JP2002129938A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the prevention of a particulate filter from regenerated during its regeneration. SOLUTION: In this exhaust emission control device of an internal combustion engine, a particulate filter 22 is arranged in an exhaust port 10, unburned HC is supplied into the particulate filter 22 from an internal combustion engine body 1 when exhaust gas temperature is lower than low temperature oxidizing reaction temperature, thereafter not only the exhaust gas temperature is raised up to the temperature exceeding the low temperature oxidizing reaction temperature but also the unburned HC is, in principal, prohibited to supply to the particulate filter 22 and the unburned HC is avoided to change into soot before reaching the particulate filter in the raised temperature exhausted gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, there has been known an exhaust gas purifying apparatus for an internal combustion engine in which a particulate filter is disposed in an engine exhaust passage and unburned HC is supplied to the particulate filter. An example of this type of exhaust gas purifying apparatus for an internal combustion engine is disclosed in, for example, JP-A-58-38311. In the exhaust gas purifying apparatus for an internal combustion engine described in JP-A-58-38311, when unburned HC is supplied to the particulate filter, the unburned HC is oxidized in the particulate filter. Is raised.

[0003]

However, Japanese Patent Application Laid-Open No. 58-1983
In the exhaust gas purifying apparatus for an internal combustion engine described in Japanese Unexamined Patent Publication No. 3-38311, unburned HC is stored in the particulate filter until most of the fine particles deposited on the particulate filter are burned regardless of the exhaust gas temperature. Continues to be supplied. That is, in the exhaust gas purifying apparatus for an internal combustion engine described in Japanese Patent Application Laid-Open No. 58-38311, even if the exhaust gas temperature rises to a temperature equal to or higher than the low-temperature oxidation reaction temperature, the unburned HC is stored in the particulate filter. Will continue to be supplied. On the other hand, if unburned HC is supplied to the particulate filter when the exhaust gas temperature is equal to or higher than the low-temperature oxidation reaction temperature, the unburned HC in the exhaust gas changes to soot before reaching the particulate filter. Therefore, despite trying to burn and remove the fine particles deposited on the particulate filter, the fine particles are supplied as soot to the particulate filter, and as a result, the regeneration of the particulate filter, that is, Reduction of the amount of fine particles deposited on the particulate filter is prevented.

[0004] In view of the above problems, an object of the present invention is to provide an exhaust gas purifying apparatus for an internal combustion engine which can prevent the regeneration of a particulate filter from being hindered.

[0005]

According to the first aspect of the present invention, an exhaust gas of an internal combustion engine is provided in which a particulate filter is disposed in an engine exhaust passage so as to supply unburned HC to the particulate filter. In the purification device, when the exhaust gas temperature is lower than the low-temperature oxidation reaction temperature, unburned HC is supplied to the particulate filter, and then the exhaust gas temperature is raised to a temperature equal to or higher than the low-temperature oxidation reaction temperature, and the particulate filter is And an exhaust gas purifying apparatus for an internal combustion engine in which supply of unburned HC to the exhaust gas is basically prohibited.

In the exhaust gas purifying apparatus for an internal combustion engine according to the first aspect, unburned HC is supplied to the particulate filter when the exhaust gas temperature is lower than the low-temperature oxidation reaction temperature.
Therefore, by suppressing the unburned HC from changing to soot before reaching the particulate filter, the unburned HC is oxidized in the particulate filter, thereby burning the particulates deposited on the particulate filter. Prepare to remove. Further, after the unburned HC is supplied to the particulate filter when the exhaust gas temperature is lower than the low-temperature oxidation reaction temperature,
The temperature of the exhaust gas is raised to a temperature equal to or higher than the low-temperature oxidation reaction temperature. Therefore, the particulate filter is heated not only by the unburned HC that oxidizes and generates heat in the particulate filter, but also heated by the heated exhaust gas. As a result, the particulates deposited on the particulate filter can be removed by burning. Further, when the exhaust gas temperature is raised to a temperature equal to or higher than the low-temperature oxidation reaction temperature, supply of unburned HC to the particulate filter is basically prohibited. Therefore, the unburned HC in the heated exhaust gas is prevented from changing to soot before reaching the particulate filter, and as a result, soot is supplied to the particulate filter. Thus, it is possible to prevent the reproduction of the particulate filter from being hindered. That is, it is possible to prevent the reduction of the fine particles deposited on the particulate filter from being hindered.

According to the second aspect of the present invention, when the exhaust gas passes through the particulate filter wall, the particulate matter in the exhaust gas is trapped inside the particulate filter wall. An exhaust gas purifying apparatus for an internal combustion engine according to claim 1, which constitutes a filter.

