JP2018062906A - Exhaust gas aftertreatment system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas aftertreatment system for an internal combustion engine capable of inhibiting a temperature of a catalyst for eliminating NOx in exhaust gas from becoming a high temperature or a low temperature by using a heat storage material that radiates heat when receiving a pressure and thus of suppressing lowering of an NOx elimination ratio.SOLUTION: An exhaust gas aftertreatment system 20 for an internal combustion engine includes: a catalyst 42 for eliminating NOx in exhaust gas; a heat storage material 71; a pressure application member 72; flow passage selector valves 80a, 80b; and a control device 10 for controlling the flow passage selector valves so as to obtain a state via the heat storage material when an upstream side exhaust gas temperature that is a temperature of exhaust gas upstream of a first section 5 is a high temperature or a low temperature and so as to obtain a state not via the heat storage material when the upstream side exhaust gas temperature is an intermediate temperature, and for controlling the pressure application member so as not to apply a pressure to the heat storage material when the upstream side exhaust gas temperature is the high temperature or the intermediate temperature and so as to apply the pressure to the heat storage material when the upstream side exhaust gas temperature is the low temperature.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an exhaust aftertreatment system for an internal combustion engine.

  2. Description of the Related Art Conventionally, there has been known an exhaust aftertreatment system in which an exhaust passage is provided with a catalyst that removes NOx in exhaust gas from an internal combustion engine, and NOx in exhaust gas is removed by the catalytic action of this catalyst (see, for example, Patent Document 1).

JP-A-60-190613

  In general, a catalyst that removes NOx in exhaust gas has a relatively low NOx purification rate when the temperature of the catalyst is low or high, and a relatively good NOx purification rate when the temperature is medium. Become. By the way, in recent years, a heat storage material that radiates heat when pressure is applied has been developed, such as trititanium pentoxide. However, until now, no technology has been developed that suppresses the decrease in the NOx purification rate by suppressing the temperature of the catalyst from becoming low or high by using a heat storage material that radiates heat when receiving such pressure. It was.

  The present invention has been made in view of the above, and an object of the present invention is to use a heat storage material that dissipates heat when subjected to pressure, so that the temperature of the catalyst for removing NOx in the exhaust becomes low or high. This is to provide an exhaust aftertreatment system for an internal combustion engine that can suppress the decrease in the NOx purification rate.

  In order to achieve the above object, an exhaust aftertreatment system for an internal combustion engine according to the present invention is disposed in an exhaust passage of the internal combustion engine, a catalyst for removing NOx in the exhaust, and an upstream side of the catalyst in the exhaust passage. Heat storage that branches off from the first location and is disposed in a secondary exhaust passage connected to a second location upstream of the catalyst and downstream of the first location in the exhaust passage, and radiates heat when subjected to pressure A pressure applying member that applies pressure to the heat storage material, and a state through the heat storage material in which exhaust gas upstream of the first location flows into the catalyst after passing through the heat storage material in the sub exhaust passage. A flow path switching valve for switching between a state where the exhaust gas upstream of the first location does not pass through the heat storage material and flows into the catalyst without passing through the heat storage material, and a temperature of the exhaust gas upstream of the first location When the upstream exhaust temperature is high The flow path switching valve is controlled so that the state through the heat storage material is obtained when the temperature is low and the upstream exhaust gas temperature is medium, and the state through which the heat storage material is not through is obtained when the upstream exhaust temperature is medium. When the exhaust temperature is the high temperature and the intermediate temperature, no pressure is applied to the heat storage material, and the pressure applying member is applied such that pressure is applied to the heat storage material when the upstream exhaust temperature is the low temperature. A control device for controlling.

According to the present invention, when the upstream exhaust gas temperature is high, the heat of the exhaust gas can be absorbed by the heat storage material, and the exhaust gas whose temperature has decreased can be caused to flow into the catalyst. Thereby, since it can suppress that the temperature of the catalyst which removes NOx in exhaust_gas | exhaustion becomes high, the fall of the NOx purification rate resulting from the temperature of this catalyst becoming high can be suppressed. In addition, when the upstream exhaust temperature is low, the heat storage material is dissipated by applying pressure to the heat storage material, and the temperature of the exhaust gas is increased by the heat dissipation of the heat storage material. Can be allowed to flow into. Thereby, since it can suppress that the temperature of the catalyst which removes NOx in exhaust_gas | exhaustion becomes low temperature, the fall of the NOx purification rate resulting from the temperature of this catalyst becoming low temperature can be suppressed.

