JP3757860B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust emission control device for an internal combustion engine.
[0002]
[Prior art]
Diesel engines are economical, but it is important to remove particulate matter (particulate matter: hereinafter referred to as “PM”) unless otherwise specified. It has become a challenge. For this reason, a technique of providing a particulate filter (hereinafter simply referred to as “filter”) for collecting PM in an exhaust system of a diesel engine so that PM is not released into the atmosphere is well known.
[0003]
This filter can prevent PM in the exhaust gas from being collected once and released into the atmosphere. However, PM trapped in the filter may accumulate on the filter and cause clogging of the filter. If this clogging occurs, the pressure of the exhaust gas upstream of the filter may increase, leading to a decrease in the output of the internal combustion engine and damage to the filter. In such a case, the PM deposited on the filter can be removed by igniting and burning. The removal of PM deposited on the filter in this way is called filter regeneration.
[0004]
However, in order to ignite and burn the PM collected by the filter, it is necessary to raise the temperature of the filter. However, since the exhaust temperature of a diesel engine is usually lower than this temperature, the PM is burned and removed. Was difficult.
[0005]
Therefore, it is conceivable to heat and raise the temperature of the filter up to a temperature at which PM collected by an electric heater, burner or the like is generated, but this requires a large amount of energy to be supplied from the outside. To solve this problem, for example, according to Japanese Patent Laid-Open No. 10-272324, a fuel addition device and fuel from the fuel addition device are burned in the presence of a catalyst upstream of the filter, and PM collected in the filter is burned. There is provided a heating device having a catalytic combustion section that heats the exhaust to a temperature that can be controlled.
[0006]
Thus, by burning the fuel in the catalytic combustion section upstream of the filter, the exhaust can be heated uniformly and the entire filter can be heated, so that the filter can be regenerated satisfactorily.
[0007]
[Problems to be solved by the invention]
By the way, PM collected by the filter includes insoluble components such as soot (SOOT) and soluble organic fractions (hereinafter referred to as SOF) such as unburned hydrocarbons (HC). include. These components have different temperatures required for combustion.
[0008]
However, according to the publication, the temperature of the filter is raised to 600 ° C. or higher. At this temperature, soot and SOF can be combusted, but SOF can be combusted even at 600 ° C. or lower. Therefore, if the PM collected in the filter is mainly composed of SOF, it is not necessary to heat the filter to 600 ° C., and the fuel for heating the filter can be reduced.
[0009]
The present invention has been made in view of the above-described problems, and it is an object of the present invention to provide a technique for suppressing deterioration of fuel consumption during filter regeneration in an exhaust purification device for an internal combustion engine.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the exhaust gas purification apparatus for an internal combustion engine of the present invention employs the following means. That is,
A filter capable of temporarily collecting particulate matter in the exhaust,
A collection amount determination means for determining the amount of particulate matter collected by the filter;
A filter heating means for raising the temperature of the filter to remove particulate matter collected by the filter;
With
When the trapped amount of the particulate matter determined by the trapped amount determining means is not less than the first predetermined amount, the filter temperature raising means raises the filter to the first temperature, and thereafter When the trapped amount of the particulate matter determined by the trapped amount determining means is equal to or greater than a second predetermined amount that is less than the first predetermined amount, the filter temperature raising means causes the filter to move from the first temperature. The temperature is raised to a higher second temperature.
[0011]
The greatest feature of the present invention is that when particulate matter of a first predetermined amount or more is collected in the filter, the filter is heated to the first temperature, and a combustible component at the first temperature is obtained. When the particulate matter remains over the second predetermined amount, the filter is further heated to the second temperature to burn combustible components at the second temperature.
[0012]
In the exhaust gas purification apparatus for an internal combustion engine configured as described above, particulate matter contained in the exhaust gas is collected by a filter. Since the collected particulate matter accumulates on the filter and causes clogging, the filter needs to be regenerated. Therefore, the temperature raising means raises the temperature of the filter to the first temperature when the trapped amount of the particulate matter reaches or exceeds the first predetermined amount. Thereby, the combustible component burns at the first temperature. Here, if the main component collected in the filter is combustible at the first temperature, the particulate matter collected in the filter burns and the regeneration of the filter is completed. However, when the main component is not combusted at the first temperature, it is necessary to further increase the temperature. Therefore, after the temperature of the filter has been raised to the first temperature, if a second predetermined amount of particulate matter that is less than the first predetermined amount remains, the second temperature higher than the first temperature. The filter is heated to a temperature of 2, and particulate matter combustible at the second temperature is burned to regenerate the filter.
[0013]
In this manner, stepwise temperature rise by the particulate matter components collected by the filter is possible.
[0014]
In the present invention, the collection amount determination means may determine the amount of particulate matter collected by the filter based on the differential pressure before and after the filter.
[0015]
When the amount of particulate matter collected by the filter increases, the differential pressure before and after the filter increases, so the amount of particulate matter collected can be determined based on the differential pressure before and after the filter. In addition, for example, it is possible to determine the amount of trapped particulate matter by reducing the pre-filter pressure (back pressure upstream of the filter) or the amount of intake air.
[0016]
In the present invention, the first temperature is a temperature at which the SOF content of the particulate matter can be combusted, while the second temperature is a temperature at which the SOOT content of the particulate matter can be combusted. good.
[0017]
In the exhaust gas purification apparatus for an internal combustion engine thus configured, the SOF component is combusted at the first temperature, and the SOOT is combusted at the second temperature. Therefore, when the particulate matter collected by the filter is mainly composed of SOF, it is burned at the first temperature and the regeneration of the filter can be completed.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, specific embodiments of an exhaust emission control device for an internal combustion engine according to the present invention will be described with reference to the drawings. Here, the case where the exhaust gas purification apparatus for an internal combustion engine according to the present invention is applied to a diesel engine for driving a vehicle will be described as an example.
[0019]
FIG. 1 is a diagram showing a schematic configuration of an engine 1 and an intake / exhaust system to which the exhaust purification apparatus according to the present embodiment is applied.
[0020]
An engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine having four cylinders 2.
[0021]
The engine 1 includes a fuel injection valve 3 that injects fuel directly into the combustion chamber of each cylinder 2. Each fuel injection valve 3 is connected to a pressure accumulation chamber (common rail) 4 that accumulates fuel to a predetermined pressure. A common rail pressure sensor 4 a that outputs an electrical signal corresponding to the fuel pressure in the common rail 4 is attached to the common rail 4.
