JP2008002358A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable regeneration processing of only a downstream side NOx storage-reduction catalyst device, in an exhaust emission control device of an internal combustion engine having an upstream side NOx storage-reduction catalyst device and the downstream side NOx storage-reduction catalyst device. <P>SOLUTION: This exhaust emission control device has a first fuel supply means 4 supplying additional fuel supplied to a first NOx storage-reduction catalyst device 1, and a second fuel supply means 5 supplying the additional fuel between the first NOx storage-reduction catalyst device and a second NOx storage-reduction catalyst device 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine.

Internal combustion engine carrying out the lean burn like a diesel engine are known, the exhaust passage of such an internal combustion engine, NO _X occluding and reducing catalyst device for purifying NO _X is arranged. In order to sufficiently purify NO _x in the exhaust gas, it has been proposed to arrange two NO _x storage reduction catalyst devices in series in the exhaust passage (see, for example, Patent Document 1).

The NO _X storage reduction catalyst device cannot store NO _X without limitation, and has a maximum NO _X storage capacity. Thus, NO _X occluding and reducing catalyst device, before the amount occluded NO _X reaches the maximum storable amount, regeneration process of reduction and purification by releasing occluded NO _X is required. In order to release NO _X from the NO _X storage reduction catalyst device, it is only necessary to reduce the oxygen concentration in the exhaust gas. The NO _X thus released is reduced and purified if a reducing substance exists in the exhaust gas. Is done. Thus, the regeneration process is performed by making the air-fuel ratio of the exhaust gas flowing into the NO _x storage reduction catalyst device richer than the stoichiometric air-fuel ratio.

JP-A-11-210526 JP-A-6-146870 Japanese Patent No. 2825137 JP2000-130212A JP-A-6-336914 JP-A-2005-133610

In the background art described above, in order to regenerate the NO _x storage reduction catalyst device, the combustion air-fuel ratio is changed from lean to rich. However, if the combustion air-fuel ratio is changed in this way, a torque shock is generated, so that a measure is required to prevent the driver from feeling the torque shock. In the regeneration process, additional fuel is supplied into the cylinder in the expansion stroke or the exhaust stroke so as not to generate a torque shock, or additional fuel is supplied to the engine exhaust system upstream of the upstream NO _x storage reduction catalyst device. It is conceivable that the air-fuel ratio of the exhaust gas is made rich, for example.

Such additional fuel, in _the NO _X storage reduction catalyst device on the upstream side, while being used to consume the oxygen in the exhaust gas, released by reduction of the oxygen concentration from the upstream side of the NO _X occluding and reducing catalyst device It is also used for NO _x reduction and purification. Thus, when that downstream of the NO _X occluding and reducing catalyst device by introducing the exhaust gas of a rich air-fuel ratio to the reproduction processing only _the NO _X storage reduction catalyst device downstream is also desired, the upstream-side NO _X It is necessary to supply a portion for regenerating the storage reduction catalyst device, and the amount of additional fuel becomes relatively large.

Thus, not only the downstream NO _x storage reduction catalyst device cannot be regenerated, but when a relatively large amount of fuel flows into the upstream NO _x storage reduction catalyst device in this way, engine exhaust particularly When additional fuel is supplied to the system, the oxidation catalyst supported on the upstream NO _x storage reduction catalyst device may be wetted by the liquid fuel and may not function well.

If the oxidation catalyst of the upstream NO _x storage reduction catalyst device does not function well, the oxygen in the exhaust gas cannot be burned well and the oxygen concentration in the exhaust gas does not decrease for, it is impossible even to realize good reproduction process in _the nO _X storage reduction catalyst device downstream well upstream of the nO _X occluding and reducing catalyst device.

Accordingly, an object of the present invention, in the exhaust purification system for an internal combustion engine having a _the NO _X storage reduction catalyst device on the upstream side of the NO _X occluding and reducing catalyst device and the downstream side, reproduction of only _the NO _X storage reduction catalyst device downstream Is to make it possible.

Combustion exhaust gas control apparatus according to claim 1 according to the invention, comprising a first 2NO _X occluding and reducing catalyst device of the 1NO _X occluding and reducing catalyst device and the downstream side of the upstream side arranged in series in the engine exhaust system in the exhaust purification system of the engine, between the first fuel supply means for supplying additional fuel to be supplied, and the second 1NO _X occluding and reducing catalyst device and the second 2NO _X occluding and reducing catalyst device to said first 1NO _X occluding and reducing catalyst device And a second fuel supply means for supplying additional fuel therebetween.

An exhaust purification system of an internal combustion engine according to claim 2 of the present invention, both the exhaust gas control apparatus according to claim 1, wherein said 1NO _X occluding and reducing catalyst device and the second 2NO _X occluding and reducing catalyst device When the regeneration process is performed, the additional fuel supplied by the first fuel supply means so that the air-fuel ratio of the exhaust gas flowing into the first NO _X storage reduction catalyst device becomes the stoichiometric air-fuel ratio or the rich air-fuel ratio. the amount is determined by the second fuel supply means so that the rich air-fuel ratio for the air-fuel ratio of the exhaust gas flowing into the first 2NO _X occluding and reducing catalyst device to playback processing said first 2NO _X occluding and reducing catalyst device The amount of additional fuel to be supplied is determined.

An exhaust purification system of an internal combustion engine according to claim 3 of the present invention, both the exhaust gas control apparatus according to claim 2, wherein said 1NO _X occluding and reducing catalyst device and the second 2NO _X occluding and reducing catalyst device When the regeneration process is performed, the amount of additional fuel supplied by the first fuel supply means and the first amount so that the air-fuel ratio of the exhaust gas flowing out from the second NO _x storage reduction catalyst device becomes the stoichiometric air-fuel ratio. The amount of additional fuel supplied by the two fuel supply means is determined.

An exhaust purification system of an internal combustion engine according to claim 4 of the present invention, both the exhaust gas control apparatus according to claim 3, wherein said 1NO _X occluding and reducing catalyst device and the second 2NO _X occluding and reducing catalyst device When performing the regeneration process, when the outflow of NO _x together with the fuel is estimated or detected from the first NO _x storage reduction catalyst device, the amount of additional fuel supplied by the second fuel supply means is increased to increase the amount of the additional fuel. air-fuel ratio of the exhaust gas flowing out from the 2NO _X occluding and reducing catalyst device as a rich air-fuel ratio, to increase the increase amount of the fuel by the estimated or detected outflow amount of NO _X is large enough the second fuel supply means It is characterized by that.

An exhaust purification system of an internal combustion engine according to claim 5 of the present invention, in the exhaust purification system of an internal combustion engine according to any one of claims 2 to 4, wherein said 1NO _X occluding and reducing catalyst device and the second 2NO _When the regeneration processing of both the _X storage reduction catalyst devices is performed, the amount of additional fuel supplied by the first fuel supply means is determined so that the second NO _X storage reduction catalyst device is within a set temperature range. It is characterized by that.

