JP2005048753A - Exhaust gas purification device - Google Patents

Abstract

PROBLEM TO BE SOLVED To improve processing performance by suppressing discharge of unprocessed PM due to separation of PM from a barrier layer.
SOLUTION: Concavities and convexities comprising a large number of concave portions 41 and convex portions 42 are provided on the inner surface of a barrier layer 40. The PM in the exhaust gas is charged by the internal electrode 30, sucked to the outer peripheral electrode 20 side having the opposite polarity, and deposited on the adsorption surface of the barrier layer. The deposited PM is processed by applying a high voltage between both electrodes. The adsorbed / deposited PM is well held in the recess 41, and is prevented from being peeled / dropped off, and is incinerated by the heating element 43 disposed at the bottom of the recess 41.
[Selection] Figure 2

Description

  The present invention relates to an exhaust gas purification apparatus that purifies exhaust gas using plasma generated by applying a high voltage to a pair of electrodes.

As a technique for purifying exhaust gas from an internal combustion engine, an exhaust gas purification device (plasma reactor) that purifies exhaust gas using plasma generated by applying an alternating voltage to a pair of opposed electrodes has been proposed. . For example, Patent Document 1 discloses an apparatus having a structure in which exhaust gas is filtered by sandwiching a fiber filter between a pair of wire meshes forming electrodes and arranging them in a flow path of the exhaust gas. In this device, PM (Particulate Matter, particulate matter) in the exhaust gas collected by the fiber filter is radical (free radicals, free radicals) due to the energy of the plasma generated by applying a high voltage between the electrodes. HC is changed to H ₂ O and CO ₂ , C is changed to CO _2, and a part of PM is burned and incinerated. However, such an apparatus has a drawback in that exhaust resistance increases because the entire amount of supplied exhaust gas passes through the fiber filter.

JP 2001-295629 A

  Therefore, instead of such a configuration, an apparatus having a configuration in which a barrier layer made of an insulator is provided so as to cover the inner surface of the cylindrical outer peripheral electrode can be considered. In this apparatus, the PM in the exhaust gas supplied to the space between the barrier layer and the internal electrode is charged by the discharge from the internal electrode, and is sucked to the outer peripheral electrode side having the opposite polarity to the PM. Deposited on the adsorption surface. The deposited PM is processed by applying a high voltage between both electrodes. This configuration has an advantage that PM can be effectively collected while suppressing the exhaust resistance as compared with a configuration using a fiber filter.

  However, since the particle size of the PM adsorbed on the barrier layer becomes larger as the deposition progresses, it is peeled off from the barrier layer before the high voltage treatment and discharged to the downstream side of the apparatus. It may not be possible to process.

  Therefore, an object of the present invention is to provide an apparatus capable of improving processing performance by suppressing discharge of unprocessed PM due to separation of PM from a barrier layer.

  A first aspect of the present invention includes a cylindrical outer peripheral electrode and an inner electrode inserted into the outer peripheral electrode, and uses both plasmas generated by applying a high voltage between the electrodes. In the exhaust gas purification apparatus for purifying exhaust gas supplied between the electrodes, the exhaust gas purification device further comprises a barrier layer made of an insulator and arranged to cover the inner surface of the outer peripheral electrode, and the inner surface of the barrier layer is provided with irregularities. An exhaust gas purification device characterized by the above.

  In the first aspect of the present invention, PM in the exhaust gas supplied between the barrier layer and the internal electrode is charged by the discharge from the internal electrode, and is sucked to the outer peripheral electrode side having the opposite polarity to the PM. Deposited on the adsorption surface. The deposited PM is processed by applying a high voltage between both electrodes. Here, in the first aspect of the present invention, since the unevenness is provided on the inner surface of the barrier layer, the adsorbed / deposited PM is well held in the recesses in the unevenness, and the peeling / dropping is suppressed. Therefore, in the first aspect of the present invention, the processing performance can be improved by suppressing the discharge of unprocessed PM. Moreover, since PM accumulates mainly in the recess, it is possible to prevent the occurrence of spark discharge due to contact between the deposited PM and the internal electrode.

