JP3334632B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine, and more particularly to a technique for removing sulfur oxides (SOx) stored in a storage type NOx catalyst.

[0002]

2. Related Art In an internal combustion engine, if the air-fuel ratio is set to a lean air-fuel ratio, oxygen is excessively present, and the conventional three-way catalyst cannot sufficiently purify NOx (nitrogen oxide) in exhaust gas due to its purification characteristics. Recently, a storage NOx catalyst capable of purifying NOx even in an oxygen-excess atmosphere has been developed and put into practical use.

[0003] occlusion-type NOx catalyst occludes NOx in the exhaust gas in an oxygen excess state (oxidation atmosphere), as the nitrate X-NO _3, N of NOx was suction built with CO (carbon monoxide) over state (reduction atmosphere) It is configured as a catalyst having the property of reducing to ₂ (nitrogen) (carbonate X-CO ₃ is generated at the same time). Speaking of the in-cylinder injection type internal combustion engine, for example, the air-fuel ratio is controlled to the stoichiometric air-fuel ratio or a value close to the stoichiometric air-fuel ratio before the NOx storage amount of the storage NOx catalyst is saturated. (This is referred to as a rich spike), thereby generating a CO-rich reducing atmosphere, purifying and reducing the stored NOx (NOx purge), and regenerating the stored NOx catalyst.

By the way, S (sulfur) component is contained in fuel.
(Sulfur component), and this S component reacts with oxygen
To form SOx (sulfur oxide), which is converted to sulfate X-
SO _FourAs a storage NOx catalyst instead of NOx
It is. In other words, the storage NOx catalyst contains nitrate and sulfate
Will be occluded. However, sulfates are nitrates
Higher salt stability and rich air-fuel ratio
(Reducing atmosphere with reduced oxygen concentration)
Of the sulfate remaining on the NOx storage catalyst
The amount increases with time. Thus, the amount of sulfate increased.
Increases, the storage capacity of the storage NOx catalyst increases over time.
And the performance as a storage NOx catalyst deteriorates.
Is unfavorable (S poisoning).

[0005] However, the thus stored SO 2
It is known that x is removed (S purge) by setting the air-fuel ratio to a rich state and setting the catalyst to a high temperature state. For example, the storage amount of SOx is estimated, and the estimated value becomes a predetermined amount. Japanese Unexamined Patent Publication No. Hei 7-217474 discloses a technique for enriching the air-fuel ratio when it is determined that the temperature has reached and raising the temperature of the exhaust gas by retarding the ignition timing to bring the catalyst to a high temperature state.

[0006]

However, in the technique disclosed in the above publication, the amount of occluded SOx is estimated based only on the fuel injection time and the engine speed, for example. It is not preferable that the determination as to whether or not the amount has been reached is not always an appropriate determination.

That is, the amount of SOx generated by combustion largely depends on the air-fuel ratio, fuel properties (sulfur component content in fuel), etc., and the estimated value of the SOx storage amount has reached a predetermined amount. When the determination is made, the actual SOx storage amount has already reached a saturated state depending on the conditions such as the air-fuel ratio and the fuel property, and the NOx is inadvertently discharged as it is without being stored in the storage NOx catalyst. There is.

Conversely, when it is determined that the estimated value of the amount of stored SOx has reached a predetermined amount, the actual amount of stored SOx may be small depending on conditions such as the air-fuel ratio and fuel properties.
In such a situation, if the air-fuel ratio is set to the rich air-fuel ratio state and the S purge is repeatedly performed, the fuel efficiency is deteriorated, which is not preferable. The present invention has been made in order to solve such a problem, and an object of the present invention is to accurately estimate the amount of SOx stored in a storage NOx catalyst and efficiently store the stored SOx. It is an object of the present invention to provide a removable exhaust gas purification device for an internal combustion engine.

