JP2004197576A - Emission control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology with which a particulate collected with a particulate filter installed in an exhaust passage of an internal combustion engine can be suitably trapped. <P>SOLUTION: The emission control device of the internal combustion engine is provided with the particulate filter installed in the exhaust passage of the internal combustion engine, and an oxidation removal means for oxidation removing the particulate collected with the particulate filter. When an operating condition that an intake air flow of the internal combustion engine is reduced in the oxidation processing of the particulate filter is established, and the amount of heat released from the particulate filter into the exhaust gas is suppressed from rapidly decreasing. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exhaust gas purification technology for an internal combustion engine mounted on an automobile or the like, and particularly to an exhaust gas purification device for an internal combustion engine provided with a particulate filter that traps particulates in exhaust gas.
[0002]
[Prior art]
2. Description of the Related Art In recent years, a technique for suppressing the emission of particulates (PM) such as soot into the atmosphere has been desired for an internal combustion engine mounted on an automobile or the like.
[0003]
In response to such a demand, there is known a technique in which a particulate filter is arranged in an exhaust passage of an internal combustion engine, and fine particles discharged from the internal combustion engine are collected by the particulate filter.
[0004]
Since the amount of fine particles that can be collected by the particulate filter is limited, it is necessary to appropriately remove the fine particles collected by the particulate filter from the particulate filter. As a method of removing the fine particles trapped in the particulate filter, the inside of the particulate filter is set to an oxidizing atmosphere (that is, an oxygen-excess atmosphere) while raising the temperature of the particulate filter to a temperature range in which the fine particles can be oxidized. Is generally used to oxidize and remove fine particles, but if the temperature of the particulate filter becomes excessively high at this time, there is a possibility that the particulate filter may be thermally degraded.
[0005]
Therefore, in an exhaust gas purifying 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 was estimated from the exhaust gas temperature downstream of the particulate filter, and the estimated value was estimated. A technique for adjusting the amount of exhaust gas flowing into a particulate filter according to a temperature has been proposed (for example, see Patent Document 1).
[0006]
[Patent Document 1]
JP-A-2002-106325
[Patent Document 2]
JP 05-222916 A
[Patent Document 3]
JP-A-04-19315
[Problems to be solved by the invention]
By the way, since 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, the temperature change of the exhaust gas downstream of the particulate filter is delayed with respect to the temperature change of the particulate filter. May be.
[0007]
In such a case, there is a possibility that the temperature of the particulate filter is significantly higher than the predetermined temperature when the exhaust gas temperature downstream of the particulate filter reaches or exceeds a predetermined temperature.
[0008]
The present invention has been made in view of the above problems, and has as its object to provide a technique capable of suitably removing fine particles collected by a particulate filter.
[0009]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above problems. That is, the present invention provides a particulate filter provided in an exhaust passage of an internal combustion engine for collecting particulates in exhaust gas, and an exhaust gas for an internal combustion engine provided with an oxidation removing means for oxidizing and removing particulates collected by the particulate filter. In the purifying apparatus, when the operating condition for reducing the intake air amount of the internal combustion engine is satisfied while oxidizing and removing the particulate matter trapped in the particulate filter, the reduction rate of the exhaust gas flowing into the particulate filter is reduced. Thus, a rapid decrease in the amount of heat released from the particulate filter into the exhaust gas is suppressed.
[0010]
It is known that the fine particles collected by the particulate filter are oxidized and removed from the particulate filter in an atmosphere of high temperature (for example, 500 ° C. to 700 ° C.) and excess oxygen.
[0011]
For this reason, when removing the fine particles trapped by the particulate filter from the particulate filter, the oxidation removing means sets the particulate filter to a temperature range in which the fine particles can be oxidized (hereinafter, referred to as a fine particle oxidation temperature range). Oxidation removal processing including temperature raising processing for raising the temperature and air-fuel ratio processing for setting the air-fuel ratio of the exhaust gas to an air-fuel ratio with an excess of oxygen (lean air-fuel ratio) is executed.
