JP2010025014A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely restrain discharge of a toxic component in the atmosphere, when reducing NOx by an NOx catalyst, in an exhaust emission control device of an internal combustion engine. <P>SOLUTION: This exhaust emission control device of the internal combustion engine has: the NOx catalyst; an oxidation catalyst arranged on the downstream side of this NOx catalyst; and an active oxygen supply device for supplying active oxygen (ozone) to the oxidation catalyst. When determining that HC poisoning is caused in the oxidation catalyst when reducing the NOx by the NOx catalyst, the ozone for eliminating its HC poisoning is supplied to the oxidation catalyst (Step 102). Thus, the HC poisoning is quickly recovered. When determining that CO flows out of the NOx catalyst, ozone is supplied to the oxidation catalyst (Step 108). Thus, the CO flowing out of the NOx catalyst is surely purified by the synergistic effect of the ozone and Ag in the oxidation catalyst. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification device for an internal combustion engine.

As an exhaust gas purifying device such as a diesel engine or a lean burn engine, one using an NOx storage reduction catalyst is known (for example, see Patent Document 1). This NOx catalyst can collect and store NOx in the exhaust gas when the air-fuel ratio of the exhaust gas is lean. When NOx occluded in the NOx catalyst is reduced, HC as a reducing agent is supplied to the NOx catalyst by a method such as fuel addition to the exhaust system or post injection, for example. When the reducing agent is supplied to the NOx catalyst, the stored NOx is desorbed and reduced and purified to N ₂ .

JP 2006-214310 A JP 2006-218772 A

  Patent Document 2 discloses an exhaust gas purification device including a NOx catalyst, an oxidation catalyst disposed downstream thereof, and a device for supplying ozone to an exhaust passage between the two catalysts. In this apparatus, the hydrocarbon compound contained in the exhaust gas that has passed through the NOx catalyst is purified by the synergistic effect of the oxidation catalyst and ozone.

  In a system such as that described in Patent Document 2, when fuel is added as a reducing agent to exhaust gas, HC derived from the fuel (particularly high boiling point HC) becomes liquid and becomes an oxidation catalyst. It may adhere (adsorb) to active sites. In such a case, contact between the exhaust gas and the active point is hindered, resulting in a decrease in the activity of the oxidation catalyst. When NOx is reduced by the NOx catalyst, harmful components in the exhaust gas flowing out from the NOx catalyst may not be sufficiently purified by the oxidation catalyst due to a decrease in the activity of the oxidation catalyst as described above.

  The present invention has been made to solve the above-described problems, and is an internal combustion engine that can reliably prevent harmful components from being released into the atmosphere when NOx is reduced by a NOx catalyst. An object is to provide an exhaust gas purification device.

In order to achieve the above object, a first invention is an exhaust gas purification apparatus for an internal combustion engine,
A NOx catalyst disposed in the exhaust passage of the internal combustion engine for purifying NOx in the exhaust gas;
A reducing agent supply means for supplying a reducing agent to the NOx catalyst when NOx is reduced by the NOx catalyst;
An oxidation catalyst that is installed downstream of the NOx catalyst and oxidizes harmful components in exhaust gas flowing out of the NOx catalyst;
An active oxygen supply device for supplying active oxygen to the oxidation catalyst;
HC poisoning determination means for determining HC poisoning of the oxidation catalyst;
HC poisoning recovery means for supplying active oxygen for recovering HC poisoning by the active oxygen supply device when the HC poisoning determining means determines that the oxidation catalyst is HC poisoned;
It is characterized by providing.

The second invention is the first invention, wherein
The oxidation catalyst contains Ag as a catalyst component,
CO outflow determining means for determining the outflow of CO from the NOx catalyst when a reducing agent is supplied to the NOx catalyst;
When the CO outflow determining means determines that CO flows out of the NOx catalyst, the active oxygen supply device supplies the active oxygen for purifying the CO by a synergistic effect with Ag in the oxidation catalyst. Purification means;
It is characterized by providing.

