JP2006226231A - Exhaust gas purification device for internal combustion engine - Google Patents

Abstract

In an exhaust gas purification apparatus for an internal combustion engine having a plurality of parallel exhaust passages, the size of the exhaust gas purification device can be made as small as possible, and the temperature of a catalyst for exhaust gas purification provided in the exhaust passage can be easily maintained. To do.
In an exhaust purification device for an internal combustion engine, a plurality of exhaust passages 2 and 3 through which exhaust from the internal combustion engine flows and a plurality of exhaust passages are provided, and a plurality of exhausts for adjusting an exhaust flow rate of the exhaust passages. And a plurality of exhaust gas purifying means 8 and 9 for purifying exhaust gas flowing through the exhaust passages, provided in each of the plurality of exhaust gas passages. Other exhaust purification means 9 surrounds one exhaust purification means 8 and the exhaust purification means are arranged concentrically.
[Selection] Figure 1

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine that performs exhaust gas purification.

  In an internal combustion engine, in order to prevent the particulate matter in the exhaust from being released into the atmosphere, a filter is provided in the exhaust passage, and the particulate matter is collected by the filter. However, the trapped amount of particulate matter in the filter has a limit capacity. If the trapped amount is excessively large, the back pressure in the exhaust passage increases, resulting in an increase in the engine load of the internal combustion engine.

Therefore, it is necessary to oxidize and remove the particulate matter collected by the filter. In the oxidation removal of the collected particulate matter, efficient oxidation removal can be performed by sending stable exhaust gas with less pulsation to the filter. Therefore, two exhaust passages for the internal combustion engine are provided in parallel, and a filter is installed in each, so that the amount of exhaust flowing into one of the filters can be maintained stably regardless of the operating state of the internal combustion engine, and efficient particles A technique for performing oxidation removal of a substance is disclosed (for example, see Patent Document 1).
JP-A-5-59930 JP 2004-92512 A JP 2003-83045 A

  By constructing the exhaust gas purification device of the internal combustion engine in parallel with a plurality of exhaust passages, the object is to be provided with a filter, a NOx storage reduction catalyst, etc. provided in one passage while being hardly affected by the operating state of the internal combustion engine. It becomes possible to supply the exhaust flow rate. However, by providing the exhaust passages in parallel, the overall size of the exhaust emission control device becomes large, and the mountability to the vehicle deteriorates. Further, since the heat radiation area is large, it is difficult to raise and maintain the temperature of the catalyst for exhaust purification provided in each passage.

  In the present invention, in view of the above-described problems, in an exhaust gas purification apparatus for an internal combustion engine having a plurality of parallel exhaust passages, the size of the exhaust gas purification device can be made as compact as possible, and exhaust purification provided in the exhaust passage can be achieved. The object is to facilitate the temperature rise and maintenance of the catalyst.

  In order to solve the above-described problems, the present invention focuses on the mutual positional relationship between exhaust purification means such as catalysts provided in a plurality of exhaust passages through which exhaust from an internal combustion engine flows. By devising the arrangement of each exhaust purification means, it is possible to reduce the overall size of the exhaust purification device, and one exhaust purification means fulfills the function of the heat insulation structure of the other exhaust purification means, thereby purifying the exhaust. This is because the temperature rise and maintenance of the means can be facilitated.

  Therefore, the present invention is an exhaust purification device for an internal combustion engine, and is provided in each of a plurality of exhaust passages through which exhaust from the internal combustion engine flows and the plurality of exhaust passages, and a plurality of exhaust passages for adjusting the exhaust flow rate of the exhaust passages Each of the plurality of exhaust passages, and a plurality of exhaust purification means for purifying the exhaust gas flowing through the exhaust passages. Other exhaust purification means surround the exhaust purification means, and the exhaust purification means are arranged substantially concentrically.

In the exhaust gas purification apparatus for an internal combustion engine described above, a plurality of exhaust passages are provided, and an exhaust adjustment valve and an exhaust purification means are provided in each exhaust passage. Therefore, the exhaust flow rate flowing through each exhaust passage, in other words, the exhaust flow rate flowing into the exhaust purification means provided in each exhaust passage can be arbitrarily adjusted by the corresponding exhaust adjustment valve. As a result, the exhaust flow rate that is not influenced by the operating state of the internal combustion engine in one exhaust purification unit by flowing the remaining exhaust gas into the other exhaust purification unit while maintaining the exhaust flow rate flowing into one exhaust purification unit substantially constant Can be controlled.

  Here, in the plurality of exhaust gas purification means, it is possible to efficiently use the space when arranging the exhaust gas purification means by surrounding the exhaust gas purification means hierarchically with the other exhaust gas purification means. Thus, the volume of the space required for the exhaust purification device, particularly the space required for installation of the exhaust purification means can be suppressed, and downsizing can be achieved. In addition, since one exhaust purification unit is hierarchically surrounded by another exhaust purification unit, the other exhaust purification unit functions as a heat insulating structure for the one exhaust purification unit. As a result, the temperature rise and maintenance of one exhaust purification means can be easily performed.

  Moreover, in the mutual relationship on arrangement | positioning of one exhaust gas purification means and another exhaust gas purification means, each is arrange | positioned concentrically. By arranging each other in this manner, the heat distribution in the plurality of exhaust purification means becomes more uniform, so that the load on each exhaust purification means caused by heat, such as generation of strain due to thermal stress, can be reduced.

