JP2009121264A - Exhaust gas after-treatment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas after-treatment device capable of promptly regenerating a filter for collecting particulate matters without causing excessive temperature rise while preventing deterioration of fuel economy. <P>SOLUTION: In the case where the filter is forcedly regenerated by supplying fuel to an oxidation catalyst along with auxiliary fuel injection, when a difference between a target temperature Tft at an exhaust gas inlet portion of the filter and a detected temperature Tf at the exhaust gas inlet portion of the filter exceeds a predetermined value ΔT1 during forced regeneration (S20), at least the auxiliary fuel injection is stopped (S26). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust aftertreatment device, and more particularly to a technique for preventing an excessive temperature rise during regeneration of a filter that captures particulate matter contained in exhaust of a diesel engine.

The exhaust passage of a vehicle diesel engine generally includes a filter that captures particulate matter (PM) such as soot together with an exhaust purification catalyst, so that harmful substances (CO, HC, NOx, etc.) in the exhaust are contained. While being removed by oxidation or reduction, the emission of PM into the atmosphere is prevented.
By the way, although PM accumulates on the filter, the PM is burned and removed by heating and heating the filter, thereby regenerating the filter. Therefore, generally, so-called forced regeneration is performed in which the filter is forcibly heated and heated appropriately according to the amount of PM deposited on the filter.

In order to raise the temperature of the filter by heating, it is effective to raise the exhaust temperature. For example, in a diesel engine, auxiliary fuel injection (post injection) is performed during the exhaust stroke after main injection, and unburned fuel is discharged into the exhaust passage or A technique has been developed in which the temperature of the exhaust gas is raised by reacting with an oxidation catalyst provided upstream of the filter.
Also, since PM is mainly a hydrocarbon (HC) component, for example, when the amount of PM deposited on the filter is large, when the exhaust temperature is raised by post injection, the PM instantly burns and the filter In order to prevent such excessive temperature rise, the technology that stops post-injection according to the amount of HC adsorbed to the exhaust aftertreatment device even during forced regeneration to prevent such excessive temperature rise Is known (see Patent Document 1).
JP 2004-36543 A

On the other hand, recently, in order to effectively utilize the reaction at the oxidation catalyst provided on the upstream side of the filter, it is conceivable to separately inject fuel (injection into the exhaust pipe) into the exhaust passage upstream of the oxidation catalyst during forced regeneration. ing. Thereby, the temperature increase rate of the filter can be increased, and the forced regeneration of the filter can be effectively performed.
Further, even when such fuel injection in the exhaust pipe is performed, it is necessary to activate the oxidation catalyst on the upstream side of the filter. Therefore, post injection is generally performed in order to increase the exhaust temperature. .

  However, if fuel injection in the exhaust pipe and post-injection are performed, depending on the operating conditions, much of the fuel (HC) by post-injection may reach the oxidation catalyst (HC slip), and in this case, the amount of PM to the filter Not only due to the amount of deposit, but also there is a problem that the fuel of the HC slip together with the fuel injection in the exhaust pipe reacts with the oxidation catalyst and the filter easily overheats.

In addition, the occurrence of HC slip due to such post injection is not preferable because fuel injection is unnecessarily led to deterioration of fuel consumption.
In this case, it is conceivable to prevent overheating of the filter by stopping both fuel injection in the exhaust pipe and post injection, for example, even during forced regeneration. If both are stopped, the oxidation catalyst may not be in an active state after the post-injection is stopped, and then the oxidation catalyst becomes active again even if the fuel injection in the exhaust pipe and the post-injection are restarted. There is a problem that the filter cannot be heated and heated quickly.

Thus, if the fuel injection in the exhaust pipe and the post-injection cannot be resumed promptly, it takes time for the forced regeneration as a whole, which may affect the operation of the diesel engine and the vehicle, which is not preferable.
The present invention has been made to solve such problems, and an object of the present invention is to provide an exhaust that can quickly regenerate a filter that captures particulate matter while preventing deterioration of fuel consumption without overheating. It is to provide a post-processing apparatus.

