JP2000161044A - Regeneration control device for particulate filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress increase of a fuel consumption amount of an engine and satisfactorily regenerate a particulate filter. SOLUTION: An independent particulate filter(DPF) 40 is arranged on each exhaust port of a cylinder in a diesel engine 1. An electronic control unit(ECU) 30 of the engine performs one of the operations; phase lag of fuel injection timing into the cylinder, injection in an expansion process, throttling of intake, throttling of exhaust when an amount of the particulates captured by the DPF is increased and the engine is operated within a specified operation area, for increasing the exhaust temperature of the engine and burning the captured particulates. The ECU succeeds the regeneration operation, even when the engine operation area is out of the regeneration area during executing the regeneration, until the DPF temperature sensed by a temperature sensor 53 is reduced to a specified value or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a particulate filter regeneration control device for controlling a particulate filter regeneration operation for collecting particulates in exhaust gas from an internal combustion engine.

[0002]

2. Description of the Related Art The exhaust gas of an internal combustion engine, especially a diesel engine, contains a relatively large amount of exhaust particulates mainly composed of carbon or the like. For this reason, various particulate removal means for preventing the release of these particulates to the atmosphere have been proposed.

As a means for removing particulates, there has been proposed a method of arranging a particulate filter made of, for example, a ceramic in an exhaust passage of an engine and collecting particulates in exhaust gas passing through the filter. When such a particulate filter is used, the amount of particulate collected by the filter increases with the operation of the engine, and the exhaust pressure loss at the filter increases. Therefore, in order to prevent a decrease in engine performance due to an increase in exhaust pressure loss, it is necessary to periodically burn the particulates collected by the filter and regenerate the particulate filter.

In this case, especially in a diesel engine, since the exhaust gas temperature is relatively low, the particulate does not spontaneously ignite except during a considerably high load operation, and some auxiliary means for raising the particulate temperature to the ignition temperature. It is necessary to carry out a reproduction operation using. An example of a particulate filter regeneration control device for performing this type of regeneration operation is disclosed in, for example, Japanese Patent Application Laid-Open No. 5-29602.
There is one described in Japanese Patent No.

[0005] The apparatus disclosed in this publication is provided in a filter when the particulate collection amount of the particulate filter is equal to or more than the first collection amount and the state in which the particulate filter temperature is equal to or more than a predetermined value continues for a certain period of time. The electric heater is energized to increase the filter temperature and ignite the particulates, thereby regenerating the particulate filters. Further, in the apparatus of the above publication, when the particulate collection amount of the particulate filter is equal to or larger than the second collection amount larger than the first collection amount, the filter temperature is equal to or smaller than the predetermined value. Even in such a case, the electric heater is energized to increase the filter temperature, and the particulate filter is regenerated.

Generally, when a particulate filter regeneration operation is performed by using auxiliary means such as an electric heater, the engine exhaust temperature at the time of executing the regeneration operation becomes important. For example,
When the exhaust gas temperature is low, the filter temperature is also low. Therefore, if the filter temperature is raised to the ignition temperature of the particulates by using an electric heater or the like, a large amount of energy is required and the fuel consumption of the engine increases. For this reason, the regeneration control device of the above-mentioned publication does not normally perform the regeneration of the filter unless the filter temperature is higher than the predetermined temperature.

Further, even if the particulate filter trapped in the filter is burning during execution of the particulate filter regeneration operation, if the engine operating state changes and the exhaust gas temperature drops, the filter is cooled by low-temperature exhaust gas. I will.
In such a case, it is necessary to maintain the filter temperature equal to or higher than the particulate ignition temperature with an electric heater or the like in order to maintain the combustion of the particulates. Similarly, the fuel consumption of the engine is reduced due to the large energy consumption. Will cause an increase.

Therefore, when the regeneration operation of the normal particulate filter is performed, an operation region (regeneration operation region) of the engine in which the exhaust gas temperature is equal to or higher than a predetermined value is set in advance, and the operation state of the engine is determined by the regeneration operation. The regeneration operation of the particulate filter is performed when the vehicle enters the region, and the regeneration operation is stopped when the engine operation state changes during the regeneration operation and the vehicle is out of the regeneration operation region, thereby reducing the engine fuel consumption. We try to prevent the increase.

