JP2003206726A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine that can prevent the burning of a DPF due to an excessive temperature rise when an exhaust flow rate of an engine is shifted to a low-load low- speed rotation range wherein the flow rate drops, during the regeneration of DPF. <P>SOLUTION: When the exhaust flow rate is shifted to the low-load and low- speed range during the regeneration of the DPF8, a burner 14 is actuated to supply combustion gas to a turbine 4b of a turbosupercharger 4. An increase in turbine work promotes supercharging, and an increase in the exhaust flow rate of the engine 1 promotes the heat radiation of the DPF8 accordingly to suppress an excessive temperature rise. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an internal combustion engine (hereinafter,
The present invention relates to an exhaust emission control device provided with an exhaust system of an engine) and provided with a particulate filter for collecting particulates in exhaust gas.

[0002]

[Related Background Art] Exhaust gas discharged from a diesel engine contains particulate matter in addition to HC, CO, NOx, etc., and a particulate filter is used as a post-treatment device for treating this particulate matter. Proposed. For example, a filter supporting a catalyst is provided in the exhaust system of the engine to collect particulates contained in exhaust gas, while the exhausted temperature is relatively high during operation, the accumulated particulates are used as a catalyst. To oxidize and incinerate by using (continuous regeneration).
Further, when the operation state in which the continuous regeneration action is not obtained is continued and the particulate deposition amount exceeds the allowable amount, additional fuel is injected in the expansion stroke or the exhaust stroke by, for example, post injection to raise the filter. It is heated and the particulates are forcibly removed by incineration (forced regeneration).

[0003]

The above-mentioned filter during regeneration is heated by receiving the combustion heat of particulates, and is radiated to the exhaust gas flowing inside to be cooled so that the functions of both are balanced. Thus, the temperature is maintained at an appropriate temperature, that is, the temperature at which the combustion of particulates after ignition is continued and the burnout due to self-heating is prevented.

However, the operating state of the engine greatly changes according to the running state of the vehicle. For example, in a low load and low rotation range including idle operation, the exhaust gas flow rate is extremely reduced and the oxygen concentration in the exhaust gas is increased. The phenomenon occurs.
A decrease in the exhaust gas flow rate acts to increase the temperature of the filter due to insufficient heat radiation, and an increase in the oxygen concentration also acts to increase the temperature of the filter due to accelerated combustion of particulates. However, if the temperature shifts to, the filter may be overheated and burned.

An object of the present invention is to provide an exhaust gas purifying apparatus for an internal combustion engine, which can prevent burnout due to excessive temperature rise of the filter regardless of the operating condition of the engine when the filter is regenerated to burn off particulates. Especially.

[0006]

In order to achieve the above object, the invention of claim 1 is a filter provided in an exhaust system of an internal combustion engine for collecting particulates in exhaust gas, and a filter upstream side of the exhaust system. And a turbocharger that is provided in the intake system of the internal combustion engine and that is composed of a compressor that supercharges the intake air that is driven by the turbine and is introduced into the internal combustion engine; Combustion gas supply means for supplying combustion gas, filter regeneration determination means for determining whether or not the filter is in regeneration, and operating state determination means for determining whether or not the internal combustion engine is in a predetermined operating state in which exhaust flow rate decreases And a control means for activating the combustion gas supply means when the filter regeneration determining means determines that the filter is being regenerated and the operating state determining means determines that it is in the predetermined operating state. It is those with a.

Therefore, the particulates in the exhaust gas are collected by the filter and gradually deposited, and the deposited particulates are oxidized and incinerated by catalytic action when the internal combustion engine is in an operating state where the exhaust temperature is relatively high, for example. On the other hand (continuous regeneration), when the exhaust temperature rises positively or unburned fuel is supplied to the filter, it is forcibly oxidized and incinerated and removed (forced regeneration). It is determined by means.

On the other hand, for example, when the internal combustion engine is in a low-load low-speed range including idle operation, when fuel supply is stopped due to vehicle deceleration, or when the exhaust flow rate is throttled by the operation of the exhaust brake, A predetermined operating state in which the exhaust gas flow rate of the internal combustion engine decreases and the oxygen concentration in the exhaust gas increases, and the predetermined operating state is determined by the operating state determination means.

