JP2002301320A - Diesel Partiate Filter - Google Patents

Abstract

(57) Abstract: coating the carrier layer having a reducing action of the nitrogen oxides NO _x in the surface of the ceramic fiber material to obtain a diesel putty alive Yoo rate filter to reduce the generation of nitrogen oxides NO _x. SOLUTION: A diesel filter 1 is provided.
Is BaPrO _{3 on the} surface of the wire rod of the silicon carbide ceramic fiber material 5.
Of the perovskite-type compound 7 is coated. The filter bodies 4 and 20 are made of a nonwoven fabric in which the ceramic fiber material 5 coated with the support layer 6 is laminated irregularly. An intermediate layer 8 is provided between the support layer 6 and the perovskite compound 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel particulate filter which collects a particulate contained in exhaust gas of a diesel internal combustion engine.

[0002]

2. Description of the Related Art In a diesel internal combustion engine, since fuel is burned with excess air, oxygen O ₂ is present in exhaust gas and a large amount of nitrogen oxide NO _x is emitted. On the other hand, in a gasoline internal combustion engine, combustion is performed at a stoichiometric mixture ratio, and oxygen O ₂
But without much there, there is no problem of nitrogen oxides NO _x.

[0003] Conventionally, nitrogen oxides have been produced from diesel internal combustion engines.
For NO _x is prevented from being discharged to the outside, diesel putty alive Yoo rate filter are known that incorporate the various catalysts. For example, a diesel-patterned filter having a zeolite-based catalyst (Cu-ZSM-5) built into a diesel-passed filter allows the exhaust gas to pass through the voids of the diesel-passed filter as in a gasoline internal combustion engine. Things. That is,
Particles of nitrogen oxide NO _x that are small compared to oxygen O ₂ particles,
Adsorbed between the zeolite tunnel-like molecules. The zeolite-based catalyst uses hydrocarbon HC as a reducing agent to reductively decompose nitrogen oxides NO _x . However, since the zeolite-based catalyst is hindered by exhaust gas particles and is not sufficiently utilized, the purification rate of nitrogen oxides NO _{x in} exhaust gas is 20 to 40%. Also, since zeolite-based catalysts require methanol or ethanol as hydrocarbon HC as a reducing agent,
The structure of the diesel filter is complicated, and practical use is difficult.

[0004] Further, in a diesel particulate filter in which a catalyst device is incorporated, when graphite or particulate electrolyte is deposited on the wall surface of the void, nitrogen oxide NO
_x may come in contact with graphite or pateulate, and the hydrocarbon may no longer act as a reducing agent.

[0005] As an exhaust gas treatment filter for collecting particulate matter such as carbon, soot, and hydrocarbon HC from exhaust gas of a diesel internal combustion engine, for example, those using inorganic fibers in addition to cordierite are known. Have been. In the case of using an inorganic fiber fiber as a filter body, a twisted yarn obtained by twisting an inorganic fiber material into a thread shape is laminated in a wound form, and the inorganic fiber material is woven in a diamond shape to be felt. The filter body described above captures the particulates such as carbon, soot, and smoke of the exhaust gas discharged from the diesel internal combustion engine on the surface and inside of the filter body, so that the filter body can be made smaller than a honeycomb type filter made of cordierite.

The heat-resistant filter disclosed in Japanese Patent Application Laid-Open No. 6-108820 has a filtration layer in which heat-resistant fibers are irregularly accumulated between gas-permeable partitions, and at least the passage of a fluid to be filtered in the partitions. The partition arranged on the downstream side in the direction is formed of a planar structure made of heat-resistant fibers.

A compound having a perovskite-type crystal structure, a so-called perovskite-type compound, has oxygen vacancies, has a remarkably high ionic conductivity, and has a nitrogen oxide NO.
_It has the property of decomposing _x .