[0009]

To achieve the above object SUMMARY OF THE INVENTION According to the first aspect of the present invention, occlusion degree of sulfur components to occlusion-type NOx catalyst by the sulfur component storage degree calculation means in the air-fuel ratio The amount of sulfur component stored in the storage NOx catalyst is calculated based on the fuel injection amount correlation value calculated by the fuel injection amount correlation value calculation means and the sulfur component. It is estimated based on the storage degree of the sulfur component calculated by the storage degree calculating means.

Accordingly, sulfur component occluded in the occlusion-type NOx catalyst (S component), i.e., that the amount of deposition of sulfur oxides (SOx) are estimated taking into account the occlusion degree that varies depending on the air-fuel ratio That is, the SOx deposition amount is set to an appropriate value that actually matches. Therefore, the removal timing of the sulfur component by the sulfur component removal means, that is, the removal timing of SOx, that is, the execution timing of the S purge is made extremely appropriate, and the execution interval of the S purge becomes long, so that the NOx is inadvertently discharged. In addition, it is possible to preferably prevent the fuel consumption from being deteriorated due to frequent S purge. Also, billing
According to the invention of the item 2, the sulfur component is stored in the NOx storage catalyst.
The degree of occlusion is further adjusted according to the catalyst temperature.
Is stored in the storage NOx catalyst.
Amount of sulfur oxide (SOx) deposited depends on catalyst temperature
Estimated taking into account the changing degree of occlusion, the amount of SOx deposited
Is further set to an appropriate value according to the actual situation. Claims
According to the third aspect of the present invention, the sulfur component is absorbed into the storage NOx catalyst.
Calculated so that the degree of storage is more in accordance with the fuel properties
Is stored in the storage NOx catalyst.
Changes in the amount of sulfur oxide (SOx) deposited
Is estimated in consideration of the degree of occlusion,
Further, it is set to an appropriate value according to the actual situation. Claim 4
According to the invention, the fuel property is output from the knock sensor.
It is easily detected based on force information.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the accompanying drawings. Referring to FIG. 1, there is shown a schematic configuration diagram of an exhaust gas purifying apparatus for an internal combustion engine according to the present invention mounted on a vehicle. Hereinafter, the configuration of the exhaust gas purifying apparatus according to the present invention will be described with reference to FIG.

Engine body (hereinafter simply referred to as engine) 1
For example, in-cylinder injection spark ignition capable of performing fuel injection in an intake stroke (intake stroke injection mode) or fuel injection in a compression stroke (compression stroke injection mode) by switching a fuel injection mode (operation mode), for example. It is an inline 4-cylinder gasoline engine. The in-cylinder injection type engine 1 can be easily operated at a stoichiometric air-fuel ratio (stoichiometric ratio), at a rich air-fuel ratio (rich air-fuel ratio operation), or at a lean air-fuel ratio (lean air-fuel ratio). In particular, in the compression stroke injection mode, it is possible to operate at a super lean air-fuel ratio.

As shown in FIG. 1, the cylinder head 2 of the engine 1 is provided with an electromagnetic fuel injection valve 6 together with a spark plug 4 for each cylinder, whereby fuel is injected into the combustion chamber 8. Direct injection is possible. And
A fuel supply device (both not shown) having a fuel tank is connected to the fuel injection valve 6 via a fuel pipe.

Further, an intake port is formed in the cylinder head 2 in a substantially upright direction for each cylinder, and one end of an intake manifold 10 is connected to communicate with each intake port. A throttle valve 11 is connected to the other end of the intake manifold 10. The throttle valve 11 is provided with a throttle sensor 11a for detecting a throttle opening θth.

An exhaust port is formed in the cylinder head 2 in a substantially horizontal direction for each cylinder, and one end of an exhaust manifold 12 is connected to communicate with each exhaust port. Reference numeral 13 in the figure denotes a crank angle sensor for detecting a crank angle, and the crank angle sensor 13 is capable of detecting an engine rotation speed Ne. Reference numeral 18 denotes a knock sensor that detects knocking by detecting a change in vibration of the engine 1, for example.

