JP2006037885A - Double-tube exhaust manifold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a double-tube exhaust manifold capable of securing a smooth flow of exhaust gas and suppressing generation of excessive stress in an entire inner pipe. <P>SOLUTION: The double-tube exhaust manifold 10 has an outer pipe 20 and the inner pipe 30 arranged so as to be separated from the inner peripheral face of the outer pipe 20 by a space part 23. The inner pipe 30 includes a main pipe 50 (first inner pipe) and branch pipes 60, 70 (second inner pipes) joined to the middle of the main pipe 50. The main pipe 50 and branch pipes 60, 70 are arranged inside the outer pipe 20 while forming gaps S between end parts 51a, 52a of opening parts 51, 52 formed on the main pipe 50 and end parts 60a, 70a of the branch pipes 60, 70. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a double pipe exhaust manifold.

  Some exhaust manifolds of vehicles have a double pipe structure in which an inner pipe is coaxially arranged in an outer pipe in order to enhance a heat insulating effect and a soundproofing effect. This type of double-pipe exhaust manifold is made by connecting multiple inner pipes so that they can expand and contract along the axial direction in order to provide the inner pipe with the function of absorbing the difference in thermal expansion between the inner pipe and the outer pipe. (See Patent Document 1).

  In the double-pipe exhaust manifold of Patent Document 1, one inner pipe is formed with a slit along the axial direction at an end thereof, and forms a so-called “monaca-like” connection end (hereinafter, “monaca-like connection”). End ”). The other inner pipe is composed of a pipe member into which one end is inserted into the monaca-like connection end. And the one end part of a pipe member is inserted | pinched from the outer side by a monaca-shaped connection edge part, and the fixing pieces which protrude toward a radial direction outward from the edge of a slit are integrated by welding. Thus, the pipe member and the monaca-like connection end are configured to be slidable even in a close contact state, and the inner pipes are connected to each other while allowing an expansion / contraction movement in the axial direction due to thermal expansion.

  However, in the above connection structure, in order to allow expansion and contraction movement in the axial direction, a straight portion is provided at the pipe member and the monaca-like connection end portion, and the pipe member and the monaca-like connection end portion are positioned on the coaxial straight line. There must be. The exhaust manifold is one of the parts that must be arranged in a limited space around the engine without interfering with other parts. For this reason, when a linear part is provided in a plurality of inner pipes, the bending radius in the curved part must be small (the curvature is large). As a result of the bending radius of the inner tube being reduced, the smooth flow of exhaust gas may be hindered, and bending of the inner tube is also difficult.

Further, the inner tube generally has a three-dimensional complicated bent shape, and not only for expansion and contraction along the axial direction but also for expansion and contraction in the lateral direction (direction perpendicular to the axial direction). Movement is restricted. For this reason, there is a problem that if only the axial expansion and contraction motion is allowed, an unreasonable stress is generated in the inner tube, causing problems such as deformation.
JP 2002-106339 A

  An object of the present invention is to provide a double-pipe exhaust manifold that can ensure a smooth flow of exhaust gas and suppress excessive stress from being generated in the entire inner pipe.

The invention according to claim 1, which achieves the above object, comprises a double-pipe exhaust manifold having an outer pipe and an inner pipe disposed with a space between the inner peripheral surface of the outer pipe.
The inner pipe includes a first inner pipe and a second inner pipe that joins in the middle of the first inner pipe,
The first and second inner pipes are arranged in the outer pipe while forming a gap between the end of the opening formed in the first inner pipe and the end of the second inner pipe. This is a double pipe exhaust manifold.

  Since a gap is formed between the end of the opening formed in the first inner pipe and the end of the second inner pipe, the end of the opening of the first inner pipe and the second Even if the end portion of the inner tube is thermally expanded, contact between the first inner tube and the second inner tube can be prevented.

