JP4044836B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust purification technology for an internal combustion engine mounted on an automobile or the like, and more particularly to an exhaust purification device for an internal combustion engine provided with a particulate filter that collects particulates in the exhaust.
[0002]
[Prior art]
2. Description of the Related Art In recent years, a technique for suppressing the release of particulates (PM) such as soot into the atmosphere has been desired for internal combustion engines mounted on automobiles and the like.
[0003]
In response to such demands, a technique is known in which a particulate filter is disposed in an exhaust passage of an internal combustion engine, and particulates discharged from the internal combustion engine are collected by the particulate filter.
[0004]
Pa Fine particles collected by the particulate filter The child is Removed from the particulate filter as appropriate. Be made There is a need. As a method of removing the particulates collected by the particulate filter, the particulate filter is heated to an oxidizing atmosphere (that is, an oxygen-excessive atmosphere) while raising the temperature of the particulate filter to a temperature range where the particulates can be oxidized. Thus, the method of oxidizing and removing the fine particles is generally used. However, if the temperature of the particulate filter becomes excessively high at that time, there is a possibility that the particulate filter is thermally deteriorated.
[0005]
Therefore, in the exhaust gas purification apparatus for an internal combustion engine equipped with a particulate filter, when removing particulates collected by the particulate filter, the temperature of the particulate filter is estimated from the exhaust temperature downstream of the particulate filter, and estimated. A technique for adjusting the amount of exhaust gas flowing into the particulate filter in accordance with the temperature has been proposed (see, for example, Patent Document 1).
[0006]
[Patent Document 1]
Special Open 2 No. 002-106325
[Patent Document 2]
Japanese Patent Laid-Open No. 05-222916
[Patent Document 3]
Japanese Patent Laid-Open No. 04-19315
[Problems to be solved by the invention]
By the way, the exhaust gas temperature downstream of the particulate filter changes according to the amount of heat transferred between the particulate filter and the exhaust gas, so the exhaust gas temperature change downstream of the particulate filter is delayed with respect to the particulate filter temperature change. There is a case.
[0007]
In such a case, the temperature of the particulate filter may greatly exceed the predetermined temperature when the exhaust gas temperature downstream of the particulate filter reaches a predetermined temperature or higher.
[0008]
This invention is made | formed in view of the above subjects, and it aims at providing the technique which can remove suitably the microparticles | fine-particles collected by the particulate filter.
[0009]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above-described problems. That is, the present invention provides an exhaust gas for an internal combustion engine that includes a particulate filter that is provided in an exhaust passage of the internal combustion engine and collects particulates in the exhaust gas, and an oxidation removal unit that oxidizes and removes the particulates collected by the particulate filter. In the purification device, if the operating condition for reducing the intake air amount of the internal combustion engine is satisfied while the particulates collected by the particulate filter are removed by oxidation, the rate of reduction of the exhaust amount flowing into the particulate filter is reduced. Therefore, a rapid decrease in the amount of heat released from the particulate filter into the exhaust gas is suppressed.
[0010]
It is known that fine particles collected by the particulate filter are oxidized and removed from the particulate filter at a high temperature (for example, 500 ° C. to 700 ° C.) and in an oxygen-excess atmosphere.
[0011]
For this reason, when removing the particulates collected by the particulate filter from the particulate filter, the oxidation removing means removes the particulate filter to a temperature range where the particulates can be oxidized (hereinafter referred to as particulate oxidation temperature range). An oxidation removal process including a temperature raising process for raising the temperature and an air-fuel ratio process for setting the air-fuel ratio of the exhaust to an oxygen-excess air-fuel ratio (lean air-fuel ratio) is executed.
[0012]
When the oxidation removal process as described above is performed, the particulates are oxidized in the particulate filter, and it is considered that the particulate filter excessively rises in temperature due to the oxidation heat of the particulates. Since a part of the heat of the filter is released into the exhaust, if the amount of exhaust flowing into the particulate filter is large to some extent, there is no risk that the particulate filter will be excessively heated.