As shown in FIG.
An exhaust pipe (exhaust passage) 14 is connected to the exhaust pipe 14. A muffler (not shown) is connected to the exhaust pipe 14 via a small proximity three-way catalyst 20 close to the engine 1 and an exhaust purification catalyst device 30. Have been. The exhaust pipe 14 is provided with a high temperature sensor 16 for detecting the exhaust gas temperature. The exhaust purification catalyst device 30 includes two catalysts, a storage NOx catalyst 30a and a three-way catalyst 30b, and the three-way catalyst 30b is disposed downstream of the storage NOx catalyst 30a. ing.

The storage type NOx catalyst 30a has a function of temporarily storing NOx in an oxidizing atmosphere and reducing NOx to N ₂ (nitrogen) or the like mainly in a reducing atmosphere where CO is present. More specifically, the storage NOx catalyst 30a uses platinum (Pt) and rhodium (R) as noble metals.
h) and the like, and an alkali metal such as barium (Ba) or an alkaline earth metal is employed as the storage material.

A NOx sensor 32 for detecting the NOx concentration is provided between the storage type NOx catalyst 30a and the three-way catalyst 30b.
Is provided. Further, an input / output device, a storage device (R
OM, RAM, nonvolatile RAM, etc.), central processing unit (C
PU), an ECU (electronic control unit) 40 including a timer counter and the like.
With 0, comprehensive control of the exhaust gas purification device for an internal combustion engine according to the present invention is performed. On the input side of the ECU 40, the above-described high temperature sensor 16, knock sensor 18, NOx sensor 3
2 and the like are connected, and detection information from these sensors is input.

On the other hand, the output side of the ECU 40 is connected to the above-described ignition plug 4 and the fuel injection valve 6 via an ignition coil. The ignition coil, the fuel injection valve 6 and the like are connected to various sensors. The optimum values such as the fuel injection amount and the ignition timing calculated based on the detection information are output.
As a result, an appropriate amount of fuel is injected from the fuel injection valve 6 at an appropriate timing, and ignition is performed by the spark plug 4 at an appropriate timing.

In practice, the ECU 40 determines the target in-cylinder pressure corresponding to the engine load, that is, the target average effective pressure, based on the throttle opening information θth from the throttle sensor 11a and the engine rotation speed information Ne from the crank angle sensor 13. Pe is determined, and the fuel injection mode is set from a map (not shown) according to the target average effective pressure Pe and the engine rotation speed information Ne. For example, when the target average effective pressure Pe and the engine rotation speed Ne are both low, the fuel injection mode is the compression stroke injection mode, and fuel is injected in the compression stroke, while the target average effective pressure Pe increases or the engine rotation speed increases. When the speed Ne increases, the fuel injection mode is set to the intake stroke injection mode, and fuel is injected during the intake stroke.

The target air-fuel ratio (target A / A) is set as a control target based on the target average effective pressure Pe and the engine speed Ne.
F) is set, and the appropriate amount of fuel injection is set to the target A /
It is determined based on F. The catalyst temperature Tcat is estimated from the exhaust gas temperature information detected by the high temperature sensor 16. Specifically, the high temperature sensor 16 is connected to the storage NOx catalyst 30.
A temperature difference map (not shown) is set in advance by an experiment or the like in accordance with the target average effective pressure Pe and the engine rotation speed information Ne in order to correct an error that occurs due to the inability to directly install the apparatus in the area a. Therefore, the catalyst temperature Tcat is uniquely estimated when the target average effective pressure Pe and the engine speed information Ne are determined.

Hereinafter, the operation of the exhaust gas purifying apparatus thus configured according to the present invention will be described. In other words, SOx is also stored in the storage NOx catalyst 30a as described above, and it is necessary to remove the SOx. Here, however, the estimation of the storage amount of the SOx (poisoned S amount Qs) is performed. Method, ie, S (sulfur) of the storage NOx catalyst 30a
A method for determining deterioration will be described.

