JP3565145B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exhaust gas purification device for an internal combustion engine.
[0002]
[Prior art]
2. Description of the Related Art In recent years, for internal combustion engines such as vehicle-mounted engines, particularly diesel engines, it has been required to reduce the emission of fine particles (particulates) containing soot as a main component contained in exhaust gas into the atmosphere. In order to satisfy such demands, it is conceivable to provide a filter as described in, for example, Japanese Patent Publication No. Hei 7-106290 in the exhaust system of a diesel engine, and to collect particulates in the exhaust with this filter. In the filter described in the above publication, a platinum group metal and an alkaline earth metal oxide are supported on the particulate collection surface, and the collected particulates are discharged at an exhaust temperature (about 400 ° C.) during normal operation of the diesel engine. ℃). This makes it difficult for particulates to accumulate on the filter during normal operation, and suppresses an increase in exhaust resistance due to clogging of the filter.
[0003]
[Problems to be solved by the invention]
However, depending on the operating condition of the diesel engine, the exhaust gas temperature may not rise to about 400 ° C. even during normal operation, or the amount of particulates contained in the exhaust gas may increase more than usual. If the amount of particulates collected by the filter exceeds the amount of particulates burned out on the filter, the particulates that cannot be burned out gradually accumulate on the filter.
[0004]
In this filter, when a predetermined amount or more of particulates accumulates, the ability to burn off the particulates is extremely reduced, and it is no longer possible to burn the particulates themselves to regenerate them. As a result, the filter is clogged by the particulates, which increases the exhaust resistance of the diesel engine.
[0005]
The present invention has been made in view of such circumstances, and an object of the present invention is to remove fine particles (particulates) collected by a filter well and to suppress clogging of the filter due to the fine particles. It is an object of the present invention to provide an exhaust gas purifying apparatus for an internal combustion engine that can be used.
[0006]
[Means for Solving the Problems]
Hereinafter, the means for achieving the above object and the effects thereof will be described.
In order to achieve the above object, according to the first aspect of the present invention, a collecting surface provided in an exhaust system of an internal combustion engine for collecting and oxidizing and removing fine particles contained in exhaust gas of the internal combustion engine is provided on an exhaust upstream side and an exhaust downstream side. And a reversing means for reversing the positional relationship between the upstream and the downstream of the exhaust gas on the two collecting surfaces, and the reversing means so as to reduce the deviation of the accumulation amount of the fine particles between the two collecting surfaces. And control means for controlling the
[0007]
According to the above configuration, even if one of the collecting surfaces is located on the exhaust upstream side and the accumulation of the fine particles proceeds, the positional relationship is reversed by the reversing means, so that the other collecting surface is on the exhaust upstream side. And the one collecting surface is positioned on the exhaust downstream side. In this state, fine particles are collected and oxidized and removed on the other collecting surface located on the exhaust upstream side, so that fine particles are newly deposited on the one collecting surface located on the downstream side of the exhaust gas. Oxidation and removal of the already deposited fine particles proceed without any problem. When the reversal of the positional relationship is further performed by the reversing means, the positional relationship between the two collecting surfaces returns to the original state, and the phenomenon opposite to the above occurs on these collecting surfaces. By reversing the positional relationship between the two collecting surfaces, fine particles collected on these collecting surfaces can be oxidized and removed satisfactorily, and clogging of the filter can be suppressed.
[0008]
In addition, the amount of fine particles deposited on both collecting surfaces is different from each other for some reason, and a deviation may occur between the amounts of fine particles deposited on both collecting surfaces. According to the above configuration, the reversing means is controlled so as to reduce the deviation, and the positional relationship between the two collecting surfaces is adjusted. Oxidation removal of the fine particles is promoted as compared with the trapping surface of the particles. Therefore, it is possible to accurately reduce the accumulation amount of the fine particles on the collecting surface where the accumulation amount of the fine particles is large, thereby suppressing an increase in the accumulation amount of the fine particles in the entire filter, and oxidizing and removing the fine particles in the filter. The ability can be maintained at a high level.
[0009]
According to a second aspect of the present invention, in the first aspect of the present invention, the control unit may be configured such that, of the two collecting surfaces, the one with the smaller amount of the fine particles is on the exhaust gas upstream side and the one with the larger amount of the fine particles. The control means is controlled so that the frequency at which the exhaust gas flows downstream is higher than the frequency at which the positional relationship between the exhaust gas and the two collecting surfaces is reversed.
[0010]
Fine particles deposited on the collecting surface are easily oxidized and removed when the collecting surface is located on the downstream side of the exhaust gas. Therefore, according to the above configuration, it is possible to accurately promote the oxidative removal of the fine particles on the collection surface on which the fine particles are deposited.
[0011]
According to a third aspect of the present invention, in the first or second aspect of the present invention, the control means repeats the reversal of the positional relationship between the two collecting surfaces by the reversing means at predetermined intervals when a predetermined condition is satisfied. The control is performed, and the repetitive control is started from a state in which, of the two collecting surfaces, the one with the smaller amount of the fine particles is on the exhaust upstream side and the one with the larger amount of the fine particles is on the exhaust downstream side. Thus, the reversing means is controlled.
[0012]
Oxidation and removal of fine particles deposited on the trapping surface are more easily promoted when located on the exhaust downstream side than when located on the exhaust upstream side. For this reason, according to the above configuration, when the predetermined condition is satisfied and the repetitive control is performed, immediately after the start, the collection surface with the larger amount of accumulated fine particles is located on the downstream side of the exhaust gas. In terms of surface, the removal of fine particles by oxidation can be promoted accurately.
[0013]
According to a fourth aspect of the present invention, in any one of the first to third aspects of the present invention, a detecting unit for detecting a deviation of the amount of the fine particles deposited between the two collecting surfaces is provided, and the control unit includes: When the deviation detected by the detecting means is larger than a predetermined level, the reversing means is controlled so that the deviation of the accumulation amount of the fine particles between the two collecting surfaces becomes small.
[0014]
According to the above configuration, the reversing means is controlled so as to reduce the deviation of the amount of fine particles deposited between the two collecting surfaces only when the deviation is larger than the predetermined level. Can be suppressed.
[0015]
As the predetermined level, for example, it is conceivable to adopt a level corresponding to the minimum value of the deviation that can be detected by the detecting means. In this case, even if there is a deviation in the amount of accumulated fine particles between the two collecting surfaces, the deviation can be eliminated early after the start of the generation.