  The second aspect of the present invention is characterized in that at least a part of the entire length of the barrier layer, the tip of the convex portion in the unevenness gradually approaches the internal electrode as it goes downstream in the supply direction. 1. An exhaust gas purifying apparatus according to 1.

  In the second aspect of the present invention, even when the PM is peeled off or dropped from the upstream side of the apparatus, the PM is collided / depressed by the convex portion on the downstream side and is adsorbed by the concave portion on the downstream side by the suction force of the outer peripheral electrode. The Therefore, the outflow of PM to the outside of the apparatus can be further effectively suppressed.

  According to a third aspect of the present invention, in the exhaust gas purifying apparatus according to claim 1 or 2, the concave portion in the unevenness is formed in a circumferential direction of the barrier layer.

  In the third aspect of the present invention, since the concave portion is formed in the circumferential direction of the barrier layer, PM can be well held in the concave portion.

  The fourth aspect of the present invention is the exhaust gas purifying apparatus according to any one of claims 1 to 3, wherein a heating element is disposed at the bottom of the recess.

  In the fourth aspect of the present invention, since the heating element is disposed at the bottom of the concave portion, it can be efficiently processed at a site where PM is concentrated.

  According to a fifth aspect of the present invention, in the exhaust gas purifying apparatus according to claim 4, the arrangement density of the heating elements is different from each other in two regions upstream and downstream in the supply direction.

  In the fifth aspect of the present invention, the performance of the heat treatment of PM can be changed according to the position of the barrier layer by changing the arrangement density of the heating elements.

  The sixth aspect of the present invention is the exhaust gas purifying apparatus according to claim 5, wherein the arrangement density of the heating elements increases at least downstream of the barrier layer as it goes downstream. .

  In an apparatus configured to charge PM by the internal electrode and adsorb it to the outer peripheral electrode side, the PM deposition position on the outer peripheral electrode side tends to be biased toward the downstream side. In the sixth aspect of the present invention, the arrangement density of the heating elements is increased. Since it is increased toward the downstream, PM accumulated on the downstream side can be treated well, and when the PM that has separated from the upstream side and collected has been collected on the downstream side, it can be treated with high possibility. Can be effectively prevented from flowing out to the downstream side.

  The seventh aspect of the present invention is the exhaust gas purifying apparatus according to any one of claims 1 to 6, wherein a cylindrical guide body is disposed inward of the barrier layer along the supply direction. It is.

  In the seventh aspect of the present invention, even when the PM is peeled off from the barrier layer, the outflow of the PM is reduced or regulated by the guide body, so that the peeled PM may be adsorbed to the recess on the downstream side. Can be improved. Further, since the guide body is installed along the exhaust gas supply direction, the influence on the exhaust resistance can be reduced.

  The eighth aspect of the present invention is the exhaust gas purifying apparatus according to claim 7, wherein the guide body is provided with a large number of through holes.

  In the eighth aspect of the present invention, PM can be passed from the internal electrode side to the outer peripheral electrode side through the through hole of the guide body.

  The exhaust gas purification according to any one of claims 1 to 8, wherein the ninth aspect of the present invention carries a catalyst substance to promote the treatment of exhaust gas on at least a part of the inner surface of the barrier layer. Device.

  In the ninth aspect of the present invention, the treatment of exhaust gas can be further promoted by the action of the catalyst substance.

  Embodiments of the present invention will be described below with reference to the drawings. The exhaust gas purification apparatus of the present embodiment is configured as a plasma reactor, and 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 path of the internal combustion engine Incorporated into.