  In the exhaust gas purification apparatus for an internal combustion engine, in the plurality of exhaust gas control valves, the exhaust gas adjustment valve controls the opening degree of each exhaust gas control valve and adjusts the exhaust gas flow rate to the exhaust gas purification unit corresponding to the exhaust gas control valve. In the case of further comprising a valve control means, when the temperature of the exhaust purification means located inside among the plurality of exhaust purification means is raised, the exhaust control valve control means sends exhaust to the exhaust purification means located inside. It is also possible to suppress the inflow of exhaust gas to the exhaust gas purification means located outside of the plurality of exhaust gas purification means.

  The exhaust regulating valve control means controls the opening degree of the exhaust regulating valve provided in each exhaust passage, and is provided in the exhaust passage, that is, the exhaust passage provided with the exhaust regulating valve. It has a function of adjusting the flow rate of the exhaust gas flowing into the exhaust gas purification means. Here, among the plurality of exhaust gas purification means, the “exhaust gas purification means positioned inside” and the “exhaust gas purification means positioned outside” determine the inner side and the outer side in a relative relationship between them. That is, as described above, in the exhaust gas purification apparatus for an internal combustion engine provided so that a plurality of exhaust gas purification means are hierarchically surrounded, the exhaust gas purification means located on the inner side in relation to the two exhaust gas purification means, The exhaust purification means located outside is determined, and the same applies to the invention described below.

  Here, the reason why the exhaust gas is preferentially flowed into the exhaust purification means located inside the exhaust purification means located outside by the exhaust adjustment valve control means is that the exhaust purification means located inside is located outside. Since it is surrounded by more exhaust gas purification means than the exhaust gas purification means, the heat dissipation can be suppressed. As a result, in the exhaust gas purification apparatus for an internal combustion engine described above, the exhaust gas purification means located on the inner side is more likely to be warmed. Therefore, the exhaust gas is preferentially allowed to flow into the exhaust gas purification means located on the inner side. Can be achieved.

  In addition, when exhaust is flowing into the exhaust purification means located on the inner side, the inflow of exhaust gas to the exhaust purification means located on the outer side is completely interrupted by the exhaust control valve control means, or the exhaust flow rate thereof Is preferably controlled to be less than the exhaust gas flow rate to the exhaust gas purification means located inside.

Here, in the exhaust gas purification apparatus for an internal combustion engine, when exhaust gas is caused to flow into the exhaust gas purification unit located inside by the exhaust gas control valve control unit and the temperature thereof is increased, among the plurality of exhaust passages When the back pressure of any of the exhaust passages exceeds a predetermined pressure, the exhaust control valve control means increases the opening of the exhaust control valve corresponding to the exhaust purification means located outside and exhausts the exhaust purification valve located outside. The amount of exhaust flowing into the means may be increased.

  When exhaust is preferentially caused to flow into the exhaust purification means located inside by the exhaust control valve control means, depending on the operating state of the internal combustion engine, the exhaust flow rate flowing into the exhaust purification means located outside may decrease. There is a risk that the back pressure of the exhaust passage will increase and the engine load of the internal combustion engine will increase. Therefore, in such a case, the exhaust inflow amount to the exhaust gas purification means located on the outside is increased to suppress an excessive increase in the back pressure of the exhaust passage. Therefore, the predetermined pressure is defined as the back pressure in the exhaust passage when it is determined that the engine load of the internal combustion engine increases.

  Further, in the exhaust gas purification apparatus for an internal combustion engine, in the plurality of exhaust gas control valves, the exhaust gas adjustment valve is configured to control an opening degree of each exhaust gas control valve and adjust an exhaust gas flow rate to an exhaust gas purification unit corresponding to the exhaust gas control valve. In the case where the valve control means is further provided, when the exhaust temperature from the internal combustion engine is equal to or lower than a predetermined exhaust temperature, the exhaust control valve control means supplies the exhaust purification means positioned inside among the plurality of exhaust purification means. The exhaust inflow may be suppressed, and the exhaust may be allowed to flow into the exhaust purification means located outside of the plurality of exhaust purification means.

  Here, the reason why the exhaust gas is preferentially caused to flow into the exhaust gas purification unit located outside the exhaust gas purification unit positioned inside by the exhaust gas control valve control unit is to prevent the temperature reduction of the exhaust gas purification unit located inside. It is. That is, the exhaust purification means located on the inner side is surrounded by more exhaust purification means than the exhaust purification means located on the outer side, and the heat radiation can be suppressed. Therefore, when the exhaust gas temperature is low, the exhaust gas is preferentially flowed to the exhaust gas purification unit located outside, so that the temperature of the exhaust gas purification unit located inside can be prevented from decreasing. Therefore, the predetermined exhaust temperature is defined as an exhaust temperature that is low enough to lower the temperature of the exhaust purification means located inside.

  Further, when exhaust gas is allowed to flow into the exhaust gas purification means located outside, the inflow of exhaust gas to the exhaust gas purification means located inside is completely interrupted by the exhaust gas control valve control means from the viewpoint of preventing a temperature drop. It is preferable. However, when the temperature of the exhaust purification means located on the inside is relatively high, there is a case where there is no problem in the exhaust purification capability even if the temperature is somewhat lowered. Therefore, when exhaust gas is flowing into the exhaust purification means located outside by the exhaust adjustment valve control means, if the temperature of the exhaust purification means located inside exceeds a predetermined bed temperature, the exhaust adjustment valve control means The exhaust adjustment valve corresponding to the exhaust purification means located inside may be increased in opening to increase the amount of exhaust flowing into the exhaust purification means located inside.

