JP4061999B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas purification apparatus for an internal combustion engine provided with an exhaust particulate trap for collecting exhaust particulates in an internal combustion engine represented by a diesel engine, and more particularly to a technique for preventing cracks and melting damage during regeneration.
[0002]
[Prior art]
For example, in a diesel engine as an internal combustion engine, processing of exhaust particulates (so-called PM) in exhaust gas is a big problem, and an exhaust particulate trap is arranged in an exhaust passage to collect exhaust particulates, and the collected exhaust Various exhaust purification devices that regenerate the exhaust particulate trap by burning and removing the exhaust particulate when the particulate reaches a predetermined level have been studied.
[0003]
In Japanese Patent Laid-Open No. 2001-254616, when it is necessary to regenerate the exhaust particulate trap by burning and removing the exhaust particulate collected in the exhaust particulate trap, the fuel is discharged during the expansion stroke or exhaust stroke after the main injection ends. The combustion of exhaust particulates is promoted by performing post injection from the injection valve, but the temperature of the exhaust particulate trap being regenerated is monitored, and the temperature of the exhaust particulate trap is above a predetermined value and the rate of temperature change is above a predetermined value. If there is, the playback operation is stopped.
[0004]
In JP-A-8-319819, the engine is operating at a high rotation and high load, and the exhaust temperature is changed from 600 ° C. to an operation state in which exhaust particulates such as idling are rapidly burned. In some cases, an excessive increase in temperature is avoided by increasing the EGR from the normal level.
[0005]
[Problems to be solved by the invention]
However, as described in Japanese Patent Application Laid-Open No. 2001-254616, even when the temperature of the exhaust particulate trap is equal to or higher than a predetermined value and the temperature change rate is equal to or higher than a predetermined value, the post-injection is stopped and the regeneration operation is stopped. Although the temperature of the exhaust gas flowing into the exhaust particulate trap decreases, conversely, the exhaust air-fuel ratio increases and the oxygen concentration that promotes combustion of the exhaust particulate increases. For this reason, it is impossible to stop the re-burning of the exhaust particulate once ignited, and the re-combustion of the exhaust particulate is continued. There is a risk of high temperatures locally. Therefore, the exhaust particulate trap cannot be sufficiently prevented from cracking or melting.
[0006]
Further, in the technique disclosed in Japanese Patent Laid-Open No. 8-319819, when the operating state is changed so as to cause rapid combustion of exhaust particulates, the EGR is increased more than usual. It seems that increasing the EGR and reducing the oxygen concentration in this way seems to suppress the reburning of the exhaust particulates at first glance, but in reality, increasing the EGR increases the exhaust temperature and increases the exhaust gas from the exhaust system. Since the exhaust flow rate flowing into the exhaust particulate trap decreases by taking out the EGR gas and the amount of heat taken out from the exhaust particulate trap decreases, the exhaust particulate trap temperature tends to rise due to the combustion of the exhaust particulate. Therefore, as in JP 2001-254616 A, it is not possible to sufficiently prevent the exhaust particulate trap from cracking or melting.
[0007]
[Means for Solving the Problems]
In the exhaust emission control device for an internal combustion engine according to the present invention, an exhaust catalyst for oxidizing and purifying inflowing exhaust components is disposed in the exhaust passage of the internal combustion engine, and further, an exhaust particulate trap for trapping inflowing exhaust particulates on the downstream side. Is placed. And A NOx trap catalyst is further placed between the oxidation catalyst and the exhaust particulate trap. The Also, It is also possible to integrate the oxidation catalyst with the NOx trap catalyst.
[0008]
In the present invention, the temperature detecting means for detecting the temperature of the exhaust particulate trap, the combustion speed detecting means for detecting the combustion speed of the exhaust particulate trapped in the exhaust particulate trap, and the fuel is injected in the expansion stroke or the exhaust stroke. Fuel injection means for enabling post injection. And an exhaust air / fuel ratio control means for making the exhaust air / fuel ratio rich by the post injection when the temperature of the exhaust particulate trap exceeds a predetermined temperature and the combustion speed of the exhaust particulates exceeds a predetermined speed. Yes.
[0009]
When the exhaust air-fuel ratio becomes rich by post injection as described above, oxygen in the exhaust discharged from the internal combustion engine reacts with unburned HC and CO generated by post injection by the oxidation catalyst, and exhaust particulate trap The amount of oxygen in the exhaust gas flowing into the exhaust gas (exhaust oxygen concentration) becomes almost zero. Therefore, combustion of the exhaust particulates is stopped, and an excessive temperature rise of the exhaust particulate trap is suppressed.
[0010]
Further, as the exhaust air-fuel ratio control means, means other than post injection, such as a reduction in the intake air amount to the internal combustion engine and an increase in the exhaust gas recirculation amount can be used.
[0011]
【The invention's effect】
According to the present invention, regardless of whether or not the exhaust particulate trap is being regenerated, the ignition conditions of the exhaust particulate trapped in the exhaust particulate trap are started and the exhaust particulate change is rapidly progressed. Even when this occurs, it is possible to reliably suppress the combustion speed of the exhaust particulates and prevent the exhaust particulate trap temperature from rising rapidly. Therefore, it is possible to reliably prevent cracking and melting damage of the exhaust particulate trap.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
[0013]
FIG. 1 is a system configuration diagram of an exhaust purification system according to a first embodiment of the present invention.
[0014]
In FIG. 1, 1 indicates a diesel engine (hereinafter simply referred to as an engine), and 3 indicates an exhaust passage of the engine 1.
[0015]
The present embodiment is an example in which the present invention is applied to an engine 1 having four cylinders # 1 to # 4 and having a four-cylinder serial arrangement in which the firing order is # 1- # 3- # 4- # 2. The four cylinders are divided into a cylinder group A consisting of # 2 cylinders and # 3 cylinders, and a cylinder group B consisting of # 1 cylinders and # 4 cylinders so that the firing order does not continue, and each has an exhaust system. The upstream part of is connected.
[0016]
The reason why the cylinder group is divided into the cylinder group A consisting of # 2 and # 3 cylinders and the cylinder group B consisting of # 1 and # 4 cylinders is as follows. This is because the reduction of the air charging efficiency is suppressed. When priority is given to the layout of the exhaust system, the cylinder group A is set to # 1, # 2 cylinders, and the cylinder group B is set to # 3, # 4 cylinders. It can also be.
[0017]
In addition, for example, in the case of considering exhaust interference suppression in a six-cylinder in-line engine whose ignition order is # 1- # 5- # 3- # 6- # 2- # 4, set the cylinder group A to # 1, # 2. , # 3 cylinder, and cylinder group B is # 4, # 5, # 6 cylinder. In the present invention, the “cylinder group” is composed of one or more cylinders and does not necessarily include a plurality of cylinders.
[0018]
The upstream portion of the exhaust passage 3 connected to the exhaust port of the engine 1 is divided into two systems of an exhaust passage 3a and an exhaust passage 3b. The exhaust port of the cylinder group A is connected to the exhaust passage 3a and the cylinder group B is connected to the exhaust passage 3a. The exhaust port is connected to the exhaust passage 3b. Both passages 3a and 3b merge with each other at the downstream junction 3c. In addition, the upstream part of each channel | path 3a, 3b is comprised as a pair of exhaust pipe corresponding to the number of cylinders, respectively.
[0019]
A first catalyst casing 20a is interposed in the exhaust passage 3a corresponding to the cylinder group A. Inside the first catalyst casing 20a, a first oxidation catalyst 21a that oxidizes and purifies inflowing exhaust components, and NOx is absorbed when the exhaust air-fuel ratio of the inflowing exhaust is lean, and the inflowing exhaust A first NOx trap catalyst 22a that releases NOx when the oxygen concentration is lowered is sequentially arranged. That is, the oxidation catalyst 21a is located upstream of the NOx trap catalyst 22a. Similarly, a second catalyst casing 20b is interposed in the exhaust passage 3b corresponding to the cylinder group B, and a second oxidation catalyst 21b and a second NOx trap catalyst 22b are contained therein. Arranged in order.
[0020]
Further, the passages 3a and 3b are joined at the junction 3c downstream of the first catalyst casing 20a and the second catalyst casing 20b. The turbine of the turbocharger is located immediately downstream of the junction 3c. 3d is connected. A casing 23 having an exhaust particulate trap 23a therein is arranged in series downstream of the turbine 3d.
[0021]
Examples of the oxidation catalysts 21a and 21b include a catalyst in which a precious metal such as Pd or Pt is supported based on activated alumina, a mixture of a precious metal such as Pd or Pt and zeolite supported on a base of active alumina, or a precious metal. Zeolite (especially Pt) ion-exchanged or a combination of these materials can be used.
[0022]
Further, as the exhaust particulate trap 23a, a known wall flow honeycomb type, a structure in which a ceramic fiber is wound in several layers on a bottomed cylindrical core member provided with a large number of holes in a cylindrical portion, etc. It is desirable to support the oxidation catalyst as described above on the surface of the exhaust particulate trap 23a in order to promote the recombustion of the collected exhaust particulates.
[0023]
Exhaust temperature sensors 36a and 36b for detecting exhaust temperatures (T1a and T1b) of these inlet portions (exit portions of the oxidation catalysts 21a and 21b) are provided at the inlet portions of the NOx trap catalysts 22a and 22b, respectively. ing. An exhaust pressure sensor 38 for detecting the exhaust pressure P1 is provided at the inlet of the exhaust particulate trap 23a, and an exhaust temperature sensor 37 for detecting the exhaust temperature T2 is provided at the outlet.
