JP6433064B2 - Exhaust purification device manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing an exhaust gas purification apparatus including a heat insulating exhaust circulation pipe provided in an exhaust pipe line of an automobile.

  2. Description of the Related Art Conventionally, there has been known an exhaust purification device that can ensure an exhaust gas temperature necessary for combustion of particulate matter in an exhaust pipe of an automobile (see Patent Document 1). This exhaust purification device has a catalytic converter composed of a cylindrical body, a cone-shaped upstream end, and a cone-shaped downstream end, and the catalytic converter has a clamshell structure that combines a pair of halves of the same shape It has become. The half-shaped body is formed of a two-layer structure comprising an outer shell and an inner shell having a diameter smaller than that of the outer shell, and the flange of the outer shell and the flange of the inner shell projecting in the radial direction are welded together, A pair of halves are welded at the flange portion to form a cylindrical shape.

  A sealed space is formed between the inner shell and the outer shell at the cylindrical body, the upstream end portion, and the downstream end portion, and the air in the sealed space is sucked by the decompression pump so that the sealed space becomes a decompressed air layer. It has become. That is, the cylindrical body, the upstream end, and the downstream end are provided with heat insulation by the reduced pressure air layer between the inner shell and the outer shell so that the exhaust gas temperature necessary for the combustion of the particulate matter can be secured. Make up the tube.

JP 2007-205336 A

  By the way, the temperature of the exhaust gas in the exhaust pipe of an automobile is maintained by not only burning particulate matter collected by a collection filter, but also purifying by oxidizing and reducing harmful substances contained in the exhaust gas with a catalyst. Insulating exhaust gas distribution pipes play a major role in maintaining the exhaust gas temperature.

  However, the catalytic converter corresponding to the adiabatic exhaust circulation pipe of Patent Document 1 conducts heat to the flange portion extending in the pipe direction of the pair of halves, and the flange portion functions like a heat sink. Since it has a pipe structure that dissipates heat, it is inferior to the heat insulation level of the pipe structure itself. Therefore, when the sealed space is an atmospheric pressure air layer, it is difficult to ensure the required heat insulation, and it is essential to depressurize the sealed space to form a reduced pressure air layer. Moreover, since the operation | work which welds the part of the both flanges extended long in an exhaust pipe line direction is needed, there also exists a malfunction that the effort which a welding operation requires becomes large.

The present invention is proposed in view of the above problems, and the level of heat insulation of the pipe structure itself is very high, so that the exhaust gas temperature in the exhaust pipe of the automobile can be more reliably maintained, and the necessary welding is performed. It is an object of the present invention to provide a method for manufacturing an exhaust gas purification apparatus including an adiabatic exhaust gas distribution pipe that can greatly reduce work.

The manufacturing method of the exhaust emission control device of the present invention includes an inner cylinder having a substantially curved outer circumferential surface over the circumferential direction, and a substantially curved outer circumferential surface over the circumferential direction. An outer cylinder provided on the outer periphery of the inner cylinder so that the end and the other end abut each other along the outer peripheral surface of the inner cylinder, and the one end and the other end respectively. The inner cylinder and the outer cylinder are welded circumferentially, and the outer peripheral surface of the inner cylinder and the inner peripheral surface of the outer cylinder are spaced apart from each other between the one end and the other end. Is formed, and the exhaust gas purification apparatus includes a heat insulating exhaust circulation pipe in which the air gap forms an air layer, and an exhaust gas purification body stationaryly accommodated in the inner cylinder of the heat insulating exhaust gas circulation pipe. A tubular inner cylinder base material is used, and the exhaust pipe is inserted into the inner cylinder base material so that the pipe of the inner cylinder base material extends. The inner cylinder straight pipe part and the inner cylinder taper part are formed on both sides of the inner cylinder by spinning, thereby forming the inner cylinder taper part on both sides of the inner cylinder base part, and on the tip side of the inner cylinder taper part on both sides, respectively. The inner cylinder is formed with the inner cylinder straight pipe portion having a smaller diameter than the inner cylinder base, and a straight tubular outer cylinder base material is used, upstream of the exhaust pipe in the direction in which the pipe of the outer cylinder base material extends. The outer cylinder straight pipe part and the outer cylinder taper part are formed by spinning, thereby forming the outer cylinder taper part on the exhaust pipe upstream side of the outer cylinder base part, and the outer cylinder on the tip side of the outer cylinder taper part. By forming the straight tube portion of the outer cylinder having a smaller diameter than the base portion, and forming a contact portion on the downstream side of the exhaust pipe in the direction in which the tube of the outer tube base material extends by reducing the diameter of the exhaust pipe, A first step of forming the outer cylinder having the contact portion on the downstream side of the path; and an exhaust pipe downstream side of the outer cylinder A second step of interposing the inner cylinder and abutting and aligning the inner cylinder straight pipe portion on the upstream side of the exhaust pipe and the outer cylinder straight pipe section; and the inner cylinder straight pipe on the upstream side of the exhaust pipe The inner cylinder and the outer cylinder are circumferentially welded at a predetermined position of the outer cylinder and the outer cylinder straight pipe section, and the inner cylinder and the outer cylinder are welded at a position where the contact portion of the outer cylinder contacts the inner cylinder. And a third step of welding the tube in a circumferential shape .
According to this, by the pipe structure in which the inner cylinder and the outer cylinder have a substantially curved outer peripheral surface in the circumferential direction, a part that significantly reduces the heat insulation property such as a flange extending in the pipe line direction can be eliminated. The level of thermal insulation of the tube structure itself can be greatly increased. Therefore, it is possible to more reliably keep the exhaust gas temperature in the exhaust pipe of the automobile. For example, even when the air layer between the inner cylinder and the outer cylinder is an atmospheric air layer, the required exhaust gas temperature can be reduced. Keep warm. In addition, it reduces the time-consuming welding work such as welding of flanges that extend in the direction of the exhaust pipe, and basically only welds the inner and outer cylinders circumferentially at one end and the other end. Since the pipe structure can be configured, the required welding work can be greatly reduced. Furthermore, since an air heat insulation layer is provided only at a location necessary for exhaust purification, and it is only necessary to form an abutting portion on the downstream side of the exhaust pipe without providing an air heat insulation layer between the tapered portions. Improvement and reduction in manufacturing cost can be achieved. In addition, the exhaust gas purification device can be obtained in which high-temperature exhaust gas is reliably supplied to the exhaust gas purification body with a highly heat insulating pipe structure, and an exhaust gas purification device that is extremely excellent in exhaust gas purification performance can be obtained. Also, the inner cylinder straight pipe part and the inner cylinder taper part, the outer cylinder straight pipe part and the outer cylinder taper part are formed by spinning process, and the contact part is formed by diameter reduction process by a reduced diameter mold, thereby causing plastic deformation. The strength of the tube structure can be increased by improving the rigidity by increasing the moment of inertia of the cross section of the spiral irregularities formed by work hardening and spinning, and by increasing the wall thickness by reducing the diameter. In addition, when the air layer is a reduced pressure air layer, the inner cylinder taper portion and the outer cylinder taper portion having high strength can more reliably prevent dents due to depressurization, thereby improving the strength and stability of the exhaust purification device. Can be increased.

