JP2012041906A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device of an internal combustion engine, capable of preventing deterioration of a DPF due to extreme temperature rise, while reducing deterioration of fuel economy and oil dilution, by establishing optimum forcible regeneration conditions according to the deposit amount of PM.SOLUTION: The forcible regeneration is started and a target regeneration temperature is raised according to a total deposit amount (S10 to S16), the temperature deviation ΔT is calculated by subtracting the target regeneration temperature T2 in the step B from the practical regeneration temperature Tx during forcible regeneration processing (S18), the starting timing of the step B is delayed in the next time forcible regeneration and the forcible regeneration time is delayed in the step A assuming that extreme temperature rise occurs in the case in the temperature deviation ΔT is a predetermined temperature deviation or more (S22 to S32). Further, the starting timing of the step B is accelerated of the next forcible regeneration time assuming that the extreme temperature rise does not occur and the forcible regeneration condition is switched so as to shorten the forcible regeneration time in the step A in the case the temperature deviation ΔT is smaller than the predetermined temperature deviation (S34 to S36).

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine, and more particularly to a forced regeneration technology for a diesel particulate filter that forcibly removes particulate matter deposited on a diesel particulate filter.

  2. Description of the Related Art A diesel particulate filter (hereinafter referred to as DPF) is known as an exhaust aftertreatment device that purifies exhaust from a diesel engine. The DPF is provided in the exhaust passage and collects particulate matter (particulate matter, hereinafter referred to as PM) in the exhaust. In order to remove the PM collected and accumulated in the DPF, an oxidation catalyst is provided upstream of the DPF, and an unburned fuel is caused to flow into the oxidation catalyst to cause an oxidation reaction. A technique for forcibly regenerating DPF by raising the temperature and burning and removing PM trapped in the DPF is known.

  For example, for a predetermined period from the start of forced regeneration, post-injection is performed in the expansion stroke after main injection, and unburned fuel generated by post-injection is burned with an oxidation catalyst located upstream of the DPF, and the DPF inlet After maintaining the temperature at a predetermined temperature, the forced regeneration is feedback controlled so that the outlet temperature of the DPF becomes higher than the predetermined temperature, and PM accumulated in the center of the DPF is gradually burned to thereby improve the PM. Overheating of the DPF due to rapid combustion of the DPF, after the elapse of a predetermined period, after the risk of PM decreasing and overheating of the DPF is resolved, the outlet temperature of the DPF is raised to a temperature higher than the predetermined temperature. A technique is known in which the PM accumulated on the periphery of the DPF is reliably burned and removed without being left unburned, while preventing the excessive temperature rise of the DPF by continuing to hold (Patent Document 1).

JP 2008-133664 A

As described above, in the exhaust gas purification apparatus for an internal combustion engine disclosed in Patent Document 1, after maintaining the DPF inlet temperature at a predetermined temperature for a predetermined period determined by a test or the like from the start of forced regeneration, the outlet temperature of the DPF is changed. The temperature is set higher than a predetermined temperature, and the PM accumulated in the DPF is suppressed from being excessively heated and reliably removed by combustion.
However, the amount of PM deposited on the DPF varies greatly depending on the operating condition of the internal combustion engine and the interval between forced regenerations.

Accordingly, if the regeneration period and regeneration temperature are set in advance, if the amount of accumulated PM is small, forced regeneration is continued even after the accumulated PM is completely burned and removed. Further, when the amount of accumulated PM is large, there is a possibility that an excessive temperature rise will occur in the DPF due to rapid combustion of PM.
Therefore, the continuation of forced regeneration after complete combustion of PM is the continuation of the post-injection period, fuel consumption deteriorates, and the amount of fuel adhering to the cylinder wall surface increases due to post-injection. Are mixed with each other, and so-called oil dilution occurs. Further, excessive temperature rise of the DPF accelerates the deterioration of the DPF, which is not preferable.

  The present invention has been made to solve such a problem, and the object of the present invention is to set the optimum forced regeneration conditions according to the amount of accumulated PM, thereby reducing fuel consumption deterioration and oil dilution. An object of the present invention is to provide an exhaust emission control device for an internal combustion engine that can prevent the deterioration of the DPF due to excessive temperature rise.

  In order to achieve the above object, in the exhaust gas purification apparatus for an internal combustion engine according to claim 1, a filter provided in an exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust, and heating the filter Compulsory regeneration means for forcibly regenerating the particulate matter deposited on the filter and forcibly regenerating the filter; outlet temperature detection means for detecting the outlet temperature of the filter; and calculating the total amount of particulate matter deposited on the filter A plurality of target accumulation temperatures, a target regeneration temperature for executing the forced regeneration, and a reference deposition amount of the particulate matter corresponding to the target regeneration temperature, and the total deposition amount is the reference deposition And the forced regeneration control means for executing the forced regeneration stepwise by increasing the temperature of the filter to the corresponding target regeneration temperature, the forced regeneration control means further comprising the outlet Based on the outlet temperature detected by the degree detecting means, and changes the next forced regeneration time reproduction condition.

