JP2006177305A - Exhaust purification device for internal combustion engine and exhaust purification method for internal combustion engine - Google Patents

Abstract

Provided is a technique capable of removing particulate matter deposited on a particulate filter without providing a plurality of particulate filters.
A particulate filter, a first shut-off valve provided in an exhaust passage on the upstream side of the filter, and a first shut-off valve connected between the first shut-off valve and the filter are introduced. And holding the exhaust gas to the exhaust gas holding means 7 by closing the first shut-off valve 4 and holding the exhaust gas to the first shut-off valve 4 side. Make exhaust flow backward.
[Selection] Figure 1

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine and an exhaust gas purification method for the internal combustion engine.

  By providing a particulate filter (hereinafter referred to as a filter) in the exhaust passage of the internal combustion engine, particulate matter (hereinafter referred to as PM) in the exhaust can be collected by the filter. When a catalyst is supported on this filter, PM can be oxidized and removed by the action of the catalyst.

  However, even if the catalyst is supported on the filter, PM may be deposited on the filter without being oxidized and removed. Since such PM is deposited away from the catalyst, it is difficult to obtain the effect of the catalyst and induces further PM deposition.

On the other hand, a technique is known in which the flow direction of the exhaust gas in the filter is reversed, and the PM accumulated on the filter end face is separated by the force of the exhaust gas flowing backward (see, for example, Patent Document 1). According to this prior art, since PM is peeled from the filter, it is possible to suppress clogging of the filter.
JP 2002-357115 A Japanese Patent Laid-Open No. 8-232639 JP 2000-8840 A JP 2002-147217 A

  However, in the conventional filter that reverses the flow direction of the exhaust, the exhaust separated from the filter is allowed to flow downstream as it is regardless of whether the flow is forward or reverse. Therefore, PM peeled off from the end face of the filter when switching between the forward flow and the reverse flow is not collected again by this filter. And since PM which peeled from the filter is flowed to the downstream of a filter with exhaust_gas | exhaustion, in order to suppress discharge | release of PM to air | atmosphere, it was necessary to provide another filter downstream. Further, the conventional structure that reverses the flow direction of the exhaust gas in the filter has a complicated structure, and the exhaust gas may leak from a valve for reversing the flow of the exhaust gas, for example.

  The present invention has been made in view of the above problems, and provides a technique capable of removing particulate matter deposited on a particulate filter without providing a plurality of particulate filters. Objective.

In order to achieve the above object, an exhaust gas purification apparatus for an internal combustion engine according to the present invention comprises:
A particulate filter provided in an exhaust passage of the internal combustion engine;
A first shut-off valve that is provided in an exhaust passage upstream of the particulate filter and blocks the flow of exhaust gas in the exhaust passage;
Exhaust holding means connected between the first shut-off valve and the particulate filter, for introducing and temporarily holding the exhaust during this period;
With
By closing the first shut-off valve and introducing exhaust gas into the exhaust gas holding means to hold the exhaust gas, the exhaust gas flows back from the particulate filter to the first shut-off valve side.

  The most significant feature of the present invention is that when the exhaust gas is introduced into the exhaust gas holding means, the exhaust gas flows back in the particulate filter, so that the particulate matter deposited on the particulate filter is separated from the particulate filter. Or finely pulverizing the particles and then easily oxidizing the particulate matter flowing into the particulate filter.

  In the present invention, when the exhaust gas flows from the first cutoff valve in the direction of the particulate filter, the forward flow is used, and when the exhaust gas flows from the particulate filter in the direction of the first cutoff valve, the reverse flow is used.

  Here, when the first shut-off valve is closed, the inflow of exhaust gas from the internal combustion engine to the particulate filter stops. At this time, if the exhaust gas from the first cutoff valve to the particulate filter is introduced into the exhaust gas holding means, the pressure in the exhaust passage between the first cutoff valve and the particulate filter decreases. Therefore, the exhaust gas in the particulate filter and the exhaust gas downstream of the particulate filter flow into the exhaust gas holding means between the first shutoff valve and the particulate filter. At that time, the exhaust gas flows backward in the particulate filter. Therefore, a force is applied to the particulate matter deposited on the particulate filter in a direction different from that in the forward exhaust flow, and the particulate matter is separated from the particulate filter. Moreover, it is made fine by the exhaust which flows backward. The particulate matter separated from the particulate filter is held in the exhaust holding means together with the exhaust, or remains in the exhaust passage upstream of the particulate filter.