  In order to achieve the above object, an exhaust aftertreatment device according to claim 1 is provided in an exhaust passage of an internal combustion engine and is located upstream of the filter in the exhaust passage and a filter that captures particulate matter in the exhaust. An oxidation catalyst provided in the exhaust system, a fuel injection control means for performing sub fuel injection in an exhaust stroke after performing main fuel injection by a fuel injection valve of an internal combustion engine, and an exhaust gas upstream of the oxidation catalyst in the exhaust passage. An exhaust passage fuel supply means for supplying fuel to the oxidation catalyst, and when the particulate matter captured by the filter is removed and the filter needs to be regenerated, the fuel injection control means causes the auxiliary fuel to The exhaust temperature is raised by performing injection to raise the temperature of the oxidation catalyst, and the oxidation reaction is performed by supplying fuel to the oxidation catalyst by the exhaust passage fuel supply means. The forced regeneration means for forcibly regenerating the filter by burning and removing the particulate matter captured by the filter and forcibly regenerating the filter. A filter inlet target temperature setting means for setting a target temperature of the exhaust inlet portion of the filter at the time of performing the filter, and a filter inlet temperature detecting means for detecting the temperature of the exhaust inlet portion of the filter, and the forced regeneration means includes: The sub fuel injection is stopped at least when the difference between the target temperature set by the filter inlet target temperature setting means and the temperature detected by the filter inlet temperature detecting means is equal to or greater than a predetermined value. .

According to a second aspect of the present invention, there is provided the exhaust aftertreatment device according to the first aspect, wherein the forced regeneration means has a difference between a target temperature set by the filter inlet target temperature setting means and a temperature detected by the filter inlet temperature detection means. When it is equal to or greater than a predetermined value, the supply of fuel by the exhaust passage fuel supply means is stopped, and the auxiliary fuel injection is stopped after a lapse of a predetermined time.
According to a third aspect of the present invention, there is provided the exhaust aftertreatment device according to the first or second aspect, wherein the forced regeneration means is configured to obtain a target temperature set by the filter inlet target temperature setting means and a temperature detected by the filter inlet temperature detecting means. When the difference becomes less than a second predetermined value which is smaller than the predetermined value, the sub fuel injection and the fuel supply by the exhaust passage fuel supply means are resumed.

  According to the exhaust aftertreatment device of claim 1, when the filter is forcibly regenerated by performing the auxiliary fuel injection by the fuel injection control means and the fuel supply by the exhaust passage fuel supply means, the filter inlet target temperature setting means When the difference between the target temperature set by the above and the temperature detected by the filter inlet temperature detecting means is equal to or greater than a predetermined value, at least the auxiliary fuel injection is stopped.

  Accordingly, when the temperature of the exhaust inlet portion of the filter is higher than a preset target temperature by a predetermined value or more, the filter tends to rise in temperature, and at this time, the operating condition of the internal combustion engine changes, for example, the auxiliary fuel injection When a so-called HC slip occurs in which the fuel (HC) from the fuel reaches the oxidation catalyst, both the fuel from the HC slip and the fuel from the exhaust passage fuel supply means react on the oxidation catalyst, and the temperature of the filter further rises and overheats. However, at least by stopping the auxiliary fuel injection, it is possible to prevent excessive temperature rise of the filter, to prevent thermal deterioration of the filter, and to improve the durability of the filter. Further, by canceling the auxiliary fuel injection, it is possible to eliminate useless fuel injection and prevent deterioration of fuel consumption.