Further, in the exhaust gas purification apparatus for an internal combustion engine according to claim 2, the forced regeneration control means according to claim 1, wherein the deviation between the target regeneration temperature and the outlet temperature is lower than a predetermined temperature deviation at the next forced regeneration. A predetermined amount is added to the reference accumulation amount corresponding to the target regeneration temperature.
Further, in the exhaust gas purification apparatus for an internal combustion engine according to claim 3, the forced regeneration control means according to claim 1 or 2, wherein if the deviation between the target regeneration temperature and the outlet temperature is not less than a predetermined temperature deviation, A correction amount is calculated from a deviation between the total deposition amount when the deviation reaches the predetermined temperature deviation, the reference deposition amount corresponding to the target regeneration temperature, and the total deposition amount, and the reference deposition is performed at the next forced regeneration. The correction amount is subtracted from the amount.

According to a fourth aspect of the present invention, there is provided an exhaust gas purification apparatus for an internal combustion engine according to the first aspect, wherein if the deviation between the target regeneration temperature and the outlet temperature is lower than a predetermined temperature deviation, the forced regeneration control means A first predetermined temperature is added to the target regeneration temperature.
Further, in the exhaust gas purification apparatus for an internal combustion engine according to claim 5, in the claim 1 or 4, if the deviation between the target regeneration temperature and the outlet temperature is not less than a predetermined temperature deviation, the forced regeneration control means The second predetermined temperature is subtracted from the target regeneration temperature during forced regeneration.

  According to the first aspect of the present invention, a plurality of target regeneration temperatures, which are target temperatures for executing forced regeneration, and reference deposition amounts, which are deposition amounts of particulate matter that switches the target regeneration temperature in response to the target regeneration temperatures, are set. When the total accumulation amount calculated by the total accumulation amount calculation means reaches one of a plurality of set reference accumulation amounts, the filter is heated to a target regeneration temperature corresponding to the reference accumulation amount and forced regeneration is executed. The target regeneration temperature is gradually switched to the high temperature side according to the transition of the total accumulation amount, and the regeneration condition at the next forced regeneration is changed based on the exit temperature detected by the exit temperature detecting means. I am doing so.

  As a result, the regeneration condition for the next forced regeneration can be optimized depending on the outlet temperature of the filter, and the amount of fuel used for the forced regeneration can be optimized. Can be suppressed. Further, the regeneration condition for the next forced regeneration can be optimized by the outlet temperature of the filter, and the occurrence of excessive temperature rise in the filter can be suppressed, so that the DPF can be prevented from deteriorating.

  According to the invention of claim 2, if the temperature deviation which is the deviation between the target regeneration temperature and the outlet temperature is lower than the predetermined temperature deviation, the predetermined amount is added to the reference accumulation amount corresponding to the target regeneration temperature. In the next forced regeneration, the target regeneration temperature can be switched to the higher temperature side earlier than the current regeneration with respect to the accumulation amount of the particulate matter, so that the forced regeneration period can be shortened.

Thereby, since the amount of fuel used for forced regeneration can be reduced, it is possible to suppress oil dilution while suppressing deterioration of fuel consumption.
According to the invention of claim 3, if the temperature deviation, which is the deviation between the target regeneration temperature and the outlet temperature, is not less than a predetermined temperature deviation, the temperature deviation is based on the pressure difference detected by the pressure difference detecting means. Calculate the estimated deposition amount at the time of overheating, which is the amount of particulate matter deposited when the specified temperature deviation is reached, and deposit that is the deviation between the reference deposition amount at the target regeneration temperature and the estimated deposition amount at the time of overheating. The correction amount is calculated from the amount deviation, and the correction amount is subtracted from the reference accumulation amount corresponding to the target regeneration temperature at the next forced regeneration.

  As a result, if an excessive temperature rise occurs in which the outlet temperature of the filter is higher than the target regeneration temperature by a predetermined temperature deviation, the correction amount is subtracted from the reference accumulation amount at the target regeneration temperature, and the filter accumulates on the filter during the next forced regeneration. Since the target regeneration temperature is not switched to the high temperature side until the amount of particulate matter is reduced, it is possible to prevent an excessive temperature rise of the filter from the next time and to prevent deterioration of the filter.

According to the invention of claim 4, if the temperature deviation which is the deviation between the target regeneration temperature and the outlet temperature is lower than the predetermined temperature deviation, the first predetermined temperature is added to the target regeneration temperature, and the next forced Since the forced regeneration temperature can be increased during regeneration, the particulate matter deposited on the filter can be burned in a short time, and the forced regeneration period can be shortened.
Thereby, since the amount of fuel used for forced regeneration can be reduced, it is possible to suppress oil dilution while suppressing deterioration of fuel consumption.

  According to the invention of claim 5, if the temperature deviation which is the deviation between the target regeneration temperature and the outlet temperature is equal to or greater than the predetermined temperature deviation, the second predetermined temperature is subtracted from the target regeneration temperature. Since the forced regeneration temperature can be lowered during forced regeneration, it is possible to prevent excessive temperature rise of the filter during forced regeneration and protect the filter from the next time.

