JP2000087788A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow SOx occluded by an occlusion type NOx catalyst to be properly removed while minimizing aggravated acceleration feeling. SOLUTION: The state of acceleration of a vehicle is evaluated by acceleration evaluation means based on a predetermined acceleration criterion value. This acceleration criterion value is changed to a larger side (S12) when sulfur content removal necessity evaluation means determines that removal be necessary of sulfur content in fuel occluded by an occlusion type NOx catalyst (S10). Unless a vehicle is evaluated as being in an accelerated state based on the revised acceleration criterion value, sulfur content removal inhibition means will not inhibit removal of sulfur content (S16). That is, the sulfur content removal means ensures that sulfur content is properly removed even, when the vehicle is in a mild acceleration state (S18).

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. Description of the Related Art In an internal combustion engine, if the air-fuel ratio is 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 the oxygen excess condition (oxidized atmosphere) and NOx in the exhaust gas as nitrate X-NO _3, NOx and NOx was suction built with CO (carbon monoxide) over state (reduction atmosphere) (A carbonate X-CO ₃ is generated at the same time). The released NOx is reduced to N ₂ (nitrogen) by excess CO on the same catalyst, or reduced to N ₂ on a three-way catalyst disposed downstream. In practice, for example, the air-fuel ratio is periodically switched to a rich air-fuel ratio operation in an intake stroke in which the air-fuel ratio is controlled to a 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 This generates a reducing atmosphere rich in CO, and releases the stored NOx (NOx).
(Purge) to regenerate the storage 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.
Then, the NOx storage capacity of the storage NOx catalyst increases with time.
And the performance as a storage-type NOx catalyst deteriorates.
This is not preferable (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 Patent Application Laid-Open No. Hei 7-217 discloses a technique for enriching the air-fuel ratio when it is determined that the temperature of the catalyst is high by raising the exhaust gas temperature by retarding the ignition timing (combustion control).
No. 474, for example.

[0006]

According to the techniques disclosed in the above publications, when it is determined that the SOx occlusion amount has reached a predetermined amount, the ignition timing is always retarded so as to perform the S purge. I have to. However, if the S purge is always performed regardless of the operating state of the engine when it is determined that the storage amount of SOx has reached a predetermined value as in the above-described technique, the S purge is performed particularly during acceleration traveling of the vehicle. In such a case, the combustion of the internal combustion engine may be temporarily deteriorated, and the acceleration feeling may be deteriorated.

Therefore, even when it is determined that the SOx occlusion amount has reached the predetermined amount, it is conceivable that the S purge is not performed during the acceleration running or the like. In this case, the S purge is not performed at all during the acceleration running or the like. Is not performed, it is not preferable because the S purge may not be performed for a long time when driving in an urban area where acceleration and deceleration are repeated.

The present invention has been made to solve such a problem, and an object thereof is to provide a storage type N.
It is an object of the present invention to provide an exhaust gas purifying apparatus for an internal combustion engine that can surely remove SOx stored in an Ox catalyst while suppressing deterioration such as acceleration feeling.

[0009]

According to the first aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine having a storage-type NOx catalyst, based on a predetermined acceleration determination value. The acceleration determination unit determines the acceleration state of the vehicle. This acceleration determination value is determined when the sulfur component in the fuel stored in the storage NOx catalyst is determined to be necessary by the sulfur component removal necessity determination unit. Changed to the large side. When it is determined that the vehicle is in the accelerated state based on the changed acceleration determination value, the sulfur component removal prohibiting means prohibits the removal of the sulfur component, that is, the vehicle is in the acceleration state based on the changed acceleration determination value. Unless it is determined that the sulfur component is within the range, the sulfur component is satisfactorily removed by the sulfur component removing means. That is, when it is determined that the removal of the sulfur component is necessary, the removal of the sulfur component is favorably performed not only in the steady operation state but also in the slow acceleration state where the acceleration is normally determined.

[0010] Accordingly, while the deterioration of the acceleration feeling caused by controlling the combustion parameters at the time of removing the sulfur component (SOx) (S purge) is prevented as much as possible, when the removal of the sulfur component is necessary, the sulfur component is surely removed. The components are made removable. That is, according to the present invention, it is possible to achieve both prevention of deterioration of the acceleration feeling and removal of the sulfur component.

[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, and the throttle valve 11 is provided with a throttle sensor 11a for detecting a throttle opening TPS.