[0013]
However, if the intake air amount of the internal combustion engine decreases during the execution of the oxidation removal process, the amount of exhaust gas flowing into the particulate filter also decreases accordingly, so that the amount of heat released from the particulate filter into the exhaust gas decreases. Become.
[0014]
In particular, when the flow rate of exhaust gas flowing into the particulate filter decreases rapidly, the amount of heat released from the particulate filter into the exhaust gas decreases sharply, and there are particulates in the middle of oxidation when the exhaust amount decreases. Then, it is assumed that the oxidation heat of the fine particles is not released into the exhaust gas but is trapped in the particulate filter. Furthermore, there is a possibility that fine particles may continue to oxidize in the particulate filter even after the exhaust flow rate that flows into the particulate filter sharply decreases, and the oxidation heat generated at that time is not released into the exhaust gas but the particulate filter. It is assumed that it is trapped inside.
[0015]
Therefore, when the exhaust gas flow rate flowing into the particulate filter is suddenly reduced, heat tends to be trapped in the particulate filter, and the particulate filter may be excessively heated.
[0016]
On the other hand, if the rate of decrease in the amount of exhaust flowing into the particulate filter is reduced, the amount of heat released from the particulate filter into the exhaust does not decrease rapidly, making it difficult for heat to accumulate in the particulate filter. Become.
[0017]
Therefore, the exhaust gas purification apparatus for an internal combustion engine according to the present invention reduces the amount of exhaust gas flowing into the particulate filter when an operating condition for reducing the intake air amount of the internal combustion engine is satisfied during the oxidation removal processing of the particulate filter. By providing an exhaust amount adjusting means for lowering the temperature, the excessive temperature rise of the particulate filter can be suppressed.
[0018]
As a method of reducing the reduction rate of the exhaust amount flowing into the particulate filter, for example, (1) By decreasing the reduction rate of the intake air amount, the reduction rate of the exhaust amount flowing into the particulate filter is indirectly reduced. And (2) a method of directly reducing the reduction rate of the exhaust amount flowing into the particulate filter.
[0019]
As a method of reducing the reduction rate of the intake air amount, a method of reducing the valve closing speed of the intake throttle valve, a method of increasing the supercharging pressure of intake air by restricting the nozzle opening of the variable nozzle centrifugal supercharger, A method of increasing the engine speed by changing the gear ratio of the automatic transmission to the deceleration side can be exemplified.
[0020]
As a method of directly reducing the reduction rate of the exhaust amount flowing into the particulate filter, there is a method of reducing the exhaust amount recirculated by the exhaust recirculation mechanism, or the secondary air is introduced into the exhaust upstream of the particulate filter. Examples of the supply method can be given.
[0021]
In the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the exhaust gas amount adjusting means suppresses a decrease in the exhaust gas flowing into the particulate filter for a predetermined period from the time when the operating condition for reducing the intake air amount of the internal combustion engine is established. The exhaust amount may be gradually decreased after a predetermined period.
[0022]
In this case, the amount of exhaust is reduced after the heat release from the particulate filter into the exhaust is sufficiently performed, so that it becomes more difficult for heat to accumulate in the particulate filter.
[0023]
Further, in the exhaust gas purification apparatus for an internal combustion engine according to the present invention, when the exhaust gas amount adjusting means is reducing the decrease rate of the exhaust gas flowing into the particulate filter, the oxidation removing means performs the temperature increasing process as described above. Execution may be interrupted.
[0024]
In this case, since the temperature of the particulate filter is likely to decrease due to heat radiation from the particulate filter into the exhaust, heat does not accumulate in the particulate filter.
[0025]
However, in the case where the temperature of the particulate filter is excessively lowered from the particulate oxidation temperature range described above, it is difficult to restart the particulate filter oxidation removal process quickly. The oxidation removing means may continue the temperature raising process so that the temperature of the particulate filter does not excessively decrease from the particulate oxidation temperature range.
