JP5552259B2 - Exhaust manifold with double pipe structure - Google Patents

Description

  The present invention relates to an exhaust manifold having a double pipe structure in which a gap is provided inside an outer pipe and an inner pipe is built therein.

  Generally, an exhaust manifold of an internal combustion engine collects exhaust gas discharged from each exhaust port of the internal combustion engine into one by a collecting pipe and then discharges it to a catalyst or the like attached downstream of the collecting pipe. It is.

  However, recently, in order to improve the exhaust gas purification performance by increasing the temperature of the catalyst at an early stage, a thin inner tube with a low heat capacity is provided inside the outer tube with strength. An exhaust manifold having a double pipe structure has been proposed (see, for example, Patent Documents 1 and 2).

  In the exhaust manifold having the double pipe structure, a predetermined gap is formed by interposing a spacer such as a wire mesh ring between the outer pipe and the inner pipe, and the inner pipe is axially formed with respect to the outer pipe. It is a floating structure that can move relative to each other.

  The inner pipe and the outer pipe are fixed at a plurality of locations by spot welding, the upstream end of the inner pipe is connected to each exhaust port of the internal combustion engine, and the downstream end of the inner pipe is connected to the catalyst or the like. It is connected.

  Therefore, the catalyst temperature can be raised to a predetermined temperature at an early stage by the exhaust heat of the exhaust gas discharged from the internal combustion engine.

  As described above, the inner pipe in the exhaust manifold having a double pipe structure is formed with a small thickness so that the heat capacity is lowered, and the outer pipe is thick in order to ensure strength and heat resistance. It is formed in meat.

Japanese Utility Model Publication No. 4-116624 JP 2001-132872 A

  However, the conventional double-pipe structure exhaust manifold has the following problems.

  That is, the inner pipe becomes hot because high-temperature exhaust gas flows therethrough, and is easily deformed by heat.

  On the other hand, the outer tube is covered with a gap from the inner tube, and is less likely to be deformed by heat than the inner tube.

  The inner pipe is attached to the outer pipe by spot welding.

  Therefore, a difference in thermal expansion occurs between the thin inner tube exposed to high-temperature exhaust gas and the thick outer tube exposed to the outside air. Due to this thermal expansion difference, a part of the inner tube is formed. There has been a problem that the reliability of the exhaust manifold is reduced due to the occurrence of wrinkles and cracks due to distortion.

  The present invention has been made to solve the above-described problems, and aims to reduce distortion due to a difference in thermal expansion between a thin inner pipe and a thick outer pipe in an exhaust manifold having a double-pipe structure. An exhaust manifold having a double pipe structure capable of improving strength is provided.

To solve the above problem,
The present invention relates to an exhaust manifold having a double-pipe structure in which a gap is provided inside an outer pipe and the inner pipe is internally provided. The inner pipe is formed by a pair of halves each having a flange portion formed on a side edge. Are joined together at the flange portion, and extend along a plurality of branch pipes, a collecting pipe in which the plurality of branch pipes gather together, an outermost branch pipe, and a joint portion of the collecting pipe. A welded flange portion, and at least the outermost branch pipe is covered with a thick inner pipe holding member spot-welded to the outer pipe, and the outermost branch pipe the outer peripheral surface, by fixing the the inner tube holding member and the branch pipe by spot welding, as viewed from the axial direction of the branch pipe, the center line connecting the said centering of the branch pipe flange perpendicular And a reference line passing through the center of the branch pipe An outer spot welds positioned on the flange portion side, and the inner spot welds than the reference line positioned on the opposite side of the flange portion, is formed, the outermost and before Kisotogawa spot welds and the center of the straight line and the center line and the angle connecting the branch pipe is set in the center and wider than the angle formed between the straight line and the center line connecting the previous SL inside the spot weld and the branch pipe It is characterized by that.

  That is, in the present invention, a thick-walled inner tube holding member is sheathed on the upper end side of the exhaust flow of the inner tube formed to be thin, and the inner tube holding member is spot-welded to the inner tube, The inner tube holding member and the outer tube are spot welded, and the inner tube holding member is attached in a state of being interposed between the inner tube and the outer tube.

  Here, the term “thin” means that the inner tube holding member is thinner than the inner tube holding member, and the term “thick” means that the inner tube is thicker than the inner tube. It means that it has been.

  Therefore, when the inner pipe becomes high temperature, the inner pipe holding member spot welded to the inner pipe also has substantially the same temperature, so there is almost no temperature difference (thermal expansion difference) between the two. It is possible to prevent the inner tube from being distorted.

