JP2006029216A - Exhaust emission control device and exhaust emission control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device and an exhaust emission control system making worming up performance of a catalyst good without deteriorating fuel economy. <P>SOLUTION: This invented exhaust emission control system 300 is provided with a exhaust emission control catalyst 110 which is reduced (cerium oxide contained therein) by itself when an inside of the exhaust gas passage 30 becomes reducing atmosphere. A control device (ECU) 350 stopping an engine 10 after putting the inside of the exhaust gas passage 30 into the reducing atmosphere at the time of stop of the engine 10 is also provided. A first flow passage stop valve 130 positioned in a downstream of the exhaust emission control catalyst 110 in the exhaust gas passage 30, closing the exhaust gas passage 30 right after stop of the engine 10, and opening the exhaust gas passage 30 at the time of start of the engine 10 is provided. And further an air supply device 120 positioned in an upstream of the exhaust emission control catalyst 110 in the exhaust gas passage 30 and supplying air in the exhaust gas passage 30 is provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust purification device and an exhaust purification system.

  Conventionally, various exhaust purification apparatuses and exhaust purification systems have been proposed for the purpose of purifying exhaust from internal combustion engines such as automobiles. In recent years, various exhaust purification devices and exhaust purification systems have been proposed in particular for the purpose of efficiently purifying a large amount of HC that is generated when the engine is started (see, for example, Patent Document 1 and Patent Document 2).

Japanese Patent Laid-Open No. 6-93832 JP-A-5-293384

  In the exhaust purification system disclosed in Patent Document 1, an HC adsorbent is provided at a position upstream of the exhaust purification catalyst in the exhaust passage. As a result, since a large amount of HC generated when the internal combustion engine is started can be temporarily adsorbed and held by the HC adsorbent, the HC that is exhausted without being purified until the exhaust purification catalyst is activated. Can be reduced.

  By the way, as the HC adsorbent, zeolite, aluminosilicate, mordenite and the like can be used, and these are excellent in HC adsorption and water absorption. For this reason, while the internal combustion engine is stopped, the HC adsorbent absorbs moisture contained in the exhaust gas existing in the exhaust flow path, and the internal combustion engine is started (at the time of cold start). ) Has a problem that the HC adsorption performance decreases.

  On the other hand, the exhaust purification system disclosed in Patent Document 1 is provided with shut-off means for shutting off the exhaust passage on the upstream side and downstream side of the HC adsorbent. Cut off. Accordingly, it is described that moisture adsorption on the HC adsorbent can be suppressed while the internal combustion engine is stopped, and a decrease in HC adsorption performance at the start of the internal combustion engine (during cold start) can be suppressed. Has been.

  However, in the exhaust gas purification system disclosed in Patent Document 1, the catalyst is not sufficiently activated before the HC adsorbent reaches the HC desorption temperature, and thus HC cannot be sufficiently purified. In particular, by providing the HC adsorbent upstream of the exhaust purification catalyst, exhaust heat is taken away by the HC adsorbent, so that the warm-up performance of the exhaust purification catalyst disposed downstream thereof is reduced. However, this was a major factor in reducing the HC purification rate.

  Further, the exhaust gas purification system disclosed in Patent Document 2 uses an exhaust gas purification catalyst provided with a catalyst layer having a three-way performance and a catalyst layer having an HC purification performance. In this exhaust purification system, it is described that HC can be efficiently purified by introducing secondary air to the fuel lean side at the time of engine start in which a large amount of HC is generated. Furthermore, it is described that the warm-up characteristic of the catalyst can be improved by the reaction heat generated when HC is purified.

  However, when the secondary air is introduced to the fuel lean side, the exhaust gas purification catalyst is heated by the heater (honeycomb heater) and the catalyst is not activated early, so that HC can be efficiently purified. There wasn't. Therefore, if the exhaust gas purification catalyst is not heated by the heater (honeycomb heater) when the engine is started, it cannot be expected to improve the warm-up characteristic of the catalyst due to the reaction heat generated when HC is purified. That is, in the exhaust purification system disclosed in Patent Document 2, it is indispensable to heat the exhaust gas purification catalyst with a heater (honeycomb heater) in order to improve the warm-up performance of the catalyst. This is not preferable because the fuel consumption deteriorates.

  The present invention has been made in view of the present situation, and an object of the present invention is to provide an exhaust purification device and an exhaust purification system that can improve the warm-up performance of a catalyst without deteriorating fuel consumption. .

  The exhaust purification device of the present invention is an exhaust purification catalyst located in an exhaust passage of an internal combustion engine, and the exhaust purification catalyst is reduced when the inside of the exhaust passage becomes a reducing atmosphere, and the exhaust passage. A first passage opening / closing means that is located downstream of the exhaust purification catalyst and capable of opening and closing the exhaust passage, and is located upstream of the exhaust purification catalyst in the exhaust passage. An exhaust gas purifying device that is positioned and capable of supplying an oxygen-containing gas into the exhaust flow path.

Further preferably, the exhaust purification catalyst is a metal oxide, and the oxidation number of the metal element forming the metal oxide in the case where the exhaust flow path becomes an oxidizing atmosphere and a reducing atmosphere. It is preferable that the exhaust gas purification apparatus includes a metal oxide that causes a redox reaction with change.
Further preferably, any one of the above exhaust purification apparatuses, comprising second passage opening / closing means that is positioned upstream of the exhaust purification catalyst in the exhaust passage and capable of opening and closing the exhaust passage. Good to be.

Furthermore, it is preferable that any one of the above exhaust purification apparatuses includes an HC adsorbing material that adsorbs HC in the exhaust at a position upstream of the exhaust purification catalyst in the exhaust passage.
Further preferably, an HC adsorbent that adsorbs HC in the exhaust is provided in a position upstream of the exhaust purification catalyst in the exhaust flow path, and the second flow path opening / closing means includes the HC adsorbent. It is preferable that the exhaust gas purification device is located on the upstream side.

  The exhaust purification system of the present invention is an exhaust purification catalyst located in an exhaust passage of an internal combustion engine, and the exhaust purification catalyst is reduced when the inside of the exhaust passage becomes a reducing atmosphere, and the internal combustion engine When stopping the engine, after setting the inside of the exhaust passage to a reducing atmosphere, the internal combustion engine operation control means for stopping the internal combustion engine, and located in the exhaust passage in the downstream side of the exhaust purification catalyst, First flow path opening / closing means for opening and closing the exhaust flow path, wherein the exhaust flow path is closed immediately after the internal combustion engine is stopped, and the exhaust flow path is opened when the internal combustion engine is started. An exhaust purification system comprising gas supply means located upstream of the exhaust purification catalyst in the exhaust passage and supplying an oxygen-containing gas into the exhaust passage when the internal combustion engine is started. is there.

Further preferably, the internal combustion engine operation control means is the exhaust purification system according to which the internal combustion engine is stopped after operating the internal combustion engine by making the air / fuel ratio of the internal combustion engine smaller than the stoichiometric air / fuel ratio. And good.
Further, preferably, an air-fuel ratio sensor that is located downstream of the exhaust purification catalyst in the exhaust flow path and detects an air-fuel ratio of the internal combustion engine, the internal combustion engine operation control means includes the internal combustion engine When stopping the engine, the air-fuel ratio of the internal combustion engine is made smaller than the stoichiometric air-fuel ratio until the air-fuel ratio sensor detects a value smaller than the stoichiometric air-fuel ratio of the internal combustion engine. It is preferable that the exhaust gas purification system is stopped after being stopped.

Further preferably, the exhaust purification catalyst is a metal oxide, and the oxidation number change of the metal element forming the metal oxide is different between when the exhaust passage is in an oxidizing atmosphere and in a reducing atmosphere. Any one of the above-described exhaust gas purification systems including a metal oxide that causes an oxidation-reduction reaction accompanied with NO is preferable.
Further preferably, the gas supply means is any one of the above-described exhaust purification systems that supplies an oxygen-containing gas into the exhaust flow passage in an amount necessary to oxidize the exhaust purification catalyst in a reduced state. And good.

Further preferably, the second flow path opening / closing means is located upstream of the exhaust purification catalyst in the exhaust flow path and opens and closes the exhaust flow path, and the exhaust gas is discharged immediately after the internal combustion engine is stopped. Any one of the above exhaust purification systems may be provided with a second flow path opening / closing means that closes the flow path and opens the exhaust flow path when the internal combustion engine is started.
Further preferably, the exhaust gas purification system according to any one of the above, further comprising an HC adsorbing material that adsorbs HC in the exhaust gas at a position upstream of the exhaust gas purification catalyst in the exhaust gas flow path.

Further preferably, an HC adsorbing material that adsorbs HC in the exhaust is provided at a position upstream of the exhaust purification catalyst in the exhaust flow path, and the second flow path opening / closing means includes the exhaust flow path. Of these, the exhaust purification system may be located upstream of the HC adsorbent.
Furthermore, it is preferable that any one of the above-described exhaust purification systems includes HC desorption timing estimation means for estimating a timing at which HC desorbs from the HC adsorbent.
Further preferably, the gas supply means is configured so that an HC removal timing estimated by the HC removal timing prediction means coincides with an oxidation end time at which an oxidation reaction of the exhaust purification catalyst in a reduced state ends. It is preferable that the exhaust gas purification system supply an oxygen-containing gas into the exhaust flow path.

The exhaust purification apparatus of the present invention includes an exhaust purification catalyst that reduces itself when the inside of the exhaust passage becomes a reducing atmosphere. For this reason, when the internal combustion engine is stopped with the inside of the exhaust passage set in a reducing atmosphere, the exhaust purification catalyst can be brought into a reduced state. Note that the reduction of the exhaust purification catalyst means that a substance (for example, cerium oxide or the like) contained in the exhaust purification catalyst is reduced. Specifically, it means that CeO ₂ is reduced to Ce ₂ O ₃ in an exhaust purification catalyst containing cerium oxide.