When the internal combustion engine shifts to a predetermined operating state during regeneration of the filter, the exhaust gas flow rate is reduced, resulting in insufficient heat radiation of the filter. At this time, the combustion gas supply means is operated by the control means and the turbine upstream side. Since the combustion gas is supplied to the exhaust gas, the supercharging is promoted by the increase of the turbine work and the exhaust gas flow rate of the internal combustion engine is increased. As a result, the insufficient heat radiation of the filter is eliminated, and the excessive temperature rise of the filter is suppressed.

In addition, since the combustion gas containing little or no oxygen is mixed with the exhaust gas of the internal combustion engine, the oxygen concentration of the exhaust gas is reduced, the combustion of particulates is suppressed by the filter, and the overheating of the filter is increased. The suppression of temperature becomes more reliable. According to a second aspect of the present invention, a filter is provided in the exhaust system of the internal combustion engine to collect particulates in the exhaust gas, a combustion gas supply means for supplying combustion gas to the upstream side of the exhaust system filter, and the filter is being regenerated. Filter regeneration determination means for determining whether or not, the operating state determination means for determining whether the internal combustion engine is in a specific operating state to stop fuel supply, the filter regeneration determination means determines that the filter is being regenerated, And a control means for operating the combustion gas supply means when the operating state determination means determines that the operating state is the specific operating state.

Therefore, the particulates in the exhaust gas are collected by the filter and gradually deposited, and the deposited particulates are oxidized and incinerated and removed by a catalytic action when the internal combustion engine is in an operating state where the exhaust gas temperature is relatively high. On the other hand (continuous regeneration), when the exhaust temperature rises positively or unburned fuel is supplied to the filter, it is forcibly oxidized and incinerated and removed (forced regeneration). It is determined by means.

On the other hand, fuel supply to the internal combustion engine is stopped, for example, as the vehicle decelerates, and the operating state at this time is determined as the specific operating state by the operating state determination means. In the specific operation state, the intake air is not used for combustion and is discharged as it is, and the exhaust gas contains sufficient oxygen. Therefore,
If the internal combustion engine shifts to a specific operating state during regeneration of the filter, the combustion of particulates is excessively promoted by oxygen in the exhaust gas, but at this time the combustion gas supply means is operated by the control means and the upstream side of the filter is activated. Since the combustion gas is supplied, the oxygen concentration of the exhaust gas is reduced by containing almost no oxygen or by mixing the combustion gas with a high concentration,
As a result, the combustion of particulates is suppressed, and the excessive temperature rise of the filter is suppressed.

According to a third aspect of the present invention, the turbocharger includes a wastegate valve for bypassing the exhaust gas on the upstream side of the turbine of the exhaust system to the downstream side of the turbine on the exhaust system, and the control means operates the combustion gas supply means. It sometimes closes the wastegate valve. Therefore, since the waste gate valve is closed when the combustion gas supply means operates, all the combustion gas from the combustion gas supply means is supplied to the turbine side, and is effectively utilized for increasing turbine work. As a result, supercharging by the turbocharger is further promoted, the exhaust gas flow rate of the internal combustion engine is increased, and insufficient heat dissipation of the filter is more reliably resolved.

According to a fourth aspect of the invention, the turbocharger includes a waste gate valve for bypassing exhaust gas on the upstream side of the turbine of the exhaust system to the downstream side of the turbine of the exhaust system, and intakes the air intake of the combustion gas supply means. The system is equipped with a switching valve that communicates with the downstream side of the compressor and controls the amount of intake air to the combustion gas supply means between the air intake and the intake system. Equipped with a deposition amount estimating means for estimating, the control means opens the switching valve and the waste gate valve when the deposition amount of the particulates estimated by the deposition amount estimating means exceeds a predetermined value, and When the combustion gas supply means is operated, while the filter regeneration determining means determines that the filter is being regenerated, and the operating state determining means determines that it is in the predetermined operating state, the switching valve is turned on. It closes the wastegate valve while the valve is intended for and operating a combustion gas supply means.

Therefore, when the particulate deposit amount estimated by the deposit amount estimating means exceeds a predetermined value,
The switching valve is opened by the control means, a part of the intake air is supplied to the combustion gas supply means, and the temperature of the exhaust gas is raised by the combustion gas generated from the combustion gas supply means. It is forcibly removed by incineration. Since the waste gate valve at this time is opened, most of the heated exhaust gas is bypassed to the turbine downstream side without passing through the turbine, and the turbine work hardly increases. Therefore, the exhaust gas has Energy is effectively used to raise the temperature of the filter.

