JP2007154729A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve fuel economy by accurately determining completion timing of DPF regeneration process and reducing frequency of post injection. <P>SOLUTION: In regeneration process raising temperature of exhaust gas by post injection to heat a filter (DPF) 13 and raise temperature thereof, and burning particulate matter (PM) collected by the DPF 13, temperature difference DPFDT1 between outlet temperature DPT1 and inlet temperature DPT2 of the DPF 13 is calculated (S2), and regeneration process is completed (S30) when temperature difference DPFDT1 gets larger than pre-established high temperature side temperature difference established value ST1 (S24) and then temperature difference DPFDT1 gets lower than low temperature side temperature difference established value ST2 established lower than the high temperature side temperature difference established value ST1 (S29). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine that can accurately determine the end of regeneration of a filter that collects particulate matter in exhaust gas.

  Conventionally, in a diesel engine, particulate matter (PM) contained in exhaust gas is collected by a filter (DPF: Diesel Particulate Filter) interposed in the exhaust passage. The DPF passes the inflowing exhaust gas through the porous partition and collects PM at the surface and pores of the partition.

  Further, PM collected in the DPF is deposited with time. Therefore, when the collected DPF becomes excessive, the flow path resistance in the filter increases, the back pressure of the diesel engine increases, and the output decreases. Therefore, it is necessary to regenerate the accumulated PM by periodically incinerating it by heating.

  As a technique for burning PM, it is conceivable to heat the DPF itself. However, when the DPF is heated to a temperature higher than necessary, there is a problem that deterioration is promoted and durability is lowered. Further, when an electric heater is used as the heating means, there is a disadvantage that the power consumption is more than necessary and the fuel consumption is deteriorated. Combustion can also be considered by raising the exhaust gas temperature by excessive fuel injection, but this case is also not preferable because it affects the output characteristics and deteriorates fuel consumption.

  Therefore, in general, apart from the normal fuel injection, means for increasing the exhaust gas temperature by performing post-injection (post-injection) into the cylinder in the expansion stroke or exhaust stroke after the compression stroke is adopted. Yes.

  When performing the regeneration process of the DPF, the temperature increase of the exhaust temperature sensor disposed downstream of the DPF is monitored during the regeneration process, and when the increase rate becomes higher than the set temperature, or the exhaust temperature sensor When the absolute value of the monitored temperature becomes higher than the set temperature, it is determined that the regeneration process is finished. In this case, the end time may be determined in combination with the differential pressure before and after the DPF.

  For example, in Patent Document 1 (Japanese Patent Laid-Open No. 2001-254616), the exhaust gas temperature (DPF temperature) downstream of the DPF during the regeneration process is monitored, and the DPF gas temperature is higher than a predetermined set temperature, and A technique is disclosed in which regeneration is determined to end when the change rate of the DPF temperature becomes higher than a predetermined set change rate.

In Patent Document 2 (Japanese Patent Application Laid-Open No. 2005-90359), a target temperature at the time of DPF regeneration is set, and after the DPF is raised to the target temperature, the time when the DPF exceeds the target temperature is integrated. An effective regeneration time is calculated, and a regeneration amount corresponding to the PM combustion removal amount is estimated based on the effective regeneration time. A technique is disclosed in which the reproduction process is terminated when the reproduction amount reaches a predetermined target value.
JP 2001-254616 A JP 2005-90359 A

  By the way, the regeneration process of the DPF is often performed during traveling, and depending on the operating conditions of the diesel engine, it is determined whether the increase in the exhaust temperature detected by the exhaust temperature sensor is due to the regeneration process or due to the operating conditions. It can be difficult. For example, since the exhaust gas temperature after combustion is high in a transient state or in a high-speed operation region, the exhaust gas temperature detected by the exhaust temperature sensor is also increasing.

