JP2001271632A - Exhaust emission control method and exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To purify components other than fine particles in exhaust gas, in an exhaust emission control method and an exhaust emission control device which adopts a new method. SOLUTION: A particulate filter 22 is arranged in an engine exhaust passage. The discharge amount of fine particles per unit time to be discharged from a combustion chamber 5 is made smaller than the oxidizable and removable amount of fine particles per unit time oxidizable and removal without generating luminous flames on the particulate filter 22, and the fine particles in exhaust gas are oxidized and removed, without generating luminous flames when they flow into the particulate filter 22. A catalyst, capable of purifying components other than the fine particles in exhaust gas is, carried on the particulate. When the amount of components other than fine particles flowing downstream of the particulate filter exceeds the preset amount, the amount of components other than fine particles discharged from the combustion chamber is reduced in the range, in which the discharge amount of fine particles is smaller than the oxidizable and removable amount of fine particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in a diesel engine, a particulate filter is disposed in an engine exhaust passage in order to remove fine particles contained in exhaust gas, and the fine particles in the exhaust gas are once collected by the particulate filter. In addition, the particulate filter is regenerated by igniting and burning the fine particles collected on the particulate filter. However, the particulate matter collected on the particulate filter does not ignite and burn unless the temperature becomes higher than about 600 ° C., whereas the exhaust gas temperature of the diesel engine is usually considerably lower than 600 ° C. Therefore, it is difficult to ignite and burn the particulates collected on the particulate filter with the heat of the exhaust gas, and to ignite the particulates collected on the particulate filter with the heat of the exhaust gas, The temperature must be low.

By the way, it has been known that if a catalyst is supported on a particulate filter, the ignition temperature of fine particles can be reduced. Therefore, various types of particulate filters supporting a catalyst have conventionally been used in order to lower the ignition temperature of fine particles. Is known. For example, Tokuho 7-10
Japanese Patent No. 6290 discloses a particulate filter in which a mixture of a platinum group metal and an alkaline earth metal oxide is supported on the particulate filter. With this particulate filter, it is almost 350 ° C to 400 ° C.
The particles are ignited at a relatively low temperature of ° C. and then burned continuously.

[0004] In a diesel engine, when the load increases, the exhaust gas temperature reaches from 350 ° C to 400 ° C. Therefore, at first glance, the particulate filter described above causes the exhaust gas heat to ignite and burn fine particles when the engine load increases. Looks like it can. However, actually, even when the temperature of the exhaust gas reaches 350 ° C. to 400 ° C., the fine particles may not ignite, and even if the fine particles ignite, only a part of the fine particles burn, and a large amount of the fine particles remains unburned. Is generated.

That is, when the amount of fine particles contained in the exhaust gas is small, the amount of fine particles adhering to the particulate filter is small.
When the temperature rises to 400 ° C., the fine particles on the particulate filter are ignited and then continuously burned. However, when the amount of fine particles contained in the exhaust gas increases, the fine particles adhered on the particulate filter accumulate on the fine particles before the fine particles completely burn, and as a result, the fine particles accumulate on the particulate filter. Deposit in a shape. When the fine particles are deposited on the particulate filter in this manner, some of the fine particles that easily come into contact with oxygen are burned, but the remaining fine particles that are hard to contact with oxygen do not burn, and thus a large amount of fine particles burn. Will remain. Therefore, when the amount of fine particles contained in the exhaust gas increases, a large amount of fine particles will continue to be deposited on the particulate filter.

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

On the other hand, if the exhaust gas temperature can be raised to a high temperature of 600 ° C. or more at this time, the deposited fine particles ignite, but in this case, another problem occurs. That is, in this case, when the deposited fine particles are ignited, they emit a bright flame and burn. At this time, the temperature of the particulate filter is kept at 80 ° C. for a long time until the combustion of the deposited fine particles is completed.
Maintain at 0 ° C. or higher. However, when the particulate filter is exposed to a high temperature of 800 ° C. or more for a long time as described above, the particulate filter deteriorates early, and thus a problem arises that the particulate filter must be replaced with a new one early. .

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

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

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

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

In order to solve such a problem, the amount of fine particles contained in the exhaust gas and the amount of fine particles that can be burned on the particulate filter are controlled so as not to deposit a large amount of fine particles in a stacked manner. An exhaust gas purification method and an exhaust gas purification device have already been filed by the present applicant (Japanese Patent Application No. 2000-43571).

[0013]

Since the exhaust gas contains components such as nitrogen oxides (NO _x ) in addition to the fine particles, it is necessary to remove the fine particles and to purify the components other than the fine particles. Is also desirable from the viewpoint of purifying exhaust gas. Therefore, an object of the present invention is to enable a method other than fine particles in exhaust gas to be purified in an exhaust gas purification method and an exhaust gas purification device employing a novel method.

