JP4140387B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust emission control device for an internal combustion engine.
[0002]
[Prior art]
A particulate filter for collecting particulates in the exhaust gas is arranged in the engine exhaust passage, and a reference state intake air amount that is an intake air amount when the engine operation state is a predetermined reference state is detected, When the reduction amount of the reference state intake air amount with respect to the comparison target value is larger than a predetermined set amount, the lean air-fuel ratio is used under the lean air-fuel ratio in order to oxidize and remove the fine particles accumulated on the particulate filter. An internal combustion engine in which a temperature raising process for raising the temperature of a particulate filter is performed is known (see Patent Document 1).
[0003]
As the amount of accumulated particulates on the particulate filter increases, the pressure loss in the particulate filter gradually increases, and as a result, the reference state intake air amount gradually decreases. That is, roughly speaking, the reference state intake air amount itself or the decrease amount of the reference state intake air amount with respect to the comparison target value represents an increase amount of the amount of accumulated particulates on the particulate filter. Therefore, in this internal combustion engine, the temperature raising process is performed when the amount of decrease in the reference state intake air amount with respect to the comparison target value is larger than the set amount.
[0004]
[Patent Document 1]
JP 2002-89234 A
[Patent Document 2]
JP 2000-97011 A
[Patent Document 3]
Japanese Patent Laid-Open No. 11-229848
[0005]
[Problems to be solved by the invention]
However, the pressure loss of intake system components or exhaust system components, for example, an air cleaner, gradually increases with time. For this reason, for example, when the air cleaner is replaced with a new one and the pressure loss of the air cleaner decreases, the reference state intake air amount may increase significantly even when the amount of accumulated particulates on the particulate filter is large. In this case, if the temperature rise control is not performed due to the large reference state intake air amount, the amount of accumulated particulates on the particulate filter may be considerably increased. That is, the amount of decrease in the reference state intake air amount with respect to the comparison target value in this case does not accurately represent the amount of accumulated particulate matter, and therefore, even if it is determined whether or not the temperature raising process should be performed based on this amount of decrease. However, there is a problem that it is not always possible to perform the optimum temperature raising process.
[0006]
SUMMARY OF THE INVENTION An object of the present invention is to provide an exhaust gas purification apparatus for an internal combustion engine that can accurately determine whether or not a temperature increase process for a particulate filter should be performed.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problem, according to the first invention, when the particulate filter for collecting particulates in the exhaust gas is disposed in the engine exhaust passage, and the engine operating state is a predetermined reference state, The reference state intake air amount that is the amount of intake air is detected, and when the detected reference state intake air amount is less than the allowable lower limit amount, the particulates deposited on the particulate filter are removed by oxidation. Therefore, in the exhaust gas purification apparatus for an internal combustion engine, which performs a temperature raising process for raising the temperature of the particulate filter under a lean air-fuel ratio, the next temperature raising process is performed after the previous temperature raising process is performed. Until the reference state intake air amount detected this time is larger than the allowable upper limit amount determined according to the previously detected reference state intake air amount. They are to perform.
[0008]
In order to solve the above problem, according to the second invention, a particulate filter for collecting particulates in the exhaust gas is disposed in the engine exhaust passage, and the engine operating state is set in a predetermined reference state. When the reference state intake air amount that is the intake air amount at the time is detected, and the detected reference state intake air amount is less than the allowable lower limit amount, the particulates deposited on the particulate filter are removed. In an exhaust gas purification apparatus for an internal combustion engine in which a temperature raising process for raising the temperature of the particulate filter is performed under a lean air-fuel ratio in order to remove oxidation, the next rise after the previous temperature raising process is performed. Until the temperature processing is performed, when the reference state intake air amount detected this time is larger than the allowable upper limit amount determined according to the reference state intake air amount detected last time, The change amount of the currently detected reference state intake air amount with respect to the detected reference state intake air amount is obtained and stored, and thereafter the detected reference state intake air amount is corrected based on the stored change amount. When the corrected reference state intake air amount becomes smaller than the allowable lower limit amount, the temperature raising process is performed.
