JP4292868B2 - Exhaust gas purification device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas purification apparatus that purifies exhaust gas using plasma.
[0002]
[Prior art]
Conventionally, as an apparatus for purifying exhaust gas of an internal combustion engine incorporated in an exhaust system of a vehicle internal combustion engine, exhaust gas purification that purifies exhaust gas using plasma generated by applying a high voltage to the opposite electrode An apparatus (plasma reactor) is known (for example, refer to Patent Document 1). This exhaust gas purification device is configured as a so-called wall flow type purification device, and collects a casing (purification container) incorporated in an exhaust system and particulate matter (hereinafter referred to as “PM material”) in exhaust gas. And a ceramic filter. The filter is disposed inside the casing, and defines an upstream exhaust gas passage in the outer peripheral portion thereof, and defines a downstream exhaust gas passage in the central portion thereof.
[0003]
The exhaust gas introduced into the casing of the exhaust gas purification apparatus flows into the upstream exhaust gas passage near the inner peripheral surface of the casing, and after flowing through the bent portion of the ceramic filter, the downstream exhaust gas passage Flows out of the casing through. And while exhaust gas distribute | circulates a ceramic filter, PM substance in exhaust gas is collected by a filter. Further, the PM material collected by the filter is extinguished or incinerated by the plasma.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-295629
[Problems to be solved by the invention]
However, in the conventional exhaust gas purification apparatus configured as described above, basically, a region for charging the PM substance in the exhaust gas (a region where an electric field is formed) and a region for collecting the PM substance are provided. However, it is limited to the portion of the ceramic filter that is bent into a bowl shape. For this reason, in the above-mentioned conventional exhaust gas purification device, it is difficult to further improve the collection efficiency and processing efficiency of PM substances, and the emergence of an exhaust gas purification apparatus capable of more efficiently collecting and treating PM substances is required. It has been.
[0006]
Accordingly, an object of the present invention is to provide an exhaust gas purifying apparatus capable of efficiently collecting and processing particulate matter.
[0007]
[Means for Solving the Problems]
The exhaust gas purifying apparatus according to the present invention is an exhaust gas purifying apparatus that purifies exhaust gas using plasma, a purification container into which exhaust gas is introduced, a honeycomb structure, and a flow of exhaust gas disposed at the center of the honeycomb structure. And a plurality of processing units each including an outer peripheral electrode disposed on the outer periphery of the honeycomb structure, and the processing units are arranged in parallel in the purification container.
[0008]
In this exhaust gas purification apparatus, a plurality of processing units each including a honeycomb structure, a rod-shaped electrode, and an outer peripheral electrode are used. Therefore, in this exhaust gas purifying apparatus, the distance between the rod-shaped electrode and the outer peripheral electrode in each processing unit can be shortened as compared with the case where one processing unit is used. Without increasing, it is possible to enhance the electric field formed between the rod-shaped electrode and the outer peripheral electrode and to control the electric field with good responsiveness. As a result, according to this exhaust gas purifying apparatus, the PM substance in the exhaust gas is efficiently charged for each processing unit and collected in the honeycomb structure, and the PM substance collected for each processing unit is collected. It becomes possible to process efficiently.
[0009]
In this case, any one of the plurality of processing units includes a central electrode located at the center of the purification container, and the central electrode protrudes from the honeycomb structure toward the exhaust gas inlet of the purification container, and the tip thereof It is preferable to have a plurality of discharge protrusions.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of an exhaust gas purifying apparatus according to the present invention will be described in detail with reference to the drawings.
[0011]
FIG. 1 is a cross-sectional view showing an embodiment of an exhaust gas purifying apparatus according to the present invention, and FIG. 2 is a cross-sectional view taken along line II-II in FIG. The exhaust gas purification apparatus 1 shown in these drawings is suitable when applied to a vehicle. In order to purify exhaust gas discharged from a combustion chamber of an internal combustion engine (not shown), an exhaust system of the internal combustion engine is used. It is incorporated between the exhaust pipe L1 and the exhaust pipe L2. As shown in FIGS. 1 and 2, the exhaust gas purification apparatus 1 has a purification container 2, and the exhaust gas discharged from the combustion chamber of the internal combustion engine through the exhaust pipe L <b> 1 is inside the purification container 2. Is introduced. Then, the exhaust gas purified inside the purification container 2 is discharged to the outside through the exhaust pipe L2.