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. As shown in FIG. 1, an exhaust pipe (exhaust passage) 14 is connected to the exhaust manifold 12, and a small close three-way catalyst 20 and an exhaust purification catalyst device 30 close to the engine 1 are connected to the exhaust pipe 14. A muffler (not shown) is connected via the terminal. Also, exhaust pipe 1
4 is provided with a high temperature sensor 16 for detecting the exhaust gas temperature.

The exhaust purification catalyst device 30 is provided with two catalysts, that is, a storage type NOx catalyst 30a and a three-way catalyst 30b, and the three-way catalyst 30b has a storage type NOx catalyst 3a.
0a is disposed downstream. The storage NOx catalyst 30a temporarily stores NOx in an oxidizing atmosphere,
It has a function of 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 is configured as a catalyst having platinum (Pt), rhodium (Rh), or the like as a noble metal, and an alkali metal such as barium (Ba) or an alkaline earth metal as a storage material. Has been adopted.

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. Various sensors such as the high-temperature sensor 16 and the NOx sensor 32 described above are connected to the input side of the ECU 40, 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.

Actually, 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 TPS from the throttle sensor 11a and the engine 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 the 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 intake stroke injection modes include an intake lean mode that is a lean air-fuel ratio, a stoichiometric feedback mode that is a stoichiometric air-fuel ratio, and an open loop mode that is a rich air-fuel ratio.

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 purification apparatus thus configured according to the present invention will be described. That is, SOx is also stored in the storage NOx catalyst 30a as described above, and the SOx is removed by combustion control.
Hereinafter, the combustion control according to the present invention will be described. Referring to FIG. 2, there is shown a flowchart of a combustion control routine according to the present invention, which will be described below with reference to the flowchart.

First, in step S10, it is determined whether or not the NOx catalyst has deteriorated by S (sulfur), that is, whether or not the amount of SOx stored in the storage type NOx catalyst 30a (the poisoned S amount Qs) has reached a predetermined amount. (Sulfur component removal necessity determination means). Here, the poisoning S amount Qs is a value obtained by estimation. Hereinafter, an estimation method (detection method) of the poisoning S amount Qs will be briefly 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). Qs = Qs (n−1) + ΔQf · K−Rs (1) where Qs (n−1) is the previous value of the poisoning S amount, ΔQf is the fuel injection integrated amount per execution cycle, and K is Correction coefficient, Rs
Indicates the reproduction S amount per execution cycle.

That is, the current poisoning S amount Qs is integrated by correcting the integrated fuel injection amount ΔQf per execution cycle with the correction coefficient K, and subtracting the regenerated S amount Rs per execution cycle from the integrated value. It is required by that. The correction coefficient K is
For example, as shown in the following equation (2), 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 poisoning according to the catalyst temperature Tcat. It consists of the product of the three correction coefficients K3.

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 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 determination result of step S10 is true (Yes).
If it is determined that the NOx catalyst has deteriorated by S, the process proceeds to step S12. In step S12, a determination threshold value ΔT of the throttle opening change rate ΔTPS calculated based on the throttle opening information TPS from the throttle sensor 11a.
PSB is changed from value b to value a (a> b) (acceleration determination value changing means). Here, the threshold value ΔTPSB is, for example, an acceleration determination value used as a switching determination threshold value for switching from the intake lean mode to the stoichiometric feedback mode or the open loop mode, and the value b is determined in advance based on an experiment or the like for the switching determination. This is an appropriately set reference determination value. Since the value b is a small value, the throttle opening change rate ΔTPS
Is smaller than the value b, the engine 1 can be considered to be in a steady operation state.

Normally, when the vehicle is accelerating, for example, the throttle opening change rate ΔTPS is equal to the threshold value ΔTPSB
When the value is larger than (value b), that is, when the vehicle is not in the steady running state and the engine 1 is not in the steady running state,
When the S purge is performed as described above, the acceleration feeling deteriorates. Therefore, it is preferable that priority is given to prevention of deterioration of the acceleration feeling and the S purge is not performed.

However, after it is determined that the NOx catalyst has deteriorated in S, the S purge should be performed in order to secure the NOx purifying ability. Therefore, here, NO
x When it is determined that the catalyst has deteriorated by S, the threshold value ΔTPSB of the throttle opening change rate ΔTPS is set so that only the extreme deterioration of the acceleration feeling is suppressed and the S purge is performed preferentially.
Is set to a value a (a> b) larger than the normal value b, and the execution of the S purge is permitted when the vehicle is in a moderate acceleration state.