[0024]
Between the intake collector 2c and the exhaust passage 3b of the intake passage 2, an EGR passage 4 for recirculating a part of the exhaust is provided, and the opening can be continuously variably controlled by a stepping motor. An EGR valve 5 is interposed. The opening degree of the EGR valve 5 is controlled by the engine control unit 30.
[0025]
The intake passage 2 includes an air cleaner 2a at an upstream position, and a compressor 2b of a supercharger is disposed downstream thereof. An intake throttle valve 6 that is opened and closed by an actuator (for example, a stepping motor type) is disposed upstream of the intake collector 2c. The opening degree of the intake throttle valve 6 is controlled by the engine control unit 30.
[0026]
The EGR and the intake throttle valve 6 correspond to “air amount control means” in claim 3.
[0027]
The fuel supply system of the engine 1 includes a fuel tank 60 that stores diesel oil as diesel fuel, a fuel supply passage 16 that supplies fuel to the fuel injection device 10 of the engine 1, and a fuel supply device 16 of the engine 1. And a fuel return passage 19 for returning the return fuel (spill fuel) to the fuel tank 60.
[0028]
The fuel injection device 10 of the engine 1 is a known common rail type fuel injection device, and generally includes a supply pump 11, a common rail (accumulation chamber) 14, and a fuel injection valve 15 provided for each cylinder. After the fuel pressurized by the supply pump 11 is temporarily stored in the common rail 14 via the fuel supply passage 12, the high-pressure fuel in the common rail 14 is distributed to the fuel injection valves 15 of each cylinder.
[0029]
Further, in order to control the pressure of the common rail 14, a part of the fuel discharged from the supply pump 11 is returned to the fuel supply passage 16 through the overflow passage 17 having a one-way valve 18. Specifically, a pressure control valve 13 that changes the flow passage area of the overflow passage 17 is provided, and the pressure control valve 13 changes the flow passage area of the overflow passage 17 in accordance with a duty signal from the control unit 30. Thereby, the substantial fuel discharge amount from the supply pump 11 to the common rail 14 is adjusted, and the pressure of the common rail 14 is controlled.
[0030]
The fuel injection valve 15 is an electronic injection valve that is opened and closed by an ON-OFF signal from the engine control unit 30, and injects fuel into the combustion chamber by the ON signal and stops injection by the OFF signal. The fuel injection amount increases as the period of the ON signal applied to the fuel injection valve 15 increases, and the fuel injection amount increases as the fuel pressure of the common rail 14 increases. The injection period of the fuel injection valve 15, that is, the period of the ON signal and the fuel pressure of the common rail 14 are controlled by the engine control unit 30.
[0031]
The engine control unit 30 includes a signal from the water temperature sensor 31 (water temperature Tw), a signal from the crank angle sensor 32 for crank angle detection (a crank angle signal serving as a basis for the engine speed Ne), and a signal from the crank angle sensor 33 for cylinder discrimination. (Cylinder discrimination signal Cyl), a signal of the pressure sensor 34 for detecting the pressure of the common rail 14 (common rail pressure PCR), a signal of the accelerator opening sensor 35 for detecting the depression amount of the accelerator pedal corresponding to the load (accelerator opening (load ) L), respectively. Further, the signals (T1a, T1b) of the exhaust temperature sensors 36a, 36b at the inlet portions of the NOx trap catalysts 22a, 22b, the signal (T2) of the exhaust temperature sensor 37 at the outlet portion of the exhaust particulate trap 23a, and the exhaust particulate trap 23a. A signal (P1) of the exhaust pressure sensor 38 for detecting the exhaust pressure at the inlet of the engine is also input.
[0032]
Next, the contents of the control of the exhaust emission control device executed by the engine control unit 30 will be described based on the flowcharts of FIGS.
[0033]
FIG. 3 is a basic control routine related to the control of the entire diesel engine 1.
[0034]
In this engine basic control routine, in step 100, the water temperature Tw, the engine speed Ne, the cylinder discrimination signal Cyl, the common rail pressure PCR, the accelerator opening (load) L, the outlet of the first oxidation catalyst 21a (first NOx) The exhaust temperature T1a at the inlet of the trap catalyst 22a), the exhaust temperature T1b at the outlet of the second oxidation catalyst 21b (inlet of the second NOx trap catalyst 22b), the exhaust pressure P1 at the inlet of the exhaust particulate trap 23a, and The exhaust temperature T2 at the outlet is read, and the process proceeds to step 200.
[0035]
In step 200, common rail fuel injection control (common rail pressure control, main injection control for engine output control) is performed. In the present invention, the common rail fuel injection control itself is not the main part, and will be described briefly.
[0036]
The common rail fuel injection control searches a predetermined map stored in advance in the ROM of the control unit 30 using the engine speed Ne and the main fuel injection amount (preset according to the load L) Qmain as parameters. Then, the target reference pressure PCR0 of the common rail 14 is obtained, and feedback control of the pressure control valve 13 is executed so that the target reference pressure PCR0 is obtained.
[0037]
Then, in order to obtain the main fuel injection amount Qmain, a predetermined map stored in the ROM of the control unit 30 is searched using the main fuel injection amount Qmain and the common rail pressure PCR as parameters, and the main injection start timing Mstart is determined. And the main injection period Mperiod (msec), and based on the crank angle signal (Ne) of the crank angle sensor 32 for crank angle detection and the cylinder discrimination signal (Cyl) of the crank angle sensor 33 for cylinder discrimination, the main injection is performed. During the period from the start timing Mstart to Mperiod, the fuel injection valve 15 of the cylinder to be injected is opened.
[0038]
If the required main fuel injection amount Qmain is the same, the higher the common rail pressure PCR, the shorter the main injection period Mperiod. If the common rail pressure PCR is the same, the greater the required main fuel injection amount Qmain, the larger the main injection period Mperiod. Becomes longer.
[0039]
Further, for example, when the cooling water temperature is low, the ignition start timing is relatively delayed, so that the main injection start timing Mstart is advanced and the combustion is started so as not to increase the discharge amount of HC, CO, and exhaust particulates (especially SOF). Controls such as keeping the time constant are also performed.
[0040]
Then, the process proceeds to step 300, and the protection judgment of the exhaust particulate trap 23a is performed. In other words, the ignition combustion of the exhaust particulates collected in the exhaust particulate trap 23a is started and the recombustion of the exhaust particulates proceeds rapidly. If the combustion speed of the exhaust particulates is not suppressed, the exhaust particulate trap 23a Therefore, it is determined whether or not the exhaust particulate trap 23a needs to be protected because the exhaust particulate trap 23a may be cracked or melted. In the flowchart, “DPF” means “exhaust particulate trap”, and “PM” means “exhaust particulate”. As will be described later, the DPF protection flag is set to 1 if protection is necessary.
[0041]
In step 400, it is determined whether the DPF protection flag is 1 and the exhaust particulate trap 23a needs to be protected.
[0042]
If Yes in step 400 and the exhaust particulate trap 23a needs to be protected, the process proceeds to step 2000, and the protection control of the exhaust particulate trap 23a is continued or started, and the process returns.
[0043]
If it is No in step 400 and it is not necessary to protect the exhaust particulate trap 23a, the process proceeds to step 500, where the aftertreatment system (the NOx trap catalysts 22a and 22b that need to be regenerated and the exhaust particulate trap 23a are combined, It is determined whether or not the regeneration flag indicating the regeneration control of the post-processing system is 1, that is, whether or not the post-processing system needs to be regenerated.
[0044]
If the result of step 500 is Yes and the regeneration of the post-processing system is necessary, the process proceeds to step 1000, and the regeneration control of the post-processing system is continued or started and returns.
[0045]
However, even when the regeneration control of the aftertreatment system is being performed, if it is determined in step 400 that the exhaust particulate trap 23a needs to be protected, regeneration of the aftertreatment system is interrupted.
[0046]
If NO in step 500 and the regeneration of the aftertreatment system is not necessary, engine exhaust basic control is performed in step 600, PM trap limit determination of the exhaust particulate trap 23a is performed in step 700, and NOx trap is determined in step 800. A determination is made on regeneration of the catalyst (the first NOx trap catalyst 22a and the second NOx trap catalyst 22b), and a return is made.
[0047]
FIG. 4 is a subroutine regarding the protection judgment of the exhaust particulate trap 23a performed in step 300 of FIG.
[0048]
In the DPF protection determination routine of FIG. 4, in step 310, the exhaust gas temperature T2 at the outlet of the exhaust particulate trap 23a (which represents the temperature of the exhaust particulate trap 23a) is changed to the regenerated exhaust particulate trap 23a. It is determined whether or not a first predetermined temperature at which combustion is actively performed (for example, 500 ° C. in an exhaust particulate trap with an oxidation catalyst) is exceeded. In the case of the exhaust particulate trap with an oxidation catalyst, the combustion of the exhaust particulate starts at about 400 ° C. or higher, but the combustion is not active at this temperature, and there is no possibility of cracking or melting.
[0049]
If the determination in step 310 is No, the process proceeds to step 360 to set the DPF protection flag to 0, and returns to the basic control routine through steps 370 and 380 described later.
[0050]
If the determination in step 310 is Yes, the process proceeds to step 320, and the rate of increase in the exhaust temperature T2 at the outlet of the exhaust particulate trap 23a (dT2 / dTime: the rate of increase in the exhaust temperature T2 at the outlet of the exhaust particulate trap 23a per unit time) ) Exceeds a predetermined value (for example, an increase of 50 ° C. or more per second up to the present time).
[0051]
If the determination in step 320 is No, the process proceeds to step 360 where the DPF protection flag is set to 0, and the process returns to the basic control routine through steps 370 and 380 described later.
[0052]
If the determination in step 320 is Yes, the process proceeds to step 330 and whether or not the post-processing system regeneration flag is 1, that is, whether or not the regeneration control of the post-processing system is started or continued. Determine.