An exhaust purification system of an internal combustion engine according to claim 6 of the present invention, both the exhaust gas control apparatus according to claim 1, wherein said 1NO _X occluding and reducing catalyst device and the second 2NO _X occluding and reducing catalyst device in carrying out the regeneration process, after performing the reproduction process of the first 2NO _X occluding and reducing catalyst device and supplying additional fuel by said second fuel supply means, an additional fuel is supplied by the first fuel supply means which comprises carrying out the regeneration process of the first 1NO _X occluding and reducing catalyst device Te.

An exhaust purification system of an internal combustion engine according to claim 7 of the present invention, in the exhaust purification system of an internal combustion engine according to claim 1, is disposed S trap device on the upstream side of the first 1NO _X occluding and reducing catalyst device the between the first 1NO _X occluding and reducing catalyst device and the second 2NO _X occluding and reducing catalyst device, wherein the NO _X sensor for detecting the NO _X concentration is disposed.

An exhaust purification system of an internal combustion engine according to claim 8 of the present invention, in the exhaust purification system of an internal combustion engine according to claim 7, also on the downstream side of the first 2NO _X occluding and reducing catalyst device, detecting the NO _X concentration The NO _x sensor is arranged.

An internal combustion engine exhaust gas purification apparatus according to a ninth aspect of the present invention is the exhaust gas purification apparatus for the internal combustion engine according to the first aspect, wherein an S trap device is disposed upstream of the first NO _x storage reduction catalyst device. The additional fuel supplied by the first fuel supply means passes through the S trap device, and when it is predicted that SO _X is released from the S trap device due to the passage of the additional fuel, The supply of the additional fuel by the first fuel supply means is stopped or suppressed.

According to a tenth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the ninth aspect, the SO _X is released when the S trap device is at a set temperature or higher. It is predicted that the set temperature is lowered as the SO _X storage amount in the S trap device increases.

According to the exhaust purification system of an internal combustion engine according to claim 1 according to the present invention, the first 2NO _X occluding and reducing catalyst device of the 1NO _X occluding and reducing catalyst device and the downstream side of the upstream side arranged in series in the engine exhaust system between the exhaust gas purifying apparatus for an internal combustion engine, a first fuel supply means for supplying additional fuel to be supplied to the first 1NO _X occluding and reducing catalyst device, the first 1NO _X occluding and reducing catalyst device and the 2NO _X occluding and reducing catalyst device comprising in order to and a second fuel supply means for supplying additional fuel, for example, in such case where the 1NO _X occluding and reducing catalyst device has deteriorated, the minimum additional fuel supplied by the second fuel supply means Only the second NO _x storage reduction catalyst device can be regenerated.

According to the exhaust purification system of an internal combustion engine according to claim 2 according to the present invention, both the exhaust gas control apparatus according to claim 1, the 1NO _X occluding and reducing catalyst device and the 2NO _X occluding and reducing catalyst device in carrying out the regeneration process, the additional amount of fuel air-fuel ratio of the exhaust gas flowing into the first 1NO _X occluding and reducing catalyst device is supplied by the first fuel supply means such that the stoichiometric air-fuel ratio or rich air-fuel ratio are determined, added to the air-fuel ratio of the exhaust gas flowing into the first 2NO _X occluding and reducing catalyst device is supplied by the second fuel supply means so that the rich air-fuel ratio for reproducing processing first 2NO _X occluding and reducing catalyst device for the amount of fuel is determined, place a large amount of additional fuel required for both the first 1NO _X occluding and reducing catalyst device and the 2NO _X occluding and reducing catalyst device by the first fuel supply means for reproduction processing is supplied Compared to, the additional fuel supply of the second fuel supply means, it is possible to reduce the additional amount of fuel supplied by the first fuel supply means, it flows a large amount of additional fuel to the first 1NO _X occluding and reducing catalyst device It carried to a 1NO _X occluding and reducing catalyst device Te oxidation catalyst can be prevented a problem such as a decrease function is wetted by a large amount of additional fuel, the 1NO _X occluding and reducing catalyst device and the 2NO _X occluding and reducing catalyst Good reproduction processing of the apparatus can be realized.

According to the exhaust purification system of an internal combustion engine according to claim 3 of the present invention, both the exhaust gas control apparatus according to claim 2, the 1NO _X occluding and reducing catalyst device and the 2NO _X occluding and reducing catalyst device When the regeneration process is performed, the additional fuel amount and the second fuel supply supplied by the first fuel supply means so that the air-fuel ratio of the exhaust gas flowing out from the second NO _x storage reduction catalyst device becomes the stoichiometric air-fuel ratio. The amount of additional fuel supplied by the means is determined. Thus, when the additional amount of fuel supplied by the first fuel supply means is greater than the amount of fuel required to regenerate process the first 1NO _X occluding and reducing catalyst device, the additional fuel supplied by the second fuel supply means the amount is less than the amount of fuel required to reduce and purify the released NO _X from the 2NO _X occluding and reducing catalyst device, the shortfall as supplemented by the surplus fuel flowing from the first 1NO _X occluding and reducing catalyst device it is, the excess fuel is likely to react reformed in the first 1NO _X occluding and reducing catalyst device, to reduce and purify satisfactorily released NO _X in the first 2NO _X occluding and reducing catalyst device. Further, when the additional amount of fuel supplied by the first fuel supply means is less than the amount of fuel required to regenerate process the first 1NO _X occluding and reducing catalyst device, the additional amount of fuel supplied by the second fuel supply means is larger than the fuel amount required to reduce and purify the released NO _X from the 2NO _X occluding and reducing catalyst device, since at this time the reduction purification of the released NO _X in the 1NO _X occluding and reducing catalyst device becomes insufficient Although NO _X flows out from the 1NO _X occluding and reducing catalyst device, the NO _X is satisfactorily reduced and purified with release NO _X in the first 2NO _X occluding and reducing catalyst device. In either case, the air-fuel ratio of the exhaust gas flowing out from the second NO _x storage reduction catalyst device becomes the stoichiometric air-fuel ratio, and the additional fuel supplied by the first fuel supply means and the second fuel supply means is combined to give the first NO _The minimum additional fuel required to regenerate the _X storage reduction catalyst device and the second NO _X storage reduction catalyst device is supplied.

