JP2018206494A - Plasma reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma reactor capable of improving reliability by ensuring insulation between adjacent discharge electrodes and insulation between a discharge electrode and a case. A plasma reactor of the present invention is configured by providing electrode panels 30 including a dielectric 33 and a discharge electrode 34 in parallel at intervals, and a gas is passed between the electrode panels 30 to discharge a dielectric barrier. Generates plasma by. The outer peripheral portion 101 of the discharge electrode 34 includes an upstream side end portion 102, a downstream side end portion, and a side portion side end portion 104, 105. The upstream end 102 has a shape having a corner 107 in a plan view. The discharge start voltage at the outer peripheral portion 101 of the discharge electrode 34 is lower than the discharge start voltage at the central portion 100 of the discharge electrode 34. [Selection diagram] FIG. 9

Description

  The present invention relates to a plasma reactor, and more particularly to a plasma reactor suitable for an apparatus for purifying exhaust gas from an internal combustion engine (engine).

  Conventionally, exhaust gas from an engine or incinerator is passed through a plasma field, so that CO (carbon monoxide), HC (hydrocarbon), NOx (nitrogen oxide), and PM (particulate matter) contained in the exhaust gas are in particulate form. Plasma reactors for treating harmful substances such as substances have been proposed.

  For example, the discharge electrodes provided on the dielectric are arranged in parallel with a gap, and a voltage is applied between the discharge electrodes to generate a low temperature plasma (non-equilibrium plasma) due to the dielectric barrier discharge, thereby flowing between the discharge electrodes. Various techniques for oxidizing and removing PM in exhaust gas have been proposed (see, for example, Patent Documents 1 to 3). Specifically, Patent Documents 1 to 3 are technologies that include a pair of discharge electrodes (conductive films) facing each other and generate a plasma by applying a voltage between the discharge electrodes. In Patent Documents 1 and 2, each discharge electrode is provided with a plurality of through holes. In particular, in Patent Document 2, through holes are arranged in a plurality of types of arrangement patterns in one discharge electrode. Moreover, in patent document 3, it is comprised so that the distance between adjacent discharge electrodes may differ for every area | region.

Japanese Patent No. 4746986 (FIG. 3 etc.) Japanese Patent No. 4104627 (FIG. 3 etc.) Japanese Patent No. 4863743 (FIGS. 4 to 6, FIG. 8, etc.)

  By the way, when the plasma reactor is used in a vehicle or the like, exhaust gas containing soot (PM) flows into a gas flow path formed between adjacent discharge electrodes. Note that PM in the exhaust gas tends to accumulate on the upstream portion of the gas flow passage, particularly on the side portion where the flow velocity is relatively low in the upstream portion, so that the accumulated PM is at the upstream end of the discharge electrode. There is a high possibility of adhering to the end portion on the side or side portion.

  However, in the prior arts described in Patent Documents 1 and 2, the discharge starting point is present at the edge of the through-hole, but the discharge starting point is at the upstream end or the side end of the discharge electrode. There is almost no part to become. Moreover, in the prior art described in Patent Document 3, not only a portion serving as a starting point of discharge does not exist at the upstream end or the side end, but also the through hole itself does not exist. Therefore, in these cases, since it is difficult for plasma to be generated at the upstream end and the side end, it is difficult to remove the deposited PM using plasma.

  As a result, there is a problem in that insulation between adjacent discharge electrodes cannot be ensured because conduction between adjacent discharge electrodes is caused through PM. In addition, when the laminate of the electrode panel including the discharge electrode is accommodated in the case and the case containing the laminate is attached to the exhaust pipe, the discharge electrode and the case are electrically connected via the PM. There is a problem that insulation between the discharge electrode and the case cannot be secured. Therefore, in these cases, a leakage current is generated, so that the amount of plasma generated with respect to the input power is reduced, and the exhaust gas purification efficiency may be lowered.

  The present invention has been made in view of the above problems, and its purpose is to improve reliability by ensuring insulation between adjacent discharge electrodes and insulation between the discharge electrodes and the case. It is to provide a possible plasma reactor.

  As means for solving the above problems (means 1), a plurality of electrode panels each provided with a dielectric and a discharge electrode are provided in parallel with a space between them, and a gas is allowed to flow between the plurality of electrode panels to form a dielectric. A plasma reactor for generating plasma by barrier discharge, wherein an outer peripheral portion of the discharge electrode has an upstream end located on a gas inflow side, a downstream end located on a gas outflow side, An upstream end and a side end located between the downstream end, and the upstream end has a shape having a corner in plan view, and the discharge There is a plasma reactor characterized in that a discharge start voltage at the outer periphery of the electrode is lower than a discharge start voltage at the center of the discharge electrode.