On the other hand, when the internal combustion engine shifts to a predetermined operating state during regeneration of the filter, the waste gate valve is closed together with the operation of the combustion gas supply means, so that all the combustion gas from the combustion gas supply means is turbined. Is supplied to the side to be used for increasing the turbine work, further promoting supercharging and increasing the exhaust gas flow rate, and more reliably eliminating the insufficient heat radiation of the filter.

Further, since the temperature of the filter is raised during the forced regeneration by using the combustion gas supply means in this way, it is possible to omit the dedicated temperature raising means for carrying out the forced regeneration. According to a fifth aspect of the present invention, when the control means determines that the filter is being regenerated by the filter regeneration determination means, and the operation state determination means determines that the predetermined operation state continues for a predetermined time or longer, the combustion gas supply is performed. It activates the means.

Therefore, even if the internal combustion engine shifts to the predetermined operating state during the regeneration of the filter, there is no possibility that the filter will fall into a situation of insufficient heat radiation when the duration is short.
In this case, the combustion gas supply means is stopped and held to prevent its unnecessary operation.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION [First Embodiment] The first embodiment in which the present invention is embodied in an exhaust emission control device for a diesel engine will be described below.
An embodiment will be described. FIG. 1 is an overall configuration diagram showing an exhaust emission control device for a diesel engine of this embodiment. The engine 1 of the present embodiment is configured as a common rail type diesel engine, supplies high pressure fuel accumulated in a common rail (not shown) to the fuel injection valve 2 of each cylinder, and the fuel injection valve 2 at an arbitrary injection timing and injection amount. It is configured to be capable of injecting into each cylinder.

The intake passage 3 of the engine 1 is provided with a compressor 4a of the turbocharger 4 and an intercooler 5 from the upstream side. The intake air introduced from an air cleaner (not shown) is supercharged by the compressor 4a and cooled by the intercooler 5, and then introduced into the cylinder of each cylinder to burn the fuel injected from the fuel injection valve 2. Used.

In the exhaust passage 6 of the engine 1, the turbine 4b of the turbocharger 4 coaxially connected to the compressor 4a from the upstream side, the oxidation catalyst 7, the diesel engine,
Particulate filter (hereinafter abbreviated as DPF) 8
The post-processing device 9 is configured by the oxidation catalyst 7 and the DPF 8 (filter). The upstream side of the turbine 4b and the downstream side of the turbine 4b of the exhaust passage 6 are connected by a bypass passage 10, and a wastegate valve 11 is provided in the bypass passage 10. A part of the exhaust gas is bypassed to the bypass passage 10 side according to the opening degree of the waste gate valve 11, whereby the supercharging pressure of the turbocharger 4 is adjusted.

The DPF 8 is made of a honeycomb type ceramic carrier, and alternately closes upstream and downstream openings of many exhaust gas passages to allow the exhaust gas to flow through the porous wall surface forming the exhaust gas passages. Then, the exhaust gas discharged from each cylinder is discharged into the atmosphere through the oxidation catalyst 7 and the DPF 8 after rotating the turbine 4b through the exhaust passage 6 and the particulates contained when passing through the DPF 8 are collected. It

Intake passage 3 downstream of the compressor 4a
The exhaust passage 6 on the upstream side of the turbine 4b is connected via a burner passage 12, a switching valve 13 is provided on the intake passage 3 side of the burner passage 12, and a burner 14 (combustion gas) on the exhaust passage 6 side. Supply means) is provided. When the switching valve 13 is opened, part of the intake air flowing through the intake passage 3 is supplied to the burner 14, the fuel is burned in the burner 14 using the air, and the combustion gas is discharged to the exhaust passage 6 side. Supplied.

On the other hand, in the passenger compartment, an input / output device (not shown), a storage device (ROM, RAM, etc.) for storing control programs and control maps, and a central processing unit (CP) are provided.
U), an ECU (electronic control unit) 21 including a timer counter and the like is installed. An accelerator sensor 2 for detecting the accelerator operation amount APS is provided on the input side of the ECU 21.
2. Rotation speed sensor 2 for detecting engine rotation speed Ne
3, the exhaust gas temperature T1, upstream and downstream of the DPF8
Various sensors such as temperature sensors 24a and 24b for detecting T2 are connected, and various devices such as the fuel injection valve 2, waste gate valve 11, switching valve 13 and burner 14 are connected to the output side. .

