JP2003328747A - Pipe fitting and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pipe joint which is connected to an exhaust pipe of an engine as an exhaust manifold or the like, which has a small number of components and a small number of welded parts, and which can be easily connected to and separated from a pipe. I do. SOLUTION: In an exhaust manifold 10 used as a pipe joint for an exhaust pipe of an engine, a first opening 11 connected to a plurality of parallel pipes (exhaust pipes) 3 and one pipe (joint) are provided. And a second opening 13 detachably connected to the pipe 7 at each of the separated ends, and a wall portion 12 connecting them.
Was integrally molded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The claimed invention is a pipe joint (generally called an exhaust manifold) which is connected to an exhaust pipe of an engine and is used for merging or branching exhaust gas. It relates to a manufacturing method.

[0002]

2. Description of the Related Art An exhaust pipe of a motorcycle is constructed, for example, as shown in FIG. That is, first, four exhaust pipes 3 having the same number as the number of cylinders extend from the engine 2 toward the lower front portion, and are connected to two exhaust manifolds 10 provided below (the conventional one is 10 ', which will be described later). Manifold 10 has two inlet openings and one inlet
The two outlet pipes are provided, and the downstream side of the four exhaust pipes 3 is integrated with the two joint pipes 7 through these. Each of the two joint pipes 7 is connected to two mufflers 8 on the right side and the left side of the vehicle body via the branch pipe 7e.

Each of the above-mentioned manifolds 10 is a pipe joint that connects two exhaust pipes 3 on the upstream side and one joint pipe 7 on the downstream side. Since high-temperature exhaust gas passes inside, it is made of metal (stainless steel, etc.) with excellent heat resistance and oxidation resistance. Since it is not a simple cylindrical shape, the conventional exhaust manifold 1
For 0 ', a split type configuration as shown in FIG. 5 is adopted. That is, 2 which is almost symmetrical with respect to the plane including the axis
The wall portions 22 are formed by joining the pieces 22X and 22Y to form a hollow body (monaca structure) like a monaca shell, and then welding the outer mating portion 22Z (FIG. 5 (b)). -See (c)). As shown in FIG. 5A, the openings 21 on the upstream side are arranged so as to be in contact with each other.
Insert the exhaust pipe 3 of the book, and weld the connecting portion all around. Then, the short pipe 4 is inserted into the opening 23 on the downstream side and the connection portion is welded all around, and the downstream end portion of the short pipe 4 is inserted inside the joint pipe 7, and the gasket 6 and the band 7d are inserted. Use to connect separably.

The downstream portion of the short pipe 4 is connected to the joint pipe 7
The reason for making it separable is to facilitate later maintenance and component replacement. The downstream portion of the manifold 10 'is not directly connected to the joint pipe 7, but the short pipe 4 is integrated and connected as described above because the manifold 10' is a joined body of two pieces 22X and 22Y. Therefore, the second opening 23 has irregularities on both the inner peripheral surface and the outer peripheral surface, and it is difficult to make a tight connection with other pipes by a method other than the entire circumference welding.

Further, the short pipe 4 (or the manifold 1)
0 ') may be connected by the connecting pipe 5 as shown in FIGS. 5 (a) and 5 (d). This is because the exhaust pipes existing in parallel are connected to each other so that the exhaust gas can flow in and out, so that the pressure fluctuations in the exhaust pipes are alleviated and the torque adjustment of the engine is realized. Specifically, a hole 4e is formed in a part of the side wall of the short pipe 4, the peripheral edge portion 5e of the end opening of the connecting pipe 5 is overlapped around the hole, and the connecting pipe 5 is connected by welding. .

[0006]

The conventional exhaust manifold shown in FIG. 5 is formed only by welding a plurality of components at a number of points. For example, the manifold 10 'itself is formed by welding the two pieces 22X and 22Y, and the short pipe 4 needs to be integrated on the downstream side in order to be a pipe joint that is easily connected to the pipe. Moreover, it is also necessary to weld each part continuously not by spot welding or the like, but on the entire length of the two pieces 22X and 22Y and the entire circumference between the two pieces 22X and 22Y. Therefore, there is a disadvantage that a considerable manufacturing cost is required.