[0053]
If the determination in step 330 is No, step 340 is skipped and the process proceeds to step 350. If YES in step 330, that is, if the regeneration control of the post-processing system is being performed, the regeneration control of the post-processing system is temporarily interrupted as described in the basic control routine, so the process proceeds to step 340. Then, the counting of various index values (such as the regeneration index values of the exhaust particulate trap 23a and the NOx trap catalysts 22a and 22b and the exhaust air / fuel ratio enrichment time) for the regeneration control of the aftertreatment system is temporarily suspended, and the process proceeds to step 350.
[0054]
In step 350, the DPF protection flag is set to 1 and the process returns to the basic control routine.
[0055]
In step 370, it is determined whether or not the post-processing system regeneration flag is 1, and if this flag is 1, the post-processing system is under regeneration control. Resumes the index value of the regeneration control of the system.
[0056]
FIG. 5 is a subroutine related to engine exhaust basic control performed in step 600 of FIG. 3 described above. In order to obtain a predetermined engine exhaust emission performance, a predetermined EGR control corresponding to the engine operating region is performed. Do.
[0057]
In step 610, it is determined based on the engine speed Ne and the main fuel injection amount Qmain whether or not the operation region is to be subjected to EGR. That is, because the operation frequency is high and the air excess ratio is relatively large, even if EGR is performed and NOx is reduced, other exhaust components and fuel efficiency are not deteriorated, or if EGR is performed, smoke or It is determined whether or not the exhaust particulate discharge amount increases or the output decreases.
[0058]
If it is the EGR area in step 610, the process proceeds to step 620, and if it is not the EGR area, the process proceeds to step 650.
[0059]
In step 650, EGR is stopped or held. That is, the EGR valve 5 is closed and the intake throttle valve 7 is kept open.
[0060]
In step 620, target EGR data for executing EGR (that is, drive signals for the EGR valve 5 and the intake throttle valve 7) is stored in the ROM of the control unit 30 using the engine speed Ne and the main fuel injection amount Qmain as parameters. A predetermined map stored in advance is searched for. In step 630, the target EGR data obtained in step 620 is further corrected based on the water temperature Tw. For example, when the coolant temperature is low, the EGR is corrected to decrease, and the process proceeds to step 640.
[0061]
That is, the lower the water temperature, the lower the temperature of the engine combustion chamber, so that the ignition start timing is relatively delayed. Therefore, in order not to increase the discharge amount of HC, CO, and exhaust particulates (especially SOF), it is desirable to keep the combustion start timing constant by correcting the decrease in EGR.
[0062]
In step 640, the EGR valve 5 and the intake throttle valve 7 are drive-controlled based on the respective drive signal values after the water temperature correction, and EGR is performed.
[0063]
FIG. 6 is a subroutine regarding the PM trap limit of the exhaust particulate trap 23a performed in step 700 of FIG. Here, the limit of the exhaust particulates of the exhaust particulate trap 23a and the necessity of regeneration thereof are determined.
[0064]
That is, when the exhaust particulate trap 23a cannot be regenerated during normal operation, the exhaust particulate trap amount in the exhaust particulate trap 23a gradually increases. However, if the exhaust particulate trap amount is excessive, the back pressure The engine power performance is not allowed to deteriorate due to the rise. Also, when the exhaust particulate combustion conditions are met, the amount of heat generated by the exhaust particulate recombustion becomes excessive, and the exhaust particulate trap 23a is likely to burn out. Therefore, the exhaust particulate trap limit is set to a level that can prevent such a situation, and it is determined whether or not the exhaust particulate trap limit has been reached, and the exhaust particulate trap 23a is preferentially regenerated. It is trying to make it. As will be described later, in this embodiment, basically, the exhaust particulate trap 23a is also regenerated at the same time when the NOx trap catalysts 22a and 22b are regenerated, so the frequency of reaching the exhaust particulate trap limit is relatively low. .
[0065]
In the subroutine of FIG. 6, in step 710, the exhaust particulate trap limit pressure previously obtained through experiments or the like corresponding to the engine speed Ne and the load L is obtained from predetermined map data stored in advance in the ROM of the control unit 30. Search and go to step 720.
[0066]
In step 720, it is determined whether or not the actual value P1 of the exhaust pressure by the exhaust pressure sensor 38 is equal to or higher than the exhaust particulate trap limit pressure in step 710. If No, the process returns to the basic control routine.
[0067]
If Yes in step 720, that is, if the actual value P1 of the exhaust pressure exceeds the exhaust particulate trap limit pressure and the forced regeneration of the exhaust particulate trap 23a is necessary, the routine proceeds to step 730, where the post-processing system regeneration flag Set to 1. This flag becomes a reproduction start signal for the post-processing system.
[0068]
In step 740, the DPF regeneration flag is set to 1. The DPF regeneration flag serves as a regeneration start signal for the exhaust particulate trap 23a.
[0069]
Further, the routine proceeds to step 750, where the counting of the index value (for example, the total time of regeneration) for the end of regeneration of the exhaust particulate trap is started and returns.
[0070]
FIG. 7 is a subroutine relating to the necessity determination of regeneration of the NOx trap catalysts 22a and 22b performed in step 800 of FIG.
[0071]
In Step 810, the NOx absorption amount (NOx absorption amount per unit time) of the NOx trap catalysts 22a and 22b is stored in the ROM of the control unit 30 using the engine speed Ne and the load L (or main fuel injection amount Qmain) as parameters. The predetermined map data stored in advance is searched for.
[0072]
In step 810, after obtaining the basic NOx absorption amount per unit time, the process proceeds to step 820, and correction is made based on the water temperature Tw. Specifically, when the cooling water temperature is low, the NOx absorption amount is corrected to decrease, and the routine proceeds to step 830. This is because the lower the water temperature, the lower the temperature of the engine combustion chamber. Therefore, even if the combustion start timing is kept constant, the lower the engine combustion chamber temperature, the longer the combustion period and the lower the combustion temperature. , NOx emissions tend to decrease. Therefore, the NOx absorption amount is also reduced.
[0073]
In step 830, the corrected NOx absorption amount per unit time is sequentially accumulated at predetermined time intervals synchronized with the unit time, and the process proceeds to step 840.
[0074]
In step 840, it is determined whether or not the accumulated NOx absorption amount exceeds a predetermined absorption limit amount set for the NOx trap catalysts 22a and 22b, that is, whether regeneration (NOx release / reduction) is necessary. To do. If the determination in step 840 is No and no reproduction is required, the process returns.
[0075]
On the other hand, if the determination in step 840 is Yes, that is, if it is determined that regeneration of the NOx trap catalysts 22a and 22b is necessary, the post-processing system regeneration flag is set to 1 in step 850. That is, it is a reproduction start signal for the post-processing system.
[0076]
In step 860, the NOx regeneration flag is set to 1. That is, it is used as a NOx regeneration start signal for the NOx trap catalysts 22a and 22b.
[0077]
Further, the process proceeds to step 870, where the counting of the index value for the end of NOx regeneration (for example, the total regeneration time) is started and the process returns.
[0078]
FIG. 8 is a subroutine relating to regeneration control of the aftertreatment system (NOx trap catalysts 22a and 22b and exhaust particulate trap 23a) performed in step 1000 of FIG.
[0079]
In step 1010, it is determined whether or not the DPF regeneration flag is 1, that is, whether or not the exhaust particulate trap 23a needs to be preferentially regenerated. If No, that is, if there is no need for preferential reproduction, the routine proceeds to step 1020. If yes, that is, if the exhaust particulate trap 23a needs to be preferentially regenerated, the process proceeds to step 1100 to perform forced regeneration control of the exhaust particulate trap 23a.
[0080]
In step 1020, it is determined whether or not the NOx regeneration flag for the NOx trap catalysts 22a and 22b is 1, that is, whether or not regeneration of the NOx trap catalysts 22a and 22b is necessary. If NO, that is, NOx regeneration is not required, the process returns. If YES, that is, if regeneration of the NOx trap catalysts 22a and 22b is necessary, the process proceeds to step 1200 to perform NOx trap catalyst regeneration control.
[0081]
FIG. 9 is a subroutine related to the forced regeneration control of the exhaust particulate trap 23a performed in the above step 1100 (FIG. 8). This subroutine should be forced to regenerate the exhaust particulate trap 23a. The purpose is to urgently regenerate the exhaust particulate trap 23a in some cases (for example, when the exhaust particulate emission amount increases due to continuous operation or the like at a low air density such as a high altitude). For this forced regeneration, assuming that the temperature of the exhaust particulate trap 23a is an exhaust particulate trap supporting an oxidation catalyst, it is raised to at least about 400 ° C., which is the ignition temperature of the exhaust particulate, and maintained for several minutes. I have to.
[0082]
More specifically, in a recent engine, the time required to regenerate the NOx trap catalyst by enriching the exhaust air-fuel ratio needs to be about 1 to 2% in terms of operating frequency (several seconds per time). If within). The time required to regenerate the exhaust particulate trap 23a is sufficient if, for example, the catalyst-supported exhaust particulate trap 23a has an operation frequency of about 2 to 4% at a temperature of 400 ° C. or higher. There is no need to perform a forced temperature increase operation (regeneration operation in a lean state) only for the regeneration of the exhaust particulate trap 23a.
[0083]
However, in normal operation, the operation frequency at a temperature of 400 ° C. or higher is only about 1 to 2%, and a frequency shortage of about 3% at maximum occurs. For this reason, a forced temperature raising operation is required only for the regeneration of the exhaust particulate trap 23a.