[0012]
The purification container 2 is formed in a substantially cylindrical shape with metal or the like, and has an inlet end portion 21 and an outlet end portion 22 connected to the exhaust pipe L1 or L2, and an expanded diameter having a larger inner diameter than the exhaust pipes L1 and L2. And a cone portion 24 formed between the inlet end portion 21 and the enlarged diameter portion 23 and between the outlet end portion 22 and the enlarged diameter portion 23. Further, the insulating member 3 formed in a cylindrical shape is fixed to the inner peripheral surface of the enlarged diameter portion 23 of the purification container 2.
[0013]
As shown in FIGS. 1 and 2, a plurality of processing units 7 each including a honeycomb structure 4, a rod-like electrode 5, and an outer peripheral electrode 6 are provided inside the purification container 2 (in this embodiment, seven bodies). ) It is installed side by side. In the present embodiment, six processing units 7 are arranged at equal intervals on the inner peripheral surface of the insulating member 3 in the purification container 2, and the center of these six processing units 7, that is, the purification container 2. One processing unit 7 is arranged so as to be located at the center of the center. Among the outer peripheral electrodes 6 of the six processing units 7, the adjacent outer peripheral electrodes 6 are in contact with each other as shown in FIG. Further, the outer peripheral electrode 6 of the one processing unit 7 is in contact with the outer peripheral electrode 6 of the six processing units 7.
[0014]
The honeycomb structure 4 of each processing unit 7 is used for collecting PM substances in the exhaust gas flowing into the purification container 2. Each honeycomb structure 4 is made of ceramic (for example, cordierite or alumina) and has a number of cells extending in the exhaust gas flow direction (extension direction of the purification container 2). The honeycomb structure 4 carries an oxidation catalyst such as Pt / CeO ₂ , Mn / CeO ₂ , Fe / CeO ₂ , Ni / CeO ₂ , Cu / CeO ₂ . In the present embodiment, the honeycomb structure 4 of each processing unit 7 is formed of the same material and the same size.
[0015]
The rod-like electrode 5 of each processing unit 7 is arranged at the center of the honeycomb structure 4 and extends in the exhaust gas flow direction (the cell extending direction of the honeycomb structure 4). In the present embodiment, each rod-like electrode 5 protrudes from the honeycomb structure 4 toward the exhaust gas outlet (exhaust pipe L2). And each rod-shaped electrode 5 merges in the downstream (exhaust pipe L2 side) of each honeycomb structure 4, and is connected to the high voltage power supply 10 via the electric power feeding terminal 8 grade | etc.,. Thereby, it can prevent that collection of PM substance is prevented by the electric power feeding part with respect to each rod-shaped electrode 5. FIG. As the high-voltage power source 10, any one of a DC high-voltage power source, an AC high-voltage power source, and a DC pulse power source can be used.
[0016]
The outer peripheral electrode 6 paired with the inner rod-shaped electrode 5 via the honeycomb structure 4 is formed in a cylindrical shape by a metal mesh or a metal paste, and is laminated on the outer peripheral surface of each honeycomb structure 4. The outer peripheral electrodes 6 of the processing units 7 are in contact with each other as described above, and are grounded via the terminals 9. In this embodiment, a high voltage is applied between each rod-like electrode 5 and each outer peripheral electrode 6 by the high-voltage power supply 10 with each rod-like electrode 5 as a negative electrode.
[0017]
Further, the rod-like electrode 5c of the processing unit 7 located at the center of the purification container 2 functions as a central electrode of the exhaust gas purification device 1, and from the honeycomb structure 4 toward the exhaust gas inlet (exhaust pipe L1) of the purification container 2. It protrudes. A plurality of discharge protrusions 5d are provided at the tip of the rod-like electrode 5c as the center electrode. Each discharge protrusion 5d is formed in a spine shape and extends radially from the tip of the rod-like electrode 5c. By adopting such a configuration, it is possible to generate an electric field satisfactorily inside the purification container 2 and efficiently generate plasma.