  As shown in FIG. 1, the exhaust gas purification apparatus 1 includes a purification container 10 that is formed in a substantially cylindrical shape from a heat-resistant conductive material such as metal. The upstream end (left end in the figure) of the purification container 10 is connected to an exhaust pipe L1 constituting the exhaust system of the internal combustion engine, and the downstream end of the purification container 10 is connected to an exhaust pipe L2 constituting the exhaust system of the internal combustion engine. The Then, as indicated by the white arrow in FIG. 1, exhaust gas discharged from the combustion chamber of the internal combustion engine is introduced into the purification container 10 through the exhaust pipe L <b> 1 and purified inside the purification container 10. The exhaust gas discharged is discharged to the outside through the exhaust pipe L2.

  In FIG. 2, a substantially cylindrical outer peripheral electrode 20 is disposed inside the purification container 10. Further, a thin rod-like internal electrode 30 is inserted so as to be positioned on the longitudinal axis of the outer peripheral electrode 20. The outer peripheral electrode 20 and the internal electrode 30 are insulatively fixed to the purification container 10 via an electrode seat 31 and a sleeve 32 made of insulator or the like, and the upstream end of the internal electrode 30 has an insulating support 33. Is held by.

  A barrier layer 40 is formed on the inner surface of the outer peripheral electrode 20, and an insulating layer 50 is formed on the outer surface of the outer peripheral electrode 20. The barrier layer 40 and the insulating layer 50 are integrally formed of the same material, and both of them cover the entire surface of the outer peripheral electrode 20. A holding material 11 made of an insulator is provided between the insulating layer 50 and the purification container 10.

  On the inner surface of the barrier layer 40, a large number of annular recesses 41 are formed in a multistage shelf shape. Between the concave portions 41 adjacent to each other, a convex portion 42 having an annular or inward flange shape over the entire circumference of the barrier layer 40 is formed. As a result, the concave portion 41 and the convex portion 42 are arranged in the exhaust gas supply direction (see FIG. In the middle and left and right directions (indicated by white arrows). The groove widths (the dimensions in the upstream / downstream direction) of the recesses 41 are equal to each other for all the recesses 41.

  The plurality of convex portions 42 partially overlap each other in the upstream / downstream direction, and the tip of the rear convex portion 42 of the pair of adjacent convex portions 42 is similarly compared to the tip of the front convex portion 42. The radius of the circle formed by the tip of the convex portion 42 is arranged so as to gradually decrease from the inlet side to the outlet side of the purification container 10. In the example shown in FIG. 2, a large number of convex portions 42 are divided into six groups, and the height of the convex portions 42 of the outlet side (downstream side) group is relatively high between adjacent groups, and Within each group, the heights of the convex portions 42 are equal to each other. On the other hand, the distance between the bottom of the recess 41 and the outer peripheral electrode 20 is equal for all the recesses 41.

  A large number of substantially annular heating elements 43 made of Ni—Cr are arranged along the bottom of the recess 41. The ends of the adjacent heating elements 43 are connected in series by a conductive wire (not shown), and the conductive wires 44 are led out from the heating elements 43 at the front end and the rear end via the electrode seat 45 and the sleeve 46. ing. The thicknesses (cross-sectional areas) of the large number of heating elements 43 are the same.

  The arrangement density of the heating elements 43 (that is, the number of turns of the heating elements 43 per unit distance in the upstream and downstream directions of the barrier layer 40) is made different in two regions that are different from each other in the front and rear directions in the gas supply direction in the barrier layer 40. Yes. The arrangement density of the heating elements 43 is gradually increased toward the rear side in the upstream / downstream direction, and is highest at the rear end portion (right end portion in the drawing) of the barrier layer 40.

  A cylindrical guide body 12 is installed on the inner side of the barrier layer 40 so as to be coaxial with the purification container 10 along the upstream and downstream directions. The guide body 12 is fixed to the holding material 11 by a stay 13. A large number of circular through holes 12 a are formed on the entire surface of the guide body 12. The purification container 10 is connected to the front and rear exhaust pipes L1, L2 by a flange 14 provided at an end thereof.