  Therefore, in the invention described in the means 1, the upstream end portion of the discharge electrode has a shape having a corner portion in plan view. Since this corner is likely to be a starting point of discharge, discharge occurs in many places at the upstream end having the corner, and plasma is surely generated. Therefore, when the PM in the exhaust gas accumulated at the upstream end is oxidized and removed using plasma, the PM can be efficiently removed. As a result, conduction between adjacent discharge electrodes via PM and conduction between the discharge electrodes and the case (which accommodates the laminated body of electrode panels) are also prevented via PM. And insulation between the discharge electrode and the case can be ensured. Therefore, the reliability of the plasma reactor can be improved.

The plasma reactor has a structure in which a plurality of electrode panels including a dielectric and a discharge electrode are provided in parallel at intervals. Here, examples of the dielectric forming material include ceramics such as alumina (Al ₂ O ₃ ), aluminum nitride (AlN), yttrium oxide (Y ₂ O ₃ ), and mixtures thereof. Examples of the material for forming the discharge electrode include tungsten (W), molybdenum (Mo), ruthenium oxide (RuO ₂ ), silver (Ag), copper (Cu), and platinum (Pt).

  In addition, it is preferable that the discharge electrode has a shape in which both the upstream side end portion and the side portion side end portion have corner portions in plan view. In this way, in addition to the upstream end portion having the corner portion, the discharge is generated at many places also at the side end portion having the corner portion, so that plasma is surely generated. Therefore, the PM deposited on the upstream side end and the side side end can be efficiently removed using plasma. Therefore, it is possible to prevent electrical conduction between adjacent discharge electrodes and electrical conduction between the discharge electrode and the case due to PM deposition on the upstream side end and the side side end.

  By the way, PM deposited on the side end portion tends to be deposited easily in a region near the upstream end portion. Therefore, the side end portion only needs to have a shape in which the region near the upstream end portion has a corner portion in plan view, and the other region has a shape having a corner portion in plan view. You don't have to. That is, the manufacturing cost can be kept low because the corners only need to be provided in a partial region of the side end portion.

  Moreover, it is preferable that the discharge electrode has a shape in which at least one of the upstream end portion and the side end portion has a convex portion in plan view. Since this convex portion is likely to be the starting point of discharge, electric discharge is generated in many places at the end portion having the convex portion, and plasma is surely generated. Therefore, PM deposited at the end can be efficiently removed using plasma. Therefore, it is possible to prevent conduction between adjacent discharge electrodes and conduction between the discharge electrode and the case due to PM deposition on the end portion.

  In particular, the convex portion of the upstream end portion preferably has a shape that is pointed in a plan view. In this case, since the convex portion is surely the starting point of the discharge, the discharge is generated in many places at the upstream end portion having the convex portion, and the plasma is surely generated. Therefore, since PM deposited on the upstream end can be more efficiently removed using plasma, conduction between adjacent discharge electrodes and conduction between the discharge electrode and the case due to PM deposition can be reliably prevented. .

  In the case where the plurality of discharge electrodes include the first electrode and the second electrode adjacent to the first electrode, at least a part of the corner provided in the first electrode, and the second electrode It may be arranged so that at least a part of the corners provided in each other does not overlap each other. In this way, a dielectric barrier discharge is generated between the corner of the first electrode and the corner of the second electrode existing obliquely below the first electrode. As a result, plasma can be generated in a wider range at the upstream end (or the side end) having the corners. Therefore, PM deposited on the upstream end (or the side end) can be reliably removed.

1 is a schematic cross-sectional view showing a plasma reactor in the present embodiment. The perspective view which shows a plasma reactor. The top view which shows a plasma reactor. The perspective view which shows a plasma panel laminated body, a clamp, a power supply terminal, and a mat. The perspective view which shows a plasma panel laminated body, a clamp, and a power supply terminal. The schematic sectional drawing which shows an electrode panel. The perspective view which shows an electrode panel. The top view which shows an electrode panel. The principal part top view which shows an electrode panel. The principal part top view which shows an electrode panel in other embodiment. The principal part top view which shows an electrode panel in other embodiment. In other embodiment, the principal part top view which shows a discharge electrode. The top view which shows the relationship between the 1st electrode and 2nd electrode in other embodiment.

  Hereinafter, an embodiment of the plasma reactor 1 of the present invention will be described in detail with reference to the drawings.

  As shown in FIGS. 1 to 3, the plasma reactor 1 of the present embodiment is a device that removes PM contained in exhaust gas of an automobile engine (not shown), and is attached to an exhaust pipe 2. . The plasma reactor 1 includes a power source 3, a case 10, and a plasma panel laminate 20.

  The case 10 is formed in a rectangular cylinder shape using, for example, stainless steel. A first cone portion 11 is connected to a first end portion (left end portion in FIG. 1) of the case 10, and a second cone portion 12 is connected to a second end portion (right end portion in FIG. 1) of the case 10. Yes. Further, the first cone portion 11 is connected to the upstream portion 4 (engine portion) of the exhaust pipe 2, and the second cone portion 12 is connected to the downstream portion 5 (opposite side of the engine side) of the exhaust pipe 2. Part). The exhaust gas from the engine flows into the case 10 from the upstream portion 4 of the exhaust pipe 2 through the first cone portion 11, passes through the case 10, and then passes through the second cone portion 12 to the exhaust pipe. 2 flows out to the downstream part 5.

