JP2010071203A - Dpf regeneration control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diesel particulate filter (DPF) regeneration control device performing prompt regeneration by shortening time required for regenerating a DPF while preventing excessive temperature rise of the DPF by a simple control without using a complicated control estimating and calculating PM (particulate matter) accumulation or the like changing momentarily. <P>SOLUTION: This DPF regeneration control device includes: a DPF inlet temperature raising means 42 raising the inlet exhaust gas temperature of the DPF 37 to PM regenerable temperature; and a DPF inlet temperature control means 44 periodically changing to raise or drop the DPF inlet temperature under a regeneration process by controlling the DPF inlet temperature raising means 42. The DPF inlet temperature control means 44 sets high temperature and low temperature in a periodic change, and also performs regeneration control by setting high-temperature time and low-temperature time in one cycle. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a regeneration control device for a DPF (diesel particulate filter) that collects PM (particulate matter) used as an exhaust gas treatment device of a diesel engine.

The DPF is generally used for removing PM discharged from a diesel engine from exhaust gas, and is formed by molding ceramic or the like into a honeycomb monolith. PM accumulates in this DPF during operation. If the amount of accumulation eventually exceeds the allowable value, clogging occurs and the exhaust pressure is increased to adversely affect the operability. It must be forced to be regenerated.
When performing forced regeneration of the DPF, it is necessary to keep the temperature of the gas flowing into the DPF high. Fuel supply to the exhaust gas after-treatment device (DOC (diesel oxidation catalyst) + DPF), that is, combustion, to increase the gas temperature Post injection into the room, addition of light oil into the exhaust passage, and the like are performed.
The temperature of the exhaust gas flowing into the DPF rises due to the oxidation heat generated when the injected fuel is oxidized in the DOC. The temperature at which PM burns in the DPF is generally 600 to 650 ° C., and it is necessary to raise the temperature to that temperature.

From the viewpoint of shortening the forced regeneration time of the DPF, it is necessary to keep the gas temperature passing through the DPF at a high temperature. On the other hand, the gas temperature passing through the DPF is increased while a large amount of PM is deposited on the DPF. If so, there is a risk that a large amount of PM burns at once and overheats.
For this reason, various improvement proposals have been made, such as control for keeping the DPF inlet temperature constant at the target inlet temperature and control for changing the target inlet temperature to the rolling state in accordance with the regeneration state of the DPF.

  For example, in Patent Document 1 (Japanese Patent Laid-Open No. 2007-239740), as shown in FIG. 8A, an oxidation catalyst 03 and a DPF 05 are disposed in the exhaust passage 02 of the engine 01, and the temperature is set upstream and downstream of the DPF 05. A configuration in which the sensors 07 and 09 are installed and the reactant injection device 011 is further installed upstream of the oxidation catalyst 03 is shown. As shown in FIG. 8B, the temperature and temperature of the measured or measured DPF 05 Change the inlet gas temperature target value of DPF05 from time to time according to the change rate, temperature change gradient, PM deposition amount in DPF05, PM deposition amount change rate, etc., and set the optimal target value to reduce the risk of overheating of DPF05 It shows an operating method that allows rapid DPF regeneration without it.

JP 2007-239740 A

However, in the technique related to the DPF inlet temperature control disclosed in Patent Document 1, the exhaust gas temperature that changes from moment to moment is measured, and based on the measured value, the DPF temperature, temperature change rate, change gradient, PM Since the target value of the DPF inlet gas temperature is set by calculating the amount of deposition, etc., it is difficult to obtain quick control with a time delay in setting the target value and shortening the regeneration processing time. Since an error is likely to occur in the estimation calculation of the accumulation amount or the like, it is difficult to perform accurate regeneration control.
In addition, there is a problem that the control logic becomes complicated because estimation calculation processing such as the PM accumulation amount and the accumulation amount change rate must be performed based on the measured value of the exhaust gas temperature that changes every moment.

  In view of the problems of the prior art, the present invention is required for regeneration of the DPF while preventing overheating of the DPF by simple control without using complicated control for estimating and calculating the PM deposition amount that changes from time to time. It is an object of the present invention to provide a DPF regeneration control apparatus that enables rapid regeneration by shortening the time.