[0084]
In contrast, according to the present invention, when the regeneration of the NOx trap catalysts 22a and 22b is performed, the time frequency required for regeneration of the exhaust particulate trap 23a by simultaneously raising the temperature of the exhaust particulate trap 23a to 400 ° C. or higher under lean conditions. Like to get. That is, regeneration of the NOx trap catalysts 22a and 22b and regeneration of the exhaust particulate trap 23a in a lean state are basically performed separately, improving the utilization efficiency of energy used for regeneration and minimizing deterioration in fuel consumption. I try to stop.
[0085]
In the subroutine of FIG. 9, in step 1110, after the regeneration is started, it is determined from the exhaust particulate trap regeneration index value whether the predetermined regeneration of the exhaust particulate trap 23a is completed.
[0086]
As the index value for the exhaust particulate trap regeneration end, for example, the total regeneration time can be used as described above. However, the exhaust temperature at the outlet of the exhaust particulate trap 23a is not limited to the lapse of time since the regeneration is started. T2 and the multiplier of time are integrated, or the enrichment of cylinder group A and cylinder group B is alternately repeated at predetermined time intervals, and the total number (or time) of enrichment is counted, or a combination thereof It is desirable to select an optimum method according to the characteristics of the system.
[0087]
If YES in step 1110, that is, if it is determined that regeneration of the exhaust particulate trap 23a has been completed, the routine proceeds to step 1130, where the exhaust particulate trap regeneration control is initialized. That is, post injection, which will be described later, is stopped, and the post-processing system regeneration flag, the exhaust particulate trap regeneration flag, and the NOx trap catalyst regeneration flag are set to zero. Then, the NOx absorption amount integrated value, the exhaust particulate trap regeneration index value, and the NOx trap catalyst regeneration index value are reset to 0, respectively, and the process returns.
[0088]
Here, the reason for resetting the NOx trap catalyst regeneration flag to 0 and resetting the NOx absorption amount integrated value to 0 even though the regeneration of the exhaust particulate trap 23a is performed is that the exhaust particulate trap 23a is regenerated as described above. For this purpose, even if it is an exhaust particulate trap supporting an oxidation catalyst, it is necessary to raise it to at least about 400 ° C., which is the ignition temperature of exhaust particulate, and maintain it for several minutes. On the other hand, the enrichment time required for the regeneration of the NOx trap catalysts 22a and 22b is a few seconds and a short time.
[0089]
In the present embodiment, in the first rich air-fuel ratio that is performed in the cylinder group A and the cylinder group B for the forced regeneration of the exhaust particulate trap 23a, the temperature target of the exhaust particulate trap 23a is set to 500 ° C. (first predetermined value). The target of the inlet temperature of the NOx trap catalyst 22a, 22b corresponding to the cylinder group to be enriched (necessarily set to a temperature higher than the inlet temperature of the exhaust particulate trap 23a) corresponding to the enriched cylinder group is 600 ° C. Set each to, and keep for a few minutes. Therefore, regeneration of the NOx trap catalysts 22a and 22b can be realized at the same time.
[0090]
If NO in step 1110, that is, if the regeneration of the exhaust particulate trap 23a has not ended, the process proceeds to step 1111 and the target EGR data necessary for assisting the first rich air-fuel ratio conversion for regeneration of the exhaust particulate trap 23a. That is, the drive signal Eduty1 of the EGR valve 5 and the drive signal Tduty1 of the intake throttle valve 6 are stored in advance in the ROM of the control unit 30 using the engine speed Ne and the load L (or main fuel injection amount Qmain) as parameters. Search for a given map. Then, the process proceeds to step 1112, where the EGR valve 5 and the intake throttle valve 6 are driven and controlled based on the respective drive signals, and EGR is performed to assist the first rich air-fuel ratio. Then, the process proceeds to Step 1113.
[0091]
Here, in the first rich air-fuel ratio for regeneration of the exhaust particulate trap 23a, the oxidation reaction amount of the unburned fuel component and oxygen in the oxidation catalysts 21a and 21b arranged upstream of the NOx trap catalysts 22a and 22b is determined. The temperature rise is promoted by increasing the second rich air-fuel ratio for NOx regeneration, which will be described later.
[0092]
In order to increase the amount of oxidation reaction, it is necessary to increase only the amount of unburned fuel component, and it is necessary to increase the amount of oxygen in the exhaust gas flowing into the oxidation catalyst. Therefore, it is necessary to carry out the control with less than the case of the EGR control No. 5 or the second rich air-fuel ratio to be described later. For this, an optimum value is obtained in advance by experiments or the like.
[0093]
In step 1113, first rich air-fuel ratio post-injection data corresponding to the first rich air-fuel ratio EGR is obtained. That is, the post injection amount Qpost1, the post injection period Pperiod1, and the post injection timing Pstart1 required for the first rich air-fuel ratio are made parameters of the engine speed Ne and the load L (or the main fuel injection amount Qmain) as parameters. It searches and searches from the predetermined map memorize | stored. The first rich air / fuel ratio post-injection data is also set in advance by obtaining an optimum value through experiments or the like.
[0094]
In addition, this post injection is performed in the exhaust stroke from the expansion stroke of each cylinder separately from the main injection, and is not a fuel injection for obtaining an output. Accordingly, a part of the post-injected fuel is combusted in the cylinder to raise the exhaust temperature and promote the oxidation reaction of the oxidation catalysts 21a and 21b, and the rest is in the unburned state (HC, CO). , 21b. In other words, since all of the post-injected fuel does not burn in the cylinder, the oxidation catalyst 21a, 21b has oxygen (O ₂ ) And unburned fuel components (HC, CO) will flow in.
[0095]
And a part of unburned fuel and oxygen react with oxidation catalyst 21a, 21b, oxygen is consumed, and temperature rises further. Similarly to the case where the engine is burned in a rich state (for example, an air-fuel ratio of 13 or less), exhaust containing almost no oxygen and a large amount of unburned components as a reducing agent flows into the NOx trap catalysts 22a and 22b.
[0096]
After retrieving the first rich air-fuel ratio post-injection data in step 1113, the process proceeds to step 1114, and it is determined from the index value (for example, the passage of time) whether the enrichment of the cylinder group A is completed.
[0097]
If the enrichment of the cylinder group A is not completed in step 1114, the process proceeds to step 1115, and the fuel of the cylinder group A (# 2, # 3 cylinders) to be post-injected according to the first rich air-fuel ratio post-injection data. The injection valve 15 is driven to open based on signals from a crank angle sensor 32 for detecting a crank angle and signals from a crank angle sensor 33 for determining a cylinder. That is, post injection is performed for the cylinder group A.
[0098]
In step 1116, post injection feedback control (for example, Qpost1 increase / decrease, or Pstart1 advance / retard) is performed based on the signal (T1a) of the exhaust temperature sensor 36a. In other words, in order to realize regeneration of the NOx trap catalyst 22a and regeneration of the exhaust particulate trap 23a at the same time, the basic necessary for regeneration of the post-processing system is performed by correcting the post-injection so as to obtain the necessary exhaust conditions without excess or deficiency Ensure exhaust conditions.
[0099]
If the enrichment of the cylinder group A has been completed in step 1114, the process proceeds to step 1118, and it is determined from the index value (for example, the passage of time) whether the enrichment of the cylinder group B has been completed. If the enrichment of the cylinder group B is completed in step 1118, the process returns.
[0100]
If the enrichment of the cylinder group B has not been completed, the routine proceeds to step 1119, where the fuel injection valve of the cylinder group B (# 1, # 4 cylinder) to be post-injected according to the first rich air-fuel ratio post-injection data. 15 is driven to open based on the signals of the crank angle sensor 32 for detecting the crank angle and the crank angle sensor 33 for determining the cylinder. That is, post injection is performed for the cylinder group B.
[0101]
Then, the process proceeds to step 1120, and similarly to step 1116, post injection feedback control (for example, Qpost2 increase / decrease, or Pstart2 advance / retard) is performed based on the signal (T1a) of the exhaust temperature sensor 36b.
[0102]
After securing the basic exhaust conditions necessary for regeneration of the aftertreatment system in step 1116 or step 1120, the process proceeds to step 1117, and the exhaust particulate matter is based on the signal (T2) of the exhaust temperature sensor 37 at the outlet of the exhaust particulate trap 23a. In order to obtain a target temperature of 500 ° C. (same as the first predetermined temperature) of the trap 23a, the post-injection re-feedback control is performed and a return is obtained.
[0103]
Here, when the first rich air-fuel ratio control is being performed in the cylinder group A based on the determination in steps 1114 and 1118, the first rich air-fuel ratio control is not performed in the cylinder group B. Conversely, when the first rich air-fuel ratio control is performed in the cylinder group B, the first rich air-fuel ratio control is not performed in the cylinder group A.
[0104]
For this reason, the rich exhaust gas and the normal lean exhaust gas merge at the junction 3c of the exhaust passage 3, but the exhaust of the diesel engine is at least about λ≈1.5 and basically has an excess air ratio. large. For this reason, even if one of the cylinder groups is enriched to the exhaust air / fuel ratio 13 (λ≈0.9), the average exhaust air / fuel ratio after the merging is at least about 18 (λ≈1.2). (4 to 5%). Since exhaust gas containing a large amount of oxygen component that has been heated by the catalytic reaction of the oxidation catalysts 21a and 21b and the NOx trap catalysts 22a and 22b flows into the exhaust particulate trap 23a, the exhaust particulate trap 23a is forcibly regenerated.
[0105]
FIG. 10 is a subroutine related to the regeneration control of the NOx trap catalysts 22a and 22b performed in step 1200 of FIG.
