JP2001336414A - Method for purifying exhaust gas and its apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously oxidize and remove particulates in exhaust gas in a particulate filter. SOLUTION: A particulate filter 22 is arranged in an exhaust gas passage of an engine. An amount of exhaust particulates discharged from a combustion chamber 5 per a unit time is reduced in a particulate filter 22 to be smaller than that to be oxidized and removed in a unit time without generating luminous flames. Thus, particulates in exhaust gas is continuously oxidized and removed in the particulate filter 22 without generating luminous flames.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in a diesel engine, a particulate filter is disposed in an engine exhaust passage in order to remove fine particles contained in exhaust gas, and the fine particles in the exhaust gas are once collected by the particulate filter. In addition, the particulate filter is regenerated by igniting and burning the fine particles collected on the particulate filter. However, the fine particles trapped on the particulate filter do not ignite unless the temperature becomes higher than about 600 ° C., whereas the exhaust gas temperature of a diesel engine is usually much lower than 600 ° C. Therefore, it is difficult to ignite the fine particles collected on the particulate filter with the heat of the exhaust gas, and the ignition temperature of the fine particles is required to ignite the fine particles collected on the particulate filter with the heat of the exhaust gas. Must be lowered.

By the way, it has been known that if a catalyst is supported on a particulate filter, the ignition temperature of the fine particles can be reduced. Is known. For example, Japanese Patent Publication 7-1062
No. 90 discloses a particulate filter in which a mixture of a platinum group metal and an alkaline earth metal oxide is supported on the particulate filter. In this particulate filter, fine particles are ignited at a relatively low temperature of about 350 ° C. to 400 ° C., and then continuously burned.

[0004]

In a diesel engine, when the load increases, the exhaust gas temperature increases from 350 ° C. to 400 ° C. Therefore, the above-mentioned particulate filter apparently reduces the exhaust gas heat when the engine load increases. It seems that the particles can be ignited and burned. However, in practice, the exhaust gas temperature is 350 ° C to 4 ° C.
Even when the temperature reaches 00 ° C., the fine particles may not ignite, and even if the fine particles are ignited, only a part of the fine particles will burn, and a large amount of fine particles will remain unburned.

That is, when the amount of fine particles contained in the exhaust gas is small, the amount of fine particles adhering to the particulate filter is small. At this time, when the temperature of the exhaust gas changes from 350.degree. And then continuously burned. However, if the amount of particulates contained in the exhaust gas increases, other particulates accumulate on the particulate filter before the particulate attached on the particulate filter completely burns, and as a result, the particulates are stacked on the particulate filter. Deposited on When the fine particles are deposited on the particulate filter in this manner, some of the fine particles that are likely to come into contact with oxygen are burned, but the remaining fine particles that are hard to come into contact with oxygen do not burn, and thus a large amount of fine particles are generated. It will remain unburned. Therefore, when the amount of fine particles contained in the exhaust gas increases, a large amount of fine particles continue to be deposited on the particulate filter.

On the other hand, when a large amount of fine particles are deposited on the particulate filter, the deposited fine particles gradually become difficult to ignite and burn. It is considered that the difficulty of burning in this way is probably due to the fact that carbon in the fine particles changes to graffite or the like which is difficult to burn during deposition.
In fact, if a large amount of fine particles continue to deposit on the particulate filter, the deposited fine particles do not ignite at a low temperature of 350 ° C. to 400 ° C., and a high temperature of 600 ° C. or more is required to ignite the deposited fine particles. However, in a diesel engine, the exhaust gas temperature does not usually reach a high temperature of 600 ° C. or more. Therefore, if a large amount of fine particles are continuously deposited on the particulate filter, it becomes difficult to ignite the fine particles deposited by the exhaust gas heat. .

On the other hand, if the exhaust gas temperature can be raised to a high temperature of 600 ° C. or more at this time, the deposited fine particles ignite, but in this case, another problem occurs. That is, in this case, when the deposited fine particles are ignited, they emit a bright flame and burn. At this time, the temperature of the particulate filter is set to 800 for a long time until the combustion of the deposited fine particles is completed.
Maintained above ℃. However, when the particulate filter is exposed to a high temperature of 800 ° C. or more for a long time as described above, the particulate filter deteriorates early, and thus a problem arises that the particulate filter must be replaced with a new one early. .

Further, when the deposited fine particles are burned, the ash condenses into large lumps, and the lumps of the ash cause clogging of the pores of the particulate filter. The number of clogged pores gradually increases over time, and thus the pressure loss of the exhaust gas flow in the particulate filter increases. When the pressure loss of the exhaust gas flow is increased, the output of the engine is reduced, and this also causes a problem that the particulate filter must be replaced with a new one at an early stage.

Once such a large amount of fine particles are deposited in a layered manner, various problems as described above occur. Therefore, the amount of fine particles contained in the exhaust gas and the amount of fine particles combustible on the particulate filter are reduced. In consideration of the balance, it is necessary to prevent a large amount of fine particles from depositing in a layered manner. However, in the particulate filter described in the above publication, no consideration is given to the balance between the amount of fine particles contained in the exhaust gas and the amount of fine particles that can be burned on the particulate filter. The problem will arise.

Further, in the particulate filter described in the above-mentioned publication, when the exhaust gas temperature becomes lower than 350 ° C., the fine particles are not ignited, and thus the fine particles accumulate on the particulate filter. In this case, if the amount of deposition is small, the deposited fine particles are burned when the exhaust gas temperature changes from 350 ° C. to 400 ° C., but if a large amount of fine particles are deposited in a stack, the exhaust gas temperature changes from 350 ° C. to 400 ° C. When the particles accumulate, they do not ignite, and even if they are ignited, some of the particles do not burn, resulting in unburned residues.

In this case, if the temperature of the exhaust gas is increased before a large amount of fine particles are deposited in a stack, the deposited fine particles can be burned without remaining unburned. However, in the particulate filter described in the above-mentioned publication, Such a thing is not considered at all, and when a large amount of fine particles are deposited in a stacked manner, all the deposited fine particles cannot be burned unless the exhaust gas temperature is raised to 600 ° C. or more.

[0012]

According to a first aspect of the present invention, a particulate filter for removing particulates in exhaust gas discharged from a combustion chamber is provided as a particulate filter per unit time. If the amount of fine particles discharged from the particulate filter is smaller than the amount of oxidizable particles that can be oxidized and removed without emitting a luminous flame per unit time on the particulate filter, the luminous flame is generated when the particles in the exhaust gas flow into the particulate filter. Using a particulate filter that can be oxidized and removed without generating emissions, the amount of discharged particulates is reduced so that the amount of discharged particulates is smaller than the amount of particulates that can be oxidized and removed when the engine is in an operating state where the amount of discharged particulates can be smaller than the amount of particulates that can be removed by oxidation. At least one of the amount of fine particles and the amount of fine particles that can be removed by oxidation is controlled.

In the second invention, in the first invention,
A noble metal catalyst is supported on the particulate filter. According to a third aspect, in the second aspect, the active oxygen releasing agent according to the second aspect, which takes in oxygen and retains oxygen when there is excess oxygen in the surroundings, and releases the retained oxygen in the form of active oxygen when the surrounding oxygen concentration decreases. Is carried on a particulate filter, and when fine particles adhere to the particulate filter, active oxygen is released from the active oxygen releasing agent,
Fine particles adhering to the particulate filter are oxidized by the released active oxygen.

In the fourth invention, in the third invention,
The active oxygen releasing agent comprises an alkali metal or an alkaline earth metal or a rare earth or transition metal. According to a fifth aspect, in the fourth aspect, the alkali metal and the alkaline earth metal comprise a metal having a higher ionization tendency than calcium. In the third aspect in the sixth invention, the active oxygen release agent, the exhaust gas flowing into the particulate filter air-fuel ratio when the lean exhaust gas flowing into the particulate filter to absorb NO _x in the exhaust gas air-fuel ratio is a function of releasing NO _x absorbed and becomes the stoichiometric air-fuel ratio or rich.

According to a seventh aspect, in the first aspect,
The amount of fine particles that can be removed by oxidation is a function of the temperature of the particulate filter. In the seventh invention in the eighth invention, the particulate removable weight oxide in addition to the temperature of the particulate filter is at least one function of the oxygen concentration or the concentration of NO _x in the exhaust gas.

In the ninth invention, in the seventh invention,
The amount of particulates that can be removed by oxidation is stored in advance at least as a function of the temperature of the particulate filter. According to a tenth aspect, in the first aspect, when the amount of discharged particulates and the amount of particulates that can be removed by oxidation are close to each other when the engine is in an operating state where the amount of discharged particulates can be made smaller than the amount of particulates that can be removed by oxidation, Is controlled so that at least one of the amount of discharged fine particles and the amount of fine particles removable by oxidation is smaller than the amount of fine particles removable by oxidation and the difference between the amount of discharged fine particles and the amount of fine particles removable by oxidation is increased.

In an eleventh aspect based on the tenth aspect, the difference between the amount of discharged particulates and the amount of particulates that can be removed by oxidation is increased by increasing the temperature of the particulate filter. In a twelfth aspect based on the tenth aspect, the difference between the amount of discharged fine particles and the amount of oxidizable and removable fine particles is increased by reducing the amount of discharged fine particles.

According to a thirteenth aspect, in the tenth aspect, the difference between the amount of particulates discharged and the amount of particulates that can be oxidized and removed is increased by increasing the oxygen concentration in the exhaust gas. In the fourteenth invention, as a particulate filter for removing particulates in exhaust gas discharged from the combustion chamber, the amount of particulates discharged from the combustion chamber per unit time is reduced per unit time on the particulate filter. When the amount of fine particles in the exhaust gas that can be oxidized and removed without emitting a bright flame is smaller than the amount of fine particles in the exhaust gas, the particulate filter can be oxidized and removed without emitting a bright flame when the fine particles in the exhaust gas flow into the particulate filter. Calculate the amount of oxidized particles that can be oxidized and removed per unit time without emitting a flaming flame above. Emission particulates or oxidation so that it is less than the particulates At least Sa possible amount of particulates so as to control the other.

In the fifteenth aspect, as a particulate filter for removing particulates in exhaust gas discharged from the combustion chamber, the amount of particulates discharged from the combustion chamber per unit time is measured on the particulate filter as a unit. If the amount of particulates in the exhaust gas that can be removed by oxidation without emitting bright flame per hour is less than the amount of particulates that can be removed by oxidation, if the particulates in the exhaust gas flow into the particulate filter, they are oxidized and removed without emitting bright flame and flow into the particulate filter. particulate fuel ratio of the exhaust gas has the function of releasing the NO _x absorbed and the air-fuel ratio of the exhaust gas flowing into the absorbing particulate filter NO _x in the exhaust gas becomes the stoichiometric air-fuel ratio or rich when the lean to Use a filter to reduce the amount of discharged particulates compared to the amount of particulates that can be removed by oxidation. At least one of the amount of exhaust particulates and the amount of particulates that can be oxidized and removed is controlled so that the amount of exhaust particulates is smaller than the amount of particulates that can be removed by oxidation when the engine is in an operating state that can be reduced. In the sixteenth aspect, a particulate filter for removing particulates in the exhaust gas discharged from the combustion chamber is arranged in the engine exhaust passage, and the particulate filter is configured to emit the particulate matter discharged from the combustion chamber per unit time. When the amount of fine particles is smaller than the amount of oxidizable particles that can be oxidized and removed without emitting a bright flame per unit time on the particulate filter, the fine particles in the exhaust gas oxidize without emitting a bright flame when flowing into the particulate filter. Using a particulate filter that can be removed, the amount of particulates discharged or oxidized and removed so that the amount of particulates discharged is less than the amount of particulates that can be oxidized and removed when the engine is operating, where the amount of particulates that can be removed is smaller than the amount of particulates that can be removed by oxidation. A control means for controlling at least one of the possible fine particle amounts is provided. .

In a seventeenth aspect based on the sixteenth aspect, a noble metal catalyst is supported on the particulate filter. In the eighteenth invention, in the seventeenth invention,
When excess oxygen is present in the surroundings, the active oxygen releasing agent that takes in oxygen to retain oxygen and releases the retained oxygen in the form of active oxygen when the surrounding oxygen concentration decreases is carried on the particulate filter, When fine particles adhere to the filter, active oxygen is released from the active oxygen releasing agent, and the released active oxygen oxidizes the fine particles adhered to the particulate filter.