  Therefore, when the regeneration process of the DPF is executed at the time of transition and at high speed operation, the end time of the regeneration process may not be accurately determined. The injection amount will also increase. Since post-injection does not contribute to combustion, if post-injection is continued more than necessary, there is an inconvenience that fuel efficiency is deteriorated.

  In view of the above circumstances, the present invention provides an exhaust gas for an internal combustion engine that can accurately determine the end timing in the regeneration process of a filter that collects particulate matter in exhaust gas, reduce post-injection frequency, and improve fuel efficiency. An object is to provide a purification device.

  To achieve the above object, according to a first aspect of the present invention, there is provided an exhaust purification system for an internal combustion engine in which a filter for collecting particulate matter in exhaust gas is arranged in the middle of an exhaust passage and a regeneration process for the filter is started at a preset regeneration timing. In the apparatus, temperature difference detecting means for detecting a temperature difference between the outlet temperature and the inlet temperature of the filter during regeneration processing, and when the temperature difference becomes lower than a preset first temperature difference set value, And a reproduction process ending unit for ending the reproduction process.

  According to a second aspect of the present invention, there is provided an exhaust purification apparatus for an internal combustion engine in which a filter that collects particulate matter in exhaust gas is disposed in the middle of an exhaust passage and the regeneration process of the filter is started at a preset regeneration timing. A temperature difference detecting means for detecting a temperature difference between the outlet temperature and the inlet temperature of the filter, and a change amount of the temperature difference after the regeneration process is started is greater than a preset first temperature difference change amount, And a regeneration process end means for forcibly terminating the regeneration process when the outlet temperature becomes higher than a preset outlet temperature set value.

  According to a third aspect of the present invention, there is provided an exhaust purification apparatus for an internal combustion engine in which a filter that collects particulate matter in exhaust gas is disposed in the exhaust passage and the regeneration process of the filter is started at a preset regeneration timing. A temperature difference detecting means for detecting a temperature difference between the outlet temperature and the inlet temperature of the filter, and a change amount of the temperature difference after the regeneration process is started is smaller than a preset first temperature difference change amount, The filter regeneration processing is terminated when the temperature difference becomes lower than a preset second temperature difference change amount set value.

  According to the present invention, it is possible to accurately determine the end time in the regeneration process of the filter that collects particulate matter in the exhaust gas and terminate the regeneration process, so the frequency of post injection is reduced, and accordingly, Fuel consumption can be improved.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 to 6 show a first embodiment of the present invention. FIG. 1 is a schematic configuration diagram of a diesel engine.

  Reference numeral 1 in FIG. 1 denotes an engine body of a diesel engine that is representative of an internal combustion engine. An intake port 2 and an exhaust port 3 are opened at the upper portion of the combustion chamber of the engine body 1 and an injector 4 is exposed. Reference numeral 5 denotes an intake valve and 6 denotes an exhaust valve.

  An intake passage 7 communicates with the intake port 2 upstream, and an intake chamber 8 is formed in the middle thereof. Further, an air cleaner 9 is attached to the air intake port of the intake passage 7, and an intake air amount sensor 11 for detecting the intake air amount is provided immediately downstream thereof.

  Further, an exhaust passage 10 communicates with the exhaust port 3 downstream, and a diesel oxidation catalyst (DOC: Diesel Oxidation Catalyst) 12 and a DPF (Diesel Particulate Filter) 13 are interposed in the exhaust passage 10 from the upstream side. . Further, a DPF inlet temperature sensor 14 and a DPF outlet temperature sensor 15 for detecting an inlet temperature and an outlet temperature of the DPF 13 are respectively provided immediately upstream and downstream of the DPF 13 in the exhaust passage 10.

  The DOC 12 is formed by supporting a noble metal such as platinum or palladium or a metal oxide such as alumina on the surface of a ceramic carrier made of, for example, a cordierite honeycomb structure, and mainly hydrocarbons in exhaust gas. Particulate matter (PM) in exhaust gas is reduced by oxidizing and gasifying (HC) by catalytic reaction.