According to the exhaust aftertreatment device of the second aspect, when the difference between the target temperature set by the filter inlet target temperature setting means and the temperature detected by the filter inlet temperature detection means is equal to or greater than a predetermined value, the exhaust passage fuel supply is performed. The fuel supply by the means is stopped, and the auxiliary fuel injection is stopped after a predetermined time.
Therefore, by stopping not only the sub fuel injection but also the fuel supply by the exhaust passage fuel supply means, it is possible to further prevent the temperature of the filter from being excessively raised, while the oxidation reaction on the oxidation catalyst is also stopped. In this case, it is necessary to wait for the oxidation catalyst to become active again even if it is attempted to resume the sub fuel injection and the fuel supply by the exhaust passage fuel supply means. The auxiliary fuel injection is stopped after a predetermined time from the stop of the fuel supply by the exhaust passage fuel supply means, so that the oxidation catalyst can be maintained in an active state, and the fuel supply by the sub fuel injection and the exhaust passage fuel supply means is possible. Can be resumed promptly. As a result, forced regeneration can be completed in a short time, and the filter can be quickly regenerated without overheating. For example, when an exhaust aftertreatment device is mounted on the vehicle, the driving feeling of the vehicle is improved. Can do.

According to the exhaust aftertreatment device of claim 3, when the difference between the target temperature set by the filter inlet target temperature setting means and the temperature detected by the filter inlet temperature detection means becomes less than the second predetermined value which is smaller than the predetermined value. The fuel supply by the auxiliary fuel injection and the exhaust passage fuel supply means is resumed.
Therefore, after restarting the sub fuel injection and the fuel supply by the exhaust passage fuel supply means, the sub fuel injection and the fuel supply by the exhaust passage fuel supply means are stopped again so as not to cause an excessive temperature rise. It can be avoided as much as possible.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a system configuration diagram of a four-cylinder diesel engine (hereinafter referred to as an engine) to which an exhaust aftertreatment device according to the present invention mounted on a vehicle is applied, and the exhaust according to the present invention is based on FIG. The configuration of the post-processing device will be described.
The engine 1 includes a high-pressure accumulator chamber (hereinafter referred to as a common rail) 2 common to each cylinder, and light oil that is high-pressure fuel supplied from a fuel injection pump (not shown) and stored in the common rail 2 is provided in each cylinder. The fuel is supplied to the injectors 4 and injected into the respective cylinders from the injectors 4.

The intake passage 6 is equipped with a turbocharger 8. The intake air drawn from the air cleaner 7 flows into the compressor 8a of the turbocharger 8 from the intake passage 6, and the intake air supercharged by the compressor 8a is intercooler 10. And the intake manifold 14 through the intake control valve 12.
On the other hand, an exhaust port (not shown) through which exhaust is discharged from each cylinder of the engine 1 is connected to an exhaust pipe (exhaust passage) 20 via an exhaust manifold 18. An EGR passage 24 that communicates the exhaust manifold 18 and the intake manifold 14 via the EGR valve 22 is provided between the exhaust manifold 18 and the intake manifold 14.

The exhaust pipe 20 passes through the turbine 8 b of the turbocharger 8 and is connected to the exhaust aftertreatment unit 30 via the exhaust throttle valve 26. The rotating shaft of the turbine 8b is connected to the rotating shaft of the compressor 8a, and the turbine 8b receives the exhaust flowing in the exhaust pipe 20 and drives the compressor 8a.
The exhaust aftertreatment unit 30 is configured to accommodate an oxidation catalyst 36 and a diesel particulate filter (hereinafter referred to as DPF) 38 on the exhaust downstream side of the oxidation catalyst 36. The DPF 38 is provided to purify the exhaust of the engine 1 by collecting particulate matter (hereinafter referred to as PM) in the exhaust.

The DPF 38 is made of a honeycomb-type ceramic carrier, and a large number of passages that connect the upstream side and the downstream side are provided side by side, and the upstream side opening and the downstream side opening of the passage are alternately closed. Collects PM in the exhaust gas by circulating inside.
Since the oxidation catalyst 36 oxidizes NO in the exhaust gas to generate NO ₂ , by arranging the oxidation catalyst 36 and the DPF 38 in this way, the PM collected and deposited in the DPF 38 is normally It reacts with NO ₂ supplied from the oxidation catalyst 36 and oxidizes, whereby the DPF 38 is continuously regenerated.

