JP2003214154A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove SOF adhered to a NOX catalyst. <P>SOLUTION: NOX catalysts 6a, 6b for purifying NOX in exhaust emission emitted from an internal combustion engine are provided in branched emission passages 3a, 3b. The catalyst maintains SOX when the surrounding atmosphere is under lean atmosphere, while it desorbs the maintained SOX therefrom when the atmosphere is converted to rich atmosphere and the temperature exceeds a SOX desorbing temperature. When SOX is to be desorbed from the catalyst, the temperature of the catalyst is increased to the SOX desorbing temperature and a SOX desorption treatment converting the surrounding atmosphere to the rich atmosphere is performed, thereby desorbing SOX from the catalyst. While the desorption treatment is being performed, the surrounding atmosphere of the catalyst is temporarily put under lean atmosphere in prescribed operating conditions showing a reduction in SOX desorption efficiency due to the adhesion of SOF. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification device for an internal combustion engine.

[0002]

NO _X to purify the Related Art Nitrogen oxides in the exhaust gas discharged from an internal combustion engine of a compression ignition type a (NO _X)
An exhaust gas purification device provided with a catalyst in the engine exhaust passage is disclosed
No. 00-186537. NO _X catalyst according to this publication is to reduce and purify by surrounding reducing agent to release the NO _X which is absorbed and oxygen concentration around the NO _X when excessive oxygen is present around is absorbed and reduced You can Usually, because it contains excess oxygen in the exhaust gas discharged from an internal combustion engine of a compression ignition type, NO _X catalyst will continue to absorb the NO _X in the exhaust gas.

[0003] However, NO _X since the catalyst there is a limit to the amount of NO _X that can absorb, NO NO _X catalyst is absorbed _X
Of before the amount reaches the upper limit, unless reduced and purified NO _X that is absorbed in the NO _X catalyst, NO _X catalyst no longer absorb NO _X Shiezu, NO _X is to NO _X catalyst downstream It will be leaked. Therefore, in the above publication, before the amount of NO _X absorbed by the NO _X catalyst reaches its upper limit value, exhaust gas with a rich air-fuel ratio is supplied from the combustion heater to the NO _X catalyst, and the NO _X catalyst absorbs it. The NO _x that is being discharged is reduced and purified by the reducing agent in the exhaust gas.

By the way, since the fuel contains a sulfur component, sulfur oxides (SO _x ) are produced in the internal combustion engine. Then, the NO _X catalyst also absorbs SO _X in the exhaust gas. In this case, the amount of NO _{X that} can be absorbed by the NO _X catalyst is reduced. Therefore, in the above publication, in order to release the SO _X that is absorbed in the NO _X catalyst from the NO _X catalyst, and to supply a rich air-fuel ratio of the gas the NO _X catalyst from the combustion heater.

[0005]

By the way, the rich air-fuel ratio gas discharged from the combustion heater contains a soluble organic component (SOF). This SOF is NO _X
Catalyst surface, particularly, adhering to the noble metal catalyst surface of the NO _X catalyst, thereby lowering the catalytic function of the NO _X catalyst. That is, as described above, to release the NO _X catalyst from the SO _X, the rich air-fuel ratio of the gas is supplied to the NO _X catalyst from the combustion heater, SOF adheres to the NO _X catalyst, the catalytic function descend. In this case, the NO _X catalyst is gradually changed to S.
Since it becomes difficult to release O _X , it takes a long time to supply the rich air-fuel ratio gas from the combustion heater to the NO _X catalyst in order to release SO _X. As a result, the fuel efficiency of the combustion heater deteriorates. Therefore, an object of the present invention is to remove SOF adhering to the NO _X catalyst.

[0006]

In order to solve the above problems, in the first invention, an NO _x catalyst for purifying NO _{x in} exhaust gas discharged from an internal combustion engine is provided in an engine exhaust passage. and, NO _X catalyst retains the SO _X when the surrounding atmosphere is a lean atmosphere, when it should disengaging the SO _X from the NO _X catalyst, NO _X catalyst with raising the temperature of the NO _X catalyst to a SO _X leaving temperature In an exhaust gas purification device configured to separate SO _X from the NO _X catalyst by executing SO _X separation processing that makes the surrounding atmosphere a rich atmosphere, the atmosphere around the NO _X catalyst temporarily changes during the SO _X separation processing. The atmosphere is lean. According to this, a large amount of oxygen exists around the NO _x catalyst.

According to a second aspect of the invention, in the first aspect of the invention, the engine exhaust passage is branched into two exhaust branch passages arranged in parallel, and the NO _x catalysts are respectively arranged in these exhaust branch passages.

According to a third aspect of the present invention, in the first aspect, a flow rate control valve for controlling the amount of exhaust gas flowing into the NO _x catalyst is further provided, and the flow rate control valve of the flow rate control valve is controlled when the SO _x removal process is executed. The atmosphere around the NO _x catalyst is made rich while the opening is reduced to reduce the amount of exhaust gas flowing into the NO _x catalyst, and the opening of the flow rate control valve is temporarily increased to the NO _x catalyst. By increasing the amount of exhaust gas flowing in, the atmosphere around the NO _X catalyst is temporarily made lean.

[0009] In the fourth invention, in the third aspect, the flow regulating valve in the engine exhaust passage of the NO _X catalyst upstream or are arranged in the NO _X catalyst downstream of the engine exhaust passage.

According to a fifth aspect of the present invention, in the first aspect, the combustion type heater is further provided, and when the SO _X desorption process is executed, the NO type is supplied by supplying a rich air-fuel ratio gas to the NO _x catalyst. The temperature of the _X catalyst is raised and the atmosphere around the NO _X catalyst is made a rich atmosphere, while the NO _X catalyst is temporarily supplied with a lean air-fuel ratio gas from the combustion heater to generate NO _X.
The atmosphere around the catalyst is temporarily made lean.

In the sixth invention, in the first invention, N
O_XFlow rate to regulate the amount of exhaust gas flowing into the catalyst
NO control valve_XNO in the engine exhaust passage upstream of the catalyst_XUnder catalyst
And the combustion type
Further equipped with a heater, SO _XWhen executing the leaving process,
The operation of the internal combustion engine and the operation of the combustion heater are controlled to N
O_XThe temperature of the catalyst is raised and the NO_XThe catalyst temperature is SO_X
When the temperature rises to the release temperature, the flow rate adjustment valve on the upstream side
NO by reducing the opening_XThe amount of exhaust gas flowing into the catalyst
While reducing the flow rate control valve opening on the downstream side,
The optimum opening for operating the
The air-fuel ratio gas to NO_XBy feeding the catalyst
NO_XThe atmosphere around the catalyst is rich, while
NO from the combustion heater_XTemporarily lean air-fuel ratio on the catalyst
NO by supplying the gas_XAtmosphere around catalyst
Is temporarily made lean.

[0012] In the seventh invention, in the first aspect, further comprising a fuel addition device for adding fuel to the NO _X catalyst, fuel from fuel addition device during execution of the SO _X withdrawal process the NO _X catalyst The temperature of the NO _X catalyst is raised to the SO _X desorption temperature by adding and the atmosphere around the NO _X catalyst is made a rich atmosphere.
By temporarily reducing the amount of fuel added to the NO _x catalyst from the fuel addition device, the atmosphere around the NO _x catalyst is temporarily made lean.