The manufacturing method of the exhaust emission control device of the present invention includes an inner cylinder having a substantially curved outer circumferential surface over the circumferential direction, and a substantially curved outer circumferential surface over the circumferential direction. An outer cylinder provided on the outer periphery of the inner cylinder so that the end and the other end abut each other along the outer peripheral surface of the inner cylinder, and the one end and the other end respectively. The inner cylinder and the outer cylinder are welded circumferentially, and the outer peripheral surface of the inner cylinder and the inner peripheral surface of the outer cylinder are spaced apart from each other between the one end and the other end. Is formed, and an air purifying apparatus is provided with a heat insulating exhaust circulation pipe in which the air gap constitutes an air layer, and an exhaust gas purification body that is stationaryly accommodated in the inner cylinder of the heat insulating exhaust gas distribution pipe. In the direction in which the pipe of the inner cylinder base material extends, the exhaust purification body is inserted into the inner cylinder base material. The inner cylinder straight pipe part and the inner cylinder taper part are formed on the side by spinning, so that the inner cylinder taper part is formed on both sides of the inner cylinder base part, and the inner cylinder taper part is respectively formed on the tip side of the inner cylinder taper part on both sides. Forming the inner cylinder in which the inner cylinder straight pipe portion having a smaller diameter than the cylinder base is formed, using a flat outer cylinder base material, the outer cylinder base material on the outer cylinder base, and on the exhaust pipe of the outer cylinder base An outer cylinder taper part on the flow side, an outer cylinder straight pipe part positioned on the exhaust pipe upstream side of the outer cylinder taper part and having a smaller diameter than the outer cylinder base part is formed by drawing press processing, and the outer cylinder base part A first step of forming the outer cylinder having the abutting portion on the downstream side of the exhaust pipe by forming the abutting portion on the opposite side of the cylindrical taper portion by a diameter reducing process using a reduced diameter mold; and the outer cylinder The inner cylinder is inserted from the exhaust pipe downstream side of the exhaust pipe, and the inner cylinder straight pipe part and the outer cylinder straight pipe part on the upstream side of the exhaust pipe are in contact with each other And aligning the inner cylinder and the outer cylinder circumferentially at predetermined positions of the inner cylinder straight pipe section and the outer cylinder straight pipe section on the upstream side of the exhaust pipe, and the outer cylinder And a third step of welding the inner cylinder and the outer cylinder in a circumferential shape at a position where the abutting portion abuts on the inner cylinder .
According to this, by the pipe structure in which the inner cylinder and the outer cylinder have a substantially curved outer peripheral surface in the circumferential direction, a part that significantly reduces the heat insulation property such as a flange extending in the pipe line direction can be eliminated. The level of thermal insulation of the tube structure itself can be greatly increased. Therefore, it is possible to more reliably keep the exhaust gas temperature in the exhaust pipe of the automobile. For example, even when the air layer between the inner cylinder and the outer cylinder is an atmospheric air layer, the required exhaust gas temperature can be reduced. Keep warm. In addition, it reduces the time-consuming welding work such as welding of flanges that extend in the direction of the exhaust pipe, and basically only welds the inner and outer cylinders circumferentially at one end and the other end. Since the pipe structure can be configured, the required welding work can be greatly reduced. Furthermore, since an air heat insulation layer is provided only at a location necessary for exhaust purification, and it is only necessary to form an abutting portion on the downstream side of the exhaust pipe without providing an air heat insulation layer between the tapered portions. Improvement and reduction in manufacturing cost can be achieved. In addition, the exhaust gas purification device can be obtained in which high-temperature exhaust gas is reliably supplied to the exhaust gas purification body with a highly heat insulating pipe structure, and an exhaust gas purification device that is extremely excellent in exhaust gas purification performance can be obtained. In addition, the inner cylinder straight pipe part and the inner cylinder taper part are formed by spinning, the outer cylinder straight pipe part and the outer cylinder taper part are formed by drawing press work, and the contact part is formed by diameter reduction processing by a reduced diameter mold. By doing so, it is possible to increase the strength of the tube structure by improving work rigidity by plastic deformation, increasing rigidity by increasing the moment of section in the spiral irregularities formed by spinning process, and increasing the wall thickness by reducing the diameter. In addition, when the air layer is a reduced pressure air layer, the inner cylinder taper portion and the outer cylinder taper portion having high strength can more reliably prevent dents due to depressurization, thereby improving the strength and stability of the exhaust purification device. Can be increased. Moreover, the processing cost can be further reduced by using the drawing press processing.

The exhaust purification device manufacturing method according to the present invention includes a circumferential direction between the inner cylinder base and the outer cylinder base and between the inner cylinder taper and the outer cylinder taper upstream of the exhaust pipe. The air layer which is continuous in a series is provided.
According to this, since a continuous air layer is provided in the circumferential direction in a state where there is no portion that reduces heat insulation across the entire gap between the base portions and between the taper portions, the level of heat insulation is improved. This can be further improved. For example, when an exhaust purification body such as a catalyst carrier, a collection filter, or both of them is accommodated in the inner cylinder base, the required exhaust purification performance is secured and maintained by keeping the exhaust gas temperature by a highly heat insulating tube structure. Can be achieved.

The method for manufacturing an exhaust emission control device according to the present invention is characterized in that the air layer of the heat insulating exhaust circulation pipe is a decompressed air layer.
According to this , the heat insulation level can be further improved by making the air layer a reduced pressure air layer. In addition, since the heat-insulated exhaust circulation pipe can be formed with a small number of welding locations, it is possible to reduce a decrease in yield due to poor welding when a reduced pressure air layer is used, and to reduce the risk of air flowing in due to breakage of the welded portion. It becomes possible to maintain the reduced pressure state of the reduced pressure air layer for a long period of time, and the stability of the reduced pressure state can be improved.