[0009]
According to the third invention, in the first or second invention, when the air cleaner disposed in the intake passage is replaced, the reference state intake air amount detected this time is larger than the allowable upper limit amount. .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a case where the present invention is applied to a compression ignition type internal combustion engine. The present invention can also be applied to a spark ignition type internal combustion engine.
[0012]
Referring to FIG. 1, 1 is an engine body, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is an electrically controlled fuel injection valve, 7 is an intake valve, 8 is an intake port, 9 Is an exhaust valve, and 10 is an exhaust port. The intake port 8 is connected to a surge tank 12 via a corresponding intake branch pipe 11, and the surge tank 12 is connected to an air cleaner 14 via an intake duct 13. A throttle valve 16 driven by a step motor 15 is disposed in the intake duct 13. In the embodiment according to the present invention, the throttle opening degree is maintained at the maximum opening degree in almost all operation regions, and is made smaller than the maximum opening degree when the required load L becomes considerably small, and small when the required load L becomes zero. To be.
[0013]
On the other hand, the exhaust port 10 is connected to a casing 19 via an exhaust manifold 17 and an exhaust pipe 18. A particulate filter 20 for collecting particulates in the exhaust gas is accommodated in the casing 19, and a catalyst having oxidation ability is supported on the particulate filter 20.
[0014]
The electronic control unit 30 is composed of a digital computer, and is connected to a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Microprocessor) 34, and a battery 35a connected to each other by a bidirectional bus 31. A B-RAM (backup RAM) 35, an input port 36, and an output port 37 are provided. An air flow meter 40 for detecting the amount of intake air is attached in the intake duct 13 upstream of the throttle valve 16. Further, an accelerator pedal (not shown) is connected to a depression amount sensor 41 that generates an output voltage proportional to the depression amount of the accelerator pedal. The amount of depression of the accelerator pedal represents a required load. The output voltages of these sensors 40 and 41 are input to the input port 36 via the corresponding AD converter 38. Further, a rotational speed sensor 42 that generates an output pulse representing the engine rotational speed is connected to the input port 36. On the other hand, the output port 37 is connected to the fuel injection valve 6 and the throttle valve driving step motor 15 via a corresponding drive circuit 39.
[0015]
In the internal combustion engine shown in FIG. 1, fuel injection for obtaining engine output performed near the compression top dead center is temporarily stopped during engine deceleration operation. That is, when the required load L becomes zero and the engine speed NE is higher than the first threshold value NE1 at this time, the fuel injection is temporarily stopped. Next, when the required load L becomes greater than zero or the engine speed NE becomes lower than the second threshold value NE2 (<NE1), fuel injection is resumed.
[0016]
Now, fine particles mainly made of carbon solid contained in the exhaust gas are collected on the particulate filter 20. The internal combustion engine shown in FIG. 1 is continuously combusted under a lean air-fuel ratio, and the particulate filter 20 carries a catalyst having oxidation ability. If the temperature is maintained at a temperature at which the fine particles can be oxidized, for example, 250 ° C. or higher, the fine particles are oxidized on the particulate filter 20 and removed.
[0017]
However, if the temperature of the particulate filter 20 is not maintained at a temperature that can oxidize the particulates, or if the amount of particulates flowing into the particulate filter 20 per unit time becomes considerably large, the particulates that accumulate on the particulate filter 20. And the pressure loss of the particulate filter 20 gradually increases.
[0018]
Therefore, in the embodiment according to the present invention, it is determined whether or not the amount of deposited particulates on the particulate filter 20 should be decreased, and when it is determined that the amount of deposited particulates should be decreased, the exhaust gas flowing into the particulate filter 20 is determined. The temperature of the particulate filter 20 is increased to, for example, 600 ° C. or higher and maintained at 600 ° C. or higher while the air-fuel ratio of the engine is kept lean. When this temperature raising process is performed, the fine particles deposited on the particulate filter 20 are ignited and burned and removed, and the amount of the fine particles deposited on the particulate filter 20 is reduced to almost zero, for example.
