JP2006274906A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device capable of enhancing the durability and also a forced regeneration of good efficiency by executing the forced regeneration while an ash depositing form different from the depositing form of particulates is taken into consideration. <P>SOLUTION: The exhaust emission control device is equipped with a corrective value setting means 56 to set the corrective value for correction of the regenerating timing so that the thickness of particulates deposited on a particulate filter 2 at start of a forced regeneration becomes approximately constant in compliance with the effective capturing surface area of the particulate filter 2 decreasing with the deposit of the ash contained in the exhaust gas on the particulate filter 2 and a regeneration timing correcting means 58 to correct the regenerating timing on the basis of the corrective value upon setting the time as the regenerating timing when the predetermined conditions are met. A regeneration control means 52 performs forced regeneration of the particulate filter 2 at the corrected regeneration timing. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust purification device, and more particularly to an exhaust purification device including a particulate filter for collecting particulates contained in engine exhaust.

Conventionally, a particulate filter is provided in the exhaust passage of an engine such as a diesel engine, and particulates contained in the exhaust discharged from the engine are collected by the particulate filter so that the particulates are not released into the atmosphere. Technology is known.
In such a particulate filter, the collected particulates accumulate in the particulate filter and the exhaust resistance increases. Therefore, the particulate filter is forcibly burned in some way to regenerate the particulate filter. That is, it is necessary to forcibly regenerate the filter.

As a method for forcibly regenerating the particulate filter, HC is supplied into the exhaust gas from a fuel addition valve provided in the exhaust passage, or fuel is injected into the cylinder in the expansion stroke or exhaust stroke of the engine. Is known to increase the exhaust temperature.
Such forced regeneration is performed when it is estimated that the amount of accumulated particulate matter on the particulate filter exceeds a predetermined amount, and the estimated amount of particulate accumulation is estimated based on the operating time of the engine and the particulate matter. This is based on the exhaust pressure difference before and after the filter. At this time, if the particulate accumulation amount is not estimated accurately, the forced regeneration of the particulate filter is performed more than necessary, which may cause problems such as excessive consumption of fuel and deterioration of fuel consumption. There is sex.

  On the other hand, in addition to particulates, exhaust contains a substance called ash caused by engine oil, wear powder generated in the engine, or particulate ash remaining by forced regeneration. This ash also accumulates on the particulate filter together with the particulate, but unlike the particulate, it is not incinerated by forced regeneration of the particulate filter and remains in the particulate filter. If the amount of ash remaining in the particulate filter increases, it becomes difficult to accurately estimate the amount of particulate accumulated in the particulate filter, and forced regeneration of the particulate filter is performed at an appropriate time. The problem of being unable to do so occurs.

  Therefore, almost no particulate is accumulated in the particulate filter immediately after the forced regeneration of the particulate filter is completed, so it is estimated based on the exhaust pressure difference before and after the particulate filter and the exhaust flow rate to the particulate filter. The amount of accumulated deposit was regarded as the amount of accumulated ash, and the timing of forced regeneration was determined based on the estimated amount of accumulated particulates corrected by this estimated amount of accumulated ash, so that the occurrence of such problems was prevented. An exhaust purification device has been proposed (for example, Patent Document 1).

More specifically, the amount of accumulated ash estimated during forced regeneration of the particulate filter is subtracted from the amount of accumulation estimated based on the exhaust pressure difference before and after the particulate filter and the exhaust flow rate to the particulate filter. The amount of accumulated particles is estimated, and when the estimated amount of accumulated particulates exceeds a predetermined determination value, forced regeneration is performed.
JP 2003-83036 A

  In the exhaust emission control device of Patent Document 1, ash is considered to be equivalent to particulates, and the estimated ash accumulation is simply based on the accumulation amount estimated based on the exhaust pressure difference before and after the particulate filter and the exhaust flow rate to the particulate filter. The amount of particulate deposition is estimated by subtracting the amount, and the particulate filter is forcibly regenerated based on the estimated amount of deposition.

That is, in the exhaust emission control device of Patent Document 1, whether or not forced regeneration is necessary is determined based on the premise that ash is accumulated in the particulate filter in the same form as the particulates.
In practice, however, the ash deposition pattern in the particulate filter is completely different from the particulate deposition pattern. Here, the difference between the particulate deposition form and the ash deposition form in the particulate filter will be described below with reference to FIGS.