1 is a configuration diagram schematically showing an overall configuration of an internal combustion engine system to which an exhaust gas aftertreatment system for an internal combustion engine according to an embodiment is applied. FIG. 2A is a schematic enlarged view in which the peripheral structure of the auxiliary exhaust passage and the urea SCR device in the internal combustion engine system is enlarged. FIG.2 (b) is the typical enlarged view to which the peripheral structure (A part) of the thermal storage apparatus 70 of Fig.2 (a) was expanded. It is a figure which shows typically the relationship between the NOx purification rate of a urea SCR catalyst, and the temperature of a urea SCR catalyst. It is an example of the flowchart which shows the control process of the flow-path switching valve and pressure provision member by a control apparatus.

  Hereinafter, an exhaust aftertreatment system 20 for an internal combustion engine according to an embodiment of the present invention (hereinafter abbreviated as “exhaust aftertreatment system 20”) will be described with reference to the drawings. FIG. 1 is a configuration diagram schematically showing an overall configuration of an internal combustion engine system 1 to which an exhaust aftertreatment system 20 according to the present embodiment is applied. The internal combustion engine system 1 includes an internal combustion engine 2, an exhaust passage 4, a control device 10, and an exhaust aftertreatment system 20.

  In the present embodiment, a diesel engine is used as an example of the internal combustion engine 2. In FIG. 1, the number of cylinders 3 of the internal combustion engine 2 is four as an example, but the number of cylinders 3 is not limited to this. The exhaust passage 4 is a passage through which the exhaust discharged from the cylinder 3 of the internal combustion engine 2 passes. The upstream end of the exhaust passage 4 is branched and connected to the exhaust port of each cylinder 3.

  The control device 10 controls the fuel injection amount and fuel injection timing of the internal combustion engine 2 and also controls the operation of the exhaust aftertreatment system 20 described later. The control device 10 includes a microcomputer having a CPU 11 having a function as a control unit for executing various control processes, a storage unit 12 for storing various information, programs, and the like necessary for the operation of the CPU 11. As the storage unit 12, a storage device such as a ROM or a RAM is used.

  The exhaust aftertreatment system 20 includes an exhaust purification device 30 disposed in the exhaust passage 4 and a urea SCR (Selective Catalytic Reduction) device 40 disposed in the exhaust passage 4 on the downstream side of the exhaust purification device 30. . The exhaust aftertreatment system 20 further includes a temperature sensor 50, a sub exhaust passage 60, a heat storage device 70, and flow path switching valves 80a and 80b. Note that the exhaust aftertreatment system 20 according to the present embodiment includes the control device 10 that controls the exhaust aftertreatment system 20 as a part of its constituent elements.

The exhaust purification device 30 includes an oxidation catalyst 31 and a filter 32 disposed on the downstream side of the oxidation catalyst 31. The oxidation catalyst 31 removes harmful substances such as carbon monoxide (CO) and hydrocarbons (HC) contained in the exhaust gas from harmless water (H ₂ O) and carbon dioxide (CO ₂ ) by the catalytic action of the oxidation catalyst 31. It is a catalyst that purifies harmful substances in exhaust by changing to substances. As long as it has such a function, the specific configuration of the oxidation catalyst 31 is not particularly limited, but the oxidation catalyst 31 according to the present embodiment is, for example, platinum as a carrier through which exhaust can pass. It has a configuration in which a noble metal catalyst such as (Pt) or palladium (Pd) is supported.

  The filter 32 may be a filter that can collect PM such as soot contained in the exhaust gas, and its specific configuration is not particularly limited. In the present embodiment, as an example of the filter 32, a wall-through type diesel particulate filter is used.

The urea SCR device 40 supplies urea water into the exhaust gas, and selectively reduces NOx in the exhaust gas using ammonia (NH ₃ ) generated from the urea water supplied into the exhaust gas as a reducing agent. The device to be removed. The specific configuration of the urea SCR device 40 is not particularly limited as long as it has such a function, but in the present embodiment, as an example, a urea water supply unit 41, a urea SCR catalyst 42, And an ammonia slip catalyst 43.

