JP3525859B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a particulate filter for collecting particulates in exhaust gas discharged from a combustion chamber is disposed in an engine exhaust passage, and exhaust gas is exhausted when the exhaust gas passes through a wall of the particulate filter. 2. Description of the Related Art There is known an exhaust gas purifying apparatus for an internal combustion engine configured to collect fine particles in a gas. An example of this type of exhaust gas purifying apparatus for an internal combustion engine is disclosed in, for example, Japanese Patent Publication No. 7-106290.

[0003]

SUMMARY OF THE INVENTION However, Japanese Patent Laid-Open No. 7-1
In the exhaust gas purifying apparatus for an internal combustion engine described in JP 06290 Gazette, the flow of exhaust gas passing through the particulate filter is not reversed. For this reason, the fine particles collected on the wall of the particulate filter cannot be dispersed on one side and the other side 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 is not sufficiently transmitted to all the fine particles. Therefore, in the exhaust gas purifying apparatus for an internal combustion engine described in Japanese Patent Application Laid-Open No. 7-106290, when the amount of particulates flowing into the particulate filter exceeds a certain amount, all the particulates are removed from one side of the wall of the particulate filter. As the particles are trapped on the surface, the particle removing action of the particulate filter is not sufficiently transmitted to all the particles, and as a result, the particles are deposited on the walls of the particulate filter. Therefore, the particulate filter is clogged and the back pressure increases.

[0004] In view of the above problems, the present invention reverses the flow of exhaust gas passing through a particulate filter,
By sufficiently transmitting the oxidizing and removing effect of oxidizing and removing the fine particles trapped on the walls of the particulate filter to all the fine particles, the fine particles are prevented from being deposited on the walls of the particulate filter, and the flow of exhaust gas is prevented. When the particles are reversed, the possibility that the particles are detached from the particulate filter is reduced, and even if the particles are detached from one particulate filter,
It is an object of the present invention to provide an exhaust gas purifying apparatus for an internal combustion engine capable of securing a time required for oxidizing and removing particles by trapping the particles with another particulate filter.

[0005]

According to the first aspect of the present invention, a particulate filter for collecting particulates in exhaust gas discharged from a combustion chamber is disposed in an engine exhaust passage. In the exhaust gas purifying apparatus for an internal combustion engine, wherein the particulates in the exhaust gas are trapped when the gas passes through the wall of the particulate filter, the particulates temporarily trapped on the wall of the particulate filter An oxidizing agent for releasing active oxygen for oxidizing the particulate filter is supported on the wall of the particulate filter, and exhaust gas backflow means for reversing the flow of exhaust gas passing through the wall of the particulate filter is provided; By reversing the flow of the exhaust gas passing through the wall of the particulate filter, the fine particles trapped on the wall of the particulate filter are removed. The particulate filter is dispersed on one side and the other side of the wall of the particulate filter, thereby reducing the possibility that fine particles trapped on the wall of the particulate filter are deposited without being oxidized and removed, A plurality of particulate filters are arranged in series, and these
Providing reducing agent supply means between the particulate filters,
If the temperature of the particulate filter is
Exhaust gas flow when within the temperature range
The present invention provides an exhaust gas purifying apparatus for an internal combustion engine in which a reversal is prohibited and a reducing agent is supplied .

[0006]

According to the second aspect of the present invention, the combustion chamber
Putty for collecting fine particles in exhaust gas discharged from
The exhaust filter is located in the engine exhaust passage
When gas passes through the walls of the particulate filter
Internal combustion adapted to trap particulates in exhaust gas
In the exhaust gas purifying apparatus for an engine, the particulate matter
To oxidize fine particles temporarily collected on the filter wall
An oxidizing agent that releases active oxygen at the particulate flow rate
Supported on the filter wall, and
Exhaust gas to reverse the flow of exhaust gas through the wall
A backflow means, and the wall of the particulate filter
By reversing the flow of exhaust gas passing through
Particles collected on the wall of the particulate filter
One side of the wall of the particulate filter and the other
Surface and thereby the particulate matter is dispersed.
The particles trapped on the filter wall will not be removed by oxidation.
Reduces the possibility of sedimentation
A plurality of filters in series, and
Emissions from the combustion chamber per unit time
The amount of emitted fine particles is the unit on the particulate filter
Oxidation that can be oxidized and removed without luminous flame per hour
When the amount is smaller than the amount of fine particles that can be
Luminous flame is emitted when particles flow into the particulate filter
Oxidized and removed without performing
The amount temporarily exceeded the amount of fine particles that can be removed by oxidation.
Particles on the particulate filter
When the amount of deposited particles is less than a certain limit,
Is less than the amount of fine particles that can be removed by oxidation.
Particles on the particulate filter emit a bright flame
Particulate filter that can be removed by oxidation
And the amount of fine particles that can be removed by oxidation is particulate.
Depends on the temperature of the filter,
Normally less than the amount of fine particles that can be removed by oxidation
The amount of the discharged fine particles is temporarily smaller than the amount of the oxidizable and removable fine particles.
Even if the amount increases, the amount of the discharged
When the amount of fine particles that can be removed
Only a small amount of particulates below a certain limit
The amount of discharged particulates and the
Control measures to maintain the temperature of the particulate filter
A step is provided, whereby particles in the exhaust gas are
Acid without curling flame on curated filter
There is provided an exhaust gas purifying apparatus for an internal combustion engine, which is configured to remove and convert the exhaust gas .

[0008]

According to the third aspect of the present invention, the combustion chamber
Putty for collecting fine particles in exhaust gas discharged from
The exhaust filter is located in the engine exhaust passage
When gas passes through the walls of the particulate filter
Internal combustion adapted to trap particulates in exhaust gas
In the exhaust gas purifying apparatus for an engine, the particulate matter
To oxidize fine particles temporarily collected on the filter wall
An oxidizing agent that releases active oxygen at the particulate flow rate
Supported on the filter wall, and
Exhaust gas to reverse the flow of exhaust gas through the wall
A backflow means, and the wall of the particulate filter
By reversing the flow of exhaust gas passing through
Particles collected on the wall of the particulate filter
One side of the wall of the particulate filter and the other
Surface and thereby the particulate matter is dispersed.
The particles trapped on the filter wall will not be removed by oxidation.
Reduces the possibility of sedimentation
A plurality of filters in series, and the backflow means includes an exhaust gas
Passes through the wall of the particulate filter in the first direction
Forward flow mode and exhaust gas particulate filter
Through the wall in a second direction opposite to the first direction
Inert gas supplied into the combustion chamber.
As the amount of reactive gas increases, soot generation gradually increases.
Inert gas supplied to the combustion chamber
As the amount of fuel is further increased,
Temperature of fuel and surrounding gas is lower than soot formation temperature
Using an internal combustion engine that hardly generates soot,
In the forward flow mode of the backflow means, the amount of soot generation reaches a peak.
Less than the amount of inert gas supplied to the combustion chamber.
Performs combustion with a small amount of active gas, and reverses the reverse flow means.
In the flow mode, the generation of soot
The amount of inert gas supplied into the combustion chamber is larger than the amount
In order to perform combustion that generates almost no soot
An exhaust emission control device for a fuel engine is provided.

[0010]

According to the fourth aspect of the present invention, a plurality of direct
Reducing agent between the particulate filters arranged in a row
4. The internal combustion engine according to claim 2, further comprising a supply unit.
An exhaust emission control device is provided.

[0012]

According to the fifth aspect of the present invention, as the particulate filter, the amount of fine particles discharged from the combustion chamber per unit time is oxidized on the particulate filter without emitting a bright flame per unit time. When the amount of the oxidizable and removable particles is smaller than the amount of the oxidizable and removable particles, when the particles in the exhaust gas flow into the particulate filter, they are oxidized and removed without emitting a bright flame, and the amount of the discharged particles is temporarily reduced to the amount of the oxidizable and removable particles. Even when the amount of the particulates increases, the particulates on the particulate filter emit a luminous flame when the amount of the discharged particulates becomes smaller than the amount of the oxidizable and removable particulates when the particulates are deposited only below a certain limit on the particulate filter. Particulate filter that can be removed without oxidation Used, the amount of the oxidizable and removable particles depends on the temperature of the particulate filter, the amount of the discharged particles is usually smaller than the amount of the oxidizable and removable particles, and the amount of the discharged particles is temporarily oxidizable and removable. Even if the amount of fine particles becomes larger than the amount of fine particles, the discharged fine particles are so deposited that only particles of a certain amount or less that can be oxidized and removed when the amount of fine particles discharged becomes smaller than the amount of fine particles that can be removed by oxidation are not deposited on the particulate filter. 2. The internal combustion engine according to claim 1 , further comprising control means for maintaining the amount and the temperature of the particulate filter, whereby the particulates in the exhaust gas are oxidized and removed on the particulate filter without producing a bright flame. An exhaust gas purification device for an engine is provided.

[0014]

According to the invention described in claim 6, the putty is provided.
As a combustion filter, the combustion chamber per unit time
The amount of particulates discharged from
Acid without emitting a luminous flame per unit time
When the amount of fine particles that can be removed by oxidation
Particles in the exhaust gas flow to the particulate filter
When it enters, it can be oxidized and removed without emitting a bright flame,
The amount of the discharged fine particles is temporarily reduced by the oxidation-removable fine particles.
Even if it exceeds the amount, on the particulate filter
When particles accumulate below a certain limit in
The amount of the discharged fine particles is smaller than the amount of the fine particles that can be removed by oxidation.
Particles on particulate filter when exhausted
That can be oxidized and removed without producing a bright flame
The amount of fine particles that can be removed by oxidation
Depends on the temperature of the particulate filter,
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 the discharged fine particles is temporarily reduced by the oxidation removal.
Even if the amount of particulates exceeds
The amount of fine particles has become smaller than the amount of fine particles that can be removed by oxidation.
Only particles below a certain amount that can be oxidized and removed
Discharge so that it does not accumulate on the particulate filter
Maintains fine particle content and particulate filter temperature
Control means for controlling exhaust gas
Of fine particles on a particulate filter
Oxidation and removal without emission
Normally less than the amount of fine particles that can be removed by oxidation
The amount of the discharged fine particles is temporarily smaller than the amount of the oxidizable and removable fine particles.
Even if the amount increases, the amount of the discharged
When the amount of fine particles that can be removed
Only a small amount of particulates below a certain limit
The amount of discharged particulates and the amount of
Internal combustion engine to maintain the temperature of the particulate filter
The driving condition according to claim 1 or 3, wherein the operating condition is controlled.
An exhaust purification device for an internal combustion engine is provided.

[0016]

According to the invention described in claim 7, the discharge is performed.
The amount of fine particles is usually smaller than the amount of fine particles that can be removed by oxidation.
And the amount of discharged particulates can be temporarily removed by oxidation.
Even if the amount of fine particles exceeds the
When the amount of particles is smaller than the amount of fine particles that can be removed by oxidation.
Only a small amount of fine particles that can be oxidized and removed
In order to prevent accumulation on the curated filter,
Maintain the particle amount and the temperature of the particulate filter
3. The operating condition of the internal combustion engine for controlling the operation of the engine.
The exhaust gas purifying apparatus for an internal combustion engine according to (1) is provided.