  As shown in FIGS. 1, 4, and 5, the plasma panel laminate 20 is housed in the case 10, and includes an upstream end surface 21 into which exhaust gas flows, a downstream end surface 22 from which exhaust gas flows, It has a substantially rectangular parallelepiped shape having four gas non-passing surfaces 23, 24, 25 and 26. The upstream side end surface 21 and the downstream side end surface 22 are located on opposite sides of the plasma panel laminate 20. The gas non-passing surfaces 23 to 26 are located between the upstream end surface 21 and the downstream end surface 22.

  The plasma panel laminate 20 has a structure in which a plurality of electrode panels 30 are laminated. Each electrode panel 30 is arranged in parallel with the passage direction F1 of exhaust gas flowing from the upstream end face 21 side to the downstream end face 22 side (direction from the first cone part 11 toward the second cone part 12), and is equal to each other. They are provided in parallel at intervals (0.5 mm in this embodiment). More specifically, the plasma panel laminate 20 has a gas flow path 27 (see FIG. 1) through which exhaust gas passes between adjacent electrode panels 30. The gas flow path 27 includes an opening 28 that opens at the upstream end face 21 and the downstream end face 22.

  As shown in FIG. 1, the first wiring 6 and the second wiring 7 are alternately and electrically connected to each electrode panel 30 along the thickness direction of the plasma panel laminate 20. The first wiring 6 is electrically connected to the first terminal of the power supply 3, and the second wiring 7 is electrically connected to the second terminal of the power supply 3.

As shown in FIGS. 1 and 6 to 9, the electrode panel 30 of the present embodiment has a first main surface 31, a second main surface 32, a first end surface 37 and a second end surface 38, and is 100 mm long. X It has a substantially rectangular plate shape with a width of 200 mm. The first main surface 31 and the second main surface 32 are located on opposite sides in the thickness direction of the electrode panel 30. Further, the first end surface 37 and the second end surface 38 are located on opposite sides of the gas flow path 27 in the surface direction. Further, the electrode panel 30 has an upstream side surface 115 that constitutes the upstream end surface 21 of the plasma panel laminate 20 and a downstream side surface 116 that constitutes the downstream end surface 22 of the plasma panel laminate 20. The electrode panel 30 has a structure in which a discharge electrode 34 (thickness 10 μm) is built in a rectangular plate-shaped dielectric 33. In the present embodiment, the dielectric 33 is made of ceramic such as alumina (Al ₂ O ₃ ), and the discharge electrode 34 is made of tungsten (W).

  As shown in FIGS. 6 and 7, the dielectric 33 has a recess 35 that opens at the second main surface 32. The recess 35 extends in the lateral direction of the electrode panel 30 and opens at both end faces of the electrode panel 30. In the plasma panel laminate 20 of the present embodiment, the gas flow path 27 described above is formed between the inner surface of the recess 35 and the first main surface 31 of the electrode panel 30 adjacent to the lower layer side. The lowermost electrode panel 30 constituting the plasma panel laminate 20 is not formed with the recess 35 because the electrode panel 30 does not exist on the lower layer side.

  As shown in FIGS. 7 and 8, one conductive structure 40 is provided on each side portion of the recess 35 in the electrode panel 30 to conduct the first main surface 31 side and the second main surface side 32 side. It has been. Each conduction structure 40 includes a through-hole conductor 41, a first pad 42, and a second pad 43. The through-hole conductor 41 penetrates the electrode panel 30 in the thickness direction. The through-hole conductor 41 provided in one conduction structure 40 passes through an extending portion 36 that extends from the discharge electrode 34 to the outer peripheral side. The first pad 42 is formed on the first main surface 31 and is electrically connected to the end of the through-hole conductor 41 on the first main surface 31 side. On the other hand, the second pad 43 is formed on the second main surface 32 and is electrically connected to the end of the through-hole conductor 41 on the second main surface 32 side. The first pad 42 and the second pad 43 each have a rectangular shape, and the surface thereof is plated with Ni or the like.

  As shown in FIGS. 4 and 5, the plasma reactor 1 includes three first clamps 50, 51, 52 that sandwich and fix each electrode panel 30 (plasma panel laminate 20) from the gas non-passing surface 24 side. The second clamps 53, 54, and 55 are provided to fix the electrode panels 30 by sandwiching them from the gas non-passing surface 26 side. Each clamp 50-55 is formed by bending a metal plate (for example, a stainless steel plate made of a material such as SUS430). Further, the first clamps 50 to 52 are arranged at equal intervals along the exhaust gas passage direction F1 on the gas non-passing surface 24, and the second clamps 53 to 55 are disposed on the gas non-passage surface 26 in the exhaust gas passage direction. It arrange | positions at equal intervals along F1.