  However, if the inner pipe holding member becomes high temperature, a temperature difference is generated with respect to the outer pipe spot-welded to the inner pipe holding member.

  However, since the inner tube holding member is formed thick, the inner tube holding member and the outer tube are thermally expanded at the same rate.

  Therefore, according to the present invention, by interposing the thickly formed inner tube holding member between the inner tube and the outer tube, the difference in thermal expansion generated between the inner tube and the outer tube is dispersed. Since it is relaxed, the strain of the inner tube can be reduced as compared with the conventional one, and the strength of the inner tube is also improved.

  In particular, in an exhaust manifold having a double-pipe structure, the inner pipe is generally manufactured by forming a metal thin plate into a cylindrical shape, so that a flange portion welded in the longitudinal direction is formed on the outer end of the inner pipe. Is formed.

In the inner pipe in which such a flange portion is formed, since the strength of the flange portion is high in the side wall portion of the inner pipe, the spot welded portion formed on the inner pipe holding member, the flange portion, The distance (L) is preferably separated from the distance (L) because it is less likely to cause distortion, as can be understood from ε (strain) = ΔL / L.

However, when performing spot welding by exterior of the inner pipe holding member within said tube, the spot weld, since substantially formed uniformly at the same intervals, and the front Kigai side spot weld the flange portion And will be in close proximity.

  Therefore, in the present invention, the angle formed by the outer spot welded portion is set to be wider than the angle formed by the inner spot welded portion with respect to the center line connecting the center of the inner tube and the flange portion. I try to do it.

  Therefore, the outer spot welded portion can be formed at a position away from the flange portion, and the strain between the flange portion and the outer spot welded portion can be reduced.

  In addition, if each of the outer spot welded portion and the inner spot welded portion is formed, distortion generated in the inner tube is reduced as compared with the case where the spot welded portions are formed at substantially the same interval as described above. The strain of the inner tube can be further reduced, and the strength of the inner tube can be further improved.

Specifically, the outer spot welds and the inner spot weld, as viewed in the axial direction of the branch pipe, with respect to the center line, since it is respectively formed at a position axisymmetric, the inner pipe This strain is preferable because it can be reduced uniformly over the entire inner tube.

Further, a cylindrical reinforcing pipe is connected to an end of the collecting pipe of the present invention opposite to the branch pipe, and a plurality of spot welds are formed in the circumferential direction in the collecting pipe and the reinforcing pipe. The plurality of spot welds formed in the circumferential direction are formed on the side farther from the branch pipe than the central position in the longitudinal direction of the reinforcing pipe.

  In the present invention, the same effect as described above is obtained not only at the upstream end of the exhaust manifold having a double-pipe structure but also at the connecting portion at the downstream end.

  That is, a cylindrical reinforcing pipe is connected to the downstream end of the inner pipe as a connecting member for connecting to the catalyst or the like.

  Even in the case of connecting such a reinforcing pipe, the distance between the spot welded portion for welding the reinforcing pipe and the inner pipe and the flange portion is preferable because it is less likely to cause distortion as in the above case. .

Therefore, in the present invention, the plurality of spot welds formed in the circumferential direction are formed as far as possible from the flange portion of the inner pipe by forming the spot welds on the downstream side of the longitudinal center of the reinforcing pipe. Therefore, it is possible to further reduce the distortion of the inner tube and further improve the strength of the inner tube.

  According to the exhaust manifold of the double pipe structure of the present invention, it is possible to reduce the distortion due to the difference in thermal expansion between the inner pipe and the outer pipe, thereby improving the strength of the inner pipe.

It is a whole perspective view of the state where a part of outer cylinder which showed one embodiment of the present invention was notched. It is a disassembled perspective view of this embodiment. It is a principal part enlarged view of the state which expanded the broken-line part (I) of FIG. It is principal part sectional drawing of the state which carried out the longitudinal section of the inner pipe holding member of FIG. 3 by the spot welding part. It is the principal part enlarged view which showed other embodiment of this invention, (a) is a top view of the principal part in the state which expanded the broken-line part (b) of FIG. 3, (b) is FIG. It is principal part sectional drawing which shows the state longitudinally cut in the spot-welded part of ().

  Hereinafter, an exhaust manifold A having a double-pipe structure according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is an overall perspective view in a state where a part of the outer cylinder of the present embodiment is cut out, FIG. 2 is an exploded perspective view of the present embodiment, and FIG. 3 is a broken line portion (A) in FIG. It is a principal part enlarged view of the state expanded.

  In addition, the same number is attached | subjected to the site | part which is common in FIGS. 1-3, and the overlapping description is abbreviate | omitted.

