JP2009007977A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine, using rear stage catalyst parts for suitably supplying reducing agent when front stage catalyst parts and the rear stage catalyst parts are provided in an exhaust passage for the internal combustion engine, and when a reducing agent adding valve is provided in the exhaust passage on the upstream sides of the front stage catalyst parts. <P>SOLUTION: The exhaust emission control device comprises: bypass lines 15 formed between the outer peripheral face of each of the front stage catalyst parts 4, 5 and the inner peripheral face of the exhaust passage 2 to encircle the outer peripheral faces of the front stage catalyst parts 4, 5; and bypass control means 12 provided in the bypass lines for shutting off or opening the bypass lines 15. When reducing agent is supplied to the rear stage catalyst parts 6, 7, the reducing agent is added by the reducing agent adding valve 8 which is provided in the exhaust passage 2 on the upstream sides of the front stage catalyst parts 4, 5, and the bypass lines 15 are opened by the bypass control means 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine including a plurality of catalysts arranged in series in an exhaust passage of the internal combustion engine.

  As an exhaust emission control device for an internal combustion engine, one having a front-stage catalyst section and a rear-stage catalyst section each including at least one catalyst having an oxidation function is known. The rear stage catalyst part is provided in the exhaust passage on the downstream side of the front stage catalyst part. In some cases, a reducing agent addition valve for adding a reducing agent into the exhaust gas is provided in the exhaust passage on the upstream side of the upstream catalyst unit. When the reducing agent addition valve is provided at such a position, it is not possible to supply the reducing agent directly to the rear catalyst unit without passing the front catalyst unit.

  Therefore, one end is connected to a portion of the exhaust passage downstream from the reducing agent addition valve and upstream from the front catalyst portion, and the other end is connected to a portion downstream from the front catalyst portion and upstream from the rear catalyst portion in the exhaust passage. In some cases, a bypass passage and an on-off valve for blocking or opening the bypass passage may be provided. According to such a configuration, the reducing agent can be supplied to the downstream catalyst unit via the bypass passage by adding the reducing agent into the exhaust gas from the reducing agent addition valve while opening the bypass passage by the opening / closing valve. . That is, a part of the reducing agent added from the reducing agent addition valve can be supplied to the rear catalyst unit without going through the front catalyst unit.

  However, when the bypass passage as described above is provided, the reducing agent attached to the inner wall surface of the bypass passage increases as the bypass passage becomes longer. For this reason, it may be difficult to supply a sufficient amount of the reducing agent directly to the downstream catalyst unit.

Patent Document 1 describes a technique in which a reforming catalyst for reforming the fuel injected from the fuel injection means is provided upstream of the NOx catalyst provided in the exhaust passage. Patent Document 1 discloses a technique in which a reforming catalyst is disposed in the center of an exhaust passage, and a detour in which exhaust flows is formed on the outer periphery of the reforming catalyst.
JP 2005-127257 A

  The present invention provides a rear-stage catalyst in the case where a front-stage catalyst section and a rear-stage catalyst section are provided in an exhaust passage of an internal combustion engine, and a reducing agent addition valve is provided in an exhaust passage upstream of the front-stage catalyst section. It aims at providing the technique which can supply a reducing agent suitably by a part.

  The present invention includes a bypass passage formed so as to surround the outer peripheral surface of the front-stage catalyst portion between the outer peripheral surface of the front-stage catalyst portion and the inner peripheral surface of the exhaust passage, and exhaust gas upstream of the front-stage catalyst portion. The reducing agent added from the reducing agent addition valve provided in the passage is supplied to the rear catalyst unit together with the exhaust gas via the bypass passage.