  In addition, the 1st clamps 50 and 51 arrange | positioned at the upstream part and center part of the gas non-passing surface 24, and the 2nd clamps 53 and 54 arrange | positioned at the upstream part and center part of the gas non-passing surface 26 are as follows. , Only the function of sandwiching each electrode panel 30 in the stacking direction is provided. On the other hand, the first clamp 52 disposed in the downstream portion of the gas non-passing surface 24 and the second clamp 55 disposed in the downstream portion of the gas non-passing surface 26 sandwich each electrode panel 30 in the stacking direction. In addition to the function, it has a function of electrically connecting to the discharge electrode 34.

  4 and 5, each of the clamps 50 to 55 includes a clamp body 56 and a pressing plate 57. The clamp body 56 extends in the stacking direction of the electrode panels 30. The holding plate 57 is formed integrally with the clamp body 56 and is disposed at both ends of the clamp body 56. Each pressing plate 57 is a leaf spring having elasticity and a folded structure. Each pressing plate 57 is in pressure contact with the gas non-passing surface 23 and the gas non-passing surface 25 of the plasma panel laminate 20. Both pressing plates 57 constituting the clamps 52 and 55 are provided with the first pad 42 formed on the gas non-passing surface 23 (the first main surface 31 of the uppermost electrode panel 30) and the gas non-passing surface 25 ( It is in pressure contact with the second pad 43 formed on the second main surface 32) of the lowermost electrode panel 30. The protruding length of the pressing plate 57 constituting the clamps 52 and 55 from the clamp main body 56 is longer than the protruding length of the pressing plate 57 constituting the other clamps 50, 51, 53 and 54 from the clamp main body 56. It has become.

  As shown in FIGS. 2 to 5, the plasma reactor 1 includes a pair of power supply terminals 61 and 62. The power supply terminals 61 and 62 of this embodiment have the same structure as the spark plug. More specifically, the power supply terminals 61 and 62 include an external connection portion, a conductive seal containing metal powder, an insulator, a metal shell, talc, packing, and the like. The external connection portion is connected to the central shaft 63 via a conductive seal. The center shaft 63 has a tip portion disposed in the insulator. The power supply terminal is not limited to the one in the present embodiment, and may have another structure as long as the structure is such that the external connection portion and the case 10 are insulated by an insulator. .

  In addition, the power supply terminal 61 has a distal end portion exposed from the case 10, and a proximal end portion (center shaft 63) that presses against the holding plate 57 (specifically, the gas non-passing surface 23) of the first clamp 52. It is electrically connected to the holding plate 57). Similarly, the power supply terminal 62 has a distal end portion exposed from the case 10 and a proximal end portion (center shaft 63) pressed against the holding plate 57 (specifically, the gas non-passing surface 23) of the second clamp 55. The presser plate 57) is electrically connected. The power supply terminals 61 and 62 protrude in the same direction. In the present embodiment, the tip of the power supply terminal 61 is connected to the first wiring 6 (see FIG. 1), and the tip of the power supply terminal 62 is connected to the second wiring 7 (see FIG. 1). Connected.

  As shown in FIGS. 1 and 4, a mat 71 having a rectangular ring shape when viewed from the side is interposed between the case 10 and the plasma panel laminate 20. The mat 71 has a function of fixing the plasma panel laminate 20 to the case 10. Further, the mat 71 covers the outer surface of the plasma panel laminate 20. Specifically, the mat 71 includes a substantially rectangular plate-shaped first mat piece 72 covering the gas non-passing surface 23, a substantially rectangular plate-shaped second mat piece 73 covering the gas non-passing surface 24, and a gas non-passing surface. 25, a third mat piece 74 having a substantially rectangular plate shape covering 25, and a fourth mat piece 75 having a substantially rectangular plate shape covering the gas non-passing surface 26. The mat 71 is configured by bonding the mat pieces 72 to 75 to each other using an adhesive tape or the like as necessary. Here, as a material constituting the mat 71, for example, an insulating material such as ceramic fiber, metal fiber, and foam metal can be used.

  As shown in FIG. 4, the mat 71 of the present embodiment is formed with two notches 81 and 82 that penetrate the mat 71 in the thickness direction. The first clamp 52 is located in the inner area of the notch 81, and the second clamp 55 is located in the inner area of the notch 82. More specifically, the notches 81 and 82 include a groove 83 that penetrates the second mat piece 73 in the thickness direction and a pair of recesses 84 that penetrate the mat pieces 72 and 74 in the thickness direction. The groove 83 extends along the stacking direction of the electrode panel 30 and divides the second mat piece 73. On the other hand, the concave portion 84 is formed only in a part of the outer peripheral portion of the mat pieces 72 and 74 so that the mat pieces 72 and 74 are not divided. The clamp body 56 of the clamps 52 and 55 is disposed in the groove 83, and the pressing plate 57 of the clamps 52 and 55 and the center shaft 63 of the power supply terminals 61 and 62 are disposed in the recess 84. Yes.