  According to the present invention, the level of heat insulation of the pipe structure itself is very high, the temperature of the exhaust gas in the automobile exhaust pipe can be more reliably maintained, and the necessary welding work can be greatly reduced. It is possible to obtain a heat insulating exhaust flow pipe that can be produced, and a highly heat insulating exhaust gas purification device that includes this heat insulating exhaust flow pipe.

(A) is a front view of an exhaust emission control device provided with the heat insulation exhaust circulation pipe of 1st Embodiment by this invention, (b) is the longitudinal cross-sectional view. (A)-(d) is sectional explanatory drawing explaining the 1st example of a process until it forms the inner cylinder in which the exhaust gas purification body was inserted from the straight tubular inner cylinder base material in 1st Embodiment. (A)-(c) is sectional explanatory drawing explaining the 2nd example of the process until it forms the inner cylinder in which the exhaust gas purification body was inserted from the straight tubular inner cylinder base material in 1st Embodiment. Cross-sectional explanatory drawing explaining the process of forming an outer cylinder taper part and an outer cylinder straight pipe part in the one side of a straight tubular outer cylinder member in 1st Embodiment. (A)-(c) is a process until an inner cylinder is inserted into an outer cylinder base material in which an outer cylinder taper part and an outer cylinder straight pipe part are formed on one side in the first embodiment to form an exhaust purification device. FIG. (A)-(d) is sectional explanatory drawing which shows the example of a welding part. (A) is a front view of an exhaust emission control device provided with the heat insulation exhaust flow pipe of 2nd Embodiment by this invention, (b) is the longitudinal cross-sectional view. (A), (b) is sectional explanatory drawing explaining the example of a process until it forms an outer cylinder from a straight tubular outer cylinder base material in 2nd Embodiment. (A)-(c) is sectional explanatory drawing explaining the example of a process until it forms an outer cylinder from a flat outer cylinder base material in 2nd Embodiment. Cross-sectional explanatory drawing which shows the state which inserted the inner cylinder in the outer cylinder in 2nd Embodiment.

[Adiabatic Exhaust Gas Distribution Pipe, Exhaust Purification Device, and Manufacturing Method Thereof]
As shown in FIG. 1, the heat insulation exhaust gas distribution pipe 1 of the first embodiment constitutes a part of an exhaust gas purification device 10 in which an exhaust gas purification body 11 is stationaryly accommodated, and is substantially over the circumferential direction. An inner cylinder 2 having a curved outer peripheral surface and an outer cylinder 3 having a substantially curved outer peripheral surface in the circumferential direction are provided. The inner cylinder 2 and the outer cylinder 3 are each made of metal and integrally formed from one metal base material. For example, the inner cylinder 2 has a thin wall thickness of 0.8 to 2.0 mm. The wall thickness is set to 0.6 to 2.0 mm.

  The inner cylinder 2 has a substantially cylindrical inner cylinder base 21, and inner cylinder taper portions 22a and 22b are formed on both sides thereof. The inner cylinder taper portions 22a and 22b are each formed in a cone shape that gradually decreases in diameter from the inner cylinder base portion 21 toward the tip, and the inner cylinder taper portions 22a and 22b have a smaller diameter than the inner tube base portion 21 on the tip side. Substantially cylindrical inner tube straight pipe portions 23a and 23b are formed, respectively. In this example, the inner cylinder taper part 22a and the inner cylinder straight pipe part 23a are arranged on the exhaust pipe upstream side, the inner cylinder taper part 22b and the inner cylinder straight pipe part 23b are arranged on the exhaust pipe downstream side, and the inner cylinder The straight pipe portions 23a and 23b are respectively connected to other exhaust pipes constituting an exhaust pipe line not shown.

  The outer cylinder 3 also has a substantially cylindrical outer cylinder base 31, and outer cylinder taper portions 32a and 32b are formed on both sides thereof. The outer cylinder taper portions 32 a and 32 b are also formed in a cone shape that gradually decreases in diameter from the outer cylinder base portion 31 toward the tip, and the outer cylinder taper portions 32 a and 32 b have a smaller diameter than the outer tube base portion 31 on the tip side. Substantially cylindrical outer tube straight pipe portions 33a and 33b are respectively formed. In this example, the outer cylinder taper part 32a and the outer cylinder straight pipe part 33a are arranged on the exhaust pipe upstream side, and the outer cylinder taper part 32b and the outer cylinder straight pipe part 33b are arranged on the exhaust pipe downstream side, The straight pipe portions 33a and 33b are connected to other exhaust pipes constituting exhaust pipes (not shown).

  The outer cylinder 3 is provided on the outer periphery of the inner cylinder 2 so that one end in the exhaust pipe direction and the other end abut each other along the outer peripheral surface of the inner cylinder 2. In the first embodiment, the outer cylinder straight pipe portions 33a and 33b corresponding to one end and the other end of the outer cylinder 3 are arranged along the outer peripheral surfaces of the inner cylinder straight pipe portions 23a and 23b of the inner cylinder 2, respectively. The outer cylinder 3 is provided on the outer periphery of the inner cylinder 2 so as to abut.

  The outer cylinder 3 is welded circumferentially to the inner cylinder 2 at outer cylinder straight pipe portions 33a and 33b corresponding to one end and the other end. In the illustrated example, the outer cylinder 3 is connected to the tip of the outer cylinder straight pipe portion 33a. The tip of the inner cylinder straight pipe portion 23a is joined by the welded portion 4a by edge welding, and the tip of the outer cylinder straight pipe portion 33b and the tip of the inner cylinder straight pipe portion 23b are joined by the welded portion 4b by edge welding. (See FIG. 6A).