If the short pipes 4 (or the manifolds 10 ') are connected to each other by the connecting pipe 5, it takes more work and the cost increases. This is because when the circular hole 4e is formed in the cylindrical side wall, the peripheral edge of the hole 4e does not exist in one plane. That is, it is necessary to form a complicated peripheral edge portion 5e having a three-dimensional (three-dimensional) shape also on the end portion of the connecting pipe 5 that is overlapped around the hole 4e, and then perform non-simple welding between them. The need also arises.

The invention as claimed in claim 1 is a pipe joint connected to an exhaust pipe of an engine, such as the above-mentioned manifold, in which the number of constituent parts and the number of welded parts are small, and connection / separation to the pipe is easy, and It is an object of the present invention to provide a preferable manufacturing method for such a pipe joint.

[0009]

According to a first aspect of the present invention, there is provided a pipe joint used in an exhaust pipe of an engine (such as the above-mentioned exhaust manifold) in which a first opening is connected to a plurality of pipes. And a second opening connected to one pipe are provided at each of the separated ends, and a wall surface portion connecting them is integrally formed. "Integrally molding" does not mean that two or more parts are combined but is formed as an integrated part from the beginning by casting, forging, or a hydraulic forming method described later. Since this pipe joint is used for an engine exhaust pipe, the pipe joint is made of a metal having high heat resistance and oxidation resistance. Further, the terms "first" and "second" in the above-mentioned "first opening" and "second opening" are names for distinction and do not indicate the order of passage of exhaust gas. The case where the two openings are located on the upstream side of the exhaust is also included in the invention of this claim. The exhaust manifold 10 shown in FIG. 1 is an example of the pipe joint of this claim.

Since this pipe joint is formed by integrally molding the wall surface portion connecting the first opening portion and the second opening portion, two pieces are joined as in the conventional case (see the manifold 10 'in FIG. 5). Naturally, the number of constituent parts is small and the number of places where welding is required is small as compared with those obtained, and the appearance is preferable. But this is not the only advantage of this fitting. This is because the following characteristic actions, which cannot be easily predicted, accompany.

One of the characteristic actions of this pipe joint is that the inner peripheral surface or the outer peripheral surface such as the second opening can be easily made smooth by integrally molding the wall surface portion as described above. When the two wall pieces are joined to form the wall surface, irregularities can be formed on both the inner and outer peripheral surfaces (the irregularities do not disappear unless they are finished by machining, etc.) -The irregularities on the outer peripheral surface can be made quite small. Therefore, the pipe can be easily connected to the second opening, and the second opening can be separated from the second opening, for example, through a gasket (packing), without smooth finishing by machining or the like. The tubes can be tightly connected.

The fact that the pipe can be connected to the second opening means that the pipe is directly connected without using the short pipe (reference numeral 4 in FIG. 5) as described above, and the pipe is connected to the pipe. It means that the spaces can be separated. If the pipe joint and the pipe can be separated from each other, the exhaust pipe configured using the pipe joint can be easily maintained. This point is also a characteristic action of the above pipe joint. That is, by integrally molding the wall surface portion as described above, many problems can be solved at the same time.

The pipe joint according to claim 2 further comprises a second joint.
A step or a protrusion that serves as a gasket stopper is provided integrally with the wall surface portion at a position apart from the opening end in the opening. The step or protrusion is the second
Inwardly or outwardly on the entire circumference or part of the second opening, at a position separated from the opening end by a distance substantially corresponding to the length of gaskets mounted between the opening and the pipe connected thereto. It may be formed in the direction. In the example of FIG. 1, reference numeral 12d is
It is an outward projection that serves as a gasket stopper.

In many cases, the second opening is a portion which can be detachably connected to a single tube in an inserted state (inserted inside the tube or covered with the outside). A tube is inserted into the outside or inside through gaskets. Since the position of the gaskets is likely to shift during insertion, it is desirable to provide the opening and the pipe with a portion that functions as a gasket stopper. In the pipe joint of this claim, a step or a protrusion that serves as such a gasket stopper is provided in the second opening portion (a portion apart from the opening end) and is integrally formed with the wall surface portion of the pipe joint. . Therefore, according to this pipe joint, the pipe joint using the gaskets and the pipe can be easily connected in the second opening, and moreover, it is necessary to increase the number of parts, the welding process, etc. in order to provide the step or the protrusion. There is no advantage.