In the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, when the exhaust gas passes through the wall of the particulate filter, fine particles in the exhaust gas are trapped inside the wall of the particulate filter. A particulate filter is configured. Therefore, when the particulate filter is to be regenerated due to an increase in the amount of fine particles deposited on the particulate filter, it becomes difficult for the exhaust gas to pass through the wall of the particulate filter, and the exhaust gas pressure rises. The temperature of the curated filter is determined not as a static temperature but rather as a total temperature. Therefore, as compared with the case where the temperature of the particulate filter is determined as the static temperature, the temperature of the particulate filter can be increased, and the fine particles deposited on the particulate filter can be easily burned.

According to the third aspect of the present invention, there is provided the exhaust gas purifying apparatus for an internal combustion engine according to the first aspect, wherein the particulate filter is disposed in the exhaust port or immediately downstream of the exhaust port.

According to the third aspect of the present invention, the particulate filter is disposed in the exhaust port or immediately downstream of the exhaust port. Therefore, compared with the case where the particulate filter is arranged in the exhaust port or further downstream than immediately downstream of the exhaust port, the temperature of the particulate filter is reduced by the shock wave of the exhaust gas discharged from the internal combustion engine body. The temperature can be higher than the temperature, so that the unburned HC can be oxidized in the particulate filter even when the exhaust gas temperature is still low. In order to make the temperature of the particulate filter higher than the exhaust gas temperature, the engine exhaust passage from the cylinder of the internal combustion engine to the particulate filter must be independent for each cylinder, that is, the exhaust gas discharged from the cylinder It is necessary that the shock wave of the gas can reach the particulate filter.

According to the fourth aspect of the present invention, even when the exhaust gas temperature is equal to or higher than the low-temperature oxidation reaction temperature, when the exhaust gas temperature is just before rising to the high-temperature oxidation reaction temperature, the particulate filter can be used. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein supply of unburned HC to the exhaust gas is permitted.

In the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, when the exhaust gas temperature is equal to or higher than the low-temperature oxidation reaction temperature, that is, when the supply of unburned HC to the particulate filter is basically prohibited. Even when the temperature of the exhaust gas is just before rising to the high temperature oxidation reaction temperature,
Supplying unburned HC to the particulate filter is permitted. Therefore, compared to a case where the supply of unburned HC to the particulate filter is prohibited even immediately before the exhaust gas temperature rises to the high temperature oxidation reaction temperature, the temperature of the particulate filter is raised earlier and the particulate filter is removed. Can be played.

According to the fifth aspect of the present invention, even when the exhaust gas temperature is equal to or higher than the low-temperature oxidation reaction temperature, when the unburned HC in the particulate filter is likely to disappear, the particulate filter is rejected. An exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein supply of unburned HC is permitted.

In the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, when the unburned HC in the particulate filter is exhausted, the unburned HC in the particulate filter is removed.
When the exhaust gas temperature is equal to or higher than the low-temperature oxidation reaction temperature, that is, the unburned HC is supplied to the particulate filter in consideration of the fact that the particulate filter cannot be heated by the exhaust gas and the particulate filter cannot be heated unless the exhaust gas is heated. Even when supply is basically prohibited, unburned H in the particulate filter
When C is likely to disappear, supply of unburned HC to the particulate filter is permitted. Therefore, it is possible to prevent the unburned HC in the particulate filter from disappearing and the particulate filter from being unable to be heated by the unburned HC in the particulate filter.

According to the present invention, an exhaust turbocharger is disposed downstream of the particulate filter, a NOx catalyst is disposed downstream thereof, and an oxidation catalyst is disposed downstream thereof. An exhaust gas purification device for an internal combustion engine according to claim 1 is provided.

In the exhaust gas purifying apparatus for an internal combustion engine according to the sixth aspect, since the NOx catalyst is disposed downstream of the particulate filter, the exhaust gas that has passed through the particulate filter without being used for heating the particulate filter. The NOx catalyst can be reduced by the fuel HC.
Furthermore, since the oxidation catalyst is arranged downstream of the NOx catalyst, unburned HC that has passed through the NOx catalyst without being used for reduction of the NOx catalyst is purified by the oxidation catalyst. Therefore, it is possible to prevent the unburned HC from being discharged.

According to the present invention, when the exhaust gas temperature is lower than the low-temperature oxidation reaction temperature, an auxiliary fuel different from the main fuel is additionally injected from 40 ° to 50 ° after the compression top dead center. As a result, unburned HC is added to the particulate filter.
The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the exhaust gas is supplied.

In the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, when the exhaust gas temperature is lower than the low-temperature oxidation reaction temperature, the auxiliary fuel additionally injected from 40 ° to 50 ° after the compression top dead center is a It is possible to reach the particulate filter in an unburned HC state without burning after reaching the particulate filter and without changing to soot before reaching the particulate filter. In view of the above, when the exhaust gas temperature is lower than the low-temperature oxidation reaction temperature, an auxiliary fuel different from the main fuel is additionally injected from 40 ° to 50 ° after the compression top dead center. Therefore, by suppressing the unburned HC from changing to soot before reaching the particulate filter, the particulate filter is oxidized by oxidizing the unburned HC so as to oxidize the fine particles deposited on the particulate filter. Prepare to remove.

