JP3456429B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification device for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, there is known an internal combustion engine in which a particulate filter for collecting particulates in exhaust gas is arranged in an engine exhaust passage. However, as the engine operating time increases, the amount of particulates collected by the particulate filter increases and the engine back pressure increases, so the particulates collected by the particulate filter before the engine back pressure becomes higher than the maximum allowable pressure. It is necessary to remove the curate, that is, regenerate the particulate filter.

Therefore, a burner is arranged in the engine exhaust passage upstream of the particulate filter, and the hot exhaust gas of this burner is introduced into the particulate filter to burn and remove the particulate, thereby regenerating the particulate filter. An exhaust gas purification device for an internal combustion engine is known (see Japanese Patent Laid-Open No. 60-47937). Increasing the temperature of the exhaust gas flowing into the particulate filter in this way is one of the methods for regenerating the particulate filter, and various methods have been proposed in the past to increase the temperature of the exhaust gas flowing into the particulate filter. ing. That is, in addition to using the burner, for example, there is a method of delaying the main fuel injection timing in a diesel engine, a method of increasing the EGR gas amount more than in normal operation, and the like.

[0004]

For example, when a burner is used, fuel is required for the burner even when the temperature of the exhaust gas flowing into the particulate filter is relatively high.
Even when the temperature of the exhaust gas flowing into the particulate filter is relatively low, it is possible to reliably raise the temperature of the particulate filter to the temperature required for regeneration. on the other hand,
With the method of delaying the main fuel injection timing, the particulate filter cannot be heated to the required temperature when the temperature of the exhaust gas flowing into the particulate filter is low, but the fuel consumption rate does not increase so much. Therefore, for example, both a regeneration method using a burner and a regeneration method using the main fuel injection timing retard control are provided, and when the temperature of the exhaust gas flowing into the particulate filter is low, the particulate filter is regenerated by the regeneration method using a burner. When the temperature of the exhaust gas flowing into the particulate filter is high, if the regeneration method is performed by the main fuel injection timing retard control, it is possible to reliably regenerate the particulate filter while reducing the fuel consumption rate.

In other words, if a plurality of regeneration methods are provided and these regeneration methods are selectively used, it is possible to reliably regenerate the particulate filter while maintaining high energy efficiency. The above publication does not disclose any such technical idea.

[0006]

According to a first aspect of the present invention for solving the above problems, an exhaust gas of an internal combustion engine in which a particulate filter for collecting particulates in exhaust gas is arranged in an engine exhaust passage. In the purifying device, a plurality of regenerating means for regenerating the particulate filter are provided, the engine operating state region is divided into a plurality of regions, and each region is
Different regeneration means are set for
The region to which the engine operating state belongs most frequently
Region, the determined region and the determined region
Energy efficiency is better than the regeneration means set for the
Select the area where a high playback method is set and
The engine operating condition is
Particulate when not belonging to the selected area
The regeneration action of the filter is prohibited, and then the engine operating condition is
When operating in the selected area, the engine operating state
The particulate filter is regenerated by the regenerating means set for the area . That is, in the first aspect, the engine operating state is based on the engine operating state history.
The area to which the most frequently belongs is determined, and the determined area
The playback area set for the determined area.
Select the area where the playback method with high energy efficiency is set.
Selected and when the particulate filter should be regenerated
When the engine operating condition does not belong to this selected area
The regeneration function of the particulate filter is prohibited and
When the engine operating state shifts to this selected area in
Is set for the area to which the engine operating state belongs.
The stage regenerates the particulate filter. Therefore, it becomes possible to always use the regenerating means necessary for surely regenerating the particulate filter while maintaining high energy efficiency.

[0007]

Further, in the first aspect according to the second aspect, and natural reproduction means for said reproducing means to reproduce naturally particulate filter, a plurality of forced regeneration means for forcibly reproduce the particulate filter The forced regeneration means are different from each other in energy efficiency and temperature rising performance. That is, in the second invention, it is possible energy efficiency and heated performance select the playback means so as to optimally maintain.

[0009]

Further, in the first aspect according to the third invention for solving the above problems, the particulate amount seeking particulate amount trapped in the particulate filter becomes more than a set amount When it does, it judges that the particulate filter should be regenerated. That is, in the third invention, when the particulate amount does not belong to the region the engine operating state is selected even if more than a set amount is prohibited regenerative action of the particulate filter, then the engine operating condition selected areas Belongs to, the particulate filter is reproduced by the reproducing means set for this selected area.