The third invention is the first or second invention, wherein
An active oxygen supply device for NOx catalyst for supplying active oxygen to the upstream side of the NOx catalyst;
NOx purification means for supplying active oxygen for purifying NOx with the NOx catalyst by the active oxygen supply device for NOx catalyst;
It is characterized by providing.

  According to the first invention, when it is determined that the oxidation catalyst arranged downstream of the NOx catalyst is HC poisoned, the HC poisoning is recovered by supplying active oxygen to the oxidation catalyst. Can be made. As a result, HC poisoning of the oxidation catalyst can be quickly recovered, so that harmful components that flow out of the NOx catalyst when the reducing agent is supplied to the NOx catalyst can be reliably purified in the oxidation catalyst. Further, since the active oxygen for eliminating the HC poisoning is supplied after determining the occurrence of the HC poisoning, the amount of active oxygen used can be saved. For this reason, the electric power required in order to produce | generate active oxygen can be saved.

  According to the second invention, active oxygen can be supplied to the oxidation catalyst when it is determined that CO flows out of the NOx catalyst. For this reason, the outflowing CO can be purified with high efficiency even in a low temperature state such as immediately after start-up or during low-load operation due to the synergistic effect of Ag and active oxygen in the oxidation catalyst.

  According to the third aspect of the present invention, the active oxygen is supplied to the upstream side of the NOx catalyst by the active oxygen supply device for the NOx catalyst, so that the NOx is increased in the NOx catalyst even in a low temperature state such as immediately after starting or during low load operation. It can be purified (absorbed) efficiently.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. As shown in FIG. 1, the system of the present embodiment includes an internal combustion engine 10. In the present embodiment, the internal combustion engine 10 is a four-cylinder compression ignition internal combustion engine (diesel engine) including four cylinders 13. In FIG. 1, for convenience, the size of the exhaust system is drawn larger than the actual size with respect to the size of the internal combustion engine 10.

  The internal combustion engine 10 of this embodiment includes a turbocharger 19. The intake air compressed by the compressor of the turbocharger 19 flows into each cylinder 13 via the intake manifold 11. Each cylinder 13 is provided with a fuel injector 14 for directly injecting fuel into the cylinder. The high pressure fuel stored in the common rail 18 is supplied to each fuel injector 14. Fuel in a fuel tank (not shown) is pressurized by the supply pump 17 and supplied to the common rail 18. Exhaust gas discharged from each cylinder 13 joins at the exhaust manifold 12 and flows into the turbine of the turbocharger 19. The exhaust gas that has passed through the turbine flows through the exhaust passage 15.

  A NOx catalyst 20 and an oxidation catalyst 21 are installed in the exhaust passage 15. The oxidation catalyst 21 is disposed on the downstream side of the NOx catalyst 20. A first ozone supply nozzle 22 is provided on the upstream side of the NOx catalyst 20. A second ozone supply nozzle 23 is installed between the NOx catalyst 20 and the oxidation catalyst 21. In the illustrated configuration, the first ozone supply nozzle 22 is disposed inside the casing 26 of the NOx catalyst 20 and on the front side (upstream side) of the NOx catalyst 20. The second ozone supply nozzle 23 is disposed inside the casing 27 of the oxidation catalyst 21 and on the front side (upstream side) of the oxidation catalyst 21.

  The first ozone supply nozzle 22 is provided with a plurality of first ozone supply ports 24. The second ozone supply nozzle 23 is provided with a plurality of second ozone supply ports 25. The first ozone supply nozzle 22 and the second ozone supply nozzle 23 are connected to an ozone generator 29 via an ozone supply passage 28. With such a configuration, the ozone generated in the ozone generator 29 can be injected from the first ozone supply port 24 and the second ozone supply port 25. The ozone injected from the first ozone supply port 24 is mixed with the exhaust gas on the upstream side of the NOx catalyst 20. The ozone injected from the second ozone supply port 25 is mixed with the exhaust gas downstream of the NOx catalyst 20 and upstream of the oxidation catalyst 21.

The ozone generator 29 may be of any other type besides generating ozone (O ₃ ) while flowing dry air or oxygen as a raw material in a discharge tube to which a high voltage can be applied. be able to. The dry air or oxygen used as a raw material here is a gas taken from outside the exhaust passage 15, for example, a gas contained in the outside air.