  Furthermore, the exhaust purification apparatus of the present invention includes first flow path opening / closing means that is located downstream of the exhaust purification catalyst in the exhaust flow path and can open and close the exhaust flow path. For this reason, since the inflow of air (oxygen) from the downstream side to the exhaust purification catalyst can be prevented by closing the exhaust passage by the first passage opening / closing means while the internal combustion engine is stopped, the engine is in the reduced state. Oxidation of the exhaust purification catalyst can be suppressed.

  Furthermore, the exhaust purification apparatus of the present invention includes gas supply means that is located upstream of the exhaust purification catalyst in the exhaust flow path and can supply an oxygen-containing gas into the exhaust flow path. For this reason, when the internal combustion engine is started, the oxygen supply gas is supplied into the exhaust passage by the gas supply means, whereby the oxidation reaction of the exhaust purification catalyst in the reduced state can be promoted. Since the catalyst layer can be heated by the oxidation reaction heat at this time, the catalyst can be activated early. Note that the oxygen-containing gas refers to a gas containing oxygen, and examples thereof include air and oxygen.

As described above, according to the exhaust emission control device of the present invention, it is possible to improve the warm-up property of the catalyst. Furthermore, according to the exhaust emission control device of the present invention, the warm-up performance of the catalyst can be improved without using a heater (honeycomb heater), so there is no possibility that the fuel consumption will deteriorate.
The number of exhaust purification catalysts is not limited to one, and a plurality of exhaust purification catalysts may be provided. Further, when a plurality of exhaust purification catalysts are provided, the gas supply means may be provided at a plurality of locations upstream of each exhaust purification catalyst.

  Furthermore, in the exhaust purification apparatus of the present invention, the exhaust purification catalyst is a metal oxide, and the metal element that forms the metal oxide is formed when the inside of the exhaust passage is in an oxidizing atmosphere and in a reducing atmosphere. It is preferable to include a metal oxide that causes a redox reaction involving a change in oxidation number. Since such a metal oxide generates a relatively large oxidation reaction heat during the oxidation reaction, the warm-up property of the catalyst can be further improved. Examples of the metal oxide that causes a redox reaction accompanied by a change in the oxidation number of the metal element include cerium oxide, praseodymium oxide, nickel oxide, chromium oxide, and cobalt oxide. Of these, cerium oxide and praseodymium oxide are preferable because they generate particularly large heat of oxidation reaction.

  Furthermore, the exhaust purification apparatus of the present invention preferably includes a second flow path opening / closing means that is located upstream of the exhaust purification catalyst in the exhaust flow path and can open and close the exhaust flow path. . While the internal combustion engine is stopped, the exhaust flow path is closed by the second flow path opening / closing means together with the first flow path opening / closing means, thereby preventing the inflow of air (oxygen) from the upstream side to the exhaust purification catalyst. Therefore, the oxidation of the exhaust purification catalyst in the reduced state can be further suppressed. As a result, when air (oxygen) is supplied by the gas supply means at the time of starting the internal combustion engine, larger heat of oxidation reaction can be generated in the exhaust purification catalyst.

  Furthermore, while the internal combustion engine is stopped, the first and second flow path opening / closing means closes the upstream side and the downstream side of the exhaust purification catalyst, thereby suppressing moisture adsorption to the exhaust purification catalyst. it can. This makes it possible to reduce the amount of heat taken as the heat of vaporization of the adsorbed water out of the oxidation reaction heat in the exhaust purification catalyst. Thereby, the warm-up property of the catalyst can be further improved.

  Furthermore, in the exhaust purification apparatus of the present invention, it is preferable that an HC adsorbent that adsorbs HC in the exhaust is provided in a position upstream of the exhaust purification catalyst in the exhaust flow path. As a result, since a large amount of HC generated when the internal combustion engine is started can be temporarily adsorbed and held by the HC adsorbent, the HC that is exhausted without being purified until the exhaust purification catalyst is activated. Can be reduced.

  By the way, in the conventional exhaust purification device in which the HC adsorbent is provided on the upstream side of the exhaust purification catalyst, the exhaust heat is taken away by the HC adsorbent, so that the warm-up property of the exhaust purification catalyst arranged on the downstream side thereof There was a problem that would decrease. In contrast, in the exhaust purification device of the present invention, as described above, when the internal combustion engine is started, the exhaust purification catalyst itself can be heated by the oxidation reaction heat of the exhaust purification catalyst, and the catalyst can be activated early. is there. For this reason, even if the HC adsorbent is provided upstream of the exhaust purification catalyst, it is possible to improve the warm-up property of the catalyst.

Furthermore, in the exhaust emission control device of the present invention, it is preferable that the second flow path opening / closing means is located upstream of the HC adsorbent.
As the HC adsorbent, zeolite, aluminosilicate, mordenite and the like can be used, and these are excellent in HC adsorption and water absorption. For this reason, conventionally, in an exhaust emission control device equipped with an HC adsorbent, the HC adsorbent absorbs moisture contained in the exhaust gas remaining in the exhaust passage while the internal combustion engine is stopped. As a result, there is a problem that the HC adsorption performance at the time of starting the internal combustion engine is deteriorated. In contrast, the internal combustion engine is stopped by providing the third flow path opening / closing means at the upstream position in addition to the position downstream of the HC adsorbent (first flow path opening / closing means) in the exhaust flow path. During this time, the adsorption of moisture to the HC adsorbent can be suppressed by closing the exhaust passage by the both passage opening and closing means. Thereby, the fall of HC adsorption performance at the time of start-up of an internal-combustion engine can be controlled.

  The exhaust purification system of the present invention includes an exhaust purification catalyst that reduces itself when the inside of the exhaust passage becomes a reducing atmosphere. Further, when the internal combustion engine is stopped, an internal combustion engine operation control means is provided for stopping the internal combustion engine after setting the inside of the exhaust passage to a reducing atmosphere. Thereby, when the internal combustion engine is stopped, the exhaust purification catalyst can be brought into a reduced state.

  Further, in the exhaust purification system of the present invention, the exhaust passage is located downstream of the exhaust purification catalyst in the exhaust passage, and the exhaust passage is closed immediately after the internal combustion engine is stopped, and the exhaust passage is opened when the internal combustion engine is started. One channel opening / closing means is provided. Thereby, since the inflow of air (oxygen) from the downstream side to the exhaust purification catalyst can be prevented until the internal combustion engine is stopped and started, the reduced state of the exhaust purification catalyst can be maintained.

  Further, the exhaust purification system of the present invention includes gas supply means that is located upstream of the exhaust purification catalyst in the exhaust passage and supplies oxygen-containing gas into the exhaust passage when the internal combustion engine is started. Yes. As a result, the internal combustion engine can be started and an oxygen-containing gas (air, oxygen, etc.) necessary and sufficient to oxidize the exhaust purification catalyst in the reduced state can be supplied, and the oxidation reaction of the exhaust purification catalyst is promoted. be able to. Since the catalyst layer can be heated by the oxidation reaction heat at this time, the catalyst can be activated early.

As described above, in the exhaust purification system of the present invention, the warm-up property of the catalyst can be improved. Furthermore, in the exhaust purification system of the present invention, the warming performance of the catalyst can be improved without using a heater (honeycomb heater), so there is no possibility that fuel consumption will deteriorate.
The number of exhaust purification catalysts is not limited to one, and a plurality of exhaust purification catalysts may be provided. When a plurality of exhaust purification catalysts are provided, the gas supply means may be provided at a plurality of locations upstream of each exhaust purification catalyst.

  Furthermore, in the exhaust gas purification system of the present invention, it is preferable to stop the internal combustion engine after operating the internal combustion engine with the air / fuel ratio of the internal combustion engine made smaller than the stoichiometric air / fuel ratio. By operating the internal combustion engine with the air-fuel ratio of the internal combustion engine smaller than the stoichiometric air-fuel ratio, the inside of the exhaust passage can be appropriately made a reducing atmosphere.

  Furthermore, in the exhaust purification system of the present invention, an air-fuel ratio sensor for detecting the air-fuel ratio of the internal combustion engine is provided downstream of the exhaust purification catalyst. Until the small value is detected, it is preferable that the air-fuel ratio is made smaller than the stoichiometric air-fuel ratio and the internal combustion engine is operated and then stopped. Thereby, when the internal combustion engine is stopped, the exhaust purification catalyst can be surely brought into a reduced state. For example, an oxygen sensor can be used as the air-fuel ratio sensor. The air-fuel ratio of the internal combustion engine can be calculated (estimated) from the output of the oxygen sensor.

  Furthermore, in the exhaust purification system of the present invention, the exhaust purification catalyst is a metal oxide, and when the inside of the exhaust passage is in an oxidizing atmosphere or in a reducing atmosphere, the metal element that forms the metal oxide is used. It is preferable to include a metal oxide that causes a redox reaction involving a change in oxidation number. Since such a metal oxide generates a relatively large oxidation reaction heat during the oxidation reaction, the warm-up property of the catalyst can be further improved.

  Furthermore, in the exhaust purification system of the present invention, it is preferable that the gas supply means supplies the oxygen-containing gas into the exhaust passage in an amount necessary for oxidizing the exhaust purification catalyst in the reduced state. When supplying the oxygen-containing gas into the exhaust passage by the gas supply means, if the supply amount of the oxygen-containing gas (the oxygen contained therein) is small, the exhaust purification catalyst in the reduced state may be sufficiently oxidized. Can not. For this reason, when the internal combustion engine is started, the catalyst layer is not sufficiently heated by the oxidation reaction heat. Conversely, when the supply amount of the oxygen-containing gas is excessive, the catalyst is cooled by excessive oxygen (air).