  The urea water supply unit 41 is disposed in the exhaust passage 4 upstream of the urea SCR catalyst 42 and downstream of the filter 32. More specifically, the urea water supply unit 41 according to the present embodiment is upstream of the urea SCR catalyst 42 and downstream of the connection location of the auxiliary exhaust passage 60 in the exhaust passage 4 (second location 6 described later). It is arranged on the side part. As a specific example of the urea water supply unit 41, in this embodiment, a urea water injection valve that injects urea water into the exhaust gas in response to an instruction from the control device 10 is used. When the urea water supply instruction is received (for example, when the urea water supply start switch is turned ON by the user), the control device 10 causes the urea water injection valve as the urea water supply unit 41 to inject urea water. .

  The urea SCR catalyst 42 is a catalyst that removes NOx in the exhaust (that is, “NOx removal catalyst”), and specifically, selectively reduces NOx in the exhaust using ammonia generated by hydrolysis of urea. This is a catalyst for removing NOx. The specific type of the urea SCR catalyst 42 is not particularly limited, and for example, base metal oxides such as vanadium (V) and molybdenum (Mo), zeolite, and the like can be used. The ammonia slip catalyst 43 is disposed downstream of the urea SCR catalyst 42 and is an oxidation catalyst that oxidizes ammonia that has passed through the urea SCR catalyst 42.

When urea water is supplied into the exhaust gas from the urea water supply unit 41, urea in the urea water is hydrolyzed, and as a result, ammonia is generated. This ammonia reduces NOx under the catalytic action of the urea SCR catalyst 42. As a result, nitrogen (N ₂ ) and water (H ₂ O) are generated. In this way, the urea SCR device 40 attempts to reduce NOx in the exhaust. Moreover, according to this embodiment, since the ammonia slip catalyst 43 is provided, it is effectively suppressed that ammonia is discharged to the outside of the internal combustion engine system 1.

  The temperature sensor 50 detects the temperature of the exhaust gas upstream of the first location 5 (the branch location of the auxiliary exhaust passage 60 in the exhaust passage 4; see FIG. 2A) (hereinafter referred to as “upstream exhaust temperature”). Then, the detection result is transmitted to the control device 10. The specific location of the temperature sensor 50 in the exhaust passage 4 is not particularly limited as long as it has such a function, but the temperature sensor 50 according to the present embodiment is an example of the exhaust passage 4. The filter 32 is disposed downstream of the first filter 32 and upstream of the first location 5 to detect the temperature of the exhaust gas in this portion.

  Next, details of the auxiliary exhaust passage 60, the heat storage device 70, and the flow path switching valves 80a and 80b will be described. FIG. 2A is a schematic enlarged view in which the peripheral structure of the auxiliary exhaust passage 60 and the urea SCR device 40 in the internal combustion engine system 1 is enlarged. FIG.2 (b) is the typical enlarged view to which the peripheral structure (A part) of the thermal storage apparatus 70 of Fig.2 (a) was expanded.

  As shown in FIG. 2A, the auxiliary exhaust passage 60 branches from the first location 5 upstream of the urea SCR catalyst 42 in the exhaust passage 4 and is upstream of the urea SCR catalyst 42 in the exhaust passage 4. And it is connected to the second location 6 on the downstream side of the first location 5.

  The heat storage device 70 is disposed in the sub exhaust passage 60. As shown in FIG. 2B, the heat storage device 70 includes a heat storage material 71 and a pressure applying member 72. The pressure applying member 72 is a member that applies pressure to the heat storage material 71 by being controlled by the control device 10. As an example of the pressure applying member 72, in the present embodiment, a piezoelectric material disposed so as to entirely cover the outer peripheral side surface of the heat storage material 71 is used. Specifically, the piezoelectric material includes an outer peripheral side surface of the cylindrical heat storage material 71 (this is a surface facing the inner peripheral surface of the sub exhaust passage 60) and a sub exhaust existing outside the heat storage material 71. It arrange | positions between the internal peripheral surfaces of the channel | path 60. FIG. The piezoelectric material is electrically connected to the control device 10 and generates pressure when receiving electric supply from the control device 10. Thereby, the piezoelectric material applies pressure to the heat storage material 71.

  In addition, although the specific material of a piezoelectric material is not specifically limited, In this embodiment, titanium zirconate lead (Lead Zirconate Titanate; PZT) is used as an example.

  Moreover, the arrangement | positioning aspect of a piezoelectric material should just be an aspect which can provide a pressure to the thermal storage material 71, and is not limited to the arrangement | positioning aspect shown in FIG.2 (b). For example, the piezoelectric material shown in FIG. 2B covers the heat storage material 71 so as to be in direct contact with the heat storage material 71, but the piezoelectric material covers the heat storage material 71 via another member (that is, the heat storage material). 71 may be configured to indirectly cover 71).