[0016]
According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the detecting means estimates the accumulation amount of the fine particles on the two collecting surfaces based on a parameter related to a pressure of an exhaust system of the internal combustion engine. Based on these estimated accumulation amounts, the deviation of the accumulation amount of the fine particles between the two collecting surfaces is detected.
[0017]
The pressure of the exhaust system changes in accordance with the amount of accumulated fine particles on the collecting surface, and the parameter related to the pressure also changes. Therefore, according to the above configuration, it is possible to accurately detect a deviation between the accumulation amounts based on the accumulation amounts of the fine particles on the two collecting surfaces, which are estimated based on the parameter that changes according to the pressure of the exhaust system. .
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a four-stroke diesel engine will be described with reference to FIGS.
[0019]
As shown in FIG. 1, of the intake passage 13 and the exhaust passage 14 connected to the combustion chamber 12 of the diesel engine 11, the intake passage 13 is provided with a throttle valve 16 that is opened and closed by an electric motor 15. The exhaust passage 14 is provided with an air-fuel ratio sensor 17 that outputs a signal corresponding to the oxygen concentration in the exhaust gas, and a pressure sensor 18 that outputs a signal corresponding to the pressure in the exhaust passage 14. Then, air is sucked into the combustion chamber 12 through the intake passage 13 during the intake stroke, and fuel injected from the fuel injection valve 19 is burned in the combustion chamber 12 during the compression stroke. Reciprocates. In the exhaust stroke, the exhaust gas after fuel combustion is sent from the combustion chamber 12 to the exhaust passage 14. A part of the exhaust gas in the exhaust passage 14 is returned to the intake passage 13 through an EGR passage 22 provided with an EGR valve 21, and the other part is discharged to the atmosphere after being purified by an exhaust purification device 23. .
[0020]
The exhaust gas purifying device 23 includes a filter 24 for collecting and oxidizing and removing fine particles (particulates) mainly composed of soot in the exhaust gas, an exhaust guide mechanism 23a for guiding the exhaust gas to pass through the filter 24, A switching valve 25 for switching the exhaust gas flow path, an actuator 26 for driving the switching valve 25, and an electronic control unit (hereinafter, referred to as ECU) 27 for controlling the actuator 26 are provided. The ECU 27 is for controlling the operation of the diesel engine 11 and is provided in an automobile on which the engine 11 is mounted.
[0021]
The ECU 27 is connected to the electric motor 15, the air-fuel ratio sensor 17, the pressure sensor 18, the fuel injection valve 19, the EGR valve 21, and the actuator 26. A fuel supply device 28 for supplying fuel to the fuel supply 14 is connected. The ECU 27 further includes an accelerator position sensor 30 for detecting the amount of depression of an accelerator pedal 29, a brake switch 32 for detecting the depression of a brake pedal 31, and a crank position sensor for outputting a signal corresponding to the rotation of the output shaft of the diesel engine 11. 33 and the like are connected.
[0022]
The ECU 27 obtains the accelerator depression amount based on the detection signal from the accelerator position sensor 30, and obtains the engine speed based on the detection signal from the crank position sensor. The ECU 27 controls the drive of the electric motor 15 based on the accelerator pedal depression amount to adjust the opening of the throttle valve 16, and controls the fuel injection valve 19 based on the engine speed and the accelerator pedal depression amount to control the fuel injection. Adjust the injection volume.
[0023]
Further, the ECU 27 controls the drive of the EGR valve 21 based on the engine speed, the accelerator pedal depression amount, and the like, and controls the EGR valve 21 so that the air-fuel ratio obtained based on the detection signal from the air-fuel ratio sensor 17 becomes a predetermined target value. The opening of 21 (EGR opening) is corrected. That is, if the air-fuel ratio is leaner than the target value, the EGR amount is increased by correcting the EGR opening to the open side, and the proportion of the EGR gas in the entire gas sucked into the combustion chamber 12 is increased. To reduce the proportion of air. If the air-fuel ratio is richer than the target value, the EGR opening is corrected to the closed side to reduce the EGR amount, and the proportion of the EGR gas in the entire gas drawn into the combustion chamber 12 is reduced. To increase the proportion of air. By performing such correction of the EGR opening, the air-fuel ratio obtained based on the detection signal from the air-fuel ratio sensor 17 is controlled to a target value. The correction amount of the EGR opening is a value that changes according to the pressure in the exhaust passage 14. This is because the EGR amount changes according to the pressure in the exhaust passage 14, and the EGR opening is corrected so as to suppress a deviation of the air-fuel ratio from a target value due to the change.
[0024]
Further, when there is a request to raise the temperature of the filter 24 provided in the exhaust gas purification device 23, the ECU 27 sends fuel from the fuel supply device 28 to the exhaust passage 14 with the air-fuel ratio kept lean, and this fuel and oxygen are The reaction is performed by the filter 24 to increase the temperature of the filter 24. Examples of the situation where the temperature of the filter 24 is required to be raised include, for example, immediately after the start of the start of the diesel engine 11 and when removing the sulfur compound (SOx) stored in the filter 24. Also, instead of using the fuel supply device 28 as described above when supplying fuel to the exhaust passage 14, fuel is supplied from the fuel injection valve 19 during the exhaust stroke to supply fuel to the exhaust passage 14. Alternatively, the unburned fuel may be supplied to the exhaust passage 14 by greatly increasing the EGR amount.
[0025]
Next, the flow structure of exhaust gas passing through the filter 24 of the exhaust gas purification device 23 will be described in detail with reference to FIGS. 2 and 3 are plan views of the exhaust guide mechanism 23a of the exhaust purification device 23 as viewed from above, and FIG. 4 is a plan view of the exhaust guide mechanism 23a.
[0026]
The exhaust guide mechanism 23a includes a switching portion 34 in the exhaust passage 14 to which a portion upstream and a portion downstream of the mechanism 23a are respectively connected. A guide passage 35 is provided for returning the exhaust gas having passed through 24 to the switching section 34. In the guide passage 35, a first connection portion 35a is provided between one side (lower side in the figure) of the filter 24 and the switching section 34, and the other side (upper side in the figure) of the filter 24 is connected to the switching section 34. A second connection portion 35b is provided between them. The switching section 34 is provided with a switching valve 25 driven by an actuator 26.