  For the outer peripheral electrode 20, the inner electrode 30, and the guide body 12, it is preferable to use a metal material excellent in conductivity, heat resistance, and corrosion resistance, for example, stainless steel. It is preferable to use a wire net or punching material, a rod material for the internal electrode 30, and a plate-like member such as a wire net in addition to the punching material for the guide body 12. For the barrier layer 40, the insulating layer 50, and the holding material 11, it is preferable to use an insulating ceramic material such as alumina or silica (silicon dioxide) mat.

  A catalytic substance is supported on the entire inner surface of the barrier layer 40. As the catalyst material, in addition to a noble metal such as platinum, a base metal such as vanadium, copper or manganese and a metal oxide such as alumina are suitable.

  In FIG. 1 again, a high voltage power supply unit 54 for applying a high voltage to the outer peripheral electrode 20 and the inner electrode 30 is connected to a DC power supply (in this embodiment, an auxiliary battery of a vehicle) 51, and is also shown in the figure. Inverter circuit, transformer, rectifier diode, etc. are not included. The low voltage power supply unit 60 for applying a low voltage to the heating element 43 includes a DC power supply and a switching circuit not shown. The high voltage power supply unit 54 and the low voltage power supply unit 60 are connected to an engine ECU 70 that controls the internal combustion engine to which the exhaust gas purification apparatus 1 is applied. Note that the DC power supply of the low voltage power supply unit 60 may use the DC power supply 51 before boosting the high voltage power supply unit 54.

The engine ECU 70 includes a CPU, a ROM, a RAM, an input / output port, a storage device, and the like (not shown). The input / output port of the engine ECU 70 includes a voltmeter 52 that detects a voltage value applied to the outer peripheral electrode 20 and the internal electrode 30, and a current that detects a current value discharged between the outer peripheral electrode 20 and the internal electrode 30. A total of 53, an accelerator opening sensor, an engine speed sensor, an intake manifold pressure sensor, an intake air flow meter, an O ₂ sensor, an A / F (air / fuel ratio) sensor, etc. (not shown) are connected, and the engine ECU 70 detects these. Each value is calculated based on the signal and processed as described below.

  The engine ECU 70 follows a predetermined control program and the like, and drives pulses for driving the inverter circuit of the power supply unit 54 based on signals indicating the state of the internal combustion engine from the voltmeter 52, ammeter 53, and various sensors. A voltage instruction signal for instructing a signal (gate signal) or a value of a voltage applied from the power supply unit 54 to the outer peripheral electrode 20 and the inner electrode 30 is generated.

  When a drive pulse signal (gate signal) or a voltage instruction signal is given from the engine ECU 70 to the power supply unit 54, the DC voltage from the DC power supply 51 is converted into an AC voltage by the inverter circuit in the power supply unit 54. The AC voltage applied to the transformer from the inverter circuit is boosted by the transformer and rectified by the diode, whereby a DC pulse voltage is applied to the outer peripheral electrode 20 and the inner electrode 30.

  The operation of the present embodiment configured as described above will be described below. When the ignition switch is turned on by the user to start the vehicle, the engine ECU 70 gives a power ON signal to the high voltage power supply unit 54 to start the operation of the high voltage power supply unit 54. In addition, after the power supply unit 54 is started, the engine ECU 70 generates a drive pulse signal and a voltage instruction signal in accordance with the operating state of the internal combustion engine, and supplies them to the high voltage power supply unit 54. Thereby, a DC pulse voltage is applied to the outer peripheral electrode 20 and the inner electrode 30.