[0014]

According to a first aspect of the present invention, a particulate filter for removing fine particles in exhaust gas discharged from a combustion chamber is provided from the combustion chamber per unit time to achieve the above object. When the amount of the discharged fine particles is smaller than the amount of oxidizable particles that can be oxidized and removed without emitting a luminous flame per unit time on the particulate filter, the luminous flame is generated when the fine particles in the exhaust gas flow into the particulate filter. Even if the particulates are removed by oxidation without emission and the amount of discharged particulates temporarily exceeds the amount of particulates that can be removed by oxidation, the amount of particulates that can be removed by oxidation will be reduced if the particulates are deposited on the particulate filter below a certain limit. Particles on the particulate filter produce a bright flame when Using a particulate filter is oxidized removed, particulate removable by oxidation amount is dependent on the temperature of the particulate filter without,
When the amount of discharged fine particles is smaller than the amount of fine particles that can be removed by oxidation, and even if the amount of discharged fine particles temporarily becomes larger than the amount of fine particles that can be removed by oxidation, the amount of discharged fine particles becomes smaller than the amount of fine particles that can be removed by oxidation. The amount of discharged particulates and the temperature of the particulate filter are maintained so that only a certain amount of particulates that can be oxidized and removed to a certain extent or less are deposited on the particulate filter, whereby particulates in the exhaust gas are illuminated on the particulate filter by the luminous flame. A catalyst capable of removing components other than fine particles in exhaust gas by oxidizing and removing the components without generating a catalyst, supported on a particulate filter, and purifying components other than fine particles by the catalyst. The amount of components other than fine particles flowing downstream of the particulate filter is predicted. Amount of discharged particulate when exceeding the amounts specified is to reduce the amount of components other than fine particles discharged from the combustion chamber in a range of less than particulate removable by oxidation amount.

In the second invention, in the first invention,
When excess oxygen exists around the catalyst, NO _x
Comprising a _the NO _x absorbent which and the ambient oxygen concentration holds NO _x capture releasing NO _x held to reduce, by supplying the reducing agent to _the NO _x absorbent, to reduce the oxygen concentration around it by then releasing the NO _x from the NO _x absorbent, so as to purify the reducing agent NO _x.

In the third invention, in the second invention,
Amount of NO _x discharged from the combustion chamber per unit time becomes smaller the larger the amount of discharged particulate. In a fourth aspect based on the second aspect, the NO _x absorbent comprises a noble metal. In the second invention in the fifth invention, NO if _x absorbent is lowered oxygen concentration around the oxygen released in the form of active oxygen, NO when the fine particles are deposited on _the NO _x absorbent on the particulate Active oxygen is released from the _x- absorber, and the released active oxygen oxidizes the fine particles attached on the NO _x absorbent.

In the sixth invention, in the fifth invention,
The NO _x absorbent comprises an alkali metal or alkaline earth metal or rare earth or transition metal. According to a seventh aspect, in the sixth aspect, the alkali metal and the alkaline earth metal are made of a metal having a higher ionization tendency than calcium. In the fifth invention in the eighth aspect, and so as to oxidize the particulates deposited on _the NO _x absorbent by temporarily rich air-fuel ratio of part or all of the exhaust gas.

According to a ninth aspect, in order to achieve the above object,
The exhaust gas discharged from the combustion chamber in the engine exhaust passage
Particulate filter to remove fine particles
Place this unit filter as a particulate filter
The amount of particulates emitted from the combustion chamber
Emits a luminous flame per unit time on the filter
Than the amount of fine particles that can be oxidized and removed without oxidation
When the amount is small, particulates in the exhaust gas are particulate
Oxidation removal without emission of bright flame when entering the filter
Fine particles that can be temporarily oxidized and removed.
Particulate fill even if the amount exceeds
When particles accumulate below a certain limit on the
The amount of discharged particles is smaller than the amount of particles that can be removed by oxidation.
Particles on the particulate filter shine
Particulates that can be oxidized and removed without producing a flame
The amount of fine particles that can be removed by oxidation
Depends on the temperature of the filter.
Is usually smaller than the amount of fine particles that can be removed by oxidation, and
The amount of emitted fine particles temporarily exceeds the amount of fine particles that can be removed by oxidation.
Even then, the amount of fine particles that can be removed by oxidation
Below a certain limit that can be removed by oxidation when the
Only the lower amount of fine particles is deposited on the particulate filter
And the amount of particulate matter
Equipped with control means for maintaining the temperature of
Therefore, the particulates in the exhaust gas are
It is oxidized and removed without emitting a bright flame on top, and exhaust
Catalyst capable of purifying components other than fine particles in gas
Supported on a particulate filter, and the catalyst
Exhaust gas purification that purifies components other than fine particles
In the device, it flows downstream of the particulate filter
Amount of components other than fine particles exceeds a predetermined amount
Sometimes the amount of discharged particulate is smaller than the amount of particulate that can be removed by oxidation
The amount of components other than fine particles discharged from the combustion chamber in the range
Emission NO to be eliminated _xIt is provided with an amount reducing means.

According to a tenth aspect, in the ninth aspect, when the catalyst contains excess oxygen in the surroundings, N
The ambient oxygen concentration and holds NO _x captures the O _x is provided with _the NO _x absorbent to release the NO _x held to decrease, by supplying a reducing agent to the _the NO _x absorbent, the oxygen concentration around to release the NO _x from the NO _x absorbent by reducing, so as to purify the reducing agent NO _x.