The poisoning S amount Qs is basically set based on the integrated fuel injection amount Qf, and is calculated by the following equation at each execution cycle of a fuel injection control routine (not shown) (Sulfur Component accumulation amount estimation means). Qs = Qs (n−1) + ΔQf · K−Rs (1) Here, Qs (n−1) is the previous value of the poisoning S amount, and ΔQf is the integrated fuel injection amount per execution cycle (fuel injection (Amount correlation value), K is a correction coefficient (degree of occlusion), and Rs is a regeneration S amount per execution cycle.

That is, the current poisoning S amount Qs is determined by the fuel injection integrated amount ΔQf per execution cycle of the fuel injection control routine.
Is corrected by the correction coefficient K and integrated, and the reproduction S amount Rs per execution cycle is subtracted from the integrated value. Here, the integrated fuel injection amount ΔQf is calculated based on the fuel injection amount determined based on the target A / F as described above (fuel injection amount correlation value calculating means).

Incidentally, as shown in the following equation (2), the correction coefficient K is an S poisoning coefficient K1 corresponding to the air-fuel ratio A / F, an S poisoning coefficient K2 corresponding to the S content (fuel property), and Catalyst temperature Tc
It consists of the product of three correction coefficients of the S poisoning coefficient K3 according to at (sulfur component occlusion degree calculating means). K = K1, K2, K3 (2) As shown in FIG. 2A, the S poisoning coefficient K1 corresponding to the air-fuel ratio A / F is set to a small value in the rich air-fuel ratio based on the experimental data. The lean air-fuel ratio takes a large value (for example, 1/4 at the rich air-fuel ratio and 2/3 at the stoichiometric ratio with respect to the lean air-fuel ratio). That is, when the target A / F is set to the rich air-fuel ratio and the engine 1 is operating at the rich air-fuel ratio, it is assumed that SOx is hardly stored in the storage NOx catalyst 30a, while the target A / F is set to the lean air-fuel ratio. When the engine 1 is operating at a lean air-fuel ratio as the fuel ratio, a substantially constant amount of SOx is stored in the storage type N in accordance with the fuel amount.
That is, it is assumed that the oxygen is stored in the Ox catalyst 30a.

As shown by the solid line in FIG. 2 (b), the S poisoning coefficient K2 according to the S content (fuel property) increases as the S content in the fuel increases, based on experimental data. (For example, a proportional relationship). That is, the amount of SOx generated is S (sulfur) contained in the fuel.
Since it depends on the component, the correction is performed according to the content of the S component.

Incidentally, since it is actually impossible to measure the S content every fuel replenishment, the knocking sensor 18 detects the knocking generated at the time of combustion and detects the currently used fuel. The S content in the medium is estimated.
This is based on the fact that a low-octane-number low-quality fuel generally has a high S content, and a high-octane-number high-quality fuel has a low S content. That is, for example, in a combustion state in which knocking is likely to occur due to information from the knock sensor, that is, when the ignition timing cannot be advanced so much due to knocking (when the ignition timing advance correction value is small), the octane number is low. When it can be determined that the content is large, and when knocking is unlikely to occur, that is, when the ignition timing can be advanced a lot (when the ignition timing advance correction value is large), it can be determined that the S content is small with a high octane number. It is.

In Japan, two types of fuels, such as regular gasoline and premium gasoline, whose quality is kept constant, are sold. In such a case, FIG. As shown by the broken line, the S content is divided into two steps in a stepwise manner. That is, it is determined that the quality is high and the S content is very small in the case of premium gasoline, and the S poisoning coefficient K2 is set to a value close to 0, and is set to a large value in the case of regular gasoline.

Also, the S poisoning coefficient K3 according to the catalyst temperature
As shown in FIG. 2C, based on the experimental data, the catalyst temperature Tcat is a medium temperature (for example, 300 to 500
(About ° C). That is, when the catalyst temperature Tcat is low, the degree of activity is low, and when the catalyst temperature Tcat is high, the SOx is in the purging direction. Therefore, it is determined that the amount of SOx stored in the storage NOx catalyst 30a is relatively small.

