JP2009103066A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device of an internal combustion engine, which more accurately estimates a PM accumulation amount in a particulate filter by taking into account an influence of reduction in an area of a pipe that becomes larger as the PM accumulation amount increases. <P>SOLUTION: In a PM accumulation amount calculation processing repeated periodically, the previous value of the PM accumulation amount is called (S60), and a degree of reduction of the pipe area in the DPF is calculated (S70) based on the PM accumulation amount and the structure of the DPF (for example, a cell wall thickness or a cell density). An inclination value after correction is calculated from the degree of reduction of the pipe area (S80), and the inclination of a characteristic line indicating the relation between the DPF pressure difference and the PM accumulation amount is corrected. The PM accumulation amount (current value) in the DPF is estimated from the characteristic after correction thus obtained (S90). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine.

  Today, with increasing awareness of environmental protection, excellent exhaust purification performance is required for internal combustion engines. In particular, in a diesel engine, removal of so-called exhaust particulates (or particulate matter, particulate matter, PM) such as black smoke discharged from the engine is important for further spread. For this purpose, a diesel particulate filter (DPF) is often provided in the middle of the exhaust pipe.

  Although most of the PM in the exhaust gas is removed by the DPF collecting the PM, the PM continues to accumulate in the DPF, but the DPF clogs and burns the accumulated PM. It is necessary to regenerate the DPF. In order to burn the PM accumulated in the DPF, a method such as post injection after main injection in the cylinder is employed.

  Since fuel is consumed to regenerate the DPF, frequent DPF regeneration leads to deterioration of fuel consumption. On the other hand, if the number of times of DPF regeneration is too small, the amount of deposition becomes excessive, and the temperature rises during the regeneration process, which may damage the DPF. Therefore, DPF regeneration must be performed at an appropriate time. Therefore, it is necessary to develop a system that estimates the amount of PM accumulated in the DPF as accurately as possible by some method, and executes regeneration when the estimated value reaches a level that requires DPF regeneration.

  Patent Document 1 below utilizes the fact that the differential pressure, which is the difference in pressure between the inlet and outlet of the particulate filter, increases due to an increase in ventilation resistance due to an increase in the amount of exhaust particulates deposited on the particulate filter. A technique for detecting this differential pressure and determining that it is time to regenerate when the detected differential pressure exceeds a predetermined value is disclosed.

Japanese Patent Laid-Open No. 7-332065

  It is known that the relationship between the PM deposition amount and the DPF differential pressure is generally (or approximated) to the relationship shown in FIG. That is, as the operation of the internal combustion engine continues and PM accumulation on the DPF progresses, the first characteristic line 21 is moved from the initial point 20 shown in FIG. Moves on the second characteristic line 23 to the upper right in the figure. The first characteristic line 21 corresponds to the stage in which PM is deposited in the wall of the filter wall of the DPF, and the second characteristic line 23 corresponds to the stage in which PM is deposited on the wall surface of the filter wall.

  As shown in FIG. 12, the first characteristic line 21 and the second characteristic line 23 move upward in the drawing as the volume flow rate of the exhaust gas increases. If the characteristics shown in FIG. 12 are obtained in advance, the amount of PM accumulated in the DPF can be estimated by obtaining the DPF differential pressure value and the exhaust volume flow rate. What is necessary is just to regenerate | regenerate DPF whenever the amount of PM accumulation estimated in this way becomes excess.

  The characteristic line shown in FIG. 12 is a straight line or a linear expression. However, there are cases where the relationship between the DPF differential pressure and the PM deposition amount cannot be accurately described with a straight line. It is related to the reduction of the pipeline area. A commonly used DPF is alternately sealed with a so-called honeycomb structure as shown in FIG. As PM accumulates in such a DPF, the pipeline through which the exhaust passes gradually becomes narrower. This is shown in FIG.