[0018]

According to the eighth aspect of the present invention, the backflow means includes: a forward flow mode in which exhaust gas passes through the wall of the particulate filter in the first direction; A reverse flow mode that passes in a second direction opposite to the one direction, and as the amount of inert gas supplied into the combustion chamber increases, the amount of soot generated gradually increases and peaks And the amount of inert gas supplied into the combustion chamber is further increased, so that the temperature of the fuel and the surrounding gas during combustion in the combustion chamber becomes lower than the generation temperature of soot, and soot is almost generated. Using an internal combustion engine that no longer runs, during the forward flow mode of the backflow means, performs combustion in which the amount of inert gas supplied into the combustion chamber is smaller than the amount of inert gas at which the generation amount of soot becomes a peak,
In the backflow mode of the backflow means, the amount of the inert gas supplied into the combustion chamber is larger than the amount of the inert gas at which the generation amount of soot becomes a peak, and the combustion is performed so that almost no soot is generated. Item 3. An exhaust gas purification device for an internal combustion engine according to item 1 or 2 .

[0020]

According to the ninth aspect of the present invention, the exhaust gas purifying apparatus for an internal combustion engine according to any one of the first to third aspects, wherein the oxidizing agent is carried inside a wall of the particulate filter. Is provided.

[0022]

According to the tenth aspect of the present invention, the acid
Agent is carried inside the wall of the particulate filter
Are, the by reversing the flow of exhaust gas through the walls of the particulate filter, according to claim 1 which is adapted to move the temporarily trapped particulate in the interior of the wall of the particulate filter Any of 3
An exhaust gas purification device for an internal combustion engine according to claim 1 is provided.

[0024]

According to the eleventh aspect of the present invention, the fine particles trapped on the wall of the particulate filter are dispersed to substantially the same extent on one side and the other side of the wall of the particulate filter. An exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 3 is provided.

[0026]

[0027]

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 gas purifying apparatus 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, 9 Denotes an exhaust valve, and 10 denotes an exhaust port. The intake port 8 is connected to a surge tank 12 via a corresponding intake branch pipe 11, and the surge tank 12 is connected to a compressor 15 of an exhaust turbocharger 14 via an intake duct 13. A throttle valve 17 driven by a step motor 16 is arranged in the intake duct 13, and a cooling device 18 for cooling intake air flowing through 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 engine cooling water cools the intake air. On the other hand, the exhaust port 10 is connected to the exhaust manifold 1.
9 and an exhaust pipe 20 connected to the exhaust turbine 21 of the exhaust turbocharger 14, and the outlet of the exhaust turbine 21 incorporates a first particulate filter 22 and a second particulate filter 122 arranged in series. It is connected to the casing 23. The first particulate filter 22 and the second particulate filter 122 have substantially the same structure.

The first particulate filter 22 and the second particulate filter 122 are configured to allow exhaust gas to flow in both the forward flow direction and the reverse flow direction. Reference numeral 71 denotes a first particulate filter 22 and a second particulate filter 122
The first passage 72, which becomes the upstream passage of the first particulate filter 22 when passing through the first particulate filter 22, flows through the first particulate filter 22 and the second particulate filter 122 in the reverse flow direction. This is the second passage that becomes the upstream passage of the second particulate filter 122 when the second particulate filter 122 is operated. 75 is a first particulate filter 22 and a second particulate filter 12
A reference numeral 73 denotes 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 denotes an exhaust switching valve driving device.
Reference numeral 76 denotes a fuel addition device for adding and supplying fuel as a reducing agent to the connection passage 75, and reference numeral 77 denotes a fuel addition device driving device that drives the fuel addition 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 electrically controlled EGR control valve 25 is disposed in the EGR passage 24. The EGR passage 24
A cooling device 26 for cooling the EGR gas flowing in the EGR passage 24 is disposed around the cooling device 26. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 26, and the engine cooling water cools the EGR gas. On the other hand, each fuel injection valve 6 is connected to a fuel reservoir, a so-called common rail 27, via a fuel supply pipe 26. An electric control type variable discharge fuel pump 28 is provided in the common rail 27.
The fuel supplied from the common rail 27 is supplied to the fuel injection valve 6 through 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.
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 is connected to each other by a bidirectional bus 31. A ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Microprocessor) 34, an input port 35, An output port 36 is provided. The output signal of the fuel pressure sensor 29 is input to the input port 35 via the corresponding AD converter 37. Further, a temperature sensor 39 for detecting a temperature representing the temperature of the first particulate filter 22 and the second particulate filter 122 is mounted in the connection passage 75, and the output signal of the temperature sensor 39 corresponds to the temperature sensor 39. Is input to the input port 35 via the AD converter 37. A load sensor 41 that generates an output voltage proportional to the depression amount L of the accelerator pedal 40 is connected to the accelerator pedal 40, and the output voltage of the load sensor 41 is input to the input port 35 via the corresponding AD converter 37. . Further input port 35
Is connected to a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, by 30 °.
On the other hand, the output port 36 is connected to the fuel injection valve 6, the throttle valve driving step motor 1 through the corresponding drive circuit 38.
6, connected to the EGR control valve 25, the fuel pump 28, the exhaust switching valve driving device 74, and the driving device 77 for the fuel addition device.

FIG. 2 shows a first particulate filter 2.
2 shows the structure of No. 2. As described above, since the second particulate filter 122 has the same structure as the first particulate filter 22, the structure of the second particulate filter 122 will not be described in detail. In FIG. 2, (A) is a particulate filter 2.
2 shows a front view, and FIG. 2B shows a side sectional view of the particulate filter 22. As shown in FIGS. 2A and 2B, the first particulate filter 22 has a honeycomb structure and includes a plurality of exhaust passages 50 and 51 extending in parallel with each other. These exhaust passages are constituted by an exhaust gas inflow passage 50 whose downstream end is closed by a plug 52 and an exhaust gas outflow passage 51 whose upstream end is closed by a plug 53. Note that FIG.
In FIG. 5A, the hatched portion indicates the plug 53. Therefore, the exhaust gas inflow passages 50 and the exhaust gas outflow passages 51 are alternately arranged via the thin partition walls 54.
In other words, the exhaust gas inflow passage 50 and the exhaust gas outflow passage 51 are each surrounded by the four exhaust gas outflow passages 51, and each exhaust gas outflow passage 51 is surrounded by the four exhaust gas inflow passages 50. It is arranged so that. The particulate filter 22 is formed of, for example, a porous material such as cordierite.
As shown by an arrow in (B), the gas flows through the surrounding partition wall 54 and flows out into the adjacent exhaust gas outflow passage 51.

In the embodiment according to the present invention, the peripheral wall surfaces of the exhaust gas inflow passages 50 and the exhaust gas outflow passages 51, that is, on both side surfaces of each partition wall 54, the outer end surface of the plug 53 and the plugs 52,5
A support layer made of, for example, alumina is formed on the entire inner end face of the support 3. On this support, a noble metal catalyst and excess oxygen in the surroundings take in oxygen to retain oxygen. In addition, an oxygen storage / active oxygen releasing agent that releases the retained oxygen in the form of active oxygen when the surrounding oxygen concentration decreases oxidizes the fine particles temporarily collected on the surface of the partition wall 54 of the particulate filter. Supported as an oxidation catalyst.

In this case, in the embodiment according to the present invention, platinum Pt is used as a noble metal catalyst, and an alkali metal such as potassium K, sodium Na, lithium Li, cesium Cs, and rubidium Rb is used as an oxygen storage / active oxygen release agent. At least one selected from alkaline earth metals such as barium, 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 release agent, 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, and strontium Sr is used. Is preferred.

Next, the action of the particulate filter 22 for removing fine particles in the exhaust gas will be described.
Although the case where potassium and potassium K are supported will be described as an example, the same fine particle removing action can be performed 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 takes place under excess air, so that the exhaust gas contains a large amount of excess air. That is, when the ratio of air to fuel supplied into the intake passage and the combustion chamber 5 is referred to as the air-fuel ratio of the exhaust gas, the air-fuel ratio of the exhaust gas is lean in a compression ignition type internal combustion engine as shown in FIG. ing. Further, since NO is generated in the combustion chamber 5, the exhaust gas contains NO. Further, sulfur S is contained in the fuel, and the sulfur S reacts with oxygen in the combustion chamber 5 to become SO ₂ .
Therefore, SO ₂ is contained in the exhaust gas. Therefore, exhaust gas containing excess oxygen, NO, and SO ₂ flows into the exhaust gas inflow passage 50 of the particulate filter 22.

FIGS. 3A and 3B show an exhaust gas inflow passage.
50 is an enlarged view of the surface of the carrier layer formed on the inner peripheral surface of the substrate 50.
It is represented in a formula. 3 (A) and 3 (B).
60 indicates platinum Pt particles, and 61 indicates potassium.
Shows oxygen storage / active oxygen release agent containing K
You. As described above, the exhaust gas contains a large amount of excess oxygen.
Exhaust gas is particulate filter 2
When the gas flows into the exhaust gas inflow passage 50 of FIG.
As shown, these oxygen O_TwoIs O_Two ^-Or O ^2-In the form of
It adheres to the surface of platinum Pt. On the other hand, NO in exhaust gas
O on the surface of platinum Pt_Two ^-Or O^2-Reacts with NO_TwoWhen
(2NO + O_Two→ 2NO_Two). Then the generated N
O_TwoPart of oxygen is oxidized on platinum Pt and oxygen storage and activity
While being absorbed in the oxygen releasing agent 61 and binding to potassium K
3A, nitrate ions NO_Three ^-Form of
Diffuses into the oxygen storage / active oxygen release agent 61 with potassium nitrate
Umm KNO_ThreeGenerate

On the other hand, as described above, SO is contained in the exhaust gas.
_TwoIs also included in this SO_TwoIs the same mechanism as NO
Absorbed by the oxygen storage / active oxygen release agent 61
You. That is, as described above, the oxygen O_TwoIs O_Two ^-Or O^2-of
Adhered to the surface of platinum Pt in the form of SO
_TwoIs O on the surface of platinum Pt_Two ^-Or O^2-Reacts with SO _Three
It becomes. Then the generated SO_ThreePart of is on platinum Pt
While being oxidized, it is absorbed into the oxygen storage / active oxygen release agent 61.
Is collected and combined with potassium K to form sulfate ion SO._Four ^2-
Is diffused into the oxygen storage / active oxygen release agent 61 in the form of
Potassium K_TwoSO_FourGenerate In this way, oxygen absorption
The storage / active oxygen release catalyst 61 contains potassium nitrate KNO_Three
And potassium sulfate K_TwoSO_FourIs generated.

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

As described above, when the fine particles 62 adhere to the surface of the oxygen storage / active oxygen release agent 61, the oxygen concentration decreases at the contact surface between the fine particles 62 and the oxygen storage / active oxygen release agent 61. When the oxygen concentration decreases, oxygen storage with high oxygen concentration
A concentration difference occurs between the active oxygen releasing agent 61 and the inside of the active oxygen releasing agent 61, so that the oxygen in the oxygen storing / active oxygen releasing agent 61 moves toward the contact surface between the fine particles 62 and the oxygen storing / active oxygen releasing agent 61. And As a result, the oxygen storage / active oxygen release agent 6
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,
O is released from the oxygen storage / active oxygen release agent 61 to the outside. The NO released to the outside is oxidized on 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 61_TwoSO_FourMokari
Umm K, Oxygen O and SO_TwoDecomposed into oxygen O
To the contact surface between 62 and oxygen storage / active oxygen releasing agent 61
Yes, SO_TwoFrom the oxygen storage / active oxygen release agent 61 to the outside
Released. SO released outside_TwoIs the platinum P on the downstream side
t is oxidized on the oxygen and is again an oxygen storage / active oxygen release agent
It is absorbed in 61. However, potassium sulfate K_TwoSO_Four
Is potassium nitrate KNO _Threecompared to
Hard to release active oxygen.

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

The conventional particulate filter 2
When the fine particles deposited in a layered form on 2 are burned, the particulate filter 22 glows red and burns with a flame. Such combustion with a flame cannot be sustained unless it is at a high temperature, so that the temperature of the particulate filter 22 must be maintained at a high temperature in order to maintain the combustion with such a flame.