[0009]

However, if the execution of the particulate filter regeneration operation is determined only on the basis of the exhaust gas temperature (engine operation range) as described above, the engine operation can be performed even during the regeneration operation. If the state changes and the vehicle goes out of the regeneration operation region, the regeneration operation is immediately stopped, and there is a problem that the regeneration of the particulates becomes insufficient.

On the other hand, in order to solve this problem, even if the engine operating state is out of the regeneration operation range during the regeneration operation, auxiliary means such as an electric heater are used until all the collected particulates burn. When the regenerating operation is continued by using the regenerating operation, the particulates are sufficiently regenerated, but the fuel consumption of the engine is increased as described above.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a particulate filter regenerating apparatus that can sufficiently regenerate a particulate filter while suppressing an increase in fuel consumption of an engine. .

[0012]

According to the present invention, there is provided a regeneration control device for a particulate filter for trapping particulates in exhaust gas of an internal combustion engine, wherein the internal combustion engine operates within a predetermined regeneration operation region. Regeneration control means for performing a regeneration operation for burning the particulates collected by the particulate filter when the regeneration operation is being performed, wherein the regeneration control means changes the operating condition of the internal combustion engine during the regeneration operation and causes the regeneration. A regeneration control device for a particulate filter characterized by continuing regeneration operation when the temperature of the particulate filter satisfies a predetermined temperature condition when the temperature falls outside the operating range.

That is, according to the present invention, even when the engine operating state is out of the regeneration operation range during the execution of the regeneration operation of the particulate filter, if the particulate filter temperature satisfies the predetermined temperature condition, the regeneration is performed as it is. Continue the operation. When the engine operation state changes from the regeneration operation region to the non-regeneration operation region (the operation region outside the regeneration operation region), the exhaust gas temperature decreases, but the filter temperature does not immediately decrease but gradually decreases. Therefore, even if the engine operating state changes from the regeneration operation region to the non-regeneration operation region, the regeneration operation can be continued without greatly increasing the energy required for the regeneration operation until the actual filter temperature decreases. Also in the present invention, if the actual filter temperature drops to a temperature that is inappropriate for the regeneration operation (a temperature at which the energy consumed by the regeneration operation is greatly increased), the regeneration operation is stopped. Since the execution time of the regeneration operation is longer than before, the amount of the burning particulates increases, and the regeneration of the particulate filter becomes better.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a schematic configuration when a particulate filter regeneration control device of the present invention is applied to an automobile diesel engine. In FIG. 1, reference numeral 1 denotes an automobile internal combustion engine. In the present embodiment, the engine 1 is a four-cylinder diesel engine, and each cylinder is provided with an in-cylinder fuel injection valve 111 that injects fuel directly into the cylinder. The fuel is supplied from a high-pressure fuel injection pump 113 to a common rail (accumulator) 115 to which each fuel injection valve 111 is connected.
And injected from the common rail into each cylinder at a predetermined timing by each fuel injection valve 111.

In FIG. 1, reference numeral 21 denotes an intake manifold for connecting the intake port of each cylinder to the intake passage 2, and reference numeral 31 denotes an exhaust manifold for connecting the exhaust port of each cylinder to the exhaust passage 3. In the present embodiment, the supercharger 35 for supercharging the engine 1
The exhaust passage 3 is connected to an exhaust inlet of the supercharger 35, and the intake passage 2 is connected to an intake discharge outlet of the supercharger 35. The intake passage 2 is provided with an intercooler 25 for cooling intake air supplied from the supercharger 35 and an intake throttle valve 27. The intake throttle valve 27 is
An appropriate type of actuator 27a, such as a stepper motor or a negative pressure actuator, which operates in response to a signal from the ECU 30, which will be described later, is provided with an opening corresponding to the signal from the ECU 30 to limit the intake flow rate of the engine. In addition, turbocharger 3
An exhaust throttle valve 37 provided with an actuator 37a similar to the intake throttle valve 27 is provided in the exhaust passage 3 on the downstream side of 5, and performs an exhaust throttle by setting an opening in accordance with a signal from the ECU 30.