  The DPF 13 is a filter that collects PM. For example, a heat-resistant ceramic such as cordierite is formed into a honeycomb structure so that a large number of cells serving as gas flow paths are staggered on the inlet side or the outlet side. It is sealed and formed. When exhaust gas flows into the DPF 13, it flows downstream while passing through the porous partition walls of the DPF 13, and during that time, PM in the exhaust gas is collected and gradually accumulated.

  In addition, when the DPF 13 is regenerated, unburned HC is intentionally discharged by post-injection, and this is oxidized by the DOC 12. The DPF 13 is heated and heated by the heat obtained at that time, and is collected by the DPF 13. The DPF 13 is forcibly regenerated by incinerating the existing PM.

  Further, the exhaust system is provided with a differential pressure sensor 16 for detecting a differential pressure between the inlet pressure and the outlet pressure of the DPF 13.

  Detection signals from these sensors 11, 14, 15.16 are input to an engine control unit (ECU) 21. The ECU 21 is configured mainly by a computer such as a microcomputer, has a well-known CPU, ROM, RAM, and the like, and is based on parameters indicating operating states detected by various sensors according to a control program stored in the ROM. The fuel injection amount, the injection timing, etc. are set, the amount of PM collected by the DPF 13 (PM collection amount) is estimated, and the start time and end time of the regeneration process of the DPF 13 based on the estimated PM collection amount Determine.

  Specifically, the DPF regeneration process executed by the ECU 21 is performed according to the DPF regeneration process routine shown in FIG. This routine is executed at predetermined intervals after turning on the ignition switch.

  In this routine, first, the PM collection amount PMi is estimated in step S1. Various estimations of the PM collection amount PMi have been conventionally proposed. For example, it is estimated from the differential pressure between the inlet pressure and the outlet pressure of the DPF 13 detected by the differential pressure sensor 16. That is, when PM accumulates on the DPF 13, the flow path resistance increases, and the differential pressure before and after the DPF 13 increases. The PM collection amount PMi is estimated by searching. In this case, based on the engine operating state detected by each sensor, the PM emission amount from the end of the previous regeneration process is calculated, and this is integrated to estimate the PM collection amount PMi. May be.

  Next, the process proceeds to step S2, and the PM collection amount PMi is compared with the PM collection amount PMα for regeneration timing determination set in advance as an experiment as a threshold for determining the start time of the regeneration process. When PMi has not reached the regeneration timing determination PM trapping amount PMα (PMi <PMa), the routine is exited as it is. On the other hand, when the PM collection amount PMi has reached the regeneration timing determination PM collection amount PMα (PMi ≧ PMa), the process proceeds to step S3.

  In step S3, the DPF regeneration process is executed and the routine is exited. This DPF regeneration process is executed according to the DPF regeneration process routine shown in FIG.

  In this routine, first, post-injection control processing is executed in step S11. In this post-injection control process, first, a predetermined post-injection amount of fuel is injected from the injector 4 in the expansion stroke or exhaust stroke after compression top dead center (ATDC). In this embodiment, it is set to inject around about ATDC 200 ° CA, that is, after the start of the exhaust stroke.

  Unburned HC is discharged from the exhaust port 3 by the fuel injected from the injector 4 in the expansion stroke or exhaust stroke, and the unburned HC is heated by the oxidation reaction in the DOC 12. Then, the exhaust gas heated to the oxidation temperature by the DOC 12 is supplied to the DPF 13, the DPF 13 is heated and heated, and the PM collected in the DPF 13 is incinerated and regenerated. At that time, if the temperature of the DPF 13 is raised too much, the catalyst deteriorates, so the post injection amount Inp is controlled.