In an eighth aspect of the present invention, in the first aspect of the present invention, when the period in which the atmosphere around the NO _x catalyst is a rich atmosphere exceeds a predetermined period during execution of the SO _x removal process, NO The atmosphere around the _X catalyst is made lean.

According to a ninth aspect, in the first aspect, an SO _X amount detection sensor for detecting the amount of SO _{X in} the gas flowing out from the NO _X catalyst is further provided, and the SO _X removal process is being performed. the amount of SO _X detected by the SO _X amount detection sensor when exceeded a predetermined amount, NO _X catalyst surrounding atmosphere is a lean atmosphere at.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An exhaust emission control device of the present invention will be described below with reference to the drawings. FIG. 1 shows an internal combustion engine equipped with the exhaust emission control device of the present invention. In the embodiment described below, the internal combustion engine is a compression ignition type internal combustion engine,
The present invention is also applicable to a spark ignition type internal combustion engine. In FIG. 1, 1 is an engine body, 2 is an intake passage, and 3 is an exhaust passage. A throttle valve 4 is arranged in the intake passage 3. A step motor 5 is connected to the throttle valve 4.

The exhaust passage 3 has two exhaust branch passages arranged in parallel,
That is, the first exhaust branch passage 3a and the second exhaust branch passage 3
Branch to b. The first NO in the first exhaust branch passage 3a
_{The X} catalyst 6a is arranged. The first 1NO _X catalyst 6a upstream of the exhaust branch passage 3a first temperature sensor 7a for detecting the temperature is mounted. Furthermore, the first NO _x catalyst 6
A first air-fuel ratio sensor 8a for detecting the air-fuel ratio of the exhaust gas is attached to the first exhaust branch passage 3a upstream of a.

On the other hand, a second NO _x catalyst 6b is arranged in the second exhaust branch passage 3b. The exhaust branch passage 3b of the upstream first 2NO _X catalyst 6b second temperature sensor 7b for detecting the temperature is mounted. Further, the second exhaust branch passage 3b of the upstream first 2NO _X catalyst 6b, the second air-fuel ratio sensor 8b for detecting the air-fuel ratio of the exhaust gas is attached.

The first exhaust branch passage 3a and the second exhaust branch passage 3b join together downstream of the NO _x catalysts 6a, 6b.

An exhaust passage branch region where the exhaust branch passages 3a, 3b branch from the exhaust passage 3, that is, the NO _x catalyst 6a,
A flow rate control valve (hereinafter, referred to as an upstream side flow rate control valve) 9 for adjusting the amount of exhaust gas flowing into each exhaust branch passage 3a, 3b is arranged upstream of 6b. Upstream flow control valve 9
A step motor 10 is connected to. The opening degree of the upstream side flow control valve 9 is reduced for the second NO _x catalyst 6b,
When the upstream side flow control valve 9 is positioned at the operating position shown in FIG. 1 (A), the amount of exhaust gas flowing into the second NO _x catalyst 6b becomes small, and almost all exhaust gas is in the first exhaust branch. It flows into the first NO _x catalyst 6a via the passage 3a. On the other hand, the opening degree of the upstream side flow control valve 9 is reduced for the first NO _x catalyst 6a, and the upstream side flow control valve 9 is shown in FIG.
When positioned in the operating position shown in (B), the amount of exhaust gas flowing into the first NO _x catalyst 6a becomes small, and almost all of the exhaust gas is passed through the second exhaust branch passage 3b to the second NO _x catalyst. Flows into 6b.

Furthermore, exhaust branch passage merging region exhaust branch passages 3a, 3b merge, i.e., NO _X catalyst 6a, 6b
A flow rate control valve (hereinafter, referred to as a downstream side flow rate control valve) 11 for controlling the amount of exhaust gas flowing into each of the exhaust branch passages 3a and 3b is arranged downstream. Downstream flow control valve 11
A step motor 12 is connected to. Opening of the downstream-side flow rate adjustment valve 11 is reduced to a 2NO _X catalyst 6b, when the downstream-side flow rate adjustment valve 11 is positioned at the operating position shown in FIG. 1 (A), to a 2NO _X catalyst 6b The amount of exhaust gas flowing in is reduced. On the other hand, the opening degree of the downstream-side flow rate adjustment valve 11 is reduced to a 1NO _X catalyst 6a, the downstream-side flow rate adjustment valve 11 is positioned at the operating position shown in FIG. 1 (B), first 1NO _X catalyst The amount of exhaust gas flowing into 6a is reduced.

The downstream flow control valve 11 prevents the exhaust gas flowing out from one exhaust branch passage from flowing into the other exhaust branch passage. That is, the downstream flow control valve 11
Is positioned at the operating position shown in FIG. 1 (A), the exhaust gas flowing out from the first exhaust branch passage 3a is prevented from flowing into the second exhaust branch passage 3b.
On the other hand, when the downstream flow control valve 11 is positioned at the operating position shown in FIG. 1B, the exhaust gas flowing out from the second exhaust branch passage 3b flows into the first exhaust branch passage 3a. Is prevented.

The downstream flow control valve 11 is positioned corresponding to the operating position of the upstream flow control valve 9. For example, when the upstream side flow control valve 9 is positioned at the operating position shown in FIG. 1A, the downstream side flow control valve 1
1 is positioned in the operating position shown in FIG. On the other hand, when the upstream flow control valve 9 is positioned at the operating position shown in FIG. 1 (B), the downstream flow control valve 11 is positioned at the operating position shown in FIG. 1 (B). It

The combustion gas passage 13 is provided in the exhaust passage branching region.
The combustion heater 14 is connected via the. Air is drawn into the combustion heater 14 through the heater intake passage 15. An intake amount control valve 16 for controlling the amount of air taken into the combustion heater 14 is arranged in the heater intake passage 15. A fuel tank 18 is connected to the combustion heater 14 via a fuel passage 17. The fuel tank 18 is also connected to the engine body 1 via the fuel passage 17. A fuel pump 19 having a variable discharge amount is arranged in the fuel passage 17.

The combustion heater 14 is equipped with an ignition device such as a glow plug, and fuel is supplied from the fuel tank 18 to the ignition device, and the high temperature gas can be discharged by burning the fuel. The NO _x catalysts 6a, 6b are heated by the high temperature gas discharged from the combustion heater 14. The intake of air to the combustion heater 14
For example, it is performed by an intake fan. Here, the combustion heater 14 is adjusted by adjusting the amount of air taken into the combustion heater 14 and the amount of fuel supplied to the ignition device.
The amount of gas exhausted from the and its air-fuel ratio can be adjusted.

Exhaust gas recirculation from the exhaust passage 3 upstream of the exhaust passage branch region to the intake passage 2 downstream of the throttle valve 4 (EG
R) The passage 20 extends. An EGR control valve 21 is arranged in the EGR passage 20. A step motor 22 is connected to the EGR control valve 21. When the EGR control valve 21 is opened, exhaust gas is introduced from the exhaust passage 3 into the intake passage 2 via the EGR passage 20. The amount of exhaust gas introduced into the intake passage 2 is controlled by adjusting the opening degree of the EGR control valve 21.

