JP2006029212A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure capable of maintaining durability and reliability of a device over a long period, in the exhaust emission control device for purifying exhaust gas by the action of high voltage. <P>SOLUTION: Respective discharge tubes 4a are arranged between a pair of support blocks 15 and 16, and an end surface in the longitudinal direction of the discharge tubes 4a is joined to annular installing step parts 25 and 26 formed on the port edge of through-holes 15a and 16a. Sealability between the discharge tubes 4a and the support blocks 15 and 16 can be improved, to thereby maintain the durability and reliability of the device over a long period. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust gas purification apparatus that processes exhaust gas from an internal combustion engine by applying a high voltage.

As a technique for purifying exhaust gas from an internal combustion engine such as a vehicle, in recent years, it has a cylindrical outer peripheral electrode and a rod-shaped inner electrode extending in the exhaust gas flow direction along the axis of the outer peripheral electrode. In other words, a so-called transmission type or straight flow type exhaust gas purifying apparatus has been proposed in which a high voltage is applied to the gas to generate a plasma state and purify the passing exhaust gas (see, for example, Patent Document 1). In such an apparatus, a substance such as NOx in the exhaust gas passing through is converted to N ₂ etc., and PM (particulate matter) in the exhaust gas is charged by discharge from the internal electrode, and the charge and PM is adsorbed on the outer peripheral electrode side by interaction with the electric field between the inner and outer electrodes, or is captured by a collecting device provided at the rear, and is generated by active gas (NO ₂ , O ₃ , OH, etc.) generated by discharge Incinerated at low temperature.

JP 2002-30920 A

  By the way, the discharge tube 50 in the apparatus of Patent Document 1 is formed by fixing a large-diameter insulating cylinder 52 at both ends of a metal small-diameter and cylindrical outer peripheral electrode 51 as shown in FIG. Mounting frames 54 and 55 are provided to fix the discharge tube 50 to the casing 53. The discharge tubes are inserted into holes provided in the mounting frames 54 and 55, and the holes and the insulating cylinder 52 are provided. It is supported by engagement with. On the axial center of the discharge tube 50, an internal electrode made of a wire is stretched at a position indicated by a two-dot chain line in the drawing.

  However, in the structure of Patent Document 1, when a vibration is applied to the apparatus, a force in the peeling direction acts on a fixed portion between the outer peripheral electrode 51 and the insulating cylinder 52, so that the discharge tube 50 is moved from the upstream side of the casing 53. There is a possibility that the exhaust gas leaks and the purification performance is deteriorated and the other sealed portions are deteriorated due to the change of the internal pressure.

  Moreover, in the structure of patent document 1, it is necessary to connect to each of the some discharge tube 50, and an assembly process is complicated, and also the problem of durability of a connection part may arise.

  Accordingly, an object of the present invention is to provide a structure capable of maintaining the durability and reliability of an apparatus for a long period in an exhaust gas purification apparatus that purifies exhaust gas by the action of a high voltage.

  1st this invention is equipped with the cylindrical discharge tube and the internal electrode extended through the inner side of the said discharge tube, The exhaust gas purification apparatus which purifies exhaust gas by the discharge between the said internal electrode and the said discharge tube The discharge tube is installed between a pair of support blocks each having a through hole for communicating with the discharge tube, and an end face in the longitudinal direction of the discharge tube is provided at a lip of the through hole. The exhaust gas purifying apparatus is characterized by being joined to the formed annular mounting step.

  In the first aspect of the present invention, the discharge tube is installed between a pair of support blocks, and the end surface in the longitudinal direction of the discharge tube is joined to an annular mounting step formed at the edge of the through hole. Therefore, the sealing performance between the discharge tube and the support block can be improved, and thereby the durability and reliability of the apparatus can be maintained for a long time.

  A second aspect of the present invention is the exhaust gas purifying apparatus according to claim 1, comprising a plurality of the discharge tubes, and a flexible plate-like conductive plate is inserted between the plurality of discharge tubes. The exhaust gas purifying apparatus is characterized in that the plurality of discharge tubes are electrically connected to each other by contact of the conductive plate.

  In the second aspect of the present invention, the plurality of discharge tubes are brought into conduction with each other by the contact of the flexible conductor, so that the conduction can be maintained even if there is a positional deviation between the plurality of discharge tubes, and vibration is caused in operation. Since the displacement of each discharge tube is suppressed by the elastic force of the conductor even when the is added, the durability and reliability of the apparatus can be maintained for a long time.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  In FIG. 1, an exhaust gas purification apparatus 1 according to an embodiment of the present invention is suitable when applied to a vehicle, and is configured as a plasma reactor or a corona reactor. The exhaust gas purification apparatus 1 is incorporated in an exhaust pipe constituting an exhaust system of the internal combustion engine in order to purify exhaust gas discharged from a combustion chamber of the internal combustion engine (not shown).