[0019]
Here, there are various methods for raising the temperature of the particulate filter 20. For example, an electric heater is disposed at the upstream end of the particulate filter 20 and flows into the particulate filter 20 or the particulate filter 20 by the electric heater. The exhaust gas to be heated, the method of heating the particulate filter 20 by secondarily injecting fuel into the exhaust passage upstream of the particulate filter 20 and burning the fuel, and the exhaust gas discharged from the internal combustion engine There is a method of raising the temperature of the particulate filter 20 by raising the temperature of the exhaust gas. Here, in order to increase the temperature of the exhaust gas discharged from the internal combustion engine, for example, the fuel injection timing can be retarded, or additional fuel can be injected during the expansion stroke or the exhaust stroke. .
[0020]
By the way, as the amount of particulate matter deposited on the particulate filter 20 increases and the pressure loss of the particulate filter 20 increases, the amount of intake air gradually decreases. Accordingly, in the embodiment according to the present invention, the intake air amount (hereinafter referred to as the reference state intake air amount) Gn is detected every time the engine operation state becomes a predetermined reference state, and the detected reference state intake air amount Gn is detected. When the temperature becomes smaller than the allowable lower limit amount LL, the above-described temperature rise process is performed.
[0021]
FIG. 2 shows the reference state intake air amount Gn (i) detected i-th (i = 1, 2,...) After the temperature raising process is completed. As shown in FIG. 2, the reference state intake air amount Gn (i) gradually decreases as the number of detections i increases. Next, for example, when the reference state intake air amount Gn (k) detected for the kth time is smaller than the allowable lower limit amount LL, the temperature raising process is performed as indicated by an arrow T in FIG. Since the pressure loss of the particulate filter 20 is reduced when the temperature raising process is performed, the reference state intake air amount Gn (i) increases again.
[0022]
Any engine operating state may be used as long as the reference state is a constant state, but in the embodiment according to the present invention, the fuel supply stop time during the engine deceleration operation described above is set as the reference state. In this way, it is possible to eliminate the influence of engine speed fluctuations on the intake air amount.
[0023]
On the other hand, the allowable lower limit amount LL is set as follows in the embodiment according to the present invention. That is, a result obtained by subtracting, for example, a constant value Z from the reference state intake air amount Gn (1) when the engine operating state becomes the reference state for the first time after the temperature raising process is completed is set as the allowable lower limit amount LL (LL = Gn (1) -Z). In other words, when the decrease amount (= Gn (1) −Gn (i)) of the reference state intake air amount Gn (i) with respect to the reference value Gn (1) becomes larger than the threshold value Z, the temperature raising process is performed. Is done.
[0024]
When the engine operating state becomes the reference state for the first time after the temperature raising process is completed, the amount of accumulated particulates on the particulate filter 20 is considerably small. Therefore, the reference state intake air amount Gn (1) at this time has the amount of accumulated particulates. This is the amount of intake air when it is considerably low. Then, it can be considered that the amount of decrease in the reference state intake air amount Gn (i) with respect to the reference state intake air amount Gn (1) represents the amount of accumulated particulate matter. Therefore, in the embodiment according to the present invention, when the reduction amount (= Gn (1) −Gn (i)) of the reference state intake air amount Gn (i) with respect to the reference value Gn (1) is larger than the threshold value Z. In addition, it is determined that the amount of the deposited fine particles on the particulate filter 20 is larger than the allowable amount, and at this time, the temperature raising process is performed. The allowable lower limit amount LL is stored in the B-RAM 35 every time it is calculated. The reference value Gn (1) is stored in the B-RAM 35 every time it is detected, and the reference value Gn (1) is allowed each time the reference state intake air amount Gn (i) (i = 2, 3,...) Is detected. The limit amount LL can also be calculated.