  The exhaust manifold A having a double-pipe structure has a thin inner pipe 1 whose upstream end communicates with each exhaust port (not shown) of the internal combustion engine and whose downstream end communicates with a catalyst (not shown), The inner tube 1 is provided with a thick outer tube 2 that is externally provided with a gap, and a thick inner tube holding member 3 that is spot welded between the inner tube 1 and the outer tube 2. The details will be described below.

  The inner tube 1 is formed by forming a thin metal plate having high heat resistance and corrosion resistance, for example, a stainless steel plate or a steel plate into a cylindrical shape by sheet metal or welding.

Inner tube 1 of this embodiment includes a plurality of cylindrical branch tube 11, these partial Toki tube 11 tubular collector pipe 12 which is set within one and joins the downstream side are integrally formed ing.

  Specifically, as shown in FIG. 2, the open sides of the substantially Y-shaped branch pipe 11 and the collecting pipe 12 that are divided into two vertically are polymerized and merged, and the outside of each branch pipe 11 and the collecting pipe 12 is merged. At the end, a flange portion 13 is formed in the longitudinal direction, and the inner tube 1 is formed by welding the flange portion 13.

In the present embodiment, the two branch pipes 11 are illustrated, but the present invention is not limited to this, and three or more branch pipes 11 may be used.

  In the present embodiment, the connecting pipe 51 having heat resistance extends from the respective upstream ends of the branch pipes 11 to the flanges 5 attached to the internal combustion engine so as to cover the branch pipes 11.

  Depending on the shape of the inner tube 1, the connecting tube 51 and the outer tube 2 can be integrally formed.

  The outer tube 2 is a thick metal material having rigidity, and is integrally formed of a metal material such as stainless steel, steel steel, or cast iron having high heat resistance and corrosion resistance.

  Specifically, as shown in FIG. 2, the outer pipe 2 is a tunnel-like box that covers the branch pipe 11 and the collecting pipe 12 according to the shapes of the two branch pipes 11 and the collecting pipe 12. More specifically, the box is divided into two parts in the vertical direction, the open sides are polymerized and combined, and the outer end 2 is welded to form the outer tube 2.

  Further, the outer tube 2 is externally provided so as to provide a gap with the inner tube 1. In this embodiment, the ring-shaped wire mesh 4 is externally fitted at appropriate positions of the branch tube 11 and the collecting tube 12. Thus, by covering the outer tube 2, a gap corresponding to the thickness of the wire mesh 4 is formed in the inner tube 1 and the outer tube 2.

  The inner tube 1 has a floating structure that can move relative to the outer tube 2 in the axial direction. By interposing the wire mesh 4, the gap is formed and the inner tube 1 is passed through. It is possible to cope with distortion (elongation, shrinkage) in the axial direction of the inner pipe 1 caused by a high exhaust gas temperature.

  In the present embodiment, the outer side of the front and rear ends of the inner tube 1, more specifically, a notch portion 14 is formed from the front and rear ends of the inner tube 1 toward the flange portion 13 to cope with the distortion in the circumferential direction of the inner tube 1. Like to do.

  The inner tube holding member 3 is formed according to the outer shapes of the inner tube 1 and the outer tube 2 so as to be joined to the inner tube 1 and the outer tube 2.

  In the present embodiment, the inner pipe holding member 3 that is externally mounted on the two branch pipes 11 and formed integrally with each other is illustrated.

  Specifically, the inner tube holding member 3 is divided into two parts in the vertical direction, and each inner tube holding member 3 has the same thickness as the outer tube 2 and has an outer peripheral portion and an outer portion of each branch tube 11. The band-shaped ring part 31 joined to the inner peripheral part of the pipe 2 and a connecting piece 32 integrally formed so as to connect the ring parts 31 are formed.

  The inner tube holding member 3 is not limited to this embodiment, and may be joined to the inner tube 1 and the outer tube 2 in order to conduct heat with the inner tube 1 and the outer tube 2, It is preferable to integrally form the ring portion 31 by connecting the connection pieces 32 as in the present embodiment, because the temperature difference generated in each branch pipe 11 can be made uniform.

  Further, in the ring portion 31 of the inner tube holding member 3 as in the present embodiment, since it is wound around the entire circumference of the end portion of the inner tube 1, particularly the strength of the end portion of the inner tube 1 can be increased, This is preferable because rattling and the like can be prevented.

  The inner tube holding member 3 configured as described above is attached in the following manner.

FIG. 4 is a cross-sectional view of the main part in a state in which the inner tube holding member 3 of FIG.
In addition, the same code | symbol is attached | subjected to the site | part which is common in FIGS. 1-3, and the overlapping description is abbreviate | omitted.