The ECU 21 then determines the accelerator operation amount AP.
Target values such as the injection timing and injection amount of the fuel injection valve 2, the supercharging pressure of the turbocharger 4, the EGR rate by an EGR valve (not shown), etc. are set based on the detection information such as S and engine speed Ne. The fuel injection valve 2, the waste gate valve 11, the EGR valve, etc. are controlled based on the target value of. On the other hand, the amount of particulates accumulated on the DPF 8 gradually increases due to the collection of particulates, but the accumulated particulates continue when the engine 1 is in a predetermined operating state (for example, an operating state in which the exhaust temperature is relatively high). It is oxidized and incinerated.

Further, if the operating state in which the continuous regeneration operation is not obtained is continued, the particulate accumulation amount in the DPF 8 gradually increases and exceeds the allowable amount. Therefore, assuming such a situation, the ECU 21 Is actively performing forced regeneration to incinerate particulates, the details of which will be described below. FIG. 2 is a flowchart showing a particulate accumulation amount determination routine executed by the ECU 21, and the ECU 21 always executes this routine at a predetermined control interval while the engine 1 is operating. First, in step S2, the detection information from each sensor is input, and in step S4, it is determined whether or not the particulate accumulation amount A of the DPF 8 is equal to or greater than a preset regeneration start determination value A1 (deposition amount estimating means). The particulate deposition amount A is DPF8.
Since there is a correlation with the differential pressure before and after (that is, the pressure loss of the DPF 8) and the exhaust flow rate, the deposition amount A is estimated based on a map that defines these relationships, for example.

When the particulate accumulation amount A is less than the regeneration start determination value A1, a negative determination (NO) is made in step S4, and the routine ends. When the particulate accumulation amount A gradually increases due to the continued operation to reach the regeneration start determination value A1 or more, the ECU 21 determines in step S
The determination of YES (affirmation) is made in step 4, the forced regeneration process is executed in step S6, and then the routine ends.

FIG. 3 is a flow chart showing a forced regeneration routine executed by the ECU 21. When the forced regeneration process is executed in step S6, the ECU 21 starts the routine, and first, in step S12, the detection information is input. In step S14, it is determined whether the particulates are ignited. This determination is made by the temperature sensor 24.
a, 24b is performed based on the exhaust gas temperatures T1 and T2 on the upstream and downstream sides of the DPF 8 detected, and the average value of the exhaust gas temperatures T1 and T2 is a predetermined temperature, for example, a state of 600 ° C. or higher for a predetermined time. When it continues, it is determined to be ignition.

When the determination in step S14 is NO,
In step S16, the switching valve 13 is opened and the burner 14 is operated at a high output (a large amount of heat supplied), and then
In step S18, the waste gate valve 11 is opened. E
In the subsequent step S20, the CU 21 determines whether or not the particulate accumulation amount A is equal to or less than the regeneration end determination value A2 (<A1), and when the determination is NO, ends the routine.

A part of the intake air is supplied to the burner 14 by opening the switching valve 13, and the temperature of exhaust gas is raised by the combustion gas generated from the burner 14. Since the waste gate valve 11 is opened, most of the heated exhaust gas does not pass through the turbine 4b and the bypass passage 1
After passing 0, it is bypassed to the downstream side of the turbine 4b. Therefore, the turbine work at this time hardly increases, and the energy contained in the exhaust gas is effectively used.
It is used to raise the temperature.

By repeating the above steps S12 to S20, the temperature of the oxidation catalyst 7 and the DPF 8 is gradually raised, and when the particulates on the DPF 8 are ignited, the EC
U21 determines YES in the above step S14, and operates the burner 14 with a small output while keeping the switching valve 13 open in step S22 (small amount of heat supplied). As a result, the effect of raising the temperature of the DPF 8 by the burner 14 is reduced, but since the particulates have already been ignited, they are burned and removed by continuing the combustion.

When the particulate accumulation amount A gradually decreases and becomes equal to or less than the regeneration end determination value A2, the ECU 21 makes a YES determination in step S20 and stops the forced valve opening control of the wastegate valve 11 in step S24. In subsequent step S26, the switching valve 13 is closed and the burner 14 is stopped, and then the routine ends. In the present embodiment, the combustion gas from the burner 14 is used for forced regeneration, but the present invention is not limited to this. For example, post-injection is performed in the expansion stroke or exhaust stroke after main injection, The particulates may be oxidized and incinerated by heating the exhaust gas by burning the additional fuel or by burning the additional fuel directly on the DPF 8. Further, instead of the post injection, the unburned fuel may be supplied from the unburned fuel supply means provided in the exhaust passage 6 to obtain the same effect as the post injection.