  When the pipe area becomes smaller, there is a property that the DPF differential pressure value due to pipe friction between the wall surface in the pipe and the exhaust passing therethrough increases. The characteristic of the straight line in FIG. 12 does not take into account such a reduction in the pipe area. In consideration of the reduction of the pipe area, the straight line in FIG. 12 becomes larger as the PM deposition amount is larger, and generally has a downward convex curve.

  If such a correction is performed in consideration of the reduction of the pipe area, the PM deposition amount can be estimated more accurately. However, such corrections are not considered in the conventional literature including the above-mentioned Patent Document 1.

  Therefore, in view of the above problems, the problem to be solved by the present invention is to estimate the PM deposition amount in the particulate filter more accurately by taking into consideration the influence of the decrease in the pipe area that increases as the PM deposition amount increases. An object of the present invention is to provide an exhaust emission control device for an internal combustion engine.

Means for Solving the Problems and Effects of the Invention

  In order to achieve the above object, an exhaust emission control device for an internal combustion engine according to the present invention includes a particulate filter disposed in the middle of an exhaust passage and collecting particulate matter, and an inlet side and an outlet side of the particulate filter By the corrected characteristic obtained by correcting the difference between the pressure difference between the pressure difference between the pressure difference and the amount of particulate matter deposited and the degree of decrease in the pipe line area of the particulate filter due to the particulate matter deposition, Estimating means for estimating the amount of particulate matter deposited on the particulate filter, and regeneration means for regenerating the particulate filter by burning the particulate matter deposited when the estimated amount of the deposit by the estimating means increases. It is provided with.

  Thus, in the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the accumulated amount of particulate matter in the particulate filter is estimated by the corrected characteristic added with the correction taking into account the reduction of the pipe area in the particulate filter. Therefore, the deposition amount can be estimated with higher accuracy than the conventional estimation. Therefore, since the particulate filter can be regenerated at an appropriate time, it is possible to realize an exhaust emission control device in which deterioration of fuel consumption due to frequent regeneration and excessive temperature rise during regeneration due to excessive accumulation amount are suppressed.

  In addition, the estimation unit stores a characteristic between a differential pressure that is a pressure difference between the inlet side and the outlet side of the particulate filter and a deposition amount of particulate matter when the pipe area is constant. In the characteristic stored in the pre-characteristic storage means and the pre-correction characteristic storage means, the inclination for performing correction to increase the inclination that is the increase rate of the differential pressure with respect to the accumulation amount as the degree of decrease in the pipe area increases. Correction means, and the characteristic corrected by the inclination correction means may be the corrected characteristic.

  As a result, the inclination correction means performs correction to increase the inclination in the pre-correction characteristics as the degree of reduction in the pipe area increases, so that correction that appropriately reflects the reduction in the pipe area in the particulate filter can be performed. Therefore, the accumulated amount can be accurately estimated by the corrected characteristics that have been properly corrected, and the particulate filter can be regenerated at an appropriate time. Therefore, fuel consumption deterioration due to frequent regeneration can also be regenerated due to excessive accumulation amount. It is possible to realize an exhaust emission control device in which excessive temperature rise is suppressed.

  In addition, the estimation unit stores a characteristic between a differential pressure that is a pressure difference between the inlet side and the outlet side of the particulate filter and a deposition amount of particulate matter when the pipe area is constant. Pre-characteristic storage means; and in the characteristics stored in the pre-correction characteristic storage means, the accumulation amount reduction correction means for performing correction to reduce the accumulation amount as the degree of decrease in the pipe area increases, The characteristic corrected by the amount decrease correction unit may be the corrected characteristic.

  As a result, the accumulation amount decrease correction means performs correction for decreasing the accumulation amount as the degree of decrease in the pipeline area increases, so that the correction appropriately reflecting the reduction in the pipeline area in the particulate filter can be performed. Therefore, the accumulated amount can be accurately estimated by the corrected characteristics that have been properly corrected, and the particulate filter can be regenerated at an appropriate time. Therefore, fuel consumption deterioration due to frequent regeneration can also be regenerated due to excessive accumulation amount. It is possible to realize an exhaust emission control device in which excessive temperature rise is suppressed.