  As shown in FIG. 7 to FIG. 9, the discharge electrode 34 penetrates in the thickness direction of the discharge electrode 34, and is constituted by a plurality of first linear portions 91 and a plurality of second linear portions 92. A plurality of through holes 93 are provided. Note that the length, width, and thickness of the first linear portion 91 and the second linear portion 92 are appropriately determined in consideration of an applied voltage and the like. Further, in the discharge electrode 34, the plurality of first linear portions 91 extend linearly along the exhaust gas passage direction F1, and are spaced at a constant interval in the direction orthogonal to the passage direction F1 (width direction of the recess 35). Is provided. Further, in the discharge electrode 34, a plurality of second linear portions 92 extend linearly along the width direction of the recess 35, and are provided at regular intervals in the passing direction F1. For this reason, the 1st linear part 91 and the 2nd linear part 92 come to comprise the square grid | lattice form of 0.5 mm square by planar view. Accordingly, the through-hole 93 formed by the first linear portion 91 and the second linear portion 92 also has a square shape having four corner portions 94 in plan view.

  As shown in FIGS. 8 and 9, the outer peripheral portion 101 of the discharge electrode 34 includes an upstream end portion 102 located on the exhaust gas inflow side, a downstream end portion 103 located on the exhaust gas outflow side, The two side end portions 104 and 105 are included. The upstream end 102 and the downstream end 103 are located on opposite sides of the discharge electrode 34. The side portion side ends 104 and 105 are located between the upstream end portion 102 and the downstream end portion 103, and are located on opposite sides of the discharge electrode 34.

  As shown in FIG. 9, the upstream end of each first linear portion 91 is located at the upstream end 102. The upstream end portion of each first linear portion 91 has a shape having a convex portion (upstream convex portion 106) in plan view. Each upstream convex portion 106 projects upstream from the edge 95 on the upstream side 115 side of the second linear portion 92 located on the most upstream side 115 side along the planar direction of the electrode panel 30. And the front-end | tip of each upstream convex part 106 is arrange | positioned so that it may not be exposed from the upstream side surface 115. FIG. In other words, each upstream convex portion 106 is arranged in a state where the tip is separated from the upstream side surface 115. Here, the protruding amounts of the upstream convex portions 106 from the edge 95 of the second linear portion 92 are equal to each other, and are 0.5 mm in the present embodiment. In addition, although the upstream convex part 106 of this embodiment comprises the upstream edge part of the 1st linear part 91, the upstream convex part 106 is a structure different from the 1st linear part 91. FIG. There may be. That is, the upstream convex portion 106 may be formed in a separate process from the first linear portion 91. Furthermore, the upstream convex part 106 and the 1st linear part 91 may be offset and arrange | positioned in the direction (left-right direction in FIG. 9) orthogonal to the passage direction F1 of exhaust gas. In addition, each upstream convex portion 106 has a pentagonal shape in plan view, and a tip portion has a pointed shape having three corner portions 107 in plan view. Of the three corner portions 107, the corner portion 107 positioned at the tip of the upstream convex portion 106 is a right angle (90 ° in the present embodiment), and the remaining two corner portions 107 are obtuse angles (the present embodiment). Is 135 °).

  Moreover, the side part side edge part 104 has the edge part of the 1st end surface 37 side of each 2nd linear part 92 located, and the side part side edge part 105 has each 2nd linear part 92 side. The end on the second end face 38 side is located. The end of each second linear portion 92 on the first end surface 37 side has a shape having a convex portion (first side portion convex portion 108) in plan view over the entire side end portion 104. doing. Further, the end of each second linear portion 92 on the second end face 38 side has a convex portion (second side portion convex portion 109) in plan view over the entire side portion side end portion 105. Is made. Each first side portion convex portion 108 protrudes laterally along the planar direction of the electrode panel 30 from the edge 96 on the first end surface 37 side of the first linear portion 91 located closest to the first end surface 37 side. ing. The front end of each first side portion convex portion 108 is arranged so as to slightly protrude from the formation region of the concave portion 35 toward the first end surface 37 side in plan view and is not exposed from the first end surface 37. Similarly, each 2nd side part convex part 109 protrudes from the edge 97 by the side of the 2nd end surface 38 of the 1st linear part 91 located in the 2nd end surface 38 side most. The tips of the second side-side convex portions 109 are arranged so as to slightly protrude from the formation region of the concave portion 35 toward the second end surface 38 in a plan view and are not exposed from the second end surface 38. Here, the protruding amount of each first side portion convex portion 108 from the end edge 96 of the first linear portion 91 and each second side portion convex portion from the end edge 97 of the first linear portion 91. The protruding amounts 109 are equal to each other, and are 0.7 mm in this embodiment. In addition, although the side part convex part 108,109 of this embodiment comprises a part of 2nd linear part 92, the side part convex part 108,109 is different from the 2nd linear part 92. It may be a body configuration. That is, the side protrusions 108 and 109 may be formed in a separate process from the second linear portion 92. Further, the side-side convex portions 108 and 109 and the second linear portion 92 may be arranged offset in a direction (vertical direction in FIG. 9) parallel to the exhaust gas passage direction F1. Moreover, each convex part 108,109 has comprised the planar view rectangular shape, and has comprised the front-end | tip part in the shape which has the two corner | angular parts 110 by planar view. Each corner 110 is a right angle.

