JP3494114B2 - Exhaust gas purification method and exhaust gas purification device - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an exhaust gas purifying method and an exhaust gas purifying apparatus.

[0002]

2. Description of the Related Art Particulates containing soot as a main component are contained in the exhaust gas of an internal combustion engine, especially a diesel engine. Since particulates are harmful substances, it has been proposed to place a filter in the engine exhaust system to trap the particulates before they are released into the atmosphere. In such a filter, it is necessary to burn off the collected particulates in order to prevent an increase in exhaust resistance due to clogging.

In such a filter regeneration, the particulate matter is ignited and burned at about 600 ° C., but the exhaust gas temperature of the diesel engine is usually considerably lower than 600 ° C., and usually means for heating the filter itself or the like is required. Is. Japanese Patent Publication No. 7-106290 discloses that when a platinum group metal and an alkaline earth metal oxide are supported on a filter, the particulates on the filter are continuously discharged at about 400 ° C. which is the exhaust gas temperature of a diesel engine during normal operation. Burning out is disclosed.

[0004]

However, even if this filter is used, the exhaust gas temperature is not always about 400 ° C., and a large amount of particulates is released from the diesel engine depending on the operating condition. Occasionally, particulates that could not be burned off each time may gradually accumulate on the filter.

When particulates are deposited to some extent in this filter, the ability of burning out particulates is extremely lowered, and the filter can no longer be regenerated by itself. As described above, if the filter of this type is simply arranged in the engine exhaust system, clogging may occur relatively early. Therefore, it is an object of the present invention to take in oxygen in the presence of excess oxygen in the surroundings to retain the oxygen and to release the retained oxygen in the form of active oxygen when the concentration of oxygen in the surroundings is reduced. Accordingly, it is an object of the present invention to provide an exhaust gas purification device for an internal combustion engine, which can satisfactorily oxidize and remove the collected particulates and prevent clogging.

[0006]

In the first aspect of the present invention, in order to achieve the above object, a particulate filter disposed in an engine exhaust system for removing fine particles in exhaust gas, and a particulate filter supported by the particulate filter. When excess oxygen exists in the surroundings, it incorporates oxygen and retains it, and when the surrounding oxygen concentration decreases, it has an active oxygen releasing agent that releases oxygen in the form of active oxygen, and particulates in exhaust gas are particulated. Oxygen in the exhaust gas that flows into the particulate filter when the particulates deposited on the particulate filter should be removed by oxidation in the exhaust gas purification method that allows the filter to oxidize and remove without emitting a bright flame. Particulate while performing oxygen concentration fluctuation processing to increase or decrease the concentration
The particulates deposited on the filter are removed by oxidation .

In the second invention, in the first invention,
As a particulate filter for removing particulates in the exhaust gas discharged from the combustion chamber, the amount of particulates discharged from the combustion chamber per unit time does not cause a bright flame on the particulate filter per unit time. If the amount of fine particles in the exhaust gas that can be oxidized and removed is smaller than the amount of fine particles that can be oxidized and removed, if the fine particles in the exhaust gas flow into the particulate filter, they will be oxidized and removed without emitting a luminous flame, and the amount of discharged fine particles will be temporarily higher than the amount of fine particles that can be oxidized and removed. Even if the amount increases, if the amount of particles deposited on the particulate filter is less than a certain limit, the amount of discharged particles becomes less than the amount of particles that can be removed by oxidation. Oxidation using a particulate filter Even if the amount of fine particles that can be removed depends on the temperature of the particulate filter, the amount of fine particles that are discharged is usually smaller than the amount of fine particles that can be removed by oxidation, and even if the amount of fine particles that is discharged is temporarily higher than the amount of fine particles that can be removed by oxidation. After that, when the amount of discharged particulate becomes less than the amount of particulate that can be removed by oxidation, maintain the temperature of the particulate amount of particulate and the temperature of the particulate filter so that only a certain amount or less of particulate that can be oxidized and removed accumulates on the particulate filter. As a result, the fine particles in the exhaust gas can be oxidized and removed on the particulate filter without emitting a bright flame.

In the third invention, in the second invention,
The main injection for injecting fuel into the combustion chamber for driving the internal combustion engine is executed, and thereafter, the sub-injection for injecting fuel into the combustion chamber is executed separately, and the amount of fuel injected by the sub-injection is adjusted. By changing it, the oxygen concentration variation process is executed. In a fourth aspect based on the second aspect, the internal combustion engine has a plurality of combustion chambers, and the oxygen concentration in the exhaust gas discharged from a part of the combustion chambers is changed to the oxygen concentration in the exhaust gas discharged from the remaining combustion chambers. The oxygen concentration variation process is executed by making the concentration higher than the oxygen concentration.

In a fifth aspect based on the fourth aspect, main injection is performed to inject fuel into a combustion chamber for driving an internal combustion engine, and thereafter, fuel is injected into a part of the combustion chamber separately from the main injection. the oxygen concentration in the exhaust gas discharged from a portion of the combustion chamber by executing sub injection to less than the oxygen concentration in the exhaust gas discharged from the remaining combustion chamber.

According to the sixth aspect of the invention, in the third or fifth aspect of the invention, the secondary injection is executed in the latter half of the expansion stroke or in the exhaust stroke. In a seventh aspect based on the second aspect, when the amount of fine particles deposited on the particulate filter exceeds a predetermined amount of fine particles,
Alternatively, the oxygen concentration fluctuation process is executed at predetermined intervals or during idle operation.

In the eighth invention, in the second invention,
The oxygen concentration fluctuation processing is executed when it is predicted that the amount of fine particles that can be removed by oxidation will decrease. In the ninth invention, in the second invention, when the deceleration of the internal combustion engine is detected, the amount of fine particles that can be removed by oxidation is predicted to be small, and the amount of air taken into the combustion chamber is increased or decreased to increase the oxygen content. The density variation process is executed.

According to the tenth aspect of the invention, in the ninth aspect, the oxygen concentration variation process is executed and the reducing agent is mixed in the exhaust gas. 2 in the 11th invention
In the second invention, the precious metal catalyst is supported on the particulate filter. In the twelfth invention, in the first invention, the active oxygen releasing agent is made of an alkali metal, an alkaline earth metal, a rare earth or a transition metal.

According to a thirteenth invention, in the twelfth invention, the alkali metal and the alkaline earth metal are metals having a higher ionization tendency than calcium. In the fourteenth invention, in the eleventh invention, the oxygen concentration in the exhaust gas is reduced by temporarily making the air-fuel ratio of a part or the whole of the exhaust gas rich, and the fine particles adhering to the particulate filter are oxidized. I am trying to let you.