1 is an overall configuration diagram of an engine to which an exhaust gas purification apparatus for an internal combustion engine according to the present invention is applied. It is a figure which shows the normal forced regeneration process of the fuel-injection control apparatus of the internal combustion engine which concerns on this invention in time series. 6 is a part of a flowchart showing a forced regeneration processing condition switching control routine according to the first embodiment of the present invention. It is the remainder of the flowchart which shows the switching control routine of the forced regeneration process condition which concerns on 1st Example of this invention. FIG. 6 is a diagram showing time-series forced regeneration processing when there is no excessive temperature rise in step B as an example in forced regeneration processing condition switching control according to the first embodiment of the present invention. FIG. 6 is a diagram showing time-sequential forced regeneration processing when there is an excessive temperature rise in step B as an example in forced regeneration processing condition switching control according to the first embodiment of the present invention. It is a figure which shows the relationship between the deposition amount deviation and correction amount which concern on 1st Example of this invention. It is a part of flowchart which shows the switching control routine of the forced regeneration process condition which concerns on 2nd Example of this invention. It is the remainder of the flowchart which shows the switching control routine of the forced regeneration process condition which concerns on 2nd Example of this invention. It is a figure which shows the forced regeneration process in case there is no excessive temperature rise in step B as an example in the forced regeneration process condition switching control which concerns on 2nd Example of this invention in time series. It is a figure which shows the forced regeneration process at the time of an excessive temperature rise in step B as an example in the forced regeneration process condition switching control which concerns on 2nd Example of this invention in time series.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an overall configuration diagram of an engine (internal combustion engine) 1 to which an exhaust gas purification apparatus for an internal combustion engine according to the present invention is applied. FIG. 2 shows a normal forced regeneration process in time series. 2 shows the change in the PM accumulation amount and the reference accumulation amount of the target regeneration temperature, the lower part shows the change in the target regeneration temperature at each reference accumulation amount, and steps A, B, and C have a constant target regeneration temperature. This shows the range of forced regeneration processing.

  The engine 1 is, for example, a common rail type in-line multi-cylinder diesel engine. The cylinder head 2 of the engine 1 is provided with an electromagnetic fuel injection nozzle 4 for each cylinder facing the combustion chamber 3. Each fuel injection nozzle 4 is connected to a common rail 6 by a high-pressure pipe 5, and the common rail 6 is connected to a high-pressure pump 8 via a high-pressure pipe 7. The high-pressure pump 8 has a function of supplying the fuel (light oil) stored in the fuel tank 9 to the common rail 6. The fuel supplied to the common rail 6 is stored in a high-pressure state and burns from each fuel injection nozzle 4. It is injected into the chamber 3.

The cylinder head 2 is formed with an intake port 10 and an exhaust port 11 communicating with the combustion chamber 3 for each cylinder. An intake pipe 12 is connected to the intake port 10 and an exhaust pipe 13 is connected to the exhaust port 11. ing. The cylinder head 2 is provided with an intake valve 14 that opens and closes the intake port 10 and an exhaust valve 15 that opens and closes the exhaust port 11.
The intake pipe 12 is provided with an electromagnetic intake throttle valve 16 that adjusts the amount of intake air, and an airflow sensor 17 that detects the intake flow rate upstream thereof.

Between the exhaust pipe 13 and the intake pipe 12, an EGR pipe 18 provided with an EGR valve 19 which is an electromagnetic on-off valve is provided. One end of the EGR pipe 18 is connected to the exhaust pipe 13 in the vicinity of the exhaust port 11, and the other end is connected to the intake pipe 12 in the vicinity of the intake port 10, and the exhaust pipe 13 and the intake pipe 12 are communicated.
A diesel oxidation catalyst (hereinafter referred to as DOC) 20 and a DPF (filter) 21 are provided in the exhaust pipe 13 in order from the upstream side. The DOC 20 is formed, for example, by accommodating a first oxidation catalyst 22 and a second oxidation catalyst 23 in a cylindrical case. The first oxidation catalyst 22 is provided on the exhaust upstream side, and the second oxidation catalyst 23 is provided downstream from the first oxidation catalyst 22. The first oxidation catalyst 22 and the second oxidation catalyst 23 are formed by supporting a catalyst noble metal such as platinum (Pt), palladium (Pd), rhodium (Rh) on a porous wall forming a passage. In addition to oxidizing the CO and HC in the exhaust gas to convert them into CO ₂ and H ₂ O, it has the function of oxidizing NO in the exhaust gas to generate NO ₂ .

The DPF 21, for example, has a function of alternately closing the upstream side and the downstream side of the honeycomb carrier passage with plugs to collect PM in the exhaust, and further, on the porous wall forming the passage. It is formed by supporting a catalytic noble metal such as platinum (Pt), palladium (Pd), rhodium (Rh).
An exhaust temperature sensor 24 that detects the exhaust temperature immediately after passing through the first oxidation catalyst 22 is provided between the first oxidation catalyst 22 and the second oxidation catalyst 23. An exhaust gas temperature sensor (exit temperature detector) 25 that detects the exhaust gas temperature immediately after passing through the DPF 21 is provided on the downstream side of the DPF 21. Further, a differential pressure sensor (pressure difference detection means) 26 for detecting the differential pressure between the upstream side and the downstream side of the DPF 21 is provided.