The heat storage material 71 is a member that stores ambient heat when no pressure is applied from the pressure applying member 72 and radiates heat when the stored heat is received from the pressure applying member 72. As an example of the material of such a heat storage material 71, in the present embodiment, a ceramic heat storage material (that is, a heat storage ceramic) is used, and as a specific example of such a heat storage material, titanium trioxide (Ti ₃ O ₅ ). Is used.

  This trititanium pentoxide has good heat retention performance (that is, heat can be retained for a long time). In this respect, titanium trioxide is particularly preferable as the material of the heat storage material 71.

  In addition, since the heat storage material 71 according to the present embodiment is disposed inside the sub exhaust passage 60, the exhaust gas in the sub exhaust passage 60 can pass through the heat storage material 71. As an example of this, the heat storage material 71 according to the present embodiment has a structure having a plurality of holes through which exhaust gas can pass. Thereby, it is suppressed that the flow of exhaust gas is inhibited by the heat storage material 71.

  Referring again to FIG. 2A, the flow path switching valve 80 a is disposed at a portion between the first location 5 and the second location 6 in the exhaust passage 4. The flow path switching valve 80 b is disposed in a portion upstream of the heat storage device 70 in the sub exhaust passage 60. In the present embodiment, as an example of the flow path switching valve 80a and the flow path switching valve 80b, an open / close valve that opens and closes in response to an instruction from the control device 10 is used.

  As shown in FIG. 2A, when the control device 10 controls the flow path switching valve 80a to be in a closed state and controls the flow path switching valve 80b to be in an open state, the control device 10 is upstream of the first location 5. The exhaust gas flows into the urea SCR catalyst 42 after passing through the heat storage material 71 in the sub exhaust passage 60. On the other hand, for example, as shown in FIG. 1, when the control device 10 controls the flow path switching valve 80 a to be in the open state and controls the flow path switching valve 80 b to be in the closed state, the control device 10 is located upstream from the first location 5. Exhaust gas flows into the urea SCR catalyst 42 without passing through the heat storage material 71 in the auxiliary exhaust passage 60.

That is, in the flow path switching valves 80a and 80b according to the present embodiment, the exhaust upstream of the first location 5 flows into the catalyst (urea SCR catalyst 42) after passing through the heat storage material 71 of the sub exhaust passage 60. State (referred to as “heat storage material passing state”) and state where the exhaust gas upstream of the first location 5 flows into the catalyst (urea SCR catalyst 42) without passing through the heat storage material 71 (“heat storage material non-passing state”) Corresponds to a member having a function as a flow path switching valve.

  Next, the relationship between the NOx purification rate of the urea SCR catalyst 42 and the temperature of the urea SCR catalyst 42 will be described, and then the details of the control processing of the control device 10 will be described.

FIG. 3 is a diagram schematically showing the relationship between the NOx purification rate of the urea SCR catalyst 42 and the temperature of the urea SCR catalyst 42. Temperature of the urea SCR catalyst 42 is the temperature _{T a} or, NOx purification rate of the urea SCR catalyst 42 in the case of the temperature _{T b} below a temperature range (referred to as "medium temperature") is at a temperature lower than the temperature _{T a} of the urea SCR catalyst 42 temperature range (referred to as "low temperature") or, the temperature of the urea SCR catalyst 42 is compared to the temperature range higher than the temperature T _b (referred to as "high temperature") it is larger.

  That is, the NOx purification rate of the urea SCR catalyst 42, which is a NOx removal catalyst, is relatively low when the temperature is low or high, and is relatively good when the temperature is medium. Therefore, the control device 10 executes a control process described below in order to suppress the temperature of the urea SCR catalyst 42 from becoming low or high, and to suppress a decrease in the NOx purification rate.

  Specifically, the control device 10 obtains the state via the heat storage material when the upstream exhaust temperature (that is, the exhaust temperature upstream from the first location 5) is high or low, and the upstream side When the exhaust gas temperature is medium, the flow path switching valves 80a and 80b are controlled so that a state not passing through the heat storage material is obtained, and the pressure is applied to the heat storage material 71 when the upstream exhaust temperature is high or low. The pressure applying member 72 is controlled so that pressure is applied to the heat storage material 71 when the upstream exhaust gas temperature is low. This control process will be described in detail with reference to a flowchart as follows.