More specifically, the exhaust gas purification apparatus for an internal combustion engine according to the present invention is
A pre-catalyst portion configured to include at least one catalyst having an oxidation function provided in an exhaust passage of the internal combustion engine;
A rear-stage catalyst section that is provided in the exhaust passage downstream of the front-stage catalyst section and includes at least one catalyst having an oxidation function;
A reducing agent addition valve that is provided in the exhaust passage on the upstream side of the front-stage catalyst portion and adds a reducing agent into the exhaust;
A bypass passage formed so as to surround the outer peripheral surface of the front catalyst portion between the outer peripheral surface of the front catalyst portion and the inner peripheral surface of the exhaust passage;
Bypass control means provided in the bypass passage and blocking or opening the bypass passage;
When the reducing agent is supplied to the downstream catalyst unit, the reducing agent is added from the reducing agent addition valve, and the bypass passage is opened by the bypass control means.

  According to the present invention, a part of the reducing agent added from the reducing agent addition valve can be supplied to the rear catalyst unit through the bypass passage. That is, the reducing agent can be directly supplied to the subsequent stage catalyst part without passing through the previous stage catalyst part. Thereby, it can suppress that the supply amount of the reducing agent to a back | latter stage catalyst part runs short. Further, the amount of the reducing agent added from the reducing agent addition valve in order to supply a sufficient amount of the reducing agent to the downstream catalyst unit can be further reduced.

  According to the present invention, a part of the reducing agent added from the reducing agent addition valve also flows into the pre-catalyst portion. Then, the exhaust gas flowing through the bypass passage is heated by the oxidation heat generated by oxidizing the reducing agent in the upstream catalyst section. Therefore, it is possible to suppress the temperature decrease of the exhaust gas flowing through the bypass passage, and thus it is possible to suppress the temperature decrease of the rear catalyst portion when supplying the reducing agent to the rear catalyst portion.

  In the present invention, the outer peripheral surface of the front catalyst part may be covered with the outer peripheral wall. In addition, the pre-catalyst portion may include an oxidation catalyst and an occlusion reduction type NOx catalyst (hereinafter simply referred to as a NOx catalyst) provided in series from the upstream side in the outer peripheral wall. In this case, a through hole may be formed in the outer peripheral wall located between the oxidation catalyst and the NOx storage reduction catalyst. The through hole communicates the inside and the outside of the outer peripheral wall. When the bypass control means has an inlet on / off valve that shuts off or opens the exhaust inlet in the bypass passage and an outlet on / off valve that shuts off or opens the exhaust outlet in the bypass passage, the NOx catalyst has a reducing agent. In addition, the reducing agent may be added from the reducing agent addition valve and the inlet on / off valve may be opened and the outlet on / off valve may be closed by the bypass control means.

  According to this, when supplying the reducing agent to the NOx catalyst, the reducing agent added from the reducing agent addition valve flows into the bypass passage from the inlet of the bypass passage together with the exhaust gas, but does not flow out from the outlet of the bypass passage. Then, the reducing agent that has flowed into the bypass passage passes through the through hole and flows into the outer peripheral wall of the preceding catalyst portion and is supplied to the NOx catalyst. That is, the reducing agent can be directly supplied to the NOx catalyst without passing through the oxidation catalyst. Accordingly, it is possible to suppress a shortage of the supply amount of the reducing agent to the NOx catalyst. Further, the amount of reducing agent added from the reducing agent addition valve in order to supply a sufficient amount of reducing agent to the NOx catalyst can be further reduced.

  According to the present invention, even when the reducing agent addition valve is provided in the exhaust passage on the upstream side of the front catalyst part, the reducing agent can be suitably supplied to the rear catalyst part.

  Hereinafter, specific embodiments of an exhaust emission control device for an internal combustion engine according to the present invention will be described with reference to the drawings.

<Example 1>
<Schematic configuration of exhaust system of internal combustion engine>
Here, a case where the present invention is applied to a diesel engine for driving a vehicle will be described as an example. FIG. 1 is a diagram showing a schematic configuration of an exhaust system of an internal combustion engine according to the present embodiment.

  The internal combustion engine 1 is a diesel engine for driving a vehicle. An exhaust passage 2 is connected to the internal combustion engine 1. The exhaust passage 2 is provided with a turbine housing 20b of a turbocharger 20 having a compressor housing 20a and a turbine housing 20b.