In FIG. 1, reference numeral 33 denotes an EGR passage which connects the engine exhaust system and the intake system and recirculates part of the engine exhaust to the intake system, and 23 denotes an EGR valve arranged in the EGR passage. E
The GR valve 23 includes an appropriate actuator (not shown) such as a stepper motor and a negative pressure actuator.
The opening degree corresponding to the signal from the ECU is taken, and the flow rate of exhaust gas (EGR gas) returned to the intake system through the EGR passage 33 is controlled in accordance with the engine operating state.

In this embodiment, a particulate filter (diesel particulate filter, hereinafter referred to as "DPF") 40 is provided in an exhaust branch pipe connecting the exhaust manifold 31 to each exhaust port. DPF4
No. 0 has a large number of through-holes formed of a heat-resistant porous material such as ceramics and forming an exhaust passage in the axial direction (exhaust flow direction). Each of these through holes is closed at one of the upstream end and the downstream end in the exhaust flow direction by a plug, and the through hole whose upstream end is closed and the through hole whose downstream end is closed alternately adjoin each other. It is arranged. For this reason, the exhaust gas discharged from the exhaust port of each cylinder flows into the through hole in which the upstream end of each DPF is opened (the downstream end is closed), and passes through the porous partition separating the through holes from each other. Then, the downstream end flows into the open through hole and flows out of the DPF from the downstream end. Particulates contained in the exhaust gas are collected when the exhaust gas passes through the porous partition.

In this embodiment, the DPF 4 having a relatively small capacity is used.
0 is provided adjacent to the exhaust port of each cylinder,
Because high-temperature exhaust from the cylinder flows directly into the DPF,
The temperature of the PF 40 can be kept high. Further, since each DPF 40 has a small capacity, the amount of particulates that can be collected is small, and it is necessary to set the execution interval of the DPF regeneration operation to be described later relatively short. Over time, the DPF temperature rises and particulate combustion starts. Further, since the amount of collected particulates is small, the combustion of the collected particulates can be completed in a short time, and the time required for the regeneration operation can be reduced. In this embodiment, since a diesel engine is used as the engine 1, the engine exhaust temperature during normal operation is relatively low. In the present embodiment, the so-called separation type DPF in which the small-capacity DPF 40 is disposed at the exhaust port of each cylinder is employed. The regeneration of the DPF 40 can be completed.

In FIG. 1, reference numeral 30 denotes an electronic control unit (ECU) of the engine 1. In the present embodiment, the ECU 30 is a microcomputer having a known configuration including a RAM, a ROM, and a CPU. The ECU 30 performs basic control such as fuel injection control of the engine 1, and also controls the DPF 40 in accordance with the engine operating state as described later. It has a function as playback control means for performing a playback operation.

In order to perform these controls, a signal corresponding to the amount of engine intake air from an air flow meter 51 provided in the engine intake passage and a temperature sensor 53 provided in the exhaust manifold 31 are provided to an input port of the ECU 30. D
A signal corresponding to the exhaust gas temperature after passing through the PF 40 is input, and a pulse signal is input from the rotation speed sensor 55 disposed near the engine crankshaft (not shown) at every constant rotation angle of the engine crankshaft. ing. Further, in the present embodiment, a signal representing the accelerator pedal depression amount (accelerator opening) of the driver is input to an input port of the ECU 30 from an accelerator opening sensor 57 disposed near an accelerator pedal (not shown) of the engine 1. Have been. The ECU 30 converts the output of the air flow meter 51, the output of the accelerator opening sensor 57, and the output of the temperature sensor 53 at predetermined intervals into an A / D, and obtains the intake air amount Q, the accelerator opening ACCP, and the exhaust temperature T in a predetermined area of the RAM of the ECU 30. At the same time, the engine speed NE is calculated from the interval of the pulse signal from the speed sensor 55 and stored in a predetermined area of the RAM. E
The CU 30 determines in advance R based on the accelerator opening ACCP detected by the accelerator opening sensor 57 and the engine speed NE.
The engine basic fuel injection amount and fuel injection timing are calculated based on the relationship stored in the OM, and the basic fuel injection amount is corrected according to the engine operating state to set the engine fuel injection amount QIJ and the fuel injection timing. I do. In the present invention, the method for setting the fuel injection amount and the fuel injection timing is not particularly limited, and any of the known methods for a diesel engine can be used.