In a nineteenth aspect based on the eighteenth aspect, the active oxygen releasing agent comprises an alkali metal, an alkaline earth metal, a rare earth or a transition metal. According to a twentieth aspect, in the ninth aspect, the alkali metal and the alkaline earth metal comprise a metal having a higher ionization tendency than calcium. In 18 th invention is a 21 th invention, the active oxygen release agent, the exhaust gas flowing into the particulate filter air-fuel ratio when the lean exhaust gas flowing into the particulate filter to absorb NO _x in the exhaust gas air-fuel ratio is a function of releasing NO _x absorbed and becomes the stoichiometric air-fuel ratio or rich.

In a twenty-second aspect based on the sixteenth aspect, the amount of fine particles removable by oxidation is a function of the temperature of the particulate filter. According to a twenty-third aspect, in the twenty-second aspect, in addition to the temperature of the particulate filter, the amount of particulates that can be removed by oxidation is determined by the oxygen concentration in the exhaust gas or the NO.
_x is at least one function of the density.

According to a twenty-fourth aspect, in the twenty-second aspect, there is provided a storage means for preliminarily storing the amount of fine particles removable by oxidation in the form of a function of the temperature of the particulate filter. In a twenty-fifth aspect based on the sixteenth aspect, in the sixteenth aspect, the control means is configured such that the amount of the discharged fine particles and the amount of the fine particles that can be oxidized and removed are close to each other when the engine is in an operating state in which the amount of the fine particles can be reduced. In some cases, at least one of the discharged fine particle amount and the oxidatively removable fine particle amount is controlled so that the discharged fine particle amount is smaller than the oxidatively removable fine particle amount and the difference between the discharged fine particle amount and the oxidatively removable fine particle amount is increased.

In a twenty-sixth aspect based on the twenty-fifth aspect, the control means increases the difference between the amount of particulates discharged and the amount of particulates that can be removed by oxidation by increasing the temperature of the particulate filter. In a twenty-seventh aspect based on the twenty-sixth aspect, the control means increases the temperature of the particulate filter by controlling at least one of the fuel injection amount and the fuel injection timing so as to increase the exhaust gas temperature.

In a twenty-eighth aspect based on the twenty-seventh aspect, the control means increases the exhaust gas temperature by delaying the main fuel injection timing or by injecting auxiliary fuel in addition to the main fuel. In a twenty-ninth aspect based on the twenty-sixth aspect, in the twenty-sixth aspect, as the engine increases the amount of recirculated exhaust gas, the amount of soot generated gradually increases and reaches a peak, and when the amount of recirculated exhaust gas further increases, soot is almost completely reduced. The control means increases the exhaust gas temperature by making the recirculated exhaust gas amount larger than the recirculated exhaust gas amount at which the generation amount of soot is peaked, thereby increasing the temperature of the particulate filter. To rise.

According to a thirtieth aspect, in the twenty-sixth aspect, a hydrocarbon supply device is disposed in an exhaust passage upstream of the particulate filter, and hydrocarbons are supplied from the hydrocarbon supply device into the exhaust passage. Raise the temperature of. In the 31st invention, 26
In the second invention, an exhaust control valve is disposed in an exhaust passage downstream of the particulate filter, and the temperature of the particulate filter is increased by closing the exhaust control valve.

According to a thirty-second aspect, in the thirty-sixth aspect, there is provided an exhaust turbocharger having a wastegate valve for controlling an amount of exhaust gas bypassing the exhaust turbine, wherein the wastegate valve is opened. Raises the temperature of the particulate filter. According to a thirty-third aspect, in the twenty-fifth aspect, the control means increases the difference between the amount of the discharged fine particles and the amount of the fine particles that can be oxidized and removed by reducing the amount of the discharged fine particles.

In a thirty-fourth aspect based on the thirty-third aspect, the control means controls the fuel injection amount, the fuel injection timing, the fuel injection pressure, or the auxiliary fuel injection so that the amount of the emitted fine particles decreases. According to a thirty-fifth aspect, in the thirty-third aspect, there is provided a supercharging means for supercharging the intake air, and the control means reduces the amount of discharged particulates by increasing the supercharging pressure.

In a thirty-sixth aspect based on the thirty-third aspect, there is provided an exhaust gas recirculation device for recirculating exhaust gas into the intake passage, and the control means reduces the exhaust gas recirculation rate to reduce the exhaust gas recirculation rate. Reduce the amount of fine particles.
In a thirty-seventh aspect based on the twenty-fifth aspect, the control means increases the oxygen concentration in the exhaust gas to increase the difference between the amount of exhaust particulates and the amount of particulates that can be removed by oxidation.

In a thirty-eighth aspect based on the thirty-seventh aspect, there is provided an exhaust gas recirculation device for recirculating exhaust gas into the intake passage, and the control means reduces the exhaust gas recirculation rate to reduce the exhaust gas recirculation rate. Increase the oxygen concentration in the gas. In a thirty-ninth aspect based on the thirty-seventh aspect, there is provided a secondary air supply device for supplying secondary air into an exhaust passage upstream of the particulate filter, wherein the control means includes a secondary air supply device in the exhaust passage upstream of the particulate filter. By supplying secondary air, the oxygen concentration in the exhaust gas is increased.

In the fortieth aspect, a particulate filter for removing particulates in exhaust gas discharged from the combustion chamber is disposed in the engine exhaust passage, and the particulate filter is discharged from the combustion chamber per unit time as a particulate filter. When the amount of discharged fine particles is smaller than the amount of oxidizable particles that can be oxidized and removed without emitting a luminous flame per unit time on the particulate filter, a luminous flame is generated when the fine particles in the exhaust gas flow into the particulate filter. Calculating means for calculating the amount of oxidized fine particles which can be oxidized and removed per unit time on a particulate filter using a particulate filter which can be oxidized and removed without any trouble, and the amount of oxidized fine particles which can be removed by oxidation When the engine is running, which can be less than Amount of discharged particulate is provided with a control means for controlling at least one of the discharge amount of particulates or particulate removable by oxidation amount to be less than the amount removed oxide particles. In the forty-first aspect, a particulate filter for removing particulates in exhaust gas exhausted from the combustion chamber is disposed in the engine exhaust passage, and the particulate filter emits exhaust gas discharged from the combustion chamber per unit time. When the amount of fine particles is smaller than the amount of oxidizable particles that can be oxidized and removed without emitting a bright flame per unit time on the particulate filter, the fine particles in the exhaust gas oxidize without emitting a bright flame when flowing into the particulate filter. NO air-fuel ratio of the exhaust gas is absorbed and the air-fuel ratio of the exhaust gas flowing into the absorbing particulate filter NO _x in the exhaust gas becomes the stoichiometric air-fuel ratio or rich when the lean flowing into removal allowed provided and the particulate filter _Use a particulate filter that has the function to release _x At least one of the amount of discharged particulates or the amount of particulates that can be oxidized and removed is controlled so that the amount of particulates discharged is smaller than the amount of particulates that can be removed by oxidation when the engine is running, where the amount of particulate output can be smaller than the amount of particulates that can be removed by oxidation. Control means for performing the operation.

[0032]

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. Referring to FIG. 1, 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 Denotes an exhaust valve, and 10 denotes an exhaust port. The intake port 8 is connected to a surge tank 12 via a corresponding intake branch pipe 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 cooling device 18 for cooling the intake air flowing through the intake duct 13 is arranged around the cooling device 18. 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 the engine cooling water. On the other hand, the exhaust port 10 is connected to an exhaust turbine 21 of the exhaust turbocharger 14 via an exhaust manifold 19 and an exhaust pipe 20, and an outlet of the exhaust turbine 21 is connected to a casing 23 having a built-in 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 electrically controlled EGR control valve 25 is disposed in the EGR passage 24. Also, the EGR passage 24
A cooling device 26 for cooling the EGR gas flowing in the EGR passage 24 is disposed around the cooling device 26. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 26, and the EGR gas is cooled by the engine cooling water. 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 through 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. The fuel pump 28 is controlled 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 a ROM (read only memory) 32 and a RAM
(Random access memory) 33, CPU (microprocessor) 34, input port 35 and output port 36
Is provided. The output signal of the fuel pressure sensor 29 corresponds to A
The data is input to the input port 35 via the D converter 37. The particulate filter 22 has a temperature sensor 39 for detecting the temperature of the particulate filter 22.
The output signal of the temperature sensor 39 is input to the input port 35 via the corresponding AD converter 37. 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 every time the crankshaft rotates, for example, by 30 °. 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 25, and the fuel pump 2 via the corresponding drive circuit 38.
8 is connected.

FIG. 2A shows the relationship between the required torque TQ, the depression amount L of the accelerator pedal 40, and the engine speed N. In FIG. 2A, each curve represents an equal torque curve, a curve indicated by TQ = 0 indicates that the torque is zero, and the remaining curves are TQ = a, TQ
The required torque gradually increases in the order of Q = b, TQ = c, TQ = d. The required torque TQ shown in FIG.
As shown in (B), the ROM is previously stored in the form of a map as a function of the depression amount L of the accelerator pedal 40 and the engine speed N.
32. In the embodiment according to the present invention, FIG.
A required torque TQ according to the depression amount L of the accelerator pedal 40 and the engine speed N is first calculated from the map shown in FIG. 3B, and the fuel injection amount and the like are calculated based on the required torque TQ.

FIG. 3 shows the structure of the particulate filter 22. 3 (A) shows a front view of the particulate filter 22, and FIG. 3 (B) shows a side cross-sectional view of the particulate filter 22. As shown in FIGS. 3A and 3B, the particulate filter 22 has a honeycomb structure and includes a plurality of exhaust passages 50 and 51 extending parallel to 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. In FIG. 3 (A), the hatched portion is the plug 5
3 is shown. Therefore, the exhaust gas inflow passages 50 and the exhaust gas outflow passages 51 are alternately arranged with the thin partition walls 54 interposed therebetween. In other words, the exhaust gas inflow passage 50 and the exhaust gas outflow passage 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. It is arranged so that.

The particulate filter 22 is formed of a porous material such as cordierite, so that the exhaust gas flowing into the exhaust gas inflow passage 50 is
As shown by an arrow in (B), it flows out into the adjacent exhaust gas outflow passage 51 through the inside of the surrounding partition wall 54.
In the embodiment according to the present invention, a carrier layer made of, for example, alumina is provided on the peripheral wall surface of each exhaust gas inflow passage 50 and each exhaust gas outflow passage 51, that is, on both side surfaces of each partition wall 54 and on the inner wall surface of the pores in the partition wall 54. Is formed on the support, a noble metal catalyst on the support, and an activity that takes in oxygen when there is excess oxygen around and retains oxygen, and releases the retained oxygen in the form of active oxygen when the surrounding oxygen concentration decreases. An oxygen releasing agent is supported.

In this case, in the embodiment according to the present invention, platinum Pt is used as a noble metal catalyst, and an alkali metal such as potassium K, sodium Na, lithium Li, cesium Cs, rubidium Rb, or barium Ba is used as an active oxygen releasing agent. , Calcium Ca, alkaline earth metals such as strontium Sr, lanthanum La, rare earths such as yttrium Y, cerium Ce, and tin Sn, iron F
At least one selected from transition metals such as e is used.

In this case, as the active oxygen releasing agent, an alkali metal or alkaline earth metal having a higher ionization tendency than calcium Ca, ie, potassium K, lithium Li,
It is preferable to use cesium Cs, rubidium Rb, barium Ba, strontium Sr, or cerium Ce. Next, the action of removing particulates in exhaust gas by the particulate filter 22 will be described by taking as an example the case where platinum Pt and potassium K are carried on a carrier. The same effect of removing fine particles can be obtained by using.