  That is, when the temperature of the exhaust purification means located on the inside is a temperature at which it is determined that there is no problem with the exhaust purification ability even when the low temperature exhaust gas flows, that is, the above-described predetermined floor temperature, the exhaust purification means located on the outside. By exhausting the exhaust gas into not only the means but also the exhaust purification means located inside, the exhaust purification means located outside is prevented from being excessively cooled.

  Here, in the exhaust gas purification apparatus for an internal combustion engine, when each of the plurality of exhaust gas purification means has a filter that collects particulate matter in the exhaust gas, from the filter located inside among the plurality of filters. You may make it perform the oxidation removal of the particulate matter collected by each filter in order of the filter located outside.

In order to oxidize and remove the particulate matter collected by the filter, it is necessary to raise the filter temperature to a temperature at which the particulate matter is oxidized and removed. Then, in the filter whose temperature has been raised, the collected particulate matter is oxidized and removed, so that oxidation heat is generated. Therefore, if the temperature of the filter is raised in order from the inside to the outside in the hierarchically formed filter (exhaust gas purification means), the filter temperature is raised under a more adiabatic condition, so that it is more efficient. The filter temperature rises. Furthermore, since the outer filter is warmed by heat generated by oxidation removal of the inner filter, the outer filter temperature can be increased more easily.

  Further, in the exhaust gas purification apparatus for an internal combustion engine as described above, when each of the plurality of exhaust gas purification means has a storage reduction type NOx catalyst, the storage reduction type NOx located inside of the plurality of storage reduction type NOx catalysts. The NOx purification rate in the high temperature region of the catalyst may be larger than the NOx purification rate in the high temperature region of the NOx storage reduction catalyst located outside of the plurality of NOx storage reduction catalysts.

  As described above, the NOx storage reduction catalyst (exhaust gas purification means) located on the inner side is in a situation where a more adiabatic effect can be obtained than the NOx storage reduction catalyst located on the outer side. Therefore, the temperature of the NOx storage reduction catalyst located on the inner side becomes higher on average than the temperature of the NOx storage reduction catalyst located on the outer side. Therefore, by changing the NOx purification rate in the high temperature region between the inner and outer storage reduction type NOx catalysts as described above, it is possible to achieve NOx purification according to the temperature distribution in the storage reduction type NOx catalyst. In other words, by changing the NOx purification rate in the high temperature region, the NOx purification performance of the inner and outer NOx storage reduction catalysts is leveled.

  Further, in the exhaust gas purification apparatus for an internal combustion engine as described above, when each of the plurality of exhaust gas purification means has a storage reduction type NOx catalyst, the storage reduction type NOx located inside of the plurality of storage reduction type NOx catalysts. The NOx purification rate in the low temperature region of the catalyst may be larger than the NOx purification rate in the low temperature region of the NOx storage reduction catalyst located outside of the plurality of NOx storage reduction catalysts.

  As described above, the NOx storage reduction catalyst located on the inner side is in a situation where a more adiabatic effect can be obtained as compared to the NOx storage reduction catalyst located on the outer side, and therefore its temperature is likely to rise. Therefore, by increasing the NOx purification rate in the low temperature region of the NOx storage reduction catalyst located on the inner side where the temperature is likely to rise, the exhaust purification device can purify exhaust at a lower temperature. On the other hand, by increasing the NOx purification rate on the high temperature side of the NOx storage reduction catalyst located on the outside where the temperature is unlikely to rise, the exhaust purification device can purify exhaust at a higher temperature.

  Here, in the exhaust gas purification apparatus for an internal combustion engine described above, two exhaust passages, two exhaust adjustment valves, and two exhaust gas purification means may be provided. That is, an exhaust gas purification apparatus for an internal combustion engine, which is provided in each of two exhaust passages through which exhaust from the internal combustion engine flows and the two exhaust passages, and two exhaust control valves for adjusting the exhaust flow rate of the exhaust passages And two exhaust purification means provided in each of the two exhaust passages for purifying the exhaust gas flowing through the exhaust passage. In the two exhaust purification means, one of the exhaust purification means is hierarchically arranged. Other exhaust purification means surround the periphery, and each exhaust purification means is arranged concentrically. Then, the exhaust flow rate is controlled by the above-described exhaust regulating valve control means.

  In an exhaust gas purification apparatus for an internal combustion engine having a plurality of parallel exhaust passages, the size of the exhaust gas purification device is made as small as possible and the temperature of a catalyst for exhaust gas purification provided in the exhaust passage is easily increased and maintained. It becomes possible.