According to the eighth aspect of the present invention, when the amount of fine particles deposited on the particulate filter is equal to or more than a predetermined value, a sub fuel separate from the main fuel is provided from 30 ° to 40 ° after the compression top dead center. An exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the temperature of the exhaust gas is raised to a temperature equal to or higher than the low-temperature oxidation reaction temperature by additionally injecting fuel.

In the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, the auxiliary fuel additionally injected from 30 ° to 40 ° after the compression top dead center is post-burned before reaching the particulate filter and exhausted. In view of the fact that the gas can be heated, when the amount of fine particles deposited on the particulate filter is equal to or more than a predetermined value, 30 ° to 40 ° after the compression top dead center
An additional fuel different from the main fuel is additionally injected. for that reason,
The particulate filter is heated by the heated exhaust gas, and the particulates deposited on the particulate filter can be burned and removed.

According to the ninth aspect of the invention, when the NOx catalyst disposed downstream of the particulate filter is to be reduced, the NOx catalyst is reduced from 40 ° to 50 ° after the compression top dead center.
Alternatively, there is provided the exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein an auxiliary fuel different from the main fuel is additionally injected at 50 ° or more after the compression top dead center.

In the exhaust gas purifying apparatus for an internal combustion engine according to the ninth aspect, the secondary fuel additionally injected from 40 ° after compression top dead center or 50 ° after compression top dead center is unburned HC. In view of the fact that it is possible to reach the particulate filter in the state of the above, and it is possible to reach the NOx catalyst disposed downstream of the particulate filter when passing through the particulate filter, When the disposed NOx catalyst is to be reduced, an additional fuel other than the main fuel is additionally injected from 40 ° after compression top dead center to 50 ° or after 50 ° after compression top dead center. Therefore, the NOx catalyst can be reduced by the unburned HC that has reached the NOx catalyst.

[0023]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram of a first embodiment of an exhaust gas purifying apparatus for an internal combustion engine according to the present invention. In FIG. 1, 1 is an internal combustion engine main body, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is an electrically controlled fuel injection valve, 7 is an intake valve, 8 is an intake port, 9 is Exhaust valve, 10
Is an exhaust port. The intake port 8 is connected to a surge tank 12 via a corresponding exhaust manifold 11, and the surge tank 12 is connected to a compressor 15 of an exhaust turbocharger 14 via an intake duct 13. A throttle valve 17 driven by a step motor 16 is disposed in the intake duct 13. A mass flow detector 17a for detecting the mass flow of the intake air is disposed in the intake duct 13 upstream of the throttle valve 17. Further, an intercooler 18 for cooling intake air flowing through the intake duct 13 is provided around the intake duct 13.
Is arranged. In the present embodiment, the engine cooling water is guided into the intercooler 18, and the intake air is cooled by the engine cooling water.

On the other hand, the exhaust port 10 is connected to the exhaust manifold 1
The exhaust turbine 21 is connected to the exhaust turbine 21 of the exhaust turbocharger 14 through the exhaust pipe 9 and the exhaust pipe 20, and the outlet of the exhaust turbine 21 is connected to the NOx catalyst 60 and the oxidation catalyst 61.
A particulate filter 22 is arranged in the exhaust port 10. Instead of arranging the particulate filter 22 in the exhaust port 10, in other embodiments,
It is also possible to arrange the particulate filter 22 in the exhaust manifold 19 immediately downstream of the exhaust port 10. In any case, the particulate filter 22
Are arranged so that the temperature of the particulate filter 22 becomes higher than the exhaust gas temperature by the shock wave of the exhaust gas discharged from the internal combustion engine body 1. For details,
In order to make the temperature of the particulate filter 22 higher than the exhaust gas temperature, the exhaust port 10 and the particulate filter 22 are arranged such that the exhaust passage extending from the cylinder of the internal combustion engine to the particulate filter 22 is independent for each cylinder. Is arranged. In this embodiment, the center of the flow of the exhaust port 10 and the center of the inlet of the particulate filter 22 are arranged so as to face each other.

The exhaust manifold 19 and the surge tank 12 are connected to each other via an exhaust gas recirculation passage (EGR passage) 24, and an electrically controlled EGR control valve 25 driven by a step motor is disposed in the EGR passage 24. ing. Further, an EGR cooler 26 for cooling the EGR gas flowing in the EGR passage 24 is disposed around the EGR passage 24. In the present embodiment, the engine cooling water is guided into the EGR cooler 26, and the engine cooling water cools the EGR gas. Each fuel injection valve 6 is connected to a fuel reservoir, a so-called common rail 27, via a fuel supply pipe 6a. Fuel is supplied into the common rail 27 from a fuel pump 28 of an electrically controlled variable discharge amount, and the fuel supplied into the common rail 27 is supplied to the fuel injection valve 6 through each fuel supply pipe 6a. A fuel pressure sensor 2 for detecting the fuel pressure in the common rail 27 is provided on the common rail 27.
The discharge amount of the fuel pump 28 is controlled based on the output signal of the fuel pressure sensor 29 so that the fuel pressure in the common rail 27 becomes the target fuel pressure.