  Further, the estimation means increases the differential pressure as the deposition amount increases, according to a characteristic between a differential pressure that is a pressure difference between the inlet side and the outlet side of the particulate filter and a deposition amount of the particulate matter. A corrected characteristic storage unit that stores the corrected characteristic may be provided, and the characteristic stored in the corrected characteristic storage unit may be the corrected characteristic.

  As a result, the accumulated amount is estimated using the corrected characteristic in which the difference between the differential pressure and the accumulated amount is corrected to increase the differential pressure as the accumulated amount increases. Correction that properly reflects the decrease can be performed. Therefore, the accumulated amount can be accurately estimated by the corrected characteristics that have been properly corrected, and the particulate filter can be regenerated at an appropriate time. Therefore, fuel consumption deterioration due to frequent regeneration can also be regenerated due to excessive accumulation amount. It is possible to realize an exhaust emission control device in which excessive temperature rise is suppressed.

  Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 is a schematic diagram of Embodiment 1 of an exhaust gas purification apparatus 1 for an internal combustion engine according to the present invention.

  It is assumed that the exhaust emission control device 1 is configured for a four-cylinder diesel engine 2 (hereinafter simply referred to as an engine). Air is supplied to the engine 2 from an intake pipe 3 connected to the engine 2. An air flow meter 4 is disposed in the intake pipe 3 to measure the intake air amount. An intake throttle 12 is disposed in the intake pipe 3, and the amount of intake air supplied to the engine 2 is increased or decreased by adjusting the opening.

  The engine 2 is equipped with an injector 13 to supply fuel into the cylinder. Exhaust gas is discharged to an exhaust pipe 5 connected to the engine 2. The electronic control unit 10 (ECU) controls fuel injection to the engine 2 by the injector 13 and adjustment of the opening degree of the intake throttle 12. The ECU 10 has a structure having a CPU that performs various calculations and a memory 11 that stores various information.

  A diesel particulate filter 6 (DPF) is disposed in the middle of the exhaust pipe 5. The DPF 6 carries an oxidation catalyst, which is a so-called DPF with an oxidation catalyst (C-DPF). Exhaust temperature sensors 7 and 8 are arranged on the inlet side and the outlet side of the DPF 6 respectively, and the exhaust temperature at each position is measured. Further, a differential pressure sensor 9 for measuring a differential pressure (DPF differential pressure) which is a difference between exhaust pressures at the inlet side and the outlet side of the DPF 6 is also provided. The measured values of the air flow meter 4, the exhaust temperature sensors 7 and 8, and the differential pressure sensor 9 are sent to the ECU 10.

  For example, the DPF 6 may have a structure in which the inlet side and the outlet side are alternately clogged in a so-called honeycomb structure. The exhaust gas discharged during the operation of the engine 2 contains particulate matter (PM), and this PM is collected inside or on the surface of the DPF wall when the exhaust gas passes through the DPF wall having the above structure of the DPF 6. Is done. Every time the amount of PM deposited on the DPF 6 becomes sufficiently large, the deposited PM must be removed by burning to regenerate the DPF 6.

  As a method for regenerating the DPF 6, for example, post injection is performed from the injector 13. Post injection includes so-called multi-post injection in which post injection is performed a plurality of times after main injection, and single post injection in which post injection is performed once. The former is used for raising the temperature of the exhaust gas, in which combustion is performed by post-injection to raise the exhaust gas temperature, and the DPF is heated by this exhaust gas temperature to burn PM. The latter post-injection does not burn in the cylinder, but hydrocarbons (HC) discharged in an unburned state react with the catalyst in the DPF and oxidize to raise the temperature of the DPF and burn the PM. Used at temperature.

  The procedure of the DPF regeneration end process in the first embodiment is shown in FIG. The processing in FIG. 2 may be executed by the ECU 10.

