JP3525857B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification device for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, a particulate filter for collecting fine particles in exhaust gas discharged from a combustion chamber is arranged in an engine exhaust passage, and exhaust gas is exhausted when passing through a wall of the particulate filter. 2. Description of the Related Art There is known an exhaust emission control device for an internal combustion engine, which is designed to collect fine particles in gas. An example of this type of exhaust gas purification apparatus for an internal combustion engine is disclosed in Japanese Patent Publication No. 7-106290.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the exhaust gas purification device for an internal combustion engine described in Japanese Patent Publication No. 06290, the flow of exhaust gas passing through the particulate filter is not reversed. Therefore, the particulates collected on the wall of the particulate filter cannot be dispersed on one surface and the other surface of the wall of the particulate filter. As a result, when a certain amount or more of fine particles are collected on the wall of the particulate filter, the action of removing the fine particles cannot be sufficiently transmitted to all the fine particles. Therefore, in the exhaust gas purification device for an internal combustion engine described in Japanese Patent Application Laid-Open No. 7-106290, when the amount of fine particles flowing into the particulate filter exceeds a certain amount, all the fine particles fall on one of the walls of the particulate filter. As the particles are trapped on the surface, the particle removing action of the particulate filter cannot be sufficiently transmitted to all particles, and as a result, the particles are deposited on the wall of the particulate filter. Therefore, the particulate filter is clogged and the back pressure increases.

In view of the above problems, the present invention reverses the flow of exhaust gas passing through a particulate filter,
Oxidation and removal of the particulates trapped on the walls of the particulate filter Prevents particulates from accumulating on the walls of the particulate filter by sufficiently transmitting the oxidative removal action to all the particulates, and it is not oxidized and removed. In addition, it is possible to prevent the particulates temporarily collected in the particulate filter from being detached from the particulate filter and discharged as it is, and to prevent the back pressure from increasing more than necessary. An object of the present invention is to provide an exhaust gas purification device for an internal combustion engine.

[0005]

According to the invention described in claim 1 SUMMARY OF THE INVENTION, to place the particulate filter for trapping particulate in exhaust gas discharged from the combustion chamber to the engine exhaust passage, the Collected on the wall of the particulate filter
Acid for removing oxidized fine particles in a short time
The oxidant that emits oxygen is added to the wall of the particulate filter.
The particles on the wall of the particulate filter.
In parallel with collecting the collected fine particles,
Of the internal combustion engine that is oxidized and removed by the active oxygen released from
In the exhaust gas purification device, the particulate filter
Exhaust to reverse the flow of exhaust gases through the walls of
Equipped with gas backflow means, the activity released from the oxidant
Based on the amount of fine particles oxidized and removed by oxygen,
When the flow of exhaust gas is reversed by the gas-gas backflow means
An exhaust gas purification apparatus for an internal combustion engine that determines a period is provided.

[0006]

According to the second aspect of the present invention, an inflowing particulate amount estimating means for estimating the amount of particulates flowing into the particulate filter is provided, and the amount of particulates flowing into the particulate filter is removed by the oxidation. The exhaust gas purification device for an internal combustion engine according to claim 1, wherein the flow of the exhaust gas is reversed when the ratio of the amount of fine particles exceeds a predetermined value.

In the exhaust gas purifying apparatus for an internal combustion engine according to a second aspect of the present invention, when the ratio of the amount of fine particles that have been oxidized and removed to the amount of fine particles that have flowed into the particulate filter exceeds a predetermined value, that is, The exhaust gas flow is reversed when the purification rate exceeds the target purification rate. Therefore, it is possible to achieve the target purification rate of the fine particles while avoiding the fine particles being discharged as they are and increasing the back pressure more than necessary.

According to the third aspect of the present invention, the inflowing particulate amount estimating means for estimating the amount of particulates flowing into the particulate filter is provided, and the amount of particulates flowing into the particulate filter is oxidized and removed. The exhaust gas purification device for an internal combustion engine according to claim 1, wherein the flow of the exhaust gas is reversed during deceleration operation of the internal combustion engine after the ratio of the amount of fine particles exceeds a predetermined value.

In the exhaust gas purifying apparatus for an internal combustion engine according to a third aspect of the present invention, the deceleration of the internal combustion engine after the ratio of the amount of fine particles that have been oxidized and removed to the amount of fine particles that have flowed into the particulate filter exceeds a predetermined value. When driving, that is,
The exhaust gas flow is reversed when it is necessary to switch the exhaust gas backflow means to bypass the exhaust gas during deceleration operation of the internal combustion engine after the target purification rate of the particulates has been achieved. Therefore, it is possible to achieve the target purification rate of the fine particles while avoiding that the fine particles are discharged as they are and to increase the back pressure unnecessarily, and the exhaust gas backflow means is switched more frequently than necessary. Can be avoided.

According to the fourth aspect of the present invention, an inflowing particulate amount estimating means for estimating the amount of particulates that have flowed into the particulate filter is provided, and the amount of particulates that have flowed into the particulate filter and the oxide removed. The exhaust gas purification device for an internal combustion engine according to claim 1, wherein the flow of the exhaust gas is reversed when the difference from the amount of fine particles exceeds a predetermined value.

In the exhaust gas purifying apparatus for an internal combustion engine according to a fourth aspect of the present invention, when the difference between the amount of the particulates that have flowed into the particulate filter and the amount of the particulates that have been oxidized and removed exceeds a predetermined value, that is, the particulates. The flow of exhaust gas is reversed when the amount of particulates deposited on the curate filter exceeds a threshold value. Therefore, it is possible to prevent the particulates from being discharged as they are without being oxidized and removed and increasing the back pressure more than necessary before the amount of the particulates deposited on the particulate filter exceeds the threshold value. .

According to the fifth aspect of the present invention, an inflowing particulate amount estimating means for estimating the amount of particulates flowing into the particulate filter is provided, and the amount of particulates flowing into the particulate filter and the oxidized and removed. The exhaust gas purification device for an internal combustion engine according to claim 1, wherein the flow of the exhaust gas is reversed during deceleration operation of the internal combustion engine after the difference from the amount of fine particles exceeds a predetermined value.

According to another aspect of the exhaust gas purifying apparatus of the internal combustion engine of the present invention, the difference between the amount of fine particles flowing into the particulate filter and the amount of fine particles removed by oxidation exceeds a predetermined value. During deceleration operation, that is, after the amount of particulates deposited on the particulate filter exceeds the threshold value and it is necessary to switch the exhaust gas backflow means to bypass the exhaust gas during deceleration operation of the internal combustion engine. , The exhaust gas flow is reversed. Therefore, while avoiding that the particulates are discharged without being oxidized and removed and the back pressure is unnecessarily increased until the amount of particulates deposited on the particulate filter exceeds the threshold value, It is possible to avoid switching the gas backflow means more frequently than necessary.

According to a sixth aspect of the present invention, the exhaust gas flow is reversed when the amount of fine particles removed by oxidation exceeds a predetermined value. A purification device is provided.

According to another aspect of the exhaust gas purifying apparatus of the internal combustion engine of the present invention, when the amount of fine particles removed by oxidation exceeds a predetermined value, that is, the amount of fine particles removed by oxidation exceeds the target amount of fine particles removed by oxidation. When, the exhaust gas flow is reversed. Therefore, it is possible to achieve the target amount of fine particles for oxidation removal while avoiding that the fine particles are discharged as they are and increasing the back pressure more than necessary.

According to a seventh aspect of the present invention, the flow of exhaust gas is reversed during deceleration operation of the internal combustion engine after the amount of fine particles removed by oxidation exceeds a predetermined value. An exhaust gas purification device for an internal combustion engine according to item 1.

In the exhaust gas purifying apparatus for an internal combustion engine according to claim 7, during the deceleration operation of the internal combustion engine after the amount of fine particles which have been oxidized and removed exceeds a predetermined value, that is, the target amount of fine particles which are to be oxidized and removed. The flow of exhaust gas is reversed after the following has been achieved and the exhaust gas backflow means has to be switched to bypass the exhaust gas during deceleration operation of the internal combustion engine. Therefore, it is possible to achieve the target amount of fine particles for oxidation removal while avoiding that the fine particles are discharged as they are and to increase the back pressure unnecessarily, and the exhaust gas backflow means is switched more frequently than necessary. Can be avoided.

According to the invention described in claim 8, the internal combustion engine according to any one of claims 1 to 7, wherein the reverse of the flow of the exhaust gas is prohibited during the acceleration operation of the internal combustion engine. An exhaust emission control device for an engine is provided.

In the exhaust gas purification apparatus for the internal combustion engine according to the eighth aspect, it is prohibited to reverse the flow of the exhaust gas during the acceleration operation of the internal combustion engine. Therefore, as the flow of the exhaust gas is reversed during the acceleration operation of the internal combustion engine where the amount of exhaust gas is relatively large, the fine particles before being oxidized and removed are temporarily collected by the particulate filter. It is possible to prevent the fine particles contained in the particulate filter from being detached from the particulate filter and directly discharged.

According to a ninth aspect of the present invention, the exhaust gas backflow means has a bypass mode in which the exhaust gas is bypassed without flowing into the particulate filter, and the particulate filter is provided. The exhaust gas backflow means is prohibited from being placed in the bypass mode when the temperature raising control for raising the temperature of the curate filter is being performed.
An exhaust gas purification apparatus for an internal combustion engine according to any one of 7) is provided.

In the exhaust gas purification device for the internal combustion engine according to the ninth aspect, it is prohibited that the exhaust gas backflow means is placed in the bypass mode when the temperature raising control for raising the temperature of the particulate filter is being performed. To be done. Therefore, even though the exhaust gas temperature rise control of the internal combustion engine is being executed in an attempt to raise the temperature of the particulate filter, the exhaust gas that has been raised in temperature bypasses the particulate filter and rises in the particulate filter. It is possible to avoid becoming unable to heat.

According to the tenth aspect of the present invention, as the particulate filter, the amount of particulates discharged from the combustion chamber per unit time is oxidized on the particulate filter without emitting a luminous flame per unit time. When the amount of fine particles that can be removed by oxidation is smaller than the amount of fine particles that can be removed by oxidation, as soon as the fine particles in the exhaust gas flow into the particulate filter, they are oxidized and removed in a short time without emitting a bright flame, and the amount of the discharged fine particles is temporary. When the amount of particulates deposited on the particulate filter is less than a certain limit even when the amount of particulates that can be oxidized and removed becomes larger than the amount of particulates that are discharged, when the amount of particulates that is discharged becomes less than the amount of particulates that can be oxidized and removed Putty where fine particles can be oxidized and removed without emitting a luminous flame Using a particulate filter, the amount of fine particles that can be oxidized and removed depends on the temperature of the particulate filter, the amount of fine particles that are discharged is usually smaller than the amount of fine particles that can be oxidized and removed, and the amount of discharged fine particles is temporarily Even if the amount of fine particles that can be removed by oxidation becomes larger than the amount of fine particles that can be removed by oxidation, the amount of fine particles below a certain limit that can be oxidized and removed can be deposited on the particulate filter when the amount of fine particles that are discharged becomes smaller than the amount of fine particles that can be removed by oxidation. A control means for maintaining the amount of the discharged particulates and the temperature of the particulate filter is provided, whereby the particulates in the exhaust gas can be oxidatively removed on the particulate filter without emitting a bright flame. An exhaust gas purification apparatus for an internal combustion engine according to any one of 9 above is provided.

In the exhaust gas purifying apparatus for an internal combustion engine according to the tenth aspect, it is assumed that the amount of discharged fine particles is usually smaller than the amount of fine particles that can be removed by oxidation, and the amount of discharged fine particles temporarily becomes larger than the amount of fine particles that can be removed by oxidation. After that, when the amount of discharged particulate becomes less than the amount of particulate that can be removed by oxidation, the amount of particulate discharged and the temperature of the particulate filter are maintained so that only a certain amount of particulate that can be oxidized and removed will deposit on the particulate filter. As a result, the fine particles in the exhaust gas can be oxidized and removed without producing a bright flame on the particulate filter.
Therefore, unlike the conventional case, it is not necessary to remove the particles by emitting a bright flame after the particles are deposited in a laminated form on the particulate filter, and the particles are deposited before the particles are deposited in a laminated form on the particulate filter. By oxidizing, the fine particles in the exhaust gas can be removed.

According to the invention as set forth in claim 11, the amount of the discharged fine particles is usually smaller than the amount of the oxidatively removable fine particles, and the discharged fine particle amount is temporarily larger than the oxidatively removable fine particle amount. Even so, when the amount of the discharged fine particles becomes less than the amount of the fine particles capable of being oxidized and removed, only the amount of fine particles of a certain limit or less that can be oxidized and removed is deposited on the particulate filter so that the fine particle amount and the particulate filter are discharged. An exhaust gas purifying apparatus for an internal combustion engine according to claim 10, wherein the operating conditions of the internal combustion engine are controlled to maintain the temperature.

In the exhaust gas purifying apparatus for an internal combustion engine according to claim 11, it is assumed that the amount of discharged fine particles is usually smaller than the amount of fine particles that can be removed by oxidation, and the amount of discharged fine particles temporarily becomes larger than the amount of fine particles that can be removed by oxidation. Also, maintain the temperature of the discharged particulate amount and the particulate filter so that when the amount of discharged particulate becomes less than the amount of particulate that can be removed by oxidation, only a certain amount of particulate that can be oxidized and removed will deposit on the particulate filter. Therefore, the operating conditions of the internal combustion engine are controlled. Specifically, the amount of discharged fine particles becomes smaller than the amount of fine particles that can be removed by oxidation, or even if the amount of discharged fine particles temporarily exceeds the amount of fine particles that can be removed by oxidation, the amount of fine particles that are discharged thereafter becomes the amount of fine particles that can be removed by oxidation. The operating conditions of the internal combustion engine are controlled on the basis of the amount of discharged particulates and the temperature of the particulate filter so that when the amount becomes smaller, only a certain amount of particulates that can be oxidized and removed are deposited on the particulate filter. Therefore, the operating conditions of the internal combustion engine, operating conditions in which the amount of discharged particulate is less than the amount of particulates that can be removed by oxidation,
Alternatively, even if the amount of discharged fine particles temporarily exceeds the amount of fine particles that can be removed by oxidation, when the amount of discharged fine particles becomes smaller than the amount of fine particles that can be removed by oxidation, only particulates below a certain limit that can be oxidized and removed can be particulated. Unlike when accidentally meeting operating conditions that do not deposit on the filter, make sure that the amount of particulates discharged is less than the amount of particulates that can be removed by oxidation, or that the amount of particulates that are discharged temporarily exceeds the amount of particulates that can be removed by oxidation. Even if the discharged particulate amount becomes smaller than the oxidizable / removable particulate amount thereafter, only a certain amount or less of the particulate that can be oxidatively removed can be deposited on the particulate filter. Therefore, as compared with the case where the operating conditions of the internal combustion engine coincidentally, the fine particles can be more reliably oxidized before they are accumulated in a laminated state on the particulate filter.

According to the twelfth aspect of the present invention, the oxidant takes in oxygen to retain oxygen when excess oxygen exists in the surroundings, and when the oxygen concentration in the surroundings decreases, the retained oxygen is converted into active oxygen. An exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 11, which is an oxygen storage / active oxygen release agent that is released in a form.

In the exhaust gas purifying apparatus for an internal combustion engine according to the twelfth aspect, the oxygen storage / active oxygen releasing agent carried by the particulate filter absorbs and retains oxygen when excess oxygen exists in the surroundings. When the ambient oxygen concentration decreases, the retained oxygen is released in the form of active oxygen. Therefore, unlike the conventional case where the particles are removed by emitting a luminous flame after being deposited in a laminated form on the particulate filter, before the particles are deposited in a laminated form on the particulate filter. The active oxygen released by the oxygen storage / active oxygen release agent can oxidize and remove the fine particles without emitting a bright flame.