On the other hand, by supplying the oxygen-containing gas into the exhaust passage in an amount necessary to oxidize the exhaust purification catalyst in the reduced state, the above problem does not occur and the engine is started. The catalyst layer can be efficiently and suitably heated by the heat of oxidation reaction. Thereby, the warm-up property of the catalyst can be improved.
As such an exhaust purification system, for example, means for measuring (calculating) the supply amount of the oxygen-containing gas supplied into the exhaust passage by the gas supply means, and exhaust gas in which the supply amount of the oxygen-containing gas is in a reduced state And an exhaust purification system including means for stopping the supply of the oxygen-containing gas from the gas supply means into the exhaust passage when the amount necessary for oxidizing the purification catalyst is reached.

  Further, the exhaust purification system of the present invention is located upstream of the exhaust purification catalyst in the exhaust flow path, closes the exhaust flow path immediately after the internal combustion engine is stopped, and opens the exhaust flow path when the internal combustion engine is started. It is preferable that a two-channel opening / closing means is provided. In this exhaust purification system, the first flow path opening / closing means and the second flow path opening / closing means can close the upstream side and the downstream side of the exhaust purification catalyst in the exhaust flow path while the internal combustion engine is stopped. it can. Thereby, while the internal combustion engine is stopped, the oxidation of the exhaust purification catalyst in the reduced state can be further suppressed. For this reason, when the internal combustion engine is started and air (oxygen) is supplied by the gas supply means, a larger oxidation reaction heat can be generated in the exhaust purification catalyst.

  Furthermore, while the internal combustion engine is stopped, the first flow path opening / closing means and the second flow path opening / closing means close the upstream side and the downstream side of the exhaust purification catalyst in the exhaust flow path, thereby exhaust purification. Water adsorption on the catalyst can also be suppressed. As a result, the amount of heat taken as the heat of vaporization of the adsorbed moisture in the oxidation reaction heat in the exhaust purification catalyst can be reduced, so that the warm-up property of the catalyst can be further improved.

Furthermore, in the exhaust purification system of the present invention, it is preferable that an HC adsorbent is provided at a position upstream of the exhaust purification catalyst. As a result, since a large amount of HC generated when the internal combustion engine is started can be temporarily adsorbed and held by the HC adsorbent, the HC that is exhausted without being purified until the exhaust purification catalyst is activated. Can be reduced.
By the way, as described above, conventionally, when the HC adsorbent is provided upstream of the exhaust purification catalyst, exhaust heat is taken away by the HC adsorbent, so that the exhaust purification catalyst disposed downstream thereof. There has been a problem that the warm-up property of the machine is lowered. In contrast, in the exhaust purification system of the present invention, as described above, when the internal combustion engine is started, the exhaust purification catalyst itself can be heated by the oxidation reaction heat of the exhaust purification catalyst, and the catalyst can be activated early. Therefore, even if the HC adsorbent is provided upstream of the exhaust purification catalyst, the warm-up property of the catalyst can be improved.

  Furthermore, in the exhaust purification system of the present invention, it is preferable that the second flow path opening / closing means is located upstream of the HC adsorbent in the exhaust flow path. By providing the second flow path opening / closing means at a position upstream of the HC adsorbent, the flow path opening / closing means (the first flow opening / closing means for opening / closing the exhaust flow path between the upstream position and the downstream position of the HC adsorbent) , Second channel opening / closing means) can be provided. Therefore, while the internal combustion engine is stopped, moisture adsorption to the HC adsorbent with high water absorption can be suppressed by closing the exhaust passage by the first and second passage opening / closing means. Thereby, the fall of HC adsorption performance at the time of start-up of an internal-combustion engine can be controlled.

  Furthermore, it is preferable that the exhaust purification system of the present invention further includes HC desorption timing estimation means for estimating the timing of HC desorption from the HC adsorbent. As described above, in the exhaust purification system of the present invention, the oxygen-containing gas is supplied from the gas supply means to promote the oxidation reaction of the exhaust purification catalyst in a reduced state (for example, cerium oxide contained in the exhaust purification catalyst). Thus, the heat of oxidation reaction at this time is used for heating the catalyst. Therefore, in order to efficiently purify HC, the oxygen supply gas is supplied by the gas supply means while keeping an eye on the timing when HC desorbs from the HC adsorbent (in other words, when the HC adsorbent reaches the HC desorption temperature). Thus, it is preferable to heat the catalyst with heat of oxidation reaction. On the other hand, in the exhaust purification system of the present invention, the HC desorption timing can be estimated by the HC desorption timing estimation means, so that by supplying the oxygen-containing gas by the gas supply means in anticipation of the estimated HC desorption timing, Can be efficiently purified.

Furthermore, in the exhaust purification system of the present invention, the gas supply means is arranged so that the HC departure timing estimated by the HC departure timing prediction means coincides with the oxidation end timing at which the oxidation reaction of the exhaust purification catalyst in the reduced state ends. It is preferable to supply the oxygen-containing gas into the exhaust passage.
As described above, in the exhaust purification system of the present invention, by supplying the oxygen-containing gas from the gas supply means, the oxidation reaction of the exhaust purification catalyst in the reduced state is promoted, and the oxidation reaction heat at this time is converted to the catalyst heat. It is used for heating. Accordingly, the temperature of the catalyst rises as the oxidation of the exhaust purification catalyst proceeds, and when the entire amount of the exhaust purification catalyst in the reduced state is oxidized, the temperature rise due to the supply of the oxygen-containing gas reaches a peak.

  On the other hand, in the exhaust purification system of the present invention, the HC desorption timing estimated by the HC desorption timing predicting means and the oxidation end timing at which the oxidation reaction of the exhaust purification catalyst in the reduced state coincides with each other. Since the oxygen-containing gas is supplied into the exhaust passage by the supply means, the HC desorption timing can coincide with the peak of the temperature rise of the catalyst due to the heat of oxidation reaction. Therefore, in the exhaust gas purification system of the present invention, the temperature rising effect of the catalyst due to the oxidation reaction heat can be utilized to the maximum, and HC separated from the HC adsorbent can be efficiently purified.

(Production of exhaust purification catalyst)
First, a honeycomb substrate made of cordierite having a cell partition wall thickness of 75 μm, a cell density of 62 cells / cm ² (400 cells / inch ² ), a capacity of 0.9 L was prepared.
Next, 100 g of CeO ₂ supporting Pt at a rate of 0.3 wt%, 100 g of γ-Al ₂ O ₃ (specific surface area of about 130 m ² / g) supporting Pt at a rate of 1.24 wt%, and Rh 60 g of ZrO ₂ (specific surface area is about 60 m ² / g) supported at a ratio of 0.66 wt%, 3 g of aluminum nitrate, and 3 g of aluminum hydroxide in a solid content were mixed. Furthermore, ion exchange water was added to this mixture to prepare a catalyst slurry having a solid content of 35%.

  Next, this catalyst slurry was coated on the honeycomb substrate by a known method, and then the excess catalyst slurry was removed. Next, the honeycomb base material coated with the catalyst slurry was heated and dried at 120 ° C., and then fired in the atmosphere at 250 ° C. for 1 hour to produce an exhaust purification catalyst 110. In Example 1, the coating amount of the catalyst slurry was 240 g / l. The catalyst loading was 1.5 g Pt and 0.4 g Rh per liter of honeycomb substrate.

  As shown in FIG. 1, the exhaust purification device 100 of the first embodiment is provided in an exhaust passage 30 of a gasoline engine 10 having a displacement of 2.4 L. The exhaust purification catalyst 110, the air supply device 120, the first A flow path opening / closing valve 130 is provided. The exhaust purification catalyst 110 is provided in the exhaust passage 30 at a position corresponding to a normal actual vehicle. The air supply device 120 is provided upstream of the exhaust purification catalyst 110 in the exhaust flow path 30, and can supply air into the exhaust flow path 30. The first flow path opening / closing valve 130 is provided on the downstream side of the exhaust purification catalyst 110 in the exhaust flow path 30 and can open and close the exhaust flow path 30.

  The exhaust purification catalyst 110 used in the first embodiment and the second to fourth embodiments to be described later is mounted in advance at a predetermined position and performing feedback control in which the air-fuel ratio of the engine 10 is the stoichiometric air-fuel ratio (stoichiometric). The test operation was performed for 10 hours at an inlet gas temperature of 800 ° C. In addition, silencers 21 and 22 are provided at positions downstream of the first flow path opening / closing valve 130 in the exhaust flow path 30.

With respect to the exhaust gas purification device 100 of the first embodiment, a warm-up evaluation test was performed.
Specifically, first, with the first flow path on / off valve 130 opened, the air-fuel ratio was stoichiometric (A / F = 14.6), and the engine 10 was continuously operated at 2000 rpm. Thereafter, the engine 10 was stopped and the first flow path opening / closing valve 130 was closed after idling with the air-fuel ratio set to the fuel rich side (A / F = 14.3). Thereafter, it was allowed to cool at room temperature for about 12 hours. Next, the first flow path opening / closing valve 130 is opened and air is supplied into the exhaust flow path 30 by the air supply device 120 for about 5 seconds, and then the engine 10 is started, and in the idle state for 20 seconds after the engine is started. HC emissions were measured.

  As shown in FIG. 2, the exhaust purification apparatus 200 according to the second embodiment is compared with the exhaust purification apparatus 100 according to the first embodiment, in addition to the first flow path opening / closing valve 130 located on the downstream side of the exhaust purification catalyst 110, The difference is that a second flow path opening / closing valve 230 is also provided at a position upstream of the exhaust purification catalyst 110 (specifically, between the exhaust purification catalyst 110 and the air supply device 120), and the rest is substantially the same. is there. For the exhaust purification apparatus 200 of the second embodiment, the warm-up evaluation test was performed and the HC emission amount was measured in the same manner as the exhaust purification apparatus 100 of the first embodiment. In the exhaust purification device 200 of the second embodiment, the second flow path opening / closing valve 230 is opened / closed at the same timing as the first flow path opening / closing valve 130.