According to the exhaust purification system of an internal combustion engine according to claim 4 according to the present invention, both the exhaust gas control apparatus according to claim 3, the 1NO _X occluding and reducing catalyst device and the 2NO _X occluding and reducing catalyst device of the carrying out the regeneration process, when the outflow of the NO _X is estimated or detected with the fuel from the 1NO _X occluding and reducing catalyst device, the reduction purification of the NO _X reasons cold etc. in a 1NO _X occluding and reducing catalyst device In this case, even if the fuel flowing out from the first NO _x storage reduction catalyst device and NO _x simply flow into the second NO _x storage reduction catalyst device, the reduction of NO _x is similarly performed. purification is likely to be insufficient, whereby the air-fuel ratio is a rich air-fuel ratio of the exhaust gas flowing out from the 2NO _X occluding and reducing catalyst device by increasing the additional amount of fuel supplied by the second fuel supply means Na In this way, the larger the estimated or detected amount of outflow NO _x is, the more fuel is increased by the second fuel supply means. Thus, in the 2NO _X occluding and reducing catalyst device, to actively reduce and purify of the NO _X by increasing the fuel, the outlet NO _X and release NO _X from the 2NO _X occluding and reducing catalyst device from the first 1NO _X occluding and reducing catalyst device securely To reduce and purify.

According to the exhaust purification system of an internal combustion engine according to claim 5 according to the present invention, in the exhaust purification system of an internal combustion engine according to any one of claims 2 to 4, the 1NO _X occluding and reducing catalyst device and the 2NO _When the regeneration processing of both of the _X storage reduction catalyst devices is performed, the additional fuel supplied by the first fuel supply means burns in the first NO _X storage reduction catalyst device to increase the exhaust gas temperature. the of the 2NO _X occluding and reducing catalyst device by the inflow raising the temperature. The NO _X storage reduction catalyst device has a set temperature range in which NO _X storage action is active, and the smaller the amount of additional fuel supplied by the first fuel supply means, the more the NO _X storage reduction catalyst device flows into the second NO _X storage reduction catalyst device. by utilizing the fact that the temperature of exhaust gas is lowered, so that the temperature of the set temperature range of the 2NO _X occluding and reducing catalyst device, additional amount of fuel supplied is determined by the first fuel supply means. Thus, reproduction processing immediately after the is complete, to the 2NO _X occluding and reducing catalyst device is within the set temperature range, even if the first 1NO _X occluding and reducing catalyst device becomes the set temperature range second 2NO _X occluding and reducing The catalyst device can store NO _x in the exhaust gas satisfactorily.

According to the exhaust purification system of an internal combustion engine according to claim 6 according to the present invention, both the exhaust gas control apparatus according to claim 1, the 1NO _X occluding and reducing catalyst device and the 2NO _X occluding and reducing catalyst device in carrying out the regeneration process, after performing the reproduction processing of the 2NO _X occluding and reducing catalyst device and supplying additional fuel by the second fuel supply means, first 1NO to supply additional fuel by the first fuel supply means The regeneration process of the _X storage reduction catalyst device is carried out. Thereby, even if NO _X flows out during reproduction of the first 1NO _X occluding and reducing catalyst device, the 2NO _X occluding and reducing catalyst device, so that it is possible to reduce and purify sufficient NO _X and playback processing is completed Thus, NO _x flowing out from the first NO _x storage reduction catalyst device can be purified well without being released into the atmosphere.

According to the exhaust purification device for an internal combustion engine according to claim 7 of the present invention, in the exhaust purification device for the internal combustion engine according to claim 1, the S trap device is disposed upstream of the first NO _x storage reduction catalyst device. Has been. Since the NO _X storage reduction catalyst device stores not only NO _X but also SO _X , and SO _X cannot be easily released, the maximum amount of NO _X that can be stored is reduced. Thus, by the S trap device disposed upstream of the first 1NO _X occluding and reducing catalyst device, SO _X in the exhaust gas is to be absorbed by the S trap device, the SO _X into _the NO _X storage reduction catalyst device Occlusion is prevented. However, SO _X cannot be stored in the S trap device without limitation, and when SO _X cannot be stored further, SO _X is stored in the first NO _X storage reduction catalyst device, and NO _X is stored. _{Even if} the maximum storable amount of _X is reduced and finally the regeneration process is performed, the first NO _X storage reduction catalyst device cannot store NO _X at all. If NO _X is detected by the NO _X sensor even after the regeneration process is completed, the first NO _X storage reduction catalyst device stores the maximum amount of SO _X and cannot store NO _{X at} all. There, at this time, by exchanging the S trap device and the 1NO _X occluding and reducing catalyst device can be up to the 2NO _X occluding and reducing catalyst device is prevented from being occluding SO _X.

According to the exhaust purification system of an internal combustion engine according to claim 8 according to the present invention, in the exhaust purification system of an internal combustion engine according to claim 7, in the downstream side of the 2NO _X occluding and reducing catalyst device, the NO _X concentration NO _X sensor for detecting is arranged. Thereby, as described above, the arranged NO _X sensor between the first 1NO _X occluding and reducing catalyst device and the 2NO _X occluding and reducing catalyst device, the replacement timing of the S trap device and the 1NO _X occluding and reducing catalyst device it is possible to determine, in immediately after completion of the reproduction process, and the estimated concentration of NO _X in the exhaust gas flowing into the first 1NO _X occluding and reducing catalyst device, the difference between the NO _X concentration detected by the NO _X sensor setpoint if smaller, the 1NO _X occluding and reducing catalyst device can be judged that _the NO _X storage ability, including the case of SO _X storage is considerably reduced, the first fuel supply for regeneration processing is useless The supply of additional fuel by the means can be stopped. Further, in the state where the 2NO _X occluding and reducing catalyst device has not almost absorb NO _X, the concentration of NO _X in the exhaust gas flowing out from the 1NO _X occluding and reducing catalyst device detected by the NO _X sensor, the 2NO _X if the difference between the concentration of NO _X in the exhaust gas flowing out from the 2NO _X occluding and reducing catalyst device detected by the NO _X sensor arranged downstream of the storage reduction catalyst device is smaller than the set value, the 2NO _X occluding It can be determined that the NO _x storage capacity of the reduction catalyst device is considerably lowered, and the regeneration process is wasted, so that the supply of additional fuel by the second fuel supply means can be stopped.

According to the exhaust purification device for an internal combustion engine according to claim 9 of the present invention, in the exhaust purification device for the internal combustion engine according to claim 1, the S trap device is disposed upstream of the first NO _x storage reduction catalyst device. The additional fuel supplied by the first fuel supply means passes through the S trap device, and when it is predicted that SO _X is released from the S trap device due to the passage of the additional fuel, the first fuel is supplied. The supply of additional fuel by the fuel supply means is stopped or suppressed. Thereby, SO _X is released from the S trap, and this SO _X is prevented or suppressed from being stored in the first NO _X storage reduction catalyst device.