  The exhaust gas purification apparatus 1 includes an upstream case 2a, a downstream case 2b, and an intermediate case 3. The upstream case 2a, the downstream case 2b, and the intermediate case 3 are formed of a metal, particularly a heat resistant material such as SUS. The exhaust gas discharged from the combustion chamber of the internal combustion engine is introduced into the upstream case 2a in the direction indicated by the white arrow in FIG. The exhaust gas purified inside the intermediate case 3 is discharged to the outside from the downstream case 2b through an exhaust pipe (not shown).

  The upstream case 2a and the downstream case 2b have end portions 21a and 21b that are substantially the same diameter and substantially cylindrical as the exhaust pipe, and large-diameter portions 22a that have a substantially racetrack-shaped cross-sectional shape that is larger in diameter than the exhaust pipe. 22b, and cone portions 24a and 24b formed between the end portion 21a and the large diameter portion 22a and between the end portion 21b and the large diameter portion 22b. The end portions 21a and 21b constitute an inlet or an outlet for connecting to the exhaust pipe.

  Between the upstream case 2a and the downstream case 2b, a cylindrical intermediate case 3 having a substantially racetrack cross-sectional shape is airtightly coupled. Support blocks 15 and 16 are airtightly fixed to the upstream and downstream openings of the intermediate case 3 via an alumina mat 17. The support blocks 15 and 16 are each integrally formed from an insulator such as alumina.

  In the present embodiment, the processing unit 6 is configured by the discharge tube 4 a, the outer peripheral electrode 4 b, and the internal electrode 5. Between the support blocks 15 and 16, a plurality (24 in this embodiment) of discharge tubes 4a are fixed in parallel to each other. Each discharge tube 4a has a cylindrical shape, and a cylindrical outer peripheral electrode 4b is provided on the outer peripheral surface thereof. Flat annular end faces perpendicular to the axial direction are formed at both ends in the longitudinal direction of the discharge tube 4a, that is, upstream and downstream ends, respectively. It is preferable to use a ceramic such as an insulator or an insulator such as alumina for the discharge tube 4a. It is preferable to use a conductor having heat resistance and corrosion resistance such as SUS for the outer peripheral electrode 4b.

  The support blocks 15 and 16 are provided with a large number of circular through holes 15a and 16a, and mounting step portions 25 and 26 are formed at the inner edge portions of the through holes 15a and 16a, respectively. ing. The mounting steps 25 and 26 have an annular shape (cylindrical in this embodiment) complementary to the end shape of the discharge tube 4a. The upstream end and the downstream end of each discharge tube 4a are fixed to the mounting step portions 25 and 26 of the support blocks 15 and 16 with a flat and annular gasket 27 (see FIG. 4) having heat resistance and elasticity, respectively. Has been. As a material of the gasket 27, asbestos, heat resistant resin, heat resistant rubber, metal, or the like can be used. The inner diameter of the discharge tube 4a is equal to the hole diameter of the through holes 15a and 16a, and the axial center of the discharge tube 4a is matched with the axial center of the through holes 15a and 16a.

  The arrangement of the through holes 15a in the support block 15 is as shown in FIG. That is, a set of four through-holes 15a in one vertical row is arranged in parallel with each other, and a set of three through-holes 15a in a single vertical row is arranged between these columns and on both sides, for a total of four. Arranged in columns. The through-holes 15a in each column are arranged so that the vertical position is shifted by the approximate radius of the outer peripheral electrode 4b with respect to the adjacent through-holes 15a, thereby reducing the distance between the columns and thus the width-direction dimension of the entire apparatus. The reduction of is planned. The discharge tube 4a is fixed to each of the through holes 15a arranged in this way.

  The internal electrode 5 is substantially rigid and is disposed on the central axis of the discharge tube 4a and the central axis of the outer peripheral electrode 4b and extends in the flow direction of the exhaust gas. For each internal electrode 5, it is preferable to use a tungsten press-fired product or SUS having good discharge characteristics.