The first temperature sensor 7a, the second temperature sensor 7b, the first air-fuel ratio sensor 8a, and the second air-fuel ratio sensor 8b are connected to an electronic control unit (not shown), and their output signals are output. It is transmitted to the electronic control unit. On the other hand, the step motor 5 for driving the throttle valve, the step motor 10 for driving the upstream flow rate adjusting valve, the step motor 12 for driving the downstream flow rate adjusting valve, the fuel pump 19, and the EG.
The step motor 22 for driving the R control valve is connected to an electronic control unit, and these operations are controlled by the electronic control unit.

The first NO _X catalyst 6a holds NO _X by absorbing and adsorbing NO _X when excess oxygen exists in the surroundings, that is, when the surrounding atmosphere is a lean atmosphere, and the oxygen concentration in the surroundings decreases. when, for example, when the ambient atmosphere becomes rich atmosphere comprising the _the NO _X holding agent to release the NO _X holding, a noble metal catalyst capable of reducing purify NO _X by hydrocarbons. Configuration of the 2NO _X catalyst 6b is the same as that of the first 1NO _X catalyst 6a.

Since the compression ignition type internal combustion engine is normally operated at a lean air-fuel ratio, the exhaust gas discharged from the internal combustion engine contains an excess of oxygen. Further, since the compression ignition type internal combustion engine NO _X is produced, also includes NO _X in the exhaust gas. Therefore, during normal operation of the internal combustion engine, exhaust gas containing excess oxygen flows into the NO _x catalysts 6a and 6b,
The NO _x catalysts 6a and 6b continue to absorb and adsorb NO _x in the inflowing exhaust gas one after another.

However, the NO _x catalysts 6a and 6b absorb and
There is an upper limit to the amount of NO _{x that} can be retained by adsorption. Therefore, when the flow rate control valve 9, 11 is continuously positioned in the operation position shown in FIG. 1 (A), first 1NO _X
The amount of NO _X retained by the catalyst 6a (hereinafter referred to as the NO _X retained amount) reaches its upper limit value. In this case, the first NO _x
The catalyst 6a can not absorb and adsorb the NO _X longer, NO _X flows out NO _X catalyst 6a, to 6b downstream.

Therefore, in this embodiment, when the NO _X holding amount of the first NO _X catalyst 6a reaches the upper limit value or immediately before reaching the upper limit value, the operating position of the upstream side flow rate control valve 9 is determined. is switched to the operation position shown in 1 (B), the amount of exhaust gas flowing into the first 1NO _X catalyst 6a is reduced to substantially zero, and, FIG. 1 the operating position of the downstream-side flow rate adjustment valve 11 ( The operating position shown in FIG. 1A is switched to a position slightly closer to the operating position shown in FIG. 1B, and the combustion type heater 14 is opened with the first exhaust branch passage 3a slightly opened. From rich air-fuel ratio gas (hereinafter,
N for supplying the heater gas) to the first NO _x catalyst 6a
O _X purification processing is executed. Here, the rich air-fuel ratio gas is a gas whose oxygen concentration is lower than the oxygen concentration in the exhaust gas normally discharged from the internal combustion engine and which contains a relatively large amount of hydrocarbons (HC).

[0031] When Hitagasu of the thus rich air-fuel ratio is supplied to the 1NO _X catalyst 6a, since the atmosphere around the 1NO _X catalyst 6a is rich atmosphere, the first 1NO _X catalyst 6a holds NO _X Is released, and thus the released NO _X is reduced and purified by using HC in the heater gas as a reducing agent. As a result, the first NO _x catalyst 6a can again hold NO _x by absorption and adsorption. That is, the NO _X holding capacity of the first NO _X catalyst 6a is restored. Incidentally, while the NO _X purification process to the first 1NO _X catalyst 6a is running, the exhaust gas discharged from an internal combustion engine flows into the first 2NO _X catalyst 6b, NO _X is first 2NO _X catalyst in the exhaust gas 6b is retained by absorption / adsorption.

In this embodiment, the first NO _X catalyst 6
When the NO _x purification process for a is completed, the operating position of the downstream flow control valve 11 is switched to the operating position shown in FIG. 1 (B), and the exhaust gas flowing out from the second exhaust branch passage 3b becomes the first position. 1 Prevent the gas from flowing into the exhaust branch passage 3a. Then, the operating positions of the flow rate control valves 9 and 11 are maintained at the operating positions shown in FIG. 1B until the NO _X holding amount of the second NO _X catalyst 6b reaches the upper limit value. Then, when the NO _X holding amount of the second NO _X catalyst 6b reaches its upper limit value or immediately before reaching its upper limit value, the operating position of the upstream side flow rate control valve 9 is shown in FIG. 1 (A). The operating position is changed to the operating position where the amount of the exhaust gas flowing into the second NO _x catalyst 6b is reduced to almost zero, and the operating position of the downstream side flow control valve 11 is set to the operation shown in FIG. 1 (A). The position is switched to a position slightly closer to that of FIG. 1B than the position and the second exhaust branch passage 3b is opened slightly, and the rich air-fuel ratio heater gas is fed from the combustion heater 14 to the second NO _x.
It was supplied to the catalyst 6b, allowed to recover _the NO _X holding ability of the 2NO _X catalyst 6b.

[0033] Thereafter, the NO _X purification process for NO _X purification process and the 2NO _X catalyst 6b for the first 1NO _X catalyst 6a is repeated.

By the way, since the fuel supplied to the engine body 1 also contains the sulfur component (S), sulfur oxide (SO _X ) is generated in the internal combustion engine, and this SO _X is contained in the exhaust gas. Is also included. The NO _X catalysts 6a and 6b also retain such SO _X by absorption and adsorption. In this case, the NO _X holding ability of the NO _X catalysts 6a and 6b is reduced, and the NO _X purification process is executed more frequently on these NO _X catalysts. SO _X retained on the NO _X catalysts 6a and 6b
When the temperature of the NO _x catalysts 6a, 6b rises to the SO _x desorption temperature (for example, 600 ° C) and the surrounding atmosphere becomes a rich atmosphere, the NO _x catalysts 6a, 6b are desorbed.

Therefore, in this embodiment, each NO _x catalyst 6 is used.
The NO _x retention capacity (ie, catalytic function) of a and 6b is S
When it is determined that the NO _X holding capacity has been reduced by the O _X , the SO _X leaving process for leaving the SO _X from the NO _X catalyst having the lowered NO _X holding capacity is executed.

Specifically, when it is determined that the NO _X holding capacity of the first NO _X catalyst 6a is reduced by SO _X , each flow rate adjustment is performed as in the case where the NO _X purification process is executed. With the operating positions of the valves 9 and 11 switched, a high-temperature rich air-fuel ratio heater gas is supplied from the combustion heater 14 to the first NO _x catalyst 6a, whereby the temperature of the first NO _x catalyst 6a changes to the SO _x release temperature. And the atmosphere around the first NO _x catalyst 6a is made a rich atmosphere. Thus, the first NO _x catalyst 6
SO _x is released from a.

Of course, even when it is determined that the NO _X holding capacity of the second NO _X catalyst 6b has been reduced by SO _X , the flow rate control valves 9 as well as when the NO _X purification process is executed. , 11 with the operating positions switched, the heater gas with high temperature and rich air-fuel ratio is used as the second NO _x.
It is supplied to the catalyst 6b.