On the other hand, in the present invention, the fine particles 62 are oxidized without emitting a bright flame as described above, and at this time, the surface of the particulate filter 22 does not glow. That is, in other words, in the present invention, the fine particles 62 are oxidized and removed at a considerably lower temperature than in the prior art. Therefore, the fine particles 6 which do not emit a bright flame according to the present invention 6
The action of removing fine particles by oxidation of 2 is completely different from the action of removing fine particles by conventional combustion accompanied by a flame.

Since the platinum Pt and the oxygen storage / active oxygen releasing agent 61 are activated as the temperature of the particulate filter 22 increases, the amount of the active oxygen O that can be released per unit time by the oxygen storage / active oxygen releasing agent 61 is determined. Increases as the temperature of the particulate filter 22 increases. Therefore, the amount of oxidizable particles that can be oxidized and removed on the particulate filter 22 without emitting a luminous flame per unit time increases as the temperature of the particulate filter 22 increases.

The solid line in FIG. 5 shows the amount G of oxidizable and removable fine particles and the amount of sulfate produced per unit time that can be oxidized and removed without emitting luminous flame. In FIG. 5, the horizontal axis represents the temperature TF of the particulate filter 22. When the amount of the fine particles discharged from the combustion chamber 5 per unit time is referred to as a discharged fine particle amount M, when the discharged fine particle amount M is smaller than the oxidation-removable fine particles G, that is, in the region I of FIG. As soon as all the fine particles 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 how the fine particles are oxidized in such a case. That is, when the amount of active oxygen is insufficient to oxidize all the fine particles, as shown in FIG. 4A, when the fine particles 62 adhere to the oxygen storage / active oxygen releasing agent 61, a part of the fine particles 62 Only the fine particles are oxidized, and the finely oxidized fine particles remain on the carrier layer. Next, when the state of the shortage of the active oxygen amount continues, the fine particles which 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. It becomes covered with the fine particle portion 63.

The residual fine particle portion 6 covering the surface of the carrier layer
3 gradually changes to a carbon material which is hardly oxidized, and thus the residual fine particle portion 63 is likely to remain as it is. Further, when the surface of the carrier layer is covered with the residual fine particle portion 63, the oxidizing action of NO and SO ₂ by platinum Pt and the releasing action of active oxygen by the 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 remaining fine particle portion 63 one after another. That is, the fine particles are deposited in a layered manner. When the fine particles are deposited in a layered manner in this way, even if the fine particles are easily oxidized, they are no longer oxidized by the active oxygen O because they are separated from platinum Pt and the oxygen storage / active oxygen releasing agent 61. Therefore, further fine particles accumulate on the fine particles 64 one after another. That is, when the state in which the amount M of discharged fine particles is larger than the amount G of fine particles that can be removed by oxidation continues, the fine particles are deposited on the particulate filter 22 in a layered manner. Unless the temperature of the filter 22 is increased, the deposited fine particles cannot be ignited and burned.

As described above, in the region I of FIG. 5, the fine particles are oxidized in a short time without emitting a bright flame on the particulate filter 22, and in the region II of FIG. Deposit in a shape. Therefore, the particulates are
In order to prevent the particles from being deposited in a layered manner on top, the amount M of discharged fine particles must always be smaller than the amount G of fine particles that can be removed by oxidation.

As can be seen from FIG. 5, the particulate filter 22 used in the embodiment of the present invention can oxidize the fine particles even if the temperature TF of the particulate filter 22 is considerably low. In the compression ignition type internal combustion engine shown, the amount M of discharged particulates and the temperature TF of the particulate filter 22
Can always be maintained to be smaller than the amount G of particles that can be removed by oxidation. Therefore, in the first embodiment according to the present invention, the amount M of discharged fine particles and the temperature TF of the particulate filter 22 are maintained such that the amount M of discharged fine particles is always smaller than the amount G of fine particles that can be removed by oxidation. If the amount M of discharged fine particles is always smaller than the amount G of fine particles that can be removed by oxidation, the fine particles hardly accumulate on the particulate filter 22, and thus the back pressure hardly increases. Therefore, the engine output does not decrease.

On the other hand, as described above, once the fine particles are deposited in layers on the particulate filter 22, even if the amount M of discharged fine particles becomes smaller than the amount G of fine particles that can be removed by oxidation, the fine particles are oxidized by the active oxygen O. It is difficult. However, when the unoxidized fine particle portion is beginning to remain, that is, when the fine particles are deposited only below a certain limit, the exhaust fine particle amount M
Is smaller than the amount G of fine particles that can be removed by oxidation, the remaining fine particles are oxidized and removed by the active oxygen O without emitting a bright flame. Therefore, in the second embodiment, the amount M of discharged fine particles is usually smaller than the amount G of fine particles that can be removed by oxidation,
And the amount M of discharged fine particles is temporarily the amount G of fine particles that can be oxidized and removed.
Even if the amount increases, as shown in FIG. 4B, the surface of the carrier layer is not covered by the residual fine particle portion 63, that is, when the amount M of discharged fine particles becomes smaller than the amount G of fine particles that can be removed by oxidation. The amount M of discharged fine particles and the temperature TF of the particulate filter 22 are maintained so that only a small amount of particles less than a certain limit that can be oxidized and removed is not deposited on the particulate filter 22.

Immediately after the start of the engine, the temperature TF of the particulate filter 22 is low. Therefore, it is considered that the second embodiment is more suitable for actual driving. 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, the particulates are deposited on the particulate filter 22 in a layered manner. May be. In such a case, the particulates deposited on the particulate filter 22 can be oxidized without emitting a bright flame by temporarily making the air-fuel ratio of a part or the whole of the exhaust gas rich.

That is, when the air-fuel ratio of the exhaust gas is made rich, that is, when the oxygen concentration in the exhaust gas is reduced, the active oxygen O is released from the oxygen storage / active oxygen releasing agent 61 to the outside at once, and the active oxygen O is released 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 on the particulate filter 22 in a layered manner, or the air-fuel ratio of the exhaust gas may be made rich periodically. As a method of making the air-fuel ratio of the exhaust gas rich, for example, when the engine load is relatively low, the EG
R rate (EGR gas amount / (intake air amount + EGR gas amount))
Of the throttle valve 17 and the opening of the EGR control valve 25 so that the average air-fuel ratio in the combustion chamber 5 becomes rich. be able to.

As described above, the higher the temperature TF of the particulate filter 22, the higher the ability of the particulate filter 22 to oxidize and remove fine particles. However, as shown in FIG. 5B, when the temperature of the exhaust gas is increased to increase the temperature of the particulate filter 22, the amount of sulfate generated in the exhaust gas increases. Therefore, in this embodiment,
The sulfate generation allowable value S1 and the corresponding sulfate generation temperature TF1 are determined, and when the temperature TF of the particulate filter 22 becomes higher than the sulfate generation temperature TF1, control for improving the sulfate reduction ability as described later is performed. Done.

FIG. 6 shows an example of an engine operation control routine. Referring to FIG. 6, first, at step 100, it is determined whether or not 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 of the throttle valve 17 is controlled in step 101 so that the amount M of discharged particulates becomes smaller than the amount G of particulates that can be removed by oxidation. The opening of the control valve 25 is controlled, and step 103
In, 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 of the throttle valve 17 is controlled in step 104 so that the EGR rate becomes 65% or more. ,
In step 105, the opening of the EGR control valve 25 is controlled, and in step 106, the fuel injection amount is controlled so that the average air-fuel ratio in the combustion chamber 5 becomes rich.

Incidentally, the fuel and the lubricating oil contain calcium Ca, and therefore, the calcium Ca is contained in the exhaust gas. This calcium Ca generates calcium sulfate CaSO ₄ when SO ₃ is present. This calcium sulfate CaSO ₄ is solid and does not thermally decompose even at high temperatures. Therefore, when the calcium sulfate CaSO ₄ is generated, the pores of the first particulate filter 22 and the second particulate filter 122 are closed by the calcium sulfate CaSO ₄ , and as a result, the exhaust gas is reduced to the first particulate filter. It is difficult to flow through the filter 22 and the second particulate filter 122. In this case, when an alkali metal or alkaline earth metal having a higher ionization tendency than calcium Ca, such as potassium K, is used as the oxygen storage / active oxygen release agent 61, SO ₃ diffused into the oxygen storage / active oxygen release agent 61 becomes potassium. Combined with K to form potassium sulfate K ₂ SO ₄ and calcium C
a flows out into the exhaust gas outflow passage 51 through the partition walls 54 of the particulate filters 22 and 122 without being combined with SO ₃ . Therefore, the particulate filter 2
The clogging of the 2,122 pores is eliminated. Therefore, as described above, the oxygen storage / active oxygen release agent 61 is an alkali metal or alkaline earth metal having a higher ionization tendency than calcium Ca, that is, potassium K and lithium L.
It is preferable to use i, cesium Cs, rubidium Rb, barium Ba, and strontium Sr.

FIG. 7 is an enlarged sectional view of the partition wall 54 of the first particulate filter 22 shown in FIG.
Although not shown, the second particulate filter 122
The cross section of the partition wall is also the same as the cross section of the partition wall of the first particulate filter 22 shown in FIG. In FIG. 7, 6
6 is an exhaust gas passage extending inside the partition wall 54;
Is a base material of the particulate filter, and 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 fine particles temporarily collected on the surface of the partition wall 54 of the particulate filter. 161 is an oxygen storage / carrying device carried inside the partition wall 54 of the particulate filter.
It is an active oxygen release agent. The oxygen storage / active oxygen release agent 161 also has the same oxidizing function as the oxygen storage / active oxygen release agent 261 and can oxidize fine particles temporarily trapped inside the partition wall 54 of the particulate filter. it can.

FIG. 8 shows the first particulate filter 22 and the second particulate filter 1 shown in FIG.
It is an enlarged view of 22. More specifically, FIG. 8A is an enlarged plan view of the first particulate filter and the second particulate filter, and FIG. 8B is an enlarged side view of the first particulate filter and the second particulate filter. FIG. 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 is a diagram when the exhaust switching valve 73 is in the forward flow position, FIG. 9B is a diagram when the exhaust switching valve 73 is in the reverse flow position, and FIG. FIG. 7 is a diagram when the valve 73 is at a bypass position. When the exhaust switching valve 73 is at the forward flow position, as shown in FIG. 9A, 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 passes through the first passage 71. Through one of the particulate filters 22 and then into the connecting passage 75
, And then the second particulate filter 12
2 and finally through the second passage 72 and again through the exhaust switching valve 73 to return to the exhaust pipe. When the exhaust switching valve 73 is at the reverse flow position, as shown in FIG. 9B, the exhaust gas that has passed through the exhaust switching valve 73 and flowed into the casing 23 first passes through the second passage 72, and then passes through the second passage 72. Second particulate filter 122, connection passage 7
5 and the first particulate filter 22 in FIG.
It passes in the opposite direction to the case shown in (A), finally passes through the first passage 71, passes through the exhaust switching valve 73 again, and returns to the exhaust pipe. When the exhaust 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 is in the casing 23
The gas passes through the exhaust switching valve 73 without flowing into the inside. The switching of the exhaust switching valve 73 is performed, for example, every time the internal combustion engine is decelerated.