  A fuel addition injector (exhaust passage fuel supply means) 28 for injecting fuel (light oil) into the exhaust pipe 20 and thus toward the oxidation catalyst 36 is provided on the exhaust upstream side of the oxidation catalyst 36. This fuel addition injector 28 supplies fuel to the oxidation catalyst 36 at the time of forced regeneration of the DPF 38 that forcibly burns and removes PM collected mainly in the DPF 38. That is, when it is necessary to forcibly remove the PM deposited on the DPF 38, fuel is injected from the fuel addition injector 28 (hereinafter referred to as fuel injection in the exhaust pipe), and this causes an oxidation reaction on the oxidation catalyst 36. The DPF 38 is heated by the reaction heat of this oxidation reaction, PM is rapidly burned and removed, and the DPF 38 is forcibly regenerated.

An upstream pressure sensor 40 that detects the exhaust pressure on the exhaust upstream side of the oxidation catalyst 36 and the DPF 38 is provided on the upstream side of the oxidation catalyst 36, and the downstream side that detects the exhaust pressure on the exhaust downstream side of the DPF 38 on the downstream side. A pressure sensor 42 is provided.
A DPF inlet temperature sensor (filter inlet temperature detecting means) 44 is provided between the oxidation catalyst 36 and the DPF 38 to detect the exhaust temperature at the inlet of the DPF 38 and thus the temperature of the inlet portion of the DPF 38.

The ECU (Electronic Control Unit) 50 is a control device for performing comprehensive control including operation control of the engine 1, and includes a CPU, a memory, a timer counter, and the like, and performs various control amount calculations. Then, various devices are controlled based on the control amount.
In addition to the upstream pressure sensor 40, the downstream pressure sensor 42, and the DPF inlet temperature sensor 44 described above, various sensors are connected to the input side of the ECU 50 in order to collect information necessary for various controls. On the other hand, on the output side, various devices such as the injector 4, the intake control valve 12, the EGR valve 22, the exhaust throttle valve 26, and the fuel addition injector 28 of each cylinder that are controlled based on the calculated control amount are connected. Yes.

Thus, the ECU 50 calculates the fuel supply amount to each cylinder of the engine 1, the fuel supply control for controlling the fuel supply amount from the injector 4 based on the calculated fuel supply amount, the drive control of the fuel addition injector 28, and the like. Various controls are performed.
In particular, in the exhaust aftertreatment device according to the present invention, the engine 1 uses the auxiliary fuel injection (hereinafter referred to as the late post) from the injector 4 in the exhaust stroke (for example, late in the exhaust stroke) mainly for the purpose of raising the exhaust gas temperature in addition to the main fuel injection. Injection)), and the late post injection can be performed by a command from the ECU 50 (fuel injection control means). That is, by performing late post injection based on the command of the ECU 50, it is possible to discharge most of the fuel by late post injection to the exhaust pipe 20 as unburned fuel, and exhaust the unburned fuel and residual oxygen in the exhaust. It is possible to raise the exhaust temperature by reacting in the pipe 20.

As a result, in the case of performing forced regeneration of the DPF 38, if the late post injection is performed, the exhaust temperature can be raised and the oxidation catalyst 36 can be raised, and the oxidation catalyst 36 can be activated (for example, The catalyst temperature is 250 ° C. or higher) or can be maintained in the active state, and the oxidation reaction on the oxidation catalyst 36 can be favorably caused.
The operation and effect of the exhaust aftertreatment device according to the present invention configured as described above will be described below.

Referring to FIG. 2, a control routine of forced regeneration control executed by the ECU 50 in the exhaust aftertreatment device according to the present invention is shown in a flowchart (forced regeneration means), and will be described below based on the flowchart.
In step S10, it is determined whether or not forced regeneration is necessary. Here, it is determined that forced regeneration is necessary when the PM accumulated in the DPF 38 reaches a predetermined amount. For example, the PM accumulation amount is estimated based on the clogged state of the DPF 38, and the estimated value is It is determined whether or not the predetermined amount has been reached. Specifically, the clogging state of the DPF 38 is determined based on the pressure difference between the upstream pressure sensor 40 and the downstream pressure sensor 42 to estimate the PM accumulation amount.