[0026]
For example, as a method of raising the temperature of the particulate filter, when a method of supplying an unburned fuel component to the particulate filter after supporting the oxidation catalyst on the particulate filter, the oxidation removing means is The supply amount of the unburned fuel component to the particulate filter may be reduced.
[0027]
In the exhaust gas purification apparatus for an internal combustion engine according to the present invention, when the operating condition for reducing the intake air amount of the internal combustion engine is satisfied, the operation amount of the accelerator pedal decreases or becomes zero, or the transmission shift of the transmission A case where the ratio is changed to the speed increasing side can be exemplified.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
A specific embodiment of an exhaust emission control device for an internal combustion engine according to the present invention will be described with reference to the drawings.
[0029]
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an exhaust gas purification apparatus according to the present invention is applied and its intake and exhaust system.
[0030]
An internal combustion engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine having four cylinders 2.
[0031]
The internal combustion engine 1 includes a fuel injection valve 3 that injects fuel directly into the combustion chamber of each cylinder 2. Each fuel injection valve 3 is connected to a pressure accumulation chamber (common rail) 4, and the common rail 4 communicates with a fuel pump 6 through a fuel supply pipe 5.
[0032]
An intake passage 7 is connected to the internal combustion engine 1, and the intake passage 7 is connected to an air cleaner box 8. An air flow meter 9 that outputs an electrical signal corresponding to the mass of the intake air flowing through the intake passage 7 is attached to the intake passage 7 downstream of the air cleaner box 8.
[0033]
A compressor housing 10 a of a variable displacement centrifugal supercharger (variable displacement turbocharger) 10 is provided in a portion of the intake passage 7 downstream of the air flow meter 9.
[0034]
An intercooler 11 is attached to the intake passage 7 downstream from the compressor housing 10a. Further, an intake throttle valve 12 for adjusting the flow rate of the intake air flowing through the intake passage 7 is provided in the intake passage 7 downstream from the intercooler 11, and an intake throttle actuator 13 is attached to the intake throttle valve 12. It has been.
[0035]
An exhaust passage 14 is connected to the internal combustion engine 1, and the exhaust passage 14 is connected to a muffler downstream. A turbine housing 10 b of the variable capacity centrifugal supercharger 10 is disposed in the exhaust passage 14. An exhaust purification catalyst 15 for purifying harmful gas components in the exhaust is disposed in a portion of the exhaust passage 14 downstream of the turbine housing 10b.
[0036]
The exhaust purification catalyst 15 is a catalyst in which an oxidation catalyst, a NOx storage reduction catalyst, a three-way catalyst, etc. are supported on a particulate filter (referred to as a particulate filter 15).
[0037]
In the exhaust passage 14 downstream of the particulate filter 15, an air-fuel ratio sensor 16 that outputs an electric signal corresponding to the air-fuel ratio of the exhaust flowing in the exhaust passage 14, and the temperature of the exhaust flowing in the exhaust passage 14 And an exhaust gas temperature sensor 17 for outputting an electrical signal corresponding to the above.
[0038]
A portion of the intake passage 7 downstream of the intake throttle valve 12 and a portion of the exhaust passage 14 upstream of the turbine housing 10 b are communicated with each other via an exhaust recirculation passage (EGR passage) 18. A flow rate adjustment valve (EGR valve) 19 is provided in the middle of the EGR passage 18.
[0039]
Further, a fuel addition valve 21 for adding fuel to the exhaust gas flowing through the exhaust port 20 is attached to the exhaust port 20 of the first cylinder 2 of the internal combustion engine 1, and the fuel addition valve 21 passes through the fuel passage 22. It is connected to the fuel pump 6 via
[0040]
The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU) 25 for controlling the internal combustion engine 1. The ECU 25 is an arithmetic logic operation circuit including a CPU, ROM, RAM, backup RAM, and the like.