Further, in the first aspect according to the fourth aspect, so that changing the set amount in response to the selected area. That is, in the fourth aspect, it is changed according to the area or reproducing means timing is selected to perform the regeneration of the particulate filter. Further, according to the fifth invention to solve the above problems, in the exhaust purification system of an internal combustion engine arranged particulate filter in the engine exhaust passage for collecting particulates in exhaust particulate filter For retarding the main fuel injection timing in order to regenerate the main fuel injection timing in comparison with the normal operation, and for regenerating the particulate filter, secondary fuel injection is performed in the engine expansion stroke or the exhaust stroke and the EGR gas amount is changed. A secondary injection EGR regenerating unit that increases more than in normal operation is provided, and when the engine load is higher than a preset load when the particulate filter is to be regenerated, the retard angle regenerating unit regenerates the particulate filter. 2 when the engine load is lower than the set load when the particulate filter should be regenerated.
The particulate filter is regenerated by the next injection EGR regeneration means. That is, the retard regeneration means has relatively high energy efficiency but relatively low temperature raising performance, while the secondary injection EGR regeneration means has relatively low energy efficiency but relatively high temperature raising performance. Therefore, in the fifth aspect , the retard regeneration means is used when the engine load is relatively high and the temperature of the exhaust gas flowing into the particulate filter is high, and when the engine load is relatively low and the temperature of the exhaust gas flowing into the particulate filter is low. The secondary injection EGR regeneration means is used.

[0012] According to a sixth aspect of the invention in order to solve the above problems, in the exhaust purification system of an internal combustion engine arranged particulate filter in the engine exhaust passage for collecting particulates in exhaust, Exhaust flow rate control means capable of controlling the exhaust flow rate flowing into the particulate filter is provided, and secondary fuel injection is performed in the engine expansion stroke or exhaust stroke to regenerate the particulate filter, and the EGR gas amount is set to be lower than that in normal operation. Secondary injection EGR regeneration means that also increases the amount of secondary injection, and secondary fuel injection is performed in the engine expansion stroke or exhaust stroke to regenerate the particulate filter, and the exhaust flow rate flowing into the particulate filter is reduced from that during normal operation. When the particulate filter is to be regenerated, the engine is equipped with a secondary injection exhaust flow rate regeneration means. When the load is higher than the preset load, the secondary injection EGR regeneration means regenerates the particulate filter, and when the particulate filter is to be regenerated, when the engine load is lower than the preset load, the secondary injection exhaust gas flow rate regeneration The particulate filter is regenerated by the means. That is, the secondary injection EGR regeneration means has relatively high energy efficiency but relatively low temperature raising performance, and the secondary injection exhaust gas flow rate regeneration means has relatively low energy efficiency but relatively high temperature raising performance.
Therefore, in the sixth aspect of the invention, when the engine load is relatively high and the temperature of the exhaust gas that flows into the particulate filter is relatively high, the secondary injection EGR regeneration means is used, and the exhaust gas that flows into the particulate filter when the engine load is relatively low is used. When the temperature is relatively low, the secondary injection exhaust flow rate regeneration means is used.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a case where the present invention is applied to a diesel engine. However, the present invention can also be applied to a spark ignition type engine. Referring to FIG. 1, the engine body 1 has, for example, four cylinders # 1, # 2, # 3.
Equipped with # 4. Each cylinder is connected to a surge tank 3 via a corresponding intake branch pipe 2, and the surge tank 3 is connected via an intake duct 4 and an intercooler 5 to a supercharger, for example, an outlet portion of a compressor 6c of an exhaust turbocharger 6. To be done. The inlet of the compressor 6c is connected to the air cleaner 8 via the air suction pipe 7. Inside the intake duct 4 between the surge tank 3 and the intercooler 5, a throttle valve 10 driven by an actuator 9 is arranged. Each cylinder is equipped with a fuel injection valve 11 that directly injects fuel into the combustion chamber. Each fuel injection valve 11 is connected via a common fuel pressure accumulating chamber 12 to a fuel pump 13 whose discharge amount can be controlled. The discharge amount of the fuel pump 13 is controlled so that the fuel pressure in the fuel pressure accumulating chamber 12 becomes the target fuel pressure.

On the other hand, a branch portion 15 of the exhaust manifold 14 is connected to each cylinder, and a particulate filter 16 is housed in each branch portion 15. The collecting portion of the exhaust manifold 14 is connected to the inlet portion of the exhaust turbine 6t of the exhaust turbocharger 6, and the exhaust turbine 6t
The outlet part of is connected to a casing 20 containing the NOx absorbent 19 via an exhaust pipe 18, and the casing 20 is connected to an exhaust pipe 21. Also, the exhaust turbine 6t and NOx
In the exhaust pipe 18 between the absorbents 19, a reducing agent supply valve 22 for injecting the reducing agent toward the exhaust gas upstream in order to supply the reducing agent to the NOx absorbent 19 is provided with the NOx absorbent 19.
Is located adjacent to. The reducing agent supply valve 22 is connected to the fuel pressure accumulating chamber 12, and therefore the fuel (HC) of the engine is used as the reducing agent in this embodiment. As the reducing agent, for example, gasoline, isooctane, hexane, heptane, light oil, kerosene, butane, hydrocarbon such as propane, hydrogen, ammonia, urea and the like can be used.

