JP2006009675A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately enable the detection that a DPF for trapping an exhaust particulate (PM) discharged from an engine is completely regenerated. <P>SOLUTION: Exhaust temperature sensors 52a, 52b are installed before and after a particulate filter 42. In the case where the operating condition of the engine 1 is in the operating condition at the regenerating time including post injection, etc., when the detected temperature difference between the exhaust temperatures 52a, 52b becomes smaller than the predetermined determination threshold value, an ECU deems that combustion of PM accumulated in the particulate filter 42 has converged and determines the complete regeneration of the particulate filter 42 is finished. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine provided with a particulate filter, and more particularly to regeneration of a particulate filter.

  In a diesel engine, exhaust particulate matter (hereinafter referred to as PM as appropriate) contained in exhaust gas discharged from the engine becomes a problem, and an exhaust aftertreatment device equipped with a particulate filter for collecting PM is mounted. Is being considered. The particulate filter is regenerated by periodically burning and removing the collected PM to recover the PM collecting ability. In order to burn PM, the temperature of the particulate filter needs to be sufficiently high.

  As a method of raising the temperature of the particulate filter, a method of raising the temperature of exhaust gas discharged from the engine by an intake throttle, an injection delay angle, an increase in EGR, etc., or an exhaust gas discharged from the engine by post injection or the like by providing an oxidation catalyst A method is known in which the amount of unburned HC is intentionally increased to generate heat of catalytic reaction. When the particulate filter is regenerated, the operating state of the engine is changed to an operating state including these methods for increasing the temperature of the particulate filter, that is, an operating state during regeneration.

  Starting and ending regeneration of the particulate filter at an appropriate time is important in order to avoid deterioration of the particulate filter and damage due to rapid combustion during regeneration, and the particulate filter regeneration start time. In order to determine the end time, the amount of PM collected and deposited by the particulate filter (PM deposition amount) is estimated. When the PM accumulation amount exceeds the upper limit value, the engine operating state is set to the regeneration operation state, and when regeneration proceeds and the PM accumulation amount reaches the lower limit value, the regeneration operation state is canceled. If the lower limit is set to 0, complete regeneration that burns and removes all PM accumulated on the particulate filter is achieved. In order to improve fuel efficiency, the complete regeneration is performed only once within a predetermined number of regenerations of the particulate filter.

The PM accumulation amount is estimated based on the differential pressure before and after the particulate filter and the exhaust flow rate in order to determine the regeneration start timing and regeneration end timing (Patent Document 1 below) or exhausted from the engine. There is a technique that estimates the PM discharge flow rate based on the operating state of the engine and integrates this to increase the accumulation amount (Patent Document 2 below). The method of integrating the PM discharge flow rate is basically not accurate enough to calculate based on the differential pressure before and after the particulate filter and the exhaust flow rate, so the differential pressure before and after the particulate filter In an operating state where the calculation accuracy of the PM accumulation amount based on the exhaust flow rate is reduced, the integrated value of the PM exhaust flow rate is calculated based on the differential pressure before and after the particulate filter and the exhaust flow rate immediately before entering the operating state. There is a limited usage of adding to the calculated PM deposition amount.
JP 7-317529 A JP 2004-019529 A

  By the way, the completion of the complete regeneration of the particulate filter is determined when the PM accumulation amount becomes 0 as described above. However, in Patent Document 1, a deviation between the equation and map used for estimation and the actual deposition phenomenon in which the combustion and deposition of PM proceed simultaneously and alternately causes the estimation error, and the actual deposition amount becomes zero. The estimated PM accumulation amount becomes 0 before the estimated accumulation amount, or even if the actual accumulation amount becomes 0, the estimated PM accumulation amount does not decrease to 0. This leads to a situation in which the driving state during regeneration is excessively prolonged, or estimation errors are accumulated and the estimation accuracy further decreases.

  Further, the technique disclosed in Patent Document 2 that estimates the PM emission amount based on the operating state of the engine is originally a process in which the accuracy is not sufficient and the PM accumulation amount is removed by combustion and the accumulation amount decreases. Some cannot be used.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an exhaust emission control device for an internal combustion engine that can accurately determine the end time of complete regeneration of a DPF.