In an eleventh aspect based on the tenth aspect, the amount of NO _x discharged from the combustion chamber per unit time decreases as the amount of discharged particulates increases. In a twelfth aspect based on the ninth aspect, in the ninth aspect, the particulate filter includes a plurality of exhaust passages extending in parallel with each other, and one of the adjacent exhaust passages is closed at the upstream end by a plug and is adjacent to the exhaust passage. The other end of the exhaust passage is closed at the downstream end by a stopper, and a catalyst is carried on the wall surface of the exhaust passage and the wall of the stopper.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. FIG. 1 shows a case where the present invention is applied to a compression ignition type internal combustion engine. The present invention can also be applied to a spark ignition type internal combustion engine. 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 mass flowmeter 13a for detecting the mass flow rate of the air to be taken in is attached to the intake pipe 13b on the upstream side of the compressor 15. A throttle valve 17 driven by a step motor 16 is 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 an exhaust turbine 21 of the exhaust turbocharger 14 via an exhaust manifold 19 and an exhaust pipe 20, and an outlet of the exhaust turbine 21 is connected to a casing 23 having a built-in particulate filter 22.

The exhaust manifold 19 and the surge tank 12 are connected to each other through an exhaust gas recirculation (hereinafter, EGR) passage 24, and an electrically controlled EGR passage is provided in the EGR passage 24.
A control valve 25 is arranged. A cooling device 26 for cooling the EGR gas flowing in the EGR passage 24 is disposed around the EGR passage 24. In the embodiment shown in FIG. 1, 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 6a. Fuel is supplied into the common rail 27 from a fuel pump 28 of an electrically controlled variable discharge amount, and the fuel supplied into the common rail 27 is supplied to the fuel injection valve 6 through each fuel supply pipe 6a. A fuel pressure sensor 29 for detecting the fuel pressure in the common rail 27 is attached to the common rail 27, and the fuel pump 28 is controlled so that the fuel pressure in the common rail 27 becomes the target fuel pressure based on the output signal of the fuel pressure sensor 29. Is controlled.

The electronic control unit 30 is composed of a digital computer, and is connected to a read only memory (ROM) 32, a random access memory (RAM) 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. A temperature sensor 39 for detecting the temperature of the particulate filter 22 is attached to the particulate filter 22, and an output signal of the temperature sensor 39 is set to a corresponding AD signal.
The signal is input to the input port 35 via the converter 37. The output signal of the mass flow meter 13a is output to the corresponding AD converter 37.
Through the input port 35.

[0024] On the downstream side of the exhaust pipe 20a of the particulate filter 22 is attached NO _x sensor 39a that can detect the concentration of nitrogen oxides in the exhaust gas (NO _x), the output of the NO _x sensor 39a The signal is input to the input port 35 via the corresponding AD converter 37. A load sensor 41 that generates an output voltage proportional to the depression amount L of the accelerator pedal 40 is connected to the accelerator pedal 40, and the output voltage of the load sensor 41 is input to the input port 35 via the corresponding AD converter 37. . Further, the input port 35 is connected to a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, by 30 °. On the other hand, the output port 36 is connected to the fuel injection valve 6, the throttle valve driving step motor 16, the EGR control valve 25, and the fuel pump 2 via the corresponding drive circuit 38.
8 is connected.

FIG. 2 shows the structure of the particulate filter 22. 2A is a front view of the particulate filter 22, and FIG. 2B is a side sectional view of the particulate filter 22. As shown in FIGS. 2A and 2B, the particulate filter 22 has a honeycomb structure and includes a plurality of exhaust passages 50 and 51 extending in parallel with each other. These exhaust passages are constituted by an exhaust gas inflow passage 50 whose downstream end is closed by a plug 52 and an exhaust gas outflow passage 51 whose upstream end is closed by a plug 53.

In FIG. 2A, hatched portions indicate plugs 53. Therefore, the exhaust gas inflow passage 50 and the exhaust gas outflow passage 51 are formed of thin partition walls 54.
Are alternately arranged via 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. Are arranged as follows.

The particulate filter 22 is formed of a porous material such as cordierite, for example, so that the exhaust gas flowing into the exhaust gas inflow passage 50 is surrounded by the surroundings as shown by arrows in FIG. Partition wall 54
It flows out into the adjacent exhaust gas outflow passage 51 through the inside. In the embodiment of the present invention, the peripheral wall surface of each exhaust gas inflow passage 50 and each exhaust gas outflow passage 51, that is, each partition 54
A layer of a carrier made of, for example, alumina is formed over the entire surface on both side surfaces of the plug, the outer end face of the plug 53 and the inner end faces of the plugs 52 and 53, and a noble metal catalyst and excess oxygen And an active oxygen releasing agent that takes in oxygen to retain oxygen when it is present and releases the retained oxygen in the form of active oxygen when the surrounding oxygen concentration decreases.

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

As an active oxygen releasing agent, calcium C
It is preferable to use an alkali metal or alkaline earth metal having a higher ionization tendency than a, that is, potassium K, lithium Li, cesium Cs, rubidium Rb, barium Ba, and strontium Sr. Next, the action of removing particulates in the exhaust gas by the particulate filter 22 will be described by taking as an example a case where platinum Pt and potassium K are carried on a carrier, but other noble metals, alkali metals,
A similar effect of removing fine particles can be obtained by using an alkaline earth metal, a rare earth, or a transition metal.