  The upstream end of each internal electrode 5 is fixed to an electrode support frame 8 as shown in FIG. 1 and FIG. 2 outside the discharge tube 4a and the outer peripheral electrode 4b, whereby the two are electrically connected. . The electrode support frame 8 is made of a heat-resistant conductive material such as metal, particularly SUS, and as shown in FIG. 2, seven support arms 8 a having a longitudinal direction as a longitudinal direction and the seven support arms 8 a are crossed. In this manner, the two support arms 8a provided obliquely are combined. In the present embodiment, the two support arms 8a provided in a skewed manner generally avoid the shielding of the front surface of the through hole 15a of the support block 7a as much as possible at the boundary portion between the through holes 15a. Located on the front. In addition, since PM deposition tends to concentrate in the center of the exhaust gas flow path for hydrodynamic reasons, these two support arms 8a that run obliquely support that the amount of PM passing is relatively large. Shifting up and down is arranged so as to avoid the central portion of the block 7a, thereby suppressing leakage due to PM accumulation.

  The downstream side of each internal electrode 5 is fixed to the electrode support frame 18 outside the discharge tube 4a and the outer peripheral electrode 4b. In addition, by making the coupling between one or both ends of the internal electrode 5 and one or both of the electrode support frames 8 and 18 slidable, bending due to the elongation of the internal electrode 5 can be suppressed. .

  As shown in FIG. 3, between the plurality of outer peripheral electrodes 4b, 4b, an electrically connecting mesh 9 made of net-like SUS is inserted in a meandering manner. The electrically connected mesh 9 is a flexible conductor in the present invention, and is held so as not to drop from between the outer peripheral electrodes 4b and 4b by its own elastic force. Due to the contact of the electrical connection mesh 9, the outer peripheral electrodes 4 b are electrically connected to each other.

  In FIG. 1 again, a power supply line 10 is connected to the electrode support frame 8, and the power supply line 10 is connected to a power supply unit (not shown). Further, a sleeve 11 covering the power supply line 10 and a holding material 12 are fixed to the electrode support frame 8, and the electrode support frame 8 is fixed to the support block 7 a via the sleeve 11 and the holding material 12. . The sleeve 11 and the holding material 12 are made of an insulating material such as an insulator.

  A conductive wire 13 is connected to one of the 24 outer peripheral electrodes 4b, and the conductive wire 13 is electrically grounded by being connected to an appropriate body ground point of a vehicle body (not shown). . The conductive wire 13 is covered with a sleeve 14 made of an insulator such as an insulator, and the sleeve 14 is fixed to the intermediate case 3. Since the plurality of outer peripheral electrodes 4 b are electrically connected to each other by the electrical connection mesh 9, the outer peripheral electrodes 4 b of all the processing units 6 are grounded by the conductive wires 13. As the power supply unit, any one of a DC high voltage power supply, an AC high voltage power supply, a DC pulse power supply, and a DC / pulse superimposed power supply can be used.

In the exhaust gas purification apparatus 1 configured as described above, a high voltage is applied between the outer peripheral electrode 4b and the internal electrode 5 of each processing unit 6 by using the internal electrode 5 as an anode in accordance with the start of the internal combustion engine. Applied. When the exhaust gas from the combustion chamber of the started internal combustion engine is introduced from the upstream case 2a into the discharge tube 4a, air discharge between the internal electrode 5 and the outer peripheral electrode 4b of each processing unit 6 occurs. plasma state occurs, the predetermined substance such as NOx in the exhaust gas is activated and is the reaction is promoted is converted into substances such as N _2. Further, PM in the supplied exhaust gas is charged by the discharge from the internal electrode 5, and is adsorbed on the inner peripheral surface of the discharge tube 4a by the interaction with the electric field between the internal electrode 5 and the outer peripheral electrode 4b. The combustion or oxidation is promoted by the active gas generated by the application of.

  Here, in this embodiment, each discharge tube 4a is installed between a pair of support blocks 15 and 16, and the end face in the longitudinal direction of the discharge tube 4a is formed at the rim of the through holes 15a and 16a. Since it joins with the annular mounting step portions 25 and 26, the sealing performance between the discharge tube 4a and the support blocks 15 and 16 can be improved, and thereby the durability and reliability of the apparatus can be maintained for a long time.

  Further, in the present embodiment, a heat-resistant flat and annular gasket 27 (FIG. 4) is used for sealing between the upstream and downstream ends of the discharge tube 4a and the mounting step portions 25 and 26 of the support blocks 15 and 16. Therefore, it is possible to obtain higher heat resistance as compared with the case of using an inorganic adhesive for sealing the portion, and also to move the discharge tube 4a in the axial direction when vibration during operation is applied. The buffer can be well buffered, and the risk of scraping, cracking, etc. on the opposing surfaces of the discharge tube 4a and the support blocks 15 and 16 can be suppressed.