  When preventing the contact between the first inner pipe and the second inner pipe, it is not necessary to provide a straight portion for allowing the axial expansion and contraction movement at the junction between the first inner pipe and the second inner pipe. Therefore, for the double-pipe exhaust manifold that must be arranged in a limited space, the design flexibility of the first inner pipe and the second inner pipe is increased, and the bending radius at the curved portion is increased (the curvature is reduced). Can do. As a result of the increase in the bending radius of the inner pipe, a smooth flow of exhaust gas can be secured, and the bending of the inner pipe can be facilitated.

  Since the first inner tube and the second inner tube are not in contact with each other, even if the first inner tube and the second inner tube have a three-dimensional complicated bent shape, the first inner tube and the second inner tube Each of the tubes is allowed to relatively freely extend and contract in both the axial direction and the direction perpendicular to the axial direction. Therefore, it is possible to suppress excessive stress from being generated in the entire inner tube, and to prevent deformation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
1A is a perspective view showing the double-pipe exhaust manifold 10 according to the first embodiment, FIG. 1B is a perspective view showing only the inner pipe 30 in FIG. 1A, and FIG. FIG. 2 is a cross-sectional view showing a main part of FIG.

  Referring to FIG. 1 (A) and FIG. 2, the double-pipe exhaust manifold 10 includes a plurality of parts arranged with a space 23 between the outer pipe 20 and the inner peripheral surface of the outer pipe 20. An inner tube 30. The outer tube 20 is formed by abutting two divided members having a so-called “monaca shape”. One end of the outer tube 20 is fixed to a flange portion 41 attached to the shilling head by welding, and the other end is fixed to a flange portion 42 attached to the catalyst device side by welding. Each inner tube 30 provided in the outer tube 20 has an upstream end fixed to the flange portion 41 by welding. The downstream end of each inner pipe 30 is a free end without being welded, and has a structure that can be freely expanded and contracted.

  The inner pipe 30 in the present embodiment includes a main pipe 50 (corresponding to a first inner pipe) and two branch pipes 60 and 70 (corresponding to a second inner pipe) that join in the middle of the main pipe 50. Yes. In the main pipe 50, openings 51 and 52 are formed at the junctions 81 and 82 with the branch pipes 60 and 70. The main pipe 50 and the branch pipes 60, 70 form a gap S between the end 51 a of the opening 51 formed in the main pipe 50 and the end 60 a of the branch pipe 60, and are similarly formed in the main pipe 50. The gap 52 is formed between the end 52 a of the opening 52 and the end 70 a of the branch pipe 70, and is disposed in the outer pipe 20. With reference to FIG. 2 showing the vicinity of the merging portion 81 in cross section, gaps S (CL1, CL2) are formed between the end portion 51a of the opening 51 and the end portion 60a of the branch pipe 60.

  The ends 60 a and 70 a of the branch pipes 60 and 70 are slightly inserted into the openings 51 and 52 of the main pipe 50, and the ends 51 a and 52 a of the openings 51 and 52 are the ends 60 a and 70 a of the branch pipes 60 and 70. It overlaps so as to cover. The overlap amount OL is 2 mm to 4 mm which is substantially equal to the thermal expansion amount.

  The internal space of the inner tube 30 communicates with the space portion 23 through the gap S. The double pipe exhaust manifold 10 has ring-shaped protrusions 53 a, 53 b, 54 a, 54 b, 61, 71 in order to partition the space portion 23 communicating with the gap S. In the present specification, “partition” means that the ring-shaped protrusions 53a, 53b, 54a, 54b, 61, 71 are in pressure contact with the inner peripheral surface of the outer tube 20, and the space portion 23 communicating with the gap S is another space. In addition to being completely cut off from the portion 23, the ring-shaped protrusions 53 a, 53 b, 54 a, 54 b, 61, 71 are close to the inner peripheral surface of the outer tube 20, the distance between them is minimized, and the gap S communicates It is meant to include a form in which the space portion 23 is not completely cut off from the other space portions 23. FIG. 2 shows a state in which the ring-shaped protrusions 53a, 53b, 54a, 54b, 61, 71 are close to the inner peripheral surface of the outer tube 20 and the distance between them is minimized.