Further, the exhaust manifold 14 downstream of the particulate filter 16 and the intake duct 4 downstream of the throttle valve 10 are connected to an exhaust gas recirculation (hereinafter referred to as EGR) passage 2.
An EGR control valve 25, which is connected to each other via 3 and is driven by an actuator 24, is arranged in the EGR passage 23. In this way, E is provided upstream of the reducing agent supply valve 22.
When the GR passage 23 is provided, the secondary fuel supplied from the reducing agent supply valve 22 is prevented from being returned to the engine intake passage together with the EGR gas.

Further, an actuator 25 is provided in the exhaust pipe 18 located between the exhaust turbine 6t and the reducing agent supply valve 22.
An exhaust throttle valve 26 driven by is arranged. The exhaust throttle valve 26 is normally kept fully open. The electronic control unit (ECU) 30 is composed of a digital computer, and ROMs connected to each other via a bidirectional bus 31.
(Read-only memory) 32, RAM (random access memory) 33, CPU (microprocessor) 34,
B-RAM (Backup R
AM) 35, an input port 36, and an output port 37. A mass flow sensor 38 for detecting the mass flow rate of intake air is arranged in the air suction pipe 7. A fuel pressure sensor 39 that generates an output voltage proportional to the fuel pressure in the fuel pressure accumulating chamber 12 is arranged in the fuel pressure accumulating chamber 12. The particulate filter 1 is provided at the branch portion 15 of the exhaust manifold 14 located upstream of the particulate filter 16.
A temperature sensor 40a that generates an output voltage proportional to the temperature of the exhaust gas that flows into the particulate filter 16 that represents the temperature TPF of 6 is arranged, and the temperature TNA of the NOx absorbent 19 is provided in the exhaust pipe 21 downstream of the NOx absorbent 19. NOx to represent
A temperature sensor 40b, which generates an output voltage proportional to the temperature of the exhaust gas flowing out from the absorbent 19, is arranged. Further, the depression amount sensor 41 indicates the depression amount DEP of the accelerator pedal.
Generates an output voltage proportional to. These sensors 38, 3
The output voltages of 9, 40a, 40b and 41 are input to the input port 36 via the corresponding AD converters 42, respectively. Further, the input port 36 is connected to a rotation speed sensor 43 that generates an output pulse representing the engine rotation speed. on the other hand,
The output port 37 is connected to each fuel injection valve 7, actuators 9, 24, 25, fuel pump 13, and reducing agent supply valve 22 via a corresponding drive circuit 44.

The NOx absorbent 19 uses, for example, alumina as a carrier, and potassium K, sodium N, etc. are provided on the carrier.
a, lithium Li, at least one selected from alkali metals such as cesium Cs, alkaline earths such as barium Ba and calcium Ca, and rare earths such as lanthanum La and yttrium Y, and platinum Pt and palladium P.
d, a noble metal such as rhodium Rh, and iridium Ir are supported. The ratio of the total amount of fuel and the total amount of air supplied to the exhaust passage, the combustion chamber, and the intake passage upstream of a certain position in the engine exhaust passage to the exhaust air flowing through that position When called the fuel ratio, this NOx
The absorbent 19 absorbs NOx when the air-fuel ratio of the inflowing exhaust gas is lean, and performs the NOx absorbing / releasing action of releasing the absorbed NOx when the oxygen concentration in the inflowing exhaust gas decreases.

In this embodiment, the air-fuel ratio of the air-fuel mixture burned in each cylinder during normal operation is kept lean, so that NOx in the exhaust gas discharged from each cylinder during normal operation is absorbed by the NOx absorbent 19. To be done. However, since the NOx absorbing capacity of the NOx absorbent 19 is limited, it is necessary to release NOx from the NOx absorbent 19 before the NOx absorbing capacity of the NOx absorbent 19 is saturated.
Therefore, in the present embodiment, the NOx absorption amount of the NOx absorbent 19 is obtained, and when the NOx absorption amount becomes larger than a preset set amount, the reducing agent is temporarily supplied to the NOx absorbent 19 from the reducing agent supply valve 22. The NOx in the NOx absorbent 19 is released and reduced.

On the other hand, the exhaust gas discharged from the engine contains particulates of soot, carbon, organic soluble components (SOF), sulfate, etc., which are collected by the particulate filter 16. It However, since the engine back pressure increases as the amount of the particulates collected by the particulate filter 16 increases, the particulate filter 1 is added before the engine back pressure increases.
It is necessary to remove the particulates from 6, that is, to perform the regeneration operation of the particulate filter 16.