Thus, the amount of poisoning S per execution cycle Δ
Qs will be more accurately estimated. The reproduction S amount Rs per execution cycle is calculated from the following equation (3). Rs = α · R1 · R2 · dT (3) where α is a regeneration rate (set value) per unit time, dT indicates an execution cycle of the fuel injection control routine, and R1 and R2 are respectively A regeneration capacity coefficient according to the catalyst temperature Tcat and a regeneration capacity coefficient according to the air-fuel ratio A / F are shown.

The regeneration capacity coefficient R1 according to the catalyst temperature Tcat
As shown in FIG. 3A, based on experimental data, is set to increase exponentially as the catalyst temperature Tcat increases. That is, the SOx increases exponentially rapidly as the catalyst temperature Tcat increases.
0a tends to be easily removed, and therefore the reproduction capability coefficient R1 is increased accordingly.

Regeneration capacity coefficient R2 according to air-fuel ratio A / F
As shown in FIG. 3 (b), based on the experimental data, the air-fuel ratio A / F is made substantially constant at a rich air-fuel ratio,
It is designed to decrease as the air-fuel ratio becomes extremely lean.
That is, as described above, SOx is favorably removed in a reducing atmosphere having a rich air-fuel ratio, whereas when the air-fuel ratio becomes a lean air-fuel ratio, it is occluded by the occlusion type NOx catalyst 30a. The performance coefficient R2 is set accordingly.

That is, SOx is reduced and removed when the catalyst temperature Tcat is heated to a high temperature and the air-fuel ratio A / F becomes a rich air-fuel ratio. Based on these FIGS. 3 (a) and 3 (b), SOx is reduced. By obtaining the regeneration capacity coefficients R1 and R2 corresponding to the catalyst temperature Tcat and the air-fuel ratio A / F, the regeneration S amount Rs per execution cycle can be properly calculated.
The current poisoning S amount Qs can be obtained more accurately.

When it is determined that the poisoning S amount Qs has reached a predetermined amount, that is, the S deterioration determination threshold value, the storage NOx
Removal of SOx from the catalyst 30a, that is, S purge is started. At this time, since the estimation of the poisoning S amount Qs is accurate as described above, the determination is extremely appropriate. That is, according to the present invention, there is no possibility that the execution interval of the S purge becomes long and NOx is inadvertently discharged, and that the fuel efficiency is not deteriorated due to the frequent S purge being performed. Thus, the S purge is performed efficiently.

When the S purge is started, the target A / F is set to the rich air-fuel ratio, and, for example, the two-stage injection or the ignition timing retard is performed to raise the exhaust gas temperature (sulfur component removing means). The two-stage injection is such that the fuel injection is divided into two times, and the main injection is performed in the compression stroke or the intake stroke and the sub-injection is performed in the expansion stroke. It is like burning and raising the temperature of exhaust gas. Further, the ignition timing retard is such that the exhaust gas temperature is increased by slowing down the combustion and continuing the combustion even after the exhaust gas. Here, the details of the control contents of these two-stage injection and ignition timing retard are omitted.

As a result, the inside of the storage NOx catalyst 30a is set to a reducing atmosphere, and the temperature is satisfactorily raised to a predetermined high temperature (for example, 650 ° C.), so that SOx is removed satisfactorily. After the start of the S purge, for example, the poisoning S amount Qs calculated by the above equation (1) becomes equal to the regeneration S amount.
If it is determined that the amount has decreased to a predetermined value (for example, a value 0 or a value near the value 0) or less due to an increase in the amount Rs, the S purge is terminated.

By the way, as described above, the storage NOx
The storage amount of SOx stored in the catalyst 30a, that is, the poisoning S amount Qs is accurately estimated, and SOx is removed satisfactorily. However, the storage NOx catalyst 30a usually deteriorates with time due to thermal deterioration or the like, and SOx is deteriorated. NOx storage capacity is reduced irrespective of the poisoning caused by NOx. That is, the amount of NOx that can be stored in the storage-type NOx catalyst 30a decreases with time.