[0027]
The switching valve 25 has a first valve position (FIG. 2) for flowing exhaust gas from the first connection portion 35a to the second connection portion 35b by the actuator 26, and a first connection portion from the second connection portion 35b to the first connection portion. It is switched between a second valve position (FIG. 3) for flowing the exhaust towards 35a. When the exhaust in the exhaust passage 14 flows from the upstream side to the downstream side of the exhaust guide mechanism 23a, when the switching valve 25 is in the first valve position (FIG. 2), the exhaust is indicated by a broken line arrow in FIG. Flow from one side (first connection portion 53a side) to the other side (second connection portion 53b side) of the filter 24 (hereinafter referred to as a forward flow). When the switching valve 25 is in the second valve position (FIG. 3), the exhaust gas flows from the other side to one side as shown by a broken arrow in FIG. Therefore, by switching the switching valve 25 between the first valve position and the second valve position, the direction of the exhaust gas passing through the filter 24 can be reversed between the forward flow and the reverse flow, whereby The exhaust upstream side and the exhaust downstream side of the filter 24 can be reversed.
[0028]
The switching of the switching valve 25 as described above is performed through the ECU 27 when the temperature of the filter 24 is raised, for example. As described above, the temperature of the filter 24 is increased by feeding fuel into the exhaust passage 14 and causing the fuel and oxygen to react on the filter 24. Here, FIG. 6 shows the temperature of each part of the filter 24 when the fuel and oxygen react, that is, the exhaust inlet, the center, and the exhaust outlet. In the figure, broken lines indicate the temperature of each part when the exhaust gas flows from the exhaust upstream to the exhaust downstream, and solid lines indicate the temperature of each part when the exhaust upstream and the exhaust downstream are reversed. When the reversal of the exhaust upstream side and the exhaust downstream side does not occur (dashed line), the heat of reaction between the fuel and oxygen is transmitted to the exhaust outlet by the flow of the exhaust, and the temperature of the exhaust outlet is increased. After that, a part of the heat amount in the reaction heat is discarded from the exhaust outlet to the exhaust downstream side. On the other hand, when the exhaust upstream side and the exhaust downstream side are reversed at an appropriate interval, the heat discarded from the exhaust outlet to the exhaust downstream side causes the exhaust to flow in the reverse direction based on the above-described reverse rotation, so that the heat is discharged toward the central part. Will return to. In this manner, by reversing the exhaust upstream side and the exhaust downstream side, the temperature of the entire filter 24 can be quickly increased.
[0029]
Specifically, when a request for raising the temperature of the filter 24 is made, the ECU 27 controls the actuator 26 to move the switching valve 25 to the position shown in FIG. In such a manner, repetitive control for switching between the first valve position and the second valve position is performed every predetermined time (for example, every ten and several seconds). As a result, the exhaust gas passing through the filter 24 is switched from the forward flow to the backward flow or from the backward flow to the forward flow, and the portion of the filter 24 which has been the exhaust inlet becomes the exhaust outlet and the portion which was the exhaust outlet. Is the exhaust inlet. By performing the repetitive control in this way, the temperature of the entire filter 24 quickly rises.
[0030]
The switching of the switching valve 25 is performed not only in a special situation such as when the temperature of the filter 24 is raised, but also in a normal operation in order to suppress the accumulation of particulates in the filter 24 described later. Is Such switching of the switching valve 25 during normal operation is performed, for example, every time the diesel engine 11 shifts to an operating state in which particulates are less likely to occur. This is because when the switching valve 25 is switched between the first valve position and the second valve position, the exhaust gas in the exhaust gas passage 14 passes through the guide passage 35 as shown in FIG. This is because it is a position that flows downstream without passing through, so that it is preferable to switch the switching valve 25 when particulates are hardly generated as much as possible.
[0031]
It is possible to determine whether or not the diesel engine 11 has shifted to an operation state in which particulates are unlikely to occur, for example, based on the depression of the brake pedal 31. This is because the accelerator pedal 29 is not depressed when the brake pedal 31 is depressed, and the amount of fuel injected into the combustion chamber 12 is small. Further, instead of making the above determination based on the depression of the brake pedal 31, it is also possible to make the determination based on the depression of the accelerator pedal 29 or the fuel cut of the diesel engine.
[0032]
Next, a detailed structure of the filter 24 will be described with reference to FIGS. 8 is a front view of the filter 24 of FIGS. 2 and 3 as viewed from one side (the lower side in the figure), and FIG. 9 is a cross-sectional view of the filter 24 of FIG. 8 as viewed from the direction of arrows AA. .
[0033]
As shown in FIGS. 8 and 9, the filter 24 is of an oval shape when viewed from the front, and is a wall flow type filter having a honeycomb structure formed of a porous material such as cordierite. The filter 24 is provided with a large number of passages 37 defined by lattice-shaped partitions 36 so as to extend in the axial direction (the left-right direction in FIG. 9). One of the two adjacent passages 37 in each of the passages 37 is closed by a plug 38 on one side of the filter 24 (the left side in FIG. 9), and the other is plugged on the other side (the right side in FIG. 9) of the filter 24. It is closed by 39.
[0034]
Then, as shown in FIG. 9, regardless of whether the exhaust gas is a forward flow flowing from one side of the filter 24 to the other side or a reverse flow flowing from the other side to the one side of the filter 24, the exhaust gas passing through the filter 24 must be a partition wall. Pass 36. At this time, the particulates in the exhaust collide with and are collected on the surface of the partition 36 on the exhaust upstream side and on the surface of the partition 36 on the exhaust upstream side in the pores. In order to oxidize and remove the particulates collected in this way, on the surface of the partition 36 on the exhaust upstream side and the exhaust downstream side, and preferably on the surface of the partition 36 on the exhaust upstream side and the exhaust downstream side in the pores of the partition 36. Also, an active oxygen releasing agent and a noble metal catalyst described below are supported using alumina or the like.
[0035]
Here, the active oxygen releasing agent promotes the oxidation of particulates by releasing active oxygen. Preferably, when excess oxygen is present in the surroundings, it takes in oxygen to retain oxygen and retain surrounding oxygen. When the oxygen concentration decreases, the retained oxygen is released in the form of active oxygen.
[0036]
Platinum Pt is usually used as the noble metal catalyst, and alkali metals such as potassium K, sodium Na, lithium Li, cesium Cs, and rubidium Rb, barium Ba, calcium Ca, strontium Sr are used as active oxygen releasing agents. At least one selected from the group consisting of alkaline earth metals such as lanthanum La, rare earths such as yttrium Y, and transition metals is used.