  FIG. 7 is a conceptual diagram showing a particulate deposition state in a state where ash is not deposited on the particulate filter 2. The particulate filter 2 is made of a honeycomb-type ceramic carrier, and a large number of passages 2a communicating the upstream side and the downstream side are arranged side by side, and the upstream side opening and the downstream side opening of the passage are alternately closed. For this reason, the exhaust gas flowing into the particulate filter 2 from the passage 2a having an opening on the upstream side passes through the porous wall 2b forming each passage 2a and opens on the downstream side, as indicated by arrows. It flows out out of the passage 2a having a downstream side of the particulate filter 2.

  Then, assuming that the flow of exhaust gas into the particulate filter 2 is started from a state where nothing is deposited on the porous wall 2b of the particulate filter 2, when the exhaust gas passes through the porous wall 2b, Particulates 4 contained in the exhaust are captured by the porous wall 2b and are deposited almost uniformly from the upstream end to the downstream end of the porous wall 2b as shown in FIG.

On the other hand, FIG. 8 is a conceptual diagram showing a deposition state of the particulate 4 in a state where the ash 6 is deposited on the particulate filter 2. 8, the particulate filter 2 is the same as the particulate filter described in FIG. 7, and portions common to FIG. 7 will be described using the same reference numerals as in FIG. 7.
The ash 6 is discharged from the engine while being contained in the exhaust together with the particulates 4, and once trapped by the porous wall 2b when the exhaust passes through the porous wall 2b, like the particulate 4. , Almost uniformly deposited from the upstream end to the downstream end of the wall 2b. After that, when a predetermined amount of the particulate 4 is deposited and the particulate filter 2 is forcibly regenerated, the particulate 4 is combusted while the ash 6 is not combusted. As the particulate 4 is combusted, the ash is ashed in the passage 2a. 6 floats. Then, with the subsequent inflow of exhaust gas, the ash 6 floating in the passage 2a is accumulated from the most downstream side of the passage 2a opening upstream.

  As a result, the effective collection surface area of the particulate filter 2 is reduced by the amount of accumulation of the ash 6, and the particulate 4 is collected only at the portion where the ash 6 is not accumulated as shown in FIG. Become. Accordingly, assuming that the particulate filter 2 needs to be forcibly regenerated when the particulate 4 is deposited to a predetermined thickness, and the ash 6 occupies almost half of the passage 2a in FIG. 8, the case of FIG. When almost half the amount of the particulates 4 is deposited, the forced regeneration of the particulate filter 2 must be performed.

  As described above, since the particulate accumulation state and the ash accumulation state in the particulate filter are completely different from each other, the estimated ash accumulation amount is subtracted from the estimated accumulation amount as in the exhaust gas purification apparatus of Patent Document 1. If the particulate accumulation amount is obtained, and the forced regeneration is started simply when the particulate deposition amount exceeds a predetermined amount, the thickness of the particulates when the forced regeneration is started is not necessarily the same.

As a result, as the thickness of the accumulated particulate increases, the temperature rises abruptly due to the self-ignition of the particulates, so that the possibility of overheating of the particulate filter increases. If the temperature of the particulate filter is excessively high, cracking or melting may occur, which may lead to black smoke leakage.
Conversely, if forced regeneration of the particulate filter is started while the accumulated particulates are thin, forced regeneration is performed with the particulate filter still having sufficient capacity to collect. This will increase the frequency of fuel consumption and cause problems such as deterioration in fuel consumption and drivability.

  The present invention has been made in view of such problems, and the object of the present invention is to achieve durability by performing forced regeneration in consideration of the ash accumulation form different from the particulate accumulation form. It is another object of the present invention to provide an exhaust emission control device that improves the efficiency and enables efficient forced regeneration.

  In order to achieve the above object, an exhaust gas purification apparatus for an internal combustion engine according to the present invention includes a particulate filter that is disposed in an exhaust passage of an engine and collects particulates in the exhaust, and the particulate filter at a predetermined regeneration time. In an exhaust emission control device comprising a regeneration control means for incinerating accumulated particulates and forcibly regenerating the particulate filter, the ash contained in the exhaust gas is reduced by depositing on the particulate filter. Corresponding to the effective collection surface area of the particulate filter, a correction value for correcting the regeneration time so that the thickness of the particulate deposited on the particulate filter at the start of the forced regeneration is substantially constant The correction value setting means for setting the value and the time when a predetermined condition is satisfied A reproduction time correction unit that sets the reproduction time and corrects the reproduction time based on the correction value set by the correction value setting unit, and the reproduction control unit reproduces the reproduction corrected by the reproduction time correction unit. The particulate filter is forcibly regenerated at a certain time (Claim 1).

