JP7381423B2 - Exhaust purification device - Google Patents

Description

The present disclosure relates to an exhaust purification device.

Patent Document 1 listed below describes an exhaust gas purification catalyst that processes exhaust gas discharged from an engine. This exhaust gas purification catalyst has a carrier having a honeycomb structure or a monolith structure, a coating layer containing a chemical heat storage material that generates heat by reacting with water vapor in exhaust gas, and a catalyst layer supported on the coating layer. . The chemical heat storage material contained in the coating layer activates the catalyst early by reacting with water vapor contained in the exhaust gas to generate heat when the exhaust gas temperature is low.

Japanese Patent Application Publication No. 2011-218302

In the above-mentioned exhaust gas purification catalyst, by dehydrating the chemical heat storage material when the temperature of the exhaust gas is high, the chemical heat storage material is regenerated into a state capable of generating heat. However, depending on driving conditions, the chemical heat storage material may not be able to be sufficiently dehydrated because the vehicle may stop before the exhaust gas temperature becomes sufficiently high. In this case, it becomes impossible to generate heat from the heat storage material during cold start of the vehicle, and it becomes difficult to activate the catalyst early.

Therefore, there is a need to provide an exhaust gas purification device that can regenerate the heat storage material at an appropriate timing.

In one embodiment, the first catalyst device is provided in an exhaust passage through which exhaust gas from an engine flows, and includes a heat storage material that generates heat through a hydration reaction and absorbs heat through a dehydration reaction; a second catalyst device that is provided in the exhaust passage on the downstream side of the first catalyst and reduces nitrogen oxides contained in exhaust gas; a reducing agent supply section that supplies a reducing agent to the second catalyst; and a first catalyst. The control device includes a resistance value measuring section that measures an electrical resistance value inside the device, a heating section that heats the first catalyst device, and a control device that controls the operation of the heating section. The first catalyst device is heated by the heating section when the electrical resistance value inside the device is lower than a predetermined threshold value.

Generally, as the hydration reaction of the heat storage material progresses, the electrical resistance value of the heat storage material decreases. In the exhaust gas purification device of the above aspect, the heating section heats the first catalyst device when the electrical resistance value of the first catalyst device including the heat storage material is lower than a predetermined threshold value, so that the hydration reaction progresses. The heat storage material can be dehydrated. Therefore, it becomes possible to regenerate the heat storage material into a state capable of generating heat at an appropriate timing.

In one embodiment, the heat storage material may include magnesium oxide. Magnesium oxide generates heat through a hydration reaction, producing magnesium hydroxide as a hydrate. On the other hand, the produced magnesium hydroxide absorbs heat through a dehydration reaction at high temperatures and returns to magnesium oxide. By using magnesium oxide having such properties as a heat storage material, the second catalyst device can be activated early, for example, during a cold start.

In one embodiment, the heating section may include an electric heater that heats the first catalytic device. In this embodiment, the first catalytic device can be easily heated by an electric heater.

In one embodiment, the first catalytic device may further include an oxidation catalyst. This oxidation catalyst can oxidize and purify harmful substances contained in exhaust gas.

In one embodiment, the heating section may include a fuel supply device that supplies fuel to the exhaust passage. By supplying fuel from the fuel supply device, the first catalyst device can be heated by the heat generated by the oxidation of the fuel.

In one embodiment, the resistance value measuring section may include a pair of electrodes attached to the first catalyst device, and may obtain an electrical resistance value between the pair of electrodes. In this embodiment, the state of the hydration reaction of the heat storage material can be estimated based on the electrical resistance value between the pair of electrodes.

According to one aspect and various embodiments of the present invention, the heat storage material can be regenerated at an appropriate timing.

1 is a diagram schematically showing an engine system including an exhaust purification device according to an embodiment. FIG. 1 is a diagram schematically showing an exhaust gas purification device. FIG. 2 is a cross-sectional view schematically showing the structure of an oxidation catalyst and a filter device. FIG. 7 is a diagram showing a change over time in the temperature of exhaust gas in an exhaust passage when a heat storage material generates heat. FIG. 6 is a diagram showing a change over time in the temperature of exhaust gas in an exhaust passage when a heat storage material absorbs heat. FIG. 3 is a diagram showing the relationship between the degree of hydration reaction of a heat storage material and the electrical resistance value. FIG. 3 is a diagram showing a change over time in the temperature of a selective reduction catalyst after a cold start. It is a figure showing an exhaust gas purification device concerning another embodiment.