FIG. 10 is a view showing a state in which the fine particles inside the partition 54 of the particulate filter move in accordance with the switching of the position of the exhaust switching valve 73.
More specifically, FIG. 10A is an enlarged cross-sectional view of the partition wall 54 of the particulate filters 22 and 122 when the exhaust switching valve 73 is at the forward flow position (see FIG. 9A).
(B) is an enlarged sectional view of the partition wall 54 of the particulate filters 22 and 122 when the exhaust switching valve 73 is switched from the forward flow position to the reverse flow position (see FIG. 9B). As shown in FIG. 10A, the exhaust switching valve 73
When the exhaust gas flows from the upper side to the lower side, the fine particles 162 existing in the exhaust gas passage 66 inside the partition are separated by the flow of the exhaust gas into the oxygen storage / active oxygen releasing agent inside the partition. 161 and has accumulated 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 present in the exhaust gas passage 66 inside the partition wall are removed. 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 release agent 161,
Becomes fully oxidized. Also, when the exhaust gas switching valve 73 is disposed at the forward flow position (FIG. 10)
Part of the fine particles deposited on the oxygen storage / active oxygen releasing agent 261 on the surface of the partition wall of the particulate filter (see (A)) is partially removed by switching the exhaust switching valve 73 from the forward flow position to the reverse flow position. It desorbs from the oxygen storage / active oxygen release agent 261 on the surface of the partition wall of the curated filter (see FIG. 10B). The desorption amount of the fine particles increases as the temperature of the particulate filters 22 and 122 increases, and increases as the amount of exhaust gas increases. The higher the temperature of the particulate filters 22 and 122, the greater the amount of desorbed fine particles. The higher the temperature of the particulate filters 22 and 122, the weaker the binding force of the SOF as a binder for depositing the fine particles. Because it becomes.

That is, when the exhaust gas switching valve 73 is switched from the forward flow position shown in FIG. 9A to the reverse flow position shown in FIG. 9B, the exhaust gas is temporarily collected on the surface of the second particulate filter 122. Some of the fine particles that have been removed from the second particulate filter 122. The detached fine particles are supplied to the second particulate filter 12.
9 is collected by the first particulate filter 22 disposed downstream of the exhaust gas flow (see FIG. 9).
(B)). Therefore, the second particulate filter 1
It is prevented that the fine particles detached from 22 are discharged as they are. Further, the fine particles undergo an oxidative removal action in the second particulate filter 122 before being desorbed from the second particulate filter 122, and are desorbed from the second particulate filter 122 to be separated from the first particulate filter 122. After being collected by the filter 22, the first particulate filter 22 undergoes an oxidative removal action. That is, compared to the case where only one particulate filter is provided,
It becomes possible to exert an oxidative removal action on the fine particles over a long time.

Similarly, when the reverse flow position of the exhaust switching valve 73 shown in FIG. 9B is switched to the forward flow position shown in FIG. 9A, the exhaust gas is temporarily captured on the surface of the first particulate filter 22. Part of the collected fine particles desorbs from the first particulate filter 22. The desorbed fine particles are collected by a second particulate filter 122 disposed downstream of the first particulate filter 22 in the exhaust gas flow (FIG. 9).
(A)). Therefore, the first particulate filter 2
This prevents the fine particles desorbed from 2 from being discharged as they are. Before the particles are separated from the first particulate filter 22, they are subjected to an oxidative removal action in the first particulate filter 22, and are separated from the first particulate filter 22 to remove the second particulates. After being collected by the filter 122, the second particulate filter 122 undergoes an oxidative removal action.

In this embodiment, the exhaust gas switching valve 73 is switched from the forward flow position shown in FIG. 9A to the reverse flow position shown in FIG. 9B, and from the reverse flow position shown in FIG. Switching to the forward flow position shown in (A) is performed by removing the fine particles trapped by the partition walls 54 of the particulate filters 22 and 122 from the partition walls 54 of the particulate filters 22 and 122.
In such a manner as to be distributed on the upper surface and the lower surface (see FIG. 7). By switching the exhaust switching valve 73 in this manner, the possibility that the fine particles trapped in the partition walls 54 of the particulate filters 22 and 122 are deposited without being oxidized and removed is reduced. Preferably, the fine particles trapped by the partition walls 54 of the particulate filters 22 and 122 are substantially equally dispersed on the upper and lower surfaces of the partition walls 54 of the particulate filters 22 and 122.

FIG. 11 shows the fuel addition device 76 shown in FIG.
5 is a flowchart illustrating a control method. Shown in FIG.
As described above, when this routine is started, first, in step 2
00, the first pulse detected by the temperature sensor 39.
Particulate filter 22 and second particulate
The temperature TF representing the temperature of the filter 122 is read.
It is. Next, at step 201, this temperature TF is
It is determined whether it is higher than TT. This threshold TT is
When fuel is added as a reducing agent, the fuel adding device 76
Particulate fill downstream of exhaust gas flow
Catalyst supported on the heaters 22 and 122,
Temperature at which the storage / active oxygen releasing agent 61 can be sufficiently activated
Is set to If NO, add fuel
In addition, due to the sulfur component contained in the fuel,
When the rate filters 22 and 122 are poisoned by SOF
Judge and terminate this routine without adding fuel.
You. On the other hand, when YES, the fuel is added.
Therefore, the downstream side of the exhaust gas flow from the fuel addition device 76
Combustion in the particulate filters 22 and 122
Can be activated and also have added fuel
By reducing action, SO _ThreeAnd NO_TwoGeneration is greatly suppressed
It is determined that it is possible to
Fuel is added from the fuel adding device 76.

Next, at step 203, it is determined whether or not the temperature TF representing the temperature of the particulate filters 22 and 122 is higher than the above-mentioned sulfate generation temperature TF1 (FIG. 5). If YES, it is determined that the generated sulfate needs to be reduced, and the process proceeds to step 204. In step 204, the addition of fuel performed in step 202 is continued, and the switching of the position of the exhaust switching valve 73 (FIG. 9) is prohibited. On the other hand, when the determination is NO, it is determined that it is not necessary to supply fuel as a reducing agent to one of the particulate filters 22 and 122 in order to reduce the generated sulfate, and the position of the exhaust switching valve 73 is switched. This routine ends without prohibition.

FIG. 12 shows the change in output torque and the smoke when the air-fuel ratio A / F (horizontal axis in FIG. 12) is changed by changing the opening of the throttle valve 17 and the EGR rate during low engine load operation. , HC, CO, and NOx are shown. As can be seen from FIG. 12, in this experimental example, the smaller the air-fuel ratio A / F, the higher the E
When the GR rate increases and is equal to or lower than the stoichiometric air-fuel ratio (≒ 14.6), the EGR rate is equal to or higher than 65%.
As shown in FIG. 12, when the air-fuel ratio A / F is reduced by increasing the EGR rate, the amount of smoke generated when the air-fuel ratio A / F becomes about 30 when the EGR rate becomes close to 40%. Start growing. Then, further EG
When the R rate is increased and the air-fuel ratio A / F is reduced, the amount of smoke generated increases sharply and reaches a peak. Then further EG
When the R ratio is increased and the air-fuel ratio A / F is reduced, the smoke is sharply reduced, the EGR ratio is set to 65% or more, and the smoke becomes almost zero when the air-fuel ratio A / F is around 15.0. That is, almost no soot is generated. At this time, the output torque of the engine slightly decreases, and the generation amount of NOx becomes considerably low. On the other hand, at this time, the generation amounts of HC and CO begin to increase.

FIG. 13A shows the change in the combustion pressure in the combustion chamber 5 when the air-fuel ratio A / F is around 21 and the amount of generated smoke is the largest, and FIG. 13B shows the air-fuel ratio A / F. F is 18
The graph shows changes in the combustion pressure in the combustion chamber 5 when the amount of generated smoke is almost zero in the vicinity. FIG. 13 (A) and FIG.
As can be seen from comparison with FIG. 13B, the combustion pressure is lower in the case of FIG. 13B where the amount of smoke generation is almost zero than in the case of FIG. 13A where the amount of smoke generation is large. You can see that.

The following can be said from the experimental results shown in FIGS. That is, first, when the air-fuel ratio A / F is 15.0 or less and the amount of generated smoke is almost zero, the amount of generated NOx is considerably reduced as shown in FIG. The decrease in the amount of generated NOx means that the combustion temperature in the combustion chamber 5 has decreased. Therefore, it can be said that the combustion temperature in the combustion chamber 5 has decreased when little soot is generated. . The same can be said from FIG. That is, FIG. 13B in which soot is hardly generated.
In the state shown in (1), the combustion pressure is low, and the combustion temperature in the combustion chamber 5 is low at this time.

Second, when the amount of generated smoke, that is, the amount of generated soot becomes almost zero, as shown in FIG.
O emission increases. This means that hydrocarbons are emitted without growing to soot. That is, linear hydrocarbons and aromatic hydrocarbons contained in the fuel as shown in FIG. 14 are thermally decomposed when the temperature is increased in a state of lack of oxygen, soot precursors are formed, and then mainly, A soot consisting of a solid aggregate of carbon atoms is produced. in this case,
The actual process of soot formation is complicated, and it is not clear what form the soot precursor takes, but in any case, FIG.
Hydrocarbons such as those shown in FIG. 4 will grow to soot via soot precursors. Therefore, as described above, when the amount of generated soot becomes almost zero, HC and C are reduced as shown in FIG.
At this time, HC is a soot precursor or a hydrocarbon in a state before the increase in O emission amount.

These considerations based on the experimental results shown in FIGS. 12 and 13 are summarized as follows. When the combustion temperature in the combustion chamber 5 is low, the amount of soot generation becomes almost zero. Is discharged from the combustion chamber 5. As a result of further detailed experimental research on this, when the temperature of the fuel and the surrounding gas in the combustion chamber 5 is lower than a certain temperature, the growth process of the soot is stopped halfway, that is, the soot is Does not occur at all,
It has been found that soot is generated when the temperature of the fuel and its surroundings in the combustion chamber 5 exceeds a certain temperature.

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

Once soot has been produced, it cannot be purified by post-treatment using a catalyst having an oxidizing function. On the other hand, the soot precursor or the hydrocarbon in a state before the soot can be easily purified by a post-treatment using a catalyst having an oxidation function. Considering the post-treatment with the catalyst having the oxidation function, it is extremely difficult to discharge the hydrocarbon from the combustion chamber 5 in the state of the precursor of soot or in the state before the soot, or to discharge the hydrocarbon from the combustion chamber 5 in the form of soot. There is a big difference. The new combustion system employed in the present invention discharges hydrocarbons from the combustion chamber 5 in the form of a soot precursor or previous state without producing soot in the combustion chamber 5 and removes the hydrocarbons. The core is to oxidize with a catalyst having an oxidation function.

Now, in order to stop the growth of hydrocarbons before the soot is generated, the temperature of the fuel and the surrounding gas during combustion in the combustion chamber 5 are set to a temperature lower than the temperature at which the soot is generated. Need to be suppressed. In this case, it has been found that the endothermic effect of the gas around the fuel when the fuel is burned has an extremely large effect on suppressing the temperature of the fuel and the gas around the fuel. That is, if there is only air around the fuel, the evaporated fuel immediately reacts with the 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 becomes extremely high locally. That is, at this time, the air separated from the fuel hardly absorbs the heat of combustion heat of the fuel. In this case, since the combustion temperature locally becomes extremely high, the unburned hydrocarbons that have received the combustion heat will generate soot.

On the other hand, when fuel is present in a mixed gas of a large amount of inert gas and a small amount of air, the situation is slightly different.
In this case, the fuel vapor diffuses to the surroundings, reacts with oxygen mixed in the inert gas, and burns. In this case, since the combustion heat is absorbed by the surrounding inert gas, 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 effect of the inert gas.

In this case, in order to suppress the temperature of the fuel and the surrounding gas to a temperature lower than the temperature at which the soot is generated, an amount of the inert gas that can absorb a sufficient amount of heat to do so is required. . Therefore, if the fuel amount increases, the required amount of inert gas 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 regard, since CO ₂ and EGR gas have relatively large specific heats, it can be said that it is preferable to use EGR gas as the inert gas.