  Specifically, as shown in FIG. 5, the DPF outlet temperature DPT1 detected by the DPF outlet temperature sensor 15 is compared with the target temperature To, and the post injection amount Inp is set so that the DPF outlet temperature DPT1 converges to the target temperature To. Feedback control. At that time, the lower limiter Tomin and the upper limiter Tomax are set, and when the PF outlet temperature DPT1 becomes equal to or lower than the lower limiter Tomin, the amount is immediately increased, and when it becomes equal to or higher than the upper limiter Tomax, the amount is immediately decreased.

  For example, when the recyclable temperature of the DPF 13 is 600 ° C. and the melting temperature is about 800 ° C., the lower limiter Tomin is set to 600 ° C., and the upper limit limiter Tomax is set to 800 ° C. Further, the target temperature To is set to an intermediate value (700 ° C.) between the limiters Tomin and Tomax.

  Thereafter, the process proceeds to step S12, and DPF regeneration end determination processing is executed. The DPF regeneration end determination process is performed according to the DPF regeneration end determination process routine shown in FIG.

  In this routine, first, in step S21, the DPF outlet temperature DPT1 detected by the DPF outlet temperature sensor 15 and the DPF inlet temperature DPT2 detected by the DPF inlet temperature sensor 14 are read. Then, the process proceeds to step S22, and the DPF outlet inlet temperature difference DPFDT1 is calculated from the difference between the DPF outlet temperature DPT1 and the DPF inlet temperature DPT2 (DPFDT1 ← DPT1-DPT2). As shown in FIGS. 6A and 6B, when the DPF 13 is heated and the PM trapped inside is combusted, the temperature of the exhaust gas discharged from the DPF 13 increases. In the initial stage of the DPF regeneration process, the collected PM remaining amount is large, so that the DPF outlet inlet temperature difference DPFDT1 (= DPT1-DPT2) gradually increases.

  Next, the process proceeds to step S23, and the DPF outlet inlet temperature difference change amount DTT1 is calculated from the difference between the DPF outlet inlet temperature difference DPFDT1 calculated in step S22 and the DPF outlet inlet temperature difference DPFDT1 (n-1) calculated at the previous routine execution. Calculate (DTT1 ← DPFDT1-DPFDT1 (n-1)).

  Thereafter, in step S24, the DPF outlet inlet temperature difference DPFDT1 is compared with the high temperature side temperature difference set value ST1 as the second temperature difference setting means. The high temperature side temperature difference set value ST1 is a determination value for continuing the DPF regeneration process. The DPF regeneration process is continued at least until the DPF outlet inlet temperature difference DPFDT1 exceeds the high temperature side temperature difference set value ST1. . The high temperature side temperature difference set value ST1 is a value when PM starts combustion, and is set in advance by experiments.

  Then, when it is estimated that the PM of DPFDT1 ≦ ST1 has not yet been burned or the PM is burned insufficiently, the routine jumps to step S26. On the other hand, when it is estimated that DPFDT1> ST1 PM combustion is sufficient, the process proceeds to step S25, the PM combustion determination flag FLAG is set (FLAG ← 1), and the process proceeds to step S26. The initial value of this PM combustion determination flag FLAG is 0.

  In step S26, the DPF outlet temperature DPT1 is compared with the outlet temperature set value ST5. The outlet temperature set value ST5 is a temperature slightly lower than the exhaust gas temperature at which the DPF 13 may be melted, and is set in advance by experiments. If there is no possibility of melting of DPT1 <ST5, the process proceeds to step S28. On the other hand, when the temperature rapidly rises to a temperature at which DPT1 ≧ ST5 is likely to be damaged, the process branches to step S27 and compares the DPF outlet inlet temperature difference change amount DTT1 with the first temperature difference change amount set value ST3. . This first temperature difference change amount setting value ST3 indicates whether the temperature rise of the DPF outlet temperature DPT1 is caused by operating conditions such as acceleration operation or high speed operation or DPF regeneration processing. Is a value for determining from a change in the DPF outlet temperature DPT1 with reference to the above, and is set in advance by experimentation or the like.