In order to solve the above-mentioned problem, according to the first aspect of the present invention, there is provided a particulate filter that collects exhaust particulates in exhaust gas discharged from an internal combustion engine, and the exhaust particulates collected and deposited by the particulate filter. In the exhaust gas purification apparatus for an internal combustion engine, the particulate filter is regenerated by burning and removing the internal combustion engine by bringing the internal combustion engine into a predetermined regeneration operation state.
Heat generation intensity detection means for detecting heat generation intensity in the particulate filter;
Control means for switching the operating state of the internal combustion engine, when the heat generation intensity detected by the heat generation intensity detection means is less than or equal to a preset heat generation intensity threshold when the internal combustion engine is in the regeneration operation state. And a regeneration control means for canceling the regeneration operating state on the assumption that all of the collected and accumulated exhaust particulates are burned and removed and the particulate filter is completely regenerated.

  The deposited PM is removed by combustion. When PM is removed and combustion converges, there is no heat generation. Therefore, it is known that the particulate filter has been completely regenerated because the heat generation intensity is equal to or less than the heat generation intensity threshold.

  According to a second aspect of the present invention, in the configuration of the first aspect of the invention, the heat generation intensity detecting means makes the heat generation intensity threshold variable in accordance with an operating state of the internal combustion engine.

  HC is discharged from the internal combustion engine depending on the operating state, and this is burned by the particulate filter. Therefore, even if the particulate filter is completely regenerated, the heat generation intensity may not be sufficiently reduced due to heat generation due to the combustion of the unburned HC. Further, the heat generation intensity varies depending on the operation state even in the same PM accumulation state. Therefore, it is possible to accurately determine whether the particulate filter has been completely regenerated by making the heat generation intensity threshold variable according to the operating state of the internal combustion engine that defines the amount of HC emission and the variation in the heat generation intensity. Judgment can be made.

  According to a third aspect of the present invention, in the configuration of the first or second aspect of the present invention, it is determined whether or not the particulate filter has completely regenerated during a predetermined operating state period set in advance by the internal combustion engine. It is a judgment prohibition period that prohibits.

  In an operating state in which the heat generation intensity varies greatly, it is possible to avoid erroneous determination of whether or not the particulate filter has been completely regenerated by prohibiting it from being determined whether or not the particulate filter has been completely regenerated. it can.

  According to a fourth aspect of the present invention, in the configuration of the first to third aspects of the invention, the regeneration control means determines the accumulated amount of the exhaust particulates on the particulate filter based on the state of the internal combustion engine or the particulate filter. When the estimated accumulation amount reaches a preset accumulation amount threshold value, it is set to switch to the regeneration operation state, and the heat generation intensity detected by the heat generation intensity detection means is A correction means is provided for correcting the deposition amount based on the estimated error in the estimation of the deposition amount from the next time, assuming that the estimated deposition amount at the time when the generation intensity becomes lower than the generation intensity threshold.

  If the estimated value of the accumulation amount at the time when the particulate filter is completely regenerated is not 0, this is an estimation error. Therefore, in the estimation of the accumulation amount, by correcting the accumulation amount based on the estimation error, the estimation accuracy is improved during the operation of the internal combustion engine, and the regeneration start timing of the particulate filter is not reached. It is possible to appropriately determine the reproduction end time when the reproduction is ended.

  According to a fifth aspect of the present invention, in the configuration of the first to fourth aspects of the present invention, the heat generation intensity detecting means comprises a pair of temperature detecting means for detecting the temperature of the exhaust gas before and after the particulate filter, It is determined that the greater the difference in exhaust gas temperature between before and after the particulate filter, the greater the heat generation intensity.

  If there is PM combustion in the particulate filter, the temperature of the exhaust gas flowing out of the particulate filter due to the heat generation rises higher than the temperature of the exhaust gas flowing into the particulate filter. Since it is only necessary to provide a temperature sensor, implementation is easy.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration of a main part of a diesel engine system that is an internal combustion engine provided with the exhaust emission control device of the present invention. An injector 31 is provided in a one-to-one correspondence with each cylinder 11 of the engine 1 that is an internal combustion engine provided with an exhaust emission control device, and injects fuel supplied from a common rail (not shown). The engine 1 is of the EGR type that can include exhaust gas in the intake air, and the intake passage 21 and the exhaust passage 22 are connected by the EGR passage 23 so that a part of the exhaust gas recirculates to the intake passage 21. Yes. The recirculation amount of the exhaust gas is adjusted by an EGR control valve 33 provided in the EGR passage 23.