If the determination result in step S10 is false (No), nothing is done and the routine is exited. If the determination result is true (Yes), the process proceeds to step S12.
In step S12, the target temperature of the inlet portion of the DPF 38, that is, the filter inlet target temperature Tft (for example, a value near 600 ° C.) is set (filter inlet target temperature setting means). That is, in the forced regeneration, as described above, the DPF 38 is heated and the PM is burned and removed. For example, according to the estimated value of the amount of accumulated PM, the inlet temperature of the DPF 38 and thus the target temperature of the entire DPF 38 An appropriate temperature is set in advance.

In step S14, late post injection is started to perform forced regeneration. As described above, the main purpose of the late post-injection is to raise the temperature of the oxidation catalyst 36 by raising the exhaust gas temperature, so that the oxidation catalyst 36 can be heated up for the fuel injection amount of the late post-injection. The amount is set as appropriate.
In step S16, the fuel addition injector 28 is driven to start fuel injection in the exhaust pipe. The injection amount of the fuel injection in the exhaust pipe is also appropriately set so that the inlet temperature of the DPF 38 is an amount that can ensure the inlet target temperature Tft.

In step S18, the actual filter inlet temperature Tf is detected based on the information from the DPF inlet temperature sensor 44.
In step S20, the filter inlet temperature Tf is compared with the filter inlet target temperature Tft, and the difference ΔT between the filter inlet temperature Tf and the filter inlet target temperature Tft is greater than or equal to a predetermined value ΔT1 (for example, 40 ° C.). Determine whether or not.

If the difference ΔT between the filter inlet temperature Tf and the filter inlet target temperature Tft is equal to or greater than a predetermined value ΔT1 (for example, 40 ° C.), the temperature of the DPF 38 may be abnormally increased. In such a case, it is considered that the DPF 38 may be excessively heated and thermally deteriorated, and the process proceeds to step S22 to stop fuel injection in the exhaust pipe.
In step S24, it is determined whether or not a predetermined time t1 (for example, 10 seconds) has elapsed since the difference ΔT has become equal to or greater than a predetermined value ΔT1. When the determination result is false (No) and the predetermined time t1 has not yet elapsed, the process waits for the predetermined time t1 to elapse. On the other hand, when it is determined that the determination result is true (Yes) and the predetermined time t1 has elapsed, the process proceeds to step S26, and the late post injection is stopped.

That is, when the difference ΔT between the filter inlet temperature Tf and the filter inlet target temperature Tft becomes equal to or greater than the predetermined value ΔT1, first the fuel injection in the exhaust pipe is stopped, and then the late post injection is stopped after a predetermined time t1 has elapsed. .
When the fuel injection in the exhaust pipe and the late post injection are stopped in this way, for example, when the operating condition of the engine 1 changes suddenly, the fuel (HC) by the late post injection does not react sufficiently in the exhaust pipe 20. A so-called HC slip may occur in which the fuel (HC) reaches the oxidation catalyst 36 as it is. When the HC slip occurs, both the fuel by the HC slip and the fuel by the fuel injection in the exhaust pipe react on the oxidation catalyst 36. However, the DPF 38 may be further heated to overheat, but by stopping the fuel injection in the exhaust pipe and the late post injection, the overheating of the DPF 38 can be prevented and the thermal deterioration of the DPF 38 can be prevented. It can be prevented in advance. In particular, by stopping late post injection, useless fuel injection by late post injection can be eliminated and fuel consumption can be prevented from deteriorating.