On the other hand, in this embodiment, the above forced reproduction,
Alternatively, when the particulates are incinerated and removed by the continuous regeneration described above, the excessive temperature rise suppression process for suppressing the excessive temperature rise of the DPF 8 is executed. FIG. 4 is a flowchart showing an excessive temperature rise suppression routine executed by the ECU 21,
The ECU 21 executes this routine in parallel with the particulate accumulation amount determination routine. First, the ECU 21
Inputs the detection information in step S32, and the subsequent step S
At 34, it is determined whether the forced regeneration is in progress (more specifically, whether or not the particulates have been ignited by the forced regeneration) (filter regeneration determination means). When the determination is YES, the process proceeds to step S36, and the current operating state of the engine 1 is shown in FIG.
It is determined whether or not it is in a predetermined low load and low rotation range (including idle operation) indicated by a (operational state determination means).

This determination is made based on, for example, the engine speed Ne detected by the rotation speed sensor 23 and the fuel injection amount correlated with the engine load, and when it is not in the above-mentioned low load and low rotation range, in step S36. The determination is NO, and the routine ends. In this case, the switching valve 13 is kept closed and the burner 14 is kept stopped, while the opening degree of the wastegate valve 11 is adjusted based on the original supercharging pressure control.

On the other hand, if the determination in step S36 is YES, assuming that the engine is in the low load / low speed range, the ECU 21 proceeds to step S38 and increments the timer t,
In a succeeding step S40, it is determined whether or not the timer t has reached a predetermined value t0, and when the determination is NO, the routine ends. Further, when the determination in step S40 is YES, that is, when the operation in the low load and low rotation range continues for the period corresponding to the predetermined value t0, the process proceeds to step S42 regardless of the boost pressure control. The wastegate valve 11 is closed, the switching valve 13 is opened in the subsequent step S44, and the burner 14 is operated (control means).

By closing the wastegate valve 11, all the combustion gas generated by the burner 14 is supplied to the turbine 4b side, and the temperature of the exhaust gas at the turbine inlet rises, whereby the exhaust gas is provided to the turbine 4b. Energy is increased. As a result, the turbine work is increased to promote supercharging by the compressor 4a, so that the intake air amount of the engine 1 is increased, and the exhaust flow rate is significantly increased as compared with the normal low load and low rotation range.

Further, since the combustion gas from the burner 14 that contains little oxygen or contains little oxygen is mixed with the exhaust gas of the engine 1, the oxygen concentration of the exhaust gas is much larger than that in the normal low load and low rotation range. Is reduced to. In addition, in order to prevent over-rotation of the turbine 4b, a process of opening the waste gate valve 11 may be added when the turbine rotation speed exceeds an allowable value.

On the other hand, if it is determined that the forced regeneration is not in progress in step S34, and if the determination is NO, step S4
At 6 it is determined whether or not the particulates are ignited (filter regeneration determining means). The ignition at this time is the ignition caused by the continuous regeneration, and for example, the above-mentioned step S
As with 14, the judgment is made based on the exhaust gas temperatures T1 and T2, and N
When it is O, the routine is ended.

When the determination is YES, step S4
In step 8, it is determined whether the particulate accumulation amount A is equal to or more than the rapid combustion determination value A3. As the rapid combustion determination value A3, for example, the forced regeneration start and end determination values A1, A2
Is set to an intermediate value (A2 <A3 <A1), and when the determination is NO, it is considered that rapid combustion does not occur because the amount of accumulated particulates is small, and the routine ends. On the other hand, when the determination in step S48 is YES, it is considered that rapid combustion may occur due to a large amount of particulates, the process proceeds to step S36, and thereafter, the same processes in steps S38 to 44 as in the case of forced regeneration are performed.

As a result of the above processing by the ECU 21, the rapid combustion of particulates is suppressed as described below. As is well known, the exhaust flow rate of the engine 1 is extremely reduced in the low load and low rotation range including the idle operation, and
The oxygen concentration in the exhaust gas increases. Therefore, during oxidation / incineration removal of particulates by forced regeneration or continuous regeneration,
When the engine 1 reaches the low load and low rotation speed range, the exhaust gas flow rate decreases, resulting in insufficient heat dissipation of the DPF 8, and the increase in oxygen concentration excessively promotes the combustion of particulates, which may cause an excessive temperature rise of the DPF 8. Occurs.