According to the thirteenth aspect of the present invention, the backflow means comprises a forward flow mode in which exhaust gas passes through the wall of the particulate filter in the first direction, and exhaust gas passes through the wall of the particulate filter in the first direction. It has a backflow mode that passes in a second direction opposite to the one direction, and as the amount of inert gas supplied to the combustion chamber is increased, the amount of soot generated gradually increases and peaks. And the amount of the inert gas supplied to the combustion chamber is further increased, the temperature of the fuel and the gas around it during combustion in the combustion chamber becomes lower than the soot generation temperature, and soot is almost generated. Using an internal combustion engine that does not turn off, in the forward flow mode of the backflow means, the combustion is performed in which the amount of the inert gas supplied to the combustion chamber is less than the amount of the inert gas at which the amount of soot is peaked, Of reflux means The combustion in which the soot generation amount is greater than the inert gas amount at which the soot generation peaks and the soot generation hardly occurs in the flow mode. An exhaust gas purification apparatus for an internal combustion engine according to any one of the above is provided.

In the exhaust gas purifying apparatus for an internal combustion engine according to a thirteenth aspect, in the forward flow mode of the back flow means, the amount of the inert gas supplied to the combustion chamber is larger than the amount of the inert gas at which the amount of soot is peaked. In the reverse flow mode of the reverse flow means, the amount of soot generated is higher than the amount of inert gas that reaches the peak, and the amount of inert gas supplied to the combustion chamber is larger and soot is hardly generated. To be done. In other words, because the amount of inert gas supplied to the combustion chamber is greater than the amount of inert gas at which the amount of soot is peaked and combustion is performed with almost no soot, it is included in the exhaust gas at that time. The action of removing HC of the fine particles can be promoted by the contained HC and CO. Further, the exhaust gas is caused to flow backward when the combustion is performed in which the amount of the inert gas supplied to the combustion chamber is larger than the amount of the inert gas at which the soot generation amount reaches the peak, and the soot is hardly generated. Therefore, fine particles are deposited on one surface of the particulate filter when the combustion is performed in which the amount of the inert gas supplied to the combustion chamber is smaller than the amount of the inert gas in which the generation amount of soot becomes the peak, Even if the catalyst on the surface of the particulate filter has been poisoned with sulfur, HC, CO-containing exhaust gas flowing from the surface on the opposite side of the particulate filter and passing through the inside of the wall of the particulate filter causes Fine particles deposited on one surface of the particulate filter can be removed by oxidation without being affected by sulfur poisoning.

According to the fourteenth aspect of the present invention, the oxidizer is carried inside the wall of the particulate filter, and the flow of exhaust gas passing through the wall of the particulate filter is reversed. The exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 13, wherein the particulates temporarily collected are moved inside the wall of the particulate filter.

In the exhaust gas purifying apparatus for the internal combustion engine according to the fourteenth aspect, since the oxidizing agent is carried inside the wall of the particulate filter, the oxidizing agent inside the wall of the particulate filter causes the wall of the particulate filter to fall. The particulates inside the can be oxidized and removed inside the wall of the particulate filter. Furthermore, in the exhaust gas purification device for an internal combustion engine according to claim 14, by reversing the flow of the exhaust gas passing through the wall of the particulate filter, the particulates temporarily collected inside the wall of the particulate filter are collected. Can be moved. Therefore, the oxidant removing action of oxidizing and removing fine particles inside the wall of the particulate filter by the oxidizing agent inside the wall of the particulate filter moves the fine particles temporarily trapped inside the wall of the particulate filter. Can be promoted by

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a first embodiment in which the exhaust purification system for an internal combustion engine of 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, and 9 is an intake port. Indicates an exhaust valve, and 10 indicates an exhaust port, respectively. 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 arranged in the intake duct 13, and a cooling device 18 for cooling intake air flowing in the intake duct 13 is arranged around the intake duct 13. 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 the exhaust manifold 1
9 and the exhaust pipe 20 are connected to the exhaust turbine 21 of the exhaust turbocharger 14, and the outlet of the exhaust turbine 21 is connected to a casing 23 containing a particulate filter 22.

The particulate filter 22 is constructed so as to allow the exhaust gas to flow in both forward and backward directions. Reference numeral 71 denotes a first passage which serves as an upstream passage of the particulate filter 22 when the exhaust gas passes through the particulate filter 22 in the forward flow direction, and 72 denotes particulate when the exhaust gas passes through the particulate filter 22 in the reverse flow direction. The second passage serves as an upstream passage of the filter 22. Reference numeral 73 is an exhaust switching valve for switching the flow of exhaust gas between a forward flow direction, a reverse flow direction, and a bypass state, and 74 is an exhaust switching valve drive device.

The exhaust manifold 19 and the surge tank 12 are connected to each other via an exhaust gas recirculation (hereinafter referred to as EGR) passage 24, and an electric control type EGR control valve 25 is arranged in the EGR passage 24. In addition, the EGR passage 24
A cooling device 26 for cooling the EGR gas flowing in the EGR passage 24 is arranged around the device. 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 26. Into the common rail 27, an electrically controlled fuel pump 28 having a variable discharge amount is provided.
The fuel is supplied from the fuel injection valve 6, and the fuel supplied into the common rail 27 is supplied to the fuel injection valve 6 via each fuel supply pipe 26. A fuel pressure sensor 29 for detecting the fuel pressure in the common rail 27 is attached to the common rail 27, and the common rail 27 is detected based on the output signal of the fuel pressure sensor 29.
The discharge amount of the fuel pump 28 is controlled so that the internal fuel pressure becomes the target fuel pressure.

The electronic control unit 30 is composed of a digital computer, and has a ROM (read only memory) 32, a RAM (random access memory) 33, a CPU (microprocessor) 34, an input port 35, and an input port 35, which are connected to each other by a bidirectional bus 31. An output port 36 is provided. The output signal of the fuel pressure sensor 29 is input to the input port 35 via the corresponding AD converter 37. Further, a temperature sensor 39 for detecting the temperature of the particulate filter 22 is attached inside the casing 23, and the output signal of this temperature sensor 39 is input to the input port 35 via the corresponding AD converter 37. Accelerator pedal 40
A load sensor 41 that generates an output voltage proportional to the depression amount L of the accelerator pedal 40 is connected to the load sensor 4
The output voltage of 1 is input to the input port 35 via the corresponding AD converter 37. Further, the input port 35 is connected to a crank angle sensor 42 that generates an output pulse each time the crankshaft rotates, for example, 30 °. On the other hand, the output port 36 is connected to the fuel injection valve 6, the throttle valve driving step motor 16, the EGR control valve 25, the fuel pump 28, and the exhaust switching valve drive device 74 via the corresponding drive circuit 38.

FIG. 2 shows the structure of the particulate filter 22. In FIG. 2, (A) shows a front view of the particulate filter 22, and (B) shows a side sectional view of the particulate filter 22. Figure 2
As shown in (A) and (B), the particulate filter 22 has a honeycomb structure and is provided with a plurality of exhaust flow passages 50, 51 extending in parallel with each other. These exhaust flow passages are composed of an exhaust gas inflow passage 50 whose downstream end is closed by a plug 52 and an exhaust gas outflow passage 51 whose upstream end is closed by a plug 53. Note that the hatched portion in FIG.
3 is shown. Therefore, the exhaust gas inflow passages 50 and the exhaust gas outflow passages 51 are alternately arranged via the thin partition walls 54. In other words, in the exhaust gas inflow passage 50 and the exhaust gas outflow passage 51, each exhaust gas inflow passage 50 is surrounded by four exhaust gas outflow passages 51, and each exhaust gas outflow passage 51 is surrounded by four exhaust gas inflow passages 50. Are arranged as follows. The particulate filter 22 is formed of, for example, a porous material such as cordierite, and therefore the exhaust gas that has flowed into the exhaust gas inflow passage 50 is inside the surrounding partition wall 54 as indicated by the arrow in FIG. And flows out into the adjacent exhaust gas outflow passage 51.

In the embodiment according to the present invention, the peripheral wall surfaces of each exhaust gas inflow passage 50 and each exhaust gas outflow passage 51, that is, both side surfaces of each partition wall 54, the outer end surface of the plug 53, and the plugs 52, 5 are provided.
A layer of a carrier made of, for example, alumina is formed over the entire inner end surface of No. 3, and the noble metal catalyst and oxygen in the surroundings absorb oxygen to retain oxygen on the carrier. Moreover, since the oxygen storage / active oxygen release agent that releases the retained oxygen in the form of active oxygen when the ambient oxygen concentration decreases, oxidizes the fine particles temporarily collected on the surface of the partition wall 54 of the particulate filter. It is supported as an oxidation catalyst.

In this case, platinum Pt is used as the noble metal catalyst in the embodiment of the present invention, and an alkali metal such as potassium K, sodium Na, lithium Li, cesium Cs, or rubidium Rb is used as the oxygen storage / active oxygen releasing agent. At least one selected from alkaline earth metals such as barium Ba, calcium Ca, and strontium Sr, rare earths such as lanthanum La, and yttrium Y, and transition metals is used. In this case, as the oxygen storage / active oxygen releasing agent, use is made of an alkali metal or alkaline earth metal having a higher ionization tendency than calcium Ca, that is, potassium K, lithium Li, cesium Cs, rubidium Rb, barium Ba, strontium Sr. Is preferred.

Next, regarding the action of removing particulates in the exhaust gas by the particulate filter 22, platinum Pt is deposited on the carrier.
The case of supporting potassium K and potassium will be described as an example, but the same fine particle removing action can be achieved by using other noble metals, alkali metals, alkaline earth metals, rare earths, and transition metals. In a compression ignition type internal combustion engine as shown in FIG. 1, combustion is performed under an excess of air, so that the exhaust gas contains a large amount of excess air. That is, when the ratio of air and fuel supplied into the intake passage and the combustion chamber 5 is called the air-fuel ratio of exhaust gas, the air-fuel ratio of exhaust gas becomes lean in a compression ignition type internal combustion engine as shown in FIG. ing. Further, NO is generated in the combustion chamber 5, so the exhaust gas contains NO. Further, the fuel contains sulfur S, and this sulfur S reacts with oxygen in the combustion chamber 5 to become SO ₂ .
Therefore, the exhaust gas contains SO ₂ . Therefore, the exhaust gas containing excess oxygen, NO and SO ₂ flows into the exhaust gas inflow passage 50 of the particulate filter 22.

FIGS. 3A and 3B show the exhaust gas inflow passage.
50 is an enlarged view of the surface of the carrier layer formed on the inner peripheral surface of 50.
It is expressed as a formula. In addition, in FIG. 3 (A) and (B)
Reference numeral 60 indicates platinum Pt particles, and 61 indicates Kaliu.
It shows an oxygen storage / active oxygen release agent containing Mu K
It As described above, the exhaust gas contains a large amount of excess oxygen.
Because it is rare, the exhaust gas is particulate filter 2
When it flows into the exhaust gas inflow passage 50 of No. 2, as shown in FIG.
As shown, these oxygen O₂Is O₂ ^-Or O ^2-In the form of
Adheres to the surface of platinum Pt. On the other hand, NO in the exhaust gas
O on the surface of platinum Pt₂ ^-Or O^2-Reacts with NO₂When
Naru (2NO + O₂→ 2 NO₂). Then generated N
O₂Oxygen storage / activity while some of the oxygen is oxidized on platinum Pt
It is absorbed in the oxygen release agent 61 and does not bind to potassium K.
As shown in FIG. 3 (A), nitrate ion NO₃ ^-Form of
Diffuses into the oxygen storage / active oxygen release agent 61 at
Umm KNO₃To generate.

On the other hand, as described above, SO is contained in the exhaust gas.
₂Also included, this SO₂The same mechanism as NO
Is absorbed by the oxygen storage / active oxygen release agent 61
It That is, as described above, oxygen O₂Is O₂ ^-Or O^2-of
Adheres to the surface of platinum Pt in the form of
₂Is O on the surface of platinum Pt₂ ^-Or O^2-Reacts with SO ₃
Becomes SO generated next₃Part of Pt on Pt
While being further oxidized, it is absorbed in the oxygen storage / active oxygen release agent 61.
Sulfate ion SO is collected and bound with potassium K_Four ^2-
In the form of oxygen storage / active oxygen release agent 61 diffuses into sulfuric acid
Potassium K₂SO_FourTo generate. In this way oxygen absorption
KNO 3 in the storage / active oxygen release catalyst 61₃
And potassium sulfate K₂SO_FourIs generated.

On the other hand, in the combustion chamber 5, fine particles mainly composed of carbon C are produced, so that the exhaust gas contains these fine particles. The particulates contained in the exhaust gas are exhaust gas particulate filter 2
2 is flowing in the exhaust gas inflow passage 50, or when the exhaust gas inflow passage 50 is moving from the exhaust gas inflow passage 50 to the exhaust gas outflow passage 51, as shown by 62 in FIG. It comes into contact with and adheres to the surface of the storage / active oxygen release agent 61.

When the fine particles 62 adhere to the surface of the oxygen storage / active oxygen release agent 61 in this way, the oxygen concentration decreases at the contact surface between the fine particles 62 and the oxygen storage / active oxygen release agent 61. Oxygen storage with high oxygen concentration when the oxygen concentration decreases
A concentration difference occurs between the active oxygen releasing agent 61 and the oxygen in the oxygen storage / active oxygen releasing agent 61 will move toward the contact surface between the fine particles 62 and the oxygen storage / active oxygen releasing agent 61. And As a result, the oxygen storage / active oxygen release agent 6
The potassium nitrate KNO ₃ formed in 1 is decomposed into potassium K, oxygen O and NO, and the oxygen O moves toward the contact surface between the fine particles 62 and the oxygen storage / active oxygen release agent 61, and N
O is released from the oxygen storage / active oxygen release agent 61 to the outside. The NO released to the outside is oxidized on the platinum Pt on the downstream side and is again absorbed in the oxygen storage / active oxygen release agent 61.

On the other hand, at this time, an oxygen storage / active oxygen release agent
Potassium sulfate K formed in 61₂SO_FourMokari
Um K and oxygen O and SO₂Oxygen O is finely divided into
62 toward the contact surface between the oxygen storage / active oxygen release agent 61
Yes, SO₂From the oxygen storage / active oxygen release agent 61 to the outside
Is released. SO released to the outside₂Is the platinum P on the downstream side
Oxidized on t and again oxygen storage / active oxygen release agent
It is absorbed in 61. However, potassium sulfate K₂SO_Four
Is stabilized with potassium nitrate KNO ₃compared to
It is difficult to release active oxygen.

On the other hand, oxygen O toward the contact surface between the fine particles 62 and the oxygen storage / active oxygen release agent 61 is potassium nitrate KN.
Oxygen decomposed from compounds such as O ₃ . Oxygen O decomposed from the compound has high energy and has extremely high activity. Therefore, the fine particles 62 and oxygen storage
Oxygen toward the contact surface with the active oxygen release agent 61 is active oxygen O. When these active oxygen O come into contact with the fine particles 62, the fine particles 62 are immediately oxidized without emitting a bright flame, and the fine particles 62 disappear completely. Therefore, the fine particles 62 do not deposit on the particulate filter 22.