FIG. 15 shows the relationship between the EGR rate and the smoke when the EGR gas is used as the inert gas and the degree of cooling of the EGR gas is changed. That is, in FIG. 15, curve A shows a case where the EGR gas is cooled strongly and the EGR gas temperature is maintained at approximately 90 ° C., and curve B shows a case where the EGR gas is cooled by a small cooling device. , Curve C shows the case where the EGR gas is not forcibly cooled. As shown by the curve A in FIG. 15, when the EGR gas is strongly cooled, the amount of soot generation peaks at a point where the EGR rate is slightly lower than 50%. In this case, the EGR rate is increased to approximately 55% or more. Then, almost no soot is generated. On the other hand, as shown by the curve B in FIG. 15, when the EGR gas is slightly cooled, the amount of soot generation peaks at a point where the EGR rate is slightly higher than 50%, and in this case, the EGR rate is increased to approximately 65% or more. So that almost no soot is generated. As shown by the curve C in FIG. 15, when the EGR gas is not forcibly cooled, the amount of soot generation reaches a peak near the EGR rate of 55%. Above a percentage, soot is hardly generated. FIG. 15 shows the amount of smoke generated when the engine load is relatively high. When the engine load decreases, the EGR rate at which the amount of soot peaks slightly decreases, and the EGR rate at which almost no soot is generated Also lowers slightly. As described above, the lower limit of the EGR rate at which almost no soot is generated varies depending on the degree of cooling of the EGR gas and the engine load.

FIG. 16 shows the mixing of EGR gas and air necessary to reduce the temperature of fuel during combustion and the surrounding gas to a temperature lower than the temperature at which soot is generated when EGR gas is used as the inert gas. A gas amount, a ratio of air in this mixed gas amount, and a ratio of EGR gas in this mixed gas are shown. In FIG. 16, the vertical axis indicates the total intake gas amount drawn into the combustion chamber 5, and the dashed line Y indicates the total intake gas amount that can be drawn into the combustion chamber 5 when supercharging is not performed. ing. The horizontal axis indicates the required load. Referring to FIG. 16, the proportion of air, that is, the amount of air in the mixed gas, indicates the amount of air necessary to completely burn the injected fuel. That is, in the case shown in FIG. 16, the ratio between the amount of air and the amount of injected fuel is the stoichiometric air-fuel ratio. On the other hand, in FIG. 16, the ratio of the EGR gas, that is, the amount of the EGR gas in the mixed gas, is set so that when the injected fuel is burned, the temperature of the fuel and the surrounding gas is made lower than the temperature at which the soot is formed. The minimum required EGR gas amount is shown. This EGR gas amount is approximately 55% or more in terms of 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 indicated by a solid line X in FIG. 16, and the ratio between the air amount and the EGR gas amount in the total intake gas amount X is as shown in FIG. The temperature of the fuel and the gas around it will be lower than the temperature at which soot is produced, so that no soot is generated. Further, the amount of NOx generated at this time is about 10 p.pm or less, and therefore, the amount of generated NOx is extremely small.

When the fuel injection amount increases, the amount of heat generated when the fuel burns increases. Therefore, in order to maintain the temperature of the fuel and the surrounding gas at a temperature lower than the temperature at which the soot is generated, the heat generated by the EGR gas is required. Must be increased. Therefore, as shown in FIG. 16, the EGR gas amount must be increased as the injected fuel amount increases. 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. 16, in the region where the required load is larger than Lo, as the required load increases, Unless the EGR gas ratio is reduced, the air-fuel ratio cannot be maintained at the stoichiometric air-fuel ratio. In other words, when supercharging is not performed, if the air-fuel ratio is to be maintained at the stoichiometric air-fuel ratio in a region where the required load is larger than Lo, the EGR rate decreases as the required load increases, and In a region where the required load is larger than Lo, the temperature of the fuel and the surrounding gas cannot be maintained at a temperature lower than the temperature at which soot is generated.

However, although not shown, when the EGR gas is recirculated through the EGR passage to the inlet side of the supercharger, that is, into the air intake pipe of the exhaust turbocharger, the EGR rate becomes 55% or more in a region where the required load is larger than Lo. ,
For example, it can be maintained at 70 percent, and thus the temperature of the fuel and its surrounding gas can be kept 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 suction gas boosted by the compressor of the exhaust turbocharger also becomes 70%, and thus the pressure is increased by the compressor. To the extent possible, the temperature of the fuel and its surrounding gas can be kept below the temperature at which soot is produced. Therefore, the operating range of the engine that can generate low-temperature combustion can be expanded. When the EGR rate is set to 55% or more in a 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. 16 shows the case where the fuel is burned under the stoichiometric air-fuel ratio.
Even if the air amount is smaller than that shown in FIG. 2, that is, even if the air-fuel ratio is made rich, the amount of NOx
ppm or less, and even if the air amount is larger than the air amount shown in FIG. 16, that is, even if the average value of the air-fuel ratio is 17 to 18 lean, soot generation is prevented. Meanwhile, the amount of generated NOx 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 excess fuel does not grow to soot, and thus no soot is generated. 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 is high. Not generated at all.
Further, only a very small amount of NOx is generated. In this way, when low-temperature combustion is being performed, soot is not generated regardless of the air-fuel ratio, that is, whether the air-fuel ratio is rich, the stoichiometric air-fuel ratio, or the average air-fuel ratio is lean, The generation amount of NOx becomes 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 surrounding gas 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 under low load operation where the calorific value due to combustion is relatively small. Can be Therefore, in the embodiment according to the present invention, during the low load operation in the engine, the first combustion, that is, the low-temperature combustion is performed by suppressing the temperature of the fuel during combustion and the gas around it at a temperature below the temperature at which the growth of hydrocarbons stops halfway. In addition, the second combustion, that is, the combustion that is usually performed conventionally, is performed during the high load operation of the engine. Here, the first combustion, that is, the 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 is peaked, and soot is almost generated. The second combustion, that is, the combustion that has been performed conventionally, is a combustion in which the amount of inert gas in the combustion chamber is smaller than the amount of inert gas at which the amount of soot generation peaks. Say that.

FIG. 17 shows a first operation region I 'where the first combustion, that is, low-temperature combustion is performed, and a second operation region II' where the combustion by the conventional combustion method is performed. Is shown. In FIG. 17, the vertical axis L indicates the amount of depression of the accelerator pedal 40, that is, the required load, and the horizontal axis N
Indicates the engine speed. In FIG. 17, X
(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 ′. Are shown as the second boundary. The determination of the change of the operation region from the first operation region I 'to the second operation region II' is made based on the first boundary X (N), and the change from the second operation region II 'to the first operation region. The determination of the change of the operation region to I 'is made based on the second boundary Y (N). That is, if the required load L exceeds a first boundary X (N), which is a function of the engine speed N, when the operating state of the engine is in the first operating region I 'and low-temperature combustion is being performed. It is determined that the region has shifted to the second operation region II ′, and combustion is performed by a conventional combustion method. Next, when the required load L becomes lower than a second boundary Y (N) which is a function of the engine speed N, it is determined that the operation region has shifted to the first operation region I ′, and low-temperature combustion is performed again.

The two boundaries of the first boundary X (N) and the second boundary Y (N) having a lower load than the first boundary X (N) are provided as follows. For three reasons. The first reason is that the combustion temperature is relatively high on the high load side of the second operation region II ′, and 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 immediately start unless the required load L becomes considerably low, that is, when the required load L becomes lower than the second boundary Y (N). The second reason is that a hysteresis is provided for a change in the operation region between the first operation region I ′ and the second operation region II ′.

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

FIG. 18 shows the output of an air-fuel ratio sensor (not shown). As shown in FIG. 18, 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. 19 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. FIG.
As shown in FIG. 9, in the first operating region I 'where the required load L is low, the opening of the throttle valve 17 is gradually increased from almost fully closed to about 2/3 as the required load L increases. The opening degree of the EGR control valve 25 is gradually increased from near full closure to full opening as the required load L increases. Further, in the example shown in FIG. 19, the EGR rate is set to approximately 70% in the first operation region I ′,
The air-fuel ratio is a slightly lean air-fuel ratio.

In other words, in the first operation region I ', EG
The throttle valve 17 is adjusted so that the R ratio becomes approximately 70% and the air-fuel ratio becomes a slightly lean air-fuel ratio.
And the opening of the EGR control valve 25 are controlled. 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 is delayed as the required load L is increased, and the injection completion timing θE is delayed as the injection start timing θS is delayed. In addition,
At the time of idling, the throttle valve 17 is closed to almost fully closed, and at this time, the EGR control valve 25 is also closed to almost fully closed. When the throttle valve 17 is closed close to the fully closed state, the pressure in the combustion chamber 5 at the start of compression decreases, so that the compression pressure decreases. When the compression pressure decreases, the piston 4
As a result, the vibration of the engine body 1 is reduced. That is, at the time of idling, the throttle valve 17 is closed to almost fully closed 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 in steps from approximately 70 percent to less than 40 percent, and the air-fuel ratio is increased in steps. That is, since the EGR rate jumps over the EGR rate range (FIG. 15) in which a large amount of smoke is generated, a large amount of smoke is generated when the operation region of the engine changes from the first operation region I ′ to the second operation region II ′. I can't. In the second operation region II ', the conventional combustion is performed. In the second operation region II ', the throttle valve 17 is maintained in a fully opened state except for a part, and the opening of the EGR control valve 25 is gradually reduced as the required load L increases. In this operating region II ', the EGR rate decreases as the required load L increases, and the air-fuel ratio decreases as the required load L increases. However, the air-fuel ratio is a lean air-fuel ratio even when the required load L increases. In the second operation region II ′, the injection start timing θS is set near the compression top dead center TDC.

FIG. 20A shows the target air-fuel ratio A / F in the first operation region I '. In FIG. 20A, A / F = 15.5, A / F = 16, A / F = 17,
Each curve represented by A / F = 18 has a target air-fuel ratio of 1
5.5, 16, 17, and 18, and the air-fuel ratio between the curves is determined by proportional distribution. FIG.
As shown in (A), the air-fuel ratio is lean in the first operating region I ', and in the first operating region I', the target air-fuel ratio A / F becomes leaner as the required load L decreases. You. That is, the lower the required load L, the smaller the amount of heat generated by combustion. Therefore, as the required load L decreases, the EGR
Even if the rate is reduced, low-temperature combustion can be performed. EGR
As the rate decreases, the air-fuel ratio increases,
As shown in (A), the target air-fuel ratio A / F increases as the required load L decreases. As the target air-fuel ratio A / F increases, the fuel consumption rate increases. Therefore, in order to make the air-fuel ratio as lean as possible, the embodiment according to the present invention increases the target air-fuel ratio A / F as the required load L decreases. .

The target air-fuel ratio A / F shown in FIG. 20A is previously stored in a ROM 3 as a function of the required load L and the engine speed N as shown in FIG.
2 is stored. Also, the throttle valve 1 required to set the air-fuel ratio to the target air-fuel ratio A / F shown in FIG.
As shown in FIG. 21 (A), the target opening 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.
EGR required to achieve target air-fuel ratio A / F shown in (A)
The target opening SE of the control valve 25 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.

FIG. 22A shows the target air-fuel ratio A when the second combustion, that is, the normal combustion by the conventional combustion method is performed.
/ F. Note that A / F in FIG.
= 24, A / F = 35, A / F = 45, and A / F = 60 indicate target air-fuel ratios of 24, 35, 45, and 6, respectively.
0 is shown. Target air-fuel ratio A shown in FIG.
/ F is a function of the required load L and the engine speed N as shown in FIG.
Is stored within. Further, 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 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.
As shown in FIG. 23 (B), the target opening degree SE of the EGR control valve 25 required to obtain the target air-fuel ratio A / F shown in FIG. It is stored in the ROM 32.