In the fifteenth aspect of the invention, in order to achieve the above object, a particulate filter disposed in an engine exhaust system for removing fine particles in exhaust gas, and excess oxygen around the particulate filter are supported. When it is present, it is equipped with an active oxygen release agent that takes in oxygen and retains it, and releases oxygen in the form of active oxygen when the surrounding oxygen concentration decreases, and the fine particles in the exhaust gas are emitted on a particulate filter on a bright flame. In an exhaust gas purification device that is capable of being oxidized and removed without generating, increases or decreases the oxygen concentration in the exhaust gas flowing into the particulate filter when the particulates accumulated on the particulate filter should be removed by oxidation. On the particulate filter while executing the oxygen concentration fluctuation process.
A means for oxidizing and removing the fine particles deposited on the substrate is provided.

In the sixteenth invention, in the fifteenth invention, a particulate filter for removing fine particles in the exhaust gas discharged from the combustion chamber is arranged in the engine exhaust passage, and this particulate filter is used as a unit time. When the amount of particulates exhausted from the combustion chamber is less than the amount of oxidatively removable particulates that can be oxidized and removed on the particulate filter per unit time without emitting a luminous flame, the particulates in the exhaust gas are collected in the particulate filter. When it flows in, it is oxidatively removed without emitting a luminous flame, and even if the amount of discharged fine particles temporarily exceeds the amount of fine particles that can be removed by oxidation, if the amount of fine particles deposited on the particulate filter is below a certain limit, the amount of discharged fine particles is reduced. When the amount of fine particles that can be removed by oxidation is less than the amount of putty Uses a particulate filter that can oxidize and remove the particulates on the particulate filter without emitting a bright flame.The amount of particulates that can be removed by oxidation depends on the temperature of the particulate filter, and the amount of discharged particulates is greater than the amount of particulates that can be removed by oxidation. Normally, even if the amount of discharged fine particles temporarily exceeds the amount of fine particles that can be removed by oxidation, after that, when the amount of discharged fine particles becomes less than the amount of fine particles that can be removed by oxidation, the amount of particles that are less than a certain limit that can be oxidized and removed Equipped with a control means for maintaining the amount of particulates discharged and the temperature of the particulate filter so that only particulates are deposited on the particulate filter, so that the particulates in the exhaust gas are not emitted a bright flame on the particulate filter. I try to remove it by oxidation.

In a seventeenth aspect based on the fifteenth aspect, the particulate filter has a plurality of exhaust flow passages extending in parallel with each other, and one of the adjacent exhaust flow passages has its upstream end closed by a plug. The downstream end of the other adjacent exhaust flow passage is closed by a plug, and the catalyst is carried on the wall surface of the exhaust flow passage and the wall surface of the plug.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to the illustrated embodiments. FIG. 1 shows a case where the present invention is applied to a compression ignition type internal combustion engine. The present invention can also be applied to a spark ignition type internal combustion engine. The internal combustion engine shown in FIG. 1 has a plurality of cylinders, that is, a combustion chamber, 1 is an engine 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 an exhaust valve, and 10 is an exhaust port. The intake port 8 is connected to the surge tank 1 via the corresponding intake branch pipe 11.
2, the surge tank 12 is connected to the compressor 15 of the exhaust turbocharger 14 via the intake duct 13. A mass flow meter 13a for detecting the mass flow rate of the air taken in is attached to the intake pipe 13b on the upstream side of the compressor 15. A throttle valve 17 driven by a step motor 16 is disposed in the intake duct 13, and the intake duct 13 is further provided around the intake duct 13.
A cooling device 18 is arranged for cooling the intake air flowing therein. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 18, and the intake air is cooled by this engine cooling water. On the other hand, the exhaust port 10 is connected to the exhaust turbocharger 1 via the exhaust manifold 19 and the exhaust pipe 20.
4 is connected to the exhaust turbine 21, and the outlet of the exhaust turbine 21 is connected to a casing 23 containing a particulate filter 22.

The exhaust manifold 19 and the surge tank 12 are connected to each other via an exhaust gas recirculation (hereinafter referred to as EGR) passage 24, and an electric control type EGR control valve 25 is arranged in the EGR passage 24. A cooling device 26 for cooling the EGR gas flowing in the EGR passage 24 is arranged around the EGR passage 24. In the embodiment shown in FIG. 1, engine cooling water is introduced into the cooling device 26, and the engine cooling water cools the EGR gas. On the other hand, 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 via each fuel supply pipe 6a. A fuel pressure sensor 29 for detecting the fuel pressure in the common rail 27 is attached to the common rail 27, and the fuel pump 28 is arranged so that the fuel pressure in the common rail 27 becomes the target fuel pressure based on the output signal of the fuel pressure sensor 29. Is controlled.

The electronic control unit 30 is composed of a digital computer, and has a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Microprocessor) 34, an input port 35, and an input port 35, which are connected to each other by a bidirectional bus 31. 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. Further, a temperature sensor 39 for detecting the temperature of the particulate filter 22 is attached to the particulate filter 22, and the output signal of this temperature sensor 39 corresponds to the AD.
It is input to the input port 35 via the converter 37. The output signal of the mass flowmeter 13a corresponds to the corresponding AD converter 37.
Is input to the input port 35 via. A load sensor 41 that generates an output voltage proportional to the depression amount L 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. . Further, the input port 35 is connected to a crank angle sensor 42 that generates an output pulse each time the crankshaft rotates, for example, 30 °. on the other hand,
The output port 36 is connected via a corresponding drive circuit 38 to the fuel injection valve 6, the throttle valve driving step motor 16, and the EG.
It is connected to the R control valve 25 and the fuel pump 28.

FIG. 2 shows the structure of the particulate filter 22. 2A is a front view of the particulate filter 22, and FIG. 2B is a side sectional view of the particulate filter 22. Figure 2
As shown in (A) and (B), the particulate filter 22 has a honeycomb structure and is provided with a plurality of exhaust flow passages 50, 51 extending in parallel with each other. These exhaust flow passages are composed of 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 hatched portion in FIG. 2A indicates the plug 53. Therefore, the exhaust gas inflow passages 50 and the exhaust gas outflow passages 51 are alternately arranged via the thin partition walls 54. In other words, in the exhaust gas inflow passage 50 and the exhaust gas outflow passage 51, each exhaust gas inflow passage 50 is surrounded by four exhaust gas outflow passages 51, and each exhaust gas outflow passage 51 is surrounded by four exhaust gas inflow passages 50. Is arranged as.

The particulate filter 22 is made of a porous material such as cordierite, so that the exhaust gas flowing into the exhaust gas inflow passage 50 is surrounded by the surrounding gas as indicated by the arrow in FIG. 2 (B). Partition wall 54
The gas passes through the inside and flows out into the adjacent exhaust gas outflow passage 51. In the embodiment of the present invention, the peripheral wall surfaces of each exhaust gas inflow passage 50 and each exhaust gas outflow passage 51, that is, each partition wall 54.
A layer of a carrier made of, for example, alumina is formed over the entire surface on both sides of the plug, the outer end surface of the plug 53, and the inner end surfaces of the plugs 52, 53. Is present, the active oxygen release agent is incorporated to retain oxygen by retaining oxygen and retain the oxygen, and release the retained oxygen in the form of active oxygen when the ambient oxygen concentration decreases.