Specifically, an ash accumulation amount detection unit that detects the amount of the ash accumulated on the particulate filter is further provided, and the correction value setting unit preliminarily determines the ash accumulation amount detected by the ash accumulation amount detection unit. The correction value is calculated by multiplying a set correction coefficient (claim 2).
Further, the ash accumulation amount detection means detects the amount of the ash accumulated on the particulate filter when the forced regeneration is finished (Claim 3).

  More specifically, it further comprises a differential pressure detection means for detecting an exhaust pressure difference before and after the particulate filter, and the regeneration timing correction means is configured so that the exhaust pressure difference detected by the differential pressure detection means is a predetermined regeneration. A time when the start determination value is exceeded is set as the regeneration timing, and either the exhaust pressure difference detected by the differential pressure detection means or the regeneration start determination value is corrected with the correction value. (Claim 4).

Alternatively, the regeneration time correction means sets, as the regeneration time, a time when the integrated value of the fuel amount supplied to operate the engine becomes a predetermined regeneration start determination value or more, and the integrated value of the fuel amount One of the reproduction start determination values is corrected with the correction value (Claim 5).
Alternatively, the regeneration time correction means sets the regeneration time when the integrated value of the operating time of the engine is equal to or greater than a predetermined regeneration start determination value, and sets the integrated value of the operation time and the regeneration start determination value. Either one is corrected by the correction value (claim 6).

  According to the exhaust emission control device of claims 1 to 6, the ash contained in the exhaust gas corresponds to an effective collection surface area of the particulate filter that is reduced by accumulating on the particulate filter, and the particulates are started at the start of forced regeneration. Set a correction value to correct the regeneration time so that the particulate thickness accumulated in the filter is almost constant, and perform forced regeneration of the particulate filter at the regeneration time corrected based on this correction value Therefore, forced regeneration is performed when the thickness of the particulates deposited on the particulate filter is substantially the same.

  As a result, the particulates at the start of forced regeneration are too thick, leading to overheating, causing cracks in the particulate filter, leakage of black smoke due to melting, etc. The forced regeneration is executed while the thickness of the battery is thin, and it is possible to prevent the occurrence of the problem that the frequency of forced regeneration increases and the fuel consumption and drivability deteriorate.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a system configuration diagram of a four-cylinder diesel engine (hereinafter referred to as an engine) to which an exhaust emission control device according to an embodiment of the present invention is applied. The exhaust emission control device according to the present invention is based on FIG. The structure of will be described.
The engine 10 includes a high-pressure accumulator chamber (hereinafter referred to as a common rail) 12 common to each cylinder, and supplies high-pressure light oil stored in the common rail 12 to an injector 14 provided in each cylinder. Light oil is injected into the cylinder.

  The intake passage 16 is equipped with a turbocharger 18, and intake air drawn from an air cleaner (not shown) flows into the compressor 18a of the turbocharger 18 from the intake passage 16, and the intake air supercharged by the compressor 18a is intercooler. 20 and the intake control valve 60 are introduced into the intake manifold 22. An intake flow rate sensor 24 for detecting the intake air flow rate to the engine 10 is provided upstream of the compressor 18 a in the intake passage 16.

On the other hand, an exhaust port (not shown) through which exhaust is discharged from each cylinder of the engine 10 is connected to an exhaust pipe (exhaust passage) 28 via an exhaust manifold 26. Note that an EGR passage 32 that communicates the exhaust manifold 26 and the intake manifold 22 via the EGR valve 30 is provided between the exhaust manifold 26 and the intake manifold 22.
The exhaust pipe 28 passes through the turbine 18 b of the turbocharger 18 and is connected to the exhaust aftertreatment device 34 via the exhaust throttle valve 62. The turbine 18b is connected to the compressor 18a, receives the exhaust flowing in the exhaust pipe 28, and drives the compressor 18a.

In the exhaust aftertreatment device 34, an oxidation catalyst 36 is accommodated on the upstream side in the casing, and on the downstream side of the oxidation catalyst 36, a particulate filter (hereinafter referred to as a filter) 2 that captures particulates in the exhaust gas. Contained.
The oxidation catalyst 36 is NO in the exhaust is oxidized to generate NO _2, and supplies to the filter 2 of the NO ₂ as oxidizing agent. Further, the filter 2 is the same as that described with reference to FIGS. 7 and 8 described above, and is made of a honeycomb-type ceramic carrier, and a large number of passages communicating the upstream side and the downstream side are arranged in parallel. The upstream opening and the downstream opening of the passage are closed alternately.