On the other hand, the output port of the ECU 30 is connected to a fuel injection valve 11 of each cylinder via a fuel injection circuit (not shown) in order to control the amount and timing of fuel injection into each cylinder.
1, and is connected to a high-pressure fuel pump 113 via a drive circuit (not shown) to control the amount of fuel pumped from the pump 113 to the common rail 115. Also,
The output port of the ECU 30 is further connected to an actuator 27 of the intake throttle valve 27 via a drive circuit (not shown).
a, Actuator 37a of exhaust throttle valve 37 and EGR
The opening degree of the intake throttle valve 27 and the exhaust throttle valve 37 and the EG passing through the EGR valve 23 are connected to the actuator of the valve 23.
The R gas amount is controlled.

Next, the regeneration operation of the DPF 40 in this embodiment will be described. In the present embodiment, the DPF 40 has a different regeneration method depending on the operating state (load state) of the engine.
To play back. FIG. 2 is a diagram showing the area division of the engine operating state (load state) in the present embodiment, in which the vertical axis represents the engine output torque (fuel injection amount QIJ), and the horizontal axis represents the engine speed NE. I have. In this embodiment, the output torque and the number of revolutions are divided into four regions as indicated by I to IV in FIG. 2, and different regeneration operations of the DPF 40 are performed for each region.

Hereinafter, the reproduction operation in each area will be described. (1) Region I (Natural regeneration region) As shown in FIG. 2, the region I is a region near the full load of the engine. In this region, the exhaust gas temperature of the engine also increases according to the load, and the temperature of the DPF 40 becomes equal to or higher than the particulate ignition temperature (for example, 600 ° C.) without performing an auxiliary temperature raising operation. For this reason, when the engine operation state is in the region I, the DPF 40 is naturally regenerated. The DPF regeneration in the region I does not require any special operation for regeneration, so that the fuel consumption of the engine does not increase.

(2) Region II (Fuel Injection Timing Retardation) Region II is a state in which the engine load is lower than in region I.
Since the engine exhaust temperature has also decreased according to the load, the DPF
The temperature is below the ignition temperature of the particulates.
For this reason, the particulate does not start burning naturally, and even during the combustion, the DPF temperature may become lower than the particulate combustion lower limit temperature (for example, 400 ° C.) and the combustion may stop. Therefore, in order to regenerate the DPF, it is necessary to perform a regeneration operation different from the normal operation to raise the DPF temperature. In the present embodiment, in the region II, the exhaust gas temperature is raised by retarding the fuel injection timing to maintain the DPF temperature at a high temperature. When the fuel injection timing is retarded, the combustion timing of fuel in the cylinder is delayed, so that relatively high temperature combustion gas is discharged in the exhaust stroke without sufficiently lowering the temperature in the expansion stroke, and the exhaust temperature rises .
In this load range, the exhaust gas temperature is relatively high even during normal operation, so that the increase in engine fuel consumption is relatively small.

(3) Region III (Expansion stroke injection, EGR
In this region, the exhaust gas temperature in the normal operation is in the region I or II.
Since the temperature becomes lower, it is difficult to raise the exhaust gas temperature to the ignition temperature of particulates only by retarding the fuel injection timing. For this reason, in the region III, in addition to the normal fuel injection (main fuel injection), additional fuel injection (expansion stroke injection) is performed during the expansion stroke of each cylinder, and the EGR valve 2
3 is opened to introduce EGR gas into each cylinder. Since the EGR gas is hot, the intake air temperature of each cylinder of the engine rises,
Further, since the fuel injected during the expansion stroke burns, the exhaust gas temperature further rises. In this region, the additional fuel injection is performed during the expansion stroke, so that the fuel consumption of the engine increases more than in region II.

(4) Region IV (Expansion stroke injection, combined use of intake / exhaust throttle) In region IV, the engine load is low and the exhaust temperature is considerably low. In this region, the exhaust gas temperature does not rise to a temperature sufficient for particulate combustion unless the fuel injection amount of the expansion stroke injection is significantly increased. On the other hand, the engine output also rises due to the combustion of the fuel injected during the expansion stroke. Therefore, if the fuel injection amount in the expansion stroke is greatly increased, the engine output torque will increase. Accordingly, in this region, the fuel injection amount in the expansion stroke is greatly increased, and either or both of the intake throttle by the intake valve 27 and the exhaust throttle by the exhaust valve 37 are performed to suppress an increase in engine output torque. This makes it possible to regenerate the DPF without greatly deteriorating the operability of the engine.
It is larger than III.