[0041]
In addition to the air flow meter 9, the air-fuel ratio sensor 16, and the exhaust gas temperature sensor 17, the ECU 25 is attached to a crank position sensor 23 and a water temperature sensor 24 that are attached to the internal combustion engine 1, and a vehicle in which the internal combustion engine 1 is mounted. Various sensors such as the accelerator position sensor 26 are connected via electric wiring, and the output signals of the various sensors described above are input to the ECU 25.
[0042]
On the other hand, the fuel injection valve 3, the intake throttle actuator 13, the EGR valve 19, the fuel addition valve 21 and the like are connected to the ECU 25 via electric wiring, and the ECU 25 is connected to the fuel injection valve 3, the intake throttle actuator 13, the EGR valve. 19 and the fuel addition valve 21 can be controlled.
[0043]
For example, the ECU 25 executes input of output signals of various sensors, calculation of engine speed, calculation of fuel injection amount, calculation of fuel injection timing, and the like in a basic routine to be executed at regular intervals. Various signals input by the ECU 25 and various control values obtained by the ECU 14 in the basic routine are temporarily stored in the RAM of the ECU 25.
[0044]
Further, the ECU 25 reads various control values from the RAM in interrupt processing triggered by input of signals from various sensors and switches, elapse of a predetermined time, or input of a pulse signal from the crank position sensor 23, and the like. The fuel injection valve 3 is controlled according to the control value.
[0045]
Further, the ECU 25 executes exhaust purification control as described below as interrupt processing based on the crank position sensor 23 or interrupt processing at regular intervals.
[0046]
In the exhaust gas purification control, the ECU 25 collects particulates (PM: PM) collected in the particulate filter 15 when an oxidation removal processing execution condition (hereinafter referred to as PM oxidation removal execution condition) of the particulate filter 15 is satisfied. In order to remove Particulate Matter, PM oxidation removal processing is executed.
[0047]
An example of the PM oxidation removal process execution condition is a condition that the amount of PM collected by the particulate filter 15 is a certain amount or more.
[0048]
As a method for determining whether or not the amount of PM collected by the particulate filter 15 is equal to or larger than a certain amount, a differential pressure across the particulate filter 15 (exhaust pressure upstream of the particulate filter 15 and particulate filter 15). A method of determining that the amount of PM trapped by the particulate filter 15 is equal to or greater than a certain amount when the differential pressure with respect to the exhaust gas pressure further downstream is equal to or greater than a certain pressure, or from the end of the previous execution of PM oxidation removal processing A method of determining that the amount of PM collected by the particulate filter 15 is equal to or greater than a certain amount when the integrated value of the fuel injection amount is equal to or greater than a certain amount can be exemplified.
[0049]
When it is determined that the PM oxidation removal process execution condition is established by the above-described method, the ECU 25 increases the temperature of the particulate filter 15 to raise the temperature to a high temperature range of about 500 ° C to 700 ° C. A temperature process is performed, and an air-fuel ratio process is performed to make the exhaust gas flowing into the particulate filter 15 an oxygen-excess atmosphere.
[0050]
As a method for executing the temperature raising process, for example, (1) a method of increasing the exhaust temperature to transmit the heat of the exhaust to the particulate filter 15, and (2) oxidizing unburned fuel in the particulate filter 15, Examples thereof include a method of raising the temperature of the particulate filter 15 itself by the reaction heat generated at the time.
[0051]
As a specific method of the above (1), a method of retarding the combustion timing of the air-fuel mixture in the internal combustion engine 1, fuel is subsidiarily supplied from the fuel injection valve 3 of the cylinder 2 during the expansion stroke in the internal combustion engine 1. Examples thereof include a method of extending the combustion period by injecting (sub-injection), a method of causing low-temperature combustion in the internal combustion engine 1 by increasing the amount of EGR gas, and the like.
[0052]
Specific methods of the above (2) include a method of adding fuel into the exhaust from the fuel addition valve 21, a method of performing sub-injection from the fuel injection valve 3 of the cylinder 2 during the exhaust stroke in the internal combustion engine 1, and the like. It can be illustrated.