Here, an embodiment of an exhaust gas purification apparatus for an internal combustion engine according to the present invention will be described based on the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an exhaust emission control device for an internal combustion engine 1 according to the present invention. Exhaust gas generated in the internal combustion engine 1 is sent to the exhaust passage. The exhaust passage of the exhaust emission control device according to the present invention is first composed of two exhaust passages, an inner exhaust passage 2 and an outer exhaust passage 3. In the middle of the inner exhaust passage 2, an inner exhaust purification means for performing exhaust purification is provided, which is composed of an inner oxidation catalyst 6 and an inner filter 8. The inner oxidation catalyst 6 is an oxidation catalyst that oxidizes unburned fuel components and the like in the exhaust gas, and the inner filter 8 is a filter that mainly collects particulate matter in the exhaust gas. This is a filter on which “NOx catalyst” is supported. Further, the inner filter 8 is located on the downstream side of the inner oxidation catalyst 6. On the other hand, in the middle of the outer exhaust passage 3, an outer exhaust purification means for performing exhaust purification is provided, which is composed of an outer oxidation catalyst 7 and an outer filter 9. The outer oxidation catalyst 7 is an oxidation catalyst that oxidizes unburned fuel components and the like in the exhaust gas, and the outer filter 9 is a filter that mainly collects particulate matter in the exhaust gas and carries a NOx catalyst. is there. Further, the outer filter 9 is located on the downstream side of the outer oxidation catalyst 7.

  Here, the inner exhaust purification means is disposed so as to be surrounded by the outer exhaust purification means. Specifically, the outer oxidation catalyst 7 is arranged concentrically around the inner oxidation catalyst 6 so as to surround it, and the outer filter 9 is arranged concentrically around the inner filter 8 so as to surround it. ing. Further, the NOx purification rate in the high temperature region of the NOx catalyst supported on the inner filter 8 is set to be larger than the NOx purification rate in the high temperature region of the NOx catalyst supported on the outer filter 9.

  Further, the inner exhaust passage 2 upstream of the inner oxidation catalyst 6 is provided with an inner fuel addition valve 4 for adding fuel to the exhaust, and the outer exhaust passage 3 upstream of the outer oxidation catalyst 7 is in the middle of exhaust. An outer fuel addition valve 5 for adding fuel is provided. Further, the inner exhaust passage 2 on the downstream side of the inner filter 8 is provided with an inner exhaust adjustment valve 10 that adjusts the flow rate of the exhaust gas flowing through the inner exhaust passage 2, and is provided in the outer exhaust passage 3 on the downstream side of the outer filter 9. Is provided with an outer exhaust adjustment valve 11 for adjusting the flow rate of the exhaust gas flowing through the outer exhaust passage 3. The inner exhaust passage 2 and the outer exhaust passage 3 merge at the downstream side of the inner exhaust adjustment valve 10 and the outer exhaust adjustment valve 11 to form an exhaust passage 12.

  1 is provided with an electronic control unit (hereinafter referred to as “ECU”) 20 for controlling each element of the internal combustion engine 1 and the exhaust purification device. The ECU 20 includes a CPU, a ROM, a RAM, and the like for storing various programs and maps to be described later, and controls the operating conditions of the internal combustion engine 1 according to the operating conditions of the internal combustion engine 1 and the driver's request. Unit.

  Here, the opening degree of the inner exhaust adjustment valve 10 and the outer exhaust adjustment valve 11 is adjusted by a control signal from the ECU 20. That is, the opening degree of each exhaust adjustment valve is adjusted by a command from the ECU 20, and the flow rate of exhaust gas flowing through each exhaust passage, that is, the flow rate of exhaust gas flowing into each oxidation catalyst or each filter is adjusted.

  Further, exhaust temperature sensors that detect exhaust temperatures between the inner oxidation catalyst 6 and the inner filter 8, between the outer oxidation catalyst 7 and the outer filter 9, downstream of the inner filter 8, and downstream of the outer filter 9. 30, 31, 32, and 33 are provided. Each exhaust temperature sensor is electrically connected to the ECU 20, and it is possible to detect the exhaust temperature at each part of the ECU 20 and to estimate the exhaust temperature flowing into each filter, the temperature of each filter, and the like. .

  The exhaust emission control device for the internal combustion engine 1 configured as described above has a structure in which the inner exhaust passage 2 is surrounded by the outer exhaust passage 3, and thus the size thereof is made as compact as possible. That is, it is possible to reduce the size of the exhaust purification device and to improve the mountability to a vehicle or the like, rather than simply arranging the inner exhaust passage 2 and the outer exhaust passage 3 in parallel. In the present embodiment, the inner exhaust passage 2 and the outer exhaust passage 3 are two, but three or more exhaust passages may be provided hierarchically as in the present embodiment.

  Further, the exhaust discharged from the internal combustion engine 1 flows into the inner exhaust passage 2 and the outer exhaust passage 3, and the exhaust is purified by the provided inner exhaust purification means and outer exhaust purification means. For example, the unburned fuel component in the exhaust is oxidized by the inner oxidation catalyst 6 and the outer oxidation catalyst 7, or the particulate matter in the exhaust is collected by the inner filter 8 and the outer filter 9, and is supported on each of them. NOx reduction purification is performed by the NOx catalyst.

  Here, in order to efficiently perform exhaust purification using each oxidation catalyst or each filter, the oxidation catalyst or the NOx catalyst needs to reach an activation temperature at which the catalytic function can be exhibited, and is collected by the filter. In order to oxidize and remove particulate matter, it is necessary to raise the filter temperature to a target temperature. An example relating to the control of the temperature rise of the filter in the exhaust emission control device of the internal combustion engine 1 is shown in FIG. FIG. 2 is a flowchart regarding control of the exhaust adjustment valve (hereinafter referred to as “exhaust adjustment valve control”) for increasing the temperature of the filter. The exhaust gas control valve control in this embodiment is a routine that is repeatedly executed by the ECU 20 at a constant cycle.