Therefore, in such a case, it is preferable that the SOx is not absorbed as much as possible with the decrease in the NOx storage capacity.
The deterioration determination threshold value is reduced, that is, the S purge is performed early, so that the NOx occlusion capacity can always be sufficiently ensured. That is, referring to FIG.
The time change of the poisoning S amount Qs is shown.
As described above, the S deterioration determination threshold value, which was the value Qs1 in the first S purge, is reduced to the value Qs2 in the second time, and the value Q is reduced in the third time.
Make it even smaller with s3. As a result, the S purge is performed at an early stage in response to the aging of the storage NOx catalyst 30a, and the storage NOx catalyst 30a
Ox is always kept in a state in which it can be occluded well.

In FIG. 4, the poisoning S amount Qs increases while repeatedly increasing and decreasing in a sawtooth manner, which indicates that the S purge is performed even during a normal operation.
That is, when the vehicle travels on an uphill road, the target A
/ F is often set to a rich air-fuel ratio. In such a case, a reducing atmosphere is formed and the storage NOx catalyst 30a is heated above the predetermined high temperature (for example, 650 ° C.), and S / S This shows that the purge is preferably performed spontaneously.

In the above embodiment, the poisoning S amount Qs is calculated based on the integrated fuel injection amount Qf. However, instead of the integrated fuel injection amount Qf, the poisoning S amount Qs is calculated based on the travel distance of the vehicle correlated with the fuel injection amount. The poisoning S amount Qs may be estimated. In this case, the poisoning S amount Qs is obtained by the following equation instead of the above equation (1).
Required from (4). Qs = Qs (n−1) + (V · dT) · K−Rs (4) where V is the vehicle speed, and (V · dT) is the mileage (fuel) per execution cycle of the fuel injection control routine. (Fuel injection amount correlation value calculation means).

Further, for example, once the battery is removed, the calculation data of the poisoning S amount Qs stored in the storage device of the ECU 40 is reset and erased halfway, but in such a case, Accordingly, the S purge is forcibly performed regardless of the S deterioration determination. Or
The initial value of the poisoning S amount Qs is set to a sufficiently large value close to the S deterioration determination threshold, so that the first S purge is performed early. As a result, the calculated value of the poisoning S amount Qs always coincides with the actual SOx occlusion amount without traveling while the actual poisoning S amount Qs is large. The estimation of Qs continues to be appropriate.

In the above-described embodiment, the S purge is terminated when it is determined that the poisoning S amount Qs has decreased to a predetermined value (for example, a value 0 or a value near the value 0). Thus, the S purge may be performed for a predetermined time set in advance, and the S purge may be terminated when the predetermined time has elapsed.

[0043]

As described above in detail, according to the exhaust gas purifying apparatus for an internal combustion engine of the first aspect of the present invention, the storage NO
degree and corresponding occlusion degree of sulfur components in the x catalyst air-fuel ratio
The amount of sulfur component stored in the storage NOx catalyst is estimated based on the fuel injection amount correlation value corresponding to the fuel injection amount and the degree of storage of the sulfur component. I have.