[0106]
Basically, the regeneration control of the NOx trap catalysts 22a and 22b has a shorter interval than the urgent forced regeneration control of the exhaust particulate trap 23a and is frequently performed. Accordingly, if the first rich air-fuel ratio control that is the same as the forced regeneration control in the emergency of the exhaust particulate trap 23a is performed, the fuel consumption deteriorates. Therefore, the inlet temperature of the NOx trap catalyst corresponding to the enriched cylinder group is NOx. The second rich air-fuel ratio is targeted at a lower limit temperature of 500 ° C. at which the trap catalyst can be regenerated, and the temperature of the exhaust particulate trap 23a is set at a lower limit temperature of 400 ° C. (second predetermined temperature) at which the exhaust particulate trap 23a can be regenerated. Implementation control is implemented.
[0107]
In the subroutine of FIG. 10, in step 1210, it is determined from the NOx trap catalyst regeneration index value whether regeneration of the NOx trap catalysts 22a and 22b is completed.
[0108]
If YES in step 1210, that is, if regeneration is completed, the process proceeds to step 1211 to initialize the NOx trap catalyst regeneration control. That is, the post injection is stopped, and the post-processing system regeneration flag and the NOx trap catalyst regeneration flag are set to zero. Then, the NOx absorption amount integrated value and the NOx trap catalyst regeneration index value are reset to 0, respectively, and a return is made.
[0109]
Note that the index value for the end of regeneration of the NOx trap catalyst does not have to be just the lapse of time since regeneration is started.
[0110]
If NO in step 1210, that is, if regeneration of the NOx trap catalysts 22a and 22b has not ended, the process proceeds to step 1211 and the target EGR required to assist the second rich air-fuel ratio for regeneration of the NOx trap catalyst. Data, that is, the drive signal Eduty2 of the EGR valve 5 and the drive signal Tduty2 of the intake throttle valve 6 are stored in advance in the ROM of the control unit 30 using the engine speed Ne and the load L (or main fuel injection amount Qmain) as parameters. Find and search for a given map. In step 1212, the EGR valve 5 and the intake throttle valve 6 are driven and controlled based on the respective drive signals, and EGR is performed to assist the second rich air-fuel ratio. Then, the process proceeds to Step 1213.
[0111]
Here, in the second rich air-fuel ratio for regeneration of the NOx trap catalysts 22a and 22b, the oxidation reaction between the unburned fuel component and oxygen in the oxidation catalysts 21a and 21b disposed upstream of the NOx trap catalysts 22a and 22b. Although the amount is increased as compared with the basic exhaust control in FIG. 5, an optimum value is previously set by experiment or the like so as to reduce the degree of increase compared to the first rich air-fuel ratio for forced regeneration of the exhaust particulate trap 23a. Ask.
[0112]
In step 1213, second rich air / fuel ratio post-injection data corresponding to the second rich air / fuel ratio EGR is obtained. That is, a predetermined map stored in the ROM of the control unit 30 with the post injection amount Qpost2, the post injection period Pperiod2, and the post injection timing Pstart2 as parameters of the engine speed Ne and the load L (or the main fuel injection amount Qmain). Search from and ask. The second rich air-fuel ratio post-injection data is also set in advance by obtaining an optimum value through experiments or the like.
[0113]
After searching for the second rich air-fuel ratio post-injection data in step 1213, the process proceeds to step 1214, and it is determined from the index value (for example, the passage of time) whether or not the enrichment of the cylinder group A has been completed.
[0114]
If the enrichment of the cylinder group A is not completed in step 1214, the process proceeds to step 1215, and the fuel of the cylinder group A (# 2, # 3 cylinder) to be post-injected according to the second rich air-fuel ratio post-injection data. The injection valve 15 is driven to open based on signals from the crank angle sensor 32 for detecting the crank angle and the crank angle sensor 33 for determining the cylinder. That is, post injection is performed for the cylinder group A.
[0115]
In step 1216, post injection feedback control (for example, Qpost2 increase / decrease, or Pstart2 advance / retard) is performed based on the signal (T1a) of the exhaust temperature sensor 36a.
[0116]
On the other hand, if the enrichment of the cylinder group A has been completed in step 1214, the process proceeds to step 1218 to determine whether the enrichment of the cylinder group B has been completed from the index value (for example, the passage of time). If the enrichment of the cylinder group B has been completed in step 1218, a return is made.
[0117]
If the enrichment of the cylinder group B has not been completed, the process proceeds to step 1219, and the fuel injection valve 15 of the cylinder group B (# 1, # 4 cylinder) to be post-injected is determined according to the second rich air-fuel ratio post-injection data. Based on the signals from the crank angle sensor 32 for detecting the crank angle and the crank angle sensor 33 for determining the cylinder, the valve is opened. That is, post injection is performed for the cylinder group B.
[0118]
Then, the process proceeds to step 1220, and post-injection feedback control (for example, increase / decrease in Qpost2 or advance / delay of Pstart2) is performed based on the signal (T1a) of the exhaust temperature sensor 36b as in step 1216.
[0119]
After securing the basic exhaust conditions necessary for regeneration of the aftertreatment system in step 1216 or step 1220, the process proceeds to step 1217, and the exhaust particulate matter is based on the signal (T2) of the exhaust temperature sensor 37 at the outlet of the exhaust particulate trap 23a. The post-injection refeedback control is performed so that a lower limit temperature of 400 ° C. (same as the second predetermined temperature) at which the trap 23a can be regenerated is obtained, and a return is obtained.
[0120]
Next, FIG. 11 shows details of protection control of the exhaust particulate trap 23a performed in step 2000 of FIG. As described above, this protection control is performed in the DPF protection determination routine of FIG. 4, in which the exhaust temperature T2 at the outlet of the exhaust particulate trap 23a exceeds the first predetermined temperature (500 ° C.) and the rate of increase of the exhaust temperature T2 This is started when (dT2 / dTime) exceeds a predetermined value (for example, 50 ° C. increase per second), and the internal temperature of the exhaust particulate trap 23a does not rapidly increase and does not exceed the allowable heat resistant temperature. As described above, the subroutine is related to control for suppressing the exhaust particulate combustion rate and protecting the exhaust particulate trap 23a so that the exhaust particulate trap 23a is not cracked or melted.
[0121]
In the DPF protection control routine of FIG. 11, in step 2010, target EGR data necessary for assisting the third rich air-fuel ratio to protect the exhaust particulate trap 23a, that is, the drive signal Eduty3 of the EGR valve 5 and the intake throttle A drive signal Tduty3 for the valve 6 is obtained by searching a predetermined map stored in advance in the ROM of the control unit 30 using the engine speed Ne and the load L (or main fuel injection amount Qmain) as parameters. In step 2020, the EGR valve 5 and the intake throttle valve 6 are driven and controlled based on the respective drive signals, and EGR is performed to assist the third rich air-fuel ratio. Then, the process proceeds to Step 2030.
[0122]
Here, in the third rich air-fuel ratio for protecting the exhaust particulate trap 23a, in order to suppress the exhaust particulate combustion speed in the exhaust particulate trap 23a, the NOx trap catalysts 22a, 22b are used in regions other than the low rotation and low load. It is necessary to reduce the exhaust flow rate (oxygen amount) flowing into the oxidation catalysts 21a and 21b disposed upstream to reduce the amount of oxidation reaction between the unburned fuel component and oxygen. Rather, the intake throttle or EGR is strengthened within a possible range (up to the upper limit allowable in terms of exhaust performance without deteriorating operability). Also for this, an optimum value is obtained in advance by experiments or the like. Further, in the region of low rotation and low load, control is performed with the same value as the exhaust basic control of FIG. 5 so that the exhaust flow rate is not excessively reduced. Note that, under the first and second rich air-fuel ratios before the third rich air-fuel ratio, as described above, the exhaust flow rate is large.
[0123]
In step 2030, third rich air-fuel ratio post-injection data corresponding to the above-described third rich air-fuel ratio EGR is obtained. That is, a predetermined map stored in the ROM of the control unit 30 with the post injection amount Qpost3, the post injection period Pperiod3, and the post injection timing Pstart3 as parameters of the engine speed Ne and the load L (or the main fuel injection amount Qmain). Search from and ask. The third rich air / fuel ratio post-injection data is also set in advance by obtaining an optimum value through experiments or the like.
[0124]
After searching for the third rich air-fuel ratio post-injection data in step 2030, the process proceeds to step 2040, where the fuel injection valves 15 of all cylinders (# 1 to # 4) are connected to the crank angle sensor 32 for crank angle detection and the cylinder discrimination. The valve is driven to open based on the signal from the crank angle sensor 33. That is, post injection is executed for all cylinders.
[0125]
Then, the routine proceeds to step 2050, and based on the signal (T1a) of the exhaust temperature sensor 36a, the feedback control of the post injection is performed so that the inlet temperature of the NOx trap catalyst becomes the target temperature, that is, the lower limit temperature at which the NOx trap catalyst can be regenerated. (For example, Qpost3 increase / decrease, or Pstart3 advance / retard) and return.
[0126]
Under this third rich air-fuel ratio, oxygen in the exhaust discharged from the engine 1 reacts with HC and CO generated by post-injection in the oxidation catalysts 21a and 21b, so that at the inlet of the exhaust particulate trap 23a. The amount of oxygen in the exhaust gas can be almost zero, and combustion of exhaust particulates can be suppressed. As a result, cracking and melting damage of the exhaust particulate trap 23a are avoided.
[0127]
The exhaust temperature of the exhaust particulate trap 23a rises due to the oxidation reaction heat of HC and CO in the oxidation catalysts 21a and 21b, and the temperature of the exhaust particulate trap 23a also rises, but the exhaust caused by such oxidation reaction heat. The temperature rise of the particulate trap 23a is reduced by reducing the heat of the oxidation reaction itself by reducing the amount of oxygen flowing in by air throttling or EGR, and in particular compared to the temperature rise of the exhaust particulate trap 23a due to rapid combustion of exhaust particulates. Is so small that it can be ignored.
