JP2005076539A - Catalytic converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalytic converter, preventing or avoiding various kinds of problems resulting from the transmission of the heat of exhaust gas flowing in a bypass line passing through the center of the catalytic converter to a honeycomb body. <P>SOLUTION: The catalytic converter comprises a catalyst supporting honeycomb body 10 stored in a cylindrical case 20 and the bypass line B passing through a central portion of the honeycomb body 10. In a boundary region between the bypass line B and the honeycomb body 10 encircling it, a double inner tube is provided which consists of a first inner tube 21 and a second inner tube 22. Between the first inner tube 21 and the second inner tube 22, a hollow heat insulating layer 27 is held where the double inner tube is sealed at its upstream end to preclude the entry of exhaust gas from the upstream side. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a catalytic converter that is a kind of an exhaust gas purification device for an engine or that is used by being disposed in a part of an exhaust path of an exhaust gas purification device.

  2. Description of the Related Art Conventionally, an exhaust gas purification device including a honeycomb body that supports an exhaust gas purification catalyst is known. For example, Patent Document 1 has a large number of mesh-like vent holes in the axial direction, which are manufactured by stacking and laminating flat plate strips and corrugated strip strips of thin metal plates and winding them together in a spiral shape. Disclosed is a honeycomb core for supporting a catalyst, which is formed by forming a cylindrical hollow portion at the center of winding thereof (that is, a honeycomb core having an annular cross section perpendicular to the axis). Usually, a metal cylinder (pipe) is disposed in a cylindrical hollow portion of the honeycomb core body, and the honeycomb core body is loaded in a cylindrical metal case to constitute a catalytic converter. When the catalytic converter is mounted on an actual vehicle, the pipe passing through the center of the honeycomb core body is used as a bypass passage for bypassing the honeycomb core body with exhaust gas from the engine.

  By the way, in the conventional catalytic converter, when the exhaust gas flows through the bypass passage constituted by a single pipe, various problems are caused by a large amount of heat of the exhaust gas being transferred to the pipe and the honeycomb core body surrounding the pipe. Was produced. For example, heat transferred through the pipe wall causes non-uniform heat distribution (ie, excessive thermal gradient in the radial direction) between the inner and outer peripheral portions of the honeycomb core body, resulting in the honeycomb core. Circumferential tensile stress is generated in the body, and as a result, the metal strip in the wound and laminated state may be cut and chipped into a foil shape, or a part of the strip may be displaced and fall off. It was. Further, the catalyst material (for example, a noble metal catalyst) may be deteriorated at a high temperature by heat transferred to the honeycomb core body through the pipe wall. Furthermore, the honeycomb core body may be pressed and damaged between the pipe and the cylindrical metal case that are excessively thermally expanded by the exhaust heat, or the pipe itself may be cracked.

No. 7-33875

  An object of the present invention is to provide a catalytic converter capable of preventing or avoiding various problems caused by the heat of exhaust gas flowing through a bypass passage passing through the center of the catalytic converter being transferred to the honeycomb body. It is in.

  The invention of claim 1 is a catalytic converter comprising a catalyst-supporting honeycomb body having a large number of vent holes extending in the axial direction, and a central passage that passes through the central portion of the honeycomb body in the axial direction. In the boundary region between the central passage and the honeycomb body surrounding the central passage, the first inner pipe that defines the central passage and the second inner pipe that surrounds the first inner pipe with a space therebetween. A double inner pipe is provided, and between the first inner pipe and the second inner pipe, the upstream end of the double inner pipe or the vicinity thereof is sealed from the upstream side. The catalytic converter is characterized in that a hollow heat insulating layer that prevents the exhaust gas from entering is secured.