[0044] Thus, the sulfur component occluded in the occlusion-type NOx catalyst (S component), i.e. sulfur oxide deposition amount (SOx) can be estimated by considering the occlusion degree that varies depending on the air-fuel ratio, the SOx The deposition amount can be set to an appropriate value according to the actual situation.
Therefore, the removal of the sulfur component by the sulfur component removing means, that is, S
The removal timing of Ox, that is, the execution timing of the S purge can be made extremely appropriate, and the execution interval of the S purge can be prevented from being extended to prevent careless emission of NOx. Deterioration can be suitably prevented. Claim 2
According to the exhaust gas purification device for a fuel engine, the storage NOx catalyst
The amount of stored sulfur oxides (SOx) depends on the catalyst temperature.
Can be estimated by taking into account the degree of storage that changes
The volume can be set to an appropriate value based on the actual situation. In addition,
According to the exhaust gas purifying apparatus for an internal combustion engine according to claims 3 and 4, the occlusion type
The amount of sulfur oxide (SOx) stored in the NOx catalyst
Estimation taking into account the degree of occlusion that changes depending on the fuel properties
The amount of SOx deposition to a more appropriate value
Wear.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a correction coefficient of the poisoning S amount Qs, which shows the relationship between the S poisoning coefficient K1 and the air-fuel ratio A / according to the air-fuel ratio A / F (a), and the S-content It is a figure which shows the relationship (b) with the S content of the S poisoning coefficient K2 and the catalyst temperature Tcat of the S poisoning coefficient K3 according to the catalyst temperature Tcat.

FIG. 3 shows the relationship between the regeneration capacity coefficient R1 and the catalyst temperature Tcat according to the catalyst temperature Tcat used for calculating the regeneration S amount Rs (a).
And the air-fuel ratio A of the regeneration capacity coefficient R2 according to the air-fuel ratio A / F
FIG. 10 is a diagram showing a relationship (b) with / F.

FIG. 4 is a time chart showing a time change of a poisoning S amount Qs when an S purge is performed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine (internal combustion engine) 4 Spark plug 6 Fuel injection valve 11 Throttle valve 11a Throttle sensor 13 Crank angle sensor 16 High temperature sensor 18 Knock sensor 30a Storage type NOx catalyst 40 Electronic control unit (ECU)

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-9-317447 (JP, A) JP-A-7-217474 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01D 53/86 F01N 3/08 B01D 53/34 B01D 53/81

Claims (4)

(57) [Claims] 1. An exhaust passage provided in an exhaust passage of an internal combustion engine, the NO in the exhaust when the internal combustion engine is in a lean air-fuel ratio operating state.
a storage type NOx catalyst that stores x and reduces the stored NOx when in a stoichiometric air-fuel ratio operation or a rich air-fuel ratio operation state, and a fuel injection amount correlation that calculates a fuel injection amount correlation value corresponding to the fuel injection amount. degree corresponding value calculation means, said storage extent to occlusion-type NOx catalyst of the sulfur component contained in the fuel is discharged into the exhaust passage to the air-fuel ratio
Sulfur component occlusion degree calculating means that calculates so as to obtain the fuel injection amount correlation value calculated by the fuel injection amount correlation value calculating means and the sulfur component occlusion degree calculated by the sulfur component occlusion degree calculating means. The storage type NO
x sulfur component accumulation amount estimating means for estimating the accumulation amount of sulfur component occluded in the x catalyst, and sulfur occluded by the occlusion type NOx catalyst based on the sulfur component accumulation amount estimated by the sulfur component accumulation amount estimating means. An exhaust gas purifying apparatus for an internal combustion engine, comprising: a sulfur component removing means for removing a component. 2. The method according to claim 1, wherein said sulfur component occlusion degree calculating means further comprises:
To the exhaust passage to a degree corresponding to the catalyst temperature
Storage degree of the sulfur component to be stored in the storage NOx catalyst
2. The internal combustion engine according to claim 1, wherein the operation is performed.
Exhaust gas purification device. 3. The method according to claim 2, wherein the sulfur component occlusion degree calculating means further comprises:
Discharged to the exhaust passage to a degree according to the fuel properties
Storage degree of the sulfur component to be stored in the storage NOx catalyst
3. The method according to claim 1, wherein the calculation is performed.
Exhaust purification device for fuel engine. 4. The method according to claim 1, wherein the sulfur component occlusion degree calculating means is an internal combustion engine.
A knock sensor for detecting knocking of the engine;
Fuel properties are detected based on output information from the
4. The exhaust of an internal combustion engine according to claim 3, wherein
Purification device.