Particulates collected and deposited in the filter 2 react with NO ₂ supplied from the oxidation catalyst 36 and burn, so that the filter 2 is continuously regenerated.
Between the oxidation catalyst 36 and the filter 2, an inlet temperature sensor 38 that detects an exhaust temperature on the inlet side of the filter 2 and an inlet pressure sensor 40 that detects an exhaust pressure on the inlet side of the filter 2 are provided. Further, on the downstream side of the filter 2, an outlet pressure sensor 42 that detects the exhaust pressure on the outlet side of the filter 2 and an outlet temperature sensor 44 that detects the exhaust temperature on the outlet side of the filter 2 are provided.

The ECU 46 is a control device for performing comprehensive control of the exhaust gas purification apparatus according to the present invention including the engine 10, and includes a CPU, a memory, a timer counter, and the like, and calculates various control amounts. Various devices are controlled based on the control amount.
In addition to the above-described intake flow rate sensor 24, inlet temperature sensor 38, inlet pressure sensor 40, outlet pressure sensor 42, and outlet temperature sensor 44, the input side of the ECU 46 collects information necessary for performing various controls. Various sensors such as an engine speed sensor 48 for detecting the engine speed and an accelerator opening sensor 50 for detecting the depression amount of the accelerator pedal are connected, and control is performed on the output side based on the calculated control amount. Various devices such as the injector 14, the EGR valve 30, the intake control valve 60, and the exhaust throttle valve 62 of each cylinder are connected.

  The ECU 46 also performs calculation of the fuel supply amount to each cylinder of the engine 10 and control of fuel supply from the injector 14 based on the calculated fuel supply amount. The fuel supply amount (main injection amount) necessary for the operation of the engine 10 is stored in advance based on the engine speed detected by the speed sensor 48 and the accelerator opening detected by the accelerator opening sensor 50. Read from the map and decide. The amount of fuel supplied to each cylinder is adjusted by the valve opening time of the injector 14, and each injector 14 is driven to open in a driving time corresponding to the determined fuel amount.

  In the exhaust gas purification apparatus for an internal combustion engine configured as described above, the particulates accumulated on the filter 2 are incinerated and removed by continuous regeneration using the oxidation catalyst 36. In low speed, low load operation, etc., the exhaust temperature does not rise to the activation temperature of the oxidation catalyst 36, and NO in the exhaust may not be oxidized and continuous regeneration may not be performed. If such a state continues, particulates excessively accumulate in the filter 2 and the filter 2 may be clogged. Therefore, forced regeneration is appropriately performed according to the particulate accumulation state in the filter 2. .

FIG. 2 shows a control block for performing forced regeneration control in the ECU 46. The regeneration control unit (regeneration control means) 52 performs fuel regeneration at a predetermined regeneration time based on the detection values from the rotation speed sensor 48 and the inlet temperature sensor 38. The injection valve 14 is controlled to perform forced regeneration of the filter 2.
The ash accumulation amount detection unit (ash accumulation amount detection means) 54 detects an ash accumulation amount when the forced regeneration by the regeneration control unit 52 is completed, and a correction value setting unit (correction value setting means) 56. Is to set the correction value for the regeneration time by multiplying the ash accumulation amount detected by the ash accumulation amount detector 54 by a preset correction coefficient α. The regeneration time correction unit (reproduction time correction means) 58 corrects the time when the regeneration control unit 52 performs forced regeneration with the correction value set by the correction value setting unit 56.

Here, the concept of correcting the regeneration time accompanying the accumulation of ash will be described below.
As described in FIG. 8, the ash 6 accumulates from the downstream side of the passage 2 a that opens upstream in the filter 2, whereby the effective surface area of the filter 2 that can collect the particulates 4 gradually decreases. Assuming that the amount of ash that can be accumulated in one passage is M and the amount of ash that is currently accumulated is m, the effective surface area that can collect particulates in one passage is that ash is accumulated. If no is 1, then 1-m / M.

Since the particulates are deposited almost uniformly on the surface where no ash is deposited, the time until the particulates are deposited to a predetermined thickness is 1 when the ash is not deposited. Accordingly, it will be 1-m / M.
That is, if the ash is not deposited and the forced regeneration is performed when the operation time T0 has elapsed, the forced regeneration is started when the accumulated particulates have the same thickness regardless of the ash accumulation amount. In order to achieve this, the time when the time T1 represented by the following formula (1) has elapsed may be set as the regeneration time.