Hereinafter, various embodiments will be described in detail with reference to the drawings. In each drawing, the same or equivalent parts are given the same reference numerals, and redundant explanations of the same or equivalent parts will be omitted.

FIG. 1 is a diagram schematically showing an engine system including an exhaust gas purification device according to an embodiment. The exhaust purification device 30 shown in FIG. 1 is mounted on a vehicle such as a truck, and purifies exhaust gas generated by the engine 10 of the vehicle. Note that in this specification, nitrogen monoxide (NO), nitrogen dioxide (NO ₂ ), and the like generated from the engine 10 are collectively referred to as nitrogen oxides (NOx).

As shown in FIG. 1, the engine system 1 shown in FIG. 1 includes an engine 10, a fuel supply device 20, and an exhaust purification device 30. The engine 10 is, for example, a diesel engine, and includes a plurality of cylinders 10a. An intake manifold 12 that supplies air into the plurality of cylinders 10a and an exhaust manifold 13 that discharges exhaust gas from the plurality of cylinders 10a are connected to the plurality of cylinders 10a.

An intake pipe 14 is connected to the intake manifold 12. A compressor 15 and an intercooler 16 are provided in the intake pipe 14 in this order from the upstream side of intake air. An introduction pipe 17 through which intake air flows is connected to the compressor 15. An air cleaner 18 is provided in the introduction pipe 17.

An exhaust pipe 25 is connected to the exhaust manifold 13 via a turbine 19 . The exhaust pipe 25 provides an exhaust passage 26 through which exhaust gas from the engine 10 flows (see FIG. 2). Turbine 19 is connected to compressor 15 via a connection shaft. The turbine 19 is rotated by the flow of exhaust gas discharged from the exhaust manifold 13 of the engine 10. The compressor 15 rotates as the turbine 19 rotates, takes in air (intake air) from the introduction pipe 17 , and sends compressed air to the intake pipe 14 . That is, the compressor 15 and the turbine 19 constitute a turbocharger. Air introduced into the intake pipe 14 passes through the intake manifold 12 and is introduced into the plurality of cylinders 10a. The air introduced into the plurality of cylinders 10a is compressed within each cylinder 10a, and fuel, which will be described later, is injected into the compressed air, so that the fuel is combusted within the cylinders 10a.

The fuel supply device 20 includes a fuel tank 21, a fuel pump 22, a fuel supply path 23, and a plurality of injectors 24. The fuel pump 22 pumps fuel such as light oil stored in the fuel tank 21 to the plurality of injectors 24 via the fuel supply path 23 . The plurality of injectors 24 are installed close to the plurality of cylinders 10a of the engine 10, and inject the fuel supplied from the fuel tank 21 into the plurality of cylinders 10a, respectively. Note that the amount of fuel injected from the plurality of injectors 24 to the engine 10 is controlled by a control device 40, which will be described later.

The fuel injected by the injector 24 is combusted within each cylinder 10a, causing a piston disposed within each cylinder 10a to reciprocate within the cylinder 10a. As the piston reciprocates, the crankshaft connected to the engine 10 rotates, and the propeller shaft of the vehicle rotates via the clutch. Exhaust gas discharged from the exhaust manifold 13 by combustion of fuel is discharged into the exhaust pipe 25.

The exhaust purification device 30 of one embodiment is a device that purifies harmful substances contained in exhaust gas, and includes an aftertreatment device 30A. The after-treatment device 30A is connected to the exhaust pipe 25. FIG. 2 is a cross-sectional view schematically showing the post-processing device 30A. As shown in FIG. 2, the after-treatment device 30A includes an oxidation catalyst (first catalyst device) 31, a filter device (first catalyst device) 32, a selective reduction catalyst (second catalyst device) 33, and an ammonia reduction catalyst. It is equipped with 34. The oxidation catalyst 31, the filter device 32, the selective reduction catalyst 33, and the ammonia reduction catalyst 34 are housed in a case 30c that constitutes the exhaust passage 26 together with the exhaust pipe 25, and are arranged in this order from the upstream side in the flow direction of the exhaust gas. ing.

As shown in FIG. 2, the oxidation catalyst 31 is provided upstream of the exhaust passage 26. The oxidation catalyst 31 oxidizes and purifies hydrocarbons (HC) and carbon monoxide (CO) contained in the exhaust gas from the engine 10.

The filter device 32 is arranged downstream of the oxidation catalyst 31 in the exhaust passage 26 . The filter device 32 is, for example, a DPF (Diesel Particulate Filter), and collects particulate matter (PM) contained in exhaust gas.