In this embodiment, each NO _X catalyst 6
When it is determined that the execution interval of the NO _x purification processing for a and 6b is shorter than a predetermined interval, or when the SO _x concentration in the fuel and the fuel consumption amount in the combustion type heater 14 are changed to the NO _x catalysts 6a and 6b. The amount of SO _X held is estimated, and when it is determined that the estimated amount exceeds a predetermined amount, it is determined that the catalytic functions of the NO _X catalysts 6a and 6b are reduced by SO _X. .

In this embodiment, the operating positions of the flow rate control valves 9 and 11 are the same as those shown in FIG. 1A each time the NO _x purification process or the SO _x removal process is executed. Although it is switched to the position shown in FIG. 1 (B), the operating positions of both the flow rate control valves 9 and 11 may be switched as follows.

That is, when the NO _x purification process or the SO _x removal process is not executed, the operating positions of both flow rate control valves 9 and 11 are the same as those shown in FIG. 1 (A).
Is positioned in an intermediate position between the position shown (B), the one of the NO _X catalyst 6a, NO _X with respect 6b
When the purification process or the SO _X removal process is to be executed, the operating positions of both the flow rate control valves 9 and 11 are positioned according to the embodiment described above with respect to the NO _X catalysts 6a and 6b. The operating positions of both the flow rate control valves 9 and 11 may be positioned at the original intermediate positions.

According to this, NO_XPurification treatment or SO_X
When the disengagement process is not executed, the exhaust gas is
O_XSince the catalysts 6a and 6b evenly flow into each catalyst, each NO_Xcatalyst
NO that must be retained in 6a and 6b_XThe amount of
It becomes half each. Therefore, each NO_XCatalyst 6a, 6b
NO in exhaust gas even if the capacity is small_XAre these NO _X
It is held well by the catalysts 6a and 6b. According to
According to this, the exhaust emission can be kept high.
One, NO_XThe mountability of the catalyst on the vehicle is improved.

By the way, a so-called soluble organic component (SOF) is contained in the rich air-fuel ratio gas (heater gas) supplied from the combustion heater 14 to the NO _X catalyst during the NO _X purification process and the SO _X removal process. ) Is included in a relatively large amount. This SOF is the surface of the NO _x catalysts 6a, 6b,
In particular, if it adheres to the surface of the noble metal catalyst, its catalytic function will decrease.

Since the execution period of the NO _x purification process is much shorter than the execution period of the SO _x removal process, the SOF adhering to the NO _x catalysts 6a and 6b during the execution of the NO _x purification process.
Is relatively small. Therefore, even if SOF adheres to the NO _x catalyst during the execution of the NO _x purification process, the NO _x purification capability of the NO _x catalyst does not decrease so much.

[0044] However, since the execution period of the SO _X withdrawal process is very long, the catalyst capacity of the NO _X catalyst during the SO _X withdrawal process is made to decrease the deposition of SOF, therefore, NO _X catalyst 6a, 6b of Of SO _X is slowed down, and in some cases, SO _X is hardly separated from the NO _X catalysts 6a and 6b.

Therefore, in the first embodiment, when it is determined that a predetermined condition is satisfied during execution of the SO _X removal processing, the heater gas supplied from the combustion heater 14 to the NO _X catalyst is changed. The air-fuel ratio is temporarily set to the lean air-fuel ratio. According to this, NO _X catalyst 6a, since the 6b is supplied an oxygen-rich Hitagasu, NO _X catalyst 6a, around 6b atmosphere is temporarily lean atmosphere, moreover, NO _X catalyst 6a at this time , the temperature of 6b is at a high temperature, SOF adhering the NO _X catalyst is once oxidized and removed by oxygen surrounding.

In the first embodiment, when the period in which the atmosphere around the NO _x catalysts 6a and 6b is rich atmosphere exceeds the predetermined period during execution of the SO _x removal process, the predetermined period is set. It is determined that the specified conditions are satisfied. In the first embodiment, during the execution of the SO _X withdrawal process, NO _X catalyst 6a, temporarily period to lean atmosphere atmosphere around 6b is the NO _X catalyst 6a,
The temperature of 6b is prevented from becoming too high, and the heater gas of the rich air-fuel ratio is returned to NO from the combustion type heater 14 again.
_X catalysts 6a, the NO _X catalyst 6a when fed to 6b,
6b Immediately make the surrounding atmosphere rich,
It is determined. From such a viewpoint, for example, when the period during which the heater gas of the rich air-fuel ratio is supplied from the combustion heater 14 exceeds, for example, 30 seconds, it is determined that the predetermined condition is satisfied, and the combustion heater From 14,
For example, the lean air-fuel ratio heater gas is supplied for 2 seconds.

FIG. 2 shows a flowchart for executing the SO _X withdrawal process of the first embodiment. In the flowchart shown in FIG. 2, first, at step 10, it is judged if the rich flag F1 is set (F1 = 1). The rich flag F1 is set when it is determined that the SO _X removal processing should be executed, and reset when it is determined that a sufficient amount of SO _X has been released from the NO _X catalysts 6a and 6b. It is a flag.

When it is determined in step 10 that F1 = 0, the routine ends. On the other hand, when it is determined in step 10 that F1 = 1, the routine proceeds to step 11 and the opening degree of the flow rate control valves 9, 11 for the NO _x catalysts 6a, 6b to be subjected to SO _x removal processing. Is reduced, and then in step 12, the combustion-type heater 14 supplies the heater gas with a rich air-fuel ratio.

Next, at step 13, it is judged if the lean flag F2 is set (F2 = 1). The lean flag F2 is set when it is determined that the heater gas having the lean air-fuel ratio should be supplied to the NO _x catalysts 6a and 6b, and it is determined that a sufficient amount of SOF has been oxidized and removed from the NO _x catalysts 6a and 6b. It is a flag that is reset when

When it is determined in step 13 that F2 = 0, the routine ends. On the other hand, when it is determined in step 13 that F2 = 1, the routine proceeds to step 14 and the combustion heater 1
A heater gas having a lean air-fuel ratio is supplied from No. 4, and then in step 15, the flag F2 is reset.

Further, as shown in FIG. 3, the SO _x detection sensors 23a and 23b for detecting the amount or concentration of SO _{x in} the gas flowing out from the NO _x catalysts 6a and 6b are N-type.
The amount of O _X catalyst downstream of the exhaust branch passages 3a, in the second embodiment attached to 3b is, NO _X catalyst 6a of SO _X withdrawal process is performed, SO _X in the gas flowing out from 6b Alternatively, the SO _X detection sensor 23 corresponding to the concentration
a, 23b detected, SO _X detected here
When the amount or concentration of exceeds a predetermined amount or concentration (for example, 20 ppm), it is determined that the predetermined condition is satisfied.

Further, in the SO _X release processing of the third embodiment, when it is determined that the predetermined conditions are satisfied as described above in the exhaust purification system of the internal combustion engine having the configuration shown in FIG. The operation of the combustion heater 14 is stopped and the NO _X catalyst 6 that has been subjected to SO _X removal processing
For a and 6b, the openings of the flow rate control valves 9 and 11 are temporarily increased. According to this, the exhaust gas discharged from the internal combustion engine is supplied to the NO _x catalysts 6a, 6b, and the oxygen concentration of the exhaust gas at this time is high, so the NO _x catalysts 6a, 6b
b The atmosphere around b temporarily becomes a lean atmosphere, and since the temperature of the NO _x catalysts 6a and 6b at this time is high, the SOF adhering to the NO _x catalyst is oxidized and removed at once by the oxygen around it. It

FIG. 4 shows a flow chart for executing the SO _X withdrawal process of the third embodiment. In the flowchart shown in FIG. 4, first, at step 20, it is judged if the rich flag F1 is set (F1 = 1). The rich flag F1 here is the same as the rich flag F1 shown in FIG.