[0037]
In this case, as the active oxygen releasing agent, an alkali metal or an alkaline earth metal having a higher ionization tendency than calcium Ca, that is, potassium K, lithium Li, cesium Cs, rubidium Rb, barium Ba, and strontium Sr may be used. preferable.
[0038]
Next, how the particulates collected by the filter 24 carrying such an active oxygen releasing agent are oxidized and removed will be described by taking platinum Pt and potassium K as an example. The same effect of removing particulates occurs even when other noble metals, alkali metals, alkaline earth metals, rare earths, and transition metals are used.
[0039]
In a diesel engine, since combustion is usually performed under excess air, the exhaust gas contains a large amount of excess air, and the air-fuel ratio obtained based on the detection signal from the air-fuel ratio sensor 17 is a lean value. ing. In addition, NO is contained in the exhaust gas because NO is generated in the combustion chamber 12, and sulfur S contained in the fuel reacts with oxygen in the combustion chamber 12 to produce SO.₂SO₂Is also included. Thus, the filter 24 contains excess oxygen, NO, and SO.₂  Will flow in. Here, enlarged views of the exhaust contact surface of the filter 24 are schematically shown in FIGS.
[0040]
As described above, since the exhaust gas contains a large amount of excess oxygen, when the exhaust gas contacts the exhaust contact surface of the filter 24, as shown in FIG.₂Is O₂ ⁻Or O^2-Adheres to the surface of platinum Pt in the form of On the other hand, NO in the exhaust gas becomes O 2 on the surface of platinum Pt.₂ ⁻Or O^2-Reacts with NO₂It becomes. (2NO + O₂→ 2NO₂). NO generated next₂Is absorbed in the active oxygen releasing agent 40 while being oxidized on the platinum Pt, and combined with potassium K to form nitrate ions NO₃ ⁻Diffuses into the active oxygen releasing agent 40 in the form of potassium nitrate KNO₃Generate In this way, the harmful NOx contained in the exhaust gas is absorbed by the filter 24, and the amount of emission into the atmosphere can be greatly reduced.
[0041]
On the other hand, as described above, SO₂Is also included in this SO₂Is also absorbed into the active oxygen releasing agent 40 by the same mechanism as NO. That is, as described above, the oxygen O₂Is O₂ ⁻Or O^2-Is attached to the surface of platinum Pt in the form of SO₂Is O on the surface of platinum Pt₂ ⁻Or O^2-Reacts with SO₃It becomes. Then the generated SO₃Is partially absorbed into the active oxygen releasing agent 40 while being further oxidized on the platinum Pt.₄ ^2-Is diffused into the active oxygen releasing agent 40 in the form of potassium sulfate K₂SO₄Generate Thus, potassium nitrate KNO is contained in the active oxygen releasing agent 40.₃And potassium sulfate K₂SO₄Is generated.
[0042]
As shown in FIG. 11, the particulates 41 in the exhaust gas adhere to the surface of the active oxygen releasing agent 40 carried on the filter 24. At this time, the oxygen concentration decreases at the contact surface between the particulate 41 and the active oxygen releasing agent 40. When the oxygen concentration decreases, a concentration difference occurs between the active oxygen releasing agent 40 having a high oxygen concentration and the oxygen in the active oxygen releasing agent 40 moving toward the contact surface between the particulate 41 and the active oxygen releasing agent 40. try to. As a result, potassium nitrate KNO formed in the active oxygen releasing agent 40₃Is decomposed into potassium K, oxygen O and NO, oxygen O is directed to the contact surface between the particulate 41 and the active oxygen releasing agent 40, and NO is released from the active oxygen releasing agent 40 to the outside. The NO released to the outside is oxidized on platinum Pt on the downstream side, and is again absorbed in the active oxygen releasing agent 40.
[0043]
On the other hand, at this time, the potassium sulfate K formed in the active oxygen releasing agent 40₂SO₄Also potassium K, oxygen O and SO₂Oxygen O moves toward the contact surface between the particulate 41 and the active oxygen releasing agent 40,₂Is released from the active oxygen releasing agent 40 to the outside. SO released outside₂Is oxidized on platinum Pt on the downstream side, and is again absorbed in the active oxygen releasing agent 40. However, potassium sulfate K₂SO₄Is stable because potassium nitrate KNO₃It is difficult to release active oxygen as compared with.
[0044]
On the other hand, oxygen O toward the contact surface between the particulate 41 and the active oxygen releasing agent 40 is potassium nitrate KNO₃And potassium sulfate K₂SO₄Is oxygen decomposed from such a compound. Oxygen O decomposed from the compound has high energy and extremely high activity. Therefore, the oxygen going to the contact surface between the particulate 41 and the active oxygen releasing agent 40 becomes the active oxygen O. When the active oxygen O comes in contact with the particulate 41, the particulate 41 is oxidized.
[0045]
Incidentally, since the platinum Pt and the active oxygen releasing agent 40 are activated as the temperature of the filter 24 increases, the amount of active oxygen O released from the active oxygen releasing agent 40 per unit time increases as the temperature of the filter 24 increases. I do. Therefore, the amount of fine particles capable of oxidizing and removing particulates per unit time on the filter 24 (the amount G of oxidizable and removable particles) increases as the temperature of the filter 24 increases. Here, the transition of the amount G of the oxidizable particles that can be removed with respect to the change of the filter temperature TF is shown by a solid line in FIG.
[0046]
In FIG. 12, when the actual amount of particulates discharged from the combustion chamber 12 per unit time (discharged particle amount M) is smaller than the oxidizable / removable particle amount G, that is, the discharged particle amount M is lower than the solid line. When in the region I on the side, all the particulates discharged from the combustion chamber 12 are collected by the filter 24 and oxidized and removed within a short time.
[0047]
On the other hand, when the amount M of discharged fine particles is larger than the amount G of fine particles that can be removed by oxidation, that is, when the amount M of discharged fine particles is in the region II above the solid line, all the particulates discharged from the combustion chamber 12 are oxidized. Insufficient active oxygen is needed. FIGS. 13 to 15 schematically show how the particulates are oxidized in such a case.