  According to the first aspect, the central portion is formed by the double inner tube composed of the first inner tube that defines the central passage of the catalytic converter and the second inner tube that surrounds the first inner tube with a space therebetween. A hollow heat insulating layer (for example, an air layer) is secured in a boundary region between the passage and the honeycomb body surrounding the passage, that is, around the central passage. The hollow heat insulating layer seals the upstream end of the double inner tube or the vicinity thereof, thereby preventing the exhaust gas from entering from the upstream side. For this reason, even when high-temperature exhaust gas flows through the central passage, heat transfer from the central passage to the honeycomb body is alleviated by the hollow heat insulating layer secured around the central passage. Therefore, an uneven heat distribution (that is, an excessive thermal gradient in the radial direction) hardly occurs between the inner peripheral portion and the outer peripheral portion of the honeycomb body, and the honeycomb body is temporarily caused by such a thermal distribution (thermal gradient). Even if tensile stress in the circumferential direction occurs, the tensile stress in the circumferential direction does not become excessive, so that the honeycomb body can be prevented from being damaged. Further, since the heat transfer from the central passage to the honeycomb body is relaxed by the hollow heat insulating layer, it is possible to prevent the catalyst material carried on the honeycomb body from being deteriorated at high temperature.

  According to a second aspect of the present invention, in the catalytic converter according to the first aspect, the first inner pipe and the second inner pipe are connected to the upstream end of the double inner pipe or the vicinity thereof over the entire circumference. An all-around connecting portion is provided.

  According to the second aspect, the all-around connecting portion that connects the first inner tube and the second inner tube over the entire circumference at or near the upstream end of the double inner tube is the upstream end of the double inner tube. It functions as a sealing means that seals the portion or the vicinity thereof and makes it impossible for the exhaust gas to enter the hollow heat insulating layer from the upstream side, and contributes to maintaining the heat insulating performance of the hollow heat insulating layer. In addition, since the first inner pipe and the second inner pipe are interconnected via the entire circumference connecting portion, the connection location of both inner pipes in the range along the axial direction or the longitudinal direction of both inner pipes is It is limited to only one place along one circumference corresponding to the all-around connecting portion. For this reason, even when a high-temperature exhaust gas flows in the first inner pipe and the first inner pipe expands greatly compared to the second inner pipe, the first inner pipe is restrained by the second inner pipe. Without thermal expansion in the axial direction. Therefore, the occurrence of thermal stress concentration based on the difference in thermal expansion between the first inner tube and the second inner tube can be avoided, and damage to the double inner tube due to thermal stress concentration can be prevented.

  The invention according to claim 3 is the catalytic converter according to claim 2, wherein the first inner pipe and the second inner pipe are not connected to the downstream end of the double inner pipe or the vicinity thereof. An annular spacer portion that is useful for maintaining a distance between the first and second inner pipes and preventing exhaust gas from entering the hollow heat insulating layer from the downstream side is provided.

  According to claim 3, the annular spacer portion is provided at a downstream end portion of the double inner pipe or in the vicinity thereof, so that the annular spacer portion is located at a predetermined distance in the axial direction from the all-round connection portion. At the same time, it contributes to maintaining the distance between the first and second inner tubes. Further, the annular spacer portion is located at or near the downstream end of the double inner pipe and can substantially block the downstream opening of the hollow heat insulating layer, so that the exhaust gas downstream of the catalytic converter flows backward and becomes hollow. It is possible to prevent entry into the heat insulation layer as much as possible. Further, the annular spacer portion does not connect the first inner tube and the second inner tube, that is, the non-connected state between the first inner tube and the second inner tube at or near the downstream end of the double inner tube. To maintain. For this reason, in spite of the arrangement of the annular spacer portion, the connection location of both inner tubes in the range along the axial direction or the longitudinal direction of both inner tubes is along one circumference corresponding to the all-round connection portion. The structure of being limited to only one place is maintained, and the effect (avoidance of thermal stress concentration) as mentioned in claim 2 is maintained.

  According to a fourth aspect of the present invention, in the catalytic converter according to any one of the first to third aspects, the catalytic converter further includes a cylindrical case that accommodates the honeycomb body, and an inner peripheral surface of the honeycomb body is provided on the inner peripheral surface of the honeycomb body. One of the downstream end and the upstream end is connected to the outer peripheral surface of the second inner pipe, and the outer peripheral surface of the honeycomb body is connected to the other of the downstream end and the upstream end. By connecting to the inner peripheral surface of the cylindrical case, the honeycomb body is held between the cylindrical case and the double inner tube.