  In addition, the welding part which welds the outer cylinder 3 and the inner cylinder 2 circumferentially in one edge part and the other edge part is not limited to the welding parts 4a and 4b by edge welding, and is suitable in the applicable range. For example, as shown in FIG. 6 (b), the outer cylinder straight pipe portions 33a and 33b and the inner cylinder straight pipe portions 23a and 23b are in contact with each other in a plane shape, such as a welded portion 41a by lap welding of penetration or non-penetration welding. When the inner cylinder straight pipe portion 23a of the inner cylinder 2 protrudes from the structure to be welded or the outer cylinder straight pipe portion 33a of the outer cylinder 3, as shown in FIG. 6C, the outer cylinder straight pipe portion 33a. The tip of the inner tube and the outer peripheral surface portion of the inner cylinder straight pipe portion 23a are welded by a welded portion 42a or the like by overlap fillet welding, or the outer cylinder straight portion of the outer cylinder 3 rather than the inner cylinder straight pipe portion 23a of the inner cylinder 2 When the pipe part 33a protrudes, as shown in FIG. 6 (d), the tip of the inner cylinder straight pipe part 23a and the inner peripheral surface of the outer cylinder straight pipe part 33a It is possible to adopt a configuration such that the weld at the weld portion 43a due fillet welding overlapping portions. Moreover, the welding method to apply is appropriate in the range which can be applied, such as laser welding, seam welding, and arc welding.

  A gap 5 is formed between the one end and the other end of the inner cylinder 2 and the outer cylinder 3 so that the outer peripheral surface of the inner cylinder 2 and the inner peripheral surface of the outer cylinder 3 are separated from each other. In the first embodiment, between the outer peripheral surface of the inner cylindrical taper portion 22a and the inner peripheral surface of the outer cylindrical taper portion 32a, the outer peripheral surface of the inner cylindrical base portion 21 and the inner peripheral surface of the outer cylindrical base portion 31 And a gap 5 is formed between the outer peripheral surface of the inner cylindrical tapered portion 22b and the inner peripheral surface of the outer cylindrical tapered portion 32b.

  The gap 5 is formed so as to be continuous in the circumferential direction over the entire length thereof, and the entire gap 5 becomes an air layer A, and the air layer continues in the circumferential direction over the entire length of the gap 5. A is provided. The height of the gap 5 or the layer thickness of the air layer A is preferably about 0.5 mm to 10 mm. In addition, the air layer A may be a normal atmospheric pressure air layer, but when a higher degree of heat insulation is required, it is preferable that the air layer A be a reduced pressure air layer whose pressure is reduced from the atmospheric pressure. In the case of a reduced pressure air layer, the atmosphere is finally sucked from the planned welding location by a vacuum pump immediately before forming the welded portion 4b etc. for final welding, and the final state is maintained so that the state is maintained. A welded portion 4b and the like are formed.

  In the heat insulation exhaust gas flow pipe 1 of the first embodiment, the exhaust gas purification body 11 is stationaryly accommodated in the inner cylinder base portion 21 which is the inner cylinder 2, and the exhaust gas purification device 10 is configured. In the illustrated example, a holding mat 12 formed of alumina fiber or ceramic fiber is interposed between the inner peripheral surface of the inner cylinder base 21 and the exhaust purification body 11, and the inner cylinder base 21 has an inner periphery. The exhaust purification body 11 is fixed by being pressed from the periphery by the peripheral surface and the holding mat 12. The exhaust purification body 11 is appropriate as long as it has a function of purifying exhaust gas. For example, a catalyst carrier that oxidizes and reduces harmful substances contained in exhaust gas with a catalyst, a collection filter that collects particulate matter, or Both of them can be used.

  When manufacturing the exhaust purification device 10 including the heat insulating exhaust circulation pipe 1 of the first embodiment, for example, a straight tubular inner cylinder base material 20 is used, and the exhaust purification body 11 is inserted into the inner cylinder base material 20. Thus, the inner cylinder 2 is formed by forming the inner cylinder straight pipe portions 23a, 23b and the inner cylinder taper portions 22a, 22b on both sides of the inner cylinder base material 20 in the direction in which the pipe extends.

  An example of this process is shown in FIG. In the process example of FIG. 2, first, the exhaust gas purification body 11 in which the holding mat 12 is provided around the straight tubular inner base material 20 is inserted to a substantially intermediate portion corresponding to the inner cylinder base 21 (FIG. 2A). reference). Thereafter, the inner cylinder base material 20 is held by the clamp 101 and subjected to spinning processing by one or a plurality of rollers 102, and the inner cylinder straight pipe portion 23a and the inner cylinder base pipe 20a are formed on one side in the tube extending direction of the inner cylinder base material 20. The cylindrical taper portion 22a is formed by spinning (see FIG. 2B).

  Further, the outer peripheral surface of the portion corresponding to the inner cylinder base portion 21 is subjected to spinning processing, and the diameter of the portion is slightly reduced so that the holding mat 12 and the exhaust purifier 11 are pressed by the inner peripheral surface. The exhaust purifying body 11 is placed at a portion corresponding to the inner cylinder base 21 (see FIG. 2C). Thereafter, the other cylinder in the direction in which the pipe of the inner cylinder base material 20 extends is also spun by the roller 102, and the inner cylinder straight pipe part 23b and the inner cylinder taper part 22b are formed by spinning to obtain the inner cylinder 2. (See FIG. 2 (d)).

  The holding mat 12 and the exhaust purifying body 11 are placed in the inner cylinder base material 20 in addition to the placement in the step of FIG. 2C, for example, after the insertion of FIG. 2 or the process of forming inner cylinder straight pipe portions 23a, 23b and inner cylinder taper portions 22a, 22b on one side and the other side, or FIG. After the holding mat 12 provided around the exhaust purifying body 11 is press-fitted from the inner peripheral surface of the inner cylinder base material 20 and the holding mat 12 and the exhaust purifying body 11 are fixed by this press-fitting, It is also possible to use a process of forming the inner cylinder straight pipe portions 23a, 23b and the inner cylinder taper portions 22a, 22b on the one side and the other side.

  Moreover, it is also possible to use another process example of FIG. 3 instead of the process example of FIG. In the process example of FIG. 3, the inner cylinder base material 20 is held by a clamp 101 and subjected to spinning processing by one or a plurality of rollers 102. The pipe part 23a and the inner cylinder taper part 22a are formed by spinning (see FIG. 3A).

  Next, the exhaust purification body 11 around which the holding mat 12 is provided is press-fitted and inserted into a portion corresponding to the inner cylinder base 21 to place the holding mat 12 and the exhaust purification body 11 (see FIG. 3B). . Note that, instead of being fixed by press-fitting, after insertion of the exhaust purification body 11 around which the holding mat 12 is provided, the outer peripheral surface of a portion corresponding to the inner cylinder base portion 21 or a part thereof is subjected to a spinning process or the like to reduce the diameter. The holding mat 12 and the exhaust purifying body 11 may be stationary. Thereafter, the other cylinder in the direction in which the pipe of the inner cylinder base material 20 extends is also spun by the roller 102, and the inner cylinder straight pipe part 23b and the inner cylinder taper part 22b are formed by spinning to obtain the inner cylinder 2. (See FIG. 3C).

