JP4117069B2 - 2-pass double exhaust pipe and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust pipe used in a multi-cylinder engine for a vehicle.
[0002]
[Prior art]
The exhaust pipe connected to the exhaust manifold of the vehicle engine is a double pipe to improve the heat insulation effect for better exhaust purification, and the inner pipe is divided into two passages to avoid exhaust interference Is known (for example, JP-A-9-264128). In this prior art, as shown in FIG. 7, the exhaust pipe A is an inner pipe a and the outer pipe b are double pipes and a heat insulating gap c is interposed, and the inner pipe a is connected to a passage e ₁ , by a diametric partition plate d. e ₂ is divided into two. Then, the partition plate d, provided by bending a flange d _1, d ₂ in the longitudinal direction, is welded to the inner tube a the flange d _1, d _2, both ends of the inner tube a and the outer tube b, the It is welded to the end flange f without changing the diameter, and the flange f is connected to the flange g of the exhaust manifold B.
[0003]
According to this configuration, in order to avoid the interference of the exhaust gas passing through the passages e ₁ and e ₂ , the flanges d ₁ and d ₂ must be air-tightly welded to the inner pipe a. The work is also cumbersome. Further, the inner tube a and the outer tube b must be welded concentrically to the end flange f, and this operation is also troublesome. For this reason, if the said prior art is used, it will become unavoidable.
[0004]
Japanese Patent Application Laid-Open No. 9-209747 discloses that two sets of inner and outer double D-shaped tubes are used and two outer D-shaped tubes are fixed to a flange. In this prior art, since four inner and outer D-shaped tubes are used, this also inevitably increases the cost.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to obtain an exhaust pipe that can easily ensure airtightness between two passages and can be easily manufactured, and a method for manufacturing the exhaust pipe.
[0006]
[Means for Solving the Problems]
Means for achieving the above object is as described in each claim, and the exhaust pipe of claim 1 is provided with an outer pipe and an inner pipe which are doubled through a heat insulation gap, and the inner pipe is diametrically oriented. In a two-passage double exhaust pipe in which two passages for exhaust are formed by providing a partition, a flat portion of a pair of D-shaped tubes formed of a material thinner than the outer tube is combined to form an inner tube. As a material, an ERW tube having a straight ERW portion is used, the ERW portion is positioned on a flat surface portion of the D-shaped tube, and two D-shaped tubes are joined by shifting the position of the ERW portion, One end portion of the outer tube is reduced in diameter and brought into close contact with one end portion of the inner tube, and a flange is fitted to the reduced diameter portion, and the flange, the outer tube and the inner tube are joined together by welding. The inner tube and the outer tube are bent with the section as a neutral surface, and the other ends of the outer tube and the inner tube are joined so as to be heat-extensible. To.
[0007]
According to this means, since the two exhaust passages are formed by the two D-shaped tubes, the airtightness between the exhaust passages is perfect, and there is no possibility of causing exhaust interference. Also, the flange that fixes the outer pipe of the double pipe to the reduced diameter end only welds the flange and the reduced diameter portion, so that welding is simple and absorbs the difference in thermal expansion between the inner and outer pipes. be able to. At the time of bending, the flat portion of the D-shaped tube becomes a curved neutral surface, so that bending can be easily performed with little resistance. Moreover, although the electric sewing pipe which can be obtained cheaply as a D-shaped pipe is used, since the electric sewing part is located in a plane part, the deformation amount of an electric sewing part is small at the time of a bending process, and concentration of stress is prevented. Moreover, since the position of the electric sewing parts of the two D-shaped pipes is shifted, even if the electric sewing parts protrude, the positions of the D-shaped pipes are stabilized when the plane parts are overlapped.
[0008]
The exhaust pipe of claim 2 is characterized in that, in claim 1, the flat portions of the two D-shaped tubes are joined by spot welding or line welding at both ends in the width direction near the ends of the tubes and near the curved portions. And According to this means, even when the welding amount is small, the airtightness between the tubes is maintained, and the two D-shaped tubes are prevented from being displaced from each other during bending or use.
[0009]
The exhaust pipe according to claim 3 is characterized in that, in claim 1, both ends in the width direction of the flat portion of the two D-shaped pipes are welded over substantially the entire length. According to this means, since both ends are welded over substantially the entire length of the D-shaped tube, the rigidity of the inner tube is increased and the rigidity as a double tube is also increased. Moreover, since this visible part welds a visible part, even if it is welding over a full length, it can weld easily.
[0011]
Next, in the manufacturing method of claim 4 , the flat portions of two D-shaped tubes having a D-shaped cross section are brought into contact with each other, and both end portions of the contact surfaces are welded to form an inner tube. , Inserted into the outer tube that can form a heat insulating gap on the outside thereof, one end portion of the outer tube is reduced in diameter and closely contacted with one end portion of the inner tube, spot welding is performed on this tightly contacted portion to form a double tube, A pressure transmission medium is put into the heat insulation gap, bent, and after removing the pressure transmission medium, a heat expansion absorbing mechanism is provided in the heat insulation gap on the other end side of the double pipe, and at least the one end part of the outer pipe The flange is welded to the side. According to this means, one end side of the gap between the inner and outer pipes is closed and the other end side is opened, so that the pressure transmission medium used during bending can be easily inserted and discharged.
[0012]
According to a fifth aspect of the present invention, there is provided a manufacturing method according to the fourth aspect , wherein when the double pipe is bent, a pressure transmission medium is inserted into the heat insulating gap and a short unit having a D-shaped cross section is connected to bendable. The flexible mandrel is inserted into two D-shaped tubes, and the flexible mandrel is bent while moving. According to this means, since the flexible mandrel having a D-shaped cross section is inserted into the D-shaped tube, the unexpected distortion of the inner tube is prevented.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a double-passage double exhaust pipe according to the present invention. The exhaust pipe 1 is a double pipe having an outer pipe 2 and an inner pipe 3 with a heat insulating gap 4 interposed therebetween. This inner tube 3 uses two D-shaped tubes 3a having a semicircular cross section shown in FIG. 2, and the plane portion 3a ₁ is overlapped as shown in FIG. The spot welded portion 5 is welded to form a circular tubular contour by the two curved surface portions 3a ₂ and 3a ₂ .
[0014]
As the material of the D-shaped tube 3a, for example, bending a plate in a circular tube, electric-resistance-welded pipe welded by electric resistance welded portion 3a ₁₁ the opposite end is used, the electric sewing pipe seam welded portion 3a ₁₁ is included in the flat portion 3a ₁ The D-shaped tube 3a is formed by molding into a D shape as described above. In this case, the electric resistance welded portion 3a ₁₁ is at a position deviated from the center of the planar portion 3a _1, when the overlapped two planar portions 3a ₁ as shown in FIG. 3, the two electric resistance welded portion 3a _11, 3a ₁₁ is with respect to the center Are positioned symmetrically. This is because even if the electric stitching portion 3a ₁₁ protrudes from the plate surface, stability is caused when they are overlapped.
[0015]
As the electric sewing tube, for example, a SUS tube having a thickness of 0.8 mm and an outer diameter of 50.8 mm is used. The inner tube 3 having an outer diameter of 63.2 mm is formed by superimposing two SUS pipes into a D shape. Form. For the outer tube 2, for example, a 1.2 mm thick SUS electric sewing tube is used.
[0016]
The inner pipe 3 formed by welding two D-shaped pipes 3a is inserted into the outer pipe 2 as shown in part by phantom lines in FIG. 4, and one end of the outer pipe 2 is drawn to reduce the diameter. 2a, which is brought into close contact with the inner pipe 3 by the reduced diameter portion 2a, and is further integrated by spot welding. Then, as is well known, a pressure transmission medium such as a granular material is inserted into the heat insulating gap 4 formed between the pipes 2 and 3, and this double pipe is pressed around the bending die by a fixed die and a pushing die. And bending to form the curved portion 6. In this case, if the inner tube 3 is filled with the pressure transmission medium, the bending process can be performed more accurately.
[0017]
FIG. 5 shows a bending method different from the bending method using only the pressure transmission medium described above. The pressure transmission medium is interposed in the heat insulating gap 4, and the inside of each D-shaped tube 3a of the inner tube 3 is possible. A flexible mandrel 8 is inserted to prevent unexpected deformation.
[0018]
As shown in FIG. 6A, the flexible mandrel 8 is formed by connecting a plurality of ball core bars 9a and 9b having a substantially semicircular shape when viewed from the front to the core body 10 so as to be bent. As shown in FIG. 6 (b), stepped holes 11a and 11b are formed in the ball cores 9a and 9b, and an integral ball pin 12 is inserted into the stepped hole 11a.
[0019]
The pin 12 with a sphere has a flange 12a at one end and a sphere portion 12b at the other end, and a ring groove for a circlip 13 is provided at an intermediate portion. The spherical part 12b has a spherical part larger than a hemisphere, and the diameter of the base part is smaller than the diameter of the spherical body, and the base part is constricted. If the circlip 13 is mounted by passing the pin 12 with a sphere through the stepped hole 11a of the ball core 9a at the end from the sphere 12b side, the pin 12 with the sphere is held by the ball core 9a.
[0020]
Split pins 14A and 14B are inserted into another ball core 9b. The split pins 14A and 14B are formed by dividing one pin into two in the axial direction, and in a superposed state, a spherical concave portion 14a is formed at one end and a spherical portion 14b is formed at the other end. In order to assemble the ball core 9b to the ball core 9a, the split pins 14A and 14B are placed in a free state, and the split pins 14A and 14B are overlapped so as to cover the spherical portion 12b of the pin 12 with the spherical recess 14a. When the overlapped split pins 14A and 14B are passed through the stepped hole 11b and the circlip 13 is fitted, the split pins 14A and 14B are held by the ball core 9b and sandwich the ball portion 12b and swing with the pin 12. Connected freely.
[0021]
Next, as means for connecting the split pins 14A and 14B to the cored bar body 10, split nuts 15A and 15B having a recess 15a for receiving the split pin ball portion 14b are used. A flange portion 16 having a through hole is provided in an intermediate portion of the core metal body 10, a nut hole 17 is formed on one side thereof, and a bolt seat hole 18 and a screw hole 19 are formed in a stepped manner on the other side. It is installed. First, the split nuts 15A and 15B are overlapped, the ball portion 14b of the split pin is sandwiched by the recess 15a, the split nuts 15A and 15B are inserted into the nut holes 17, and the bolt 20 is inserted from the bolt seat hole 18 side into the split nuts 15A and 15B. By screwing into the threaded portion and fastening, the split nuts 15A and 15B are fixed, and the ball portion 14b is rotatably held in the recess 15a.
[0022]
Next, the flexible mandrel 8 is completed by screwing the pull rod 21 into the screw hole 19. In the illustrated embodiment, two ball cores 9a and 9b are used, but an appropriate number of the same as the ball core 9b using the split pins can be added.
[0023]
Then, the inner side of the curved portion 6 of the double tube in FIG. 5A is applied to the bending die, the fixed die is applied to the outer left end side, the bending die is applied to the right end side, and the double tube is bent by pressurization. The double tube is curved with the flat surface portion 3a ₁ as a neutral surface. Then, the pulling rod 21 is pulled according to the movement of the bending position, and the ball cores 9a, 9b are moved to the bending position to prevent abnormal deformation.
[0024]
After the bending process, the flexible mandrel 8 and the pressure transmission medium 7 are discharged, and the flange 23 is fitted to the reduced diameter portion 2a at one end of the outer tube 2 as shown in FIG. The Further, a flange 25 is fitted to the other end side of the outer tube 2 and fixed by a welded portion 26. On the other end side, the inner tube 3 is not fixed to the flange 25, and is supported on the outer tube 2 by a thermal elongation absorbing mechanism 27 in which a convex portion whose diameter is increased in a ring shape is inscribed in the outer tube 2. Has been. By supporting in this way, expansion and contraction are allowed even if a difference in thermal elongation occurs between the inner and outer tubes, and generation of excessive thermal stress is prevented.
[0025]
Further, as shown in FIG. 8, a heat expansion / shrinkage mechanism 28 in which a concave portion obtained by reducing the diameter of the outer tube in a ring shape is circumscribed to the inner tube 3 may be provided, and a wire mesh ring (not shown) is provided near the end of the heat insulating space. You may press fit into.
[0026]
【The invention's effect】
As is apparent from the above description, according to the means of claim 1, since the exhaust passage is formed by two D-shaped tubes, there is an advantage that exhaust leakage between the D-shaped tubes does not occur. Since the flange is welded to both ends of the book, there is an advantage that the pipe structure and the welded structure are simple. Further, since the electro-sewn portion is on the neutral plane of bending, excessive stress is not generated during bending, and the two flat portions can be stably stacked even when the electro-sewn portion is exposed.
[0027]
In addition, since the flat portion of the D-shaped tube is a neutral neutral surface, there is little resistance to bending, and since the flat portion is two separate flat portions, the two-piece thickness is integrated. Less bending resistance than
[0028]
According to the means of claim 2, since the pipe end portions and the curved portion vicinity of the two D-shaped pipes are spot-welded or line-welded on both sides in the width direction of the flat portion, a freely deformable portion that is not welded is freely set. It is possible to reduce the amount of welding compared to conventional products.
[0029]
According to the third aspect of the invention, since the welded portion faces the outside, welding is easy, and the rigidity of the inner pipe is increased by the long welded portion.
[0031]
According to the means of claim 4, the double passage double exhaust pipe of claim 1 can be manufactured.
[0032]
According to the means of claim 5 , the flexible mandrel prevents the unexpected distortion of the D-shaped tube, and there is an advantage that a product having a desired shape can be obtained.
[Brief description of the drawings]
1A and 1B show an embodiment of an exhaust pipe of the present invention, wherein FIG. 1A is a longitudinal sectional view, FIG. 2B and FIG. 1C are end views, and FIG. 2A is an end view of a D-shaped pipe; ) Is a side view [Fig. 3] (a) is an end view of an inner tube, (b) is a side view [Fig. 4] A longitudinal sectional view of a double tube [Fig. 5] (a) is a longitudinal sectional view during bending. FIGS. 6A and 6B are end views. FIG. 6A is a perspective view of a flexible mandrel. FIG. 7B is a longitudinal sectional view. FIG. 7A is an explanatory view of the prior art. (1)-(1) cross-sectional view [Fig. 8] Cross-sectional view of another form of thermal elongation absorption mechanism [Explanation of symbols]
1 2 passage double exhaust pipe 2 outer pipe 2a reduced diameter part 3 inner pipe 4 heat insulation gap 3a D-shaped pipe 3a ₁ plane part 3a ₁₁ electric stitching part 5, 24, 25 welded part 6 curved part 8 flexible mandrel 9a, 9b ball Core metal 10 Core metal body 12 Pin 14A, 14B Split pin 15A, 15B Split nut 23, 25 Flange 27, 28 Thermal expansion absorbing mechanism

Claims (5)

In a two-passage double exhaust pipe, which is provided with a double outer pipe and an inner pipe through a heat insulating gap, and a diametrical partition is provided on the inner pipe to form two exhaust passages, the material is thinner than the outer pipe. The formed flat portion of the pair of D-shaped tubes is combined to form an inner tube, and an electric sewing tube having a linear electric sewing portion is used as the material of the D-shaped tube, and the electric sewing portion is used as the flat portion of the D-shaped tube. The two D-shaped pipes are connected to each other by shifting the position of the electro-sewn portion, and one end portion of the outer tube is reduced in diameter to be in close contact with one end portion of the inner tube, and a flange is fitted to the reduced diameter portion. The flange, outer tube and inner tube are joined together by welding, the inner tube and the outer tube are bent with the flat surface of the D-shaped tube as a neutral surface, and the other ends of the outer tube and the inner tube are thermally stretched. A two-passage double exhaust pipe characterized in that it can be connected.  2. A two-pass double discharge characterized in that the flat portions of two D-shaped tubes are joined by spot welding or wire welding at both ends in the width direction in the vicinity of the ends of the tubes and in the vicinity of the curved portions. trachea.  2. The double-passage double exhaust pipe according to claim 1, wherein both ends in the width direction of the flat portion of the two D-shaped pipes are welded over substantially the entire length. Two D-shaped pipes having a D-shaped cross-section are brought into contact with each other, and the D-shaped pipe is made of an ERW having a straight ERW as a material of the D-shaped pipe. The two D-shaped pipes are connected to each other by shifting the position of the electric seam, and the both ends of the abutting surface are welded to form an inner pipe. Is inserted into the outer tube, one end of the outer tube is reduced in diameter and brought into close contact with one end of the inner tube, spot welding is performed on the tightly bonded portion to form a double tube, and pressure is transmitted to the heat insulating gap. A medium is inserted and bent, and after the pressure transmission medium is removed, a thermal elongation absorbing mechanism is provided on the other end of the double pipe, and a flange is welded to at least the one end of the outer pipe. A method for manufacturing a two-passage double exhaust pipe. In Claim 4 , when bending the said double pipe, while putting a pressure transmission medium in the said heat insulation gap, two flexible mandrels which connected so that a short unit with a D-shaped section could be bent. A method for producing a double-passage double exhaust pipe, wherein the double-passage exhaust pipe is inserted into a D-shaped pipe and curved while moving the flexible mandrel.

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