  In the following, the internal combustion engine does not change significantly in the steady operation state, and the exhaust volume flow rate does not change or is very small even in the process of increasing the PM accumulation amount. The case where it can be considered that the characteristic lines 21 and 23 do not need to be changed according to the exhaust volume flow rate is shown.

  First, the intake air amount is measured in S10. This may be measured by the air flow meter 4. The intake air amount here may be a mass flow rate per unit time. Next, in S20, information on the fuel injection amount from the injector 13 is acquired. The fuel injection amount here may be a command value of the fuel injection amount from the ECU 10, for example.

  Next, in S30, the internal temperature of the DPF 6 is measured. For this purpose, the measured values of the exhaust temperature sensor 7 on the inlet side and the exhaust temperature sensor 8 on the outlet side of the DPF 6 may be used. For example, the measured value of the exhaust temperature sensor 7 or the exhaust temperature sensor 8 may be regarded as the internal temperature of the DPF 6. The average value of the measured values of the exhaust temperature sensor 7 and the exhaust temperature sensor 8 may be regarded as the internal temperature of the DPF 6. Further, a model for estimating the internal temperature of the DPF 6 from the measured value of the exhaust temperature sensor 7 or the exhaust temperature sensor 8 may be obtained in advance, and the internal temperature of the DPF 6 may be estimated using this.

  Next, in S40, the differential pressure of the DPF 6 is measured. This may be measured by the differential pressure sensor 9. Next, an exhaust volume flow rate is calculated in S50. In this specification, the term “flow rate” refers to a flow rate per unit time, that is, a flow velocity. The calculation may be performed according to the following equation (E1).

In the formula (E1), V (m ³ / sec) is a volume flow rate per unit time of the exhaust gas. G (g / sec) is the mass flow rate per unit time of intake air measured in S10. Q (cc / sec) is the fuel injection amount per unit time calculated from the fuel injection amount acquired in S20. Tdpf (K) is the DPF temperature obtained in S30. ΔP (kPa) is the differential pressure of DPF 6 obtained in S40. P0 (kPa) is atmospheric pressure. Since the volume flow rate of the exhaust gas is obtained, it is determined as one of the characteristic lines shown in FIG.

V (m ³ / sec)
= [G (g / sec) /28.8 (g / mol)]
× 22.4 × 10 ⁻³ (m ³ / mol)
× [T (K) / 273 (K)]
× [P0 (kPa) / (P0 (kPa) + ΔP (kPa))]
+ Q (cc / sec) /207.3 (g / mol)]
× 0.84 (g / cc) × 6.75 (mol)
× 22.4 × 10 ⁻³ (m ³ / mol)
× [P0 (kPa) / (P0 (kPa) + ΔP (kPa))] (E1)

  Next, in S60, the previous values of the PM accumulation amount and the DPF differential pressure are called up. As described above, the flow of FIG. 2 is periodically repeated. The value in the previous process is called the previous value, and the value in the current (current) process is called the current value. The previous values of the PM accumulation amount and the DPF differential pressure are values of the PM accumulation amount and the DPF differential pressure that are stored in the memory 11 in step S100 described later at the time of the previous processing.

  Next, in S70, the reduction degree of the pipe area is calculated. For this procedure, a relationship (for example, a functional relationship) for determining the pipe area reduction degree from the PM accumulation amount may be obtained in advance for the structure of the DPF 6 to be used. The pipe area reduction degree may be calculated from this functional relationship and the PM accumulation amount (previous value) called in S60. Here, the structure of the DPF 6 is, for example, a cell wall thickness or a cell density (the number of cells per unit area in an axial orthogonal cross section).

  Next, in S80, a corrected inclination value is calculated. The corrected inclination value is a value obtained by correcting the inclination of the characteristic line in FIG. 12 as the pipe area decreases. For this procedure, the relationship shown in FIG. 4 is used. FIG. 4 shows the relationship between the degree of decrease in the pipeline area and the inclination value, with the dotted line indicating no correction and the solid line indicating after correction.