The selective reduction catalyst 33 is provided downstream of the filter device 32 in the exhaust passage 26 . The selective reduction catalyst 33 reduces NOx contained in the exhaust gas to nitrogen (N ₂ ) and water (H ₂ O) using, for example, ammonia (NH ₃ ) as a reducing agent. The selective reduction catalyst 33 contains, for example, copper zeolite or iron zeolite as a catalyst component. The selective reduction catalyst 33 is activated when the temperature is, for example, 180° C. or higher, and reduces NOx contained in the exhaust gas.

The ammonia reduction catalyst 34 is provided downstream of the selective reduction catalyst 33 in the exhaust passage 26 . The ammonia reduction catalyst 34 includes, for example, a zeolite catalyst, and oxidizes and purifies excess ammonia that has slipped (passed) through the selective reduction catalyst 33.

A reducing agent supply device 35 is provided between the filter device 32 and the selective reduction catalyst 33 in the flow direction of the exhaust gas. The reducing agent supply device 35 supplies a reducing agent to the selective reduction catalyst 33. For example, the reducing agent supply device 35 injects urea water into the exhaust passage 26 on the upstream side of the selective reduction catalyst 33. The injected urea water is decomposed into ammonia (NH ₃ ) by the heat of the exhaust gas, and is supplied to the selective reduction catalyst 33 together with the exhaust gas. The ammonia supplied to the selective reduction catalyst 33 reduces NOx contained in the exhaust gas on the selective reduction catalyst 33. Note that the reducing agent supply device 35 has a valve body that controls the injection amount of the reducing agent, and the opening degree of the valve body is controlled by a control device 40 that will be described later.

Further, the post-processing device 30A is provided with temperature sensors 36 and 37 that measure the temperature of the exhaust gas flowing inside the post-processing device 30A. The temperature sensor 36 is provided upstream of the oxidation catalyst 31 in the exhaust passage 26 and measures the temperature of the exhaust gas introduced into the oxidation catalyst 31. The temperature sensor 37 is provided between the filter device 32 and the selective reduction catalyst 33 in the flow direction of the exhaust gas, and measures the temperature of the exhaust gas introduced into the selective reduction catalyst 33. The temperature sensors 36 and 37 output information indicating the measured temperature of the exhaust gas to a control device 40, which will be described later.

The oxidation catalyst 31 and the filter device 32 will be explained in more detail. FIG. 3 is a cross-sectional view schematically showing the structure of the oxidation catalyst 31 and the filter device 32. As shown in FIG. 3, the oxidation catalyst 31 includes a carrier 51, a catalyst layer 52, and a heat storage material 53. The carrier 51 is made of, for example, cordierite or silicon carbide (SiC). The catalyst layer 52 is formed on the surface of the carrier 51 and contains a catalyst component such as platinum. This noble metal catalyst is an oxidation catalyst that oxidizes substances contained in exhaust gas. The heat storage material 53 is supported on the catalyst layer 52. The heat storage material 53 has the property of causing a hydration reaction and generating heat (heat of hydration) when it comes into contact with moisture contained in exhaust gas, and causing a dehydration reaction and absorbing heat when exposed to high-temperature exhaust gas. . Examples of the heat storage material 53 that causes the hydration reaction and dehydration reaction include alkaline earth metals, zeolite, lanthanum sulfate, and magnesium oxide.

Further, like the oxidation catalyst 31, the filter device 32 includes a carrier 51, a catalyst layer 52, and a heat storage material 53. The carrier 51 of the filter device 32 is made of, for example, a porous ceramic body in order to trap particulate matter contained in the exhaust gas.

As shown in FIG. 2, the post-processing device 30A further includes heaters 31h, 32h and a resistance value measuring section 38. The heaters 31h and 32h are, for example, electric heaters, and generate heat when electric power is applied from a power source (not shown), causing a dehydration reaction to occur in the heat storage material 53 supported on the oxidation catalyst 31 and the filter device 32. The heaters 31h and 32h function as heating units that heat the oxidation catalyst 31 and the filter device 32, respectively.