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to use a silicon carbide fiber material in a filter body for collecting a particulate contained in exhaust gas from a diesel internal combustion engine and to carry the silicon carbide fiber material on a wire surface of the silicon carbide fiber material. reducing nitrogen oxides NO _x in the exhaust gas by reducing nitrogen oxides NO _x in the presence of a perovskite-type compound, it is to provide a diesel putty alive Yoo rate filter.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention is directed to a diesel particulate filter comprising a ceramic fiber material for collecting a particulate contained in exhaust gas of a diesel internal combustion engine.
Wherein the wire surfaces of the ceramic fibrous material carrying layer containing the perovskite-type compound is coated with a reducing action of the nitrogen oxides NO _x, is composed of a nonwoven fabric obtained by randomly laminating the ceramic fiber material coated with the support layer It is characterized by having.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The diesel particulate filter according to the present invention is a carrier layer comprising a perovskite-type compound exhibiting an order-disorder transition of oxygen defects on the surface of a silicon carbide ceramic fiber material or a silicon nitride ceramic fiber material wire. , And a ceramic fiber material is mixed irregularly to form a filter body. When high-temperature exhaust gas flows in a zigzag manner in the gaps between the fibers in the laminated portion of the filter body, solid particulate particulates contained in the exhaust gas are collected by the filter body and deposited in the gaps between the fibers.
Since the ceramic fiber materials are stacked on each other, when the exhaust gas containing nitrogen oxide NO _x collides with the carrier layer coated on the ceramic fiber material, it reacts with ions due to oxygen vacancies in the carrier layer, and the nitrogen oxide NO _x Is reduced. Pateikiyureto also collide with filter body, since ceramic fiber material in the presence of a supported layer is not in close contact with each other, the exhaust gas containing nitrogen oxides NO _x is if with impact velocity of the nitrogen oxides NO _x The reduction reaction occurs quickly.

Accordingly, the diesel particulate filter of the present invention reduces the nitrogen oxides NO _x of the exhaust gas by the reducing action of the support layer of the ceramic fiber material, and reduces the particulate matter contained in the exhaust gas to the ceramic fiber material. Are collected and reduced. Moreover, although the greater the amount of generation of nitrogen oxides NO _x in the hot exhaust gases, perovskites activated at high temperatures, while the reducing action of the nitrogen oxides NO _x becomes active, the nitrogen oxides NO _x in low-temperature exhaust gas Low emission and no perovskite activation required. Although low-temperature exhaust gas generates a large amount of carbon, it is collected by the filter itself. Oxygen for perovskite activation
O ₂ require, but diesel internal combustion engine including a large amount of oxygen O ₂ in the exhaust gas, reduction of nitrogen oxides NO _x is performed well. That is, the perovskite has a heat resistance temperature of 900 ° C.
On the order, order making cation at a temperature 400 to 500 ° C. or above - a compound showing a disorder transition, ion conductivity is improved by increase in temperature, the nitrogen oxides NO _x
Decomposes well.

In order to form a perovskite-supporting layer on the surface of a ceramic fiber wire, glass is coated on silicon carbide SiC fiber and then sintered with perovskite powder adhered thereto. When the load on the diesel internal combustion engine is large and the temperature of the combustion gas rises, the perovskite activation temperature is 400 to 500 ° C., so that perovskite ionization becomes active and the reduction action of nitrogen oxide NO _x becomes active. On the other hand, when the temperature of the combustion gas decreases, the ionization of the perovskite also decreases, but there is no problem in the case of a low-temperature combustion gas because the generation amount of nitrogen oxides NO _x also decreases.
There are many gaps in the silicon carbide SiC fiber of the filter body.Therefore, when the patitilate trapped in the silicon carbide SiC fiber enters the gap of the silicon carbide SiC fiber, the perovskite is activated, and the nitrogen oxide NO _x is released from the patitiyule. unplug was reduced, to reduce the nitrogen oxide NO _x.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a preferred embodiment of a diesel-patterned filter according to the present invention. As shown in FIG. 1, the diesel particulate filter 1 is housed in, for example, a case 3 incorporated in an exhaust pipe of a diesel internal combustion engine, and exhaust gas discharged from the diesel internal combustion engine is filtered by filter bodies 4, 20. The arrow G
When flowing transversely in the direction indicated by, the particulates such as black smoke, carbon, soot, and hydrocarbons HC contained in the exhaust gas are collected by the filter bodies 4, 20, and the collected particulates are heated and incinerated, and the filter body is heated. 4, 20 are reproduced. The filter bodies 4 and 20 are formed by bending a ceramic fiber described later into a tubular and pleated shape as shown in FIG. The filter main bodies 4 and 20 are energized to the wire net 9 to heat the filter main bodies 4 and 20, as in the prior art, and the patters collected in the filter main bodies 4 and 20 are heated and incinerated for regeneration. In FIG. 2, the filter bodies 4 and 20 are:
Although it is configured to be sequentially bent into a corrugated shape, it may be configured to be a cylindrical shape such as a cylindrical shape, a flat plate shape, a wavy shape, a fold shape, or the like.