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

On the other hand, in the present invention, the fine particles 62 are oxidized without emitting a luminous flame as described above, and at this time, the surface of the particulate filter 22 does not become red hot. In other words, in other words, in the present invention, the fine particles 62 are oxidized and removed at a much lower temperature than in the conventional case. Therefore, the fine particles 6 which do not emit bright flame according to the present invention
The function of removing fine particles by the oxidation of No. 2 is completely different from the function of removing fine particles by the conventional combustion accompanied by a flame.

By the way, since the platinum Pt and the oxygen storage / active oxygen release agent 61 are activated as the temperature of the particulate filter 22 becomes higher, the amount of active oxygen O which can be released by the oxygen storage / active oxygen release agent 61 per unit time. Increases as the temperature of the particulate filter 22 increases. Therefore, the amount of oxidatively removable fine particles that can be oxidatively 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. 5 shows the amount G of oxidatively removable fine particles that can be oxidatively removed per unit time without emitting a luminous flame. In FIG. 5, the horizontal axis indicates the temperature TF of the particulate filter 22. The amount of fine particles discharged from the combustion chamber 5 per unit time is referred to as the discharged fine particle amount M. When the discharged fine particle amount M is smaller than the oxidatively removable fine particles G, that is, in the region I of FIG. As soon as all the particles thus made come into contact with the particulate filter 22, they are oxidized and removed on the particulate filter 22 in a short time without emitting a bright flame.

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

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

As described above, in the region I of FIG. 5, the fine particles are oxidized on the particulate filter 22 in a short time without emitting a bright flame, and in the region II of FIG. 5, the fine particles are stacked on the particulate filter 22. Deposits in the shape of. Therefore, the particulates are not included in the particulate filter 22.
In order to prevent the particles from being accumulated in a stacked state on the upper side, it is necessary to keep the discharged fine particle amount M smaller than the oxidatively removable fine particle amount G at all times.

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

On the other hand, as described above, once the fine particles are deposited in a layered manner on the particulate filter 22, even if the discharged fine particle amount M becomes smaller than the oxidatively removable fine particle amount G, the fine particles are oxidized by the active oxygen O. Is difficult. However, when the unoxidized fine particle portion begins to remain, that is, when the fine particles are accumulated below a certain limit, the exhaust fine particle amount M
Is less than the amount G of fine particles that can be removed by oxidation, the remaining fine particle portion is oxidized and removed by the active oxygen O without emitting a luminous flame. Therefore, in the second embodiment, the amount M of discharged fine particles is usually smaller than the amount G of fine particles that can be removed by oxidation,
In addition, the amount M of discharged fine particles is the amount G of fine particles that can be temporarily oxidized and removed.
As shown in FIG. 4 (B), the surface of the carrier layer is not covered by the residual fine particle portion 63 even if the amount becomes larger, that is, when the discharged fine particle amount M becomes smaller than the oxidatively removable fine particle amount G. The amount M of discharged particulates and the temperature TF of the particulate filter 22 are maintained so that only a certain amount or less of particulates that can be oxidized and removed are stacked on the particulate filter 22.

Immediately after the engine is started, the temperature TF of the particulate filter 22 is low. Therefore, at this time, the discharged particulate amount M becomes larger than the oxidatively removable particulate amount G. Therefore, considering the actual driving, it is considered that the second embodiment is more practical. On the other hand, even if the amount M of discharged particulates and the temperature TF of the particulate filter 22 are controlled so that the first embodiment or the second embodiment can be executed, particulates are accumulated in a laminated form on the particulate filter 22. There is a case. In such a case, the particulates deposited on the particulate filter 22 can be oxidized without emitting a bright flame by temporarily increasing the air-fuel ratio of a part or the whole of the exhaust gas.

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 decreased, the active oxygen O is released from the oxygen storage / active oxygen release agent 61 to the outside at once and is released all at once. The fine particles deposited by the active oxygen O are burned and removed at once without emitting a bright flame. In this case, the air-fuel ratio of the exhaust gas may be made rich when the particulates are deposited in layers on the particulate filter 22, or the air-fuel ratio of the exhaust gas may be made periodically rich. As a method of making the air-fuel ratio of the exhaust gas rich, for example, when the engine load is relatively low, EG
R rate (EGR gas amount / (intake air amount + EGR gas amount))
Of the throttle valve 17 and the EGR control valve 25 are controlled so that the ratio becomes 65% or more, and the injection amount is controlled so that the average air-fuel ratio in the combustion chamber 5 becomes rich at this time. be able to.

FIG. 6 shows an example of the engine operation control routine. Referring to FIG. 6, first, at step 100, it is judged if the average air-fuel ratio in the combustion chamber 5 should be made rich. When it is not necessary to make the average air-fuel ratio in the combustion chamber 5 rich, the opening degree of the throttle valve 17 is controlled in step 101 so that the amount M of discharged particulate becomes smaller than the amount G of particulate that can be removed by oxidation, and in step 102 EGR The opening degree of the control valve 25 is controlled, and step 103
At, the fuel injection amount is controlled.

On the other hand, when it is determined in step 100 that the average air-fuel ratio in the combustion chamber 5 should be made rich, the opening degree of the throttle valve 17 is controlled in step 104 so that the EGR rate becomes 65% or more. ,
The opening degree of the EGR control valve 25 is controlled in step 105, and the fuel injection amount is controlled in step 106 so that the average air-fuel ratio in the combustion chamber 5 becomes rich.

By the way, the fuel and the lubricating oil contain calcium Ca, and therefore the exhaust gas contains calcium Ca. This calcium Ca produces calcium sulfate CaSO ₄ when SO ₃ is present. This calcium sulfate CaSO ₄ is a solid and does not thermally decompose even at high temperatures. Therefore, when calcium sulfate CaSO ₄ is generated, the pores of the particulate filter 22 are blocked by the calcium sulfate CaSO ₄ , and as a result, the exhaust gas becomes difficult to flow in the particulate filter 22. In this case, if an alkali metal or alkaline earth metal having a higher ionization tendency than calcium Ca, such as potassium K, is used as the oxygen storage / active oxygen release agent 61, SO ₃ diffused in the oxygen storage / active oxygen release agent 61 is potassium. It combines with K to form potassium sulfate K ₂ SO ₄ , and calcium Ca flows out into the exhaust gas outflow passage 51 through the partition wall 54 of the particulate filter 22 without combining with SO ₃ . Therefore, the particulate filter 2
The pores of No. 2 will not be clogged. Therefore, as described above, as the oxygen storage / active oxygen release agent 61, alkali metal or alkaline earth metal having a higher ionization tendency than calcium Ca, that is, potassium K, lithium Li, cesium Cs, rubidium Rb, barium Ba, strontium Sr is used. It will be preferred to use.

FIG. 7 is an enlarged sectional view of the partition wall 54 of the particulate filter 22 shown in FIG. 2 (B). In FIG. 7, reference numeral 66 denotes an exhaust gas passage extending inside the partition wall 54, 67 denotes a particulate filter base material, 261
Is an oxygen storage / active oxygen release agent carried on the surface of the partition wall 54 of the particulate filter. As described above, the oxygen storage / active oxygen release agent 261 has a function of oxidizing the fine particles temporarily collected on the surface of the partition wall 54 of the particulate filter. Reference numeral 161 denotes an oxygen storage / active oxygen release agent carried inside the partition wall 54 of the particulate filter. This oxygen storage / active oxygen release agent 161 is also the oxygen storage / active oxygen release agent 261.
It has an oxidation function similar to, and can oxidize the particulates temporarily collected inside the partition wall 54 of the particulate filter.

FIG. 8 is an enlarged view of the particulate filter 22 shown in FIG. Specifically, FIG. 8A is an enlarged plan view of the particulate filter, and FIG. 8B is an enlarged side view of the particulate filter. FIG. 9 is a diagram showing the relationship between the switching position of the exhaust switching valve and the flow of exhaust gas. Specifically, FIG. 9A shows the exhaust switching valve 7
3 is in the forward flow position, FIG. 9B is a view in which the exhaust gas switching valve 73 is in the reverse flow position, and FIG. 9C is a view in which the exhaust gas switching valve 73 is in the bypass position.
When the exhaust switching valve 73 is in the forward flow position, FIG.
As shown in, the exhaust gas that has passed through the exhaust switching valve 73 and flowed into the casing 23 first passes through the first passage 71 and then the particulate filter 22,
Finally, the exhaust passage valve 73 is passed through the second passage 72 again.
Is returned to the exhaust pipe. When the exhaust gas switching valve 73 is in the reverse flow position, as shown in FIG. 9 (B), the exhaust gas that has passed through the exhaust gas switching valve 73 and has flowed into the casing 23 first passes through the second passage 72 and then the path. The curate filter 22 passes in the opposite direction to that shown in FIG. 9A, finally passes through the first passage 71, passes through the exhaust gas switching valve 73 again, and is returned to the exhaust pipe. When the exhaust gas switching valve 73 is in the bypass position, the pressure in the first passage 71 and the pressure in the second passage 72 become equal as shown in FIG. Exhaust gas passes through the exhaust gas switching valve 73 as it is without flowing into the casing 23.

FIG. 10 is a view showing a state in which the fine particles inside the partition wall 54 of the particulate filter move in response to the switching of the position of the exhaust gas switching valve 73.
Specifically, FIG. 10 (A) is an enlarged cross-sectional view of the partition wall 54 of the particulate filter 22 when the exhaust gas switching valve 73 is in the forward flow position (see FIG. 9 (A)), and FIG. 10 (B) is the exhaust gas switching valve. 73 is the forward flow position to the reverse flow position (Fig. 9 (B))
FIG. 7 is an enlarged cross-sectional view of the partition wall 54 of the particulate filter 22 when switched to (see). As shown in FIG. 10 (A), when the exhaust gas switching valve 73 is arranged at the forward flow position and the exhaust gas is flowing from the upper side to the lower side, the fine particles 162 existing in the exhaust gas passage 66 inside the partition wall are exhausted. It is pressed against the oxygen storage / active oxygen release agent 161 inside the partition wall by the flow of gas, and is deposited on it. Therefore, the fine particles 162 that are not in direct contact with the oxygen storage / active oxygen release agent 161 are not sufficiently oxidized. Next, as shown in FIG. 10 (B), when the exhaust gas switching valve 73 is switched from the forward flow position to the reverse flow position and the exhaust gas flows from the lower side to the upper side, the fine particles 162 existing in the exhaust gas passage 66 inside the partition wall are discharged. It is moved by the flow of exhaust gas. As a result, the fine particles 162 that have not been sufficiently oxidized are brought into direct contact with the oxygen storage / active oxygen releasing agent 161, and are sufficiently oxidized. Further, when the exhaust switching valve 73 is arranged at the forward flow position (see FIG. 10A), some of the fine particles deposited on the oxygen storage / active oxygen release agent 261 on the partition wall surface of the particulate filter are The exhaust switching valve 73 is switched from the forward flow position to the reverse flow position, so that the oxygen storage / active oxygen release agent 261 on the partition wall surface of the particulate filter is desorbed (FIG. 10).
(See (B)). The desorption amount of the fine particles increases as the temperature of the particulate filter 22 increases, and also increases as the exhaust gas amount increases. The higher the temperature of the particulate filter 22 is, the larger the amount of desorbed particles becomes.
This is because as the temperature of the particulate filter 22 increases, the binding force of SOF as a binder that deposits the particles becomes weaker.

In the present embodiment, the exhaust switching valve 73 shown in FIG. 9A is switched from the forward flow position to the reverse flow position shown in FIG. 9B, and from the reverse flow position shown in FIG. 9B to FIG. The switching to the forward flow position shown in (A) is performed by dispersing the fine particles collected in the partition wall 54 of the particulate filter 22 between the upper surface and the lower surface (see FIG. 7) of the partition wall 54 of the particulate filter 22. Be seen. By switching the exhaust gas switching valve 73 in this manner, it is possible to reduce the possibility that the particulates collected in the partition wall 54 of the particulate filter 22 will be accumulated without being oxidized and removed. Preferably, the fine particles trapped in the partition wall 54 of the particulate filter 22 are dispersed to the upper surface and the lower surface of the partition wall 54 of the particulate filter 22 in substantially the same degree.

FIG. 11 is a diagram showing the relationship between the vehicle speed (engine speed), the inflowing particulate amount (integrated value) flowing into the particulate filter, and time during steady operation of the internal combustion engine. Specifically, FIG. 11 (A) is a diagram showing the relationship between the time and the amount of inflowing particulates when the vehicle speed (engine speed) is relatively high, and FIG. 11 (B) shows the vehicle speed (engine speed). It is a figure showing the relation between time and the amount of inflow particulates when it is comparatively low. As shown in FIG. 11, the higher the vehicle speed (engine speed), the more the amount of inflowing particles increases. That is, the amount of inflowing particulates increases faster in the case of FIG. 11A than in the case of FIG. FIG. 12 is a diagram showing the relationship between the vehicle speed (engine speed), the inflow particulate amount (integrated value) flowing into the particulate filter, and time during transient (deceleration) operation of the internal combustion engine. As shown in FIG. 12, during the deceleration operation period of the internal combustion engine (time t1 to time t2), the amount of inflowing fine particles (integrated value) does not increase due to the fuel cut.

FIG. 13 is a diagram showing the relationship between the amount of fine particles removed by oxidation and time. Here, the amount of fine particles removed by oxidation refers to an integrated value of the amount of fine particles oxidized and removed in the particulate filter 22 out of the fine particles flowing into the particulate filter 22. That is, the curve G shown in FIG.
It is a value obtained by integrating (TF) with time. As shown in FIG. 13, the temperature TF of the particulate filter 22 increases as time elapses for a while after the oxidation and removal of the particulates is started, and accordingly, the particulates that can be removed by oxidation per unit time. The quantity G (TF) also increases over time (see FIG. 5). As a result, the amount of fine particles that can be removed by oxidation (the integrated value of G (TF)) increases in a higher-order curve. After a while, the particulate filter 2
When the temperature TF of 2 becomes constant, the amount of fine particles G that can be removed by oxidation G
Since (TF) becomes a constant value, the amount of fine particles that can be removed by oxidation (the integrated value of G (TF)) increases in a linear curve. Figure 1
Although only one curve is shown in No. 3, this curve differs depending on the inflowing particulate amount (FIGS. 11 and 12) and the operating conditions of the internal combustion engine.

FIG. 14 is a diagram showing the relationship between the amount of inflow particulates (integrated value), the amount of oxidation-removed particulates (integrated value), the amount of deposited particulates (integrated value) and time during steady operation of the internal combustion engine. Specifically, FIG. 14A shows the amount of inflow particulates (integrated value), the amount of oxidation-removed particulates (integrated value), the amount of deposited particulates (integrated value), and time when the exhaust gas flow is not reversed by the exhaust switching valve 73. 1 is a diagram showing the relationship between FIG.
4 (B) shows the amount of inflow particulates (integrated value), the amount of oxidation-removed particulates (integrated value), the amount of accumulated particulates (integrated value), and time when the exhaust gas flow is reversed by the exhaust gas switching valve 73 in the present embodiment. It is the figure which showed the relationship of. As shown in FIG. 14, the amount of particulates deposited (integrated value) on the particulate filter 22 is obtained by subtracting the amount of particulates removed by oxidation (integrated value) from the amount of particulates inflow (integrated value) (however, the particulate filter 22 The amount of fine particles desorbed from is also included in this amount of accumulated fine particles.)