  In this way, since the particulate matter deposited on the particulate filter can be peeled off from the particulate filter, the particulate matter that flows into the particulate filter next can be easily taken into the pores. it can. In addition, when the catalyst is supported on the particulate filter, the chance of contact between the particulate matter and the catalyst can be increased, so that the particulate matter can be easily oxidized and removed. And since the particulate matter peeled from the particulate filter is held in the exhaust gas holding means, it can be suppressed that the particulate matter is released into the atmosphere.

  The present invention further includes a second shutoff valve provided in the exhaust passage downstream of the particulate filter and shutting off the flow of exhaust gas in the exhaust passage, and exhausted from the particulate filter to the first shutoff valve side. The second shut-off valve can be closed when reversing the flow.

  When the first shut-off valve and the second shut-off valve are closed, a space closed by an exhaust passage including a particulate filter (hereinafter referred to as a closed space) is formed. The exhaust gas holding means is connected to this closed space. Here, when the second shut-off valve is closed first and then the first shut-off valve is closed, the exhaust gas is introduced into the exhaust holding means after the pressure upstream of the second shut-off valve rises due to the exhaust from the internal combustion engine. Therefore, it becomes possible to easily introduce the exhaust into the exhaust holding means.

In the present invention, the exhaust holding means includes
A holding part for temporarily holding exhaust gas on the first shut-off valve side of the particulate filter;
A communication passage connecting the exhaust passage between the first shut-off valve and the particulate filter and the holding portion;
A third shut-off valve that shuts off the flow of exhaust gas in the communication path;
Decompression means for decompressing the inside of the holding unit;
Consists of
Exhaust gas can be made to flow backward from the particulate filter to the first cutoff valve side by setting the pressure of the holding portion to a negative pressure, closing the first cutoff valve, and opening the third cutoff valve.

  If the pressure in the holding part becomes negative by the pressure reducing means, a difference occurs in the pressure between the closed space and the holding part, and this pressure difference can be further increased. As a result, the flow rate of the exhaust gas flowing backward in the particulate filter can be increased, and the force applied to the particulate matter can be further increased. Thereby, exfoliation and atomization of the particulate matter from the particulate filter can be further promoted. Moreover, there is no need to increase the pressure in the enclosed space.

  In the present invention, exhaust return means for returning the exhaust gas held by the exhaust gas holding means to the exhaust passage between the particulate filter and the internal combustion engine can be further provided.

  The particulate matter separated from the particulate filter is held together with the exhaust gas in the exhaust gas holding means. By returning the particulate matter to the upstream side of the particulate filter, the particulate matter held in the exhaust gas holding means is retained. The material is again collected on the particulate filter. At this time, since the particulate matter is hardly deposited on the upstream end face of the particulate filter, most of the particulate matter is taken into the pores of the particulate filter. In the pores, the catalytic activity is high, and the particulate matter is easily oxidized and removed. That is, the particulate matter deposited without being oxidized and removed by the particulate filter is separated from the particulate filter by the exhaust gas flowing backward, and the particulate matter is particulated when the exhaust flow becomes a forward flow. By returning to the upstream side of the filter, it is possible to collect the particulate matter originally deposited on the particulate filter at a place where the activity of the catalyst is high, and the particulate matter can be easily oxidized and removed. Become.

  In the present invention, the exhaust gas can be made to flow backward from the particulate filter to the first cutoff valve side when the vehicle is decelerated.

