WO2013005335A1

WO2013005335A1 - Exhaust purification apparatus for internal combustion engine

Info

Publication number: WO2013005335A1
Application number: PCT/JP2011/065633
Authority: WO
Inventors: 優一祖父江; 中山　茂樹; 寛真西岡; 克彦押川; 佳久塚本; 寛大月; 大地今井; 潤一松尾; 菅原　康
Original assignee: トヨタ自動車株式会社
Priority date: 2011-07-01
Filing date: 2011-07-01
Publication date: 2013-01-10

Abstract

Provided is an exhaust purification apparatus for an internal combustion engine with a DPF disposed in the exhaust system of the internal combustion engine, such that accumulation of ash in the DPF can be suppressed, and increases in pressure loss and PM regeneration temperature as well as a decrease in fuel efficiency can be suppressed over a long period. A surface of the DPF is coated with a solid acid with an acid strength greater than the acid strength of SO₃ and smaller than the acid strength of SO₄. Ash regeneration operation control for removing the ash accumulated in the DPF by making particles of ash finer through control for increasing the temperature of the DPF and air-fuel ratio control for the atmosphere within the DPF is performed on the basis of the amount of accumulated ash acquired by an ash accumulation amount acquisition means.

Description

Exhaust gas purification device for internal combustion engine

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

In order to reduce the number of particles of particulate matter (hereinafter referred to as “PM”) in the exhaust gas of the internal combustion engine, a diesel particulate filter (hereinafter referred to as “DPF”) is installed in the exhaust gas passage of the internal combustion engine, Generally, PM in exhaust gas is collected and removed.

In this case, since the PM collected in the DPF gradually accumulates, regeneration (hereinafter referred to as “PM regeneration”) is performed periodically or by detecting a decrease in the performance of the DPF and burning and removing the PM collected in the DPF. ”).

PM regeneration operation is usually performed by heating the DPF while supplying a reducing agent such as hydrocarbon (HC) to the DPF.

Various improvements have been proposed to improve the performance and reduce the cost of the PM regeneration operation that collects PM in the exhaust gas using the DPF and burns and removes the PM collected in the DPF. Has been.

However, in the conventional DPF, if the use of the DPF is continued, even if the PM regeneration operation is performed, the pressure loss of the DPF gradually increases, and if the PM regeneration temperature is not gradually increased, sufficient regeneration is achieved. There is a problem that it will not be performed, and fuel consumption deteriorates. This problem is caused by the accumulation of ash inside the DPF.

Ash is generated when the engine oil mixed in the cylinder of the engine burns, and the generated ash particles are covered with PM in the DPF. The ash particles covered with PM are exposed to high temperature conditions during the PM regeneration operation in the DPF, and the PM covering the ash particles is burned and removed. Ash deposition occurs because the ash particles are agglomerated and increased in size by further applying heat to the ash particles from which the PM has been burned and removed.

However, there is no effective solution to the accumulation of ash so far, and in order to minimize the influence of the accumulation of ash on the DPF, for example, a large-capacity DPF is installed in advance. Measures were taken.

That is, the improvement to the conventional DPF and the improvement to the regeneration operation of the DPF are intended to improve the collection efficiency of the DPF and improve the performance of the PM regeneration operation, and not to the accumulation of ash. As an object for improving the performance of the PM regeneration operation, for example, there is an invention disclosed in Patent Document 1, and Patent Document 1 shows a configuration of a DPF capable of burning PM at a relatively low temperature. Yes.

The structure of the DPF disclosed in Patent Document 1 is characterized in that, in the DPF and the exhaust gas purification method using the DPF, a catalyst made of a solid superacid having an active metal supported on the DPF is held on the filter surface. is there.

That is, the invention of Patent Document 1 reduces the combustion temperature of PM with a solid super strong acid carrying an active metal, and regenerates DPF at a lower temperature than before, preferably continuously, and CO, HC, NO, NO ₂ can be removed at the same time.

Therefore, the invention of Patent Document 1 is intended to improve the performance of the PM regeneration operation, and does not correspond to the accumulation of ash. If the use of the DPF is continued, the PM regeneration operation is performed. However, this does not solve the problem that the pressure loss of the DPF gradually increases, and unless the PM regeneration temperature is gradually increased, sufficient regeneration cannot be performed and the fuel consumption deteriorates.