T1 = T0 · (1-m / M) (1)
Here, when the above formula (1) is modified and arranged, the following formula (2) is obtained.
T1 = T0−α · m (2)
However, α = T0 / M.
Therefore, if the coefficient (correction coefficient) α is obtained in advance by experiments or the like, the particulates are deposited to almost the same thickness by correcting the regeneration start time with a correction value obtained by multiplying the accumulation amount of ash by the coefficient α. Sometimes forced regeneration can be started.

Based on this idea, the regeneration timing correction unit 58 corrects the start time of forced regeneration, and the regeneration control unit 52 executes forced regeneration of the filter 2 when the corrected regeneration time comes.
FIG. 3 is a flowchart showing the contents of the forced regeneration start and end determination control performed based on this idea. The forced regeneration is performed by repeating the control flow of FIG. 3 at a predetermined control cycle. Determination of the start of forced regeneration control in a state where the forced regeneration is not performed and determination of termination of forced regeneration control during execution of forced regeneration are performed.

  First, in step S102 of FIG. 3, it is determined whether or not the value of the forced regeneration flag F1 is 1. The forced regeneration flag F1 indicates whether or not forced regeneration is necessary. When the value is 1, forced regeneration is necessary, and when the value is 0, forced regeneration is not necessary. The initial set value of the forced regeneration flag F1 is 0, and the process proceeds from step S102 to step S104 in the first control cycle.

  In step S104, it is determined whether or not the value T of a timer counter (not shown) that has accumulated the operating time of the engine 10 since the previous forced regeneration is greater than the regeneration start determination value T1. . The regeneration start determination value T1 is corrected at the end of the previous forced regeneration so that the forced regeneration is started when the thickness of the particulates deposited on the filter 2 is substantially the same. The correction method will be described later. To do. Note that the initial value T0 is set with respect to T1 before the first forced regeneration is performed. This initial value T0 is the time required for deposition until the particulates have a predetermined thickness in a state where ash is not deposited on the filter 2.

  If it is determined in step S104 that the operation time T of the engine 10 accumulated by the timer counter has not reached the regeneration start determination value T1, the current control cycle is terminated, and the processing from step S102 is performed again in the next control cycle. Do. Therefore, while the operation time T of the engine 10 does not reach the regeneration start determination value T1, the value of the forced regeneration flag F1 is maintained at 0, and the forced regeneration is unnecessary.

When the operating time T of the engine 10 accumulated by the timer counter after the previous forced regeneration reaches the regeneration start determination value T1, the process proceeds from step S104 to step S106, the value of the forced regeneration flag F1 is changed to 1, and the step The process proceeds to S108.
In step S108, the accumulated value T of the timer counter that has accumulated the operating time of the engine 10 since the end of the previous forced regeneration is reset to 0, the accumulation of the timer counter is restarted, and the current control cycle ends. Since the forced regeneration control described later is started when the value of the forced regeneration flag F1 becomes 1 in step S106, the timer counter reset in step S108 is to add the execution time of the forced regeneration control this time. Become.

In the next control cycle, the value of the forced regeneration flag F1 is 1. Therefore, the process proceeds from step S102 to step S110, and the accumulated value of the timer counter that restarts the accumulation after the value of the forced regeneration flag F1 becomes 1. It is determined whether T, that is, the forced regeneration execution time T is longer than the regeneration end determination value T2.
When the forced regeneration execution time T is less than the regeneration end determination value T2, the current control cycle is terminated, and the process proceeds again from step S102 to step S110 in the next control cycle.

When the forced regeneration execution time T reaches the regeneration end determination value T2, the process proceeds from step S110 to step S112, and the value of the forced regeneration flag F1 is changed to 0 indicating that the forced regeneration is not required. Therefore, when the forced regeneration time reaches T2, forced regeneration of the filter 2 ends.
When the process further proceeds from step S112 to step S114, the integrated value T of the timer counter that has accumulated the elapsed time since the start of forced regeneration is reset to 0, and the integration of the timer counter is restarted. When the forced regeneration flag F1 becomes 0 in step S112, the forced regeneration control ends as described later. Therefore, the timer counter reset in step S114 is now the operating time of the engine 10 after the forced regeneration ends. Will be accumulated.

  In the next step S116, the regeneration start determination value T1 is corrected and set by subtracting the correction amount obtained by multiplying the ash accumulation amount A by the correction coefficient α stored in advance from the time T0. As described above, the correction coefficient α is a coefficient for correcting the regeneration start time so that the forced regeneration is started when the accumulated particulate thickness is almost the same regardless of the amount of accumulated ash. The time T0 is the time required to deposit the particulates until the particulates reach a predetermined thickness in a state where the ash is not deposited on the filter 2.