The electric control unit 30 is composed of a digital computer, and is connected to a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Microprocessor) 34, an input port 35, An output port 36 is provided. The output signal of the fuel pressure sensor 29 is input to the input port 35 via the corresponding AD converter 37. The output signal of the mass flow detector 17a is output from the corresponding AD converter 37.
Through the input port 35. A load sensor 41 that generates an output voltage proportional to the amount of depression of the accelerator pedal 40 is connected to the accelerator pedal 40, and the output voltage of the load sensor 41 is input to the input port 35 via the corresponding AD converter 37. The input port 35 is connected to a crank angle sensor 42 that generates an output pulse each time the crankshaft rotates, for example, by 30 °.
The output signal of the exhaust gas temperature sensor 43 for detecting the temperature of the exhaust gas in the exhaust port 10 is supplied to the corresponding AD converter 3
7 to the input port 35. On the other hand, the output port 36 is connected to the fuel injection valve 6, the throttle valve driving step motor 16, the EGR control valve driving step motor (not shown), and the fuel pump 28 via the corresponding drive circuit 38.

FIG. 2 is a detailed view of the particulate filter shown in FIG. Specifically, FIG. 2A is an end view of the particulate filter 22, and FIG. 2B is a longitudinal sectional view of the particulate filter 22. As shown in FIG. 2, the particulate filter 22 has a honeycomb structure and includes a plurality of exhaust passages 50 and 51 extending in parallel with each other. These exhaust passages are constituted by an exhaust gas inflow passage 50 whose downstream end is closed by a plug 52 and an exhaust gas outflow passage 51 whose upstream end is closed by a plug 53. The exhaust gas inflow passages 50 and the exhaust gas outflow passages 51 are alternately arranged via thin partition walls 54. That is, the exhaust gas inflow passages 50 and the exhaust gas outflow passages 51 are each surrounded by the four exhaust gas outflow passages 51, and each exhaust gas outflow passage 51 is surrounded by the four exhaust gas inflow passages 50. (See FIG. 4A). The particulate filter 22 is formed of, for example, a porous material such as cordierite. Therefore, the exhaust gas flowing into the exhaust gas inflow passage 50 passes through the surrounding partition wall 54 as shown by an arrow in FIG. And flows into the adjacent exhaust gas outflow passage 51.

FIG. 3 is a diagram showing a comparison between the pressure in the engine exhaust passage near the combustion chamber and the pressure in the engine exhaust passage far from the combustion chamber. In FIG. 3, the vertical axis represents pressure, and the horizontal axis represents time. The solid line in FIG. 3 indicates the pressure in the engine exhaust passage at a position near the combustion chamber 5, and the broken line in FIG. 3 indicates the pressure in the engine exhaust passage at a position distant from the combustion chamber 5. . Particulate filter 2 of the present embodiment
Numeral 2 is arranged at a position close to the combustion chamber 5 so that a shock wave of exhaust gas discharged from the internal combustion engine body 1 is transmitted to the particulate filter 22. Accordingly, the pressure in the engine exhaust passage at the position where the particulate filter 22 is disposed is as shown by a solid line in FIG.

FIG. 4 is a diagram showing a comparison between the particulate filter temperature and the exhaust gas temperature on the upstream side of the particulate filter. In FIG. 4, the vertical axis indicates temperature, and the horizontal axis indicates time. 4 indicates the temperature of the particulate filter 22, and the broken line in FIG. 4 indicates the exhaust gas temperature in the exhaust port 10 on the upstream side of the particulate filter 22.
According to an experiment conducted by the inventor, the shock wave of the exhaust gas discharged from the internal combustion engine body 1
It has been confirmed that when the particulate filter 22 is disposed near the combustion chamber 5 so as to be transmitted to the combustion chamber 2, the temperature of the particulate filter 22 becomes higher than the exhaust gas temperature. Therefore, in this embodiment, since the particulate filter 22 is disposed in the exhaust port 10 relatively close to the combustion chamber 5, the temperature of the particulate filter 22 is higher than the exhaust gas temperature.

In the present embodiment, when the temperature of the particulate filter 22 is increased, first, when the exhaust gas temperature is lower than the low-temperature oxidation reaction temperature (about 450 ° C.), the fuel injection amount from the fuel injection valve 6 is increased. The unburned HC is supplied to the particulate filter 22. Then
When the temperature of the exhaust gas rises to a temperature higher than the low-temperature oxidation reaction temperature (about 450 ° C.) and the temperature of the particulate filter 22 rises from about 600 ° C. to about 650 ° C., it is necessary to supply unburned HC to the particulate filter 22. It is prohibited in principle.