(5) Non-regenerative operation area In a state where the engine load is lower than the area IV (area V in FIG. 2), the engine exhaust temperature is greatly reduced. Therefore, in each of the above methods, the engine exhaust temperature is increased to the particulate ignition temperature. It will be difficult to make it happen. Therefore, in the region V of FIG.
F is not reproduced.

In this embodiment, the ECU 30 includes the DPF 40
The amount of the collected particulates is constantly monitored, the amount of the collected particulates reaches a predetermined amount, and the engine is operated in any one of the operating regions II to IV. In such a case, the regeneration of the DPF 40 is started by a regeneration method according to the operation region. The amount of particulates collected by the DPF 40 can be calculated, for example, by detecting a differential pressure between the inlet and the outlet of the DPF 40. In the present embodiment, the ECU 30 controls the collected amount counter based on the engine operating state. The amount of trapped particulates is calculated by increasing or decreasing the amount.

That is, the amount of particulates generated in the engine is determined by the engine load state (eg, engine fuel injection amount and engine speed). Therefore, in the present embodiment, the actual engine is operated in advance by changing the combination of the engine fuel injection amount and the number of revolutions, and the amount of particulates discharged per unit time from the engine is experimentally obtained. It is stored in the ROM of the ECU 30 in the form of a numerical table using the rotation speed. The ECU 30 calculates the amount of particulates generated per unit time from the numerical value table using the fuel injection amount and the rotation speed of the engine at regular intervals during the operation of the engine,
The collection counter is increased by a value obtained by multiplying the generated amount by a predetermined collection rate. As a result, the value of the collection counter indicates the amount collected by the DPF 40 among the particulates generated by the engine. On the other hand, when the temperature of the DPF 40 increases due to the natural regeneration region (region I in FIG. 2) or the execution of the regeneration operation, the particulates trapped in the DPF burn. In this case, the amount of particulates burned per unit time is determined by the DPF temperature. DPF4
The zero temperature is substantially equal to the exhaust gas temperature at the outlet of the DPF 40. For this reason, in the present embodiment, the relationship between the exhaust gas temperature detected by the temperature sensor 53 at the outlet of the DPF 40 and the amount of particulate combustion per unit time in the DPF 40 is experimentally obtained in advance, and the exhaust gas temperature is used in the ROM of the ECU 30. It is stored in the form of a numerical table. The ECU 30 performs the operation of increasing the value of the collection counter in accordance with the amount of particulates generated by the engine as described above, and based on the exhaust gas temperature, per unit time of the particulates collected in the DPF from the numerical value table. Calculate the amount of combustion,
The value of the collection counter is reduced by the calculated amount of combustion.

That is, the ECU 30 increases the value of the collection counter by the amount of particulates collected in the DPF at regular intervals during the operation of the engine, and when the DPF temperature rises due to a change in the engine operation state or execution of the regeneration operation. , The value of the trapping counter is reduced by the amount of particulates burned on the DPF. As a result, the value of the collection counter always accurately represents the amount of particulates present in the DPF 40.

In this embodiment, the exhaust gas temperature detected by the temperature sensor 53 provided at the outlet of the DPF is used as the temperature of the DPF 40. However, a temperature sensor is arranged on the DPF 40 itself to directly detect the DPF temperature. May be. As described above, in the present embodiment, when the engine is operating in the region I, the DPF regeneration operation starts spontaneously regardless of the amount of particulates collected in the DPF 40. In the case of IV, the reproduction operation is started only when the particulate amount exceeds a predetermined value. In this case, the regenerating operation to be started is an operation according to the driving region as described above. Also, if the value of the above-mentioned collection counter becomes 0 during the execution of the regeneration operation in the regions II to IV (that is, when the entire amount of the collected particulates burns), the regeneration operation ends.