An electronic control unit (hereinafter referred to as ECU, total accumulation amount calculation means, forced regeneration control means) 30 is a control device for performing comprehensive control including operation control of the engine 1, and includes an input / output device and a storage device (ROM, RAM, nonvolatile RAM, etc.), a central processing unit (CPU) and the like are included.
On the input side of the ECU 30, in addition to the air flow sensor 17, the exhaust temperature sensors 24 and 25, and the differential pressure sensor 26 described above, a crank angle sensor 31 that detects the crank angle of the engine 1 and an accelerator that detects the amount of depression of the accelerator pedal. A position sensor 32 and a vehicle speed sensor 33 for detecting the vehicle speed are connected, and detection information from these sensors is input.

  On the other hand, various output devices such as the fuel injection nozzle 4, the intake throttle valve 16 and the EGR valve 19 are connected to the output side of the ECU 30, and these various output devices are connected to the ECU 30 based on detection information from various sensors. The calculated fuel injection amount, fuel injection timing, EGR amount, and the like are output, and thereby the intake throttle valve 16, the fuel injection nozzle 4, the EGR valve 19, and the like are controlled at an appropriate timing.

Further, when the DOC 20 is arranged upstream of the DPF 21 as described above, during normal engine operation, NO ₂ generated in the DOC 20 flows into the DPF 21 and is collected and accumulated in the DPF 21. It reacts with the ingredient soot to oxidize it. Oxidized soot becomes CO _{2 and} is removed from the DPF 21, thereby performing continuous regeneration in which the DPF 21 is continuously regenerated.

  On the other hand, depending on the operating condition of the engine 1, the DPF 21 may not be sufficiently regenerated only by the continuous regeneration. Therefore, as shown in FIG. 2, the ECU 30 calculates the total accumulation amount as the PM accumulation amount in the DPF 21 from the differential pressure detected by the differential pressure sensor 26. The calculated total accumulation amount is set in advance in an experiment, taking into account variations in the engine 1, variations in the operation pattern, and the like, and the accumulation amount serving as a timing for switching a plurality of (three in this embodiment) target regeneration temperatures. Is the reference regeneration amount (corresponding to (i), (ii), (iii), (iv) in FIG. 2)), the target regeneration temperature (which is the target value of the forced regeneration temperature corresponding to the reference deposition amount) The forced regeneration temperature is increased so as to satisfy T1, T2, and T3 in FIG. The forced regeneration is performed by forcibly burning and removing PM by raising the forced regeneration temperature stepwise according to the total deposition amount.

  In the forced regeneration, post-injection (sub-injection) of fuel is performed so that the forced regeneration temperature is reached after, for example, the expansion stroke after the main injection of fuel during operation of the engine 1, and unburned fuel (HC, CO, etc.) Exhaust gas containing the gas is exhausted to the exhaust pipe 13. The unburned fuel mixed in the exhaust flows into the DOC 20 and is oxidized, and the exhaust temperature is increased by the reaction heat of oxidation. As a result, the high-temperature exhaust gas flows into the DPF 21 on the exhaust downstream side, and the PM deposited on the DPF 21 can be heated and burned to forcibly regenerate the DPF 21 (forced regeneration means).

By the way, considering the variation of the engine 1 and the variation of the operation pattern in the setting values set in advance through experiments or the like, the reference accumulation is performed so that the forced regeneration temperature and regeneration time are such that excessive temperature rise does not occur in the DPF 21. The amount is set. As described above, since the reference accumulation amount takes into account various variations, the forced regeneration temperature is set low so that excessive temperature rise does not occur, and the regeneration time is long so that the PM deposited on the DPF 21 can be completely removed. It is set and there is a problem that fuel consumption deteriorates.
[First embodiment]
Therefore, in the exhaust gas purification apparatus for an internal combustion engine according to the first embodiment of the present invention, forced regeneration is performed while solving such problems, and hereinafter, forced regeneration according to the first embodiment of the present invention. Processing condition switching control will be described.

  FIG. 3 shows a part of a flowchart showing a forced regeneration processing condition switching control routine according to the first embodiment of the present invention, and FIG. 4 shows the rest of the flowchart showing the forced regeneration processing condition switching control routine. Yes. FIG. 5 shows, as an example, forced regeneration processing when there is no excessive temperature rise in time series, and FIG. 6 shows, as an example, forced regeneration processing when there is an excessive temperature rise, in time series. 5 and 6 show the change in the PM deposition amount and the reference deposition amount of the target regeneration temperature, the lower row shows the change in the target regeneration temperature at each reference deposition amount, and steps A, B, and C represent the target regeneration. The range of the forced regeneration process where temperature is constant is shown. The upper solid line indicates the PM deposition amount before correction, the two-dot chain line indicates the corrected PM deposition amount, the lower solid line indicates the target regeneration temperature, the broken line indicates the actual regeneration temperature, and the alternate long and short dash line indicates the corrected target regeneration temperature. ing. FIG. 7 shows the relationship between the accumulation amount deviation and the correction amount.