Using the regeneration start determination value T1 set in this way, the forced regeneration start time is determined in step S104 as described above, so that it is compulsory when the accumulated particulate thickness is almost the same regardless of the ash accumulation amount. Playback starts.
The ash accumulation amount A used at this time is considered to increase according to the number of times of forced regeneration, and the ash accumulation amount A is stored in advance corresponding to the number of times of forced regeneration according to the relationship shown in FIG. It is detected by reading from the map.

In this way, by correcting the forced regeneration execution time by the ash accumulation amount A and the correction coefficient α, the forced regeneration execution time is gradually advanced with a slope −α as shown in FIG.
By performing the forced regeneration start and end determination control as described above, the value of the forced regeneration flag F1 is switched to 1 or 0, and the forced regeneration control is performed based on the value of the forced regeneration flag F1.

The forced regeneration control is performed at a predetermined control cycle according to the flowchart of FIG.
First, in step S202, it is determined whether or not the value of the forced regeneration flag F1 is 1. When the value of the forced regeneration flag F1 is 0, the forced regeneration of the filter 2 is not necessary, so the current control cycle is terminated, and the value of the forced regeneration flag F1 is determined again in the next control cycle.
On the other hand, when the value of the forced regeneration flag F1 is 1, the process proceeds to step S204, and based on the detected value of the inlet temperature sensor 38, the temperature Tc of the oxidation catalyst 36 becomes 250 ° C. or higher, and the oxidation catalyst 36 is reached. It is determined whether or not is activated.

When the catalyst temperature Tc is less than 250 ° C., the process proceeds to step S206, and the temperature increase control of the oxidation catalyst 36 is performed.
In this temperature increase control, the temperature of the oxidation catalyst 36 is raised to the activation temperature (for example, 250 ° C.) by supplying high-temperature exhaust gas to the oxidation catalyst 36, and the intake control valve 60 and the exhaust throttle valve 62 are increased. Is controlled in the closing direction, and the first additional fuel injection is performed in the expansion stroke of each cylinder. The injection timing of the first additional fuel is relatively earlier than the end of the expansion stroke. By injecting the additional fuel into the cylinder at such timing, the additional fuel and the high-temperature combustion gas in the cylinder are generated. As a result of mixing, additional fuel is combusted in the exhaust port and the exhaust manifold 26, and high temperature exhaust gas is supplied to the oxidation catalyst 36, whereby the temperature of the oxidation catalyst 36 rises.

In step S206, the temperature raising control of the oxidation catalyst 36 is performed to finish the control cycle, and the control is performed again from step S202 in the next control cycle. At this time, since the value of the forced regeneration flag F1 is 1, the process proceeds to step S204, and while it is determined that the catalyst temperature Tc is less than 250 degrees, the catalyst temperature increase control by the injection of the first additional fuel is repeated. It is.
In this way, the temperature increase control by the injection of the first additional fuel is repeated, and when the temperature Tc of the oxidation catalyst 36 becomes 250 ° C. or higher, the process proceeds from step S204 to step S208. In step S208, based on the detected value of the inlet temperature sensor 38, it is determined whether or not the temperature Tc of the oxidation catalyst 36 is equal to or higher than a predetermined temperature. This predetermined temperature is a temperature at which the particulates burn most efficiently in the filter 2, and in this embodiment, the predetermined temperature is 600 ° C.

If it is determined in step S208 that the catalyst temperature Tc is 600 ° C. or higher, the process proceeds to step S210. If it is determined that the catalyst temperature Tc is less than 600 ° C., the process proceeds to step S212.
In steps S210 and S212, the second additional fuel is injected into each cylinder so that the temperature of the exhaust gas supplied to the filter 2 is maintained at 600 ° C., and the second additional fuel is injected in the exhaust stroke. It has come to be. By injecting the second additional fuel into each cylinder at such injection timing, the second additional fuel reaches the oxidation catalyst 36 without being burned in the cylinder or the exhaust manifold 26, and is at the activation temperature. Combustion occurs in the oxidation catalyst 36 and the filter 2. By this combustion, the exhaust temperature rises to 600 ° C., and the particulates deposited on the filter 2 are incinerated.