  Moreover, in this embodiment, since the some discharge tube 4a is mutually connected by contact of the flexible electrical connection mesh 9, even if there is position shift between the some discharge tubes 4a, conduction can be maintained. Since the displacement of each discharge tube 4a is suppressed by the elastic force of the electrical connection mesh 9, the durability and reliability of the apparatus can be maintained for a long time.

  In addition, this invention is not limited to the aspect as described in the said embodiment, A various deformation | transformation is possible. For example, in the above embodiment, as shown in FIG. 4, a flat and annular gasket 27 is sandwiched between the mounting step portions 25 and 26 of the support blocks 15 and 16 and the end face in the longitudinal direction of the discharge tube 4a. However, the joining structure between the support block and the discharge tube in the present invention is not limited to this, and for example, as shown in FIG. 5, the cylinders of the mounting step portions 25 and 26 of the support blocks 15 and 16 are provided. A cylindrical and annular gasket 28 may be disposed between the surface and the outer peripheral surface of the discharge tube 4a. In this case, there is an advantage that vibration in the radial direction of the discharge tube 4a can be buffered. Further, a male screw may be formed on the peripheral surface of the end portion of the discharge tube 4a and a female screw may be formed on the cylindrical surface of the mounting step portions 25 and 26 of the support blocks 15 and 16, and both may be screwed together. .

  Moreover, in the said embodiment, although the discharge tube 4a and the outer periphery electrode 4b were made into the cylindrical shape, it is good also as other shapes, such as a rectangular tube shape. Further, a part of the support arms 8a and 18a (for example, in the vicinity of the edge of the through hole 15a) or the entire surface may be covered with an insulating layer. Moreover, you may carry | support a catalyst substance on an outer periphery electrode, an internal electrode, or a discharge tube.

  In the above embodiment, the mesh-like electrically connected mesh 9 made of SUS is used as the flexible conductor. However, as the conductor in the present invention, for example, a mat-like or non-woven fabric formed by randomly collecting metal fibers Various other materials that have a surface structure suitable for conduction and can maintain elasticity, such as a thin fiber body and an embossed metal thin plate, can be used. In the present embodiment, each electrically connecting mesh 9 is in contact with the outer peripheral electrode 4b at seven points. However, the conductor in the present invention may be supported between a plurality of discharge tubes by its elastic force. For example, the number of points of contact with the discharge tube or the outer peripheral electrode can be arbitrarily plural, and particularly preferably three or more.

  Furthermore, in the present invention, a honeycomb structure such as ceramics is installed in a space surrounded by the outer peripheral electrode 4b, and the exhaust gas can be reformed by the action of electric power regardless of whether plasma is used or whether PM is filtered. Various configurations can be used, and all belong to the category of the present invention. Needless to say, the present invention can be applied to internal combustion engines other than vehicles.

It is a vertical side view which shows the exhaust gas purification apparatus which concerns on embodiment of this invention. It is a front view which shows an intermediate | middle case, a support block, and an electrode support frame. It is the sectional view on the AA line of FIG. 1 which shows the internal structure of an exhaust gas purification apparatus. It is a principal part enlarged view which shows the structure of the coupling | bond part of a support block and a discharge tube. It is a principal part enlarged view which shows the other structural example of the coupling | bond part of a support block and a discharge tube. It is a vertical side view which shows an example of the support structure of the conventional discharge tube.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exhaust gas purification apparatus 2a Upstream side case 2b Downstream side case 3 Intermediate case 4a Discharge tube 4b Outer electrode 5 Internal electrode 6 Processing unit 8, 18 Electrode support frame 9 Electrical connection mesh 10 Feed line 15, 16 Support block 15a, 16a Through-hole 25, 26 Mounting step 27, 28 Gasket

Claims (2)

In an exhaust gas purification apparatus comprising a cylindrical discharge tube and an internal electrode extending through the inside of the discharge tube, and purifying exhaust gas by discharge between the internal electrode and the discharge tube,
The discharge tube is installed between a pair of support blocks each having a through hole for communicating with the discharge tube, and an end face in the longitudinal direction of the discharge tube is formed at a lip of the through hole. An exhaust gas purifying apparatus characterized by being joined to an annular mounting step. The exhaust gas purification device according to claim 1,
A plurality of the discharge tubes are provided, a flexible conductor is inserted between the plurality of discharge tubes, and the plurality of discharge tubes are electrically connected to each other by contact of the conductors. Exhaust gas purification device.

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