  Further, if the late post injection is stopped after a predetermined time t1 from the stop of the fuel injection in the exhaust pipe in this way, if the late post injection and the fuel injection in the exhaust pipe are stopped at the same time, the oxidation catalyst 36 is stopped. Since the above oxidation reaction is also stopped, the oxidation catalyst 36 may not be in an active state, and the oxidation catalyst 36 may become active again if an attempt is made to restart the late post injection and the fuel injection in the exhaust pipe thereafter. Although it is necessary to wait, the oxidation catalyst 36 can be maintained in the active state, and the late post injection and the fuel injection in the exhaust pipe can be promptly restarted. Thereby, forced regeneration can be completed in a short time, and the DPF 38 can be promptly regenerated without excessive temperature rise.

In step S28, whether or not the difference ΔT between the filter inlet temperature Tf and the filter inlet target temperature Tft is less than a predetermined value (second predetermined value) ΔT2 (<ΔT1: for example, 20 ° C.) smaller than the predetermined value ΔT1. Is determined.
When the difference ΔT between the filter inlet temperature Tf and the filter inlet target temperature Tft is less than a predetermined value ΔT2 (for example, 20 ° C.), the difference ΔT becomes sufficiently small and the DPF 38 no longer abnormally increases in temperature. It can be determined that has been removed. Therefore, if the determination result in step S28 is false (No), the stop of the late post injection and the fuel injection in the exhaust pipe is maintained, whereas if the determination result is true (Yes), the process returns to step S14 and the rate is returned. Resume post injection and fuel injection in the exhaust pipe.

  In this way, by restarting the late post injection and the fuel injection in the exhaust pipe after the difference ΔT between the filter inlet temperature Tf and the filter inlet target temperature Tft becomes sufficiently small, the late post injection is performed again so that the excessive temperature rise does not occur. The late post injection and the exhaust pipe fuel injection can be restarted at an appropriate timing while avoiding the suspension of the fuel injection in the exhaust pipe as much as possible. As a result, the DPF 38 can be quickly regenerated without overheating.

  If the determination result in step S20 is false (No), the process proceeds to step S30, where the forced regeneration completion determination is performed. If the determination result is false (No), late post injection and fuel injection in the exhaust pipe are performed. On the other hand, if the determination result is true (Yes) and it is determined that the forced regeneration is completed, the forced regeneration is terminated. Specifically, whether or not the forced regeneration is completed is determined by monitoring the amount of PM accumulated on the DPF 38 based on the differential pressure between the upstream pressure sensor 40 and the downstream pressure sensor 42 as described above. Alternatively, the completion may be determined when a certain period of time has elapsed excluding the stop period of the late post injection and the fuel injection in the exhaust pipe.

  Referring to FIG. 3, the filter inlet target temperature Tft (broken line), the filter inlet temperature Tf (solid line), and the temperature of the oxidation catalyst 36 (one-dot chain line) when the forced regeneration control is performed, the filter inlet temperature Tf The time change of the difference ΔT from the filter inlet target temperature Tft and the time change of each fuel injection amount of the late post injection and the fuel injection in the exhaust pipe are shown in the time chart. As shown in FIG. When the difference ΔT between the filter inlet temperature Tf and the filter inlet target temperature Tft becomes equal to or greater than the predetermined value ΔT1, first, the fuel injection in the exhaust pipe is stopped. Is prevented. When the difference ΔT becomes less than the predetermined value ΔT2, the late post injection and the fuel injection in the exhaust pipe are quickly restarted while the temperature of the oxidation catalyst 36 is kept relatively high.

  As described above, according to the exhaust aftertreatment device according to the present invention, in the forced regeneration in which the late post injection and the fuel injection in the exhaust pipe are performed, the wasteful fuel injection by the late post injection is eliminated and the deterioration of the fuel consumption is prevented. The DPF 38 can be quickly regenerated without overheating. In addition, the late post injection and the fuel injection in the exhaust pipe can be restarted quickly while maintaining the temperature of the oxidation catalyst 36 relatively high, and the forced regeneration is completed in a short time so that the DPF 38 can be quickly recovered without overheating. Is possible. Thereby, the durability performance of DPF38 can be improved, for example, the driving | operation feeling of a vehicle can be improved.