  The slope value indicated by the dotted line is a constant value regardless of the degree of decrease in the pipeline area, corresponding to the characteristic line in FIG. 12 being a straight line. On the other hand, the corrected inclination value increases as the degree of decrease in the pipe area increases. This corresponds to the fact that the DPF differential pressure increases more for the same increase in the PM deposition amount as the pipe area becomes smaller. The relationship shown in FIG. 4 may be obtained in advance and stored in the memory 11.

  Next, the PM accumulation amount is estimated in S90. The accumulation amount estimated here is set as the current value of the PM accumulation amount. The calculation procedure in S90 will be described with reference to FIG. Black dots shown in FIG. 3 are points indicating the DPF differential pressure and the PM deposition amount obtained by periodically processing the flow of FIG.

  Due to the increase in the PM deposition amount, the second characteristic line 23 described above is moved from the lower left to the upper right in the figure. Point 100 is the previous value of the DPF differential pressure and the PM accumulation amount, that is, the point called in S60. That is, the previous value of the DPF differential pressure is ΔP1, and the previous value of the PM accumulation amount is PM1. In the case of FIG. 3, until the point 100 is reached, the correction of the characteristic line 23 due to the reduction of the pipe area is extremely small, and it can be considered that the characteristic line 23 has been traced.

  However, it is assumed that the current inclination value obtained in S80 is clearly different from the inclination of the characteristic line 23. It is assumed that the current value of the DPF differential pressure obtained in S40 is ΔP2. At this time, as shown in FIG. 3, the straight line of the slope value obtained in S80 is extended from the point 100, and the intersection of this and the straight line whose DPF differential pressure value is ΔP2 is the point 101 representing the current value. To do. That is, the current value of the DPF differential pressure is ΔP2, and the current value of the PM accumulation amount is PM2. The above is the process in S90.

  Next, in S100, the PM accumulation amount (current value) and the DPF differential pressure (current value) are stored in the memory 11. That is, in the case of the above description, the current value ΔP2 of the DPF differential pressure and the current value PM2 of the PM accumulation amount are stored in the memory 11. The PM accumulation amount (current value) and the DPF differential pressure (current value) stored in S100 are called up in S60 of the next process in the flow of FIG.

  As described above, by correcting the inclination in consideration of the pipe line reduction, a characteristic line capable of estimating the deposition amount more accurately can be obtained. In the first embodiment, only the characteristic line 23 is corrected. This is because, in the characteristic line 21, PM accumulates in the filter wall of the DPF, so that the pipe area does not decrease. The same applies to Examples 2 and 3 below.

  Next, Example 2 will be described. In the second embodiment, the flowchart of FIG. 2 in the first embodiment is replaced with the flowchart of FIG. The apparatus configuration of FIG. 1 is also used in the second embodiment. Only differences from the first embodiment will be described below.

  In the flowchart of FIG. 5, S10 to S50 are the same as those in FIG. Next, in S110, the PM accumulation amount without correction is calculated. This will be described with reference to FIG. It is assumed that the point indicating the DPF differential pressure and the PM deposition amount has moved on the characteristic line 23 from the left in the drawing with the increase in the PM deposition amount, and the previous value is the point 200. It is assumed that the current value of the DPF differential pressure measured in S40 is ΔP3. In S110, the PM accumulation amount without correction is estimated by the characteristic line 23 without correction. That is, the intersection 201 of the straight characteristic line 23 without correction and the straight line with the DPF differential pressure of ΔP3 is obtained. The PM accumulation amount without correction is PM4.

  Next, in S120, the accumulation amount decrease value is calculated. The accumulation amount decrease value is obtained from the exhaust volume flow rate obtained in S50 and the uncorrected PM accumulation amount obtained in S110. For this purpose, a function or a map for determining the accumulation amount decrease value is created from the exhaust volume flow rate and the PM accumulation amount without correction, and stored in the memory 11. The function or map is determined so as to satisfy the tendency shown in FIGS.