  When the DPF outlet inlet temperature difference change amount DTT1 of DTT1 ≦ ST3 is small, that is, when the DPF inlet temperature DPT2 is higher than the DPF outlet temperature DPT1, it is determined that the operating condition is satisfied, and the process returns to step S28. On the other hand, when the DPF outlet inlet temperature difference change amount DTT1 when DTT1> ST3 is large, the DPF outlet temperature DPT1 is considerably higher than the DPF inlet temperature DPT2, so that it is determined that the temperature rise is caused by the DPF regeneration process, and step S31. Proceed to In step S31, the post injection is stopped, the DPF regeneration process is forcibly terminated, and the process proceeds to step S32.

  As described above, in this embodiment, when the regeneration amount per unit time due to the combustion of PM collected in the DPF 13 greatly exceeds the expected value and the DPF 13 may be melted, the DPF regeneration process is in progress. Even if it exists, the DPF 13 can be effectively protected from melting damage by forcibly terminating it. Even if the DPF outlet temperature DPT1 is higher than the outlet temperature set value ST5, if it is due to operating conditions such as acceleration operation and high-speed operation, the DPF regeneration process can be continued. Also, the DPF regeneration process can be performed. As a result, post-injection in the low-speed regeneration region can be abolished, and fuel efficiency can be greatly improved accordingly.

  On the other hand, when the process proceeds from step S26 or step S27 to step S28, the value of the PM combustion determination flag FLAG is referred to. Then, when FLAG = 0, that is, after the DPF regeneration process is started, when the DPF outlet inlet temperature difference DPFDT1 does not exceed the high temperature side temperature difference set value ST1, the routine is directly exited, and the DPF shown in FIG. The process proceeds to step S13 of the reproduction processing routine. In step S13, it is checked whether or not the DPF regeneration process is completed. Since the DPF regeneration process is continued, the process returns to step S11 and the DPF regeneration process is repeated.

  In step S28, when FLAG = 1, that is, when the DPF outlet inlet temperature difference DPFDT1 exceeds the high temperature side temperature difference set value ST1, the process proceeds to step S29, and the DPF outlet inlet temperature difference DPFDT1 and the first temperature difference. The low temperature side temperature difference set value ST2 as setting means is compared. The low temperature side temperature difference set value ST2 is set to a value lower than the high temperature side temperature difference set value ST1. As shown in FIG. 6 (a), in the previous stage where the regeneration rate of the DPF regeneration process (see FIG. 6 (d)) is still low, the amount of PM collected in the DPF 13 is large. The DPF outlet temperature DPT1 greatly increases due to combustion. Therefore, the DPF outlet inlet temperature difference DPFDT1 also increases as shown in FIG. On the other hand, at the latter stage where the regeneration rate becomes high, the amount of PM collected in the DPF 13 is incinerated and decreased, so the DPF outlet temperature DPT1 also decreases and the DPF outlet inlet temperature difference DPFDT1 decreases.

  In this embodiment, the low temperature side temperature difference set value ST2 is set to a value of about 70 to 80% of the regeneration rate, and when the DPF outlet inlet temperature difference DPFDT1 falls below the low temperature side temperature difference set value ST2, the DPF regeneration is terminated. As shown in FIG. 6D, the DPF regeneration process is efficiently performed until the regeneration rate reaches 70 to 80%. However, when the regeneration rate exceeds 70 to 80%, the regeneration efficiency drops sharply. Therefore, when the DPF regeneration process is continued until the regeneration rate reaches 100%, the time required for the DPF regeneration process becomes longer, and during this time, post injection is continued, resulting in a deterioration in fuel consumption.

  On the other hand, in this embodiment, the PM remaining amount in the DPF 13 is estimated from the DPF outlet inlet temperature difference DPFDT1, and when the regeneration rate reaches 70 to 80%, the post injection is stopped and the DPF regeneration process is terminated. Therefore, efficient reproduction can be performed.