  The present invention solves such a problem, and includes an exhaust gas aftertreatment device for a diesel engine provided with a DPF (diesel particulate filter) for collecting DOC (diesel oxidation catalyst) and PM (particulate matter) in an exhaust passage. In a DPF regeneration control device that burns and removes PM accumulated in the DPF by regeneration processing at a predetermined time, the DOC is activated by pilot injected fuel injected into a combustion chamber and flows into the DPF inlet by oxidation heat The DPF inlet temperature raising means for raising the exhaust gas temperature to be raised and raising the inlet temperature of the DPF to the recyclable temperature of the DPF, and the DPF inlet temperature during the regeneration process by controlling the DPF inlet temperature raising means And a DPF inlet temperature control means for periodically changing the DPF inlet temperature control means. Changes in the high-temperature side temperature and a low-temperature side temperature both set respectively, and performs regeneration processing control by setting the high temperature-side time and the low-temperature side time in one cycle.

According to this invention, the DPF inlet temperature control means for periodically changing the exhaust gas temperature flowing into the DPF during the regeneration process of the DPF periodically at a temperature at which PM can be completely combusted (for example, 600 ° C. to 650 ° C.), The DPF inlet temperature control means is characterized in that the high temperature side temperature and the low temperature side temperature of the periodic change are respectively set, and the high temperature side time and the low temperature side time in one cycle of the periodic change are set to perform the regeneration process control. is there.
That is, since the high temperature exhaust gas and the low temperature exhaust gas alternately flow from the start time of the regeneration process, the high temperature exhaust gas passes through the DPF and ignites a large amount of PM at the start time of the regeneration process, thereby burning the PM. The speed can be increased, and the time required for burning PM can be shortened as compared with the case where the exhaust gas temperature is increased in the latter stage of the regeneration process.
On the other hand, if the DPF inlet temperature is set high in the first half of the regeneration process, the risk of overheating increases, but since not only high temperature but also low temperature exhaust gas flows alternately, the danger of overheating is suppressed.
Thus, by periodically changing the DPF inlet temperature from the start of regeneration to during the regeneration process, the time required for burning PM can be shortened while avoiding the danger of excessive temperature rise of the DPF. .
In addition, since the amount of fuel injected into the exhaust gas to raise the exhaust gas temperature can be reduced, it contributes to the improvement of fuel consumption.

  Furthermore, according to the present invention, the DPF inlet temperature control means sets the high temperature side temperature and the low temperature side temperature of the cyclic change, and sets and controls the high temperature side time and the low temperature side time in one cycle. In particular, since the regeneration process is controlled by managing the time, the regeneration process can be performed by simple control without using complicated control for estimating and calculating the PM deposition amount that changes from moment to moment.

In this invention, it is preferable that the DPF inlet temperature control means control the cycle time of the periodic change to be constant and control the high temperature side time to become longer in the later stage of regeneration.
Thus, since the time kept on the high temperature side becomes longer as the latter stage of the regeneration, the risk that the DPF overheats can be reduced. That is, since the amount of accumulated PM decreases as the regeneration period is late, the increase in the combustion rate is small even if the time for holding at the high temperature side is lengthened. Further, in order to eliminate PM remaining unburned in the DPF and completely burn out the PM, it is preferable to extend the time for keeping the high temperature side in the late stage of regeneration.

In this invention, it is preferable that the DPF inlet temperature control means increase the high temperature side temperature as the regeneration period is late.
In this case as well, as with the setting for increasing the high temperature side time, the amount of accumulated PM decreases as the regeneration period is late. Also in the sense that the PM that remains unburned in the DPF is eliminated and the PM is completely burned out, it is preferable to increase the temperature on the high temperature side in the later stage of regeneration.

  In this invention, it is preferable that the low temperature side temperature is set to a constant temperature of the DPF regeneration temperature. By setting the low temperature side temperature constant (for example, 600 ° C.), the DPF inlet temperature control can be performed. Simplified.

Further, in this invention, preferably, a DPF outlet temperature sensor for detecting the outlet temperature of the DPF is provided, and when the detected value by the DPF outlet temperature sensor is equal to or higher than an allowable value, it is determined that the DPF is overheated. The DPF inlet temperature control means may extend the low temperature side time in one cycle.
Thus, when it is determined that the DPF is overheated, the low temperature side time is made longer than the time until it is determined that the temperature is overheated, thereby effectively suppressing the temperature rise of the DPF. Overheating can be prevented.