  A diesel particulate filter (referred to as DPF) 4 is installed in the exhaust passage 22 of the engine 1. In the DPF 4, a catalyst unit 41 is arranged on the upstream side in a part of the exhaust passage 22, and a filter unit 42 that is a particulate filter is arranged on the downstream side. The filter part 42 is a main body part of the DPF 4, and porous heat-resistant ceramics such as cordierite as a base material is formed in a honeycomb structure so that a large number of cells that become gas flow paths are staggered on the inlet side or the outlet side. It is what was sealed. The exhaust gas discharged from the engine 1 flows downstream while passing through the porous partition walls of the DPF 4, and PM is collected and gradually accumulated during that time. The catalyst unit 41 is for regenerating the DPF 4 by burning and removing the PM deposited on the filter unit 42, and is constituted by an oxidation catalyst such as Pt. When the engine 1 enters an operation state during regeneration including post-injection in response to a request for complete regeneration of the DPF 4, HC that becomes post-injection is supplied to the catalyst unit 41 and burned by the action of the oxidation catalyst, and becomes high temperature due to combustion heat. Exhaust exhaust gas flows into the filter part 42 and burns and removes PM.

  In order to estimate the amount of PM deposited on the filter unit 42 of the DPF 4 (hereinafter referred to as PM deposition amount as appropriate), a differential pressure sensor 51 that detects the differential pressure across the DPF 4 is provided.

  The exhaust passage 22 is provided with exhaust temperature sensors 52a and 52b which are a pair of exhaust temperature detecting means for detecting the temperature of exhaust gas (referred to as exhaust temperature). The exhaust temperature sensor 52 a is provided on the upstream side of the filter unit 42, and the exhaust temperature sensor 52 b is provided on the downstream side of the filter unit 42. Hereinafter, as appropriate, the exhaust temperature detected by the exhaust temperature sensor 52a is referred to as a pre-DFF temperature, and the exhaust temperature detected by the exhaust temperature sensor 52b is referred to as a post-DFF temperature. The exhaust temperature sensors 52a and 52b constitute a heat generation intensity detection means 52 that detects the intensity of heat generation in the filter section 42, as will be described in detail later.

  The output signals of the differential pressure sensor 51 and the exhaust temperature sensors 52a and 52b are input to the ECU 6. The ECU 6 is configured mainly with a microcomputer or the like, and the output signals of various sensors including the differential pressure sensor 51 and the exhaust temperature sensors 52a and 52b are input to the ECU 6, and the state of each part is known. It is like that. The state of each part known by sensors is general to a normal engine, such as engine speed, cooling water temperature, intake air temperature, and the like. The ECU 6 calculates the fuel injection amount, the injection timing, the EGR rate, etc. according to the states of these parts, and controls the injector 31, the EGR control valve 32, and the like. Moreover, it is set as the driving | running state at the time of reproduction | regeneration including post injection.

  2 and 3 show control routines executed by a microcomputer constituting the ECU 6 as a regeneration control means. These routines are executed at a predetermined cycle by the timer interrupt in the ECU 6. FIG. 2 is for estimating the PM accumulation amount, and FIG. 3 is for completely regenerating the DPF 4.

  In FIG. 2, an estimated PM accumulation amount base is calculated in step S101. The estimated PM accumulation amount base is a basic value of the estimated value of the PM accumulation amount, and is calculated based on the exhaust gas flow rate and the differential pressure across the DPF. The exhaust gas flow rate is obtained, for example, by converting the detected flow rate of an air flow meter (not shown) into a volume.

  Subsequent step S102 is a process as a correction unit, and the calculated value is obtained by subtracting the estimated amount correction amount from the estimated PM accumulation amount base. The estimated amount correction amount will be described later.