[0012]
When the above-described oxidation removal processing is performed, the particulates are oxidized in the particulate filter. Therefore, it is conceivable that the temperature of the particulate filter rises excessively due to the heat of oxidation of the particulates. Since a part of the heat of the filter is released into the exhaust gas, if the amount of exhaust gas flowing into the particulate filter is large to some extent, there is no possibility that the temperature of the particulate filter rises excessively.
[0013]
However, if the amount of intake air of the internal combustion engine decreases during the oxidation removal process, the amount of exhaust flowing into the particulate filter also decreases accordingly, so the amount of heat released from the particulate filter into the exhaust decreases. Become.
[0014]
In particular, when the flow rate of the exhaust gas flowing into the particulate filter decreases rapidly, the amount of heat released from the particulate filter into the exhaust gas sharply decreases. Then, it is assumed that the heat of oxidation of the fine particles is not released into the exhaust gas but remains in the particulate filter. Further, even after the exhaust gas flow rate flowing into the particulate filter is rapidly reduced, the fine particles may continue to be oxidized in the particulate filter, and the oxidizing heat generated at that time is not released into the exhaust gas and the particulate filter is not released. It is assumed that they are kept inside.
[0015]
Therefore, when the flow rate of exhaust gas flowing into the particulate filter is rapidly reduced, heat tends to be trapped in the particulate filter, and the temperature of the particulate filter may be excessively increased.
[0016]
On the other hand, when the rate of reduction of the amount of exhaust gas flowing into the particulate filter is reduced, the amount of heat released from the particulate filter into the exhaust gas does not rapidly decrease, so that heat is less likely to be trapped in the particulate filter. Become.
[0017]
Therefore, the exhaust gas purifying apparatus for an internal combustion engine according to the present invention is capable of reducing the rate of decrease in the amount of exhaust gas flowing into the particulate filter when an operating condition for reducing the amount of intake air of the internal combustion engine is satisfied during the oxidation removal processing of the particulate filter. With the provision of the exhaust gas amount adjusting means for reducing the temperature, the excessive temperature rise of the particulate filter can be suppressed.
[0018]
As a method of reducing the rate of decrease of the amount of exhaust gas flowing into the particulate filter, for example, (1) reducing the rate of decrease of the amount of intake air to indirectly reduce the rate of reduction of the amount of exhaust gas flowing into the particulate filter And (2) a method of directly reducing the reduction rate of the amount of exhaust gas flowing into the particulate filter.
[0019]
As a method of decreasing the decreasing speed of the intake air amount, a method of decreasing the closing speed of the intake throttle valve, a method of increasing the supercharging pressure of the intake by reducing the nozzle opening of the variable nozzle centrifugal supercharger, For example, a method of increasing the engine speed by changing the speed ratio of the automatic transmission to the reduction side can be exemplified.
[0020]
As a method of directly reducing the reduction rate of the amount of exhaust gas flowing into the particulate filter, a method of reducing the amount of exhaust gas recirculated by the exhaust gas recirculation mechanism, a method of discharging secondary air into exhaust gas upstream of the particulate filter. A supply method and the like can be exemplified.
[0021]
In the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, the exhaust gas amount adjusting means suppresses a decrease in the amount of 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 satisfied. Alternatively, the exhaust amount may be gradually reduced after a predetermined period has elapsed.
[0022]
In this case, since the amount of exhaust gas is reduced after sufficient heat radiation from the particulate filter into the exhaust gas, heat is less likely to be trapped in the particulate filter.
[0023]
Further, in the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, when the exhaust gas amount adjusting means reduces the rate of reduction of the amount of exhaust gas flowing into the particulate filter, the oxidation removing means performs the above-described temperature increasing process. The execution may be interrupted.
[0024]
In this case, the temperature of the particulate filter tends to decrease due to heat radiation from the particulate filter into the exhaust gas, so that heat does not remain in the particulate filter.