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

FIGS. 4A and 4B schematically show enlarged views of the surface of the carrier layer formed on the inner peripheral surface of the exhaust gas inflow passage 50 and the inner wall surface of the pores in the partition wall 54. .
In FIGS. 4A and 4B, reference numeral 60 denotes platinum Pt.
And 61 denotes an active oxygen releasing agent containing potassium K. When the exhaust gas because the exhaust gas as described above contains a large amount of excess oxygen flows into the exhaust gas inflow passages 50 of the particulate filter 22 4 These oxygen O ₂ as shown in (A)
There O ₂ ^- it is attached to or O the surface of the platinum Pt in ^2-form. On the other hand, NO in the exhaust gas reacts with O ₂ ⁻ or O ²⁻ on the surface of platinum Pt to become NO ₂ (2NO + O ₂ → 2NO).
₂ ). Next, a part of the generated NO ₂ is absorbed in the active oxygen releasing agent 61 while being oxidized on the platinum Pt, and is combined with potassium K to form nitrate ion NO ₃ ⁻ as shown in FIG. And diffuses into the active oxygen releasing agent 61, and a part of the nitrate ion NO ₃ ⁻ generates potassium nitrate KNO ₃ .

On the other hand, as described above, SO is contained in the exhaust gas.
_Two Is also included in this SO_Two Is the same mechanism as NO
The active oxygen is released into the active oxygen releasing agent 61. That is,
As described above, oxygen O_Two Is O_Two ^- Or O^2-In the form of platinum P
t on the surface of SO_Two Is platinum P
O on the surface of t_Two ^- Or O^2-Reacts with SO_Three Becomes Next
SO generated_Three Is partially oxidized on platinum Pt
While being absorbed into the active oxygen releasing agent 61, potassium K
Sulfate ion SO while binding_Four ^2- Active oxygen release agent in the form of
Diffusion into 61, potassium sulfate K_Two SO_Four Generate
Thus, the active oxygen releasing catalyst 61 contains potassium nitrate.
Mu KNO_Three And potassium sulfate K_Two SO _Four Is generated
You.

On the other hand, fine particles mainly composed of carbon C are generated in the combustion chamber 5, and therefore, these fine particles are contained in the exhaust gas. These fine particles contained in the exhaust gas are used as the particulate filter 2 in the exhaust gas.
2B, when flowing in the exhaust gas inflow passage 50 or when going from the exhaust gas inflow passage 50 to the exhaust gas outflow passage 51, as shown by 62 in FIG. It contacts and adheres to the surface of the oxygen releasing agent 61.

As described above, the fine particles 62 form the active oxygen releasing agent 6
1 and the fine particles 62 and the active oxygen releasing agent 6
At the contact surface with No. 1, the oxygen concentration decreases. When the oxygen concentration decreases, a difference in concentration occurs between the active oxygen releasing agent 61 having a high oxygen concentration and the oxygen in the active oxygen releasing agent 61 is directed toward the contact surface between the fine particles 62 and the active oxygen releasing agent 61. Try to move. As a result, potassium nitrate KNO ₃ formed in the active oxygen releasing agent 61 becomes potassium K and oxygen O
Is decomposed into NO and the oxygen O is directed to the contact surface between the fine particles 62 and the active oxygen releasing agent 61, and NO is
1 to the outside. The NO released to the outside is oxidized on platinum Pt on the downstream side, and is absorbed again in the active oxygen releasing agent 61.

On the other hand, at this time, the active oxygen releasing agent 61
Potassium sulfate K being formed_Two SO _Four Also potassium K and acid
Elementary O and SO_Two And oxygen O is activated with the fine particles 62
Toward the contact surface with the oxygen releasing agent 61,_Two Is active oxygen
It is released from the release agent 61 to the outside. S released outside
O_Two Is oxidized on the downstream platinum Pt and becomes active again
It is absorbed in the oxygen releasing agent 61.

On the other hand, the oxygen O heading toward the contact surface between the fine particles 62 and the active oxygen releasing 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 extremely high activity. Therefore, the fine particles 6
Oxygen toward the contact surface between 2 and the active oxygen releasing agent 61 is active oxygen O. When the active oxygen O comes into contact with the fine particles 62, the oxidizing action of the fine particles 62 is promoted, and the fine particles 6
2 can be oxidized within a short time of several minutes to several tens of minutes without emitting a bright flame. While the fine particles 62 are thus oxidized, other fine particles adhere to the particulate filter 22 one after another. Therefore, in practice, a certain amount of fine particles is constantly deposited on the particulate filter 22, and some of the deposited fine particles are oxidized and removed. In this way, the fine particles 62 adhering to the particulate filter 22 are continuously burned without emitting a bright flame. Note that NO _x repeats binding and separation of oxygen atoms in the active oxygen releasing agent 61 while repeating nitrate ion NO ₃ ^−.
It is thought that it diffuses in the form of, and active oxygen is also generated during this time. The fine particles 62 are also oxidized by this active oxygen. Further, the fine particles 62 thus adhered on the particulate filter 22 are oxidized by the active oxygen O, but the fine particles 62 are also oxidized by the oxygen in the exhaust gas.

When the particulates accumulated in a layer on the particulate filter 22 are burned, the particulate filter 22 becomes red hot and burns with a flame. The combustion with such a flame cannot be sustained 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 maintain 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 the surface of the particulate filter 22 does not glow at this time. That is, in other words, in the present invention, the fine particles 62 are oxidized and removed at a considerably low temperature. Therefore, the action of removing fine particles 62 that do not emit a luminous flame by oxidation according to the present invention is completely different from the action of removing fine particles by combustion accompanied by a flame.

Incidentally, platinum Pt and active oxygen releasing agent 6
1 is activated as the temperature of the particulate filter 22 increases, so that the amount of active oxygen O that the active oxygen releasing agent 61 can release per unit time increases as the temperature of the particulate filter 22 increases. Naturally, the fine particles are more easily oxidized and removed as the temperature of the fine particles themselves is higher. Accordingly, the amount of fine particles that can be oxidized and removed on the particulate filter 22 without emitting a bright flame per unit time increases as the temperature of the particulate filter 22 increases.

The solid line in FIG. 6 indicates the amount G of the oxidizable particles that can be oxidized and removed without emitting a bright flame per unit time, and the horizontal axis in FIG. 6 indicates the temperature TF of the particulate filter 22. . FIG. 6 shows the amount of fine particles G that can be oxidized and removed per second when the unit time is 1 second, that is, any unit time such as 1 minute or 10 minutes can be adopted as the unit time. it can. For example, when 10 minutes is used as the unit time, the amount G of oxidizable and removable particles per unit time represents the amount G of oxidizable and removable particles per 10 minutes. As shown in FIG. 6, the amount G of the oxidizable particles that can be oxidized and removed without generating a bright flame increases as the temperature of the particulate filter 22 increases. Now, when the amount of the fine particles discharged from the combustion chamber 5 per unit time is referred to as a discharged fine particle amount M, the discharged fine particle amount M is the same as the fine particles G that can be oxidized and removed per unit time.
When the amount M of discharged fine particles per second is smaller than the amount G of oxidizable and removable fine particles per second, for example,
Alternatively, when the amount M of discharged fine particles per 10 minutes is smaller than the amount G of fine particles that can be removed by oxidation per 10 minutes, that is, in the region I of FIG. 6, all the fine particles discharged from the combustion chamber 5 shine on the particulate filter 22. It can be sequentially oxidized and removed within a short time without producing a flame.

On the other hand, when the amount M of discharged fine particles is larger than the amount G of fine particles that can be removed by oxidation, that is, in the region II in FIG. 6, the amount of active oxygen is insufficient to sequentially oxidize all the fine particles. FIGS. 5A to 5C show how the fine particles are oxidized in such a case. That is, when the amount of active oxygen is insufficient to sequentially oxidize all the fine particles, FIG.
As shown in (2), when the fine particles 62 adhere to the active oxygen releasing agent 61, only a part of the fine particles 62 is oxidized, and the finely oxidized fine particles remain on the carrier layer. Next, when the state of the insufficient amount of active oxygen continues, the fine particles which have not been oxidized remain one after another on the carrier layer, and as a result, the surface of the carrier layer remains as shown in FIG. 5 (B). It becomes covered with the fine particle portion 63.

The residual fine particle portion 6 covering the surface of the carrier layer
3 gradually changes to a carbon material that is hardly oxidized, and thus the residual fine particle portion 63 tends 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 from the active oxygen releasing agent 61 are suppressed. As a result, as shown in FIG. 5C, another fine particle 64 is deposited on the remaining fine particle portion 63 one after another. That is, the fine particles are deposited in a layered manner. When the fine particles are deposited in a layered manner in this manner, these fine particles are separated from the platinum Pt and the active oxygen releasing agent 61, so that even if the fine particles are easily oxidized, they 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, when the state in which the amount M of discharged fine particles is larger than the amount G of fine particles that can be removed by oxidation continues, the fine particles are deposited on the particulate filter 22 in a layered manner. Unless the temperature of the filter 22 is increased, the deposited fine particles cannot be ignited and burned.

As described above, in the region I of FIG. 6, the fine particles are oxidized within a short time without emitting a bright flame on the particulate filter 22, and in the region II of FIG. Deposited in the shape of Therefore, the fine particles are
In order to prevent the particles from being deposited in a layered manner on top, the amount M of discharged fine particles must always be smaller than the amount G of fine particles that can be removed by oxidation.

As can be seen from FIG. 6, the particulate filter 22 used in the embodiment of the present invention can oxidize the fine particles even if the temperature TF of the particulate filter 22 is considerably low. In the compression ignition type internal combustion engine shown, the amount M of discharged particulates and the temperature TF of the particulate filter 22
Can be maintained so as to be usually smaller than the amount G of fine particles that can be removed by oxidation. Therefore, in the embodiment according to the present invention, the amount M of discharged fine particles and the temperature TF of the particulate filter 22 are maintained so that the amount M of discharged fine particles is usually smaller than the amount G of fine particles that can be removed by oxidation.

If the amount M of discharged fine particles is normally kept smaller than the amount G of fine particles that can be removed by oxidation, the fine particles will not be deposited on the particulate filter 22 in a stacked manner. As a result, the pressure loss of the exhaust gas flow in the particulate filter 22 is maintained at a substantially constant minimum pressure loss value without changing at all. In this way, a decrease in the engine output can be kept to a minimum.

The action of removing fine particles by oxidation of the fine particles is performed at a considerably low temperature. Therefore, the temperature of the particulate filter 22 does not rise so much, and there is almost no risk of the particulate filter 22 being deteriorated. In addition, since fine particles do not accumulate on the particulate filter 22 in a layered manner, there is less danger of ash agglomeration, and therefore, there is less danger that the particulate filter 22 will be clogged.

The clogging is mainly caused by calcium sulfate CaSO ₄ . That is, the fuel and the lubricating oil contain calcium Ca, and therefore the exhaust gas contains calcium Ca. This calcium Ca is SO ₃
Produces calcium sulfate CaSO ₄ when present. This calcium sulfate CaSO ₄ is solid and does not thermally decompose even at high temperatures. Therefore, calcium sulfate CaSO ₄ is generated, and if the pores of the particulate filter 22 are closed by the calcium sulfate CaSO ₄ , clogging occurs.

In this case, however, the active oxygen releasing agent 6
When an alkali metal or an alkaline earth metal having a higher ionization tendency than calcium Ca, such as potassium K, is used, SO ₃ diffused into the active oxygen releasing agent 61 combines with potassium K to form potassium sulfate K ₂ SO ₄ . Then, the calcium Ca flows out of the exhaust gas outflow passage 51 through the partition wall 54 of the particulate filter 22 without binding to SO ₃ . Therefore, the particulate filter 2
No clogging of the two pores occurs. Therefore, as described above, as the active oxygen releasing agent 61, an alkali metal or an alkaline earth metal having a higher ionization tendency than calcium Ca, that is, potassium K, lithium Li, cesium Cs,
It is preferable to use rubidium Rb, barium Ba, and strontium Sr.

