JP2000117341A - Tube bulging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tube bulging method capable of making a bulging quantity of a branched tube larger by increasing a material flow in forming. SOLUTION: In a tube bulging method, in which, while applying a fluid pressure inside a straight tube stock 7 arranged in a tube hole 2 of a forming die 1, both tube ends are compressed and a branch tube 8, projecting from part of a tube side face toward a branched hole 3 of the forming die 1, is formed, before the branched tube 8 is bulged outward from the tube stock 7, a tube side face part, where the branch tube 8 is bulged, is deformed inward beforehand.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a pipe bulge forming method for forming a convex overhang at an intermediate portion of a pipe.

[0002]

2. Description of the Related Art Conventionally, as a method of branching a branch pipe from the side of the pipe, for example, as shown in FIG. 7, a fluid pressure is applied to a straight pipe material set in a pipe hole of a molding die by applying a fluid pressure to the inside thereof. A bulge forming method is known, in which both ends of the pipe are compressed while the tip of the pipe is flat, and a branch pipe is formed while pressing the protrusion that protrudes from a part of the side of the pipe toward the branch hole of the mold. I have.

[0003]

However, in the above-mentioned conventional pipe bulge forming method, since the material is only deformed in the overhanging direction by the internal pressure while compressing both ends of the pipe, the material flowing toward the branch pipe is The amount of supply is limited to the amount of material flow accompanying the overhang deformation, and there is a problem that the amount of overhang of the branch pipe is reduced. In other words, the overhang amount of the branch pipe increases as the overhang limit due to the internal pressure increases, and the overhang limit due to the internal pressure is determined by the amount of the material supplied toward the branch pipe.

A method of supplying a material to the overhanging portion to prevent cracks is called bulging. However, as shown in FIG. 8, when the pipe material is thin, buckling occurs in the pipe axial direction. However, the material cannot be supplied to the overhang portion, and the amount of overhang of the branch pipe is determined by the elongation limit of the material due to the internal pressure.

An object of the present invention is to provide a pipe bulge forming method capable of securing a large amount of overhang of a branch pipe by increasing the amount of material flowing during molding.

[0006]

Means for Solving the Problems (Solution 1) Solution 1 of the above-mentioned problem (Claim 1) is to apply a liquid pressure to a straight tubular pipe material set in a pipe hole of a molding die while applying a hydraulic pressure to both ends of the pipe. In a pipe bulge forming method of forming a branch pipe that compresses and protrudes from a part of the side surface of the pipe toward a branch hole of a forming die, the branch pipe is stretched before the branch pipe is projected outside from the pipe material. The side surface portion of the pipe to be discharged is deformed inward in advance. (Solution 2) The solution 2 of the above-mentioned problem (Claim 2) is:
2. The pipe bulge forming method according to claim 1, wherein a core metal slidable in a hole axis direction is set in a branch hole of the molding die, and a tip end of the metal core is positioned at the same position as an outer peripheral position of the pipe material. A first step of preform molding by setting the pipe at a slightly outer position and compressing both ends of the pipe while increasing the internal pressure while applying fluid pressure to the inside of the pipe material; A second step in which the tip of the pipe is advanced deeply inward from the outer peripheral position of the pipe material to deform the side surface of the pipe inward, and, following the second step, both ends of the pipe while applying fluid pressure to the inside of the pipe material A third step in which the inner pressure is gradually increased by compressing the pipe, and the tip of the cored bar is retracted to the position of the first step; and after the third step, both ends of the pipe are applied while applying fluid pressure to the inside of the pipe material. Compress part to gradually increase internal pressure Raised, and characterized in that the fourth step of retracting the tip of the metal core to a position far from the outer peripheral position of the pipe, and by molding. (Solution Means 3) Solution Means 3 (Claim 3) of the above problem is:
3. The bulge forming method for a pipe according to claim 2, wherein the core bar has a large-diameter cylindrical base having an outer diameter corresponding to the inner diameter of the branch hole, and an outer diameter smaller than the base protruding from an end face of the large-diameter cylindrical base. And a spherical end formed at the end of the small-diameter cylindrical portion. (Solution 4) The solution 4 of the above problem (Claim 4) is:
The pipe formed by the pipe bulge forming method according to any one of claims 1 to 3 is a T-shaped pipe applied as a component of an exhaust manifold of an automobile equipped with a multi-cylinder engine.