[0022]
The common rail 4 communicates with a fuel pump 6 through a fuel supply pipe 5. This fuel pump 6 is a pump that operates using the rotational torque of the output shaft (crankshaft) of the engine 1 as a drive source, and a pump pulley 6 a attached to the input shaft of the fuel pump 6 is connected to the output shaft (crankshaft) of the engine 1. ) And the belt pulley 7 are connected to each other.
[0023]
In the fuel injection system configured as described above, when the rotational torque of the crankshaft is transmitted to the input shaft of the fuel pump 6, the fuel pump 6 transmits the rotational torque transmitted from the crankshaft to the input shaft of the fuel pump 6. The fuel is discharged at a pressure according to the pressure.
[0024]
The fuel discharged from the fuel pump 6 is supplied to the common rail 4 via the fuel supply pipe 5, accumulated in the common rail 4 up to a predetermined pressure, and distributed to the fuel injection valves 3 of each cylinder 2. When a drive current is applied to the fuel injection valve 3, the fuel injection valve 3 opens, and as a result, fuel is injected from the fuel injection valve 3 into the cylinder 2.
[0025]
Next, an intake branch pipe 8 is connected to the engine 1, and each branch pipe of the intake branch pipe 8 communicates with a combustion chamber of each cylinder 2 via an intake port (not shown).
[0026]
The intake branch pipe 8 is connected to an intake pipe 9. An air flow meter 11 that outputs an electrical signal corresponding to the mass of the intake air flowing through the intake pipe 9 is attached to the intake pipe 9.
[0027]
An intake throttle valve 13 for adjusting the flow rate of the intake air flowing through the intake pipe 9 is provided at a portion of the intake pipe 9 located immediately upstream of the intake branch pipe 8. The intake throttle valve 13 is provided with an intake throttle actuator 14 that is configured by a step motor or the like and that drives the intake throttle valve 13 to open and close.
[0028]
The intake pipe 9 located between the air flow meter 11 and the intake throttle valve 13 is provided with a compressor housing 15a of a centrifugal supercharger (turbocharger) 15 that operates using exhaust energy as a drive source. The intake pipe 9 downstream of 15a is provided with an intercooler 16 for cooling the intake air that has been compressed in the compressor housing 15a and has reached a high temperature.
[0029]
In the intake system configured as described above, the intake air flows into the compressor housing 15 a via the intake pipe 9.
[0030]
The intake air flowing into the compressor housing 15a is compressed by the rotation of the compressor wheel built in the compressor housing 15a. The intake air that has been compressed in the compressor housing 15a and has reached a high temperature is cooled by the intercooler 16, and then the flow rate is adjusted by the intake throttle valve 13 as necessary to flow into the intake branch pipe 8. The intake air that has flowed into the intake branch pipe 8 is distributed to the combustion chambers of the respective cylinders 2 through the respective branch pipes, and is burned using the fuel injected from the fuel injection valves 3 of the respective cylinders 2 as an ignition source.
[0031]
On the other hand, an exhaust branch pipe 18 is connected to the engine 1, and each branch pipe of the exhaust branch pipe 18 communicates with a combustion chamber of each cylinder 2 via an exhaust port (not shown).
[0032]
The exhaust branch pipe 18 is connected to the turbine housing 15 b of the centrifugal supercharger 15. The turbine housing 15b is connected to an exhaust pipe 19, and the exhaust pipe 19 is connected to a muffler (not shown) downstream.
[0033]
In the middle of the exhaust pipe 19, a particulate filter (hereinafter simply referred to as a filter) 20 carrying an NOx storage reduction catalyst is provided. An exhaust gas temperature sensor 24 that outputs an electrical signal corresponding to the temperature of the exhaust gas flowing through the exhaust pipe 19 is attached to the exhaust pipe 19 upstream of the filter 20. One end of an upstream introduction pipe 37a for introducing exhaust gas is connected upstream of the filter 20, and one end of a downstream introduction pipe 37b is connected downstream of the filter 20. The other ends of the upstream introduction pipe 37 a and the downstream introduction pipe 37 b are connected to the differential pressure sensor 37. The differential pressure sensor 37 outputs an electrical signal corresponding to the differential pressure of the exhaust gas introduced from the upstream side introduction pipe 37a and the downstream side introduction pipe 37b.
[0034]
The exhaust pipe 19 downstream of the filter 20 is provided with an exhaust throttle valve 21 for adjusting the flow rate of the exhaust gas flowing through the exhaust pipe 19. The exhaust throttle valve 21 is provided with an exhaust throttle actuator 22 that is configured by a step motor or the like and that drives the exhaust throttle valve 21 to open and close.
[0035]
In the exhaust system configured as described above, the air-fuel mixture (burned gas) combusted in each cylinder 2 of the engine 1 is discharged to the exhaust branch pipe 18 through the exhaust port, and then centrifugally supercharged from the exhaust branch pipe 18. Flows into the turbine housing 15b of the machine 15. The exhaust gas flowing into the turbine housing 15b rotates the turbine wheel rotatably supported in the turbine housing 15b using the energy of the exhaust gas. At that time, the rotational torque of the turbine wheel is transmitted to the compressor wheel of the compressor housing 15a described above.
[0036]
Exhaust gas discharged from the turbine housing 15b flows into the filter 20 through the exhaust pipe 19, and particulate matter (hereinafter simply referred to as PM) in the exhaust gas is collected and harmful gas components are removed or purified. The Exhaust gas from which PM has been collected by the filter 20 and from which harmful gas components have been removed or purified is adjusted in flow rate by the exhaust throttle valve 21 as necessary, and then released into the atmosphere via the muffler.
[0037]
Further, the exhaust branch pipe 18 and the intake branch pipe 8 have an exhaust recirculation passage (hereinafter referred to as an EGR passage) 25 for recirculating a part of the exhaust gas flowing through the exhaust branch pipe 18 to the intake branch pipe 8. It is communicated through. In the middle of the EGR passage 25, a flow rate adjusting valve is configured with an electromagnetic valve or the like, and changes the flow rate of exhaust gas (hereinafter referred to as EGR gas) flowing through the EGR passage 25 in accordance with the magnitude of applied power. (Hereinafter referred to as an EGR valve) 26 is provided.