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. The fuel injection amount Q 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.

Next, the operation control of this embodiment will be described with reference to FIG. Referring to FIG. 25, first, in step 1100, it is determined whether or not a flag I indicating that the operating state of the engine is in 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 process proceeds to step 1101 to determine whether the required load L has become larger than the first boundary X (N). Is 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
And the flag I is reset.
Going to 09, the second combustion is performed.

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

In step 1103, the target opening ST of the throttle valve 17 is calculated from the map shown in FIG. 21A, and the opening of the throttle valve 17 is set to the target opening ST. Next, at step 1104, the target opening SE of the EGR control valve 25 is calculated from the map shown in FIG.
The opening of the EGR control valve 25 is set as the target opening SE.
Next, at step 1105, the mass flow rate of the intake air (hereinafter simply referred to as the intake air amount) Ga detected by the mass flow rate detector (not shown) is taken in.
At 106, the target air-fuel ratio A is obtained from the map shown in FIG.
/ F is calculated. Next, at step 1107, a fuel injection amount Q necessary for setting 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 opening of the EGR control valve 25 immediately change the required load L and the engine speed. The target opening degrees ST and SE according to N are made to match. Therefore, for example, when the required load L is increased, the amount of air in the combustion chamber 5 is increased immediately, and the generated torque of the engine is immediately increased. On the other hand, when the opening of the throttle valve 17 or the opening of the EGR control valve 25 changes to change the amount of intake air, the change in the amount of intake air Ga is detected by the mass flow rate detector, and the detected amount of intake air Ga Is controlled based on the fuel injection amount Q. That is, the fuel injection amount Q is changed after the intake air amount Ga is actually changed.

In step 1110, the target fuel injection amount Q is calculated from the map shown in FIG. 24, and the fuel injection amount is set as the 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 SE of the EGR control valve 25 is calculated from the map shown in FIG. 23B, and the opening of the EGR control valve 25 is set to this target opening SE. Next, at step 1113, the intake air amount Ga detected by the mass flow detector is taken. 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. Next, at step 1116, it is determined whether or not the actual air-fuel ratio (A / F) _R is larger than the target air-fuel ratio A / F. (A / F) _R
If> A / F, the routine proceeds to step 1117, where the throttle opening correction value ΔST is decreased by a constant value α,
Next, the routine proceeds to step 1119. (A /
F) If _R ≦ A / F, the routine proceeds to step 1118, where the correction value ΔST is increased by a constant value α, and then the routine proceeds to step 1119. In step 1119, the final target opening ST is calculated by adding the correction value ΔST to the target opening ST of the throttle valve 17, and the final target opening ST is calculated.
The opening 7 is 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.

As described above, when the required load L or the engine speed N changes during the second combustion, the fuel injection amount immediately matches the target fuel injection amount Q corresponding to the required load L and the engine speed N. I'm sullen. For example, required load L
Is increased, the fuel injection amount is immediately increased, and thus the generated torque of 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 of the throttle valve 20 is controlled so as to be / F. That is, the air-fuel ratio is changed after the fuel injection amount Q changes.

In the embodiments described above, the fuel injection amount Q is controlled by open loop when low-temperature combustion is performed, and the air-fuel ratio decreases the opening 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 controlled by the EGR control when the second combustion is being performed. The control can also be performed by changing the opening of the valve 31.

In this embodiment, FIGS. 9A and 10
In the forward flow mode shown in (A), the normal combustion described above, that is, EG as an inert gas at which the generation amount of soot reaches a peak.
The combustion in which the amount of the EGR gas supplied into the combustion chamber 5 is smaller than the amount of the R gas is performed, and FIG. 9 (B) and FIG.
In the backflow mode shown in (B), the low-temperature combustion described above, that is, EG as an inert gas at which the generation amount of soot reaches a peak.
The combustion in which the amount of the EGR gas supplied into the combustion chamber 5 is larger than the amount of the R gas and little soot is generated is executed.

Further, in the present embodiment, the amount of fine particles discharged from the combustion chamber 5 per unit time can be removed by oxidation on the particulate filters 22 and 122 without generating a bright flame per unit time. Usually, the amount is smaller than the amount of fine particles, that is, the region I in FIG.
Even if the amount of discharged fine particles is temporarily larger than the amount of fine particles that can be oxidized and removed and is located in the region II of FIG. The operating conditions of the internal combustion engine are controlled so as to maintain the amount of discharged particulates and the temperature of the particulate filters 22 and 122 so that only a small amount of particulates that can be removed is less than a certain limit on the particulate filters 22 and 122.

According to the present embodiment, as shown in FIG. 7, oxygen storage as an oxidizing agent for releasing active oxygen for oxidizing fine particles temporarily trapped in the partition walls 54 of the particulate filters 22 and 122. The active oxygen releasing agent 261 is carried on the partition walls 54 of the particulate filters 22 and 122, and as shown in FIG.
The flow of the exhaust gas passing through the partition walls 54 of the second and 122 is reversed, so that the particulate filters 22, 1
The fine particles collected by the partition walls of the 22 are dispersed on the upper and lower surfaces (see FIG. 7) of the partition walls of the particulate filters 22 and 122. Therefore, it is possible to prevent most of the fine particles flowing into the particulate filter from being collected on one surface of the partition wall of the particulate filter, and to prevent the particulate filters 22 and 1 from being trapped.
Oxidation removal action can be exerted on the fine particles downstream of the exhaust gas flow from the partition wall 54 of the 22. The above-described oxidation removing action is achieved by the particulate filters 22, 122.
Storage / active oxygen release agent 261 on the surface of partition wall 54
(See FIG. 7) is an essential requirement, so that it can be achieved even when there is no oxygen storage / active oxygen release agent 161 (see FIG. 7) inside the partition wall 54 of the particulate filters 22 and 122. It is.

Further, according to the present embodiment, as described above, the fine particles trapped by the partition walls 54 of the particulate filters 22 and 122 cause the particulate filters 22 and 12 to separate.
The possibility that the fine particles trapped by the partition walls 54 of the particulate filters 22 and 122 accumulate without being oxidized and removed by being dispersed on one surface and the other surface of the second partition wall 54 is as follows. This can be reduced compared to the case where no dispersion is performed. Therefore, the particulate filter 2
It is possible to sufficiently transmit the oxidizing / removing action of oxidizing and removing the fine particles trapped in the partition walls 54 of the particulate filters 22 and 122 to all the fine particles. Can be prevented. In order to sufficiently transmit the oxidizing and removing action to all the fine particles, the oxygen storage / active oxygen release agent 261 (see FIG. 7) on the surface of the partition wall 54 of the particulate filters 22 and 122 is an essential requirement. , 122 partition wall 54
Oxygen storage / active oxygen release agent 161 in the interior (see FIG. 7)
Can be achieved even if is not present.

According to the present embodiment, since the particulate filters 22 and 122 are arranged in series as shown in FIG. 8, even if the flow of the exhaust gas is reversed, the pressure in the connection passage 75 is not so high. It does not change. Therefore, the possibility that the fine particles are desorbed from the particulate filters 22 and 122 into the connection passage 75 as the flow of the exhaust gas is reversed is reduced. In addition, if one of the particulate filters 22 or 122
Even if fine particles are desorbed from the particles, the time required for oxidizing and removing the fine particles can be secured by trapping the fine particles with another particulate filter 122 or 22.

According to this embodiment, as shown in FIGS. 7 and 10, an oxidation catalyst as an oxidation catalyst for oxidizing the fine particles 162 temporarily trapped inside the partition walls 54 of the particulate filters 22 and 122 is used. An oxygen storage / active oxygen release agent 161 is supported inside the partition walls 54 of the particulate filters 22 and 122. Therefore, the fine particles 162 inside the partition walls 54 of the particulate filters 22 and 122 are removed by the oxygen storage / active oxygen releasing agent 161 inside the partition walls 54 of the particulate filters 22 and 122. Can be oxidized and removed. Further, according to the present embodiment, the exhaust gas switching valve 73 is provided as an exhaust gas backflow means for moving the fine particles 162 temporarily trapped inside the partition walls 54 of the particulate filters 22 and 122. Therefore, the particulate filter 2 is controlled by the oxygen storage / active oxygen releasing agent 161 inside the partition walls 54 of the particulate filters 22 and 122.
The oxidizing and removing action of oxidizing and removing the fine particles 162 inside the partition walls 54 of the second and 122 partitions is performed by the particulate filter 22.
Particles 1 temporarily trapped inside the partition wall 122
This can be facilitated by moving 62 (see FIG. 10).

Further, according to the present embodiment, the space between the plurality of particulate filters 22 and 122 arranged in series,
That is, a fuel addition device 76 that supplies fuel as a reducing agent is provided in the connection passage 75. Therefore, when the fuel is supplied to the particulate filters 22 and 122 in step 202 in FIG. 11, the combustion in the oxygen storage / active oxygen releasing agent 61 as a catalyst carried on the particulate filters 22 and 122 is extremely reduced. It becomes active and the temperature of the particulate filters 22 and 122 can be improved. Further, since the fuel is supplied as the reducing agent, the production of sulfate and NO ₂ can be significantly suppressed.

According to the present embodiment, in step 201 of FIG.
When it is determined that the temperature of the fuel cell 2 has reached a temperature sufficient to activate the catalyst, the fuel is supplied to the particulate filters 22 and 122 by the fuel addition device 76 in step 202 as a reducing agent. More specifically, when it is determined in step 201 that the temperature of the particulate filters 22, 122 has reached a temperature sufficient to activate the catalyst, in step 202, the particulate filters 22, 12
When fuel is added as a reducing agent to 2 and it is determined in step 201 that the temperature of the particulate filters 22 and 122 is not high enough to activate the catalyst, no fuel is added to the particulate filters 22 and 122. Therefore, the particulate filters 22, 12
When the sulfur-containing fuel is added to the particulate filters 22, 122 when the temperature of the sulfur-containing fuel is not sufficient to activate the catalyst, the particulate filters 22, 12 are not used.
2 can be prevented from being SOF-poisoned.

Further, according to the present embodiment, in step 203 of FIG.
2 is within the temperature range in which sulfate may be generated, that is, the temperature T representative of the temperatures of the particulate filters 22 and 122.
When F is higher than the sulfate formation temperature TF1 (FIG. 5), the reversal of the exhaust gas flow is prohibited in step 204, and the supply of fuel as the reducing agent is continued in step 202. Therefore, the reducing agent can be mainly supplied to one of the particulate filters 22 and 122 arranged in series, and one of the particulate filters 22 and 122 can be supplied.
The sulfate can be reduced by the reducing agent even in the details of the above, and therefore, the production of sulfate can be greatly suppressed. In addition, by prohibiting the reversal of the exhaust gas flow in step 204, it is possible to prevent the temperature of the particulate filters 22 and 122 from rising due to the reversal of the exhaust gas flow. Therefore, the production of sulfate can be significantly suppressed.

Further, according to the present embodiment, even if the amount of discharged fine particles is usually smaller than the amount of fine particles that can be oxidized and removed, and if the amount of discharged fine particles temporarily exceeds the amount of fine particles that can be easily removed by oxidation, the amount of discharged fine particles is thereafter reduced. When the amount of the particulates becomes smaller than the amount that can be oxidized and removed, the particulate filters 22 and 122 only have a certain amount or less that can be oxidized and removed.
By maintaining the amount of discharged particulates and the temperature of the particulate filters 22 and 122 so as not to accumulate on the particulate filter, particulates in the exhaust gas are reduced.
2, 122, it is oxidized and removed without emitting a bright flame. Therefore, it is not necessary to emit a luminous flame and remove the fine particles after the fine particles are deposited on the particulate filter as in the conventional case, and the fine particles are collected before the fine particles are deposited on the particulate filter. By oxidizing, fine particles in the exhaust gas can be removed.