Here, when the combustion gas from the burner 14 is supplied to the turbine 4b as described above, the exhaust flow rate of the engine 1 greatly increases as the supercharging is promoted.
While the heat radiation of F8 is promoted, the oxygen concentration of the exhaust gas is greatly reduced by the mixing of the combustion gas, so the combustion of particulates is suppressed, and as a result, the excessive temperature rise of DPF8 is suppressed. Therefore, according to the exhaust emission control device of the present embodiment, when the particulates are burned and removed by forced regeneration or continuous regeneration, it is possible to prevent burnout due to excessive temperature rise of the DPF 8.

When the DPF 8 is regenerated, the engine 1
Even if shifts to a low load / low speed range, the temperature rise corresponding to the heat capacity of the DPF 8 is delayed when the duration is short, so there is no risk that the DPF 8 will suffer from insufficient heat dissipation. Since 14 is stopped and held, there is also an advantage that unnecessary operation of the burner 14 can be prevented.

On the other hand, the burner 14 for suppressing the excessive temperature rise of the DPF 8 during regeneration is utilized to make the DPF 8 during forced regeneration.
Since the temperature is raised, the dedicated temperature raising means for carrying out the forced regeneration, such as the post injection and the unburned fuel supply means, can be omitted. In the above embodiment,
The oxidation catalyst 7 is provided on the upstream side of the DPF 8.
Alternatively, a metal having an oxidizing function may be supported on 8.

[Second Embodiment] Next, a second embodiment in which the present invention is embodied in another exhaust emission control system for a diesel engine will be described. In this embodiment, in place of the low load / low speed range of the first embodiment, the DPF 8 excessively rises at the time of fuel cut (hereinafter, referred to as F / C) in which fuel injection is stopped particularly when the vehicle decelerates. The purpose is to suppress the temperature, and the overall configuration thereof and the forced regeneration control of FIGS. 2 and 3 are the same, so description thereof will be omitted and the different points will be mainly described.

FIG. 6 is a flow chart showing an excessive temperature rise suppression routine executed by the ECU 21 of this embodiment.
Similarly to the first embodiment shown in FIG. 4, U21 determines that the forced regeneration is in progress after inputting the detection information in step S52, and makes a YES determination in step S56, or the rapid combustion determination value A3 or more. If it is determined that the particulates in step S56 are ignited and the determinations in steps S56 and 58 are YES, the process proceeds to step S60.

In step S60, it is determined whether or not F / C is being executed instead of the low load / low speed region of the first embodiment (operating state determination means), and if NO, the routine ends. If it is in F / C, a YES decision is made.
In subsequent steps S62 and S64, F / C is equal to the predetermined value t.
When it is determined that the exhaust brake has continued for the period corresponding to 0, the process proceeds to step S66 and it is determined whether the exhaust brake is in operation.

The operation of the exhaust brake can be canceled by the driver by a switch (not shown). If the cancel operation does not operate the exhaust brake, NO is activated.
And the wastegate valve 11 is determined in step S68.
Is opened, the switching valve 13 is opened in the subsequent step S70, the burner 14 is operated, and then the routine is ended.

On the other hand, when it is judged YES in step S66 while the exhaust brake is operating, the process proceeds to step S72 to close the wastegate valve 11 and then open the switching valve 13 in step S70. At the same time, the burner 14 is operated (control means). Since the combustion gas from the burner 14 reduces braking by the exhaust brake, the driver may have a feeling of idling. Therefore, in this case, it is desirable to appropriately limit the combustion gas from the burner 14 to the extent that no idling feeling is given.

Here, regardless of the operating state of the exhaust brake, in the region where the F / C shown in FIG. 5B is performed, most of the intake air is not used for combustion and is discharged as it is, so Contains sufficient oxygen, and the combustion of particulates may be excessively promoted. However, since the combustion gas is mixed with the exhaust gas by the process of step S70, the oxygen concentration is significantly reduced, and the combustion of particulates is suppressed.

On the other hand, when the exhaust brake is not operating in F / C, the exhaust flow rate of the engine 1 changes substantially in proportion to the engine rotation speed Ne due to motoring. For example, in the case of a small engine having an idle rotation speed of 650 rpm, The exhaust flow rate increases about 5 times when there is no load at the rated rotation of 3200 rpm. Therefore, in this case, even if the waste gate valve 11 is opened in step S68, a sufficient exhaust flow rate is secured as compared with the low load / low speed region.