[0007]

(Embodiment 1) Embodiment 1 is a pipe bulge forming method according to the first to fourth aspects of the present invention. [Regarding Bulge Forming Apparatus] FIG. 1A shows an outline of a pipe bulge forming method and a bulge forming apparatus according to the first embodiment, wherein 1 is a forming die, 2 is a pipe hole, 3 is a branch hole, and 4 is Core metal, 5 is a first compression piston, 6 is a second compression piston, 7
Is a pipe material, and 8 is a branch pipe.

The molding die 1 is formed with a pipe hole 2 penetrating both side surfaces and a branch hole 3 reaching the pipe hole 2 from the upper surface. A core 4 for controlling the bulge forming of the branch pipe 8 is provided in the branch hole 3 so as to be slidable in the hole axis direction. Further, a first compression piston 5 and a second compression piston 6 for compressing both ends of the pipe are provided in the pipe hole 2 so as to be slidable in the hole axis direction. A fluid passage 9 for pressurizing and depressurizing the internal space of the pipe member 7 is provided.

The core 4 has a large-diameter cylindrical base 4a having an outer diameter corresponding to the inner diameter of the branch hole 3, and a small-diameter cylinder protruding from an end face of the large-diameter cylindrical base 4a and having an outer diameter smaller than the base 4a. It has a shape having a portion 4b and a spherical tip 4c formed at the tip of the small-diameter cylindrical portion 4b.

As described above, since the core metal 4 having the spherical tip 4c is in contact with the pipe member 7, the branch pipe is deformed by the internal pressure during the bulge forming process.
As a result, spherical deformation occurs along the shape of c, and there is no material deformation in which stress is concentrated, and cracking of the pipe member 7 can be prevented. Further, since the core metal 4 has an annular space formed between the spherical end portion 4c in contact with the pipe member 7 and the branch hole 3, a margin for material deformation can be secured by setting the annular space. It also serves to increase material flow. [About bulge forming method] First, the outline of the bulge forming method will be described with reference to FIG.

As shown in FIG. 1 (a), both ends of the pipe are compressed while applying a liquid pressure to a straight pipe member 7 set in the pipe hole 2 of the forming die 1, and a part of the side surface of the forming die is compressed. 1
In a pipe bulge forming method for forming a branch pipe 8 protruding toward the branch hole 3 of the above, before the branch pipe 8 is extended outside from the pipe material 7, as shown in FIG.
The side surface of the pipe from which the branch pipe 8 protrudes was previously deformed inward.

Next, the details of the bulge forming method will be described with reference to FIGS.

In the first step, as shown in FIG. 2, the spherical tip 4c of the metal core 4 set in the branch hole 3 is set at substantially the same position as the outer peripheral position of the pipe member 7, and While applying the above fluid pressure, both ends of the pipe are compressed to increase the internal pressure of the pipe material 7, and preform molding (preliminary molding) is performed to bulge the side surface of the pipe to become the branch pipe 8 into a donut shape.

In the second step, as shown in FIG. 3, following the first step, the spherical front end portion 4c of the metal core 4 is advanced deeply inward from the outer peripheral position of the pipe member 7, and
The pipe side part to be deformed inward.

In the third step, as shown in FIG. 4, following the second step, both ends of the pipe are compressed while applying the fluid pressure from the fluid passage 9 to gradually increase the internal pressure of the pipe member 7, The spherical front end portion 4c of the metal core 4 is retracted almost to the position of the first step.

In the fourth step, as shown in FIG. 5, following the third step, both ends of the pipe are compressed while applying the fluid pressure from the fluid passage 9 to gradually increase the internal pressure of the pipe member 7. The spherical tip portion 4c of the metal core 4 is retracted to a position far away from the outer peripheral position of the pipe member 7.

As described above, from the pipe member 7 to the branch pipe 8
Before the branch pipe 8 is extended outward, the pipe side portion on which the branch pipe 8 extends is deformed inward in advance. Therefore, the amount of material supplied toward the branch pipe 8 depends on the amount of material flow accompanying the inside deformation and the amount of material flow accompanying the overhang deformation. The supply amount is the sum of the supply amount and the overhang amount of the branch pipe 8 can be increased.