As shown in FIG. 14B, in this embodiment, the ratio of the amount of fine particles removed by oxidation to the amount of fine particles inflow (=
The amount of fine particles removed by oxidation / the amount of fine particles flowing in is the target purification rate (=
When (PMA1-PMA2) / PMA1 is exceeded (time t3), the exhaust gas flow is reversed by the exhaust switching valve 73. That is, the exhaust gas switching valve 73 is switched from the forward flow position (FIG. 9A) to the reverse flow position (FIG. 9B), or from the reverse flow position (FIG. 9B) to the forward flow position (FIG. A)). On the other hand, FIG.
As shown in (A), when the exhaust gas flow is not reversed at time t3 and the exhaust gas continues to flow from one side, the amount of accumulated particulates (integrated value) becomes too large, and the pressure loss of the particulate filter 22 increases. Will end up. As a result, back pressure increases more than necessary. Further, although not shown, if the reversal of the exhaust gas flow is performed before the time t3, if the reversal of the exhaust gas flow is performed at the time t3, it should have been oxidized and removed by the time t3. The accumulated fine particles are detached from the particulate filter 22 due to the impact when the exhaust gas flow is reversed, and are discharged as they are. That is, the two problems described above can be overcome by reversing the exhaust gas flow at the timing of this embodiment.

FIG. 15 is a diagram showing the relationship between the amount of inflow particulates (integrated value), the amount of oxidation-removed particulates (integrated value), the amount of deposited particulates (integrated value) and time during transient operation of the internal combustion engine. Specifically, FIG. 15A shows the amount of inflow particulates (integrated value), the amount of oxidation-removed particulates (integrated value), the amount of deposited particulates (integrated value), and time when the exhaust gas flow is not reversed by the exhaust switching valve 73. 1 is a diagram showing the relationship between FIG.
5B shows the amount of inflow particulates (integrated value), the amount of oxidation-removed particulates (integrated value), the amount of accumulated particulates (integrated value), and time when the exhaust gas flow is reversed by the exhaust switching valve 73 in the present embodiment. It is the figure which showed the relationship of.

As shown in FIG. 15B, in the present embodiment, the ratio of the amount of fine particles removed by oxidation to the amount of fine particles flowing in (=
The amount of fine particles removed by oxidation / the amount of fine particles flowing in is the target purification rate (=
(PMA3-PMA4) / PMA3 = (PMA1-PM
When (A2) / PMA1) is exceeded (time t4), the exhaust gas flow is reversed by the exhaust switching valve 73. That is, the exhaust gas switching valve 73 is switched from the forward flow position (FIG. 9A) to the reverse flow position (FIG. 9B) or from the reverse flow position (FIG. 9B) to the forward flow position (FIG. 9B).
(A)). On the other hand, as shown in FIG. 15 (A), if the exhaust gas flow is not reversed at time t4 and the exhaust gas continues to flow from one side, the amount of accumulated particulates (integrated value) becomes too large, and the particulate filter 22 is discharged. The pressure loss increases. As a result, back pressure increases more than necessary. Although not shown, if the exhaust gas flow is reversed between the time t1 and the time t2 prior to the time t4 due to the deceleration of the internal combustion engine (time t1 to time t2), the reverse flow of the exhaust gas flow is performed. If the process is performed at time t4, the deposited particulates that should have been oxidized and removed by time t4 are desorbed from the particulate filter 22 due to the impact when the exhaust gas flow reverses, and are discharged as they are. That is, the two problems described above can be overcome by reversing the exhaust gas flow at the timing of this embodiment.

FIG. 16 is a flow chart showing the switching control method of the exhaust switching valve of this embodiment. As shown in FIG. 16, when this routine is started, first, in step 200, the inflowing particulate amount (see FIGS. 11 and 12) is calculated. Specifically, as shown in FIGS. 11 and 12, a plurality of maps of the inflowing particulate amount according to the operating conditions of the internal combustion engine are stored in the ROM 32, which are suitable for the operating history of the internal combustion engine up to the present. Is selected from a plurality of maps in the ROM 32, and the current inflow particulate amount (integrated value) is calculated. Next, at step 201, the amount of fine particles removed by oxidation (see FIGS. 13, 14, and 15) is calculated. Specifically, the temperature of the particulate filter 22 detected by the temperature sensor 39, the relationship between the amount of particulates G (TF) that can be removed by oxidation stored in the ROM 32 and the temperature of the particulate filter 22 (FIG. 5), internal combustion The current oxidation removal particulate amount (integrated value) is calculated based on the engine operation history and the inflow particulate amount (integrated value) history.

Next, at step 202, the particulate purification rate (= current oxidation-removed particulate amount (integrated value) / current inflow particulate amount (integrated value)) is calculated. Then step 20
In 3, the particulate purification rate calculated in step 202 is the target purification rate (= (PMA1-PMA2) / PMA
1) (see FIG. 14) is determined. YE
When S, the routine proceeds to step 204, where the exhaust gas flow is reversed. That is, the exhaust gas switching valve 73 is switched from the forward flow position (FIG. 9A) to the reverse flow position (FIG. 9B), or from the reverse flow position (FIG. 9B) to the forward flow position (FIG. A)). On the other hand, when NO, the position of the exhaust switching valve 73 is maintained as it is.

FIG. 17 is a flow chart showing an exhaust gas flow reverse rotation prohibition control method of this embodiment. This exhaust gas flow reverse rotation prohibition control is executed by being interrupted during execution of the switching control of the exhaust switching valve shown in FIG. When this routine is started, first, at step 300, it is judged if the internal combustion engine is being accelerated. When YES, the reverse of the exhaust gas flow is prohibited in step 301. That is, execution of step 204 in FIG. 16 is prohibited. On the other hand, when NO, reversal of the exhaust gas flow is not prohibited. That is, step 204 in FIG.
When it is time to execute step 204, step 204 is executed.

FIG. 18 is a flow chart showing the bypass mode prohibition control method of this embodiment. This bypass mode prohibition control is also executed by interrupting the execution of the switching control of the exhaust switching valve shown in FIG. When this routine is started, first, at step 400, it is judged if the temperature raising control for raising the exhaust gas temperature of the internal combustion engine is being executed. If YES, step 401
And the switching to the bypass mode is prohibited. That is, the forward flow position (FIG. 9A) can be switched to the bypass position (FIG. 9C) and the reverse flow position (FIG. 9B) can be switched to the bypass position (FIG. 9C). Both are banned. On the other hand, if NO, switching to the bypass mode is not prohibited.

FIG. 19 shows changes in output torque and smoke when the air-fuel ratio A / F (horizontal axis in FIG. 19) is changed by changing the opening of the throttle valve 17 and the EGR rate during engine low load operation. , HC, CO, NOx represent an example of an experiment showing a change in the emission amount. As can be seen from FIG. 19, in this experimental example, as the air-fuel ratio A / F becomes smaller, E
When the GR rate becomes large and is equal to or less than the stoichiometric air-fuel ratio (≈14.6), the EGR rate becomes 65% or more.
As shown in FIG. 19, when the air-fuel ratio A / F is reduced by increasing the EGR rate, the EGR rate becomes around 40% and the amount of smoke generated when the air-fuel ratio A / F becomes about 30. Start growing. Then, further EG
When the R ratio is increased and the air-fuel ratio A / F is decreased, the amount of smoke generated sharply increases and reaches a peak. Then further EG
When the R ratio is increased and the air-fuel ratio A / F is decreased, the smoke sharply decreases this time, the EGR ratio is increased to 65% or more, and the smoke becomes almost zero when the air-fuel ratio A / F is around 15.0. That is, soot is hardly generated. At this time, the output torque of the engine is slightly reduced, and the amount of NOx generated is considerably reduced. On the other hand, at this time, the amounts of HC and CO generated start to increase.

FIG. 20 (A) shows changes in the combustion pressure in the combustion chamber 5 when the air-fuel ratio A / F is around 21 and the amount of smoke is the largest, and FIG. 20 (B) shows the air-fuel ratio A / F. F is 18
The graph shows the change in combustion pressure in the combustion chamber 5 when the amount of smoke generated is near zero. 20A and FIG.
As can be seen from a comparison with (B), the combustion pressure is lower in the case shown in FIG. 20 (B) where the amount of smoke generated is substantially zero than in the case shown in FIG. 20 (A) where the amount of smoke generated is large. I understand.

The following can be said from the experimental results shown in FIGS. 19 and 20. That is, first, when the air-fuel ratio A / F is 15.0 or less and the amount of smoke generated is almost zero, the amount of NOx generated is considerably reduced as shown in FIG. A decrease in the amount of NOx generated means that the combustion temperature in the combustion chamber 5 has decreased, and therefore, it can be said that the combustion temperature in the combustion chamber 5 is low when soot is hardly generated. . The same can be said from FIG. That is, soot is hardly generated in FIG.
In the state shown in (1), the combustion pressure is low, and therefore the combustion temperature in the combustion chamber 5 is low at this time.

Second, when the amount of smoke produced, that is, the amount of soot produced, becomes almost zero, HC and C are generated as shown in FIG.
O 2 emissions increase. This means that hydrocarbons are discharged without growing to soot. That is, linear hydrocarbons and aromatic hydrocarbons contained in the fuel as shown in FIG. 21 are thermally decomposed to form soot precursors when the temperature is raised in a state of insufficient oxygen, and then mainly soot is formed. Soot is produced that consists of a solid in which the carbon atoms are assembled. in this case,
The actual soot formation process is complicated, and it is not clear what the form of the soot precursor is.
Hydrocarbons such as those shown in 1 will grow to soot via the soot precursor. Therefore, as described above, when the soot generation amount becomes almost zero, as shown in FIG.
Although the amount of discharged O increases, HC at this time is a soot precursor or a hydrocarbon in the state before it.

When these considerations based on the experimental results shown in FIGS. 19 and 20 are summarized, the soot generation amount becomes almost zero when the combustion temperature in the combustion chamber 5 is low, and at this time, the soot precursor or the soot precursor The hydrocarbons in this state are discharged from the combustion chamber 5. As a result of further detailed experimental research on this, when the temperature of the fuel in the combustion chamber 5 and the gas around it is below a certain temperature, the soot growth process stops halfway, that is, soot is generated. Never occurred,
It has been found that soot is produced when the temperature of the fuel in the combustion chamber 5 and its surroundings exceeds a certain temperature.

By the way, the temperature of the fuel and its surroundings when the hydrocarbon production process is stopped in the state of the soot precursor, that is, the above-mentioned certain temperature depends on various factors such as the type of fuel and the compression ratio of the air-fuel ratio. It cannot be said how many times it changes, but this certain temperature has a deep relationship with the NOx generation amount, and therefore, this certain temperature can be defined to some extent from the NOx generation amount. it can. That is, as the EGR rate increases, the temperature of the fuel during combustion and the gas surrounding it decrease, and the amount of NOx generated decreases. At this time, soot is hardly generated when the amount of NOx generated becomes around 10 p.pm or less. Therefore, the above certain temperature is NO
It almost coincides with the temperature when the amount of x generation is around 10 p.pm or less.

Once soot is produced, this soot cannot be purified by a post-treatment using a catalyst having an oxidizing function. On the other hand, the soot precursor or the hydrocarbon in the state before it can be easily purified by a post-treatment using a catalyst having an oxidizing function. Considering the post-treatment with a catalyst having an oxidizing function as described above, it is extremely difficult to determine whether the hydrocarbon is discharged from the combustion chamber 5 in the state of the soot precursor or in the state before it, or is discharged from the combustion chamber 5 in the form of soot. There is a big difference. The new combustion system employed in the present invention allows hydrocarbons to be discharged from the combustion chamber 5 in the form of soot precursors or pre-presence conditions without producing soot in the combustion chamber 5 The core is to oxidize with a catalyst having an oxidizing function.

Now, in order to stop the growth of hydrocarbons before the soot is generated, the temperature of the fuel and the gas around it in the combustion chamber 5 during combustion is set to a temperature lower than the temperature at which the soot is generated. It needs to be suppressed. In this case, it has been found that, in order to suppress the temperature of the fuel and the gas around it, the endothermic action of the gas around the fuel when the fuel burns has an extremely large effect. That is, if there is only air around the fuel, the evaporated fuel immediately reacts with oxygen in the air and burns. In this case, the temperature of the air separated from the fuel does not rise so much, and only the temperature around the fuel locally becomes extremely high. That is, at this time, the air separated from the fuel hardly absorbs the combustion heat of the fuel. In this case, since the combustion temperature locally becomes extremely high, the unburned hydrocarbons that have received this heat of combustion generate soot.

On the other hand, the situation is slightly different when the fuel is present in a mixed gas of a large amount of inert gas and a small amount of air.
In this case, the evaporated fuel diffuses into the surroundings, reacts with oxygen mixed in the inert gas, and burns. In this case, the combustion heat is absorbed by the surrounding inert gas, so that the combustion temperature does not rise so much. That is, the combustion temperature can be kept low. That is, the presence of the inert gas plays an important role in suppressing the combustion temperature, and the combustion temperature can be suppressed low by the endothermic action of the inert gas.

In this case, in order to suppress the temperature of the fuel and the gas around it to a temperature lower than the temperature at which soot is produced, an amount of inert gas sufficient to absorb the amount of heat required to do so is required. . Therefore, if the fuel amount increases, the required amount of inert gas also increases accordingly. In this case, the larger the specific heat of the inert gas, the stronger the endothermic action, and therefore the inert gas is preferably a gas having a large specific heat. In this respect, since CO ₂ and EGR gas have a relatively large specific heat, it can be said that it is preferable to use EGR gas as the inert gas.

FIG. 22 shows the relationship between the EGR rate and smoke when EGR gas is used as the inert gas and the cooling degree of the EGR gas is changed. That is, in FIG. 22, the curve A shows the case where the EGR gas is strongly cooled and the EGR gas temperature is maintained at about 90 ° C., and the curve B shows the case where the EGR gas is cooled with 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. 22, when the EGR gas is strongly cooled, the soot generation amount reaches a peak when the EGR rate is slightly lower than 50%, and in this case, the EGR rate is almost 55% or more. If so, soot is hardly generated. On the other hand, as shown by the curve B in FIG. 22, when the EGR gas is slightly cooled, the soot generation amount reaches a peak when the EGR rate is slightly higher than 50%, and in this case, the EGR rate is approximately 65% or more. If so, soot is hardly generated. Further, as shown by the curve C in FIG. 22, when the EGR gas is not forcibly cooled, the soot generation amount peaks near the EGR rate of 55%, and in this case, the EGR rate is almost 70%. Almost no soot is generated if the percentage is exceeded. Note that FIG. 22 shows the amount of smoke generated when the engine load is relatively high, and when the engine load decreases, the EGR rate at which the amount of soot generated reaches a peak decreases slightly, and the EGR rate at which soot hardly occurs is shown. The lower limit of is also slightly lowered. Thus, the lower limit of the EGR rate at which soot is hardly generated changes depending on the cooling degree of EGR gas and the engine load.

FIG. 23 shows a mixture of EGR gas and air required to bring the temperature of the fuel and its surrounding gas at the time of combustion to a temperature lower than the temperature at which soot is generated when EGR gas is used as the inert gas. The amount of gas, the ratio of air in this mixed gas amount, and the ratio of EGR gas in this mixed gas are shown. In FIG. 23, the vertical axis represents the total intake gas amount sucked into the combustion chamber 5, and the chain line Y represents the total intake gas amount that can be sucked into the combustion chamber 5 when supercharging is not performed. ing. The horizontal axis shows the required load. Referring to FIG. 23, the ratio of air, that is, the amount of air in the mixed gas, indicates the amount of air required to completely burn the injected fuel. That is, in the case shown in FIG. 23, the ratio between the air amount and the injected fuel amount is the stoichiometric air-fuel ratio. On the other hand, in FIG. 23, the ratio of the EGR gas, that is, the amount of the EGR gas in the mixed gas makes the temperature of the fuel and its surrounding gas lower than the temperature at which soot is formed when the injected fuel is burned. The minimum required EGR gas amount is shown. The EGR gas amount is approximately 55% or more when expressed by the EGR rate, and is 70% or more in the embodiment shown in FIG. That is, the total intake gas amount sucked into the combustion chamber 5 is shown by the solid line X in FIG. 23, and the ratio of the air amount to the EGR gas amount in this total intake gas amount X is set to the ratio shown in FIG. The temperature of the fuel and the gas around it is lower than the temperature at which soot is produced, and thus no soot is generated. Further, the NOx generation amount at this time is around 10 p.pm or less, so that the NOx generation amount becomes extremely small.