  As shown in FIGS. 1 and 9, the plasma reactor 1 of the present embodiment is used, for example, to remove PM contained in exhaust gas. In this case, when a pulse voltage (for example, peak voltage: 5 kV (5000 V), pulse repetition frequency: 100 Hz) is applied between the electrode panels 30 adjacent to each other from the power supply 3, the opening edge or the convex portion 106 of each through-hole 93. , 108 and 109, dielectric barrier discharge occurs starting from corners 107 and 110, and plasma due to dielectric barrier discharge is generated between the discharge electrodes. Note that the discharge start voltage (voltage for generating plasma) at the outer peripheral portion 101 of the discharge electrode 34 (specifically, the corner portions 107 and 110 of the convex portions 106, 108, and 109) is the central portion 100 ( Specifically, it is lower than the discharge start voltage at the opening edge of the through-hole 93). Then, the PM contained in the exhaust gas flowing through the gas flow path 27 is oxidized (combusted) and removed by the generation of plasma.

  Next, a method for manufacturing the plasma reactor 1 will be described.

  First, the 1st-3rd ceramic green sheet used as the dielectric material 33 is formed using the ceramic material which has an alumina powder as a main component. In addition, as a formation method of a ceramic green sheet, well-known shaping | molding methods, such as tape shaping | molding and extrusion molding, can be used. Then, laser processing is performed on each ceramic green sheet to form a through hole for the through-hole conductor 41. The through hole may be formed by punching, drilling, or the like.

  Next, using a conventionally known paste printing apparatus (not shown), the through hole for the through-hole conductor 41 is filled with a conductive paste (in this embodiment, a tungsten paste) to form the through-hole conductor 41. Through-hole conductors are formed.

  Next, the first ceramic green sheet is placed on a support base (not shown). Furthermore, a conductive paste is printed on the back surface of the first ceramic green sheet using a paste printing apparatus. As a result, an unsintered electrode having a thickness of 10 μm to be the discharge electrode 34 is formed on the back surface of the first ceramic green sheet. In addition, as a printing method of the unsintered electrode with respect to the 1st ceramic green sheet, well-known printing methods, such as screen printing, can be used.

  Then, after the conductive paste is dried, the second ceramic green sheet and the third ceramic green sheet are sequentially laminated on the back surface of the first ceramic green sheet on which the unfired electrodes are printed, in the sheet lamination direction. Apply pressing force. As a result, the ceramic green sheets are integrated to form a ceramic laminate. Further, using a paste printing device, a conductive paste is printed on the main surface of the first ceramic green sheet to form the unfired first pad 42 and conductive on the back surface of the third ceramic green sheet. The non-sintered second pad 43 is formed by printing the conductive paste. The third ceramic green sheet is laminated after being subjected to a punching process that matches the shape of the recess 35.

  Next, after performing a drying process or a degreasing process according to a known technique, the ceramic green sheet and the unfired electrode are heated to a predetermined temperature (for example, about 1400 ° C. to 1600 ° C.) at which alumina and tungsten can be sintered. Simultaneous firing is performed. As a result, alumina in the first to third ceramic green sheets and tungsten in the conductive paste are simultaneously sintered, and the dielectric 33, the discharge electrode 34, the through-hole conductor 41, the first pad 42, and the second The pad 43 is formed by simultaneous firing, and the first to third ceramic green sheets become the electrode panel 30. At this time, the upstream end of each first linear portion 91 located at the upstream end 102 of the discharge electrode 34 has a shape having the upstream convex portion 106. Furthermore, the end on the first end surface 37 side of each second linear portion 92 located at the side portion side end portion 104 of the discharge electrode 34 has a shape having the first side portion convex portion 108, and the discharge electrode The end portions on the second end face 38 side of the respective second linear portions 92 positioned at the side portion end portions 105 of the 34 have a shape having the second side portion convex portions 109.