  First, after positioning the ring portion 31 of the inner pipe holding member 3 on the upstream side of the exhaust flow of each inner pipe 1, the inner pipe holding member 3 is fixed to the inner pipe 1 by spot welding.

At this time, the spot welded portion 6 which is a welding mark is formed at the spot welded position. In this embodiment, the center O and the flange portion of the branch pipe 11 are viewed from the axial direction of the branch pipe 11. An inner spot weld 61 located on the opposite side of the flange portion 13 from a reference line (not shown) that is orthogonal to the center line OL connecting 13 and passes through the center of the branch pipe 11, and the reference line As shown in FIG. 4, the outer spot welded portion 62 located on the flange portion 13 side is provided with a predetermined angle with respect to the center line OL connecting the center O of the inner tube 1 and the flange portion 13.

Specifically, the angle θ1 formed by the straight line and the center line OL connecting the center O of the outer-side spot welds 62 and the branch pipe 11, connecting the inner side spot welds 61 and the center O of the branch pipe 11 linear And an angle θ2 that is wider than the angle θ2 formed by the center line OL .

In this embodiment, the inner spot weld 61 is formed at a position angle θ2 is 30 °, the outer spot welds 62 illustrates those formed at a position where the angle θ1 is 45 °.

  However, the angles [theta] 1 and [theta] 2 are not limited to the present embodiment. In short, the angle [theta] 1> [theta] 2 may be set.

  In addition, since the inner tube holding member 3 of the present embodiment is vertically symmetric divided into upper and lower parts, the spot welding is preferably formed at the vertically symmetric positions of the inner tube holding member 3, respectively.

  That is, as shown in FIG. 4, if the inner spot welded portion 61 and the outer spot welded portion 62 are respectively formed at positions that are vertically symmetrical with respect to the center line OL, the distortion of the inner tube 1 is uniform throughout. Since it can reduce, it is preferable.

  After the inner tube holding member 3 is spot welded to the inner tube 1 in this way, the outer tube 2 is sheathed so as to cover the inner tube 1, and the inner surface of the outer tube 2 is attached to the inner tube holding member 3. At the same time, the appropriate place where the inner pipe holding member 3 and the outer pipe 2 are joined is spot welded and fixed.

  And the exhaust manifold A of the double pipe structure of this embodiment can be easily formed by welding and fixing the joining part of the outer pipes 2.

  According to the exhaust pipe manifold A of the double pipe structure of the present embodiment configured as described above, the thick inner pipe holding member 3 is interposed between the inner pipe 1 and the outer pipe 2 and interposed. Therefore, the difference in thermal expansion generated between the inner tube 1 and the outer tube 2 can be dispersed and relaxed.

  That is, if the inner pipe 1 becomes high temperature due to the exhaust gas temperature, the inner pipe holding member 3 spot-welded to the inner pipe 1 also has substantially the same temperature, so there is almost no temperature difference between them. It is possible to prevent the inner tube 1 from being distorted.

  Further, if the inner tube holding member 3 becomes high temperature, a temperature difference will occur with the outer tube 2 spot welded to the inner tube holding member 3, but the inner tube holding member 3 of this embodiment is Since it is formed thick, the inner tube holding member 3 and the outer tube 2 are thermally expanded at the same rate.

  Therefore, according to the present embodiment, the inner tube holding member 3 formed thick is joined between the inner tube 1 and the outer tube 2 to be interposed between the inner tube 1 and the outer tube 2. Since the difference in thermal expansion is dispersed and relaxed, the strain generated in the inner tube 1 can be reduced, and the strength of the inner tube 1 can be improved.

  Furthermore, according to the present embodiment, the angle θ1 formed by the outer spot welded portion 62 with respect to the center line OL is set to be wider than the angle θ2 formed by the inner spot welded portion 61.

  Therefore, the outer spot welded portion 62 can be formed at a position away from the flange portion 13, the strain between the flange portion 13 and the outer spot welded portion 62 can be reduced, and the strain of the inner tube 1 can be reduced. This can be further reduced, and the strength of the inner tube 1 can be further improved.

  5A and 5B are main part enlarged views showing other embodiments, and FIG. 5A is a plan view of the main part in an enlarged state of a broken line part (b) of FIG. FIG. 5B is a cross-sectional view of the main part showing a state in which the spot welded part in FIG.

  In addition, the same code | symbol is attached | subjected to the site | part which is common in FIGS. 1-4, the overlapping description is abbreviate | omitted, and only the characteristic of this embodiment is demonstrated below.