  In this invention, it is preferable that the DPF inlet temperature raising means includes an throttle of an intake throttle valve provided in the intake passage and an early post-injection of the first injection of fuel with a certain delay from the main fuel injection timing. The DPF inlet temperature control means includes a throttle amount of the intake throttle valve, an early post injection amount, and a late post injection amount, the second post injection in the vicinity of the bottom dead center after the early post injection. At least one of them may be controlled.

  Thus, by controlling at least one of the throttle amount of the intake throttle valve, the early post injection amount, and the late post injection amount, or a combination thereof, the set high temperature side temperature and low temperature side temperature are set. The feedback control can be performed so as to coincide with the above, and the DPF inlet temperature can be periodically changed up and down.

  According to the present invention, the DPF inlet temperature during the regeneration process is periodically changed up and down, and the regeneration process is controlled by time management. Therefore, complicated control for estimating and calculating the PM deposition amount that changes from time to time is used. The reproduction process can be performed in a short time with simple control.

  Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only.

(Embodiment 1)
FIG. 1 is an overall configuration diagram of exhaust gas treatment of a diesel engine including a DOC (diesel engine oxidation catalyst) and a DPF (diesel particulate filter) according to Embodiment 1 of the present invention.
In FIG. 1, a diesel engine (hereinafter referred to as “engine 1”) includes an exhaust turbocharger 7 having an exhaust turbine 3 and a compressor 5 driven coaxially with the exhaust turbine 3, and from the compressor 5 of the exhaust turbocharger 7. The discharged air enters the air cooler (not shown) through the air pipe 9, and the air cooled by the air cooler passes through the intake manifold 13 after the intake flow rate is controlled by the intake throttle valve 11. Then, the air is sucked into the engine 1 from an intake port 15 provided for each cylinder.

In the engine 1, the fuel injection timing and the injection amount are controlled by the fuel injection control device 17, and the fuel is injected from the fuel injection valve 19 provided for each cylinder at the injection timing and the injection amount. The injected high-pressure fuel is burned by mixing with the air.
In addition, an EGR (exhaust gas recirculation) pipe 23 is branched from the middle of the exhaust passage 21, and a part of the exhaust gas (EGR gas) passes through the EGR pipe 23 and is cooled by an EGR cooler (not shown). 11 through the EGR valve 25 to the intake manifold 13 in the downstream portion.

  The combustion gas, that is, the exhaust gas 27 combusted in the engine 1 drives the exhaust turbine 3 of the exhaust turbo supercharger 7 through the exhaust manifold and exhaust passage 21 in which exhaust ports 29 provided for each cylinder are gathered. Then, after it becomes a power source for the compressor 5, it enters the DOC 35 of the exhaust gas aftertreatment device 33 through the exhaust passage 21. The exhaust gas aftertreatment device 33 is constituted by a DOC 35 and a DPF 37 on the downstream side thereof.

  When the DPF 37 is regenerated, the temperature of the exhaust gas is raised by the oxidation heat generated when the DOC 35 is activated and the fuel in the exhaust gas 27 is oxidized by the DOC 35, and together with the heated exhaust gas, the combustion chamber 39 The fuel pilot-injected into the DPF 37 is sent to the DPF 37 to combust the PM deposited on the DPF 37.

  The regeneration process of the DPF is performed by the regeneration control device 40. The regeneration control device 40 activates the DOC 35 to raise the exhaust gas temperature flowing into the inlet of the DPF 37 by oxidation heat, and raises the inlet temperature of the DPF 37 to a recyclable temperature of the DPF 37; It comprises DPF inlet temperature control means 44 that controls the DPF inlet temperature raising means 42 to periodically change the DPF inlet temperature during the regeneration process up and down.

The DPF inlet temperature raising means 42 includes a throttle valve control device 46 that controls the opening and closing of the throttle valve 11 and the fuel injection control device 17, and the operation is controlled by a signal from the DPF inlet temperature control means 44.
The DPF inlet temperature control means 44 receives the opening signal of the throttle valve 11, the temperature signals from the inlet temperature sensor 48 and outlet temperature sensor 50 of the DPF 37, and the pressure signals from the inlet pressure sensor 52 and outlet pressure sensor 54 of the DPF 37. Based on the differential pressure sensor 56, differential pressure signals are respectively input.