[0025]
Here, the reference state intake air amount Gn (i) gradually decreases even with the passage of time of intake system components or exhaust system components other than the particulate filter 20. In this case, the intake system components or exhaust system components include, for example, an EGR passage, an EGR control valve, and an exhaust gas drive type in an internal combustion engine equipped with an EGR (exhaust gas recirculation) device in addition to an air cleaner 14, an intake pipe and an exhaust pipe An internal combustion engine equipped with a supercharger includes a turbocharger turbine, a compressor, a wastegate valve, and the like. However, Gn (i) immediately after the temperature raising process is the amount of intake air when the amount of particulate matter deposited on the particulate filter 20 is considerably small regardless of whether the intake system component or the exhaust system component changes over time. Therefore, the decrease amount of the reference state intake air amount Gn (i) with respect to the reference value Gn (1) or the reference state intake air amount Gn (i) itself is irrespective of the magnitude of the time-dependent change of the intake system components or the exhaust system components. This represents the amount of deposited fine particles.
[0026]
As described above, the reference state intake air amount Gn (i) gradually decreases as time elapses. However, for example, when the air cleaner 14 is replaced with a new one and, as a result, the pressure loss of the air cleaner 14 is reduced, the reference state intake air amount Gn (i) is greatly increased even when the amount of accumulated particulates on the particulate filter 20 is large. May increase. The reference state intake air amount Gn (i) in this case no longer represents the amount of accumulated particulates, and therefore it is determined whether or not the temperature raising process is to be performed based on the reference state intake air amount Gn (i) in this case. However, it cannot be accurately determined whether or not the temperature raising process should be performed.
[0027]
Therefore, in the embodiment according to the present invention, when the currently detected reference state intake air amount Gn (i) is significantly larger than the previously detected reference state intake air amount Gn (i-1), for example, the air cleaner 14 is replaced. At this time, the temperature raising process is performed. After the temperature raising process is performed, the reduction amount of the reference state intake air amount Gn (i) with respect to the reference value Gn (1) or the reference state intake air amount Gn (i) itself represents the amount of accumulated particulates. Become.
[0028]
More specifically, as indicated by an arrow R in FIG. 3, the currently detected reference state intake air amount Gn (i) is determined according to the previously detected reference state intake air amount Gn (i-1). When the amount is larger than the allowable upper limit amount UL, it is determined that the air cleaner 14 has been replaced, and the temperature raising process is performed as indicated by an arrow T. This allowable upper limit amount UL is set in the form of a result obtained by subtracting, for example, a constant value X from the previously detected reference state intake air amount Gn (i−1) (UL = Gn (i−1) −X). In other words, a decrease amount (= Gn (i−1) −Gn (i)) of the currently detected reference state intake air amount Gn (i) with respect to the previously detected reference state intake air amount Gn (i−1). When it is less than the threshold value X, the temperature raising process is performed.
[0029]
That is, if the air cleaner 14 is not replaced, the reference state intake air amount Gn (i) detected this time should be smaller than the allowable upper limit amount UL as shown by a broken line in FIG. As indicated by the solid line, when Gn (i)> UL, it can be determined that the air cleaner 14 has been replaced.
[0030]
FIG. 4 shows a routine for executing the fine particle oxidation control described above. This routine is executed by interruption every predetermined time.
[0031]
Referring to FIG. 4, first, at step 100, it is judged if the current engine operating state is the reference state. When the current engine operating state is not the reference state, the processing cycle is terminated, and when it is the reference state, the routine proceeds to step 101 where the intake air amount Gn at this time is detected. This reference state intake air amount Gn corresponds to Gn (i) described with reference to FIG. In the following step 102, it is determined whether or not the currently detected reference state intake air amount Gn is smaller than the allowable lower limit amount LL. When Gn <LL, the routine proceeds to step 103 where the above-described temperature increase process is performed. In the following step 104, it is determined whether or not the current engine operation state is a reference state. When the engine operation state becomes the reference state, that is, when the engine operation state becomes the reference state for the first time after the temperature raising process is completed, the routine proceeds to step 105 where the intake air amount Gn at this time is detected. This reference state intake air amount Gn corresponds to Gn (1) described with reference to FIG. In the subsequent step 106, an allowable lower limit amount LL is set based on the reference state intake air amount Gn detected in step 105 (LL = Gn−Z). Next, the routine proceeds to step 107, where the reference state intake air amount Gn detected at step 105 is stored as the previously detected reference state intake air amount GnO.