As a result, the chance of executing the S purge in the case where the threshold value ΔTPSB is not changed is increased, and the S purge is reliably performed when the removal of SOx is required while preventing the acceleration feeling from deteriorating as much as possible. It is possible to do. When the threshold value ΔTPSB is set to the value a, the operation mode is set to the S purge mode in step S14,
Next, the process proceeds to step S16.

On the other hand, if the determination result of step S10 is false (N
In o), if it is not determined that the NOx catalyst has degraded by S, the process proceeds to step S20, and the threshold value ΔTPSB is set to the above-described normally used value b. That is, when the threshold value ΔTPSB is set to the value a as described above, the value a is returned to the value b. In this case, normal combustion control is performed in the next step S22 without performing S purge (sulfur component removal prohibition means). That is, when it is not determined that the NOx catalyst has deteriorated in S, the fuel injection mode is determined based on the map based on the target average effective pressure Pe and the engine rotation speed Ne and the acceleration determination value (threshold ΔTPSB). Parameter control is performed.

In step S16, it is determined whether the throttle opening change rate ΔTPS is equal to or greater than a threshold value ΔTPSB (value a) (acceleration determining means). If the determination result is true (Yes) and the throttle opening change rate ΔTPS is equal to or greater than the threshold value ΔTPSB (value a), that is, if it is determined that the vehicle is traveling not in slow acceleration but in large acceleration, the above-described steps are performed. Proceed to S22,
Normal combustion control is performed without performing S purge. That is, when the vehicle is greatly accelerated beyond the moderately accelerated state, priority is given to accelerated traveling without performing the S purge. As a result, the acceleration feeling is preferably prevented from greatly deteriorating against the driver's intention.

On the other hand, if the result of the determination in step S16 is false (N
In o), if the throttle opening change rate ΔTPS is smaller than the threshold value ΔTPSB (value a) and it is determined that the vehicle is in a steady running state or in a moderately accelerated state, the process proceeds to step S18, and the S purge is performed. (Sulfur component removing means). That is, when the vehicle is in a steady running state or in a moderately accelerated state, the target A / F (combustion parameter) is set to the rich air-fuel ratio, and the ignition timing (combustion parameter) is retarded to raise the exhaust gas temperature. Two-stage injection is performed. As for the two-stage injection, for example, the exhaust gas temperature is raised such that the main injection of the main combustion is performed during the compression stroke and the sub-injection is performed during the expansion stroke. Thereby, SOx is favorably removed.

As described above, in the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, when it is determined that the NOx catalyst has deteriorated by S, the threshold value ΔTPSB of the throttle opening change rate ΔTPS is set to a value larger than the normal value b. a (a> b) so that the determination condition is relaxed so that the S purge is performed not only when the vehicle is in a steady running state but also in a moderately accelerating state.

Therefore, the S-purge can be surely performed when SOx removal is necessary, while the S-purge is not always performed in the accelerated running state, while the acceleration feeling is prevented from being deteriorated as much as possible. In addition, it is possible to achieve both the prevention of deterioration of the acceleration feeling and the removal of SOx. By the way, in the above embodiment, whether or not to execute the S purge is determined in accordance with the acceleration state of the vehicle. However, as another embodiment, whether or not to perform the S purge is determined in consideration of the operating state of the engine 1. You may make it. That is, the target average effective pressure (engine load) P
e, the threshold value ΔTPSB of the throttle opening change rate ΔTPS may be switched according to the engine rotation speed Ne.

Referring to FIG. 3, the relationship between the target average effective pressure Pe and the engine speed Ne and the threshold value ΔTPSB is shown as a map.
e and the engine rotation speed Ne are small, and in the range A of the low-medium rotation / low-medium load region, the threshold value ΔTPSB is set to the value a so that the S purge is performed even at moderate acceleration, and the target average effective pressure Pe
And the engine rotation speed Ne is high, and in the range B of the high rotation / high load region, the running state in which the S purge is performed with the threshold value ΔTPSB as the value b may be limited to the steady running state.