  Here, when the first shut-off valve or the second shut-off valve is closed, the flow of exhaust gas from the internal combustion engine is shut off, which affects the operating state of the internal combustion engine. However, when the vehicle is decelerating, the operation of the internal combustion engine is stopped by the fuel cut, so that the influence on the operation state of the internal combustion engine can be reduced. Moreover, since the rotational force of the internal combustion engine can be reduced by closing the first cutoff valve and the second cutoff valve, the deceleration force of the vehicle can be increased.

  In the present invention, the apparatus further comprises particulate matter amount estimating means for estimating the amount of particulate matter collected by the particulate filter, and collected by the particulate filter estimated by the particulate matter amount estimating means. When the amount of the particulate matter exceeds a predetermined amount, the exhaust gas can be made to flow backward from the particulate filter to the first shutoff valve side.

  As described above, when the first shut-off valve and the second shut-off valve are closed, the operating state of the internal combustion engine is affected. Therefore, the first shut-off valve and the first shut-off valve only when the particulate matter needs to be removed from the particulate filter. By closing the second shut-off valve, it is possible to reduce the number of times it affects the operating state of the internal combustion engine. That is, the predetermined amount is an amount that requires the removal of particulate matter from the particulate filter. For example, the predetermined amount may cause damage to the particulate filter or the accumulation amount that may affect the operating state of the internal combustion engine. A certain amount of deposition can be obtained. Even if there is no such fear, the predetermined amount may be determined in order to periodically remove the particulate matter.

In the present invention, there is further provided a particulate matter forced removal means for raising the temperature of the particulate filter to oxidize and remove the particulate matter collected by the particulate filter, from the particulate filter to the first cutoff valve. After the exhaust gas is made to flow backward to the side, the particulate matter can be oxidized and removed by the particulate matter forced removal means.

  Here, the particulate matter collected by the particulate filter can be oxidized and removed by raising the temperature of the particulate filter. However, the particulate matter deposited on the particulate filter is difficult to oxidize even at high temperatures. In that respect, the particulate matter deposited on the particulate filter is separated from the particulate filter by the backflow of exhaust gas, and then returned to the particulate filter, so that the particulate matter is finely divided and oxidized at high temperature. It can be made easy. As a result, the amount of energy for raising the temperature of the particulate filter can be reduced.

  In order to achieve the above object, an exhaust gas purification method for an internal combustion engine according to the present invention is configured to cause the pressure on the downstream side of the particulate filter to be relatively higher than the pressure on the upstream side to cause the exhaust gas to flow backward in the particulate filter. The first step of discharging the particulate matter collected by the particulate filter to the internal combustion engine side from the particulate filter, and then the pressure on the upstream side of the particulate filter is set to be higher than the pressure on the downstream side. And a second step of collecting the particulate matter which has been relatively raised and discharged by the particulate filter.

  If the pressure on the downstream side of the particulate filter is relatively higher than the pressure on the upstream side, the gas in the particulate filter flows backward and flows to the internal combustion engine side. Thereby, a force is applied to the particulate matter deposited on the particulate filter in a direction different from that in the forward flow, and the particulate matter is separated from the particulate filter. Further, if the pressure difference between the downstream side and the upstream side of the particulate filter is large, the gas can flow vigorously in the particulate filter, and the particulate matter deposited on the particulate filter can be blown away. After that, if the pressure on the upstream side of the particulate filter is relatively higher than the pressure on the downstream side, the particulate matter that has flowed upstream of the particulate filter flows again into the particulate filter. At this time, the adhering amount of the particulate matter on the upstream end face of the particulate filter is reduced, and the particulate matter is easily taken into the pores of the particulate filter. Further, since the particulate matter is finely divided by being peeled off from the particulate filter, it can be easily oxidized.

  In the exhaust gas purification apparatus for an internal combustion engine and the exhaust gas purification method for an internal combustion engine according to the present invention, the exhaust gas is caused to flow backward in the particulate filter, and the particulate matter deposited on the particulate filter is peeled off from the particulate filter. Further, by temporarily holding the particulate matter on the upstream side, the particulate matter deposited on the particulate filter can be removed without providing a plurality of particulate filters.