  As shown in FIGS. 3 and 4, first, in step S10, a reference deposition amount in which the total deposition amount, which is the PM deposition amount in the DPF 21, is set in advance by experiments or the like based on the differential pressure detected by the differential pressure sensor 26. It is determined whether or not the value is a or more. If the determination result is true (Yes) and the total deposition amount is greater than or equal to the reference deposition amount a, the process proceeds to step S12. If the determination result is false (No) and the total deposition amount is less than the reference deposition amount a, the process returns to step S10. Process.

In step S12, the forced regeneration process in step A shown in FIG. 5 or 6 is started at the target regeneration temperature T1 (corresponding to (i) in FIGS. 5 and 6). Then, the process proceeds to step S14.
In step S14, it is determined from the differential pressure detected by the differential pressure sensor 26 whether or not the total deposition amount, which is the PM deposition amount in the DPF 21, has become equal to or less than a reference deposition amount b set in advance through experiments or the like. If the determination result is true (Yes) and the total accumulation amount is equal to or less than the reference accumulation amount b, the process proceeds to step S16. If the determination result is false (No) and the total accumulation amount is not equal to or less than the reference accumulation amount b. Then, the process of step S14 is performed again.

In step S16, the forced regeneration process in step B shown in FIG. 5 or 6 is started at the target regeneration temperature T2 (corresponding to (ii) in FIGS. 5 and 6). Then, the process proceeds to step S18.
In step S18, the target regeneration temperature T2 of the current forced regeneration process step (in this case, step B) is subtracted from the actual regeneration temperature Tx, which is the temperature detected by the exhaust temperature sensor 25, to calculate a temperature deviation ΔT. Then, the process proceeds to step S20.

  In step S20, it is determined whether or not the temperature deviation ΔT calculated in step S18 is greater than or equal to a predetermined temperature deviation set in advance through experiments or the like. If the determination result is true (Yes) and the temperature deviation ΔT is equal to or greater than the predetermined temperature deviation, it is determined that the DPF 21 has overheated, the process proceeds to step S22, the determination result is false (No), and the temperature deviation ΔT is the predetermined temperature deviation. If it is smaller, the process proceeds to step S34.

In step S22, the overheated total deposition amount Dx, which is the amount of PM accumulated in the DPF 21 at the time when the temperature deviation ΔT is equal to or greater than the predetermined temperature deviation, that is, when the overheated temperature is generated in the DPF 21 is calculated (FIG. 6). (Applicable to (v)). Then, the process proceeds to step S24.
In step S24, the accumulation amount deviation ΔD is calculated by subtracting the total accumulation amount Dx at the time of overheating calculated in step S22 from the reference accumulation amount b in the current forced regeneration process step (here, step B). Then, the process proceeds to step S26.

In step S26, the correction amount x is calculated from the relationship diagram between the accumulation amount deviation and the correction amount in FIG. 7 and the accumulation amount deviation ΔD calculated in step S24. Then, the process proceeds to step S28.
In step S28, the corrected reference accumulation amount b "is calculated by subtracting the correction amount x calculated in step S26 from the reference accumulation amount b of the current forced regeneration processing step (here, step B). Proceed to S30.

In step S30, in the next forced regeneration, the reference accumulation amount for switching the target regeneration temperature in the same step (here, step B) as the current step is set as the corrected reference accumulation amount b ″ calculated in step S28, and step A is changed to step A ″. The forced regeneration time is extended (corresponding to FIG. 6 (ii ")), and the process proceeds to step S32.
In step S32, the forced regeneration process is terminated (corresponding to (iv) in FIGS. 5 and 6), and the process exits from the routine.

Next, in step S34, a corrected reference deposition amount b ′ is calculated by adding a predetermined amount set in advance through experiments or the like to the reference deposition amount b in the current forced regeneration processing step (here, step B). . Then, the process proceeds to step S36.
In step S36, the reference regeneration amount B ′ calculated in step S34 is set as the reference accumulation amount for switching the target regeneration temperature in the same step (here, step B) as the current step at the next forced regeneration, and the forced regeneration processing step A is performed. In step A ′, the forced regeneration time is shortened (corresponding to FIG. 5 (ii ′)). Then, the process proceeds to step S38.

  In step S38, it is determined from the differential pressure detected by the differential pressure sensor 27 whether or not the total accumulation amount, which is the PM accumulation amount in the DPF 21, has become equal to or less than a reference accumulation amount c set in advance through experiments or the like. If the determination result is true (Yes) and the total accumulation amount is equal to or less than the reference accumulation amount c, the process proceeds to step S40. If the determination result is false (No) and the total accumulation amount is not equal to or less than the reference accumulation amount c. Return to step S18.