Therefore, in the present embodiment, the particulate collection amount of the particulate filter 16 is obtained, and the particulate filter 16 is regenerated when the particulate collection amount becomes larger than a predetermined upper limit threshold value. I am trying to do it. Next, the reproducing operation of the particulate filter 16 will be described in detail. In the present embodiment, as shown in FIG. 2 (A), there are five engine operating state regions I, II, III, which are determined by the accelerator pedal depression amount DEP representing the engine load and the engine speed N.
It is divided into IV and V.

In the region I, the particulate filter 16
Since the temperature of the exhaust gas flowing into the exhaust gas is quite high, the particulate filter 16 does not need to be supplied with energy from the outside.
The particulates trapped in the fuel cell spontaneously start burning, and thus the particulate filter 16 is regenerated. The natural reproduction method in which the particulate filter 16 is naturally reproduced in this manner is referred to as a first reproduction method.

However, since the particulate filter 16 is not naturally regenerated in the areas other than the area I, it is necessary to forcibly regenerate the particulate filter 16.
Therefore, in the present embodiment, the particulate filter 16
It has three forced playback methods to force playback. The first is a method of delaying the main fuel injection timing from that during normal operation. If the main fuel injection timing is retarded relative to that during normal operation, the temperature of the exhaust gas discharged from the engine combustion chamber becomes higher, so the temperature of the exhaust gas flowing into the particulate filter 16 becomes higher, and thus the particulate filter 16 is regenerated. can do. Such a reproducing method is referred to as a second reproducing method.

The second is a method of increasing the opening degree DEGR of the EGR control valve 25 while performing the secondary fuel injection as compared with the normal operation. When the second fuel injection, that is, the secondary fuel injection is performed from the fuel injection valve 7 in the expansion stroke or the exhaust stroke separately from the main fuel injection performed around the compression top dead center, the particulate filter 16 is maintained in the oxidizing atmosphere. Since this secondary fuel burns in the particulate filter 16, the temperature of the particulate filter 16 is raised. Further, at this time, if the opening degree DEGR of the EGR control valve 25 is increased and the EGR gas amount is increased, the amount of fresh air supplied into the engine combustion chamber decreases, so that the temperature of the exhaust gas flowing into the particulate filter 16 is easily increased. Can be increased. Such a reproducing method is referred to as a third reproducing method. Note that the fuel produced by the secondary fuel injection hardly contributes to the engine output.

The third method is to regenerate the particulate filter 16 by reducing the opening degree DEX of the exhaust throttle valve 26 from that during normal operation while performing secondary fuel injection. When the secondary fuel injection is performed, the temperature of the exhaust gas flowing into the particulate filter 16 is raised as described above.
Further, at this time, if the opening degree DEX of the exhaust throttle valve 26 is reduced to reduce the exhaust gas flow rate flowing into the particulate filter 16, the exhaust gas flow rate to be heated is reduced, so that the temperature of the exhaust gas flowing into the particulate filter 16 is further reduced. It can be easily increased. Such a reproducing method is referred to as a fourth reproducing method.

In the second regeneration method, it is necessary to increase the main fuel injection amount so that the engine output torque does not decrease, but the increase amount is small. However, since there is a limit to the amount of retardation of the main fuel injection timing, it is not possible to raise the temperature of the particulate filter 16 significantly and quickly.
In the third regeneration method, the fuel is consumed for the secondary fuel injection, but the temperature of the particulate filter 16 can be significantly and quickly raised. 2 in the fourth reproduction method
In addition to the fuel for the next fuel injection, it is necessary to increase the main fuel injection amount so that the engine output torque does not decrease. However, since the exhaust flow rate to be heated is reduced,
It is possible to raise the temperature of the particulate filter 16 significantly and promptly as compared with the above-mentioned regeneration method. Therefore,
The fuel consumption rate in the first regeneration method is the smallest,
Fuel consumption rate increases in the order of the second regeneration method, the third regeneration method, and the fourth regeneration method, and the temperature rising performance is excellent in the order of the second regeneration method, the third regeneration method, and the fourth regeneration method. It will be.

Considering the fuel consumption rate, it is most preferable to use the second regeneration method. However, in the regions III and IV, since the temperature of the exhaust gas flowing into the particulate filter 16 is low, the temperature of the particulate filter 16 cannot be sufficiently raised when the second regeneration method is used. Similarly, if the third regeneration method is used in the region IV, the temperature of the particulate filter 16 cannot be sufficiently raised, and if the third regeneration method is used in the region III, the fuel consumption rate increases. Therefore, the region II uses the second reproducing method, the region III uses the third reproducing method, and the region IV uses the fourth reproducing method. The correspondence between the areas and the reproduction methods set for the respective areas is shown in FIG.