  Although the ring-shaped protrusions can be formed on the inner tube 30 and / or the outer tube 20, in the illustrated example, the ring-shaped protrusions 53a, 53b, 54a, 54b, 61, 71 are respectively connected to the main tube 50 and the branch tubes 60, 70. Is formed. Specifically, the main pipe 50 includes ring-shaped protrusions 53a, 53b, 54a on the upstream side of the joining portion 81, the downstream side of the joining portion 81, the upstream side of the joining portion 82, and the downstream side of the joining portion 82, respectively. 54b is formed. The branch pipe 60 is formed with a ring-shaped protrusion 61 in the vicinity of the junction 81, and the branch pipe 70 is also formed with a ring-shaped protrusion 71 in the vicinity of the junction 82.

  Each of the ring-shaped protrusions 53 a, 53 b, 54 a, 54 b, 61, 71 is an annular protrusion or a bead-shaped protrusion having a semicircular cross section or a triangular cross section formed along the circumferential direction of the inner tube 30.

  Although the above-described ring-shaped protrusions 53a, 53b, 54a, 54b, 61, 71 can form a predetermined space 23 between the outer tube 20 and the inner tube 30, the ring-shaped protrusions 53a, 53b, 54a , 54 b, 61, 71 in addition to protrusions 55 a, 55 b, 56 a, 56 b, 62, 72 for generating the space 23. It is because the space part 23 can be formed reliably and the heat insulation effect and the soundproofing effect can be enhanced. Further, the metal mesh for supporting the inner tube 30 with respect to the outer tube 20 by adopting a configuration in which the inner tube 30 is supported with respect to the outer tube 20 by the protrusions 55a, 55b, 56a, 56b, 62, 72. It is no longer necessary to use a member such as a support bracket.

  The protrusions can be formed on the inner tube 30 and / or the outer tube 20, but in the illustrated example, the protrusions 55a, 55b, 56a, 56b, 62, 72 are formed on the main tube 50 and the branch tubes 60, 70, respectively. It is. Specifically, the main pipe 50 includes protrusions 55a and 55b on the upstream side of the ring-shaped protrusion 53a, the downstream side of the ring-shaped protrusion 53b, the upstream side of the ring-shaped protrusion 54a, and the downstream side of the ring-shaped protrusion 54b. , 56a, 56b are formed. In the branch pipe 60, a protrusion 62 is formed on the upstream side of the ring-shaped protrusion 61, and in the branch pipe 70, a protrusion 72 is formed on the upstream side of the ring-shaped protrusion 71.

  Each protrusion 55a, 55b, 56a, 56b, 62, 72 is an embossed convex portion having a conical shape or a semicircular cross-sectional shape formed so as to make point contact with the outer tube 20, and the circumferential direction of the inner tube 30 A plurality of dots are provided along the line. The protrusions 55a, 55b, 56a, 56b, 62, 72 are formed not only at positions corresponding to the merging portions 81, 82 but also at predetermined spans in order to reliably support the inner tube 30 in the outer tube 20. May be. Since the projections 55a, 55b, 56a, 56b, 62, 72 having a conical or semicircular cross section are in contact with only the outer tube 20 and the tip, the contact area between the inner tube 30 and the outer tube 20 is small, and heat conduction is also achieved. Few. Therefore, a large number of protrusions 55a, 55b, 56a, 56b, 62, and 72 can be formed within a predetermined allowable heat conduction range. As a result, even if the thickness of the inner tube 30 is reduced, the support of the inner tube 30 is highly rigid.

  The ends 51 a and 52 a of the openings 51 and 52 of the main pipe 50 do not protrude from the flow path cross section of the branch pipes 60 and 70, and the ends 60 a and 70 a of the branch pipes 60 and 70 do not protrude from the flow path cross section of the main pipe 50. It is desirable. This is to ensure a smooth flow of exhaust gas.

  The ends 51a and 52a of the openings 51 and 52 of the main pipe 50 and / or the ends 60a and 70a of the branch pipes 60 and 70 preferably have a bell mouth shape. This is because the exhaust gas can flow more smoothly at the junctions 81 and 82 between the main pipe 50 and the branch pipes 60 and 70.