According to the exhaust gas purification apparatus for an internal combustion engine according to claim 10 of the present invention, in the exhaust gas purification apparatus for the internal combustion engine according to claim 9, SO _X is released when the S trap device is equal to or higher than a set temperature. Therefore, the set temperature is increased as the SO _X storage amount in the S trap device is smaller. As a result, the opportunity to stop or suppress the supply of additional fuel by the first fuel supply means is reduced, and a favorable regeneration process of the first NO _x storage reduction catalyst device can be performed.

FIG. 1 is a schematic view of an engine exhaust system showing an exhaust gas purification apparatus for an internal combustion engine according to the present invention. Engine is to implement lean combustion such as a diesel engine, during the exhaust gases include a relatively large number of NO _X. Thereby, the exhaust system, the 1NO _X occluding and reducing catalyst device 1 and 2NO _X occluding and reducing catalyst device 2 for purifying NO _X are arranged in series. The 1NO _X occluding and reducing catalyst device 1 on the upstream side, for example, as a relatively small, if placed in the engine room, the heat capacity is located near the engine body is small, the exhaust gas is activated immediately after the engine start the NO _X in it can be satisfactorily occluded. However, the first NO _x storage reduction catalyst device 1 that is made compact cannot sufficiently store NO _x in the exhaust gas when the amount of exhaust gas is large. Thereby, a relatively large the first 2NO _X occluding and reducing catalyst device 2 on the downstream side, by arranging the vehicle floor or the like, can be even when the amount of exhaust gas is large sufficiently absorb NO _X in the exhaust gas . Of course, both the first 1NO _X occluding and reducing catalyst device 1 and 2NO _X occluding and reducing catalyst device 2 may be arranged under the vehicle floor.

The first NO _x storage reduction catalyst device 1 and the second NO _x storage reduction catalyst device 2 have a monolith support or pellet support on which a NO _x storage catalyst and a noble metal catalyst such as platinum Pt are supported using alumina or the like. It is. The NO _x storage catalyst is selected from, for example, alkali metals such as potassium K, sodium Na, lithium Li and cesium Cs, alkaline earth metals such as barium Ba and calcium Ca, and rare earths such as lanthanum La and yttrium Y. Is at least one. This _the NO _X storage catalyst, when the air-fuel ratio of the burnt gas flowing into the lean, i.e., occludes NO _X when the oxygen concentration is high, the air-fuel ratio becomes the stoichiometric air-fuel ratio or rich, that is, lowering the oxygen concentration then, do the absorption and release action of NO _X to release the occluded NO _X. As a noble metal catalyst that functions as an oxidation catalyst, platinum Pt is usually used.

The exhaust gas from diesel engines, also includes particulates, for example, the first 2NO _X occluding and reducing catalyst device 2 may be a wall-flow type particulate filter carrying the _the NO _X storage catalyst and the noble metal catalyst . The NO _x storage catalyst releases active oxygen when NO _x is absorbed and released, and this active oxygen oxidizes and removes particulates without generating a luminous flame. Thereby, the collected particulates can be automatically oxidized and removed.

In any of the 1NO _X occluding and reducing catalyst device 1 and 2NO _X occluding and reducing catalyst device 2, it is impossible to occlude unlimited NO _X, respectively, has a maximum storable amount. In the present embodiment, NO _X in the exhaust gas, in order to be inserted in either of the first 1NO _X occluding and reducing catalyst device 1 and 2NO _X occluding and reducing catalyst device 2, for example, per unit time for each engine operating condition advance map the of the NO _X emissions, if integrating the NO _X emissions in each engine operating state, the integrated value of the 1NO _X occluding and reducing catalyst device 1 and 2NO _X occluding and reducing catalyst device 2 NO _X It can be the amount of occlusion. When the _the NO _X storage amount became previous setting to reach total storable amount of the first 1NO _X maximum storable amount of storage reduction catalyst device 1 and the maximum storable amount of the 2NO _X occluding and reducing catalyst device 2 and it is possible to determine regeneration timing and that to release the occluded NO _X from the 1NO _X occluding and reducing catalyst device 1 and 2NO _X occluding and reducing catalyst device 2 is reduced and purified by. As described above, the regeneration process may be performed as the regeneration time for each set vehicle travel time or for each set vehicle travel distance without determining the regeneration time.

FIG. 2 is a first flowchart for performing the reproduction process. First, in step 101, it is determined whether or not it is a reproduction time. When this determination is denied, the process is terminated as it is, but when the determination is affirmed, the process proceeds to step 102. In step 102, additional fuel quantity by the first fuel supply means FI for feeding additional fuel to the first 1NO _X occluding and reducing catalyst device 1 is supplied is determined. In the present embodiment, the first fuel supply means FI is the first fuel supply device 4 that supplies additional fuel to the engine exhaust system on the upstream side of the first NO _x storage reduction catalyst device 1. However, the first fuel supply means FI may be, for example, a cylinder fuel injection valve that supplies additional fuel into the cylinder in the expansion stroke or the exhaust stroke.

Setting the amount of the aforementioned used to determine the regeneration timing, for example, the maximum storable amount A2 of example 80 percent of the 2NO _X occluding and reducing catalyst device to the maximum storable amount A1 of the 1NO _X occluding and reducing catalyst device (or 90%) plus (A1 + A2 * 0.8). Here, the 2NO _X occluding and reducing catalyst device 2, in order to have a larger capacity than the 1NO _X occluding and reducing catalyst device 1, the maximum storable amount A2 becomes greater than A1. NO _X in the exhaust gas, in order easily occluded in the 1NO _X occluding and reducing catalyst device positioned upstream, as regeneration timing, the maximum storable in the 1NO _X occluding and reducing catalyst device 1 located upstream and NO _X amount A1 is occluded, the first 2NO _X occluding and reducing catalyst device 2 located downstream, with a margin, it is assumed a state in which 80 percent of the maximum storable amount A2 is occluded Is done.

The additional fuel amount Q1 supplied by the first fuel supply means FI is the maximum amount of fuel that can be stored in the first NO _X storage reduction catalyst device 1 and the fuel amount qs that is required to make the current lean air-fuel ratio exhaust gas the stoichiometric air-fuel ratio. a fuel amount obtained by adding the total set fuel quantity qe of the fuel quantity qr1 necessary to reduce and purify the NO _X amount A1 (Q1 = qs + qr1 + qe). For additional fuel amount Q1 supplied by the first fuel supply means FI is the only minimum amount necessary for reproducing a first 1NO _X occluding and reducing catalyst device 1 (qs + qr1) to set the fuel quantity qe is added In addition, in the first NO _x storage reduction catalyst device 1, the oxidation catalyst is not wetted by a large amount of fuel and the function is not deteriorated. Thus, the air-fuel ratio of the exhaust gas flowing into the first NO _X storage reduction catalyst device 1 becomes a rich air-fuel ratio.