Further, as a disclosure of a catalyst structure similar to the invention of Patent Document 1, there is an invention of Patent Document 2, which is selected from platinum, palladium and rhodium as a catalyst for a diesel engine exhaust gas purification device. By using a catalyst having at least one kind of noble metal and a solid super strong acid, it is possible to purify SOF (Soluable Organic Fraction), unburned hydrocarbons, etc. contained in particulate matter in diesel engine exhaust gas from a low temperature range. Further, it is described that the effect of suppressing oxidation of sulfur dioxide is exhibited even in a high temperature range, and the invention of Patent Document 2 aims at an effect similar to the invention of Patent Document 1 and does not relate to DPF. Therefore, it does not correspond to the accumulation of ash on the DPF. If the use of the DPF is continued, the pressure loss of the DPF gradually increases and the PM regeneration temperature gradually increases even if the PM regeneration operation is performed. If this is not done, it will not solve the problem that sufficient regeneration will not be performed and fuel consumption will deteriorate.

JP 2006-289175 A Japanese Patent Laid-Open No. 10-033985

The present invention can advantageously perform the ash regeneration operation according to the amount of ash deposited on the DPF, suppress the ash accumulation on the DPF, increase the pressure loss over a long period, increase the PM regeneration temperature, An object of the present invention is to provide an exhaust emission control device for an internal combustion engine that can suppress a reduction in fuel consumption.

That is, the present invention provides a preferable means for obtaining the amount of ash deposited on the DPF in a configuration in which the ash deposited on the DPF is discharged with a reduced particle size and the DPF is regenerated (hereinafter referred to as “ash regeneration”). This configuration provides an epoch-making DPF that has an advantageous effect of suppressing an increase in pressure loss, an increase in PM regeneration temperature, and a reduction in fuel consumption over a long period of time.

According to the present invention, the accumulated ash can be discharged with a reduced particle size. As a further effect, a DPF that is smaller than the conventional DPF can be used from the beginning of the installation of the DPF. Not only cost reduction, but also energy cost of PM regeneration operation can be reduced. In addition, the fact that a small DPF can be used means that the space for mounting the DPF on the vehicle can be reduced, and the weight of the vehicle on which the DPF is mounted can be reduced.

The inventor of the present application studied the problem of ash accumulation inside the DPF, analyzed the cause of ash accumulation, and the main components of ash were calcium (Ca) contained in engine oil and SOx in exhaust gas. It was found that ash is ion-bonded, CaSO ₄ is the main component, and Ca salt has a high melting point, so that in the exhaust gas, ash flows into the DPF as a solid and aggregates to increase the particle size.

Furthermore, the inventors of the present application have confirmed by experiments that the size of ash is on the order of submicrons, and that the ash slips through the DPF when the ash size is reduced to the order of nanomicrons.

Furthermore, the inventors of the present application, a CaSO ₄ that large grain size to the size of submicron, when placed in a reducing atmosphere, it becomes SO ₃ SO ₄ of CaSO ₄ is reduced, the bond between Ca weakened, At this time, if an acid stronger than SO ₃ is present on the surface of the DPF, the bond between Ca and SO _{3 in} the CaSO ₃ is cleaved, and the Ca ions are stronger than the SO ₃ on the surface of the DPF. It was confirmed by experiments that the atoms were dispersed and bonded in an atomic form.

Furthermore, the inventors of the present application, Ca ions associated with stronger acid than SO ₃ on the surface of the DPF is different from the stronger acid than SO ₃ on the surface of the DPF, if a stronger acid is present in the atmosphere It was confirmed by an experiment that it binds to a stronger acid in the atmosphere, is released from the DPF, and passes through the DPF to be discharged.

To summarize the above, if the acid strength of this acid is stronger than SO ₃ on the surface of the DPF and the acid strength of this acid is stronger than SO ₃ and weaker than SO ₄ , the particle size will be submicron. CaSO ₄ deposited in the DPF turned into, in a reducing atmosphere, becomes CaSO ₃ SO ₄ is reduced in CaSO _4, Ca ions CaSO ₃ is bonded with the acid on the surface of the DPF, on the surface of the DPF Disperse in atomic form. Next, if SO ₄ is present in the atmosphere, the Ca on the surface of the DPF combines with the SO _{4 in} the atmosphere and becomes sub-nanometer-sized CaSO ₄ and is released from the DPF.