Further, in the present embodiment, for example, if the operating region changes from II to IV while the engine is operating in the operating region I and the particulate combustion continues,
It does not immediately shift to the regeneration operation in the operation range from II to IV. That is, even if the operating region changes from I to IV, the DPF temperature does not immediately decrease from the region II to the temperature corresponding to IV, but gradually decreases over a certain period of time. Therefore, for example, from the region I to the region II
Even if the operating state shifts to the above, if the temperature rise operation is light (for example, the fuel injection is retarded with a smaller retardation amount than the regeneration operation in the region II) while the DPF temperature is high, the burning of the particulates can be sufficiently continued. It is possible. In this case, by continuing the combustion of the particulates by the mild temperature raising operation, the increase in the fuel consumption of the engine can be reduced as compared with the case where the regeneration operation in the region II is executed. For this reason, in the present embodiment, when the operating state changes to another area during the particulate combustion in the area I, a slight temperature increase operation is performed while the DPF temperature is high so that the particulate combustion is continued. ing.

As described above, the DPF used in the present embodiment is of a separation type, and the amount of particulates that can be collected is relatively small, but the time required for regeneration is shortened instead. For this reason, even when the operating state shifts from the region I to another region, the probability that the regeneration is completed (the entire amount of particulates is burned) before the DPF temperature decreases is relatively large. Therefore, as described above, even when the operating state shifts from the region I to another region, the frequency of completion of the regeneration of the DPF by only a slight temperature raising operation increases, so that the engine fuel consumption for the DPF regeneration operation is reduced. The increase is suppressed.

On the other hand, the same operation is performed when the operation state changes to the region V (non-regeneration operation region) during DPF regeneration in the regions II to IV. Also in this case, the DPF temperature is a temperature at which combustion can be maintained for a certain period of time after the engine operating state has changed to the region V. Therefore, in the present embodiment, if the operating state shifts to the non-regenerative operation region during the execution of the DPF regeneration operation, the regeneration operation is not immediately stopped, and while the DPF temperature is in the range in which the particulate combustion can be maintained, the region IV is maintained. A regeneration operation (combined use of expansion stroke injection and intake and exhaust throttling) is performed. As a result, the probability of completion of the particulate combustion increases, and the DPF is sufficiently regenerated. Further, after the engine operating state is in the region V, the DPF decreases as the exhaust gas temperature decreases.
Although the temperature also decreases, in the present embodiment, when the DPF temperature decreases to such a degree that particulate combustion cannot be maintained only by the regeneration method in the region IV, the DPF regeneration operation is stopped. Therefore, it is possible to prevent the regeneration of the DPF by greatly increasing the exhaust gas temperature even when the temperature of the DPF decreases, and to suppress an increase in the fuel consumption of the engine.

FIGS. 3 and 4 are flowcharts for specifically explaining the above-described DPF regeneration operation of the present embodiment.
4 shows a DPF regeneration operation start condition determination operation, and FIG.
Each of the reproduction operation stop condition determination operations is shown. 3 and 4 are performed by a routine executed by the ECU 30 at regular intervals. In the operation of FIG. 3, D is calculated using the value of the particulate collection counter PC described above.
When the particulate collection amount of the PF 40 has reached the predetermined value PC ₀ and the engine is operating in any one of the regions II to IV in FIG. 2, the forced regeneration operation ((2) above) , The playback operation described in (4) is started.

That is, when the operation of FIG. 3 starts,
In step 301, the value of the trapping amount counter PC, the engine fuel injection amount QIJ, and the engine speed NE, which are separately calculated by a trapping amount counter arithmetic operation (not shown), are separately read. Next, at step 303, the current D
It is determined based on the value of the parameter RX whether or not the regeneration operation of the PF 40 is being performed (the particulate is burning). Here, the value of the parameter RX represents the type of the reproduction operation that is currently being executed, as will be described later. RX = 1 indicates that the natural regeneration (particulate combustion) is currently being performed in the region I. , RX = 2 indicates that the forced regeneration operation (retarding the fuel injection timing) in the region II is being executed. RX = 3 and RX = 4 correspond to the region I, respectively.
Regeneration operation in II and region IV (expansion stroke injection and E
GR and the expansion stroke injection and the intake / exhaust throttle). Further, RX =
Reference numeral 5 indicates that the above-described mild temperature raising operation (the fuel injection timing is retarded with a small retardation) is being executed. In addition,
RX = 0 indicates that particulate combustion is not currently being performed.