The resistance value measuring section 38 includes a pair of electrodes 38a, a pair of electrodes 38b, and a resistance value measuring device 38c. The pair of electrodes 38a is placed inside the oxidation catalyst 31, and the pair of electrodes 38b is placed inside the filter device 32. The resistance value measuring device 38c is electrically connected to the pair of electrodes 38a and the pair of electrodes 38b, and measures the electric resistance value between the pair of electrodes 38a and the electric resistance value between the pair of electrodes 38b. The measured electric resistance value of the tube between the pair of electrodes 38a and the electric resistance value between the pair of electrodes 38b are the electric resistance values of the oxidation catalyst 31 and the filter device 32. The resistance value measuring device 38c outputs the measured electrical resistance value to a control device 40, which will be described later.

As described above, the heat storage material 53 supported on the oxidation catalyst 31 and the filter device 32 comes into contact with water contained in the exhaust gas from the engine 10 to cause a hydration reaction. The heat storage material 53 generates heat due to this hydration reaction, and heats the exhaust gas passing through the oxidation catalyst 31 and the filter device 32. FIGS. 4(a) and 4(b) show an example of changes over time in the temperature of the exhaust gas measured by the temperature sensors 36 and 37, respectively, when the heat storage material 53 generates heat due to the hydration reaction. As shown in FIGS. 4(a) and 4(b), when the heat storage material 53 generates heat due to a hydration reaction with moisture contained in the exhaust gas, the exhaust gas measured between the filter device 32 and the selective reduction catalyst 33 The temperature increase Δt _B per unit time is larger than the temperature rise Δt _A per unit time of the exhaust gas measured on the upstream side of the oxidation catalyst 31 . That is, by heating the heat storage material 53, the temperature of the exhaust gas introduced into the selective reduction catalyst 33 increases, and the selective reduction catalyst 33 is heated.

On the other hand, the heat storage material 53 undergoes a dehydration reaction when exposed to high temperature exhaust gas. When a dehydration reaction occurs in the heat storage material 53, the heat storage material 53 absorbs the heat of the exhaust gas flowing through the oxidation catalyst 31 and the filter device 32. FIGS. 5A and 5B show an example of changes over time in the temperature of the exhaust gas measured by the temperature sensors 36 and 37, respectively, when the heat storage material 53 absorbs heat due to the dehydration reaction. As shown in FIGS. 5(a) and 5(b), when a dehydration reaction occurs in the heat storage material 53, the temperature of the exhaust gas increases per unit time Δt measured between the filter device 32 and the selective reduction catalyst 33. _B becomes smaller than the temperature rise Δt _A of the exhaust gas per unit time measured upstream of the oxidation catalyst 31.

FIG. 6 shows the relationship between the degree of progress of the hydration reaction of the heat storage material 53 and the electrical resistance value. As shown in FIG. 6, when the heat storage material 53 undergoes a hydration reaction, water molecules are added to the heat storage material 53, thereby reducing the electrical resistance value. For example, when magnesium oxide is used as the heat storage material 53, magnesium hydroxide is produced by a hydration reaction. Magnesium hydroxide has a lower electrical resistance value than magnesium oxide. Therefore, when the amount of magnesium hydroxide present inside the oxidation catalyst 31 or the filter device 32 increases due to the hydration reaction, the electrical resistance value of the oxidation catalyst 31 or the filter device 32 decreases. Conversely, when magnesium hydroxide is dehydrated and the amount of magnesium oxide present inside the oxidation catalyst 31 or the filter device 32 increases, the electrical resistance value of the oxidation catalyst 31 or the filter device 32 increases.

Referring again to FIG. As shown in FIG. 1, the exhaust purification device 30 further includes a control device 40. The control device 40 is an electronic control unit that includes a CPU [Central Processing Unit], a ROM [Read Only Memory], a RAM [Random Access Memory], a CAN [Controller Area Network] communication circuit, etc., and controls the overall operation of the exhaust purification device 30. control. The control device 40 realizes various functions described later by, for example, loading a program stored in a ROM into a RAM and executing the program loaded into the RAM by a CPU.

The control device 40 is communicably connected to, for example, heaters 31h and 32h, a reducing agent supply device (reducing agent supply section) 35, temperature sensors 36 and 37, and a resistance value measuring section 38. For example, the control device 40 acquires temperature information of exhaust gas measured by the temperature sensors 36 and 37, and controls the amount of reducing agent supplied from the reducing agent supply device 35 based on the acquired temperature information. For example, when the temperature of the exhaust gas measured by the temperature sensor 37 reaches the activation temperature (for example, 180° C.), the control device 40 controls the reducing agent supply device 35 to inject urea water.