  A flow rate adjusting mechanism 30 is installed between the ozone generator 29 and the first ozone supply nozzle 22 and the second ozone supply nozzle 23. The flow rate adjusting mechanism 30 can individually adjust the ozone flow rate to the first ozone supply nozzle 22 and the ozone flow rate to the second ozone supply nozzle 23. That is, according to the flow rate adjustment mechanism 30, the ozone supply amount from the first ozone supply port 24 and the ozone supply amount from the second ozone supply port 25 can be individually controlled.

In the present embodiment, the NOx catalyst 20 is an NOx storage reduction (NSR) catalyst. The catalyst component of the NOx catalyst 20 has a structure in which, for example, a noble metal such as platinum Pt and a NOx occlusion material are supported on the surface of alumina (Al ₂ O ₃ ). Examples of the NOx storage material include at least selected from alkali metals such as potassium K, sodium Na, lithium Li and cesium Cs, alkaline earths such as barium Ba and calcium Ca, and rare earths such as lanthanum La and yttrium Y. One can be used. In the NOx catalyst 20 of the present embodiment, as shown in FIG. 2, Pt is used as a noble metal, and Ba is used as a NOx storage material (hereinafter simply referred to as “storage material”). In this specification, the term “occlusion” includes all concepts similar to “holding”, “adsorption”, “absorption”, and the like.

  In the cylinder of the internal combustion engine 10, combustion is performed at an air-fuel ratio leaner than the stoichiometric air-fuel ratio during normal operation. For this reason, a large amount of oxygen is contained in the exhaust gas during normal operation. Therefore, NOx cannot be purified by a three-way reaction during normal operation. On the other hand, in the present embodiment, during normal operation, NOx contained in the exhaust gas is absorbed by the NOx catalyst 20 to prevent NOx from being discharged into the atmosphere.

The oxidation catalyst 21 has a function of oxidizing hydrocarbon components (hereinafter referred to as “HC”) and CO (carbon monoxide) in the exhaust gas to purify them to CO ₂ and H ₂ O. As the catalyst component of the oxidation catalyst 21, for example, Pt / CeO ₂ , Mn / CeO ₂ , Fe / CeO ₂ , Ni / CeO ₂ , Cu / CeO ₂ or the like can be used. Moreover, the oxidation catalyst 21 of this embodiment further contains Ag (silver) as a catalyst component.

  An exhaust fuel addition injector 32 is installed in the cylinder head of the internal combustion engine 10. The exhaust fuel addition injector 32 injects fuel for use as a reducing agent into the exhaust gas. The installation location of the exhaust fuel addition injector 32 is not limited to the cylinder head, but may be installed in the exhaust passage 15 upstream of the NOx catalyst 20.

  The system of this embodiment further includes an exhaust temperature sensor 34 that detects the temperature of the exhaust gas in the exhaust passage 15 and an ECU (Electronic Control Unit) 50. The ECU 50 includes internal combustion engines such as the fuel injector 14, the ozone generator 29, the flow rate adjusting mechanism 30, the exhaust fuel addition injector 32, the exhaust temperature sensor 34, the crank angle sensor 46, the air flow meter 47, and the accelerator position sensor 48. Various sensors and actuators for controlling the engine 10 are electrically connected.

The storage material of the NOx catalyst 20 absorbs NOx (nitrogen oxide) by forming a nitrate (Ba (NO ₃ ) _{2 in} this embodiment). The storage material can well absorb NO ₂ , NO ₃ , and N ₂ O ₅ out of NOx. On the other hand, most of NOx originally contained in the exhaust gas is NO (nitrogen monoxide). NO cannot be absorbed by the occlusion material as it is. Therefore, usually, the NOx catalyst 20, by a noble metal (platinum Pt in this embodiment) as a catalyst, NO ₂ is produced and NO in exhaust gas and oxygen O ₂ react, absorbing the NO ₂ The material is made to absorb.