Thus, if the additional fuel quantity Q1 is fed by the first fuel supply means FI, for oxygen in the exhaust gas in some first 1NO _X occluding and reducing catalyst device 1 by qs is consumed most of the additional fuel, the NO _X of the maximum storable amount A1 is discharged from 1NO _X occluding and reducing catalyst device 1, thus released NO _X is almost all reduced and purified by a part of the additional fuel qr1. As a result, the exhaust gas having an air-fuel ratio richer than the stoichiometric air-fuel ratio including a part qe of the additional fuel flows out from the first NO _X storage reduction catalyst device 1.

At step 103, thus it is more additional fuel second fuel supply means RI supplied to the first 1NO _X occluding and reducing catalyst exhaust gas flowing out of the device 1. In this embodiment, the second fuel supply means RI is a first 1NO _X occluding and reducing catalyst device 1 and the second fuel supply device for supplying additional fuel into the exhaust system between the first 2NO _X occluding and reducing catalyst device 2 5 is there. This additional amount of fuel Q2, the fuel amount obtained by subtracting the set fuel amount qe described above from the fuel quantity qr2 necessary to reduce and purify 80 percent of the NO _X of the 2NO _X occluding and reducing catalyst device 2 of the maximum storable amount A2 (Q2 = qr2-qe).

Thus, to the first 2NO _X occluding and reducing catalyst device 2, including a little oxygen comprises fuel amount qr2 necessary to reduce and purify 80 percent of the NO _X of the 2NO _X occluding and reducing catalyst device 2 of the maximum storable amount A2 There will be no exhaust gas flowing in. As a result, almost all of the stored NO _x is released from the second NO _x storage reduction catalyst device 2, and the slight fuel amount qe of the fuel amount qr2 in the exhaust gas is reduced to the first NO _x storage reduction catalyst device 1. the has been vaporized reformed when it passes through very satisfactorily reduced and purified release NO _X in the first 2NO _X occluding and reducing catalyst device 2. Further, the additional fuel amount Q2 (qr2-qe) supplied by the second fuel supply means RI is also reduced by a part qe of the additional fuel amount Q1 supplied by the first fuel supply means FI. liable to evaporate in 2NO _X occluding and reducing catalyst device 2, can be satisfactorily reduced and purified release NO _X. In this regeneration process, the air-fuel ratio of the exhaust gas flowing out from the 2NO _X occluding and reducing catalyst device 2 becomes substantially the stoichiometric air-fuel ratio.

The additional fuel amount supplied by the first fuel supply unit FI and the second fuel supply unit RI may be set to qs + qr1 + qr2 together. For example, as the additional fuel amount Q1 ′ supplied by the first fuel supply means FI, the fuel amount qs required to set the exhaust gas having the current lean air-fuel ratio to the stoichiometric air-fuel ratio and the first NO _X storage reduction catalyst device 1 the NO _X of the maximum storable amount A1 may be the sum of the fuel quantity qr1 necessary to reduce and purify. In this case, the additional fuel quantity Q2 supplied by the second fuel supply means RI 'is the required 80 percent of the NO _X of the 2NO _X occluding and reducing the maximum storable amount A2 of the catalytic converter 2 to reduce and purify The fuel amount is qr2.

Further, as the additional fuel amount Q1 ″ supplied by the first fuel supply means FI, the fuel amount qs necessary for setting the exhaust gas having the current lean air-fuel ratio to the stoichiometric air-fuel ratio and the first NO _X storage reduction catalyst device 1 A fuel amount obtained by subtracting the set fuel amount qe ″ from the sum of the fuel amount qr1 necessary for reducing and purifying the maximum storable amount NO _X may be used. In this case, flows into the first 2NO _X occluding and reducing catalyst device 2 to a 1NO _X occluding and reducing catalyst device portion of the emitted NO _X from 1 (an amount corresponding to the subtracted set fuel quantity qe ") is not reduced and purified , and thus be reduced and purified in the first 2NO _X occluding and reducing catalyst device 2. additional fuel quantity Q2 supplied by the second fuel supply means RI "is the first 2NO _X occluding and reducing the maximum storable amount A2 of the catalytic converter 2 80 percent of the NO _X set fuel quantity qe the fuel amount qr2 necessary to reduce and purify "is the amount of fuel is added. in either case, additional large amount to a 1NO _X occluding and reducing catalyst device 1 is not as oxidation catalyst fuel is supplied to degraded wetted by the fuel. in these cases, the air-fuel ratio of the exhaust gas flowing out from the 2NO _X occluding and reducing catalyst device 2 becomes substantially the stoichiometric air-fuel ratio Set fuel amount qe ” As the maximum value may be a fuel quantity qr1 the required NO _X of the 1NO _X occluding and reducing the maximum storable amount A1 of the catalytic converter 1 for reduction and purification. At this time, the air-fuel ratio of the exhaust gas flowing into the first NO _x storage reduction catalyst device 1 becomes the stoichiometric air-fuel ratio.

Moreover, additional fuel amount supplied by the first fuel supply means FI is, the fuel amount qs necessary to exhaust gas the stoichiometric air-fuel ratio, NO of the 1NO _X occluding and reducing catalyst device maximum storable amount A1 of 1 _{In the} case where the fuel amount qr1 necessary for reducing and purifying _X is added or more (when the additional fuel amount is Q1 ′ or Q1 described above), NO _X is reduced and purified. if with croton fuel from the 1NO _X occluding and reducing catalyst device 1 NO _X flows out, because of the temperature is low, such as the amount of exhaust gas is large or the 1NO _X occluding and reducing catalyst device 1, the 1NO _X occluding and reducing catalyst device considered one in NO _X and could not be sufficiently reduced and purified, in this state, also in the 2NO _X occluding and reducing catalyst device 2, the release NO _X and NO _X flowing from the 1NO _X occluding and reducing catalyst device 1 Well It cannot be reduced and purified.

Thereby, when the amount of additional fuel by the first fuel supply means FI is Q1 (or Q1 ′) described above, for example, between the first NO _X storage reduction catalyst device 1 and the second NO _X storage reduction catalyst device 2 when the 1NO _X sensor 6 by a 1NO _X occluding and reducing catalyst device 1 from NO _X for detecting the concentration of the deployed NO _X has been detected that the outflow between (at this time, corresponds to the outflow amount of NO _X The amount of additional fuel in the second fuel supply means RI is larger than the aforementioned Q2 (or Q2 ′), that is, the first fuel supply means FI and the second fuel supply means RI. reducing the total additional amount of fuel supplied is, the fuel amount qs necessary to the air-fuel ratio of the exhaust gas the stoichiometric air-fuel ratio, the NO _X of the 1NO _X occluding and reducing the maximum storable amount A1 of the catalyst device 1 by Fuel amount qr1 required for purification Is greater than the sum of the fuel quantity qr2 the required 80 percent of the NO _X of the maximum storable amount A2 of the 2NO _X occluding and reducing catalyst device 2 to reduce and purify.