  In S101, it is determined whether or not the internal combustion engine 1 is in an operating state. That is, it is determined whether or not exhaust gas is discharged from the internal combustion engine 1. If it is determined that the internal combustion engine 1 is in the operating state, the process proceeds to S102, and if it is determined that the internal combustion engine 1 is not in the operating state, this control is terminated.

  In S102, it is determined whether or not the temperature of the inner filter 8 is lower than the light-off temperature. The temperature of the inner filter 8 is estimated based on the temperature of the exhaust exhausted from the inner filter 8 detected by the exhaust temperature sensor 32. Here, the light-off temperature is a temperature at which the NOx catalyst supported on the inner filter 8 is activated. Therefore, in S102, the active state of the NOx catalyst carried on the inner filter 8 is determined. When the temperature of the inner filter 8 is lower than the light-off temperature, that is, when the NOx catalyst is not in the active state, the process proceeds to S103. On the other hand, when the temperature of the inner filter 8 is not lower than the light-off temperature, this control is terminated.

  In S103, it is determined whether or not the outer exhaust adjustment valve 11 can be fully closed. As will be described later, the temperature of the inner filter 8 is increased by preferentially flowing the exhaust from the internal combustion engine 1 into the inner filter 8. At this time, it is not preferable that the outer exhaust adjustment valve 11 be fully closed to increase the back pressure of the exhaust passage and greatly increase the engine load of the internal combustion engine. Therefore, the operating state of the internal combustion engine 1 is an operating state in which the outer exhaust adjustment valve 11 can be fully closed, in other words, the exhaust amount discharged by fully closing the outer exhaust adjustment valve 11 is the engine exhaust amount. It is determined whether the amount is such that the load does not increase significantly. If it is determined that the outer exhaust adjustment valve 11 can be fully closed, the process proceeds to S104. If it is determined that the outer exhaust adjustment valve 11 cannot be fully closed, the process proceeds to S107.

In S104, it is determined whether or not the temperature of the inner filter 8 is lower than the exhaust temperature flowing into the inner filter 8. That is, it is determined whether or not the temperature of the inner filter 8 can be raised by the exhaust temperature. Here, the exhaust temperature detected by the exhaust temperature sensor 30 is used as the exhaust temperature. If it is determined that the temperature of the inner filter 8 is lower than the exhaust temperature, the process proceeds to S105, and if it is determined that the temperature of the inner filter 8 is not lower than the exhaust temperature, the process proceeds to S108.

  In S105, the opening degree of the inner exhaust adjustment valve 10 is fully opened, and then the process proceeds to S106, the opening degree of the outer exhaust adjustment valve 11 is fully closed, and this control is finished. Further, in S107, both the opening degree of the inner exhaust adjustment valve 10 and the outer exhaust adjustment valve 11 are fully opened, and this control is finished. Further, in S108, the opening degree of the outer exhaust regulating valve 11 is fully opened, and this control is finished.

  In this control, first, when the temperature of the inner filter 8 is increased by the processes of S105 and S106, the exhaust from the internal combustion engine 1 is preferentially flown to the inner filter 8 without flowing to the outer filter 9. Since the inner filter 8 is disposed so as to be surrounded by the outer filter 9, the heat dissipation amount is smaller than that of the outer filter 9. Accordingly, the temperature is likely to rise earlier than the outer filter 9 and the temperature can be easily maintained. Therefore, the exhaust gas purification ability of the exhaust gas purification device can be quickly raised by preferentially flowing the exhaust gas through the inner filter 8. Further, the NOx purification rate in the high temperature region of the NOx catalyst supported on the inner filter 8 is set to be larger than the NOx purification rate in the high temperature region of the NOx catalyst supported on the outer filter 9. Further, NOx purification according to the temperature distribution in the inner filter 8 and the outer filter 9 can be performed.

  Next, depending on the processing of S107, the opening degree of the inner exhaust adjustment valve 10 and the outer exhaust adjustment valve 11 is fully opened in order to avoid an increase in the back pressure in the exhaust passage of the internal combustion engine 1. At this time, an increase in the back pressure is avoided while increasing the temperature of the inner filter 8 and the outer filter 9. Further, when the process of S108 is performed, it means that the temperature of the inner filter 8 is sufficiently increased. Therefore, the temperature of the outer filter 9 is increased depending on the process of S108. At this time, the temperature of the outer filter 9 is increased by the heat of the exhaust gas, and the temperature is also increased by the heat propagated from the inner filter 8 included therein.

  According to this control, in the exhaust purification device of the internal combustion engine 1 having the inner exhaust passage 2 and the outer exhaust passage 3 provided in parallel, the temperature rise and maintenance of the inner filter 8 and the outer filter 9 carrying the NOx catalyst are prevented. It becomes easy.

  In the present embodiment, the NOx purification rate in the high temperature region of the NOx catalyst supported on the inner filter 8 is set to be larger than the NOx purification rate in the high temperature region of the NOx catalyst supported on the outer filter 9. However, instead of this, the NOx purification rate in the low temperature region of the NOx catalyst supported on the inner filter 8 is made larger than the NOx purification rate in the low temperature region of the NOx catalyst supported on the outer filter 9. May be set. By doing so, the inner filter 8 and the outer filter 9 can purify NOx in the exhaust gas in a wider temperature range.