  The second additional fuel is stored in a map that uses the engine speed detected by the speed sensor 48 and the main injection amount (load) determined by the ECU 46 as parameters, and this map is the second additional fuel injection. There are two types of maps, an increase map with a relatively large amount and a decrease map with a relatively small amount. In step S210, since the catalyst temperature Tc is 600 ° C. or higher, a relatively small amount of second additional fuel is injected using the reduction map. In step S212, the catalyst temperature Tc is less than 600 ° C. To inject a relatively large amount of the second additional fuel. As a result, the temperature of the exhaust gas discharged from the oxidation catalyst 36 and supplied to the filter 2 is maintained at around 600 ° C.

  When the second additional fuel is injected in step S210 or S212, the current control cycle is terminated, and the process is repeated from step S202 in the next control cycle. Therefore, as described above, the temperature of the exhaust gas discharged from the oxidation catalyst 36 and supplied to the filter 2 is 600 ° C. until the value of the forced regeneration flag F1 is set to 0 in the forced regeneration end determination control according to the flowchart of FIG. The forced regeneration of the filter 2 is performed while being maintained back and forth. When it is determined that the forced regeneration is finished and the value of the forced regeneration flag F1 is set to 0, the control is terminated without proceeding from step S202 to step S204 in the next control cycle. finish.

  As described above, regardless of the ash accumulation amount, the correction coefficient α for correcting the regeneration start time and the ash accumulation amount A so that the forced regeneration is started when the accumulated particulates have substantially the same thickness. Since the regeneration start determination value T1 is corrected with the correction value obtained by multiplying by and the forced regeneration start time is determined using the corrected regeneration start determination value T1, regardless of the amount of ash accumulated, Forced regeneration is started when the deposited particulates have substantially the same thickness.

As a result, the particulate filter is too thick at the start of forced regeneration, resulting in excessive temperature rise and damage or melting of the particulate filter, or forced regeneration is performed while the particulate is thin, It is possible to prevent the occurrence of problems such as increase in the frequency of reproduction and deterioration in fuel consumption and drivability.
Although the description of the exhaust emission control device according to one embodiment of the present invention is finished above, the present invention is not limited to the above embodiment.

For example, in the above embodiment, the regeneration start determination value T1 is corrected with a correction value obtained by multiplying the correction coefficient α and the ash accumulation amount A. However, the regeneration start determination value T1 is a fixed value, and the timer counter The operating time of the engine 10 accumulated by the above may be corrected by adding the correction value.
In the above embodiment, the forced regeneration timing is determined based on the operation time of the engine 10, but the forced regeneration timing determination method is not limited to this.

  For example, when the inlet pressure sensor 40 and the outlet pressure sensor 42 are used as differential pressure detection means, the exhaust pressure difference before and after the filter 2 is obtained based on the detection values of these sensors, and the exhaust pressure difference becomes equal to or greater than the regeneration start determination value. May be the regeneration period. In this case as well, the same effect as in the above embodiment can be obtained by correcting the regeneration start determination value with the correction value obtained by multiplying the correction coefficient α and the ash deposition amount A, as in the above embodiment. it can. The regeneration start determination value may be a fixed value, and the detected exhaust pressure difference before and after the filter 2 may be corrected by adding the correction value.

  Alternatively, based on the fuel supply amount to the engine 10 calculated by the ECU 46, an integrated value of the fuel supplied to the engine 10 after the end of the previous forced regeneration is obtained, and the integrated value of the fuel supply amount is greater than or equal to the regeneration start determination value. The time when it becomes may be set as the reproduction time. In this case as well, the same effect as in the above embodiment can be obtained by correcting the regeneration start determination value with the correction value obtained by multiplying the correction coefficient α and the ash deposition amount A, as in the above embodiment. it can. Alternatively, the regeneration start determination value may be a fixed value, and the fuel supply amount integrated value may be corrected by adding the correction value.

As described above, there are various methods for determining the execution time of the forced regeneration, but any correction method is obtained by multiplying the correction coefficient α and the ash deposition amount A as in the above embodiment. By performing correction with values, the same effects as in the above embodiment can be obtained.
In the above embodiment, it is assumed that the amount of accumulated ash increases according to the number of times of forced regeneration, and the relationship shown in FIG. 5 is read out from a map stored in advance corresponding to the number of times of forced regeneration. The ash accumulation amount is detected, but since almost no particulates are accumulated on the filter 2 at the end of forced regeneration, the ash accumulation amount is estimated based on the exhaust pressure difference before and after the filter 2 at the end of forced regeneration. May be detected. Further, instead of the number of forced regenerations, the ash accumulation amount may be estimated and detected based on the accumulated travel distance of the vehicle, or may be estimated from the consumed fuel amount, the oil consumption rate, the ash content, and the like. You may do it.