Thereby, in the 2NO _X occluding and reducing catalyst device 2, so as to present the fuel than that corresponding to the NO _X amount flowing from the discharge amount of NO _X and a 1NO _X occluding and reducing catalyst device 1, in the actively reducing action satisfactorily reduced and purified NO _X. In this case, the air-fuel ratio of the exhaust gas flowing out from the 2NO _X occluding and reducing catalyst device 2 becomes richer than the stoichiometric air-fuel ratio. Increment of additional fuel quantity of the second fuel supply means RI (Q2 or Q2 '), it is preferable to increase as the amount of NO _X flowing out from the 1NO _X occluding and reducing catalyst device 1 is large.

Further, in the first NO _x storage reduction catalyst device 1, the fuel is burned using oxygen in the exhaust gas, and the released NO _x is reduced. Since these are exothermic reactions, the temperature of the exhaust gas flowing out from the first NO _x storage reduction catalyst device 1 is increased. By the way, the NO _x storage reduction catalyst device has a temperature range (for example, 250 to 500 ° C.) that favorably stores NO _x , and even if the regeneration process is completed, the NO _x storage reduction catalyst device has this temperature. If it is out of the range, NO _x in the exhaust gas cannot be stored well. As a result, the additional fuel supplied by the first fuel supply means FI has the temperature of the second NO _X storage reduction catalyst device 2 within the above-mentioned temperature range due to the exhaust gas temperature raised in the first NO _X storage reduction catalyst device 1. It is preferable to be determined as follows. After the additional fuel amount of the first fuel supply unit FI is determined in this way, the additional fuel amount of the second fuel supply unit RI may be determined as described above.

Additional amount of fuel supplied by the first fuel supply means FI, a fuel for reducing purify NO _X of the maximum storable amount of the 1NO _X occluding and reducing catalyst device 1 to the fuel quantity qs to consume oxygen in the exhaust gas When the fuel amount is obtained by adding the amount qr1, the temperature of the exhaust gas is raised most. Even if the amount of additional fuel by the first fuel supply means FI is further increased, the exhaust gas temperature cannot be increased. On the other hand, the lower the amount of additional fuel, the lower the temperature rise of the exhaust gas. Additional fuel quantity to the fuel quantity qs to make the air-fuel ratio of the exhaust gas the stoichiometric air-fuel ratio is possible weight loss, whereby the exhaust gas from the 1NO _X occluding and reducing catalyst device 1, the 2NO _X occluding and reducing catalyst device 2 Is more than the above-mentioned temperature range, it is preferable to reduce the amount of additional fuel by the first fuel supply means FI.

As described above, when the NO _X that is not reduced and purified from the 1NO _X occluding and reducing catalyst device 1 flows out together with the fuel, if reproduction processing of the 2NO _X occluding and reducing catalyst device 2 is completed, the 1NO _X occluding and reducing it can be satisfactorily reduced and purified in the NO _X the first 2NO _X occluding and reducing catalyst device 2 flowing out of the catalytic converter 1. FIG. 3 is a second flowchart for carrying out such a reproduction process. First, in step 201, it is determined whether or not it is a reproduction time. When this determination is denied, the process is terminated as it is, but when the determination is affirmed, the process proceeds to step 202. In step 202, to regenerate the first 2NO _X occluding and reducing catalyst device 2 for the first, additional fuel amount by the second fuel supply means RI is supplied is determined. Additional fuel amount by the second fuel supply means RI is a 80 percent of the NO _X of the maximum storable amount A2 of the 2NO _X occluding and reducing catalyst device 2 to the fuel quantity qs for the air-fuel ratio of the exhaust gas the stoichiometric air-fuel ratio This is the fuel amount obtained by adding the fuel amount qr2 to be reduced and purified. Thereby, reproducing processing is performed in the first 2NO _X occluding and reducing catalyst device 2.

Then, in step 203, to regenerate the first 1NO _X occluding and reducing catalyst device 1, additional fuel quantity by the first fuel supply means FI is supplied is determined. Additional fuel quantity by the first fuel supply means FI will reduce and purify NO _X in the first 1NO _X occluding and reducing catalyst device maximum storable amount A1 of 1 to the fuel quantity qs for the air-fuel ratio of the exhaust gas the stoichiometric air-fuel ratio This is the fuel amount to which the fuel amount qr1 is added. As a result, even if the reduction and purification of the released NO _X is insufficient in the regeneration process of the first NO _X storage reduction catalyst device 1 and the fuel flows into the second NO _X storage reduction catalyst device 2 together with the NO _X , the second NO _X storage reduction catalyst device and 2 the reproduction process is completed, but this can not be occluded nO _X flowing from the 1NO _X occluding and reducing catalyst device 1 due to the low oxygen concentration in the exhaust gas in time, the 2NO _X storage in the reducing catalyst device 2, in order emitted nO _X is absent, good nO _X flowing fuel from a 1NO _X occluding and reducing catalyst device 1 using flowing from the 1NO _X occluding and reducing catalyst device 1 Can be reduced and purified.

By the way, the NO _X storage reduction catalyst device also stores SO _X in the exhaust gas by the same mechanism as NO _X. When SO _x is occluded, the maximum occlusion amount of NO _x is reduced accordingly. Since SO _x is stored as a stable sulfate, in order to release it, the NO _x storage reduction catalyst device must be heated to about 650 ° C. to reduce the oxygen concentration in the exhaust gas. However, the NO _x storage reduction catalyst device is thermally deteriorated by such a temperature rise to about 650 ° C. Accordingly, it is desirable that the NO _X storage reduction catalyst device does not store SO _X , and in this embodiment, the S trap device 3 is disposed upstream of the first NO _X storage reduction catalyst device 1, It is designed to store SO _X in the exhaust gas.

The S trap device 3 basically has the same configuration as the NO _x storage reduction catalyst device, and preferably carries a large amount of an NO _x storage catalyst for storing SO _x . In the S trap device 3, NO _x is also occluded, but when SO _x in the exhaust gas arrives, NO _x and SO _x are replaced, so that SO _x is occluded and NO _x is released.

In this way, SO _X in the exhaust gas is occluded in the S trap device 3, but the S trap device 3 cannot occlude SO _x indefinitely, and the S trap 3 can store the maximum amount of SO _x that can be occluded. _{When X} is stored, SO _X in the exhaust gas is stored in the first NO _X storage reduction catalyst device 1. Then, when the SO _X of the maximum storable amount A1 In a 1NO _X occluding and reducing catalyst device 1 is occluded, the SO _X in the exhaust gas will be absorbed in the first 2NO _X occluding and reducing catalyst device 2. With such SO _X from being occluded to the first 2NO _X occluding and reducing catalyst device 2, it is replaced in addition to the S trap device 3 and the 1NO _X occluding and reducing catalyst device 1 until the 2NO _X occluding and reducing catalyst device 2 I will have to.