[0032]
On the other hand, when Gn ≧ LL in step 102, the routine proceeds to step 108, where the allowable upper limit amount UL is set based on the previously detected reference state intake air amount GnO (UL = GnO−X). This reference state intake air amount GnO corresponds to Gn (i-1) described with reference to FIG. In the following step 109, it is determined whether or not the currently detected reference state intake air amount Gn is larger than the allowable upper limit amount UL. When Gn> UL, the routine proceeds to step 103 where a temperature raising process is performed. Next, the process proceeds from step 104 to step 107 in sequence. On the other hand, when Gn ≦ UL, the routine proceeds to step 107 and the processing cycle is terminated.
[0033]
Next, another embodiment according to the present invention will be described with reference to FIG.
[0034]
In FIG. 5, the solid line represents the actual reference state intake air amount Gn (i) detected by the air flow meter 40. In the example shown in FIG. 5, as indicated by an arrow R, the reference state intake air amount Gn (j) detected at the j-th time is larger than the allowable upper limit amount UL.
[0035]
In the above-described embodiment, when the reference state intake air amount Gn (j) exceeds the allowable upper limit amount UL, the temperature raising process is started immediately. However, at this time, the amount of deposited fine particles on the particulate filter 20 may be considerably small. In this case, it is not preferable to perform the temperature raising process from the viewpoint of energy consumption.
[0036]
On the other hand, as shown in FIG. 5, the reference state intake air amount Gn (j) detected at the j-th time is compared with the reference state intake air amount Gn (j-1) detected at the (j-1) -th time. It changes by Y (= Gn (j) −Gn (j−1)). Generally speaking, the amount of change Y is due to, for example, the effect of replacing the air cleaner 14.
[0037]
Then, if the change amount Y is subtracted from the reference state intake air amount Gn detected after the reference state intake air amount Gn exceeds the allowable upper limit amount UL, this subtraction result eliminates the influence of the replacement of the air cleaner 14. It will be that.
[0038]
Therefore, in the embodiment according to the present invention, after Gn (i)> UL, the reference state intake air amount correction value GnC is obtained by subtracting the change amount Y from the reference state intake air amount Gn detected by the air flow meter 40. (= Gn−Y) is obtained, and when the reference state intake air amount correction value GnC becomes smaller than the allowable lower limit amount LL, the temperature raising process is performed. If it does in this way, energy can be used effectively for particulate oxidation control.
[0039]
Specifically, as shown in FIG. 5, when the reference state intake air amount Gn (j) detected at the jth time is larger than the allowable upper limit amount UL, the reference state detected at the (j−1) th time. A change amount Y (= Gn (j) −Gn (j−1)) of Gn (j) with respect to the intake air amount Gn (j−1) is calculated and stored. In addition, after the (j + 1) th time, the reference state intake air amount correction value GnC (i) is sequentially calculated as indicated by the broken line in FIG. 5 by subtracting the change amount Y from Gn (i). .
[0040]
Next, for example, when the reference state intake air amount Gn (k) detected for the kth time is smaller than the allowable lower limit amount LL, a temperature raising process is performed as indicated by an arrow T in FIG. At this time, although the detected Gn (k) is larger than the allowable lower limit amount LL, in another embodiment according to the present invention, the temperature raising process is performed.
[0041]
Therefore, generally speaking, the reference state intake air amount Gn (i) detected this time is greater than the allowable upper limit UL between the previous temperature raising process and the next temperature raising process. If there is too much, the change amount Y of the currently detected reference state intake air amount Gn (i) with respect to the previously detected reference state intake air amount Gn (i-1) is obtained and stored, and the reference state detected thereafter The intake air amount Gn (i) is corrected based on the change amount Y, and the temperature raising process is performed when the corrected reference state intake air amount GnC becomes smaller than the allowable lower limit amount LL. Become.
[0042]
6 and 7 show a routine for executing the fine particle oxidation control according to another embodiment of the present invention described above. This routine is executed by interruption every predetermined time.