In the embodiment of the present invention, platinum Pt is used as the noble metal catalyst, and as the active oxygen releasing agent, potassium K, sodium Na, lithium Li, cesium Cs, alkali metals such as rubidium Rb, barium Ba, calcium Ca. , At least one selected from alkaline earth metals such as strontium Sr, lanthanum La, rare earths such as yttrium Y, and transition metals.

Calcium C is used as the active oxygen releasing agent.
It is preferable to use an alkali metal or alkaline earth metal having a higher ionization tendency than a, that is, potassium K, lithium Li, cesium Cs, rubidium Rb, barium Ba, or strontium Sr. Next, the action of removing particulates in the exhaust gas by the particulate filter 22 will be described by taking as an example the case where platinum Pt and potassium K are supported on the carrier, but other precious metals, alkali metals,
The same fine particle removing action is achieved by using an alkaline earth metal, a rare earth metal, or a transition metal.

In a compression ignition type internal combustion engine as shown in FIG. 1, combustion is performed under excess air, and therefore the exhaust gas contains a large amount of excess air. That is, when the ratio of the air supplied to the intake passage and the combustion chamber 5 to the fuel is called the air-fuel ratio of the exhaust gas, the air-fuel ratio of the exhaust gas becomes lean in the compression ignition internal combustion engine as shown in FIG. There is. Further, since NO is generated in the combustion chamber 5, NO is contained in the exhaust gas.
It is included. Further, the fuel contains sulfur S, and this sulfur S reacts with oxygen in the combustion chamber 5 to become SO ₂ . Therefore, the exhaust gas contains SO ₂ . Therefore, the exhaust gas containing excess oxygen, NO and SO ₂ flows into the exhaust gas inflow passage 50 of the particulate filter 22.

FIGS. 3A and 3B schematically show enlarged views of the surface of the carrier layer formed on the inner peripheral surface of the exhaust gas inflow passage 50. In FIGS. 3A and 3B, 60 indicates particles of platinum Pt, and 61 indicates an active oxygen release agent containing potassium K. As described above, since the exhaust gas contains a large amount of excess oxygen, when the exhaust gas flows into the exhaust gas inflow passage 50 of the particulate filter 22, the oxygen O ₂ as shown in FIG. platinum Pt in or O ^2- in the form ^- but O ₂
Adhere to the surface of. On the other hand, NO in the exhaust gas is platinum Pt
Reacts with O ₂ ⁻ or O ²⁻ on the surface of NO ₂ to become NO ₂ (2NO + O ₂ → 2NO ₂ ). NO ₂ produced next
Of the active oxygen releasing agent 61 while being oxidized on platinum Pt
As shown in FIG. 3 (A), it is absorbed into the active oxygen-releasing agent 61 in the form of nitrate ion NO ₃ ⁻ and bound to potassium K to generate potassium nitrate KNO ₃ .

On the other hand, as described above, the exhaust gas contains SO.
₂Also included, this SO₂The same mechanism as NO
The oxygen is absorbed in the active oxygen release agent 61. Ie
As described above, oxygen O₂Is O₂ ^-Or O^2-In the form of platinum
SO attached to the surface of Pt in the exhaust gas₂Is platinum
O on the surface of Pt₂ ^-Or O^2-Reacts with SO₃Tona
It SO generated next₃Part of Pt on Pt
Is absorbed into the active oxygen release agent 61 while being oxidized to
Sulfate ion SO while binding with Um K_Four ^2-Active acid in the form of
Diffuses into the element-releasing agent 61, potassium sulfate K₂SO_FourLive
To achieve. In this way, the active oxygen release catalyst 61 contains glass.
Potassium acid KNO₃And potassium sulfate K ₂SO_FourRaw
Is made.

On the other hand, fine particles mainly composed of carbon C are produced in the combustion chamber 5, and therefore, the exhaust gas contains these fine particles. These fine particles contained in the exhaust gas, when the exhaust gas is flowing in the exhaust gas inflow passage 50 of the particulate filter 22,
Alternatively, from the exhaust gas inflow passage 50 to the exhaust gas outflow passage 51
3B, it contacts and adheres to the surface of the carrier layer, for example, the surface of the active oxygen release agent 61, as shown by 62 in FIG. 3B.

Thus, the fine particles 62 are the active oxygen releasing agent 6
When it adheres to the surface of No. 1, the fine particles 62 and the active oxygen releasing agent 6
The oxygen concentration decreases at the contact surface with 1. When the oxygen concentration decreases, a difference in concentration occurs between the active oxygen release agent 61 and the active oxygen release agent 61 having a high oxygen concentration. Therefore, the oxygen in the active oxygen release agent 61 is directed toward the contact surface between the fine particles 62 and the active oxygen release agent 61. Try to move. As a result, potassium nitrate KNO ₃ formed in the active oxygen release agent 61 is converted into potassium K and oxygen O.
Is decomposed into NO and NO, the oxygen O moves toward the contact surface between the fine particles 62 and the active oxygen release agent 61, and NO changes into the active oxygen release agent 6
It is released from the outside. The NO released to the outside is oxidized on the platinum Pt on the downstream side and is again absorbed in the active oxygen release agent 61.

On the other hand, at this time, a form is formed in the active oxygen releasing agent 61.
Potassium sulfate K₂SO _FourAlso potassium K and acid
Element O and SO₂Is decomposed into and oxygen O is activated with the fine particles 62.
Toward the contact surface with the oxygen releasing agent 61,₂Is active oxygen
It is released from the release agent 61 to the outside. S released outside
O₂Is oxidized on the platinum Pt on the downstream side and becomes active again.
It is absorbed in the oxygen releasing agent 61. However, potassium sulfate K
₂SO_FourIs stabilized, so potassium nitrate KNO₃To
It is harder to release active oxygen compared to.

On the other hand, oxygen O toward the contact surface between the fine particles 62 and the active oxygen release agent 61 is oxygen decomposed from a compound such as potassium nitrate KNO ₃ or potassium sulfate K ₂ SO ₄ . Oxygen O decomposed from the compound has high energy and has extremely high activity. Therefore, oxygen toward the contact surface between the fine particles 62 and the active oxygen release agent 61 is active oxygen O. These active oxygen O are fine particles 6
Upon contact with 2, the fine particles 62 are immediately oxidized without emitting a luminous flame, and the fine particles 62 disappear completely. Therefore, the fine particles 62 do not deposit on the particulate filter 22.

As in the prior art, the particulate filter 2
When the particulates accumulated in a layered manner on 2 are burned, the particulate filter 22 becomes red hot and burns with a flame. The combustion with such a flame does not last unless it is at a high temperature, and therefore the temperature of the particulate filter 22 must be maintained at a high temperature in order to continue the combustion with such a flame.