In the region V, the temperature of the exhaust gas flowing into the particulate filter 16 is quite low, and therefore it is extremely difficult to regenerate the particulate filter 16. Therefore, in the region V, the regeneration action of the particulate filter 16 is prohibited. by the way,
The region to which the engine operating state frequently belongs differs depending on the vehicle driver. However, when the region to which the engine operating state most frequently belongs is the region II, for example, when the engine operating state belongs to the region IV, the particulate collection amount becomes larger than the upper limit threshold value. When the curate filter 16 is regenerated by the fourth regeneration method, the fuel consumption rate undesirably increases. Rather, it is possible to reduce the fuel consumption rate by prohibiting the regeneration action of the particulate filter 16 at this time and then regenerating by the second regeneration method when the engine operating state shifts to the region II. Further, if the engine operating state shifts to the region I and the engine is regenerated by the first regeneration method, the fuel consumption rate can be further reduced.

Therefore, in this embodiment, the region AFR to which the engine operating state most frequently belongs is based on the engine operating state history.
Q is determined from the regions I to IV, and the region AFRQ,
And select a region where a regeneration method with a smaller fuel consumption rate than the regeneration method set for this region is set,
If the engine operating state does not belong to the selected region (hereinafter referred to as the selected region) ASLCT when the amount of collected particulates exceeds the upper limit threshold, the regeneration action of the particulate filter 16 is prohibited, and then When the engine operating state shifts to the selected region ASLCT, the particulate filter 16 is regenerated by the regeneration method set for the region to which the engine operating state belongs.

That is, when the region AFRQ to which the engine operating state belongs most frequently is the region I, the selected region ASLCT.
Becomes the region I, the selected region ASLCT becomes the regions I and II when the region AFRQ is the region II, the selected region ASLCT becomes the regions I, II and III when the region AFRQ is the region III, and the region AFR
When Q is the area IV, the selected area ASLCT is the area I,
Regions II, III and IV will be obtained.

In FIG. 3, the region AFRQ to which the engine operating state belongs most frequently is the region II, and therefore the selected region AS.
The time chart which shows the case where LCT is the area | region I and the area | region II is shown. In FIG. 3, ON indicates that the regeneration operation of the particulate filter 16 by each regeneration method is being executed, and OFF indicates that the regeneration operation by each regeneration method is stopped. Referring to FIG. 3, the particulate collection amount SP at time a
Is greater than the upper threshold SPU. At this time, since the region DOCA to which the engine operating state belongs is the region IV, the regeneration action of the particulate filter 16 is not performed. Next, at time b, when the area DOCA shifts to the area II, the particulate filter 1 is processed by the second reproducing method.
The regeneration action of 6 is started. Next, at the time c, when the area DOCA shifts to the area I, the area DOCA is reproduced by the first reproducing method. As described above, since the particulate filter 16 is naturally reproduced in the region I, the second reproduction method is stopped at this time. Then, at time d, the area DO
When the CA moves to the area II again, the second reproducing method is executed again. Next, at time e, when the particulate collection amount SP becomes smaller than the lower limit threshold value SPL, the second regeneration method is stopped, that is, the regeneration action of the particulate filter 16 is completed.

Further, at the time f, when the regeneration operation of the particulate filter 16 is performed, the area DOC
A is, for example, area III, that is, selected area ASLCT
When moving to the outside, even if the particulate collection amount SP is larger than the lower limit threshold value SPL, the regeneration action of the particulate filter 16 is stopped. As described above, in the present embodiment, the selection region ASLCT is selected based on the engine operating state history, and the particulate filter 16 is regenerated when the engine operating state belongs to the selection region ASLCT. on the other hand,
The first to fourth reproduction methods are set in the regions I to IV, respectively. Therefore, it can be considered that at least one regeneration method is selected from a plurality of regeneration methods based on the engine operation state history, and the particulate filter 16 is regenerated by the selected regeneration method. Further, as long as the particulate collection amount SP is larger than the upper limit threshold value SPU, the particulate filter 16 is regenerated every time the engine operating state belongs to the selection region ASLCT. Therefore, it can be considered that the time when the particulate filter 16 should be regenerated is determined based on the engine operation state history.

By the way, it is not preferable to remove a large amount of particulates at once by a regeneration method having a high fuel consumption rate such as the fourth regeneration method. On the other hand, if the upper threshold SPU is made smaller, the amount of particulates to be removed in one regeneration operation can be reduced. Therefore, in this embodiment, when the fuel consumption rate of the regeneration method to be used for the regeneration operation of the particulate filter 16 is high, the upper limit threshold value SPU is set smaller than when it is low. As a result, when the fuel consumption rate of the regeneration method to be used for the regeneration action of the particulate filter 16 is high, the amount of particulates to be removed in one regeneration action is smaller than when it is low.