However, the activity of the noble metal catalyst does not appear unless the temperature is higher than a certain temperature (for example, 200 ° C. or higher). Therefore, in the conventional exhaust gas purifying apparatus, when the temperature of the NOx catalyst 20 is low, such as immediately after the start of the internal combustion engine 10 or during low load operation, NO is not oxidized to NO ₂ by the noble metal catalyst, so that NOx is occluded. I can't.

  On the other hand, in the system of the present embodiment, even when the temperature of the NOx catalyst 20 is low, ozone is added into the exhaust gas from the first ozone supply port 24 located on the upstream side of the NOx catalyst 20. , NOx can be efficiently absorbed by the NOx catalyst 20.

FIG. 2 is a diagram showing how NOx is purified (absorbed) when ozone is supplied when the NOx catalyst 20 is in a low temperature state (a state where the activity of the noble metal catalyst is not expressed). Ozone has a high oxidizing power. For this reason, ozone and NOx can react in the gas phase from a low temperature of about room temperature. That is, when ozone is supplied from the first ozone supply port 24, NO in the exhaust gas changes into NO ₂ , NO _3, or N ₂ O ₅ by reaction with ozone and then flows into the NOx catalyst 20. . An occlusion material such as Ba can sufficiently absorb NO ₂ , NO ₃ , and N ₂ O ₅ from a low temperature of about room temperature to form nitrate. For this reason, even if it is a low temperature area where the activity of the noble metal catalyst is not expressed, NOx can be absorbed by the storage material provided in the NOx catalyst 20 by supplying ozone from the first ozone supply port 24. In this way, in the present embodiment, NOx emission into the atmosphere can be reliably suppressed even at low temperatures such as immediately after starting the internal combustion engine 10 or during low load operation.

  Incidentally, the amount of NOx that can be stored by the NOx catalyst 20 is limited. In this system, before the NOx occlusion amount of the NOx catalyst 20 reaches the limit, NOx reduction control for supplying a reducing agent to the NOx catalyst 20 is executed, and the occluded NOx is separated and reduced (purified). As a method of supplying the reducing agent to the NOx catalyst 20, in this embodiment, fuel as a reducing agent is added from the exhaust fuel addition injector 32 into the exhaust gas.

  Whether or not the NOx reduction control needs to be executed can be determined as follows, for example. The ECU 50 stores a map created by examining in advance the relationship between the operating state of the internal combustion engine 10 (engine speed, load, etc.) and the amount of NOx discharged from the internal combustion engine 10. The ECU 50 calculates the total amount of NOx flowing into the NOx catalyst 20 after the previous NOx reduction by sequentially integrating the NOx emission amount calculated based on the map. When the total amount of NOx reaches a predetermined threshold value, it can be determined that execution of NOx reduction control is necessary. Alternatively, a NOx sensor may be provided on the downstream side of the NOx catalyst 20, and it may be determined that the NOx reduction control needs to be executed when the NOx concentration detected by the NOx sensor exceeds a predetermined concentration.

When the reducing agent is supplied to the NOx catalyst 20 by the NOx reduction control, the oxygen concentration in the NOx catalyst 20 decreases and NOx is desorbed from the storage material. The desorbed NOx reacts with the reducing agent by the action of the noble metal catalyst. Thereby, NOx can be reduced and purified to N ₂ .

  When a reducing agent is supplied to the NOx catalyst 20, CO is generated by a reduction reaction at the NOx catalyst 20. This CO also reacts with NOx as a reducing gas. However, some of the generated CO may not react with NOx and may flow out downstream of the NOx catalyst 20. In addition, some of the reducing agent supplied to the NOx catalyst 20 may flow out downstream of the NOx catalyst 20 as HC without being reacted.

  In the present embodiment, the oxidation catalyst 21 is provided to purify CO and HC that have flowed out downstream of the NOx catalyst 20 when the reducing agent is supplied to the NOx catalyst 20. However, when the temperature of the oxidation catalyst 21 is low, HC (particularly HC derived from a high boiling point component) flowing into the oxidation catalyst 21 is liable to be liquefied, and the liquefied HC is an active point (noble metal) of the oxidation catalyst 21. May adsorb. This phenomenon is generally called “HC poisoning”. HC poisoning is likely to occur when the exhaust gas temperature is low, such as immediately after startup or during low load operation. When HC poisoning occurs, the contact between the active sites and the exhaust gas is inhibited, so that the activity of the oxidation catalyst 21 is lowered. For this reason, CO and HC that have flowed out downstream of the NOx catalyst 20 cannot be sufficiently purified.