On the other hand, in the present invention, the fine particles 62 are oxidized without emitting a luminous flame as described above, and at this time, the surface of the particulate filter 22 does not become red hot. In other words, in other words, in the present invention, the fine particles 62 are oxidized and removed at a temperature much lower than the conventional temperature. Therefore, the particulate removing action by the oxidation of the particulate 62 which does not emit the bright flame according to the present invention is completely different from the particulate removing action by the conventional combustion accompanied by a flame.

By the way, platinum Pt and active oxygen releasing agent 6
1 becomes more active as the temperature of the particulate filter 22 becomes higher, so the amount of active oxygen O that can be released by the active oxygen release agent 61 per unit time increases as the temperature of the particulate filter 22 becomes higher. Therefore, the amount of oxidatively removable fine particles that can be oxidatively removed on the particulate filter 22 without emitting a luminous flame per unit time increases as the temperature of the particulate filter 22 increases.

The solid line in FIG. 5 shows the amount G of oxidatively removable fine particles which can be oxidatively removed without emitting a luminous flame per unit time. In FIG. 5, the horizontal axis represents the temperature TF of the particulate filter 22. When the amount of fine particles discharged from the combustion chamber 5 per unit time is referred to as the discharged fine particle amount M, when this discharged fine particle amount M is smaller than the oxidatively removable fine particles G, that is, in the region I of FIG. All the particulates that are removed are particulate filters 22.
As soon as it comes into contact with, the oxidant is removed on the particulate filter 22 in a short time without emitting a bright flame.

On the other hand, when the amount M of discharged particles is larger than the amount G of particles that can be removed by oxidation, that is, in the region II of FIG. 5, the amount of active oxygen is insufficient to oxidize all the particles. FIGS. 4A to 4C show the state of oxidation of the fine particles in such a case. That is, when the amount of active oxygen is insufficient to oxidize all the fine particles, when the fine particles 62 adhere to the active oxygen release agent 61 as shown in FIG. 4A, only a part of the fine particles 62 is oxidized. As a result, the fine particles that have not been sufficiently oxidized remain on the carrier layer. Next, when the state in which the amount of active oxygen is insufficient continues, the fine particles that are not oxidized one after another remain on the carrier layer, and as a result, the surface of the carrier layer is changed as shown in FIG. 4 (B). The residual fine particle portion 63 is covered.

This residual fine particle portion 6 covering the surface of the carrier layer
3 gradually deteriorates into a carbon material that is difficult to be oxidized, and thus the residual fine particle portion 63 is likely to remain as it is. Further, when the surface of the carrier layer is covered with the residual fine particle portion 63, the oxidizing action of NO and SO ₂ by platinum Pt and the releasing action of active oxygen by the active oxygen releasing agent 61 are suppressed. As a result, as shown in FIG. 4C, another fine particle 64 is deposited on the residual fine particle portion 63 one after another. That is, the fine particles are deposited in a laminated form. When the fine particles are stacked in this manner, since the fine particles are separated from the platinum Pt and the active oxygen release agent 61, even fine particles that are easily oxidized are no longer oxidized by the active oxygen O. Therefore, further fine particles are deposited on the fine particles 64 one after another. That is, the fine particles are deposited in a laminated form. When the particles are stacked in this manner, the particles 64 are no longer oxidized by the active oxygen O, so that further particles are successively deposited on the particles 64. That is, if the state in which the amount M of discharged particulates is larger than the amount G of particulates that can be removed by oxidation continues, the particulates are accumulated in a layered manner on the particulate filter 22, thus raising the exhaust gas temperature to a high temperature or the particulate filter. Unless the temperature of 22 is raised to a high temperature, the deposited particles cannot be ignited and burned.

As described above, in the region I of FIG. 5, the fine particles are oxidized on the particulate filter 22 in a short time without emitting a bright flame, and in the region II of FIG. 5, the fine particles are laminated on the particulate filter 22. Deposits in the shape of. Therefore, in order to prevent the particulates from accumulating on the particulate filter 22 in a stacked state, the discharged particulate amount M must be always smaller than the oxidatively removable particulate amount G.

As can be seen from FIG. 5, in the particulate filter 22 used in the embodiment of the present invention, it is possible to oxidize the fine particles even if the temperature TF of the particulate filter 22 is considerably low, and therefore, in FIG. In the illustrated compression ignition type internal combustion engine, the amount M of discharged particulate and the temperature TF of the particulate filter 22 can be maintained so that the amount M of discharged particulate is always smaller than the amount G of particulate that can be removed by oxidation. Therefore, in the first embodiment according to the present invention, the amount M of discharged particulate and the temperature TF of the particulate filter 22 are set to the amount M of discharged particulate.
Is always kept smaller than the amount G of fine particles that can be removed by oxidation. If the amount M of discharged particulates is always smaller than the amount G of particulates that can be removed by oxidation, almost no particulates are deposited on the particulate filter 22, and thus the back pressure hardly rises. Therefore, the engine output does not decrease.

On the other hand, as described above, once the particles are deposited in a layered manner on the particulate filter 22, even if the amount M of discharged particles becomes smaller than the amount G of particles that can be removed by oxidation, the particles are oxidized by the active oxygen O. It is difficult to get it done. However, when the fine particles that have not been oxidized start to remain, that is, when the fine particles are accumulated below a certain limit, if the exhaust fine particle amount M becomes less than the oxidatively removable fine particle amount G, the residual fine particle portions are treated with active oxygen. O is removed by oxidation without emitting a bright flame. Therefore, in the second embodiment, the amount M of discharged fine particles is usually smaller than the amount G of fine particles that can be oxidized and removed, and even if the amount M of discharged fine particles temporarily becomes larger than the amount G of fine particles that can be oxidized and removed, FIG. In order to prevent the surface of the carrier layer from being covered with the residual fine particle portion 63, that is, when the amount M of discharged fine particles becomes smaller than the amount G of fine particles that can be removed by oxidation, the amount of fine particles is less than a certain limit that can be oxidized and removed. However, the amount M of discharged particulate and the temperature TF of the particulate filter 22 are maintained so that the particulate filter 22 is not stacked on the particulate filter 22.

Particularly, immediately after the engine is started, the temperature TF of the particulate filter 22 is low, and therefore, the amount M of discharged particulate becomes larger than the amount G of particulate that can be removed by oxidation at this time. Therefore, considering the actual driving, it is considered that the second embodiment is more practical. On the other hand, even if the amount M of discharged particulate and the temperature TF of the particulate filter 22 are controlled so that the first embodiment or the second embodiment can be carried out, particulates are deposited in a laminated form on the particulate filter 22. There is a case. In such a case, it is necessary to oxidize and remove the particulates (hereinafter referred to as deposited particulates) accumulated in a laminated form on the particulate filter 22. Hereinafter, the method for removing deposited particulate oxidation according to the present invention will be described.