When the exhaust gas atmosphere is a stoichiometric or rich atmosphere, it is the above-described reducing atmosphere, and when it is a lean atmosphere, the lean atmosphere contains SO ₄ . Therefore, if control for making the atmosphere stoichiometric or rich and control for making the lean atmosphere next are performed on the above-mentioned DPF, ash Ca ions deposited on the DPF in the stoichiometric or rich atmosphere are converted to DPF. Then, in a lean atmosphere, Ca on the surface of the DPF is combined with SO ₄ in the lean atmosphere and released from the DPF, and the fine particle size is reduced to a sub-nanometer size. CaSO ₄ is converted to pass through the DPF and discharged.

That is, in the above process, the first CaSO ₄ having a large particle size of submicron and deposited on the DPF is finally released again from the DPF as CaSO _4. No. ₄ is reduced in size to a sub-nanometer size and passes through the DPF and is discharged.

By the way, when performing the above ash regeneration operation, the increase in the pressure loss of the DPF is usually detected and the timing of the ash regeneration operation is determined, but the increase in the pressure loss of the DPF includes the increase in the pressure loss due to PM accumulation. Therefore, in order to know the state of ash deposition, for example, a procedure is required in which the relationship between ash deposition and PM deposition is obtained separately, and the ash deposition is obtained separately based on this relationship. is doing.

Therefore, an ash regeneration operation can be advantageously performed by providing a means for directly knowing the ash accumulation state.

According to the first aspect of the present invention, there is provided an exhaust purification device for an internal combustion engine in which a DPF is disposed in an exhaust system of the internal combustion engine, wherein the DPF is a DPF whose surface is coated with a solid acid, The acid strength is larger than the acid strength of SO ₃ and smaller than the acid strength of SO _4. Further, the ash regeneration operation control for removing the ash deposited in the DPF and the amount of ash deposited in the DPF are as follows. An ash accumulation amount acquisition means, wherein the control of the ash regeneration operation includes control for increasing the temperature of the DPF, and control of the air-fuel ratio of the atmosphere in the DPF, and the air-fuel ratio of the atmosphere in the DPF This control is to first change the stoichiometric or air-fuel ratio rich atmosphere and then change to the air-fuel ratio lean atmosphere during the control to increase the temperature of the DPF. Based on the amount of the deposited ash, which is characterized by controlling the ash regeneration operation, the exhaust gas purification apparatus is provided for an internal combustion engine.

That is, according to the first aspect of the present invention, there is provided a preferable ash accumulation amount acquisition means for acquiring the accumulation amount of ash accumulated in the DPF, and the relationship between the ash accumulation and the PM accumulation is obtained by the ash accumulation amount acquisition means. Without using it, the amount of ash deposited can be determined directly. Therefore, the ash regeneration operation can be advantageously performed according to the amount of ash deposited on the DPF, and the ash is completely removed, suppressing an increase in pressure loss, an increase in PM regeneration temperature, and a decrease in fuel consumption over a long period of time. An exhaust emission control device for an internal combustion engine is provided.

According to the second aspect of the present invention, the ash deposition amount acquisition means comprises: a NOx amount detection means for detecting the NOx amount in the exhaust gas flowing out from the DPF; and an ammonia supply means for supplying an ammonia component to the DPF. , Detecting the NOx amount in the exhaust gas flowing out from the DPF, then supplying the ammonia component to the DPF, and further detecting the NOx amount in the exhaust gas flowing out from the DPF after supplying the ammonia component to the DPF, The amount of ash deposited on the DPF is acquired based on a difference between the NOx amount before supplying the ammonia component to the DPF and the NOx amount after supplying the ammonia component. An exhaust emission control device for an internal combustion engine is provided.

That is, according to the second aspect of the present invention, preferred ash deposition amount acquisition means for acquiring the accumulation amount of ash deposited in the DPF is provided, and the ash deposition amount acquisition means utilizes ammonia to generate an acid point of the solid acid. Of these, the acid points that are not bonded to Ca of ash are counted, so that the ash accumulation amount can be directly measured by this ash accumulation amount acquisition means without using the relationship between ash accumulation and PM accumulation. Can be sought. Therefore, the ash regeneration operation can be advantageously performed according to the amount of ash deposited on the DPF, and the ash is completely removed in the ash regeneration operation, increasing the pressure loss over a long period of time, increasing the PM regeneration temperature, and fuel consumption An exhaust emission control device for an internal combustion engine that can suppress the reduction of the engine is provided.