Therefore, in the present embodiment, when HC poisoning of the oxidation catalyst 21 occurs, the HC poisoning is recovered by supplying ozone into the oxidation catalyst 21. FIG. 3 is a diagram showing a mechanism for recovering the HC poisoning of the oxidation catalyst 21 by adding ozone. Since ozone has a high oxidizing power, HC adsorbed on the active sites of the oxidation catalyst 21 can be oxidized quickly and reliably. That is, as shown in FIG. 3, by supplying ozone to the oxidation catalyst 21, HC adsorbed on the active sites is quickly oxidized by ozone and removed as CO, CO ₂ , H ₂ O. Thereby, HC poisoning of the oxidation catalyst 21 is eliminated, and the activity can be recovered.

  However, even if the HC poisoning of the oxidation catalyst 21 is eliminated, if the temperature of the oxidation catalyst 21 is low, such as immediately after start-up or during low load operation, the oxidation catalyst 21 normally oxidizes CO sufficiently. Can not.

  Further, the reactivity between ozone and CO is lower than the reactivity between ozone and NO or HC. For this reason, it is also difficult to oxidize CO by directly reacting ozone and CO in the gas phase.

  In view of the above points, the present inventors have conducted intensive research to realize reliable purification of CO flowing out of the NOx catalyst 20, and as a result, when the catalyst containing Ag (silver) coexists with ozone. The present inventors have found that excellent CO oxidation activity is exhibited from a low temperature. FIG. 4 is a diagram showing the relationship between the temperature of the catalyst containing Ag and the CO purification rate by the catalyst. As shown in this figure, according to the catalyst containing Ag, when ozone does not coexist, the CO purification rate at low temperature is low, but when ozone coexists, it is high even at low temperature. CO purification rate is obtained.

The mechanism by which Ag-containing catalyst oxidizes CO when ozone coexists is considered as shown in FIG. That is, it is considered that when Ag reacts with ozone, it changes to Ag ₂ O or AgO, which is a stronger oxidizing agent, and CO is oxidized to CO ₂ by this Ag ₂ O or AgO.

  In the present embodiment, as described above, the oxidation catalyst 21 contains Ag as a catalyst component. Therefore, by adding ozone from the second ozone supply port 25, the oxidation catalyst 21 can exhibit excellent CO oxidation activity due to the synergistic effect of Ag and ozone. For this reason, CO flowing out of the NOx catalyst 20 can be reliably purified by the oxidation catalyst 21 even at a low temperature.

[Specific Processing in Embodiment 1]
FIG. 6 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. This routine is executed when NOx reduction control is performed. According to the routine shown in FIG. 6, first, it is determined whether or not the activity of the oxidation catalyst 21 is reduced (step 100).

  The determination in step 100 can be performed as follows, for example. The ECU 50 has a history of the operating state of the internal combustion engine 10 (engine speed, fuel injection amount from the fuel injector 14, exhaust gas temperature detected by the exhaust temperature sensor 34, fuel addition amount from the exhaust fuel addition injector 32, etc.). Is remembered. The amount of HC adhering to the oxidation catalyst 21 increases as the fuel injection amount or fuel addition amount increases, and increases as the exhaust gas temperature decreases and as the engine speed decreases. A map created by examining these relationships in advance is stored in the ECU 50, and the amount of HC adhering to the oxidation catalyst 21 is calculated based on this map and the history of operating conditions. When the calculated HC adhesion amount exceeds a predetermined threshold value, it is determined that HC poisoning has occurred, that is, the activity of the oxidation catalyst 21 has decreased. On the other hand, when the calculated HC adhesion amount does not exceed the threshold value, it is determined that the activity of the oxidation catalyst 21 has not decreased.