[0038]
An EGR cooler 27 that cools the EGR gas flowing in the EGR passage 25 is provided in the middle of the EGR passage 25 and upstream of the EGR valve 26. The EGR cooler 27 is provided with a cooling water passage (not shown), and a part of the cooling water for cooling the engine 1 circulates.
[0039]
In the exhaust gas recirculation mechanism configured as described above, when the EGR valve 26 is opened, the EGR passage 25 becomes conductive, and a part of the exhaust gas flowing through the exhaust branch pipe 18 flows into the EGR passage 25. Then, it is guided to the intake branch pipe 8 through the EGR cooler 27.
[0040]
At that time, in the EGR cooler 27, heat exchange is performed between the EGR gas flowing in the EGR passage 25 and the cooling water of the engine 1 to cool the EGR gas.
[0041]
The EGR gas recirculated from the exhaust branch pipe 18 to the intake branch pipe 8 through the EGR passage 25 is guided to the combustion chamber of each cylinder 2 while being mixed with fresh air flowing from the upstream side of the intake branch pipe 8.
[0042]
Here, the EGR gas contains water (H₂O) and carbon dioxide (CO₂) And the like, and since an inert gas component having a high heat capacity is not included, if the EGR gas is contained in the air-fuel mixture, the combustion temperature of the air-fuel mixture is lowered. Therefore, the amount of nitrogen oxide (NOx) generated is suppressed.
[0043]
Further, when the EGR gas is cooled in the EGR cooler 27, the temperature of the EGR gas itself is reduced and the volume of the EGR gas is reduced. Therefore, when the EGR gas is supplied into the combustion chamber, the atmospheric temperature in the combustion chamber is reduced. Is not increased unnecessarily, and the amount of fresh air (volume of fresh air) supplied into the combustion chamber is not unnecessarily reduced.
[0044]
Next, the filter 20 according to the present embodiment will be described.
[0045]
FIG. 2 is a cross-sectional view of the filter 20. FIG. 2A is a diagram illustrating a cross-section in the horizontal direction of the filter 20. FIG. 2B is a view showing a longitudinal section of the filter 20.
[0046]
As shown in FIGS. 2A and 2B, the filter 20 is a so-called wall flow type having a plurality of exhaust flow passages 50 and 51 extending in parallel with each other. These exhaust flow passages include an exhaust inflow passage 50 whose downstream end is closed by a plug 52 and an exhaust outflow passage 51 whose upstream end is closed by a plug 53. In FIG. 2A, hatched portions indicate plugs 53. Therefore, the exhaust inflow passages 50 and the exhaust outflow passages 51 are alternately arranged via the thin partition walls 54. In other words, the exhaust inflow passage 50 and the exhaust outflow passage 51 are arranged such that each exhaust inflow passage 50 is surrounded by four exhaust outflow passages 51 and each exhaust outflow passage 51 is surrounded by four exhaust inflow passages 50.
[0047]
The filter 20 is made of a porous material such as cordierite, so that the exhaust gas flowing into the exhaust inflow passage 50 is adjacent to the surrounding partition wall 54 as shown by an arrow in FIG. To the exhaust outlet passage 51.
[0048]
In the embodiment according to the present invention, a carrier layer made of alumina, for example, is formed on the peripheral wall surfaces of each exhaust inflow passage 50 and each exhaust outflow passage 51, that is, on both side surfaces of each partition wall 54 and on the pore inner wall surface in each partition wall 54. The NOx storage reduction catalyst is supported on the carrier.
[0049]
Next, the function of the NOx storage reduction catalyst carried by the filter 20 according to the present embodiment will be described.
[0050]
The filter 20 uses, for example, alumina as a carrier, and an alkali metal such as potassium (K), sodium (Na), lithium (Li), or cesium (Cs), and barium (Ba) or calcium (Ca). ), An alkaline earth such as lanthanum (La) or yttrium (Y), and a noble metal such as platinum (Pt). In this embodiment, barium (Ba) and platinum (Pt) are supported on a support made of alumina, and O 2 is further supported.₂Ceria with storage capability (Ce₂O_ThreeThe NOx storage reduction catalyst is added.
[0051]
The NOx catalyst configured in this way occludes (absorbs and adsorbs) nitrogen oxides (NOx) in the exhaust when the oxygen concentration of the exhaust flowing into the NOx catalyst is high.
[0052]
On the other hand, the NOx catalyst releases the stored nitrogen oxide (NOx) when the oxygen concentration of the exhaust gas flowing into the NOx catalyst decreases. At that time, if a reducing component such as hydrocarbon (HC) or carbon monoxide (CO) is present in the exhaust, the NOx catalyst converts nitrogen oxide (NOx) released from the NOx catalyst to nitrogen (N₂).
[0053]
By the way, when the engine 1 is operated with lean combustion, the air-fuel ratio of the exhaust discharged from the engine 1 becomes a lean atmosphere, and the oxygen concentration of the exhaust becomes high, so that nitrogen oxide (NOx) contained in the exhaust is NOx. When the lean combustion operation of the engine 1 is continued for a long period of time, the NOx storage capacity of the NOx catalyst is saturated, and nitrogen oxides (NOx) in the exhaust gas are removed by the NOx catalyst. Without being released into the atmosphere.
[0054]
In particular, in a diesel engine such as the engine 1, a lean air-fuel ratio mixture is combusted in most operating regions, and the exhaust air-fuel ratio becomes lean air-fuel ratio in most operating regions accordingly. The NOx occlusion capacity is easily saturated. Here, the lean air-fuel ratio means, for example, 20 to 50 in a diesel engine, and a region in which NOx cannot be purified by a three-way catalyst.
[0055]
Therefore, when the engine 1 is in lean burn operation, before the NOx occlusion capacity of the NOx catalyst is saturated, the oxygen concentration in the exhaust gas flowing into the NOx catalyst is lowered and the concentration of the reducing agent is increased and occluded in the NOx catalyst. It is necessary to reduce the formed nitrogen oxides (NOx).
[0056]
As a method for reducing the oxygen concentration in this way, after adding fuel in the exhaust gas or increasing the amount of recirculated EGR gas to increase the amount of soot generation to a maximum, the amount of EGR gas is further increased. There are conceivable methods such as low-temperature combustion (Japanese Patent No. 3116876), sub-injection in which fuel is injected again during an expansion stroke that does not become engine output after main injection for injecting fuel for engine output. In the present embodiment, a reducing agent supply mechanism for adding fuel (light oil) as a reducing agent to the exhaust gas flowing through the exhaust pipe 19 upstream from the filter 20 is provided, and the fuel is added from the reducing agent supply mechanism into the exhaust gas. As a result, the oxygen concentration of the exhaust gas flowing into the filter 20 is decreased and the concentration of the reducing agent is increased.