[0025]
However, when the temperature of the particulate filter is excessively lowered from the particulate oxidation temperature range described above, it becomes difficult to quickly restart the oxidation removal processing of the particulate filter. Alternatively, the oxidation removing means may continue the temperature increasing process to such an extent 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 supporting an oxidation catalyst on the particulate filter and then supplying an unburned fuel component to the particulate filter is adopted, the oxidation removing unit is The supply amount of the unburned fuel component to the particulate filter may be reduced.
[0027]
In the exhaust gas purifying 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 is reduced or becomes zero, or the speed change of the transmission is performed. A case where the ratio is changed to the speed increasing side can be exemplified.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
A specific embodiment of an exhaust gas purification 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 device according to the present invention is applied and an intake and exhaust system thereof.
[0030]
The 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 for directly injecting fuel into a combustion chamber of each cylinder 2. Each fuel injection valve 3 is connected to a pressure accumulation chamber (common rail) 4, which communicates with a fuel pump 6 via 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 electric 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 10a 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 of the compressor housing 10a. Further, an intake throttle valve 12 for adjusting a flow rate of intake air flowing through the intake passage 7 is provided in the intake passage 7 downstream of the intercooler 11, and an intake throttle actuator 13 is attached to the intake throttle valve 12. Have been.
[0035]
An exhaust passage 14 is connected to the internal combustion engine 1, and the exhaust passage 14 is connected downstream to a muffler. A turbine housing 10b of the variable displacement centrifugal turbocharger 10 is arranged in the exhaust passage 14. An exhaust purification catalyst 15 for purifying harmful gas components in exhaust gas 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, an NOx storage reduction catalyst, a three-way catalyst, and the like are supported on a particulate filter (hereinafter, referred to as a particulate filter 15).
[0037]
An exhaust passage 14 downstream of the particulate filter 15 has an air-fuel ratio sensor 16 that outputs an electric signal corresponding to the air-fuel ratio of the exhaust flowing through the exhaust passage 14, and a temperature of the exhaust flowing through the exhaust passage 14. And an exhaust gas temperature sensor 17 for outputting an electric 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 10b are communicated via an exhaust gas recirculation passage (EGR passage) 18. A flow regulating valve (EGR valve) 19 is provided in the middle of the EGR passage 18.
[0039]
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. It is connected to the fuel pump 6 through the above.
[0040]
The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU: Electronic Control Unit) 25 for controlling the internal combustion engine 1. The ECU 25 is an arithmetic and logic operation circuit including a CPU, a ROM, a RAM, a backup RAM, and the like.
[0041]
The ECU 25 includes, in addition to the air flow meter 9, the air-fuel ratio sensor 16, and the exhaust gas temperature sensor 17, a crank position sensor 23 and a water temperature sensor 24 attached to the internal combustion engine 1, and an ECU 25 installed in a vehicle equipped with the internal combustion engine 1. Various sensors such as the accelerator position sensor 26 are connected via electric wiring, and output signals of the above-described various sensors are input to the ECU 25.
[0042]
On the other hand, the ECU 25 is connected to the fuel injection valve 3, the intake throttle actuator 13, the EGR valve 19, the fuel addition valve 21, and the like via electric wiring. 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 the input of output signals of various sensors, the calculation of the engine speed, the calculation of the fuel injection amount, the calculation of the fuel injection timing, and the like in a basic routine to be executed at regular intervals. Various signals input by the ECU 25 in the basic routine and various control values obtained by the calculation of the ECU 14 are temporarily stored in the RAM of the ECU 25.
[0044]
Further, the ECU 25 reads various control values from the RAM in an interrupt process 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 the following exhaust gas purification control as an interruption process based on the crank position sensor 23 or an interruption process at regular time intervals.
[0046]
In the exhaust gas purification control, when the condition for executing the oxidation removal process of the particulate filter 15 (hereinafter referred to as the condition for executing the PM oxidation removal process) is satisfied, the ECU 25 determines that the particulate matter (PM: A PM oxidation removal process is performed to remove Particulate Matter.