In this case, on the contrary, the DPF 8 may be overcooled and the combustion of particulates may be interrupted. Therefore, when the average value of the exhaust gas temperatures T1 and T2 falls below a predetermined temperature, the burner 14 is activated. At the same time, the waste gate valve 11 may be opened to increase the temperature of the exhaust gas. Further, when the exhaust brake is operating in F / C, the exhaust flow rate is reduced to, for example, about 30% of that when the exhaust brake is not operating, so the exhaust flow rate decreases when the engine rotation speed Ne is lower than the rated rotation. But step S7
Since the waste gate valve 11 is closed at 2, supercharging is promoted and a sufficient exhaust flow rate is secured.

Therefore, during the F / C, regardless of the operating state of the exhaust brake, the burner 14 is operated to reduce the oxygen concentration of the exhaust gas and suppress the combustion of particulates, while reducing the exhaust flow rate. When the exhaust brake is activated, the exhaust gas flow rate is increased by promoting supercharging, and the heat radiation of the DPF 8 is promoted. Therefore, burnout due to excessive temperature rise of the DPF 8 can be prevented in advance.

Although the embodiment has been described above, the aspect of the present invention is not limited to this embodiment. For example, in each of the above embodiments, the exhaust gas purification device for a common rail type diesel engine is embodied, but the engine type and the like are not limited to this, and for example, it is embodied as an exhaust gas purification device for a normal diesel engine. Good.

In each of the above embodiments, the engine 1 is provided with the turbocharger 4, and the promotion of supercharging by the burner 14 is utilized to eliminate the insufficient heat radiation of the DPF 8. However, the turbocharger 4 is not always required. Instead, it may be a naturally aspirated engine. Even in this case, the oxygen concentration of the exhaust gas can be reduced by the combustion gas from the burner 14.
As described in the embodiment, it is possible to suppress the increase in the oxygen concentration of the exhaust gas during F / C, and prevent the excessive temperature rise of the DPF 8 due to this.

On the other hand, in the above embodiment, the oxidation catalyst 7 is provided on the upstream side of the DPF 8 in order to perform continuous regeneration when the exhaust gas temperature is relatively high. It is also applicable to an apparatus in which the catalyst 7 is omitted and the incineration and removal of particulates is performed by an external heat source such as an electric heater. Further, in each of the above-described embodiments, the intake air flowing through the intake passage 3 is used for combustion of the burner 14, but exhaust gas flowing through the exhaust passage 6 side may be used instead of the intake air. Even in this case, since the exhaust gas contains sufficient oxygen in the low load and low rotation speed range and the F / C range, the burner 14 can be operated without any trouble.

[0056]

As described above, according to the exhaust gas purifying apparatus for an internal combustion engine of the first aspect of the present invention, when the internal combustion engine shifts to a predetermined operating state in which the exhaust flow rate decreases during regeneration of the filter, Burnout due to excessive temperature rise can be prevented in advance. According to the exhaust gas purifying apparatus for an internal combustion engine of the second aspect of the present invention, when the internal combustion engine shifts to a specific operating state in which fuel supply is stopped during regeneration of the filter, burnout due to excessive temperature rise of the filter is prevented in advance. be able to.

According to the exhaust gas purifying apparatus for an internal combustion engine of the third aspect of the present invention, in addition to the first aspect of the present invention, supercharging by the turbocharger is further promoted to increase the exhaust gas flow rate, and thus the filter Insufficient heat dissipation can be eliminated more reliably.
According to the exhaust gas purifying apparatus for an internal combustion engine of the invention of claim 4, in addition to the invention of claim 1, at the time of forced regeneration of the filter, the temperature of the filter is raised by utilizing the combustion gas supply means, thereby performing the forced regeneration. It is possible to omit a dedicated temperature raising means for the purpose, and it is possible to effectively raise the temperature of the filter by the energy that the exhaust gas has, and on the other hand, when the filter is in a predetermined operating state during regeneration, it is possible to more reliably eliminate the insufficient heat radiation of the filter. it can.

According to the exhaust gas purifying apparatus for an internal combustion engine of the fifth aspect of the invention, in addition to the first aspect of the invention, it is possible to prevent unnecessary operation of the combustion gas supply means.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an exhaust emission control device for a diesel engine of a first embodiment.

FIG. 2 is a flowchart showing a particulate accumulation amount determination routine executed by an ECU.

FIG. 3 is a flowchart showing a forced regeneration routine executed by the ECU.

FIG. 4 is a flowchart showing an excessive temperature rise suppression routine executed by the ECU.

FIG. 5 is a map showing the operating area of the burner.