According to the invention described in each claim, an ash regeneration configuration is provided, and the ash regeneration operation can be advantageously performed according to the amount of accumulated ash, and the ash is completely removed in the ash regeneration operation, There is a common effect of providing an exhaust purification device for an internal combustion engine that can suppress an increase in pressure loss, an increase in PM regeneration temperature, and a decrease in fuel consumption over a long period of time.

FIG. 1 is a flowchart illustrating a schematic configuration of an embodiment of control when the present invention is applied to an exhaust gas purification apparatus for an internal combustion engine.
FIG. 2 is a diagram for explaining a schematic configuration of an embodiment of apparatus arrangement when the present invention is applied to a DPF.
FIG. 3 is a diagram for explaining the principle of control of the present invention.
FIG. 4 is a diagram for explaining the principle of the present invention.
FIG. 5 is a diagram for explaining the principle of the present invention.
FIG. 6 is a diagram for explaining the principle of the present invention.
FIG. 7 is a diagram for explaining the principle of control of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the plurality of accompanying drawings, the same or corresponding members are denoted by the same reference numerals.

FIG. 2 is a diagram showing a basic configuration of the present invention. A solid acid corresponding to an acid strength of SO ₃ or more and SO ₄ or less is formed on the surface of DPF 2, specifically, on the surface of the DPF substrate of DPF 2. Apply. Exhaust gas from the internal combustion engine 1 is guided to the DPF 2, PM in the exhaust gas is collected and removed by the DPF 2, and the exhaust gas from which the PM has been removed is discharged. The outlet of the DPF is provided with NOx amount detection means 50 for detecting the NOx amount in the exhaust discharged from the DPF2. Since the PM collected in the DPF gradually accumulates, PM regeneration operation is performed periodically or by detecting a decrease in the performance of the DPF and burning and removing the PM collected in the DPF.

However, when the PM regeneration operation is repeatedly performed, as shown in FIG. 4, the ash 3 accumulates in the DPF, and even when the PM regeneration operation is performed, the pressure loss of the DPF gradually increases, and the PM regeneration temperature is increased. There is a problem in that sufficient regeneration cannot be performed unless the value is gradually increased, and fuel consumption deteriorates.

In the present invention, as shown in FIG. 5, the ash 3 deposited in the DPF is reduced in size, so that the particles reduced in size pass through the filter gap of the DPF and are discharged together with the exhaust gas.

The present invention will be described in detail with reference to FIG. 6. First, as shown in FIG. 6A, when the DPF is continuously used, the ash particles generated by the engine and covered with the PM are regenerated into the PM within the DPF. Ashes 3 exposed to high temperature conditions during operation are burned and removed from the PM particles covering the ash particles, and heat is further applied to the ash particles from which the PM has been burned and removed to aggregate the ash particles, thereby increasing the particle size. accumulate. At this time, the particles of ash 3 are mainly composed of calcium sulfate (CaSO ₄ ). However, when the atmosphere is a reducing atmosphere, for example, a stoichiometric atmosphere or a rich atmosphere in FIG. It is reduced to calcium (CaSO ₃ ). Therefore, when the solid acid 6 having an acid strength of SO ₃ or more is present on the DPF substrate 5, as shown in FIG. 6B, calcium (Ca) in the ash particles is stronger than SO _3. It binds to solid acid 6 which is an acid, and ash 3 decomposes. At this time, Ca is dispersed atomically on the solid acid 6. Next, when Ca dispersed atomically on the solid acid 6 is exposed to an atmosphere containing SO ₄ , for example, the exhaust from the internal combustion engine usually contains SOx, and the lean atmosphere in order to sO ₄ is contained in a large amount, when exposed to a lean atmosphere, as shown in FIG. 6 (c), Ca dispersed in atomic form on the solid acid 6, sO ₄ is stronger acid than the solid acid 6 And is sulfated again to form calcium sulfate (CaSO ₄ ), which is released from the solid acid. Calcium sulfate (CaSO ₄ ) at this time is a particle having a fine particle size of 1 nanometer or less, and the fine particle size passes through the DPF as an aerosol. The accumulated ash is removed.

In this case, the acid strength of the solid acid 6 applied on the DPF substrate 5 must be larger than the acid strength of SO ₃ and smaller than the acid strength of SO ₄ . When the acid strength of the solid acid 6 is equal to or lower than the acid strength of SO ₃ , Ca in the ash particles reduced to CaSO ₃ does not bind to the solid acid 6 and therefore ash 3 does not decompose, and This is because when the solid acid 6 is a super strong acid that is equal to or higher than the acid strength of SO ₄ , even if SO ₄ exists in the atmosphere, Ca is not released from the solid acid 6.