Further, the control device 40 controls the operation of the heaters 31h and 32h based on the electrical resistance values of the oxidation catalyst 31 and the filter device 32 measured by the resistance value measuring section 38. For example, when the electrical resistance value of the oxidation catalyst 31 measured by the resistance value measurement unit 38 is lower than a predetermined threshold value, the control device 40 heats the oxidation catalyst 31 by applying a voltage to the heater 31h. Similarly, when the electrical resistance value of the filter device 32 measured by the resistance value measurement unit 38 is lower than a predetermined threshold value, the control device 40 applies a voltage to the heater 32h to heat the filter device 32.

Here, when the electrical resistance value of the oxidation catalyst 31 or the filter device 32 is lower than a predetermined threshold value, the hydration reaction of the heat storage material 53 supported on the oxidation catalyst 31 or the filter device 32 is progressing, and the electric resistance value is lower than the predetermined threshold value. It is assumed that the patient is unable to generate heat. Therefore, the control device 40 dehydrates the heat storage material 53 supported on the oxidation catalyst 31 and the filter device 32 by heating the oxidation catalyst 31 and the filter device 32 with the heaters 31h and 32h. As a result, the heat storage material 53 is regenerated into a state capable of generating heat through a hydration reaction.

On the other hand, if the electrical resistance values of the oxidation catalyst 31 and the filter device 32 are greater than or equal to the predetermined threshold, the hydration reaction of the heat storage material 53 supported on the oxidation catalyst 31 and the filter device 32 has not progressed, and heat generation is possible. It is assumed that the state is Therefore, the control device 40 stops the operation of the heaters 31h and 32h when the electrical resistance values of the oxidation catalyst 31 and the filter device 32 measured by the resistance value measuring section 38 are equal to or higher than a predetermined threshold value.

Next, the effects of the exhaust gas purification device 30 will be described in more detail using examples and comparative examples. In the example, the exhaust purification device 30 shown in FIG. 2 was used to measure the change over time in the temperature of the selective reduction catalyst 33 when the engine 10 was cold started. On the other hand, in a comparative example, the same device as the exhaust purification device 30 except that it did not include the heat storage material 53 was used to measure the change over time in the temperature of the selective reduction catalyst 33 when the engine 10 was cold started. FIG. 7 shows changes over time in the temperature of the selective reduction catalyst 33 measured in Examples and Comparative Examples. As shown in FIG. 7, in the exhaust purification device 30, when the engine 10 is cold-started, the heat storage material 53 supported on the oxidation catalyst 31 and the filter device 32 reacts with moisture contained in the exhaust gas to generate heat. It was confirmed that the time required for activation of the selective reduction catalyst 33 could be shortened compared to the example.

Next, an exhaust gas purification device according to another embodiment will be described. Below, differences from the exhaust gas purification device 30 shown in FIG. 2 will be mainly explained, and duplicate explanations will be omitted.

FIG. 8 is a diagram schematically showing an exhaust purification device 50 according to an embodiment shown separately. The exhaust gas purification device 50 includes an aftertreatment device 30B. The aftertreatment device 30B is different from the aftertreatment device 30A shown in FIG. 2 in that it includes a fuel supply device 39 instead of the heaters 31h and 32h.

The fuel supply device 39 is provided upstream of the oxidation catalyst 31 in the exhaust passage 26 and injects fuel into the exhaust passage 26 . Fuel injected into the exhaust passage 26 from the fuel supply device 39 is added to the exhaust gas and supplied to the oxidation catalyst 31 and the filter device 32.

When the electrical resistance values of the oxidation catalyst 31 and the filter device 32 measured by the resistance value measurement unit 38 are lower than a predetermined threshold value, the control device 40 of the exhaust purification device 50 controls the fuel supply device 39 to reduce the exhaust gas. Fuel is injected into the passage 26. The fuel supplied to the oxidation catalyst 31 and the filter device 32 is oxidized by the catalyst component contained in the catalyst layer 52, and the heat storage material 53 is heated by the heat generated by the oxidation reaction. As a result, the heat storage material 53 is dehydrated and regenerated into a state capable of generating heat through a hydration reaction. In this embodiment, the fuel supply device 39 functions as a heating section that heats the oxidation catalyst 31 and the filter device 32.

As explained above, the above-described exhaust gas purification devices 30 and 50 include the oxidation catalyst 31 including the heat storage material 53 and the filter device 32. When the exhaust gas containing moisture is supplied to the oxidation catalyst 31 and the filter device 32, the heat storage material 53 undergoes a hydration reaction and generates heat. As a result, the exhaust gas passing through the oxidation catalyst 31 and the filter unit is heated, so that the time required for the selective reduction catalyst 33 to become activated when the engine 10 is cold-started, for example, can be shortened.