  An oxidation catalyst 4 is provided downstream of the turbine housing 20 b in the exhaust passage 2, and a NOx catalyst 5 is provided immediately downstream of the oxidation catalyst 4. The outer diameters of the oxidation catalyst 4 and the NOx catalyst 5 are smaller than the inner diameter of the exhaust passage 2, and the oxidation catalyst 4 and the NOx catalyst 5 are separated from the inner wall of the exhaust passage 2 and are located at the radial center of the exhaust passage 2. is set up. The outer peripheral surfaces of the oxidation catalyst 4 and the NOx catalyst 5 are covered with an outer peripheral wall 9. With such a configuration, the bypass passage 15 is formed between the outer peripheral surface of the oxidation catalyst 4 and the NOx catalyst 5 and the inner peripheral surface of the exhaust passage 2 so as to surround the outer peripheral surface of the oxidation catalyst 4 and the NOx catalyst 5.

  The upstream and downstream ends of the bypass passage 15 are respectively closed by the inlet side partition wall 11 and the outlet side partition wall 14. Here, the structure of the entrance side partition 11 and the exit side partition 14 which concern on a present Example is demonstrated based on FIG. 2A is a cross-sectional view showing the AA cross section of FIG. 1, and FIG. 2B is a cross-sectional view showing the BB cross section of FIG.

  As shown in FIG. 2A, the inlet side partition wall 11 according to the present embodiment is formed with two inlets 11a through which exhaust flows. Each inlet 11a is provided with an inlet opening / closing valve 12 for blocking or opening the inlet 11a. The inlet on / off valve 12 is driven by an actuator 13. In the present embodiment, the number of the inlets 11a provided in the inlet side partition wall 11 is not limited to two.

  Further, as shown in FIG. 2B, eight outlets 14a through which exhaust flows out are formed in the outlet side partition wall 14 according to the present embodiment. In the present embodiment, the number of outlets 14a provided in the outlet side partition wall 14 is not limited to eight.

  In the present embodiment, the bypass passage 15 is opened when the inlet opening / closing valve 12 is opened. When the bypass passage 15 is opened, the exhaust gas flowing into the bypass passage 15 from the inlet 11a flows bypassing the oxidation catalyst 4 and the NOx catalyst 5, and flows out from the outlet 14a.

The exhaust passage 2 further downstream than the NOx catalyst 5 is provided with a particulate filter (hereinafter simply referred to as a filter) 6 for collecting particulate matter (hereinafter referred to as PM) in the exhaust. ing. An oxidation catalyst 7 is supported on the filter 6.

  In this embodiment, the oxidation catalyst 4 and the NOx catalyst 5 correspond to the front catalyst part according to the present invention, and the filter 6 carrying the oxidation catalyst 7 corresponds to the rear catalyst part according to the present invention. In this embodiment, the inlet on / off valve 12 corresponds to the bypass control means according to the present invention.

  Furthermore, a fuel addition valve 8 is provided upstream of the oxidation catalyst 4 in the exhaust passage 2 to add fuel as a reducing agent into the exhaust. The hatched portion in FIG. 1 represents the spray of fuel injected from the fuel addition valve 8. As represented by the hatched portion, fuel is injected conically from the fuel addition valve 8 according to this embodiment. The injected fuel reaches both the upstream end of the oxidation catalyst 4 and the upstream end of the bypass passage 15. In this embodiment, the fuel addition valve 8 corresponds to the reducing agent addition valve according to the present invention.

The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU) 10 for controlling the internal combustion engine 1. A fuel addition valve 8 and an actuator 13 are electrically connected to the ECU 10. These are controlled by the ECU 10.

<Filter regeneration control>
In this embodiment, filter regeneration control is performed to remove the PM collected by the filter 6. In order to remove PM collected by the filter 6, it is necessary to supply fuel to the filter 6. The fuel supplied to the filter 6 is oxidized in the oxidation catalyst 7, and the temperature of the filter 6 is raised by the oxidation heat generated at that time. As a result, PM is oxidized and removed from the filter 6.