The case where the particulates are deposited on the particulate filter 22 in a laminated state is the case where the amount M of discharged particulates exceeds the amount G of particulates that can be removed by oxidation. That is, this is a case where the amount of active oxygen released from the active oxygen release agent 61 per unit time (hereinafter, released active oxygen amount) is small enough to completely oxidize and remove the fine particles. As described above, the active oxygen release agent 61 absorbs oxygen when the ambient oxygen concentration increases, and releases the absorbed oxygen in the form of active oxygen when the ambient oxygen concentration decreases. Therefore, in the present invention, when the deposited particulates are to be removed by oxidation, the oxygen concentration in the exhaust gas flowing into the particulate filter 22 is positively increased or decreased in a predetermined cycle.
According to this, the active oxygen releasing agent 61 releases active oxygen at once when the ambient oxygen concentration becomes low, so that it is possible to oxidize and remove the deposited fine particles, and when the ambient oxygen concentration becomes high, oxygen is released at once. The active oxygen can be released all at once when the surrounding oxygen concentration decreases next. Thus, the deposited particles can be removed by oxidation.

Next, a specific method of executing the above-mentioned accumulated particulate oxidation removal processing will be described. There are mainly the following three methods as concrete execution methods of this embodiment. In the first method, after performing main injection for injecting fuel into each combustion chamber for driving the internal combustion engine, sub-injection for injecting fuel into each combustion chamber in the latter half of the expansion stroke or the exhaust stroke is performed separately from this main injection. When performing the sub-injection, the amount of fuel injected into the combustion chamber (hereinafter referred to as the sub-injection fuel amount) is changed at a predetermined cycle for each sub-injection.
Thus, the oxygen concentration in the exhaust gas flowing into the particulate filter 22 is positively increased or decreased. The sub-injection fuel amount here is determined according to the temperature of the active oxygen releasing agent 61, that is, the operating characteristics of the active oxygen releasing agent 61 and the operating state of the internal combustion engine, but the air-fuel ratio of the exhaust gas with a large oxygen concentration is It is preferably in the range of 17 to 20, and the air-fuel ratio of the exhaust gas having a low oxygen concentration is in the range of 11 to 14. Of course, it is also possible to execute the sub-injection in which the auxiliary injection fuel amount is not zero in the latter half of the expansion stroke or the exhaust stroke, and to execute the sub-injection in which the auxiliary injection fuel amount is zero in the other latter half of the expansion stroke or the exhaust stroke. Good. Also, if enriched in this way, the poisoning on the metal surface will be restored, and the subsequent oxidation activity will be improved.
It will accelerate the oxidation of the particles.

An example of the operation control routine of the internal combustion engine which adopts the first method described above is shown in FIG. Referring to FIG. 6, first, at step 10, it is judged if the deposited particulate oxidation removal processing should be executed. When it is determined in step 10 that it is not necessary to execute the accumulated particulate oxidation removal processing, the opening degree of the throttle valve 17 is controlled in step 20 so that the discharged particulate amount M becomes smaller than the oxidation removable particulate amount G, and the step is performed. Two
1, the opening degree of the EGR control valve 25 is controlled, only the main injection is executed in step 22, and the flag F is set in step 23. The flag F is reset when the sub-injection is performed so that the oxygen concentration in the exhaust gas is relatively low (step 15), and the sub-injection is performed so that the oxygen concentration in the exhaust gas is relatively high. At this time (step 19) and when only the main injection is performed (step 23).

On the other hand, when the accumulated particulate oxidation removal processing should be executed in step 10, it is determined in step 11 whether the flag F is set (F = 1). When F = 1 in step 11, the opening degree of the throttle valve 17 is controlled in step 12 so that the amount M of discharged particulate becomes smaller than the amount G of particulate that can be removed by oxidation, and in step 13, the EGR control valve 2
The opening degree of 5 is controlled, the main injection and the sub-injection are executed in step 14 so that the oxygen concentration in the exhaust gas becomes relatively small, and the flag F is reset in step 15.

On the other hand, when F = 0 in step 11, the opening degree of the throttle valve 17 is controlled in step 16 so that the discharged particulate amount M becomes smaller than the oxidatively removable particulate amount G, and in step 17, the EGR control valve is controlled. The opening degree of 25 is controlled, the main injection and the sub-injection are executed in step 18 so that the oxygen concentration in the exhaust gas becomes relatively small, and the flag F is set in step 19.

In the second method, a main injection for injecting fuel into the combustion chamber for driving the internal combustion engine is executed in a part of the combustion chambers, and thereafter, separately from this main injection, in the latter half of the expansion stroke or the exhaust stroke. A sub-injection is performed to inject fuel into the combustion chamber. That is, the main injection and the sub-injection are executed in a predetermined cycle in some of the combustion chambers, and only the main injection is executed in the remaining combustion chambers. Thus, exhaust gas with a low oxygen concentration flows out from some of the combustion chambers, and exhaust gas with a high oxygen concentration flows out from the remaining combustion chambers. In the internal combustion engine, the exhaust stroke is executed in each combustion chamber in a predetermined order. Therefore, the oxygen concentration in the exhaust gas flowing into the particulate filter 22 positively increases or decreases in a predetermined cycle. The amount of sub-injection fuel here is also determined according to the temperature of the active oxygen release agent 61, that is, the operating characteristics of the active oxygen release agent 61 and the operating state of the internal combustion engine.

An example of the operation control routine of the internal combustion engine which employs the second method described above is shown in FIG. Note that this routine is applied to control in some combustion chambers.
Referring to FIG. 7, first, at step 30, it is judged if the accumulated particulate oxidation removal processing should be executed.
When it is determined in step 30 that it is not necessary to execute the accumulated particulate oxidation process, the opening degree of the throttle valve 17 is controlled in step 34 so that the discharged particulate amount M becomes smaller than the oxidatively removable particulate amount G in step 34. The opening degree of the EGR control valve 25 is controlled in step 35, and only the main injection is executed in step 36.

On the other hand, when it is judged in step 30 that the accumulated particulate oxidation removing process should be executed, the opening degree of the throttle valve 17 is adjusted in step 31 so that the discharged particulate amount M becomes smaller than the oxidation removable particulate amount G. Is controlled, the opening degree of the EGR control valve 25 is controlled in step 32, and the main injection and the sub-injection are executed in some of the combustion chambers in step 33. Of course, before and after this, only the main injection is executed in the other remaining combustion chambers.

In the third method, the injection amount is controlled so that the average air-fuel ratio in the combustion chamber 5 becomes lean in most operating regions, and with a predetermined cycle when the engine load is relatively low. The opening degree of the throttle valve 17 and the opening degree of the EGR control valve 25 are controlled so that the EGR rate (EGR gas amount / (intake air amount + EGR gas amount)) becomes 65% or more, and at this time, the average in the combustion chamber 5 The injection amount is controlled so that the air-fuel ratio becomes rich.