[0128]
Further, in the region of low rotation and low load, the third rich air-fuel ratio is achieved by post injection without reducing the exhaust flow rate. By not reducing the exhaust flow rate in this way, the engine is operated at high rotation and high load. Thus, when the exhaust particulates are self-ignited and then shift to a low rotation / low load region such as an idle, a rapid temperature rise due to a decrease in the exhaust flow rate is avoided, and cracking and melting of the exhaust particulate trap 23a are prevented. The
[0129]
In the first embodiment, since the regeneration of the NOx trap catalysts 22a and 22b and the regeneration of the exhaust particulate trap 23a can be realized at the same time, the time and energy consumption spent for regeneration are reduced, and the influence on the deterioration of fuel consumption is minimized. Can be limited. Moreover, by using the rich and lean of the two cylinder groups, simultaneous regeneration of both can be realized without providing a special device such as an air pump.
[0130]
By supporting the oxidation catalyst on the exhaust particulate trap 23a, the regeneration temperature of the exhaust particulate trap 23a can be lowered by a catalytic reaction, energy consumption for regeneration is reduced, and the influence on fuel consumption deterioration is minimized. Can be.
[0131]
Next, FIG. 2 is a system configuration diagram of an exhaust purification apparatus according to a second embodiment of the present invention. In the following, different parts from the first embodiment will be mainly described, and the same parts will be described with the same reference numerals.
[0132]
In this second embodiment, as shown in FIG. 2, there is one exhaust system, a single catalyst casing 20 is disposed in the exhaust passage 3, and an exhaust particulate trap 23a is disposed in the downstream thereof. A holding casing 21 is arranged. Inside the catalyst casing 20 is a single oxidation catalyst 21 and a single unit that absorbs NOx when the air-fuel ratio of the inflowing exhaust gas is lean and releases NOx when the oxygen concentration of the inflowing exhaust gas is reduced. NOx trap catalyst 22 is arranged in series.
[0133]
An exhaust temperature sensor 36 for detecting the exhaust temperature T1 at the inlet portion of the NOx trap catalyst 22 (the outlet portion of the oxidation catalyst 21) is provided at the inlet portion of the NOx trap catalyst 22, and an exhaust gas is provided at the inlet portion of the exhaust particulate trap 23a. An exhaust pressure sensor 38 that detects the pressure P1 is provided, and an exhaust temperature sensor 37 that detects the exhaust temperature T2 is provided at the outlet.
[0134]
At the outlet of the NOx trap catalyst 22, for example, an air introduction passage 7 for introducing air from the downstream side of the compressor 2 b of the supercharger as an air supply source via an on-off valve 8 whose passage area can be variably controlled by a stepping motor. The tip opening 7a is connected. An electric air pump or the like may be used as the air supply source.
[0135]
The engine control unit 30 includes a signal from the water temperature sensor 31 (water temperature Tw), a signal from the crank angle sensor 32 for crank angle detection (a crank angle signal serving as a basis for the engine speed Ne), and a signal from the crank angle sensor 33 for cylinder discrimination. (Cylinder discrimination signal Cyl), a signal of the pressure sensor 34 for detecting the pressure of the common rail 14 (common rail pressure PCR), a signal of the accelerator opening sensor 35 for detecting the depression amount of the accelerator pedal corresponding to the load (accelerator opening (load ) L), respectively. Further, the signal (T1) of the exhaust temperature sensor 36 at the inlet of the NOx trap catalyst 22, the signal (T2) of the exhaust temperature sensor 37 at the outlet of the exhaust particulate trap 23a, and the exhaust pressure at the inlet of the exhaust particulate trap 23a. A signal (P1) of the exhaust pressure sensor 38 for detecting the above is input.
[0136]
Similarly to the first embodiment, the exhaust gas after-treatment system of the second embodiment also eliminates the need to separately perform the regeneration of the NOx trap catalyst 22 and the regeneration of the exhaust particulate trap 23a in a lean state. The purpose is to increase the efficiency of using the energy used for the vehicle and minimize the deterioration of fuel consumption.
[0137]
The exhaust purification aftertreatment system of the second embodiment is also controlled by the engine control unit 30, but the input signal of the exhaust temperature sensor at step 100 in the engine basic control routine of FIG. 3 is only T1 (first embodiment). In the example, there are two T1a and T1b), the forced regeneration control of the exhaust particulate trap 23a performed in step 1100 of the post-processing system regeneration control routine of FIG. 8, and the regeneration of the NOx trap catalyst performed in step 1200. The control part is different from the first embodiment.
[0138]
This will be described with reference to the flowcharts of FIGS. 12 and 13, but the description of the parts having the same functions as those of the first embodiment will be simplified.
[0139]
FIG. 12 is a subroutine relating to the forced regeneration control of the exhaust particulate trap 23a in step 1100. This subroutine, as in the first embodiment, sets the temperature target of the exhaust particulate trap 23a to 500 ° C. or higher (the same as the first predetermined temperature). ), The inlet temperature target of the NOx trap catalyst 22 is set to 600 ° C. and maintained for several minutes. Therefore, similar to the first embodiment, regeneration of the NOx trap catalyst 22 can be realized at the same time.
[0140]
In the DPF forced regeneration control routine of FIG. 12, in step 1160, it is determined from the exhaust particulate trap regeneration index value whether the predetermined regeneration of the exhaust particulate trap 23a has been completed.
[0141]
If YES in step 1160, that is, if regeneration of the exhaust particulate trap 23a is completed, the routine proceeds to step 1172, where the regeneration control of the exhaust particulate trap 23a is initialized. Specifically, the post-injection is stopped, the air supply to be described later for leaning the exhaust gas flowing into the exhaust particulate trap 23a is stopped, the aftertreatment system regeneration flag, the DPF regeneration flag, the NOx trap catalyst regeneration flag, the second 2 Set each predetermined temperature flag (temperature flag) to 0. Further, the NOx absorption amount integrated value and the exhaust particulate trap regeneration index value are reset to 0, respectively, and a return is made.
[0142]
If NO in step 1160, that is, if the regeneration of the exhaust particulate trap 23a has not ended, the routine proceeds to step 1161, where the target EGR data necessary for assisting the first rich air-fuel ratio conversion for regeneration of the exhaust particulate trap 23a. That is, the drive signal Eduty1 of the EGR valve 5 and the drive signal Tduty1 of the intake throttle valve 6 are obtained by searching a predetermined map stored in the ROM of the control unit 30. Then, the routine proceeds to step 1162, where the EGR valve 5 and the intake throttle valve 6 are drive-controlled based on the respective drive signals, and EGR is performed to assist the first rich air-fuel ratio. Then, the process proceeds to Step 1163.
[0143]
In step 1163, first rich air-fuel ratio post-injection data corresponding to the first rich air-fuel ratio EGR is obtained. That is, the post injection amount Qpost1, the post injection period Pperiod1, and the post injection timing Pstart1 are obtained by searching from a predetermined map stored in the ROM of the control unit 30.
[0144]
After retrieving the first rich air-fuel ratio post-injection data in step 1163, the process proceeds to step 1164, and the fuel injection valve 15 is connected to the crank angle detecting crank angle sensor 32 and the cylinder according to the first rich air-fuel ratio post-injection data. The valve is driven to open based on the signal from the crank angle sensor 33. That is, post injection is executed for all cylinders.
[0145]
Then, the process proceeds to step 1165, where post-injection feedback control (for example, increase / decrease in Qpost1 or advance / delay of Pstart1) is performed based on the signal T1 of the exhaust temperature sensor 36. That is, in order to realize regeneration of the NOx trap catalyst 22 and regeneration of the exhaust particulate trap 23a at the same time, post-injection correction is performed so that necessary exhaust conditions can be obtained without excess or deficiency, and the basic necessary for regeneration of the post-processing system. Ensure exhaust conditions.
[0146]
After securing the basic exhaust conditions necessary for regeneration of the aftertreatment system in step 1165, the process proceeds to step 1166, and it is determined whether or not the temperature flag is 1. This temperature flag is a flag indicating that the temperature T2 of the exhaust particulate trap 23a has reached the lower limit temperature of 400 ° C. (second predetermined temperature) at which the exhaust particulate trap 23a can be regenerated.
[0147]
If Yes in step 1166, that is, if the temperature of the exhaust particulate trap 23a (exit temperature T2) has reached the lower limit temperature of 400 ° C. at which the exhaust particulate trap 23a can be regenerated, the process proceeds to step 1167.
[0148]
In step 1167, in order to regenerate the exhaust particulate trap 23a, the air supply data necessary for leaning the exhaust air-fuel ratio (for example, the air-fuel ratio of 18 or more), that is, the drive control signal Qair1 of the on-off valve 8 is obtained. Using Ne and load L (or main fuel injection amount Qmain) as parameters, a search is made from a predetermined map that is obtained in advance through experiments and stored in the ROM of the control unit 30.
[0149]
In step 1167, data relating to the air supply for regeneration of the exhaust particulate trap 23a is retrieved. Then, the process proceeds to step 1168, and the on-off valve 8 is opened based on the drive control signal Qair1 so that the necessary amount of air is supplied. To drive.
[0150]
Then, the process proceeds to step 1169, and based on the signal (T2) of the exhaust temperature sensor 37 at the outlet of the exhaust particulate trap 23a, the temperature of the exhaust particulate trap 23a is obtained at the target 500 ° C. (same as the first predetermined temperature). As described above, the feedback control of the supply air amount, that is, the increase / decrease correction of Qair1 is performed, the exhaust condition necessary for the regeneration of the exhaust particulate trap 23a is ensured, and the process returns.
