge mode is entered and the two-stage injection is executed to raise the temperature of the exhaust gas to store the storage NOx.
By raising the temperature of the catalyst 25 and feeding back the catalyst temperature Tcat to the ECU 28 to correct the main A / F or the ignition timing, the storage type NOx catalyst 25 is stably maintained at a predetermined high temperature TcatH, and the S purge is good. I'm trying to run it.

Therefore, for example, when the vehicle is traveling in an urban area and the operating state in which acceleration and deceleration are repeated is continued, the poisoning S amount Qs of the occlusion type NOx catalyst 25 increases, but it depends on the poisoning S amount Qs. By changing the condition for executing the S purge, regardless of the operating state of the engine 11, the SOx stored in the storage type NOx catalyst 25 is suppressed while suppressing the deterioration of the fuel consumption.
It is possible to properly switch to the S purge mode for discharging the.

In the above-described embodiment, the degree of purification ability deterioration is estimated by comparing the S purge determination reference value with A1 to A8 and the poisoned S amount Qs, but this number is not limited. Further, the storage type NOx catalyst deteriorates over time due to heat deterioration and the like, and the NOx storage capacity decreases regardless of S poisoning. In that case, the S purge determination reference value is decreased each time the S purge execution frequency is increased. For example, the S purge may be performed early. Specifically, each of the S purge determination criteria A1 to A8 may be a map for the number of S purges performed or a map for the travel distance. Furthermore, the S purge may be executed by obtaining the poisoning S amount Qs by calculation based on the integrated fuel injection amount and detecting the degree of reduction in purification efficiency.

Further, the conditions for executing the S purge in accordance with the degree of reduction in the purification capacity are the catalyst temperature Tcat, the average predetermined vehicle speed V ₂₁ ,
Although V ₂₂ and acceleration / deceleration operation are used, the conditions are not limited to these. For example, the determination condition S based on the average predetermined vehicle speed
The steps 46 and S47 may be any steps as long as it is possible to determine that the vehicle is in a high-speed stable driving state, that the cruise control device is operating, or that the vehicle is traveling on a suburban road or highway that can be driven at high speed by the navigation device. What is done may be used as the determination condition. Further, by providing a hysteresis to the vehicle speed, the step of S47 is performed at the instantaneous vehicle speed 90.
The S-purge operation may be started at km / h or higher and canceled at 70 km / h or lower, and the step S46 may be started at an instantaneous vehicle speed of 60 km / h or higher and canceled at 40 km / h or lower. Alternatively, the determination vehicle speed in steps S46 and S47 may be further subdivided to increase the number of steps. Then, the S purge execution conditions may be omitted, integrated, and the order may be changed from these conditions, or new conditions may be added. That is, it is only necessary to change the operation region of S purge execution according to the degree of deterioration of the storage type NOx catalyst.

In the above embodiment, the engine 11
Although the in-cylinder injection spark ignition in-line four-cylinder gasoline engine is used, the engine 11 may be an intake pipe injection lean burn engine as long as it uses the occlusion type NOx catalyst 25.

[0069]

As described above in detail in the embodiments, according to the exhaust gas purifying apparatus for an internal combustion engine of the present invention, the regenerating means for regenerating the catalyst purifying ability in accordance with the degree of reduction in the purifying ability of the occlusion type NOx catalyst. By changing the execution condition of, the sulfur component occluded in the occluding NOx catalyst can be surely released and the occluding NOx catalyst can be regenerated regardless of the operating state of the internal combustion engine while suppressing deterioration of fuel efficiency. it can.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an exhaust gas purification device for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a flowchart of S purge control by the exhaust emission control device of the present embodiment.

FIG. 3 is an occlusion type NOx by the exhaust emission control device of the present embodiment.
6 is a flowchart of catalyst deterioration determination control.

FIG. 4 is an occlusion type NOx by the exhaust emission control device of the present embodiment.
6 is a flowchart of catalyst deterioration determination control.