(Comparative Example 1)
The exhaust purification device of the first comparative example is different from the exhaust purification device 100 of the first embodiment in that the air supply device 120 and the first flow path opening / closing valve 130 are not provided, and the others are substantially the same. . The exhaust purification device of Comparative Example 1 was also subjected to a warm-up evaluation test, and HC emissions were measured. In the first comparative example, unlike the first embodiment, the engine 10 is stopped after the idling operation is performed with the air-fuel ratio on the fuel lean side (fuel cut is performed). Further, in the first comparative example, unlike the first embodiment, since the air supply device 120 and the first flow path opening / closing valve 130 are not provided, the supply of air into the exhaust flow path 30 by the air supply device, and the first The exhaust passage 30 is not opened or closed by the passage opening / closing valve 130.

  Next, FIG. 3 shows the results of the warm-up evaluation test of the exhaust purification apparatuses 100 and 200 of Examples 1 and 2 and the exhaust purification apparatus of Comparative Example 1. FIG. 3 shows the accumulated HC discharge amount for 20 seconds after the engine is started. As shown in FIG. 3, in the exhaust purification apparatuses 100 and 200 of Examples 1 and 2 of the present invention, both of the accumulated HC emissions for 20 seconds after engine startup were smaller than in the exhaust purification apparatus of Comparative Example 1. This is probably because the exhaust purification apparatuses 100 and 200 of Examples 1 and 2 of the present invention were able to activate the catalyst earlier than the exhaust purification apparatus of Comparative Example 1.

Here, the reason why the exhaust purification apparatuses 100 and 200 according to the first and second embodiments of the present invention can activate the catalyst earlier than the exhaust purification apparatus according to the first comparative example will be examined. In Comparative Example 1, the engine 10 was stopped after the idling operation was performed by setting the air-fuel ratio of the engine 10 to the fuel lean side (implementing fuel cut). Therefore, in Comparative Example 1, it is considered that when the engine 10 was stopped, the exhaust purification catalyst 110 (specifically, cerium oxide contained in the exhaust purification catalyst 110) was in an oxidized state (CeO ₂ ). Next, after cooling, the engine 10 is started and idling is performed. Therefore, in the first comparative example, it is considered that the exhaust purification catalyst 110 is heated only by the exhaust heat of the engine 10.

On the other hand, in the first and second embodiments, the air-fuel ratio is set to the fuel rich side (A / F = 14.3) and the idling operation is performed to bring the exhaust passage 30 into the reducing atmosphere, and then the engine 10 is stopped. ing. Thus, in Examples 1 and 2, it is considered that when the engine 10 was stopped, the exhaust purification catalyst 110 (specifically, cerium oxide) could be reduced (Ce ₂ O ₃ ). Further, in the first and second embodiments, the engine 10 is stopped and the first flow path opening / closing valve 130 is closed. Thereby, the inflow of air (oxygen) from the downstream side to the exhaust purification catalyst 110 can be prevented, and the oxidation of the exhaust purification catalyst 110 in a reduced state (specifically, Ce ₂ O ₃ ) can be suppressed. It is done.

Furthermore, in the first and second embodiments, after cooling, when the engine 10 is started, the first flow path opening / closing valve 130 is opened and air is supplied into the exhaust flow path 30 by the air supply device 120 for about 5 seconds. Yes. Thus, it is considered that the oxidation reaction of the exhaust purification catalyst 110 (specifically, Ce ₂ O ₃ ) in the reduced state was promoted, and the catalyst layer was heated by the oxidation reaction heat at this time. That is, in Examples 1 and 2, it is considered that the catalyst layer could be heated by the oxidation reaction heat when Ce ₂ O ₃ was oxidized to CeO ₂ in addition to the exhaust heat of the engine 10. For this reason, it is considered that in Examples 1 and 2, the catalyst could be activated earlier than in Comparative Example 1. From the above, it can be said that both the exhaust purification apparatuses 100 and 200 of Examples 1 and 2 of the present invention have better catalyst warm-up than the exhaust purification apparatus of Comparative Example 1.

  Next, when the results of Example 1 and Example 2 were compared, Example 2 had a smaller cumulative HC emission amount for 20 seconds after engine startup than Example 1. In the second embodiment, this is the position upstream of the exhaust purification catalyst 110 (in detail, the exhaust purification catalyst 110 and the air supply) in addition to the first flow path opening / closing valve 130 located downstream of the exhaust purification catalyst 110. This is probably because the second flow path opening / closing valve 230 is also provided between the device 120 and the device 120.

That is, while the engine 10 is stopped, the exhaust flow path 30 is closed by the second flow path opening / closing valve 230 together with the first flow path opening / closing valve 130, so that the air (oxygen) from the upstream side to the exhaust purification catalyst 110 (oxygen) This is probably because the oxidation of the exhaust purification catalyst 110 (specifically, Ce ₂ O ₃ ) in the reduced state could be further suppressed. Accordingly, in the second embodiment, compared to the first embodiment, when the engine 10 is started, the exhaust purification catalyst 110 contains more Ce ₂ O ₃ (reduced cerium oxide). It is considered that when the air was supplied from the air supply device 120, the exhaust purification catalyst 110 was able to generate larger heat of oxidation reaction.

Further, while the engine 10 is stopped, the adsorption of moisture to the exhaust purification catalyst 110 is also suppressed by closing the exhaust passage 30 by the second passage on-off valve 230 together with the first passage on-off valve 130. This is thought to be due to this. Thus, in Example 2, it is considered that the amount of heat taken as the heat of vaporization of the adsorbed water out of the oxidation reaction heat in the exhaust purification catalyst 110 could be reduced as compared with Example 1.
For the reasons described above, it is considered that the exhaust purification device 200 of the second embodiment was able to activate the catalyst earlier than the exhaust purification device 100 of the first embodiment. Therefore, it can be said that the exhaust gas purification apparatus 200 of the second embodiment has better catalyst warm-up performance than the exhaust gas purification apparatus 100 of the first embodiment.

  As shown in FIG. 4, the exhaust purification system 300 of the third embodiment is provided in the exhaust passage 30 of the gasoline engine 10 having a displacement of 2.4 L. The exhaust purification catalyst 110, the air supply device 120, the first A flow path opening / closing valve 130, an oxygen sensor 340, and a control device (ECU) 350 are provided. Specifically, with respect to the exhaust purification device 100 of the first embodiment, the exhaust flow path 30 is downstream of the exhaust purification catalyst 110 (specifically, between the exhaust purification catalyst 110 and the first flow path opening / closing valve 130). The exhaust gas purification system is provided by providing the oxygen sensor 340 at the position and the air supply device 120, the first flow path opening / closing valve 130, and the control device 350 for controlling the oxygen sensor 340.

  In the exhaust purification system 300 of the third embodiment, since the air supply device 120 is connected to the control device 350, the control device 350 supplies the air from the air supply device 120 into the exhaust flow path 30, and the air Can be controlled. Furthermore, since the first flow path opening / closing valve 130 is connected to the control device 350, the control device 350 can control the timing at which the first flow path opening / closing valve 130 opens and closes the exhaust flow path 30. Furthermore, since the oxygen sensor 340 is connected to the control device 350, the control device 350 can detect the output of the oxygen sensor 340 and calculate the current air-fuel ratio based on this output value. Therefore, the air-fuel ratio control can be performed so that the engine 10 is operated at the target air-fuel ratio based on the calculated current air-fuel ratio and the target air-fuel ratio (for example, the theoretical air-fuel ratio). In the third embodiment, the control device 350 includes internal combustion engine control means.

Here, the air-fuel ratio control in the exhaust purification system 300 of the third embodiment will be described with reference to the flowchart shown in FIG. In the third embodiment, during the operation of the engine 10, a series of processes shown in the flowchart of FIG. 5 is set to be repeated at predetermined time intervals (16 milliseconds in the third embodiment). ing.
First, in step S1, the control device 350 determines whether or not the transmission gear position is neutral. Here, in the case of neutral, it can be determined that the vehicle has stopped and that the engine 10 will be stopped soon.

If it is determined in step S1 that it is neutral (Yes), the process proceeds to step S3, and it is determined whether or not the output of the oxygen sensor 340 is equal to or higher than a preset target value B (V). In the third embodiment, the engine 10 is normally operated with the air-fuel ratio set to a stoichiometric state (A / F = 14.6). In this case, the output value of the oxygen sensor 340 is about 0. 0. It is known to show 42V. Therefore, when the output value of the oxygen sensor 340 is less than 0.42V, the exhaust gas in the exhaust passage 30 is in an oxidizing atmosphere. Can be judged to be in a reducing atmosphere.
Here, the value of the target value B can be set arbitrarily, but in the third embodiment, two different values of B = 0.6, 0.8 (V) (both are exhaust passages). The value when the inside of 30 is a reducing atmosphere) was set, and air-fuel ratio control was performed respectively.

On the other hand, if it is determined in step S1 that the vehicle speed is equal to or higher than the predetermined value A (No), the process proceeds to step S2, and it is determined whether or not the vehicle speed is less than the predetermined value A (for example, 5 km / h). To do. That is, in step S2, it is determined whether or not the vehicle will stop soon.
When it is determined that the vehicle speed is less than the predetermined value A (Yes), the process proceeds to step S3. Conversely, when it is determined that the vehicle speed is equal to or higher than the predetermined value A (No), a series of processing is performed. Once the process is completed and the predetermined time has elapsed, the above processing is performed again from step S1.

  In step S3, if the output of the oxygen sensor 340 does not reach the target value B (for example, 0.6) (V) (No), the process proceeds to step S4, and the control device 350 causes the air / fuel ratio of the engine 10 ( A / F) is set to C (a value on the richer side than stoichiometry, C <14.6), and the engine 10 is operated. Thus, by operating the engine 10 in the fuel rich state, the output value of the oxygen sensor 340 can be increased and brought close to the target value B (V).

  On the other hand, when the output of the oxygen sensor 340 reaches the target value B (V) in step S3 (Yes), the process proceeds to step S5, and it is determined whether or not the key switch is OFF. If it is determined that the key switch is not OFF (No), after the predetermined time has elapsed, the above processing is performed again from step S1. Conversely, if it is determined that the key switch is OFF, the process proceeds to step S6 and the engine 10 is stopped. Subsequently, it progresses to step S7, the 1st flow-path on-off valve 130 is closed, and a series of processes are complete | finished.