[0048]
That is, when active oxygen is insufficient to oxidize all the particulates, when the particulates 41 adhere to the active oxygen releasing agent 40 as shown in FIG. 13, only a part of the particulates 41 is oxidized. Is done. The particulates that have not been sufficiently oxidized remain on the surface of the filter 24 on the upstream side of the exhaust of the partition 36 or on the surface of the filter 36 on the upstream of the exhaust in the pores of the partition 36. Next, when the state where the amount of active oxygen is insufficient continues, the particulate portion that has not been oxidized one after another remains in the above portion. As a result, as shown in FIG. 14, the surface of the partition wall 36 on the exhaust upstream side and the surface of the partition wall 36 on the exhaust upstream side are covered with the residual particulate portion 42.
[0049]
Such a residual particulate portion 42 gradually changes to a carbon material which is hardly oxidized. When the above-mentioned portion is covered with the residual particulate portion 42, NO, SO₂And the active oxygen releasing action of the active oxygen releasing agent 40 is suppressed. In this state, a large amount of time is required to oxidize the residual particulate portion 42. Therefore, another particulate 43 is formed on the residual particulate portion 42 one after another as shown in FIG. Will be deposited. The particulates thus deposited in a stacked state are at a distance from the platinum Pt and the active oxygen releasing agent 40, so that, for example, even if the particulates are easily oxidized, they are not oxidized by the active oxygen. Therefore, if the state in which the amount M of discharged fine particles is larger than the amount G of fine particles that can be removed by oxidation continues, further particulates are deposited one after another on the particulates, and the deposited amount of the particulates continues to increase. .
[0050]
As described above, when the amount M of discharged particulates is larger than the amount G of particles that can be removed by oxidation, the particulates accumulate on the filter 24. Therefore, if the amount M of discharged particles is always smaller than the amount G of particles that can be removed by oxidation, The accumulation of the particulates can be suppressed. However, the amount M of discharged fine particles cannot always be made smaller than the amount G of fine particles that can be oxidized and removed. Depending on the operation state of the diesel engine 11, the amount M of discharged fine particles exceeds the amount G of oxidizable and removable particles, and the particle Curates may accumulate. In order to suppress the accumulation of particulates on the filter 24, the switching valve 25 is switched between the first valve position and the second valve position each time the brake pedal 31 is depressed as described above, for example. The direction of flow of the exhaust gas passing through is switched between forward flow and reverse flow.
[0051]
Next, how the accumulation of particulates on the filter 24 is suppressed by switching the flow direction of the exhaust gas as described above will be described with reference to FIGS. 16 and 17. 16 and 17 are enlarged sectional views showing the partition wall 36 of the filter 24. FIG. 16 shows a state of the partition wall 36 when the flow of exhaust gas is, for example, a forward flow. 2 shows the state of the partition 36 after being switched.
[0052]
In the partition wall 36 of the filter 24, the surface on the exhaust upstream side of the partition wall 36 and the surface on the exhaust upstream side in the pores of the partition wall 36 collide and collect particulates as one collecting surface, and the active oxygen releasing agent is used. Remove by oxidation. However, when the state in which the amount M of discharged fine particles exceeds the amount G of fine particles that can be oxidized and removed is continued, the oxidized removal of the collected particulates becomes insufficient. Therefore, for example, if the flow of the exhaust gas is a forward flow, the particulates remain on the one collecting surface as shown by the hatching in a lattice shape in FIG. 16, and the accumulated amount of the particulates on the same collecting surface. Increase.
[0053]
Thereafter, when the switching valve 25 is switched based on the depression of the brake pedal 31, the flow of the exhaust is switched from the forward flow indicated by the arrow in FIG. 16 to the reverse flow indicated by the arrow in FIG. Thus, the surface on the exhaust downstream side of the partition wall 36 and the surface on the exhaust downstream side in the pores of the partition wall 36 are now replaced by the surface on the exhaust upstream side of the partition wall 36 and the pores of the partition wall 36. The surface is located on the upstream side of the exhaust gas, and as the other collecting surface, the particulates are collided and collected and oxidized and removed by the active oxygen releasing agent. As described above, when the flow of the exhaust gas is switched between the forward flow and the reverse flow based on the switching of the switching valve 25, the positional relationship between the one collection surface and the other collection surface between the exhaust upstream and the exhaust downstream. Is reversed, and the collecting surface for collecting the particulates is switched.
[0054]
As described above, when the other trapping surface is located upstream of the exhaust gas, the particulates are trapped and oxidized and removed at this trapping surface. It does not accumulate, but rather oxidizes and removes the accumulated particulates. That is, at this time, the particulates are collected on the other collecting surface located on the exhaust upstream side and are oxidized and removed by the active oxygen released from the active oxygen releasing agent. When the portion flows downstream together with the exhaust gas, the particulates remaining on one of the collecting surfaces located downstream of the exhaust gas are oxidized and removed. In addition, the particulates remaining on the one collecting surface are separated from the collecting surface by the flow of the exhaust gas in the reverse flow direction and are subdivided as shown in FIG. Flows mainly toward the downstream side. At this time, the finely divided particulates come into direct contact with the active oxygen releasing agent supported on the inner surface of the pores, and are oxidized and removed by oxygen released from the active oxygen releasing agent.
[0055]
In this way, the particulates remaining on the other collecting surface located downstream of the exhaust gas are oxidized and removed, and the amount of particulates deposited on the other collecting surface is reduced. Further, when the switching valve 25 is switched again based on the depression of the brake pedal 31, the flow of the exhaust gas returns to the forward flow, and the positional relationship between the upstream and downstream of the exhaust of the two collecting surfaces also returns to the original state. On the surface, the opposite phenomenon occurs. Therefore, by performing the reversal of the positional relationship between the two collecting portions at predetermined intervals (every time the brake is depressed), the particulates collected by these collecting portions are oxidized and removed satisfactorily, and the accumulation of the particulates is caused. Clogging of the filter 24 can be suppressed.
[0056]
By the way, the amount of particulates deposited on one collecting surface and the other collecting surface is different from each other for some reason, and a deviation may occur between the amounts of particulates deposited on these collecting surfaces. In the present embodiment, the ECU 27 controls the actuator 26 to switch the switching valve 25 so as to switch the flow of exhaust gas in the exhaust guide mechanism 23a so as to reduce the above-described deviation. That is, the filter 24 is switched based on the switching of the switching valve 25 so that the particulate removal is promoted more oxidatively removed on the collecting surface having the larger amount of particulates than on the collecting surface having the smaller amount of the particulates. The flow direction of the passing exhaust gas is controlled, and the positional relationship between the upstream and downstream of the exhaust gas on the collecting surface is adjusted. By adjusting the positional relationship between the two collecting surfaces in this manner, the amount of the accumulated particulates can be accurately reduced on the collecting surface having the larger amount of the particulates. An increase in the amount can be accurately suppressed. Therefore, clogging due to the accumulation of particulates in the filter 24 is more unlikely to occur, and the ability of the filter 24 to remove and oxidize particulates can be maintained at a high level.
