The present invention relates to a method for manufacturing a plasma treatment device for exhaust gas purification, in which harmful components contained in exhaust gas are removed.
PCT international publication No. WO2004/004869, or, the equivalent U.S. Pat. No. 7,326,264, discloses a plasma treatment device for exhaust gas purification. The plasma treatment device has a honeycomb body made of porous ceramic material. In the honeycomb body, a plurality of longitudinal holes is formed so as to extend in the honeycomb body. Each longitudinal hole has a diamond-shaped cross-section to form a diamond arrangement. The holes are defined by partition walls which collect particulate matter as harmful components contained in exhaust gas. Metal electrodes are embedded in the partition walls located at the corners of the diamond-shaped cross-sections of the holes. The metal electrodes in the form of conductive wire extend along the holes, and are connected to an electric power source. When the electric power source applies electric voltage between the metal electrodes, plasma is generated in the holes. As a result, the particulate matter collected by the partition walls are oxidized and removed from the honeycomb body.
In manufacturing the plasma treatment device in which the metal electrodes extend along the longitudinal holes in the honeycomb body, as is the case of the above reference, a process for embedding the metal electrodes in the honeycomb body is required. However, the honeycomb body is made of brittle ceramic material, and the honeycomb body and the metal electrodes are not easily integrated. Therefore, it is difficult to improve efficiency in manufacturing the plasma treatment device.
The present invention is directed to provide a method for manufacturing a plasma treatment device for exhaust gas purification so as to easily integrate metal electrodes with a honeycomb body and to improve efficiency in manufacturing thereof.
In accordance with the present invention, a method for manufacturing a plasma treatment device for exhaust gas purification is provided. The plasma treatment device for exhaust gas purification includes a honeycomb body and a plurality of metal electrodes. In the present invention, “honeycomb body” includes not only a structure having an arrangement with hexagonal cross-sections, but also structures having arrangements with rectangular, or other polygonal cross-sections, or circular cross-sections, as long as the structures include longitudinal holes for the plasma treatment device. The honeycomb body is made of dielectric and has therein a plurality of holes which introduces exhaust gas thereinto. The metal electrodes extend along the holes, and are interposed between the holes. The plasma treatment device purifies exhaust gas by applying electric voltage between the metal electrodes to generate plasma inside the holes. The method for manufacturing the plasma treatment device includes steps of positioning the metal electrodes in an extrusion die, providing dielectric material for the honeycomb body into the extrusion die, and performing extrusion so as to form the honeycomb body thereby integrating the honeycomb body with the metal electrodes.
The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:
A first preferred embodiment according to the present invention will be described with reference to
As shown in
The plasma treatment device 1 has metal electrodes 3A, 3B, 3C, 3D, and 3E. The metal electrode 3A covers the outer periphery of the honeycomb body 2. The metal electrodes 3B, 3C, 3D, and 3E are embedded in the honeycomb body 2. As shown in
As shown in
Referring back to
The following will describe the operation of the plasma treatment device 1 of the first preferred embodiment according to the present invention. As shown in
When the amount of PM collected and accumulated by the honeycomb body 2 reaches a predetermined value, the AC-power source 4 applies electric voltage between the metal electrodes 3A, 3B, 3C, 3D, and 3E. The metal electrodes 3A, 3B, 3C, 3D, and 3E are connected to the AC-power source 4 in such a way that the polarities of adjacent two of the metal electrodes 3A, 3B, 3C, 3D, and 3E are different with each other. Therefore, the partition walls 2B covering the metal electrodes 3B, 3C, 3D, and 3E and the inner surface of the metal electrode 3A serve as dielectrics, and generate plasma inside the holes 2A located between the metal electrodes 3A, 3B, 3C, 3D, and 3E. The plasma generated inside the holes 2A oxidizes and removes the PM collected by the partition walls 2B of the honeycomb body 2.
The following will describe a method for manufacturing the plasma treatment device 1 according to the first preferred embodiment of the present invention.