In step S40, the forced regeneration process in step C shown in FIG. 5 or 6 is started at the target regeneration temperature T3 (corresponding to (iii) in FIGS. 5 and 6). Then, the process proceeds to step S42.
In step S42, the target regeneration temperature T3 of the current forced regeneration process step (here, step C) is subtracted from the actual regeneration temperature Tx, which is the temperature detected by the exhaust temperature sensor 25, to calculate a temperature deviation ΔT. Then, the process proceeds to step S44.

  In step S44, it is determined whether or not the temperature deviation ΔT calculated in step S42 is greater than or equal to a predetermined temperature deviation set in advance through experiments or the like. If the determination result is true (Yes) and the temperature deviation ΔT is equal to or greater than the predetermined temperature deviation, it is determined that the DPF 21 has overheated, the process proceeds to step S46, the determination result is false (No), and the temperature deviation ΔT is the predetermined temperature deviation. If it is smaller, the process proceeds to step S56.

In step S46, the total temperature deposit amount Dx at the time of overheating, which is the amount of PM accumulated in the DPF 21 at the time when the temperature deviation ΔT is equal to or greater than the predetermined temperature deviation, that is, when the overheating temperature is generated in the DPF 21 is calculated. Then, the process proceeds to step S48.
In step S48, the accumulation amount deviation ΔD is calculated by subtracting the total accumulation amount Dx at the time of overheating calculated in step S46 from the reference accumulation amount c in the current forced regeneration process step (here, step C). Then, the process proceeds to step S50.

In step S50, the correction amount x is calculated from the relationship diagram between the accumulation amount deviation and the correction amount in FIG. 7 and the accumulation amount deviation ΔD calculated in step S48. Then, the process proceeds to step S52.
In step S52, the corrected reference accumulation amount c ″ is calculated by subtracting the correction amount x calculated in step S50 from the reference accumulation amount c in the current forced regeneration processing step (here, step C). Proceed to S54.

In step S54, the reference accumulation amount for switching the target regeneration temperature in the same step (here, step c) as the current step at the next forced regeneration is set as the corrected reference deposition amount c ″ calculated in step S52, and the forced regeneration time in step B Then, the process returns to step S32.
Next, in step S56, a corrected reference deposition amount c ′ is calculated by adding a predetermined amount set in advance through experiments or the like to the reference deposition amount c in the current forced regeneration processing step (here, step C). . Then, the process proceeds to step S58.

In step S58, the reference accumulation amount for switching the target regeneration temperature in the same step (in this case, step C) as the current step at the next forced regeneration is set to the corrected reference deposition amount c ′ calculated in step S56. Reduce forced regeneration time. Then, the process proceeds to step S60.
In step S60, it is determined from the differential pressure detected by the differential pressure sensor 26 whether or not the total accumulation amount, which is the PM accumulation amount in the DPF 21, has become equal to or less than a reference accumulation amount d set in advance through experiments or the like. If the determination result is true (Yes) and the total accumulation amount is equal to or less than the reference accumulation amount d, the process returns to step S32, and if the determination result is false (No) and the total accumulation amount is not equal to or less than the reference accumulation amount d. Return to step S42.

  Thus, according to the exhaust gas purification apparatus for an internal combustion engine according to the first embodiment of the present invention, the temperature deviation ΔT calculated by subtracting the target regeneration temperature from the actual regeneration temperature Tx during the forced regeneration process is equal to or greater than a predetermined temperature deviation. In this case, assuming that an excessive temperature rise has occurred in the DPF 21, at the next forced regeneration, the start of the step where the excessive temperature rise has occurred is delayed to extend the forced regeneration time. Further, when the temperature deviation ΔT is smaller than the predetermined temperature deviation, it is assumed that no excessive temperature rise has occurred and the start of the step where the excessive temperature rise has not occurred at the next forced regeneration is shortened to shorten the forced regeneration time. The forced regeneration conditions are switched to perform forced regeneration with the optimum processing time.

Therefore, every time the forced regeneration is executed, the forced regeneration process can be performed with the optimum processing time, and the amount of fuel used for the forced regeneration can be optimized. Can be suppressed.
Further, in this embodiment, the forced regeneration time is corrected based on the temperature deviation ΔT between the actual regeneration temperature Tx and the target regeneration temperature at the previous forced regeneration, so that excessive temperature rise does not occur in the DPF 21 in advance. It is possible to set the playback conditions. In addition, the target regeneration temperature is switched so as to increase gradually from a low value. If the temperature rises excessively during regeneration, forced regeneration is terminated without proceeding to the next step. Even if an excessive temperature rise occurs, it is possible to reliably protect the DPF 21 and to prevent the DPF 21 from being deteriorated due to the excessive temperature rise.
[Second Embodiment]
Next, the contents of switching control of forced regeneration processing conditions according to the second embodiment of the present invention will be described.