  Next, another embodiment of the exhaust regulating valve control performed in the exhaust purification device of the internal combustion engine 1 shown in FIG. 1 will be described based on FIG. The exhaust gas control valve control in this embodiment is a routine that is repeatedly executed by the ECU 20 at a constant cycle. In FIG. 3, the same processing as that in the exhaust control valve control shown in FIG. 2 is denoted by the same reference numeral, and detailed description thereof is omitted.

In the present embodiment, the process of S201 is performed instead of the process of S103. In S201, the limit opening of the outer exhaust control valve 11 is calculated. Here, the limit opening is that the back pressure of the exhaust passage generated when the inner exhaust adjustment valve 10 is fully opened and the outer exhaust adjustment valve 11 is fully closed is higher than a predetermined pressure at which the engine load becomes relatively high. In the case where it is determined, the opening degree of the outer exhaust adjustment valve 11 necessary for reducing the back pressure to a predetermined pressure. Therefore, the limit opening is determined based on the operating state of the internal combustion engine 1 related to the exhaust amount discharged from the internal combustion engine 1. When the process of S201 ends, the process proceeds to S104. Since the process of S103 is eliminated, the process of S107 is also eliminated.

  In this control, when the process of S105 is completed, the process proceeds to S202. In S202, the opening degree of the outer exhaust adjustment valve 11 is adjusted based on the limit opening degree calculated in S201. After the process of S202, this control is terminated.

  In this control, when the temperature of the inner filter 8 is increased, the processing of S105 and S202 makes it possible to start up the exhaust gas purification capacity of the exhaust gas purification device at an early stage, and excessively increase the back pressure in the exhaust passage. Can also be avoided.

  Next, another embodiment of the exhaust regulating valve control performed in the exhaust purification device of the internal combustion engine 1 shown in FIG. 1 will be described based on FIG. The exhaust gas control valve control in this embodiment is a routine that is repeatedly executed by the ECU 20 at a constant cycle. In FIG. 4, the same processing as that of the exhaust control valve control shown in FIGS. 2 and 3 is denoted by the same reference numeral, and detailed description thereof is omitted.

  In the present embodiment, the processes from S301 to S303 are performed instead of the process of S108. In this control, if it is determined in S104 that the temperature of the inner filter 8 is not lower than the exhaust temperature, the process proceeds to S301. In S301, it is determined whether or not the exhaust temperature flowing into the inner filter 8 is lower than a predetermined exhaust temperature TEX. Here, the predetermined exhaust temperature TEX is a low exhaust temperature at which the activity of the NOx catalyst carried thereon is weakened when the exhaust flows into the inner filter 8 whose temperature has increased. Therefore, in S301, it is determined whether or not the activity of the filter 8 is reduced by flowing low temperature exhaust gas into the inner filter 8. If it is determined that the exhaust temperature is lower than the predetermined exhaust temperature TEX, the process proceeds to S302. On the other hand, when it is determined that the exhaust temperature is not lower than the predetermined exhaust temperature TEX, this control is terminated.

  In S302, the opening degree of the inner exhaust control valve 10 is adjusted. That is, since the exhaust temperature is relatively low, the inner exhaust adjustment valve 10 is opened so as to suppress the amount of exhaust flowing into the inner filter 8 so that the exhaust does not flow into the inner filter 8 and the temperature of the inner filter 8 decreases. The degree is adjusted. When the process of S302 ends, the process proceeds to S303. In S303, the opening degree of the outer exhaust control valve 11 is fully opened, and this control is finished.

  In this control, when the temperature of the inner filter 8 is increased, the processing of S105 and S202 makes it possible to quickly raise the exhaust purification capacity of the exhaust purification device, and excessively increase the back pressure in the exhaust passage. Can also be avoided. Further, when the exhaust gas temperature is relatively low, it is possible to suppress the temperature drop of the inner filter 8 by flowing the exhaust gas preferentially through the outer filter 9.

  Next, another embodiment of the exhaust regulating valve control performed in the exhaust purification device of the internal combustion engine 1 shown in FIG. 1 will be described based on FIG. The exhaust gas control valve control in this embodiment is a routine that is repeatedly executed by the ECU 20 at a constant cycle. In FIG. 5, the same reference numerals are assigned to the same processes as those in the exhaust adjustment valve control shown in FIGS. 2, 3, and 4, and detailed description thereof is omitted.

In this control, if it is determined in S102 that the temperature of the inner filter 8 is not lower than the light-off temperature, the process proceeds to S401. In S401, it is determined whether or not the temperature of the inner filter 8 is higher than a predetermined bed temperature TF. Here, the predetermined bed temperature TF is a temperature at which the activity of the NOx catalyst carried on the inner filter 8 does not decrease, and is specifically a temperature slightly higher than the light-off temperature. If it is determined that the temperature of the inner filter 8 is higher than the predetermined bed temperature TF, the process proceeds to S402. On the other hand, if it is determined that the temperature of the inner filter 8 is not higher than the predetermined bed temperature TF, this control is terminated.

  In S402, it is determined whether or not the temperature of the outer filter 9 is lower than the light-off temperature. The temperature of the outer filter 9 is estimated based on the temperature of the exhaust discharged from the outer filter 9 detected by the exhaust temperature sensor 33. Therefore, in S402, the active state of the NOx catalyst carried on the outer filter 9 is determined. When the temperature of the outer filter 9 is lower than the light-off temperature, that is, when the NOx catalyst is not in an active state, the process proceeds to S403. On the other hand, when the temperature of the outer filter 9 is not lower than the light-off temperature, this control is terminated.