In particular, the pipe joint according to claim 3 includes an outwardly projecting portion in a part of the wall surface portion, and the projecting portion has an opening at the tip and is inserted into a pipe other than the above ( It is characterized in that it is formed so that it can be connected by being inserted inside the tube or being covered with the outside). "Outward protrusion" provided on part of the wall surface as described above
Corresponds to a portion projecting in a direction intersecting the flow direction of exhaust gas between the first opening and the second opening. Also, "tubes other than the above"
And refers to tubes other than the tubes connected to the first opening and the second opening. In the example of FIG. 1, reference numeral 12e (or 12g) is a "protrusion" and reference numeral 5 is a "tube".

It is generally not easy to connect another pipe on the side wall of the pipe or the pipe joint in a direction intersecting with the flow direction. Also in the conventional pipe fitting (manifold 10 ') shown in FIG. 5, when the connecting pipe (5) is connected to a part of the short pipe (4), both the peripheral portion of the hole and the peripheral portion of the connecting pipe are three-dimensional. It had to be a complicated shape. However, in the pipe joint of this claim, instead of making a hole in the wall surface portion to connect another pipe, the wall surface portion is provided with an outwardly projecting portion and the projecting portion is connected to another pipe. , That problem can be solved. In other words, if the projections are projected according to the direction of the pipe and the size is such that it can be inserted into the pipe easily, connection between the pipe joint and the pipe is extremely easy, including welding between the two. It can be carried out. This is because the periphery of the hole or the tip of the tube can be contained in one plane, and it is not necessary to form a complicated shape (see FIGS. 1 (a), (c), and (d)).

In particular, the pipe joint according to the fourth aspect is characterized in that the wall surface portion is integrally formed by a hydraulic forming method. The hydraulic forming method is a pipe material (material of the pipe) by applying hydraulic pressure to the inside.
Is a method of stretch-forming (see FIG. 4).

In order to integrally form the wall surface portion, means such as casting, powder metallurgy, and forging may be used, but in those cases, a complicated mold including a core is used to form a structure through which exhaust gas passes. In addition to the need to adopt a configuration, the wall surface tends to be thick. In that respect, the pipe joint of this claim is
Since the wall surface portion is integrally formed by the hydraulic forming method, there is no such inconvenience. That is, molding can be performed easily and at low cost without using a core, and it is also easy to make the wall portion thin and lightweight. The opening at the tip of the above-mentioned "outward protrusion" is formed by a hydropiercing method in which a pin provided on a part of the die is inwardly projected to form a hole in the process of hydraulic forming. Alternatively, the molded product may be opened in a separate step after being taken out of the mold.

A method for manufacturing a pipe joint according to claim 5 is
A first opening engaging with the outside of a plurality of juxtaposed tubes and 1
Pipe joints for engine exhaust pipes (therefore made of metal having heat resistance / oxidation resistance, etc.) that are provided at each of the distant end portions and are connected to each other by an integral wall surface portion No.), hydraulic forming (hydroforming)
It is characterized by being formed by a method. The first opening is an opening that fits on the outside of a plurality of tubes that are in contact with each other (or almost in contact with each other) in parallel. ), A trilobal shape (when fitted on the outside of three tubes), a four-leaf shape (when fitted on the outside of four tubes), and the like. The second opening is fitted into the outside of the tube or inserted into the inside of the tube to be connected to one tube, and has a circular or polygonal opening along the cross section of the tube.

According to this manufacturing method, the first
-A pipe joint having the second opening can be easily manufactured. This is because, in the case of the hydraulic forming method, for example, a tubular member having a general circular cross section is put in a mold, and an arbitrary shape can be given to the wall surface portion by applying hydraulic pressure from the inside of the tubular member. Since there is no need to use a core, there is an advantage that the mold can be easily constructed, and it is easy to form a thin and lightweight wall portion. The use of tubing with a smooth surface also smoothes the inner and outer surfaces of the pipe fitting (the inner peripheral surface that does not contact the mold remains particularly smooth) so it can be separated from the pipe (that is, a gasket rather than a welded connection). Suitable for forming connecting pipe joints.

In the method for manufacturing the pipe joint according to the sixth aspect, particularly, two pipe joints are integrally formed by a hydraulic forming method so that the first openings are connected to each other.
After that, it is characterized in that two pipe joints are formed by cutting in the middle part (the middle part of the part where the first openings are connected).