  In addition, if the process which spins also the part corresponding to the whole outer peripheral surface of the inner cylinder base part 21 and the whole outer peripheral surface of the outer cylinder base part 31 is used, work hardening by plastic deformation and thickness increase by diameter reduction will increase the pipe structure. The strength can be increased, which is favorable. In particular, when the air layer A is a reduced pressure air layer, the dent can be more reliably prevented.

  A part of the processing to the outer cylinder base material 30 is performed before, after or in parallel with the formation of the inner cylinder 2. That is, a straight tubular outer base material 30 is used, and as shown in FIG. 4, the outer cylindrical base material 30 is held by a clamp 101 and subjected to spinning processing by one or a plurality of rollers 102. The outer cylinder straight pipe part 33a and the outer cylinder taper part 32a are formed by spinning on one side in the direction in which the 30 pipes extend.

  Then, as shown in FIG. 5 (a), the inner cylinder 2 is inserted from the other side of the outer cylinder base material 30 in which the outer cylinder straight pipe part 33a and the outer cylinder taper part 32a are formed on one side, The inner cylinder straight pipe part 23a and the one-side outer cylinder straight pipe part 33a are aligned. The inner tube straight pipe portion 23a on one side and the outer tube straight tube portion 33a on one side are formed with a diameter and size that come into contact with each other in advance. In the aligned state, the inner tube straight tube portion 23a and the one side The outer tube straight pipe portion 33a comes into contact therewith.

  Next, the inner cylinder 2 and the outer cylinder base material 30 are welded circumferentially at predetermined positions of the inner cylinder straight pipe part 23a on one side and the outer cylinder straight pipe part 33a on the one side. In the example of FIG. 5 (a), the tip of the outer cylinder straight pipe portion 33a and the tip of the inner cylinder straight pipe portion 23a are welded by the welded portion 4a by edge welding. You may weld with a welding part like.

  Thereafter, as shown in FIG. 5 (b), the other cylinder in the direction in which the pipe of the outer cylinder base material 30 extends is also spun by the roller 102 to spin the outer cylinder straight pipe part 33b and the outer cylinder taper part 32b. Thus, the outer cylinder 3 having the outer cylinder straight pipe portion 33b and the outer cylinder taper portion 32b on the other side is obtained. At this time, the outer cylinder straight pipe portion 33 b is formed so as to contact the inner cylinder straight pipe portion 23 b of the inner cylinder 2.

  Thereafter, the inner cylinder 2 and the outer cylinder 3 are welded circumferentially at predetermined positions of the other-side inner cylinder straight pipe portion 23b and the other-side outer cylinder straight pipe portion 33b. Complete. In the example of FIG. 5C, the tip of the outer cylinder straight pipe portion 33b and the tip of the inner cylinder straight pipe portion 23b are welded by the welded portion 4b by edge welding. You may weld with a welding part like.

  According to the first embodiment, the tubular structure in which the inner cylinder 2 and the outer cylinder 3 have a substantially curved outer circumferential surface in the circumferential direction, such that the heat insulation is remarkably reduced like a flange extending in the pipeline direction. Can be eliminated, and the level of thermal insulation of the tube structure itself can be greatly increased. Accordingly, it is possible to more reliably keep the exhaust gas temperature in the exhaust pipe of the automobile. For example, it is necessary even when the air layer A between the inner cylinder 2 and the outer cylinder 3 is an atmospheric pressure air layer. It is possible to keep the exhaust gas temperature warm.

  Furthermore, the taper portions 22a and 32a, the base portions 21 and 31, and the gap 5 between the taper portions 22b and 32b are continuously continuous in the circumferential direction without any portion that reduces the heat insulation property. Since the air layer A is provided, the heat insulation level can be further improved. Further, in the exhaust purification device 10 in which the exhaust purification body 11 such as a catalyst carrier, a collection filter, or both of them is accommodated in the inner cylinder base 21, the required purification performance is achieved by keeping the exhaust gas temperature warm by the highly heat insulating tube structure. The exhaust purification device 10 can be secured and maintained, and can exhibit the purification performance even when the engine is started when the exhaust purification device 10 is cold. Thus, the exhaust purification device 10 having extremely excellent exhaust purification performance can be obtained.

  Further, it is possible to reduce time-consuming welding work such as welding of a flange extending long in the direction of the exhaust pipe, and basically the inner cylinder 2 and the outer cylinder 3 are welded circumferentially at one end and the other end. Since the pipe structure can be configured only by this, the required welding work can be greatly reduced.

  Further, when the air layer A is a reduced pressure air layer, the level of heat insulation can be further improved. Furthermore, since the heat-insulating exhaust circulation pipe 1 can be formed with a small number of welding locations, it is possible to reduce the yield reduction due to the welding failure and the reduced pressure state being opened, and the atmosphere is caused by damage to the welds 4a and 4b. The risk of flowing in can be reduced, the reduced pressure state of the reduced pressure air layer can be easily maintained over a long period of time, and the stability of the reduced pressure state can be enhanced.

  Further, when forming the heat insulation exhaust flow pipe 1 or the exhaust purification device 10, the inner cylinder straight pipe portions 23a, 23b, the inner cylinder taper portions 22a, 22b, the outer cylinder straight pipe portions 33a, 33b, and the outer cylinder taper portion 32a, By forming 32b by spinning process, work hardening by plastic deformation, rigidity improvement by increasing the moment of section in spiral irregularities formed by spinning process, and increasing the strength of pipe structure by increasing wall thickness by reducing diameter Can do. Further, when the air layer A is a reduced pressure air layer, the strong inner cylinder taper portions 22a and 22b and the outer cylinder taper portions 32a and 32b can more reliably prevent the depression due to the reduced pressure, and the adiabatic exhaust. The strength and stability of the flow pipe 1 and the exhaust purification device 10 can be increased.