The embodiment according to the present invention is intended to maintain the amount M of discharged particulates smaller than the amount G of particulates that can be removed by oxidation in basically all operating states. However, in practice, it is almost impossible to make the amount M of discharged fine particles smaller than the amount G of fine particles that can be removed by oxidation in all operating states. For example, when the engine is started, the temperature of the particulate filter 22 is usually low. Therefore, at this time, the amount M of discharged fine particles is generally larger than the amount G of fine particles that can be removed by oxidation. Therefore, in the embodiment according to the present invention, when the engine is in an operating state in which the amount M of discharged fine particles can be made smaller than the amount G of fine particles capable of being oxidized and removed, except for a special case such as immediately after the start of the engine, the amount M of discharged fine particles is reduced. It is set to be smaller than the amount G.

When the amount M of discharged fine particles is larger than the amount G of fine particles that can be removed by oxidation as immediately after the start of the engine, the non-oxidized fine particles begin to remain on the particulate filter 22. However, when the fine particles which have not been oxidized start to remain, that is, when the fine particles are deposited only below a certain limit, and the discharged fine particle amount M becomes smaller than the oxidizable and removable fine particle amount G, the residual fine particle portion is reduced. Is oxidized and removed by the active oxygen O without emitting a bright flame. Therefore, in the embodiment according to the present invention, in a special operation state such as immediately after the start of the engine, when the amount M of the discharged fine particles becomes smaller than the amount G of the fine particles that can be oxidized and removed, only particles of a certain amount or less that can be oxidized and removed are removed. The amount M of discharged fine particles and the amount of the particulate
A temperature TF of 2 is maintained.

Even if the amount M of discharged particulates and the temperature TF of the particulate filter 22 are maintained as described above, particulates may be deposited on the particulate filter 22 in a stacked manner for some reason. Even in such a case, if the air-fuel ratio of a part or the whole of the exhaust gas is temporarily made rich, the fine particles deposited on the particulate filter 22 are oxidized without emitting a bright flame. That is, when the air-fuel ratio of the exhaust gas is made rich, that is, when the oxygen concentration in the exhaust gas is reduced, active oxygen O is released from the active oxygen releasing agent 61 to the outside at once, and the active oxygen O released at once is As a result, the deposited fine particles are burned and removed in a short time without emitting a bright flame. On the other hand, if the air-fuel ratio is maintained lean, the surface of the platinum Pt is covered with oxygen, so-called platinum Pt.
t oxygen poisoning occurs. Such oxidising effect on poisoning occurs when NO _x is reduced the absorption efficiency of the NO _x to be reduced, the active oxygen release amount from the active oxygen release agent 61 is lowered by thus. N, however the air-fuel ratio is eliminated oxygen poisoning to oxygen on the platinum Pt surface is consumed when it is rich, and hence the air-fuel ratio becomes stronger oxidizing effect on switching is the NO _x from rich to lean
The absorption efficiency of O _x is increased, and thus the active oxygen releasing agent 6
1 increases the amount of active oxygen released. Therefore, when the air-fuel ratio is occasionally switched from lean to rich while the air-fuel ratio is maintained lean, the oxygen poisoning of platinum Pt is eliminated each time, so that the amount of active oxygen released when the air-fuel ratio is lean increases. Thus, the oxidizing action of the fine particles on the particulate filter 22 can be promoted. Cerium Ce has a function of taking in oxygen (Ce ₂ O ₃ → 2CeO ₂ ) when the air-fuel ratio is lean and releasing active oxygen (2CeO ₂ → CeO ₃ ) when the air-fuel ratio becomes rich. Therefore, cerium C is used as the active oxygen releasing agent 61.
When e is used, when the air-fuel ratio is lean, the fine particles are oxidized by the active oxygen released from the active oxygen releasing agent 61 when the fine particles adhere to the particulate filter 22, and when the air-fuel ratio becomes rich, a large amount of the active oxygen releasing agent 61 The fine particles are oxidized because the active oxygen is released.
Therefore, even when cerium Ce is used as the active oxygen releasing agent 61, the oxidation reaction of the fine particles on the particulate filter 22 can be promoted by occasionally switching the air-fuel ratio from lean to rich.

FIG. 6 shows the amount G of oxidizable and removable particles as a function of only the temperature TF of the particulate filter 22.
In practice the concentration of oxygen in the exhaust gas is, NO _x in the exhaust gas
It is also a function of the concentration, the unburned HC concentration in the exhaust gas, the degree of oxidization of the particulates, the space velocity of the exhaust gas flow in the particulate filter 22, the exhaust gas pressure, and the like.
Therefore, it is preferable to calculate the amount G of the particulates that can be removed by oxidation taking into account the effects of all the above-described factors including the temperature TF of the particulate filter 22.

However, of these factors, the temperature TF of the particulate filter 22 has the largest influence on the amount G of particles that can be oxidized and removed, while the oxygen concentration and NO _x in the exhaust gas have a relatively large effect. Concentration. 7A shows a change in the temperature TF of the particulate filter 22 and a change in the amount G of the oxidizable particles when the oxygen in the exhaust gas changes. FIG. 7B shows the temperature TF of the particulate filter 22. and shows a change in amount G of the particulate removable by oxidation when the concentration of NO _x in the exhaust gas has changed. Incidentally, FIG. 7 (A), the dotted line in (B) shows the time the oxygen concentration and NO _x concentration in the exhaust gas is a reference value, in FIG. 7 (A) [O
₂ ] ₁ indicates the case where the oxygen concentration in the exhaust gas is higher than the reference value, and [O ₂ ] ₂ indicates the case where the oxidation concentration is higher than [O ₂ ] ₁ , respectively. In FIG. NO] ₁
When the high concentration of NO _x in the exhaust gas than the reference value,
[NO] ₂ indicates the case where the NO _x concentration is higher than [NO] ₁ .

When the oxygen concentration in the exhaust gas is increased, the amount G of fine particles that can be removed by oxidation alone increases, but the amount of oxygen taken into the active oxygen releasing agent 61 further increases. Active oxygen also increases. Therefore, as shown in FIG. 7 (A), the higher the oxygen concentration in the exhaust gas, the greater the amount G of particles that can be removed by oxidation. On the other hand, NO in the exhaust gas is oxidized on the surface of platinum Pt to NO ₂ as described above. Part of the NO ₂ thus generated is absorbed into the active oxygen releasing agent 61, and the remaining NO ₂ is released from the surface of the platinum Pt to the outside. At this time, when the fine particles come into contact with NO ₂ , the oxidation reaction is accelerated. Therefore, as shown in FIG. 7 (B), the higher the NO _x concentration in the exhaust gas, the larger the amount G of fine particles that can be oxidized and removed. However, the action of promoting the oxidation of the fine particles by NO ₂ occurs only when the exhaust gas temperature is between approximately 250 ° C. and approximately 450 ° C. Therefore, as shown in FIG. 7 (B), when the NO _x concentration in the exhaust gas increases. When the temperature TF of the particulate filter 22 is between approximately 250 ° C. and 450 ° C., the amount G of particles that can be removed by oxidation increases.

As described above, it is preferable to calculate the amount G of fine particles capable of being oxidized and removed in consideration of all factors affecting the amount G of fine particles oxidizable and removed. However, in the embodiment according to the present invention and the temperature TF of the particulate filter 22 that have the greatest effect on the amount G of the particulate removable by oxidation among these factors, only the oxygen concentration and NO _x concentration in the exhaust gas to provide a relatively large impact The amount G of fine particles that can be removed by oxidation is calculated based on the following equation.

That is, in the embodiment according to the present invention, as shown in FIGS. 8A to 8F, each temperature TF of the particulate filter 22 (200 ° C., 250 ° C., 300 ° C.)
℃, 350 ℃, 400 ℃, advance in the form of a map as a function of the NO _x concentration in the exhaust gas amount G of the particulate removable by oxidation with oxygen concentration in the respective exhaust gas [O _2] [NO] in 450 ° C.) ROM 32 And the amount of fine particles G that can be removed by oxidation in accordance with the temperature TF, the oxidation concentration [O ₂ ] and the NO _x concentration [NO] of each particulate filter 22.
Is calculated from the maps shown in FIGS. 8A to 8F by proportional distribution.

The oxygen concentration in the exhaust gas [O_Two ] And
And NO_x The concentration [NO] is determined by the oxygen concentration sensor and NO._x Dark
It can be detected using a degree sensor. However
In the embodiment according to the present invention, the oxygen concentration in the exhaust gas [O_Two ]
9 as a function of the required torque TQ and the engine speed N.
The information is previously stored in the ROM 32 in the form of a map as shown in FIG.
Remember, NO in exhaust gas_x Require concentration [NO]
FIG. 9B as a function of the torque TQ and the engine speed N.
Is stored in advance in the ROM 32 in the form of a map as shown in FIG.
From these maps, the oxygen concentration in the exhaust gas [O
_Two ] And NO _x The concentration [NO] is calculated.

On the other hand, the amount M of discharged fine particles depends on the model of the engine.
However, when the model of the engine is determined, the required torque TQ and
And a function of the engine speed N. FIG. 10A is shown in FIG.
Of the exhausted particulate matter M of the internal combustion engine,
M₁ , M_Two , M_Three , M_Four , M _Five Is the amount of fine particles discharged (M₁ 
<M_Two <M_Three <M_Four <M_Five ). FIG.
In the example shown in (A), as the required torque TQ increases,
The amount M of discharged fine particles increases. It should be noted that FIG.
Is the required torque TQ and the engine speed.
R as a function of N in the form of a map shown in FIG.
It is stored in the OM32.

As described above, according to the present invention, when the amount M of discharged fine particles can be made smaller than the amount G of fine particles capable of being oxidized and removed, except for a special operation state immediately after the start of the engine, the amount M of discharged fine particles can be reduced to the amount of fine particles oxidizable and removed. At least one of the discharged particle amount M and the oxidizable / removable particle amount G is controlled so as to be smaller than G, that is, so as to satisfy the relationship of the discharged particle amount M <the oxidizable / removable particle amount G.

More specifically, in the embodiment according to the present invention, when the amount M of discharged fine particles approaches the amount G of fine particles oxidizable and removed in order to satisfy the relationship of the amount M of discharged fine particles <the amount G of fine particles removable by oxidation, for example, The amount M is an allowable amount (G−
When α is larger than α), at least one of the discharged fine particle amount M and the oxidizable and removable fine particle amount G is controlled so that the difference between the discharged fine particle amount M and the oxidatively removable fine particle amount G is increased.

Next, an operation control method will be described with reference to FIG. Referring to FIG. 11, first, at step 100, the opening of the throttle valve 17 is controlled, and then, at step 101, the opening of the EGR control valve 25 is controlled. Next, at step 102, injection control from the fuel injection valve 6 is performed. Next, in step 103, FIG.
The amount M of discharged fine particles is calculated from the map shown in FIG. Next, at step 104, (A) to (F) of FIG.
Temperature TF of the particulate filter 22, the oxygen concentration [O _2] and concentration of NO _x [NO] amount G of the particulate removable by oxidation in accordance with the exhaust gas in the exhaust gas is calculated from the map shown in.

Next, at step 105, the amount M of discharged fine particles
It is determined whether or not a flag indicating that the value has become larger than an allowable value (G-α) smaller than the oxidizable / removable fine particle amount G by a certain value α. If the flag has not been set, the routine proceeds to step 106, where it is determined whether or not the amount M of discharged particulate is smaller than the allowable value (G-α). When M <G−α, that is, when the amount M of discharged fine particles is smaller than the allowable value (G−α), the processing cycle is completed. On the other hand, when it is determined in step 106 that M ≧ G−α, that is, when the amount M of discharged particulates is larger than the allowable value (G−α), step 107 is performed.
, The flag is set, and then the routine proceeds to step 108. When the flag is set, the process jumps from step 105 to step 108 in the subsequent processing cycle.

In step 108, the amount M of discharged fine particles is compared with a control release value (G-β) obtained by subtracting a constant value β from the amount G of fine particles removable by oxidation. Here, α and β are α <β
Therefore, the allowable value (G-α) and the control release value (G-β) are equal to the allowable value (G-α)> control release value (G−β).
β). When M ≧ G−β, that is, when the amount M of discharged particulate is larger than the control release value (G−β), the routine proceeds to step 109, where control is performed to continue the continuous oxidizing action of the particulate in the particulate filter 22. . That is, the amount M of discharged fine particles and the amount G of fine particles that can be removed by oxidation.
At least one of the amount M of discharged fine particles and the amount G of fine particles that can be oxidized and removed is controlled so that the difference between the two becomes greater.