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, if the ratio of air and fuel supplied to 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 in the compression ignition type internal combustion engine as shown in FIG. I have. Since NO is generated in the combustion chamber 5, NO is contained in the exhaust gas.
It is included. Further, the fuel contains sulfur S, which 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 schematically show enlarged views of the surface of the carrier layer formed on the inner peripheral surface of the exhaust gas inflow passage 50. FIG. 3A and 3B, reference numeral 60 denotes platinum Pt particles, and reference numeral 61 denotes an active oxygen releasing agent containing potassium K. When the exhaust gas because the exhaust gas as described above contains a large amount of excess oxygen flows into the exhaust gas inflow passages 50 of the particulate filter 22 3 These oxygen O ₂ as shown in (A) platinum Pt in or O ^2- in the form ^- but O ₂
Adheres to the surface of On the other hand, NO in the exhaust gas is platinum Pt.
Reacts with O ₂ ⁻ or O ²⁻ on the surface of NO to form NO ₂ (2NO + O ₂ → 2NO ₂ ). NO ₂ generated
Is partially oxidized on platinum Pt while active oxygen releasing agent 61
As shown in FIG. 3 (A), it is absorbed into the active oxygen releasing agent 61 and diffuses into the active oxygen releasing agent 61 in the form of nitrate ion NO ₃ ⁻ to form potassium nitrate KNO ₃ .

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
The active oxygen is released into the active oxygen releasing agent 61 by the system. Ie
As described above, oxygen O_TwoIs O_Two ^-Or O^2-Platinum in the form of
SO on the surface of Pt and in the exhaust gas_TwoIs platinum
O on the surface of Pt_Two ^-Or O^2-Reacts with SO_ThreeTona
You. Then the generated SO_ThreePart of the surface is further platinum on Pt
While being oxidized into the active oxygen releasing agent 61,
Sulfate SO while binding to_Four ^2-Active acid in the form of
Potassium sulfate K_TwoSO_FourRaw
To achieve. In this way, the active oxygen releasing catalyst 61 contains nitric acid.
Potassium KNO_ThreeAnd potassium sulfate K _TwoSO_FourIs raw
Is done.

On the other hand, fine particles mainly composed of carbon C are generated in the combustion chamber 5, and therefore these fine particles are contained in the exhaust gas. These fine particles contained in the exhaust gas are generated when the exhaust gas flows in the exhaust gas inflow passage 50 of the particulate filter 22.
Alternatively, the exhaust gas outflow passage 51
3B, it comes into contact with and adheres to the surface of the carrier layer, for example, the surface of the active oxygen releasing agent 61 as indicated by 62 in FIG.

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

At this time, potassium sulfate K ₂ SO ₄ formed in the active oxygen releasing agent 61 is also decomposed into potassium K, oxygen O and SO _2, and oxygen O is formed between the fine particles 62 and the active oxygen releasing agent 61. Towards the contact surface, while SO ₂ is released from the active oxygen releasing agent 61 to the outside. The SO ₂ released to the outside is oxidized on platinum Pt on the downstream side,
It is again absorbed in the active oxygen releasing agent 61. However, since potassium sulfate K ₂ SO ₄ is stable, potassium nitrate KN
It is harder to release active oxygen than O ₃ .

The fine particles 62 and the active oxygen releasing agent 61
The oxygen O heading toward the contact surface is oxygen decomposed from compounds such as potassium nitrate KNO ₃ and potassium sulfate K ₂ SO ₄ . Oxygen O decomposed from the compound has high energy and extremely high activity. Therefore, the oxygen that goes to the contact surface between the fine particles 62 and the active oxygen releasing agent 61 is active oxygen O. When the active oxygen O comes into contact with the fine particles 62, the fine particles 62 are immediately oxidized without emitting a bright flame, and the fine particles 62 are completely eliminated.
Therefore, the fine particles 62 are
Does not accumulate on top.

The conventional particulate filter 2
When the fine particles deposited in a stack on the combustor 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. In other words, 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 action of removing fine particles 62 that do not emit bright flame by oxidation according to the present invention is completely different from the action of removing fine particles by conventional combustion involving a flame.

By the way, platinum Pt and active oxygen releasing agent 6
1 is activated as the temperature of the particulate filter 22 increases, so that the amount of active oxygen O that the active oxygen releasing agent 61 can release per unit time increases as the temperature of the particulate filter 22 increases. Therefore, the amount of oxidizable particles that can be oxidized and removed on the particulate filter 22 without emitting luminous flame per unit time increases as the temperature of the particulate filter 22 increases.

The solid line in FIG. 5 indicates the amount of fine particles G that can be oxidized and removed without emitting a bright flame per unit time. In FIG. 5, the horizontal axis indicates the temperature TF of the particulate filter 22. When the amount of fine particles discharged from the combustion chamber 5 per unit time is referred to as a discharged fine particle amount M, when the discharged fine particle amount M is smaller than the oxidizable and removable fine particles G, that is, when the discharged fine particle amount M is in the region I in FIG. As soon as all the fine particles discharged from the filter contact 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 in 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. In other words, when the amount of active oxygen is insufficient to oxidize all the fine particles, the fine particles 62 are used as the active oxygen releasing agent 6 as shown in FIG.
When the fine particles 62 adhere to the surface of the carrier 1, only a part of the fine particles 62 is oxidized, and the finely oxidized fine particles remain on the carrier layer. Next, when the state of the 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, as shown in FIG. It becomes covered with the residual fine particle portion 63.