  Here, the routine of the filter regeneration control according to the present embodiment will be described based on the flowchart shown in FIG. This routine is stored in advance in the ECU 10 and is repeatedly executed at predetermined intervals during the operation of the internal combustion engine 1.

  In this routine, the ECU 10 first determines in S101 whether or not an execution condition for the filter regeneration control is satisfied. The execution condition of this filter regeneration control is determined in advance based on the integrated value of the fuel injection amount in the internal combustion engine 1, the travel distance of the vehicle on which the internal combustion engine 1 is mounted, and the like. If an affirmative determination is made in S101, the ECU 10 proceeds to S102, and if a negative determination is made, the ECU 10 once ends the execution of this routine.

  In S <b> 102, the ECU 10 opens the inlet opening / closing valve 12 by the actuator 13.

  Next, the ECU 10 proceeds to S103 and executes fuel addition from the fuel addition valve 8. Thereafter, the ECU 10 once terminates execution of this routine.

  According to the above routine, when the filter regeneration control is executed, fuel is added from the fuel addition valve 8 with the bypass passage 15 opened. Therefore, a part of the fuel added from the fuel addition valve 8 is supplied to the filter 6 through the bypass passage 15. The fuel flowing through the bypass passage 15 is directly supplied to the filter 6 without being oxidized in the oxidation catalyst 4 and the NOx catalyst 5. Therefore, a shortage of fuel supply to the filter 6 can be suppressed. In addition, since the temperature of the filter 6 can be raised efficiently, the amount of fuel added from the fuel addition valve 8 to sufficiently oxidize and remove PM can be further reduced.

  Further, according to this embodiment, part of the fuel added from the fuel addition valve 8 also flows into the oxidation catalyst 4 and the NOx catalyst 5. The fuel is oxidized in the oxidation catalyst 4 and the NOx catalyst 5, and the exhaust gas flowing through the bypass passage 15 is heated by the oxidation heat generated at that time. Therefore, the temperature drop of the exhaust gas flowing through the bypass passage 15 can be suppressed as compared with the conventional case where a bypass passage that bypasses the oxidation catalyst 4 and the NOx catalyst 5 is provided outside the exhaust passage 2. As a result, since the temperature drop of the exhaust gas flowing into the filter 6 can be suppressed, the temperature drop of the filter 6 when the fill regeneration control is executed can be suppressed. Therefore, the oxidation of PM can be further promoted.

  In the present embodiment, since the bypass passage 15 is provided in the exhaust passage 2, it is not necessary to consider the handling of the bypass passage as in the case where the bypass passage is provided outside the exhaust passage 2. Therefore, it becomes possible to provide a bypass passage more easily. Further, since the length of the bypass passage can be made shorter than when the bypass passage is provided outside the exhaust passage 2, the amount of fuel adhering to the inner wall surface of the bypass passage can be reduced.

In this embodiment, when a NOx catalyst is supported on the filter 6 or when a NOx catalyst is provided instead of the filter 6, when NOx or SOx stored in the NOx catalyst is reduced. It is necessary to supply fuel to the NOx catalyst. Also in this case, fuel may be added from the fuel addition valve 8 in a state where the inlet on-off valve 12 is opened and the bypass passage 15 is opened similarly to the execution of the filter regeneration control. According to this, NOx or SOx stored in the NOx catalyst can be reduced more efficiently.

<Example 2>
FIG. 4 is a diagram showing a schematic configuration of an exhaust system of the internal combustion engine according to the present embodiment. Here, only the differences from the schematic configuration of the exhaust system of the internal combustion engine according to the first embodiment will be described, and the same reference numerals are assigned to the same configurations as the schematic configuration of the exhaust system of the internal combustion engine according to the first embodiment. The description is omitted.

  In the present embodiment, a plurality of through holes 18 are formed at positions on the outer peripheral wall 9 between the oxidation catalyst 4 and the NOx catalyst 5. The inside and the outside (bypass passage 15) of the outer peripheral wall 9 communicate with each other through the through hole 18.

  Here, the configuration of the outlet side partition 14 according to the present embodiment will be described with reference to FIG. FIG. 5 is a cross-sectional view showing a BB cross section of FIG.