FIG. 5 is a diagram showing the relationship between the area A and the area B. In FIG. 5, the vertical axis Te indicates the engine torque, and the horizontal axis Ne indicates the engine speed. Also,
A region A indicates a region where supply of unburned HC to the particulate filter 22 is permitted. In the region A, the exhaust gas temperature is usually lower than the low-temperature oxidation reaction temperature (about 450 ° C.). On the other hand, a region B indicates a region where supply of unburned HC to the particulate filter 22 is basically prohibited. In the region B, the exhaust gas temperature is usually lower than the low-temperature oxidation reaction temperature (about 450 ° C.).
℃) or higher. Therefore, whether or not the exhaust gas temperature is equal to or higher than the low-temperature oxidation reaction temperature (about 450 ° C.) may be determined based on the output value of the temperature sensor 43. Instead, the engine operating condition is within the region A. Alternatively, it is also possible to make a determination based on whether the area is within the area B.

That is, according to this embodiment, unburned HC is supplied to the particulate filter 22 when the exhaust gas temperature is lower than the low-temperature oxidation reaction temperature, such as during low engine load operation. By oxidizing the unburned HC in the particulate filter 22 while suppressing the change of the unburned HC into soot before reaching the
Preparations can be made for burning and removing the fine particles deposited on the surface. That is, the unburned HC can be stored in the particulate filter 22. The unburned HC stored in the particulate filter 22 during engine low load operation is
Next, when the load increases, such as during the acceleration operation of the engine, it is oxidized at once. As a result, the temperature of the particulate filter 22 rises, and the
The fine particles deposited on the surface are oxidized and removed.

In the present embodiment, after the unburned HC is supplied to the particulate filter 22 when the exhaust gas temperature is lower than the low-temperature oxidation reaction temperature, the exhaust gas temperature is reduced to a temperature equal to or higher than the low-temperature oxidation reaction temperature. Since the temperature is raised, the particulate filter 22 is heated not only by the unburned HC that generates oxidative heat in the particulate filter 22, but also by the heated exhaust gas. As a result, the particulates deposited on the particulate filter 22 can be removed by burning. In the present embodiment, an external heater or the like is not used in order to raise the temperature of the exhaust gas to a temperature higher than the low-temperature oxidation reaction temperature (about 450 ° C.). Engine operating conditions that result in high exhaust gas temperatures apply.

When the exhaust gas temperature is raised to a temperature higher than the low-temperature oxidation reaction temperature, supply of unburned HC to the particulate filter 22 is basically prohibited. Unburned H in gas
It is suppressed that C changes to soot before it reaches the particulate filter 22. As a result, it is possible to prevent the regeneration of the particulate filter 22 from being hindered due to the supply of soot to the particulate filter 22. That is, it is possible to prevent the reduction of the fine particles deposited on the particulate filter 22 from being hindered.
When the temperature of the particulate filter 22 becomes higher than 600 ° C., even if the temperature of the exhaust gas decreases, the fire for burning the fine particles continues to exist, and when the temperature of the exhaust gas becomes higher than 450 ° C. again, instantaneously. The burning of fine particles becomes possible. Whether or not the fire has continued can be determined by detecting the differential pressure across the particulate filter 22.

In this embodiment, as shown in FIG. 2, when the exhaust gas passes through the partition wall 54 of the particulate filter 22, fine particles in the exhaust gas are collected inside the partition wall 54 of the particulate filter 22. Thus, the particulate filter 22 is configured. Therefore, since the amount of fine particles deposited on the particulate filter 22 has increased,
2 needs to be regenerated, the exhaust gas becomes difficult to pass through the partition wall 54 of the particulate filter 22 and the exhaust gas pressure rises. As a result, the temperature of the particulate filter 22 is not a static temperature but rather a total temperature. Is determined as When this state continues, the kinetic energy of the gas is converted into a temperature, and the exhaust gas temperature and the temperature of the particulate filter 22 increase. Therefore, compared with the case where the temperature of the particulate filter 22 is determined as the static temperature, the temperature of the particulate filter 22 can be increased, and the fine particles deposited on the particulate filter 22 can be easily removed without an external heater. Can be burned.

In this embodiment, since the particulate filter 22 is disposed in the exhaust port 10,
The temperature of the particulate filter 22 is made higher than the exhaust gas temperature by the shock wave of the exhaust gas discharged from the internal combustion engine main body 1 as compared with the case where the particulate filter 22 is arranged further downstream than inside the exhaust port 10. Therefore, the unburned HC can be oxidized in the particulate filter 22 even when the exhaust gas temperature is still low.