  FIG. 4 is an example of a flowchart showing a control process of the flow path switching valves 80 a and 80 b and the pressure applying member 72 by the control device 10. The control apparatus 10 repeatedly executes the flowchart of FIG. 4 simultaneously with the start of the internal combustion engine 2. Moreover, each step of FIG. 4 is specifically performed by the CPU 11 of the control device 10.

First, in step S10, the control device 10 determines whether or not the upstream exhaust temperature is high. Specifically, the control device 10 acquires the upstream exhaust temperature by acquiring the detection result of the temperature sensor 50, and the acquired upstream exhaust temperature is a temperature T _b stored in the storage unit 12 in advance. By determining whether or not it is higher, it is determined whether or not the upstream exhaust temperature is high.

Here, as the temperature T _b , a value that is considered to cause a decrease in the NOx purification rate of the urea SCR catalyst 42 when exhaust gas having a temperature higher than this temperature flows into the urea SCR catalyst 42 can be used. . This temperature _Tb is obtained in advance by conducting experiments, simulations, etc., to obtain an appropriate value and stored in the storage unit 12. In the case of using the urea SCR catalyst 42 as a catalyst for NOx removal as in the present embodiment, it is possible to use a value selected from a range of 380 ° C. to 430 ° C. As an example of the temperature T _b.

When it determines with YES by step S10, the control apparatus 10 performs step S20. In step S20, the control device 10 controls the flow path switching valve 80a to be in a closed state and controls the flow path switching valve 80b to be in a valve open state, so that the flow state of the exhaust is changed to a state via the heat storage material. As a result, the exhaust gas upstream from the first location 5 flows into the urea SCR catalyst 42 after passing through the heat storage material 71. In step S <b> 20, no pressure is applied from the pressure applying member 72 to the heat storage material 71.

  By executing step S20, the heat of the exhaust gas is absorbed by the heat storage material 71, and the exhaust gas whose temperature has decreased can be caused to flow into the urea SCR catalyst 42. Thereby, since it can suppress that the temperature of the urea SCR catalyst 42 becomes high temperature, the fall of the NOx purification rate resulting from the temperature of the urea SCR catalyst 42 becoming high temperature can be suppressed. After execution of step S20, the control device 10 executes a return, and executes the flowchart from the start.

On the other hand, when it determines with NO by step S10, the control apparatus 10 performs step S30. In step S30, the control device 10 determines whether or not the upstream exhaust temperature is medium. Specifically, in the control device 10, the upstream exhaust temperature acquired based on the detection result of the temperature sensor 50 is not less than the temperature T _{a and not} more than the temperature T _b stored in the storage unit 12 in advance (that is, the temperature T _a ˜ By determining whether or not the temperature T _b ), it is determined whether or not the upstream exhaust temperature is a medium temperature.

Here, as the temperature Ta, _a value that is considered to decrease the NOx purification rate of the urea SCR catalyst 42 when exhaust gas having a temperature lower than this temperature flows into the urea SCR catalyst 42 can be used. . The temperature T _a in advance, experimentally, simulation or the like to previously obtain the appropriate values have been stored in the storage section 12. In the case of using the urea SCR catalyst 42 as a catalyst for NOx removal as in the present embodiment, it is possible to use a value selected from a range of 200 ° C. to 250 DEG ° C. As an example of the temperature T _a.

  When it determines with YES by step S30, the control apparatus 10 performs step S40. In step S40, the control device 10 controls the flow path switching valve 80a to be in an open state and controls the flow path switching valve 80b to be in a closed state, thereby bringing the exhaust gas into a state not passing through the heat storage material. As a result, the exhaust gas upstream of the first location 5 flows into the urea SCR catalyst 42 without passing through the heat storage material 71. In step S40, no pressure is applied from the pressure applying member 72 to the heat storage material 71.

  By executing step S40, the middle temperature exhaust gas flows into the urea SCR catalyst 42, whereby the urea SCR catalyst 42 can be brought to a middle temperature. Thereby, the NOx purification rate of the urea SCR catalyst 42 can be improved. After execution of step S40, the control device 10 executes a return and executes the flowchart again from the start.