[0057]
As shown in FIG. 1, the reducing agent supply mechanism is attached so that its injection hole faces the exhaust branch pipe 18, and is opened by a signal from the ECU 35 to inject fuel and a reducing agent injection valve 28. A reducing agent supply path 29 that guides the fuel discharged from the fuel pump 6 to the reducing agent injection valve 28, and a shutoff that is provided in the reducing agent supply path 29 and blocks the flow of fuel in the reducing agent supply path 29. And a valve 31.
[0058]
In such a reducing agent supply mechanism, high-pressure fuel discharged from the fuel pump 6 is applied to the reducing agent injection valve 28 via the reducing agent supply path 29. Then, the reducing agent injection valve 28 is opened by a signal from the ECU 35 and fuel as a reducing agent is injected into the exhaust branch pipe 18.
[0059]
The reducing agent injected into the exhaust branch pipe 18 from the reducing agent injection valve 28 reduces the oxygen concentration of the exhaust gas flowing from the upstream side of the exhaust branch pipe 18.
[0060]
The exhaust gas having a low oxygen concentration formed in this manner flows into the filter 20, and the nitrogen oxide (NOx) occluded in the filter 20 is converted into nitrogen (N₂).
[0061]
Thereafter, the reducing agent injection valve 28 is closed by a signal from the ECU 35, and the addition of the reducing agent into the exhaust branch pipe 18 is stopped.
[0062]
The engine 1 configured as described above is provided with an electronic control unit (ECU) 35 for controlling the engine 1. The ECU 35 is a unit that controls the operating state of the engine 1 in accordance with the operating conditions of the engine 1 and the driver's request.
[0063]
Various sensors such as a common rail pressure sensor 4a, an air flow meter 11, an exhaust temperature sensor 24, a crank position sensor 33, an accelerator opening sensor 36, a differential pressure sensor 37, and the like are connected to the ECU 35 through electric wiring. The output signal is input to the ECU 35.
[0064]
On the other hand, the ECU 35 is connected to the fuel injection valve 3, the intake throttle actuator 14, the exhaust throttle actuator 22, the EGR valve 26, the reducing agent injection valve 28, the shut-off valve 31 and the like via electric wiring, The ECU 35 can be controlled.
[0065]
Here, as shown in FIG. 3, the ECU 35 includes a CPU 351, a ROM 352, a RAM 353, a backup RAM 354, an input port 356, and an output port 357, which are connected to each other by a bidirectional bus 350. , An A / D converter (A / D) 355 connected to the input port 356 is provided.
[0066]
The input port 356 receives an output signal from a sensor that outputs a digital signal format signal, such as the crank position sensor 33, and transmits the output signal to the CPU 351 and the RAM 353.
[0067]
The input port 356 is connected via an A / D 355 of a sensor that outputs a signal in an analog signal format, such as the common rail pressure sensor 4a, the air flow meter 11, the exhaust gas temperature sensor 24, the accelerator opening sensor 36, and the differential pressure sensor 37. And output those output signals to the CPU 351 and RAM 353.
[0068]
The output port 357 is connected to the fuel injection valve 3, the intake throttle actuator 14, the exhaust throttle actuator 22, the EGR valve 26, the reducing agent injection valve 28, the shutoff valve 31, etc. via electrical wiring, and is output from the CPU 351. The control signal is transmitted to the fuel injection valve 3, the intake throttle actuator 14, the exhaust throttle actuator 22, the EGR valve 26, the reducing agent injection valve 28, or the shutoff valve 31.
[0069]
The ROM 352 controls a fuel injection control routine for controlling the fuel injection valve 3, an intake throttle control routine for controlling the intake throttle valve 13, an exhaust throttle control routine for controlling the exhaust throttle valve 21, and an EGR valve 26. Application programs such as an EGR control routine for performing the above and a NOx purification control routine for adding the reducing agent to the filter 20 to reduce the stored NOx are stored.
[0070]
The ROM 352 stores various control maps in addition to the application programs described above. The control map is, for example, a fuel injection amount control map indicating the relationship between the operating state of the engine 1 and the basic fuel injection amount (basic fuel injection time), and the fuel indicating the relationship between the operating state of the engine 1 and the basic fuel injection timing. The injection timing control map, the intake throttle valve opening control map showing the relationship between the operating state of the engine 1 and the target opening of the intake throttle valve 13, the relationship between the operating state of the engine 1 and the target opening of the exhaust throttle valve 21 Exhaust throttle valve opening control map, EGR valve opening control map showing the relationship between the operating state of the engine 1 and the target opening of the EGR valve 26, the operating state of the engine 1 and the target addition amount of reducing agent (or the exhaust gas A reducing agent addition amount control map showing the relationship with the target air-fuel ratio), a reducing agent injection valve control map showing the relationship between the target addition amount of the reducing agent and the opening time of the reducing agent injection valve 28, and the like.
[0071]
The RAM 353 stores output signals from the sensors, calculation results of the CPU 351, and the like. The calculation result is, for example, the engine speed calculated based on the time interval at which the crank position sensor 33 outputs a pulse signal. These data are rewritten to the latest data every time the crank position sensor 33 outputs a pulse signal.
[0072]
The backup RAM 354 is a non-volatile memory capable of storing data even after the engine 1 is stopped.
[0073]
The CPU 351 operates in accordance with an application program stored in the ROM 352 and executes fuel injection valve control, intake throttle control, exhaust throttle control, EGR control, NOx purification control, and the like.
[0074]
For example, in the NOx purification control, the CPU 351 executes so-called rich spike control in which the oxygen concentration in the exhaust gas flowing into the filter 20 is reduced in a spike manner (short time) in a relatively short cycle.
[0075]
In the rich spike control, the CPU 351 determines whether or not the rich spike control execution condition is satisfied every predetermined cycle. As this rich spike control execution condition, for example, the filter 20 is in an active state, the output signal value (exhaust temperature) of the exhaust temperature sensor 24 is equal to or lower than a predetermined upper limit value, poisoning recovery control is not executed, Etc. can be exemplified.