In the third embodiment, the engine 10 is stopped after the output value of the oxygen sensor 340 is set to the target value B (specifically, 0.6 V or 0.8 V) by repeatedly performing the above-described series of processes. be able to. That is, the engine 10 can be stopped after the exhaust gas in the exhaust passage 30 is reduced to a reducing atmosphere. Of the series of processes described above, steps S1 to S6 are included in the internal combustion engine operation control means.
Thereafter, in the same manner as in Example 1, each was allowed to cool at room temperature for about 12 hours, and then a warm-up evaluation test was performed, and an integrated HC discharge amount for 20 seconds after engine startup was measured.

(Comparative Example 2)
The exhaust purification system of the second comparative example is different from the exhaust purification system 300 of the third embodiment in the air-fuel ratio control in the control device (ECU), and is otherwise substantially the same. Specifically, in the second comparative example, as shown in FIG. 15, when compared with the air-fuel ratio control of the third embodiment (see FIG. 5), the processing of steps V3 and V4 is performed instead of the processing of steps S3 and S4. The other processing is the same.

  In step V3, it is determined whether or not the output value of the oxygen sensor 340 has become equal to or less than the target value B (V). In the second comparative example, two different values of B = 0.1 and 0.3 (V) (both are values when the exhaust gas in the exhaust passage 30 is in an oxidizing atmosphere) are set. In each case, air-fuel ratio control was performed. When the output of the oxygen sensor 340 is larger than the target value B (V) (No), the process proceeds to Step V4, and the control device changes the air-fuel ratio (A / F) of the engine 10 to D (lean side from stoichiometric). Value,> 14.6) and run the engine 10. In this way, by operating the engine 10 in the state on the fuel lean side, the output value of the oxygen sensor 340 can be reduced and brought close to the target value B (V).

On the other hand, when the output of the oxygen sensor 340 is equal to or lower than the target value B (V) (Yes), the series of processes is terminated and the engine 10 is stopped. In Comparative Example 2, as in Example 1, the engine 10 is stopped and the first flow path opening / closing valve 130 is closed.
Thereafter, in the same manner as in Example 1, each was allowed to cool at room temperature for about 12 hours, and then a warm-up evaluation test was performed, and an integrated HC discharge amount for 20 seconds after engine startup was measured.

  Next, the results of the warm-up evaluation test of the exhaust purification system 300 of Example 3 and the exhaust purification system of Comparative Example 2 are shown in FIG. FIG. 6 shows the accumulated HC discharge amount for 20 seconds after the engine is started. In the exhaust gas purification system of Comparative Example 2 (target values B = 0.1, 0.3) indicated by x in FIG. 6, the accumulated HC emission amount was about 110 to 120 mg. In contrast, in the exhaust gas purification system 300 (target value B = 0.6, 0.8) of Example 3 indicated by ●, the integrated HC emission amount could be reduced to about 70 to 80 mg. From this result, it can be said that the exhaust purification system 300 of Example 3 was able to improve the warm-up property of the catalyst better than the exhaust purification system of Comparative Example 2.

  Here, if the graph of FIG. 6 is examined, setting the target value B = 0.42 (V) as a boundary to a value smaller than 0.42 (V) greatly increases the HC integrated amount to 0.42 (V ) When the value is set to a larger value, it can be seen that the HC integrated amount greatly decreases. From this result, when the target value B = 0.42 (V) is used as a boundary and the value is set to a value smaller than 0.42 (V), the warm-up performance of the catalyst is greatly reduced to a value larger than 0.42 (V). If set, it can be said that the warm-up performance of the catalyst is greatly increased. Therefore, until the output value B of the oxygen sensor 340 is smaller than 0.42, the air-fuel ratio is controlled to a value smaller than the stoichiometric air-fuel ratio, the engine 10 is operated, and then the engine 10 is stopped, thereby warming up the catalyst. It can be said that the functionality can be improved.

  This is because, by controlling the air-fuel ratio as described above, the exhaust gas in the exhaust passage 30 can be surely brought into a reducing atmosphere, and the exhaust purification catalyst 110 (specifically, cerium oxide) is reliably reduced. It is thought that this is because it was able to be in a state. Thus, it is considered that the warm-up property of the catalyst could be improved by utilizing the oxidation reaction heat of cerium oxide.

  As shown in FIG. 4, the exhaust purification system 400 according to the fourth embodiment is different from the exhaust purification system 300 according to the third embodiment in the control contents in the control unit (ECU) 450, and is otherwise substantially the same. is there. Specifically, in the exhaust purification system 400 of the fourth embodiment, the air supply is performed so that the control device 450 supplies air from the air supply device 120 into the exhaust passage 30 by a preset target supply amount. The amount can be controlled.

  Here, the control of the air supply amount in the exhaust purification system 400 of the fourth embodiment will be described with reference to the flowchart shown in FIG. In the fourth embodiment, during the operation of the engine 10, a series of processing shown in the flowchart of FIG. 7 is set to be repeated every predetermined time (for example, every 16 milliseconds). Further, before starting the engine 10, the engine 10 is stopped under the same conditions as in the first embodiment, and then left to cool at room temperature for about 12 hours.

  When the key switch of the engine 10 is turned ON, first, in step T1, whether or not the drive condition of the air supply device 120 is satisfied by the control device 450 (for example, whether or not the air supply device 120 operates normally). ) If the drive condition is satisfied (Yes), the process proceeds to step T2 and whether or not the integrated air supply amount supplied from the air supply device 120 into the exhaust flow path 30 has reached a preset target supply amount E. Determine whether. Here, the integrated air supply amount can be calculated by multiplying the air supply amount per unit time supplied from the air supply device 120 by the driving time of the air supply device 120.

When it is determined in step T2 that the integrated air supply amount has not reached the target supply amount E (No), the process proceeds to step T3, and the air supply device 120 is driven (if already driven). Drive continuously). Subsequently, it progresses to step T4 and the drive time of the air supply apparatus 120 is integrated | accumulated. Thereafter, after a predetermined time has elapsed, the processing is performed again from Step T1.
If it is determined in step T1 that the driving condition of the air supply device 120 is not satisfied (No), the process proceeds to step T5, and the integrated driving time of the air supply device 120 is reset. Next, the process proceeds to step T6, the air supply device 120 is stopped, and the supply of air into the exhaust passage 30 is terminated.

On the other hand, when it is determined in step T2 that the integrated air supply amount has reached the target supply amount E (Yes), the process proceeds to step T7, where the air supply device 120 is stopped and the air into the exhaust passage 30 is stopped. The supply of is terminated. Here, the target supply amount E can be set to an arbitrary value. In the fourth embodiment, the target supply amount E is set as follows. Based on the content of cerium oxide contained in the exhaust purification catalyst 110, oxygen required to oxidize the entire amount of Ce ₂ O ₃ (reduced cerium oxide) is calculated, and the amount of air including this oxygen amount is determined as the reference air. Amount. The air supplied from the air supply device 120 is estimated to have about 20% of air (oxygen) that is not used for the oxidation of Ce ₂ O ₃ , and is 1.2 times the reference air amount. The amount was set to the target supply amount E.
In the fourth embodiment, the target supply amount E is set as described above, and when the engine 10 is started, the air supply amount into the exhaust passage 30 is controlled as described above, and the same as in the first embodiment. A warm-up evaluation test was conducted to measure the accumulated HC emissions for 20 seconds after the engine was started.

(Comparative Example 3)
The exhaust purification system of the third comparative example is different from the exhaust purification system 400 of the fourth embodiment in that the target supply amount E of air supplied into the exhaust passage 30 by the air supply device 120 is different. is there. Specifically, in the third comparative example, the case where the target supply amount E is set to a value that is 0.5 times the reference air amount and the case that the target supply amount E is set to a value that is 2.5 times the reference air amount, respectively. In the same manner as described above, the processes of steps T1 to T7 were performed. Also in this comparative example 3, the warm-up evaluation test is performed in the same manner as in example 1 while controlling the amount of air supplied into the exhaust passage 30 as described above, and the integrated HC for 20 seconds after the engine is started. Emissions were measured.

  Next, the results of the warm-up evaluation test of the exhaust purification system 400 of Example 4 and the exhaust purification system of Comparative Example 3 are shown in FIG. FIG. 8 shows the accumulated HC discharge amount for 20 seconds after the engine is started. As shown in FIG. 8, in the exhaust purification system 400 of Example 4 (target supply amount E is 1.2 times the reference air amount) indicated by ●, the exhaust purification system of Comparative Example 3 indicated by Δ and × Compared with (the target supply amount E is 0.5 times and 2.5 times the reference air amount), the integrated HC emission amount could be greatly reduced. The reason for this is considered as follows.

In Comparative Example 3, when the target supply amount E is 0.5 times the reference air amount (Δ mark), oxygen sufficient to oxidize the entire cerium oxide (Ce ₂ O ₃ ) in the reduced state is provided. It cannot be supplied. For this reason, the exhaust purification catalyst 110 in the reduced state cannot be sufficiently oxidized by the oxidation reaction heat, and it is considered that the catalyst was not sufficiently heated by the oxidation reaction heat when the engine 10 was started. On the other hand, when the target supply amount E is 2.5 times the reference air amount (×), the catalyst is cooled by the excessively supplied air. It is thought that the heating of the catalyst was insufficient. Thus, in Comparative Example 3, it is considered that HC could not be sufficiently purified because the catalyst was not sufficiently heated when the engine 10 was started.