  In FIG. 3, it is determined in step S201 whether there is a request for complete regeneration of the DPF 4. The request for complete regeneration of the DPF 4 is that the estimated PM accumulation amount reaches a threshold (referred to as a regeneration start accumulation amount threshold), for example, 10 g, and the travel distance is a threshold (referred to as a travel distance threshold), for example, 1000 km or more. Requested. If a negative decision is made, it returns to return. If not required, regeneration starts when the estimated PM deposition amount reaches the regeneration start deposition amount threshold, and regeneration occurs when the regeneration is reduced to a threshold smaller than the regeneration start deposition amount threshold (referred to as a regeneration end deposition amount threshold). Exit. Complete playback is not executed. Therefore, until the travel distance reaches the travel distance threshold, regeneration starts when the PM accumulation amount reaches the regeneration start accumulation amount threshold, and when regeneration is reduced to the regeneration end accumulation amount threshold, how many regenerations stop regeneration. After this has been done, full regeneration is required. In this way, the complete regeneration is limited when the PM combustion removal progresses and the amount of accumulated PM decreases, even if post injection is performed, the combustion rate of the deposited PM does not sufficiently increase and the efficiency decreases. This is to help you.

  If an affirmative determination is made in step S201 for determining whether or not there is a request for complete regeneration of the DPF 4, regeneration control is executed in step S202, and an operation state during regeneration including post-injection is set.

  Subsequent steps S203 and S204 are processes for improving the accuracy of the determination of complete DPF regeneration. In step S203, it is determined whether or not the reproduction completion basic condition is satisfied. This is based on the condition that the estimated PM accumulation amount is a threshold (referred to as a complete regeneration accumulation amount threshold), for example, 5 g or less, and the current regeneration execution time is a threshold (referred to as a regeneration execution time threshold), for example, 30 minutes or more. Is affirmed. If a negative decision is made, it returns to return.

  If an affirmative determination is made in step S203 for determining whether or not the regeneration completion basic condition is satisfied, it is determined in step S204 whether or not the engine steady condition is satisfied. The engine steady state condition is that the amount of change in the engine speed is a threshold value (referred to as NE change amount threshold value), for example, 100 rpm or less, and the amount of change in injection amount is set to a threshold value (hereinafter referred to as an injection amount change amount threshold value), for example, 5 cubic. An affirmative determination is made on condition that it is equal to or less than mm / st. If a negative decision is made, it returns to return.

  If an affirmative determination is made in step S204 that determines whether or not the engine steady condition is satisfied, in step S205, whether or not PM combustion is possible is determined to determine whether or not the accumulated PM can be combusted. The PM combustion feasibility determination is affirmed on the condition that the exhaust temperature before DPF is a threshold value (referred to as a threshold temperature before DPF), for example, 300 ° C. or higher. If a negative determination is made, the process returns.

  When an affirmative determination is made in step S205 that determines whether or not the accumulated PM can be combusted, in step S206, a temperature increase amount THC in the DPF 4 by HC discharged from the engine 1 is calculated. The temperature increase amount THC is calculated by storing a map corresponding to the temperature increase amount THC for each of these values using the engine speed NE, the injection amount, the cooling water temperature, the pre-DPF temperature, and the intake air temperature as parameters. The calculated value is obtained by drawing this map. The map data is created by previously obtaining the relationship between the engine speed NE, the injection amount, the cooling water temperature, the pre-DPF temperature, the intake air temperature, and the temperature increase amount THC through experiments or the like.

  In subsequent step S207, a determination threshold value used in step S208 described later is calculated. The calculation of the determination threshold is performed by storing a map corresponding to each of these values using the engine speed NE, the injection amount, the post-injection amount, and the temperature before DPF as parameters, and using this map for determination. Get the base value of the threshold. The hand threshold value is obtained by adding the temperature increase amount THC from the basic value.

  In subsequent step S208, it is determined whether or not a value (temperature difference) obtained by subtracting the pre-DPF temperature from the post-DFF temperature is equal to or less than the determination threshold value. If a negative determination is made, the process returns. Since the pre-DFF temperature is the temperature of the exhaust gas flowing into the filter part 42 of the DPF 4 and the post-DFF temperature is the temperature of the exhaust gas flowing out of the filter part 42, the temperature difference is a temperature due to PM combustion in the filter part 42. It is the magnitude of the rise and represents the heat generation intensity. The greater the temperature difference, the greater the heat generation intensity.

  If an affirmative determination is made, it is determined in step S209 that complete regeneration has been completed, the regeneration operation state is canceled, and regeneration control is stopped.

  In step S210, the estimated amount correction amount is calculated. As the estimated amount correction amount, the current estimated PM accumulation amount is regarded as an offset error when the complete regeneration is completed, that is, when the actual PM accumulation amount is 0, and the next PM accumulation amount is estimated (steps S101 and S102). Amount. Thereby, the estimation accuracy of the PM deposition amount based on the differential pressure across the DPF can be improved. The correction amount may be obtained by multiplying the current estimated PM accumulation amount by a certain coefficient.

