JP3358431B2 - Metal tube processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing a metal pipe, and more particularly to a method for processing a metal pipe used as an exhaust pipe of a motorcycle or a four-wheeled vehicle.

[0002]

2. Description of the Related Art Conventionally, there have been the following methods for processing a metal pipe used as an exhaust pipe of a motorcycle or the like. That is, when the metal tube is bent or the like, the inside of the metal tube is filled with sand. This is because if the hollow metal tube is bent as it is, buckling occurs inside the bent portion of the metal tube. To prevent this,
By filling the inside with sand, it is possible to suppress a change in the cross-sectional shape of the metal tube during bending.

[0003] Further, sand is easy to fill into a metal pipe due to its fluidity. Even when the metal pipe is bent, it does not become a resistance to bending and can be processed smoothly. . Furthermore, after bending, it is easy to discharge from the inside of the metal pipe, and it is generally used as a processing method of the metal pipe.

[0004] In some cases, a metal pipe used as an exhaust pipe of a four-wheeled vehicle is a so-called double pipe.
In this case as well, it is common practice to fill the space between the two metal tubes and bend them in the same manner as described above. In addition, a method of pouring water in place of sand as a member to be filled, cooling the water, freezing it, and bending a metal tube in this state has been adopted.

[0005]

However, the above conventional example has the following disadvantages. That is, in terms of filling and discharging from the metal pipe,
It shows good characteristics from its fluidity. However, on the other hand, due to this fluidity, when a large deformation force is locally applied in bending the metal tube, sand flows inside the metal tube. As a result, in the vicinity of the bent portion having a small locality radius, the metal tube is disadvantageously wrinkled or buckled. these,
The buckling phenomenon of metal pipes causes exhaust gas exhaust resistance, especially when used as exhaust pipes of motorcycles and automobiles, and also causes corrosion of metal pipes near buckled parts. Cheap.

In the bending of the above-mentioned double pipe, the center of the inner metal pipe and the center of the outer metal pipe are eccentric, as shown in FIG. It may come in contact with. In particular, in a double pipe, it is very difficult to correct buckling and wrinkling of the inner metal pipe, which is a major problem in manufacturing.

[0007]

An object of the present invention is to provide a method for improving the inconvenience of the conventional example, and in particular for providing a method for easily bending a metal tube into a desired shape without changing its cross-sectional shape. With that purpose.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, a hollow first metal pipe and a second metal pipe disposed inside the first metal pipe are provided. The second metal tube is disposed apart from the inner wall of the first metal tube, and ends of the first metal tube and the second metal tube are joined to each other. Then, after that, a flow member containing a thermosetting material is filled between the first metal tube and the second metal tube, and the flow member is cured by heating to a curing temperature of the thermosetting material. After bending each metal tube, the flow member is reheated to the decomposition temperature of the thermosetting material, decomposed and discharged.

[0009] As described above, first, the flow member is filled between the metal tubes. Then, the metal tube is heated to a temperature at which the thermosetting material mixed with the fluid member hardens.
As a result, the heat-curable material is cured, and the fluidity of the fluid member is suppressed.

After the flow member has hardened, the metal tube is bent by a so-called roll bender. At this time, since the flowing member is hardened, wrinkles, bucklings, and the like do not occur in the bent portions of the respective metal tubes. On the other hand, since a predetermined fluidity is ensured inside the flow member, the bending process is performed together with the bending of the metal tube even when bending.

When the bending is completed, the metal tube is reheated to a predetermined temperature. The temperature of reheating is when the thermosetting material is carbonized,
This is the temperature at which the cured thermosetting material can be decomposed. Then, the flow member decomposed last is discharged to the outside of the metal tube. The discharge is performed while applying a predetermined vibration so that the discharge can be performed more smoothly. Thereby, the bending process of the hollow double tube is completed.

According to the second aspect of the present invention, a resin material is used as the heat-curable material, and the flow member is made of a sand material. Other configurations and methods are the same as those of the first aspect. . With the above configuration, in addition to the function of the first aspect, higher fluidity is ensured.

Further, the invention according to claim 3 employs a configuration and a method of using a phenol resin as the resin material, and other configurations and methods are the same as those of the invention according to claim 2. With the above configuration, the flow member is cured at an appropriate heating temperature, in addition to the effect of the invention described in claim 2.