Further, according to the present embodiment, even if the amount of the discharged fine particles is usually smaller than the amount of the fine particles that can be removed by oxidation, and the amount of the discharged fine particles temporarily exceeds the amount of the fine particles that can be removed by oxidation, the amount of the discharged fine particles is thereafter reduced. When the amount of the particulates becomes smaller than the amount that can be oxidized and removed, the particulate filters 22 and 122 only have a certain amount or less that can be oxidized and removed.
The operating conditions of the internal combustion engine are controlled so as to maintain the amount of discharged particulates and the temperature of the particulate filters 22 and 122 so as not to accumulate on the upper side. In detail, the amount of discharged fine particles should be 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 particulate filter 2 contains only a small amount of particles less than a certain limit that can be oxidized and removed when the amount becomes smaller.
The operating conditions of the internal combustion engine are controlled based on the amount of the discharged particulates and the temperatures of the particulate filters 22 and 122 so as not to accumulate on the internal combustion engine 2 and 122. Therefore, even if the operating condition of the internal combustion engine is such that the amount of exhaust particulates is smaller than the amount of particulates that can be oxidized and removed, or if the amount of exhaust particulates temporarily exceeds the amount of particulates that can be oxidized and removed, the amount of particulates thereafter becomes smaller. Unlike the case where the amount of fine particles that can be oxidized and removed is less than a certain limit that can be removed by oxidation when the amount becomes smaller than the amount that can be removed by oxidation, the amount of fine particles discharged can be reliably removed by oxidation, unlike the case where the operating condition is met. Even if the amount of fine particles is smaller than the amount of fine particles or the amount of fine particles discharged temporarily exceeds the amount of fine particles that can be oxidized and removed, a certain limit that can be oxidized and removed when the amount of discharged fine particles becomes smaller than the amount of fine particles that can be removed by oxidation Only the following amount of particulates in particulate filter 2
2, 122. Therefore, the fine particles can be more reliably oxidized before the fine particles are deposited on the particulate filters 22 and 122 in a stacked state, as compared with a case where the operating conditions of the internal combustion engine coincide with each other.

Further, according to the present embodiment, the oxygen storage / active oxygen release agent 61 carried on the particulate filters 22 and 122 captures and holds oxygen when excess oxygen exists in the surroundings. When the oxygen concentration decreases, the retained oxygen is released in the form of active oxygen (see FIG. 3). Therefore, unlike the conventional case, after the particles are deposited in a layered manner on the particulate filter, the particles emit a bright flame and are removed.
Before the fine particles 62 are deposited on the particulate filters 22 and 122 in a stacked state, the oxygen storage / active oxygen release agent 6
The fine particles 62 can be oxidized and removed by the active oxygen released by 1 without emitting a bright flame.

Further, according to this embodiment, when the exhaust gas switching valve 73 as the reverse flow means is in the forward flow mode (see FIG. 9A), the amount of EGR gas as the inert gas at which the amount of generated soot reaches a peak. Normal combustion in which the amount of EGR gas supplied into the combustion chamber 5 is smaller than that of the
In the reverse flow mode 3 (see FIG. 9B), low-temperature combustion in which the amount of EGR gas supplied into the combustion chamber 5 is larger than the amount of EGR gas at which soot generation reaches a peak and soot is hardly generated Is executed. That is, low-temperature combustion is performed in which the amount of EGR gas supplied into the combustion chamber 5 is larger than the amount of EGR gas at which the generation amount of soot is at a peak, and soot is hardly generated. HC and CO contained
Thereby, the oxidizing and removing action of the fine particles can be promoted.
Further, since the amount of the EGR gas supplied into the combustion chamber 5 is larger than the amount of the EGR gas at which the generation amount of soot becomes a peak, the exhaust gas is caused to flow backward when low-temperature combustion in which soot is hardly generated is executed. EG where the amount of soot generation peaks
When normal combustion in which the amount of the EGR gas supplied into the combustion chamber 5 is smaller than the amount of the R gas is performed, fine particles are deposited on one surface of the particulate filters 22, 122 (see FIG. 10A). ), Particulate filter 2
2,122 oxygen storage / active oxygen release agent 2 on its surface
Even if 61 is poisoned with sulfur, it flows in from the surface on the opposite side (lower side in FIG. 10) of the particulate filters 22 and 122, and the particulate filters 22 and 122
The fine particles deposited on one surface of the particulate filters 22 and 122 can be oxidized and removed by the exhaust gas containing HC and CO passing through the inside of the partition wall 54 without being affected by sulfur poisoning.

In the modification of the present embodiment, the particulate filters 22 and 122 shown in FIG.
It is also possible to provide the particulate filters 22 and 122 shown in FIG. FIG. 26 shows the first particulate filter 22 and the second particulate filter 12.
It is an enlarged view of the modification of FIG. According to this modification, the same effects as those of the above-described embodiment can be obtained.

[0113]

According to the first to third aspects of the present invention, the
Exhaust gas flow through the wall of the particulate filter
By reversing the
Collected on one side and the other side of the filter wall
Can be Therefore, most of the particles
Collected on one side of the curated filter wall
Of the particulate filter wall
Oxidative removal of fine particles downstream of the exhaust gas flow
Can be used. In addition, fine particles
Distributed on one side and the other side of the rate filter wall
Collected on the wall of the particulate filter.
Collected fine particles can be deposited without being oxidized and removed
Properties are reduced. Therefore, the particulate matter
Oxidative removal of fine particles trapped on the filter wall by active oxygen
The effect of removing oxidative removal is sufficiently transmitted to all particles.
And as a result, particulates are
Can prevent it from accumulating on the walls of the filter
You. In the invention according to claims 1 to 3,
Whether multiple rate filters are arranged in series
When the exhaust gas flow is reversed
Reduces the likelihood of particulate desorption from the swelling filter
And, if one particulate filter
Even if the particles are detached, the fine particles are removed from other particulates.
Fine particles are oxidized and removed by trapping with a filter.
The time required to leave can be secured. Also,
According to the first aspect of the present invention, the reducing agent is particulated
By supplying the filter, combustion in the catalyst is
Always active, raise the temperature of the particulate filter
Can be raised. In addition, sulfates, of NO ₂
Generation can be greatly suppressed. Also, in claim 1
In the described invention, a plurality of particulates arranged in series
Supply of reducing agent to one of the filter
It is possible for one of the particulate fills
Sulfate is reduced by reducing agent even in small details
And therefore the production of sulfate
Can be greatly suppressed. Also, the exhaust gas flow
The temperature of the particulate filter as it is reversed
Can be prevented from rising, and therefore
Sulfate generation can be greatly suppressed.

The invention according to claims 2, 5 and 6
Then, it is described in claim 2 as a particulate filter.
Particulates such as those listed are used, and
The amount of discharged particulates is usually smaller than the amount of particulates that can be removed by oxidation.
Can be removed and the amount of discharged particulates can be temporarily removed by oxidation
Even if the amount exceeds the amount of fine particles,
Is oxidized when the amount becomes smaller than the amount of fine particles that can be removed by oxidation.
Only a certain amount of fine particles that can be removed
And the amount of particulates discharged so that they do not accumulate on the filter.
Because the temperature of the particulate filter is maintained,
Particles are deposited in layers on the particulate filter
Before oxidation, the fine particles are oxidized and removed. That is, the conventional case
Fine particles are deposited on the particulate filter
It is necessary to remove fine particles by emitting a bright flame after depositing in a shape
Absent.

In addition, the inert gas at which the soot generation amount reaches a peak is
The amount of inert gas supplied into the combustion chamber is larger than the amount of gas
When combustion with little soot formation is performed, fine particles
HC and CO, which can promote the
It will be contained in the gas. Here, claims 3 and
According to the inventions described in (8) and (8), when the backflow means is in the backflow mode
In addition, the amount of soot generation is more fuel than the amount of inert gas that peaks.
The amount of inert gas supplied into the firing chamber is large and soot is almost
At this time, the exhaust gas
Oxidation and removal of fine particles by HC and CO contained in gas
The action is promoted. Also, according to this,
The catalyst on the surface of the filter has been poisoned by sulfur
From the other side of the particulate filter
And flows through the inside of the particulate filter wall
Exhaust gas containing HC and CO
The fine particles deposited on one surface of the filter are
It can be removed by oxidation without being affected.

[0116] According to the invention described in claim 4, instead of
The base agent can be supplied to the particulate filter.
When the reducing agent is supplied to the particulate filter
In this case, combustion in the catalyst becomes very active and
The temperature of the rate filter can be improved. Ma
In addition, significantly reduce the production of sulfate and NO ₂
Can be.

[0117]

Further, according to the inventions of claims 6 and 7,
If the operating conditions of the internal combustion engine are
Predetermined condition based on the temperature of the
(That is, the amount of discharged fine particles is larger than the amount of fine particles that can be removed by oxidation.
Is low, or the amount of discharged particulates is temporarily
Even if it exceeds the amount of fine particles that can be removed
When the amount of fine particles becomes smaller than the amount of fine particles that can be removed by oxidation
Only a small amount of fine particles that can be oxidized and removed
(No deposition on the curated filter)
Actively controlled by conditions. Therefore, the operation of the internal combustion engine
The condition happens to be the condition that can achieve the above specified state
The operating conditions of the internal combustion engine are more reliably
The conditions under which a given state can be achieved,
Reliable particles are layered on the particulate filter
The fine particles can be oxidized before being deposited on the surface.

[0119]

[0120]

Further, according to the ninth and tenth aspects of the present invention,
According to the particulate filter carried inside the wall
Oxidizing agent may cause particulate filter
The fine particles inside the wall are oxidized and removed.

[0122] According to the invention described in claim 10,
Exhaust gas flow through the particulate filter wall
By reversing this, the particulate filter
The fine particles temporarily collected are moved into the inside of the wall.
Oxidation inside the particulate filter wall
Particles inside the wall of particulate filter
The oxidation removal effect of oxidizing and removing
Move the temporarily trapped particles inside the ruta wall
Can be promoted by

Further , when the fine particles are a particulate filter,
If a large amount is collected on one side of the wall,
The effect of oxidizing and removing particles is insufficient. When
According to the invention as set forth in claim 11, the fine particles are
On one side and the other side of the wall of the particulate filter
Because they are almost equally dispersed and collected,
The oxidation removal effect on fine particles in
Is avoided and, as a result, the particulate filter
Removal effect on one side of the wall and the other side
The sum of the oxidizing and removing actions is maximum.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment in which an exhaust gas purification device 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.

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

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

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

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

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

FIG. 8 shows the structure of the particulate filter 22 shown in FIG.
FIG. 122 is an enlarged view of 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 view showing a state in which fine particles inside a partition wall of a particulate filter move in accordance with the position of an exhaust switching valve 73 being switched.

FIG. 11 is a flowchart showing a control method of the fuel adding device 76 shown in FIG.

FIG. 12 is a diagram showing the amounts of smoke and NOx generated.

FIG. 13 is a diagram showing a combustion pressure.

FIG. 14 is a diagram showing fuel molecules.

FIG. 15 is a diagram showing a relationship between a generation amount of smoke and an EGR rate.

FIG. 16 is a diagram showing a relationship between an injected fuel amount and a mixed gas amount.

FIG. 17 shows a first operation region I ′ and a second operation region I
It is a figure which shows I '.

FIG. 18 is a diagram showing an output of an air-fuel ratio sensor.

FIG. 19 is a diagram showing an opening degree of a throttle valve and the like.

FIG. 20 is a diagram showing an air-fuel ratio and the like in a first operation region I ′.