In the present embodiment, in order to first 1NO _X sensor 6 is disposed between the first 1NO _X occluding and reducing catalyst device 1 and the 2NO _X occluding and reducing catalyst device 2, by using this, such great thereby preventing the exchange of two of the NO _X occluding and reducing catalyst device with a cost. FIG. 4 is a third flowchart for exchanging the S trap device. First, in step 301, it is determined whether or not the reproduction process has been completed as in the first or second flowchart described above. When this determination is denied, the process is terminated as it is, but when the determination is affirmed, the process proceeds to step 302. In step 302, it is determined whether or not NO _X is detected by the first NO _X sensor 6. When this judgment is denied, the process is terminated as it is.

On the other hand, if the determination in step 302 is affirmative, the despite it is immediately after the regeneration process has been completed, NO _X has been detected in the first 1NO immediately downstream of the _X occluding and reducing catalyst device 1, the 1NO _X The storage reduction catalyst device 1 can determine that the SO _X in the vicinity of the maximum storable amount A1 is occluded and almost no NO _x can be occluded. Thus, in step 303, to replace the S trap device 3 and the 1NO _X occluding and reducing catalyst device 1. Thus, the second NO _X storage reduction catalyst device 2 is prevented from storing SO _X , and even the second NO _X storage reduction catalyst device need not be replaced.

Further, in the present embodiment, the 2NO _X sensor 7 to the downstream side of the 2NO _X occluding and reducing catalyst device 2 for detecting the concentration of NO _X in the exhaust gas is disposed. Use first 1NO _X sensor 6 and the 2NO _X sensor 7, it is possible to determine the deterioration of the 1NO _X occluding and reducing catalyst device 1 and 2NO _X occluding and reducing catalyst device 2. FIG. 5 is a fourth flowchart for this purpose. First, in step 401, it is determined whether or not the reproduction process is completed as in the first or second flowchart described above. If this determination is negative, the process ends. If the determination is positive, the process proceeds to step 402. In step 402, the NO _X concentration C0 of the current exhaust gas to be estimated based on the current engine operating conditions, NO _X in the exhaust gas flowing out from the 1NO _X occluding and reducing catalyst device 1 the exhaust gas flows into It is determined whether or not the difference from the density C1 is greater than or equal to the set value a.

If this determination is affirmative, the first NO _x storage reduction catalyst device 1 has occluded NO _x well, and the routine proceeds to step 404. However, when the result at step 402 is negative, in order to be able to satisfactorily NO _X in the first 1NO _X occluding and reducing catalyst device 1 is not occluded in spite of immediately after the regeneration process has been completed, step the 1NO _X occluding and reducing catalyst device 1 in 403 can be determined to have deteriorated.

In step 404, whether the 1NO _X occluding and reducing catalyst device 1 oxygen concentration C1 of the exhaust gas flowing out is set value C or more is determined. Unless the 1NO _X occluding and reducing catalyst device 1 is deteriorated, because the first 1NO _X occluding and reducing catalyst device 1 for storing a good NO _X, NO _X concentration in the exhaust gas at the downstream side is low. However, NO _X of the maximum storable amount A1 is occluded in the first 1NO _X occluding and reducing catalyst device 1 over time, the 1NO _X occluding and reducing catalyst device 1 will not be able to occlude NO _X. At this time, the determination in step 404 is affirmed (the determination in step 404 is affirmed immediately when the first NO _X storage reduction catalyst device 1 is deteriorated), and in step 405, the flow enters the second NO _X storage reduction catalyst device 2. whether the difference between the NO _X concentration C2 of the exhaust gas to NO _X concentration C1 in the exhaust gas flowing out from the 2NO _X occluding and reducing catalyst device 2 is the set value b or not is determined.

If not degraded first 2NO _X occluding and reducing catalyst device 2, a state that does not absorb NO _X in the reproduction processing is completed, the good storage to determine in step 405 the NO _X in the exhaust gas affirmative Should be done. Thus, this determination when the result is YES, the first 2NO _X occluding and reducing catalyst device 2 does not deteriorate, and exit. However, when the determination in step 405 is negative, NO _x cannot be stored well in spite of the state in which NO _x is not stored. In step 406, the second NO _x storage reduction catalyst. It can be determined that the device 2 has deteriorated.

Thus, the 1NO _X occluding and reducing catalyst device 1 and 2NO _X occluding and reducing catalyst device 2 can be separately degraded judge, in _the NO _X storage reduction catalyst device which is determined to deterioration of the fuel be carried out reproduction process In order to be wasted, it is preferable to stop the regeneration process to save fuel. In the present embodiment, the 2NO _X occluding and reducing catalyst device second fuel supply means RI supplying directly add the fuel to the 2, first 1NO _X occluding and reducing catalyst device first fuel supply means FI supplying additional fuel to 1 the to is provided separately, it is possible to only a reproduction process one of the first 1NO _X occluding and reducing catalyst device and the 2NO _X occluding and reducing catalyst device.

In the present embodiment, as shown in FIG. 1, the first fuel supply means 4 is disposed on the upstream side of the S trap device 3. When additional fuel passes through the S trap device 3 during the regeneration process, including when supplying additional fuel into the cylinder, the regeneration process is performed when the exhaust gas temperature is high, such as when the engine is heavily loaded. Then, the S trap device 3 closest to the engine body may be as high as about 600 ° C. At this time, the additional fuel burns in the S trap device 3 and the oxygen concentration in the exhaust gas Decreases, SO _X is released from the S trap device 3. Thus released SO _X decreases the maximum storable amount of the NO _X occluded in the 1NO _X occluding and reducing catalyst device 1.

FIG. 6 is a fifth flowchart for preventing this. First, in step 501, it is determined whether or not it is a regeneration time, as described in the first and second flowcharts. When this judgment is denied, the process is terminated as it is. On the other hand, when the determination in step 501 is affirmed, it is determined in step 502 whether or not the temperature T of the S trap device 3 to be estimated or measured is equal to or higher than a set temperature T ′. When this determination is negative, SO _X is not released even if additional fuel passes through the S trap device 3, and therefore, in step 503, regeneration processing is performed as in the first and second flowcharts. .

However, when the determination in step 502 is affirmed, in the S trap device 3, if the fuel burns and the oxygen concentration in the exhaust gas decreases, SO _x is released. The supply of additional fuel by means FI is stopped, the regeneration process is stopped, and it is waited for the temperature of the S trap device to drop. The regeneration timing determination, in order to have a 80 percent of the maximum storable amount A2 of the 2NO _X occluding and reducing catalyst device, a large amount of the NO _X in the exhaust gas even if while deferring the reproduced process into the atmosphere It will not be released.