Since the hydraulic forming method applies hydraulic pressure to the inside of the pipe material from the end opening of the pipe material, in order to change the opening of the end portion largely from the shape and size of the original pipe material. There is a special technical device. However, if the two pipe joints are molded so that the first openings are connected to each other as in the manufacturing method of this claim, the first openings are located near the center in the length direction of the pipe material. Yes, at both ends of the tubing,
In both cases, only the second opening is formed, and there is almost no change from the original shape and size. Therefore, according to this manufacturing method, the pipe joint can be easily manufactured by using a general hydraulic molding device, and the portion wasted as scrap can be reduced. It should be noted that it is not difficult to cut the molded product into two pipe joints after molding.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a mode for carrying out the invention.
~ Shown in FIG. First, FIG. 1 is a detailed view of an exhaust manifold 10 which is an example of a pipe joint. FIG. 1A is an overall vertical sectional view, FIG. 1B is a sectional view taken along line bb in FIG. 7C is a sectional view taken along line cc in FIG. 7A, and FIG. 8D is a view showing an alternative plan of the portion shown in FIG. Figure 2
2 (a) is a side view and FIG. 2 (b) is a rear view (viewed from the rear side) of the motorcycle 1 to which an exhaust pipe including the manifold 10 and the like is attached. FIG. 3 shows the exhaust pipe (upstream part thereof) of the motorcycle 1 of FIG.
3A is a side view, and FIG. 3B is a front view (a view taken along the line bb in FIG. 3A). Further, FIG. 4 is a schematic diagram showing a manufacturing process of the manifold 10 by a hydraulic forming method.

As described above, the following exhaust pipe is connected to the engine 2 of the motorcycle 1 shown in FIG. That is, the exhaust port 2 for each cylinder of the engine 2
In a, four exhaust pipes 3 equal to the number of cylinders extend toward the lower front portion, and two exhaust pipes 3 are provided in each of the two exhaust manifolds 10 provided near the lower position of the engine 2. Connected. One joint pipe 7 is connected to the downstream side of each manifold 10, and each joint pipe 7 is connected to two parallel mufflers 8 via a branch pipe 7e.

In the thus constructed exhaust pipe, each manifold 10 is used as a pipe joint for connecting two exhaust pipes 3 to one joint pipe 7. The downstream end (second opening 13 described below) of the manifold 10 is connected to the joint pipe 7 so that the upstream part and the downstream part of the exhaust pipe can be separated to facilitate maintenance of the exhaust pipe including the muffler 8. It is also designed to be separable.

The exhaust manifold 10, like other parts in the exhaust pipe, is made of stainless steel having excellent heat resistance and oxidation resistance, and its shape is as shown in FIG. That is, first, two exhaust pipes 3 having a circular cross section (integrated in the welded portion 3w) arranged in parallel so that their outer peripheral portions are in contact with each other can be inserted inward at the upstream end portion. A first opening 11 having a shape is provided (see FIG. 1A). The downstream end of the exhaust pipe 3 is inserted into the first opening 11, and the entire circumference is welded between the two. On the other hand, at the end portion on the downstream side, one joint pipe 7 having a circular cross section forms a cylindrical second opening portion 13 which is covered with the gasket 6 on the outside. Then, the first opening 11 and the second opening 1
3 and 3 are connected in a cylindrical shape by an integral wall surface portion 12.

In the wall surface portion 12 of the manifold 10, as shown in FIG. 1A, the first opening 11 to the second opening 13 are formed.
The funnel-shaped portion 12a, the circular pipe portion 12b, and the inserted portion 12c are formed in this order. Funnel shaped part 12a
Is a portion of which the cross section changes smoothly from the first opening 11 having the shape of a figure 8 toward the opening having the circular cross section. Round tube part 1
Reference numeral 2b is a portion on the downstream side of the funnel-shaped portion 12a, where an opening having a circular cross section continues. The inserted portion 12c has a circular opening similar to the circular pipe portion 12b, and is a portion to be inserted inside the joint pipe 7.

The wall surface portion 12 is further provided with a second opening 13
12c, which is a position slightly distant from the open end of the
An outwardly projecting annular projection 12d is formed at the base of the. This is formed integrally with the wall surface portion 12 by plastically deforming the stainless steel forming the wall surface portion 12, and functions as a so-called gasket stopper. In other words, when the inserted portion 12c is covered with the gasket 6 together with the expanded diameter portion 7a at the tip of the joint pipe 7 as shown in FIG. 1A, the protrusion 6d and the stepped portion 7c of the joint pipe 7 act to make the gasket 6 The position of is determined. In this way, the inserted portion 12c and the joint pipe 7 are put in the inserted state by sandwiching the gasket 6, and the expanded diameter portion 7a
By tightening the band 7d which is covered with the outside, the width of the slit 7b in the expanded diameter portion 7a is narrowed to firmly connect the joint pipe 7 and the manifold 10,
Complete the connection.