  According to claim 4, high-temperature exhaust gas flows through the first inner pipe of the double inner pipe, heat is transmitted to the honeycomb body surrounding the first exhaust pipe, and a thermal gradient is generated between the inner peripheral portion and the outer peripheral portion of the honeycomb body. Alternatively, even when a thermal difference occurs, the inner peripheral surface of the honeycomb body is only connected to the second inner pipe at the downstream end (or upstream end), so the inner peripheral portion of the honeycomb body and the second inner The tubes can thermally expand in the axial direction without being constrained to each other. Similarly, since the outer peripheral surface of the honeycomb body is only connected to the cylindrical case at the upstream end portion (or downstream end portion), the outer peripheral portion of the honeycomb body and the cylindrical case are not constrained to each other. Can expand in the direction. Therefore, there is a large thermal gradient or heat between the second inner tube, the inner peripheral portion of the honeycomb body, the outer peripheral portion of the honeycomb body, and the cylindrical case, which are concentrically arranged with respect to the central axis of the catalytic converter. Even if a difference occurs, there is no concentration of thermal stress in the inside of the honeycomb body or in the connection portion, and the honeycomb body is prevented from being damaged.

  Further, when the inner peripheral surface of the honeycomb body is connected to the outer peripheral surface of the second inner pipe at one of the downstream end portion and the upstream end portion, the outer peripheral surface of the honeycomb body is connected to the downstream end portion and the upstream end portion. The inner peripheral surface side connection position and the outer peripheral surface side connection position of the honeycomb body are shifted in the axial direction so that the other of the side end portions is connected to the inner peripheral surface of the cylindrical case. Therefore, it is possible to stably hold the honeycomb body between the cylindrical case and the double inner tube while maintaining the effect of avoiding the thermal stress concentration.

  (Supplementary note) In claims 1 to 4, "the honeycomb body is produced by stacking and laminating flat plate strips and corrugated strip strips of thin metal plates, and winding and laminating them in a spiral shape. It is preferable that the catalyst-supporting honeycomb body has a large number of vent holes extending in the axial direction by forming a cylindrical hollow portion at the center of winding. In such a honeycomb body, a flat strip or the like constructs a spiral laminated structure, and the independence of the strip constituting each layer at the inner periphery and the outer periphery of the honeycomb body is increased (that is, between the layers). Therefore, the operational effects based on the configuration as described in claim 4 are more effectively exhibited.

  According to the catalytic converter of the present invention, the double inner pipe composed of the first and second inner pipes is provided in the boundary region between the central passage and the honeycomb body surrounding the central passage to secure the hollow heat insulating layer, By relaxing the heat transfer from the passage to the honeycomb body, non-uniform heat distribution in the honeycomb body can be avoided and the honeycomb body can be prevented from being damaged, and the catalyst material supported on the honeycomb body can be prevented from being deteriorated at high temperature. be able to.

  Further, as described above, by devising the connection structure between the first and second inner pipes in the double inner pipe and the honeycomb body holding structure between the cylindrical case and the double inner pipe, It is possible to avoid thermal stress concentration in each part and prevent the catalytic converter from being damaged.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, the catalytic converter includes a catalyst-supporting honeycomb body 10, a cylindrical case 20 that accommodates the honeycomb body 10, and a double core that penetrates the center of the honeycomb body 10 in the axial direction. And inner pipes (21, 22).

  The catalyst-supporting honeycomb body 10 may be made of either metal or ceramics. However, the catalyst-supporting honeycomb body 10 is made of metal in that a cylindrical hollow portion for arranging the double inner tubes (21, 22) can be easily formed at the center thereof. It is preferable that the honeycomb body be made. The metal honeycomb body 10 is formed by stacking, for example, a flat strip 11 made of a heat-resistant thin steel plate and a corrugated strip 12 obtained by machining the heat-resistant thin steel plate into a corrugated shape. At the same time, the stacked strips 11 and 12 are wound into a collective spiral using a winding guide rod, and then the winding guide rod is extracted from the center. The honeycomb body 10 thus obtained has a substantially cylindrical shape having a large number of mesh-like vent holes 13 extending in the axial direction and a cylindrical hollow portion at the winding center. The honeycomb body 10 carries a predetermined catalyst material.

  The cylindrical case 20 is a cylindrical member made of, for example, stainless steel. The inner diameter of the cylindrical case 20 is slightly larger than the outer diameter of the honeycomb body 10, and the axial length (full length) of the cylindrical case 20 is set to be larger than the axial length of the honeycomb body 10. The honeycomb body 10 can be accommodated in the case 20.