As described above, in this embodiment, the supply of unburned HC to the particulate filter 22 is basically prohibited when the exhaust gas temperature is equal to or higher than the low-temperature oxidation reaction temperature. Even in such a case, supply of unburned HC to the particulate filter 22 is allowed when the exhaust gas temperature is immediately before rising to the high-temperature oxidation reaction temperature (about 600 ° C.). Therefore, immediately before the exhaust gas temperature rises to the high-temperature oxidation reaction temperature (about 600 ° C.), the unburned H
As compared with the case where the supply of C is prohibited, the temperature of the particulate filter 22 can be raised earlier, and the particulate filter 22 can be regenerated.

In still another embodiment, when the unburned HC in the particulate filter 22 runs out,
The particulate filter 22 cannot be heated by the unburned HC in the particulate filter 22, and unless the exhaust gas is heated, the particulate filter 22 cannot be heated.
In view of the fact that the exhaust gas cannot be heated, when the exhaust gas temperature is equal to or higher than the low-temperature oxidation reaction temperature (about 450 ° C.), that is, when supplying unburned HC to the particulate filter 22 is basically prohibited. Also, when the unburned HC in the particulate filter 22 is likely to disappear, supply of the unburned HC to the particulate filter 22 is permitted. Therefore, it is possible to prevent the unburned HC in the particulate filter 22 from disappearing and the particulate filter 22 from being unable to be heated by the unburned HC in the particulate filter 22.

Returning to the description of the first embodiment, in this embodiment, NOx is provided downstream of the particulate filter 22.
Since the catalyst 60 is disposed, the unburned HC that has passed through the particulate filter 22 without being used for heating the particulate filter 22 causes NOx catalyst 60
Can be reduced. Further, since the oxidation catalyst 61 is disposed downstream of the NOx catalyst 60, the NOx catalyst 6
Unburned HC that has passed through the NOx catalyst 60 without being used to reduce 0 is purified by the oxidation catalyst 61. Therefore, it is possible to prevent the unburned HC from being discharged into the atmosphere.

FIG. 6 is a diagram showing the relationship between the additional injection timing of the auxiliary fuel other than the main fuel, the amount of unburned HC in the exhaust gas, the amount of fine particles, and the combustion state. As shown in FIG. 6, in the temperature utilization region in which the auxiliary fuel is additionally injected from about 30 ° to about 40 ° after the compression top dead center (ATDC), the additionally injected auxiliary fuel reaches the particulate filter 22. Unburned HC is not supplied to the particulate filter 22 as unburned HC. Therefore, in this temperature utilization region,
The temperature of the particulate filter 22 is increased by exhaust gas whose temperature has increased due to afterburning of the sub-fuel.

On the other hand, when the auxiliary fuel is located after compression top dead center (ATDC)
In the catalytic action utilization region in which the additional fuel is injected from about 40 ° to about 50 °, the additionally injected auxiliary fuel is not post-burned until it reaches the particulate filter 22, and is not converted into unburned HC. Cured filter 22
And burned in the particulate filter 22. Therefore, in this catalytic action utilization area,
The temperature of the particulate filter 22 is increased by the reaction heat of the unburned HC burning in the particulate filter 22. In the case where the temperature of the particulate filter 22 is raised in the temperature utilization region and in the case where the temperature of the particulate filter 22 is raised in the catalytic action utilization region, the temperature of the particulate filter 22 is raised earlier in the latter case. become. When the amount of fine particles deposited on the particulate filter 22 is large, in order to raise the exhaust gas temperature itself in advance, from about 30 ° to about 40 ° after compression top dead center (ATDC).
In addition to the additional injection of the auxiliary fuel at an angle of 0 °, the additional injection of the auxiliary fuel is preferably performed at an angle of about 40 ° to about 50 ° after the compression top dead center (ATDC). By performing the above-described additional injection of the auxiliary fuel, it is possible to suppress the loss of the fire for burning the fine particles in the particulate filter 22.

When the auxiliary fuel reaches about 50% after compression top dead center (ATDC)
°, in the insufficient reaction region where additional injection is performed after that, although the additionally injected auxiliary fuel is supplied to the particulate filter 22 as unburned HC, the combustion state deteriorates and the exhaust gas temperature decreases. The effect of raising the temperature of the particulate filter 22 is reduced.

FIG. 7 shows a comparison between the case where the temperature of the particulate filter is raised by applying the temperature utilization region shown in FIG. 6 and the case where the temperature of the particulate filter is raised by applying the catalytic utilization region. FIG. In FIG. 7, the vertical axis indicates a particulate filter, and the horizontal axis indicates time. As shown in FIG. 7, the case where the temperature of the particulate filter 22 is increased by applying the catalytic action utilization region is earlier than the case where the temperature of the particulate filter 22 is increased by applying the temperature utilization region. Then, the temperature of the particulate filter 22 is raised.