  Hereinafter, specific embodiments of an exhaust gas purification apparatus for an internal combustion engine and an exhaust gas purification method for an internal combustion engine according to the present invention will be described based on the drawings.

  FIG. 1 is a diagram illustrating a schematic configuration of an internal combustion engine 1 according to the present embodiment.

  The internal combustion engine 1 shown in FIG. 1 is a four-cycle diesel engine.

  An exhaust passage 2 is connected to the internal combustion engine 1, and exhaust gas from the internal combustion engine 1 flows through the exhaust passage 2. This exhaust passage 2 communicates with the atmosphere downstream.

  A particulate filter 3 (hereinafter referred to as filter 3) carrying an NOx storage reduction catalyst (hereinafter referred to as NOx catalyst) is provided in the middle of the exhaust passage 2.

  A first shutoff valve 4 that shuts off the flow of exhaust gas is provided in the exhaust passage 2 downstream of the internal combustion engine 1 and upstream of the filter 3. On the other hand, the exhaust passage 2 downstream of the filter 3 is provided with a second shutoff valve 5 that shuts off the flow of exhaust.

  One end of the communication path 6 is connected to the exhaust passage 2 downstream of the first cutoff valve 4 and upstream of the filter 3, and the other end of the communication path 6 is connected to the exhaust holding tank 7. . The exhaust holding tank 7 is a tank capable of temporarily holding exhaust and PM. A third shut-off valve 8 that shuts off the flow of exhaust gas is provided in the middle of the communication path 6.

  A pump 10 is connected to the exhaust holding tank 7 through an exhaust suction passage 9. The pump 10 sucks exhaust gas and PM in the exhaust gas holding tank 7. The outlet of the pump 10 is connected to one end of the return passage 11, and the other end of the return passage 11 is connected in the middle of the exhaust passage 2, downstream of the connection portion of the communication passage 6 and upstream of the filter 3. Has been.

  A pressure sensor 12 that outputs a signal corresponding to the pressure on the upstream side of the filter 3 is attached to the upstream side of the filter 3.

  The internal combustion engine 1 is also provided with an ECU 13 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 13 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver.

  The ECU 13 is connected to the first cutoff valve 4, the second cutoff valve 5, and the third cutoff valve 8 through electrical wiring, and the ECU 10 controls them.

  The pressure sensor 12 is electrically connected to the ECU 13, and the ECU 13 calculates the pressure on the upstream side of the filter 3 based on the output signal of the pressure sensor 12.

  In this embodiment, the exhaust gas is caused to flow backward in the filter 3 in order to promote the oxidation of the PM collected by the filter 3. Here, when the exhaust gas flows from the first shut-off valve 4 toward the second shut-off valve 5, the forward flow is assumed, and when the exhaust gas flows from the second shut-off valve 5 toward the first shut-off valve 4, the reverse flow is assumed.

  FIG. 2 is a diagram schematically showing the state of PM adhesion to the filter when the PM oxidation promotion control according to the present embodiment is performed. 2A shows a state before the exhaust is made to flow backward, FIG. 2B shows a state when the exhaust is made to flow backward, and FIG. 2C shows a forward flow after the exhaust is made to flow backward. It shows the state when Moreover, the arrow in FIG. 2 has shown the direction through which exhaust_gas | exhaustion flows.

  In the state of FIG. 2A, PM covers the pores 32 of the filter 3 at the upstream end face 31 of the filter 3. Here, in the pore 32, the activity of the catalyst is high and it is easy to oxidize PM. However, once the PM covers the pore 32, the PM cannot enter the pore 32 and the upstream end surface 31 has PM. Accumulates. The PM deposited on the upstream end face 31 is difficult to be oxidized and removed because it is difficult to obtain a catalyst effect. Then, PM further adheres to this PM and induces further PM deposition. In this way, PM accumulates and hardens where it is difficult to obtain the effect of the catalyst, and forms a bridge.