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

As described above, in the region I of FIG. 5, the fine particles are oxidized within a short time without emitting a bright flame on the particulate filter 22, and in the region II of FIG. Deposit in a shape. Therefore, in order to prevent the fine particles from depositing on the particulate filter 22 in a layered manner, 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 illustrated compression ignition type internal combustion engine, it is possible to maintain the amount M of discharged particulate and the temperature TF of the particulate filter 22 so that the amount M of discharged particulate is always smaller than the amount G of particulate that can be removed by oxidation. Therefore, in the first embodiment of the present invention, the amount M of discharged particulates and the temperature TF of the particulate filter 22
Is always kept smaller than the amount G of particles that can be removed by oxidation.

The amount of discharged fine particles M is the amount of fine particles G that can be removed by oxidation.
When the amount is smaller than usual, 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, it is difficult to oxidize the fine particles with active oxygen O even if the amount M of discharged fine particles becomes smaller than the amount G of fine particles that can be removed by oxidation. is there. However, when the non-oxidized fine particle portion is beginning to remain, that is, when the fine particles are deposited only below a certain limit, if the exhaust fine particle amount M becomes smaller than the oxidizable and removable fine particle amount G, the residual fine particle portion becomes active oxygen. O is oxidized and removed without emitting a bright flame.
Therefore, in the second embodiment, even if the amount M of discharged fine particles is usually smaller than the amount G of fine particles removable by oxidation, and the amount M of discharged fine particles temporarily exceeds the amount G of fine particles removable by oxidation, FIG. As shown in (1), the amount of fine particles of a certain amount or less that can be oxidized and removed when the amount M of discharged fine particles is smaller than the amount G of fine particles that can be removed by oxidation so that the surface of the carrier layer is not covered by the residual fine particle portion 63. Only the amount M of discharged particulates and the temperature TF of the particulate filter 22 are maintained so that only the particulate filter 22 is stacked on the particulate filter 22.

In particular, immediately after the start of the engine, the temperature TF of the particulate filter 22 is low. Therefore, at this time, the amount M of discharged fine particles is larger than the amount G of fine particles that can be removed by oxidation. Therefore, it is considered that the second embodiment is more suitable for actual driving. On the other hand, the amount M of discharged particulates and the temperature TF of the particulate filter 22 are set so that the first embodiment or the second embodiment can be executed.
Is controlled even if the particulate filter 22 is controlled.
Fine particles may be deposited on the upper surface in a stacked state. In such a case, the air-fuel ratio of part or all of the exhaust gas is temporarily made rich to thereby increase the particulate filter 22.
The fine particles deposited thereon can be oxidized without emitting a bright flame.

That is, when the air-fuel ratio of the exhaust gas is made rich to lower the oxygen concentration in the exhaust gas, the active oxygen releasing agent 6
Active oxygen O is released to the outside at a stretch, and the fine particles deposited by the active oxygen O released at a stretch are oxidized and removed without emitting a bright flame. Further, the poisoning of the metal surface is recovered by the enrichment, so that the subsequent oxidation activity is improved and the oxidation of the fine particles is promoted. 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 stacked manner, or the exhaust gas may be periodically exhausted regardless of whether the particulates are deposited in a stacked manner. May be rich.

As a method of making the air-fuel ratio of the exhaust gas rich, for example, when the engine load is relatively low, the EGR rate (EG
The opening degree of the throttle valve 17 and the opening degree of the EGR control valve 25 are controlled so that the R gas amount / (intake air amount + EGR gas amount) becomes 65% or more. At this time, the average air-fuel ratio in the combustion chamber 5 is reduced. A method of controlling the injection amount so as to be rich can be used.

FIG. 6 shows an example of the operation control routine of the internal combustion engine described above. 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 in step 103, 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 degree 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.

The active oxygen releasing agent 61 functions as a NO _x absorbent together with platinum Pt. That is, as described above, NO in the exhaust gas reacts with O ₂ ⁻ or O ²⁻ on the surface of platinum Pt to become NO ₂ (2NO + O ₂ → 2N).
O _2), this part of the NO ₂ is absorbed in the active oxygen release agent 61 while being oxidized on the platinum Pt, FIG. 3 (nitric acid as shown in A) the ion NO ₃ while bonding with the potassium K ^- of It diffuses into the active oxygen releasing agent 61 in the form. Thus NO _x
There it can be said that the active oxygen release agent 61 is absorbed in the active oxygen release agent 61 functions as _the NO _x absorbent with platinum Pt. Hereinafter, the active oxygen releasing agent 61 and platinum Pt will be collectively referred to as a NO _x absorbent.

The NO _x absorbent releases the absorbed NO _x when the oxygen concentration in the surroundings decreases, and for example, the fuel component in the exhaust gas, that is, unburned hydrocarbon (unburned HC) or carbon monoxide (CO 2) ) Can be used as a reducing agent to purify NO _x . That is, for example, when the air-fuel ratio of a part or the whole of the exhaust gas is temporarily made rich, the oxygen concentration in the exhaust gas decreases, and the amount of NO ₂ generated on the surface of the platinum Pt decreases. Therefore, nitrate ions N in the NO _x absorbent
O ₃ ^- is released from the NO _x absorbent in the form of NO ₂ . At this time, the NO ₂ released from the NO _x absorbent is reduced by reacting with a large amount of unburned HC or CO contained in the exhaust gas. Thus, the NO _x absorbent can purify NO _x .