That is, the upper threshold SPU when the region AFRQ to which the engine operating state belongs most frequently is the region IV.
Is made the smallest, and the SPU when the area AFRQ is the area III, the SPU when the area AFRQ is the area II, and the SPU when the area AFRQ is the area I are made larger in this order.
FIG. 4 shows a routine for determining the selection area ASLCT. This routine is executed by interruption every predetermined set time.

Referring to FIG. 4, first, at step 50, the area DOCA to which the current engine operating state belongs is shown in FIG.
It is determined using the map of (A). Continued Step 51
Then, it is determined whether or not the current area DOCA is the same as the area AOLD in the previous processing cycle. DOC
When A = AOLD, then the routine proceeds to step 52, where the count value CA representing the time during which the region to which the engine operating state belongs is kept the same is incremented by one. Then, it proceeds to step 56. On the other hand, when DOCA ≠ AOLD in step 51, that is, when the current area DOCA is shifted from the previous area AOLD, the routine proceeds to step 53, where the count value CA is a constant value CA.
It is determined whether or not it is larger than T. When CA≤CAT, the routine jumps to step 55. If CA> CAT, then the routine proceeds to step 54, where the frequency S (AOLD) of the area AOLD is incremented by one. In this case, the count value CA represents the time during which the engine operating state is maintained at AOLD, and the frequency S (AOLD) is increased when the engine operating state is maintained at AOLD for a certain time or longer. In the following step 55, the count value CA is cleared. Then, it proceeds to step 56.

At step 56, the current area DOCA is A
It is stored as OLD. In the following step 57, the frequency S
The largest of (i) (i = I, II, III, IV) is set as AFRQ. AF is continued in step 58.
The selection area ASLCT is determined based on the RQ. Figure 5
And FIG. 6 is a routine for executing the flag control. This routine is executed by interruption every predetermined set time DLT.

Referring to FIGS. 5 and 6, first, at step 60, the region DOC to which the current engine operating state belongs.
A is determined using the map of FIG. In the following step 61, it is judged whether or not the current area DOCA is the area I. Current area DOCA is not area I (D
If OCA ≠ “I”), then proceed to step 62,
It is determined whether or not the reproduction execution flag XCR is set. The reproduction execution flag XCR is set when the particulate filter 16 is forcibly reproduced by the second to fourth reproduction methods (XCR = "1"), and is reset otherwise (XCR = "0"). ).
When the reproduction execution flag XCR is reset, the routine proceeds to step 63, where it is judged if the reproduction request flag XRD is set. The reproduction request flag XRD is set when the particulate filter 16 is to be reproduced (XRD = "1"), and is reset otherwise (XRD = "0"). When the reproduction request flag XRD is reset, the routine then proceeds to step 64, where the particulate amount dCP collected by the particulate filter 16 per unit time is calculated. This particulate amount dCP is RO in advance as a function of, for example, the integrated value of the amount of fuel injected from the fuel injection valve 11, the intake air mass flow rate Ga, the engine speed N, and the particulate collection efficiency of the particulate filter 16.
It is stored in M32. In the following step 65, the product of the interrupt time interval DLT of this routine and dCP (d
CP * DLT) is integrated to calculate the particulate collection amount SP of the particulate filter 16 (SP = SP + dCP * DLT). Continued Step 66
Then, the upper limit threshold value SPU is calculated based on the region AFRQ to which the engine operating state belongs most frequently. In the following step 67, the particulate collection amount SP is the upper limit threshold value S.
It is determined whether or not it is larger than PU. When SP ≦ SPU, the processing cycle is ended. When SP> SPU, then the routine proceeds to step 68, where the reproduction request flag XRD
Is set.

When the reproduction request flag XRD is set, the routine proceeds from step 63 to step 69, where it is judged if the current area DOCA matches the selected area ASLCT. When DOCA ≠ ASLCT, the routine proceeds to step 70, where the reproduction execution flag XCR is reset. That is, the regeneration action of the particulate filter 16 is prohibited. Next, at step 64, an addition process of the particulate collection amount SP is performed. In contrast,
When DOCA = ASLCT, the routine proceeds to step 71, where the reproduction execution flag XCR is set. That is, the regeneration action of the particulate filter 16 is started.

When the reproduction execution flag XCR is set, the routine proceeds from step 62 to step 72, and the particulate amount dRP removed from the particulate filter 16 per unit time is calculated. The particulate amount dRP is stored in advance in the ROM 32 as a function of the regeneration method, the particulate filter temperature TPF, the intake air mass flow rate Ga, and the engine speed N, for example. In the following step 73, the negative value of the product of the interrupt time intervals DLT and dRP of this routine (-dRP · DLT)
The particulate collection amount SP of the particulate filter 16 is calculated by integrating (SP = SP
-DRP / DLT). At the following step 74, it is judged if the particulate collection amount SP of the particulate filter 16 is smaller than the lower limit threshold value SPL. S
When P ≧ SPL, the processing cycle is ended, and SP <S
If it is PL, then the routine proceeds to step 75, where the reproduction execution flag XCR and the reproduction request flag XRD are reset.