As shown in FIG. 4, in the range A of the low / medium rotation / low / medium load region, the threshold value .DELTA.TPSB is not set, and the S purge is always performed even in the acceleration running state. In the range of the load area B, the running state in which the S purge is performed may be limited to the steady running state or the slow acceleration state with the threshold value ΔTPSB as the value a. In this manner, the S purge is suitably performed in the low-medium rotation / low-medium load region, and the acceleration feeling is particularly improved in the region of middle rotation / medium load or more where acceleration is large and acceleration feeling is important. It is kept good. In general, when exhaust gas temperature rise control such as retarded ignition timing or two-stage injection is performed in a high rotation / high load range, the temperature of the storage NOx catalyst 30a tends to be excessively high. Is prevented, and the life of the storage NOx catalyst 30a is extended.

In the region A of FIGS. 3 and 4, the threshold value ΔTPSB may be set to a value similar to that of the region B in the extremely low rotation / ultra low load range. In this case, if the S purge is performed in a range of extremely low rotation and extremely low load in which combustion is generally unstable, the combustion deteriorates. Is prevented.

The rate of change of throttle opening Δ is also taken into account in consideration of vehicle speed information V detected by a vehicle speed sensor (not shown).
The TPS threshold value ΔTPSB may be switched. For example, the S purge may be easily performed only when the vehicle speed V is equal to or higher than a predetermined middle vehicle speed (for example, 60 km / h). Accordingly, when the vehicle is at a high vehicle speed, the S purge is satisfactorily performed, while when the vehicle is at a low vehicle speed, the S purge is difficult to be performed, and the deterioration of drivability is further prevented.

In still another embodiment, NOx
The value of the threshold value ΔTPSB may be changed in consideration of the magnitude of the S storage amount of the catalyst. That is, while the amount of S occlusion is relatively small, there is a sufficient margin before the catalyst deteriorates in S. Therefore, the threshold value ΔTPSB is set small to give priority to prevention of deterioration of the acceleration feeling. The threshold value ΔTPSB is set to a large value with priority given to the S purge, so that the opportunity of the S purge is increased to ensure that the S purge is performed.

Specifically, for example, as shown in a map shown in FIG. 5, a threshold value ΔTPSB is first set according to the value of the poisoning S amount Qs.
The PSB is set to be small, and the S purge is performed only in a range where the deterioration of the acceleration feeling such as the steady operation or the extremely gentle acceleration is extremely small. On the other hand, when the poisoning S amount Qs is large, the threshold value ΔTPSB is set to a large value, so that the chance of performing the S purge is increased to ensure that the S purge is performed.

In this case, while the threshold value ΔTPSB is small, the chance of the S purge is reduced. Therefore, the S deterioration determination value of the poisoned S amount Qs is set to a small value, and the S purge is performed even if the S occlusion amount is relatively small. It should be implemented. For example, as shown in FIG. 5, the poisoning S amount Qs having the threshold value ΔTPSB as the value a is the value Qs2, and the poisoning S amount Qs that shifts the threshold value ΔTPSB from the value b to a value larger than the value b is the value Qs2. If Qs1, the value Qs2 is set as the S deterioration determination value when the threshold value ΔTPSB is the value a, and the value Qs1 smaller than the value Qs2 is set as the S deterioration determination value when the threshold value ΔTPSB is in a range smaller than the value a.

As the amount of S occlusion increases, the setting of the threshold value ΔTPSB (see FIGS. 3 and 4) corresponding to the above-described operating state is switched in accordance with the amount of S occlusion in order to increase the chance of S purging. It may be. That is, for example, the poisoning S
When the quantity Qs is relatively small (for example, Qs1 ≦ Qs <in FIG. 5)
In the range of Qs2), as shown in FIG. 3, in the low / medium rotation / low / medium load region (region A), the threshold value .DELTA.TPSB is set to the value "a" so that the S purge is performed even at moderate acceleration. In the load region (region B), the threshold value ΔTPSB is set to the value b, and the S purge is limited to the time of the steady operation. Then, when the poisoning S amount Qs becomes large (for example, when the range of Qs2 ≦ Qs in FIG. 5 is reached), the threshold value ΔTPSB is not set in the low / medium rotation / low / medium load region (region A) as shown in FIG. The S purge is always performed even in the acceleration running state, and the high rotation and high load region (region B)
In the description, the S purge is limited to the steady operation and the moderate acceleration with the threshold value ΔTPSB as the value a. In this case, since the operation state in which the S purge is performed is wider in the case of FIG. 4 than in the case of FIG. 3, the opportunity of the S purge can be increased as the S storage amount increases.