[0076]
When it is determined that the rich spike control execution condition as described above is satisfied, the CPU 351 controls the reducing agent injection valve 28 to inject fuel as a reducing agent from the reducing agent injection valve 28 in a spike manner. As a result, the air-fuel ratio of the exhaust gas flowing into the filter 20 is temporarily set to a predetermined target rich air-fuel ratio.
[0077]
Specifically, the CPU 351 stores the engine speed stored in the RAM 353, the output signal of the accelerator opening sensor 36 (accelerator opening), the output signal value of the air flow meter 11 (intake air amount), an air-fuel ratio sensor (illustrated). (Omitted) output signal, fuel injection amount, etc. are read out.
[0078]
The CPU 351 accesses the reducing agent addition amount control map in the ROM 352 using the engine speed, the accelerator opening, the intake air amount, and the fuel injection amount as parameters, and sets the air-fuel ratio of the exhaust to a preset target air-fuel ratio. The amount of addition of the reducing agent (target addition amount) required above is calculated.
[0079]
Subsequently, the CPU 351 accesses the reducing agent injection valve control map of the ROM 352 using the target addition amount as a parameter, and the reducing agent injection valve 28 necessary for injecting the reducing agent with the target addition amount from the reducing agent injection valve 28. The valve opening time (target valve opening time) is calculated.
[0080]
When the target valve opening time of the reducing agent injection valve 28 is calculated, the CPU 351 opens the reducing agent injection valve 28.
[0081]
When the target valve opening time has elapsed from the time when the reducing agent injection valve 28 is opened, the CPU 351 closes the reducing agent injection valve 28.
[0082]
Thus, when the reducing agent injection valve 28 is opened for the target valve opening time, a target addition amount of fuel is injected into the exhaust branch pipe 18 from the reducing agent injection valve 28. The reducing agent injected from the reducing agent injection valve 28 mixes with the exhaust gas flowing from the upstream side of the exhaust branch pipe 18 to form an air-fuel mixture having a target air-fuel ratio and flows into the filter 20.
[0083]
As a result, the air-fuel ratio of the exhaust gas flowing into the filter 20 changes its oxygen concentration in a relatively short cycle, and thus the filter 20 alternately shortens the storage and reduction of nitrogen oxides (NOx). It will repeat periodically.
[0084]
As described above, the air-fuel ratio of the exhaust gas flowing into the filter 20 is spiked to the target rich air-fuel ratio, and the nitrogen oxide (NOx) absorbed by the NOx storage reduction catalyst can be reduced.
[0085]
In the present embodiment, when supplying the reducing agent to the filter 20, fuel for engine output is mainly injected into the cylinder 2 of the engine 1 instead of adding fuel from the reducing agent injection valve 28 into the exhaust gas. Sub-injection may be performed in which fuel is injected again at a time when the engine output is not reached.
[0086]
In this way, the fuel is injected again at the time when the engine output does not become the engine output after the fuel for the engine output is injected into the cylinder 2 of the engine 1 only by the main injection to the rich air-fuel ratio side. This is because there is a possibility that problems such as smoke may occur if the shift is attempted. Further, when the main injection is increased, the combustion of the fuel becomes the engine output, so that torque fluctuations occur and the operating state deteriorates. Therefore, the sub-injection is performed in an expansion stroke or the like that hardly affects the engine output after the main injection.
[0087]
The fuel injected by the sub-injection burns in the cylinder 2 to raise the gas temperature in the cylinder 2 and lower the oxygen concentration in the cylinder 2. The gas whose temperature rises as a result of combustion in the cylinder 2 passes through the exhaust pipe 19 to reach the NOx storage reduction catalyst, raises the temperature of the NOx storage reduction catalyst, and serves as a reducing agent for the NOx storage reduction catalyst. Supply hydrocarbon (HC).
[0088]
If the sub-injection is used in this way, the temperature of the NOx catalyst can be raised early, and a reducing agent can be supplied to the NOx storage reduction catalyst.
[0089]
If the relationship between the accelerator opening, the engine speed, the sub-injection amount or the sub-injection timing is mapped in advance and stored in the ROM 352, the map, the accelerator opening, and the engine rotation can be obtained. It can be calculated from the number. Furthermore, the cooling water temperature of the engine 1 may be added as a parameter.
[0090]
Next, in the poisoning elimination control, the CPU 351 performs a poisoning elimination process to eliminate the poisoning due to the oxide of the filter 20.
[0091]
Here, the fuel of the engine 1 may contain sulfur (S), and when such fuel is burned in the engine 1, sulfur dioxide (SO₂) And sulfur trioxide (SO_Three) And other sulfur oxides (SOx).
[0092]
Sulfur oxide (SOx) flows into the filter 20 together with the exhaust gas, and is absorbed by the filter 20 by the same mechanism as nitrogen oxide (NOx).
[0093]
Specifically, when the oxygen concentration of the exhaust gas flowing into the filter 20 is high, sulfur dioxide (SO₂) And sulfur trioxide (SO_Three) And other sulfur oxides (SOx) are oxidized on the surface of platinum (Pt), and sulfate ions (SO_Four ^2-) Is absorbed by the filter 20. Furthermore, sulfate ions (SO_Four ^2-) Combines with barium oxide (BaO) to form sulfate (BaSO)._Four).
[0094]
By the way, sulfate (BaSO_Four) Is barium nitrate (Ba (NO_Three)₂) And is difficult to decompose, and even if the oxygen concentration of the exhaust gas flowing into the filter 20 is lowered, it remains in the filter 20 without being decomposed.
[0095]
Sulfate (BaSO_Four) Increases accordingly, the amount of barium oxide (BaO) that can participate in the absorption of nitrogen oxides (NOx) decreases accordingly, so that the NOx absorption capacity of the filter 20 decreases, so-called SOx poisoning. Will occur.
[0096]
As a method for eliminating SOx poisoning of the filter 20, the atmospheric temperature of the filter 20 is raised to a high temperature range of approximately 600 to 650 ° C., and the oxygen concentration of the exhaust gas flowing into the filter 20 is lowered to reduce the filter 20. Barium sulfate (BaSOSO)_Four) SO_Three ^-And SO_Four ^-Pyrolyzed, and then SO_Three ^-And SO_Four ^-Reacts with hydrocarbons (HC) and carbon monoxide (CO) in the exhaust to produce gaseous SO₂ ^-An example of the method for reduction is shown.
