JP2788702B2 - Bent pipe and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bent pipe which is formed into a predetermined shape used for a muffler or the like and which is not required to be relatively airtight, and a method for manufacturing the bent pipe. .

[0002]

2. Description of the Related Art A muffler for an automobile is divided into a plurality of chambers by partitions, and these chambers are communicated with each other to form a straight pipe having a predetermined diameter and length, or a bending pipe having a predetermined bending shape. Pipes are located.

In general, the bent pipe is manufactured using a commercially available fixed-length steel pipe as a raw material. That is, purchase a commercially available standard-length steel pipe with the diameter and thickness set at the design stage,
The bent pipe is manufactured by cutting this steel pipe to a size equal to the length of a target bent pipe linearly extended, and then performing bending on the cut steel pipe.

[0004]

In the above-mentioned conventional manufacturing method, a commercially available steel pipe is a so-called fixed-length piece having a fixed length, and has a dimension which is a constant multiple of the length of a target bent pipe. There is no guarantee to have For this reason, there is a problem that the yield decreases and the product cost increases.

[0005] Commercially available steel pipes are expensive because both drawn pipes and electric resistance welded pipes are airtight. However, since the bent pipe used for the muffler is not required to be relatively airtight, the bent pipe for the muffler manufactured using such a steel pipe has a higher cost than the required function, and There is a problem that added value is reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide a bent pipe with reduced cost and improved added value, and a method of manufacturing the same.

[0007]

In order to solve the above problems, a bent pipe according to the present invention is a bent pipe formed by forming a plate having a predetermined dimension into a cylindrical shape and bending the plate into a predetermined shape. Further, both ends in the longitudinal direction of the butted portion of the plate formed in a cylindrical shape are welded to portions corresponding to the bent portion.

[0008] A method for manufacturing a bent pipe according to the present invention comprises a forming step of forming a plate having a size corresponding to a target bent pipe into a cylindrical shape, and a preset process at a butt portion of the cylindrical shaped plate. A welding step of forming a straight pipe by welding a bent portion and a portion corresponding to both ends in the longitudinal direction, and a bending step of bending a straight pipe welded to a predetermined portion. It is.

[0009]

According to the above-mentioned bent pipe, the cost of the bent pipe can be reduced and the added value can be improved. That is, since a straight pipe was formed by welding both ends of the member formed into a cylindrical shape and portions corresponding to the bending portions, and a bent pipe was formed by bending the straight pipe into a predetermined shape,
The bent portion of the pipe is constrained by welding, and can maintain an accurate cylindrical shape and bent shape.

As described above, the bent pipe does not weld the entire length of the butted portion in the member formed into a cylindrical shape. For this reason, manufacturing costs can be reduced. Also, since the material used for the bent pipe is a plate,
The material cost is low as compared with commercially available steel pipes, and the added value can be improved.

According to the above manufacturing method, the thickness is equal to the thickness of the target bent pipe, the width is equal to the peripheral length of the target bent pipe, and the length is equal to the length when the target bent pipe is linearly extended. A plate having a length dimension is prepared, and in the forming step, the plate can be formed into a cylindrical shape by roll forming or press forming.

In the welding step, both ends in the longitudinal direction of the butted portion of the member formed into a cylindrical shape as described above are selectively welded to a bending portion corresponding to a predetermined bending shape. By this welding, a straight pipe whose required part is restricted can be formed.

In the bending step, a predetermined bent pipe can be manufactured by subjecting the straight pipe to a predetermined bending process.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a bent pipe and a method of manufacturing the bent pipe. FIG. 1 is a perspective view illustrating the structure of a bent pipe, FIG. 2 is a cross-sectional view of a muffler using the bent pipe, and FIGS. 3 (a) to 3 (g) are diagrams illustrating steps of manufacturing the bent pipe.

The bent pipe 1 shown in FIG. 1 is arranged in the automobile muffler A shown in FIG. 2 so as to be suitably used as a pipe. It is possible to use a pipe which does not require airtightness and requires only a predetermined bending shape.

The bent pipe 1 is set in advance with dimensional specifications such as wall thickness, diameter, and length and shape specifications. A welding bead 3 is attached to a butt portion 2 corresponding to the end portion 1a and the bent portion 1b of the bent pipe 1 set based on the above specification.
Is formed, and the cylindrical shape of the bent pipe 1 is restrained by the weld bead 3. For this reason, the end 1a of the bent pipe 1 is not deformed by springback, and the bent portion 1b is not deformed due to the bending.