  Thereafter, a lamination process is performed, and a plurality of obtained electrode panels 30 are laminated to form the plasma panel laminate 20. Next, the clamps 50 to 55 are used to sandwich and fix the plurality of electrode panels 30 in the stacking direction. At this time, the pair of pressing plates 57 constituting the clamps 52 and 55 are in pressure contact with the first pad 42 and the second pad 43. Further, by performing welding or the like, the center shaft 63 of the power supply terminal 61 is electrically connected to the distal end portion of the pressing plate 57 that constitutes the first clamp 52, and the pressing plate 57 that constitutes the second clamp 55. The central shaft 63 of the power supply terminal 62 is electrically connected to the tip portion. Next, after attaching the mat 71 so as to cover the outer surface of the plasma panel laminate 20, the case 10 is attached so as to cover the outer surface of the mat 71. Thereafter, the first wiring 6 is connected to the distal end portion of the power supply terminal 61, and the second wiring 7 is connected to the distal end portion of the power supply terminal 62. The plasma reactor 1 is completed through the above processes.

  Therefore, according to the present embodiment, the following effects can be obtained.

  (1) In the plasma reactor 1 of the present embodiment, the upstream convex portion 106 positioned at the upstream end portion 102 of the discharge electrode 34 has a shape having a corner portion 107 in plan view. Since the corner portion 107 is likely to be a starting point of discharge, discharge is generated at many points of the upstream end portion 102 having the corner portion 107, and plasma is surely generated. Therefore, the PM in the exhaust gas deposited on the upstream end portion 102 can be efficiently removed using plasma. As a result, since conduction between adjacent discharge electrodes 34 via PM and conduction between discharge electrode 34 and case 10 via PM are prevented, insulation between adjacent discharge electrodes 34 and discharge electrode 34 are prevented. And the case 10 can be insulated. Therefore, the reliability of the plasma reactor 1 can be improved.

  (2) In the present embodiment, the clamps 52 and 55 that are electrically connected to the discharge electrode 34 are disposed at locations away from the upstream end 102 where PM is likely to deposit, and thus the deposited PM Is prevented from adhering to the clamps 52 and 55. As a result, since conduction between the discharge electrode 34 and the case 10 via the PM and the clamps 52 and 55 is prevented, insulation between the discharge electrode 34 and the case 10 can be ensured more reliably. Therefore, the reliability of the plasma reactor 1 is further improved.

  (3) The plasma reactor 1 of this embodiment is attached to the exhaust pipe 2 via the first cone portion 11 and the second cone portion 12. As a result, the resistance in the exhaust gas flow path in which the exhaust gas flows in the order of the upstream portion 4 of the exhaust pipe 2 → the first cone portion 11 → the plasma reactor 1 → the second cone portion 12 → the downstream portion 5 of the exhaust pipe 2 is reduced. Therefore, the pressure loss in the exhaust gas passage can be suppressed. As a result, it is possible to prevent the engine output from decreasing due to pressure loss.

  In addition, you may change the said embodiment as follows.

  In the above embodiment, both the upstream end portion 102 and the side end portions 108 and 109 of the discharge electrode 34 have shapes having the corner portions 107 and 110 in plan view. However, the upstream end portion 102 and either one of the side portion end portions 108 and 109 may have a shape having a corner portion in plan view. Moreover, as FIG. 10, FIG. 11 shows, only the upstream edge parts 121 and 131 may comprise the shape which has the corner | angular parts 122 and 132 by planar view. The downstream end 103 of the discharge electrode 34 may have a shape having a corner in plan view.

  In the above embodiment, the tip of the upstream convex portion 106 has a pointed shape having three corners 107 in plan view. However, as shown in the discharge electrode 130 of FIG. 11, the distal end portion of the upstream convex portion 133 may have a shape having two corner portions 132 in plan view. Further, as shown in the discharge electrode 140 of FIG. 12, the upstream convex portion 141 may have a pointed shape having one corner portion 142 in plan view. In addition, the front-end | tip part of an upstream edge part may comprise the shape which has four or more corner | angular parts by planar view.

  In the above embodiment, the upstream side convex portion 106 included in the upstream side end portion 102, the first side portion side convex portion 108 included in the side portion side end portion 104, and the second side portion included in the side portion side end portion 105. Of the side convex portions 109, only the upstream convex portion 106 has a shape that is pointed in a plan view. However, at least one of the first side portion convex portion 108 and the second side portion convex portion 109 may have a pointed shape in plan view. Further, all of the upstream side end portion 102, the first side portion side convex portion 108, and the second side portion side convex portion 109 may have a pointed shape in plan view.

  In the above embodiment, the side portion side end portion 104 of the discharge electrode 34 has a shape having the corner portion 110 in plan view over the entire side portion side end portion 104. Moreover, in the said embodiment, the side part side edge part 105 of the discharge electrode 34 comprised the shape which has the corner | angular part 110 in planar view over the whole side part side edge part 105. FIG. However, in the side portion side end portions 104 and 105, only the region near the upstream end portion 102 may have a shape having a corner portion in a plan view. In this case, it is only necessary to provide corners only in a part of the side end portions 104 and 105, so that the manufacturing cost can be reduced.