FIG. 5 is a time chart showing a change over time in the amount of poisoning S when S purge is performed.

[Explanation of symbols]

Reference Signs List 11 engine (internal combustion engine) 13 spark plug 14 fuel injection valve 15 combustion chamber 17 throttle valve 18 throttle sensor 20 crank angle sensor 21 exhaust pipe (exhaust passage) 22 three-way catalyst 23 exhaust purification catalyst device 24 high temperature sensor 25 occlusion type NOx catalyst 26 three-way catalyst 28 electronic control unit, ECU (purification ability detection means, regeneration means, execution condition changing means, control means)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI F01N 3/24 F01N 3/28 301C 3/28 301 F02D 41/04 305A F02D 41/04 305 B01D 53/36 101A (56) Reference References JP-A 2000-18025 (JP, A) JP-A 8-232644 (JP, A) JP-A 7-217474 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F01N 3/08-3/28 B01D 53/94 F02D 41/04

Claims (7)

(57) [Claims] 1. An occlusion type NOx catalyst which is provided in an exhaust passage of an internal combustion engine and which occludes NOx in exhaust gas when the exhaust air-fuel ratio is an oxidizing atmosphere and releases or reduces NOx which is occluded in a reducing atmosphere. And a purification capacity detecting means for detecting or estimating the degree of reduction of the purification capacity of the storage type NOx catalyst due to the storage of the sulfur component contained in the exhaust gas, and the temperature of the storage type NOx catalyst and its surroundings. A regenerating unit that regenerates the purifying ability of the storage type NOx catalyst by setting a reducing atmosphere, and an execution condition of the regenerating unit depending on the degree of decrease in the purifying ability of the storage type NOx catalyst detected or estimated by the purifying ability detecting unit. And that the execution condition of the execution condition changing means corresponding to the degree of reduction in the purification capacity detected or estimated by the purification capacity detecting means is satisfied. Control means for activating the regeneration means , the execution condition changing means,
Of the storage type NOx catalyst detected or estimated by the detection means.
The internal combustion engine as an execution condition according to the degree of reduction in purification capacity
An exhaust emission control device for an internal combustion engine, characterized in that operating conditions are changed based on the speed of a vehicle equipped with the engine. 2. An exhaust gas provided in an exhaust passage of an internal combustion engine.
Stores NOx in exhaust gas when the fuel ratio is in an oxidizing atmosphere
And releases NOx stored in the reducing atmosphere.
Or NOx storage type NOx catalyst that is reduced and contained in the exhaust gas
The NOx catalyst that absorbs the sulfur component
Purification ability detection to detect or estimate the degree of reduction in purification ability of the medium
The temperature of the storage means and the temperature of the NOx storage catalyst are increased and
Purification of the storage-type NOx catalyst by setting the side to a reducing atmosphere
The regeneration means for regenerating the capacity and the purification capacity detection means are detected.
Deterioration of estimated or estimated purification capacity of the storage type NOx catalyst
Execution condition for changing the execution condition of the reproducing means according to the degree
The change means and the purification capacity detection means detect or estimate
Of the execution condition changing means according to the degree of reduction of the purification capacity.
Control for operating the reproducing means when the row condition is satisfied
And a means for changing the execution condition,
Of the storage type NOx catalyst detected or estimated by the detection means.
The internal combustion engine as an execution condition according to the degree of reduction in purification capacity
Change the driving condition based on the driving state of the vehicle equipped with Seki
An exhaust emission control device for an internal combustion engine, characterized in that 3. An exhaust gas purification device for an internal combustion engine according to claim 2.
In addition, the execution condition changing means responds to the degree of reduction in the purification capacity.
Of the vehicle equipped with the internal combustion engine as the same execution condition.
High-speed stable operation, steady operation, deceleration operation,
Either slow acceleration, accelerated operation, or idle operation
Of an internal combustion engine characterized by changing one operating condition
Exhaust purification device. 4. An exhaust gas provided in an exhaust passage of an internal combustion engine.