Accordingly, in this embodiment, when the temperature of the particulate filter 22 is to be raised and the exhaust gas temperature is lower than the low-temperature oxidation reaction temperature (about 450 ° C.), the temperature rises from about 40 ° after the compression top dead center. An auxiliary fuel other than the main fuel is additionally injected at about 50 °. As a result, the unburned HC is oxidized in the particulate filter 22 while suppressing the unburned HC from changing to soot before reaching the particulate filter 22, so that the unburned HC deposits on the particulate filter 22. Preparation for oxidizing and removing fine particles can be performed.

Further, as described above, about 30 days after the compression top dead center.
In view of the fact that the sub-fuel additionally injected from about 40 ° to about 40 ° can be post-burned before reaching the particulate filter and raise the temperature of the exhaust gas, in the present embodiment, the auxiliary fuel is deposited on the particulate filter 22. When the amount of the fine particles is more than a predetermined value, the angle is 30 ° to 40 ° after the compression top dead center.
At °, an auxiliary fuel different from the main fuel is additionally injected. As a result, the particulate filter 22 is heated by the heated exhaust gas, and the fine particles deposited on the particulate filter 22 can be burned and removed. Note that whether or not the amount of fine particles deposited on the particulate filter 22 is equal to or more than a predetermined value is determined by, for example,
It is estimated based on the differential pressure before and after the particulate filter 22 and the like.

As described above, about 40% after the compression top dead center.
The additional fuel injected from about 50 ° to about 50 ° or after about 50 ° after the compression top dead center can reach the particulate filter 22 in a state of unburned HC, and has passed through the particulate filter 22. In this case, in view of being able to reach the NOx catalyst 60 disposed downstream of the particulate filter 22, in the present embodiment,
N arranged downstream of the particulate filter 22
When the Ox catalyst 60 is to be reduced, about 40 after the compression top dead center.
An additional fuel other than the main fuel is additionally injected from about 50 ° to about 50 ° or about 50 ° after the compression top dead center. As a result, NO
The NOx catalyst 60 can be reduced by the unburned HC that has reached the x catalyst 60.

In another embodiment, when the exhaust gas temperature is low, such as when the engine is started, about 30 ° to 40 ° after the compression top dead center.
It is also possible to switch the additional fuel injection timing from about 40 ° to about 50 ° after the compression top dead center as the warm-up proceeds. In another embodiment, when the exhaust gas temperature is higher than the low-temperature oxidation reaction temperature and the soot can be naturally regenerated, the auxiliary fuel can be additionally injected at about 30 ° to 40 ° after the compression top dead center.

[0049]

According to the first aspect of the present invention, the unburned HC is oxidized in the particulate filter while the unburned HC is prevented from changing to soot before reaching the particulate filter. This makes it possible to prepare for burning and removing fine particles deposited on the particulate filter. Further, in addition to the particulate filter being heated by the unburned HC that generates and oxidizes heat in the particulate filter, the particulate filter is heated by the heated exhaust gas.
As a result, the particulates deposited on the particulate filter can be removed by burning. Further, the unburned HC in the heated exhaust gas is prevented from changing to soot before reaching the particulate filter,
As a result, it is possible to prevent the regeneration of the particulate filter from being hindered due to the supply of soot to the particulate filter. That is, it is possible to prevent the reduction of the fine particles deposited on the particulate filter from being hindered.

According to the second aspect of the present invention, when the particulate filter needs to be regenerated due to an increase in the amount of fine particles deposited on the particulate filter,
Exhaust gas becomes difficult to pass through the walls of the particulate filter and the exhaust gas pressure increases, so that the temperature of the particulate filter is determined as a whole temperature rather than a static temperature. Therefore, as compared with the case where the temperature of the particulate filter is determined as the static temperature, the temperature of the particulate filter can be increased, and the fine particles deposited on the particulate filter can be easily burned.

According to the third aspect of the present invention, compared with the case where the particulate filter is disposed in the exhaust port or further downstream than immediately downstream of the exhaust port,
The temperature of the particulate filter can be made higher than the exhaust gas temperature by the shock wave of the exhaust gas discharged from the internal combustion engine body. Therefore, even when the exhaust gas temperature is still low, the unburned HC in the particulate filter can be reduced. Can be oxidized.

According to the fourth aspect of the present invention, the supply of unburned HC to the particulate filter is prohibited even immediately before the exhaust gas temperature rises to the high-temperature oxidation reaction temperature. The temperature of the particulate filter can be raised to regenerate the particulate filter.

According to the fifth aspect of the present invention, it is possible to prevent the unburned HC in the particulate filter from being exhausted and the particulate filter from being unable to be heated by the unburned HC in the particulate filter. Can be.