[0053]
In the air-fuel ratio process, the air-fuel ratio sensor is used when a method of performing sub-injection from the fuel injection valve 3 or a method of adding fuel into the exhaust gas from the fuel addition valve 21 is adopted as a method of executing the temperature raising process described above. In this control, the amount of fuel sub-injected from the fuel injection valve 3 or the amount of fuel added to the exhaust gas from the fuel addition valve 21 is adjusted so that the output signal value of 16 becomes a value corresponding to the lean air-fuel ratio.
[0054]
When the PM oxidation removal process as described above is executed, the PM collected in the particulate filter 15 is oxidized, and the PM is removed from the particulate filter 15.
[0055]
By the way, when PM is oxidized in the particulate filter 15 by the execution of the PM oxidation removal process as described above, it is considered that the temperature of the particulate filter 15 is excessively increased by the oxidation heat of the PM. Since a part of the heat is released into the exhaust, if the amount of exhaust flowing into the particulate filter 15 is large to some extent, there is no possibility that the particulate filter 15 will be excessively heated.
[0056]
However, if the intake air amount of the internal combustion engine 1 decreases during the execution of the oxidation removal process of the particulate filter 15, the amount of exhaust gas flowing into the particulate filter 15 also decreases accordingly, so that the particulate filter 15 discharges into the exhaust gas. The amount of heat generated will be reduced.
[0057]
In particular, when the output signal (accelerator opening) of the accelerator position sensor 26 becomes “0” during the execution of the PM oxidation removal process, in other words, the internal combustion engine 1 is decelerated during the execution of the PM oxidation removal process. In this case, since the opening degree of the intake throttle valve 12 is rapidly reduced to an opening degree close to full closing, the intake air amount of the internal combustion engine 1 decreases rapidly, and the exhaust flow rate flowing into the particulate filter 15 also increases. It will decrease rapidly.
[0058]
In this case, since the amount of heat released from the particulate filter 15 into the exhaust gas is rapidly reduced, if PM in the middle of oxidation exists in the particulate filter 15 when the accelerator opening becomes “0”, the PM It is assumed that this oxidation heat is not released into the exhaust gas but is trapped in the particulate filter 15.
[0059]
Further, PM may be oxidized in the particulate filter 15 even after the exhaust flow rate flowing into the particulate filter 15 is sharply reduced. The oxidation heat generated at that time is also trapped in the particulate filter 15. It is assumed that
[0060]
Therefore, after the exhaust flow rate flowing into the particulate filter 15 is suddenly reduced, heat tends to be trapped in the particulate filter 15 and the particulate filter 15 may be excessively heated.
[0061]
On the other hand, in the exhaust purification control in the present embodiment, the ECU 25 performs the particulate filter when the output signal (accelerator opening) of the accelerator position sensor 26 becomes “0” during the execution of the PM oxidation removal process. The reduction rate of the exhaust flow rate through 15 is reduced.
[0062]
As a method of reducing the reduction rate of the exhaust flow rate flowing through the particulate filter 15, (1) a method of reducing the reduction rate of the intake air amount of the internal combustion engine 1 by reducing the closing speed of the intake throttle valve 12. (2) A method of reducing the rate of reduction of the intake air amount of the internal combustion engine 1 by reducing the amount of EGR gas, and (3) a supercharging pressure by reducing the nozzle vane opening of the variable displacement centrifugal supercharger. (4) An automatic transmission is connected to the internal combustion engine 1 and the gear ratio of the automatic transmission is changed to the deceleration side to increase the engine speed. (5) A secondary air injection valve is attached to the exhaust passage 14 upstream of the particulate filter 15, and the secondary air is increased. Method for injecting secondary air from events, can be exemplified, and the like. In the present embodiment, an example in which the reduction rate of the exhaust flow rate flowing through the particulate filter 15 is reduced by a method of reducing the valve closing speed of the intake throttle valve 12 will be described.