[Adiabatic Exhaust Flow Pipe, Exhaust Purification Device, and Manufacturing Method Thereof]
As shown in FIG. 7, the heat insulating exhaust circulation pipe 1 m of the second embodiment constitutes a part of the exhaust purification device 10 m in which the exhaust purification body 11 is stationaryly accommodated, and is substantially extending in the circumferential direction. An inner cylinder 2 having a curved outer peripheral surface and an outer cylinder 3m having a substantially curved outer peripheral surface in the circumferential direction are provided. The inner cylinder 2 and the outer cylinder 3m are each made of metal and are integrally formed from one metal base material. For example, the inner cylinder 2 is thin with a thickness of 0.8 to 2.0 mm, and the outer cylinder 3m. The wall thickness is set to 0.6 to 2.0 mm.

  The inner cylinder 2 is the same as the inner cylinder 2 in the first embodiment, and the exhaust purifying body 11 is fixedly housed in the inner cylinder base portion 21 in the inner cylinder 2 as in the first embodiment. In the illustrated example, a holding mat 12 is provided between the inner peripheral surface of the inner cylinder base 21 and the exhaust purifying body 11 and is pressed from the periphery by the inner peripheral surface of the inner cylinder base 21 and the holding mat 12. An exhaust purification body 11 is placed. The exhaust purification body 11 and the holding mat 12 can be the same as those in the first embodiment.

  The outer cylinder 3 m has a substantially cylindrical outer cylinder base 31. An outer cylinder taper part 32 a is formed on the upstream side of the outer cylinder base 31 on the exhaust pipe line, and the outer cylinder taper part 32 a extends from the outer cylinder base 31. It is formed in a cone shape that gradually decreases in diameter. A substantially cylindrical outer tube straight pipe portion 33a having a smaller diameter than the outer tube base portion 31 is formed on the distal end side of the outer tube taper portion 32a. Further, an abutting portion 34m is formed on the exhaust pipe downstream side of the outer cylinder base 31 and bent inward so as to abut on the outer peripheral surface of the inner cylinder base 31 or the inner cylinder taper portion 22b on the downstream side of the exhaust pipe. In the illustrated example, a contact portion 34m is formed on the inner cylinder base 31 so as to extend along the outer peripheral surface through an inclined portion that is tapered inwardly from the outer cylinder base 31. Yes.

  In this example, the inner cylinder straight pipe part 23a and the outer cylinder straight pipe part 33a arranged on the exhaust pipe upstream side and the inner cylinder straight pipe part 23b arranged on the exhaust pipe downstream side are not shown. It connects with another exhaust pipe which comprises a pipe line.

  The outer cylinder 3m is provided on the outer periphery of the inner cylinder 2 so that one end in the exhaust pipe direction and the other end abut each other along the outer peripheral surface of the inner cylinder 2. In the second embodiment, the outer cylinder straight pipe portion 33a corresponding to one end portion of the outer cylinder 3m is abutted along the outer peripheral surface of the inner cylinder straight pipe portion 23a of the inner cylinder 2, and the other end of the outer cylinder 3m is contacted. An abutting portion 34 m corresponding to the portion abuts along the outer peripheral surface of the inner cylinder base 21 of the inner cylinder 2.

  The outer cylinder 3m is welded circumferentially to the inner cylinder 2 at an outer cylinder straight pipe portion 33a corresponding to one end portion and an abutting portion 34m corresponding to the other end portion. The tip of the portion 33a and the tip of the inner cylinder straight pipe portion 23a are joined by a welded portion 4a by edge welding, and the tip of the abutting portion 34m and the outer peripheral surface of the inner cylinder base 21 are welded by overlap fillet welding. Joined at 4m. The welded portion between the tip of the welded portion 34m and the outer peripheral surface of the inner cylinder base portion 21 may be a welded portion by other welding such as a welded portion by lap welding of penetration or non-penetration welding in FIG. It is possible, and within the applicable range, the same welded portion structure and welding type as in the first embodiment can be used.

  Between the one end and the other end of the inner cylinder 2 and the outer cylinder 3m, the outer peripheral surface of the inner cylinder 2 and the inner peripheral surface of the outer cylinder 3m are spaced apart to form a gap 5m. In the second embodiment, between the outer peripheral surface of the inner cylindrical taper portion 22a on the exhaust pipe upstream side and the inner peripheral surface of the outer cylindrical taper portion 32a, the outer peripheral surface of the inner cylindrical base portion 21 and the outer cylindrical base portion. An air gap 5 m is formed between the inner peripheral surface of 31.

  The gap 5m is formed so as to be continuous in the circumferential direction over the entire length thereof, and the entire gap 5m becomes an air layer A ′, and the air continues in the circumferential direction over the entire length of the gap 5m. Layer A ′ is provided. The height of the gap 5 m or the thickness of the air layer A ′ is preferably about 0.5 mm to 10 mm. In addition, the air layer A ′ may be a normal atmospheric pressure air layer, but if a higher degree of heat insulation is required, the air layer A ′ is a reduced pressure air layer that is depressurized from the atmospheric pressure as in the first embodiment. It is preferable. In the case of a reduced pressure air layer, the atmosphere is sucked with a vacuum pump from the planned welding point immediately before forming the welded portion 4a or 4m for final welding, and the final pressure is maintained so that the state is maintained. A typical weld 4a or 4m is formed.

  When manufacturing the exhaust emission control device 10m including the heat insulating exhaust circulation pipe 1m of the second embodiment, the inner cylinder 2 is formed as in the first embodiment, and before, after or in parallel with the formation of the inner cylinder 2. Then, the outer cylinder base material 30m is processed. That is, a straight tubular outer base material 30m is used, and as shown in FIG. 8, the outer cylindrical base material 30m is held by a clamp 101 and subjected to spinning processing by one or a plurality of rollers 102. The outer cylinder straight pipe part 33a and the outer cylinder taper part 32a are formed by spinning on one side in the direction in which the 30 m pipe extends, and the other side is pressed by the diameter reducing mold 103 to reduce the diameter, and on the other side The outer cylinder 3m is formed by forming the contact portion 34m. A split mold can be used as the reduced diameter mold 103.

  At this time, if a step corresponding to the entire outer peripheral surface of the outer cylinder base 31 is used for spinning, work hardening by plastic deformation, rigidity due to an increase in the secondary moment of the cross-section at the spiral irregularities formed by spinning. It is favorable that the strength of the tube structure can be increased by increasing the wall thickness due to the improvement and the diameter reduction, and in particular, when the air layer A is a reduced pressure air layer, it is possible to prevent the dent more reliably.