[0097]
Therefore, in the poisoning elimination process according to the present embodiment, the CPU 351 first performs the catalyst temperature increase control for increasing the bed temperature of the filter 20 and then reduces the oxygen concentration of the exhaust gas flowing into the filter 20. .
[0098]
In the catalyst temperature increase control, the CPU 351 causes the fuel injection valve 3 to inject fuel from the fuel injection valve 3 during the expansion stroke of each cylinder 2 and adds the fuel from the reducing agent injection valve 28 into the exhaust gas. The fuel component may be oxidized in the filter 20 and the bed temperature of the filter 20 may be increased by heat generated during the oxidation.
[0099]
When the bed temperature of the filter 20 rises to a high temperature range of about 600 ° C. to 650 ° C. by the catalyst temperature raising process as described above, the CPU 351 starts from the reducing agent injection valve 28 to reduce the oxygen concentration of the exhaust gas flowing into the filter 20. Inject fuel.
[0100]
When the poisoning elimination process is performed in this manner, the oxygen concentration of the exhaust gas flowing into the filter 20 becomes low under the condition where the bed temperature of the filter 20 is high, so that the barium sulfate (BaSO) absorbed in the filter 20 is reduced._Four) Is SO_Three ^-And SO_Four ^-They are pyrolyzed into SO_Three ^-And SO_Four ^-Reacts with hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas and is reduced, so that SOx poisoning of the filter 20 is eliminated.
[0101]
On the other hand, depending on the operating state of the engine, the PM captured by the filter 20 remains unburned and accumulates, causing clogging of the filter 20. As described above, the temperature increase control by adding the fuel is also effective as one of the methods for effectively removing the unburned PM.
[0102]
Next, temperature increase control of the filter 20 by adding fuel into the exhaust will be described.
[0103]
In the temperature rise control by fuel addition, the CPU 351 executes fuel addition control for adding fuel to the exhaust gas flowing into the filter 20.
[0104]
The CPU 351 controls the reducing agent injection valve 28 to inject fuel as the reducing agent from the reducing agent injection valve 28, thereby temporarily setting the air-fuel ratio of the exhaust gas flowing into the filter 20 to a predetermined target air-fuel ratio.
[0105]
Specifically, the CPU 351 displays the engine speed, the output signal of the accelerator opening sensor 36 (accelerator opening), the output signal value of the air flow meter 11 (intake air amount), the fuel injection amount, etc. stored in the RAM 353. read out. Further, the CPU 351 accesses the reducing agent addition amount control map in the ROM 352 using the engine speed, the accelerator opening, the intake air amount, and the fuel injection amount as parameters, and sets the exhaust air / fuel ratio to a preset target air / fuel ratio. The amount of addition of the reducing agent (target addition amount) necessary for the above is calculated.
[0106]
Subsequently, the CPU 351 accesses the flow rate adjustment valve control map of the ROM 352 using the target addition amount as a parameter, and controls the reducing agent injection valve 28 necessary for injecting the target addition amount of the reducing agent from the reducing agent injection valve 28. Calculate the valve opening time (target valve opening time).
[0107]
When the target valve opening time of the reducing agent injection valve 28 is calculated, the CPU 351 opens the reducing agent injection valve 28.
[0108]
When the target valve opening time has elapsed from the time when the reducing agent injection valve 28 is opened, the CPU 351 closes the reducing agent injection valve 28.
[0109]
As described above, when the reducing agent injection valve 28 is opened for the normal target valve opening time, the fuel of the normal target addition amount is injected from the reducing agent injection valve 28 into the exhaust branch pipe 18. The reducing agent injected from the reducing agent injection valve 28 mixes with the exhaust gas flowing from the upstream side of the exhaust branch pipe 18 to form an air-fuel mixture having a target air-fuel ratio and flows into the filter 20.
[0110]
As a result, the exhaust gas flowing into the filter 20 changes its oxygen concentration in a relatively short cycle. Then, the active oxygen is released by the fuel that has flowed into the filter 20, so that the PM is easily oxidized and the amount capable of being removed by oxidation per unit time is improved. Further, the addition of fuel removes oxygen poisoning of the catalyst and increases the activity of the catalyst, so that active oxygen is easily released. Furthermore, the temperature of the filter 20 rises due to the oxidation reaction of the fuel. Then, PM is oxidized and burned by active oxygen and removed.
[0111]
As another method for supplying the reducing agent to the filter 20, low temperature combustion can be used.
[0112]
Here, the low temperature combustion will be described.
[0113]
As described above, conventionally, EGR has been used to suppress the generation of NOx. Since the EGR gas has a relatively high specific heat ratio and a large amount of heat is required to raise the temperature, the combustion temperature in the cylinder 2 decreases as the EGR gas ratio in the intake air increases. As the combustion temperature decreases, the amount of NOx generated also decreases. Therefore, the higher the EGR gas ratio, the lower the NOx emission.
[0114]
However, as the EGR gas ratio is increased, the generation amount of soot begins to increase abruptly at a certain ratio or more. Normal EGR control is performed at a lower EGR gas ratio than when soot begins to increase rapidly.
[0115]
However, as the EGR gas ratio is further increased, soot rapidly increases as described above, but there is a peak in the generation amount of this soot, and when the EGR gas ratio is further increased beyond this peak, This time, wrinkles start to decrease rapidly, and finally it hardly occurs.
[0116]
This is because when the temperature of the fuel during combustion in the combustion chamber and the surrounding gas is below a certain temperature, the growth of hydrocarbons (HC) stops at an intermediate stage before reaching soot, and the temperature of the fuel and the surrounding gas is reduced. This is because the hydrocarbon (HC) grows to soot all at once when the temperature rises above a certain temperature.
[0117]
Therefore, no soot will be generated if the combustion during combustion in the combustion chamber and the gas temperature around it are controlled below the temperature at which hydrocarbon (HC) growth stops midway. In this case, the endothermic effect of the gas around the fuel when the fuel burns greatly affects the temperature of the fuel and the surrounding gas, and the endothermic amount of the gas around the fuel, that is, EGR, according to the amount of heat generated during fuel combustion. It is possible to suppress the generation of soot by adjusting the gas ratio.
[0118]
The EGR gas ratio at the time of performing low temperature combustion is obtained in advance by experiments or the like and is mapped and stored in the ROM 352 in the ECU 35. Based on this map, EGR gas amount feedback control is performed.