As the amount of fuel injection increases, the amount of heat generated when the fuel burns increases. Therefore, in order to maintain the temperature of the fuel and the gas around it at a temperature lower than the temperature at which soot is generated, heat generated by EGR gas is used. The amount of absorption must be increased. Therefore, as shown in FIG. 23, the EGR gas amount must be increased as the injected fuel amount is increased. That is, the EGR gas amount needs to increase as the required load increases. By the way, when the supercharging is not performed, the upper limit of the total intake gas amount X sucked into the combustion chamber 5 is Y. Therefore, in FIG. 23, the required load becomes larger as the required load becomes larger in the region where the required load is larger than Lo. The air-fuel ratio cannot be maintained at the stoichiometric air-fuel ratio unless the EGR gas ratio is reduced. In other words, if the air-fuel ratio is maintained at the stoichiometric air-fuel ratio in the region where the required load is larger than Lo when supercharging is not performed, the EGR rate decreases as the required load increases, thus In the region where the required load is larger than Lo, the temperature of the fuel and the gas around it cannot be maintained below the temperature at which soot is generated.

However, although not shown, when the EGR gas is recirculated to the inlet side of the supercharger, that is, the air suction pipe of the exhaust turbocharger through the EGR passage, the EGR rate is 55% or more in the region where the required load is larger than Lo. ,
For example, it may be maintained at 70 percent, thus maintaining the fuel and surrounding gas temperatures below the temperature at which soot is produced. That is, if the EGR gas is recirculated so that the EGR rate in the air suction pipe becomes, for example, 70%, the EGR rate of the intake gas boosted by the compressor of the exhaust turbocharger also becomes 70%, so that the EGR rate is boosted by the compressor. To the extent possible, the temperature of the fuel and the gas around it can be kept below the temperature at which soot is produced. Therefore, the operating range of the engine capable of producing the low temperature combustion can be expanded. When the EGR rate is set to 55% or more in the region where the required load is larger than Lo, the EGR control valve is fully opened and the throttle valve is slightly closed.

As described above, FIG. 23 shows the case where the fuel is burned under the stoichiometric air-fuel ratio.
Even if the amount of air is less than the amount shown in, that is, even if the air-fuel ratio is made rich, the amount of NOx generated is reduced to 10 while preventing the generation of soot.
It can be around ppm or less, and even if the air amount is made larger than that shown in FIG. 23, that is, the average value of the air-fuel ratio is lean from 17 to 18, the soot generation is prevented. Meanwhile, the amount of NOx generated can be reduced to about 10 p.pm or less. 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 excessive fuel does not grow to soot, and thus soot is not generated. Further, at this time, only a very small amount of NOx is 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 becomes high, but in the present invention the combustion temperature is suppressed to a low temperature, soot Not generated at all.
Furthermore, NOx is also generated in a very small amount. Thus, regardless of the air-fuel ratio when low-temperature combustion is being performed, that is, whether the air-fuel ratio is rich, the stoichiometric air-fuel ratio, or the average air-fuel ratio is lean, soot is not generated, The amount of NOx generated is extremely small. Therefore, considering the improvement of the fuel consumption rate, it can be said that it is preferable to make the average air-fuel ratio lean at this time.

By the way, the temperature of the fuel and the gas around it during combustion in the combustion chamber can be suppressed below the temperature at which the growth of hydrocarbons stops halfway only when the engine is operating at low load, where the calorific value of combustion is relatively small. To be Therefore, in the embodiment according to the present invention, during low load operation in the engine, the temperature of the fuel and the gas around it during combustion is suppressed below the temperature at which the growth of hydrocarbons stops halfway, and the first combustion, that is, low temperature combustion is performed. In addition, the second combustion, that is, the combustion normally performed from the conventional one, is performed during the engine high load operation. It should be noted that here, the first combustion, that is, low temperature combustion, as is clear from the above description, the amount of inert gas in the combustion chamber is larger than the amount of inert gas at which the amount of soot generated peaks, and soot is almost generated. The second combustion, that is, the combustion that is normally performed in the past, is the combustion that does not have the amount of soot generated and the amount of the inert gas in the combustion chamber is smaller than the amount of the inert gas that does not reach the peak. Say that.

FIG. 24 shows the first operating region I'where the first combustion, that is, the low temperature combustion is performed, and the second operating region II 'where the second combustion, that is, the combustion by the conventional combustion method is performed. Shows. In FIG. 24, the vertical axis L represents the amount of depression of the accelerator pedal 40, that is, the required load, and the horizontal axis N.
Indicates the engine speed. Also, in FIG.
(N) indicates a first boundary between the first operating region I ′ and the second operating region II ′, and Y (N) indicates the first operating region I ′ and the second operating region II ′. Shows a second boundary between and. The change determination of the operating region from the first operating region I ′ to the second operating region II ′ is performed based on the first boundary X (N), and the second operating region II ′ to the first operating region is determined. The determination of the change of the operating region to I'is made based on the second boundary Y (N). That is, when the engine operating condition is in the first operating region I ′ and low temperature combustion is performed, the operation is performed when the required load L exceeds the first boundary X (N) which is a function of the engine speed N. It is determined that the region has moved to the second operation region II ', and combustion is performed by the conventional combustion method. Next, when the required load L becomes lower than the second boundary Y (N) which is a function of the engine speed N, it is determined that the operating region has moved to the first operating region I ′, and low temperature combustion is performed again.

The two boundaries of the first boundary X (N) and the second boundary Y (N) on the lower load side of the first boundary X (N) are provided as follows. For one reason. The first reason is that the combustion temperature is relatively high on the high load side of the second operation region II ′, and at this time, even if the required load L becomes lower than the first boundary X (N), low temperature combustion can be performed immediately. Because there is no. That is, the low temperature combustion does not start immediately unless the required load L becomes considerably low, that is, when it becomes lower than the second boundary Y (N). The second reason is that hysteresis is provided for changes in the operating region between the first operating region I ′ and the second operating region II ′.

By the way, when the engine operating region is in the first operating region I'and low temperature combustion is performed, soot is hardly generated, and instead, unburned hydrocarbons are precursors of soot or the state before that. Is discharged from the combustion chamber 5 in the form of At this time, the unburned hydrocarbons discharged from the combustion chamber 5 are satisfactorily oxidized by a catalyst (not shown) having an oxidizing function. This catalyst is an oxidation catalyst, a three-way catalyst, or NOx.
An absorbent can be used. NOx absorbent is in combustion chamber 5
If the average air-fuel ratio in the inside of the combustion chamber 5 is lean and the average air-fuel ratio in the combustion chamber 5 becomes rich, Nx is absorbed.
It has a function of releasing Ox. This NOx absorbent uses, for example, alumina as a carrier, and on this carrier, for example, potassium K, sodium Na, lithium Li, an alkali metal such as cesium Cs, alkaline earth such as barium Ba, calcium Ca, lanthanum La, yttrium Y. At least one selected from the rare earths and a noble metal such as platinum Pt are supported. Not only the oxidation catalyst,
The three-way catalyst and NOx absorbent also have an oxidizing function,
Therefore, as described above, the three-way catalyst and NOx absorbent can be used as the catalyst described above.

FIG. 25 shows the output of the air-fuel ratio sensor (not shown). As shown in FIG. 25, the output current I of the air-fuel ratio sensor changes according to the air-fuel ratio A / F. Therefore, the air-fuel ratio can be known from the output current I of the air-fuel ratio sensor.

Next, the operation control in the first operation region I'and the second operation region II 'will be schematically described with reference to FIG. FIG. 26 shows the opening of the throttle valve 17, the opening of the EGR control valve 25, and the EGR with respect to the required load L.
The ratio, the air-fuel ratio, the injection timing and the injection amount are shown. Figure 2
As shown in 6, in the first operating region I ′ where the required load L is low, the opening degree of the throttle valve 17 is gradually increased from near full closing to about 2/3 opening degree as the required load L increases. The opening degree of the EGR control valve 25 is gradually increased from near full close to full open as the required load L increases. Further, in the example shown in FIG. 26, the EGR rate is approximately 70% in the first operating region I ′,
The air-fuel ratio is considered to be slightly lean.

In other words, in the first operating region I ', EG
The throttle valve 17 has an R ratio of about 70% and a slightly lean air-fuel ratio.
And the opening degree of the EGR control valve 25 are controlled. Further, in the first operation region I ′, fuel injection is performed before the compression top dead center TDC. In this case, the injection start timing θS becomes late as the required load L becomes high, and the injection completion timing θE also becomes late as the injection start timing θS becomes late. In addition,
During idle operation, the throttle valve 17 is closed close to fully closed, and at this time, the EGR control valve 25 is also closed close to fully closed. When the throttle valve 17 is closed close to the fully closed state, the pressure in the combustion chamber 5 at the beginning of compression becomes low and the compression pressure becomes small. When the compression pressure decreases, the piston 4
Since the compression work due to is small, the vibration of the engine body 1 is small. That is, in idle operation, the throttle valve 17 is closed to close to fully close in order to suppress the vibration of the engine body 1.

On the other hand, when the operating region of the engine changes from the first operating region I'to the second operating region II ', the throttle valve 2
The opening degree of 0 is increased stepwise from about 2/3 opening degree toward the full opening direction. At this time, in the example shown in FIG.
The rate is reduced stepwise from approximately 70% to 40% or less, and the air-fuel ratio is increased stepwise. That is, since the EGR rate jumps over the EGR rate range (FIG. 22) in which a large amount of smoke is generated, a large amount of smoke is generated when the operating region of the engine changes from the first operating region I ′ to the second operating region II ′. There is nothing to do. In the second operating region II ', the combustion that is conventionally performed is performed. In the second operation region II ', the throttle valve 17 is kept in a fully opened state except for a part thereof, and the opening degree of the EGR control valve 25 is gradually reduced as the required load L increases. Further, in this operating region II ′, the EGR rate becomes lower as the required load L becomes higher, and the air-fuel ratio becomes smaller as the required load L becomes higher. However, the air-fuel ratio is a lean air-fuel ratio even if the required load L becomes high. Further, in the second operation region II ′, the injection start timing θS is near the compression top dead center TDC.

FIG. 27A shows the target air-fuel ratio A / F in the first operating region I '. In FIG. 27A, A / F = 15.5, A / F = 16, A / F = 17,
Each of the curves indicated by A / F = 18 has a target air-fuel ratio of 1
The values are 5.5, 16, 17, and 18, and the air-fuel ratio between the curves is determined by proportional distribution. FIG. 27
As shown in (A), the air-fuel ratio is lean in the first operating region I ′, and the target air-fuel ratio A / F is leaner as the required load L is lower in the first operating region I ′. It That is, the lower the required load L, the smaller the amount of heat generated by combustion. Therefore, the lower the required load L, the EGR
Low temperature combustion can be performed even if the rate is lowered. EGR
If the ratio is decreased, the air-fuel ratio becomes large, so that FIG.
As shown in (A), the target air-fuel ratio A / F is increased as the required load L decreases. The fuel consumption rate increases as the target air-fuel ratio A / F increases, and therefore, in order to make the air-fuel ratio as lean as possible, in the embodiment according to the present invention, the target air-fuel ratio A / F is increased as the required load L decreases. .

The target air-fuel ratio A / F shown in FIG. 27 (A) is previously stored in the ROM 3 in the form of a map as a function of the required load L and the engine speed N as shown in FIG. 27 (B).
It is stored in 2. In addition, the throttle valve 1 necessary for setting the air-fuel ratio to the target air-fuel ratio A / F shown in FIG.
The target opening degree ST of 7 is stored in the ROM 32 in advance in the form of a map as a function of the required load L and the engine speed N as shown in FIG.
EGR required to achieve the target air-fuel ratio A / F shown in (A)
The target opening degree SE of the control valve 25 is stored in advance in the ROM 32 in the form of a map as a function of the required load L and the engine speed N as shown in FIG. 28 (B).

FIG. 29A shows the target air-fuel ratio A when the second combustion, that is, the normal combustion by the conventional combustion method is performed.
/ F is shown. Note that the A / F in FIG.
= 24, A / F = 35, A / F = 45, and A / F = 60, the respective curves indicated by the target air-fuel ratios of 24, 35, 45, 6 respectively.
0 is shown. Target air-fuel ratio A shown in FIG. 29 (A)
/ F is a ROM 32 in advance in the form of a map as a function of the required load L and the engine speed N as shown in FIG.
It is stored in. In addition, the throttle valve 17 necessary for setting the air-fuel ratio to the target air-fuel ratio A / F shown in FIG.
The target opening degree ST is stored in the ROM 32 in advance in the form of a map as a function of the required load L and the engine speed N as shown in FIG. 30 (A), and the air-fuel ratio is shown in FIG. 29 (A).
The target opening degree SE of the EGR control valve 25 required to achieve the target air-fuel ratio A / F shown in Fig. 30 is shown in advance in the form of a map as a function of the required load L and the engine speed N as shown in Fig. 30B. It is stored in the ROM 32.

Further, when the second combustion is being performed, the fuel injection amount Q is calculated based on the required load L and the engine speed N. This fuel injection amount Q is stored in advance in the ROM 32 in the form of a map as a function of the required load L and the engine speed N as shown in FIG.

Next, the operation control of this embodiment will be described with reference to FIG. Referring to FIG. 32, first, at step 1100, it is judged if the flag I indicating that the engine operating state is the first operating region I ′ is set. When the flag I is set, that is, when the operating state of the engine is in the first operating region I ', the routine proceeds to step 1101, where it is determined whether the required load L becomes larger than the first boundary X (N). To be determined. L
When ≦ X (N), the routine proceeds to step 1103, where low temperature combustion is performed. On the other hand, in step 1101, L> X
When it is determined that (N) has been reached, step 1102
To reset flag I, then step 11
At 09, the second combustion is performed.

When it is determined in step 1100 that the flag I indicating that the operating condition of the engine is the first operating region I'is not set, that is, the operating condition of the engine is the second operating region II '. If, then step 11
In step 08, it is determined whether the required load L has become lower than the second boundary Y (N). When L ≧ Y (N), the routine proceeds to step 1110, where the second combustion is performed under the lean air-fuel ratio. On the other hand, in step 1108, L <
If it is determined that Y (N) is reached, step 110
9, the flag I is set, then step 11
Proceeding to 03, low temperature combustion is performed.

At step 1103, the target opening degree ST of the throttle valve 17 is calculated from the map shown in FIG. 28 (A), and the opening degree of the throttle valve 17 is made this target opening degree ST. Next, at step 1104, the target opening degree SE of the EGR control valve 25 is calculated from the map shown in FIG. 28 (B),
The opening degree of the EGR control valve 25 is set to this target opening degree SE.
Next, at step 1105, the mass flow rate Ga of intake air (hereinafter simply referred to as intake air amount) Ga detected by a mass flow rate detector (not shown) is taken in, and then step 1
In 106, the target air-fuel ratio A is calculated from the map shown in FIG.
/ F is calculated. Next, at step 1107, the fuel injection amount Q required to bring the air-fuel ratio to the target air-fuel ratio A / F is calculated based on the intake air amount Ga and the target air-fuel ratio A / F.