[0047]
Examples of the conditions for performing the PM oxidation removal process include a condition that the amount of PM collected by the particulate filter 15 is equal to or more than a certain amount.
[0048]
As a method for determining whether or not the amount of PM collected by the particulate filter 15 is equal to or more than a certain amount, a differential pressure across the particulate filter 15 (the exhaust pressure upstream of the particulate filter 15 and the particulate filter 15 A method of determining that the PM trapping amount of the particulate filter 15 is equal to or greater than a predetermined amount when the pressure difference (differential pressure from the downstream exhaust pressure) is equal to or higher than a certain pressure, or from the end of execution of the previous PM oxidation removal process. When the integrated value of the fuel injection amount is equal to or more than a certain amount, a method of determining that the PM trapping amount of the particulate filter 15 is equal to or more than a certain amount can be exemplified.
[0049]
When it is determined that the PM oxidation removal processing execution condition is satisfied by the method described above, the ECU 25 increases the temperature of the particulate filter 15 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]
Examples of the method of performing the temperature raising process include: (1) a method of increasing the exhaust gas temperature to transfer the heat of the exhaust gas to the particulate filter 15; and (2) oxidizing the unburned fuel in the particulate filter 15, A method of raising the temperature of the particulate filter 15 itself by reaction heat generated at the time can be exemplified.
[0051]
As a specific method of the above (1), there is a method of retarding the combustion timing of the air-fuel mixture in the internal combustion engine 1, and the fuel is secondarily supplied from the fuel injection valve 3 of the cylinder 2 during the expansion stroke in the internal combustion engine 1. Examples include a method of prolonging the combustion period by performing injection (sub-injection) and a method of performing low-temperature combustion in the internal combustion engine 1 by increasing the amount of EGR gas.
[0052]
As a specific method of the above (2), a method of adding fuel to the exhaust gas from the fuel addition valve 21, a method of performing a sub-injection from the fuel injection valve 3 of the cylinder 2 at the time of the exhaust stroke in the internal combustion engine 1, and the like. Examples can be given.
[0053]
In the air-fuel ratio process, as a method of performing the above-mentioned temperature raising process, when a method of performing sub-injection from the fuel injection valve 3 or a method of adding fuel to the exhaust gas from the fuel addition valve 21 is employed, the air-fuel ratio sensor is used. This is a control for adjusting the amount of fuel injected sub-injected from the fuel injection valve 3 or the amount of fuel added to the exhaust from the fuel addition valve 21 so that the output signal value of 16 becomes a value corresponding to the lean air-fuel ratio.
[0054]
When the PM oxidation removal processing as described above is performed, PM trapped in the particulate filter 15 is oxidized, and PM is removed from the particulate filter 15.
[0055]
By the way, when PM is oxidized in the particulate filter 15 by performing the above-described PM oxidation removal processing, it is considered that the particulate filter 15 is excessively heated by heat of oxidation of the PM. Since a part of the heat is released into the exhaust gas, if the amount of exhaust gas flowing into the particulate filter 15 is large to some extent, there is no possibility that the temperature of the particulate filter 15 will rise excessively.
[0056]
However, if the intake air amount of the internal combustion engine 1 decreases during the oxidation removal processing of the particulate filter 15, the amount of exhaust gas flowing into the particulate filter 15 decreases accordingly. 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 processing, in other words, the internal combustion engine 1 is decelerated during the execution of the PM oxidation removal processing. In this case, since the opening degree of the intake throttle valve 12 is rapidly reduced to an opening degree close to the fully closed state, the intake air amount of the internal combustion engine 1 is rapidly reduced, and the exhaust flow rate flowing into the particulate filter 15 is also reduced. It will decrease sharply.
[0058]
In this case, since the amount of heat released from the particulate filter 15 into the exhaust gas rapidly decreases, if PM that is being oxidized is present in the particulate filter 15 when the accelerator opening becomes “0”, the PM It is assumed that the heat of oxidation is not released into the exhaust gas and remains in the particulate filter 15.