[0119]
On the other hand, hydrocarbons (HC) that have stopped growing before reaching soot can be oxidized by the NOx storage reduction catalyst supported on the filter 20. Therefore, hydrocarbon (HC) generated by low temperature combustion works as a reducing agent.
[0120]
Thus, low temperature combustion is based on purifying hydrocarbons (HC) whose growth has stopped before reaching soot with a NOx storage reduction catalyst or the like. Therefore, when the NOx storage reduction catalyst or the like is not activated, it is difficult to use low temperature combustion because hydrocarbons (HC) are not purified but are released into the atmosphere.
[0121]
Further, the temperature of the fuel during combustion in the cylinder 2 and the gas temperature around it can be controlled to a temperature below the temperature at which the growth of hydrocarbon (HC) stops halfway when the engine load is small and the amount of heat generated by combustion is small. It is.
[0122]
Therefore, in the present embodiment, low-temperature combustion control is performed when the engine 1 is operating at a low rotation and low load and when the NOx storage reduction catalyst carried on the filter 20 reaches the active region.
[0123]
Whether it is in the active region or not can be determined based on an output signal of the exhaust temperature sensor 24 or the like.
[0124]
In this way, in low-temperature combustion, hydrocarbon (HC) as a reducing agent can be supplied to the NOx storage reduction catalyst while suppressing the emission of PM typified by soot, and NOx can be reduced and purified. Further, since heat is generated at this time, the temperature of the heated filter 20 can be maintained.
[0125]
When supplying the reducing agent by such low temperature combustion, the CPU 351 first obtains the target air-fuel ratio. The target air-fuel ratio can be obtained by determining a map based on the operating state of the engine 1 in advance. Next, the CPU 351 calculates a target opening degree of the intake throttle valve 13 according to the target air-fuel ratio, and controls the intake throttle valve 13 to become the target opening degree. Next, the CPU 351 calculates a target opening degree of the EGR valve 26 corresponding to the target air-fuel ratio, and controls the EGR valve 26 so as to become the target opening degree. Further, the CPU 351 calculates the fuel injection amount and the fuel injection start timing. The target opening, the fuel injection amount, and the fuel injection start timing of the intake throttle valve 13 and the EGR valve 26 are calculated based on a map obtained in advance.
[0126]
By performing low-temperature combustion in this way, the concentration of oxygen in the exhaust gas flowing into the filter 20 is reduced and the concentration of the reducing agent is increased, and the nitrogen oxide (NOx) absorbed by the filter 20 is released. It is possible to increase the temperature of the filter 20.
[0127]
Here, in an exhaust emission control device for an internal combustion engine equipped with a conventional filter, the temperature of the filter is raised to, for example, 600 ° C. or more, and PM is burned and removed. However, some PMs burn without being heated to, for example, 600 ° C. or more. When such components are mainly deposited, the filter can be regenerated without being heated to, for example, 600 ° C. . Therefore, although the deposited main component of PM burns at 600 ° C. or lower, if the temperature is raised to, for example, 600 ° C., the amount of fuel consumption increases and fuel consumption deteriorates.
[0128]
Therefore, in the present embodiment, first, when the temperature of the filter 20 is raised to, for example, 450 ° C. and it is confirmed that PM has been removed, the PM regeneration control is terminated at that point, while the removal of PM is confirmed. If not, the temperature of the filter 20 is raised to 600 ° C., for example.
[0129]
FIG. 4 is a diagram showing an example of the relationship between the vehicle travel distance and the differential pressure before and after the filter when PM regeneration control according to the present embodiment is performed.
[0130]
In (1), when the differential pressure across the filter 20 detected by the differential pressure sensor 37 is equal to or higher than the first predetermined value, the temperature of the filter 20 is raised to 450 ° C. Here, the first predetermined value is, for example, the difference between the front and rear of the filter 20 when the amount of PM that does not overheat the filter 20 is accumulated when all the PM accumulated on the filter 20 burns. Pressure. By setting the first predetermined value in this way, it is possible to regenerate the filter 20 while suppressing thermal deterioration of the filter 20.
[0131]
In {circle around (2)}, the differential pressure across the filter 20 becomes equal to or lower than the second predetermined value, and the PM regeneration control is finished. Here, the second predetermined value is a value at which the differential pressure across the filter 20 is predicted to drop below this value when the main component of PM deposited on the filter 20 is SOF. In {circle around (2)}, soot is not combusted and is deposited on the filter 20, but since the amount is small, PM regeneration control is terminated.
[0132]
In {circle around (3)}, PM accumulates again on the filter 20 and the differential pressure across the filter 20 detected by the differential pressure sensor 37 again becomes equal to or higher than the first predetermined value, so the temperature of the filter 20 is raised to 450 ° C. ing.
[0133]
In (4), when the temperature rises to 450 ° C., the differential pressure across the filter 20 does not decrease below the second predetermined value. In such a case, it is estimated that the main component of PM deposited on the filter 20 is soot.
[0134]
In (5), the temperature of the filter 20 is raised to 600 ° C. As a result, soot is burned and the differential pressure across the filter 20 is reduced.
[0135]
In (6), the SOF and soot accumulated in the filter 20 are burned, and the differential pressure across the filter 20 is reduced to a third predetermined value in the vicinity of the initial pressure loss value of the filter 20.
[0136]
Thus, according to the present embodiment, the temperature of the filter 20 can be raised in stages.
[0137]
Next, the flow of PM regeneration control according to this embodiment will be described.
[0138]
FIG. 5 is a flowchart showing a flow of PM regeneration control according to the present embodiment. This flow is executed every time the vehicle travels a certain distance.
[0139]
In step S101, the differential pressure Pb before and after the filter 20 obtained from the output signal of the differential pressure sensor 37 is read.
[0140]
In step S102, it is determined whether or not the differential pressure Pb before and after the filter 20 read in step S101 is greater than a first predetermined value. Here, the first predetermined value is the differential pressure across the filter 20 when the amount of PM that does not overheat the filter 20 is accumulated even when all of the PM accumulated on the filter 20 burns. is there.
[0141]
If an affirmative determination is made in step S102, the process proceeds to step S103. On the other hand, if a negative determination is made, the routine is terminated because there is no need to regenerate the filter 20.
[0142]
In step S103, the counter i that counts the period during which the filter 20 is heated to 450 ° C., which is the first temperature, is reset.