When it is determined in step 20 that F1 = 0, the routine ends. On the other hand, when it is determined in step 20 that F1 = 1, the routine proceeds to step 21, and the opening degree of the flow rate control valves 9 and 11 for the NO _x catalysts 6a and 6b to be subjected to SO _x removal processing. Is reduced, and then, in step 22, the combustion type heater 14 supplies the heater gas of the rich air-fuel ratio.

Next, at step 23, it is judged if the lean flag F2 is set (F2 = 1). The lean flag F2 here is also the same as the lean flag F2 shown in FIG. When it is determined in step 23 that F2 = 0, the routine ends. On the other hand, when it is determined in step 23 that F2 = 1, the routine proceeds to step 24, where the supply of the rich air-fuel ratio heater gas from the combustion heater 14 is stopped, and then in step 25, the flow rate control valve is set. The opening degrees of 9 and 11 are increased, and then in step 26, the flag F2 is reset.

The above-described embodiment can also be applied to the exhaust emission control device having the configuration shown in FIG. In the exhaust emission control device of the fourth embodiment shown in FIG. 5, upstream side flow rate control valves 9a, 9b and downstream side flow rate control valves 11a, 11b are arranged in each exhaust branch passage 3a, 3b. Corresponding step motors 10a, 10b, 12a, 12b are connected to these flow rate control valves 9a, 9b, 11a, 11b, respectively. Further, the combustion gas passage 13 is branched into two gas branch passages 13a and 13b. These gas branch passages 13
a and 13b are connected to the combustion gas passage 13 via a switching valve 24. The switching valve 24 switches whether the gas discharged from the combustion heater 14 is supplied to the first NO _x catalyst 6a or the second NO _x catalyst 6b.

Further, in the SO _X release processing of the fifth embodiment, when it is determined that SO _X should be released from the NO _X catalysts 6a and 6b, the operation of the internal combustion engine and the operation of the combustion heater 14 are performed. That is, the characteristics of the exhaust gas discharged from the internal combustion engine and the characteristics of the heater gas discharged from the combustion type heater 14 are controlled to control the NO _x catalyst 6a,
Raise the temperature of 6b. When the NO _X catalyst 6a of more to disengaging the SO _X, the temperature of 6b rises until the SO _X leaving temperature, the opening of the upstream-side flow rate adjustment valve 9 is reduced to the NO _X catalyst 6a, 6b And the NO _x
The amount of exhaust gas flowing into the catalysts 6a and 6b is reduced, and the opening of the downstream flow control valve 11 is set to the optimum opening for the operation of the combustion heater 14, and then the combustion heater 14
A gas having a rich air-fuel ratio is supplied to the NO _X catalysts 6a and 6b. On the other hand, when it is determined that the predetermined conditions are satisfied as described above, the lean air-fuel ratio heater gas is temporarily supplied from the combustion heater 14 to the NO _X catalysts 6a and 6b.

Further, in the above-described embodiment, SO _X
The opening degree of each of the flow rate control valves 9 and 11 at the time of executing the disengagement process is determined by operating parameters of the internal combustion engine, for example, engine speed,
The amount of air taken into the combustion chamber of the internal combustion engine (hereinafter simply referred to as intake air amount), the amount of fuel injected into the combustion chamber of the internal combustion engine (hereinafter simply referred to as fuel injection amount), and the internal combustion engine It is determined according to the air-fuel ratio of the exhaust gas discharged from the combustion chamber (hereinafter, simply referred to as the exhaust air-fuel ratio). That is,
With respect to these operating parameters, the opening degrees of the flow rate control valves 9 and 11 are experimentally obtained in advance and stored in the electronic control unit in the form of a map, and the opening degrees of the flow rate control valves 9 and 11 are used by using this map. Is controlled.

In the above-described embodiment, the NO _x catalyst 6 is used.
It is also applicable to an exhaust gas purification device in which the flow rate control valve 9 is arranged only upstream of a and 6b, and to an exhaust gas purification device in which the flow rate control valve 11 is arranged only downstream of the NO _x catalysts 6a and 6b. Is.

Next, an exhaust purification system of the sixth embodiment will be explained. The exhaust emission control device of the sixth embodiment is shown in FIG. The exhaust purification system of the sixth embodiment, instead of the combustion heater, and the NO _X catalyst 6a, 6b upstream of the exhaust branch passage 3a, the fuel addition device 25a to 3b, 25b is attached. These fuel addition devices 25a and 25b are connected to a fuel tank (see FIG. 1) 18 via corresponding fuel passages 17. These fuel addition device 25a, 25b can be added to the fuel corresponding NO _X catalyst 6a, in 6b. The fuel addition devices 25a and 25b are connected to an electronic control device, and their operation is controlled by the electronic control device.

In the NO _X purification processing of the present embodiment, when the NO _X holding amount of one of the NO _X catalysts 6a and 6b reaches its upper limit value, or immediately before reaching the upper limit value, the NO _{X is} reduced.
_X catalysts 6a, switching the operating position of the upstream-side flow rate adjustment valve 9 so that the amount of the exhaust gas flowing into 6b is reduced to substantially zero, and, the NO _X catalyst 6a, 6b downstream of the exhaust branch passages 3a, 3b There over switching the operating position of the downstream-side flow rate adjustment valve 11 so that the state of being opened only slightly, corresponding fuel addition device 25a, the from 25b NO _X catalyst 6a, for injecting fuel into 6b.

When fuel is added to the corresponding NO _x catalysts 6a, 6b from the fuel adding devices 25a, 25b in this way, the atmosphere around the NO _x catalysts 6a, 6b becomes a rich atmosphere, so the NO _x catalysts 6a, 6b 6b holds NO _X
And the NO _x released in this way is added to the fuel addition device 2
The fuel (HC) supplied from 5a and 25b is used as a reducing agent for reduction purification.

On the other hand, in the SO _X withdrawal process of this embodiment,
When it is estimated that the NO _X holding capacity of one of the NO _X catalysts 6a and 6b is reduced by SO _X , NO
_{As in the case where the X} purification processing is executed, the NO _x catalysts 6a and 6b corresponding to the NO _x catalysts 6a and 6b are switched from the fuel addition devices 25a and 25b while the operation positions of the flow rate control valves 9 and 11 are switched.
Fuel is supplied to the NO _x catalyst 6a,
The temperature of 6b is raised to the SO _X desorption temperature, and the atmosphere around the NO _X catalysts 6a and 6b is made a rich atmosphere.