[0053] Now the air-fuel ratio of the exhaust gas after being absorbed NO _x in _the NO _x absorbent in order to completely purify the NO _x in the exhaust gas may be made rich. However, when the air-fuel ratio of the exhaust gas is made rich, the fuel efficiency of the internal combustion engine deteriorates to a considerable extent. Therefore the air-fuel ratio of the exhaust gas as much of the NO _x in order to reduce as much as possible the deterioration of fuel efficiency of the internal combustion engine after being absorbed in _the NO _x absorbent to be rich, to decrease the number of times that the exhaust gas rich It is desirable. However, there is a limit to the amount of NO _{x that} can be absorbed by the NO _x absorbent.

[0054] Of course NO _x NO _x absorbed in the absorbent in the surface particles 62 of the NO _x absorbent, i.e. in the form of when deposited on the surface of the active oxygen release agent 61 NO NO
_x is released from the absorbent, but this NO is
It is oxidized on t and is absorbed again by the NO _x absorbent. Amount of NO _x removal action oxidation is absorbed in _the NO _x absorbent in progress for this reason the particulate 62 is hardly reduced. Therefore, the N absorbed in the NO _x absorbent
When the O _x amount reaches the limit value, NO _x flows out downstream of the particulate filter 22.

[0055] The N of the NO _x absorbent as shown in FIG. 7
The O _x purification rate R changes according to the temperature T. That _the NO _x purification rate R temperature T is a certain temperature Tp of the NO _x absorbent
Becomes a peak, becomes lower when the temperature becomes lower than the temperature Tp, and becomes higher when the temperature becomes higher than the temperature Tp. Therefore, even when the temperature T of the NO _x absorbent becomes a temperature outside the temperature range in which the NO _x purification rate R is maintained relatively high, N
The O _x absorbent cannot completely purify the NO _x , and the NO _x flows out downstream of the particulate filter 22.

[0056] Thus _the amount of NO _x discharged from the combustion chamber 5 in the present invention in order to prevent the flowing out to downstream of the NO _x particulate filter 22 (hereinafter, the exhaust NO
_(x amount) is reduced by changing the operation of the internal combustion engine so as to increase the amount of exhaust particulates. That is, NO
_x sensor concentration of NO _x detected by 39a, i.e. while maintaining the scope of the amount M of discharged particulate particulate removable weight following G oxide when it exceeds the amount that _the amount of NO _x is a predetermined, preferably oxide particles weight M decreases the exhaust NO _x amount to reach the particulate removable by oxidation amount G. That the amount M of discharged particulate changes the operation of the internal combustion engine to reduce the exhaust NO _x amount with a smaller range than the particulate removable by oxidation amount G. In this way, it is possible to prevent NO _x from flowing out of the particulate filter 22 to the downstream while removing particulates in the particulate filter 22.

[0057] As a specific method for reducing discharge amount of NO _x in this way has the following two. I.e. the amount M of discharged particulate and the air-fuel ratio A / F is made smaller by increasing the EGR rate increases emissions amount of NO _x as well as reduce the degree of opening of the throttle valve 17 as shown in FIG. 8 is reduced . Therefore, in the present invention, as the first method, the current amount of oxidizable and removable particles G is calculated, and the opening degree of the throttle valve 17 is adjusted so that the amount of discharged particles M increases within a range not exceeding the amount of oxidizable and removable particles G. by increasing the EGR rate as well as small, to reduce the discharge amount of NO _x. It is possible to prevent the NO _x flows out from the particulate filter 22 to the downstream This way. Further, since the amount M of the discharged fine particles is equal to or less than the amount G that can be oxidized and removed by the particulate filter 22, the fine particles are completely oxidized and removed.

[0058] Although the amount M of discharged particulate timing T for injecting fuel into the combustion chamber 5 from the fuel injection valve 6 becomes slow increase emissions amount of NO _x as shown in FIG. 9 is decreased. Therefore, as a second method of the present invention, the current amount G of oxidizable and removable particles is calculated, and the fuel injection timing T is delayed so as to increase the amount M of discharged particles within a range not exceeding the amount G of oxidizable and removable particles. , to reduce the discharge amount of NO _x. In this way, it is possible to prevent NO _x from flowing out from the particulates 22 to the downstream. Further, since the amount M of the discharged fine particles is equal to or less than the amount G that can be oxidized and removed by the particulate filter 22, the fine particles are completely oxidized and removed.

It should be noted that the amount M of discharged particulate with to reduce the emission amount of NO _x as described above is increased than the temperature required for the temperature of the particulate filter 22 is to ensure the desired NO _x purification rate NO _x if low
This is advantageous from the viewpoint of increasing the purification rate. Because, when the amount M of discharged particulates increases, the amount of particulates oxidized and removed in the particulate filter 22 increases, the temperature of the particulate filter 22 rises, and the temperature of the particulate filter 22 secures a desired NO _x purification rate. This is because the temperature falls within the necessary temperature range.

As described above, the particulate filter 22
The components other than the microparticles of technology widely in the exhaust gas of the present invention that the amount M of discharged particulate when the NO _x downstream flows out to reduce the emission amount of NO _x in a range that does not exceed the amount G of the particulate removable by oxidation from In an exhaust gas purifying apparatus in which a catalyst for purification is supported on a particulate filter, the present invention can be applied when a component to be purified in the catalyst flows out of the particulate filter downstream beyond an allowable limit. In this case, the emission amount of the above components from the combustion chamber may be reduced as long as the emission particle amount M does not exceed the oxidation removal removable particle amount G. According to this, it is possible to prevent components to be purified in the catalyst from flowing out of the particulate filter to the downstream.