[0063]
For example, the ECU 25 starts from the time when the output signal (accelerator opening) of the accelerator position sensor 26 indicates “0” as shown by the dotted line in FIG. 2 at normal times (when the PM oxidation removal process is not executed). While the intake throttle valve 12 is rapidly closed, the time when the output signal (accelerator opening) of the accelerator position sensor 26 indicates “0” as shown by the solid line in FIG. The intake throttle valve 12 may be gradually closed from the beginning.
[0064]
Further, the ECU 25 normally closes the intake throttle valve 12 immediately after the output signal (accelerator opening) of the accelerator position sensor 26 indicates “0” as indicated by a dotted line in FIG. When the PM oxidation removal process is executed, as indicated by a solid line in FIG. 3, the intake throttle valve 12 is closed for a predetermined time from the time when the output signal (accelerator opening) of the accelerator position sensor 26 indicates “0”. (The opening when the output signal of the accelerator position sensor 26 becomes “0” is maintained), and the intake throttle valve 12 is closed from the time when the predetermined time: t has elapsed. Good.
[0065]
As described in the explanation of FIG. 2 or FIG. 3 above, when the closing speed of the intake throttle valve 12 at the time of executing the PM oxidation removal processing is reduced from the normal time, the accelerator opening becomes “0”. The time required from when the intake throttle valve 12 is opened to near the fully closed position (hereinafter referred to as valve closing required time) is longer when the PM oxidation removal process is executed than when it is normal.
[0066]
Therefore, the exhaust flow rate that flows through the particulate filter 15 within the required valve closing time during execution of the PM oxidation removal process is larger than the exhaust flow rate that flows through the particulate filter 15 within the normal required valve closing time.
[0067]
As a result, the amount of heat released from the particulate filter 15 into the exhaust gas within the required valve closing time during execution of the PM oxidation removal process is released from the particulate filter 15 into the exhaust gas within the normal valve closing time. More than heat.
[0068]
However, if the above-described temperature raising process is continuously performed within the valve closing time, PM oxidation is continued in the particulate filter 15, which may cause excessive temperature rise of the particulate filter 15. Therefore, it is preferable to interrupt execution of the temperature raising process within the required valve closing time.
[0069]
Hereinafter, the exhaust purification control in the present embodiment will be described with reference to FIG.
[0070]
FIG. 4 is a flowchart showing an exhaust purification control routine in the present embodiment. The exhaust purification control routine is a routine that is stored in advance in the ROM of the ECU 25, and is a routine that is executed by the ECU 25 as an interrupt process triggered by the passage of a fixed time or the input of a pulse signal from the crank position sensor 23. .
[0071]
In the exhaust purification control routine, the ECU 25 first determines whether or not the PM oxidation removal process execution condition is satisfied in S401.
[0072]
If it is determined in S401 that the PM oxidation removal process execution condition is not satisfied, the ECU 25 ends the execution of this routine.
[0073]
If it is determined in S401 that the PM oxidation removal process execution condition is satisfied, the ECU 25 proceeds to S402 and executes the PM oxidation removal process. Specifically, the ECU 25 executes the above-described temperature increase process and air-fuel ratio process.
[0074]
In S403, the ECU 25 determines whether or not the PM oxidation removal process execution end condition is satisfied. As the PM oxidation removal process execution end condition, for example, the execution time of the PM oxidation removal process is a predetermined time or more, or the differential pressure across the particulate filter 15 (exhaust pressure upstream of the particulate filter 15). And the pressure difference between the exhaust pressure downstream of the particulate filter 15 and the exhaust gas pressure) is a certain pressure or less.
[0075]
The predetermined time described above is, for example, a time determined according to the amount of PM collected by the particulate filter 15, and is a time set longer as the amount of PM collected by the particulate filter 15 increases. Moreover, the above-described constant pressure is a pressure corresponding to a differential pressure before and after the particulate filter 15 does not collect PM.
[0076]
If it is determined in S403 that the PM oxidation removal process execution termination condition is not satisfied, the ECU 25 proceeds to S404 and determines whether the deceleration operation condition of the internal combustion engine 1 is satisfied. Examples of the deceleration operation condition of the internal combustion engine 1 include a condition that the engine speed is higher than a certain speed and the output signal (accelerator opening) of the accelerator position sensor 26 is “0”.