And SO_XSmell during the process of leaving
And determined that the predetermined conditions were met as described above.
When the fuel is cut off, the fuel is added from the fuel adding devices 25a and 25b.
The NO _XThe amount of fuel added to the catalysts 6a and 6b is temporarily changed.
NO by reducing to almost zero_XCatalyst 6
The atmosphere around a and 6b is temporarily made lean.
It Further, in this embodiment, at this time, NO_XCatalyst 6
Increase the leanness of the surrounding atmosphere.
Therefore, the opening degree of the upstream side flow control valve 9 is_XCatalyst 6
a, 6b is temporarily increased, and the NO_Xcatalyst
Exhaust gas discharged from the internal combustion engine is supplied to 6a and 6b.
Be done.

Here, in the SO _X removal process, the NO _X catalyst 6 is supplied from the fuel adding devices 25a and 25b per unit time.
a, the amount of fuel added to 6b is, NO _X purification process fuel addition device 25a in, NO _X catalyst 6a from 25b per unit time greater than the amount of fuel added to 6b.

In the SO _X withdrawal process of this embodiment, the amount of fuel added from the fuel adding devices 25a and 25b, and the amount of fuel temporarily reduced when it is determined that a predetermined condition is satisfied. And the period during which the amount of fuel is temporarily reduced in this manner are determined according to the operating parameters of the internal combustion engine, for example, the engine speed, the intake amount, the fuel injection amount, and the exhaust air-fuel ratio. .

Further, in this embodiment, as shown in FIG.
O _X sensor 23a, also the exhaust gas purification device comprising a 23b is applicable. Further, in this embodiment, as shown in FIG. 5, the upstream side flow control valve 9 is provided in each of the exhaust branch passages 3a and 3b.
It is also applicable to the embodiment in which a, 9b and the downstream flow rate control valves 11a, 11b are arranged. Further, in the SO _X removal processing of the present embodiment, when it is determined that the SO _X should be released from the NO _X catalysts 6a and 6b, the fuel is not added from the fuel adding devices 25a and 25b and the flow rate adjustment is performed. While maintaining the operating positions of the valves 9 and 11, the operation of the internal combustion engine is controlled, that is, the characteristic of the exhaust gas discharged from the internal combustion engine is controlled to change the temperature of the NO _x catalysts 6a and 6b to the SO _x release temperature. raised to, then switched and the fuel addition device 25a as described above the operation position of the flow control valves 9, 11, 25b the fuel from NO _X catalyst 6
It may be added to a and 6b.

Of course, also in this embodiment, SO _X
The opening degree of each of the flow rate control valves 9 and 11 at the time of executing the disengagement process is determined by operating parameters of the internal combustion engine, for example, engine speed,
It is determined according to the intake air amount, the fuel injection amount, and the exhaust air-fuel ratio.

Further, in the present embodiment, the NO _x catalysts 6a, 6 are
b It is also applicable to an exhaust gas purification device in which the flow rate control valve 9 is arranged only upstream, and is also applicable to an exhaust gas purification device in which the flow rate control valve 11 is arranged only downstream of the NO _x catalysts 6a and 6b. .

FIG. 7 shows a flow chart for executing the SO _X withdrawal process of the sixth embodiment. In the flowchart shown in FIG. 7, first, at step 30, it is judged if the rich flag F1 is set (F1 = 1). The rich flag F1 here is the same as the rich flag F1 shown in FIG.

When it is determined in step 30 that F1 = 0, the routine ends. On the other hand, when it is determined in step 30 that F1 = 1, the routine proceeds to step 31, and the opening degree of the flow rate control valves 9 and 11 for the NO _x catalysts 6a and 6b to be subjected to the SO _x removal processing. Is reduced, and then, in step 32, fuel is added from the fuel addition devices 25a and 25b.

Next, at step 33, it is judged if the lean flag F2 is set (F2 = 1). The lean flag F2 here is also the same as the lean flag F2 shown in FIG. When it is determined in step 33 that F2 = 0, the routine ends. On the other hand, when it is determined in step 33 that F2 = 1, the routine proceeds to step 34, where the addition of fuel from the fuel addition devices 25a and 25b is stopped, and then in step 35, the flow rate control valve 9, The opening degree of 11 is increased, and then, in step 36, the flag F2 is reset.

The present invention can also be applied to an exhaust gas purification device equipped with the particulate filter shown in FIG. Finally, the particulate filter (hereinafter, simply referred to as a filter) 30 shown in FIG. 8 will be described.
FIG. 8A is an end view of the filter 30, and FIG.
FIG. 4 is a vertical sectional view of the filter 30. As shown in FIGS. 8A and 8B, the filter 30 has a honeycomb structure, and includes a plurality of exhaust flow passages 50 and 51 extending in parallel with each other. About half of these exhaust flow passages are exhaust inflow passages 50 by closing their downstream end openings with plugs 52, and the other half are exhaust outflow passages 51 by closing their upstream end openings with plugs 53. There is. The exhaust gas inflow passages 50 and the exhaust gas outflow passages 51 are alternately arranged via thin partition walls 54. In other words, in the exhaust gas inflow passage 50 and the exhaust gas outflow passage 51, each exhaust gas inflow passage 50 is surrounded by the four exhaust gas outflow passages 51, and each exhaust gas outflow passage 51 is surrounded by the four exhaust gas inflow passages 50. It is arranged as described.

The filter 30 is formed of a porous material such as cordierite. Therefore, the exhaust gas that has flowed into the exhaust gas inflow passage 50 is generated as shown in FIG.
As indicated by an arrow in FIG. 5, the gas flows through the pores of the partition wall 54 and flows into the adjacent exhaust gas outflow passage 51.

In the filter 30, a carrier layer made of, for example, alumina is formed on both wall surfaces of the partition wall 54 and on the wall surface defining the pores of the partition wall, and on this carrier layer. In addition, a noble metal catalyst and an active oxygen generator are supported.

Platinum (Pt) is used as the noble metal catalyst. On the other hand, as the active oxygen generator, potassium (K), sodium (Na), lithium (Li), cesium (Cs), alkali metal such as rubidium (Rb), barium (Ba), calcium (Ca), strontium. Alkaline earth metals such as (Sr), lanthanum (La), rare earths such as yttrium (Y), cerium (Ce), transition metals such as iron (Fe), and carbon groups such as tin (Sn). At least one selected from the elements is used.

The active oxygen generating agent retains oxygen by absorbing and adsorbing excess oxygen in the presence of excess oxygen in the surroundings and releases the retained oxygen in the form of active oxygen when the concentration of oxygen in the surroundings is reduced. To generate. Next, the active oxygen generating action of the active oxygen generating agent will be described by taking as an example the case of supporting platinum and potassium on the carrier, but using other noble metals, alkali metals, alkaline earth metals, rare earths and transition metals. Even if the same active oxygen generation action is performed.

When the ratio of air to fuel supplied into the intake passage 2 and the combustion chamber of the internal combustion engine is called the air-fuel ratio of exhaust gas, the air-fuel ratio of exhaust gas discharged from the compression ignition type internal combustion engine is lean. . Therefore, the exhaust gas flowing into the filter 30 contains a large amount of excess air. Further, NO is generated in the combustion chamber of the compression ignition type internal combustion engine. Therefore, NO is contained in the exhaust gas. Further, the fuel contains a sulfur component S, and this sulfur component S reacts with oxygen in the combustion chamber to become SO ₂ . Therefore, the exhaust gas contains SO ₂ . Therefore, the exhaust gas containing excess oxygen, NO and SO ₂ will be filtered by the filter 30.
Will flow into the exhaust gas inflow passage 50.