  If the DPF outlet inlet temperature difference DPFDT1 of DPFDT1 ≧ ST2 is higher than the low temperature side temperature difference set value ST2 in step S29, the routine is directly exited, and the routine proceeds to step S13 of the DPF regeneration processing routine shown in FIG. . In step S13, it is checked whether or not the DPF regeneration process is completed. Since the DPF regeneration process is continued, the process returns to step S11 and the DPF regeneration process is repeated.

  On the other hand, when the DPF outlet inlet temperature difference DPFDT1 of DPFDT1 <ST2 falls below the low temperature side temperature difference set value ST2, the process proceeds to step S30, the DPF regeneration process is terminated, the process proceeds to step S32, and the PM combustion determination flag FLAG is cleared. Then, (FLAG ← 0) is exited, and the routine proceeds to step S13 of the DPF regeneration processing routine shown in FIG. In step S13, it is checked whether or not the DPF regeneration process has been completed. Since the DPF regeneration process has been completed, the routine is immediately exited.

  As described above, in this embodiment, even when the DPF outlet temperature DPT1 reaches the outlet temperature set value ST5 that is slightly lower than the exhaust gas temperature at which the DPF 13 may be melted during the DPF regeneration process. Whether the DPF outlet temperature DPT1 reaches the outlet temperature set value ST5 without immediately ending the DPF regeneration process is caused by operating conditions or by PM combustion. Since the DPF regeneration process is continued if it is checked based on the change amount DTT1 and is caused by the operating condition, the DPF regeneration process in the high-speed regeneration region is always possible. As a result, the DPF regeneration process in the low speed regeneration region can be omitted, and the post-injection frequency is reduced correspondingly, and the fuel consumption can be greatly improved.

  Further, since the end time of the DPF regeneration process is set to a timing (70 to 80%) before the regeneration efficiency of the DPF 13 suddenly drops, the time required for the DPF regeneration process is shortened, and the post injection frequency is further increased accordingly. Since the fuel consumption can be reduced, the fuel consumption can be further improved. In addition, since the regeneration rate indicating the end time of the DPF regeneration process is estimated from the DPF outlet inlet temperature difference DPFDT1, the end time can be accurately determined.

  FIG. 7 shows a DPF regeneration end determination processing routine according to the second embodiment of the present invention. This flowchart is applied instead of the DPF regeneration end determination processing routine shown in FIG.

  In the flowchart shown in FIG. 4 described above, when the DPF outlet inlet temperature difference DPFDT1 where DPFDT1 <ST2 falls below the low temperature side temperature difference set value ST2 in step S29, DPF regeneration is terminated. If it is determined in step S29 that DPFDT1 <ST2, the DPF regeneration process is not immediately terminated, and the DPF outlet inlet temperature difference change amount DTT1 is compared with the second temperature difference change amount set value ST4 in step S41. . The second temperature difference change amount setting value ST4 is obtained by previously obtaining a value indicating a change amount at which the regeneration rate becomes about 70 to 80% from experiments or the like.

  When DTT1 ≧ ST4, the routine is exited and the DPF regeneration process is continued. On the other hand, when DTT1 <ST4, the process proceeds to step S30, and the DPF regeneration process is terminated.

  As described above, in this embodiment, the end time of the DPF regeneration process is continued until the DPF outlet inlet temperature difference change amount DTT1 becomes equal to or less than the second temperature difference change amount set value ST4. The time can be judged more accurately.

  The present invention is not limited to the above-described embodiments. For example, the DPF inlet temperature sensor 14 may be eliminated and the DPF inlet temperature DPT2 may be estimated based on operating conditions. That is, since the exhaust gas temperature upstream of the DPF 13 is caused by the combustion state of the engine, operating conditions that have a causal relationship with the combustion state in advance through experiments or the like, such as fuel injection amount, engine speed, intake air amount Based on the above, a temperature map of the DPF inlet temperature DPT2 is created, and this data is stored in a nonvolatile memory such as a ROM provided in the ECU 21. Then, the DPF inlet temperature DPT2 is set with reference to the temperature map based on the operating conditions. By eliminating the DPF inlet temperature sensor 14, the number of parts can be reduced and the product cost can be reduced.