When the exhaust gas is made to flow backward in such a state, as shown in FIG.
M is peeled from the upstream end face 31 while being finely divided. That is, by causing the exhaust gas to flow backward, a force can be applied to the accumulated PM from a different direction so far, and the PM can be separated from the upstream end face 31. Moreover, PM can be made finer by reversing exhaust gas vigorously. In this way, the PM that has been peeled off from the filter 3 and made finer flows to the upstream side of the filter 3.

  Then, by making the exhaust flow forward again, the refined PM reaches the upstream end face 31. At this time, since the PM covering the pores 32 is removed, the PM flows into the pores 32 together with the exhaust gas. Then, PM is collected in the pores 32. Moreover, since the activity is high in the pores 32, PM is oxidized and removed. Even if the PM does not flow into the pores 32, the PM is easily oxidized and removed if it adheres to a location on the upstream end face 31 where the effect of the catalyst is easily obtained.

  Thus, in the filter 3, by changing the exhaust flow in the order of forward flow, reverse flow, and forward flow, the PM accumulated in the filter 3 is peeled off while being finely divided toward the upstream side of the filter 3, By collecting PM from the upstream side of the filter 3, oxidation removal of PM can be promoted. And since PM which peeled from the filter 3 flows into the filter 3 again, it is suppressed that PM peeled from this filter 3 is discharge | released in air | atmosphere.

  Here, in a conventional filter that reverses the flow direction of exhaust gas, exhaust gas that has passed through the filter is not returned again to the same filter, regardless of whether it is forward flow or reverse flow, and flows directly downstream. It was. Therefore, in order not to release PM into the atmosphere, it is necessary to provide a filter further downstream.

  On the other hand, in this embodiment, the PM deposited on the upstream end face 31 and the pores 32 of the filter 3 is made fine by reversing the exhaust gas, and then the PM is again collected by the filter 3 as a forward flow. There is no need to further provide a filter.

  Next, specific control of this embodiment will be described.

  FIG. 3 is a flowchart showing a flow of PM oxidation promotion control according to the present embodiment. This routine is repeatedly executed every predetermined time. In addition, before this routine is executed or before the third shut-off valve 8 is opened, the pump 10 is operated to keep the inside of the exhaust holding tank 7 at a negative pressure. Further, before the PM oxidation promotion control is executed, the first cutoff valve and the second cutoff valve are opened, and the third cutoff valve is closed.

  In step S101, the ECU 13 determines whether or not the exhaust brake is in use. Here, the exhaust brake increases the resistance of the internal combustion engine and increases the deceleration force of the vehicle by narrowing the passage area of the exhaust passage with the exhaust throttle valve. In this embodiment, the first shut-off valve 4 and the second shut-off valve 5 serve as exhaust throttle valves, and act as an exhaust brake by closing the first shut-off valve 4 or the second shut-off valve 5. Further, since the exhaust brake is performed when the vehicle is decelerated, the fuel cut is performed in the internal combustion engine 1, and even if the first shut-off valve 4 or the second shut-off valve is closed, the operation state of the internal combustion engine is maintained. The effect is small. Therefore, in the present embodiment, the exhaust gas reversely flows through the filter 3 during vehicle deceleration.

  If an affirmative determination is made in step S101, the process proceeds to step S102. On the other hand, if a negative determination is made, this routine is temporarily terminated.

In step S102, the ECU 13 opens the first cutoff valve 4, closes the second cutoff valve 5, and closes the third cutoff valve 8. By closing the second shut-off valve 5, the exhaust from the internal combustion engine 1 accumulates in the exhaust passage 2 between the internal combustion engine 1 and the second shut-off valve 5, and the pressure in the exhaust passage 2 during this time increases. Thereby, the pressure difference between the exhaust passage 2 upstream of the second shutoff valve 5 and the exhaust holding tank 7 is increased. In addition, the load on the internal combustion engine increases and the deceleration force of the vehicle increases.