The filter main bodies 4 and 20 are disposed inside the exhaust gas passage 13 having the heat shielding structure formed by the heat shielding layer 2 so as to extend from the inlet 14 to the outlet 15.
The heat shield layer 2 disposed between the case 3 and the filter bodies 4 and 20 prevents heat from being radiated to the outside through the case 3. The filter bodies 4 and 20 are fixed to the case 3 by the stoppers 12. Wire mesh 9 for filter bodies 4 and 20
Is incorporated. When the exhaust gas discharged from the diesel internal combustion engine flows into the filter bodies 4 and 20, the particulates such as carbon, smoke, hydrocarbon HC, and sulfur oxide SOx contained in the exhaust gas are collected in the filter bodies 4 and 20. The terminal 11 is connected to the wire net 9 according to a command from the electronic control unit 10.
When applying current through, Pateikiyureto trapped in the filter body 4, 20 is heated incineration, carbon dioxide CO _2, released into connexion outlet 15 such a gas such as water vapor H ₂ O.

The filter bodies 4 and 20 are formed in a cylindrical shape with a pleated body. A hollow portion 18 is opened at the entrance 14 and another region (center portion) is closed by a shielding plate 16. On the outlet 15 side, the hollow portion 18 is closed by the shielding plate 17 and the other region (center portion) 19 is opened. Accordingly, the exhaust gas flowing from the inlet 14 of the exhaust gas passage 13 flows from the hollow portion 18 across the filter bodies 4 and 20 to the center portion 19,
The exhaust gas is collected by the filter bodies 4 and 20, and the clean exhaust gas is discharged to the outlet 15. The reproduction of the filter bodies 4 and 20 is performed as follows. For example, the exhaust gas pressure is detected by a pressure sensor to determine the trapping amount of the filter bodies of the filter bodies 4 and 20. Then, the catalysts collected in the filter bodies 4 and 20 are heated and incinerated to regenerate the filter bodies 4 and 20. The wire mesh 9 is made of, for example, a nickel Ni-based metal wire, and is configured to uniformly heat the filter bodies 4 and 20.

In the embodiment shown in FIGS. 3 and 4, the diesel filter 1 is constructed by laminating a wire mesh 9 on both sides of a filter body 4 formed in a plate shape. As shown in FIG. 4, the filter body 4 is made of a silicon carbide ceramic fiber material 5, and a support layer 6 made of a perovskite type compound 7 showing an order-disorder transition of oxygen defects is formed on the surface of the wire material of the ceramic fiber material 5. Coated. The filter main body 4 is made of a nonwoven fabric in which the ceramic fiber material 5 coated with the support layer 6 is laminated irregularly.
The silicon carbide ceramic fiber material 5 is made of silicon carbide SiC fiber material or SiC-Ti-O fiber material (Si-CO, Si-Ti-CO, Si-C).
Consists of The ceramic fiber material 5 is formed by laminating long fibers irregularly in a felt shape. The wire diameter of the ceramic fiber material 5 is, for example, about 5 to 15 μm, and the length is 30 to 1 μm.
It is about 50 mm. The filter main body 4 laminated in a felt shape has a thickness of, for example, about 3 to 5 mm.

The support layer 6 of the diesel particulate filter 1 is formed by supporting a powder of a perovskite compound 7 on the surface of a wire of the ceramic fiber material 5. BaPrO ₃ or the like is used for the perovskite compound 7. When the intermediate layer 8 is formed, it is preferable to use a composite oxide of an element contained in the carrier layer 6 such as Pr-Si-ON and an element contained in the ceramic fiber material 5.

Exhaust gas from the operating diesel internal combustion engine is sent into the exhaust gas passage 13 of the diesel particulate filter 1 via an exhaust pipe. Exhaust gas at inlet 14
From the exhaust gas passage 13 and passes through a filter main body 4 arranged perpendicularly to the exhaust gas passage 13, the filter main body 4 collects soot, carbon, smoke, etc. contained in the exhaust gas and clean exhaust gas is collected. Exit 1
It is discharged to 5. The collected patillate accumulates on the filter body 4. A sensor for detecting the exhaust gas pressure or the trapped amount is provided inside the case 3, and a signal of the exhaust gas pressure or the collected amount detected by the sensor is input to the electronic control unit 10.
The electronic control unit 10 is provided with a rotation sensor for detecting an operation state of the internal combustion engine, that is, a rotation speed of the internal combustion engine, a load sensor for detecting a load on the internal combustion engine, a temperature sensor for detecting an exhaust gas temperature, and the like.