In the bent pipe 1, the butt portion 2 is not welded over the entire length. For this reason, there is no airtightness, and when a fluid is allowed to flow, the fluid may leak from an unwelded portion in the butt portion 2. However, when the bent pipe 1 disposed inside is required to mainly function as a resonance tube, such as the muffler A for an automobile, it is possible to sufficiently satisfy the function.

Next, a method of manufacturing the bent pipe 1 will be described with reference to FIG. In manufacturing the bent pipe 1, as shown in FIG. 1A, a flat plate 4 having a developed dimension based on a preset dimension specification is formed. The flat plate 4 is formed by stamping a fixed length plate having a predetermined thickness or a long plate wound in a coil shape by a press. Further, depending on the thickness of the flat plate 4, the flat plate 4 can be formed by a cutting process using a plasma torch, a laser torch, or a gas cutting torch.

In the forming step, the flat plate 4 is formed into a cylindrical shape by a roll forming machine 5 as shown in FIG. 2B, thereby forming a cylindrical body 6 as shown in FIG. The cylindrical body 6 has a length equal to the length when the bent pipe 1 is linearly extended, and the butted portion 2 is slightly opened by springback.

The forming of the cylindrical body 6 by the roll forming machine 5 is a general processing method, and is not particularly novel. As a method of forming the flat plate 4 into a cylindrical shape, there is a method of forming by pressing other than using the roll forming machine 5, and it is natural that any method may be used.

In the welding step, welding torches 7 (7a to 7c) are arranged at both ends of the cylindrical body 6 formed as described above and at portions corresponding to the bent portions as shown in FIG. By operating these welding torches 7,
To the welding bead 3 shown in FIG.
To form At this time, it is preferable to hold the cylindrical body 6 by a jig (not shown) in order to bring the butted portion 2 into close contact and prevent deformation due to welding.

When the cylindrical body 6 is to be welded, one welding torch 7a to 7c is arranged at each location to be welded as described above,
These welding torches 7a to 7c may be simultaneously operated to weld a plurality of welding portions at the same time, or one welding torch may be used to sequentially weld portions to be welded. However, considering the time required for welding, simultaneous welding with a plurality of welding torches is preferable.

By passing through the forming step and the welding step as described above, as shown in FIG.
Thus, it is possible to form a straight cylindrical body 6 whose cylindrical shape is constrained.

In the bending step, as shown in FIG.
The bending process is performed on the cylindrical body 6 by the bending machine 8 in accordance with a preset bending shape to form the bent pipe 1 shown in FIG. In this bending step, it is possible to use the same bending machine 8 as a bending machine generally used for bending pipes.

As described above, the bent pipe 1 having a predetermined shape can be manufactured. In this bent pipe 1, since the flat plate 3 is used as a material,
The material cost can be reduced and the added value can be improved as compared with a manufacturing method of bending using a commercially available steel pipe.

[0026]

As described in detail above, in the bent pipe according to the present invention, the flat plate is formed into a cylindrical shape and only the longitudinal ends and the portions corresponding to the bent portions are welded. In addition, the cylindrical shape of the bent portion can be restrained, and a function as a pipe can be provided even though welding is not performed over the entire length.
Therefore, it can be used as a bent pipe requiring only a shape without requiring airtightness.

Further, the method for manufacturing a bent pipe according to the present invention is characterized in that the bent pipe can be manufactured efficiently, the manufacturing cost can be reduced, and the added value can be improved. is there.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating the structure of a bent pipe.

FIG. 2 is a sectional view of a muffler using a bent pipe.

FIGS. 3A to 3G are diagrams illustrating a process of manufacturing a bent pipe.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS A Muffler for automobiles 1 Bending pipe 1a End 1b Bending part 2 Butting part 3 Welding bead 4 Flat plate 5 Roll forming machine 6 Cylindrical body 7, 7a-7c Welding torch 8 Bending forming machine

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) F01N 7/18 B21C 37/08 B23K 9/00-9/32 F01N 7/08

Claims (2)

(57) [Claims] 1. A bent pipe formed by forming a plate having a predetermined dimension into a cylindrical shape and performing a bending process into a predetermined shape, wherein the pipe has a longitudinal direction at an abutting portion of the cylindrical shaped plate. A bent pipe characterized in that both ends of the pipe and the parts corresponding to the bent parts are welded. 2. A forming step of forming a plate having a size corresponding to a target bending pipe into a cylindrical shape, and a predetermined bent portion and a longitudinal direction at a butt portion of the cylindrical formed plate. A method for manufacturing a bent pipe, comprising: a welding step of welding a portion corresponding to both ends to form a straight pipe; and a bending step of bending a straight pipe welded to a predetermined portion.