[0043]
Referring to FIGS. 6 and 7, first, at step 120, it is judged if the current engine operating state is the reference state. When the current engine operation state is not the reference state, the processing cycle is terminated, and when it is the reference state, the routine proceeds to step 121 where the intake air amount Gn at this time is detected. In the following step 122, it is determined whether or not the flag is set. This flag is set when the reference state intake air amount Gn is to be corrected, and is reset otherwise. When the flag is reset, the routine proceeds to step 123, where it is determined whether or not the currently detected reference state intake air amount Gn is smaller than the allowable lower limit amount LL. When Gn <LL, the routine proceeds to step 124 where the above-described temperature raising process is performed. In the following step 125, it is determined whether or not the current engine operating state is the reference state. When the engine operation state becomes the reference state, that is, when the engine operation state becomes the reference state for the first time after the temperature raising process is completed, the routine proceeds to step 126 where the intake air amount Gn at this time is detected. This reference state intake air amount Gn corresponds to Gn (1) described with reference to FIG. In the following step 127, the allowable lower limit amount LL is set based on the reference state intake air amount Gn detected in step 126 (LL = Gn−Z). Next, the routine proceeds to step 128, where the reference state intake air amount Gn detected at step 126 is stored as the previously detected reference state intake air amount GnO.
[0044]
On the other hand, when Gn ≧ LL in step 123, the routine proceeds to step 129, where the allowable upper limit amount UL is set based on the previously detected reference state intake air amount GnO (UL = GnO−X). In the following step 130, it is determined whether or not the currently detected reference state intake air amount Gn is larger than the allowable upper limit amount UL. When Gn> UL, the routine proceeds to step 131 where the change amount Y is calculated (Y = Gn−GnO). This reference state intake air amount GnO corresponds to Gn (j−1) described with reference to FIG. In the following step 132, a flag is set. Next, the routine proceeds to step 128. On the other hand, when Gn ≦ UL, the routine jumps from step 130 to step 128. In step 128 in this case, the reference state intake air amount Gn detected in step 121 is stored as the previously detected reference state intake air amount GnO.
[0045]
When the flag is set, the routine proceeds from step 122 to step 133, where the reference state intake air amount correction value GnC is calculated (GnC = Gn−Y). In the following step 134, it is determined whether or not the reference state intake air amount correction value GnC is smaller than the allowable lower limit amount LL. When GnC ≧ LL, the routine jumps to step 128, where the reference state intake air amount Gn detected at step 121 is stored as the previously detected reference state intake air amount GnO. On the other hand, when GnC <LL, the routine proceeds to step 135 to reset the flag, and then proceeds from step 124 to step 128 in sequence.
[0046]
Next, another embodiment according to the present invention will be described.
[0047]
As described above, the allowable lower limit amount LL is stored and held in the B-RAM 35 every time it is calculated. However, when the battery 35a is temporarily removed for replacement, the stored contents in the B-RAM 35 are cleared. In this case, the allowable lower limit amount LL is reset to, for example, zero, and it does not make sense to compare the reference state intake air amount Gn detected at this time with the allowable lower limit amount LL. The same applies when the reference value Gn (1) is stored in the B-RAM 35.
[0048]
Therefore, in yet another embodiment according to the present invention, it is determined whether or not the stored contents of the B-RAM 35 have been cleared. When it is determined that the stored contents of the B-RAM 35 have been cleared, a temperature raising process is performed. Yes.
[0049]
FIG. 8 shows a routine for executing fine particle oxidation control according to another embodiment of the present invention described above. This routine is executed by interruption every predetermined time.
[0050]
Referring to FIG. 8, first, at step 140, it is judged if the battery 35a has been replaced. When the battery 35a is replaced, the routine proceeds to step 141 where the above-described temperature raising process is performed. In the following step 142, it is determined whether or not the current engine operating state is a reference state. When the engine operation state becomes the reference state, that is, when the engine operation state becomes the reference state for the first time after the temperature raising process is completed, the routine proceeds to step 143 where the intake air amount Gn at this time is detected. This reference state intake air amount Gn corresponds to Gn (1) described with reference to FIG. In the following step 144, the allowable lower limit amount LL is set based on the reference state intake air amount Gn detected in step 143 (LL = Gn−Z). Next, the routine proceeds to step 145, where the reference state intake air amount Gn detected at step 143 is stored as the previously detected reference state intake air amount GnO.