  FIG. 7A shows the relationship between the uncorrected PM accumulation amount and the accumulation amount decrease value. FIG. 7B shows the relationship between the deposition amount decrease value and the exhaust volume flow rate. The accumulation amount decrease value and the meaning of FIG. 7 will be described later.

  Next, the corrected PM deposition amount is calculated in S130. This procedure will be described with reference to FIG. 6. From the point 201 obtained in S100, a point 202 moved to the left side in the figure by the amount of accumulated amount reduction obtained in S110 is obtained. The amount of PM deposited at point 202 is PM3. The difference between PM4 and PM3 is the deposition amount decrease value. The point 202 thus obtained is a point indicating the current value of the PM accumulation amount and the DPF differential pressure.

  As described above, in the second embodiment, the accumulation amount reduction value indicates the correction value, and the information on the pipeline reduction in the first embodiment is included therein. As shown in FIG. 7A, the larger the PM accumulation amount without correction, the larger the accumulation amount decrease value. This is because the pipe area of the DPF 6 decreases as the PM deposition amount increases, thereby increasing the deviation from the linear characteristics shown in FIG. As a result, the information on the degree of decrease in the pipeline area is appropriately reflected in the accumulation amount decrease value.

  Further, as shown in FIG. 7B, the larger the exhaust volume flow rate, the larger the deposition amount decrease value. This is because the larger the exhaust volume flow rate, the greater the deviation due to the reduction in the pipe area even with the same PM deposition amount, which is a finding obtained by the inventor. As described above, in the second embodiment, information on the degree of reduction in the pipeline area in the first embodiment is included in the accumulation amount decrease value. Therefore, it can be considered that the two-stage process of S70 and S80 in the first embodiment is made one stage, and in this sense, the process is more simplified.

  Next, Example 3 will be described. In the third embodiment, the flowchart of FIG. 2 in the first embodiment is replaced with the flowchart of FIG. The apparatus configuration of FIG. 1 is also used in the third embodiment. Only differences from the first embodiment will be described below.

  In the flowchart of FIG. 5, S10 to S50 are the same as those in FIG. Next, the PM accumulation amount is calculated in S140. For this procedure, the relationship between the DPF differential pressure and the PM deposition amount shown in FIG. 9 is used. The relationship shown in FIG. 9 is the relationship after the correction that reflects the influence of the decrease in the pipe area when the PM accumulation amount is increased. The characteristic line 23 that is linear in FIG. 12 is corrected to a curved line 23b that protrudes upward in the drawing.

  In the third embodiment, the relationship shown in FIG. 9 may be obtained in advance for the device configuration to be used and stored in the memory 11. Since the characteristics of FIG. 9 after the correction has already been performed in the third embodiment, it is possible to simplify the process by omitting the procedures of S70 and S80 of the first embodiment and the process of S120 of the second embodiment. Play. The corrected characteristic line 23b in FIG. 9 may be stored in the memory 11 as an n-order expression (n is an integer) such as a quadratic expression or a cubic expression.

  In addition, in the process of increasing the PM deposition amount, the exhaust (volume) flow rate does not change or is considered to be considered only when the change is very small. Even if the value fluctuates with the current value, the processing procedure of the first and second embodiments can be applied. Of these, in the first embodiment, for example, the slope value in FIG. 4 may be obtained for each exhaust (volume) flow rate and reflected by the slope correction in FIG. In the second embodiment, for example, the characteristic line 23 in FIG. 6 may be a characteristic line corresponding to the current exhaust (volume) flow rate. Further, in the third embodiment, the characteristic line 23b for each exhaust volume flow rate is stored in the memory 11, and this may be switched every moment according to the fluctuation of the exhaust volume flow rate. Thereby, it is possible to cope with fluctuations in the exhaust volume flow rate.