  In step S211, it is determined whether or not the estimated amount correction amount calculated in step S210 is excessive. Whether or not the estimated amount correction amount is excessive is determined based on whether or not the estimated amount correction amount is a threshold value (referred to as a correction amount threshold value), for example, 3 g or more. If a negative determination is made, the process returns.

  If the determination in step S211 is affirmative, it is determined in step S212 that the estimated amount estimation is abnormal, the MIL (not shown) is turned on, the driver is informed, and the process returns.

  FIG. 4 shows a state when there is a request for complete regeneration. “Post injection” indicates a state where the low level is not permitted, and a high level indicates that it is permitted. When there is a request for complete regeneration and post-injection is executed, the injected fuel burns in the catalyst unit 41 and raises the temperature of the exhaust gas flowing into the DPF 4. As a result, the temperature before DPF starts to rise, and the temperature after DPF rises with a slight delay. The post-DFF temperature is greatly increased by heat generated by burning any accumulated PM. As a result, the difference between the temperature before DPF and the temperature after DPF increases. On the other hand, if there is no accumulated PM, heat generation in the DPF 4 is slight, and the temperature after the DPF does not increase greatly. The difference between the temperature before DPF and the temperature after DPF becomes small. Thus, the heat generation intensity in the DPF 4 is known from the difference between the temperature before DPF and the temperature after DPF. Since the heat generation intensity in the DPF 4 depends on the amount of accumulated PM, the difference between the temperature before the DPF and the temperature after the DPF is equal to or less than the determination threshold value, so that there is no PM to burn, that is, the DPF 4 is completely regenerated. To be known.

  Further, even if the PM accumulation state in the DPF 4 is the same, the heat generation differs depending on the operation state. The temperature rise in the filter unit 42 includes a temperature rise due to combustion of HC discharged from the engine 1. These are factors that reduce the determination accuracy of the complete regeneration end, but the determination threshold is made variable according to the operating state of the engine 1 (steps S206 and S207), so that the complete regeneration end of the DPF 4 is more accurately determined. be able to.

  Even if there is an error in the estimation of the PM deposition amount based on the differential pressure before and after the DPF, the estimated PM deposition amount based on the differential pressure before and after the DPF is sufficiently small if the complete regeneration is nearing completion. Also, a sufficient time has elapsed since the start of reproduction. Therefore, if the estimated amount of accumulated PM based on the differential pressure before and after the DPF is not yet sufficiently small and sufficient time has not elapsed since the start of regeneration, the temperature difference between the pre-DFF temperature and the post-DFF temperature is small. It cannot be determined that complete playback has been completed. By making the period during which the regeneration completion basic condition is not satisfied as a prohibition period for determining whether or not the DPF 4 has been completely regenerated (step S203), erroneous determination can be avoided.

  Further, when the engine is in a transient state and the exhaust temperature is not constant, the value of the difference between the pre-DFF temperature and the post-DFF temperature may vary, and the accuracy of the complete regeneration determination is reduced. By making the period in which the engine steady condition is not satisfied as a period for prohibiting the determination of whether or not it is complete regeneration (step S204), erroneous determination can be avoided.

  If the temperature before the DPF is not sufficiently increased, it cannot be said that the heat generation due to the combustion of the deposited PM has converged even if the temperature difference between the temperature before the DPF and the temperature after the DPF is small, and it is determined that the complete regeneration is completed. I can't do it. By making the period in which the PM combustion condition is not satisfied as a prohibition period for determining whether or not the DPF 4 has been completely regenerated (step S205), erroneous determination can be avoided.

  In addition to or in place of the processing for increasing the determination accuracy, other processing for increasing the determination accuracy may be performed. For example, it is assumed that the determination is deterministic when the determination that the complete reproduction is completed is made a plurality of times.

  Further, the processing for increasing the determination accuracy may be omitted depending on the required specifications to reduce the control burden.

  Further, when the correction amount becomes excessive (step S211), an abnormality in the exhaust temperature or a failure of the differential pressure sensor 51 can be considered. Therefore, the PM accumulation amount is estimated by correcting the abnormal value by not performing the correction. It is possible to avoid a decrease in accuracy. When the correction amount becomes excessive (step S211), it is possible to turn on the MIL as the occurrence of an abnormality and prohibit the regeneration control.