[0059]
Further, even after the exhaust flow rate flowing into the particulate filter 15 is sharply reduced, PM may be oxidized in the particulate filter 15, and the heat of oxidation generated at that time and the basket in the particulate filter 15 may not be oxidized. It is assumed that
[0060]
Therefore, after the flow rate of exhaust gas flowing into the particulate filter 15 sharply decreases, heat tends to be trapped in the particulate filter 15, and the temperature of the particulate filter 15 may be excessively increased.
[0061]
On the other hand, in the exhaust gas purification control according to the present embodiment, the ECU 25 sets 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 processing. The speed of decrease of the flow rate of the exhaust gas flowing through No. 15 is reduced.
[0062]
As a method of decreasing the decreasing speed of the exhaust flow rate flowing through the particulate filter 15, (1) a method of decreasing the closing speed of the intake throttle valve 12 to reduce the decreasing speed of the intake air amount of the internal combustion engine 1. (2) a method of reducing the rate of reduction of the amount of intake air of the internal combustion engine 1 by reducing the amount of EGR gas; and (3) the supercharging pressure by reducing the nozzle vane opening of the variable displacement centrifugal supercharger. And (4) connecting an automatic transmission to the internal combustion engine 1 and changing the speed ratio of the automatic transmission to the reduction side. (5) A secondary air injection valve is installed in the exhaust passage 14 upstream of the particulate filter 15 to increase the rotational speed and thereby reduce the rate of decrease in the amount of intake air of the internal combustion engine 1. Method for injecting secondary air from events, can be exemplified, and the like. Note that, in the present embodiment, an example will be described in which the rate of decrease in the flow rate of exhaust gas flowing through the particulate filter 15 is reduced by a method of reducing the closing speed of the intake throttle valve 12.
[0063]
For example, during normal times (when the PM oxidation removal process is not performed), 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. 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.
[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 shown by a dotted line in FIG. During execution of the PM oxidation removal process, as shown by the solid line in FIG. 3, for a fixed time from when the output signal (accelerator opening) of the accelerator position sensor 26 indicates "0": t closes the intake throttle valve 12. The throttle valve 12 may be closed without keeping the opening degree at the time when the output signal of the accelerator position sensor 26 becomes “0”, and after the lapse of the predetermined time t. Good.
[0065]
As described in the description of FIG. 2 or FIG. 3 above, when the closing speed of the intake throttle valve 12 during the PM oxidation removal process is reduced from the normal time, the time when the accelerator opening becomes “0” The required time (hereinafter, referred to as a required valve closing time) from the time when the intake throttle valve 12 reaches an opening degree near the fully closed state (hereinafter, referred to as a required valve closing time) is longer when the PM oxidation removal process is performed than in the normal case.
[0066]
Therefore, the flow rate of exhaust gas flowing through the particulate filter 15 within the required valve closing time during execution of the PM oxidation removal process is greater than the flow rate of exhaust gas flowing through the particulate filter 15 within the required valve closing time at normal times.
[0067]
As a result, the amount of heat released into the exhaust from the particulate filter 15 within the required valve closing time during the execution of the PM oxidation removal process is released from the particulate filter 15 into the exhaust within the normal valve closing required time. More than the amount of heat.
[0068]
However, if the above-described temperature raising process is continuously executed within the valve closing required time, the oxidation of PM in the particulate filter 15 is continued, which may cause an excessive temperature rise of the particulate filter 15. Therefore, it is preferable to interrupt the execution of the temperature raising process within the required valve closing time.
[0069]
Hereinafter, the exhaust gas purification control in the present embodiment will be described with reference to FIG.
[0070]
FIG. 4 is a flowchart illustrating an exhaust gas purification control routine according to the present embodiment. The exhaust gas purification control routine is a routine stored in the ROM of the ECU 25 in advance, and is a routine executed by the ECU 25 as an interrupt process triggered by elapse of a predetermined time or input of a pulse signal from the crank position sensor 23 and the like. .