  The double inner pipe (21, 22) includes a first inner pipe 21 and a second inner pipe 22 that surrounds the first inner pipe 21 at a predetermined interval. Both the first and second inner pipes 21 and 22 are made of straight cylindrical pipe-shaped stainless steel pipes. The total length of the first and second inner tubes 21 and 22 is substantially equal to the total length of the cylindrical case 20, and the radius of the second inner tube 22 is larger than the radius of the first inner tube 21.

  In this catalytic converter, the first inner pipe 21, the second inner pipe 22 and the cylindrical case 20 are arranged concentrically around a central axis L common to them (see FIG. 1). A housing space for the honeycomb body 10 is defined between the inner peripheral surface of the cylindrical case 20 and the outer peripheral surface of the second inner tube 22. Further, the first inner pipe 21 arranged at the most central portion defines and forms a bypass passage B as a central passage that passes through the central portion of the honeycomb body 10 in the axial direction. In the boundary area between the bypass passage B and the honeycomb body 10, double inner pipes (21, 22) are disposed, and between the first inner pipe 21 and the second inner pipe 22, An interval substantially equal to the radial difference between the tubes 21 and 22 is ensured over the entire circumference.

  As shown in FIG. 2, at the upstream end of the double inner pipe (21, 22), the entire outer circumference of the first inner pipe 21 and the inner circumference of the second inner pipe 22 are connected over the entire circumference. A circumferential connecting portion 23 is provided. This all-around connecting portion 23 includes a stainless steel upstream ring 24, an annular brazing portion 25 provided between the inner peripheral surface of the ring 24 and the outer peripheral surface of the first inner tube 21, An annular brazing portion 26 is provided between the outer peripheral surface and the inner peripheral surface of the second inner tube 22. That is, the outer peripheral surface of the upstream end of the first inner tube 21 and the inner peripheral surface of the upstream end of the second inner tube 22 are the inner annular brazing portion 25, the upstream ring 24, and the outer annular brazing portion 26. It is connected all around. The all-around connecting portion 23 seals the annular opening on the upstream side of the double inner pipe (21, 22) to prevent the exhaust gas from the upstream side from entering the double inner pipe. Also serves as a stopping means. Therefore, a hollow heat insulating layer 27 that makes it impossible for the exhaust gas to enter from the upstream side is ensured between the first inner pipe 21 and the second inner pipe 22 by the all-around connecting portion 23. In the present embodiment, the hollow heat insulating layer 27 exists as an air layer.

  On the other hand, there is no inter-inner tube connecting portion like the above-mentioned all-around connecting portion 23 at the downstream end of the double inner tube (21, 22). Instead, an annular spacer portion 28 having a configuration in which the outer peripheral surface of the first inner tube 21 and the inner peripheral surface of the second inner tube 22 are not connected is provided at the downstream end of the double inner tube (21, 22). It has been. The annular spacer portion 28 is provided between a stainless steel downstream ring 29 having the same shape and dimensions as the upstream ring 24, and an inner peripheral surface of the ring 29 and an outer peripheral surface of the first inner tube 21. And an annular brazing portion 30. That is, the downstream ring 29 is attached to the outer peripheral surface of the downstream end portion of the first inner pipe 21 via the annular brazing portion 30. A slight annular gap C (non-brazed portion) is secured between the outer peripheral surface of the downstream ring 29 and the inner peripheral surface of the downstream end of the second inner tube 22. The two inner pipes 22 are not connected. The annular spacer portion 28 is located at a predetermined distance in the axial direction from the entire circumference connecting portion 23, thereby contributing to the interval maintenance between the first and second inner pipes 21 and 22 together with the entire circumference connecting portion 23. Further, the annular spacer portion 28 is located at the downstream end of the double inner pipe and substantially closes the annular opening on the downstream side of the hollow heat insulating layer 27, so that the exhaust gas downstream of the catalytic converter flows backward and the hollow heat insulating layer 27. It works to prevent as much as possible from entering.

  In the present embodiment, the first inner pipe 21 and the second inner pipe 22 are interconnected only by the entire circumference connecting portion 23 at the upstream end, and are not connected by the annular spacer portion 28 at the downstream end. For this reason, the connection place of both the inner pipes 21 and 22 in the range along the axial direction or longitudinal direction of both the inner pipes 21 and 22 is only one place along one circumference corresponding to the all-around connection part 23. Limited.