On the other hand, in the exhaust purification system 400 of the fourth embodiment, the target supply amount E is 1.2 times the reference air amount. That is, the target supply amount E is set so that the entire amount of cerium oxide (Ce ₂ O ₃ ) in the reduced state can be oxidized, and the air is supplied into the exhaust passage 30 until the target supply amount E is reached by the air supply device 120. I tried to supply. As a result, the entire cerium oxide (Ce ₂ O ₃ ) in the reduced state can be oxidized, and there is no risk that the catalyst will be cooled by excess air. Thus, it is considered that the catalyst could be efficiently and suitably heated.

  As shown in FIG. 9, the exhaust purification device 500 of the fifth embodiment has a position upstream of the exhaust purification catalyst 110 (and more than the air supply device 120) compared to the exhaust purification device 100 of the first embodiment. The difference is that the HC adsorbent 560 is provided at the upstream position), and the rest is almost the same. This HC adsorbent 560 uses the same honeycomb base material as that of the exhaust purification catalyst 110, and is mixed with 200 g of ZSM-5 type zeolite and USY type zeolite mixed at a weight ratio of 1: 1. It was prepared by coating at a ratio of / L.

With respect to the exhaust gas purification apparatus 500 of the fifth embodiment, a warm-up evaluation test was performed.
Specifically, first, as in the first embodiment, with the first flow path opening / closing valve 130 opened, the air-fuel ratio is stoichiometric (A / F = 14.6), and the engine 10 is normally operated at 2000 rpm. I continued driving. Thereafter, the engine 10 was stopped and the first flow path opening / closing valve 130 was closed after idling with the air-fuel ratio set to the fuel rich side (A / F = 14.3).

  Then, unlike Example 1, it was allowed to cool at room temperature for about 36 hours (in Example 1, about 12 hours). Next, as in the first embodiment, the first flow path opening / closing valve 130 is opened and air is supplied into the exhaust flow path 30 by the air supply device 120 for about 5 seconds, and then the engine 10 is started to start the engine. The idle state was maintained for 20 seconds. Next, unlike Example 1, after accelerating to a vehicle speed of 40 km / h in 10 seconds, the vehicle speed of 40 km / h was maintained for 40 seconds. During this period (70 seconds after the engine was started), HC emissions were measured. Thus, in this Example 5, the warm-up evaluation test was performed under the condition that HC is generated in a larger amount than in Example 1.

  Note that the exhaust purification catalyst 110 and the HC adsorbent 560 used in the fifth embodiment and later-described embodiments 6 to 10 are mounted in advance at predetermined positions before being used in the warm-up evaluation test described above. While performing feedback control to make the air-fuel ratio of the air-fuel ratio the stoichiometric air-fuel ratio (stoichiometric), a trial operation to make the incoming gas temperature 800 ° C. is performed for 50 hours.

  As shown in FIG. 10, the exhaust purification device 600 of the sixth embodiment is compared with the exhaust purification device 500 of the fifth embodiment, in addition to the first flow path opening / closing valve 130 located on the downstream side of the exhaust purification catalyst 110, The difference is that a second flow path opening / closing valve 230 is also provided at a position upstream of the exhaust purification catalyst 110 (specifically, between the exhaust purification catalyst 110 and the air supply device 120), and the rest is substantially the same. is there. For the exhaust purification device 600 of the sixth embodiment, the warm-up evaluation test was performed and the HC emission amount was measured in the same manner as the exhaust purification device 500 of the fifth embodiment. In the exhaust purification device 500 of the fifth embodiment, the second flow path opening / closing valve 230 is opened / closed at the same timing as the first flow path opening / closing valve 130.

  As shown in FIG. 11, the exhaust purification device 700 of the seventh embodiment is compared with the exhaust purification device 500 of the fifth embodiment, in addition to the first flow path opening / closing valve 130 located on the downstream side of the exhaust purification catalyst 110, The difference is that the second flow path opening / closing valve 230 is provided at a position upstream of the HC adsorbent 560, and the rest is substantially the same. For the exhaust purification apparatus 700 of this Example 7 as well, in the same manner as the exhaust purification apparatus 500 of Example 5, the warm-up evaluation test was performed and the HC emission amount was measured. In the exhaust purification device 700 of the seventh embodiment, the second flow path opening / closing valve 230 is opened and closed at the same timing as the first flow path opening / closing valve 130.

(Comparative Example 4)
The exhaust purification device of the present comparative example 4 is different from the exhaust purification device 500 of the fifth embodiment in that the air supply device 120 and the first flow path opening / closing valve 130 are not provided, and the others are substantially the same. . The exhaust purification device of Comparative Example 4 was also subjected to a warm-up evaluation test, and HC emissions were measured. In the fourth comparative example, unlike the fifth embodiment, the engine 10 is stopped after the idling operation is performed with the air-fuel ratio on the fuel lean side (fuel cut is performed). Further, in the first comparative example, unlike the first embodiment, since the air supply device 120 and the first flow path opening / closing valve 130 are not provided, the supply of air into the exhaust flow path 30 by the air supply device, and the first The exhaust passage 30 is not opened or closed by the passage opening / closing valve 130.

  Next, the results of the warm-up evaluation test of the exhaust purification apparatuses 500 to 700 of Examples 5 to 7 and the exhaust purification apparatus of Comparative Example 4 are shown in FIG. FIG. 12 shows the accumulated HC discharge amount for 70 seconds after the engine is started. As shown in FIG. 12, in the exhaust purification apparatuses 500 to 700 of Examples 5 to 7 of the present invention, all of the accumulated HC emissions for 70 seconds after the engine start were smaller than those of the exhaust purification apparatus of Comparative Example 4. . This is probably because the exhaust purification devices 500 to 700 of Examples 5 to 7 of the present invention were able to activate the catalyst earlier than the exhaust purification device of Comparative Example 4. As described above, the reason can be considered in the same manner as when the first and second embodiments and the first comparative example are compared.

  Next, when the results of Example 5 and Example 6 were compared, Example 6 had a smaller cumulative HC emission amount for 70 seconds after the engine was started. In the sixth embodiment, in addition to the first flow path opening / closing valve 130 located on the downstream side of the exhaust purification catalyst 110, the upstream side position relative to the exhaust purification catalyst 110 (specifically, the exhaust purification catalyst 110 and the air supply) This is probably because the second flow path opening / closing valve 230 is also provided between the device 120 and the device 120.

That is, in Example 6, while the engine 10 is stopped, the exhaust gas flow path 30 is closed by the second flow path open / close valve 230 together with the first flow path open / close valve 130, so that the exhaust purification catalyst 110 is also upstream. This is considered to be because the inflow of air (oxygen) to the catalyst could be prevented, and the oxidation of the exhaust purification catalyst 110 (specifically, Ce ₂ O ₃ ) in the reduced state could be further suppressed. As a result, in the sixth embodiment, compared to the fifth embodiment, the exhaust purification catalyst 110 contains more Ce ₂ O ₃ (reduced cerium oxide) when the engine 10 is started. It is considered that when the air was supplied from the air supply device 120, the exhaust purification catalyst 110 was able to generate larger heat of oxidation reaction.

Further, while the engine 10 is stopped, the adsorption of moisture to the exhaust purification catalyst 110 is also suppressed by closing the exhaust passage 30 by the second passage on-off valve 230 together with the first passage on-off valve 130. This is thought to be due to this. Thereby, in Example 6, compared with Example 5, it is thought that the amount of heat taken as the heat of vaporization of the adsorbed water out of the oxidation reaction heat in the exhaust purification catalyst 110 could be reduced.
For the reasons described above, it is considered that the exhaust purification device 600 of Example 6 was able to activate the catalyst earlier than the exhaust purification device 500 of Example 5. Therefore, it can be said that the exhaust purification device 600 of the sixth embodiment has better warm-up performance than the exhaust purification device 500 of the fifth embodiment.

Further, when the results of Example 5 and Example 7 were compared, Example 7 had a smaller cumulative HC emission amount for 70 seconds after the engine was started. In the seventh embodiment, in addition to the first flow path opening / closing valve 130 located on the downstream side of the exhaust purification catalyst 110, the second flow path opening / closing valve 230 is provided at a position upstream of the HC adsorbent 560. This is probably because of this.
That is, in the seventh embodiment, while the engine 10 is stopped, the first flow path on / off valve 130 and the second flow path on / off valve 230 are positioned at the upstream side and the downstream side of the HC adsorbent 560. It is considered that exhaust flow into the HC adsorbent 560 could be prevented because the exhaust flow path 30 could be closed. Thus, it is considered that moisture adsorption on the HC adsorbent 560 could be suppressed while the engine 10 was stopped.

In Examples 5 to 7, zeolite (specifically, ZSM-5 and USY) is included as the HC adsorbent 560, but the zeolite is excellent in HC adsorption and water absorption. ing. For this reason, in the fifth embodiment, while the engine 10 is stopped, the HC adsorbent 560 absorbs moisture contained in the exhaust gas staying in the exhaust flow path 30, and the engine 10 It is considered that the HC adsorption performance at the time of starting the engine has deteriorated.
On the other hand, in Example 7, since the water adsorption to the HC adsorbent 560 could be suppressed while the engine 10 was stopped, the decrease in the HC adsorption performance at the start of the engine 10 can be suppressed. It is thought that it was made. Therefore, it is considered that the amount of HC discharged without being purified when the engine 10 was started could be reduced.

  As shown in FIG. 13, the exhaust purification system 800 of the eighth embodiment is provided in the exhaust passage 30 of the gasoline engine 10 having a displacement of 2.4 L. The exhaust purification catalyst 110, the air supply device 120, the first A flow path opening / closing valve 130, an oxygen sensor 340, an HC adsorbent 560, and a control device (ECU) 350 are provided. That is, the HC adsorbent 560 is added to the exhaust purification system 300 (see FIG. 4) of the third embodiment.