Next, at step 108, M <G-β
Is determined, that is, when the amount M of discharged particulates becomes smaller than the control release value (G-β), the routine proceeds to step 110, where control is performed to gradually return to the original operating state, and the flag is reset. . Thus, the state of M <G is maintained. There are various ways of the continuous oxidation continuation control performed in step 109 of FIG. 11 and the return control performed in step 110 of FIG. 11. Therefore, the various methods of the continuous oxidation continuation control and the return control will be sequentially described.

One of the methods for increasing the difference between the amount M of discharged fine particles and the amount G of fine particles removable by oxidation when M ≧ (G−α) is to raise the temperature TF of the particulate filter 22. . Therefore, a method of increasing the temperature TF of the particulate filter 22 will be described first. One of the effective methods for increasing the temperature TF of the particulate filter 22 is to retard the fuel injection timing until after the compression top dead center. That is, normally the main fuel Q _m is injected near compression top dead center as shown in (I) in FIG. 12. In this case, the main injection timing of fuel Q _m is burning period becomes longer after the is retarded as shown in (II) of FIG. 12, the exhaust gas temperature rises in thus. As the exhaust gas temperature increases, the temperature TF of the particulate filter 22 increases accordingly, and as a result, the state of M <G is maintained.

The temperature of the particulate filter 22
As shown in (III) of FIG.
Sea urchin main fuel Q_m And auxiliary fuel near the intake top dead center
Fee Q _v Can also be injected. Thus, the auxiliary fuel Q
_v When additional fuel is injected, auxiliary fuel Q_v Let it burn for a minute
Exhaust gas temperature rises because more fuel is
The temperature TF of the particulate filter 22 rises.
You.

[0076] On the other hand, the heat of compression during the compression stroke to inject auxiliary fuel Q _v near this intake top dead center aldehyde from this auxiliary fuel Q _v, ketones, peroxides, intermediate products such as carbon monoxide generated by these intermediate products cause the reaction of the main fuel Q _m is accelerated. Therefore, in this case it is good combustion without causing a misfire even delaying the injection timing of the main fuel Q _m to greatly as shown in (III) of FIG. 12 is obtained. That is, the main fuel Q _m
Can be greatly delayed, so that the exhaust gas temperature becomes considerably high, and thus the temperature TF of the particulate filter 22 can be raised quickly.

[0077] In addition to the main fuel Q _m as shown in (IV) of FIG. 12 in order to raise the temperature TF of the particulate filter 22, to inject auxiliary fuel Q _p during the expansion stroke or the exhaust stroke You can also. That is, in this case,
Auxiliary fuel Q _p most is discharged into the exhaust passage in the form of unburned HC without being burned. The unburned HC is oxidized by excess oxygen on the particulate filter 22, and the temperature TF of the particulate filter 22 is increased by the heat of oxidation reaction generated at this time.

[0078] If it is determined that becomes M ≧ G-alpha in step 106 of FIG. 11 when so far in the example described, for example, the main fuel Q _m as shown in (I) in FIG. 12 is injected In step 109 of FIG.
Injection control is performed as shown in (II) or (III) or (IV). Next, in step 108 of FIG.
If it is determined that G-β has been reached, control is performed in step 110 to return to the injection method shown in FIG.

Next, a method of using low-temperature combustion to maintain M <G will be described. That is, it is known that when the EGR rate is increased, the amount of smoke generated gradually increases and reaches a peak, and when the EGR rate is further increased, the amount of smoke generated is rapidly reduced. This will be described with reference to FIG. 13 showing the relationship between the EGR rate and the smoke when the degree of cooling of the EGR gas is changed. In FIG. 13, a curve A shows a case where the EGR gas is cooled strongly and the EGR gas temperature is maintained at approximately 90 ° C., and a curve B shows a case where the EGR gas is cooled by a small cooling device. , Curve C shows the case where the EGR gas is not forcibly cooled.

As shown by the curve A in FIG. 13, when the EGR gas is cooled strongly, the amount of generated smoke reaches a peak at a point where the EGR rate is slightly lower than 50%. Above a percentage, there is almost no smoke. On the other hand, FIG.
When the EGR gas is slightly cooled as shown by the curve B of FIG. 3, the amount of smoke generation reaches a peak at a point where the EGR rate is slightly higher than 50%.
If the GR rate is set to about 65% or more, smoke is hardly generated. Further, when the EGR gas is not forcibly cooled as shown by a curve C in FIG. 13, the amount of smoke generation reaches a peak near the EGR rate of 55%, and in this case, the EGR rate becomes approximately 70%. Above a percentage, there is almost no smoke.

When the EGR gas rate is set to 55% or more, no smoke is generated because the endothermic effect of the EGR gas does not increase the temperature of the fuel and the surrounding gas during combustion, that is, the low temperature combustion is performed. As a result, hydrocarbons do not grow to soot. This low temperature combustion has the feature that it is possible to reduce the generation amount of the NO _x while suppressing the generation of smoke regardless of the air-fuel ratio. That is, when the air-fuel ratio is made rich, the fuel becomes excessive, but since the combustion temperature is suppressed to a low temperature, the excess fuel does not grow into soot, and thus no smoke is generated. Further, at this time NO _x even only an extremely small amount of generated. On the other hand, when the average air-fuel ratio is lean, or even when the air-fuel ratio is the stoichiometric air-fuel ratio, a small amount of soot is generated if the combustion temperature increases, but under low-temperature combustion, the combustion temperature is suppressed to a low temperature. There is no smoke at all,
NO _x is also not only an extremely small amount of generated.

On the other hand, when this low-temperature combustion is performed, the temperature of the fuel and the surrounding gas is lowered, but the temperature of the exhaust gas is raised. This will be described with reference to FIGS. The solid line in FIG. 14A shows the relationship between the average gas temperature Tg in the combustion chamber 5 and the crank angle when the low-temperature combustion is performed, and the broken line in FIG. 14A shows the normal combustion. 4 shows the relationship between the average gas temperature Tg in the combustion chamber 5 and the crank angle at the time of the combustion. Further, the solid line in FIG. 14B shows the relationship between the fuel and the surrounding gas temperature Tf and the crank angle when low-temperature combustion is performed, and the broken line in FIG. The graph shows the relationship between the crank angle and the temperature Tf of the fuel and the surrounding gas when the fuel is touched.

When the low-temperature combustion is being performed, the amount of EGR gas is larger than when the normal combustion is being performed. Therefore, as shown in FIG. In the middle, the average gas temperature Tg at the time of low temperature combustion indicated by the solid line is higher than the average gas temperature Tg at the time of normal combustion indicated by the broken line. At this time, FIG.
As shown in (B), the fuel and its surrounding gas temperature T
f is almost the same as the average gas temperature Tg. Next, combustion starts near the compression top dead center. In this case, when low-temperature combustion is being performed, the temperature of the fuel and its surrounding gas Tf does not increase so much as shown by the solid line in FIG. On the other hand, when normal combustion is performed, a large amount of oxygen exists around the fuel, so that the temperature of the fuel and its surrounding gas Tf becomes extremely high as shown by the broken line in FIG. 14B. . When normal combustion is performed in this manner, the temperature of the fuel and its surrounding gas Tf
Is considerably higher than when low temperature combustion is performed, but the temperature of most other gases is higher when normal combustion is performed than when low temperature combustion is performed. Therefore, as shown in FIG. 14 (A), the average gas temperature Tg in the combustion chamber 5 near the compression top dead center is lower than that in the case where low-temperature combustion is performed. It is higher than the case where there is. As a result, FIG.
As shown in (A), the temperature of the burned gas in the combustion chamber 5 after the completion of combustion is higher when low-temperature combustion is performed than when normal combustion is performed. When low-temperature combustion is performed, the exhaust gas temperature increases.

When the low-temperature combustion is performed as described above, the amount of smoke generated, that is, the amount M of discharged fine particles decreases, and the temperature of the exhaust gas increases. Therefore, when switching from normal combustion to low-temperature combustion when M ≧ G-α, the amount M of discharged particulates decreases, and the temperature TF of the particulate filter 22 increases, and the amount G of particulates that can be removed by oxidation increases. The state of M <G can be easily maintained. When this low-temperature combustion is used, M ≧ G in step 106 of FIG.
If it is determined that −α, it is switched to low-temperature combustion in step 109, and then in step 108, M <
If it is determined that G-β, the routine proceeds to step 110 to switch to normal combustion.

Next, another method for increasing the temperature TF of the particulate filter 22 to maintain the state of M <G will be described. FIG. 15 shows an internal combustion engine suitable for performing this method. Referring to FIG. 15, in this internal combustion engine, a hydrocarbon supply device 70 is disposed in an exhaust pipe 20. In this method, when it is determined in step 106 of FIG. 11 that M ≧ G−α, in step 109, the hydrocarbon supply device 70 sends the exhaust pipe 2
Hydrocarbon is supplied within zero. This hydrocarbon is oxidized by excess oxygen on the particulate filter 22, and the temperature TF of the particulate filter 22 is raised by the heat of the oxidation reaction at this time. Next, when it is determined in step 108 of FIG. 11 that M <G−β, the supply of hydrocarbons from the hydrocarbon supply device 70 is stopped in step 110. Note that the hydrocarbon supply device 70 may be arranged anywhere between the particulate filter 22 and the exhaust port 10.

Next, another method for increasing the temperature TF of the particulate filter 22 to maintain the state of M <G will be described. FIG. 16 shows an internal combustion engine suitable for performing this method. Referring to FIG. 16, in this internal combustion engine, the particulate filter 22
An exhaust control valve 73 driven by an actuator 72 is disposed in a downstream exhaust pipe 71.

In this method, when it is determined in step 106 of FIG. 11 that M ≧ G−α, the exhaust control valve 73 is almost fully closed in step 109 and the exhaust control valve 7
The amount of injection of the main fuel Q _m in order to prevent the decrease in the engine output torque due to 3 almost fully closed is made to increase. When the exhaust control valve 73 is almost fully closed,
The pressure in the upstream exhaust passage, that is, the back pressure, increases. When the back pressure increases, when the exhaust gas is discharged from the combustion chamber 5 into the exhaust port 10, the pressure of the exhaust gas does not decrease so much.
Therefore, the temperature does not decrease so much. Moreover the combustion chamber so that time and the amount of injection of the main fuel Q _m is made to increase 5
The temperature of the burned gas inside is high, so the exhaust port 1
The temperature of the exhaust gas discharged into zero becomes considerably higher. As a result, the temperature of the particulate filter 22 is rapidly increased.

Next, at step 108 in FIG.
<If it is determined to be G-beta exhaust control valve 73 is fully opened in step 110, increase the action of the injection quantity of the main fuel Q _m is stopped. Next, another method for increasing the temperature TF of the particulate filter 22 in order to maintain the state of M <G will be described. FIG. 17 shows an internal combustion engine suitable for performing this method.
Referring to FIG. 17, in this internal combustion engine, the exhaust turbine 21
Actuator 7 in exhaust bypass passage 74 bypassing the
A waste gate valve 76 controlled by the control unit 5 is disposed. The actuator 75 normally controls the opening of the waste gate valve 76 in response to the pressure in the surge tank 12, ie, the supercharging pressure, so that the supercharging pressure does not exceed a predetermined pressure.

In this method, if it is determined in step 106 of FIG. 11 that M ≧ G−α, in step 109, the waste gate valve 76 is fully opened.
The temperature of the exhaust gas decreases when passing through the exhaust turbine 21, but when the waste gate valve 76 is fully opened, most of the exhaust gas flows through the exhaust bypass passage 74, so that the temperature does not decrease. Thus, the particulate filter 22
Will rise in temperature. Next, when it is determined in step 108 of FIG. 11 that M <G-β, the waste gate valve 76 is closed in step 110, and the opening of the waste gate valve 76 is controlled so that the supercharging pressure does not exceed a predetermined pressure. Is controlled.