In forming the honeycomb body 2 by the extrusion device 5, the metal electrodes 3A, 3B, 3C, 3D, and 3E are positioned inside of the extrusion die 7. As shown in
In a state where the metal electrodes 3A, 3B, 3C, 3D, and 3E are positioned as described above, ceramic raw material is provided into the extrusion die 7. The ceramic raw material passes through the inside of the extrusion die 7, while covering the metal electrodes 3B, 3C, 3D, and 3E and the inner surface of the metal electrode 3A, and extrusion is performed. The ceramic raw material is extruded outside of the extrusion device 5 together with the metal electrodes 3A, 3B, 3C, 3D, and 3E, and goes through a drying process and a firing process. Thus, the honeycomb body 2 is manufactured so as to have the structure in that the metal electrode 3A is placed at the outer periphery and that the metal electrodes 3B, 3C, 3D, and 3E are embedded inside thereof. With such a structure, the honeycomb body 2 is reinforced by the metal electrodes 3A, 3B, 3C, 3D, and 3E, thereby improving the strength thereof.
In forming the honeycomb body 2 by extrusion, the metal electrodes 3A, 3B, 3C, 3D, and 3E are positioned inside of the extrusion die 7 to be extruded together with ceramic raw material. Therefore, ceramic material for forming the honeycomb body 2 is integrated with the metal electrodes 3A, 3B, 3C, 3D, and 3E, before the ceramic material is cured and becomes to be easily cracked. Further, the honeycomb body 2 is in advance integrated with the metal electrodes 3A, 3B, 3C, 3D, and 3E, and the number of parts is reduced in assembling the plasma treatment device 1. Therefore, the honeycomb body 2 and the metal electrodes 3A, 3B, 3C, 3D, and 3E are easily integrated, thereby improving the efficiency in manufacturing the plasma treatment device 1 for exhaust gas purification.
The following will describe a second preferred embodiment with reference to
The plasma treatment device of the second preferred embodiment differs from the method manufacturing the plasma treatment device 1 of the first preferred embodiment in providing with retaining members. The retaining members are provided at the opposite sides of the honeycomb body 2 after integrating the honeycomb body 2 with the metal electrodes 3A, 3B, 3C, 3D, and 3E.
As shown in
Thus, with the structure having the retaining members 12, 13 at the opposite ends of the honeycomb body 2, the metal electrodes 3A, 3B, 3C, 3D, and 3E are fixed to the honeycomb body 2 in such a state that the opposite ends of the metal electrodes 3A, 3B, 3C, 3D, and 3E are supported by the retaining members 12, 13. The retaining members 12, 13 restrict the movement of the metal electrodes 3A, 3B, 3C, 3D, and 3E in the direction along the holes 2A of the honeycomb body 2. Therefore, the metal electrodes 3A, 3B, 3C, 3D, and 3E are prevented from being removed from the honeycomb body 2 even in case that the metal electrodes 3A, 3B, 3C, 3D, and 3E are broken away from the honeycomb body 2.
The present invention is not limited to the above-described embodiments and may be modified into following alternative embodiments within the scope of the invention.
In the first and the second preferred embodiments, the honeycomb body 2 is formed in the rectangular cylinder shape, and the metal electrodes are formed in the rectangular cylinder shape or the wire shape, however, the configurations are not limited to the above shapes. As shown in
In the first and the second preferred embodiments, the honeycomb body 2 is the flow-through type DPF, however, the type of the honeycomb body is not limited to the flow-through type. The honeycomb body may be a wall-flow type DPF in which the metal electrodes are made of metal mesh through which exhaust gas passes.
In the first and the second preferred embodiments, the honeycomb body 2 is the DPF for collecting PM in exhaust gas, however, the function of the honeycomb body is not limited to that of the DPF. The honeycomb body may serve to oxidize harmful components such as carbon monoxide (CO) or nitrogen monoxide (NO) by generating plasma for exhaust gas purification.
Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims.
Number | Date | Country | Kind |
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P2007-317553 | Dec 2007 | JP | national |