The electronic control unit 10 receives the detection signal of the operating state of the internal combustion engine, and controls the energization of the wire net 9 in accordance with the detected value of the exhaust gas pressure or the trapping amount determined in advance from the operating state of the internal combustion engine. Then, it is configured to control the regeneration timing of the filter main body 4. That is, the electronic control unit 10 receives the detection signal from each sensor such as the exhaust gas pressure sensor and determines the operation state of the internal combustion engine. When the trapped amount reaches a preset value, the wire net 9 is energized through the electrode terminal 11 according to a command from the electronic control unit 10. Wire mesh 9
As a result, the filter main body 4 is heated, and the collected pasty rate is heated and incinerated. That is, taking advantage of the principle of the excess air ratio in the diesel internal combustion engine, Pateikiyureto is heated combusted by utilizing air contained in the exhaust gas traces passing through the filter body 4, Pateikiyureto is carbon dioxide CO _2, water vapor H ₂ O Then, it is discharged to the outlet 15.

In the embodiment shown in FIG. 5, the filter body 20 of the plate-shaped diesel particulate filter 1 which is disposed perpendicularly to the exhaust gas passage 13 has a silicon carbide SiC fiber material or silicon nitride Si ₃ N _{4 A} filter body 4 made of a non-woven fabric having a ceramic fiber material 5 of a fiber material disposed thereon and having a support layer 6 on the surface of the ceramic fiber material 5 downstream of the exhaust gas.
Is arranged. Carbon by ceramic fiber material 5 on the exhaust gas upstream side, soot, Pateikiyureto such hydrocarbons HC are collected, then the nitrogen oxides NO _x is reduced by the filter body 4 having a carrying layer 6 of the exhaust gas downstream side, the exhaust gas as a whole Is purified.

As described above, the filter main body 4 of the diesel-patterned filter 1 is made of a ceramic fiber material 5.
The carrier layer 6 serve the reducing action of the nitrogen oxides NO _x in the surface of the coating. When the internal combustion engine is driven, as shown in FIG. 6, the supply of the fuel flow rate Q increases in accordance with the increase in the load L of the internal combustion engine, the torque T increases, and the exhaust gas temperature GT increases. When the exhaust gas temperature GT is increased, as indicated by a broken line B, the nitrogen oxides NO _x when the combustion of the fuel a large amount of generated and contains a large amount of nitrogen oxides NO _x in the exhaust gas. However, in the diesel particulate filter 1 according to the present invention, since the supporting layer 6 is coated on the ceramic fiber material 5, for example, when the load of the internal combustion engine becomes 2/4 load, the exhaust gas temperature GT exceeds 500 ° C. The reduction effect of the exhaust gas on nitrogen oxides NO _x is activated by the perovskite-type compound constituting the carrier layer 6, and the solid line A in FIG.
As shown by, the nitrogen oxide NO _x of the exhaust gas is reduced to carbon dioxide gas N ₂ and oxygen O ₂ , and the nitrogen oxide NO _{x of the} exhaust gas is reduced.

When the load on the internal combustion engine is low, the amount of generated nitrogen oxides NO _x is small, so the reducing action of the carrier layer 6 on the nitrogen oxides NO _x is not so necessary. since the reduction effect on nitrogen oxides NO _x 6 becomes active, nitrogen oxides NO _x in the exhaust gas is reduced. It was but connexion, the diesel putty alive Yoo rate filter can suppress the generation of nitrogen oxides NO _x in response to the operating state of the internal combustion engine.

[0023]

The diesel particulate filter according to the present invention provides Ba ₂ In ₂ O ₅ , Ba ₃ Y which exhibits an order-disorder transition of oxygen defects on the surface of a wire of a silicon carbide ceramic fiber material.
_{Since the} carrier layer composed of a perovskite type compound of ₄ O ₉ or BaLa ₂ O ₄ is coated, nitrogen oxides NO _x contained in the exhaust gas are decomposed into carbon dioxide gas N ₂ and oxygen O ₂ by the reducing action of the perovskite type compound. And reduce nitrogen oxides NO _x in exhaust gas.