[0143]
In step S104, the counter is counted up. The CPU 351 substitutes i + 1 for the counter i.
[0144]
In step S105, fuel as a reducing agent is added to the filter 20 to raise the temperature of the filter 20 to 450 ° C. At this temperature, SOF can be combusted. As a method for raising the temperature of the filter 20, the low temperature combustion, the sub-injection, the fuel addition to the exhaust gas by the reducing agent injection valve 28, and the like are performed.
[0145]
In step S106, the differential pressure Pa across the filter 20 is read.
[0146]
In step S107, it is determined whether or not the differential pressure Pa across the filter 20 read in step S106 is greater than a second predetermined value. When a large amount of SOF is contained in the PM collected by the filter 20, the differential pressure across the filter 20 is reduced by the temperature rise of the filter 20 performed in step S105. Here, when the differential pressure across the filter 20 becomes smaller than the second predetermined value, the regeneration of the filter 20 is terminated and the PM regeneration control is terminated. On the other hand, when it does not become smaller than the second predetermined value, the regeneration process is continued at 450 ° C.
[0147]
If an affirmative determination is made in step S107, the process proceeds to step S108. On the other hand, if a negative determination is made, this routine is terminated.
[0148]
In step S108, it is determined whether or not the value of the counter i is greater than a predetermined value. If the differential pressure across the filter 20 does not become smaller than the second predetermined value even when the temperature of the filter 20 is raised to 450 ° C. for a predetermined period, the PM deposited on the filter 20 is mainly composed of soot. Therefore, it is necessary to raise the temperature of the filter 20 to a temperature at which soot can be combusted.
[0149]
If an affirmative determination is made in step S108, the process returns to step S104. On the other hand, if a negative determination is made, the process proceeds to step S109.
[0150]
In step S109, the temperature of the filter 20 is raised to 600 ° C. At this temperature, soot can be combusted.
[0151]
In step S110, the front-rear differential pressure Pe of the filter 20 is read.
[0152]
In step S111, it is determined whether or not the differential pressure Pe across the filter 20 read in step S110 is greater than a third predetermined pressure. Due to the temperature rise up to 600 ° C. performed in step S109, most of the PM deposited on the filter 20 burns. As a result, the differential pressure across the filter 20 is reduced to near the initial pressure loss value, which is the differential pressure across the filter 20 when it is new. Therefore, when the differential pressure across the filter 20 is greater than the third predetermined value, the regeneration process of the filter 20 is continued at 600 ° C., assuming that the regeneration of the filter 20 has not yet been completed. On the other hand, when it becomes smaller than the third predetermined value, the regeneration of the filter 20 is completed and the PM regeneration control is terminated. Here, the third predetermined value is a value that takes into account the deterioration over time or the like in the initial pressure loss value of the filter 20.
[0153]
If an affirmative determination is made in step S111, the process returns to step S109. On the other hand, if a negative determination is made, this routine is terminated.
[0154]
In this way, according to the present embodiment, it is possible to increase the temperature of the filter 20 in stages to achieve PM regeneration.
[0155]
Here, in the exhaust gas purification apparatus of the conventional internal combustion engine, when the regeneration process of the filter is necessary, the temperature of the filter is uniformly raised to, for example, 600 ° C. However, when the main component of PM collected by the filter is SOF, for example, it is sufficient to raise the temperature to 450 ° C., for example, so that fuel is excessively consumed and fuel consumption is deteriorated.
[0156]
In this respect, according to the present embodiment, since the temperature of the filter is raised stepwise, for example, if the regeneration of the filter is completed by raising the temperature to 450 ° C., the temperature rise can be terminated there.
[0157]
As described above, according to the present embodiment, it is possible to raise the temperature of the filter stepwise and reduce the fuel consumption.
[0158]
【The invention's effect】
In the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the temperature of the filter can be raised stepwise to reduce the amount of reducing agent consumed.
[0159]
Therefore, when fuel is used as the reducing agent, deterioration of fuel consumption can be suppressed.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram illustrating an engine to which an exhaust gas purification apparatus for an internal combustion engine according to an embodiment of the present invention is applied and an intake / exhaust system thereof.
FIG. 2A is a diagram showing a transverse cross section of a particulate filter. (B) is a figure which shows the longitudinal direction cross section of a particulate filter.
FIG. 3 is a block diagram showing an internal configuration of an ECU.
FIG. 4 is a diagram showing an example of a relationship between a vehicle travel distance and a differential pressure before and after the filter.
FIG. 5 is a flowchart showing a flow of PM regeneration control according to the embodiment of the present invention.
[Explanation of symbols]
1 ... Engine
1a ... Crank pulley
2. Cylinder
3. Fuel injection valve
4 ... Common rail
4a ... Common rail pressure sensor
5. Fuel supply pipe
6. Fuel pump
6a ... Pump pulley
8 ... Intake branch pipe
9. Intake pipe
18 ... Exhaust branch pipe
19 ... Exhaust pipe
20 ... Particulate filter
21 ... Exhaust throttle valve
24 ... Exhaust temperature sensor
25 ... EGR passage
26 ... EGR valve
27 ... EGR cooler
28 ... Reducing agent injection valve
29 ... Reducing agent supply path
31 ... Shut-off valve
33 ... Crank position sensor
34 ... Water temperature sensor
35 ... ECU
36 Accelerator opening sensor
37 ... Differential pressure sensor

Claims (3)

A filter capable of temporarily collecting particulate matter in the exhaust,
A collection amount determination means for determining the amount of particulate matter collected by the filter;
A filter temperature raising means for raising the temperature of the filter and removing particulate matter collected by the filter;
With
When the trapped amount of the particulate matter determined by the trapped amount determining means is not less than the first predetermined amount, the filter temperature raising means raises the filter to the first temperature, and thereafter When the trapped amount of the particulate matter determined by the trapped amount determining means is equal to or greater than a second predetermined amount that is less than the first predetermined amount, the filter temperature raising means causes the filter to move from the first temperature. An exhaust purification device for an internal combustion engine, wherein the temperature is raised to a higher second temperature. 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the collection amount determination unit determines the amount of particulate matter collected by the filter based on a differential pressure before and after the filter. The first temperature is a temperature at which the SOF content of the particulate matter can be combusted, while the second temperature is a temperature at which the SOOT content of the particulate matter can be combusted. 3. An exhaust emission control device for an internal combustion engine according to 1 or 2.

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