[0057]
Next, a procedure for setting the flag F for determining whether or not to perform the switching control of the switching valve 25 as described above will be described with reference to a flowchart of FIG. 18 showing a flag setting routine. This flag setting routine is executed by the ECU 27, for example, by interruption every predetermined time.
[0058]
In the flag setting routine, the processing in steps S101 to S104 is for detecting a deviation in the amount of accumulated particulates between the two collecting surfaces. In the processing in step S105, the deviation is larger than a predetermined level. It is for determining whether or not there is. Then, in the subsequent steps S106 and S107, the flag F is set to "1" or "0" depending on whether the deviation is larger than a predetermined level. When the flag F is “1 (the deviation is larger than a predetermined level)”, the switching control of the switching valve 25 as described above is performed.
[0059]
In the flag setting routine, the ECU 27 determines whether or not the flow of exhaust gas in the exhaust guide mechanism 23a is a forward flow, based on the valve position where the switching valve 25 is switched, as the process of step S101. If it is a forward flow, the pressure P in the exhaust passage 14 obtained based on the detection signal from the pressure sensor 18 by the process of step S102 is stored as a forward flow pressure Pa, and if it is a backward flow, the pressure P is obtained by the process of step S103. It is stored as the backflow pressure Pb. The forward flow pressure Pa is a value corresponding to the amount of particulates deposited on one collecting surface, and the backflow pressure Pb is a value corresponding to the amount of particulates deposited on the other collecting surface.
[0060]
This is because the more the particulates accumulate on one collecting surface, the higher the pressure P in the exhaust passage 14 during the forward flow, and the more the particulates accumulate on the other collecting surface, the higher the pressure P during the reverse flow. That's why. Therefore, based on the values of the forward pressure Pa and the backflow pressure Pb, it is possible to estimate the amount of particulates deposited on one collecting surface and the amount of particulates deposited on the other collecting surface.
[0061]
After performing any one of the above-described steps S102 and S103, the process proceeds to step S104. The ECU 27 calculates the differential pressure ΔP between the stored forward flow pressure Pa and backflow pressure Pb as the process of step S104. This differential pressure ΔP is a value corresponding to the deviation of the amount of accumulated particulates on both collecting surfaces. That is, the differential pressure ΔP increases in the positive direction as the amount of particulates deposited on one collecting surface becomes larger than the amount of particulates deposited on the other collecting surface, and the differential pressure ΔP increases. The larger the amount of curated deposit is than the amount of particulate deposited on one of the collecting surfaces, the more the amount increases in the negative direction.
[0062]
The ECU 27 determines whether the absolute value of the differential pressure ΔP is larger than a predetermined value x, that is, whether the deviation of the amount of accumulated particulates on both collection surfaces is larger than a predetermined level, in the process of step S105. Judge. Note that, as the predetermined value x, a value corresponding to the minimum value of the differential pressure ΔP capable of securing necessary accuracy is adopted. Therefore, when the above-mentioned deviation occurs, the above-described switching control of the switching valve 25 can be executed at an early stage in order to eliminate the deviation promptly.
[0063]
In the process of step S105, when it is determined that the absolute value of the differential pressure ΔP is larger than the predetermined value x, the flag F is set to “1” in the process of step S106, and the differential pressure ΔP is equal to or less than the predetermined value x. If it is determined that this is the case, the flag F is set to “0” in the processing of step S107. After executing any of the processes in step S106 and step S107, the ECU 27 temporarily ends the flag setting routine.
[0064]
Next, a switching procedure of the switching valve 25 will be described with reference to a flowchart of FIG. 19 showing a switching valve control routine. This switching valve control routine is executed by the ECU 27, for example, by interruption every predetermined time.
[0065]
In the switching valve control routine, the ECU 27 determines whether or not a request for increasing the temperature of the filter 24 has been made as the process of step 201. If there is a request for raising the temperature of the filter 24, the switching control of the switching valve 25 based on the processing of steps S202 to S204 is executed. If there is no request for raising the temperature of the filter 24, the switching of the switching valve 25 based on the processing of steps S205 to S207 is performed. Execute switching control. Hereinafter, switching control modes of the switching valve 25 according to the presence / absence of the above-mentioned temperature raising request will be described separately.
[0066]
[No heating required]
The ECU 27 determines whether or not the deviation of the amount of accumulated particulate between the two collecting surfaces is larger than a predetermined level, based on whether or not the flag F is “1” as the process of step S205. . When it is determined that “F = 1” and the deviation is not larger than the predetermined level, the ECU 27 performs step S207 on the basis of the detection signal from the brake switch 32 to depress the brake pedal 31 (brake). (Change from OFF to ON), the actuator 26 is controlled to switch the valve position of the switching valve 25 between the first valve position and the second valve position. As a result, the particulates collected by the two collecting portions of the filter 24 are oxidized and removed satisfactorily, and clogging of the filter 24 due to accumulation of the particulates is suppressed.
[0067]
Further, in the process of step S205, when it is determined that “F = 1” and the deviation is larger than a predetermined level, the ECU 27 determines in step S206 that the valve position of the switching valve 25 is the first position. The frequency at the time of the second valve position and the frequency at the time of the second valve position are adjusted. That is, if the differential pressure ΔP is positive, the ECU 27 determines that the amount of accumulated particulates is larger on one collecting surface than on the other collecting surface, and one collecting surface is located downstream of the exhaust gas and the other collecting surface is downstream. The switching of the switching valve 25 is performed by controlling the actuator 26 so that the frequency at which the collection surface is located upstream of the exhaust gas is higher than the frequency at which the positional relationship is reversed. If the differential pressure ΔP is negative, it is determined that the amount of particulates accumulated on the other collecting surface is larger than that on one collecting surface, and the other collecting surface is downstream of the exhaust gas and the other collecting surface The switching of the switching valve 25 is performed by controlling the actuator 26 so that the frequency at which the exhaust gas becomes upstream is higher than the frequency at which the positional relationship is reversed.