Further, the invention according to claim 4 employs a configuration and a method of using a resin-coated sand having a surface coated with a phenol resin as the flowable member, and the other configurations and methods are the same as those of the invention according to claim 3. The same is true. With the above-described configuration, in addition to the effect of the invention described in claim 3, the flow member is hardened when heated.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, in this embodiment, a hollow first metal tube 3 and a first metal tube 3 are provided. 3 and a second metal tube 5 disposed inside the first metal tube 3. The second metal tube 5 is spaced apart from the inner peripheral wall 3 a of the first metal tube 3. Then, the ends of the first metal tube 3 and the second metal tube 5 are joined to each other. Further, a flow member 7 containing a thermosetting material is filled between the first metal tube 3 and the second metal tube 5, and the flow member 7 is heated to a curing temperature of the thermosetting material. Hardened, each metal tube 3,5
After being bent, the flow member 7 is reheated to the decomposition temperature of the thermosetting material, decomposed, and discharged to the outside between the metal tubes 3 and 5.

More specifically, as shown in FIG. 1, the first metal pipe 3 is a hollow pipe formed in a cylindrical shape, and is used for an exhaust pipe of a four-wheeled vehicle or the like. Enough length is ensured. On the other hand, the second metal tube 5 is also formed in a cylindrical shape, and has a length equal to that of the first metal tube 3. Here, the shape and length of each of the metal tubes 3 and 5 are as follows:
It is not limited to the above, and for example, a metal pipe having a rectangular cross section may be used, and the material is not limited to iron, stainless steel, and the like generally used for an exhaust pipe and the like, for example, copper, aluminum, and the like. It may be. The material is not limited to a metal material as long as the material has a predetermined ductility.
Although the present invention particularly describes a double tube,
Of course, it can be applied to a single metal tube.

More specifically, each of the metal tubes 3 and 5 in this embodiment will be described. The first metal tube 3 has an outer diameter of 50 mm, a wall thickness of 1 mm, and a length of about 500 mm. [M
m] iron (STKM) steel pipe is used. On the other hand, as the second metal tube 5, a stainless steel (SUS) steel tube having an outer diameter of 40 [mm], a wall thickness of 1 [mm], and a length of about 500 [mm] is used. However, these dimensions are merely examples, and the present invention can be applied to metal tubes of various shapes and dimensions. Here, in FIG. 1, the entire length of each metal tube 3, 5 is shortened for convenience.

Then, the second metal tube 5 is inserted into the first metal tube 3 described above. At this time, since each of the metal tubes 3 and 5 has a difference of about 10 [mm] in outer diameter, there is a gap between the inner peripheral wall 3a of the outer metal tube 3 and the outer peripheral wall 5a of the inner metal tube 5. A predetermined gap is formed. In the present embodiment, in order to keep this gap constant over the entire circumference of each of the metal tubes 3 and 5, the two tubes are positioned so that their central axes are concentric, and as shown in FIG. Tubes 3, 5
Are joined to each other.

As shown in FIG. 1 (B), a method of joining the metal tubes 3 and 5 is to leave one end of the inner second metal tube 5 while leaving the outer first metal tube 3 as it is. It is bent to the first metal tube 3 side. Then, the mutually contacted portions are brought into close contact by spot welding. on the other hand,
The other end between the metal tubes 3 and 5 is entirely open so that a flow member 7 described later can be filled.

Next, the metal tube 3,
The bending method of No. 5 will be described in detail. First, as shown in FIG. 1, a predetermined gap is formed between the first metal tube 3 and the second metal tube 5. As a specific configuration of the flow member 7, a resin-coated sand in which the surface of sand is coated with a phenol resin is used. Here, the phenol resin has a property of curing at a predetermined temperature, and is a so-called heat-curable material.

The mixing ratio of the phenol resin to the sand is set to about 1 to 5 [wt%]. This is because the strength at the time of heating is insufficient at 1 [wt%] or less, and the change of the strength is not significantly affected even when the strength is set at 5 [wt%] or more. However, since the curing strength differs from that of the phenol resin depending on the type of the resin, different types of resin materials can be used by setting an appropriate mixing ratio according to each resin material. As an example of sand, so-called silica sand No. 7 is used.

Then, the resin-coated sand as the flow member 7 configured as described above is filled in the space formed between the metal tubes 3 and 5 (reference numeral S1 in FIG. 3). . At this time, the resin-coated sand has good fluidity like ordinary sand,
The filling operation can be easily performed. When filling
In order to perform the filling reliably and uniformly, the filling may be performed while applying a predetermined vibration.