  In step S103, the ECU 13 determines whether or not a first predetermined time has elapsed since the second cutoff valve 5 was closed. This first predetermined time is a time required for the pressure difference between the exhaust passage 2 upstream of the second shut-off valve 5 and the exhaust holding tank 7 to become so large that the PM can be separated. That is, it is the time provided for generating a pressure difference for obtaining the flow rate of exhaust gas necessary for separating the PM from the filter 3. If the negative pressure in the exhaust holding tank 7 is sufficiently large, or if the pressure in the exhaust passage 2 is sufficiently high, the first predetermined time may be set to zero.

  If an affirmative determination is made in step S103, the process proceeds to step S104. On the other hand, if a negative determination is made, the process returns to step S102.

  In step S104, the ECU 13 closes the first cutoff valve 4, closes the second cutoff valve 5, and opens the third cutoff valve 8. By closing the first shutoff valve 4, when the third shutoff valve 8 is opened, it is possible to suppress the exhaust upstream of the first shutoff valve 4 from flowing into the exhaust holding tank 7, and back flow in the filter 3. It can suppress that the quantity of exhaust to perform decreases. Further, by continuously closing the second shut-off valve 4, it is possible to suppress the pressure on the upstream side of the second shut-off valve 5 that has been raised at a high level from escaping downstream from the second shut-off valve 5. When the third shut-off valve 8 is opened, the pressure in the exhaust passage 2 is higher than the pressure in the exhaust holding tank 7, so that the exhaust in the exhaust passage 2 flows into the exhaust holding tank 7. At this time, the exhaust in the filter 3 and the exhaust in the exhaust passage 2 between the filter 3 and the second shut-off valve 5 flow back through the filter 3. Due to the momentum of the exhaust at this time, the PM in the filter 3, particularly the PM deposited on the upstream end face of the filter 3 can be peeled or blown away toward the upstream side of the filter 3. Moreover, since the 1st cutoff valve 4 is closed, the deceleration force of a vehicle is large.

  In step S105, the ECU 13 determines whether or not the exhaust brake is in use. That is, exhaust gas is caused to flow into the exhaust holding tank 7 when the exhaust brake is used in consideration of drivability. Therefore, when the exhaust brake is not used, it is immediately necessary to suppress deterioration of drivability. The first cutoff valve 4 and the second cutoff valve 5 are opened.

  Further, when the pressure difference between the exhaust passage 2 and the exhaust holding tank 7 disappears, the backflow of the exhaust gas in the filter 3 stops. At this time, the exhaust brake is continued with the first shut-off valve 4 kept closed. The second cutoff valve 5 may be opened, and the third cutoff valve 8 may be closed. Further, the inside of the exhaust holding tank 7 may be set to a negative pressure again so that the exhaust gas can be reversely flowed when the next exhaust brake is used.

  If an affirmative determination is made in step S105, the process proceeds to step S106. On the other hand, if a negative determination is made, the process returns to step S104.

  In step S106, the ECU 13 opens the first cutoff valve 4, opens the second cutoff valve 5, and closes the third cutoff valve 8. As a result, the exhaust from the internal combustion engine 1 flows through the exhaust passage 2 and passes through the filter 3 in a forward flow. Then, the PM blown to the upstream side of the filter 3 is collected by the filter 3 again. At this time, a large amount of PM is taken into the more active pores 32, so that the PM is removed by oxidation.

  And the pump 10 is operated and the inside of the exhaust holding tank 7 is maintained at a negative pressure. Here, since the PM separated from the filter 3 is also held in the exhaust holding tank 7, if the exhaust in the exhaust holding tank 7 is released into the atmosphere as it is, the PM is released into the atmosphere without being removed. It will be. Therefore, in this embodiment, the exhaust gas and PM discharged from the pump 10 are returned to the exhaust passage 2 upstream of the filter 3 via the return passage 11. As a result, PM held in the exhaust holding tank 7 is collected again by the filter 3 and taken into the pores 32, so that PM can be easily oxidized and removed.

  In this way, when the vehicle is decelerating and the exhaust brake is used, the PM accumulated on the filter 3 is peeled away toward the upstream side of the filter 3 or is blown off, and the PM is then forward-flowed. Then, by collecting again with the filter 3, the PM deposited on the filter 3 can be easily oxidized and removed.