  Next, with reference to FIG. 3 and FIG. 4, the process of the double pipe exhaust manifold 10 and an assembly procedure are demonstrated. FIG. 3A is a cross-sectional view showing the two divided outer tube constituent members 21 and 22 constituting the outer tube 20, and FIG. 3B is one of the inner tubes 30 arranged in the outer tube 20. It is sectional drawing which shows the branch pipe 60 which is. FIGS. 4A to 4C are views for explaining an assembly procedure of the double-pipe exhaust manifold 10.

  As shown in FIG. 3A, for the outer tube 20, the blank material is press-molded to form two-divided outer tube members 21 and 22 that form a “monaca shape”.

  As shown in FIG. 3B, for the branch pipe 60, the entire curved shape is formed by hydroforming a pipe rough material in a mold, and the protrusion 62 and a ring-shaped protrusion 61 (not shown) are formed. Form. By forming the inner tube 30 by hydroforming, the ring-shaped protrusions 53a, 53b, 54a, 54b, 61, 71 and the protrusions 55a, 55b, 56a, 56b, 62, 72 have a desired shape. It can be freely molded at a desired position. Further, the inner tube 30 can be easily thinned, and the temperature rise characteristic of the exhaust gas can be enhanced through the reduction of the heat capacity of the inner tube 30.

  As shown in FIGS. 4A and 4B, after the position of the branch pipe 60 is aligned with the one outer pipe constituting member 21, the branch pipe 60 is fixed to the one outer pipe constituting member 21 by spot welding. To do. FIG. 4B shows a state seen from the axial direction of FIG. Similarly, the main pipe 50 and the branch pipe 70 are fixed to one outer pipe constituting member 21 by spot welding.

  Next, as shown in FIG. 4C, the position of the other outer tube constituting member 22 is put on the one outer tube constituting member 21, the main tube 50, and the branch tubes 60, 70 that are integrated with each other. Thereafter, the mating surfaces of the outer tube constituent members 21 and 22 are welded.

  Finally, one end of the outer tube 20 and the inner tube 30 (main tube 50, branch tubes 60, 70) is fixed to the flange portion 41 by welding, and the other end of the outer tube 20 is fixed to the flange portion 42 by welding.

  Thus, since the outer tube 20 and the inner tube 30 are individually formed, the processing can be easily performed. Since the outer tube 20 and the inner tube 30 are joined by a welding operation, the assembly can be easily performed. Further, since the plurality of inner pipes 30 are not joined by welding, the assemblability is greatly improved from this viewpoint. Therefore, the double pipe exhaust manifold 10 can be manufactured with high processing accuracy and at low cost.

  Next, the operation of this embodiment will be described.

  In the double-pipe exhaust manifold 10 of the first embodiment, the main pipe 50 is supported in the outer pipe 20 in a state of being positioned with respect to the outer pipe 20 by the plurality of protrusions 55a, 55b, 56a, and 56b. The branch pipe 60 is supported in the outer pipe 20 while being positioned with respect to the outer pipe 20 by the plurality of protrusions 62, and the branch pipe 70 is similarly supported by the plurality of protrusions 72 with respect to the outer pipe 20. Are supported in the outer tube 20 in a positioned state. For this reason, the relative positional relationship between the ends 51a and 52a of the openings 51 and 52 of the main pipe 50 and the ends 60a and 70a of the branch pipes 60 and 70 is fixed. A gap S (CL1, CL2) is formed between the two.

  When the high-temperature exhaust gas discharged from the engine flows through the inner pipe 30, the inner pipe 30 thermally expands in the axial direction and the radial direction. Since the protrusions 55a, 55b, 56a, 56b, 62, 72 swell to a certain extent radially outward, the protrusions 55a, 55b, 56a, 56b, 62, 72 themselves are displaced in the axial direction of the inner tube 30. On the other hand, it becomes a support point that exerts sliding resistance, and this can limit the elongation in the axial direction to some extent. However, the end portions 51a and 52a of the opening portions 51 and 52 of the main pipe 50 and the end portions 60a and 70a of the branch pipes 60 and 70 are free ends, and the elongation in the axial direction is not limited.