  In S403, the temperature dT that can be lowered of the inner filter 8 is calculated. The lowerable temperature dT is a margin of the temperature of the inner filter 8 when the bed temperature can be maintained higher than the light-off temperature even when relatively low temperature exhaust gas flows into the inner filter 8. That is, even if a relatively low temperature exhaust gas flows, the inner filter 8 has a temperature margin corresponding to dT, so that the inner filter 8 does not lose its activity. When the process of S403 ends, the process proceeds to S404.

  In S404, the opening degree of the inner exhaust adjustment valve 10 corresponding to the lowerable temperature dT calculated in S403 is calculated. In calculating the opening, the exhaust temperature and the exhaust flow rate flowing into the inner filter 8 are taken into consideration. For example, the lower the exhaust temperature or the greater the exhaust flow rate, the smaller the opening of the inner exhaust adjustment valve 10 corresponding to a certain lowerable temperature dT. When the process of S404 ends, the process proceeds to S405.

  In S405, the opening of the inner exhaust adjustment valve 10 is adjusted based on the opening calculated in S404. Thereafter, the process proceeds to S405, the opening degree of the outer exhaust adjustment valve 11 is fully opened, and this control is finished.

  According to this control, in addition to the effect of the exhaust regulating valve control shown in FIG. 4, it is possible to avoid the temperature of the outer filter 9 from being excessively lowered without lowering the temperature of the inner filter 8 below the light-off temperature. Is possible.

  Next, another embodiment of the exhaust regulating valve control performed in the exhaust purification device of the internal combustion engine 1 shown in FIG. 1 will be described based on FIG. The exhaust gas control valve control in this embodiment is a routine that is repeatedly executed by the ECU 20 at a constant cycle.

  In S501, as in S101, it is determined whether or not the internal combustion engine 1 is in an operating state. When it is determined that the internal combustion engine 1 is in the operating state, the process proceeds to S502, and when it is determined that the internal combustion engine 1 is not in the operating state, this control is terminated.

  In S502, in the inner filter 8 and the outer filter 9, it is determined whether or not the collected particulate matter amount exceeds a predetermined amount and it is necessary to regenerate the filter for removing the particulate matter by oxidation. Specifically, the amount of particulate matter collected by the inner filter 8 and the outer filter 9 based on the amount of fuel consumed in the internal combustion engine 1, the operation history of the internal combustion engine 1, the exhaust flow rate flowing through each filter, and the like. When these values exceed a predetermined amount that is a reference value, it is determined that regeneration of each filter is necessary. If it is determined that the filter needs to be regenerated, the process proceeds to S503. If it is determined that the filter needs not be regenerated, this control is terminated.

  In S503, regeneration of the inner filter 8 is executed. Specifically, fuel is added to the exhaust from the inner fuel addition valve 4 and the inner exhaust adjustment valve 10 is closed to such an extent that the temperature of the inner filter 8 does not rise excessively. By doing in this way, the exhaust flow volume in the inner side oxidation catalyst 6 or the inner side filter 8 will be in a very low state, and the collected particulate matter is efficiently oxidized and removed. When the processing of S503 ends, the process proceeds to S504.

  In S504, it is determined whether or not the outer filter 9 is in a reproducible state, that is, whether or not the temperature of the outer filter 9 has increased to such an extent that particulate matter collected by the outer filter 9 can be removed by oxidation. Is done. Specifically, it is determined whether or not the outer filter 9 is in a reproducible state based on the exhaust temperature discharged from the outer filter 9 detected by the exhaust temperature sensor 33. If it is determined that the outer filter 9 is in a reproducible state, the process proceeds to S507. If it is determined that the outer filter 9 is not in a reproducible state, the process proceeds to S505.

  In S505, the opening amounts of the inner exhaust adjustment valve 10 and the outer exhaust adjustment valve 11 are adjusted so as to reduce the exhaust flow rate flowing into the inner filter 8 and increase the exhaust flow rate flowing into the outer filter 9. When the process of S505 ends, the process proceeds to S506.

  In S506, the temperature of the outer filter 9 is increased. Specifically, fuel is added into the exhaust gas from the outer fuel addition valve 5 to generate oxidation heat in the outer oxidation catalyst 7 to raise the exhaust gas temperature. Thereby, the temperature of the exhaust gas flowing into the outer filter 9 is increased, and the temperature of the outer filter 9 is increased.

  In S507, as in the case of the inner filter 8, regeneration of the outer filter 9 is executed. Specifically, fuel is added to the exhaust gas from the outer fuel addition valve 5 and the outer exhaust adjustment valve 11 is closed to such an extent that the temperature of the outer filter 9 does not rise excessively. After the processing of S507, this control is terminated.

  According to this control, the inner filter 8 is preferentially regenerated over the outer filter 9 when the filter is regenerated in the exhaust emission control device of the internal combustion engine 1 shown in FIG. Since the inner filter 8 is provided so as to be surrounded by the outer filter 9, the amount of heat radiation is reduced, and the inner filter 8 is efficiently regenerated. Further, since the outer filter 9 is warmed by the heat generated during the regeneration of the inner filter 8, the subsequent regeneration of the outer filter 9 is performed smoothly.