  If it is determined in step 100 that the activity of the oxidation catalyst 21 has decreased, then, in order to eliminate the HC poisoning of the oxidation catalyst 21, the second ozone supply port 25 moves to the oxidation catalyst 21. A process of supplying ozone is executed (step 102). More specifically, in this step 102, first, the amount of ozone necessary for eliminating HC poisoning is calculated based on the HC adhesion amount calculated in step 100. Next, the ozone generator 29 and the flow rate adjusting mechanism 30 are controlled so that the amount of ozone is injected from the second ozone supply port 25. According to the process of step 102, as described with reference to FIG. 3, HC poisoning of the oxidation catalyst 21 can be quickly eliminated, and its activity can be reliably recovered.

  If the HC poisoning of the oxidation catalyst 21 is eliminated by the process of step 102, or if it is determined in step 100 that the activity of the oxidation catalyst 21 has not decreased, then the NOx catalyst 20 occludes. The process of supplying a reducing agent for reducing the NOx that has been added is started (step 104). That is, fuel injection from the exhaust fuel addition injector 32 is started.

  When the supply of the reducing agent is started, it is next determined whether or not there is CO outflow from the NOx catalyst 20 (step 106). The determination in step 106 can be performed as follows, for example. The ECU 50 stores in advance a map for calculating the CO generation amount in the NOx catalyst 20 from the fuel addition amount from the exhaust fuel addition injector 32 and the exhaust gas temperature detected by the exhaust temperature sensor 34. Yes. Based on the map, the amount of CO generated in the NOx catalyst 20 is calculated. When the calculated CO generation amount is within a predetermined threshold, it is determined that almost all of the CO generated in the NOx catalyst 20 has reacted with NOx, and there is no outflow of CO from the NOx catalyst 20. . On the other hand, when the calculated CO generation amount exceeds the threshold value, it is determined that a part of the generated CO does not completely react with NOx and flows out downstream of the NOx catalyst 20.

  If it is determined in the above step 106 that CO has flowed out downstream of the NOx catalyst 20, the ozone is then supplied from the second ozone supply port 25 to the oxidation catalyst 21 in order to purify the flowed out CO. Is executed (step 108). Specifically, in this step 108, first, based on the CO generation amount calculated in the above step 106, the ozone necessary for purifying the CO flowing out from the NOx catalyst 20 by the Ag catalyst in the oxidation catalyst 21 is firstly shown. A quantity is calculated. Next, the ozone generator 29 and the flow rate adjusting mechanism 30 are controlled so that the amount of ozone is injected from the second ozone supply port 25. According to the processing of step 108, as described with reference to FIG. 5, CO can be efficiently purified even at low temperatures due to the synergistic effect of the Ag catalyst and ozone. For this reason, it can suppress reliably that CO is discharged | emitted in air | atmosphere.

In the embodiment described above, the internal combustion engine 10 is described as being of the compression ignition type, but the present invention can also be applied to a spark ignition type internal combustion engine. In the present embodiment, ozone is added to the exhaust gas as active oxygen. However, in the present invention, other types of active oxygen (for example, O ⁻ , O ²⁻ , O ₂ ⁻⁾ are used instead of ozone. , O ₃ ⁻ , O _n ^−, etc.) may be added to the exhaust gas. In the present embodiment, the ozone generated by the ozone generator 29 is distributed to the first ozone supply nozzle 22 and the second ozone supply nozzle 23 by the flow rate adjusting mechanism 30. In the invention, an ozone generator may be provided separately for the first ozone supply nozzle 22 and the second ozone supply nozzle 23. In the present embodiment, ozone is generated by the ozone generator 29 when supplying ozone. However, in the present invention, ozone is generated and stored in advance, and the stored ozone is used when necessary. You may make it supply. In this embodiment, the fuel (reducing agent) is added by the exhaust fuel addition injector 32. However, in the present invention, the method of supplying the reducing agent is not limited to this. For example, by performing a method of injecting fuel from the fuel injector 14 in the expansion stroke or the exhaust stroke (that is, post-injection) or a large amount of exhaust gas recirculation (EGR), the in-cylinder air-fuel ratio is significantly enriched from the normal time You may make it supply a reducing agent by the method of burning at low temperature (namely, low temperature rich combustion) etc. which do not produce soot.