  As shown in FIG. 2, the outer peripheral surface of the upstream end portion of the honeycomb body 10 is connected to the entire inner peripheral surface of the cylindrical case 20 via the annular brazing portion 31, and the honeycomb body The inner peripheral surface of the downstream end 10 is connected to the outer peripheral surface of the second inner tube 22 through the annular brazing portion 32. The upstream annular brazing portion 31 (the outer peripheral surface side connection position of the honeycomb body) and the downstream annular brazing portion 32 (the inner peripheral surface side connection position of the honeycomb body) are displaced in the axial direction. The honeycomb body 10 is stably held between the cylindrical case 20 and the double inner pipes (21, 22) despite being held only by the annular brazing portions 31, 32.

  In addition, as a metal (brazing | wax material) used by each said brazing part (25, 26, 30, 31, 32), a copper alloy is mention | raise | lifted, for example. An example of a brazing method that can be used is brazing in a vacuum furnace.

  According to this embodiment, the following operations and effects can be obtained.

  Due to the double inner pipe constituted by the first inner pipe 21 and the second inner pipe 22, an annular opening on the upstream side is formed by an all-around connecting portion 23 in the boundary area between the bypass passage B and the honeycomb body 10 surrounding the bypass passage B. The sealed hollow heat insulating layer 27 is secured. Therefore, even when high-temperature exhaust gas flows through the bypass passage B, heat transfer from the bypass passage B to the honeycomb body 10 is relaxed by the hollow heat insulating layer 27 secured around the bypass passage B, and the inner peripheral portion of the honeycomb body 10 Uneven heat distribution (that is, excessive thermal gradient in the radial direction) hardly occurs on the outer periphery. Therefore, even if a tensile stress in the circumferential direction is generated in the honeycomb body 10 due to the heat distribution (thermal gradient), the circumferential tensile stress is not excessively increased, and the metal constituting the honeycomb body 10 is made. It is possible to prevent the strips 11 and 12 from being cut out and chipped off in the form of foil (breakage of the honeycomb body). In addition, since heat transfer to the honeycomb body 10 is alleviated, it is possible to prevent high-temperature deterioration of the catalyst material supported on the honeycomb body 10.

  The connection place of both the inner pipes in the range along the axial direction or the longitudinal direction of the first and second inner pipes 21 and 22 is limited to only one place along one circumference corresponding to the entire circumference connection portion 23. Therefore, even when a high-temperature exhaust gas flows in the first inner pipe 21 and the first inner pipe 21 thermally expands much more than the second inner pipe 22, the first inner pipe 21 is in the second inner pipe 21. Without being constrained by the tube 22, it can be thermally expanded in the axial direction without difficulty, and thermal stress concentration based on the difference in thermal expansion between the inner tubes 21 and 22 can be avoided. If there are two or more connecting parts of the inner pipes in the range along the axial direction or the longitudinal direction of the inner pipes 21 and 22 (for example, not only in the entire circumference connecting part 23 but also in the annular spacer part 28, all When there is a circumferential connection), the axial thermal expansion of the first inner tube 21 is hindered by the two connection locations, leading to stress concentration. In this respect, according to the present embodiment, since the axially connected portion of both the inner pipes 21 and 22 is only one place, the above-described thermal stress concentration does not occur, and the double inner tube (21 22) can be prevented.

  Furthermore, according to the present embodiment, high-temperature exhaust gas flows through the first inner pipe 21, heat is transferred to the honeycomb body 10 surrounding the first exhaust pipe 21, and a thermal gradient or Even if a thermal difference occurs, the inner peripheral surface of the honeycomb body 10 is only connected to the second inner pipe 22 through the downstream annular brazing portion 32, so that the inner peripheral portion ( In particular, the metal strips 11 and 12) and the second inner tube 22 constituting the group 13 of vent holes arranged in the innermost circumference can thermally expand in the axial direction without being constrained to each other. Similarly, since the outer peripheral surface of the honeycomb body 10 is only connected to the cylindrical case 20 through the upstream brazing portion 31 on the upstream side, the outer peripheral portion of the honeycomb body 10 (especially, the vent holes arranged on the outermost periphery). The metal strips 11 and 12) constituting the 13th group and the cylindrical case 20 can be thermally expanded in the axial direction without being constrained to each other. Therefore, between the four of the second inner tube 22, the inner peripheral portion of the honeycomb body 10, the outer peripheral portion of the honeycomb body 10, and the cylindrical case 20, which are concentrically arranged with respect to the central axis L of the catalytic converter. Even if a large thermal gradient or thermal difference occurs, thermal stress does not concentrate inside the honeycomb body 10 or at the connection site, and damage to the honeycomb body 10 can be prevented.