On the other hand, when the current area DOCA is the area I (DOCA = "I"), steps 61 to 7 are executed.
6, the particulate amount dRP removed from the particulate filter 16 per unit time by the first reproduction method is calculated. In the following step 77, the particulate collection amount SP is calculated (SP = SP-dR).
P ・ DLT). In the following step 78, the reproduction execution flag X
CR is reset.

7 and 8 show a routine for executing the reproduction control. This routine is executed by interruption every predetermined set time. 7 and 8
Referring to, first, at step 100, it is judged if the reproduction execution flag XCR is set. If the regeneration execution flag XCR is set, then the routine proceeds to step 101, where the area DOCA to which the current engine operating state belongs is determined using the map of FIG. 2 (A).
In the following step 102, the current area DOCA is changed to the area II.
Is determined. When the current region DOCA is the region II (DOCA = "II"), that is, when the second regeneration method should be performed, the routine proceeds to step 103, where the correction coefficient KT (> 0) of the main fuel injection timing TMI is calculated. . The correction coefficient KT is stored in advance in the ROM 32 as a function of the particulate filter temperature TPF, the intake air mass flow rate Ga, and the engine speed N, for example. In the following step 104, the secondary fuel injection amount QSI is made zero. In the following step 105, the EGR control valve 25
The correction coefficient KEGR of the opening degree DEGR is set to zero. In the following step 106, the correction coefficient KEX of the opening degree DEX of the exhaust throttle valve 26 is made zero. Then, it proceeds to step 120.

The current area DOCA is not area II (D
When OCA ≠ “II”), the routine proceeds from step 102 to step 107, where it is judged if the current area DOCA is the area III. Current area DOCA is area II
When I (DOCA = "III"), that is, when the third regeneration method is to be performed, the routine proceeds to step 108, where the correction coefficient KT of the main fuel injection timing TMI is made zero. In the following step 109, the secondary fuel injection amount QSI is calculated, and in the following step 110, the EGR control valve opening degree DE
The GR correction coefficient KEGR (> 0) is calculated. The secondary fuel injection amount QSI and the correction coefficient KEGR are previously stored in the ROM 3 as a function of the particulate filter temperature TPF, the intake air mass flow rate Ga, and the engine speed N, for example.
2 are stored in each. In the following step 111, the correction coefficient KEX of the exhaust throttle valve opening DEX is made zero. Then, it proceeds to step 120.

When the current area DOCA is not the area III (DOCA ≠ “III”), that is, the current area D
When the OCA is in the region IV (DOCA = "IV"), that is, when the fourth regeneration method should be performed, the routine proceeds from step 107 to step 112, where the main fuel injection timing TM
The correction coefficient KT of I is set to zero. In the following step 109, the secondary fuel injection amount QSI is calculated, and in the following step 11
At 0, the correction coefficient KEGR of the EGR control valve opening degree DEGR is made zero. In the following step 111, the exhaust throttle valve opening D
A correction coefficient KEX (<0) of EX is calculated. This correction coefficient KEX is, for example, the particulate filter temperature TP.
It is stored in the ROM 32 in advance as a function of F, the intake air mass flow rate Ga, and the engine speed N. Then, it proceeds to step 120.

At step 120, the basic main fuel injection timing T
MB is calculated, and in the following step 121, the main fuel injection timing T is calculated from the basic main fuel injection timing TMB and the correction coefficient KT.
MI is calculated (TMI = TMB + KT). In the following step 122, the basic EGR control valve opening degree DEGRB is calculated, and in the following step 123, the basic EGR control valve opening degree D
The EGR control valve opening degree DEGR is calculated from EGRB and the correction coefficient KEGR (DEGR = DEGRB + KEG
R). In the following step 124, the basic exhaust throttle valve opening degree DE
XB is calculated, and in the following step 125, the exhaust throttle valve opening DEX is calculated from the basic exhaust throttle valve opening DEXB and the correction coefficient KEX (DEX = DEXB + KEX).
The basic main fuel injection timing TMB, the basic EGR control valve opening degree DEGRB, and the basic exhaust throttle valve opening degree DEX are stored in advance in the ROM 32 as functions of the intake air mass flow rate Ga and the engine speed N, for example.

In the embodiments described so far, the fuel for heating the particulate filter is supplied to the particulate filter 16 by using the secondary fuel injection, so that the particulate filter 16 is regenerated. However, an additional fuel injection valve may be arranged in the exhaust passage upstream of the particulate filter 16 and the heating fuel may be supplied from the additional fuel injection valve to the particulate filter 16. Further, in the embodiments described thus far, the flow rate of exhaust gas flowing into the particulate filter 16 is controlled by controlling the opening degree of the exhaust throttle valve 26. However, the flow rate of exhaust gas flowing into the particulate filter 16 may be controlled by controlling the opening degree of the throttle valve 10 arranged in the engine intake passage.