[0068]
By performing the switching control of the switching valve 25 as described above and adjusting the positional relationship between the two collecting surfaces, the collecting surface having the larger amount of particulates is connected to the collecting surface having the smaller amount of the particulates. In comparison, the oxidative removal of particulates is promoted. Therefore, the amount of accumulated particulates can be accurately reduced on the trapping surface having the larger amount of accumulated particulates, whereby an increase in the amount of accumulated particulates in the entire filter 24 can be accurately suppressed. Therefore, clogging due to the accumulation of particulates in the filter 24 is more unlikely to occur, and the ability of the filter 24 to remove and oxidize particulates can be maintained at a high level.
[0069]
In addition, as a method of adjusting the frequency as described above, for example, the accumulated time between one state of the positional relationship and the state of the other positional relationship is measured, and the difference between the accumulated times is determined by a predetermined value. In such a case, the switching of the switching valve 25 performed every time the brake pedal 31 is depressed may be appropriately canceled. Instead of this frequency adjustment method, the cumulative traveling distance in the state of one positional relationship and the cumulative traveling distance in the state of the other positional relationship are measured, and the difference between these cumulative traveling distances is determined in advance. It is also possible to adopt a method of appropriately canceling the switching of the switching valve 25 so that the predetermined value is obtained.
[0070]
The ECU 27 once terminates the switching valve control routine after performing the processing in either step S206 or step S207.
[There is a temperature rise request]
The ECU 27 determines whether or not the deviation of the amount of accumulated particulate between the two collecting surfaces is larger than a predetermined level based on whether or not the flag F is “1” as the process of step S202. . When it is determined that “F = 1” and the deviation is not larger than the predetermined level, the ECU 27 controls the actuator 26 to change the valve position of the switching valve 25 at predetermined time intervals in step S204. Then, iterative control for switching between the first valve position and the second valve position is started. After that, the ECU 27 once ends the switching valve control routine. By performing the above-described repetitive control, the temperature of the filter 24 is quickly raised. When the temperature of the filter 24 becomes equal to or higher than a predetermined value, the ECU 27 ends the repetitive control.
[0071]
On the other hand, if it is determined in the process of step S202 that “F = 1” and the deviation is larger than a predetermined level, the ECU 27 performs the process of step S203 and repeats the repetitive control in step S204. The valve position of the switching valve 25 is adjusted so that the start of the process is started from a state in which the trapping surface with the larger amount of accumulated particulates is downstream of the exhaust gas. That is, if the differential pressure ΔP is positive, the ECU 27 determines that the amount of accumulated particulates is larger on one collecting surface than on the other collecting surface. The actuator 26 is controlled to adjust the valve position of the switching valve 25 so that the above-described repetitive control is started from this state. If the differential pressure ΔP is negative, it is determined that the amount of particulates accumulated on the other collecting surface is larger than that on the other collecting surface. The actuator 26 is controlled to adjust the valve position of the switching valve 25 so that the above-described repetitive control is started.
[0072]
As a result, immediately after the start of the above-described repetitive control, first, the trapping surface having the larger amount of accumulated particulates is downstream of the exhaust gas, and the oxidative removal of the particulates at the trapping surface is promoted. Therefore, at the start of the repetitive control, the amount of accumulated particulates can be accurately reduced on the trapping surface having the larger amount of accumulated particulates, whereby the increase in the amount of accumulated particulates in the entire filter 24 is accurately suppressed. be able to. Therefore, clogging due to the accumulation of particulates in the filter 24 is more unlikely to occur, and the ability of the filter 24 to remove and oxidize particulates can be maintained at a high level.
[0073]
According to the embodiment described above, the following effects can be obtained.
(1) Since the valve position of the switching valve 25 is switched between the first valve position and the second valve position at predetermined intervals (every time the brake is depressed), the flow of exhaust gas passing through the filter 24 is also changed at predetermined intervals. It can be switched between forward flow and reverse flow. As a result, the positional relationship between the upstream side and the downstream side of the exhaust on the one collecting surface and the other collecting surface of the filter 24 is reversed at predetermined intervals. This makes it possible to satisfactorily oxidize and remove the particulates collected in the two collecting sections, and to suppress clogging of the filter 24 due to the accumulation of the particulates.
[0074]
(2) The switching valve during normal operation so that the frequency at which the trapping surface with the larger amount of particulates is downstream of the exhaust gas is higher than the frequency at which the trapping surface with the smaller amount of particulates is downstream of the exhaust gas. 25 switching operations are performed. In addition, the valve position of the switching valve 25 at the start of the request for increasing the temperature of the filter is set so that the start of the above-described repetitive control is started from a state in which the trapping surface having the larger amount of the accumulated particulate is downstream of the exhaust gas. I adjusted it. Thus, the amount of accumulated particulates can be accurately reduced on the collecting surface where the amount of accumulated particulates is larger, and an increase in the amount of accumulated particulates in the entire filter 24 can be accurately suppressed. Therefore, clogging due to the accumulation of particulates is less likely to occur in the filter 24, and the ability of the filter 24 to remove and oxidize particulates can be maintained at a high level.
[0075]
(3) Oxidation and removal of particulates are promoted on the trapping surface with the larger accumulation amount of particulates as compared with the collection surface with the smaller accumulation amount. The deviation of the deposition amount of the metal is reduced. If the positional relationship between the two collecting surfaces is reversed at regular intervals in the state where such a deviation occurs, the collecting surface with a larger amount of particulates is compared with the collecting surface with a smaller amount of particulates. Since the particulates are oxidized and removed slowly, there is a high possibility that a difference occurs in the amount of particulates removed between the two collecting surfaces, and the deviation may further increase. In this situation, the amount of particulates accumulated on the trapping surface with the larger amount of particulates is likely to increase due to the slow oxidation and removal of the particulates. Accordingly, clogging of the filter 24 is likely to occur. However, as described above, since the deviation of the amount of accumulated particulates between the two collecting surfaces is reduced, it is possible to suppress the occurrence of clogging due to the particulates on one of the collecting surfaces.
[0076]
(4) Only when the deviation is larger than a predetermined level, that is, when the absolute value of the differential pressure ΔP is larger than a predetermined value x, the switching of the switching valve 25 to reduce the deviation is performed. Unnecessary switching of the switching valve 25 can be suppressed.
[0077]
(5) As the predetermined level (predetermined value x), a value (level) corresponding to the minimum value of the differential pressure ΔP that can ensure required accuracy is adopted. Therefore, when the above-mentioned deviation occurs, the above-described switching of the switching valve 25 can be executed at an early stage in order to resolve the deviation promptly.