In the motorcycle 1 shown in FIG. 2, the two manifolds 10 are arranged in the lower part of the vehicle body with a space left and right, and they are connected by a connecting pipe 5. Details of the connecting pipe 5 are as shown in FIGS. 3 (a) and 3 (b). The reason why the parallel exhaust pipes are connected to each other in this way is to adjust the engine torque by relaxing the pressure fluctuation in the exhaust pipes, as described above. Manifold 1
In 0, in order to facilitate the connection with such a connecting pipe 5,
As shown in FIG. 1, a protrusion 12e is integrally provided on a part of the wall surface portion 12.

That is, as shown in FIG. 1 (a) (in FIG. 1 (a), the connecting pipe 5 is stretched, with the projections 12e being displaced in the circumferential direction of the circular pipe portion 12b). The wall surface portion 12 is raised over a height of several tens of mm in a direction perpendicular to the circular pipe portion 12b to form a protrusion 12e, and an opening 12f is formed at the tip thereof. Protrusion 12
If the outer diameter of e is adjusted to the inner diameter of the connecting pipe 5,
As shown in (c), the end of the connecting pipe 5 can be covered on the outside of the protrusion 12e. The necessary connection is completed by welding the entire circumference between the peripheral edge portion 5e of the connecting pipe 5 and the protruding portion 12e. Instead of such a protrusion 12e, a protrusion 12g having a shape in which the connecting pipe 5 is inserted inside as shown in FIG. 1D may be formed. That is, the projection 12g is provided with a diameter slightly larger than that of the connecting pipe 5, and the opening 12h having the same diameter as the outer diameter of the connecting pipe 5 is formed at the tip thereof. If the end of the connecting pipe 5 is inserted into the inside of the opening 12h and the tip end of the protrusion 12g and the connecting pipe 5 are welded all around, the manifold 10 has the same function as in the case of FIG. 1C. Can be connected to the connecting pipe 5.

The exhaust manifold 10 having the above-described shape is also characterized in that all the parts are formed as a single piece without welding. That is, the entire manifold 10 is manufactured by integral molding by the hydroforming method. Since it is integrally molded, there is an advantage that there are few constituent parts and welding is unnecessary. Also, because it is a hydroforming method, it becomes a lightweight part with no waste, and it has a smooth shape and good appearance.
There is also a merit. Since the outer periphery of the second opening 13 can be formed into a smooth surface without irregularities or steps, a separable connection using the gasket 6 can be made to the joint pipe 7, which is another characteristic of the manifold 10 thus formed. is there.

Molding of the manifold 10 by the hydroforming method is performed as shown in FIG. That is,
A stainless steel pipe (tubular material) 10M as a material is placed between the upper and lower molds 31 and 32, and the molds 31 and 32 are closed by pressing from above and below, and one end of the steel pipe 10M is stopped by a stopper 33. While sealing, liquid pressure (high pressure water or high pressure oil) is applied from the other end by the injector 34.
If the liquid pressure is sufficiently high, the wall surface of the steel pipe 10M will be the mold 3
It spreads and is plastically deformed until it is pressed against the inner surface of 1.32 to form the shape of the wall surface portion 12 of the manifold 10 shown in FIG. The groove for forming the annular protrusion 12d and the recess for forming the protrusion 12e are also formed in the mold 31.
If formed on the inner surface of 32, both the protrusion 12d and the protrusion 12e can be easily integrally formed. If a pin that has a sharp peripheral edge and can be extruded is built in the recess for the protrusion 12e of the molds 31 and 32, the so-called hydro-pierce method is used to form the manifold 10 and the tip of the protrusion 12e at the same time. The opening 12f can also be provided. The annular protrusion 12d may be formed by applying a force to the tube 10M in the length direction by the stopper 33 and the injector 34.

In order to obtain a molded product of the manifold 10 from the steel pipe 10M with good yield, it is preferable to mold two manifolds 10 simultaneously from one steel pipe 10M. That is, the first opening 11 is connected to each other so that
A method is employed in which individual manifolds 10 are molded at the same time, and after molding, the portions between the first openings 11 are cut to be divided into two. This is because it is not necessary to form a wasteful portion that becomes scrap in the portion following the first opening 11.