As described above, when the required load L or the engine speed N changes during low temperature combustion, the opening of the throttle valve 17 and the EGR control valve 25 immediately change to the required load L and the engine speed. The target opening degrees ST and SE corresponding to N are matched. Therefore, for example, when the required load L is increased, the amount of air in the combustion chamber 5 is immediately increased, and thus the torque generated by the engine is immediately increased. On the other hand, when the opening amount of the throttle valve 17 or the EGR control valve 25 changes and the intake air amount changes, the change in the intake air amount Ga is detected by the mass flow rate detector, and the detected intake air amount Ga is detected. The fuel injection amount Q is controlled based on That is, the fuel injection amount Q is changed after the intake air amount Ga actually changes.

In step 1110, the target fuel injection amount Q is calculated from the map shown in FIG. 31, and the fuel injection amount is made this target fuel injection amount Q. Then step 1111
Then, the target opening degree ST of the throttle valve 17 is calculated from the map shown in FIG. Next, at step 1112, the target opening degree SE of the EGR control valve 25 is calculated from the map shown in FIG. 30 (B), and the opening degree of the EGR control valve 25 is made this target opening degree SE. Next, at step 1113, the intake air amount Ga detected by the mass flow rate detector is taken in. Next, at step 1114, the actual air-fuel ratio (A / F) _R is calculated from the fuel injection amount Q and the intake air amount Ga. Next, at step 1115, the target air-fuel ratio A / F is calculated from the map shown in FIG. 29 (B). Next, at step 1116, it is judged if the actual air-fuel ratio (A / F) _R is larger than the target air-fuel ratio A / F. (A / F) _R
When> A / F, the routine proceeds to step 1117, where the throttle opening correction value ΔST is decreased by a constant value α,
Then, the process proceeds to step 1119. On the other hand, (A /
F) When _R ≤ A / F, the routine proceeds to step 1118, where the correction value ΔST is increased by the constant value α, and then the routine proceeds to step 1119. At step 1119, the final target opening degree ST is calculated by adding the correction value ΔST to the target opening degree ST of the throttle valve 17.
The opening of 7 is set as the final target opening ST. That is,
The opening of the throttle valve 17 is controlled so that the actual air-fuel ratio (A / F) _R becomes the target air-fuel ratio A / F.

When the required load L or the engine speed N changes during the second combustion as described above, the fuel injection amount immediately matches the target fuel injection amount Q corresponding to the required load L and the engine speed N. Be punished. Request load L
Is immediately increased, the fuel injection amount is immediately increased, and thus the torque generated by the engine is immediately increased. On the other hand, when the fuel injection amount Q is increased and the air-fuel ratio deviates from the target air-fuel ratio A / F, the air-fuel ratio becomes the target air-fuel ratio A.
The opening degree of the throttle valve 20 is controlled so that it becomes / F. That is, the air-fuel ratio is changed after the fuel injection amount Q changes.

In the above-described embodiments, the fuel injection amount Q is open-loop controlled when the low temperature combustion is performed, and the air-fuel ratio changes the opening degree of the throttle valve 20 when the second combustion is performed. It is controlled by changing.
However, the fuel injection amount Q can be feedback-controlled based on the output signal of the air-fuel ratio sensor 27 when the low temperature combustion is being performed, and the air-fuel ratio can be EGR controlled when the second combustion is being performed. It can also be controlled by changing the opening degree of the valve 31.

In this embodiment, FIG. 9A and FIG.
In the forward flow mode shown in (A), the above-described normal combustion, that is, EG as an inert gas at which the amount of soot generated peaks.
Combustion is performed in which the amount of EGR gas supplied into the combustion chamber 5 is smaller than the amount of R gas, and the combustion is performed as shown in FIGS.
In the backflow mode shown in (B), the above-mentioned low temperature combustion, that is, EG as an inert gas at which the amount of soot generated peaks.
Combustion is performed in which the amount of EGR gas supplied to the combustion chamber 5 is larger than the amount of R gas and soot is hardly generated.

Further, in this embodiment, the amount of fine particles discharged from the combustion chamber 5 per unit time is the amount of fine particles that can be oxidized and removed by the oxidation on the particulate filter 22 per unit time without emitting a luminous flame. Usually less than the amount of discharged fine particles, that is, the amount of discharged fine particles is temporarily higher than the amount of fine particles that can be oxidized and removed temporarily, and even if the discharged fine particles are located in region II of FIG. When the amount of fine particles becomes smaller than the amount of fine particles that can be removed by oxidation, only a certain amount or less of fine particles that can be removed by oxidation are deposited on the particulate filter 22.
The operating conditions of the internal combustion engine are controlled so as to maintain the amount of discharged particulate and the temperature of the particulate filter 22.

According to the present embodiment, as shown in FIG. 7, oxygen storage / activity as an oxidant that releases active oxygen for oxidizing fine particles temporarily collected in the partition wall 54 of the particulate filter 22. The oxygen releasing agent 261 is carried on the partition wall 54 of the particulate filter 22, and the flow of the exhaust gas passing through the partition wall 54 of the particulate filter 22 is reversed as shown in FIG. The fine particles collected in the above are dispersed on the upper surface and the lower surface (see FIG. 7) of the partition wall 54 of the particulate filter 22. Therefore, most of the fine particles that have flowed into the particulate filter are prevented from being collected on one surface of the partition wall of the particulate filter, and the partition wall 54 of the particulate filter 22 prevents the exhaust gas flow from flowing. Oxidation removing action can be exerted on the particles on the downstream side. The above-described oxidation removal action requires the oxygen storage / active oxygen release agent 261 (see FIG. 7) on the surface of the partition wall 54 of the particulate filter 22 as an essential requirement. It can be achieved even when the active oxygen releasing agent 161 (see FIG. 7) is not present.

Further, according to this embodiment, the fine particles trapped in the partition wall 54 of the particulate filter 22 are dispersed on one surface and the other surface of the partition wall 54 of the particulate filter 22 as described above. As a result, the possibility that the fine particles trapped in the partition walls 54 of the particulate filter 22 are deposited without being oxidized and removed is reduced as compared with the case where the fine particles are not dispersed. for that reason,
It becomes possible to sufficiently convey the oxidative removal action of oxidizing and removing the fine particles collected in the partition wall 54 of the particulate filter 22 to all the fine particles, and as a result, the fine particles are in the partition wall 54 of the particulate filter 22.
It can be prevented from accumulating on the surface. Since the oxygen storage / active oxygen releasing agent 261 (see FIG. 7) on the surface of the partition wall 54 of the particulate filter 22 is also an essential requirement for sufficiently transmitting the oxidative removal action to all the fine particles, the partition wall of the particulate filter 22. This can be achieved even when the oxygen storage / active oxygen release agent 161 (see FIG. 7) inside 54 does not exist.

Further according to the present embodiment, step 203
Then, based on the amount of the particulates that have been oxidized and removed in step 204, the timing for reversing the flow of the exhaust gas is determined next. Therefore, when the amount of fine particles that have been oxidized and removed is still small, the flow of exhaust gas is reversed without considering the amount of fine particles that have been oxidized and removed. It is possible to prevent the collected fine particles from being released from the particulate filter and being discharged as they are. Also, avoid increasing back pressure more than necessary, as in the case where the flow of exhaust gas is reversed based on the pressure loss of the particulate filter without considering the amount of fine particles removed by oxidation. You can Specifically, according to this embodiment, when it is determined in step 203 that the purification rate of fine particles exceeds the target purification rate, the flow of exhaust gas is reversed in step 204. Therefore, it is possible to achieve the target purification rate of the fine particles while avoiding the fine particles being discharged as they are and increasing the back pressure more than necessary.

Further, according to the present embodiment, step 300
When it is determined that the internal combustion engine is in accelerated operation in
In step 301, reversing the flow of exhaust gas is prohibited. Therefore, as the flow of the exhaust gas is reversed during the acceleration operation of the internal combustion engine where the amount of exhaust gas is relatively large, the fine particles before being oxidized and removed are temporarily collected by the particulate filter. It is possible to prevent the fine particles contained in the particulate filter from being detached from the particulate filter and directly discharged.

Further, according to the present embodiment, step 400
When it is determined that the temperature raising control for raising the temperature of the particulate filter 22 is being performed in step 401, the exhaust gas switching valve 73 is prohibited from being placed in the bypass position (FIG. 9C) in step 401. It Therefore, although the exhaust gas temperature raising control of the internal combustion engine is being executed in an attempt to raise the temperature of the particulate filter 22, the exhaust gas that has been raised in temperature bypasses the particulate filter 22, and the particulate filter 22 It can be avoided that the temperature of 22 cannot be raised.

Further, according to the present embodiment, FIGS.
As shown in FIG.
Oxygen storage / active oxygen release agent 16 as an oxidation catalyst for oxidizing the fine particles 162 temporarily collected inside
1 is carried inside the partition wall 54 of the particulate filter 22. Therefore, the oxygen storage / active oxygen release agent 1 inside the partition wall 54 of the particulate filter 22 is
By 61, the partition wall 54 of the particulate filter 22 is provided.
The fine particles 162 inside the particulate filter 22
It can be removed by oxidation inside the partition wall 54.
Further, according to the present embodiment, the particulate filter 2
Fine particles 162 temporarily collected inside the second partition wall 54.
An exhaust switching valve 73 is provided as an exhaust gas reverse flow means for moving the exhaust gas. Therefore, the oxygen storage / active oxygen releasing agent 161 inside the partition wall 54 of the particulate filter 22 has an oxidative removing action of oxidizing and removing the fine particles 162 inside the partition wall 54 of the particulate filter 22. This can be promoted by moving the fine particles 162 that are temporarily collected inside (see FIG. 10).

According to this embodiment, the amount of discharged fine particles is usually smaller than the amount of fine particles that can be removed by oxidation, and even if the amount of discharged fine particles temporarily exceeds the amount of fine particles that can be removed by oxidation, the amount of discharged fine particles is By maintaining the amount of discharged particulates and the temperature of the particulate filter 22 so that only a certain amount or less of particulates that can be oxidized and removed when they are less than the amount of particulates that can be oxidized and removed are deposited on the particulate filter 22, The fine particles in the exhaust gas are oxidized and removed on the particulate filter 22 without emitting a bright flame. Therefore, unlike the conventional case, it is not necessary to remove the particles by emitting a bright flame after the particles are deposited in a laminated form on the particulate filter, and the particles are deposited before the particles are deposited in a laminated form on the particulate filter. By oxidizing, the fine particles in the exhaust gas can be removed.

Further, according to the present embodiment, the amount of discharged fine particles is usually smaller than the amount of fine particles that can be removed by oxidation, and even if the amount of discharged fine particles temporarily exceeds the amount of fine particles that can be removed by oxidation, the amount of discharged fine particles is The internal combustion engine is designed to maintain the amount of discharged particulates and the temperature of the particulate filter 22 so that the particulates of a certain amount or less that can be oxidized and removed are deposited on the particulate filter 22 when the amount becomes smaller than the amount of particulates that can be oxidized and removed. Operating conditions are controlled. Specifically, the amount of discharged fine particles becomes smaller than the amount of fine particles that can be removed by oxidation, or even if the amount of discharged fine particles temporarily exceeds the amount of fine particles that can be removed by oxidation, the amount of fine particles that are discharged thereafter becomes the amount of fine particles that can be removed by oxidation. The amount of discharged particulates and the particulate filter 2 are set so that when the number of particulates becomes smaller, less than a certain amount of particulates that can be oxidized and removed are deposited on the particulate filter 22.
The operating conditions of the internal combustion engine are controlled based on the temperature of 2.
Therefore, the operating conditions of the internal combustion engine are such that the amount of discharged fine particles is smaller than the amount of fine particles that can be removed by oxidation, or even if the amount of discharged fine particles temporarily exceeds the amount of fine particles that can be removed by oxidation, the amount of fine particles discharged thereafter is Oxidized and removable amount of particulates Exhaust particulate amount can be reliably removed by oxidation, unlike when it happens to meet the operating condition where only a certain amount of particulates that can be removed by oxidation are deposited on the particulate filter. Even if the amount of fine particles is less than the amount of fine particles, or even if the amount of discharged fine particles temporarily exceeds the amount of fine particles that can be removed by oxidation, a certain limit that can be removed by oxidation when the amount of discharged fine particles becomes smaller than the amount of fine particles that can be removed by oxidation. It is possible to prevent only the following amount of particles from being deposited on the particulate filter 22. Therefore, as compared with the case where the operating conditions of the internal combustion engine happen to coincide with each other, the particles can be more reliably oxidized before they are deposited in a laminated form on the particulate filter 22.

Further, according to the present embodiment, the oxygen storage / active oxygen release agent 61 as an oxidant carried on the particulate filter 22 absorbs and retains oxygen when excess oxygen exists in the surroundings. When the ambient oxygen concentration decreases, the retained oxygen is released in the form of active oxygen (see FIG. 3). Therefore, unlike the conventional case in which the particulates are deposited and stacked on the particulate filter and then removed by emitting a bright flame, the particulates 62 are stacked and deposited on the particulate filter 22. Before, oxygen storage / active oxygen release agent 61
The active oxygen released by the particles can oxidize and remove the fine particles 62 without emitting a luminous flame.

Further, according to the present embodiment, the amount of EGR gas as the inert gas at which the amount of soot generated reaches a peak when the exhaust switching valve 73 as the backflow means is in the forward flow mode (see FIG. 9A). The normal combustion is executed in which the amount of EGR gas supplied to the combustion chamber 5 is smaller than that of the exhaust gas.
In the backflow mode of No. 3 (see FIG. 9B), the low temperature combustion in which soot is hardly generated because the amount of EGR gas supplied to the combustion chamber 5 is larger than the amount of EGR gas at which the amount of soot is peaked. Is executed. That is, since the amount of EGR gas supplied to the combustion chamber 5 is larger than the amount of EGR gas at which the amount of soot is peaked, low temperature combustion in which soot is rarely generated is executed, so that the exhaust gas at that time is HC and CO included
By this, the action of removing fine particles from oxidation can be promoted.
Further, since the amount of EGR gas supplied to the combustion chamber 5 is larger than the amount of EGR gas at which the amount of soot is peaked, exhaust gas is caused to flow backward when low temperature combustion is performed in which soot is hardly generated. , EG where the amount of soot generated peaks
Fine particles are deposited on one surface of the particulate filter 22 when normal combustion is performed in which the amount of EGR gas supplied to the combustion chamber 5 is smaller than the amount of R gas (see FIG. 10).
(See (A)), even if the oxygen storage / active oxygen release agent 261 on the surface of the particulate filter 22 is poisoned with sulfur, the surface on the opposite side of the particulate filter 22 (the lower side of FIG. 10). HC, C flowing in from the inside and passing through the inside of the partition wall 54 of the particulate filter 22.
By the O-containing exhaust gas, the particulate filter 22
The fine particles deposited on one surface of the can be removed by oxidation without being affected by sulfur poisoning.

In the above embodiment, the temperature of the particulate filter 22 detected by the temperature sensor 39,
Oxidation-removable fine particle amount G stored in the ROM 32
Based on the relationship between (TF) and the temperature of the particulate filter 22 (FIG. 5), the operation history of the internal combustion engine, and the history of the inflowing particulate amount (integrated value), the current oxidation removal particulate amount (integrated value) is calculated. However, in the modified example of the present embodiment, the current oxidation removal particulate amount (integrated value) is based on the change in pressure loss of the particulate filter 22, the operation history of the internal combustion engine, and the inflow particulate amount (integrated value) history. It is also possible to calculate According to this modification, the same effect as that of the above-described embodiment can be obtained.