  As described above, on the upstream side of the exhaust flow of the inner pipe 1, the inner pipe holding member 3 is spot-welded at a predetermined angle to reduce the distortion of the inner pipe 1 and improve the strength of the inner pipe 1. be able to.

  By the way, since only one collecting pipe 12 is provided on the downstream side of the inner pipe 1, it is not particularly necessary to provide the inner pipe holding member 3.

  However, a generally cylindrical reinforcing pipe 7 is further connected to the downstream end of the collecting pipe 12, and is connected to the catalyst or the like via the reinforcing pipe 7.

  Therefore, in the present embodiment, the same effect as described above is also obtained in the connecting portion at the downstream end of the inner pipe 1.

  That is, in the exhaust manifold A having a double-pipe structure according to the present embodiment, the cylindrical reinforcing pipe 7 connected to the downstream end of the inner pipe 1 is formed with a plurality of spot welds 8 in the circumferential direction. The spot welded portion 8 is characterized in that it is formed downstream of the longitudinal center position P of the reinforcing tube 7.

  Here, the length of the reinforcing pipe 7 is not particularly limited. However, as shown by a one-dot broken line in FIG. 5A, the length of the reinforcing pipe 7 is lower than the central position P in the longitudinal direction (the lower end of the inner pipe 1). The spot welded portion 8 is formed on the side), and the reinforcing tube 7 and the inner tube 1 are fixed.

  Even when such a reinforcing pipe 7 is connected, the distance between the spot welded portion 8 for welding the reinforcing pipe 7 and the inner pipe 1 and the flange portion 13 is distorted as the distance increases. Not likely to occur.

  Therefore, according to the present embodiment, the spot welded portion 8 is formed at a position as far as possible from the flange portion 13 of the inner tube 1 by forming the spot welded portion 8 on the downstream side of the central position P in the longitudinal direction of the reinforcing tube 7. In addition to the above effects, the inner tube 1 can be further reduced in strain and the strength of the inner tube 1 can be further improved.

In the present embodiment, the spot welds 8 are illustrated as being uniformly formed around the inner tube 1 at substantially the same interval. However, in the case of a single tube as in this embodiment, the inner tube 1 If the angle θ ′ formed by the center line OL formed by the straight line connecting the spot weld 8 formed on both sides of the center and the center O of the collecting pipe 12 and the center line OL is set wide, the spot weld 8 Is preferably formed at a position further away from the flange portion 13.

A Double-pipe exhaust manifold O (Inner pipe) center P Center position OL Center line θ1 angle θ2 Angle 1 Inner pipe 2 Outer pipe 3 Inner pipe holding member 6 Spot welded portion 61 Inner spot welded portion 62 Outer spot welded portion 7 Reinforcement tube 8 Spot weld

Claims (3)

In an exhaust manifold with a double pipe structure in which a gap is provided inside the outer pipe and the inner pipe is built in,
The inner pipe is a united structure in which a pair of halves each having a flange portion formed on a side edge portion are welded together by the flange portion, and the plurality of branch pipes and the plurality of branch pipes are A collecting pipe that collects, and the welded flange portion that extends along the outermost branch pipe and the mating portion of the collecting pipe,
At least the outermost branch pipe is covered with a thick inner pipe holding member spot welded to the outer pipe,
The inner pipe holding member and the branch pipe are fixed to the outer peripheral surface of the outermost branch pipe by spot welding, so that the center of the branch pipe and the flange portion are viewed from the axial direction of the branch pipe. The outer spot welded portion located on the flange portion side with respect to the reference line passing through the center of the branch pipe and orthogonal to the center line connecting the flange portion and the flange portion with respect to the reference line. An inner spot weld, and
The angle formed between the straight line connecting the outer spot welded portion and the center of the outermost branch pipe and the center line is formed by the straight line connecting the inner spot welded portion and the center of the branch pipe and the center line. Exhaust manifold with a double pipe structure, characterized in that it is set at a wider angle than the angle. In the double pipe structure exhaust manifold according to claim 1,
The outer spot welded portion and the inner spot welded portion are formed at positions symmetrical with respect to the center line when viewed from the axial direction of the branch pipe, respectively. Manifold. In the exhaust manifold of the double pipe structure according to claim 1 or 2,
A cylindrical reinforcing pipe is connected to an end of the collecting pipe opposite to the branch pipe, and a plurality of spot welds are formed in the collecting pipe and the reinforcing pipe in the circumferential direction.
The exhaust manifold having a double pipe structure, wherein the plurality of spot welds formed in the circumferential direction are formed on a side farther from the branch pipe than a central position in the longitudinal direction of the reinforcing pipe.

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