  As shown in FIG. 5, two outlets 14 a through which exhaust flows out are formed in the outlet-side partition wall 14 according to this embodiment. Each outlet 14a is provided with an outlet opening / closing valve 16 for blocking or opening the outlet 14a. The outlet on / off valve 16 is driven by an actuator 17. The actuator 17 is electrically connected to the ECU 10 and is controlled by the ECU 10. In the present embodiment, the number of outlets 14a formed in the outlet side partition wall 14 is not limited to two.

  In this embodiment, when both the inlet on / off valve 12 and the outlet on / off valve 16 are opened, the bypass passage 15 is opened. When the bypass passage 15 is opened, the exhaust gas flowing into the bypass passage 15 from the inlet 11a flows bypassing the oxidation catalyst 4 and the NOx catalyst 5 and flows out from the outlet 14a as in the case of the first embodiment. A part of the exhaust gas flowing into the bypass passage 15 flows into the outer peripheral wall 9 through the through hole 18.

  On the other hand, when the inlet on / off valve 12 is opened and the outlet on / off valve 16 is closed, the exhaust flows into the bypass passage 15 from the inlet 11a, but the exhaust flows out from the downstream end of the bypass passage 15. do not do. In this case, the exhaust gas flowing into the bypass passage 15 flows into the outer peripheral wall 9 through the through hole 18.

  In this embodiment, the inlet on / off valve 12 and the outlet on / off valve 16 correspond to the bypass control means according to the present embodiment.

<Filter regeneration control and NOx reduction control>
In this embodiment, filter regeneration control for removing PM collected by the filter 6 and NOx reduction control for releasing and reducing NOx occluded in the NOx catalyst 5 are performed. Hereinafter, the routine of the filter regeneration control and the NOx reduction control according to the present embodiment will be described based on the flowchart shown in FIG. This routine is stored in advance in the ECU 10 and is repeatedly executed at predetermined intervals during the operation of the internal combustion engine 1. Note that S101 and S103 in this routine are the same as those in the flowchart shown in FIG.

In this routine, if an affirmative determination is made in S101, the ECU 10 proceeds to S202, and if a negative determination is made, the ECU 10 proceeds to S203.

  In step S202, the ECU 10 opens the inlet on / off valve 12 with the actuator 13 and opens the outlet on / off valve 16 with the actuator 17. Thereafter, the ECU 10 proceeds to S103.

    On the other hand, the ECU 10 that has proceeded to S203 determines whether or not the execution condition of the NOx reduction control for reducing the NOx stored in the NOx catalyst 5 is satisfied. The execution condition of this NOx reduction control is determined in advance based on the integrated value of the fuel injection amount in the internal combustion engine 1, the travel distance of the vehicle on which the internal combustion engine 1 is mounted, and the like. If an affirmative determination is made in S203, the ECU 10 proceeds to S204, and if a negative determination is made, the ECU 10 once ends the execution of this routine.

  In step S <b> 204, the ECU 10 opens the inlet on / off valve 12 with the actuator 13 and closes the outlet on / off valve 16 with the actuator 17. Thereafter, the ECU 10 proceeds to S103.

  According to the routine described above, when the filter regeneration control is executed, fuel is added from the fuel addition valve 8 with the bypass passage 15 opened as in the first embodiment. Therefore, a part of the fuel added from the fuel addition valve 8 is supplied to the filter 6 through the bypass passage 15. Therefore, a shortage of fuel supply to the filter 6 can be suppressed. In addition, since the temperature of the filter 6 can be raised efficiently, the amount of fuel added from the fuel addition valve 8 to sufficiently oxidize and remove PM can be further reduced.

  Further, since the configuration of the bypass passage 15 itself is the same as that of the first embodiment, the same effect as that of the first embodiment can be obtained.

  Further, according to the above routine, when the NOx reduction control for reducing the NOx stored in the NOx catalyst 5 is executed, the inlet on-off valve 12 is opened and the outlet on-off valve 16 is closed. Fuel is added from the fuel addition valve 8. Therefore, the fuel flowing into the bypass passage 15 together with the exhaust flows through the through hole 18 and flows between the oxidation catalyst 4 and the NOx catalyst 5 inside the outer peripheral wall 9. This fuel is supplied to the NOx catalyst 5.