By the way, in the S trap device 3, when the stored SO _x is small, SO _x is not released when the oxygen concentration is lowered even at a relatively high temperature. As a result, the set temperature T ′ in step 502 can be increased as the SO _X storage amount decreases, and the chance of stopping the regeneration process can be reduced. Since SO _X in the exhaust gas is mainly generated by sulfur contained in the fuel, the SO _X storage amount of the S trap device 3 can be estimated from the accumulated fuel consumption of the internal combustion engine.

Further, even if the S trap device 3 is equal to or higher than the set temperature T ′, SO _X is not released unless the oxygen concentration in the exhaust gas is sufficiently lowered. rather than abort the, first 1NO _X occluding and reducing catalyst device 1 of the maximum storable amount of NO additional amount of fuel supplied to the fuel quantity qs to make the air-fuel ratio of the exhaust gas the stoichiometric air-fuel ratio by the first fuel supply means FI _The amount of fuel qr1 for reducing and purifying _X may be made smaller than the sum of fuel amounts, that is, the supply of additional fuel may be suppressed, and the amount of additional fuel in the second fuel supply means RI may be increased accordingly. In this case, as the temperature of the S trap device 3 is higher and the amount of SO _x stored in the S trap device 3 is larger, the amount of additional fuel supplied by the first fuel supply means FI is decreased. It is preferable to do.

When the S trap device 3 is above the set temperature T ′, the regeneration process of the first NO _X storage reduction catalyst device 1 is stopped, while the second NO is set to the fuel amount qs in which the air-fuel ratio of the exhaust gas is the stoichiometric air-fuel ratio. _An additional fuel amount obtained by adding the fuel amount qr2 for reducing and purifying the stored NO _X of the _X storage reduction catalyst device 2 is supplied by the second fuel supply means RI, and only the second NO _X storage reduction catalyst device 2 is regenerated. Also good.

1 is a schematic diagram of an engine exhaust system showing an exhaust gas purification apparatus for an internal combustion engine according to the present invention. It is a 1st flowchart for reproduction | regeneration processing. It is a 2nd flowchart for reproduction | regeneration processing. A third flow chart for exchanging the S trap device and the 1NO _X occluding and reducing catalyst device. A fourth flowchart for determining a deterioration of a 1NO _X occluding and reducing catalyst device and the 2NO _X occluding and reducing catalyst device. It is a 5th flowchart for reproduction processing.

Explanation of symbols

1 The 1NO _X occluding and reducing catalyst device 2 first 2NO _X occluding and reducing catalyst device 3 S trap device 4 first fuel supply device 5 second fuel supply device 6 first 1NO _X sensor 7 first 2NO _X sensor

Claims (10)

In the exhaust purification system for an internal combustion engine having a first 2NO _X occluding and reducing catalyst device of the 1NO _X occluding and reducing catalyst device and the downstream side of the arrangement in series with the upstream side to the exhaust system, supplied to the first 1NO _X occluding and reducing catalyst device by comprising a first fuel supply means for supplying additional fuel, and a second fuel supply means for supplying additional fuel between the first 1NO _X occluding and reducing catalyst device and the second 2NO _X occluding and reducing catalyst device An exhaust gas purification apparatus for an internal combustion engine characterized by the above. Wherein in carrying out the first 1NO _X occluding and reducing catalyst device and the reproduction of both of the first 2NO _X occluding and reducing catalyst device, the air-fuel ratio is the stoichiometric air-fuel ratio of the exhaust gas flowing into the first 1NO _X occluding and reducing catalyst device or additional amount of fuel supplied by the first fuel supply means so that the rich air-fuel ratio is determined, the air-fuel ratio of the exhaust gas flowing into the first 2NO _X occluding and reducing catalyst device said first 2NO _X occluding and reducing catalyst device 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the amount of additional fuel supplied by the second fuel supply unit is determined so as to obtain a rich air-fuel ratio for regeneration processing. In carrying out the regeneration process of both of said first 1NO _X occluding and reducing catalyst device and the second 2NO _X occluding and reducing catalyst device, the air-fuel ratio of the exhaust gas flowing out of the first 2NO _X occluding and reducing catalyst device becomes the stoichiometric air-fuel ratio The internal combustion engine exhaust purification according to claim 2, wherein the additional fuel amount supplied by the first fuel supply means and the additional fuel amount supplied by the second fuel supply means are determined. apparatus. In carrying out the regeneration process of both of said first 1NO _X occluding and reducing catalyst device and the second 2NO _X occluding and reducing catalyst device, when the outflow of the NO _X is estimated or detected with the fuel from the first 1NO _X occluding and reducing catalyst device The amount of additional fuel supplied by the second fuel supply means is increased so that the air-fuel ratio of the exhaust gas flowing out from the second NO _x storage reduction catalyst device becomes a rich air-fuel ratio, and the estimated or detected outflow NO 4. The exhaust emission control device for an internal combustion engine according to claim 3, wherein the amount of fuel increased by the second fuel supply means increases as the amount of _X increases. In carrying out the regeneration process of both of said first 1NO _X occluding and reducing catalyst device and the second 2NO _X occluding and reducing catalyst device, such that the first 2NO _X occluding and reducing catalyst device is within the set temperature range, the first fuel The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 2 to 4, wherein the amount of additional fuel supplied by the supply means is determined. In carrying out the regeneration process of both of said first 1NO _X occluding and reducing catalyst device and the second 2NO _X occluding and reducing catalyst device, to supply additional fuel by said second fuel supply means of the first 2NO _X occluding and reducing catalyst device 2. The exhaust gas purification of an internal combustion engine according to claim 1, wherein after the regeneration process is performed, additional fuel is supplied by the first fuel supply means to perform the regeneration process of the first NO _x storage reduction catalyst device. apparatus. Wherein the upstream side of the 1NO _X occluding and reducing catalyst device is disposed S trap device, wherein between the first 1NO _X occluding and reducing catalyst device and the second 2NO _X occluding and reducing catalyst device, NO for detecting the NO _X concentration The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein an _X sensor is disposed. 8. The exhaust gas purification apparatus for an internal combustion engine according to claim 7, wherein a NO _x sensor for detecting the NO _x concentration is also arranged downstream of the second NO _x storage reduction catalyst device. An S trap device is disposed upstream of the first NO _X storage reduction catalyst device, and the additional fuel supplied by the first fuel supply means passes through the S trap device, and the additional fuel passes therethrough. 2. The exhaust of the internal combustion engine according to claim 1, wherein when it is predicted that SO _X is released from the S trap device, supply of additional fuel by the first fuel supply means is stopped or suppressed. Purification equipment. 10. The SO _X is predicted to be released when the S trap device is equal to or higher than a set temperature, and the set temperature is lowered as the amount of SO _X stored in the S trap device increases. An exhaust gas purification apparatus for an internal combustion engine as described.

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