The operation of the DPF inlet temperature control means 44 will be described with reference to the flowchart shown in FIG. 2 and the change diagram of the DPF inlet temperature target value shown in FIG.
When the regeneration control of the DPF is started in step S1, whether or not the PM accumulated in the DPF 37 has reached a certain value in step S2 is determined based on the differential pressure signal from the differential pressure sensor 56. When the differential pressure reaches a certain value or more, it is determined that the accumulation amount is more than a certain value and regeneration is necessary, and the process proceeds to the next step S3 (point t0 in FIG. 4).

In step S3, the intake throttle valve 11 is throttled to reduce the amount of air flowing into the combustion chamber. In step S4, the DOC 35 is activated by early post injection, and the exhaust gas temperature is raised by the oxidation heat generated when the unburned fuel in the exhaust gas is oxidized.
This early post-injection refers to the first post-injection in which a small amount of fuel is injected from the main injection while the pressure in the cylinder is still high after about 10 to 20 ° after the main injection as shown in FIG. By this early post injection, the exhaust gas temperature can be increased without affecting the output of the engine. The exhaust gas heated to flow into the DOC 35 activates the DOC 35 and activates the DOC 35. Accordingly, the exhaust gas temperature is raised by the oxidation heat generated when the unburned fuel in the exhaust gas is oxidized.

In step S5, the signal from the inlet temperature sensor 48 determines whether the DPF inlet temperature has reached T1 (200 to 250 ° C.). If it has exceeded, the inlet of the DPF 37 is input by late post injection in step S6. The temperature is further increased (point t1 in FIG. 4).
This late post-injection refers to the second post-injection in which the crank angle after the early post-injection has advanced to near the bottom dead center, and the exhaust valve is opened by this late post-injection. The fuel flows out from the combustion chamber 39 to the exhaust passage 21, and the fuel burns at the inlet portion of the DPF 37 to further increase the exhaust gas temperature to promote PM combustion in the DPF 37.

In step S7, it is determined whether or not the DPF inlet temperature has reached T2 (600 ° C.) based on a signal from the inlet temperature sensor 48. If it exceeds, control of the periodic change in the inlet temperature of the DPF 37 from step S8 is performed. Is started (point t2 in FIG. 4).
This cyclic inlet temperature control is performed by controlling either the throttle amount of the intake throttle valve 11, the injection amount of early post injection, or the injection amount of late post injection, or a combination thereof to control the high temperature side and the low temperature side. Move alternately. That is, when moving to the high temperature side, the intake throttle valve 11 is throttled or the amount of early post injection or late post injection is increased, and for moving to the low temperature side, the intake throttle valve 11 is opened, or This is done by reducing the amount of early post injection or late post injection.

In step S9, the target value of the high temperature side temperature is set to T3 (650 ° C.) and held for ta seconds, and in step S10, the target value of the low temperature side temperature is set to T2 (600 ° C.) and held for tb seconds. The time of one cycle between the high temperature side and the low temperature side is tc seconds, and is set constant.
The temperatures of T2 (600 ° C.) and T3 (650 ° C.) are only examples, and may be within a temperature range in which PM deposited on the DPF can be completely combusted. Just do it.

Next, in step S11, it is determined whether the time Δt = (t3−t1) of the DPF inlet temperature control stage has reached a certain time. If it has reached, the control is terminated in step S12. Returning to S8, the periodic fluctuations between the high temperature side and the low temperature side are repeated.
Note that the time Δt = (t3−t1) of the DPF inlet temperature control stage, or the high temperature side time ta and the low temperature side time tb are set in advance based on tests. For example, ta and tb are each set to about 60 seconds, and Δt is set to about 15 to 20 minutes. The set values of ta, tb, and Δt are set in advance in the target operation time map in accordance with the accumulation amount (set differential pressure) at the start of regeneration, the engine operating conditions (engine speed, engine load) at the start of regeneration, and the like. In addition, based on this map, the throttle amount of the intake throttle valve 11, the injection amount of the early post injection, and the injection amount of the late post injection are controlled by a PID controller or the like.

  As described above, according to the present embodiment, the exhaust gas temperature flowing into the DPF 37 during the regeneration process of the DPF 37 by the DPF inlet temperature control means 44 is a temperature at which PM can be completely combusted (for example, 600 ° C. to 650 ° C.). Since the DPF inlet temperature control means 44 sets the high temperature side temperature T3 and the low temperature side temperature T2 of the cyclic change to perform the regeneration process control, the high temperature exhaust gas is regenerated. By passing through the DPF 37 from the start point of the ignition, a large amount of PM at the start point of the regeneration process can be ignited, and the PM combustion rate can be increased. Compared with the case where the exhaust gas temperature is increased in the later stage of the regeneration process, the PM The time required for burning can be shortened.