Incidentally, the temperature of the particulate filter 22 may be positively increased in order to increase the amount G of the particulates that can be oxidized and removed in accordance with the prevention of NO _x outflow. In order to increase the temperature of the particulate filter 22, means for injecting a small amount of fuel after injecting fuel for driving the engine from the fuel injection valve or for injecting fuel upstream of the particulate filter 22 is provided. Only a small amount of fuel should be injected.

FIG. 10 shows an example of the NO _x outflow prevention control routine described above. Concentration of NO _x detected by the NO _x sensor 39a, first, at step 200 and referring to FIG. 10, namely _the amount of NO _x is whether greater than zero _(the amount of NO _x> 0) is determined. Step 200
When it is determined that the NO _x amount is greater than 0 in step S201, the routine proceeds to step 201, where the current operation of the internal combustion engine is capable of completely oxidizing and removing fine particles by the particulate filter 22 (continuous oxidation region) I in FIG. Is determined. When it is determined in step 201 that the current operation of the internal combustion engine is within the continuous oxidation region I, the routine proceeds to step 202, where the amount G of particulates that can be removed by oxidation is calculated. The amount G of particulates that can be removed by oxidation is calculated from the temperature of the particulate filter 22, for example, as shown in FIG. Next, in step 203, the emission NO _x
The amount reduction control is executed. That is, as described above, the opening degree of the throttle valve 17 is reduced and the EGR rate is increased or the fuel injection timing is delayed within a range where the amount M of discharged particulate does not exceed the amount G of particulate that can be removed by oxidation. Thus, NO _x is prevented from flowing downstream of the particulate filter 22.

Incidentally, the fuel and the lubricating oil contain calcium Ca, and therefore, the calcium Ca is contained in the exhaust gas. This calcium Ca produces 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 particulate filter 22 are blocked by the calcium sulfate CaSO ₄ , and as a result, it becomes difficult for the exhaust gas to flow through the particulate filter 22.

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

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

[0066]

The particulates in the exhaust gas can be immediately oxidized and removed on the particulate filter, and components other than the particulates in the exhaust gas can be purified.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a particulate filter.

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

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

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

FIG. 6 is a flowchart for controlling the operation of the internal combustion engine.

FIG. 7 is a diagram showing a relationship between the temperature T of the NO _x absorbent and the NO _x purification rate R;

8 is a diagram showing the relationship between the air-fuel ratio A / F and the throttle opening and the EGR ratio and the discharge amount of particulates and the discharge amount of NO _x.

FIG. 9 shows the fuel injection timing T, the amount of discharged fine particles, and the discharge N.
FIG. 4 is a diagram showing a relationship with an O _x amount.

FIG. 10 is a flowchart for preventing outflow of NO _x .

[Explanation of symbols]

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

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01J 23/58 ZAB F01N 3/08 B 4D058 35/04 301 A 4G066 F01N 3/08 3/10 A 4G069 3 / 24 E 3/10 R 3/24 S F02D 41/04 355 360A F02D 41/04 355 380A 360 385A 380 41/40 D 385 F 41/40 43/00 301E 301T 43/00 301 B01J 20/06 C B01D 53/36 102H // B01J 20/06 104B 104A B01J 23/56 301A (72) Inventor Kazuhiro Ito 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Toshiaki Tanaka Toyota City Toyota City, Aichi Prefecture No. 1, Toyota Motor Co., Ltd. (72) Inventor Koichi Kimura Aichi 1 Toyota Town, Toyota City Toyota Motor Corporation (72) Inventor Koichiro Nakatani 1 Toyota Town Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 3G084 AA01 BA05 BA09 BA13 BA15 BA20 DA10 FA07 FA10 FA27 FA28 FA38 3G090 AA03 BA01 EA06 EA07 3G091 AA10 AA11 AA18 AB09 AB13 CB03 CB07 DA01 DA02 DB10 EA15 EA33 FB10 GB02Y GB03Y GB04Y GB06W GB17X HA14 HA21 HA37 3G301 HA02 HA11 HA13 JA24 JA25 KA01 MA03 PD03 MA03 Z03 4D048 AA06 AA14 AB01 AB02 AC02 BA14X BA15X BA18X BA19Y BA30X BA31Y BA32Y BA33Y BA41X BB14 CC41 CD05 DA01 DA03 DA08 EA04 4D058 JA32 MA41 MA51 SA08 TA02 TA06 UA13 4G066 AA12B AA13B AA37B02A02A02B02 BC03B BC04B BC05B BC06B BC08A BC09B BC12B BC13B BC38A BC40B BC42B BC69A BC75B CA02 CA03 CA07 CA08 CA13 CA18 EA27

Claims (12)