It is a figure showing schematic structure of the exhaust gas purification device of the internal combustion engine which concerns on the Example of this invention. It is a flowchart regarding the exhaust gas control valve control for performing the temperature rise of the filter performed in the exhaust gas purification apparatus of the internal combustion engine according to the first embodiment of the present invention. It is a flowchart regarding the exhaust gas control valve control for performing the temperature rise of the filter performed in the exhaust gas purification apparatus of the internal combustion engine according to the second embodiment of the present invention. It is a flowchart regarding the exhaust gas control valve control for performing the temperature rise of the filter performed in the exhaust gas purification apparatus of the internal combustion engine according to the third embodiment of the present invention. It is a flowchart regarding the exhaust adjustment valve control for performing the temperature rise of the filter performed in the exhaust gas purification apparatus of the internal combustion engine according to the fourth embodiment of the present invention. It is a flowchart regarding the exhaust gas control valve control for performing regeneration of the filter performed in the exhaust gas purification apparatus of the internal combustion engine according to the fifth embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 .... Internal combustion engine 2 .... Inside exhaust passage 3 .... Outside exhaust passage 4 .... Inside fuel addition valve 5 .... Outside fuel addition valve 6 .... Inside oxidation catalyst 7 ··· Outside oxidation catalyst 8 ··· Inside filter 9 ··· Outside filter 10 ··· Inside exhaust adjustment valve 11 ··· Outside exhaust adjustment valve 12 ··· Exhaust passage 20 ···・ ECU
30 ... Exhaust temperature sensor 31 ... Exhaust temperature sensor 32 ... Exhaust temperature sensor 33 ... Exhaust temperature sensor

Claims (9)

A plurality of exhaust passages through which exhaust from the internal combustion engine flows;
A plurality of exhaust adjustment valves provided in each of the plurality of exhaust passages for adjusting the exhaust flow rate of the exhaust passages;
A plurality of exhaust gas purification means provided in each of the plurality of exhaust passages for purifying exhaust gas flowing through the exhaust passage;
The exhaust gas of the internal combustion engine characterized in that, in the plurality of exhaust gas purification means, one exhaust gas purification means is hierarchically surrounded by other exhaust gas purification means, and each of the exhaust gas purification means is arranged substantially concentrically. Purification equipment. In the plurality of exhaust gas control valves, the exhaust gas control valve further includes an exhaust gas control valve control unit that controls an opening degree of each exhaust gas control valve and adjusts an exhaust gas flow rate to an exhaust gas purification unit corresponding to the exhaust gas control valve,
When the temperature of the exhaust purification means located inside among the plurality of exhaust purification means is raised, the exhaust control valve control means causes the exhaust to flow into the exhaust purification means located inside, and the plurality of exhaust purification means 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein exhaust gas flowing into an exhaust gas purification unit located outside is suppressed.   When exhaust is caused to flow into the exhaust purification means located inside by the exhaust adjustment valve control means and its temperature is raised, the back pressure of any of the plurality of exhaust passages exceeds a predetermined pressure In this case, the exhaust adjustment valve control means increases the opening of the exhaust adjustment valve corresponding to the exhaust purification means located outside and increases the amount of exhaust flowing into the exhaust purification means located outside. The exhaust emission control device for an internal combustion engine according to claim 2. In the plurality of exhaust gas control valves, the exhaust gas control valve further includes an exhaust gas control valve control unit that controls an opening degree of each exhaust gas control valve and adjusts an exhaust gas flow rate to an exhaust gas purification unit corresponding to the exhaust gas control valve,
When the exhaust gas temperature from the internal combustion engine is equal to or lower than a predetermined exhaust gas temperature, the exhaust gas control valve control unit suppresses the inflow of exhaust gas to the exhaust gas purification unit located inside of the plurality of exhaust gas purification units, and The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the exhaust gas is caused to flow into an exhaust gas purification means located outside of the exhaust gas purification means.   When exhaust is flowing into the exhaust purification means positioned outside by the exhaust control valve control means, if the temperature of the exhaust purification means positioned inside exceeds a predetermined bed temperature, the exhaust control valve control means, 5. The internal combustion engine according to claim 4, wherein an opening degree of an exhaust gas control valve corresponding to the exhaust gas purification unit located inside is increased to increase an exhaust inflow amount to the exhaust gas purification unit located inside the exhaust gas control unit. Exhaust purification device. Each of the plurality of exhaust purification means has a filter that collects particulate matter in the exhaust,
2. The exhaust gas of an internal combustion engine according to claim 1, wherein oxidation removal of particulate matter collected by each filter is performed in the order of the filter located inside from the filter located inside among the plurality of filters. Purification equipment. Each of the plurality of exhaust purification means has an NOx storage reduction catalyst,
Of the plurality of NOx storage reduction catalysts, the NOx purification rate in the high temperature region of the NOx storage reduction catalyst located inside is the high temperature of the NOx storage reduction catalyst located outside of the NOx storage reduction catalyst. The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 6, wherein the exhaust gas purification ratio is larger than a NOx purification rate in a region. Each of the plurality of exhaust purification means has an NOx storage reduction catalyst,
Among the plurality of NOx storage reduction catalysts, the NOx purification rate in the low temperature region of the NOx storage reduction catalyst located inside is the low temperature of the NOx storage reduction catalyst located outside of the NOx storage reduction catalyst. The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 6, wherein the exhaust gas purification ratio is larger than a NOx purification rate in a region.   The exhaust purification device for an internal combustion engine according to any one of claims 1 to 8, wherein two each of the exhaust passage, the exhaust adjustment valve, and the exhaust purification means are provided.

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