On the other hand, if the DPF inlet temperature is set high in the first half of the regeneration process, the risk of overheating increases, but since not only high temperature but also low temperature exhaust gas flows alternately, the danger of overheating is suppressed.
Thus, by periodically changing the DPF inlet temperature from the start of regeneration to during the regeneration process, the time required for burning PM can be shortened while avoiding the danger of excessive temperature rise of the DPF. .
In addition, since the amount of fuel injected into the exhaust gas to raise the exhaust gas temperature can be reduced, it contributes to the improvement of fuel consumption.

  Further, according to the present embodiment, the DPF inlet temperature control means 44 sets the high temperature side temperature T3 and the low temperature side temperature T2 of the periodic change as target values, and the high temperature side time ta and the low temperature side time in one cycle. Since tb is set as a target time and controlled, especially the time until the end of the regeneration process is performed by time management, so simple control without using complicated calculation control for estimating and calculating the PM deposition amount that changes from time to time is performed. And the reproduction processing time can be shortened.

(Embodiment 2)
Next, in the first embodiment, constant values are used for the high temperature side time ta and the low temperature side time tb during the time Δt = (t3−t1) of the DPF inlet temperature control stage. As shown in FIG. 5, the high temperature side time ta is lengthened as the later stage of the reproduction, and ta <ta ′ is set. One cycle time tc is constant until the end of reproduction. It should be noted that the high temperature side time ta may be lengthened stepwise (stepwise) or continuously, depending on the elapsed time of processing. Other configurations are the same as those of the first embodiment.

Thus, since the time kept on the high temperature side becomes longer as the latter stage of the regeneration, the risk that the DPF overheats can be reduced. That is, since the amount of accumulated PM decreases as the regeneration period becomes late, the increase in the combustion rate is small even if the time for holding at the high temperature side is lengthened, so the risk of overheating can be reduced.
Further, also in the sense that the PM that remains unburned in the DPF 37 is eliminated and the PM is completely burned out, it is possible to eliminate the unburned residue by extending the time for holding the PM on the high temperature side in the latter stage of regeneration.

(Embodiment 3)
Next, in the first embodiment, the high temperature side temperature T3 is a constant value during the time Δt = (t3−t1) of the DPF inlet temperature control stage, but in the third embodiment, as shown in FIG. In this way, the high temperature side temperature T3 is increased in the later stage of regeneration, and finally T4 (700 ° C.) is set as a target.
One cycle time tc is constant until the end of reproduction. Note that the high temperature side temperature T3 may be increased stepwise or continuously depending on the elapsed time of the process. Other configurations are the same as those of the first embodiment.

  In the case of the third embodiment as well, as in the setting for increasing the high temperature side time, the amount of accumulated PM decreases as the regeneration period is late. Further, in terms of eliminating PM that remains unburned in the DPF and causing PM to burn out completely, it is preferable to increase the temperature on the high temperature side in the later stage of regeneration.

Further, the low temperature side temperature T2 is preferably set to a constant temperature, and the DPF inlet temperature control is further simplified by setting the low temperature side temperature T2 to be constant (for example, 600 ° C.).
In addition, it is of course possible that the third embodiment is combined with the second embodiment to increase the high temperature side temperature T3 and the high temperature side time ta as the later stage of regeneration, and more effectively the latter stage of regeneration. Combustion can be achieved.

(Embodiment 4)
Next, Embodiment 4 will be described.
The fourth embodiment adds control for preventing the DPF 37 from being overheated during the regeneration process in the first to third embodiments, particularly in the latter stage of regeneration.
That is, as shown in FIG. 7, step S20 and step S21 of the A part are added between step S10 and step S11 in the flowchart of FIG.
In steps S9 and S10, the inlet temperature of the DPF 37 is controlled to change periodically between the high temperature side and the low temperature side. After the low temperature side time tb has elapsed, the outlet temperature sensor 50 detects the outlet temperature of the DPF 37 in step S20. Judgment is made based on whether or not the detected value exceeds the allowable temperature for overheating (for example, 750 ° C.). If exceeded, the low temperature side time tb is lengthened in step S21. That is, it is longer than the low temperature side time tb set in step S10.