[0071]
In the exhaust gas purification control routine, the ECU 25 first determines in S401 whether or not the conditions for executing the PM oxidation removal processing are satisfied.
[0072]
If it is determined in S401 that the condition for executing the PM oxidation removal process is not satisfied, the ECU 25 ends the execution of this routine.
[0073]
If it is determined in S401 that the condition for executing the PM oxidation removal process is satisfied, the ECU 25 proceeds to S402 and executes the PM oxidation removal process. Specifically, the ECU 25 executes the above-described temperature raising processing and air-fuel ratio processing.
[0074]
In S403, the ECU 25 determines whether a condition for terminating the execution of the PM oxidation removal process is satisfied. As the condition for ending the PM oxidation removal processing, for example, the execution time of the PM oxidation removal processing is equal to or longer than a predetermined time, or the differential pressure across the particulate filter 15 (the exhaust pressure upstream of the particulate filter 15). And the exhaust gas pressure downstream of the particulate filter 15) is equal to or less than a predetermined pressure.
[0075]
The above-mentioned predetermined time is, for example, a time determined according to the PM trapping amount of the particulate filter 15, and is set to be longer as the PM trapping amount of the particulate filter 15 increases. Further, the above-mentioned constant pressure is a pressure corresponding to a pressure difference before and after when the particulate filter 15 is not collecting PM.
[0076]
If it is determined in S403 that the condition for ending the PM oxidation removal process is not satisfied, the ECU 25 proceeds to S404 and determines whether the deceleration operation condition of the internal combustion engine 1 is satisfied. As the deceleration operation condition of the internal combustion engine 1, for example, 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” can be exemplified.
[0077]
If 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 from S403 again.
[0078]
When 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 above-described FIG. 2 or FIG. The intake throttle actuator 13 is controlled so that the valve speed is lower than usual.
[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]
As described above, when the ECU 25 executes the exhaust gas purification control routine, if the operating condition for reducing the intake air amount of the internal combustion engine 1 is satisfied during the execution of the PM oxidation removal processing of the particulate filter 15, the intake throttle valve 12 The required time for closing the valve becomes longer than usual, and the temperature rise processing of the particulate filter 15 is not executed within the required time for closing the valve.
[0081]
If the time required for closing the intake throttle valve 12 becomes longer than usual, the rate of reduction of the exhaust gas flow rate flowing into the particulate filter 15 decreases, so that when the operating condition for reducing the intake air amount of the internal combustion engine 1 is satisfied. Even if PM that is being oxidized exists in the particulate filter 15, the heat of oxidation of the PM is released into the exhaust gas.
[0082]
Further, in addition to the time required for closing the intake throttle valve 12 being longer than usual, and if the temperature raising process of the particulate filter 15 is not executed within the time required for closing the valve, the particulate matter is not processed within the time required for closing the valve. Since the temperature of the filter 15 decreases, the PM is not continuously oxidized in the particulate filter 15 after the operating condition for reducing the intake air amount of the internal combustion engine 1 is satisfied.
[0083]
Therefore, according to the exhaust gas purification control of the present embodiment, when the operating condition for reducing the intake air amount of the internal combustion engine 1 is satisfied during the execution of the PM oxidation removal processing of the particulate filter 15, the excessive It is possible to prevent an excessive temperature rise.
[0084]
In the exhaust gas purification control according to the present embodiment, an example has been described in which the execution of the temperature raising process is interrupted within the required valve closing time, but the temperature raising process is performed to such an extent that an excessive temperature drop of the particulate filter 15 is prevented. May be executed.