With the application of the DC pulse voltage, an electric field is formed between the internal electrode 30 and the outer peripheral electrode 20. Due to the discharge from the internal electrode 30, the PM in the exhaust gas supplied into the container 10 is charged, sucked by the outer peripheral electrode 20 having a polarity opposite to that of the internal electrode, and trapped in the recess 41 of the barrier layer 40. This PM is oxidized or burned by heat generated by the discharge, and is detoxified by CO ₂ or the like. That is, when the heating element 43 is heated, PM collected in the recess 41 reacts with HC oxide based on oxygen and N in the exhaust gas and is released as CO ₂ gas (C + O ₂ → CO ₂ ). Further, HC, CO, NOx contained in the exhaust gas from the internal combustion engine reacts with oxygen in the exhaust gas by the plasma energy to be rendered harmless to N ₂ , CO ₂ , H ₂ O, etc., and is incinerated by ignition. It is possible to

Further, with the deposition of PM, the PM particles are bonded to each other by the HC component, H ₂ O, or the like, and the particle diameter gradually increases. When the peeling force due to the exhaust gas flow or vibration exceeds the adsorption force by the outer peripheral electrode 20 due to the increase in the surface area and fluid resistance due to the increase in the particle size, the PM from the barrier layer 40 is easily peeled off. Here, in this embodiment, when it is determined that a predetermined amount or more of PM is attached to the barrier layer 40, the heating element 43 is heated by the output of the engine ECU 70, and the barrier layer 40 is heated by the Joule heat of the heating element 43. The reaction and combustion of the PM collected in the layer 40 are promoted.

The determination of the adhesion can be performed by the engine ECU 70 by various methods. For example, the reactor impedance calculated based on signals from the voltmeter 52 and the ammeter 53 falls below a predetermined value by utilizing the fact that PM contains a large amount of carbon C and the electric resistance decreases in the case of adhesion. In some cases, it can be determined that it is attached. Further, for the same reason, it can be determined that adhesion occurs when the current value calculated based on the signal from the ammeter 53 exceeds a predetermined value. Furthermore, in addition to the method of directly detecting the current adhesion state as described above, a method of integrating the elapsed time from the previous processing and the estimated deposition amount per unit time can be adopted. The calculation of the estimated deposit amount per hit includes an engine speed sensor (not shown), a pressure sensor and an air flow meter provided on the intake manifold, an O ₂ sensor and an A / F (air / fuel ratio) sensor provided on the exhaust side of the engine. Each detected value, and also air-fuel ratio information stored in a predetermined memory area on the RAM of the engine ECU 70 in the course of fuel injection control performed separately from this control, can be used. Any one of these various adhesion determinations may be used alone, or a plurality of types may be used in combination with, for example, an OR condition, and the weighted sum is compared with a predetermined reference value. May be.

Further, NO ₂ , CH ₃ CHO, and HCHO are generated by the action of the catalyst material supported on the surface of the barrier layer 40. Here, the C oxidation reaction at a lower temperature than the oxygen reaction can be started. In addition, harmful components such as CO discharged from the purification container 10 are further purified by a catalyst device provided separately at the subsequent stage.

  As described above, in the present embodiment, unlike the configuration using a fiber filter, the exhaust gas flow path is not blocked, so that the exhaust resistance can be reduced. And in this embodiment, since the unevenness | corrugation which consists of the recessed part 41 and the convex part 42 was formed in the inner surface of the barrier layer 40, the adsorbed PM is well hold | maintained at the bottom part and peripheral wall of the recessed part 41, and the peeling and dropping-off are suppressed. Is done. Therefore, peeling of unprocessed PM from the barrier layer 40 can be suppressed, and processing performance can be improved. Further, since PM is mainly deposited in the recess 41 provided at a location relatively distant from the internal electrode 30, it is possible to prevent the occurrence of spark discharge due to contact between the deposited PM and the internal electrode 30.