  In the formation of the outer cylinder 3m, the processing example of FIG. 9 can be used instead of the processing example of FIG. In the example of FIG. 9, a flat outer cylinder base material 30m ′ is used, and the outer cylinder base 31 is provided on the outer cylinder base material 30m ′, the outer cylinder taper portion 32a on the upstream side of the exhaust pipe, and the outer cylinder on the upstream side of the exhaust pipe. The straight pipe portion 33a is formed by drawing press processing, and the flat outer cylinder base material 30m ′ is subjected to drawing press so that the flange 301m ′ is present (see FIG. 9A), and the flange 301m ′ is formed. In addition to down-molding into a cylindrical shape, further drawing press molding, a portion corresponding to the outer cylinder straight pipe portion 33a is raised by burring molding, and the outer cylinder straight pipe portion 33a on one side in the tube extending direction And the outer cylinder taper portion 32a (see FIG. 9B), and then the other end is pressed by the diameter reducing mold 103 to reduce the diameter, and the contact portion 34m is formed on the other side. Thus, the outer cylinder 3m is formed (see FIG. 9C).

  After the inner cylinder 2 and the outer cylinder 3m are formed, the inner cylinder 2 is inserted from the side where the contact portion 34m, which is the other side in the direction in which the pipe of the outer cylinder 3m extends, is inserted, and as shown in FIG. The inner cylinder straight pipe portion 23a on one side of the outer cylinder 3m and the outer cylinder straight pipe portion 33a on one side of the outer cylinder 3m are brought into contact with each other, and the abutting portion 34m of the outer cylinder 3m is aligned with the inner cylinder base 21 of the inner cylinder 2. Make contact with the outer peripheral surface.

  Thereafter, the inner cylinder 2 and the outer cylinder 3m are welded circumferentially at predetermined positions of the inner cylinder straight pipe portion 23a and the outer cylinder straight pipe portion 33a, and the abutting portion 34m of the outer cylinder 3m is attached to the inner cylinder 2. The inner cylinder 2 and the outer cylinder 3m are welded in a circumferential shape at the abutting position. In the example of FIG. 7, the distal end of the outer tube straight tube portion 33 a and the distal end of the inner tube straight tube portion 23 a are welded by the welded portion 4 a by edge welding, and the distal end of the contact portion 34 m and the outer peripheral surface of the inner tube base portion 21. And are welded at a weld portion 4 m by fillet welding.

  According to the second embodiment, a continuous air layer in the circumferential direction in a state where there is no portion that reduces the heat insulating property across the entire gap 5m between the base portions 21 and 31 and between the tapered portions 22a and 32a. Since A ′ is provided, the level of heat insulation can be further improved. In the case of the exhaust gas purification device 10, the required exhaust gas purification performance can be ensured by keeping the exhaust gas temperature warm by the highly heat insulating tube structure. Can be maintained. Furthermore, since the air layer A ′ is provided only at a location necessary for exhaust purification, and the abutting portion 34m need only be formed on the downstream side of the exhaust pipe without providing the air layer A ′ between the tapered portions. The production efficiency can be improved and the production cost can be reduced.

  Further, the inner cylinder straight pipe portion 23a and the inner cylinder taper portion 22a, the outer cylinder straight pipe portion 33a and the outer cylinder taper portion 32a are formed by spinning processing, and the contact portion 34m is formed by diameter reduction processing by the diameter reducing mold 103. Manufacturing process or inner cylinder straight pipe part 23a and inner cylinder taper part 22a are formed by spinning process, outer cylinder straight pipe part 33a and outer cylinder taper part 32a are formed by drawing press process, and contact part 34m is reduced in diameter. The manufacturing process formed by reducing the diameter of the mold, the work hardening by plastic deformation, the rigidity improvement by increasing the second moment of section in the spiral irregularities formed by spinning, the strength of the pipe structure by increasing the wall thickness by reducing the diameter Can be increased. Moreover, when drawing press work is used, the processing cost can be further reduced.

  Further, when the air layer A ′ is a reduced pressure air layer, the inner cylinder taper portion 22a and the outer cylinder taper portion 32a having high strength can more reliably prevent the depression due to the reduced pressure, and the heat insulating exhaust circulation pipe 1m. The strength and stability of the exhaust purification device 10m can be improved. In addition, a corresponding effect can be obtained from the configuration corresponding to the first embodiment.

[Modifications of Embodiment, etc.]
The invention disclosed in this specification is specified by changing these partial configurations to other configurations disclosed in this specification within the applicable range in addition to the configurations of each invention and each embodiment, or It includes those specified by adding other configurations disclosed in this specification to these configurations, or those obtained by deleting these partial configurations to the extent that partial effects can be obtained and specifying them as superordinate concepts. . The following modifications are also included.

  For example, the present invention has an appropriately shaped inner cylinder having a substantially curved outer circumferential surface over the circumferential direction, and one end portion in the exhaust pipe direction having a substantially curved outer circumferential surface over the circumferential direction. And the other end of the inner cylinder 2 are included so as to be in contact with each other along the outer peripheral surface of the inner cylinder, and the shapes of the inner cylinder 2, the outer cylinder 3, and 3m of the first and second embodiments are included. For example, the inner cylinder base and the outer cylinder base may be deformed such as an elliptic cylinder or a polygonal cylinder. Moreover, the heat insulation exhaust flow pipe of this invention can be provided in the appropriate location which comprises an exhaust pipe line, and the heat insulation exhaust flow pipe which does not comprise a part of exhaust purification apparatus is also contained in this invention.

Further, in order to cut off the radiant heat and further improve the heat insulating property, copper is formed on the outer peripheral surface of the inner cylinder 2 and the inner peripheral surface of the outer cylinders 3 and 3m in the region including the gaps 5 and 5m or other regions. It is good also as a structure which gives plating, such as plating, or adheres copper foil. Further, from the viewpoint of more effectively improving the rigidity by increasing the moment of inertia of the cross section formed by the spiral irregularities formed by spinning, for example, the thickness of the inner cylinder 2 or the outer cylinder 3, 3m is 0.5 mm to 2 mm. In the case of 0.0 mm, it is preferable to perform a spinning process so that the pitch between the convex portions of the spiral concave and convex portions is 5 mm or less and the height from the bottom of the concave portion of the convex portions is 0.5 mm or more. Even when the layers A and A ′ are depressurized air layers of about 10 ⁻⁶ Pa, it is more sure that dents are generated in the inner cylinder 2 or the outer cylinders 3 and 3 m in contact with the air layers A and A ′. Can be prevented.

  The present invention can be used as, for example, an exhaust purification device provided in an exhaust pipe of an automobile or a normal exhaust pipe.