[0085]
For example, as a method of performing the temperature raising process, a method of raising the temperature of the particulate filter 15 itself by oxidizing the unburned fuel in the particulate filter 15, that is, from the fuel addition valve 21 to the exhaust gas When a method of adding fuel or a method of sub-injecting fuel from the fuel injection valve 3 of the cylinder 2 during the exhaust stroke is employed, the amount of fuel added from the fuel addition valve 21 or the amount of fuel added from the fuel injection valve 3 By reducing the amount of sub-injection, excessive temperature rise of the particulate filter 15 may be prevented, and at the same time, excessive temperature decrease of the particulate filter 15 may be prevented.
[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 processing can be restarted immediately.
[0087]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the exhaust gas of the internal combustion engine provided with the particulate filter provided in the exhaust passage of the internal combustion engine and trapping the particulates in exhaust gas, and the oxidation removal means which oxidizes and removes the particulates collected by the particulate filter In the purifying device, 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. This makes it possible to prevent the particulate filter from being excessively heated.
[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 degree of an intake throttle valve and time (1).
FIG. 3 is a diagram (2) showing the relationship between the opening degree of an intake throttle valve and time.
FIG. 4 is a flowchart illustrating an exhaust gas purification control routine.
[Explanation of symbols]
1 ... internal combustion engine
10. Variable centrifugal turbocharger
12. Intake throttle valve
13. Actuator for intake throttle
15. Particulate filter
18. EGR passage
19. EGR valve
21 ... Fuel addition valve
25 ECU

Claims (8)

A particulate filter disposed in an exhaust passage of the internal combustion engine to collect fine particles contained in exhaust gas,
Oxidation removing means for oxidizing and removing fine particles collected by the particulate filter,
When the oxidizing and removing means oxidizes and removes the fine particles trapped in the particulate filter, if the operating condition for reducing the intake air amount of the internal combustion engine is satisfied, the amount of exhaust gas flowing into the particulate filter decreases. A displacement adjusting means for reducing the speed;
An exhaust gas purifying apparatus for an internal combustion engine, comprising: The exhaust amount adjusting means suppresses a decrease in an exhaust amount flowing into the particulate filter for a predetermined period from a time when an operating condition for reducing an intake air amount of the internal combustion engine is satisfied. An exhaust gas purifying apparatus for an internal combustion engine according to claim 1. The engine further includes an intake throttle valve provided in an intake passage of the internal combustion engine, wherein the displacement control unit reduces a closing speed of the intake throttle valve when an operating condition for closing the intake throttle valve is satisfied. 3. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein Further comprising a variable nozzle centrifugal supercharger for compressing the intake air of the internal combustion engine,
3. The variable exhaust nozzle centrifugal turbocharger according to claim 1, wherein the exhaust gas amount adjusting means reduces 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 purifying apparatus for an internal combustion engine according to claim 1. An exhaust gas recirculation mechanism that recirculates part of the exhaust gas discharged from the internal combustion engine to the internal combustion engine is further provided,
The exhaust amount adjusting means controls the exhaust gas recirculation mechanism to reduce the amount of exhaust gas recirculated to the internal combustion engine when an operating condition for reducing the intake air amount of the internal combustion engine is satisfied. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein Further comprising an automatic transmission coupled to the internal combustion engine,
The exhaust amount adjusting means controls the automatic transmission to change a speed ratio of the automatic transmission to a reduction side when an operating condition for reducing an intake air amount of the internal combustion engine is satisfied. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1. Fuel supply means for supplying fuel to the particulate filter when the oxidation removal means is oxidizing and removing fine particles collected by the particulate filter;
Fuel supply control for controlling the fuel supply means so as to reduce the amount of fuel supplied to the particulate filter when the exhaust gas amount adjustment means is reducing the rate of reduction of the exhaust gas flowing into the particulate filter; Means,
The exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 6, further comprising: When the operating conditions for reducing the amount of intake air of the internal combustion engine are satisfied while oxidizing and removing fine particles trapped in the particulate filter disposed in the exhaust passage of the internal combustion engine, the particulate filter passes through the particulate filter. An exhaust gas purification method for an internal combustion engine, characterized in that the exhaust gas flow rate is reduced at a reduced rate.

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