[0151]
When No in step 1166, that is, the temperature flag is not 1 (indicating that the temperature of the exhaust particulate trap 23a (exit temperature T2) has not reached 400 ° C., which is the lower limit temperature at which the exhaust particulate trap 23a can be regenerated). Sometimes, go to step 1170.
[0152]
In step 1170, it is determined whether or not the temperature T2 at the outlet of the exhaust particulate trap 23a is 400 ° C. or higher. If yes, that is, 400 ° C. or higher, the procedure proceeds to step 1171 to set the temperature flag to 1 and return. .
[0153]
If No in step 1170, that is, less than 400 ° C., the process returns as it is.
[0154]
FIG. 13 shows a subroutine related to regeneration control of the NOx trap catalyst 22 performed in step 1200 in the second embodiment. In this subroutine, the inlet temperature of the NOx trap catalyst 22 is targeted at a lower limit temperature of 500 ° C. at which the NOx trap catalyst 22 can be regenerated, and the temperature of the exhaust particulate trap 23a is 400 ° C. (the first temperature at which the exhaust particulate trap 23a can be regenerated). The second rich air-fuel ratio control is performed with a target of (2 predetermined temperature).
[0155]
In the subroutine of FIG. 13, in step 1260, it is determined from the NOx regeneration index value whether the NOx regeneration of the NOx trap catalyst 22 is completed.
[0156]
If YES in step 1260, that is, if NOx regeneration is completed, the routine proceeds to step 1270, where NOx regeneration control is initialized. That is, the post injection is stopped, the air supply is stopped, and the aftertreatment system regeneration flag and the NOx trap catalyst regeneration flag are set to 0, respectively. Then, the NOx absorption amount integrated value and the NOx trap catalyst regeneration index value are reset to 0, respectively, and a return is made.
[0157]
If NO in step 1260, that is, if NOx regeneration of the NOx trap catalyst 22 has not ended, the process proceeds to step 1261, and target EGR data necessary for assisting the second rich air-fuel ratio conversion for NOx regeneration, that is, EGR. The drive signal Eduty2 of the valve 5 and the drive signal Tduty2 of the intake throttle valve 6 are obtained by searching a predetermined map stored in the ROM of the control unit 30. In step 1262, the EGR valve 5 and the intake throttle valve 6 are driven and controlled based on the respective drive signals, and EGR is performed to assist the second rich air-fuel ratio. Then, the process proceeds to Step 1263.
[0158]
In step 1263, second rich air / fuel ratio post-injection data corresponding to the second rich air / fuel ratio EGR is obtained. That is, the post injection amount Qpost2, the post injection period Pperiod2, and the post injection timing Pstart2 are obtained by searching from a predetermined map stored in the ROM of the control unit 30.
[0159]
After retrieving the second rich air-fuel ratio post-injection data in step 1263, the process proceeds to step 1264, and the fuel injection valve 15 is connected to the crank angle detecting crank angle sensor 32 and the cylinder according to the second rich air-fuel ratio post-injection data. The valve is driven to open based on the signal from the crank angle sensor 33. That is, post injection is executed for all cylinders.
[0160]
In step 1265, post-injection feedback control (for example, Qpost2 increase / decrease, or Pstart2 advance / retard) is performed based on the signal T1 of the exhaust temperature sensor 36 to regenerate the NOx trap catalyst 22 and exhaust particulate matter. In order to realize regeneration of the trap 23a at the same time, correction of post injection is performed to secure basic exhaust conditions necessary for regeneration of the post-processing system, and the process proceeds to Step 1266.
[0161]
In step 1266, in order to regenerate the exhaust particulate trap 23a, the air supply data necessary for leaning the exhaust air / fuel ratio (for example, the air / fuel ratio 18 or more), that is, the drive control signal Qair2 of the on-off valve 8 is obtained. Using Ne and load L (or main fuel injection amount Qmain) as parameters, a search is made from a predetermined map that is obtained in advance through experiments and stored in the ROM of the control unit 30.
[0162]
In step 1266, data related to the air supply for regeneration of the exhaust particulate trap 23a is retrieved. Then, the process proceeds to step 1267, where the on-off valve 8 is opened based on the drive control signal Qair2 so that the necessary amount of air is supplied. To drive.
[0163]
Then, the process proceeds to step 1268 so that the temperature of the exhaust particulate trap 23a can be obtained at the target 400 ° C. (the same as the second predetermined temperature) based on the signal (T2) of the exhaust temperature sensor 37 at the outlet of the exhaust particulate trap 23a. In addition, feedback control of the supply air amount is performed. That is, Qair1 increase / decrease correction is performed so that exhaust conditions suitable for regenerating the exhaust particulate trap 23a can be obtained without excess or deficiency, ensuring exhaust conditions necessary for regeneration of the exhaust particulate trap 23a, and returning.
[0164]
In the second embodiment as well, similar to the first embodiment, regeneration of the NOx trap catalyst 22 and regeneration of the exhaust particulate trap 23a can be realized at the same time, so that the time and energy consumption spent for regeneration are reduced and fuel consumption is reduced. The impact on deterioration can be minimized.
[0165]
Next, FIG. 14 is a system configuration diagram of an exhaust purification apparatus according to a third embodiment of the present invention. In the following, different parts from the first and second embodiments will be mainly described, and the same parts will be described with the same reference numerals.
[0166]
In the third embodiment, as in the second embodiment, there is one exhaust system, a single catalyst casing 20 is disposed in the exhaust passage 3, and an exhaust particulate trap 23a is disposed in the downstream thereof. A holding casing 21 is arranged. Inside the catalyst casing 20 is a single oxidation catalyst 21 and a single unit that absorbs NOx when the air-fuel ratio of the inflowing exhaust gas is lean and releases NOx when the oxygen concentration of the inflowing exhaust gas is reduced. NOx trap catalyst 22 is arranged in series. In the third embodiment, the configuration of the second embodiment is further simplified, and the air introduction passage 7 and the on-off valve 8 for introducing air described above are not provided. The other configuration is the same as that of the second embodiment.
[0167]
In the aftertreatment system for exhaust purification of the third embodiment, the exhaust air / fuel ratio of the exhaust gas flowing into the exhaust particulate trap 23a remains rich when the NOx regeneration of the NOx trap catalyst 22 is performed, and therefore the exhaust particulate trap. The reproduction of 23a is not performed.
[0168]
Further, the exhaust purification aftertreatment system of the third embodiment is also controlled by the engine control unit 30, but the basic processing is the same as that of the first and second embodiments described above. The parts of the forced regeneration control of the exhaust particulate trap 23a performed at step 1100 of the processing system regeneration control routine and the regeneration control of the NOx trap catalyst performed at step 1200 are slightly different from those of the second embodiment.
[0169]
This will be described with reference to the flowcharts of FIGS.
[0170]
FIG. 15 is a subroutine relating to forced regeneration control of the exhaust particulate trap 23a in step 1100, and this subroutine differs only in part (steps 1180 and 1181) from the subroutine of the second embodiment described in FIG. Only the different parts will be described, and the description of parts that are not particularly changed will be omitted.
[0171]
As described above, in step 1166, it is determined whether or not the temperature flag is 1. This temperature flag is a flag indicating that the temperature T2 of the exhaust particulate trap 23a has reached the lower limit temperature of 400 ° C. (second predetermined temperature) at which the exhaust particulate trap 23a can be regenerated. In the case of Yes in step 1166, that is, when the temperature of the exhaust particulate trap 23a (exit temperature T2) has reached the lower limit temperature of 400 ° C. at which the exhaust particulate trap 23a can be regenerated, in this embodiment, in the step 1180 Proceeding to 1181, the exhaust air-fuel ratio is made lean.
[0172]
In step 1180, in order to regenerate the exhaust particulate trap 23a, the target EGR data necessary for leaning the exhaust air / fuel ratio (for example, the air / fuel ratio 18 or more), that is, the drive signal Eduty4 of the EGR valve 5 and the intake throttle valve 6 The drive signal Tduty4 is obtained by searching a predetermined map stored in the ROM of the control unit 30.
[0173]
In step 1181, the EGR valve 5 and the intake throttle valve 6 are driven and controlled based on the respective drive signals to make the exhaust air-fuel ratio lean. Thereby, the regeneration of the forced exhaust particulate trap 23a is started.
[0174]
FIG. 16 is a subroutine relating to the regeneration control of the NOx trap catalyst 22 performed in step 1200, and this subroutine differs only in part (steps 1280 and 1281) from the subroutine of the second embodiment described in FIG. Therefore, only the different parts will be described, and description of parts that are not particularly changed will be omitted.
[0175]
As described above, in step 1260, it is determined from the NOx regeneration index value whether NOx regeneration of the NOx trap catalyst 22 is completed. If NO in step 1260, that is, if NOx regeneration of the NOx trap catalyst 22 has not ended. Proceeds to step 1280.
[0176]
In step 1280, the target EGR data necessary for the rich air-fuel ratio for NOx regeneration, that is, the drive signal Eduty5 of the EGR valve 5 and the drive signal Tduty5 of the intake throttle valve 6 are stored in the ROM of the control unit 30 in a predetermined manner. Search for and ask for maps. In step 1281, the EGR valve 5 and the intake throttle valve 6 are driven and controlled based on the respective drive signals to enrich the exhaust air-fuel ratio. Here, the target rich air-fuel ratio is set to about 13 (λ = 0.9) necessary for NOx regeneration. Note that when the excess air ratio decreases, the fuel efficiency deteriorates, and the torque decreases accordingly. Therefore, it is desirable to correct the main fuel injection amount Qmain to be increased according to the decrease in the excess air ratio.