9A and 9B schematically show enlarged views of the surface of the carrier layer formed on the peripheral wall surface of the exhaust gas inflow passage 50. 8 (A) and (B)
In the above, 60 represents a particle of platinum, and 61 represents an active oxygen generator containing potassium.

When the exhaust gas flows into the exhaust gas inflow passage 50 of the filter 30, as shown in FIG. 9 (A), oxygen (O ₂ ) in the exhaust gas becomes O ₂ ⁻ or O ^{2 −.} Adheres to the surface of platinum. On the other hand, NO in the exhaust gas reacts with O ₂ ⁻ or O ^{2 −} on the surface of platinum to become NO ₂ (2NO +
O ₂ → 2NO ₂ ). A portion of the NO ₂ thus generated is retained on the active oxygen generator 61 by being absorbed (adsorbed in some cases) while being oxidized on platinum, and is bound to potassium as shown in FIG. 9 (A). While nitrate ion (N
It diffuses in the active oxygen generator 61 in the form of O ₃ ⁻ ) to generate potassium nitrate (KNO ₃ ). That is, oxygen in the exhaust gas is retained in the active oxygen generator 61 by absorption in the form of potassium nitrate (KNO ₃ ).

SO ₂ in the exhaust gas is also retained by absorption (adsorption in some cases) in the active oxygen generator 61 by a mechanism similar to NO. That is, SO in exhaust gas
₂ reacts with O ₂ ⁻ or O ^{2 − on} the surface of platinum to become SO ₃ . A part of the SO ₃ thus generated is further oxidized on platinum and retained by absorption in the active oxygen generator 61, and is bound to potassium to form a sulfate ion (SO ₄ ²⁻ ).
In the form of, it diffuses into the active oxygen generator 61 to generate potassium sulfate (K ₂ SO ₄ ). That is, the oxygen in the exhaust gas is in the form of potassium sulfate (K ₂ SO ₄ ) and the active oxygen generator 61
Retained by absorption within.

Here, fine particles mainly composed of carbon (C) are produced in the combustion chamber. Therefore, the exhaust gas contains these fine particles. These fine particles contained in the exhaust gas are indicated by 62 in FIG. 9B when the exhaust gas is flowing in the exhaust gas inflow passage 50 of the filter 30 or when passing through the pores of the partition wall 54. As shown in (3), the surface of the carrier layer, for example, the surface of the active oxygen generating agent 61 is contacted and attached.

In this way, the fine particles 62 are the active oxygen generator 6
When it adheres to the surface of No. 1, the oxygen concentration decreases at the contact surface between the fine particles 62 and the active oxygen generator 61. That is, the oxygen concentration around the active oxygen generator 61 decreases. When the oxygen concentration decreases, a difference in concentration occurs between the active oxygen generating agent 61 and the active oxygen generating agent 61 having a high oxygen concentration. Try to move towards. As a result, the active oxygen generator 6
The potassium nitrate (KNO ₃ ) formed in 1 is decomposed into potassium (K), oxygen (O) and NO, and the oxygen (O) goes to the contact surface between the fine particles 62 and the active oxygen generator 61, On the other hand, NO is released from the active oxygen generator 61 to the outside. Thus, the active oxygen generator 61 produces active oxygen. The NO released to the outside is oxidized on the platinum on the downstream side and is retained again in the active oxygen generator 61.

Further, at this time, potassium sulfate (K ₂ SO ₄ ) formed in the active oxygen generator 61 is also decomposed into potassium (K), oxygen (O) and SO ₂ , and oxygen (O) is generated.
Toward the contact surface between the fine particles 62 and the active oxygen generating agent 61, while SO ₂ is released from the active oxygen generating agent 61 to the outside. Thus, the active oxygen generator 61 produces active oxygen. The SO ₂ released to the outside is oxidized on the platinum on the downstream side, and is retained by the active oxygen generator 61 again. However, since potassium sulfate is stable and difficult to decompose, potassium sulfate releases less oxygen than potassium nitrate.

Here, the active oxygen generated by the active oxygen generator 61 is consumed to oxidize and remove the fine particles attached thereto. That is, the fine particles collected by the filter 30 are oxidized and removed by the active oxygen generated by the active oxygen generator 61.

Conventionally, in the case of removing the particulates collected by the filter, the particulates are burned by raising the temperature of the filter to a relatively high temperature, thereby removing the particulates.

On the other hand, oxygen used for removing fine particles in the present invention is active oxygen decomposed from a compound such as potassium nitrate or potassium sulfate and has an unpaired electron, and therefore has extremely high reactivity. Have. Therefore, the active oxygen can oxidize and remove the fine particles even if the temperature of the filter is relatively low.

As described above, in the conventional filter, the fine particles are removed by the combustion accompanied by the flame, whereas in the filter of the present invention, the fine particles are removed by the oxidation that does not emit the bright flame. Therefore, according to the filter of the present invention, the fine particles collected therein are continuously oxidized and removed, that is, when the active oxygen (O) comes into contact with the fine particles 62, the fine particles 62 are left in a short time (from several seconds to several tens of minutes). ), The fine particles 62 are completely extinguished by being oxidized without emitting a luminous flame. Therefore, the fine particles 62 are not absorbed by the filter
It rarely deposits on top.

The active oxygen generator 61 retains NO _x in the form of nitrate ions when excess oxygen is present in the surroundings, and consequently retains oxygen. That is, the active oxygen generator 61 retains NO _X by absorbing and adsorbing NO _X when excess oxygen exists in the surroundings. On the other hand, active oxygen generator 6
1 produces active oxygen by releasing NO _X retained in the form of nitrate ions when the ambient oxygen concentration decreases. That is, the active oxygen generator 61 releases NO _X when the surrounding oxygen concentration decreases. Therefore, the active oxygen generator 61 of the present invention also functions as a NO _X holding agent.

Here, the case where the oxygen concentration around the active oxygen generator 61 decreases is as described above, in addition to the case where the surrounding atmosphere is a lean atmosphere but fine particles adhere to the active oxygen generator 61. In some cases, the air-fuel ratio of the gas flowing into the filter 30 becomes rich and the surrounding atmosphere becomes rich.

Although the surrounding atmosphere is a rich atmosphere, the NO released when the oxygen concentration around the active oxygen generator 61 decreases due to the adhesion of fine particles to the active oxygen generator 61.
As described above, _X is again held by the active oxygen generator 61 by absorption. On the other hand, NO _X in which ambient atmosphere is released when it becomes a rich atmosphere air-fuel ratio of the exhaust gas flowing into the filter 30 becomes rich, it is reduced and purified by hydrocarbons in the exhaust gas by the action of the platinum . In other words, by supplying the rich air-fuel ratio gas from the combustion heater 14 to the filter 30, the NO _X retained in the active oxygen generator 61 can be reduced and purified. Therefore, the filter 30 of the present invention is the active oxygen generator 6
A NO _x catalyst composed of 1 and platinum is provided.

[0092]

According to the present invention, the atmosphere around the NO _x catalyst is temporarily made lean during the execution of the SO _x desorption process, whereby a large amount of oxygen exists around the NO _x catalyst. Becomes Therefore, the soluble organic substance (SOF) attached to the NO _x catalyst surface is oxidized and removed.