(Modification) The embodiment of the present invention may be modified as follows.
In the above embodiment, the downstream ring 29 constituting the main part of the annular spacer portion 28 is fixed on the outer peripheral surface of the first inner pipe 21 via the annular brazing portion 30 on the inner peripheral side. Instead, as shown in FIG. 3, the downstream ring 29 may be fixed on the inner peripheral surface of the second inner tube 22 via the annular brazing portion 33 on the outer peripheral side thereof. In this case, the annular spacer portion 28 is configured by the downstream ring 29 and the annular brazing portion 33.

  As a mounting method for holding the honeycomb body 10 between the cylindrical case 20 and the double inner pipe (21, 22), a brazing mode as shown in FIG. 3 is used instead of the brazing mode shown in FIG. May be adopted. That is, the inner peripheral surface of the upstream end portion of the honeycomb body 10 is connected to the outer peripheral surface of the second inner tube 22 via the annular brazing portion 34 and the outer peripheral surface of the downstream end portion of the honeycomb body 10 is connected. The entire circumference of the cylindrical case 20 may be connected via the annular brazing portion 35. Also in this case, the upstream-side annular brazing portion 34 (the inner peripheral surface side connection position of the honeycomb body) and the downstream-side annular brazing portion 35 (the outer peripheral surface side connection position of the honeycomb body) are displaced in the axial direction. Therefore, the honeycomb body 10 is stably held between the cylindrical case 20 and the double inner pipe (21, 22) despite the holding by the two annular brazing portions 34, 35 only. .

The schematic front view of a catalytic converter. The expanded sectional view in the AA line of FIG. Sectional drawing equivalent to FIG. 2 in the example of a change.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Honeycomb body for catalyst support, 13 ... Mesh-like ventilation passage of honeycomb body, 20 ... Cylindrical case, 21 ... First inner pipe, 22 ... Second inner pipe (21 and 22 are double inner pipes) ), 23 ... All-round connection part (sealing means), 27 ... Hollow heat insulating layer, 28 ... Annular spacer part, B ... Bypass passage as a central part passage, C ... Annular gap (non-brazing part), L: Center axis.

Claims (4)

A catalytic converter comprising a catalyst supporting honeycomb body having a large number of vent passages extending in the axial direction, and a central passage that passes through the central part of the honeycomb body in the axial direction,
In the boundary region between the central passage and the honeycomb body surrounding the central passage, the first inner pipe that defines the central passage and the second inner pipe that surrounds the first inner pipe with a space therebetween. A double inner pipe is provided, and between the first inner pipe and the second inner pipe, the upstream end of the double inner pipe or the vicinity thereof is sealed from the upstream side. A catalytic converter characterized in that a hollow heat insulating layer that prevents intrusion of exhaust gas is secured.   2. An all-around connecting part for connecting the first inner pipe and the second inner pipe over the entire circumference is provided at or near the upstream end of the double inner pipe. The catalytic converter described in 1.   Without connecting the first inner pipe and the second inner pipe to the downstream end of the double inner pipe or in the vicinity thereof, the distance between the first and second inner pipes is maintained, and the hollow insulation is provided from the downstream side. The catalytic converter according to claim 2, wherein an annular spacer portion is provided to help prevent exhaust gas from entering the layer. The catalytic converter further includes a cylindrical case that houses the honeycomb body,
The inner peripheral surface of the honeycomb body is connected to the outer peripheral surface of the second inner pipe at one of the downstream end and the upstream end, and the outer peripheral surface of the honeycomb body is connected to the downstream end and the upstream 2. The honeycomb body is held between the cylindrical case and the double inner tube by connecting to the inner peripheral surface of the cylindrical case at the other of the side end portions. The catalytic converter in any one of 1-3.

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