[0177]
As described above, the case where the present invention is applied to an in-line multi-cylinder engine has been described. However, the exhaust purification device of the present invention is not limited to this, and can be applied to a V-type 6-cylinder or 8-cylinder engine. Moreover, although the said Example has shown in the example of the engine with a supercharger, a naturally aspirated engine may be sufficient.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram showing a first embodiment of the present invention.
FIG. 2 is a system configuration diagram showing a second embodiment of the present invention.
FIG. 3 is a flowchart showing a diesel engine basic control routine.
FIG. 4 is a flowchart showing a DPF protection determination routine.
FIG. 5 is a flowchart showing an engine exhaust basic control routine.
FIG. 6 is a flowchart showing an exhaust particulate trap limit judgment routine.
FIG. 7 is a flowchart showing a NOx trap catalyst regeneration determination routine.
FIG. 8 is a flowchart showing a post-processing system regeneration control routine.
FIG. 9 is a flowchart showing a DPF forced regeneration control routine.
FIG. 10 is a flowchart showing a NOx trap catalyst regeneration control routine.
FIG. 11 is a flowchart showing a DPF protection control routine.
FIG. 12 is a flowchart showing a DPF forced regeneration control routine in the second embodiment.
FIG. 13 is a flowchart showing a NOx trap catalyst regeneration control routine in the second embodiment.
FIG. 14 is a system configuration diagram showing a third embodiment.
FIG. 15 is a flowchart showing a DPF forced regeneration control routine in the third embodiment.
FIG. 16 is a flowchart showing a NOx trap catalyst regeneration control routine in a third embodiment.
[Explanation of symbols]
1 ... Engine
3 ... Exhaust passage
5 ... EGR valve
6 ... Inlet throttle valve
21, 21a, 21b ... oxidation catalyst
22, 22a, 22b ... NOx trap catalyst
23a ... Exhaust particulate trap
30 ... Engine control unit

Claims (12)

An oxidation catalyst that is disposed in the exhaust passage of the internal combustion engine and oxidizes and purifies inflowing exhaust components;
An exhaust particulate trap disposed in the exhaust passage downstream of the oxidation catalyst and trapping inflowing exhaust particulate;
Temperature detecting means for detecting the temperature of the exhaust particulate trap;
A combustion rate detecting means for detecting a combustion rate of the exhaust particulate trapped in the exhaust particulate trap;
Fuel injection means for enabling post injection for injecting fuel in an expansion stroke or an exhaust stroke;
Exhaust air-fuel ratio control means for making the exhaust air-fuel ratio rich by the post injection when the temperature of the exhaust particulate trap exceeds a predetermined temperature and the combustion speed of the exhaust particulate exceeds a predetermined speed;
NOx that is located between the oxidation catalyst and the exhaust particulate trap, traps NOx in exhaust that flows when the exhaust air-fuel ratio is lean, and desorbs and purifies NOx trapped when the exhaust air-fuel ratio is rich A trap catalyst,
An exhaust emission control device for an internal combustion engine, comprising: Regeneration timing determination means for determining the regeneration timing based on the amount of exhaust particulate trapped in the exhaust particulate trap;
Reproduction control means for performing a predetermined reproduction operation at the reproduction time,
When the temperature of the exhaust particulate trap exceeds a predetermined temperature and the combustion speed of the exhaust particulate exceeds a predetermined speed, the exhaust air / fuel ratio control means performs exhaust by post injection even during the regeneration operation. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the air-fuel ratio is made rich. An air amount control means for controlling the amount of air flowing into the cylinder of the internal combustion engine;
The exhaust purification of an internal combustion engine according to claim 1 or 2, wherein the exhaust air / fuel ratio control means makes the exhaust air / fuel ratio rich by reducing the amount of air flowing into the internal combustion engine while performing the post injection. apparatus.   When the exhaust particulate trap temperature exceeds a predetermined temperature and the combustion speed of the exhaust particulate exceeds a predetermined speed, and the operating state is a low rotation and low load, the exhaust air / fuel ratio control means The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the exhaust air-fuel ratio is made rich only by injection. The internal combustion engine according to any one of claims 1 to 4 , wherein the combustion speed detecting means considers that the combustion speed of the exhaust particulates is higher as the rate of increase in the temperature of the exhaust particulate trap per unit time is larger. Engine exhaust purification system. The NOx trap catalyst is disposed corresponding to each of a plurality of cylinder groups including one or a plurality of cylinders,
The exhaust particulate trap comprises a single exhaust particulate trap so that all exhaust exhausted from a plurality of NOx trap catalysts flows in,
NOx trap catalyst regeneration timing determination means for determining the regeneration timing of at least one of the plurality of NOx trap catalysts;
When at least one of the plurality of NOx trap catalysts is to be regenerated, the exhaust air / fuel ratio of the cylinder group corresponding to the NOx trap catalyst to be regenerated is such that the exhaust air / fuel ratio flowing into the exhaust particulate trap becomes lean. And NOx trap regeneration control means for simultaneously performing regeneration processing of the exhaust particulate trap while performing regeneration processing of the NOx trap catalyst by making the exhaust air-fuel ratio of other cylinder groups lean.
Further comprising
The exhaust air-fuel ratio control means is configured such that when at least one of the plurality of NOx trap catalysts is regenerated, the temperature of the exhaust particulate trap exceeds a first predetermined temperature, and the combustion speed of the exhaust particulate is predetermined. The exhaust air / fuel ratios of the plurality of cylinder groups are all made rich so that the exhaust air / fuel ratio flowing into the exhaust particulate trap becomes rich when the speed is exceeded, and the regeneration processing of the NOx trap catalyst is performed while performing the regeneration processing of the NOx trap catalyst. The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 5, wherein a combustion speed of exhaust particulates is suppressed. The NOx trap regeneration control means adjusts the exhaust temperature of the cylinder group having a rich exhaust air-fuel ratio when the exhaust air-fuel ratio of some cylinder groups is made rich and the exhaust air-fuel ratio of other cylinder groups is made lean. The exhaust emission control device for an internal combustion engine according to claim 6 , wherein the temperature of the exhaust particulate trap is controlled to a second predetermined temperature at which the exhaust particulate trap can be regenerated. Air supply means capable of supplying air to the upstream exhaust passage of the exhaust particulate trap;
NOx trap catalyst regeneration timing determination means for determining the regeneration timing of the NOx trap catalyst;
Further comprising
The exhaust air / fuel ratio control means includes:
When the regeneration timing of the NOx trap catalyst is determined, the exhaust air-fuel ratio flowing into the NOx trap catalyst by the post injection is made rich, and air is supplied by the air supply means and flows into the exhaust particulate trap. The exhaust air-fuel ratio is made lean, and the regeneration process of the exhaust particulate trap is simultaneously performed while performing the regeneration process of the NOx trap catalyst,
When the temperature of the exhaust particulate trap exceeds a first predetermined temperature and the combustion speed of the exhaust particulate exceeds a predetermined speed, the air supply means may reduce the air flow even during regeneration of the exhaust particulate trap. 6. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the exhaust air-fuel ratio flowing into the exhaust particulate trap is made rich by stopping supply. An exhaust particulate trap regeneration timing judging means for judging the regeneration timing of the exhaust particulate trap,
The exhaust air / fuel ratio control means, when it is determined that the exhaust particulate trap is being regenerated, exhausts exhausted by the engine until the temperature of the exhaust particulate trap exceeds a second predetermined temperature lower than the first predetermined temperature. The temperature of the exhaust particulate trap is raised by making the air-fuel ratio rich, and after the temperature of the exhaust particulate trap exceeds the second predetermined temperature, air is supplied by the air supply means and flows into the exhaust particulate trap. Regenerate the exhaust particulate trap with lean exhaust air-fuel ratio,
When the temperature of the exhaust particulate trap exceeds a first predetermined temperature and the combustion speed of the exhaust particulate exceeds a predetermined speed, the air supply means may reduce the air flow even during regeneration of the exhaust particulate trap. 9. The exhaust gas purification apparatus for an internal combustion engine according to claim 8 , wherein the exhaust air-fuel ratio flowing into the exhaust particulate trap is made rich by stopping supply. The exhaust purification device for an internal combustion engine according to any one of claims 1 to 9 , wherein the oxidation catalyst is configured integrally with the NOx trap catalyst. An oxidation catalyst that is disposed in the exhaust passage of the internal combustion engine and oxidizes and purifies inflowing exhaust components;
An exhaust particulate trap disposed in the exhaust passage downstream of the oxidation catalyst and trapping inflowing exhaust particulate;
Temperature detecting means for detecting the temperature of the exhaust particulate trap;
A combustion rate detecting means for detecting a combustion rate of the exhaust particulate trapped in the exhaust particulate trap;
Exhaust air-fuel ratio control means for making the exhaust air-fuel ratio rich when the temperature of the exhaust particulate trap exceeds a predetermined temperature and the combustion speed of the exhaust particulate exceeds a predetermined speed;
NOx that is located between the oxidation catalyst and the exhaust particulate trap, traps NOx in exhaust that flows when the exhaust air-fuel ratio is lean, and desorbs and purifies NOx trapped when the exhaust air-fuel ratio is rich A trap catalyst,
An exhaust emission control device for an internal combustion engine, comprising: The exhaust air / fuel ratio control means makes the exhaust air / fuel ratio rich by at least one of post injection for injecting fuel in an expansion stroke or exhaust stroke, a decrease in the intake air amount to the internal combustion engine, and an increase in the exhaust gas recirculation amount. The exhaust emission control device for an internal combustion engine according to claim 11 .

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