[0051]
On the other hand, when the battery 35a has not been replaced, the routine proceeds to step 146, where it is determined whether or not the current engine operating state is the reference state. When the current engine operating state is not the reference state, the processing cycle is terminated, and when it is the reference state, the routine proceeds to step 147 where the intake air amount Gn at this time is detected. In the following step 148, it is determined whether or not the currently detected reference state intake air amount Gn is smaller than the allowable lower limit amount LL. When Gn <LL, the routine proceeds to step 141 where a temperature raising process is performed. Next, the process proceeds from step 142 to step 145 sequentially. On the other hand, when Gn ≧ LL, the routine proceeds to step 145 where the reference state intake air amount Gn detected at step 147 is stored as the previously detected reference state intake air amount GnO.
[0052]
【The invention's effect】
It is possible to accurately determine whether or not to raise the temperature of the particulate filter.
[Brief description of the drawings]
FIG. 1 is an overall view of an internal combustion engine.
FIG. 2 is a diagram for explaining a temperature raising process.
FIG. 3 is a diagram for explaining an embodiment according to the present invention.
FIG. 4 is a flowchart for executing a fine particle oxidation control routine according to an embodiment of the present invention.
FIG. 5 is a diagram for explaining still another embodiment according to the present invention.
FIG. 6 is a flowchart for executing a particulate oxidation control routine according to another embodiment of the present invention.
FIG. 7 is a flowchart for executing a particulate oxidation control routine according to another embodiment of the present invention.
FIG. 8 is a flowchart for executing a fine particle oxidation control routine according to still another embodiment of the present invention.
[Explanation of symbols]
1 ... Engine body
7 ... Intake valve
14 ... Air cleaner
18 ... Exhaust pipe
20 ... Particulate filter
40 ... Air flow meter

Claims (3)

  A particulate filter for collecting particulates in the exhaust gas is arranged in the engine exhaust passage, and a reference state intake air amount that is an intake air amount when the engine operation state is a predetermined reference state is detected, When the detected reference state intake air amount is smaller than the allowable lower limit amount, the particulate filter is operated under a lean air-fuel ratio in order to oxidize and remove particulates accumulated on the particulate filter. In the exhaust gas purification apparatus for an internal combustion engine in which the temperature raising process for increasing the temperature is performed, the reference state suction detected this time is performed after the previous temperature raising process until the next temperature raising process is performed. An exhaust emission control device for an internal combustion engine, which performs a temperature raising process when the air amount is larger than an allowable upper limit amount determined according to a previously detected reference state intake air amount.   A particulate filter for collecting particulates in the exhaust gas is arranged in the engine exhaust passage, and a reference state intake air amount that is an intake air amount when the engine operation state is a predetermined reference state is detected, When the detected reference state intake air amount becomes smaller than the allowable lower limit amount, the particulate filter is operated under a lean air-fuel ratio to oxidize and remove particulates accumulated on the particulate filter. In the exhaust gas purification apparatus for an internal combustion engine in which the temperature raising process for increasing the temperature is performed, the reference state suction detected this time is performed after the previous temperature raising process until the next temperature raising process is performed. When the air amount is larger than the allowable upper limit amount determined in accordance with the reference state intake air amount detected last time, the current detection with respect to the reference state intake air amount detected last time is detected. The amount of change in the reference state intake air amount is obtained and stored, the reference state intake air amount detected thereafter is corrected based on the stored amount of change, and the corrected reference state intake air amount is the allowable amount. An exhaust gas purification apparatus for an internal combustion engine, which performs a temperature raising process when it becomes less than a lower limit amount.   3. The exhaust emission control device for an internal combustion engine according to claim 1, wherein when the air cleaner disposed in the intake passage is replaced, the reference state intake air amount detected this time becomes larger than the allowable upper limit amount.

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