An example of the operation control routine of the internal combustion engine which employs the third method described above is shown in FIG. Referring to FIG. 8, first, at step 40, it is judged if the deposited particulate oxidation removal processing should be executed. When it is determined that it is not necessary to execute the accumulated particulate oxidation removal processing in step 40, the opening degree of the throttle valve 17 is controlled in step 44 so that the discharged particulate amount M becomes smaller than the oxidation removable particulate amount G, and the step is performed. Four
In step 5, the opening degree of the EGR control valve 25 is controlled, and in step 46, fuel injection is executed.

On the other hand, when it is determined in step 40 that the particulate removal and oxidation treatment should be carried out, step 4 is performed so that the EGR rate becomes 65% or more.
In step 1, the opening degree of the throttle valve 17 is controlled, in step 42, the opening degree of the EGR control valve 25 is controlled, and step 4 is performed so that the average air-fuel ratio in the combustion chamber 5 becomes rich.
At 3, fuel injection is performed.

The timing for executing the sub-injection in the above three methods (hereinafter referred to as the sub-injection timing) is determined in consideration of the smoke generation amount in the combustion chamber and the thermal decomposition characteristic of the fuel injected by the sub-injection. It That is, the earlier the sub-injection timing, the greater the amount of smoke generated. Therefore, from the viewpoint of suppressing the amount of smoke generation to be small, the later the sub-injection timing, the better. On the other hand, the slower the sub-injection timing, the more difficult the fuel is to thermally decompose. The pyrolyzed fuel is more easily purified by the particulate filter 22 than the non-pyrolyzed fuel. Therefore, from the viewpoint of purifying the fuel at the particulate filter 22 at a high purification rate, the earlier the sub-injection timing, the better. In consideration of such a situation, in the present embodiment, the sub-injection is executed at such a timing that smoke is not generated.

Further, the higher the temperature of the particulate filter 22, the easier the fuel is purified by the particulate filter 22. That is, the particulate filter 2
If the temperature of 2 is high, fuel that has not been thermally decomposed can be purified relatively easily. Therefore, in determining the sub injection timing, the particulate filter 22
The temperature may be taken into consideration.

In addition to the above-mentioned three methods, for example, a fuel injection device for injecting fuel as a reducing agent on the upstream side of the particulate filter 22 is arranged separately from the fuel injection valve 6, and from this fuel injection device. There is also a method of injecting fuel and changing the amount of fuel injected from this fuel injection device at a predetermined cycle.

Next, the conditions for executing the above-mentioned accumulated particulate oxidation removal processing will be described. In this embodiment, when the amount of deposited particulates exceeds a predetermined allowable limit value, the above-mentioned deposited particulate oxidation removal processing is executed. Whether or not the amount of accumulated particulates exceeds the allowable limit value is determined from the pressure loss due to the particulate filter 22 and the operation history of the internal combustion engine. That is, if the pressure loss due to the particulate filter 22 is large, it is determined that the amount of accumulated fine particles exceeds the allowable limit value. Here, the pressure loss is the difference between the pressure of the exhaust gas on the upstream side of the particulate filter 22 and the pressure of the exhaust gas on the downstream side. Or, during a certain period, the particulate filter 2
The total amount of fine particles flowing into No. 2 is estimated based on the operation history of the internal combustion engine, and if the total amount of fine particles is larger than a predetermined amount, it is determined that the accumulated amount of fine particles exceeds the allowable limit value.

Further, in this embodiment, the accumulated particulate oxidation removal processing is also executed when it is predicted that the particulate oxidation removal capability of the particulate filter 22 will decrease. Whether or not it is predicted that the ability to remove and oxidize fine particles is predicted to be decreased is determined, for example, from the temperature of exhaust gas. That is, when the temperature of the exhaust gas becomes low, the temperature of the particulate filter 22 decreases, so that it is predicted that the particulate oxidation removal capability will decrease.

It should be noted that even when the vehicle is decelerated, the particulate 2
Since the temperature of the exhaust gas flowing into No. 2 sharply decreases, it can be predicted that the particulate oxidation removal capability will decrease. Therefore, at this time, the deposited particulate oxidation removal treatment should be performed, but the specific method is different from the above-mentioned three methods. That is, the particulate filter 2
The same applies in that the oxygen concentration of the exhaust gas flowing into 2 is increased or decreased in a predetermined cycle, but here the throttle valve 17 is set in advance with the EGR control valve 25 fully opened. It is fully closed or opened in a cycle.

That is, air is introduced into the combustion chamber 5 in a spike manner at a predetermined cycle with the EGR rate being maximized. In this way, the oxygen concentration of the exhaust gas flowing into the particulate filter 22 is changed in a predetermined cycle. In this case, an extremely small amount of fuel may be injected into the combustion chamber 5 within a range that does not serve as power for the internal combustion engine. According to this, the temperature of the particulate filter 22 can be positively raised by this fuel. Further, the EGR control valve 25 is fully opened and the throttle valve 17 is fully closed, so that the particulate filter 22 is
The amount of exhaust gas passing through is extremely small. This prevents the temperature of the particulate filter 22 from being lowered by the passage of exhaust gas.

Next, the conditions for prohibiting the execution of the above-mentioned accumulated particulate oxidation removal processing will be described. In this embodiment, the execution of the accumulated particulate oxidation removal process is prohibited even in the following two cases. That is, when the temperature of the particulate filter 22 is lower than a predetermined allowable minimum temperature, execution of the accumulated particulate oxidation removal process is prohibited. This is the first case. When the temperature of the particulate filter 22 is lower than the allowable minimum temperature, the fuel injected by the sub-injection is used as the particulate filter 22.
Can't be purified in. Therefore, in such a case, if the execution of the accumulated particulate oxidation removal process is prohibited, it is possible to prevent the fuel from flowing out from the particulate filter 22 to the downstream side.

Further, in consideration of the operating state of the internal combustion engine, if it is determined that the particles are likely to be generated when the secondary injection is executed, the execution of the accumulated particle oxidation removal processing is prohibited. This is the second case. Even if the fuel is injected by sub-injection to oxidize and remove the deposited particulates, if the fuel becomes particulates, the deposited particulates will rather increase. Therefore, in such a case, if the execution of the oxidation removal process of the deposited particles is prohibited, the deposited particles are prevented from increasing.

As described above, when the temperature of the particulate filter 22 is lower than the minimum permissible temperature, the execution of the particulate particulate oxidation removal process is prohibited. At this time, the temperature of the particulate filter 22 is positively increased. May be. As a concrete method, first, the amount of fuel that keeps the average air-fuel ratio of the exhaust gas lean is injected by sub-injection, and then the amount of fuel that makes the average air-fuel ratio of exhaust gas rich is injected by the sub-injection. . According to this, since a large amount of oxygen is contained in the exhaust gas when the first sub-injection is executed, the fuel injected by the sub-injection easily burns in the particulate filter 22, and therefore the next sub-injection is executed. When the temperature is raised, the temperature of the particulate filter 22 is appropriately raised,
Therefore, the fuel injected by the next sub-injection has a small amount of oxygen in the exhaust gas, but the particulate filter 2
Burns well at 2. Thus, the temperature of the particulate filter 22 is raised.