  As with the exhaust purification system 300 of the third embodiment, air-fuel ratio control as shown in the flowchart of FIG. 5 is performed on the exhaust purification system 800 of the eighth embodiment, and the output of the oxygen sensor 340 is set to the target value B (V). After reaching (specifically, the target value B is set to 0.6 and 0.8), the engine 10 is stopped. In other words, the engine 10 is stopped after the exhaust gas in the exhaust flow path 30 is made a reducing atmosphere. In the eighth embodiment, as in the third embodiment, the engine 10 is stopped and the first flow path opening / closing valve 130 is closed. Thereafter, in the same manner as in Example 5, after cooling at room temperature for about 36 hours, a warm-up evaluation test was performed, and an accumulated HC emission amount for 70 seconds after engine startup was measured.

(Comparative Example 5)
The exhaust purification system of the fifth comparative example is different from the exhaust purification system 800 of the eighth embodiment in the air-fuel ratio control in the control unit (ECU), and is otherwise substantially the same. Specifically, in the fifth comparative example, as shown in FIG. 15, when compared with the air-fuel ratio control of the third embodiment (see FIG. 5), the processing of steps V3 and V4 is performed instead of the processing of steps S3 and S4. The other processing is the same. That is, it is set so as to perform the same air-fuel ratio control as in Comparative Example 2 described above.

  In the exhaust purification system of this comparative example 5, the exhaust gas in the exhaust passage 30 is made an oxidizing atmosphere (specifically, the target values B are set to 0.1 and 0.3), and then the engine 10 is stopped. I made it. In the fifth comparative example, as in the eighth embodiment, the engine 10 is stopped and the first flow path opening / closing valve 130 is closed. Thereafter, in the same manner as in Example 5, after cooling at room temperature for about 36 hours, a warm-up evaluation test was performed, and an accumulated HC emission amount for 70 seconds after engine startup was measured.

  Comparing the results of the warm-up evaluation test of Example 8 and Comparative Example 5, as in the results of Example 3 and Comparative Example 2, the cumulative amount of HC emissions in Example 8 is larger than that in Comparative Example 5. It was possible to reduce. Further, when the target value B = 0.42 (V) is set as a boundary and the value is set to a value smaller than 0.42 (V), the warm-up property of the catalyst is greatly reduced, and when the value is set to a value larger than 0.42 (V). It was found that the warm-up property of the catalyst is greatly increased. As a result, even in the exhaust purification system provided with the HC adsorbent 560, when the engine 10 is stopped, the air-fuel ratio is controlled to be smaller than the stoichiometric air-fuel ratio, the engine 10 is operated, and the inside of the exhaust passage 30 is reduced. It can be said that the warm-up property of the catalyst can be improved by stopping the engine 10 after making the atmosphere.

  As shown in FIG. 13, the exhaust purification system 900 according to the ninth embodiment is different from the exhaust purification system 800 according to the eighth embodiment in the control performed by the control device (ECU) 450, and is otherwise substantially the same. . Specifically, in the exhaust purification system 900 of the ninth embodiment, a predetermined amount (target supply amount) of air set in advance by the control device 450 is supplied from the air supply device 120 into the exhaust flow path 30. It is possible to control. That is, the HC adsorbent 560 is added to the exhaust purification system 400 (see FIG. 4) of the fourth embodiment.

In the ninth embodiment, as in the fourth embodiment, the reference air amount (theoretically, the air amount containing oxygen necessary for oxidizing the entire amount of Ce ₂ O ₃ contained in the exhaust purification catalyst 110) is 1.2. The double air amount was set as the target supply amount E, and control as shown in the flowchart of FIG. 7 was performed when the engine 10 was started. While performing such control, a warm-up evaluation test was performed in the same manner as in Example 8 to measure the cumulative HC emission amount for 70 seconds after the engine was started. In the ninth embodiment, before the engine 10 is started, the engine 10 is stopped under the same conditions as those in the eighth embodiment, and then left to cool at room temperature for about 36 hours.

(Comparative Example 6)
The exhaust purification system of Comparative Example 6 is different from the exhaust purification system 900 of Example 9 in that the target supply amount E of air supplied into the exhaust passage 30 by the air supply device 120 is different, and the others are the same. is there. Specifically, in the present comparative example 9, when the target supply amount E is set to a value that is 0.5 times the reference air amount and when it is set to a value that is 2.5 times the reference air amount, The same control was performed. Then, while performing such control, a warm-up evaluation test was performed in the same manner as in Example 9, and the accumulated HC emission amount for 70 seconds after the engine was started was measured. Also in this comparative example 6, the engine 10 is stopped under the same conditions as in the embodiment 8 before the engine 10 is started, and then left to cool at room temperature for about 36 hours.

When the results of the warm-up evaluation test of Example 9 and Comparative Example 6 are compared, in the same way as the results of Example 4 and Comparative Example 3, in Example 9, compared to Comparative Example 6, the cumulative HC emission amount is It was possible to greatly reduce. From this result, even in the exhaust purification system provided with the HC adsorbent 560, by supplying air containing oxygen necessary to oxidize the entire cerium oxide (Ce ₂ O ₃ ) in the reduced state, the temperature of the catalyst is increased. It can be said that the functionality can be further improved.

  As shown in FIG. 13, the exhaust purification system 1000 of the tenth embodiment is different from the exhaust purification system 800 of the eighth embodiment in the control in the control device (ECU) 1050, and the other parts are almost the same. . Specifically, in the exhaust purification system 1000 of the tenth embodiment, the controller (ECU) 1050 causes the temperature of the HC adsorbent 560 to be the HC desorption temperature (once adsorbed) based on the integrated value of the intake air amount of the engine 10. It is possible to calculate the time t1 until reaching the temperature at which the HC begins to desorb, which is a temperature unique to the HC adsorbent 560 determined from the specifications of the HC adsorbent 560. Specifically, the temperature of the HC adsorbent 560 is estimated from the integrated value of the intake air amount of the engine 10 based on the relational expression between the intake air amount of the engine 10 and the temperature of the HC adsorbent 560 acquired in advance. From this estimated temperature, the time t1 until the HC adsorbent 560 reaches the HC desorption temperature (hereinafter also referred to as the HC desorption temperature arrival time t1) can be calculated.

Further, based on a predetermined air supply speed (L / s) by the air supply device 120, after the supply of air by the air supply device 120 is started, the reduced cerium oxide (Ce ₂₎ contained in the exhaust purification catalyst 110 is obtained. The time required for completing the oxidation of O ₃ ) (hereinafter also referred to as catalyst oxidation time) can be estimated.

  Therefore, in the exhaust purification system 1000 of the tenth embodiment, the HC desorption temperature arrival time t1 and the catalyst oxidation required time coincide with each other (that is, the HC desorption timing and the oxidation end timing coincide). The supply of air from the supply device 120 into the exhaust flow path 30 was controlled. As a result, the timing of HC desorption from the HC adsorbent 560 and the peak of the temperature rise of the catalyst due to the heat of oxidation reaction can be matched, so that the temperature rise effect of the catalyst due to the heat of oxidation reaction can be utilized to the maximum. Thus, it is possible to efficiently purify HC separated from the HC adsorbent 560.

  Here, control of air supply in the exhaust purification system 1000 of the tenth embodiment will be described with reference to the flowchart shown in FIG. In the tenth embodiment, when the engine 10 is started, a series of processing shown in the flowchart of FIG. 14 is set to be repeated every predetermined time (for example, every 16 milliseconds).

  When the key switch of the engine 10 is turned ON, first, in step U1, the intake air amount of the engine 10 is integrated by the control device 1050. Next, the process proceeds to step U2, and the temperature of the HC adsorbent 560 is estimated from the integrated value of the intake air amount of the engine 10. Here, as described above, the temperature of the HC adsorbent 560 is estimated based on the relational expression obtained in advance between the intake air amount of the engine 10 and the temperature of the HC adsorbent 560.

  Next, the process proceeds to step U3, and it is determined whether or not the air supply completion flag for the air supply device 120 is ON. When the air completion flag is not ON (NO), the process proceeds to Step U4, and it is determined whether or not the air supply device 120 is being driven. When it is determined in step U4 that the air supply device 120 is not driven (NO), the process proceeds to step U5, and the drive time t2 of the air supply device 120 is reset. Next, the process proceeds to step U6, where the HC desorption temperature arrival time t1 is calculated from the estimated temperature of the HC adsorbent 560.

  Next, the process proceeds to step U7, where it is determined whether or not the HC desorption temperature arrival time t1 calculated in step U6 has reached the required catalyst oxidation time. In step U7, when it is determined that the HC desorption temperature arrival time t1 is longer than the required time for catalyst oxidation (NO), the series of processes is temporarily terminated, and after a predetermined time has elapsed, the processes from step U1 are performed again. On the other hand, if it is determined in step U7 that the HC desorption temperature arrival time t1 has become equal to or shorter than the required time for catalytic oxidation (Yes), the air supply device 120 is driven to supply air into the exhaust passage 30. To start.

  Thereafter, the process is performed again from step U1 again. If it is determined in step U4 that the air supply device 120 is driven (Yes), the process proceeds to step U9, and the drive time t2 of the air supply device 120 is set. Accumulate. Next, the process proceeds to step UA, where it is determined whether or not the cumulative drive time t2 of the air supply device 120 is equal to or longer than the required catalyst oxidation time. When it is determined that the accumulated drive time t2 of the air supply device 120 is still shorter than the required time for catalyst oxidation (No), the series of processes is temporarily terminated, and after a predetermined time has elapsed, the processes from Step U1 are performed again. Do.

  On the other hand, if it is determined in step UA that the integrated drive time t2 of the air supply device 120 has become equal to or longer than the required time for catalytic oxidation (Yes), the process proceeds to step UB, where the air supply device 120 has the inside of the exhaust passage 30. Stop supplying air to the unit. Next, the process proceeds to step UC, where the air supply completion flag is turned ON. Thereafter, the process proceeds again from step U1 again, and in step U3, the process of determining that the air supply completion flag is ON (Yes) is repeatedly performed.