  However, a gap S is formed between the main pipe 50 and the branch pipes 60 and 70 between the ends 51 a and 52 a of the openings 51 and 52 formed in the main pipe 50 and the ends 60 a and 70 a of the branch pipes 60 and 70. However, because it is arranged in the outer pipe 20, even if the ends 51a, 52a of the openings 51, 52 of the main pipe 50 and the ends 60a, 70a of the branch pipes 60, 70 are thermally expanded by the heat of the exhaust gas, Contact between the main pipe 50 and the branch pipe 60 and contact between the main pipe 50 and the branch pipe 70 can be prevented.

  As described above, when preventing the main pipe 50 and the branch pipes 60 and 70 from contacting each other, a straight portion for allowing the axial expansion and contraction motion is formed in the merging portions 81 and 82 as in the technique described in Patent Document 1 described above. There is no need to provide it. That is, since the main pipe 50 and the branch pipes 60 and 70 are relatively inserted through the gap S, the main pipe 50 and the branch pipes 60 and 70 can be connected even in a bent portion. Therefore, for the double pipe exhaust manifold 10 that must be arranged in a limited space, the design flexibility of the main pipe 50 and the branch pipes 60 and 70 is increased, and the bending radius at the curved portion is increased (the curvature is reduced). Can do. As a result of the bending radius of the inner tube 30 being increased, a smooth flow of exhaust gas can be secured, and the bending of the inner tube 30 can be facilitated.

  Since the main pipe 50 and the branch pipes 60 and 70 do not come into contact with each other, even when the main pipe 50 and the branch pipes 60 and 70 have a three-dimensional complicated bent shape, the main pipe 50 and the branch pipes 60 and 70 are respectively Is allowed to relatively freely extend and contract in both the axial direction and the direction orthogonal to the axial direction. Therefore, it is possible to suppress an unreasonable stress from being generated in the entire inner tube 30 and not to cause problems such as deformation.

  Further, since the ring-shaped protrusions 53a, 53b, 54a, 54b, 61, 71 for partitioning the space portion 23 communicating with the gap S are formed on the main pipe 50 and the branch pipes 60, 70, respectively, The amount of exhaust gas leakage to the pipe 20 can be suppressed. Here, in the case where the ring-shaped protrusions 53a, 53b, 54a, 54b, 61, 71 are in pressure contact with the inner peripheral surface of the outer tube 20, the space portion 23 communicating with the gap S is completely separated from the other space portions 23. By blocking, the amount of exhaust gas leaking from the inner pipe 30 to the outer pipe 20 is suppressed. On the other hand, in the case where the ring-shaped protrusions 53a, 53b, 54a, 54b, 61, 71 are close to the inner peripheral surface of the outer tube 20 and the distance between the two is minimized, the gap S between the merging portions 81, 82 Exhaust gas leaked by the breathing action leaks exhaust gas from the inner tube 30 to the outer tube 20 due to the flow suppression effect caused by the increase in ventilation resistance by the ring-shaped protrusions 53a, 53b, 54a, 54b, 61, 71. Is suppressed. In the case of the latter form, the space in the outer tube 20 from the gap S to the ring-shaped protrusions 53a, 53b, 54a, 54b, 61, 71 forms a seal structure. Further, since the ring-shaped protrusions 53a, 53b, 54a, 54b, 61, 71 are extendable in the axial direction, the ring-shaped protrusions 53a, 53b, 54a, 54b, 61, 71 themselves extend in the axial direction. As a result, the generation of abnormal stress in the main pipe 50 and the branch pipes 60 and 70 can be suppressed.