  Further, in the present embodiment, the convex portion 42 gradually becomes smaller as the radius of the circle formed by the tip thereof becomes closer to the outlet side from the inlet side of the purification container 10 (that is, the tip of the convex portion 42 is closer to the internal electrode 30). Therefore, even when the PM peeled / dropped out from the concave portion 41 on the upstream side of the apparatus flows out beyond a certain convex portion 42, the PM is collided / depressed by the convex portion 42 on the downstream side. By the suction force of the outer peripheral electrode 20, it is attracted to the concave portion 41 in the vicinity thereof. Therefore, the outflow of PM to the outside of the apparatus can be effectively suppressed.

  Further, in the present embodiment, since the heating element 43 is disposed at the bottom of the recess 41, it can be efficiently processed at a site where PM is concentrated.

  In this embodiment, since the recess 41 is formed in the circumferential direction of the barrier layer 40, PM can be well held in the recess 41, and the heating element 43 is disposed along the bottom of the recess 41. The body 43 can be suitably used.

  Moreover, in this embodiment, since the arrangement density of the heat generating elements 43 is changed according to the position in the barrier layer 40, the performance of the PM heat treatment can be changed according to the part.

  In addition, in an apparatus configured to charge PM by an internal electrode and adsorb it to the outer peripheral electrode side, the PM deposition position on the outer peripheral electrode side tends to be downstream, but in this embodiment, the arrangement density of the heating elements 43 is increased. As the exhaust gas supply direction increases toward the rear side, the PM accumulated on the downstream side can be treated well, and the PM that has separated from the upstream side and has flowed out can also be collected on the downstream side. Can be processed with high possibility, and the outflow of PM from the apparatus to the outside on the downstream side can be effectively prevented.

  Further, in the present embodiment, even when the PM is peeled off from the barrier layer 40, the movement of the PM toward the center of the purification container 10 is deenergized by the guide body 12 which is the depressing means, so that the outflow is regulated. At the same time, it can be expected that the peeled PM is adsorbed to the recessed portion 41 downstream, and the outflow of PM from the purification container 10 can be further effectively suppressed. In addition, since the guide body 12 is configured as a cylindrical body made of a plate-like material and disposed along the front-rear direction of the apparatus, the projected area in the exhaust gas supply direction is small, thereby reducing the influence on the exhaust resistance. it can.

  Further, in the present embodiment, PM can be passed from the internal electrode 30 side to the outer peripheral electrode 20 side through the through hole 12a of the guide body 12.

In the present embodiment, the exhaust gas treatment can be further promoted by the action of the catalyst material supported on the inner surface of the barrier layer 40. Further, in the configuration of the present embodiment, a Pt—Al ₂ O ₃ catalyst is further installed in the front stage of the purification container 10 to cause a reaction of NO + O ₂ → NO ₂ by the catalyst. It may be configured to collect and burn C.

  In the embodiment described above, the shape of the concave portion 41 is a series of substantially annular shapes extending over substantially the entire circumference of the barrier layer 40. However, the concave portion in the present invention is not limited to the line shape extending in the circumferential direction. It may be in the form of a line extending parallel to the line, or in the form of a dot or checkered pattern. Further, the position and shape of the heating element may be provided, for example, at a position floating from the bottom surface of the recess, or may be embedded in the barrier layer 40 that is deeper than the bottom surface of the recess or wound from the outer peripheral side. In the above embodiment, the groove widths of the concave portions 41 are equal to each other for all the concave portions 41. However, the groove widths of the concave portions 41 can be changed as necessary. For example, the groove width in a certain region (for example, the region at the downstream end) can be changed. By making it narrower than that of the other region, it is possible to increase the arrangement density of the heating elements in that region and promote the processing.

  Further, in the above embodiment, the outer peripheral electrode 20 is cylindrical, but the cross-sectional shape of the outer peripheral electrode may be other shapes such as a rectangular tube. In addition, the outer peripheral electrode may have a shape in which the cross-sectional area changes along the axial direction like a truncated cone or other frustum shape, and in the case of a frustum shape, the cross-sectional area should be reduced toward the rear end. Thus, there is an advantage that the tip position of the convex portion can be set so as to gradually approach the internal electrode 30 without greatly changing the height of the convex portion from the base.