As described above, in the tenth embodiment, when the HC desorption temperature arrival time t1 is equal to or shorter than the required time for catalytic oxidation, the air supply device 120 is driven and the supply of air into the exhaust passage 30 is started. ing. Thereby, the timing when the HC adsorbent 560 reaches the HC desorption temperature can coincide with the timing when the heating of the exhaust purification catalyst 110 by the oxidation reaction heat of Ce ₂ O ₃ is completed. Therefore, it is possible to make the time when HC desorbs from the HC adsorbent 560 coincide with the time when the temperature of the exhaust purification catalyst 110 reaches the peak due to the oxidation reaction heat.
Thus, when HC is detached from the HC adsorbent 560, the exhaust purification catalyst 110 can be put into a state in which HC purification is possible (catalyst activation state). Or after a very short period, it can be in the state which can be purified (catalyst activation state).

  Further, in the tenth embodiment, control is performed so that no more air is supplied by the air supply device 120 after the accumulated drive time t2 of the air supply device 120 reaches the required time for catalytic oxidation. That is, air can be supplied into the exhaust passage 30 by the air supply device 120 by an amount necessary for oxidizing the cerium oxide in the reduced state. For this reason, cooling of the exhaust purification catalyst 110 due to excessive air supply can also be prevented. Therefore, in the exhaust purification system 1000 of the tenth embodiment, the HC separated from the HC adsorbent 560 can be purified most efficiently. The amount of air necessary to oxidize cerium oxide in the reduced state is the same as in Examples 4 and 9, the structure and material of the exhaust purification catalyst 110, the characteristics of the air supply device 120, and the structure of the exhaust passage 30. Needless to say, the amount of air in consideration of the amount of oxygen that does not contribute to oxidation with respect to the reference air amount (for example, 1.2 times the reference air amount).

In the above, the present invention has been described with reference to the first to tenth embodiments. However, the present invention is not limited to the above-described embodiments, and it can be applied as appropriate without departing from the scope of the present invention. Nor.
For example, in the exhaust purification systems 300 and 400 of the third and fourth embodiments, only the first flow path opening / closing valve 130 is provided at a position downstream of the exhaust purification catalyst 110 as flow path opening / closing means for opening and closing the exhaust flow path 30. It was. However, in addition to the first flow path opening / closing valve 130, the second flow path opening / closing valve 230 may be provided at a position upstream of the exhaust purification catalyst 110. Thereby, the oxidation of the reduced cerium oxide contained in the exhaust purification catalyst 110 can be further suppressed, and the adsorption of moisture to the exhaust purification catalyst 110 can also be suppressed. It becomes good.

  Also, in the exhaust purification systems 800 to 1000 of Examples 8 to 10, only the first flow path opening / closing valve 130 is provided at a position downstream of the exhaust purification catalyst 110 as flow path opening / closing means for opening and closing the exhaust flow path 30. Provided. However, in order to further improve the warm-up performance of the catalyst, in addition to the first flow path opening / closing valve 130, the second flow path opening / closing valve 230 is provided at a position upstream of the exhaust purification catalyst 110. Is preferable. Alternatively, the second flow path opening / closing valve 230 may be provided at a position upstream of the HC adsorbent 560. As a result, moisture adsorption on the HC adsorbent 560 can be suppressed while the engine is stopped, so that a decrease in the HC adsorption performance of the HC adsorbent 560 can be suppressed. Accordingly, it is possible to reduce the HC emission amount at the time of starting the engine.

1 is a schematic diagram of an exhaust purification device 100 of Example 1. FIG. It is a schematic diagram of the exhaust gas purification apparatus 200 of Example 2. It is a graph which shows the result of the warm-up property evaluation test of Examples 1, 2 and Comparative Example 1. It is a schematic diagram of the exhaust gas purification systems 300 and 400 of Examples 3 and 4. 6 is a flowchart according to the exhaust purification system 300 of Example 3. It is a graph which shows the result of the warm-up property evaluation test concerning the exhaust gas purification system 300 of Example 3. 10 is a flowchart according to an exhaust purification system 400 of Example 4. It is a graph which shows the result of the warm-up property evaluation test concerning the exhaust gas purification system 400 of Example 4. FIG. 10 is a schematic diagram of an exhaust emission control device 500 according to a fifth embodiment. FIG. 10 is a schematic diagram of an exhaust emission control device 600 according to a sixth embodiment. FIG. 10 is a schematic diagram of an exhaust purification device 700 of Example 7. It is a graph which shows the result of the warm-up property evaluation test of Examples 5, 6, 7 and Comparative Example 4. It is a schematic diagram of the exhaust gas purification systems 800, 900, and 1000 of Examples 8, 9, and 10. 12 is a flowchart according to the exhaust gas purification system 1000 of Example 10. 6 is a flowchart according to an exhaust purification system of Comparative Example 2.

Explanation of symbols

100, 200, 500, 600, 700 Exhaust purification device 300, 400, 800, 900, 1000 Exhaust purification system 110 Exhaust purification catalyst 120 Air supply device (gas supply means)
130 1st channel on-off valve (1st channel on-off means)
230 Second channel opening / closing valve (second channel opening / closing means)
340 Oxygen sensor (air-fuel ratio sensor)
350, 450, 1050 control device (internal combustion engine operation control means)
560 HC adsorbent

Claims (15)

An exhaust purification catalyst located in the exhaust flow path of the internal combustion engine, and when the inside of the exhaust flow path becomes a reducing atmosphere, an exhaust purification catalyst that is reduced itself,
A first passage opening / closing means that is located downstream of the exhaust purification catalyst in the exhaust passage and capable of opening and closing the exhaust passage;
An exhaust purification apparatus comprising: a gas supply means that is located upstream of the exhaust purification catalyst in the exhaust flow path and is capable of supplying an oxygen-containing gas into the exhaust flow path. The exhaust purification catalyst is
A metal oxide,
2. The metal oxide according to claim 1, which includes a metal oxide that causes a redox reaction accompanied by a change in the oxidation number of a metal element forming the metal oxide when the inside of the exhaust passage is an oxidizing atmosphere and a reducing atmosphere. Exhaust purification equipment. 3. The apparatus according to claim 1, further comprising a second flow path opening / closing means that is located upstream of the exhaust purification catalyst in the exhaust flow path and is capable of opening and closing the exhaust flow path. Exhaust gas purification device described in 1. The exhaust purification device according to any one of claims 1 to 3, further comprising an HC adsorbing material that adsorbs HC in the exhaust at a position upstream of the exhaust purification catalyst in the exhaust passage. An HC adsorbent that adsorbs HC in the exhaust is provided at a position upstream of the exhaust purification catalyst in the exhaust passage,
The exhaust emission control device according to claim 3, wherein the second flow path opening / closing means is located upstream of the HC adsorbent. An exhaust purification catalyst located in the exhaust flow path of the internal combustion engine, and when the inside of the exhaust flow path becomes a reducing atmosphere, an exhaust purification catalyst that is reduced itself,
An internal combustion engine operation control means for stopping the internal combustion engine after setting the inside of the exhaust passage to a reducing atmosphere when stopping the internal combustion engine;
A first passage opening / closing means that is located downstream of the exhaust purification catalyst in the exhaust passage and opens and closes the exhaust passage, and closes the exhaust passage immediately after the internal combustion engine is stopped; First flow path opening / closing means for opening the exhaust flow path when starting the internal combustion engine;
An exhaust purification system comprising: gas supply means that is positioned upstream of the exhaust purification catalyst in the exhaust passage and supplies an oxygen-containing gas into the exhaust passage when the internal combustion engine is started. The internal combustion engine operation control means includes
The exhaust purification system according to claim 6, wherein the internal combustion engine is stopped after the internal combustion engine is operated with the air / fuel ratio of the internal combustion engine being made smaller than the stoichiometric air / fuel ratio. An air-fuel ratio sensor that is located downstream of the exhaust purification catalyst in the exhaust flow path and detects the air-fuel ratio of the internal combustion engine;
The internal combustion engine operation control means includes
In stopping the internal combustion engine, the air-fuel ratio of the internal combustion engine is made smaller than the theoretical air-fuel ratio until the air-fuel ratio sensor detects a value smaller than the stoichiometric air-fuel ratio of the internal combustion engine. The exhaust purification system according to claim 7, wherein the exhaust purification system is stopped after being operated. The exhaust purification catalyst is
A metal oxide,
7. The metal oxide that includes an oxidation-reduction reaction accompanied by a change in the oxidation number of a metal element that forms the metal oxide when the exhaust passage is in an oxidizing atmosphere and in a reducing atmosphere. Item 9. The exhaust gas purification system according to any one of Items 8 to 9. 10. The gas supply unit according to claim 6, wherein the gas supply unit supplies the oxygen-containing gas into the exhaust passage in an amount necessary to oxidize the exhaust purification catalyst in a reduced state. Exhaust purification system. A second passage opening / closing means that is located upstream of the exhaust purification catalyst in the exhaust passage and opens and closes the exhaust passage, and closes the exhaust passage immediately after the internal combustion engine is stopped; The exhaust purification system according to any one of claims 6 to 10, further comprising a second passage opening / closing means that opens the exhaust passage when the internal combustion engine is started. The exhaust purification system according to any one of claims 6 to 11, further comprising an HC adsorbing material that adsorbs HC in the exhaust at a position upstream of the exhaust purification catalyst in the exhaust passage. An HC adsorbent that adsorbs HC in the exhaust is provided at a position upstream of the exhaust purification catalyst in the exhaust passage,
The exhaust gas purification system according to claim 11, wherein the second flow path opening / closing means is located upstream of the HC adsorbent in the exhaust flow path. The exhaust gas purification system according to claim 12 or 13, further comprising HC desorption time estimation means for estimating a time at which HC desorbs from the HC adsorbent. The gas supply means includes
HC departure timing estimated by the HC departure timing prediction means,
An oxidation end time at which the oxidation reaction of the exhaust purification catalyst in the reduced state ends;
The exhaust gas purification system according to claim 14, wherein an oxygen-containing gas is supplied into the exhaust flow path so that they coincide with each other.

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