The timing of the sub-injection executed to positively raise the temperature of the particulate filter 22 as described above is determined based on the amount of generated fine particles and the thermal decomposition rate as described above. The execution cycle of the lean sub-injection that injects fuel so that the average air-fuel ratio of exhaust gas is maintained lean and the rich sub-injection that injects fuel so that the average air-fuel ratio of exhaust gas becomes rich is the particulate filter. The temperature rising speed of 22 is set to be the optimum speed. That is, from the viewpoint of raising the temperature of the particulate filter 22 as quickly as possible, it is preferable that the temperature rising rate of the particulate filter 22 is faster, but if it is too fast, the deposited particulates may emit a bright flame and burn. The rate of temperature rise of the particulate filter 22 is such that the amount of oxygen absorbed by the active oxygen storage / release agent 61 when the exhaust gas having a low oxygen concentration flows into the particulate filter 22 and the exhaust gas having a high oxygen concentration becomes the particulate filter. It is determined by the amount of fuel in the exhaust gas when flowing into the exhaust gas 22. Therefore, in this embodiment, the amount of oxygen absorbed by the active oxygen absorbing / releasing agent 61 and the particulate filter 22 are set so that the temperature rising rate of the particulate filter 22 is so high that the deposited particles do not emit a luminous flame and burn. The execution cycle is determined in consideration of the amount of fuel in the exhaust gas flowing into the engine.

In addition to the above-mentioned conditions, the accumulated particulate oxidation removal processing is performed on condition that a predetermined time has elapsed and at predetermined intervals, or on condition that the vehicle has traveled a predetermined distance. It may be executed at predetermined intervals, or every time the operating state of the internal combustion engine reaches a predetermined operating state, for example, the idle operating state where the required load is extremely small. In particular, if the accumulated particulate oxidation removal processing is executed under the condition that the operating state of the internal combustion engine is in the idle operating state, the influence of the auxiliary injection on the vehicle running can be minimized.

Further, according to the present invention, in addition to the above effects, there is an effect that the temperature of the particulate filter 22 can be raised by the reaction heat when the deposited particulates are oxidized. Further, there is also an effect that the fuel acts as a reducing agent to purify the nitrogen oxides NO _x and the sulfur oxides SO _x by causing the exhaust gas containing the fuel to flow into the particulate filter 22. Further, in the case of the control for generating the exhaust gas having a high oxygen concentration and the exhaust gas having a low oxygen concentration by changing the fuel injection amount by the sub-injection, the exhaust gas having a high oxygen concentration and the exhaust gas having a low oxygen concentration are generated. There is also an effect that the generation cycle can be set with a relatively large degree of freedom.

By the way, the fuel and the lubricating oil contain calcium Ca, and therefore the exhaust gas contains calcium Ca. This calcium Ca produces calcium sulfate CaSO ₄ when SO ₃ is present. This calcium sulfate CaSO ₄ is a solid and does not thermally decompose even at high temperatures. Therefore, when calcium sulfate CaSO ₄ is produced, the calcium sulfate CaSO ₄ blocks the pores of the particulate filter 22, and as a result, the exhaust gas becomes difficult to flow in the particulate filter 22.

In this case, when an alkali metal or alkaline earth metal having a higher ionization tendency than calcium Ca, such as potassium K, is used as the active oxygen release agent 61, SO ₃ which diffuses into the active oxygen release agent 61 is bound to potassium K. To form potassium sulfate K ₂ SO ₄ , calcium Ca
Passes through the partition wall 54 of the particulate filter 22 without being combined with SO ₃ and flows into the exhaust gas outflow passage 51. Therefore, the pores of the particulate filter 22 will not be clogged. Therefore, as described above, the active oxygen releasing agent 61 is an alkali metal or alkaline earth metal having a higher ionization tendency than calcium Ca, that is, potassium K, lithium Li, and cesium C.
s, rubidium Rb, barium Ba, strontium S
It will be preferred to use r.

The present invention also relates to the particulate filter 2.
It can also be applied to the case where only a noble metal such as platinum Pt is supported on the carrier layers formed on both side surfaces of No. 2. However, in this case, the solid line showing the amount G of particles that can be removed by oxidation moves to the right side slightly as compared with the solid line shown in FIG.
In this case, active oxygen is released from NO ₂ or SO ₃ retained on the surface of platinum Pt.

[0068]

EFFECTS OF THE INVENTION Fine particles in exhaust gas can be immediately oxidized and removed on the particulate filter, and even if fine particles are deposited on the particulate filter, the fine particles can be oxidized and removed to prevent clogging. be able to.

[Brief description of drawings]

FIG. 1 is an overall view of an internal combustion engine.

FIG. 2 is a diagram showing a particulate filter.

FIG. 3 is a diagram for explaining an oxidizing action of fine particles.

FIG. 4 is a diagram for explaining a deposition action of fine particles.

FIG. 5 is a diagram showing the relationship between the amount of fine particles that can be removed by oxidation and the temperature of a particulate filter.

FIG. 6 is a flowchart for controlling the operation of the internal combustion engine that employs the first method.

FIG. 7 is a flowchart for controlling the operation of the internal combustion engine that employs the second method.

FIG. 8 is a flowchart for controlling the operation of the internal combustion engine that employs the third method.

[Explanation of symbols]

5 ... Combustion chamber 6 ... Fuel injection valve 22 ... Particulate filter 25 ... EGR control valve

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI F02D 41/12 360 F02D 41/12 360 41/40 41/40 C 43/00 301 43/00 301D 301N 45/00 314 45 / 00 314Z (58) Fields surveyed (Int.Cl. ⁷ , DB name) F01N 3/02 F02D 41/04 F02D 41/12 F02D 41/40 F02D 43/00 F02D 45/00 F01N 3/08

Claims (17)