Therefore, a solid acid corresponding to an acid strength of SO ₃ or more and SO ₄ or less is applied on the DPF base 5 and the air-fuel ratio of the atmosphere in the DPF is set to the stoichiometric or air-fuel ratio first during the ash regeneration operation. When control is performed so as to change to a rich atmosphere and then change to an air-fuel ratio lean atmosphere, the ash having a large particle size in the DPF becomes ash particles having a fine particle size, passes through the DPF, and is discharged.

By the way, when performing the ash regeneration operation as described above, it is necessary to grasp the ash accumulation state.

In order to grasp the accumulation state of ash, usually, an increase in the pressure loss of the DPF is detected and the timing of the ash regeneration operation is determined. However, the increase in the pressure loss of the DPF includes the increase in the pressure loss due to PM deposition. Therefore, in order to know the state of ash deposition, for example, a relationship between ash deposition and PM deposition is separately obtained. Based on this relationship, a procedure such as separately obtaining ash deposits is required.

FIG. 7 is a diagram for explaining how the ash accumulation state is grasped in the present invention.

The acid point of the solid acid 6 has a property of binding to ammonia. Therefore, as shown in FIG. 7 (a), if there is an acid point 62 of the solid acid 6 that is not bonded to Ca, and ammonia is supplied thereto, the ammonia is added to the acid point 62 to which Ca is not bonded. Join. Therefore, if the amount of bound ammonia can be grasped, the ash accumulation state can be grasped, and the case where the ammonia is not bound may be determined as the ash accumulation upper limit.

On the other hand, NOx has a property of reacting with ammonia bonded to the acid point 62 and decomposing into nitrogen (N ₂ ) and water (H ₂ O). That is, as shown in FIG. 7B, 1 mol of NOx reacts with 1 mol of ammonia bonded to the acid sites 62 and decomposes into nitrogen (N ₂ ) and water (H ₂ O). Therefore, in order to grasp the amount of ammonia bound to the acid point, a change in the amount of NOx flowing out from the DPF before and after supplying ammonia to the DPF is detected, and the amount of NOx reduction is grasped. . If it does in this way, the amount of ammonia couple | bonded with the acid point can be grasped | ascertained from the decrease amount of NOx, and the accumulation state of ash can be grasped | ascertained.

Therefore, when the NOx reduction amount at the DPF outlet becomes zero, the acid point 62 is saturated with Ca, and when the NOx reduction amount is close to zero, the upper limit of ash deposition is determined. Thus, when the ash regeneration control is performed, it is possible to configure an exhaust gas purification apparatus for an internal combustion engine having a DPF in which the ash is completely removed and the performance does not deteriorate forever.

FIG. 1 is a flowchart in the case where the ash accumulation state is grasped by the above-described means and the ash regeneration operation is controlled.

First, in step 100 of FIG. 1, the ash regeneration operation state before, the amount of NOx flowing out from DPF, detected by NOx detection means 50 of FIG. 2, which is referred to as _{Y 0.} Next, in step 200, the atmosphere in the DPF is changed to an air-fuel ratio rich atmosphere, and ammonia is simultaneously supplied from the ammonia supply means. Further, the routine proceeds to step 300, where the air-fuel ratio rich operation is terminated, and the NOx detection means 50 starts detecting the NOx amount Y flowing out from the DPF, and starts integrating the detected values. Then, the process proceeds to step 400 to continue the detection and integration of NOx until Y = _{Y 0.} If a Y = _{Y 0,} the process proceeds to step 500, the total amount of NOx accumulated in the DPF until Y = _{Y 0,} and acid site recovery amount Ar.

FIG. 3 shows the above control as the detected value of the NOx detecting means. In FIG. 3, the atmosphere in the DPF is changed to an air-fuel ratio rich atmosphere in Step 200 of FIG. 1, and the time range for supplying ammonia from the ammonia supply means is indicated by H. In Step 300 of FIG. Exit fuel ratio rich operation, the NOx detection means 50 detects a NOx amount Y which passes through the DPF, the time to begin accumulating NOx amount is indicated by _{T 0.} Further, the time when it becomes Y = _{Y 0} at step 400, shown in _{T 1,} the total amount of NOx stored in the total i.e. DPF of NOx that has been accumulated until the Y = _{Y 0,} indicated by Nc ing. That is, the total amount Nc of the NOx accumulated in the DPF until Y = _{Y 0} _becomes that the _(Y 0 -Y), was integrated from time _{T 0} to _{T 1.} The acid point recovery amount Ar = Nc.