  Further, when the engine 1 is stopped or the regeneration of the DPF 4 is not performed, a difference between detected temperatures of the temperature sensors 52a and 52b is obtained, and this is regarded as a characteristic difference between the two temperature sensors 52a and 52b. It is also possible to calibrate 52a and 52b. The determination threshold value may be adjusted according to the difference in the detected temperature.

  In this embodiment, the heat generation intensity is determined from the difference between the temperature before DPF and the temperature after DPF. However, the heat generation intensity is determined based on the temperature of DPF 4 and the temperature before DPF. May be.

  Further, the estimated PM accumulation amount due to the differential pressure across the DPF at the end of the complete regeneration is regarded as an estimation error, and a correction amount that cancels this is given for estimation of the PM accumulation amount from the next time. This can also be omitted depending on the required specifications.

  In the present embodiment, the DPF has a separate catalyst part and filter part. However, the present invention can also be applied to a so-called single DPF system in which an oxidation catalyst is supported on the surface of a filter base. In this case, of course, the amount of heat generated by the fuel supplied by post injection is reflected in the determination threshold. The same applies to a case where one of the pair of temperature sensors is arranged upstream of the catalyst unit and the other temperature sensor is arranged downstream of the filter unit.

  In addition, although the regeneration operation state of the engine 1 is an operation state including post-injection, the other engine is set to an operation state including a known particulate filter regeneration method such as an injection timing retardation at the regeneration of the particulate filter. It can also be applied to.

1 is an overall schematic configuration diagram of an internal combustion engine equipped with an exhaust emission control device of the present invention. It is a 1st flowchart which shows the control performed by ECU which comprises the said exhaust gas purification apparatus. It is a 2nd flowchart which shows the control performed by the said ECU. It is a timing chart explaining the action | operation of the said exhaust gas purification apparatus.

Explanation of symbols

1 engine (internal combustion engine)
21 Intake passage 22 Exhaust passage 4 DPF
41 Catalyst part 42 Filter part (Particulate filter)
51 Differential pressure sensor 52 Heat generation intensity detection means 52a, 52b Exhaust temperature sensor (temperature detection means)
6 ECU (regeneration control means, correction means)

Claims (5)

By having a particulate filter that collects exhaust particulates in exhaust gas discharged from the internal combustion engine, the exhaust particulates collected and deposited by the particulate filter are put into a predetermined regeneration operation state. In the exhaust gas purification apparatus for an internal combustion engine in which the particulate filter is regenerated by burning off,
Heat generation intensity detection means for detecting heat generation intensity in the particulate filter;
Control means for switching the operating state of the internal combustion engine, when the heat generation intensity detected by the heat generation intensity detection means is less than or equal to a preset heat generation intensity threshold when the internal combustion engine is in the regeneration operation state. An exhaust gas purification apparatus for an internal combustion engine, comprising: a regeneration control means for canceling the operation state at the time of regeneration assuming that all of the collected and accumulated exhaust particulates are burned and removed and the particulate filter is completely regenerated. .   2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the heat generation intensity detecting means makes the heat generation intensity threshold variable according to an operating state of the internal combustion engine.   3. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein it is prohibited to determine whether or not the particulate filter has completely regenerated during a predetermined operating state period in which the internal combustion engine is preset. An exhaust gas purification apparatus for an internal combustion engine having a determination prohibition period.   4. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the regeneration control unit estimates an accumulation amount of the exhaust particulates in the particulate filter based on a state of the internal combustion engine or the particulate filter. When the estimated accumulation amount reaches a preset accumulation amount threshold, the heat generation intensity detected by the heat generation intensity detection means is set to be switched to the operation state during regeneration. An exhaust emission control device for an internal combustion engine, comprising correction means for correcting an accumulation amount based on the estimated error in the estimation of an accumulation amount from the next time, using an estimated accumulation amount at a time when the value is equal to or less than a threshold as an accumulation error. 5. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the heat generation intensity detecting means comprises a pair of temperature detecting means for detecting the temperature of exhaust gas before and after the particulate filter, An exhaust emission control device for an internal combustion engine that determines that the heat generation intensity is greater as the temperature difference between the exhaust gas before and after the curate filter is greater.

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