[Brief description of drawings]

FIG. 1 is a diagram showing an internal combustion engine equipped with an exhaust emission control device of a first embodiment.

FIG. 2 is a flowchart for executing a SO _X leaving process of the first embodiment.

FIG. 3 is a diagram showing an exhaust emission control device of a second embodiment.

FIG. 4 is a flowchart for executing SO _X departure processing of the third embodiment.

FIG. 5 is a diagram showing an exhaust emission control device of a fourth embodiment.

FIG. 6 is a diagram showing an exhaust emission control device of a sixth embodiment.

FIG. 7 is a flow chart for executing SO _X departure processing of the sixth embodiment.

FIG. 8 is a diagram showing a particulate filter.

FIG. 9 is a diagram for explaining an active oxygen generating action of an active oxygen generating agent.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine main body 2 ... Intake passage 3 ... Exhaust passages 3a, 3b ... Exhaust branch passages 6a, 6b ... NO _X catalyst 9, 9a, 9b, 11, 11a, 11b ... Flow control valve 14 ... Combustion heater 18 ... Fuel tank 23a, 23b ... SO _X detection sensors 25a, 25b ... Fuel addition device 30 ... Particulate filter

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) F01N 3/24 F01N 3/24 QR 3/28 301C 301H 3/28 301 3/36 J M 3/36 R 9/00 Z F02D 43/00 301K 9/00 301T F02D 43/00 301 45/00 301A 301G 45/00 301 314T B01D 53/36 101A 314 ZAB 101B (72) Inventor Toshiaki Tanaka Toyota City, Aichi Prefecture No. 1 Toyota Motor Co., Ltd. (72) Inventor Takamitsu Asanuma No. 1 Toyota-cho, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (72) Inventor Koichi Kimura No. 1 Toyota-cho, Toyota City, Aichi Toyota Motor Co., Ltd. (72) Inventor Koichiro Nakatani 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Corporation (72) Tomorrow Akira Akira Prefecture, Toyota City, Aichi Prefecture 1 Toyota Town F-Term (Reference) 3G084 AA01 AA04 BA05 BA09 BA13 BA15 BA19 BA20 BA24 BA25 DA10 DA22 DA27 EA11 EB01 EB22 FA07 FA26 FA27 FA28 FA30 FA33 3G091 AA11 AA12 AA17 AA18 AA28 AB02 AB06 AB13 BA00 BA11 BA14 CA02 CA12 CA13 CA15 CA18 CA27 CB02 CB07 CB08 DA01 DA02 DB06 DB10 EA01 EA05 EA08 EA17 EA33 EA34 FB10 FB12 GB01W GB02W GB03W GB04W GB05W GB06W GB07W HA11 HA14 HA36 HA37 HA42 HB02 HB03 HB05 4D048 AA06 AA14 AB02 AB07 AC02 BA02Y BA14X BA15Y BA18Y BA19Y BA21Y BA30X BA36Y BB02 BB14 BC01 BD01 CC24 CC32 CC33 CC52 CC61 CD05 CD10 DA01 DA02 DA03 DA05 DA08 DA09 DA13 EA04

Claims (9)

[Claims] 1. N in exhaust gas discharged from an internal combustion engine
The NO _X catalyst for purifying O _X provided in the engine exhaust passage, when NO _X catalyst retains the SO _X when the surrounding atmosphere is a lean atmosphere, to disengaging the SO _X from the NO _X catalyst, In an exhaust gas purification device configured to separate SO _X from the NO _X catalyst by increasing the temperature of the NO _X catalyst to the SO _X removal temperature and executing SO _X removal processing to make the atmosphere around the NO _X catalyst rich atmosphere. , The exhaust gas purification apparatus, wherein the atmosphere around the NO _x catalyst is temporarily made lean during the execution of the SO _x removal processing. 2. The engine exhaust passage is branched into two exhaust branch passages arranged in parallel, and the NO _x catalyst is arranged in each of the exhaust branch passages.
The exhaust emission control device according to. 3. NO _X catalyst further comprises a flow control valve for regulating the amount of exhaust gas flowing, during the execution of the SO _X withdrawal process, to reduce the degree of opening of the flow regulating valve NO _X
The atmosphere around the NO _x catalyst is made rich while reducing the amount of exhaust gas flowing into the catalyst, and the opening of the flow control valve is temporarily increased to increase the amount of exhaust gas flowing into the NO _x catalyst. 2. The atmosphere around the NO _X catalyst is temporarily made lean by this.
The exhaust emission control device according to. 4. A flow rate control valve is NO _X catalyst upstream of the engine exhaust passage, or, an exhaust purifying apparatus according to claim 3, characterized in that it is arranged in the NO _X catalyst downstream of the engine exhaust passage. 5. further comprising a combustion heater, NO with temperature of the NO _X catalyst is raised by supplying the SO _X withdrawal process runtime from combustion heater rich air-fuel ratio in the NO _X catalyst Gas _X catalyst ambient atmosphere is a rich atmosphere, on the other hand, NO _X from the combustion type heater
The exhaust emission control device according to claim 1, wherein the atmosphere around the NO _x catalyst is temporarily made lean by supplying a gas having a lean air-fuel ratio to the catalyst. 6. Along further comprising a NO _X catalyst flow rate regulating valve for regulating the amount of exhaust gas flowing into to the NO _X catalyst upstream of the engine exhaust passage and NO _X catalyst downstream of the engine exhaust passage, comprising a combustion heater further, when the execution of the SO _X withdrawal process, the temperature is increased of the NO _X catalyst by controlling the operation and the operation of the combustion heater for an internal combustion engine, the NO _X
When the temperature of the catalyst rises to the SO _X release temperature, the opening of the upstream flow control valve is reduced to reduce the amount of exhaust gas flowing into the NO _X catalyst and the downstream flow control valve is opened. Of the rich air-fuel ratio from the combustion heater to the NO _x catalyst so that the atmosphere around the NO _x catalyst becomes a rich atmosphere. NO by temporarily supplying a lean air-fuel ratio gas to the NO _x catalyst
The exhaust emission control device according to claim 1, wherein the atmosphere around the _X catalyst is temporarily made a lean atmosphere. 7. NO_XFuel for adding fuel to the catalyst
Further equipped with an addition device, SO_XWhen the leaving process is executed
NO from fuel addition device_XBy adding fuel to the catalyst
No_XThe catalyst temperature is SO_XRaise to the release temperature
And NO _XThe atmosphere around the catalyst is rich
Meanwhile, NO from the fuel addition device_XAdded to the catalyst
NO by temporarily reducing the amount of fuel_XCatalyst circumference
The atmosphere of the enclosure is temporarily made lean.
The exhaust emission control device according to claim 1. 8. The atmosphere around the NO _x catalyst temporarily becomes lean when the period during which the atmosphere around the NO _x catalyst is rich atmosphere exceeds a predetermined period during the execution of the SO _x removal process. The exhaust emission control device according to claim 1, wherein the exhaust emission control device is an atmosphere. 9. NO _X catalyst further comprises a SO _X amount detecting sensor for detecting the amount of SO _X in the gas flowing out is detected by the SO _X amount sensor during execution of the SO _X withdrawal process The exhaust emission control device according to claim 1, wherein the atmosphere around the NO _x catalyst is temporarily made lean when the amount of SO _x contained exceeds a predetermined amount.