By extending the low temperature side time tb in this way, even when the combustion state is in a high temperature in the late stage of regeneration as in the second and third embodiments, the temperature rise of the DPF 37 is effectively suppressed and overheating is prevented. be able to.
The fourth embodiment may be implemented in combination with the first, second, and third embodiments.

  According to the present invention, the DPF inlet temperature during the regeneration process is periodically changed up and down, and the regeneration process is controlled by time management. Therefore, complicated control for estimating and calculating the PM deposition amount that changes from time to time is used. Since the regeneration process can be performed in a short time by simple control without any problems, it is suitable for a regeneration control apparatus for a DPF in an exhaust gas aftertreatment apparatus of a diesel engine.

1 is an overall configuration diagram of exhaust gas treatment of a diesel engine including a DOC (diesel oxidation catalyst) and a DPF (diesel particulate filter) according to Embodiment 1 of the present invention. 3 is a flowchart of DPF inlet temperature control means according to the first embodiment. It is explanatory drawing of early post injection and late post injection. It is explanatory drawing which shows the change state of the DPF inlet_port | entrance temperature target value which concerns on Embodiment 1. FIG. It is explanatory drawing which shows the change state of the DPF inlet_port | entrance temperature target value which concerns on Embodiment 2. FIG. It is explanatory drawing which shows the change state of the DPF inlet_port | entrance temperature target value which concerns on Embodiment 3. FIG. 6 is a flowchart of DPF inlet temperature control means according to a fourth embodiment. It is explanatory drawing which shows a prior art.

Explanation of symbols

1 Engine 11 Throttle valve 17 Fuel injection control device 19 Fuel injection valve 21 Exhaust passage 33 Exhaust gas aftertreatment device 35 DOC (diesel oxidation catalyst)
37 DPF (diesel particulate filter)
40 regeneration control device 44 DPF inlet temperature control means 46 throttle valve control device 48 inlet temperature sensor 50 outlet temperature sensor 52 inlet pressure sensor 54 outlet pressure sensor 56 differential pressure sensor

Claims (6)

An exhaust gas aftertreatment device for a diesel engine provided with a DPF (diesel particulate filter) that collects DOC (diesel oxidation catalyst) and PM (particulate matter) in an exhaust passage is provided, and the PM accumulated in the DPF is disposed at a predetermined time. In the regeneration control device for the DPF that burns and removes in the regeneration process of
A DPF inlet that activates the DOC with pilot injected fuel injected into the combustion chamber and raises the temperature of exhaust gas flowing into the inlet of the DPF by oxidation heat and raises the inlet temperature of the DPF to a renewable temperature of the DPF A temperature raising means, and a DPF inlet temperature control means for periodically changing the DPF inlet temperature during the regeneration process by controlling the DPF inlet temperature raising means, and the DPF inlet temperature control means periodically changes. A regeneration control apparatus for a DPF, which sets a high temperature side temperature and a low temperature side temperature and performs a regeneration process control by setting a high temperature side time and a low temperature side time in one cycle.   2. The DPF regeneration control device according to claim 1, wherein the DPF inlet temperature control means controls one cycle time of the periodic change to be constant, and the high temperature side time is increased as the regeneration period comes. .   The DPF regeneration control apparatus according to claim 1 or 2, wherein the DPF inlet temperature control means raises the high temperature side temperature as the regeneration becomes late.   The DPF regeneration control apparatus according to any one of claims 1 to 3, wherein the low temperature side temperature is set to a constant temperature of a DPF regeneration possible temperature.   A DPF outlet temperature sensor for detecting the outlet temperature of the DPF is provided, and when the detected value by the DPF outlet temperature sensor is equal to or greater than an allowable value, it is determined that the DPF is overheated, and the DPF inlet temperature control means is 2. The DPF regeneration control apparatus according to claim 1, wherein the low temperature side time in one cycle is lengthened.   The DPF inlet temperature raising means includes a throttle of an intake throttle valve provided in an intake passage and an early post-injection of the first fuel injection and a bottom dead center after the early post-injection with a delay from the main fuel injection timing. The DPF inlet temperature control means controls at least one of the throttle amount, the early post injection amount, and the late post injection amount of the intake throttle valve. The DPF regeneration control apparatus according to claim 1, wherein:

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