In another modification, the temperature of the particulate filter 22 may be estimated from the operation history of the internal combustion engine instead of being detected by the temperature sensor 39. Also with this modification, the same effect as that of the above-described embodiment can be obtained.

The third embodiment of the exhaust purification system for an internal combustion engine of the present invention will be described below. The configuration and operation of the present embodiment are substantially the same as the configuration and operation of the first and second embodiments described with reference to FIGS. 1 to 32, except for the points described below. Therefore, according to this embodiment, it is possible to obtain substantially the same effects as those of the first and second embodiments described above.

FIG. 33 is a flow chart showing the switching control method of the exhaust switching valve of this embodiment. As shown in FIG. 33, when this routine is started, first, in step 200, the inflowing particulate amount (see FIGS. 11 and 12) is calculated. Specifically, as shown in FIGS. 11 and 12, a plurality of maps of the inflowing particulate amount according to the operating conditions of the internal combustion engine are stored in the ROM 32, which are suitable for the operating history of the internal combustion engine up to the present. Is selected from a plurality of maps in the ROM 32, and the current inflow particulate amount (integrated value) is calculated. Next, at step 201, the amount of fine particles removed by oxidation (see FIGS. 13, 14, and 15) is calculated. Specifically, the temperature of the particulate filter 22 detected by the temperature sensor 39, the relationship between the amount of particulates G (TF) that can be removed by oxidation stored in the ROM 32 and the temperature of the particulate filter 22 (FIG. 5), internal combustion The current oxidation removal particulate amount (integrated value) is calculated based on the engine operation history and the inflow particulate amount (integrated value) history.

Next, at step 202, the fine particle purification rate (= current oxidation removal fine particle amount (integrated value) / current inflow fine particle amount (integrated value)) is calculated. Then step 20
In 3, the particulate purification rate calculated in step 202 is the target purification rate (= (PMA1-PMA2) / PMA
1) (see FIG. 14) is determined. YE
If S, the process proceeds to step 500, and if NO, this routine ends. In step 500, it is determined whether or not the deceleration operation of the internal combustion engine is in progress. If YES, the routine proceeds to step 204, where the exhaust gas flow is reversed after the deceleration operation of the internal combustion engine is completed. That is, the exhaust switching valve 73
However, the bypass position during deceleration operation of the internal combustion engine (see FIG.
(C)) is switched to the reverse flow position (Fig. 9 (B)), or the bypass position (Fig. 9 (C)) during deceleration operation of the internal combustion engine is switched to the forward flow position (Fig. 9 (A)). . On the other hand, when NO, the position of the exhaust gas switching valve 73 is maintained as it is, and this routine ends. In the modified example of the present embodiment, instead of reversing the exhaust gas flow after the end of the deceleration operation of the internal combustion engine in step 204, the exhaust gas flow is reversed during the deceleration operation period of the internal combustion engine in which the particulate emission amount from the internal combustion engine is small. You may let me.

According to the present embodiment, when it is determined in step 203 that the target purification rate of fine particles has been achieved and in step 500 that the internal combustion engine is to be decelerated, that is, in order to bypass the exhaust gas. When it is necessary to switch the exhaust switching valve 73 to, the flow of exhaust gas is reversed in step 204. Therefore, it is possible to achieve the target purification rate of the fine particles while avoiding that the fine particles are discharged as they are and to increase the back pressure unnecessarily, and the exhaust gas backflow means is switched more frequently than necessary. Can be avoided.

Hereinafter, a fourth embodiment of the exhaust emission control system for an internal combustion engine of the present invention will be described. The configuration and operation of the present embodiment are substantially the same as the configuration and operation of the first and second embodiments described with reference to FIGS. 1 to 32, except for the points described below. Therefore, according to this embodiment, it is possible to obtain substantially the same effects as those of the first and second embodiments described above.

FIG. 34 is a flow chart showing the switching control method of the exhaust switching valve of this embodiment. As shown in FIG. 34, when this routine is started, first, in step 200, the inflowing particulate amount (see FIGS. 11 and 12) is calculated. Specifically, as shown in FIGS. 11 and 12, a plurality of maps of the inflowing particulate amount according to the operating conditions of the internal combustion engine are stored in the ROM 32, which are suitable for the operating history of the internal combustion engine up to the present. Is selected from a plurality of maps in the ROM 32, and the current inflow particulate amount (integrated value) is calculated. Next, at step 201, the amount of fine particles removed by oxidation (see FIGS. 13, 14, and 15) is calculated. Specifically, the temperature of the particulate filter 22 detected by the temperature sensor 39, the relationship between the amount of particulates G (TF) that can be removed by oxidation stored in the ROM 32 and the temperature of the particulate filter 22 (FIG. 5), internal combustion The current oxidation removal particulate amount (integrated value) is calculated based on the engine operation history and the inflow particulate amount (integrated value) history.

Next, at step 600, the difference ΔPMA between the current inflowing particulate amount (integrated value) and the current oxidation-removing particulate amount (integrated value) is calculated. Next, at step 601, it is judged if the difference ΔPMA between the current inflowing particulate amount (integrated value) calculated at step 600 and the current oxidation removal particulate amount (integrated value) exceeds the threshold value TPMA1. If YES, the routine proceeds to step 204, where the exhaust gas flow is reversed. That is, the exhaust gas switching valve 73 is switched from the forward flow position (FIG. 9A) to the reverse flow position (FIG. 9B), or from the reverse flow position (FIG. 9B) to the forward flow position (FIG. A)). On the other hand, N
When it is O, the position of the exhaust switching valve 73 is maintained as it is, and this routine is ended.

According to the present embodiment, in step 601, the difference ΔPMA between the amount of fine particles that has flowed into the particulate filter 22 and the amount of fine particles that have been oxidized and removed has exceeded the predetermined value TPMA1, that is, the particulate filter. When it is determined that the amount of particulates deposited on 22 exceeds a certain threshold value, the flow of exhaust gas is reversed in step 204. Therefore, it is possible to prevent the particulates from being discharged as they are without being oxidized and removed and increasing the back pressure more than necessary until the amount of the particulates deposited on the particulate filter 22 exceeds the threshold value. it can.

The fifth embodiment of the exhaust purification system for an internal combustion engine of the present invention will be described below. The configuration and operation of this embodiment are almost the same as the configuration and operation of the first, second, and fourth embodiments described with reference to FIGS. 1 to 34, except for the points described below. Therefore, according to this embodiment, it is possible to obtain substantially the same effects as those of the above-described first, second, and fourth embodiments.

FIG. 35 is a flow chart showing the switching control method of the exhaust switching valve of this embodiment. As shown in FIG. 35, when this routine is started, first, in step 200, the inflowing particulate amount (see FIGS. 11 and 12) is calculated. Specifically, as shown in FIGS. 11 and 12, a plurality of maps of the inflowing particulate amount according to the operating conditions of the internal combustion engine are stored in the ROM 32, which are suitable for the operating history of the internal combustion engine up to the present. Is selected from a plurality of maps in the ROM 32, and the current inflow particulate amount (integrated value) is calculated. Next, at step 201, the amount of fine particles removed by oxidation (see FIGS. 13, 14, and 15) is calculated. Specifically, the temperature of the particulate filter 22 detected by the temperature sensor 39, the relationship between the amount of particulates G (TF) that can be removed by oxidation stored in the ROM 32 and the temperature of the particulate filter 22 (FIG. 5), internal combustion The current oxidation removal particulate amount (integrated value) is calculated based on the engine operation history and the inflow particulate amount (integrated value) history.

Next, at step 600, the difference ΔPMA between the current inflowing particulate amount (integrated value) and the current oxidation-removing particulate amount (integrated value) is calculated. Next, at step 601, it is judged if the difference ΔPMA between the current inflowing particulate amount (integrated value) calculated at step 600 and the current oxidation removal particulate amount (integrated value) exceeds the threshold value TPMA1. If YES, the routine proceeds to step 500, and if NO, this routine ends. In step 500, it is determined whether or not the deceleration operation of the internal combustion engine is in progress. YE
When S, the routine proceeds to step 204, where the exhaust gas flow is reversed after the deceleration operation of the internal combustion engine is completed. That is, the exhaust gas switching valve 73 is switched from the bypass position (FIG. 9 (C)) during deceleration operation of the internal combustion engine to the reverse flow position (FIG. 9 (B)), or the bypass position during deceleration operation of the internal combustion engine. (FIG. 9 (C)) is switched to the forward flow position (FIG. 9 (A)). On the other hand, when NO, the exhaust switching valve 73
The position of is maintained as it is, and this routine ends.
In the modified example of the present embodiment, instead of reversing the exhaust gas flow after the end of the deceleration operation of the internal combustion engine in step 204, the exhaust gas flow is reversed during the deceleration operation period of the internal combustion engine in which the particulate emission amount from the internal combustion engine is small. You may let me.

According to the present embodiment, it is determined in step 601 that the difference ΔPMA between the amount of fine particles that has flowed into the particulate filter 22 and the amount of fine particles that have been oxidized and removed has exceeded the predetermined value TPMA1.
When it is determined that the deceleration operation of the internal combustion engine is performed at 0, that is, in order to bypass the exhaust gas during the deceleration operation of the internal combustion engine after the amount of particulates accumulated on the particulate filter 22 exceeds the threshold value. When it is necessary to switch the exhaust gas switching valve 73, step 204
At the exhaust gas flow is reversed. Therefore, it is possible to prevent the particulates from being discharged without being oxidized and removed and increasing the back pressure unnecessarily until the amount of the particulates deposited on the particulate filter 22 exceeds the threshold value. It is possible to avoid switching the exhaust gas switching valve 73 more frequently than necessary.

The sixth embodiment of the exhaust emission control system for an internal combustion engine of the present invention will be described below. The configuration and operation of the present embodiment are substantially the same as the configuration and operation of the first and second embodiments described with reference to FIGS. 1 to 32, except for the points described below. Therefore, according to this embodiment, it is possible to obtain substantially the same effects as those of the first and second embodiments described above.

FIG. 36 is a flow chart showing the switching control method of the exhaust switching valve of this embodiment. As shown in FIG. 36, when this routine is started, first, in step 201, the amount of fine particles removed by oxidation (see FIGS. 13, 14, and 15) is calculated. Specifically, the temperature of the particulate filter 22 detected by the temperature sensor 39,
Oxidation-removable fine particle amount G stored in the ROM 32
The relationship between (TF) and the temperature of the particulate filter 22 (FIG. 5), the operation history of the internal combustion engine, and the inflow particulate amount (integrated value) obtained from the inflow particulate amount (integrated value) calculated in step 200 of FIG. 16, for example ( The present amount of fine particles for oxidation removal (integrated value) is calculated based on the history of the integrated value.

Then, in step 700, step 20
It is determined whether or not the current amount of oxidized and removed fine particles (integrated value) calculated in 1 exceeds the threshold value TPMA2. Y
In the case of ES, the routine proceeds to step 204, where the exhaust gas flow is reversed. That is, the exhaust gas switching valve 73 is switched from the forward flow position (FIG. 9A) to the reverse flow position (FIG. 9B), or from the reverse flow position (FIG. 9B) to the forward flow position (FIG. A)). On the other hand, when NO, the position of the exhaust switching valve 73 is maintained as it is,
This routine ends.

According to the present embodiment, the amount of fine particles oxidized and removed in step 700 is the target amount of fine particles Oxidized by removal T.
When it is determined that PMA2 has been exceeded, the flow of exhaust gas is reversed in step 204. Therefore, it is possible to achieve the target amount of fine particles for oxidation removal while avoiding that the fine particles are discharged as they are and increasing the back pressure more than necessary.

Hereinafter, a seventh embodiment of the exhaust emission control system for an internal combustion engine of the present invention will be described. The configuration and operation of this embodiment are almost the same as the configuration and operation of the first, second, and sixth embodiments described with reference to FIGS. 1 to 36, except for the points described below. Therefore, according to the present embodiment, it is possible to obtain substantially the same effects as those of the above-described first, second and sixth embodiments.

FIG. 37 is a flow chart showing the switching control method of the exhaust switching valve of this embodiment. As shown in FIG. 37, when this routine is started, first, in step 201, the amount of fine particles removed by oxidation (see FIGS. 13, 14, and 15) is calculated. Specifically, the temperature of the particulate filter 22 detected by the temperature sensor 39,
Oxidation-removable fine particle amount G stored in the ROM 32
The relationship between (TF) and the temperature of the particulate filter 22 (FIG. 5), the operation history of the internal combustion engine, and the inflow particulate amount (integrated value) obtained from the inflow particulate amount (integrated value) calculated in step 200 of FIG. 16, for example ( The present amount of fine particles for oxidation removal (integrated value) is calculated based on the history of the integrated value.

Then, in step 700, step 20
It is determined whether or not the current amount of oxidized and removed fine particles (integrated value) calculated in 1 exceeds the threshold value TPMA2. Y
If ES, the routine proceeds to step 500, and if NO, this routine ends. In step 500, it is determined whether or not the deceleration operation of the internal combustion engine is in progress. If YES, the routine proceeds to step 204, where the exhaust gas flow is reversed after the deceleration operation of the internal combustion engine is completed. That is, the exhaust switching valve 7
3 is a bypass position during deceleration operation of the internal combustion engine (see FIG. 9).
(C)) is switched to the reverse flow position (Fig. 9 (B)), or the bypass position (Fig. 9 (C)) during deceleration operation of the internal combustion engine is switched to the forward flow position (Fig. 9 (A)). . On the other hand, when NO, the position of the exhaust gas switching valve 73 is maintained as it is, and this routine ends. In the modified example of the present embodiment, instead of reversing the exhaust gas flow after the end of the deceleration operation of the internal combustion engine in step 204, the exhaust gas flow is reversed during the deceleration operation period of the internal combustion engine in which the particulate emission amount from the internal combustion engine is small. You may let me.

According to the present embodiment, the amount of fine particles oxidized and removed in step 700 is the predetermined value TPM.
When it is determined that A2 has been exceeded and the deceleration operation of the internal combustion engine is performed in step 500, that is,
The exhaust gas flow is reversed in step 204 when the exhaust switching valve 73 needs to be switched in order to bypass the exhaust gas during the deceleration operation of the internal combustion engine after the target oxidation removal particulate amount has been achieved. . Therefore, while avoiding that the particulates are discharged as they are and raising the back pressure unnecessarily, the target amount of particulates for oxidation removal is achieved and the exhaust gas switching valve 73 is switched more frequently than necessary. Can be avoided.

[0144]

EFFECTS OF THE INVENTION The amount of fine particles removed by oxidation is still small.
Later, when the exhaust gas flow was reversed, it was removed by oxidation.
No particulates are detached from the wall of the particulate filter.
Will be discharged from the particulate filter. This
On the other hand, the exhaust gas purification device for an internal combustion engine according to claim 1
Therefore, considering the amount of fine particles removed by oxidation,
Because the flow is reversed, the fine particles that have not been oxidized and removed
Remove from the wall of the particulate filter
Suppressed from being discharged from the rate filter
It

According to the second aspect of the present invention, it is possible to achieve the target purification rate of the fine particles while avoiding the fine particles being discharged as they are and increasing the back pressure more than necessary. .

According to the third aspect of the present invention, the target purification rate of the particulates is achieved while avoiding the particulates from being discharged as they are and the back pressure being unnecessarily increased, and the exhaust gas is exhausted. It is possible to avoid switching the gas backflow means more frequently than necessary.

According to the fourth aspect of the present invention, the fine particles are discharged without being oxidized and removed and the back pressure is increased more than necessary until the amount of the fine particles deposited on the particulate filter exceeds the threshold value. It is possible to avoid raising.