Next, a method of reducing the amount M of discharged fine particles in order to maintain the state of M <G will be described. In other words, the more the injected fuel and the air are sufficiently mixed, that is, the greater the amount of air around the injected fuel, the better the injected fuel is burned, so that no fine particles are generated. Therefore, in order to reduce the amount M of discharged fine particles, the injected fuel and the air need to be more sufficiently mixed. However, the amount of the NO _x increases since the combustion and to improve the mixing of the injected fuel and the air becomes active. Thus a method of reducing the amount M of discharged particulate may be said to method of increasing the generation amount of the NO _x In other words.

In any case, there are various methods for reducing the amount PM of discharged fine particles, and these methods will be sequentially described. The low-temperature combustion described above can be used as a method for reducing the amount PM of discharged particulates, but another effective method is a method for controlling fuel injection. For example, when the fuel injection amount is reduced, sufficient air exists around the injected fuel, and thus the amount M of discharged particulates decreases.

When the injection timing is advanced, sufficient air is present around the injected fuel, and the amount M of discharged particulates is reduced. Further, when the fuel pressure in the common rail 27, that is, the injection pressure is increased, the injected fuel is dispersed, so that the mixture of the injected fuel and the air becomes good, and thus the amount M of the discharged fine particles is reduced. The main fuel Q _m If _the are adapted to inject auxiliary fuel end of the compression stroke just before the injection of the main fuel Q to the oxygen is consumed by the combustion of the auxiliary fuel when doing so pilot injection Insufficient air around _m . Therefore, in this case, the amount M of discharged particulates is reduced by stopping the pilot injection.

That is, when the amount M of discharged particulates is reduced by controlling the fuel injection, if it is determined that M ≧ G−α in step 106 in FIG. Either the fuel injection timing is advanced, the fuel injection timing is advanced, or the injection pressure is increased, or the pilot injection is stopped, whereby the amount M of discharged particulates is reduced. Then FIG.
If it is determined in step 108 that M <G-β, the routine returns to the original fuel injection state in step 110.

Next, another method for reducing the amount M of discharged fine particles in order to maintain M <G will be described. In this method, when it is determined in step 106 of FIG. 11 that M ≧ G−α, the opening of the EGR control valve 25 is reduced in step 109 to reduce the EGR rate. When the EGR rate decreases, the amount of air around the injected fuel increases, and thus the amount M of discharged particulates decreases. Then Figure 1
If it is determined that M <G−β in Step 108 of Step 1, the EGR rate is increased to the original EGR rate in Step 110.

Next, another method for reducing the amount M of discharged fine particles in order to maintain M <G will be described. In this method, M ≧ G−α in step 106 of FIG.
Is determined in step 109, the opening of the waste gate valve 76 (FIG. 17) is reduced in order to increase the supercharging pressure. When the supercharging pressure increases, the amount of air around the injected fuel increases, and thus the amount M of discharged particulates decreases. Next, in step 108 of FIG. 11, M <G−
If it is determined to be β, in step 110, the supercharging pressure is returned to the original supercharging pressure.

Next, a method of increasing the oxygen concentration in the exhaust gas to maintain M <G will be described. When the oxygen concentration in the exhaust gas increases, the amount of fine particles G that can be removed by oxidation alone increases, but the amount of oxygen taken into the active oxygen releasing agent 61 further increases, so the amount of active oxygen released from the active oxygen releasing agent 61 Increases, and thus the amount G of fine particles that can be removed by oxidation increases.

As a method for executing this method, E
There is a method of controlling the GR rate. That is, if it is determined in step 106 of FIG. 11 that M ≧ G−α, in step 109 the EG is set so that the EGR rate decreases.
The opening of the R control valve 25 is reduced. The decrease in the EGR rate means that the proportion of the intake air amount in the intake air increases, and thus, when the EGR rate decreases, the oxygen concentration in the exhaust gas increases. As a result, the amount G of fine particles that can be removed by oxidation increases. Also, EGR
When the rate decreases, the amount M of discharged fine particles decreases as described above. Therefore, when the EGR rate decreases, the difference between the amount M of discharged fine particles and the amount G of fine particles that can be removed by oxidation rapidly increases. Next, when it is determined in step 108 of FIG. 11 that M <G−β, the EGR rate is changed to the original EG in step 110.
Returned to R rate.

Next, a method of using secondary air to increase the oxygen concentration in the exhaust gas will be described. In the example shown in FIG. 18, an exhaust pipe 77 between the exhaust turbine 21 and the particulate filter 22 is connected to the intake duct 13 via a secondary air supply conduit 78, and the secondary air supply conduit 78
The supply control valve 79 is arranged therein. In the example shown in FIG. 19, the secondary air supply conduit 78 is connected to the engine-driven air pump 8.
Connected to 0. The supply position of the secondary air into the exhaust passage may be anywhere between the particulate filter 22 and the exhaust port 10.

In the internal combustion engine shown in FIG. 18 or FIG. 19, if it is determined in step 106 of FIG. 11 that M ≧ G−α, the supply control valve 79 is opened in step 109. As a result, the secondary air is supplied from the secondary air supply conduit 78 to the exhaust pipe 77, and thus the oxygen concentration in the exhaust gas is increased. Next, when it is determined in step 108 of FIG. 11 that M <G−β, the supply control valve 79 is closed in step 110.

Next, the amount G of oxidation-removed fine particles oxidized per unit time on the particulate filter
An embodiment will be described in which G is sequentially calculated and at least one of the amount M of discharged fine particles or the amount GG of oxidation-removed fine particles is controlled so that the amount M of discharged fine particles is smaller than the calculated amount GG of oxidized fine particles. . As described above, when the fine particles adhere to the particulate filter 22, the fine particles are oxidized in a short time, but before the fine particles are completely oxidized and removed, other fine particles are sequentially oxidized and removed. Adheres to Therefore, in practice, a certain amount of fine particles is constantly deposited on the particulate filter 22, and some of the deposited fine particles are oxidized and removed. In this case, the fine particles G oxidized and removed per unit time
If G is the same as the amount M of discharged particulates, all the particulates in the exhaust gas are oxidized and removed on the particulate filter 22. However, when the amount M of discharged fine particles becomes larger than the amount GG of fine particles oxidized and removed per unit time, the amount of fine particles deposited on the particulate filter 22 gradually increases. I can't do it.

As described above, if the amount M of discharged fine particles is equal to or smaller than the amount GG of oxidation-removed fine particles, all the fine particles in the exhaust gas can be oxidized and removed on the particulate filter 22. Therefore, in this embodiment, the amount M of discharged fine particles and the amount G of fine particles
The temperature TF of the particulate filter 22, the amount M of discharged particulates, and the like are controlled so that G becomes M <GG.

Incidentally, the amount GG of the oxidation-removed fine particles can be expressed by the following equation. GG (g / sec) = C · EXP (−E / RT) · [P
M] ^l · ([O ₂ ] ^m + [NO] ⁿ ) where C is a constant, E is the activation energy, R is the gas constant,
T is the temperature TF of the particulate filter 22, [P
M] indicates the concentration (mol / cm ² ) of fine particles deposited on the particulate filter 22, [O ₂ ] indicates the oxygen concentration in the exhaust gas, and [NO] indicates the NO _x concentration in the exhaust gas.

Incidentally, the amount GG of the oxidation removal fine particles is actually
It is also a function of the unburned HC concentration in the exhaust gas, the degree of oxidization of the fine particles, the space velocity of the exhaust gas flow in the particulate filter 22, the exhaust gas pressure, etc., but these effects should not be considered here. And As can be seen from the above equation, the amount GG of oxidation-removed fine particles increases exponentially as the temperature TF of the particulate filter 22 increases.
Also, as the accumulation concentration of particulate matter [PM] increases, the amount of fine particles to be oxidized and removed increases, so that the amount GG of oxidation-removed fine particles increases as "PM" increases. Since the amount of fine particles deposited at the difficult positions increases, the rate of increase of the amount of oxidized and removed fine particles GG gradually decreases.
The relationship between [M] and [PM] ^l in the above equation is as shown in FIG.

On the other hand, if the oxygen concentration [O ₂ ] in the exhaust gas is increased, the amount of oxidized and removed fine particles GG alone increases as described above, but the amount of active oxygen released from the active oxygen releasing agent 61 further increases. . Thus the oxygen concentration [O _2] is increased when the oxidation removal amount of particulate GG in proportion to that of the exhaust gas is increased, thus to the concentration of oxygen in the exhaust gas [O _2]
FIG. 20B shows the relationship between the above equation and [O ₂ ] ^m in the above equation.

On the other hand, NO in the exhaust gas_x Concentration [NO]
When it becomes high, NO as described above_Two Increase the amount of
As a result, the amount GG of oxidation-removed fine particles increases. However, NO
From NO_Two As described above, the conversion to
It only occurs between 250 ° C and almost 450 ° C. Therefore
NO in exhaust gas_x Concentration [NO] and [NO] in the above equation ⁿ 
The relationship is that the exhaust gas temperature is approximately 250 ° C to 450 ° C.
In the meantime, the solid line [NO] in FIG.ⁿ ₁ Indicated by
As [NO] increases, [NO] ⁿ Increases
However, if the exhaust gas temperature is approximately 250 ° C. or less or approximately 450 ° C.
Above ° C, the solid line [NO] in FIG.ⁿ ₀ Indicated by
[NO] regardless of [NO] ⁿ ₀ Is almost zero
Become.

In this embodiment, the amount of oxidized and removed fine particles GG is calculated based on the above equation every time a predetermined time elapses. Assuming that the amount of the deposited fine particles at this time is PM (g), the fine particles corresponding to the amount GG of the oxygen-removed fine particles are removed from the fine particles, and the fine particles corresponding to the amount M of the discharged fine particles newly adhere to the particulate filter 22. I do. Therefore, the final deposition amount of fine particles is expressed by the following equation.

Next, an operation control method will be described with reference to FIG. Referring to FIG. 21, first, in step 200, the opening of the throttle valve 17 is controlled, and then, in step 201, the opening of the EGR control valve 25 is controlled. Next, at step 202, injection control from the fuel injection valve 6 is performed. Next, at step 103, the amount M of discharged particulates is calculated from the map shown in FIG. Next, at step 204, the amount G of oxidized and removed fine particles is calculated based on the following equation.
G is calculated.

GG = C.EXP (-E / RT). [P
M] ^l · ([O ₂ ] ^m + [NO] ⁿ ) Next, at step 205, the final particulate matter deposition amount PM is calculated based on the following equation. PM ← PM + M−GG Next, at step 206, an allowable value (GG−) in which the amount M of discharged fine particles is smaller than the amount GG of oxidation-removed fine particles by a certain value α.
It is determined whether or not a flag indicating that it has become larger than α) is set. If the flag has not been set, the routine proceeds to step 207, where it is determined whether or not the amount M of discharged particulate is smaller than the allowable value (GG-α). M
<GG-α, that is, the amount M of discharged particulates is an allowable value (GG-α
If smaller than α), the processing cycle is completed.

On the other hand, at step 207, M ≧
GG-α, that is, the amount M of discharged fine particles
Is larger than the allowable value (GG-α), the routine proceeds to step 208, where a flag is set, and then the routine proceeds to step 209. When the flag is set, the process jumps from step 206 to step 209 in the subsequent processing cycle.

In step 209, the amount M of discharged fine particles is compared with a control release value (GG-β) obtained by subtracting a fixed value β from the amount GG of oxidation-removed fine particles. Here, α and β have a relationship of α <β as described above, and therefore, the allowable value (GG−
α) and the control release value (GG-β) are allowable values (GG-α)
> Control release value (GG-β). M ≧ GG−
β, that is, the amount M of discharged particulates is equal to the control release value (GG-
If it is larger than β), the routine proceeds to step 210, in which the control for continuing the continuous oxidation action of the particulates in the particulate filter 22, that is, the control for increasing the temperature TF of the particulate filter 22 as described above, or Control for decreasing the amount M or control for increasing the oxygen concentration in the exhaust gas is performed.