Since the carrier layer is coated on the surface of the ceramic fiber material, the exhaust gas does not directly contact the ceramic fiber material, and the durability of the ceramic fiber material is improved.

[0025] Even if the collecting of the partition by the filter body and the heating and incineration of the partition to regenerate the filter body are repeated, the filter body and the wire mesh are separated and deformed, or the filter body is locally abnormal. No overheating. Further, no noise is generated in the filter body.

Since the filter main body is sandwiched between a pair of wire meshes, the filter main body is extremely easy to form, and the workability is excellent.

Since the filter body is covered on both inner and outer surfaces with a wire mesh, it is possible to prevent the ceramic fibers from being separated and scattered.

Since an intermediate layer is formed between the ceramic fiber material and the perovskite-type compound constituting the supporting layer,
The diffusion of the perovskite compound into the ceramic fiber and the thermal expansion of the ceramic fiber material are suppressed, and the durability of the filter body is improved.

Silicon carbide Si is provided on the exhaust gas upstream side of the filter body.
A ceramic fiber material such as C fiber material or silicon nitride Si ₃ N ₄ fiber material is provided, and a nonwoven fabric having a support layer on the surface of the ceramic fiber material is provided downstream of the exhaust gas. Pateikiyureto is collected, then the nitrogen oxides NO _x is reduced by the ceramic fiber material having a carrier layer of the exhaust gas downstream side, exhaust gases are purified as a whole.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a schematic configuration of a diesel particulate filter according to the present invention.

FIG. 2 is a front cross-sectional view of the diesel particulate filter taken along line AA in FIG. 1;

FIG. 3 is a side cross-sectional view of a filter main body of a diesel partilating filter according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view of a ceramic fiber material constituting the filter main body.

FIG. 5 is a side cross-sectional view of a filter main body of a diesel partilating filter according to a third embodiment of the present invention.

FIG. 6 is a diagram showing a relationship between a torque and a generation amount of nitrogen oxides NO _x with respect to a fuel flow rate of the diesel internal combustion engine.

[Explanation of symbols]

1: diesel filter 2: heat shielding layer 3: case 4: filter body 5: ceramic fiber material 6: supporting layer 7: perovskite compound 8: intermediate layer 9: wire mesh 10: electronic control device 11: terminal 12: Stopper 13: Exhaust gas passage 14: Inlet 1
5: Exit 16: Shielding plate 17: Shielding plate 18: Hollow portion 19: Central portion 20: Filter body

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C04B 35/80 F01N 3/02 321A F01N 3/02 301 3/10 A B01D 53/36 104B 321 ZAB 3 / 10 C04B 35/80 CLF term (reference) 3G090 AA02 BA04 CA01 CA04 CB11 DA02 DA12 DA18 DA20 3G091 AA18 AB05 AB13 BA00 BA04 BA14 BA15 BA20 CA03 CB08 DA01 DA02 DA10 EA01 EA03 EA17 EA32 EA33 FB02 GA03 GA10 GA03 GB00W GB01X GB10X GB13X GB15X GB17X HA14 4D019 AA01 BA05 BA06 BC07 CB04 4D048 AA06 AB02 BA15Y BA17Y BA18Y BA42X BB08 CA07 CC41 CD05 4G069 AA03 AA08 BB06B CA03 CA08 CA13 DA06 EA03 FA01 EA03 FA03

Claims (4)

[Claims] 1. A diesel diesel putty alive Yoo rate filter consisting of ceramic fiber material for collecting Pateikiyureto contained in internal combustion engine exhaust gas, a perovskite the wire surface of the ceramic fiber material having a reducing action of the nitrogen oxides NO _x A diesel-patterned filter characterized by comprising a non-woven fabric in which a support layer made of a type compound is coated and the ceramic fiber material coated with the support layer is irregularly laminated. 2. The filter according to claim 1, wherein an intermediate layer is formed between the perovskite compound forming the carrier layer and the ceramic fiber material. 3. The filter according to claim 2, wherein the intermediate layer forms a support layer and a diffusion layer, and supports a compound having a perovskite crystal structure. 4. The ceramic fiber material is a silicon carbide SiC fiber.
Material and SiC-Ti-O fiber material and silicon nitride Si _ThreeN_Four A piece of fiber material
2. The diesel part according to claim 1, further comprising:
A curate filter.