According to the sixth aspect of the present invention, the NOx catalyst can be reduced by the unburned HC that has passed through the particulate filter without being used for heating the particulate filter. Further, unburned HC that has passed through the NOx catalyst without being used for reduction of the NOx catalyst is purified by the oxidation catalyst. Therefore, it is possible to prevent the unburned HC from being discharged.

According to the seventh aspect of the present invention, the unburned HC is oxidized in the particulate filter while the unburned HC is prevented from changing to soot before reaching the particulate filter. Preparations for oxidizing and removing fine particles deposited on the particulate filter can be made.

According to the eighth aspect of the present invention, the particulate filter is heated by the heated exhaust gas, so that the particulates deposited on the particulate filter can be burned and removed.

According to the ninth aspect of the present invention, the NOx catalyst can be reduced by the unburned HC reaching the NOx catalyst.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of an exhaust gas purification device for an internal combustion engine of the present invention.

FIG. 2 is a detailed view of the particulate filter shown in FIG.

FIG. 3 is a diagram showing a comparison between a pressure in an engine exhaust passage at a position near a combustion chamber and a pressure in an engine exhaust passage at a position distant from the combustion chamber.

FIG. 4 is a diagram showing a comparison between a particulate filter temperature and an exhaust gas temperature on the upstream side of the particulate filter.

FIG. 5 is a diagram showing a relationship between a region A and a region B;

FIG. 6 is a diagram showing a relationship between an additional injection timing of an auxiliary fuel different from a main fuel, an unburned HC amount in exhaust gas, an amount of fine particles, and a combustion state.

FIG. 7 shows a comparison between a case where the temperature of the particulate filter is raised by applying the temperature utilization region shown in FIG. 6 and a case where the temperature of the particulate filter is raised by applying the catalytic utilization region. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine main body 10 ... Exhaust port 14 ... Exhaust turbocharger 19 ... Exhaust manifold 22 ... Particulate filter 60 ... NOx catalyst 61 ... Oxidation catalyst

Continued on front page F-term (reference) 3G090 AA02 BA01 DA12 DA18 DA20 EA01 EA04 3G091 AA10 AA11 AA18 AB02 AB04 AB13 BA14 CA18 CB02 CB03 HA09 HA16 3G301 HA02 HA12 HA13 JA21 KA06 KA12 LA03 LB11 LC04 MA19 MA23 PD01ZP08Z03

Claims (9)

[Claims] 1. A particulate filter is disposed in an engine exhaust passage.
In the exhaust gas purifying apparatus for an internal combustion engine configured to supply C, when the exhaust gas temperature is lower than the low-temperature oxidation reaction temperature, unburned HC is supplied to the particulate filter, and then the exhaust gas temperature is increased to the low-temperature oxidation reaction temperature or higher. And the unburned H in the particulate filter.
An exhaust gas purifying apparatus for an internal combustion engine, wherein supply of C is basically prohibited. 2. The particulate filter according to claim 1, wherein the particulate filter is configured such that particles in the exhaust gas are trapped inside the particulate filter wall when the exhaust gas passes through the particulate filter wall. Exhaust purification device for internal combustion engine. 3. The exhaust filter according to claim 1, wherein the particulate filter is disposed in the exhaust port or immediately downstream of the exhaust port.
An exhaust gas purifying apparatus for an internal combustion engine according to claim 1. 4. Even when the exhaust gas temperature is equal to or higher than the low-temperature oxidation reaction temperature, when the exhaust gas temperature is immediately before rising to the high-temperature oxidation reaction temperature, supply of unburned HC to the particulate filter is stopped. 2. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the apparatus is allowed. 5. Even when the exhaust gas temperature is equal to or higher than the low-temperature oxidation reaction temperature, when unburned HC in the particulate filter is likely to disappear, supply of unburned HC to the particulate filter is permitted. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein 6. An exhaust turbocharger is disposed downstream of the particulate filter, and NOx is disposed downstream of the exhaust turbocharger.
The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein a catalyst is disposed, and an oxidation catalyst is disposed downstream of the catalyst. 7. When the exhaust gas temperature is lower than the low-temperature oxidation reaction temperature, unburned fuel is injected into the particulate filter by additionally injecting an auxiliary fuel different from the main fuel from 40 ° to 50 ° after the compression top dead center. Claim 1 wherein HC is supplied.
An exhaust gas purifying apparatus for an internal combustion engine according to claim 1. 8. When the amount of fine particles deposited on the particulate filter is equal to or more than a predetermined value, 30 minutes after the compression top dead center.
2. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the temperature of the exhaust gas is raised to a temperature equal to or higher than the low-temperature oxidation reaction temperature by additionally injecting a sub-fuel other than the main fuel from a temperature of 40 ° to 40 °. 9. When the NOx catalyst disposed on the downstream side of the particulate filter is to be reduced, the main fuel is changed from 40 ° to 50 ° after the compression top dead center or 50 ° or more after the compression top dead center. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein another auxiliary fuel is additionally injected.