  In addition, the oxidation of PM is promoted every time the exhaust brake is used, and the PM removal capability of the filter 3 can be constantly kept high. As a result, the number of PM oxidation removals (hereinafter referred to as forced regeneration) performed by raising the temperature of the filter 3 can be reduced, so that the amount of fuel consumed for raising the temperature of the filter 3 can be reduced. Can improve fuel efficiency.

  In this embodiment, the first shut-off valve 4 is closed in step S104 after the second shut-off valve 5 is closed in step S102. However, the pressure in the exhaust passage 2 upstream of the second shut-off valve 5 is not limited. If the pressure in the exhaust holding tank 7 can be made lower than that, the first shut-off valve 4 and the second shut-off valve 5 may be closed at the same time, or the first shut-off valve 4 may be closed before the second shut-off valve 5. You may close it. Further, the pressure in the exhaust holding tank 7 is not necessarily negative.

  In this embodiment, the exhaust gas is made to flow backward in the filter 3 every time the exhaust brake is used. Instead, the exhaust gas is made to flow backward in the filter 3 immediately before the filter 3 is forcibly regenerated. It may be. On the contrary, the filter 3 may be forcibly regenerated immediately after the exhaust gas is made to flow backward in the filter 3.

  This forced regeneration of the filter 3 is performed when the amount of PM deposited on the filter 3 reaches a predetermined amount. Here, the amount of PM deposited on the filter 3 can be obtained by previously obtaining the amount of PM corresponding to the detection value of the pressure sensor 12 through experiments or the like and comparing it. In addition, a differential pressure sensor for detecting a differential pressure upstream and downstream of the filter 3 is attached to the exhaust passage 2, and the amount of PM corresponding to the detected value of the differential pressure sensor is obtained in advance through experiments or the like and compared with this. You may make it obtain by doing. Further, the PM collection amount corresponding to the operation state (exhaust temperature, fuel injection amount, engine speed) of the internal combustion engine 1 is obtained in advance by experiments and mapped, and the PM collection amount obtained from this map is integrated. Thus, the amount of accumulated PM can also be obtained. Further, the PM accumulation amount may be estimated according to the vehicle travel distance or travel time.

  Thus, if exhaust gas is made to flow backward in the filter 3 immediately before the forced regeneration of the filter 3 is performed, the PM is finely granulated, so that the PM is quickly oxidized and removed during the forced regeneration. Thereby, the time required for forced regeneration can be shortened, and fuel consumption can be improved. Further, it is possible to suppress the PM deposited on the filter 3 from being oxidized at the time of forced regeneration and overheating the filter 3.

  Further, the exhaust gas may be made to flow backward in the filter 3 when the amount of PM deposited on the filter 3 reaches a predetermined amount. In this way, the number of times the exhaust gas flows back in the filter 3 can be reduced, and the influence on drivability can be reduced.

  In the present embodiment, the second shutoff valve 5 is provided, but this is not always necessary when the pressure in the exhaust holding tank 7 can be made negative. That is, if the first shut-off valve 4 is closed and the third shut-off valve 8 is opened with a negative pressure in the exhaust holding tank 7 and the third shut-off valve 8 is opened, the exhaust flows backward in the filter 3 and is held in the exhaust holding tank 7. Can be peeled off. Further, the PM can be collected again by the filter 3 by opening the first cutoff valve 4 and then closing the third cutoff valve 8 and operating the pump 10.

  As described above, according to the present embodiment, the PM accumulated in the filter 3 and further solidified can be refined by causing the exhaust gas to flow backward in the filter 3. Then, by making the exhaust flow forward, the PM can be attached to the upstream end face 31 of the filter 3 or the PM can be taken into the pores 32. Therefore, PM can be easily removed by the NOx catalyst supported on the filter 3. As a result, the number of times of forced regeneration can be reduced or the time required for forced regeneration can be shortened, so that the amount of fuel used can be reduced and fuel efficiency can be improved. Moreover, since it can suppress that a lot of PM accumulates, it can suppress that the filter 3 overheats with the heat | fever which generate | occur | produces when a lot of PM oxidizes. Further, it is not necessary to provide a separate filter in addition to the filter 3.