  In the above embodiment, the filter 2 is forcibly regenerated by injecting additional fuel in the expansion stroke and exhaust stroke of the engine 10. However, the method of forced regeneration of the filter 2 is not limited to this, and an electric heater is used. The particulate matter is incinerated by raising the temperature of the filter 2, such as the one used to heat the filter 2 or the one in which the fuel addition valve is provided in the exhaust pipe 28 and the fuel is directly added to the exhaust. Anything can be applied.

  Finally, in the above-described embodiment, the present invention is applied to an exhaust emission control device for a diesel engine. However, the engine type is not limited to this, and particulates are removed using a filter. Any engine that regenerates the filter by incineration can be applied.

1 is an overall configuration diagram of an exhaust emission control device for an internal combustion engine according to an embodiment of the present invention. FIG. 2 is a control block diagram of forced regeneration control performed by the exhaust emission control device of FIG. 1. 2 is a flowchart of forced regeneration start and end determination control performed by the exhaust emission control device of FIG. 1. It is a flowchart of the forced regeneration control performed with the exhaust gas purification device of FIG. It is a figure which shows the relationship between the frequency | count of forced regeneration implementation, and the amount of ash deposits. It is a figure which shows the relationship between ash deposition amount and forced regeneration implementation time. It is a conceptual diagram which shows the accumulation condition of the particulate matter trapped by the filter. It is a conceptual diagram which shows the deposition condition of the particulates and ash trapped by the filter.

Explanation of symbols

2 Filter (Particulate filter)
10 Engine 28 Exhaust pipe (exhaust passage)
40 Inlet pressure sensor (Differential pressure detection means)
42 Outlet pressure sensor (Differential pressure detection means)
52 Reproduction control unit (reproduction control means)
54 Ash accumulation amount detection unit (ash accumulation amount detection means)
56 Correction value setting unit (correction value setting means)
58 Regeneration time correction unit (Regeneration time correction means)

Claims (6)

A particulate filter that is disposed in the exhaust passage of the engine and collects particulates in the exhaust, and the particulate filter that is deposited on the particulate filter at a predetermined regeneration time is incinerated to forcibly regenerate the particulate filter. In an exhaust emission control device comprising a regeneration control means for performing,
Corresponding to the effective collection surface area of the particulate filter that decreases as ash contained in the exhaust accumulates on the particulate filter, the particulates accumulated on the particulate filter at the start of the forced regeneration Correction value setting means for setting a correction value for correcting the reproduction time so that the thickness is substantially constant;
A time when a predetermined condition is satisfied is set as the playback time, and a playback time correction unit that corrects the playback time based on a correction value set by the correction value setting unit,
The exhaust emission control device, wherein the regeneration control means forcibly regenerates the particulate filter at the regeneration time corrected by the regeneration time correction means. An ash accumulation amount detecting means for detecting the amount of the ash accumulated on the particulate filter;
2. The exhaust emission control device according to claim 1, wherein the correction value setting means sets the correction value by multiplying an ash accumulation amount detected by the ash accumulation amount detection means by a preset correction coefficient. .   The exhaust purification apparatus according to claim 2, wherein the ash accumulation amount detection means detects the amount of the ash accumulated on the particulate filter when the forced regeneration is completed. Further comprising a differential pressure detecting means for detecting an exhaust pressure difference before and after the particulate filter;
The regeneration time correction means sets the regeneration time when the exhaust pressure difference detected by the differential pressure detection means is equal to or greater than a predetermined regeneration start determination value, and the detection time detected by the differential pressure detection means The exhaust emission control device according to any one of claims 1 to 3, wherein any one of an exhaust pressure difference and the regeneration start determination value is corrected by the correction value.   The regeneration time correction means sets, as the regeneration time, a time when the integrated value of the fuel amount supplied to operate the engine is equal to or greater than a predetermined regeneration start determination value, and the integrated value of the fuel amount and the The exhaust emission control device according to any one of claims 1 to 3, wherein any one of the regeneration start determination values is corrected with the correction value.   The regeneration time correcting means sets the regeneration time when the integrated value of the engine operating time is equal to or greater than a predetermined regeneration start determination value, and is either one of the integrated operation time value or the regeneration start determination value. The exhaust emission control device according to any one of claims 1 to 3, wherein one of the correction values is corrected by the correction value.

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