  When it determines with NO by step S30, the control apparatus 10 performs step S50. In step S50, the control device 10 determines whether or not the upstream exhaust temperature is low. Specifically, the control device 10 determines whether or not the upstream exhaust temperature acquired based on the detection result of the temperature sensor 50 is lower than the temperature Ta stored in the storage unit 12 in advance. It is determined whether or not the side exhaust temperature is low.

  When it determines with NO by step S50, the control apparatus 10 performs a return, and performs a flowchart again from a start. On the other hand, when it determines with YES by step S50, the control apparatus 10 performs step S60. In step S60, the control device 10 controls the flow path switching valve 80a to be in a closed state and controls the flow path switching valve 80b to be in a valve open state, so that the flow state of the exhaust is changed to a state via the heat storage material. As a result, the exhaust gas upstream of the first location 5 flows into the urea SCR catalyst 42 after passing through the heat storage material 71. In step S <b> 60, the control device 10 supplies electricity to the piezoelectric material as the pressure applying member 72. Thereby, the piezoelectric material applies pressure to the heat storage material 71.

By executing step S60, the heat storage material 71 can be dissipated, the temperature of the exhaust gas can be increased by the heat dissipation of the heat storage material 71, and the exhaust gas whose temperature has increased can flow into the urea SCR catalyst 42. Thereby, since it can suppress that the temperature of the urea SCR catalyst 42 becomes low temperature, the fall of the NOx purification rate resulting from the temperature of the urea SCR catalyst 42 becoming low temperature can be suppressed. After execution of step S60, the control device 10 executes a return and executes the flowchart again from the start.

  As described above, according to this embodiment, the temperature of the NOx removal catalyst (urea SCR catalyst 42) is suppressed from becoming low or high by using the heat storage material 71 that radiates heat when pressure is applied from the outside. Thus, it is possible to suppress a decrease in the NOx purification rate. Thereby, the NOx purification rate of the NOx removal catalyst can be improved.

  Further, according to the present embodiment, trititanium pentoxide is used as the heat storage material 71, and as described above, the heat storage material 71 has good heat retention performance. As a result, the heat storage material 71 can store a larger amount of heat before starting to release heat, and as a result, more heat can be released when radiating heat. Therefore, according to the present embodiment, for example, when the heat storage material 71 stores heat in step S20, the temperature of the exhaust gas can be effectively reduced by the heat storage material 71. For example, when the heat storage material 71 radiates heat in step S60, the heat storage material 71 can effectively increase the temperature of the exhaust gas. Thereby, it can suppress effectively that the temperature of the urea SCR catalyst 42 becomes high temperature or low temperature.

  Although the preferred embodiments of the present invention have been described above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. Is possible.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine system 5 1st location 6 2nd location 10 Control device 20 Exhaust aftertreatment system 30 of internal combustion engine Exhaust purification device 40 Urea SCR device 42 Urea SCR catalyst (catalyst which removes NOx in exhaust gas)
50 Temperature sensor 60 Sub exhaust passage 70 Heat storage device 71 Heat storage material 72 Pressure applying member 80a, 80b Flow path switching valve

Claims (3)

A catalyst disposed in the exhaust passage of the internal combustion engine for removing NOx in the exhaust;
Arranged in a sub-exhaust passage branched from the first location upstream of the catalyst in the exhaust passage and connected to a second location upstream of the catalyst and downstream of the first location in the exhaust passage. And a heat storage material that radiates heat when subjected to pressure,
A pressure applying member that applies pressure to the heat storage material; and
The exhaust state upstream of the first location passes through the heat storage material in the auxiliary exhaust passage and then flows into the catalyst, and the exhaust gas upstream of the first location passes through the heat storage material. A flow path switching valve for switching between the heat storage material non-passing state flowing into the catalyst without
When the upstream exhaust temperature, which is the temperature of the exhaust upstream of the first location, is high or low, the state through the heat storage material is obtained, and when the upstream exhaust temperature is medium temperature, the heat storage In addition to controlling the flow path switching valve so as to obtain a material non-passage state, when the upstream exhaust temperature is the high temperature and the intermediate temperature, no pressure is applied to the heat storage material, and the upstream exhaust temperature An exhaust aftertreatment system for an internal combustion engine, comprising: a control device that controls the pressure applying member so that pressure is applied to the heat storage material when the temperature is low.   The exhaust aftertreatment system for an internal combustion engine according to claim 1, wherein the catalyst is a urea SCR catalyst.   The exhaust gas aftertreatment system for an internal combustion engine according to claim 1 or 2, wherein the heat storage material is titanium trioxide.

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