If RX ≠ 0 in step 303, one of the reproduction operations is currently being performed, and there is no need to judge a new start condition of the reproduction operation, so this operation ends immediately. If RX = 0, the reproduction operation is not currently being executed, and the reproduction operation execution start condition is determined in step 305 and subsequent steps. That is, in step 305, based on the fuel injection amount QIJ and the engine speed NE read in step 301, it is determined from the map in FIG.

When operating in region I, the DPF
Since the burning of particulates has started regardless of the current particulate collection amount of step 40, step 3
07, the value of the parameter RX is set to 1 (natural reproduction is being executed).
Set to. If it is determined in step 305 that the vehicle is not currently operating in the region I, the process proceeds to step 309, where the current D
Whether or not the particulate collection amount of the PF 40 has reached a predetermined value is determined based on the value of the collection counter PC.

The particulate collection amount has not reached the predetermined value in the case was PC <PC ₀ at step 309, it is not necessary to start a new forced regeneration operation, the operation step 311 following Exit immediately without executing. If PC ≧ PC ₀ in step 309, the amount of particulates collected by the DPF 40 has increased, and it is necessary to start the regeneration operation. Therefore, in steps 311 to 321 according to the engine operating region, Set the value of the parameter RX.

That is, in steps 311 to 321, the current engine operating conditions are changed based on the values of the fuel injection amount QINJ and the engine speed NE from II to IV in the map of FIG.
(Step 3)
11, 315, 319), if any of these areas, the value of the parameter RX is set to a value of 2 to 4 according to the area (steps 313, 317, 32).
1). If the current engine operation region is not the region IV in step 319, it means that the engine is currently operating in the region V, so that the DPF 40 is not subjected to the forced regeneration operation. That is, in this case, the operation is terminated without changing the value of the parameter RX (while maintaining the value of RX = 0).

When the value of the parameter RX is set to any one of 2 to 4 by the operation of FIG. 3, the DPF 40 regeneration operation corresponding to the value of the parameter RX is performed by an operation separately executed by the ECU 30 (see (2) above). To (4) operation)
Is executed. FIG. 4 illustrates an operation of determining a stop condition of a reproduction operation being executed. In this operation, as described above,
If the engine operating state changes to another area during the particulate combustion in the engine operating area I, a slight temperature increasing operation (RX = 5) until the DPF 40 temperature falls below a predetermined temperature.
To maintain the burning of the particulates. Further, when the engine operation state changes to the region V (non-regeneration operation region) during execution of the forced regeneration operation in any of the operation regions II to IV, the DPF 40 temperature decreases to a temperature at which particulate combustion cannot be maintained. Until the above, the same forced regeneration operation as in the region IV is continued.

When the temperature of the DPF 40 drops below the above-mentioned temperature after shifting to the region V, and when the value of the trapping counter PC becomes 0 during these regenerating operations (the particulate matter collected by the regenerating operation is lost). When the entire amount has burned), the value of the parameter RX is set to 0, and the forced regeneration operation is stopped. That is, when this operation is started, in step 401, the DP detected by the temperature sensor 53 together with the values of the collection counter PC, the fuel injection amount QIJ, and the engine speed NE are displayed.
The F40 outlet exhaust gas temperature (DPF temperature) T is read.
Then, in step 403, it is determined based on the value of the parameter RX whether any reproduction operation is currently being executed. If RX = 0 in step 403, no regeneration operation (particulate combustion) is currently being performed, and there is no need to determine the conditions for stopping the regeneration operation, so this operation ends immediately.

On the other hand, in step 403, RX ≠ 0, ie,
If RX = 1 to 5, the reproduction operation is currently being executed.
Therefore, first, in step 405, the current engine
It is determined whether or not the vehicle is being driven, and
If yes, go to step 407 to set the value of parameter RX.
Is set to 1 again. Also, if the current operation area is the area I
If it is out of the range, then in step 409, DPF4
0 temperature T is the predetermined temperature T ₁It is determined whether or not this is the case. temperature
T₁Corresponds to the natural ignition temperature of particulates,
In the embodiment, for example, T₁Is set to a value around 600 degrees C
ing.