DESCRIPTION OF SYMBOLS 1, 1m ... Heat insulation exhaust flow pipe 2 ... Inner cylinder 20 ... Inner cylinder base material 21 ... Inner cylinder base part 22a, 22b ... Inner cylinder taper part 23a, 23b ... Inner cylinder straight pipe part 3, 3m ... Outer cylinder 30, 30m, 30m '... outer cylinder base material 31 ... outer cylinder base 32a, 32b ... outer cylinder taper part 33a, 33b ... outer cylinder straight pipe part 34m ... contact part 301m' ... flange 4a, 4b, 41a, 42a, 43a, 4m ... Welded part 5, 5 m ... Air gap A, A '... Air layer 10, 10 m ... Exhaust gas purification device 11 ... Exhaust gas purification body 12 ... Holding mat 101 ... Clamp 102 ... Roller

Claims (4)

An inner cylinder having a substantially curved outer circumferential surface over the circumferential direction, and a substantially curved outer circumferential surface over the circumferential direction, wherein one end and the other end in the exhaust pipe direction are An outer cylinder provided on the outer periphery of the inner cylinder so as to abut each other along the outer peripheral surface of the cylinder, and the inner cylinder and the outer cylinder are circumferentially formed at the one end and the other end, respectively. A gap is formed by welding and the outer peripheral surface of the inner cylinder and the inner peripheral surface of the outer cylinder are separated from each other between the one end and the other end, and the gap constitutes an air layer. A heat-insulating exhaust circulation pipe,
An exhaust purification body fixedly accommodated in the inner cylinder of the heat insulating exhaust circulation pipe;
An exhaust purification device manufacturing method comprising:
An inner cylinder straight pipe portion and an inner cylinder taper portion are provided on both sides of the inner cylinder base material in the direction in which the pipe extends, using a straight tubular inner cylinder base material and inserting the exhaust purification body into the inner cylinder base material. The inner cylinder taper portions are formed on both sides of the inner cylinder base portion by spinning, and the inner cylinder straight pipe portions having a smaller diameter than the inner cylinder base portion are respectively formed on the distal ends of the inner cylinder taper portions on both sides. Forming the formed inner cylinder and using a straight tubular outer cylinder base material, spinning the outer cylinder straight pipe section and the outer cylinder taper section upstream of the exhaust pipe in the direction in which the pipe of the outer cylinder preform extends. The outer cylinder taper portion is formed on the upstream side of the exhaust pipe of the outer cylinder base, and the straight outer tube portion having a smaller diameter than the outer cylinder base is formed on the distal end side of the outer cylinder taper portion. The abutting portion is formed by a diameter reducing process using a diameter reducing mold on the downstream side of the exhaust pipe in the direction in which the pipe of the outer cylinder base material extends. And by a first step of forming said outer cylinder having said contact portion to the exhaust pipe downstream,
A second step of inserting the inner cylinder from the exhaust pipe downstream side of the outer cylinder, and abutting and aligning the inner cylinder straight pipe part and the outer cylinder straight pipe part on the exhaust pipe upstream side;
The inner cylinder and the outer cylinder are welded circumferentially at predetermined positions of the inner cylinder straight pipe portion and the outer cylinder straight pipe portion on the upstream side of the exhaust pipe line, and the contact portion of the outer cylinder is the inner cylinder A third step of welding the inner cylinder and the outer cylinder in a circumferential shape at a position in contact with the outer cylinder;
An exhaust purification device manufacturing method comprising: An inner cylinder having a substantially curved outer circumferential surface over the circumferential direction, and a substantially curved outer circumferential surface over the circumferential direction, wherein one end and the other end in the exhaust pipe direction are An outer cylinder provided on the outer periphery of the inner cylinder so as to abut each other along the outer peripheral surface of the cylinder, and the inner cylinder and the outer cylinder are circumferentially formed at the one end and the other end, respectively. A gap is formed by welding and the outer peripheral surface of the inner cylinder and the inner peripheral surface of the outer cylinder are separated from each other between the one end and the other end, and the gap constitutes an air layer. A heat-insulating exhaust circulation pipe,
An exhaust purification body fixedly accommodated in the inner cylinder of the heat insulating exhaust circulation pipe;
An exhaust purification device manufacturing method comprising:
  An inner cylinder straight pipe portion and an inner cylinder taper portion are provided on both sides of the inner cylinder base material in the direction in which the pipe extends, using a straight tubular inner cylinder base material and inserting the exhaust purification body into the inner cylinder base material. The inner cylinder taper portions are formed on both sides of the inner cylinder base portion by spinning, and the inner cylinder straight pipe portions having a smaller diameter than the inner cylinder base portion are respectively formed on the distal ends of the inner cylinder taper portions on both sides. The formed inner cylinder is formed and a flat outer cylinder base material is used. The outer cylinder base is formed on the outer cylinder base material, the outer cylinder taper portion on the exhaust pipe upstream side of the outer cylinder base portion, and the outer cylinder taper. The outer cylinder straight pipe part, which is located upstream of the outer cylinder base and is smaller in diameter than the outer cylinder base part, is formed by drawing press processing, and the abutting part is compressed on the opposite side of the outer cylinder taper part of the outer cylinder base part. A first process for forming the outer cylinder having the abutting portion on the downstream side of the exhaust pipe by forming by diameter reduction processing with a diameter die. And,
A second step of inserting the inner cylinder from the exhaust pipe downstream side of the outer cylinder, and abutting and aligning the inner cylinder straight pipe part and the outer cylinder straight pipe part on the exhaust pipe upstream side;
The inner cylinder and the outer cylinder are welded circumferentially at predetermined positions of the inner cylinder straight pipe portion and the outer cylinder straight pipe portion on the upstream side of the exhaust pipe line, and the contact portion of the outer cylinder is the inner cylinder A third step of welding the inner cylinder and the outer cylinder in a circumferential shape at a position in contact with the outer cylinder;
An exhaust purification device manufacturing method comprising: The air layer continuously provided in the circumferential direction is provided between the inner cylinder base and the outer cylinder base and between the inner cylinder taper and the outer cylinder taper on the upstream side of the exhaust pipe. A method for manufacturing an exhaust emission control device according to claim 1 or 2. The method for manufacturing an exhaust emission control device according to any one of claims 1 to 3, wherein the air layer of the heat-insulating exhaust circulation pipe is a reduced pressure air layer.

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