[0078]
(6) Since the forward flow pressure Pa and the backflow pressure Pb change in accordance with the amount of particulate matter deposited on both collecting surfaces, the amount of particulate matter deposited on both collecting surfaces is determined based on the forward flow pressure Pa and the backflow pressure Pb. Can be estimated. Then, based on the calculation of the differential pressure ΔP between the forward flow pressure Pa and the backflow pressure Pb corresponding to the estimated accumulation amount, it is possible to accurately detect the deviation of the accumulation amount of the particulates on both collection surfaces. become.
[0079]
Note that the present embodiment can be modified, for example, as follows.
The differential pressure ΔP between the forward flow pressure Pa and the reverse flow pressure Pb was calculated as a value corresponding to the deviation of the amount of accumulated particulates on both collecting surfaces, but the present invention is not limited to this. For example, the pressures of the first connection portion 35a and the second connection portion 35b in the guide passage 35 of the exhaust guide mechanism 23a are respectively detected, and the above-described deviations are corresponded based on the differential pressure at the time of forward flow and the differential pressure at the time of reverse flow. The value may be calculated.
[0080]
-Instead of estimating the same from the pressure P which changes according to the amount of particulates accumulated on the collecting surface, the same may be estimated based on a parameter related to the pressure P. As such a parameter, besides the pressure P itself, for example, a correction amount for correcting the EGR opening degree so as to bring the air-fuel ratio close to the target value can be adopted. When the EGR opening is not corrected, the intake air amount of the diesel engine 11 can be used as the parameter.
[0081]
When the above-described repetitive control is performed other than when the temperature of the filter 24 is raised, the present invention may be applied to the repetitive control at that time.
-Instead of switching the switching valve 25 every time the brake is depressed during normal operation of the diesel engine 11, the switching valve 25 may be switched every predetermined time or every predetermined traveling distance. In this case, the frequency of the positional relationship between the upstream and downstream of the exhaust between the one collecting surface and the other collecting surface is adjusted by appropriately changing the predetermined time and the predetermined traveling distance that are the reference for the switching. Can be.
[0082]
As the active oxygen releasing agent carried on the partition 36 of the filter 24, a NOx storage reduction catalyst used for purifying NOx in exhaust gas may be used.
-Instead of applying the present invention to the diesel engine 11, the present invention may be applied to a gasoline engine whose exhaust contains particulates.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an entire diesel engine to which an exhaust gas purification device according to an embodiment is applied.
FIG. 2 is an enlarged plan view showing an exhaust guide mechanism of the exhaust purification device.
FIG. 3 is an enlarged plan view showing an exhaust guide mechanism of the exhaust purification device.
FIG. 4 is an enlarged side view showing the exhaust guide mechanism.
FIG. 5 is an enlarged plan view showing a switching unit of the exhaust guide mechanism.
FIG. 6 is a graph showing a temperature distribution of the filter when the temperature of the filter is raised.
FIG. 7 is a time chart showing a switching mode of a switching valve when repetitive control is performed.
FIG. 8 is an enlarged view showing the structure of a filter.
FIG. 9 is a cross-sectional view of the filter of FIG. 8 as viewed from the direction of arrows AA.
FIG. 10 is a schematic diagram for explaining the oxidizing action of particulates.
FIG. 11 is a schematic diagram for explaining the oxidizing action of particulates.
FIG. 12 is a graph showing a change in the amount of fine particles that can be oxidized and removed with respect to a temperature change of a filter.
FIG. 13 is a schematic diagram for explaining a particulate deposition effect;
FIG. 14 is a schematic view for explaining the accumulation action of particulates.
FIG. 15 is a schematic diagram for explaining a particulate deposition effect;
FIG. 16 is an enlarged sectional view showing a partition wall of the filter.
FIG. 17 is an enlarged sectional view showing a partition wall of the filter.
FIG. 18 is a flowchart showing a procedure for setting a flag F;
FIG. 19 is a flowchart showing a switching control procedure of the switching valve.
[Explanation of symbols]
Reference Signs List 11: diesel engine, 14: exhaust passage, 17: air-fuel ratio sensor, 18: pressure sensor, 21: EGR valve, 22: EGR passage, 23: exhaust purification device, 23a: exhaust guide mechanism, 24: filter, 25: switching Valves 26 Actuator 27 Electronic control unit (ECU) 29 Accelerator pedal 30 Accelerator position sensor 31 Brake pedal 32 Brake switch 33 Crank position sensor

Claims (5)

A filter that is provided in an exhaust system of the internal combustion engine and has a collecting surface that collects and oxidizes and removes fine particles contained in exhaust gas of the engine on an exhaust upstream side and an exhaust downstream side, respectively;
Reversing means for reversing the positional relationship between the exhaust upstream and exhaust downstream on the two collecting surfaces,
Control means for controlling the reversing means so that the deviation of the accumulation amount of the fine particles between the two collecting surfaces is reduced,
An exhaust gas purification device for an internal combustion engine, comprising: The frequency of the control means is such that the smaller the accumulation amount of the fine particles is on the exhaust upstream side and the larger the accumulation amount is on the exhaust downstream side between the two collecting surfaces, 2. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the control unit controls the control unit so that the frequency of the positional relationship is reversed. The control means performs repetitive control to repeat the reversal of the positional relationship between the two collecting surfaces by the reversing means at predetermined intervals when a predetermined condition is satisfied, and performs the repetitive control on the two collecting surfaces. 3. The internal combustion engine according to claim 1, wherein the reverse rotation means is controlled to start from a state in which the smaller amount of the fine particles is on the exhaust upstream side and the larger amount of the fine particles is on the exhaust downstream side. 4. Exhaust gas purification device. An exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 3,
A detection unit that detects a deviation of the accumulation amount of the fine particles between the two collection surfaces,
An internal combustion engine that controls the reversing means so that when the deviation detected by the detection means is larger than a predetermined level, the deviation in the amount of the fine particles deposited between the two collecting surfaces is reduced. Exhaust purification equipment. The detection means estimates the amount of particulates deposited on the two collecting surfaces based on a parameter related to the pressure of the exhaust system of the internal combustion engine, respectively. 5. The exhaust gas purifying apparatus for an internal combustion engine according to claim 4, wherein the deviation of the accumulation amount of the fine particles is detected.

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