  As shown in FIG. 13, the plurality of discharge electrodes include a first electrode 151 (discharge electrode) provided in a first electrode panel (not shown) and a second electrode adjacent to the first electrode panel. You may consist of the 2nd electrode 152 (discharge electrode) provided in the electrode panel (not shown). Then, at least a part of the corner part 153 provided in the first electrode 151 and at least a part of the corner part 154 provided in the second electrode 152 may be arranged so as not to overlap each other. In FIG. 13, all of the upstream convex portions 156 (corner portions 153) located at the upstream end portion 155 of the first electrode 151 and the upstream side located at the upstream end portion 157 of the second electrode 152. All of the convex portions 158 (corner portions 154) are arranged offset in a direction orthogonal to the passage direction of the exhaust gas. In this way, a dielectric barrier discharge is generated between the corner 153 of the first electrode 151 and the corner 154 of the second electrode 152 existing obliquely below the first electrode 151. As a result, plasma can be generated in a wider range at the upstream end portions 155 and 157 having the corner portions 153 and 154. Therefore, PM deposited on the upstream end portions 155 and 157 can be reliably removed.

  The first linear portion 91 and the second linear portion 92 constituting the discharge electrode 34 of the above embodiment form a square lattice shape in plan view, but form a lattice shape such as a rhombus in plan view. You may do it.

  -The mat | matte 71 of the said embodiment was comprised by joining the 1st-4th mat pieces 72-75 mutually. However, the mat may have a non-divided structure.

  -The electrode panel 30 of the said embodiment was comprised by incorporating the discharge electrode 34 in the dielectric material 33. FIG. However, the electrode panel may be formed by forming the discharge electrode 34 on the surface of the dielectric 33.

  -Although the plasma reactor 1 of the said embodiment was used for exhaust gas purification of the engine of a motor vehicle, you may use it for exhaust gas purification of engines, such as a ship, for example. Moreover, the plasma reactor 1 should just perform a plasma process, and does not need to perform the process of waste gas, and does not need to be used for purification | cleaning.

  Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the embodiment described above are listed below.

  (1) In the above means 1, the plasma reactor is characterized in that the voltage for generating plasma from the outer peripheral portion of the discharge electrode is lower than the voltage for generating plasma from the central portion of the discharge electrode.

  (2) In the above means 1, the electrode panel has a configuration in which the electrode panel has a pair of main surfaces and a pair of end surfaces, and the discharge electrode is built in the dielectric, and the outer periphery of the discharge electrode The plasma reactor is characterized in that a distance from the first surface of the discharge electrode to the main surface or a distance from the second surface of the discharge electrode to the main surface is larger than the distance from the first surface of the discharge electrode to the main surface.

DESCRIPTION OF SYMBOLS 1 ... Plasma reactor 30 ... Electrode panel 33 ... Dielectric 34, 130, 140 ... Discharge electrode 100 ... Discharge electrode center part 101 ... Discharge electrode outer peripheral part 102, 121, 131, 155, 157 ... Upstream end part 103 ... Downstream end 104, 105 ... Side side end 106, 133, 141, 156, 158 ... Upstream convex part 108 as a convex part ... First side side convex part 109 as a convex part ... As convex part 2nd side part convex part 107,110,122,132,142,153,154 ... corner | angular part 151 ... 1st electrode 152 as a discharge electrode ... 2nd electrode as a discharge electrode

Claims (6)

A plasma reactor in which a plurality of electrode panels including a dielectric and a discharge electrode are provided in parallel with a space therebetween, and a gas is caused to flow through the plurality of electrode panels to generate plasma due to dielectric barrier discharge,
The outer peripheral portion of the discharge electrode is located between an upstream end located on the gas inflow side, a downstream end located on the gas outflow side, and the upstream end and the downstream end. And the side part side end part located,
The upstream end has a shape having a corner in plan view,
A plasma reactor, wherein a discharge start voltage at an outer peripheral portion of the discharge electrode is lower than a discharge start voltage at a central portion of the discharge electrode.   2. The plasma reactor according to claim 1, wherein both of the upstream end and the side end have a shape having a corner in a plan view.   3. The plasma reactor according to claim 2, wherein at least one of the upstream side end portion and the side portion side end portion has a shape having a convex portion in a plan view.   4. The plasma reactor according to claim 3, wherein the convex portion of the upstream end portion has a pointed shape in a plan view.   The plasma according to any one of claims 2 to 4, wherein the side portion side end portion has a shape in which a region near the upstream end portion has a corner portion in a plan view. Reactor. The plurality of discharge electrodes includes a first electrode and a second electrode adjacent to the first electrode,
At least a part of the corner provided in the first electrode and at least a part of the corner provided in the second electrode are arranged so as not to overlap each other. The plasma reactor according to any one of claims 1 to 5.

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