  FIG. 8 shows a part of a flowchart showing a forced regeneration processing condition switching control routine according to the second embodiment of the present invention, and FIG. 9 shows the rest of the flowchart showing the forced regeneration processing condition switching control routine. Yes. FIG. 10 shows, as an example, forced regeneration processing when there is no excessive temperature rise in time series, and FIG. 11 shows, as an example, forced regeneration processing when there is an excessive temperature rise, in time series. 10 and 11 show the change in the PM accumulation amount and the reference accumulation amount of the target regeneration temperature, the lower part shows the change in the target regeneration temperature at each reference accumulation amount, and steps A, B, and C represent the target regeneration. The range of the forced regeneration process where temperature is constant is shown. The upper solid line indicates the PM deposition amount before correction, the two-dot chain line indicates the corrected PM deposition amount, the lower solid line indicates the target regeneration temperature, the broken line indicates the actual regeneration temperature, and the alternate long and short dash line indicates the corrected target regeneration temperature. ing.

In the second embodiment, the forced regeneration condition is changed from the correction of the reference accumulation amount to the correction of the target regeneration temperature with respect to the first embodiment, and the difference from the first embodiment will be described below. To do.
As shown in FIGS. 8 and 9, in steps S10 to S20, forcible regeneration is started (step A) from the total amount of PM accumulated in the DPF 21 as in the first embodiment, and the total amount of accumulation is the reference. When the accumulation amount b is reached, the target regeneration temperature is set to T2 (step B). Further, the target regeneration temperature T2 is subtracted from the actual regeneration temperature Tx that is the temperature detected by the exhaust temperature sensor 25 to calculate the temperature deviation ΔT. It is determined whether or not the temperature deviation ΔT is equal to or greater than a predetermined temperature deviation set in advance through experiments or the like. If the determination result is true and the temperature deviation ΔT is equal to or greater than the predetermined temperature deviation, the DPF 21 overheats. If the determination result is false (No) and the temperature deviation ΔT is smaller than the predetermined temperature deviation, the process proceeds to step S34 ′.

In step S22 ′, a corrected target regeneration temperature T2 ″ is calculated by subtracting the second predetermined temperature from the target regeneration temperature T2 of the current forced regeneration processing step (here, step B). Then, the process proceeds to step S30 ′. move on.
In step S30 ′, at the next forced regeneration, the target regeneration temperature of the same step (here, step B) as the current step is set to the corrected target regeneration temperature T2 ″ calculated in step S22 ′, and step B is forced to be step B ″. The regeneration temperature is lowered (corresponding to FIGS. 11 (ii) to (iii ")), and the process proceeds to step S32.

Next, in step S34 ′, a corrected target regeneration temperature T2 ′ is calculated by adding the first predetermined temperature to the target regeneration temperature T2 in the current forced regeneration process step (here, step B). Then, the process proceeds to step S36 ′.
In step S36 ′, the target regeneration temperature of the same step (here, step B) as the current step at the next forced regeneration is set to the corrected target regeneration temperature T2 ′ calculated in step S34 ′ and step B is forced to be step B ′. The regeneration temperature is increased (corresponding to FIGS. 10 (ii) to (iii ′)). Then, the process proceeds to step S38.

  From step S38 to S44, as in the first embodiment, the target regeneration temperature is set to T3 when the total accumulation amount of PM accumulated in the DPF 21 becomes the reference accumulation amount c (step C). In addition, the temperature deviation ΔT is calculated by subtracting the target regeneration temperature T3 from the actual regeneration temperature Tx that is the temperature detected by the exhaust temperature sensor 25. It is determined whether or not the temperature deviation ΔT is equal to or greater than a predetermined temperature deviation set in advance through experiments or the like. If the determination result is true and the temperature deviation ΔT is equal to or greater than the predetermined temperature deviation, the DPF 21 overheats. If the determination result is false (No) and the temperature deviation ΔT is smaller than the predetermined temperature deviation, the process proceeds to step S56 ′.

In step S46 ′, a corrected target regeneration temperature T3 ″ is calculated by subtracting the second predetermined temperature from the target regeneration temperature T3 in the current forced regeneration processing step (here, step C). Then, the process proceeds to step S54 ′. move on.
In step S54 ′, the forced regeneration temperature is lowered by setting the target regeneration temperature of the same step (here, step C) as the current step at the next forced regeneration to the corrected target regeneration temperature T3 ″ calculated in step S46 ′. The process proceeds to step S32.

Next, in step S56 ′, a corrected target regeneration temperature T3 ′ is calculated by adding the first predetermined temperature to the target regeneration temperature T3 of the current forced regeneration process step (here, step C). Then, the process proceeds to step S58 ′.
In step S58 ′, the forced regeneration temperature is raised as the corrected target regeneration temperature T3 ′ calculated in step S56 ′ as the target regeneration temperature in the same step (here, step C) as the current step at the next forced regeneration. Then, the process proceeds to step S60.

  As described above, according to the exhaust gas purification apparatus for an internal combustion engine according to the second embodiment of the present invention, the temperature deviation ΔT is obtained by subtracting the target regeneration temperature from the actual regeneration temperature Tx that is the temperature detected by the exhaust temperature sensor 25. Is calculated. If the temperature deviation ΔT is equal to or greater than the predetermined temperature deviation, the second predetermined temperature is subtracted from the target regeneration temperature and the corrected target regeneration temperature is calculated by assuming that the temperature is excessively high. If it is lower, the corrected target regeneration temperature is calculated by adding the first predetermined temperature to the target regeneration temperature, and the forced regeneration is performed with the target regeneration temperature as the corrected target regeneration temperature at the next forced regeneration.