  In addition, since the protrusions 55a, 55b, 56a, 56b, 62, and 72 that form the space 23 between the outer pipe 20 and the outer pipe 20 are formed in the main pipe 50 and the branch pipes 60 and 70, respectively. The positioning accuracy of the branch pipes 60 and 70 with respect to the outer pipe 20 can be improved, and the relative positions of the ends 51a and 52a of the openings 51 and 52 of the main pipe 50 and the ends 60a and 70a of the branch pipes 60 and 70 can be improved. Can be fixed. Therefore, the function of preventing contact between the main pipe 50 and the branch pipes 60 and 70 by the gap S can be surely exhibited.

  Further, the end portions 51 a and 52 a of the openings 51 and 52 of the main pipe 50 do not protrude from the flow passage cross section of the branch pipes 60 and 70, and the end portions 60 a and 70 a of the branch pipes 60 and 70 are formed in the flow passage cross section of the main pipe 50. Since it does not protrude, a smooth flow of exhaust gas is ensured.

  Further, since the end portions 51a and 52a of the openings 51 and 52 of the main pipe 50 and the end portions 60a and 70a of the branch pipes 60 and 70 have a bell mouth shape, the main pipe 50 and the branch pipes 60 and 70 In the merging portions 81 and 82, the exhaust gas can flow more smoothly. Furthermore, it is possible to reduce the amount of exhaust gas leaked into the outer pipe 20 from the gap S due to the breathing action accompanying the pressure fluctuation of the exhaust gas. Combined with the effect of suppressing the amount of exhaust gas leakage from the inner tube 30 to the outer tube 20 by the ring-shaped protrusions 53a, 53b, 54a, 54b, 61, 71, the influence on the flow of exhaust gas and the outer tube 20 side. The outflow of the high-temperature gas can be further reduced, and thermal deterioration of the outer tube 20 can be suppressed.

(Second Embodiment)
FIG. 5 is a cross-sectional view showing a main part of the double-pipe exhaust manifold 10 according to the second embodiment. FIG. 5 shows the main pipe 50 and one branch pipe 60 as in FIG.

  In the second embodiment, the end portions 60a and 70a of the branch pipes 60 and 70 (corresponding to the second inner pipe) cover the openings 51 and 52 formed in the main pipe 50 (corresponding to the first inner pipe). This is different from the first embodiment in that the ends 51a and 52a of the openings 51 and 52 overlap so as to cover the ends 60a and 70a of the branch pipes 60 and 70. To do.

  In the double-pipe exhaust manifold 10 according to the second embodiment, the inner pipe 30 includes a main pipe 50 and branch pipes 60 and 70 that join the main pipe 50 in the same manner as in the first embodiment. Yes. In the main pipe 50, openings 51 and 52 are formed at junctions 81 and 82 with the branch pipes 60 and 70. The main pipe 50 and the branch pipes 60 and 70 form the outer pipe 20 while forming a gap S between the ends 51a and 52a of the openings 51 and 52 and the ends 60a and 70a of the branch pipes 60 and 70. Is placed inside. As illustrated, a gap S (CL3, CL4) is formed between the end 51a of the opening 51 and the end 60a of the branch pipe 60.

  The openings 51 and 52 of the main pipe 50 are slightly inserted into the ends 60 a and 70 a of the branch pipes 60 and 70, and the ends 60 a and 70 a of the branch pipes 60 and 70 are the ends 51 a and 52 a of the openings 51 and 52. It overlaps so as to cover. The overlap amount OL is 2 mm to 4 mm which is substantially equal to the thermal expansion amount.

  Even in the form of overlap, the end portions 51a and 52a of the opening portions 51 and 52 of the main pipe 50 do not protrude from the cross section of the branch pipes 60 and 70, and the end portions 60a and 70a of the branch pipes 60 and 70 are the main pipe. It is desirable not to protrude into the cross section of 50 channels. Specifically, the opening diameters of the openings 51 and 52 are set to be larger than the inner diameters of the branch pipes 60 and 70 to ensure a smooth flow of exhaust gas.

  Moreover, in order to ensure the smooth flow of exhaust gas, the end parts 51a and 52a of the opening parts 51 and 52 of the main pipe 50 have a bell mouth shape.