When the resin coated sand as the flow member 7 is filled, the metal tubes 3 and 5 are heated to a temperature at which the phenol resin hardens (S2 in FIG. 3). The heating temperature is set at about 250 to 300 [° C.]. As a heating method, high-frequency induction heating, a gas burner, or the like is used. The heating time is about 5 [min]. As a result, the phenol resin of the resin-coated sand is cured, and the fluidity of the sand is suppressed.
However, since the curing temperature differs depending on the type of the resin material used, the resin material can be appropriately selected according to the purpose.

After the resin-coated sand is cured (reference S3 in FIG. 3), the metal tubes 3 and 5 are bent by a so-called roll bender (not shown) (reference S4 in FIG. 3). In the present embodiment, as shown in FIG. 2, a bending process of 60 ° was performed at a substantially central portion of the metal tubes 3 and 5.
During the bending, as described above, the resin-coated sand is hardened and present inside, so that the bent portions 9 of the metal tubes 3 and 5 do not generate wrinkles or buckling. On the other hand, since the inside of the resin-coated sand has a predetermined fluidity, the metal tubes 3 and 5 can be bent even when bending.
It bends with the bend.

When the bending is completed, the metal tubes 3 and 5 are reheated to a predetermined temperature (reference S5 in FIG. 3). The reheating temperature is a temperature at which the phenol resin is carbonized and the cured resin-coated sand can be decomposed. Specifically, about 400
It is set to ~ 500 [° C]. Then, the finally disassembled resin-coated sand (symbol S6 in FIG. 3) is discharged to the outside of the metal tubes 3 and 5 (symbol S7 in FIG. 3). The discharge is performed while applying a predetermined vibration so that the discharge can be performed more smoothly.

The metal tubes 3, 5 bent as described above
FIG. 4 shows a sectional view of the bent portion 9 of FIG. According to FIG. 4, the central axes of the outer first metal tube and the inner second metal tube coincide with each other. That is, it is understood that the relative positional relationship between the two metal tubes 3 and 5 does not change even by bending. In addition, when the method according to the present embodiment is used, a buckling phenomenon, a wrinkle, or the like does not occur in the bent portions 9 of the metal tubes 3 and 5.

[0027]

As described above, according to the present invention, a flow member is filled in a metal tube, which is cured by heating, and after bending the metal tube, the flow member is disassembled and discharged. Therefore, when bending a double pipe, there is no buckling or wrinkling in the bent portion, and the two metal pipes can be bent while maintaining concentricity with each other. Occurs.

Further, since a resin material is used as the heat-curable material, the fluid member can be cured even at a relatively low heating temperature. As a result, there is an excellent effect that even when bending a metal pipe, bending can be reliably performed only by adding a small amount of equipment to a conventional processing apparatus.

Further, since a resin material is used as the heat-curable material, by heating to a temperature higher than the curing temperature, the cured fluid member can be easily decomposed.
For this reason, after the bending of the metal tube, there is an excellent effect that the flowing member can be easily discharged to the outside.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention, and FIG.
1A shows a plan view of a metal tube, and FIG. 1B shows a cross-sectional view of the metal tube.

FIG. 2 is a side view showing a state where the metal tube disclosed in FIG. 1 is bent.

FIG. 3 is a diagram showing a flowchart of a bending process.

FIG. 4 is a sectional view of a bent portion of the metal tube disclosed in FIG. 2;

FIG. 5 is a sectional view of a bent portion when a double pipe is bent by a conventional method.

[Explanation of symbols]

 3 1st metal pipe 5 2nd metal pipe 7 Flowing member (resin coated sand) 9 Bending part

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B21D 9/15 B21D 9/00 B21D 9/18 B21D 53/84 F01N 7/08

Claims (4)

(57) [Claims] 1. A first metal tube having a hollow, and a second metal tube disposed inside the first metal tube, wherein the second metal tube is provided inside the first metal tube.
And the metal pipes are spaced apart from the inner wall of the first metal pipe, and the ends of the first metal pipe and the second metal pipe are joined to each other. And filling the flow member containing a thermosetting material between the second metal pipe and curing the flow member by heating to the curing temperature of the thermosetting material,
After bending each of the metal tubes, the flow member is reheated to a decomposition temperature of a thermosetting material, decomposed, and discharged. 2. The method according to claim 1, wherein a resin material is used as the heat-curable material, and the flow member is made of a sand material. 3. The method according to claim 2, wherein a phenol resin is used as the resin material. 4. The method for processing a metal pipe according to claim 3, wherein a resin-coated sand whose surface is coated with the phenol resin is used as the fluid member.