Stores NOx in exhaust gas when the fuel ratio is in an oxidizing atmosphere
And releases NOx stored in the reducing atmosphere.
Or NOx storage type NOx catalyst that is reduced and contained in the exhaust gas
The NOx catalyst that absorbs the sulfur component
Purification ability detection to detect or estimate the degree of reduction in purification ability of the medium
The temperature of the storage means and the temperature of the NOx storage catalyst are increased and
Purification of the storage-type NOx catalyst by setting the side to a reducing atmosphere
The regeneration means for regenerating the capacity and the purification capacity detection means are detected.
Deterioration of estimated or estimated purification capacity of the storage type NOx catalyst
Execution condition for changing the execution condition of the reproducing means according to the degree
The change means and the purification capacity detection means detect or estimate
Of the execution condition changing means according to the degree of reduction of the purification capacity.
Control for operating the reproducing means when the row condition is satisfied
Means and the internal combustion engine when the control means is operating.
Intake stroke injection according to the engine load or engine speed
Mode selection to select mode or compression stroke injection mode
And an exhaust gas purification device for an internal combustion engine, characterized by comprising:
Place 5. An exhaust gas provided in an exhaust passage of an internal combustion engine.
Stores NOx in exhaust gas when the fuel ratio is in an oxidizing atmosphere
And releases NOx stored in the reducing atmosphere.
Or NOx storage type NOx catalyst that is reduced and contained in the exhaust gas
The NOx catalyst that absorbs the sulfur component
Purification ability detection to detect or estimate the degree of reduction in purification ability of the medium
The temperature of the storage means and the temperature of the NOx storage catalyst are increased and
Purification of the storage-type NOx catalyst by setting the side to a reducing atmosphere
The regeneration means for regenerating the capacity and the purification capacity detection means are detected.
Deterioration of estimated or estimated purification capacity of the storage type NOx catalyst
Execution condition for changing the execution condition of the reproducing means according to the degree
The change means and the purification capacity detection means detect or estimate
Of the execution condition changing means according to the degree of reduction of the purification capacity.
Control for operating the reproducing means when the row condition is satisfied
Means and the internal combustion engine when the control means is operating.
Depending on load or engine speed Secondary injection or
With mode selection means for selecting the ignition timing retard
An exhaust emission control device for an internal combustion engine, which is characterized in that: 6. An exhaust gas is provided in an exhaust passage of an internal combustion engine.
Stores NOx in exhaust gas when the fuel ratio is in an oxidizing atmosphere
And releases NOx stored in the reducing atmosphere.
Or NOx storage type NOx catalyst that is reduced and contained in the exhaust gas
The NOx catalyst that absorbs the sulfur component
Purification ability detection to detect or estimate the degree of reduction in purification ability of the medium
The temperature of the storage means and the temperature of the NOx storage catalyst are increased and
Purification of the storage-type NOx catalyst by setting the side to a reducing atmosphere
The regeneration means for regenerating the capacity and the purification capacity detection means are detected.
Deterioration of estimated or estimated purification capacity of the storage type NOx catalyst
Execution condition for changing the execution condition of the reproducing means according to the degree
The change means and the purification capacity detection means detect or estimate
Of the execution condition changing means according to the degree of reduction of the purification capacity.
Control for operating the reproducing means when the row condition is satisfied
Means for controlling the storage type NOx catalyst.
The operation of the regeneration means is controlled based on the catalyst temperature.
Characterized by having a feedback control means for controlling
An exhaust emission control device for an internal combustion engine. 7. An exhaust gas purification device for an internal combustion engine according to claim 6.
And the feedback control means is
A predetermined time has passed after the operation, and the catalyst temperature is a predetermined temperature.
The feature is that feedback control is performed when the temperature exceeds
Exhaust gas purification device for internal combustion engine.