Although the description of the embodiment of the exhaust aftertreatment device according to the present invention has been completed above, the embodiment of the present invention is not limited to the above.
For example, in the above embodiment, when the difference ΔT between the filter inlet temperature Tf and the filter inlet target temperature Tft exceeds a predetermined value ΔT1, both the late post injection and the exhaust pipe fuel injection are stopped. Only the injection may be stopped, whereby the fuel due to the HC slip can be prevented from reacting on the oxidation catalyst 36, and the excessive temperature rise of the DPF 38 can be satisfactorily prevented while preventing the deterioration of fuel consumption.

  In the above embodiment, the turbocharger 8, the intake control valve 12, the EGR valve 22, the EGR passage 24, and the exhaust throttle valve 26 are provided. However, these are not essential and are not provided in the present invention. You may do it.

1 is a system configuration diagram of an entire engine including an exhaust aftertreatment device according to the present invention. It is a flowchart which shows the control routine of the forced regeneration control in the exhaust gas aftertreatment apparatus which concerns on this invention. When the forced regeneration control according to the present invention is performed, the filter inlet target temperature Tft (broken line), the filter inlet temperature Tf (solid line) and the oxidation catalyst temperature (dashed line) over time, the difference ΔT over time, and the late post injection FIG. 6 is a time chart showing a change with time of each fuel injection amount of fuel injection in the exhaust pipe.

Explanation of symbols

1 engine (diesel engine)
4 Injector 20 Exhaust pipe (exhaust passage)
28 Fuel addition injector (exhaust passage fuel supply means)
30 Exhaust aftertreatment unit 36 Oxidation catalyst 38 DPF (filter)
50 Electronic control unit (ECU)

Claims (3)

A filter that is provided in an exhaust passage of the internal combustion engine and captures particulate matter in the exhaust;
An oxidation catalyst provided in the exhaust passage and located upstream of the exhaust of the filter;
Fuel injection control means for performing sub fuel injection in the exhaust stroke after performing main fuel injection by the fuel injection valve of the internal combustion engine;
An exhaust passage fuel supply means which is provided in the exhaust passage upstream of the oxidation catalyst and supplies fuel to the oxidation catalyst;
When the particulate matter captured by the filter is removed and the filter needs to be regenerated, the fuel injection control means performs the auxiliary fuel injection to raise the exhaust temperature and raise the temperature of the oxidation catalyst. Then, by supplying fuel to the oxidation catalyst by the exhaust passage fuel supply means, an oxidation reaction is caused to raise the temperature of the filter, and the particulate matter trapped by the filter is burned and removed to force the filter. Forced regeneration means to automatically regenerate,
Filter inlet target temperature setting means for setting a target temperature of the exhaust inlet portion of the filter when the filter is forcibly regenerated by the forced regeneration means;
Filter inlet temperature detection means for detecting the temperature of the exhaust inlet portion of the filter,
The forced regeneration means stops at least the auxiliary fuel injection when the difference between the target temperature set by the filter inlet target temperature setting means and the temperature detected by the filter inlet temperature detection means is a predetermined value or more. An exhaust aftertreatment device.   When the difference between the target temperature set by the filter inlet target temperature setting means and the temperature detected by the filter inlet temperature detection means is equal to or greater than a predetermined value, the forced regeneration means is a fuel supplied by the exhaust passage fuel supply means. 2. The exhaust aftertreatment device according to claim 1, wherein the sub fuel injection is stopped after a predetermined time elapses.   When the difference between the target temperature set by the filter inlet target temperature setting means and the temperature detected by the filter inlet temperature detection means becomes less than a second predetermined value that is smaller than the predetermined value, the forced regeneration means The exhaust aftertreatment device according to claim 1 or 2, wherein fuel supply by the fuel injection and the exhaust passage fuel supply means is resumed.

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