  That is, a part of the fuel added from the fuel addition valve 8 is directly supplied to the NOx catalyst 5 without passing through the oxidation catalyst 4 (that is, not oxidized in the oxidation catalyst 4). Therefore, it is possible to suppress a shortage of the amount of fuel supplied to the NOx catalyst 5. In addition, since the NOx stored in the NOx catalyst 5 can be efficiently reduced, the amount of fuel added from the fuel addition valve 8 to sufficiently reduce NOx can be further reduced.

  Even when the fuel is supplied to the NOx catalyst 5 so as to release and reduce the SOx stored in the NOx catalyst 5, the inlet on-off valve 12 is opened and the outlet on-off is opened as in the case of the execution of the NOx reduction control. Fuel may be added from the fuel addition valve 8 with the valve 16 closed. According to this, the SOx stored in the NOx catalyst 5 can be reduced more efficiently.

  In this embodiment, when a NOx catalyst is supported on the filter 6 or when a NOx catalyst is provided in place of the filter 6, when NOx or SOx stored in the NOx catalyst is reduced. Similarly to the execution of the filter regeneration control, the fuel may be added from the fuel addition valve 8 with both the inlet on-off valve 12 and the outlet on-off valve 16 opened and the bypass passage 15 opened. According to this, NOx or SOx stored in the NOx catalyst can be reduced more efficiently.

<Reference example>
FIG. 7 is a diagram showing a schematic configuration of an exhaust system of the internal combustion engine according to the present reference example. Here, only the differences from the schematic configuration of the exhaust system of the internal combustion engine according to the first embodiment will be described, and the same reference numerals are assigned to the same configurations as the schematic configuration of the exhaust system of the internal combustion engine according to the first embodiment. The description is omitted.

  In this reference example, the outer diameter of the NOx catalyst 5 is the same as the inner diameter of the exhaust passage 2. The outer peripheral wall 9 covers only the outer diameter of the oxidation catalyst 4. That is, the bypass passage 15 is formed between the outer peripheral surface of the oxidation catalyst 4 and the inner peripheral surface of the exhaust passage 2 so as to surround the outer peripheral surface of the oxidation catalyst 4.

  Also in this reference example, the upstream and downstream ends of the bypass passage 15 are respectively closed by the inlet side partition wall 11 and the outlet side partition wall 14 shown in FIGS. It is peeling off. Therefore, when the inlet opening / closing valve 12 is opened, the bypass passage 15 is opened. When the bypass passage 15 is opened, the exhaust gas flowing into the bypass passage 15 from the inlet 11a flows bypassing the oxidation catalyst 4 and flows out from the outlet 14a.

<NOx reduction control>
Hereinafter, a routine of NOx reduction control for releasing / reducing NOx stored in the NOx catalyst 5 according to the present reference example will be described based on a flowchart shown in FIG. This routine is stored in advance in the ECU 10 and is repeatedly executed at predetermined intervals during the operation of the internal combustion engine 1. This routine is obtained by replacing S101 in the flowchart shown in FIG. 3 with S301. Therefore, only S301 will be described, and descriptions of S102 and S103 will be omitted.

  In this routine, the ECU 10 first determines in S301 whether or not an execution condition for NOx reduction control for reducing NOx stored in the NOx catalyst 5 is satisfied. The execution condition of this NOx reduction control is determined in advance based on the integrated value of the fuel injection amount in the internal combustion engine 1, the travel distance of the vehicle on which the internal combustion engine 1 is mounted, and the like. If an affirmative determination is made in S301, the ECU 10 proceeds to S102, and if a negative determination is made, the ECU 10 once ends the execution of this routine.