  In the present embodiment, the ozone generator 29 is outside the exhaust gas flow path. However, the present invention is not limited to this configuration, and the ozone generator may be in the exhaust gas flow path. In this case, discharge is performed by applying a high voltage in the exhaust gas flow path, and ozone or the like is generated to purify the exhaust gas.

  In this embodiment, Ag is used as a catalyst for oxidizing CO. However, the present invention is not limited to this, and Au or the like may be used. Further, as a catalyst for oxidizing CO, any material may be used as long as the catalyst surface is oxidized by reacting with ozone and the O is liberated at a temperature below the temperature at which the catalyst is active.

  In the first embodiment described above, the exhaust fuel addition injector 32 is added to the “reducing agent supply means” in the first invention, the ozone generator 29, the ozone supply passage 28, the flow rate adjusting mechanism 30, and the second ozone supply nozzle. 23 is the “active oxygen supply device” in the first invention, and the ozone generator 29, the ozone supply passage 28, the flow rate adjusting mechanism 30 and the first ozone supply nozzle 22 are the “NOx catalyst activation activity” in the third invention. It corresponds to “oxygen supply device”. Further, when the ECU 50 executes the process of step 100, the “HC poisoning determination means” in the first invention executes the process of step 102, so that the “HC poisoning means” in the first invention results. The "recovery means" executes the process of step 106, so that the "CO outflow determination means" in the second invention executes the process of step 108, so that the "CO purification means" in the second invention results. Are realized.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a figure which shows a mode that NOx is refine | purified (absorbed) when ozone is supplied to a NOx catalyst. It is a figure which shows the mechanism in the case of recovering HC poisoning of an oxidation catalyst by ozone addition. It is a figure which shows the relationship between the temperature of the catalyst containing Ag, and the CO purification rate by the catalyst. It is a figure which shows the mechanism in which the catalyst containing Ag oxidizes CO when ozone coexists. It is a flowchart of the routine performed in Embodiment 1 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 11 Intake manifold 12 Exhaust manifold 13 Cylinder 14 Fuel injector 15 Exhaust passage 17 Supply pump 18 Common rail 19 Turbocharger 20 NOx catalyst 21 Oxidation catalyst 22 First ozone supply nozzle 23 Second ozone supply nozzle 24 First ozone supply Port 25 Second ozone supply port 26, 27 Casing 28 Ozone supply passage 29 Ozone generator 30 Flow rate adjusting mechanism 32 Exhaust fuel addition injector 34 Exhaust temperature sensor 50 ECU

Claims (3)

A NOx catalyst disposed in the exhaust passage of the internal combustion engine for purifying NOx in the exhaust gas;
A reducing agent supply means for supplying a reducing agent to the NOx catalyst when NOx is reduced by the NOx catalyst;
An oxidation catalyst that is installed downstream of the NOx catalyst and oxidizes harmful components in exhaust gas flowing out of the NOx catalyst;
An active oxygen supply device for supplying active oxygen to the oxidation catalyst;
HC poisoning determination means for determining HC poisoning of the oxidation catalyst;
HC poisoning recovery means for supplying active oxygen for recovering HC poisoning by the active oxygen supply device when the HC poisoning determining means determines that the oxidation catalyst is HC poisoned;
An exhaust gas purifying device for an internal combustion engine, comprising: The oxidation catalyst contains Ag as a catalyst component,
CO outflow determining means for determining the outflow of CO from the NOx catalyst when a reducing agent is supplied to the NOx catalyst;
When the CO outflow determining means determines that CO flows out of the NOx catalyst, the active oxygen supply device supplies the active oxygen for purifying the CO by a synergistic effect with Ag in the oxidation catalyst. Purification means;
The exhaust gas purifying device for an internal combustion engine according to claim 1, comprising: An active oxygen supply device for NOx catalyst for supplying active oxygen to the upstream side of the NOx catalyst;
NOx purification means for supplying active oxygen for purifying NOx with the NOx catalyst by the active oxygen supply device for NOx catalyst;
The exhaust gas purifying device for an internal combustion engine according to claim 1 or 2, further comprising:

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