[0034]

According to the pipe joint of the first aspect, it is easy to make the inner and outer peripheral surfaces of the opening smooth.
The pipe can be tightly connected to the opening in a separable state, for example, via gaskets. Also, since the pipe joint and the pipe can be separably connected in such a manner,
The exhaust pipe including this pipe joint can be easily maintained. Naturally, there are advantages that the number of components and the number of welding points required are small, the cost can be reduced, and the appearance is preferable.

According to the pipe joint of the second aspect, the pipe joint using the gaskets and the like at the second opening can be easily connected to the pipe, and moreover, in order to form a step or a protrusion. There is no need to increase the number of parts or welding process. Claim 3
According to the pipe joint described in (1), particularly, another pipe extending in a direction intersecting with the flow direction of the exhaust gas can be extremely easily connected to the wall surface portion of the pipe joint. According to the pipe joint of the fourth aspect, it is possible to form the pipe joint easily and at low cost without using a core, and it is easy to make the wall portion thin and lightweight.

According to the pipe joint manufacturing method of the fifth aspect, it is possible to easily manufacture the pipe joint having the first and second openings which differ in the number of pipes to be connected. There is also an advantage that the mold configuration is simple and that it is easy to form a thin and lightweight wall portion. It is also advantageous in the sense that the inner and outer surfaces of the opening are smoothed to provide a separable connection to the tube. With the manufacturing method according to the sixth aspect, in particular, the pipe joint can be easily manufactured by using a general hydraulic molding device, and the material wasted as scrap can be reduced.

[Brief description of drawings]

FIG. 1 is a manifold 1 which is an example of a pipe joint according to the invention.
1 is a detailed view showing 0, and FIG.
The same (b) is a sectional view taken along the line bb in the same (a), the same (c) is a sectional view taken along the line cc in the same (a), and the same (d) is an alternative to the portion shown in the same (c). FIG.

2 is an external view of a motorcycle 1 to which an exhaust pipe including the manifold 10 of FIG. 1 is attached, FIG. 2 (a) is a side view, and FIG. 2 (b) is a rear view (viewed from the rear). Is.

3 shows the exhaust pipe (upstream portion thereof) of the motorcycle 1 of FIG. 2, FIG. 3 (a) is a side view, FIG. 3 (b) is a front view (bb arrow in FIG. 3 (a)). (View).

FIG. 4 is a schematic view showing a manufacturing process of the manifold 10.

FIG. 5 is a view showing a conventional manifold 10 ′ used for an exhaust pipe of a motorcycle, FIG. 1 (a) is an overall view including front and rear parts, the same (b), the same (c), the same ( Each of (d) is each sectional drawing of bbb, cc, dd in the same (a).

[Explanation of symbols]

1 motorcycle 2 engine 10 exhaust manifold 11 First opening 12 wall surface 12d protrusion (gasket stopper) 12e protrusion 13 Second opening

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Claims (6)

[Claims] 1. A pipe joint used for an exhaust pipe of an engine, wherein a first opening connected to a plurality of pipes and a second opening connected to a single pipe are separated from each other. At the end,
A pipe joint characterized in that the wall surface portion connecting them is integrally molded. 2. The pipe according to claim 1, wherein a step or a protrusion serving as a gasket stopper is provided integrally with the wall surface portion at a position apart from the opening end of the second opening. Fittings. 3. A wall surface part includes an outwardly projecting portion, and the projecting portion has an opening at its tip and is formed so as to be connected to a pipe other than the above in an inserted state. The pipe joint according to claim 1 or 2. 4. The pipe joint according to claim 1, wherein the wall surface portion is integrally formed by a hydraulic forming method. 5. A first opening engaging with the outside of a plurality of juxtaposed pipes and a second opening connected to the one pipe are provided at respective distant end portions and are integrated. A method for manufacturing a pipe joint, characterized in that a pipe joint for an engine exhaust pipe connected at a wall surface portion is formed by a hydraulic forming method. 6. Two of the above-mentioned pipe joints are integrally formed by a hydraulic forming method so that the first openings are connected to each other, and then cut at an intermediate portion to form two pipe joints. The method for manufacturing a pipe joint according to claim 5, wherein the pipe joint is used.