  Therefore, when the excessive temperature rise has not occurred, the regeneration temperature is increased and the PM accumulated in the DPF 21 is burned in a short time to shorten the forced regeneration processing time. Since the regeneration temperature is lowered to prevent excessive temperature rise, forced regeneration processing can be performed in an optimal processing time, and the amount of fuel used for forced regeneration can be optimized. As in the first embodiment, oil dilution can be suppressed while suppressing deterioration of fuel consumption.

  Similarly to the first embodiment, in this embodiment, since the forced regeneration time is corrected based on the temperature deviation ΔT between the actual regeneration temperature Tx and the target regeneration temperature at the previous forced regeneration, the DPF 21 uses the DPF 21 in advance. It is possible to set the regeneration condition so that the excessive temperature rise does not occur. In addition, the target regeneration temperature is switched so as to increase gradually from a low value. If the temperature rises excessively during regeneration, forced regeneration is terminated without proceeding to the next step. Even if an excessive temperature rise occurs, it is possible to reliably protect the DPF 21 and to prevent the DPF 21 from being deteriorated due to the excessive temperature rise.

Although the description of the embodiment of the invention is finished as above, the embodiment of the present invention is not limited to the above embodiment.
In the first embodiment, the total accumulation amount, which is the accumulation amount of PM in the DPF 21, is calculated from the differential pressure detected by the differential pressure sensor 26. However, the present invention is not limited to this. The accumulated PM amount may be known with a certain degree of accuracy, and the total accumulated PM amount may be estimated from the elapsed time or travel distance from the previous regeneration process or the integration of the exhaust flow rate passing through the DPF 21.

  Further, independently of the correction of the reference deposition amounts b and c in the first embodiment or the correction of the target regeneration temperatures T2 and T3 in the second embodiment, the regeneration interval which is the forced regeneration interval is further corrected. May be. Specifically, when an excessive temperature rise occurs in the DPF 21 during the regeneration period (steps A to C), the reference accumulation amount a at the next regeneration is reduced as the maximum temperature of the actual regeneration temperature Tx increases at this time. Correct to By correcting the reference accumulation amount a in this way, the regeneration interval is changed, and the amount of PM accumulation at the start of the next regeneration can be suppressed to prevent overheating more reliably.

1 engine (internal combustion engine)
4 Fuel injection nozzle 20 DOC
21 DPF (filter)
24 Exhaust temperature sensor 25 Exhaust temperature sensor (exit temperature detection means)
26 Differential pressure sensor (pressure difference detection means)
30 ECU (total accumulation calculation means, forced regeneration control means)

Claims (5)

A filter provided in an exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust;
Forcibly regenerating means for forcibly regenerating the filter by heating the filter to burn particulate matter deposited on the filter;
Outlet temperature detecting means for detecting the outlet temperature of the filter;
A total deposition amount calculating means for calculating a total deposition amount of the particulate matter deposited on the filter;
When a plurality of target regeneration temperatures at the time of executing the forced regeneration and a reference deposition amount of the particulate matter corresponding to the target regeneration temperature are set, and the total deposition amount reaches one of the reference deposition amounts, A forced regeneration control means for increasing the temperature of the filter to the corresponding target regeneration temperature and executing forced regeneration stepwise;
The exhaust purification device of an internal combustion engine, wherein the forced regeneration control means further changes a regeneration condition at the next forced regeneration based on the outlet temperature detected by the outlet temperature detecting means.   If the deviation between the target regeneration temperature and the outlet temperature is lower than a predetermined temperature deviation, the forced regeneration control means adds a predetermined amount to the reference accumulation amount corresponding to the target regeneration temperature at the next forced regeneration. The exhaust emission control device for an internal combustion engine according to claim 1, characterized in that it is characterized in that:   If the deviation between the target regeneration temperature and the outlet temperature is equal to or greater than a predetermined temperature deviation, the forced regeneration control means sets the total accumulation amount and the target regeneration temperature when the temperature deviation becomes the predetermined temperature deviation. The correction amount is calculated from a deviation between the corresponding reference deposition amount and the total deposition amount, and the correction amount is subtracted from the reference deposition amount at the next forced regeneration. Exhaust gas purification device for internal combustion engine.   If the deviation between the target regeneration temperature and the outlet temperature is lower than a predetermined temperature deviation, the forced regeneration control means adds a first predetermined temperature to the target regeneration temperature at the next forced regeneration. The exhaust emission control device for an internal combustion engine according to claim 1.   The forced regeneration control means subtracts a second predetermined temperature from the target regeneration temperature at the next forced regeneration when the deviation between the target regeneration temperature and the outlet temperature is a predetermined temperature deviation or more. 5. An exhaust emission control device for an internal combustion engine according to claim 1 or 4.

Images