Returning to FIG. 1, the process further proceeds to step 600, where it is determined whether or not the acid point recovery amount Ar has become smaller than the threshold value, that is, whether or not the acid point has become close to saturation due to Ca. When the acid point recovery amount Ar becomes smaller than the threshold value, it is determined that the acid point is close to saturation due to Ca, and the process proceeds to step 700 where the environment in the DPF is set to the air-fuel ratio lean and the acid point is set. The bound Ca is released as CaSO ₄ having a reduced particle size, and the ash regeneration operation is terminated. If the acid point recovery amount Ar is not smaller than the threshold value, the acid point is not yet saturated with Ca, so the process proceeds to Step 800, where the environment in the DPF is set as a reducing atmosphere and the temperature of the DPF is increased. The ash is reduced from CaSO 4 having a large particle size to CaSO 3, and the binding reaction of Ca to the acid point is further advanced to complete this control cycle.

As described above, when the ash accumulation amount is obtained by the ash accumulation amount acquisition means of the present invention and the ash regeneration operation is controlled, the ash accumulation amount can be directly grasped, and the ash accumulation amount is saturated. Thus, the ash regeneration operation can be appropriately performed. As a result, the ash is completely removed, an increase in pressure loss, an increase in the PM regeneration temperature, and a decrease in fuel consumption can be suppressed over a long period of time, and further, ash accumulation can be efficiently suppressed. An exhaust purification device for an internal combustion engine is provided.

Therefore, according to the present invention, an exhaust gas purification apparatus for an internal combustion engine having a DPF whose performance does not deteriorate indefinitely can be configured, and the present invention can dramatically improve the performance of the DPF over a long period of time. There is an advantageous effect. Furthermore, as a further effect that accompanies this effect, a DPF smaller than the conventional one can be used from the beginning of the installation of the DPF, which not only reduces the manufacturing cost of the DPF but also reduces the energy cost of the PM regeneration operation. be able to. Furthermore, the fact that a small DPF can be used has the effect that the space for mounting the DPF on the vehicle can be reduced, and the weight of the vehicle on which the DPF is mounted can be reduced. It should be noted.

1 Internal combustion engine 2 DPF
3 Ash 4 Fine particle size 5 DPF base 6 Solid acid 40 DOC
50 NOx detection means 61 Carrier 62 Solid acid point

Claims

An exhaust purification device for an internal combustion engine in which a DPF is disposed in an exhaust system of the internal combustion engine,
The DPF is a DPF having a surface coated with a solid acid,
The acid strength of the solid acid is greater than the acid strength of SO 3 and less than the acid strength of SO 4 ;
Further, control of ash regeneration operation for removing ash accumulated in the DPF;
Ash accumulation amount acquisition means for acquiring an accumulation amount of ash accumulated in the DPF,
The control of the ash regeneration operation is
Control to increase the temperature of the DPF;
An air-fuel ratio control of the atmosphere in the DPF,
The control of the air-fuel ratio of the atmosphere in the DPF is a control for changing the atmosphere to the stoichiometric or air-fuel ratio rich atmosphere first and then changing to the air-fuel ratio lean atmosphere during the control to increase the temperature of the DPF.
The ash regeneration operation is controlled based on the ash accumulation amount acquired by the ash accumulation amount acquisition means,
An exhaust purification device for an internal combustion engine.
NOx amount detection means for detecting the NOx amount in the exhaust gas flowing out from the DPF;
Ammonia supply means for supplying an ammonia component to the DPF,
The ash deposition amount acquisition means is
Detecting the amount of NOx in the exhaust gas flowing out from the DPF;
Next, an ammonia component is supplied to the DPF,
Further, the amount of NOx in the exhaust gas flowing out from the DPF after supplying the ammonia component to the DPF is detected,
Based on the difference between the NOx amount before supplying the ammonia component to the DPF and the NOx amount after supplying the ammonia component, the amount of ash deposited on the DPF is obtained,
The exhaust emission control device for an internal combustion engine according to claim 1.