Further, as a method for forcibly regenerating the particulate filter 16, a method of directly heating the particulate filter 16 by providing an electric heater on the particulate filter 16, a method of using a burner, and a mixture gas burned in the engine combustion chamber are used. A method of changing the air-fuel ratio to a richer side than in normal operation, or a method of retarding the ignition timing in normal operation in a spark ignition internal combustion engine can be used.

[0046]

The particulate filter can be reliably regenerated while maintaining high energy efficiency.

[Brief description of drawings]

FIG. 1 is an overall view of an internal combustion engine.

FIG. 2 is a diagram showing areas I to V, and a correspondence relationship between each area and a reproduction method.

FIG. 3 is a time chart for explaining a reproducing operation of the particulate filter.

FIG. 4 is a flowchart for determining a selection area ASLCT.

FIG. 5 is a flowchart for executing flag control.

FIG. 6 is a flowchart for executing flag control.

FIG. 7 is a flowchart for executing reproduction control.

FIG. 8 is a flowchart for executing reproduction control.

[Explanation of symbols]

1 ... Engine body 11 ... Fuel injection valve 16 ... Particulate filter 25 ... EGR control valve 26 ... Exhaust throttle valve

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F01N 3/02 F02M 25/07 F01N 3/36

Claims (6)

(57) [Claims] 1. An exhaust gas purifying apparatus for an internal combustion engine, wherein a particulate filter for collecting particulates in exhaust gas is arranged in an engine exhaust passage, and a plurality of regeneration means for regenerating the particulate filter are provided to operate the engine.
Divide the status area into multiple areas and play differently for each area
Set the method and set the engine operating condition based on the engine operating state history.
The area to which the state most frequently belongs belongs to the area
Determine the determined area and the determined area
Regeneration means having higher energy efficiency than the set regeneration means
Area and the area where the
The engine operating condition is selected when the filter should be regenerated.
If it does not belong to the area, the particulate filter
Prohibit live action and then the engine operating condition is
To the region to which the engine operating state belongs when
An exhaust gas purification device for an internal combustion engine, wherein a particulate filter is regenerated by a set regenerating means. 2. The regenerating means is a particulate fill.
Natural regeneration means to regenerate water naturally, and particulates
And a plurality of forced regeneration means for forcibly regenerating the filter.
Equipped, these forced regeneration means are energy efficient and temperature rising
The exhaust gas purification device for an internal combustion engine according to claim 1, wherein the functions are different from each other . 3. Collected by a particulate filter
The amount of particulates present
Is greater than the set amount, the particulate filter
The method according to claim 1, wherein it is determined that the computer should be regenerated.
Exhaust gas purification device for internal combustion engine. 4. The set amount according to the selected area
An exhaust purification system of an internal combustion engine according to claim 3 which is adapted to change the. 5. A device for collecting particulates in exhaust gas
A particulate filter for engine is installed in the engine exhaust passage
In an exhaust gas purification device for an internal combustion engine,
Normal fuel injection timing to regenerate the filter
A retard angle regeneration means that is behind time, and a particulate trap
In the engine expansion stroke or exhaust stroke to regenerate the filter
Perform secondary fuel injection and change the EGR gas amount during normal operation.
Equipped with secondary injection EGR regeneration means for increasing
When the iculate filter should be regenerated , the engine load
When the load is higher than the specified load, the retard angle regeneration means
To regenerate the particulate filter and
When the rate filter should be regenerated, the engine load is
When the load is lower than the load, the secondary injection EGR regeneration means is used to
Internal combustion engine with regenerated ticulate filter
Exhaust purification device. 6. A device for collecting particulate matter in exhaust gas.
A particulate filter for engine is installed in the engine exhaust passage
In an exhaust gas purification device for an internal combustion engine,
Exhaust flow rate control that can control the exhaust flow rate flowing into the filter
Equipped with control means to regenerate the particulate filter
In order to perform secondary fuel injection in the engine expansion stroke or exhaust stroke
The secondary that increases the EGR gas amount as compared with the normal operation
The injection EGR regeneration means and the particulate filter are
Secondary fuel injection in the engine expansion stroke or exhaust stroke
Exhausted into the particulate filter as well as
Secondary injection exhaust flow rate that reduces the air flow rate compared to normal operation
It is equipped with regeneration means and regenerates the particulate filter.
When the engine load should be higher than the preset load
If it is high, the secondary injection EGR regeneration means is used to
Play the rate filter and turn the particulate filter on.
When the engine load is lower than the set load when regenerating
The secondary injection exhaust flow rate regeneration means is used for particulates.
Exhaust gas purification device for internal combustion engine with filter regeneration
Place