[0077]
When it is determined in S404 that the deceleration operation condition of the internal combustion engine 1 is not satisfied, the ECU 25 executes the above-described processing after S403 again.
[0078]
If it is determined in S404 that the deceleration operation condition of the internal combustion engine 1 is satisfied, the ECU 25 proceeds to S405 and closes the intake throttle valve 12 as described in the description of FIG. 2 or FIG. The intake throttling actuator 13 is controlled to reduce the valve speed from the normal time.
[0079]
Subsequently, the ECU 25 proceeds to S406, interrupts the execution of the temperature raising process of the particulate filter 15, and ends the execution of this routine.
[0080]
In this way, when the ECU 25 executes the exhaust purification control routine, when the operating condition for reducing the intake air amount of the internal combustion engine 1 is satisfied during the PM oxidation removal processing of the particulate filter 15, the intake throttle valve 12 is satisfied. The required valve closing time becomes longer than usual, and the temperature raising process of the particulate filter 15 is not executed within the required valve closing time.
[0081]
If the required time for closing the intake throttle valve 12 is longer than usual, the rate of decrease in the exhaust flow rate flowing into the particulate filter 15 decreases, and therefore when the operating condition for reducing the intake air amount of the internal combustion engine 1 is established. Even if PM in the middle of oxidation is present in the particulate filter 15, the oxidation heat of the PM is released into the exhaust gas.
[0082]
Furthermore, if the required time for closing the intake throttle valve 12 becomes longer than normal, and if the temperature raising process of the particulate filter 15 is not executed within the required time for closing the valve, the particulates will be processed within the required time for closing the valve. Since the temperature of the filter 15 is lowered, the oxidation of PM is not continued in the particulate filter 15 after the operation condition for reducing the intake air amount of the internal combustion engine 1 is established.
[0083]
Therefore, according to the exhaust purification control in the present embodiment, when the operating condition for reducing the intake air amount of the internal combustion engine 1 is satisfied during the PM oxidation removal process of the particulate filter 15, the particulate filter 15 is excessive. It is possible to prevent an increase in temperature.
[0084]
In the exhaust purification control according to the present embodiment, the example in which the execution of the temperature raising process is interrupted within the valve closing required time has been described. However, the temperature raising process is performed to such an extent that excessive temperature decrease of the particulate filter 15 is prevented. May be executed.
[0085]
For example, as a method of executing the temperature raising process, a method of raising the temperature of the particulate filter 15 itself by oxidizing unburned fuel in the particulate filter 15, that is, from the fuel addition valve 21 into the exhaust gas is employed. When the method of adding fuel or the method of sub-injecting fuel from the fuel injection valve 3 of the cylinder 2 during the exhaust stroke is adopted, the amount of fuel added from the fuel addition valve 21 or the fuel injection valve 3 By reducing the sub-injection amount, it is possible to prevent an excessive temperature rise of the particulate filter 15 and at the same time prevent an excessive temperature drop of the particulate filter 15.
[0086]
In this case, when the internal combustion engine 1 returns from the deceleration operation state to the normal operation state, the PM oxidation removal process can be immediately resumed.
[0087]
【The invention's effect】
According to the present invention, the exhaust gas of the internal combustion engine provided with the particulate filter that is provided in the exhaust passage of the internal combustion engine and collects particulates in the exhaust gas, and the oxidation removing means that oxidizes and removes the particulates collected by the particulate filter. In the purification apparatus, when an operating condition for reducing the intake air amount of the internal combustion engine is satisfied during the oxidation removal processing of the particulate filter, it is possible to suppress a rapid decrease in the amount of heat released from the particulate filter into the exhaust gas. Accordingly, it is possible to prevent excessive temperature rise of the particulate filter.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied.