[Claims] 1. A particulate filter for removing particulates in exhaust gas discharged from a combustion chamber,
If the amount of particulates discharged from the combustion chamber per unit time is less than the amount of oxidizable particles that can be oxidized and removed without emitting a luminous flame per unit time on the particulate filter, the particulates in the exhaust gas will be particulate. When flowing into the filter, it is oxidized and removed without emitting luminous flame, and even if the amount of the discharged fine particles temporarily exceeds 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 oxidizable and removable fine particles, the fine particles on the particulate filter are oxidized and removed without emitting a bright flame, and the amount of the oxidizable and removable fine particles 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 becomes larger than 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. The amount of discharged particulates and the temperature of the particulate filter are maintained so that only a small amount of particulates that can be oxidized and removed below a certain limit will be deposited on the particulate filter, thereby reducing particulates in the exhaust gas. A catalyst capable of purifying components other than the fine particles in the exhaust gas was oxidized and removed without generating a bright flame on the curated filter, and a catalyst capable of purifying the components other than the fine particles in the exhaust gas was supported on the particulates. In the exhaust gas purification method, the fine particles flowing downstream of the particulate filter When the amount of the component other than the particles exceeds a predetermined amount, the amount of the component other than the fine particles discharged from the combustion chamber in a range where the amount of the discharged fine particles is smaller than the amount of the oxidizable and removable fine particles is reduced. Exhaust gas purification method. Wherein N in which the catalyst to release NO _x held that the and the oxygen concentration of the ambient hold the NO _x captures NO _x in the exhaust gas with an excess of oxygen present around lowered
To include a O _x absorbent, supplying the reducing agent to the _the NO _x absorbent to release the NO _x from the NO _x absorbent by reducing the oxygen concentration of the ambient, purifying by a reducing agent to the NO _x The exhaust gas purification method according to claim 1, wherein 3. The amount of NO _x discharged from the combustion chamber per unit time decreases as the amount of discharged particulates increases.
The exhaust gas purification method according to any one of the above. 4. The exhaust gas purifying method according to claim 2, wherein the NO _x absorbent comprises a noble metal. 5. A release oxygen when the _the NO _x absorbent is lowered oxygen concentration around in the form of active oxygen from _the NO _x absorbent when the fine particles are deposited on _the NO _x absorbent on the particulate filter to release active oxygen released exhaust gas purification method according to claim 2 which is adapted to oxidize the particulates deposited on _the NO _x absorbent by the active oxygen. 6. The exhaust gas purifying method according to claim 5, wherein the NO _x absorbent comprises an alkali metal, an alkaline earth metal, a rare earth, or a transition metal. 7. The exhaust gas purification method according to claim 6, wherein the alkali metal and the alkaline earth metal are made of a metal having a higher ionization tendency than calcium. 8. An exhaust gas purifying method according to claim 5 which is adapted to oxidize the particulates deposited on _the NO _x absorbent by temporarily rich air-fuel ratio of a part of the exhaust gas or the whole. 9. A particulate filter for removing particulates in exhaust gas exhausted from a combustion chamber is disposed in an engine exhaust passage, and the particulate filter is used as an exhaust gas discharged from the combustion chamber per unit time. If the amount of fine particles is smaller than the amount of oxidizable particles that can be oxidized and removed without emitting a bright flame per unit time on the particulate filter, the fine particles in the exhaust gas oxidize without emitting a bright flame when they flow into the particulate filter. Even if the fine particles are removed and the amount of the discharged fine particles temporarily exceeds the amount of the fine particles that can be oxidized and removed, if the fine particles are deposited on the particulate filter only below a certain limit, the amount of the fine particles discharged is the amount of the fine particles that can be oxidized and removed. When less than the fine particles on the particulate filter Using a particulate filter that allows the particles to be oxidized and removed without emitting a bright flame, the amount of the oxidizable fine particles depends on the temperature of the particulate filter, and the amount of the discharged fine particles is usually smaller than the amount of the oxidizable fine particles. Less, and even if the amount of the discharged fine particles temporarily becomes larger than the amount of the oxidizable and removable fine particles, and thereafter, when the amount of the discharged fine particles becomes smaller than the amount of the oxidizable and removable fine particles, a certain limit or less that can be oxidized and removed. Control means for maintaining the amount of discharged particulates and the temperature of the particulate filter so that only a small amount of particulates accumulate on the particulate filter. Oxidizing and removing components other than fine particles in exhaust gas. The catalysts which can be supported on the particulate filter,
In the exhaust gas purifying apparatus configured to purify components other than the fine particles by the catalyst, when the amount of the components other than the fine particles flowing downstream of the particulate filter exceeds a predetermined amount, the amount of the discharged fine particles is reduced. An exhaust gas purifying apparatus comprising exhaust NO _x amount reducing means for reducing the amount of components other than the fine particles discharged from the combustion chamber in a range smaller than the amount of the oxidizable and removable fine particles. 10. The catalyst has excess oxygen around it.
And NO in exhaust gas _xNO_xHold and
NO retained when ambient oxygen concentration decreases_xEmit
NO_xAn absorbent, and the NO_xSupply reducing agent to absorbent material
NOx by lowering the surrounding oxygen concentration_xAbsorbent
From NO_xAnd the NO_xPurifying with a reducing agent
The exhaust gas purification device according to claim 9. 11. The exhaust gas purifying apparatus according to claim 10, wherein the amount of NO _x discharged from the combustion chamber per unit time decreases as the amount of discharged particulates increases. 12. The particulate filter includes a plurality of exhaust passages extending in parallel with each other, and one of the adjacent exhaust passages has an upstream end closed by a plug and the other of the adjacent exhaust passages. The exhaust gas purifying apparatus according to claim 9, wherein the downstream end is closed by a plug, and a catalyst is supported on a wall surface of the exhaust passage and a wall surface of the plug.