Next, at step 209, M <GG-
If it is determined that β has been reached, that is, if the amount M of discharged fine particles is smaller than the control release value (GG−β), step 211 is performed.
Control to gradually return to the original operating state is performed,
The flag is reset. In the above-described embodiments, a carrier layer made of, for example, alumina is formed on both side surfaces of each partition wall 54 of the particulate filter 22 and on the inner wall surface of the pores in the partition wall 54. A catalyst and an active oxygen releasing agent are supported. In this case, particulates when the air-fuel ratio of the exhaust gas flowing into the filter 22 is lean absorbs NO _x contained in the exhaust gas particulate filter 22 on this carrier
Air-fuel ratio of the inflowing exhaust gas can be supported with _the NO _x absorbent to release the NO _x absorbed to become stoichiometric or rich.

In this case, as described above, platinum Pt is used as the noble metal, and as the NO _x absorbent, an alkali metal such as potassium K, sodium Na, lithium Li, cesium Cs, and rubidium Rb, barium Ba, and calcium Ca are used. At least one selected from alkaline earths such as strontium Sr and rare earths such as lanthanum La and yttrium Y is used. As can be seen from the comparison with the metal constituting the active oxygen releasing agent, the metal constituting the NO _x absorbent and the metal constituting the active oxygen releasing agent are almost the same.

In this case, different metals can be used as the NO _x absorbent and the active oxygen releasing agent, or the same metal can be used. NO in the case of using the same metal as the _x absorbent and the active oxygen release agent NO _x
Both functions as an absorbent and an active oxygen releasing agent are simultaneously performed. Then using platinum Pt as the precious metal catalyst, the described absorption and release action of the NO _x taking as an example the case of using potassium K as _the NO _x absorbent.

First, the NO _x absorbing effect will be examined. NO _x is absorbed by the NO _x absorbent by the same mechanism as shown in FIG. 4 (A). However, in this case, reference numeral 61 in FIG. 4A indicates a NO _x absorbent. That is, when the air-fuel ratio of the exhaust gas flowing into the particulate filter 22 is lean, a large amount of excess oxygen is contained in the exhaust gas, so that the exhaust gas flows into the exhaust gas inflow passage 50 of the particulate filter 22. As shown in FIG. 4 (A), these oxygens O ₂ adhere to the surface of platinum Pt in the form of O ₂ ⁻ or O ²⁻ . On the other hand, NO in the exhaust gas reacts with O ₂ ⁻ or O ²⁻ on the surface of the platinum Pt to become NO ₂ (2NO + O ₂ → 2NO ₂ ). Next, a part of the generated NO ₂ is oxidized on platinum Pt while N 2
O _x is absorbed into the absorbent 61, the nitrate ions NO ₃ as shown in FIG. 4 (A) while bonding with the potassium K ^- diffuses into _the NO _x absorbent 61 in the form of a portion of the nitrate ions NO
₃ ^- produces potassium nitrate KNO _3. In this way, NO is absorbed in the NO _x absorbent 61.

On the other hand, when the exhaust gas flowing into the particulate filter 22 becomes rich, nitrate ions NO ₃ ^- are decomposed into oxygen, O and NO, and NO is released from the NO _x absorbent 61 one after another. Therefore, when the air-fuel ratio of the exhaust gas flowing into the particulate filter 22 becomes rich, NO is released from the NO _x absorbent 61 in a short time, and since the released NO is reduced, NO is released into the atmosphere. It is not emitted.

In this case, NO is released from the NO _x absorbent 61 even if the air-fuel ratio of the exhaust gas flowing into the particulate filter 22 is set to the stoichiometric air-fuel ratio. However it takes some long time to release all NO _x absorbed in _the NO _x absorbent 61 to the NO from _the NO _x absorbent 61 are not only released gradually in this case. Meanwhile it can either be to use different metals as _the NO _x absorbent and the active oxygen release agent as described above, NO _x
The same metal can be used as the absorbent and the active oxygen releasing agent. Will be fulfill both functions of the function of the function and the active oxygen release agent as _the NO _x absorbent as described above at the same time in the case of using the same metal as _the NO _x absorbent and the active oxygen release agent, Such an agent which performs both functions at the same time is hereinafter referred to as an active oxygen releasing / NO _x absorbent. In this case, reference numeral 61 in FIG.
Indicates an active oxygen release / NO _x absorbent.

Such active oxygen release / NO _x absorbent 6
When using 1, fine air-fuel ratio of the exhaust gas flowing into the particulate filter 22 is NO, which at the time of lean contained in the exhaust gas is absorbed in the active oxygen release · NO _x absorbent 61, contained in the exhaust gas Is active oxygen release ・ N
When attached to the O _x absorbent 61, these fine particles are oxidized and removed within a short time by active oxygen release / active oxygen released from the NO _x absorbent 61. Thus both the particulates and NO _x in the exhaust gas at this time is able to be prevented from being discharged into the atmosphere.

On the other hand, when the air-fuel ratio of the exhaust gas flowing into the particulate filter 22 becomes rich, NO is released from the active oxygen release / NO _x absorbent 61. This NO is reduced by the unburned HC and CO, so that NO is not discharged to the atmosphere at this time. If fine particles are deposited on the particulate filter 22 at this time, these fine particles are removed by the active oxygen release / NO _x absorbent 6.
It is oxidized and removed by the active oxygen released from 1.

It should be noted that the NO _x absorbent or active oxygen release / N
Before absorption of NO _x capacity of the NO _x absorbent or the active oxygen release · _the NO _x absorbent is saturated when the O _x absorbent is used, NO from _the NO _x absorbent or the active oxygen release · _the NO _x absorbent Particulate filter 22 to release _x
The air-fuel ratio of the exhaust gas flowing into the air is temporarily made rich. That is, the air-fuel ratio is temporarily made rich occasionally when combustion is performed under the lean air-fuel ratio.

The present invention can be applied to a case where only a noble metal such as platinum Pt is supported on a carrier layer formed on both sides of the particulate filter 22. However, in this case, the solid line indicating the amount of fine particles G that can be removed by oxidation moves slightly to the right as compared with the solid line shown in FIG.
In this case, active oxygen is released from NO ₂ or SO ₃ held on the surface of platinum Pt.

Further, NO ₂ or S _{2 is} used as an active oxygen releasing agent.
O ₃ is adsorbed and held, and the adsorbed NO ₂ or SO ₃
A catalyst capable of releasing active oxygen from the catalyst may also be used.
The present invention is arranged an oxidation catalyst in the exhaust passage of the particulate filter upstream converts NO in the exhaust gas by the oxidation catalyst into NO _2, and particulate matter deposited in the NO ₂ and the particulate filter React this N
The present invention is also applicable to an exhaust gas purifying apparatus in which fine particles are oxidized by O ₂ .

[0122]

As described above, the fine particles in the exhaust gas can be continuously oxidized and removed on the particulate filter.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a required torque of an engine.

FIG. 3 is a diagram showing a particulate filter.

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

FIG. 5 is a diagram for explaining the action of depositing fine particles.

FIG. 6 is a graph showing the relationship between the amount of fine particles that can be removed by oxidation and the temperature of a particulate filter.

FIG. 7 is a diagram showing the amount of fine particles that can be removed by oxidation.

FIG. 8 is a diagram showing a map of the amount G of fine particles that can be removed by oxidation.

9 is a diagram showing a map of the oxygen concentration and NO _x concentration in the exhaust gas.

FIG. 10 is a diagram showing the amount of discharged fine particles.

FIG. 11 is a flowchart for controlling operation of the engine.

FIG. 12 is a diagram for explaining injection control.

FIG. 13 is a diagram showing the amount of smoke generated.

FIG. 14 is a diagram showing a gas temperature and the like in a combustion chamber.

FIG. 15 is an overall view showing another embodiment of the internal combustion engine.

FIG. 16 is an overall view showing still another embodiment of the internal combustion engine.

FIG. 17 is an overall view showing still another embodiment of the internal combustion engine.

FIG. 18 is an overall view showing still another embodiment of the internal combustion engine.

FIG. 19 is an overall view showing still another embodiment of the internal combustion engine.

FIG. 20 is a diagram showing a deposition concentration of fine particles and the like.

FIG. 21 is a flowchart for controlling operation of the engine.

[Explanation of symbols]

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

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01D 53/94 B01J 20/04 C 3G092 B01J 20/04 F01N 3/08 A 3G301 F01N 3/08 3/20 B 4D048 3/20 3/24 R 4D058 3/24 S 4G066 T 3/28 301C 3/28 301 F02B 37/00 302F F02B 37/00 302 F02D 9/04 E F02D 9/04 21/08 301H 21/08 301 311B 311 23/02 Z 23/02 41/38 A 41/38 B 41/40 D 41/40 F F02M 25/07 570J F02M 25/07 570 570D 570P B01D 53/36 103C (72) Inventor Nobuya Hirota 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Koichi Kimura Toyota, Toyota City, Aichi Prefecture 1 Toyota Motor Corporation (72) Inventor Koichiro Nakatani 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F term (reference) 3G005 DA02 EA16 FA35 GB28 GE09 HA05 HA12 HA13 HA18 HA19 JA03 JA05 JA39 JA45 3G062 AA01 AA05 BA04 BA05 EA10 ED08 GA05 GA06 GA09 GA15 GA17 3G065 AA00 AA01 AA03 AA09 CA12 DA06 GA04 GA08 GA10 GA14 GA46 3G090 AA03 CB18 CB25 DA13 DA18 EA04 EA05 EA06 3G091 AA02A18 AB01 A18 A18 A18 AB01 CA13 CA22 CB02 CB03 CB07 CB08 DA01 DA02 DB10 EA00 EA01 EA03 EA07 EA15 EA31 FB10 FB11 FB12 GA20 GA24 GB01X GB01Y GB02Y GB03Y GB04Y GB05W GB06W GB10X GB17X HA14 HA38 HB03 HB15 DCA AB12A03 DCA DG08 EA09 FA18 HB03Z HD01Z HE03Z HF08Z 3G301 HA01 HA02 HA04 HA11 HA13 JA24 LA08 LB04 LB11 LC04 MA11 MA18 MA19 MA23 NA08 NE17 NE19 PB08Z PD11Z PE03Z PF03Z 4D048 AA02 AA06 AA14 AB01 BA02X BAX BAX BAX BAX D01 CD05 EA04 4D058 JA32 JB06 MA44 MA54 SA08 4G066 AA13B AA16B AA21B AA27B AA72C BA07 CA28 CA37 DA02

Claims (41)