[0018]
Furthermore, as can be seen from FIG. 2, a filler 15 is disposed inside the purification container 2 so as to fill the gaps between the processing units 7 and the gaps between the processing units 7 and the insulating member 3. Thereby, the processing units 7 are integrated with each other. In the present embodiment, a porous body such as ceramic is used as the filler 15. Thereby, it is possible to prevent the exhaust gas from passing through the purification container 2 without any treatment, and to increase the dielectric constant inside the purification container 2.
[0019]
In the exhaust gas purification apparatus 1 configured as described above, exhaust gas from the combustion chamber of the internal combustion engine is introduced into the purification container 2 through the exhaust pipe L1 when the internal combustion engine is started. In addition, a high voltage is applied between the rod-shaped electrode 5 and the outer peripheral electrode 6 by the high-voltage power supply 10 in order to generate plasma in each processing unit 7 (each honeycomb structure 4) in accordance with the start of the internal combustion engine. .
[0020]
Here, as described above, the exhaust gas purification apparatus 1 includes a plurality of processing units 7 each including the honeycomb structure 4, the rod-like electrode 5, and the outer peripheral electrode 6. Therefore, in the exhaust gas purification apparatus 1, the distance between the rod-shaped electrode 5 and the outer peripheral electrode 6 in each processing unit 7 can be shortened as compared with the case where one processing unit is used. Thereby, without increasing the capacity of the high-voltage power supply 10 more than necessary, the electric field formed between the rod-like electrode 5 and the outer peripheral electrode 6 is strengthened, and the electric field in each processing unit 7 is well controlled with good responsiveness. It becomes possible.
[0021]
As a result, according to the exhaust gas purification device 1, the PM substance in the exhaust gas can be efficiently charged and collected in the honeycomb structure 4 for each processing unit 7. Further, in the exhaust gas purification apparatus 1, since the distance between the rod-like electrode 5 and the outer peripheral electrode 6 in each processing unit 7 is the same, the adsorptivity (collection rate) of the PM substance in each processing unit 7 is uniform. Can be.
[0022]
In the exhaust gas purifying apparatus 1, oxygen, nitrogen monoxide, and the like in the exhaust gas are caused by plasma generated in each processing unit 7 while the exhaust gas flows through each processing unit 7 (honeycomb structure 4). When activated (radicalized), ozone (O ₃ ), activated oxygen (O ₂ ⁻ ), nitrogen dioxide (NO ₂ ) and the like having high oxidation activity are generated. The PM material collected in the cells of the honeycomb structure 4 of each processing unit 7 reacts with these highly oxidizing active components and is burned and incinerated. Furthermore, in the exhaust gas purification apparatus 1, combustion of the PM substance is promoted by the action of the oxidation catalyst supported on the honeycomb structure 4 of each processing unit 7. Thereby, according to the exhaust gas purification apparatus 1, it becomes possible to process PM substance efficiently for every honeycomb structure 4 of each processing unit 7. And the exhaust gas well purified inside the purification container 2 is discharged to the outside through the exhaust pipe L2.
[0023]
FIG. 3 is a cross-sectional view showing another embodiment of the exhaust gas purifying apparatus according to the present invention. Note that the same reference numerals are given to the same elements as those described in relation to the above-described embodiment, and redundant descriptions are omitted.
[0024]
In the exhaust gas purifying apparatus 1A shown in FIG. 3, an outer electrode 11 formed in a cylindrical shape by a metal mesh or a metal paste or the like is laminated on an inner peripheral surface of an insulating member 3 disposed inside the purification container 2. . Further, inside the outer electrode 11, an inner electrode 12 formed in a cylindrical shape by a metal mesh or a metal paste is disposed concentrically. Further, a plurality (six in this embodiment) of partition electrodes 14 are radially arranged in the region between the outer electrode 11 and the inner electrode 12 at equal intervals. Each partition electrode 14 is also formed of a metal mesh or a metal paste.
[0025]
A honeycomb structure 4a having a generally fan-shaped cross-sectional shape is disposed in a region surrounded by the outer electrode 11, the inner electrode 12, and the partition electrodes 14 adjacent to each other. A honeycomb structure 4c formed in a shape is disposed. Each of the honeycomb structures 4a and 4c is also made of ceramic (for example, cordierite or alumina) and has a large number of cells extending in the exhaust gas flow direction (extension direction of the purification container 2). Each honeycomb structure 4a, 4c also carries an oxidation catalyst such as Pt / CeO ₂ , Mn / CeO ₂ , Fe / CeO ₂ , Ni / CeO ₂ , Cu / CeO ₂ . In the present embodiment, the honeycomb structures 4a and 4c are formed so as to have substantially the same cross-sectional area.