  Since the ring-shaped protrusion and the protrusion are the same as those of the first embodiment, illustration and description thereof are omitted.

  Even in the double pipe exhaust manifold 10 of the second embodiment, as in the first embodiment, a smooth flow of exhaust gas can be secured, and excessive stress is generated in the entire inner pipe 30. Can be suppressed.

(Other variations)
The ring-shaped protrusions 53a, 53b, 54a, 54b, 61, 71 are pressed against the inner peripheral surface of the outer tube 20 as the exhaust gas flows through the inner tube 30 and the temperature of the inner tube 30 rises. 20 may be in the form of minimizing the distance between the two adjacent to the inner peripheral surface. In such a configuration, when the engine is started, the inner tube 30 and the outer tube 20 are supported by point contact of only the protrusions 55a, 55b, 56a, 56b, 62, 72. Heat transfer is minimized, the exhaust temperature rise at the start of the engine can be accelerated, and the function of the catalyst can be improved quickly.

  Although an embodiment has been illustrated in which one ring-shaped protrusion 53a, 53b, 54a, 54b, 61, 71 is provided at a necessary portion, the present invention is not limited to this case. For example, a plurality of ring-shaped protrusions 53a, 53b, 54a, 54b, 61, 71 may be provided adjacent to each other in the axial direction at a necessary portion. Similarly, the protrusions 55a, 55b, 56a, 56b, 62, and 72 may be provided adjacent to each other in the axial direction.

FIG. 1A is a perspective view showing a double pipe exhaust manifold according to the first embodiment, and FIG. 1B is a perspective view showing only the inner pipe of FIG. 1A. It is sectional drawing which shows the principal part of FIG. 3A is a cross-sectional view showing an outer pipe component member divided into two parts constituting the outer pipe, and FIG. 3B is a cross-section showing a branch pipe that is one of the inner pipes arranged in the outer pipe. FIG. 4 (A) to 4 (C) are diagrams for explaining an assembly procedure of the double-pipe exhaust manifold. It is sectional drawing which shows the principal part of the double pipe exhaust manifold which concerns on 2nd Embodiment.

Explanation of symbols

10 Double pipe exhaust manifold,
20 outer tube,
21, 22 Outer tube component,
23 Space part,
30 inner pipe,
50 Main pipe (first inner pipe),
51, 52 opening,
51a, 52a the end of the opening,
53a, 53b, 54a, 54b, 61, 71 ring-shaped protrusions,
55a, 55b, 56a, 56b, 62, 72 protrusion,
60, 70 Branch pipe (second inner pipe),
60a, 70a End of branch pipe (end of second inner pipe),
81, 82 junction,
S gap (gap between the end of the opening formed in the first inner pipe and the end of the second inner pipe).

Claims (7)

In a double-pipe exhaust manifold having an outer pipe and an inner pipe arranged with a space between the inner peripheral surface of the outer pipe,
The inner pipe includes a first inner pipe and a second inner pipe that joins in the middle of the first inner pipe,
The first and second inner pipes are arranged in the outer pipe while forming a gap between the end of the opening formed in the first inner pipe and the end of the second inner pipe. This is a double pipe exhaust manifold.   The double-pipe exhaust manifold according to claim 1, further comprising a ring-shaped protrusion for partitioning the space that communicates with the gap.   The double-pipe exhaust manifold according to claim 2, wherein the ring-shaped protrusion is formed on each of the first and second inner pipes.   The double-pipe exhaust manifold according to claim 1, further comprising a projecting portion that generates the space portion.   5. The double pipe exhaust manifold according to claim 4, wherein the protrusion is formed on each of the first and second inner pipes.   The end of the opening of the first inner pipe does not protrude into the flow path cross section of the second inner pipe, and the end of the second inner pipe does not protrude into the flow cross section of the first inner pipe. The double-pipe exhaust manifold according to claim 1, wherein   2. The double pipe exhaust manifold according to claim 1, wherein an end of the opening of the first inner pipe and / or an end of the second inner pipe have a bell mouth shape.

Images