Schematic configuration diagram of a diesel engine according to the first embodiment The flowchart showing the DPF regeneration processing routine The flowchart showing the DPF regeneration processing routine Flowchart showing the DPF regeneration end determination processing routine (A) is a time chart showing changes in DPF outlet temperature due to post injection during DPF regeneration processing, and (b) is a time chart showing changes in post injection amount during DPF regeneration processing. (A) is a time chart showing changes in DPF outlet temperature and DPF inlet temperature, (b) is a time chart showing changes in DPF outlet inlet temperature difference, and (c) is a change in DPF outlet inlet temperature difference change amount. (D) is a time chart showing the DPF regeneration rate The flowchart which shows the DPF regeneration completion | finish determination processing routine by a 2nd form.

Explanation of symbols

1 ... Engine body,
4 ... Injector,
10: exhaust passage,
12 ... oxidation catalyst (DOC),
13 ... Filter (DPF),
14 ... Inlet temperature sensor,
15 ... outlet temperature sensor,
16 ... differential pressure sensor,
DPFDT1 ... outlet inlet temperature difference,
DPT1 ... outlet temperature,
DPT2 ... Inlet temperature,
DTT1: Change amount at the outlet inlet temperature difference,
PMα: PM collection amount for regeneration time determination,
PMi ... PM collection amount,
ST1 ... High temperature side difference set value,
ST2 ... Low temperature side temperature difference set value,
ST3 ... First temperature difference change amount set value,
ST4 ... second temperature difference change amount set value,
ST5: outlet temperature set value,
To ... Target temperature

Claims (4)

In an exhaust gas purification apparatus for an internal combustion engine, a filter that collects particulate matter in exhaust gas is disposed in the middle of an exhaust passage, and regeneration processing of the filter is started at a preset regeneration timing.
A temperature difference detecting means for detecting a temperature difference between the outlet temperature and the inlet temperature of the filter during the regeneration process;
An exhaust gas purification apparatus for an internal combustion engine, comprising: regeneration processing ending means for ending the regeneration processing of the filter when the temperature difference becomes lower than a preset first temperature difference set value. In the regeneration process end means, after the regeneration process of the filter is started, the temperature difference becomes higher than a second temperature difference set value set to a temperature higher than the first temperature difference set value, and thereafter 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the regeneration process of the filter is terminated when the temperature difference becomes lower than the first temperature difference set value. In an exhaust gas purification apparatus for an internal combustion engine, a filter that collects particulate matter in exhaust gas is disposed in the middle of an exhaust passage, and regeneration processing of the filter is started at a preset regeneration timing.
A temperature difference detecting means for detecting a temperature difference between the outlet temperature and the inlet temperature of the filter during the regeneration process;
When the change amount of the temperature difference after the regeneration process is started is larger than the preset first temperature difference change amount and the outlet temperature is higher than the preset outlet temperature set value, the regeneration process is performed. An exhaust emission control device for an internal combustion engine, comprising: a regeneration process end means for forcibly terminating the regeneration process. In an exhaust gas purification apparatus for an internal combustion engine, a filter that collects particulate matter in exhaust gas is disposed in the middle of an exhaust passage, and regeneration processing of the filter is started at a preset regeneration timing.
A temperature difference detecting means for detecting a temperature difference between the outlet temperature and the inlet temperature of the filter during the regeneration process;
When the temperature difference change amount after the regeneration process is started is smaller than the preset first temperature difference change amount and the temperature difference becomes lower than the preset second temperature difference change amount setting value. An exhaust gas purification apparatus for an internal combustion engine, wherein the regeneration process of the filter is terminated.

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