FIG. 2 is a diagram showing the relationship between the opening of the intake throttle valve and time (1)
FIG. 3 is a diagram showing the relationship between the opening of the intake throttle valve and time (2)
FIG. 4 is a flowchart showing an exhaust purification control routine.
[Explanation of symbols]
1 ... Internal combustion engine
10. ・ Variable capacity centrifugal supercharger
12. Intake throttle valve
13. ・ Intake throttle actuator
15. ・ Particulate filter
18. EGR passage
19. EGR valve
21. Fuel addition valve
25. ・ ECU

Claims (7)

A particulate filter disposed in an exhaust passage of an internal combustion engine and having a function of collecting particulates contained in the exhaust and a function of oxidizing a reducing component in the exhaust;
Ri by the supplying the fuel to the particulate filter, and oxidation removal means for performing a PM oxidation removal process you oxidizing remove particles trapped in the particulate filter,
If operating conditions to reduce the intake air amount of the internal combustion engine during the previous SL PM oxidation removal process is formed upright, reducing the intake air amount of the internal combustion engine during non-execution of the PM oxidation removal process as compared with the case where the operating condition is satisfied, and the previous SL exhaust quantity adjusting means for reducing the rate of reduction amount of the exhaust gas flowing into the particulate filter,
Fuel supply control means for reducing the amount of fuel supplied to the particulate filter when the exhaust amount adjusting means is reducing the reduction rate of the exhaust amount flowing into the particulate filter;
An exhaust emission control device for an internal combustion engine, comprising:   2. The exhaust gas amount adjusting means suppresses a decrease in an exhaust gas amount flowing into the particulate filter for a predetermined period from a time point when an operating condition for decreasing the intake air amount of the internal combustion engine is established. 2. An exhaust gas purification apparatus for an internal combustion engine according to 1. Further comprising an intake throttle valve provided in an intake passage of the internal combustion engine, the exhaust quantity adjusting means, if the operating conditions to close the front Symbol intake throttle valve during execution of the PM oxidation removal process has been established the compared if the conditions for closing the intake throttle valve is established during the non-execution of the PM oxidation removal process, according to claim 1 or, characterized in that to reduce the closing speed before Symbol intake throttle valve 2. An exhaust emission control device for an internal combustion engine according to 2. A variable nozzle centrifugal supercharger for compressing intake air of the internal combustion engine;
The exhaust amount adjusting means restricts the nozzle opening of the variable nozzle centrifugal supercharger when an operating condition for reducing the intake air amount of the internal combustion engine is satisfied. An exhaust gas purification apparatus for an internal combustion engine as described. An exhaust gas recirculation mechanism for recirculating a part of the exhaust gas discharged from the internal combustion engine to the internal combustion engine;
The exhaust amount adjusting means controls the exhaust gas recirculation mechanism to reduce the exhaust amount recirculated to the internal combustion engine when an operating condition for decreasing the intake air amount of the internal combustion engine is satisfied. The exhaust emission control device for an internal combustion engine according to claim 1. An automatic transmission connected to the internal combustion engine;
The exhaust amount adjusting means controls the automatic transmission to change the gear ratio of the automatic transmission to a deceleration side when an operating condition for reducing the intake air amount of the internal combustion engine is satisfied. The exhaust emission control device for an internal combustion engine according to claim 1. It is formed elevational operating conditions to reduce the intake air amount before SL internal combustion engine during the execution of the PM oxidation removal process for oxidizing dividing removed by the particulates trapped in the particulate filter disposed in an exhaust passage of the internal combustion engine If you decrease the rate of decrease of the flow rate of the exhaust gas flowing through the pre-Symbol particulate filter in comparison with the case operating conditions to reduce the intake air amount of the internal combustion engine during non-execution of the PM oxidation removal process is established Tomo to, be reduced the amount of fuel supplied to the pre-Symbol particulate filter in comparison with the prior operating conditions to reduce the intake air amount of the internal combustion engine the a running PM oxidation removal process is established and An exhaust gas purification method for an internal combustion engine.

Images