Further, as the amount of S occlusion increases, FIG.
You may make it expand the range of the area | region A in the middle, and narrow the range of the area | region B. This also increases the opportunity for S purge as the amount of S occlusion increases. Further, these methods of increasing the chance of S purging in accordance with the amount of S occlusion may be used in combination.

As described above, various embodiments are conceivable, but the present invention may be implemented by selecting the most appropriate method according to the characteristics of each vehicle and each engine. In addition,
In the above embodiment, the acceleration determination is performed based on the change in the throttle opening. However, the acceleration determination determines a change in the intake air amount, for example, a change in the intake air amount during one stroke with respect to the intake air amount during the previous stroke. The value may be compared with a threshold value, and the acceleration determination value is not particularly limited to that of the embodiment.

In the above embodiment, the engine 1 is a direct injection gasoline engine. However, the invention is not limited to this.
The engine 1 may be an intake pipe injection type lean burn engine or the like as long as the engine 1 switches the operation mode based on the acceleration determination.

[0046]

As described above in detail, according to the exhaust gas purifying apparatus for an internal combustion engine according to the first aspect of the present invention, the combustion parameter is controlled when the sulfur component (SOx) is removed (S purge). The removal of sulfur components when necessary, while ensuring that the deterioration of the acceleration feeling that occurs during operation is minimized, and at the same time prevent the deterioration of the acceleration feeling and remove the sulfur components. Can be.

[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 flowchart showing a control routine of combustion control according to the present invention.

FIG. 3 shows a target average effective pressure P according to another embodiment of the present invention.
4 is a map showing a relationship between e and the engine rotation speed Ne and a threshold value ΔTPSB.

FIG. 4 is a map showing a relationship between a target average effective pressure Pe and an engine rotation speed Ne and a threshold value ΔTPSB according to another example of another embodiment of the present invention.

FIG. 5 shows a poisoning S amount Q according to still another embodiment of the present invention.
6 is a map showing a relationship between s and a threshold value ΔTPSB.

[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 30a Storage type NOx catalyst 40 Electronic control unit (ECU)

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F01N 3/24 F01N 3/28 301C 3/28 301 F02D 41/04 305Z F02D 41/04 305 B01D 53/36 B F02P 5 / 15 F02P 5/15 B (72) Inventor Yuki Tamura 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation F-term (reference) 3G022 AA06 BA01 CA04 CA06 CA07 CA08 CA09 DA02 EA00 GA01 GA05 GA06 GA08 GA10 GA15 3G091 AA12 AA24 AB05 AB06 AB09 AB11 BA01 CA18 CB03 CB05 DB06 DB10 DC06 EA01 EA03 EA05 EA07 EA08 EA12 EA18 EA39 FA08 FA09 FA13 FA14 FA17 FC01 GB02Y GB03Y GB05Y GB06Y HA20 HA36 HA04 HA03 HA03 HA04 HA04 LB04 MA01 MA19 MA26 NA04 NA08 NB02 NB11 NC02 ND15 NE13 NE14 NE15 PA02Z PA11Z PA12Z PA17Z PB03Z PC01A PC02A PD12Z PE01Z PE03Z PF01Z 4D048 AA02 AA06 AB02 BA14Y BA15Y BA30Y BA33Y BA39 DA02 DA01 DA02 CC

Claims (1)

[Claims] 1. An exhaust passage for storing NOx in exhaust gas when the operating state is a lean air-fuel ratio operating state,
A storage type NOx that releases or reduces the stored NOx when in a stoichiometric air-fuel ratio operation or a rich air-fuel ratio operation state.
A catalyst, sulfur component removing means for controlling a combustion parameter to remove a sulfur component in the fuel stored in the storage NOx catalyst, and a sulfur component removal necessity determination for determining whether or not the sulfur component needs to be removed. Means, acceleration determination means for determining an acceleration state of the vehicle based on a predetermined acceleration determination value, and when the sulfur component removal necessity determination means determines that sulfur component removal is necessary, the acceleration determination value is increased. And a sulfur component removal prohibiting unit that prohibits the sulfur component removal unit from removing a sulfur component when the acceleration determination unit determines that the vehicle is in an accelerated state. An exhaust gas purification device for an internal combustion engine, comprising: