JP2000051930A - Double tube, its production method and shape member used for production of double tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the double tube capable of producing by a simple constitution and facilitating working of bending, etc., without trouble. SOLUTION: Two plate like members 11, 21 having nearly same rectangular shape are prepared by cutting a band like flat plate stock to have a suitable width. The plate like members 11, 21 are formed so as to have a long flat face part 13 continuing from one end side of a semicircle part 2 and a short flat face part continuing from an other end side 14. The short flat face parts are joined to the other plate like members 11, 21 each other. A mandrel 39 is inserted into a hollow part 7 so as to be brought into external contact with the inner faces of the plat like members 11, 21. Outer die members 42, 43 are arranged to the outer faces of the semicircle parts 12, 22 of the plate like members 11, 21. Forming roller 44, 45 are arranged at the outside of the die members 42, 43, welding parts are folded inward, the flat face parts 13, 23 are bent-deformed. Tips 17, 27 of the outer tube parts 13, 23 are respectively welded to the outer faces of the other plate like members 11, 21 so as to form welded parts 31, 32, and both are joined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of a double pipe which can be used for an exhaust pipe of a vehicle.

[0002]

BACKGROUND OF THE INVENTION The exhaust pipe of a vehicle is usually formed as a double pipe from the viewpoint of sound insulation and heat insulation. Conventionally, in manufacturing a double pipe, two pipes having different diameters are prepared, a small diameter pipe is inserted into a large diameter pipe and nested, and flanges are formed at ends of the inner pipe and the outer pipe. The inner tube and the outer tube are fixed to each other by attaching a tube.
When performing bending in the conventional double pipe configured as described above, various methods are employed so as not to crush the space between the inner pipe and the outer pipe. For example, the space between the inner pipe and the outer pipe is filled with sand, small balls, etc.
After performing predetermined bending using a bender press or the like, sand or small balls are taken out from the space. In this method, it is necessary to prepare sand, small balls, and the like that are not necessary for the final product, and the process is complicated, which is disadvantageous in cost.

[0003] Instead of sand and small balls, the space between the inner tube and the outer tube is filled with water and cooled, and bending is performed while the space is frozen. According to this method,
It is advantageous over the above-described method using sand or small balls in that the ice can be easily discharged from the space by melting the ice after processing. A method of forming a tubular member by processing a flat plate is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-323119. In this method, one flat plate is sandwiched between a pair of members having a semicircular cross section, and deformed along a cylindrical curved outer surface of the member to form a tubular member having a cylindrical outer surface.

[0004]

However, when a double pipe is formed by using the above-mentioned conventional small-diameter pipe and large-diameter pipe, there is a disadvantage in cost in bending. Also, when the double pipe is used for heat insulation, the inner pipe and the outer pipe are not fixed at the ends to absorb the difference in thermal expansion based on the temperature difference between the inner pipe and the outer pipe. It is conceivable to adopt a sliding contact structure. However, in this case, there is a problem that abnormal noise is generated due to contact between the inner tube and the outer tube. Further, when the inner tube and the outer tube are fixed, it is necessary to provide a thermal expansion absorbing structure such as a bellows structure in the middle of the inner tube, which is disadvantageous in cost. Further, according to the method disclosed in JP-A-9-323119, a tubular structure can be formed, but a double tube structure cannot be formed. Also,
Since the partition plate that divides the internal space of the pipe is inevitably left, the above-mentioned partition plate becomes a resistance to the exhaust flow for the exhaust pipe flowing inside the inner pipe such as the exhaust pipe of a vehicle. There is a problem.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and can be manufactured with a relatively simple structure, and can easily perform bending and other processing without hindrance. It is intended to provide a heavy pipe. Another object of the present invention is to provide a method for manufacturing a double pipe that can easily manufacture the double pipe. Still another object of the present invention is to provide a mold member that can be suitably used when manufacturing the double pipe. According to one feature of the present invention, first and second inner tube portions having a substantially semicircular cross-sectional shape, and the first and second inner tube portions having a substantially semicircular cross-sectional shape. A first and second outer pipes provided so as to cover the outside of the first inner pipe, wherein the first inner pipe is joined to an inner surface of a terminal end of the second inner pipe. And a first outer tube portion has a terminal portion extending continuously therefrom, and the second inner tube portion is joined to an inner surface of a terminal portion of the first inner tube portion. An initiating end and a second outer tube portion have an end portion extending therefrom continuously, and the first outer tube portion is an initiating portion extending continuously from the end portion of the first inner tube portion. And an end point joined to the outer surface of the starting point of the second outer tube, wherein the second outer tube extends continuously from the end of the second inner tube. Part and the first outer tube part Double tube is provided which is characterized by having an end portion joined to the outer surface side of the part.

Preferably, the joints of the pipe portions are welded. Further, a portion that is continuous from the end portion of the inner tube portion to the starting end portion of the outer tube portion extends substantially in the radial direction, whereby a substantially donut-shaped portion is provided between the inner tube portion and the outer tube portion. A space is formed. According to another feature of the present invention, two plate-like members having substantially the same rectangular shape are prepared, and a semicircular portion having a substantially semicircular cross section and a long continuous portion extending from one end of the semicircular portion are provided. The plate-shaped member is formed so as to have a flat portion and a short flat portion that is continuous from the other end, and the short flat portions are formed into the other plate-like shape so that the cross section forms a substantially circular hollow portion. The large flat semi-circular portions are formed so that the long flat portions extend over the outer surfaces of the semi-circular portions of the other plate-shaped members, and the large flat semi-circular portions are formed. A manufacturing method is provided wherein the tips are joined to the outer surfaces of the other plate members.

According to another feature, two plate-like members having substantially the same rectangular shape are prepared, and a semi-circular portion having a substantially semi-circular cross section and a long semi-circular portion continuous from one end of the semi-circular portion are prepared. The plate-shaped member is formed so as to have a flat portion and a short flat portion that is continuous from the other end, and the short flat portions are formed into the other plate-like shape so that the cross section forms a substantially circular hollow portion. In accordance with the member, the inner mold member having a pair of protrusions and having a substantially cylindrical outer surface is adjusted so that the mating portion between the protrusions and the two plate-like members is aligned and the hollow portion is formed. It has a substantially semicircular cross section that is disposed in the hollow portion so as to circumscribe the inner surface, joins the mating portions of the plate members, and extends along the outer surfaces of the semicircular portions of the two plate members. A pair of semi-cylindrical curved external mold members are arranged, and at a joint of the plate members, The long flat portion is bent and deformed into a semicircular cross-section so as to extend along the outer surface of the semi-cylindrical curved external mold member, and the ends of the large-diameter semicircular portions are placed on the outer surface of the other plate-like member. , And removing the inner mold member and the pair of outer mold members.

According to still another feature, two plate-like members having substantially the same rectangular shape are prepared, and a semi-circular portion having a substantially semi-circular cross section and a long flat surface continuous from one end of the semi-circular portion are provided. Part, and the plate-shaped member is formed so as to have a short flat portion that is continuous from the other end side, and the short flat portions are connected to each other plate-shaped member so as to form a hollow portion having a substantially circular cross section. The inner mold member is disposed so as to circumscribe the inner surface of the hollow portion formed by the two plate members, and the joined portion of the two plate members is joined to form the two plate members. A pair of semi-cylindrical curved external mold members each having a substantially semicircular cross-section extending along the outer surface of the semicircular portion of the plate-shaped member are arranged. Bends into a semicircular cross section to extend along the outer surface of the semi-cylindrical outer mold member Forming a large-diameter semi-circular portion, joining the ends of the large-diameter semi-circular portions to the outer surfaces of the other plate-like members, and removing the inner mold member and the pair of outer mold members. In the internal mold member arranged in a hollow portion formed by the two plate-shaped members,
There is provided an inner mold member having a substantially cylindrical outer surface having a pair of protrusions aligned with the mating portion with the two plate members.

In this case, the inner mold member may be constituted as a solid cylindrical member having a pair of projections.
A hollow member having a similar external structure may be used. In still another feature, two plate-like members having substantially the same rectangular shape are prepared, a semicircular portion having a substantially semicircular cross section, a long flat portion continuous from one end of the semicircular portion, and another end. The plate-shaped member is formed so as to have a short flat portion continuous from the side, and the short flat portions are aligned with the other plate-shaped member so as to form a hollow portion having a substantially circular cross section, and a pair of The inner mold member having a protrusion is provided such that the mating portion of the protrusion and the two plate-like members is aligned and circumscribes the inner surface of the hollow portion. It is arranged in a hollow part, the joining part of the plate-like members is joined, a pair of semi-cylindrical external mold members is arranged, and at the joint part of the plate-like members, each long flat part is bent, and the external mold is bent. Each semi-circular part of large diameter is deformed to extend along the outer surface of the member The outer mold member used in the method of manufacturing a double pipe, wherein a tip is joined to an outer surface of the other plate member, and the inner mold member and the pair of outer mold members are removed. The outer mold member has a substantially semi-circular cross-section extending along the outer surface of the semi-circular portion of the two plate-shaped members, and the plate-shaped member has a base end portion of each of the long flat portions. The outer mold member is provided so that the outer mold member is bent from the outer mold member and deformed to have a semicircular cross section so as to extend along the outer surface of the outer mold member.

The double pipe according to the present invention can be most preferably used as an exhaust pipe of a vehicle, but is not necessarily limited to this. The continuous portion connecting the inner tube portion and the outer tube portion extends substantially in the radial direction, but as the width of the continuous portion increases, the difference in diameter between the inner tube portion and the outer tube portion increases, and the inner portion increases. The space formed between the tube and the outer tube becomes larger. When bending the double pipe according to the present invention, the bending is performed by positioning the continuous part connecting the inner pipe part and the outer pipe part to be inside and outside of the bend, respectively. With this configuration, the double pipe can be bent without deforming the space formed between the inner pipe and the outer pipe.

[0011]

1 and 2, there is shown the structure of an exhaust pipe 1 of a conventional double pipe vehicle. In the conventional structure, the inner tube 2 is inserted into the small-diameter inner tube 2 and the large-diameter outer tube 3 to form a nested double structure, and both ends of the outer tube are squeezed and adhered to the outer surface of the inner tube. Place. In this case,
In a space 4 formed between the outer tube 2 and the inner tube 3, spacers 5 that are in contact with the inner tube and the outer tube at appropriate positions and at appropriate intervals are arranged. The spacer 5 has effects of mainly preventing vibration of the inner tube and the outer tube, suppressing abnormal noise caused by the vibration, and improving durability performance. Such a double pipe can be suitably used as an exhaust pipe in which a three-way catalyst for purifying exhaust gas is disposed in the inner space of the inner pipe. Since the exhaust gas purifying catalyst is active at a relatively high temperature, it is arranged immediately after the engine so as to receive the hot exhaust gas.
Since the space between the inner tube and the outer tube of the double tube acts as an adiabatic space, the inside of the inner tube can be maintained at a high temperature, while the temperature outside the outer tube is as close as possible to the outside air temperature. It is possible to maintain a very low temperature.

As a result, the temperature difference between the inner tube and the outer tube increases, and the difference in the amount of thermal expansion between the inner tube and the outer tube also becomes significant. Therefore, in the structure of FIG. 1, at the flange joints at both ends, the joint at one end fixes the inner pipe and the outer pipe by the weld joint 6, but does not fix them at the other end.
This is because it is necessary to absorb the difference in thermal expansion. But,
With such a configuration, the inner pipe 2 and the outer pipe 3 may be in sliding contact with each other at an unfixed end to generate abnormal noise, and since one end is not fixed, disadvantageous in strength. There's a problem. FIG. 3 shows the structure of the double pipe 10 of the present example. The double pipe of this example is configured by connecting two plate-shaped members. The first plate member 11 has a first inner tube portion 12 and a first outer tube portion 13, and the second plate member 21 has a second inner tube portion 22 and a second outer tube portion. 23
And

The first and second inner tube portions 12, 22 and the outer tube portions 13, 23 have a substantially semicircular cross-sectional shape, respectively, and have leading ends 14, 24, 15, 15, 25, respectively. It has end portions 16, 26, 17, 27. The transitions 18, 28 from the inner tube to the outer tube are continuous portions formed by a single plate member with the end of the inner tube and the start of the outer tube. The continuous portions 18 and 28 extend in the radial direction with a width corresponding to the diameter difference between the inner tube portion and the outer tube portion. The starting ends 14, 24 of the first and second inner pipes and the terminating ends 17, 27 of the first and second outer pipes are free ends, and are not connected to the first and second inner pipes. The ends are mutually connected to another plate-like member 1
The end portions 17 and 27 of the first and second outer tube portions are connected to the outer surfaces of the continuous portions 18 and 28 of the other plate-like members 11 and 21, respectively. It is connected.

In this structure, the first and second inner pipe portions 12,
22 and the first and second outer tube portions 13 and 23 substantially constitute a double tube. Then, in the pair of continuous portions 18 and 28 extending in the radial direction and separated by approximately 180 °, the inner tube portion and the outer tube portion are welded to each other at the welded portions 31 and 32 (33,
34). In addition, the inner pipe portion 1
2, 22 to the end 16 of the outer tube,
The portion continuing to 26 extends substantially in the radial direction, thereby forming a substantially donut-shaped space 35, 36 between the inner pipes 12, 22 and the outer pipes 13, 23. .
In the structure of the present example, the inner tube portions 12 and 22 and the outer tube portions 13 and 23
Are connected to each other with sufficient strength by the continuous portions 18 and 28, so that there is no need to support them with spacers as in a conventional double tube. Also, the space portions 35, 36 between the inner tube portions 12, 22 and the outer tube portions 13, 23 are properly maintained by bending the continuous portions 18, 28 to positions inside and outside of the bending. Thus, bending can be performed.

A method for manufacturing the above-mentioned double pipe according to the present invention will be described. First, a strip-shaped flat plate material is cut into an appropriate width to prepare two plate members 11 and 21 having substantially the same rectangular shape.
Then, as shown in FIG. 4, a semicircular portion 1 having a substantially semicircular cross section.
2. A long flat portion 13 continuous from one end 16 of the semicircular portion
And the plate-like member 11 (21) is formed so as to have a short flat portion 14 a continuous from the other end 14. Next, as shown in FIG. 5, each of the short plane portions 14a (24) is formed so as to form a hollow portion 37 having a substantially circular cross section.
a) is matched with the other plate-like member 11 (21).
In this case, as shown in FIG.
a) is welded to the long plane portions 13 (23) of each other by using a welding device 38 to form welds 32 and 34.

Next, as shown in FIG.
Then, the internal mold member, that is, the mandrel 39 is inserted so as to circumscribe the inner surface of the plate-like member 11 (21). The mandrel 39 of the present example has a substantially cylindrical shape, and is approximately 18 in the circumferential direction.
It has a pair of ridges 40 and 41 that are 0 ° apart.
Then, the mandrel 39 is inserted so that the ridge is aligned with the mating portion of the plate-like members 11 and 21. By doing so, by the ridges 40 and 41 of the mandrel 39,
When rotating the plate-like members 11 and 21 around the mandrel 39, a relative displacement between the two can be prevented. Furthermore, in this example, a pair of semi-cylindrical curved external mold members 42 and 43 having a substantially semi-circular cross-section extending along the outer surfaces of the semi-circular portions 12 and 22 of the plate-like members 11 and 21.
Place.

Further, in the apparatus of this embodiment, the mold member 42
And forming rollers 44 and 45 on the outside of each other, and as shown in FIG. 8, the long flat portions 13 and 23 are bent so that the above-mentioned welded portions 33 and 34 are wound inward as shown in FIG. Is deformed to have a semicircular cross section so as to extend along the outer surface of the curved external mold member. The large-diameter semicircular portions, that is, the tips 17 and 27 of the outer tube portions 13 and 23 are welded to each other by welding the outer surfaces of the other plate-like members 11 and 21 to each other.
1 and 32 are formed and both are joined. In addition, mandrel 3
9 and the mold members 42, 43 are removed before the weld joint. The use of the mandrel 39 and the mold member 42 is optional, and it is of course possible to manufacture the double tube of the present invention without using one or both. For example, as shown in FIG. 9, only the mandrel 39 is used, and the outer mold members 42 and 43 may be omitted.
As shown in FIG. 0, only the outer mold members 42 and 43 are used, and the mandrel 39 can be omitted.

Although the mandrel 39 is a solid member in this embodiment, the object of the present invention can be achieved by a hollow member.

[0019]

According to the present invention, a double pipe can be manufactured by an extremely simple operation as described above. The double pipe of this example is superior in strength as compared with the conventional one, and has flexibility even in processing such as bending.
Also, in the case of manufacturing, it can be manufactured with a very simple apparatus configuration using a plate-shaped member as a material, which is advantageous in terms of cost.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view, a body diagram, and the like of an exhaust pipe using a conventional double pipe.

FIG. 2 is an AA cross-sectional view of an exhaust pipe using a conventional double pipe;

FIG. 3 is a sectional view of a double pipe according to one embodiment of the present invention;

FIG. 4 is a perspective view showing one state of a process of processing a plate-shaped member that is a raw material of a double pipe according to the present invention;

FIG. 5 is a perspective view showing one state of a manufacturing process of the double pipe of the present invention;

FIG. 6 is a partially enlarged sectional view showing a joined state of a double pipe according to the present invention;

FIG. 7 is a cross-sectional view showing one state of a manufacturing process of the double pipe of the present invention;

FIG. 8 is a cross-sectional view showing one state of a manufacturing process of the double pipe of the present invention;

FIG. 9 is a sectional view showing one state of a manufacturing process in another manufacturing method of the double pipe of the present invention;

FIG. 10 is a cross-sectional view showing one state of a manufacturing process in still another manufacturing method of the double pipe of the present invention.

[Description of Signs] 10 Double tube 11, 21 Plate-like member 12, 22 Inner tube 13, 23 Outer tube 14, 24 Start of inner tube 15, 25 End of inner tube 16, 26 Outer Starting part 17, 27 of the pipe part End part 18, 28 of the outer pipe part Continuous part 31, 32, 33, 34 Welding part 35, 36 Space part 37 Hollow part 38 Welding device 39 Mandrel 40, 41 Ridge 42, 43 External mold members 44, 45 Forming rollers.

Claims (8)

[Claims] A first and a second inner tube having a substantially semicircular cross-sectional shape, and an outer surface of the first and the second inner tube having a substantially semicircular cross-sectional shape. A first and second outer tube portions provided in the second inner tube portion, wherein the first inner tube portion is joined to an inner surface of a terminal portion of the second inner tube portion. And a first outer tube portion having a terminal portion extending continuously therefrom, wherein the second inner tube portion is joined to an inner surface of the terminal portion of the first inner tube portion and a first end portion. A second outer tube portion having an end portion extending continuously therefrom, wherein the first outer tube portion has a leading end portion continuously extending from the end portion of the first inner tube portion and the second end portion. An end portion joined to an outer surface side of a starting portion of the outer tube portion, wherein the second outer tube portion continuously extends from the end portion of the second inner tube portion and the first end portion; The outer surface of the start of the outer tube Double tube characterized by having a terminal portion to be joined. 2. The double pipe according to claim 1, wherein the connection of the pipes is welding. 3. The double pipe according to claim 1, wherein a portion extending from the end of the inner pipe to the start of the outer pipe extends substantially in the radial direction. 4. A two-plate member having substantially the same rectangular shape is prepared, a semicircular portion having a substantially semicircular cross section, a long flat portion continuous from one end of the semicircular portion, and the other end. The plate-shaped member is formed so as to have a continuous short plane portion from, and the short plane portions are joined to each other with the other plate-shaped member so as to form a hollow portion having a substantially circular cross section, A large-diameter semicircle is formed so that the long flat portion extends over the outer surface of the semicircle of the other plate-like member, and the tip of each large-diameter semicircle is formed into the other plate-like member. A method of manufacturing comprising joining to an outer surface of a member. 5. A semi-circular portion having a substantially semi-circular cross section, a long flat portion continuous from one end of the semi-circular portion, and another end of the semi-circular portion having substantially the same rectangular shape. The plate-shaped member is formed so as to have a continuous short flat portion from the first plate member. The short flat portions are aligned with the other plate-shaped member so as to form a hollow portion having a substantially circular cross section. The inner mold member having a ridge and a substantially cylindrical outer surface is so formed that the mating portion between the projection ridge and the two plate-like members is aligned and circumscribes the inner surface of the hollow portion. A pair of semi-cylindrical curves having a substantially semi-circular cross section extending along the outer surface of the semi-circular portion of the two plate-shaped members, arranged in a hollow portion, joining the mating portions of the plate-shaped members; An external mold member is arranged, and each long flat portion is bent at a joint portion of the plate-shaped member. Deforming into a semicircular cross section so as to extend along the outer surface of the semi-cylindrical curved external mold member, joining the tips of the respective large-diameter semicircular portions to the outer surface of the other plate-shaped member, A method of manufacturing a double pipe, comprising removing an inner mold member and a pair of outer mold members. 6. A semi-circular portion having a substantially semi-circular cross section, a long flat portion continuous from one end of the semi-circular portion, and another end of the semi-circular portion having substantially the same rectangular shape. And forming the plate-shaped member so as to have a continuous short flat portion, and aligning each of the short flat portions with the other plate-shaped member so as to form a hollow portion having a substantially circular cross section. Are arranged so as to circumscribe the inner surface of a hollow portion formed by the two plate members, and a joining portion of the two plate members is joined, and the semicircle of the two plate members is A pair of semi-cylindrical curved external mold members each having a substantially semicircular cross-section extending along the outer surface of the portion, and bending each long flat portion at the joint of the plate-like members to form the semi-cylindrical shape. The outer mold member is deformed into a semicircular cross section so as to extend along the outer surface of In the method for manufacturing a double pipe, the tip of a semicircular portion having a large diameter is joined to the outer surface of the other plate-shaped member, and the inner mold member and the pair of outer mold members are removed. An inner mold member disposed in a hollow portion formed by the plate-shaped member, wherein the inner mold member has a substantially cylindrical outer surface having a pair of protrusions aligned with a joint portion with the two plate-shaped members. Mold members. 7. The internal mold member according to claim 6, wherein the internal mold member is constituted by a hollow member. 8. A semi-circular portion having a substantially semi-circular cross section, a long flat portion continuous from one end of the semi-circular portion, and another end of the semi-circular portion having substantially the same rectangular shape. The plate-shaped member is formed so as to have a continuous short flat portion from the first plate member. The short flat portions are aligned with the other plate-shaped member so as to form a hollow portion having a substantially circular cross section. The inner mold member having a substantially cylindrical outer surface is provided with the hollow so that the mating portion between the protrusion and the two plate-like members is aligned and circumscribes the inner surface of the hollow portion. And joining the mating portions of the plate members, disposing a pair of semi-cylindrical external mold members, and bending each long flat portion at the joint portion of the plate members to form the external mold members. To extend along the outer surface of the The outer mold member used in the method of manufacturing a double pipe, wherein ends are joined to an outer surface of the other plate member, and the inner mold member and the pair of outer mold members are removed, The outer mold member has a substantially semicircular cross-section extending along an outer surface of the semicircular portion of the two plate members, and the plate members have base ends of respective long flat portions. An external mold member that is bent from the outer mold member and deformed to have a semicircular cross section so as to extend along the outer surface of the external mold member.