  In the above embodiment, the DPF 6 constitutes a particulate filter. The procedure of S90 functions as estimation means. The injector 13 constitutes a reproducing unit. The memory 11 constitutes pre-correction characteristic storage means and post-correction characteristic storage means. The procedure of S80 constitutes an inclination correction unit. The procedure of S120 constitutes the accumulation amount decrease correction means.

1 is a schematic diagram of an exhaust gas purification apparatus for an internal combustion engine according to a first embodiment. 5 is a flowchart showing PM accumulation amount calculation processing in the first embodiment. FIG. 6 is a diagram illustrating correction of a characteristic line in the first embodiment. The figure which shows the relationship between a pipe line area reduction degree and an inclination value. 9 is a flowchart showing a PM accumulation amount calculation process in the second embodiment. FIG. 10 is a diagram illustrating correction of a characteristic line in the second embodiment. The figure which shows the relationship between accumulation amount reduction | decrease value, uncorrected PM accumulation amount, and exhaust volume flow rate. 10 is a flowchart illustrating PM accumulation amount calculation processing according to the third embodiment. FIG. 10 is a diagram illustrating correction of a characteristic line in the third embodiment. The figure which shows the structure of DPF. The figure which shows the pipe line area reduction by PM deposition to DPF. The figure which shows the characteristic line without correction | amendment showing the relationship between DPF differential pressure, exhaust volume flow volume, and PM deposition amount.

Explanation of symbols

1 Exhaust gas purification device 2 Diesel engine (internal combustion engine)
3 Intake pipe 4 Air flow meter 5 Exhaust pipe 6 Diesel particulate filter (DPF, particulate filter)
7, 8 Exhaust temperature sensor 9 Differential pressure sensor 10 Electronic control unit (ECU)
11 Memory 13 Injector 21 First Characteristic Line (Characteristic Line)
23 Second characteristic line (characteristic line)

Claims (4)

A particulate filter arranged in the middle of the exhaust passage to collect particulate matter;
The characteristic between the differential pressure which is the pressure difference between the inlet side and the outlet side in the particulate filter and the amount of particulate matter deposited depends on the degree of reduction of the particulate filter pipe area due to the particulate matter deposition. Estimating means for estimating the amount of the particulate matter deposited in the particulate filter by the corrected characteristic to which correction is applied;
An exhaust emission control device for an internal combustion engine, comprising: a regeneration means for regenerating the particulate filter by burning the particulate matter deposited when the estimated value of the accumulation amount by the estimation means increases. The estimation means includes
A pre-correction characteristic storage means for storing a characteristic between a differential pressure which is a pressure difference between the inlet side and the outlet side in the particulate filter and a deposition amount of particulate matter when the pipe area is constant;
In the characteristic stored in the pre-correction characteristic storage unit, the correction unit includes a correction unit that performs correction to increase a gradient that is an increase rate of the differential pressure with respect to the accumulation amount as the degree of decrease in the pipe area increases.
2. The exhaust emission control device for an internal combustion engine according to claim 1, wherein the characteristic corrected by the inclination correcting means is the corrected characteristic. The estimation means includes
A pre-correction characteristic storage means for storing a characteristic between a differential pressure which is a pressure difference between the inlet side and the outlet side in the particulate filter and a deposition amount of particulate matter when the pipe area is constant;
In the characteristics stored in the pre-correction characteristic storage means, the accumulation amount decrease correction means for performing correction to decrease the accumulation amount as the degree of decrease in the pipe area increases,
2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the characteristic corrected by the accumulation amount decrease correcting means is the corrected characteristic. The estimation means includes
The characteristic between the differential pressure which is the pressure difference between the inlet side and the outlet side in the particulate filter and the amount of particulate matter deposited is corrected to increase the pressure difference as the amount of deposition increases. A corrected characteristic storage means for storing,
2. The exhaust emission control device for an internal combustion engine according to claim 1, wherein the characteristic stored in the corrected characteristic storage means is the corrected characteristic.

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