Furthermore, the electric resistance value of the heat storage material 53 supported on the oxidation catalyst 31 and the filter unit decreases as the hydration reaction progresses. Therefore, in the exhaust gas purification devices 30 and 50, when the electrical resistance values of the oxidation catalyst 31 and the filter device 32 measured by the resistance value measuring section 38 are lower than a predetermined threshold value, the control device 40 controls the heaters 31h and 32h. Alternatively, the oxidation catalyst 31 and the filter device 32 are heated by operating the fuel supply device 39. As a result, the heat storage material 53 supported on the oxidation catalyst 31 and the filter device 32 is heated and dehydrated. As a result, the heat storage material 53 is regenerated into a state capable of generating heat through a hydration reaction. In this way, in the above-described exhaust purification devices 30 and 50, the heat storage material 53 is regenerated at an appropriate timing, so that the selective reduction catalyst 33 can be heated again when the engine 10 is cold started, for example.

Although exhaust gas purification devices according to various embodiments have been described above, various modifications can be made without being limited to the embodiments described above and without changing the gist of the invention.

For example, in the exhaust purification device 50 shown in FIG. 8, the oxidation catalyst 31 and the filter device 32 are heated by injecting fuel from the fuel supply device 39 attached to the exhaust pipe 25; Fuel may also be supplied. For example, the control device 40 of the exhaust purification device 50 performs main injection that injects fuel into the cylinder 10a to obtain engine output when the electrical resistance values of the oxidation catalyst 31 and the filter device 32 are lower than a predetermined threshold value. , the fuel supply device 20 is controlled so that post injection, in which fuel is additionally injected, is performed after main injection. The unburned fuel supplied into the cylinder 10a by post injection is supplied to the oxidation catalyst 31 and the filter device 32 while being added to the exhaust gas. The fuel supplied to the oxidation catalyst 31 and the filter device 32 is oxidized by the catalyst component contained in the catalyst layer 52, and the heat storage material 53 is heated by the heat generated by the oxidation reaction. As a result, the heat storage material 53 is dehydrated and regenerated into a state capable of generating heat.

Further, in the above embodiment, the oxidation catalyst 31 and the filter device 32 include the heat storage material 53, but the heat storage material 53 may be included in only one of the oxidation catalyst 31 and the filter device 32. Furthermore, the various embodiments described above can be combined to the extent that no contradiction occurs. For example, the exhaust purification device according to one embodiment may include both the heaters 31h and 32h and the fuel supply device 39.

DESCRIPTION OF SYMBOLS 10... Engine, 20, 39... Fuel supply device, 26... Exhaust passage, 30, 50... Exhaust purification device, 31... Oxidation catalyst (first catalyst device), 31h, 32h... Heater (heating part), 32... Filter device (first catalyst device), 33... selective reduction catalyst (second catalyst device), 38... resistance value measuring section, 38a, 38b... pair of electrodes, 40... control device, 53... heat storage material.

Claims (6)

A first catalytic device installed in an exhaust passage through which exhaust gas from the engine flows, the first catalytic device including a heat storage material that generates heat through a hydration reaction and absorbs heat through a dehydration reaction;
a second catalyst device that is provided in the exhaust passage on the downstream side of the first catalyst and reduces nitrogen oxides contained in the exhaust gas;
a reducing agent supply unit that supplies a reducing agent to the second catalyst;
a resistance value measuring unit that measures an electrical resistance value of the first catalyst device;
a heating section that heats the first catalyst device;
a control device that controls the operation of the heating section;
Equipped with
The control device is an exhaust purification device in which the heating section heats the first catalyst device when an electrical resistance value of the first catalyst device is lower than a predetermined threshold value. The exhaust purification device according to claim 1, wherein the heat storage material contains magnesium oxide. The exhaust gas purification device according to claim 1 or 2, wherein the heating section includes an electric heater that heats the first catalyst device. The exhaust gas purification device according to any one of claims 1 to 3, wherein the first catalyst device further includes an oxidation catalyst. The exhaust gas purification device according to claim 4, wherein the heating section includes a fuel supply device that supplies fuel to the exhaust passage upstream of the first catalyst device. The resistance value measurement unit according to any one of claims 1 to 5 has a pair of electrodes attached to the first catalyst device, and obtains an electrical resistance value between the pair of electrodes. Exhaust purification device.

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