[Claims] 1. A particulate filter for removing particulates in exhaust gas discharged from a combustion chamber,
If the amount of particulates discharged from the combustion chamber per unit time is less than the amount of oxidizable particles that can be oxidized and removed without emitting a luminous flame per unit time on the particulate filter, the particulates in the exhaust gas will be particulate. When a particulate filter is used which can be oxidized and removed without emitting a bright flame when flowing into the filter, and the amount of the discharged fine particles is smaller than the amount of fine particles which can be removed by oxidation, the amount of the discharged fine particles is reduced when the engine is operating. An exhaust gas purifying method, wherein at least one of the amount of the discharged fine particles and the amount of the fine particles that can be removed by oxidation is controlled so as to be smaller than the possible fine particle amount. 2. The exhaust gas purification method according to claim 1, wherein a noble metal catalyst is supported on the particulate filter. 3. An active oxygen-releasing agent which takes in oxygen to retain oxygen when surrounding oxygen is present and releases the retained oxygen in the form of active oxygen when the concentration of oxygen in the surroundings decreases is placed on the particulate filter. 3. The method according to claim 2, wherein the active oxygen is released from the active oxygen releasing agent when the fine particles adhere to the particulate filter on the particulate filter, and the fine particles attached to the particulate filter are oxidized by the released active oxygen. Exhaust gas purification method. 4. The exhaust gas purifying method according to claim 3, wherein the active oxygen releasing agent comprises an alkali metal, an alkaline earth metal, a rare earth, or a transition metal. 5. The exhaust gas purification method according to claim 4, wherein the alkali metal and the alkaline earth metal are made of a metal having a higher ionization tendency than calcium. 6. The active oxygen releasing agent absorbs NO _x in the exhaust gas when the air-fuel ratio of the exhaust gas flowing into the particulate filter is lean, and reduces the air-fuel ratio of the exhaust gas flowing into the particulate filter to the stoichiometric air-fuel ratio. exhaust gas purification method according to claim 3 having a function of releasing NO _x absorbed to become fuel ratio or rich. 7. The exhaust gas purifying method according to claim 1, wherein the amount of the oxidizable and removable particles is a function of the temperature of the particulate filter. 8. oxidation particulate removable amount in addition to the temperature of the particulate filter, exhaust gas purification method according to claim 7, which is at least one function of the oxygen concentration or the concentration of NO _x in the exhaust gas. 9. The exhaust gas purifying method according to claim 7, wherein the amount of the particles capable of being oxidized and removed is stored at least as a function of the temperature of the particulate filter. 10. When the amount of the discharged fine particles and the amount of the fine particles that can be oxidized and removed are close to each other when the engine is in an operating state where the amount of the discharged fine particles can be made smaller than the amount of the fine particles that can be oxidized and removed, the amount of the discharged fine particles is reduced. Claims wherein at least one of the discharged fine particle amount and the oxidatively removable fine particle amount is controlled so as to be smaller than the oxidatively removable fine particle amount and to increase the difference between the discharged fine particle amount and the oxidatively removable fine particle amount. 1
The exhaust gas purification method according to any one of the above. 11. The exhaust gas purifying method according to claim 10, wherein the difference between the amount of the discharged fine particles and the amount of the fine particles that can be removed by oxidation is increased by raising the temperature of the particulate filter. 12. The exhaust gas purification method according to claim 10, wherein the difference between the amount of the discharged fine particles and the amount of the fine particles that can be removed by oxidation is increased by reducing the amount of the discharged fine particles. 13. The exhaust gas purifying method according to claim 10, wherein the difference between the amount of the discharged fine particles and the amount of the fine particles that can be removed by oxidation is increased by increasing the oxygen concentration in the exhaust gas. 14. A particulate filter for removing particulates in exhaust gas discharged from a combustion chamber, wherein the amount of particulates discharged from the combustion chamber per unit time shines on the particulate filter per unit time. When the amount of fine particles in the exhaust gas that can be oxidized and removed without emitting a flame is smaller than the amount of fine particles in the exhaust gas, when the fine particles in the exhaust gas flow into the particulate filter, the particulate filter can be oxidized and removed without emitting a bright flame. Calculating the amount of oxidized and removed fine particles that can be oxidized and removed without emitting a luminous flame per unit time in the operating state of the engine where the amount of the emitted fine particles can be made smaller than the amount of the oxidizable and removable fine particles. The amount of the discharged fine particles or the amount of the discharged fine particles is smaller than the amount of the oxidized and removed fine particles. An exhaust gas purifying method wherein at least one of the oxidizable and removable fine particles is controlled. 15. As a particulate filter for removing particulates in exhaust gas discharged from a combustion chamber, the amount of particulates discharged from the combustion chamber per unit time shines on the particulate filter per unit time. When the amount of the fine particles in the exhaust gas that can be oxidized and removed without emitting a flame is smaller than the amount of the fine particles in the exhaust gas, when the fine particles in the exhaust gas flow into the particulate filter, the fine particles in the exhaust gas are oxidized and removed without emitting a bright flame and the exhaust gas flowing into the particulate filter is reduced. with particulate filter air-fuel ratio with a function of when the lean releasing NO _x when the air-fuel ratio of the exhaust gas is absorbed and becomes the stoichiometric air-fuel ratio or rich flowing into the particulate filter to absorb NO _x in the exhaust gas, The amount of the discharged fine particles may be smaller than the amount of the fine particles that can be removed by oxidation. Exhaust gas purification method to control the at least one of the outlet quantity of particulate particulate discharge amount exhaust to be less than the oxidation particulate removable weight or oxidation of particulate removable amount when the operating condition of the function. 16. A particulate filter for removing particulates in exhaust gas exhausted from a combustion chamber is disposed in an engine exhaust passage, and the particulate filter is configured to emit exhaust gas discharged from the combustion chamber per unit time. If the amount of fine particles is smaller than the amount of oxidizable particles that can be oxidized and removed without emitting a bright flame per unit time on the particulate filter, the fine particles in the exhaust gas oxidize without emitting a bright flame when they flow into the particulate filter. A particulate filter to be removed is used, and when the engine is in an operating state where the amount of the discharged fine particles can be made smaller than the amount of the fine particles that can be removed by oxidation, the amount of the discharged fine particles is made smaller than the amount of the fine particles that can be removed by oxidation. Control means for controlling at least one of the amount of the fine particles and the amount of the fine particles removable by oxidation is provided. Exhaust gas purifier equipped. 17. The exhaust gas purifying apparatus according to claim 16, wherein a noble metal catalyst is supported on the particulate filter. 18. An active oxygen releasing agent that takes in oxygen to retain oxygen when surrounding oxygen is present and releases the retained oxygen in the form of active oxygen when the concentration of oxygen in the surroundings decreases, is placed on the particulate filter. 18. The carrier according to claim 17, wherein when the fine particles adhere to the particulate filter, the active oxygen is released from the active oxygen releasing agent when the fine particles adhere to the particulate filter, and the released fine particles oxidize the fine particles attached to the particulate filter. Exhaust gas purification equipment. 19. The exhaust gas purifying apparatus according to claim 18, wherein the active oxygen releasing agent comprises an alkali metal, an alkaline earth metal, a rare earth, or a transition metal. 20. The exhaust gas purifying apparatus according to claim 19, wherein the alkali metal and the alkaline earth metal are made of a metal having a higher ionization tendency than calcium. 21. When the air-fuel ratio of the exhaust gas flowing into the particulate filter is lean, the active oxygen releasing agent absorbs NO _x in the exhaust gas, and the air-fuel ratio of the exhaust gas flowing into the particulate filter becomes stoichiometric. exhaust gas purifying apparatus according to claim 18 having a function of releasing NO _x absorbed to become fuel ratio or rich. 22. The exhaust gas purifying apparatus according to claim 16, wherein the amount of the particulates that can be removed by oxidation is a function of the temperature of the particulate filter. 23. oxidation particulate removable amount in addition to the temperature of the particulate filter, exhaust gas purifying apparatus according to claim 22 which is at least one function of the oxygen concentration or the concentration of NO _x in the exhaust gas. 24. The exhaust gas purifying apparatus according to claim 22, further comprising storage means for storing in advance the amount of the particles capable of being oxidized and removed as a function of the temperature of the particulate filter. 25. The control means, when the amount of the discharged particulates and the amount of the oxidizable and removable particles are close to each other in an engine operating state where the amount of the discharged particulates can be made smaller than the amount of the oxidizable and removable particles. At least one of the amount of the discharged fine particles and the amount of the fine particles removable by oxidation is controlled so that the amount of the discharged fine particles is smaller than the amount of the fine particles removable by oxidation and the difference between the amount of the discharged fine particles and the amount of the fine particles removable by oxidation is increased. An exhaust gas purification device according to claim 16. 26. The control device according to claim 2, wherein the control unit increases the temperature of the particulate filter to increase the difference between the amount of the discharged fine particles and the amount of the fine particles removable by oxidation.
6. The exhaust gas purifying apparatus according to 5. 27. The exhaust gas according to claim 26, wherein the control means increases the temperature of the particulate filter by controlling at least one of the fuel injection amount and the fuel injection timing so that the exhaust gas temperature increases. Purification device. 28. The exhaust gas purifying apparatus according to claim 27, wherein the control means increases the exhaust gas temperature by delaying the injection timing of the main fuel or injecting auxiliary fuel in addition to the main fuel. 29. The engine comprises an engine in which the amount of generated soot gradually increases and reaches a peak as the amount of recirculated exhaust gas increases, and when the amount of recirculated exhaust gas further increases, almost no soot is generated. The control means increases the exhaust gas temperature by making the recirculated exhaust gas amount larger than the recirculated exhaust gas amount at which the generation amount of soot becomes a peak, thereby increasing the temperature of the particulate filter. The exhaust gas purifying apparatus according to claim 26, wherein: 30. A hydrocarbon supply device is arranged in an exhaust passage upstream of the particulate filter, and the temperature of the particulate filter is increased by supplying hydrocarbons from the hydrocarbon supply device into the exhaust passage. An exhaust gas purification device according to claim 26. 31. The exhaust gas purification apparatus according to claim 26, wherein an exhaust control valve is disposed in an exhaust passage downstream of the particulate filter, and the temperature of the particulate filter is increased by closing the exhaust control valve. apparatus. 32. An exhaust turbocharger having a wastegate valve for controlling an amount of exhaust gas bypassing an exhaust turbine, wherein the temperature of the particulate filter is increased by opening the wastegate valve. The exhaust gas purifying apparatus according to claim 26, wherein 33. The exhaust gas purifying apparatus according to claim 25, wherein the control means increases the difference between the amount of the discharged fine particles and the amount of the fine particles that can be oxidized and removed by reducing the amount of the discharged fine particles. 34. The exhaust gas purifying apparatus according to claim 33, wherein the control means controls the fuel injection amount, the fuel injection timing, the fuel injection pressure, or the injection of the auxiliary fuel such that the amount of the emitted fine particles decreases. 35. The exhaust gas purifying apparatus according to claim 33, further comprising a supercharging unit for supercharging the intake air, wherein the control unit reduces the amount of exhaust particulates by increasing a supercharging pressure. 36. An exhaust gas recirculation device for recirculating exhaust gas into an intake passage, wherein the control means comprises:
34. The exhaust gas purifying apparatus according to claim 33, wherein the amount of exhaust particulates is reduced by reducing an exhaust gas recirculation rate. 37. The exhaust gas purifying apparatus according to claim 25, wherein the control means increases the oxygen concentration in the exhaust gas to increase the difference between the amount of the discharged fine particles and the amount of the oxidizable and removable fine particles. 38. An exhaust gas recirculation device for recirculating exhaust gas into an intake passage, wherein the control means comprises:
38. The exhaust gas purifying apparatus according to claim 37, wherein the oxygen concentration in the exhaust gas is increased by decreasing the exhaust gas recirculation rate. 39. A secondary air supply device for supplying secondary air into an exhaust passage upstream of the particulate filter, wherein the control means supplies the secondary air into an exhaust passage upstream of the particulate filter. 38. The exhaust gas purifying apparatus according to claim 37, wherein the oxygen concentration in the exhaust gas is increased by doing so. 40. A particulate filter for removing particulates in exhaust gas discharged from a combustion chamber is disposed in an engine exhaust passage, and the particulate filter is configured to discharge particulate matter discharged from the combustion chamber per unit time. If the amount of fine particles is smaller than the amount of oxidizable particles that can be oxidized and removed without emitting a bright flame per unit time on the particulate filter, the fine particles in the exhaust gas oxidize without emitting a bright flame when they flow into the particulate filter. Calculating means for calculating the amount of oxidized fine particles which can be oxidized and removed per unit time on the particulate filter without emitting a luminous flame using the particulate filter to be removed; and When the operating condition of the engine can be reduced, An exhaust gas purifying apparatus comprising a control means for controlling at least one of the amount of the discharged fine particles and the amount of the fine particles capable of being oxidized and removed so that the amount of particles is smaller than the amount of the fine particles to be removed by oxidation. 41. A particulate filter for removing particulates in exhaust gas discharged from a combustion chamber is disposed in an engine exhaust passage, and the particulate filter is configured to discharge exhaust gas discharged from the combustion chamber per unit time. If the amount of fine particles is smaller than the amount of oxidizable particles that can be oxidized and removed without emitting a bright flame per unit time on the particulate filter, the fine particles in the exhaust gas oxidize without emitting a bright flame when they flow into the particulate filter. NO air-fuel ratio of the exhaust gas is absorbed and the air-fuel ratio of the exhaust gas flowing into the absorbing particulate filter NO _x in the exhaust gas becomes the stoichiometric air-fuel ratio or rich when the lean flowing into removal allowed provided and the particulate filter using a particulate filter having a function of emitting _x, exhaust When the engine is in an operating state in which the amount of fine particles can be made smaller than the amount of fine particles capable of being oxidized and removed, the amount of the discharged fine particles or the amount of fine particles that can be oxidized and removed is small so that the amount of fine particles discharged is smaller than the amount of fine particles that can be removed by oxidation. An exhaust gas purifying device comprising a control means for controlling one of them.