FIG. 21 is a diagram showing a map of a target opening degree of a throttle valve and the like.

FIG. 22 is a diagram showing an air-fuel ratio and the like in the second combustion.

FIG. 23 is a diagram showing a map of a target opening degree of a throttle valve and the like.

FIG. 24 is a diagram showing a map of a fuel injection amount.

FIG. 25 is a flowchart for controlling operation of the engine.

FIG. 26 is an enlarged view of a modified example of the first particulate filter 22 and the second particulate filter 122.

[Explanation of symbols]

5. Combustion chamber 6 ... Fuel injection valve 20 ... exhaust pipe 22, 122 ... Particulate filter 25 ... EGR control valve 54 ... partition wall 61 ... Oxygen storage / active oxygen release agent 62 ... fine particles 73… Exhaust switching valve 76 ... Fuel addition device

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F01N 3/02 F01N 3/08

Claims (11)

(57) [Claims] 1. A particulate filter for trapping particulates in exhaust gas discharged from a combustion chamber is disposed in an engine exhaust passage, and the exhaust gas passes through a wall of the particulate filter when the exhaust gas passes through a wall of the particulate filter. In an exhaust gas purification device for an internal combustion engine in which fine particles of
An oxidizing agent that releases active oxygen for oxidizing fine particles temporarily collected on the wall of the particulate filter is supported on the wall of the particulate filter, and the exhaust gas passing through the wall of the particulate filter is Exhaust gas backflow means for reversing the flow is provided, and by reversing the flow of the exhaust gas passing through the wall of the particulate filter, the fine particles trapped on the wall of the particulate filter are removed by the particulate filter. Distributed on one side and the other side of the wall,
The particulate fine particles trapped in the wall of the filter to reduce the possibility of depositing without being oxidized and removed, placing the particulate filter in series a plurality, this
A reducing agent supply means is provided between these particulate filters.
If the temperature of the particulate filter is
Exhaust gas when the temperature is within the temperature range where
Prohibit reversing the gas flow and supply a reducing agent
Exhaust purification device for an internal combustion engine. 2. Fine particles in exhaust gas discharged from a combustion chamber
Remove the particulate filter for collecting
It is located in the air passage and the exhaust gas
Particulates in the exhaust gas are trapped when passing
In the exhaust gas purifying apparatus for an internal combustion engine,
Temporarily collected on the wall of the particulate filter
Oxidizer that releases active oxygen to oxidize the fine particles
The powder is carried on the wall of the particulate filter,
The flow of exhaust gas passing through the wall of the
Exhaust gas backflow means for reverse rotation is provided,
Reverses the flow of exhaust gas through the walls of the curated filter
By rotating, the particulate filter
The fine particles trapped on the wall are filtered by the particulate filter.
Dispersed on one side and the other side of the wall of
Particles collected on the wall of the particulate filter
Reduces the possibility of deposition without being oxidized and removed.
A plurality of particulate filters are arranged in series, and
As a particulate filter, per unit time
The amount of particulates emitted from the combustion chamber is particulate
Emitting a luminous flame per unit time on the filter
Less than the amount of fine particles that can be removed without oxidation
Sometimes particulates in the exhaust gas are
Oxidized and removed without emission of bright flame
And the amount of the discharged fine particles can be temporarily oxidized and removed.
Even if the amount of particulates exceeds
If particles are deposited only below a certain limit on the ruta
In this case, the amount of the discharged fine particles is smaller than the amount of the fine particles that can be removed by oxidation.
When it becomes less
Particles that can be oxidized and removed without emitting bright flame
The fine particles capable of being oxidized and removed using a particulate filter
Particle size depends on the temperature of the particulate filter.
The amount of the discharged fine particles is greater than the amount of the fine particles that can be removed by oxidation.
And the amount of discharged particulates temporarily
Even if it exceeds the amount of fine particles that can be removed by oxidation,
The amount of the discharged fine particles is smaller than the amount of the fine particles that can be removed by oxidation.
Less than a certain amount of fine particles that can be oxidized and removed
So that only pups accumulate on the particulate filter
The amount of the discharged fine particles and the temperature of the particulate filter
Control means to maintain the
Fine particles in gaseous gas are trapped on the particulate filter
Oxidized and removed without luminous flame
Exhaust purification device for fuel engine. 3. Fine particles in exhaust gas discharged from a combustion chamber.
Remove the particulate filter for collecting
It is located in the air passage and the exhaust gas
Particulates in the exhaust gas are trapped when passing
In the exhaust gas purifying apparatus for an internal combustion engine,
Temporarily collected on the wall of the particulate filter
Oxidizer that releases active oxygen to oxidize the fine particles
The powder is carried on the wall of the particulate filter,
The flow of exhaust gas passing through the wall of the
Exhaust gas backflow means for reverse rotation is provided,
Reverses the flow of exhaust gas through the walls of the curated filter
By rotating, the particulate filter
The fine particles trapped on the wall are filtered by the particulate filter.
Dispersed on one side and the other side of the wall of
Fine particles are collected on the walls of the Patikyure Tofiruta
Reduces the possibility of deposition without being oxidized and removed.
A plurality of particulate filters are arranged in series, and
The backflow means is used to prevent the exhaust gas from passing through the particulate filter.
A forward flow mode where the exhaust gas passes through the wall in the first direction
The wall of the particulate filter is opposite to the first direction
A reverse flow mode in which the fuel flows in the second direction,
As the amount of inert gas supplied to the firing chamber increases, soot
The amount of generation of gas gradually increases and reaches a peak,
As the amount of inert gas supplied to the
Fuel and surrounding gas temperatures during combustion in the combustion chamber
Is lower than the soot generation temperature and soot is hardly generated
Using the internal combustion engine that is
Before the amount of inert gas at which the amount of soot generation peaks
Combustion with a small amount of inert gas supplied into the combustion chamber
The soot generation amount during the backflow mode of the backflow means.
Supply into the combustion chamber more than the peak amount of inert gas
The amount of inert gas used is large and soot is hardly generated.
An exhaust gas purification device for an internal combustion engine that performs baking. 4. A particulate curriculum arranged in series
And a reducing agent supply means is provided between the filters.
4. The exhaust gas purifying apparatus for an internal combustion engine according to 3. 5. As the particulate filter,
If the amount of particulates discharged from the combustion chamber per unit time is less than the amount of oxidizable particles that can be oxidized and removed per unit time without emitting a flaming flame on the particulate filter, the particulates in the exhaust gas will be particulates. When flowing into the filter, it is oxidized and removed without emitting luminous flame, and even when the amount of the discharged fine particles is temporarily larger than the amount of oxidizable and removable fine particles, the fine particles are deposited on the particulate filter only below a certain limit. When the amount of the discharged fine particles is smaller than the amount of the fine particles that can be oxidized and removed, the fine particles on the particulate filter are oxidized and removed without emitting a bright flame, and the amount of the fine particles that can be oxidized and removed is reduced. Depends on the temperature of the filter Even if the amount of the discharged fine particles is usually smaller than the amount of the oxidizable and removable fine particles, and even if the amount of the discharged fine particles temporarily exceeds the amount of the oxidizable and removable fine particles, the amount of the discharged fine particles is thereafter reduced to the amount of the oxidizable and removable fine particles. Control means for maintaining the amount of discharged particulates and the temperature of the particulate filter so that only particulates of a certain amount or less which can be oxidized and removed when the amount becomes smaller are deposited on the particulate filter,
2. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1 , wherein the fine particles in the exhaust gas are oxidized and removed on the particulate filter without emitting a bright flame. 6. The particulate filter according to claim 1, wherein
The amount of particulates emitted from the combustion chamber per unit time is
Per unit time on the particulate filter
Oxidation-removable fine particles that can be removed by oxidation without emitting bright flame
Particles are smaller than the particle size,
When it enters the curated filter, it does not emit a bright flame
Is oxidized and removed, and the amount of discharged particulates is temporarily
Even if the amount exceeds the amount of fine particles that can be removed by oxidation,
Particles below a certain limit on the particulate filter
When only deposits occur, the amount of the discharged fine particles is reduced by the oxidation removal.
When the amount of particles that can be removed is
The fine particles on the filter are oxidized and removed without producing a bright flame.
Using a particulate filter that is left behind,
The amount of particulates that can be removed by oxidation depends on the temperature of the particulate filter.
And the amount of the discharged fine particles can be removed by oxidation.
Usually less than the amount of fine particles, and the discharged fine particles
The amount temporarily exceeded the amount of fine particles that can be removed by oxidation.
Then, the amount of the discharged fine particles is
A certain limit that can be oxidized and removed when the particle volume is less than
Only the following amount of fine particles is deposited on the particulate filter.
The amount of particulates discharged and the particulate
Control means for maintaining the temperature of the filter,
As a result, particulates in the exhaust gas are
Oxidation removal without luminous flame on the filter
Therefore, the amount of the discharged fine particles is larger than the amount of the fine particles that can be removed by oxidation.
And the amount of discharged particulates temporarily
Even if it exceeds the amount of fine particles that can be removed by oxidation,
The amount of the discharged fine particles is smaller than the amount of the fine particles that can be removed by oxidation.
Less than a certain amount of fine particles that can be oxidized and removed
Only children are deposited on the particulate filter
In addition, the amount of discharged particulates and the particulate filter
Control the operating conditions of the internal combustion engine to maintain the temperature of the engine.
An exhaust gas purifying apparatus for an internal combustion engine according to claim 1 or 3, wherein
Place. 7. The method according to claim 7, wherein the amount of the discharged fine particles is smaller than the amount of the fine particles removable by oxidation.
Is usually smaller than the amount of particles, and the amount of the discharged fine particles is
Temporarily exceeds the amount of fine particles that can be removed by oxidation.
Even after that, the amount of the discharged fine particles is reduced by the oxidation-removable fine particles.
Below a certain limit that can be oxidized and removed when the amount becomes less than
Amount of fine particles accumulate on the particulate filter
So that the amount of discharged particulates and particulates
Control operating conditions of internal combustion engine to maintain filter temperature
The exhaust gas purifying apparatus for an internal combustion engine according to claim 2, wherein
Place. 8. The reverse flow means includes: a forward flow mode in which exhaust gas passes through a wall of a particulate filter in a first direction; and a second flow mode in which exhaust gas flows through a wall of the particulate filter in a direction opposite to the first direction. A reverse flow mode passing in two directions, and when the amount of inert gas supplied into the combustion chamber is increased, the amount of soot generated gradually increases and reaches a peak, and is supplied into 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 temperature of the surrounding gas become lower than the temperature at which soot is generated, so that the soot is hardly generated. In the forward flow mode of the means, combustion is performed in which the amount of the inert gas supplied into the combustion chamber is smaller than the amount of the inert gas at which the generation amount of the soot is at a peak, and during the reverse flow mode of the backflow means, The amount generated Claim 1 and the amount of the inert gas than the amount of inert gases that click is supplied to the combustion chamber much soot was to perform hardly generated combustion
3. An exhaust gas purification device for an internal combustion engine according to item 2 . 9. An exhaust purification system of an internal combustion engine according to any one of the oxidizing agent is the particulate claim is supported on the inside of the filter wall 1-3. 10. The method according to claim 10, wherein the oxidizing agent is a particulate material.
The particles that are carried inside the filter wall and that are temporarily trapped inside the particulate filter wall are moved by reversing the flow of exhaust gas passing through the particulate filter wall. The exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 3, which is configured as described above. 11. Any of the particulates wherein the particulates are collected on the walls of the filter particulates claim 1-3 which is adapted to disperse nearly equalized to the one surface and the other surface of the wall of the filter An exhaust gas purification device for an internal combustion engine according to any one of the preceding claims.