(57) [Claims] 1. A particulate filter disposed in an engine exhaust system for removing fine particles in exhaust gas, and when excess oxygen exists in the surroundings supported by the particulate filter, oxygen is taken in and retained. Exhaust gas that is equipped with an active oxygen release agent that releases oxygen in the form of active oxygen when the ambient oxygen concentration decreases, and that allows particulates in the exhaust gas to be oxidized and removed on the particulate filter without emitting a luminous flame. In the gas purification method,
When the particulates accumulated on the particulate filter are to be removed by oxidation, the oxygen concentration fluctuation process is performed while increasing or decreasing the oxygen concentration in the exhaust gas flowing into the particulate filter while performing the particulate filter.
Exhaust gas purification method that oxidizes and removes the particulates that have accumulated on the filter . 2. A particulate filter for removing fine particles in exhaust gas discharged from a combustion chamber,
When the amount of particulates emitted from the combustion chamber per unit time is less than the amount of oxidatively removable particulates that can be oxidized and removed on the particulate filter per unit time without emitting a luminous flame, particulates in the exhaust gas are particulated. When flowing into the filter, it is oxidatively removed without emitting a luminous flame, and even if the amount of the discharged fine particles temporarily exceeds the amount of the oxidatively removable fine particles, when the fine particles are deposited below a certain limit on the particulate filter. When the amount of the discharged fine particles becomes smaller than the amount of the fine particles that can be oxidized and removed, the particulates on the particulate filter can be oxidized and removed without emitting a bright flame, and the amount of the fine particles that can be oxidized and removed is the particulate filter. Depends on the temperature of the filter and Even if the amount of discharged fine particles is usually smaller than the amount of the oxidatively removable fine particles, and the amount of the discharged fine particles temporarily becomes larger than the amount of the oxidatively removable fine particles, thereafter, the amount of the discharged fine particles is the oxidatively removable fine particle amount The above-mentioned amount of particulates discharged and the temperature of the particulate filter are maintained so that only a certain amount of particulates that can be oxidized and removed when they become smaller are deposited on the particulate filter, thereby particulates in the exhaust gas are particulated. The exhaust gas purifying method according to claim 1, wherein the exhaust gas is purified by oxidation on the curate filter without emitting a bright flame. 3. A main injection for injecting fuel into a combustion chamber for driving an internal combustion engine is executed, and thereafter, a sub-injection for injecting fuel into the combustion chamber is executed separately from the main injection, and the secondary injection is performed. The exhaust gas purification method according to claim 2, wherein the oxygen concentration fluctuation process is executed by changing the amount of fuel to be used. 4. An internal combustion engine having a plurality of combustion chambers, wherein the oxygen concentration in the exhaust gas discharged from some of the combustion chambers is made higher than the oxygen concentration in the exhaust gas discharged from the remaining combustion chambers. The exhaust gas purification method according to claim 2, wherein the oxygen concentration fluctuation processing is executed by the above method. 5. A main injection for injecting fuel into a combustion chamber for driving an internal combustion engine is executed, and then a sub-injection for injecting fuel into a part of the combustion chamber is executed separately from the main injection. exhaust gas purification method according to claim 4 which is adapted to the oxygen concentration in the exhaust gas <br/> smaller than the oxygen concentration in the exhaust gas discharged from the remaining combustion chambers of the discharged from the combustion chamber. 6. The exhaust gas purification method according to claim 3, wherein the sub injection is performed in the latter half of the expansion stroke or the exhaust stroke. 7. The oxygen concentration variation process is executed when the amount of fine particles deposited on the particulate filter exceeds a predetermined amount of fine particles, at predetermined intervals, or during idle operation. The exhaust gas purification method according to claim 2, wherein 8. The exhaust gas purification method according to claim 2, wherein the oxygen concentration variation process is executed when it is predicted that the amount of the particulates that can be removed by oxidation will decrease. 9. When the deceleration of an internal combustion engine is detected, the amount of fine particles that can be removed by oxidation is predicted to decrease, and the oxygen concentration fluctuation process is performed by increasing or decreasing the amount of air taken into the combustion chamber. The exhaust gas purification method according to claim 2, wherein the exhaust gas purification method is performed. 10. The exhaust gas purification method according to claim 9, wherein the reducing agent is mixed into the exhaust gas while the oxygen concentration fluctuation process is executed. 11. The exhaust gas purification method according to claim 2, wherein a precious metal catalyst is carried on the particulate filter. 12. The exhaust gas purification method according to claim 1, wherein the active oxygen releasing agent is made of an alkali metal, an alkaline earth metal, a rare earth or a transition metal. 13. The exhaust gas purification method according to claim 12, wherein the alkali metal and the alkaline earth metal are metals having a higher ionization tendency than calcium. 14. The oxygen concentration in the exhaust gas is lowered by temporarily enriching the air-fuel ratio of a part or the whole of the exhaust gas, and the particulates adhering to the particulate filter are oxidized. 11. The exhaust gas purification method according to item 11. 15. A particulate filter arranged in an engine exhaust system for removing fine particles in exhaust gas,
Exhaust gas is provided with an active oxygen releasing agent that is carried on a particulate filter and takes in oxygen to retain oxygen when there is excess oxygen in the surroundings, and releases oxygen in the form of active oxygen when the surrounding oxygen concentration decreases, In an exhaust gas purification device that is designed to oxidize and remove the particulates inside the particulate filter without emitting a luminous flame, the particulates that have accumulated on the particulate filter flow into the particulate filter when it is to be removed by oxidation. Particulate while performing oxygen concentration fluctuation processing to increase or decrease the oxygen concentration in the exhaust gas
An exhaust gas purification device comprising means for oxidizing and removing fine particles deposited on a filter . 16. A particulate filter for removing fine particles in exhaust gas discharged from a combustion chamber is arranged in an engine exhaust passage, and as the particulate filter, exhaust discharged from the combustion chamber per unit time. Oxidation that can be oxidatively removed on the particulate filter per unit time without emitting a bright flame When the amount of fine particles that can be removed is less than the amount of fine particles that can be removed in the exhaust gas, it oxidizes without producing a bright flame when it enters the particulate filter. Even if the amount of the discharged fine particles is temporarily increased beyond the amount of the oxidatively removable fine particles, the amount of the discharged fine particles is the amount of the oxidizable / removable fine particles when the fine particles are deposited below a certain limit on the particulate filter. When it becomes less than Using a particulate filter that can be oxidatively removed without causing particles to emit a bright flame, the oxidatively removable particulate amount is dependent on the temperature of the particulate filter, and the discharged particulate amount is usually more than the oxidative removable particulate amount. Even if the amount of the discharged fine particles becomes temporarily smaller than the amount of the fine particles that can be removed by oxidation, even if the amount of the discharged fine particles becomes temporarily larger than the amount of the fine particles that can be oxidized and removed thereafter, the amount is less than a certain limit that can be oxidized and removed. Control means for maintaining the above-mentioned discharged particulate amount and the temperature of the particulate filter so that only the amount of particulates deposited on the particulate filter is increased. 16. The exhaust according to claim 15, which is adapted to be oxidized and removed without emitting Gas purifier. 17. The particulate filter comprises a plurality of exhaust flow passages extending parallel to each other, one of the adjacent exhaust flow passages having an upstream end closed by a plug and the other of the adjacent exhaust flow passages. The exhaust gas purifying apparatus according to claim 15, wherein the downstream end is closed by a plug, and a catalyst is supported on the wall surface of the exhaust flow passage and the wall surface of the plug.