  According to the routine described above, when the NOx reduction control for reducing the NOx stored in the NOx catalyst 5 is executed, the fuel is added from the fuel addition valve 8 with the bypass passage 15 opened. Therefore, a part of the fuel added from the fuel addition valve 8 is supplied to the NOx catalyst 5 through the bypass passage 15. The fuel flowing through the bypass passage 15 is directly supplied to the NOx catalyst 5 without being oxidized in the oxidation catalyst 4. Therefore, it is possible to suppress a shortage of the amount of fuel supplied to the NOx catalyst 5. In addition, since the NOx stored in the NOx catalyst 5 can be efficiently reduced, the amount of fuel added from the fuel addition valve 8 to sufficiently reduce NOx can be further reduced.

  Even when fuel is supplied to the NOx catalyst 5 in order to release and reduce the SOx stored in the NOx catalyst 5, the inlet on-off valve 12 is opened and the bypass passage is opened as in the case of performing the NOx reduction control. The fuel may be added from the fuel addition valve 8 in a state in which 15 is opened. According to this, SOx occluded in the NOx catalyst 5 can be reduced more efficiently.

1 is a diagram illustrating a schematic configuration of an exhaust system of an internal combustion engine according to a first embodiment. 2A is a cross-sectional view showing the AA cross section of FIG. 1, and FIG. 2B is a cross-sectional view showing the BB cross section of FIG. 5 is a flowchart illustrating a routine for filter regeneration control according to the first embodiment. FIG. 3 is a diagram illustrating a schematic configuration of an exhaust system of an internal combustion engine according to a second embodiment. Sectional drawing which shows the BB cross section of FIG. 9 is a flowchart illustrating a routine for filter regeneration control and NOx reduction control according to the second embodiment. The figure which shows schematic structure of the exhaust system of the internal combustion engine which concerns on a reference example. The flowchart which shows the routine of NOx reduction control which concerns on a reference example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Exhaust passage 4 ... Oxidation catalyst 5 ... Occlusion reduction type NOx catalyst 6 ... Particulate filter 7 ... Oxidation catalyst 8 ... Fuel addition valve 9 ...・ Outer wall 10 ・ ・ ECU
11. ・ Inlet side bulkhead 11a ・ ・ Inlet 12 ・ ・ Inlet on / off valve 13 ・ ・ Actuator 14 ・ ・ Outlet side bulkhead 14a ・ ・ Outlet 15 ・ ・ Bypass passage 16 ・ ・ Outlet on / off valve 17 ・ ・ Actuator

Claims (2)

A pre-catalyst portion configured to include at least one catalyst having an oxidation function provided in an exhaust passage of the internal combustion engine;
A post-stage catalyst unit configured to include at least one catalyst provided in the exhaust passage downstream of the pre-stage catalyst unit and having an oxidation function;
A reducing agent addition valve that is provided in the exhaust passage on the upstream side of the front-stage catalyst portion and adds a reducing agent into the exhaust;
A bypass passage formed so as to surround the outer peripheral surface of the front catalyst portion between the outer peripheral surface of the front catalyst portion and the inner peripheral surface of the exhaust passage;
A bypass control means provided in the bypass passage for blocking or opening the bypass passage;
An exhaust gas purifying apparatus for an internal combustion engine, wherein when supplying the reducing agent to the rear catalyst unit, the reducing agent is added from the reducing agent addition valve and the bypass passage is opened by the bypass control means. An outer peripheral surface of the front catalyst part is covered with an outer peripheral wall;
The front catalyst part has an oxidation catalyst and an occlusion reduction type NOx catalyst provided in series in order from the upstream side in the outer peripheral wall,
A through hole is formed in the outer peripheral wall at a position between the oxidation catalyst and the NOx storage reduction catalyst to communicate the inside and the outside of the outer peripheral wall;
The bypass control means includes an inlet on-off valve that shuts off or opens an exhaust inlet in the bypass passage, and an outlet on-off valve that shuts off or opens an exhaust outlet in the bypass passage;
When supplying a reducing agent to the NOx storage reduction catalyst of the pre-stage catalyst unit, a reducing agent is added from the reducing agent addition valve, and the inlet control valve is opened by the bypass control means and the outlet switching valve 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the valve is closed.

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