1 is a diagram illustrating a schematic configuration of an internal combustion engine according to a first embodiment. It is the figure which showed schematically the adhesion state of PM to a filter when PM oxidation promotion control by the present Example 1 is performed. 2A shows a state before the exhaust is made to flow backward, FIG. 2B shows a state when the exhaust is made to flow backward, and FIG. 2C shows a forward flow after the exhaust is made to flow backward. It shows the state when 3 is a flowchart showing a flow of PM oxidation promotion control according to the first embodiment.

Explanation of symbols

1 Internal combustion engine 2 Exhaust passage 3 Particulate filter 4 First shut-off valve 5 Second shut-off valve 6 Communication passage 7 Exhaust holding tank 8 Third shut-off valve 9 Exhaust suction passage 10 Pump 11 Return passage 12 Pressure sensor 31 Upstream end face 32 Narrow Hole

Claims (8)

A particulate filter provided in an exhaust passage of the internal combustion engine;
A first shut-off valve that is provided in an exhaust passage upstream of the particulate filter and blocks the flow of exhaust gas in the exhaust passage;
Exhaust holding means connected between the first shut-off valve and the particulate filter, for introducing and temporarily holding the exhaust during this period;
With
An internal combustion engine comprising: an internal combustion engine that closes the first shut-off valve, introduces exhaust gas into the exhaust gas holding unit, and holds the exhaust gas, thereby causing the exhaust gas to flow backward from the particulate filter to the first shut-off valve side. Exhaust purification device.   A second shut-off valve that is provided in the exhaust passage downstream of the particulate filter and shuts off the flow of exhaust gas in the exhaust passage, and when the exhaust gas flows back from the particulate filter to the first shut-off valve side, The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the second shut-off valve is closed. The exhaust holding means is
A holding part for temporarily holding exhaust gas on the first shut-off valve side of the particulate filter;
A communication passage connecting the exhaust passage between the first shut-off valve and the particulate filter and the holding portion;
A third shut-off valve that shuts off the flow of exhaust gas in the communication path;
Decompression means for decompressing the inside of the holding unit;
Consists of
The exhaust gas is made to flow backward from the particulate filter to the first shut-off valve side by setting the pressure of the holding portion to a negative pressure, closing the first shut-off valve, and opening the third shut-off valve. 3. An exhaust emission control device for an internal combustion engine according to 1 or 2.   The internal combustion engine according to any one of claims 1 to 3, further comprising exhaust return means for returning the exhaust gas held by the exhaust gas holding means to an exhaust passage between the particulate filter and the internal combustion engine. Exhaust purification equipment.   5. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the exhaust gas is caused to flow backward from the particulate filter to the first shut-off valve side when the vehicle is decelerated.   The apparatus further comprises particulate matter amount estimating means for estimating the amount of particulate matter collected by the particulate filter, and the particulate matter collected by the particulate filter estimated by the particulate matter amount estimating means. 6. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein when the amount becomes a predetermined amount or more, the exhaust gas is caused to flow backward from the particulate filter to the first cutoff valve side.   It further comprises a particulate matter forced removal means for raising the temperature of the particulate filter to oxidize and remove particulate matter collected by the particulate filter, and exhaust gas flows backward from the particulate filter to the first shutoff valve side. 6. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the particulate matter is forcibly removed by oxidation by the particulate matter forced removal means. The particulate matter collected by the particulate filter is caused to flow from the particulate filter by making the pressure on the downstream side of the particulate filter relatively higher than the pressure on the upstream side and causing the exhaust gas to flow backward in the particulate filter. The first step of discharging the internal combustion engine to the internal combustion engine side, and then raising the pressure on the upstream side of the particulate filter relatively higher than the pressure on the downstream side to trap the discharged particulate matter with the particulate filter. And a second step of collecting the exhaust gas purification method for an internal combustion engine.

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