According to the fifth aspect of the present invention, the particulate matter is discharged without being oxidized and removed before the amount of the particulate matter deposited on the particulate filter exceeds the threshold value, and the back pressure is unnecessarily increased. It is possible to prevent the exhaust gas backflow means from being switched more frequently than necessary while avoiding raising the exhaust gas.

According to the invention described in claim 6, it is possible to achieve the target amount of fine particles for oxidation removal while avoiding that the fine particles are directly discharged and that the back pressure is increased more than necessary. .

According to the invention as set forth in claim 7, while avoiding that the fine particles are discharged as they are and raising the back pressure unnecessarily, the target oxidation-removed fine particle amount is achieved and the exhaust gas is exhausted. It is possible to avoid switching the gas backflow means more frequently than necessary.

According to the eighth aspect of the present invention, the fine particles are not yet oxidized and removed as the flow of the exhaust gas is reversed during the accelerated operation of the internal combustion engine in which the amount of exhaust gas is relatively large. Therefore, it is possible to prevent the particulates temporarily collected by the particulate filter from being detached from the particulate filter and discharged as they are.

According to the ninth aspect of the invention, although the exhaust gas temperature raising control of the internal combustion engine is executed in order to raise the temperature of the particulate filter, the temperature of the exhaust gas which is raised is raised. It is possible to avoid that the particulate filter is bypassed and it becomes impossible to raise the temperature of the particulate filter.

According to the tenth aspect of the present invention, unlike the conventional case, it is not necessary to emit a bright flame to remove the fine particles after the fine particles are deposited in a laminated state on the particulate filter, and the fine particles are particulate. The particulates in the exhaust gas can be removed by oxidizing the particulates before they are deposited in layers on the filter.

According to the eleventh aspect of the present invention, the operating conditions of the internal combustion engine are such that the amount of discharged fine particles is smaller than the amount of fine particles that can be removed by oxidation, or the amount of discharged fine particles is temporarily fine particles that can be removed by oxidation. Even if it exceeds the amount, if the amount of discharged particulate becomes smaller than the amount of fine particles that can be removed by oxidation, it may happen that the operating conditions happen to meet the operating conditions in which only a certain amount or less of particulate that can be oxidized and removed is deposited on the particulate filter. Differently, make sure that the amount of discharged fine particles is smaller than the amount of fine particles that can be removed by oxidation, or
Even if the amount of discharged fine particles temporarily becomes larger than the amount of fine particles that can be removed by oxidation, when the amount of discharged fine particles becomes smaller than the amount of fine particles that can be removed by oxidation, only a certain amount or less of particles that can be removed by oxidation on the particulate filter. Can be prevented from accumulating. Therefore, as compared with the case where the operating conditions of the internal combustion engine coincidentally, the fine particles can be more reliably oxidized before they are accumulated in a laminated state on the particulate filter.

According to the twelfth aspect of the present invention, unlike the conventional case where the fine particles are deposited in a laminated form on the particulate filter and then the fine particles emit a bright flame to be removed, the fine particles are removed. Before being deposited in a laminated form on the particulate filter, the active oxygen released by the oxygen storage / active oxygen release agent can oxidize and remove the fine particles without emitting a bright flame.

According to the thirteenth aspect of the present invention, the combustion is performed in which the amount of the inert gas supplied to the combustion chamber is larger than the amount of the inert gas at which the soot generation amount reaches a peak and soot is hardly generated. Therefore, HC and CO contained in the exhaust gas at that time can accelerate the oxidation and removal action of the fine particles. Further, fine particles are deposited on one surface of the particulate filter when the combustion is performed in which the amount of the inert gas supplied to the combustion chamber is less than the amount of the inert gas in which the soot generation amount becomes a peak, Even if the catalyst on the surface of the particulate filter has been poisoned with sulfur, H which has flowed in from the surface on the opposite side of the particulate filter and passed through the inside of the wall of the particulate filter.
By the exhaust gas containing C and CO, the fine particles deposited on one surface of the particulate filter can be oxidized and removed without being affected by sulfur poisoning.

According to the fourteenth aspect of the invention, the oxidant inside the wall of the particulate filter can oxidize and remove the fine particles inside the wall of the particulate filter inside the wall of the particulate filter. Furthermore, the oxidant removing action of oxidizing and removing the particulates inside the wall of the particulate filter by the oxidizing agent inside the wall of the particulate filter moves the particulates temporarily collected inside the wall of the particulate filter. Can be promoted by

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment in which an exhaust gas purification apparatus for an internal combustion engine of the present invention is applied to a compression ignition type internal combustion engine.

FIG. 2 is a diagram showing a structure of a particulate filter 22.

3 is an enlarged view of the surface of a carrier layer formed on the inner peripheral surface of the exhaust gas inflow passage 50. FIG.

FIG. 4 is a diagram showing a state of oxidation of fine particles.

FIG. 5 is a diagram showing the amount G of oxidatively removable fine particles that can be oxidatively removed without emitting a luminous flame per unit time.

FIG. 6 is a diagram showing an example of an engine operation control routine.

7 is an enlarged sectional view of a partition wall 54 of the particulate filter shown in FIG. 2 (B).

FIG. 8 is an enlarged view of the particulate filter 22 shown in FIG.

FIG. 9 is a diagram showing a relationship between a switching position of an exhaust switching valve and a flow of exhaust gas.

FIG. 10 is a diagram showing a state in which fine particles inside the partition wall 54 of the particulate filter move in response to switching of the position of the exhaust gas switching valve 73.

FIG. 11 is a diagram showing a relationship between a vehicle speed (engine speed), an inflow particulate amount (integrated value) flowing into the particulate filter, and time during steady operation of the internal combustion engine.

FIG. 12 is a diagram showing a relationship between a vehicle speed (engine speed), an inflow particulate amount (integrated value) flowing into the particulate filter, and time during a transient (deceleration) operation of the internal combustion engine.

FIG. 13 is a diagram showing the relationship between the amount of fine particles removed by oxidation and time.

FIG. 14 is a diagram showing the relationship between the amount of inflow particulates (integrated value), the amount of oxidation-removed particulates (integrated value), the amount of accumulated particulates (integrated value), and time during steady operation of the internal combustion engine.

FIG. 15 is a diagram showing the relationship between the amount of inflow particulates (integrated value), the amount of oxidation-removed particulates (integrated value), the amount of deposited particulates (integrated value), and time during transient operation of the internal combustion engine.

FIG. 16 is a flowchart showing a switching control method for the exhaust switching valve of the first embodiment.

FIG. 17 is a flowchart showing an exhaust gas flow reverse rotation prohibition control method according to the first embodiment.

FIG. 18 is a flowchart showing a bypass mode prohibition control method of the first embodiment.

FIG. 19 is a diagram showing the amount of smoke and NOx generated, and the like.

FIG. 20 is a diagram showing a combustion pressure.

FIG. 21 is a diagram showing a fuel molecule.

FIG. 22 is a diagram showing the relationship between the amount of smoke generated and the EGR rate.

FIG. 23 is a diagram showing a relationship between an injected fuel amount and a mixed gas amount.

FIG. 24 is a first operating region I ′ and a second operating region I.
It is a figure which shows I '.

FIG. 25 is a diagram showing an output of an air-fuel ratio sensor.

FIG. 26 is a diagram showing an opening degree of a throttle valve and the like.

FIG. 27 is a diagram showing an air-fuel ratio and the like in a first operating region I ′.

FIG. 28 is a diagram showing a map of a target opening degree of a throttle valve or the like.

FIG. 29 is a diagram showing an air-fuel ratio and the like in the second combustion.

FIG. 30 is a diagram showing a map of a target opening degree of a throttle valve or the like.

FIG. 31 is a diagram showing a map of a fuel injection amount.

FIG. 32 is a flowchart for controlling the operation of the engine.

FIG. 33 is a flow chart showing a switching control method for an exhaust switching valve according to a third embodiment.

FIG. 34 is a flow chart showing a switching control method for an exhaust switching valve according to a fourth embodiment.

FIG. 35 is a flowchart showing a switching control method for an exhaust switching valve according to a fifth embodiment.

FIG. 36 is a flow chart showing a switching control method for an exhaust switching valve according to a sixth embodiment.

FIG. 37 is a flowchart showing a switching control method for an exhaust switching valve according to a seventh embodiment.

[Explanation of symbols]

5 ... Combustion chamber 6 ... Fuel injection valve 20 ... Exhaust pipe 22 ... Particulate filter 25 ... EGR control valve 54 ... Partition 61 ... Oxygen storage / active oxygen release agent 62 ... Fine particles 73 ... Exhaust gas switching valve

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI F02D 21/08 301 F02D 21/08 301D 41/02 380 41/02 380E F02M 25/07 570 F02M 25/07 570J (56) Reference References: JP-A-9-94434 (JP, A) JP-A-6-19037 (JP, A) Actual development: Sho 59-30507 (JP, U) JP-B 7-106290 (JP, B2) (58) Field (Int.Cl. ⁷ , DB name) F01N 3/02 F01N 3/24 F02D 21/08 F02D 41/02 F02M 25/07

Claims (14)

(57) [Claims] 1. A particulate filter for collecting fine particles in exhaust gas discharged from a combustion chamber is arranged in an engine exhaust passage, and a particulate filter is provided on a wall of the particulate filter.
To oxidize and remove the collected fine particles in a short time
The particulate filler is an oxidant that releases active oxygen.
Particles on the wall of the particulate filter.
In parallel with collecting the particles, the collected fine particles are treated with the acid.
Internal Combustion Removed by Oxidation by Active Oxygen Released from Agent
In an exhaust emission control device for an engine, the particulate filter
To reverse the flow of exhaust gases through the wall of the filter
Equipped with exhaust gas backflow means,
Based on the amount of fine particles oxidized and removed by active oxygen
The exhaust gas reverse flow means reverses the flow of exhaust gas.
An exhaust gas purification device for an internal combustion engine that determines when to apply . 2. An inflowing particle amount estimating means for estimating the amount of particles flowing into the particulate filter,
The exhaust gas purification of an internal combustion engine according to claim 1, wherein the flow of the exhaust gas is reversed when the ratio of the amount of the particulates that have been oxidized and removed with respect to the amount of the particulates that have flowed into the particulate filter exceeds a predetermined value. apparatus. 3. An inflowing particle amount estimating means for estimating the amount of particles flowing into the particulate filter,
The exhaust gas flow is reversed during deceleration operation of the internal combustion engine after the ratio of the amount of the particulates that have been oxidized and removed to the amount of the particulates that have flowed into the particulate filter exceeds a predetermined value. An exhaust emission control device for an internal combustion engine as set forth in. 4. An inflowing particle amount estimating means for estimating the amount of particles flowing into the particulate filter,
The exhaust gas of the internal combustion engine according to claim 1, wherein the flow of the exhaust gas is reversed when the difference between the amount of fine particles that has flowed into the particulate filter and the amount of fine particles that have been oxidized and removed exceeds a predetermined value. Purification device. 5. An inflow particulate amount estimating means for estimating the amount of particulates flowing into the particulate filter is provided.
The exhaust gas flow is reversed during deceleration operation of the internal combustion engine after the difference between the amount of fine particles that has flowed into the particulate filter and the amount of fine particles that have been oxidized and removed exceeds a predetermined value. 1. An exhaust gas purification device for an internal combustion engine according to 1. 6. The exhaust gas purification device for an internal combustion engine according to claim 1, wherein the flow of the exhaust gas is reversed when the amount of the particles removed by oxidation exceeds a predetermined value. 7. The exhaust gas purification of an internal combustion engine according to claim 1, wherein the flow of exhaust gas is reversed during deceleration operation of the internal combustion engine after the amount of fine particles removed by oxidation exceeds a predetermined value. apparatus. 8. The exhaust gas purification device for an internal combustion engine according to claim 1, wherein the flow of exhaust gas is prevented from being reversed during acceleration operation of the internal combustion engine. 9. The exhaust gas backflow means has a bypass mode in which the exhaust gas is bypassed without flowing into the particulate filter, and a rising mode for raising the temperature of the particulate filter is provided. The exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 7, wherein the exhaust gas backflow means is prohibited from being placed in the bypass mode when temperature control is being performed. 10. As the particulate filter, the amount of fine particles discharged from the combustion chamber per unit time is smaller than the amount of fine particles that can be oxidized and removed on the particulate filter per unit time without oxidization and without emitting a luminous flame. When the amount is small, the particles in the exhaust gas are oxidized and removed in a short time without emitting a bright flame as soon as they flow into the particulate filter, and the amount of the discharged particles is temporarily higher than the amount of the oxidizable and removable particles. Even if the particulates are deposited on the particulate filter only below a certain limit, the particulates on the particulate filter are oxidized without emitting a bright flame when the amount of the discharged particulates is less than the amount of the oxidatively removable particulates. Using a particulate filter that can be removed, The amount of oxidatively removable fine particles depends on the temperature of the particulate filter, the amount of discharged fine particles is usually smaller than the amount of oxidizable and removable fine particles, and the amount of discharged fine particles is temporarily the amount of oxidatively removable fine particles. Even if the amount of discharged fine particles becomes greater than the amount of fine particles that can be removed by oxidation, the amount of discharged fine particles and the amount of fine particles discharged so that only a predetermined amount or less of fine particles that can be oxidized and removed can be deposited on the particulate filter. 10. A control means for maintaining the temperature of the particulate filter is provided, whereby fine particles in the exhaust gas can be oxidatively removed on the particulate filter without emitting a bright flame. An exhaust gas purification device for an internal combustion engine according to item. 11. The discharged particulate amount is usually smaller than the oxidative / removable particulate amount, and even if the discharged particulate amount temporarily exceeds the oxidative / removable particulate amount, the discharged particulate amount is thereafter reduced. When the amount of fine particles that can be removed by oxidation is reduced, the amount of discharged fine particles and the temperature of the particulate filter of the internal combustion engine are maintained so that only a certain amount or less of fine particles that can be oxidized and removed are deposited on the particulate filter. The exhaust emission control device for an internal combustion engine according to claim 10, wherein the operating conditions are controlled. 12. The oxygen storage / active oxygen, wherein the oxidant takes in oxygen to retain oxygen when excess oxygen exists in the surroundings and releases the retained oxygen in the form of active oxygen when the ambient oxygen concentration decreases. The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 11, which is a releasing agent. 13. The backflow means comprises a forward flow mode in which exhaust gas passes through a wall of the particulate filter in a first direction, and a backflow means is configured to move the exhaust gas through a wall of the particulate filter in a direction opposite to the first direction. And a backflow mode that passes in two directions, the amount of soot generated gradually increases and reaches a peak when the amount of the inert gas supplied to the combustion chamber is increased, and the soot is supplied to the combustion chamber. When the amount of the inert gas is further increased, the temperature of the fuel during combustion in the combustion chamber and the gas temperature around it become lower than the soot generation temperature, and soot is hardly generated. In the forward flow mode of the means, the amount of the inert gas supplied into the combustion chamber is smaller than the amount of the inert gas at which the amount of soot generated reaches a peak, and the combustion is performed. The amount generated is The combustion is performed such that the amount of the inert gas supplied to the combustion chamber is larger than the amount of the inert gas that becomes the smoke and soot is hardly generated.
2. An exhaust gas purification device for an internal combustion engine according to any one of 2. 14. The interior of the wall of the particulate filter by carrying the oxidant inside the wall of the particulate filter and reversing the flow of exhaust gas passing through the wall of the particulate filter. The exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 13, wherein the fine particles that have been temporarily collected in the exhaust gas are moved.