  Moreover, in the said embodiment, although the space | interval of the bottom part of the recessed part 41 and the outer periphery electrode 20 was mutually made the same about the some recessed part 41, since it is thought that the retention strength of PM is so high that this space | interval is small, this is needed as needed. It may be changed and set. For example, if the gap between the bottom of the concave portion 41 and the outer peripheral electrode 20 is set smaller than the other portions in the vicinity of the end portion on the outlet side of the purification container 10, the PM can be discharged from the rear end of the purification container 10. It can be effectively suppressed.

  In the above embodiment, the internal electrode 30 is rod-shaped. However, the tip is formed by providing a needle-like protrusion on the surface or using a triangular screw on a part or all of the internal electrode, thereby discharging the electrode. May be promoted.

  Moreover, although the thickness of many heat generating bodies 43 was made constant in the said embodiment, you may make the wire diameter of the heat generating bodies 43 of the front-and-rear both ends of the barrier layer 40 thinner than that of the middle region. Of the heating element, portions at both the inlet and outlet ends of the barrier layer 40 can be made relatively high in temperature, and by promoting combustion, accumulation of PM in the vicinity of both ends can be suppressed and abnormal discharge can be prevented. There is an advantage. For the same purpose, the resistance value of the heating element 43 at both front and rear ends of the barrier layer 40 may be higher than that in the middle region. Furthermore, in the above embodiment, the heating element is of an electrothermal type, but the heating element in the present invention may be of another type or may not be in the form of a line.

  In the present embodiment, since the voltmeter 52 and the ammeter 53 are provided, it is possible to detect the presence or absence of disconnection by measuring the voltage and current.

It is a block diagram which shows the outline of the exhaust gas purification apparatus of embodiment of this invention. It is a longitudinal cross-sectional view which shows the principal part of the exhaust gas purification apparatus of embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exhaust gas purification apparatus 10 Purification container 12 Guide body 20 Peripheral electrode 30 Internal electrode 40 Barrier layer 41 Recess 42 Projection 43 Heating element

Claims (9)

Exhaust gas supplied between the two electrodes using a plasma generated by applying a high voltage between the two electrodes, including a cylindrical outer electrode and an internal electrode inserted into the outer electrode. In exhaust gas purification equipment that purifies
Further comprising a barrier layer made of an insulator and arranged to cover the inner surface of the outer peripheral electrode,
An exhaust gas purifying apparatus, wherein irregularities are provided on an inner surface of the barrier layer.   2. The exhaust gas purifying apparatus according to claim 1, wherein at least part of the entire length of the barrier layer, the tip of the convex portion of the unevenness gradually approaches the internal electrode as it goes downstream in the supply direction. .   The exhaust gas purifying apparatus according to claim 1 or 2, wherein the recesses in the irregularities are formed in a circumferential direction of the barrier layer.   The exhaust gas purifying apparatus according to any one of claims 1 to 3, wherein a heating element is disposed at the bottom of the recess.   The exhaust gas purifying apparatus according to claim 4, wherein the arrangement density of the heating elements is different from each other in two regions upstream and downstream in the supply direction.   6. The exhaust gas purifying apparatus according to claim 5, wherein an arrangement density of the heating elements is increased at least downstream of the barrier layer as it goes downstream.   The exhaust gas purifying apparatus according to any one of claims 1 to 6, wherein a cylindrical guide body is installed inward of the barrier layer along the supply direction.   The exhaust gas purifying apparatus according to claim 7, wherein the guide body is provided with a plurality of through holes. The exhaust gas purifying apparatus according to any one of claims 1 to 8, wherein a catalyst material that should promote the treatment of exhaust gas is supported on at least a part of the inner surface of the barrier layer.

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