[0026]
Furthermore, a rod-shaped electrode 5 is disposed at substantially the center of each honeycomb structure 4a, and a rod-shaped electrode (center electrode) 5c is disposed at the center of the honeycomb structure 4c. Each rod-like electrode 5, 5 c extends in the exhaust gas flow direction (the cell extending direction of the honeycomb structure 4). And each rod-shaped electrode 5 and 5c joins in the downstream of each honeycomb structure 4a and 4c, and is connected to the high voltage power supply which is not shown in figure through the electric power feeding terminal. On the other hand, the outer electrode 11 and the inner electrode 12 are electrically connected via a plurality of partition electrodes 14, and these electrodes 11, 12 and 14 are grounded via terminals.
[0027]
In the thus configured exhaust gas purification apparatus 1A, the outer electrode 11, the inner electrode 12, the partition electrode 14 adjacent to each other, the honeycomb structure 4a and the rod-like electrode 5 constitute a plurality (six) treatment units 7A. The In this case, in the processing unit 7 </ b> A, the outer electrode 11, the inner electrode 12, and the partition electrode 14 adjacent to each other function as an outer peripheral electrode that makes a pair with the rod-shaped electrode 5. Further, inside these processing units 7A, a processing unit 7C is constituted by the inner electrode 12, functioning as an outer peripheral electrode, the honeycomb structure 4c, and the rod-shaped electrode 5c. According to the exhaust gas purifying apparatus 1A, the area for adsorbing the PM substance can be increased, and the honeycomb structures 4a and 4c can be efficiently charged by charging the PM substance in the exhaust gas for each of the processing units 7A and 7C. In addition, the PM substance collected for each of the processing units 7A and 7C can be efficiently processed.
[0028]
In the exhaust gas purification apparatuses 1 and 1A described above, the voltage applied to the electrode pair may be changed for each processing unit 7. Further, in the above-described exhaust gas purification apparatuses 1 and 1A, a plurality of processing units are disposed in the inside of the purification container. However, the present invention is not limited to this. It may be arranged in multiple (three or more layers).
[0029]
【The invention's effect】
As described above, according to the present invention, it is possible to realize an exhaust gas purifying apparatus capable of efficiently collecting and treating particulate matter.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of an exhaust gas purifying apparatus according to the present invention.
FIG. 2 is a cross-sectional view taken along the line II-II in FIG.
FIG. 3 is a schematic configuration diagram showing another embodiment of the exhaust gas purifying apparatus according to the present invention.
[Explanation of symbols]
1, 1A Exhaust gas purification device 2 Purification container 3 Insulating member 4, 4a, 4c Honeycomb structure 5, 5c Rod-like electrode 5d Discharge protrusion 6 Outer peripheral electrode 7, 7A, 7C Processing unit 8 Feed terminal 9 Terminal 10 High voltage power source 11 Outer electrode Inner electrode 14 Partition electrode 15 Filler 21 Inlet end 22 Outlet end 23 Expanded portion 24 Cone L1, L2 Exhaust pipe

Claims (2)

In an exhaust gas purification device that purifies exhaust gas using plasma,
A purification container into which exhaust gas is introduced;
A honeycomb structure, a rod-shaped electrode disposed in the center of the honeycomb structure and extending in the flow direction of the exhaust gas, and a processing unit including an outer peripheral electrode disposed on the outer periphery of the honeycomb structure,
The treatment unit is provided in the purification container ;
The processing unit includes a central electrode located at the center of the purification container, and the central electrode protrudes from the honeycomb structure toward the exhaust gas inlet of the purification container, and has a plurality of discharge protrusions at the tip thereof. An exhaust gas purifying apparatus characterized by comprising: A plurality of the processing units are provided,
Any one of the plurality of processing units includes the center electrode having the plurality of discharge protrusions at a tip,
The exhaust gas purification apparatus according to claim 1, wherein the plurality of processing units are arranged in parallel in the purification container .

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