FIG. 6 is a flowchart showing an excessive temperature rise suppression routine executed by the ECU of the second embodiment.

[Explanation of symbols]

1 engine (internal combustion engine) 4 turbocharger 4a compressor 4b turbine 8 DPF (filter) 11 wastegate valve 13 switching valve 14 burner (combustion gas supply means) 21 ECU (filter regeneration determination means, operating state determination means, control means , Accumulation amount estimation means)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02B 37/18 F02D 23/02 D F02D 23/02 41/02 380D 41/02 380 43/00 301R 43 / 00 301 301T 45/00 314Z 45/00 314 F02B 37/12 301A (72) Inventor Go Hashizume 5-3-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (72) Inventor Reiko Momomeki Tokyo Port 5-33-8, Shiba-ku, Mitsubishi Motors Industries, Ltd. (72) Inventor Kenji Kawai Shiba 5-33-8, Mitsubishi Motors, Ltd. (72) Inventor Shinichi Saito Shiba, Minato-ku, Tokyo 5-33-8 Mitsubishi Motors Corporation F-term (reference) 3G005 DA02 EA04 EA16 FA35 GA02 GB17 GB28 GD12 GD13 GD17 GD22 HA18 JA02 JA06 JA16 JA39 3G084 AA 01 BA08 BA24 CA03 DA37 EC01 EC03 FA00 FA10 FA27 FA33 3G090 AA02 BA02 CA01 CA04 CB02 CB05 CB23 DA12 DA18 DA20 DB03 DB07 EA04 EA05 3G092 AA02 AA18 DB03 DF01 DF02 DF09 DF09 ZA09 PE01 PDZ JA01 PD03 JA01 PD11 JA02 AZ01

Claims (5)

[Claims] 1. A filter provided in an exhaust system of an internal combustion engine for collecting particulates in exhaust gas, a turbine provided upstream of the filter of the exhaust system, and an intake system of the internal combustion engine. A turbocharger configured by a compressor that supercharges intake air that is driven into the turbine and introduced into the internal combustion engine; combustion gas supply means that supplies combustion gas to the turbine upstream side of the exhaust system; Filter regeneration determining means for determining whether or not the filter is in regeneration, operating state determining means for determining whether or not the internal combustion engine is in a predetermined operating state in which exhaust flow rate decreases, and the filter by the filter regeneration determining means When it is determined that the engine is being regenerated, and when the operating state determining means determines that the operating state is the predetermined operating state, the control means operates the combustion gas supply means. Exhaust purifying apparatus for an internal combustion engine characterized by comprising. 2. A filter provided in an exhaust system of an internal combustion engine for collecting particulates in exhaust gas, combustion gas supply means for supplying combustion gas to the upstream side of the filter of the exhaust system, and the filter regenerated. Filter regeneration determining means for determining whether the internal combustion engine is in a specific operating state for stopping fuel supply, and the filter regeneration determining means for regenerating the filter. And the control means for actuating the combustion gas supply means when the operation state determination means determines that the specific operation state has been established. 3. The turbocharger includes a wastegate valve for bypassing exhaust gas on the turbine upstream side of the exhaust system to the turbine downstream side of the exhaust system, and the control means operates the combustion gas supply means. The exhaust gas purification device for an internal combustion engine according to claim 1, wherein the waste gate valve is closed at times. 4. The turbocharger includes a waste gate valve for bypassing exhaust gas on the turbine upstream side of the exhaust system to the turbine downstream side of the exhaust system, and an air intake port of the combustion gas supply means on the intake side. System, which is connected to the downstream side of the compressor, is provided with a switching valve for controlling the amount of intake air to the combustion gas supply means between the air intake port and the intake system, and further, the particulates collected by the filter. The deposit amount estimating means for estimating the deposit amount of the particulate matter is provided, and the control means opens the switching valve and opens the waist when the particulate deposit amount estimated by the deposit amount estimating means exceeds a predetermined value. The gate valve is opened and the combustion gas supply means is operated, while the filter regeneration determining means determines that the filter is being regenerated, and the operating state is determined. 2. The internal combustion engine according to claim 1, wherein, when it is determined by the stage that the operation state is the predetermined operation state, the switching valve is opened, the waste gate valve is closed, and the combustion gas supply means is operated. Exhaust gas purification device for engines. 5. The control means, when the filter regeneration determining means determines that the filter is being regenerated, and the operating state determining means determines that the predetermined operating state continues for a predetermined time or more, The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the combustion gas supply means is operated.