If T ≧ T ₁ in step 409, the engine operation region is out of the region I, but the DP
Since the combustion of particulates can be maintained by performing a slight temperature raising operation with a high F temperature, the process proceeds to step 411, where the value of the parameter RX is set to 5. As a result, the fuel injection timing of the engine is slightly retarded (retarded by a smaller amount than the regeneration operation in the region II), and the DPF
The temperature drop rate of 40 is even smaller. As a result, it is possible to continue particulate combustion without performing a forced regeneration operation of the regions II to IV even in regions other than the region I and suppressing an increase in engine fuel consumption.

[0045] If the DPF temperature is not lower than T ₁ at step 409, then whether the engine operating region in steps 413 421 is changed to any one region II of IV and the QINJ and NE And if the value has changed to any one of the regions II to IV, the value of the parameter RX is reset to a value corresponding to the region (any of 2 to 4). Thus, the regeneration operation is continuously performed according to the engine operation area.

At step 421, the engine operation area is set to the area IV.
, That is, if the engine is currently operating in region V, then at step 425 the current DP
The temperature T of F40 is whether or not lower than a predetermined value T ₂ is determined. T ₂ is the minimum temperature at which the particulates can be burned, and is set to a value near, for example, 400 ° C. in the present embodiment.

If T ≧ T ₂ in step 425, the engine operation region is in the region V (non-regeneration operation region), but the DPF 40 temperature has fallen to a point where particulate combustion cannot be maintained. No, step 4
From 25, the process proceeds to step 423, where the value of the parameter RX is set to 4. As a result, the forced regeneration operation in the region IV is performed, and also in the region V, the decreasing speed of the DPF temperature is further reduced, and the burning of the particulates continues. As described above, even if the engine operation region enters the non-regenerative operation region, D
By continuing the DPF regeneration operation without interruption as long as the temperature of the PF 40 is within the range in which particulate combustion can be maintained, the possibility of DPF regeneration being completed increases. Further, the process proceeds to step 431 because it is difficult to maintain the burning of particulates in the longer reproducing operation region IV when it becomes a T <T ₂ in step 425, forcing the value of the parameter RX is set to 0 The playback operation is stopped. This prevents a large amount of energy from being consumed for raising the temperature of the DPF, and suppresses an increase in the fuel consumption of the engine.

When the current value of the particulate counter PC becomes smaller than 0 in step 427, that is, when the reproducing operation of any of RX = 1 to 5 is performed, that is, when the total amount of the collected particulates is Is burned, the value of the trapping amount counter PC is set to 0, the value of the parameter RX is set to 0 in step 431, and the regeneration operation is stopped.

[0049]

According to the present invention, the regeneration operation is continued as long as the DPF temperature is high, even if the engine operating state changes during the execution of the DPF regeneration operation and the operating range becomes unsuitable for the regeneration operation. This makes it possible to sufficiently regenerate the particulate filter while suppressing an increase in the fuel consumption of the engine.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment in which a particulate filter regeneration control device of the present invention is applied to an automobile diesel engine.

FIG. 2 is a map showing an operation region in which a particulate filter regeneration operation of the engine of FIG. 1 is performed.

FIG. 3 is a flowchart illustrating an example of a particulate filter regeneration operation start condition determination operation.

FIG. 4 is a flowchart illustrating an example of an operation for determining a stop condition of a particulate filter regeneration operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Diesel engine 111 ... In-cylinder fuel injection valve 27 ... Intake throttle valve 30 ... Electronic control unit (ECU) 3 ... Exhaust passage 31 ... Exhaust manifold 37 ... Exhaust throttle valve 33 ... EGR passage 23 ... EGR valve 40 ... Particulate filter (DPF) 53 temperature sensor

Claims (1)

[Claims] 1. A regeneration control device for a particulate filter that collects particulates in exhaust gas of an internal combustion engine, wherein the particulate filter is controlled when the internal combustion engine is operated within a predetermined regeneration operation range. Regeneration control means for performing a regeneration operation for burning the collected particulates, wherein the regeneration control means controls the particulate matter when the operating condition of the internal combustion engine changes during execution of the regeneration operation to be outside the regeneration operation range. A regeneration control device for a particulate filter, wherein the regeneration operation is continued when the temperature of the filter satisfies a predetermined temperature condition.