A method of supplying material to the overhanging portion to prevent cracks is called bulging. However, when the thickness of the pipe material is thin, the fluidity of the material increases due to internal deformation,
Buckling in the axial direction of the pipe can be prevented, and a material supply amount combining the material flow amount due to the inside deformation and the material flow amount due to the overhang deformation can be secured. [Application to Exhaust Manifold] A pipe formed by the bulge forming method is a T-shaped pipe in which the branch pipe 8 is closed. Therefore, the end of the branch pipe 8 is cut and opened to open T at the three-way opening.
The pipe is assumed to be a letter A The T-shaped pipes A are connected to each other as shown in FIG. 6 and are applied as components of an exhaust manifold 11 of an automobile equipped with a multi-cylinder engine 10.

Therefore, as compared with a general cast exhaust manifold, an exhaust manifold using a light and inexpensive molded pipe can be obtained. (Other Embodiments) In the first embodiment, an example of application to an exhaust manifold of an automobile has been described. However, the T-shaped pipe formed according to the present invention is not limited to a pipe joint to which a branch pipe is connected. It can be applied to applications.

[0020]

According to the first aspect of the present invention, both ends of the pipe are compressed while applying a liquid pressure to the straight pipe material set in the pipe hole of the molding die, and the molding die is partially opened from the side of the pipe. In the pipe bulge forming method of forming a branch pipe protruding toward the branch hole, before the branch pipe is extended from the pipe material, the pipe side portion where the branch pipe projects is deformed inward in advance, Due to the increase in the amount of material flowing during molding, an effect is obtained that a large amount of overhang of the branch pipe can be secured.

According to the second aspect of the present invention, the first aspect is provided.
In the pipe bulge forming method described in the above, a core metal slidable in the hole axis direction is set in the branch hole of the molding die, and the tip of the core metal is positioned at the same position as the outer peripheral position of the pipe material or slightly outside. The first step is to perform preform molding by compressing both ends of the pipe while increasing the internal pressure while applying fluid pressure to the inside of the pipe material. A second step in which the pipe is advanced deeply inward from the outer peripheral position to deform the side surface of the pipe inward, and, following the second step, the internal pressure is gradually reduced by compressing both ends of the pipe while applying fluid pressure to the inside of the pipe material. And the third step of retracting the leading end of the core metal to the position of the first step. Subsequently to the third step, both ends of the pipe are compressed while applying fluid pressure to the inside of the pipe material to gradually reduce the internal pressure. To the tip of the core And the fourth step of retreating to a position far away from the outer peripheral position of the packing material. In addition to the effect of the invention according to claim 1, a short manufacturing time is required in a series of steps of changing the set position of the cored bar. Bulge forming can be performed.

According to the third aspect of the present invention, there is provided the second aspect.
In the pipe bulge forming method according to the above aspect, the cored bar may be a large-diameter cylindrical base having an outer diameter corresponding to the inner diameter of the branch hole, and a small-diameter cylinder having an outer diameter smaller than the base protruding from an end surface of the large-diameter cylindrical base. In addition to the effects described in claim 2, in addition to the effect described in claim 2, cracks in the pipe material during bulge forming and a margin for material deformation are secured. Thus, an increase in the amount of flowing material can be achieved.

According to the fourth aspect of the present invention, there is provided the first aspect.
Since the pipe formed by the pipe bulge forming method according to claim 3 is a T-shaped pipe applied as a component of an exhaust manifold of a vehicle equipped with a multi-cylinder engine, the exhaust manifold is formed by a lightweight and inexpensive formed pipe. Can be provided.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a bulge forming apparatus and a bulge forming method used in a pipe bulge forming method of a first embodiment.

FIG. 2 shows a first example of the pipe bulge forming method according to the first embodiment.
It is a figure showing a process.

FIG. 3 shows a second example of the pipe bulge forming method according to the first embodiment.
It is a figure showing a process.

FIG. 4 shows a third example of the pipe bulge forming method according to the first embodiment.
It is a figure showing a process.

FIG. 5 shows a fourth example of the pipe bulge forming method according to the first embodiment.
It is a figure showing a process.

FIG. 6 is a diagram showing a state in which a T-shaped pipe manufactured by the pipe bulge forming method of the first embodiment is applied to an exhaust manifold of an automobile.

FIG. 7 is a view showing a conventional pipe bulge forming method.

FIG. 8 is a view showing a state in which a thin-walled material is formed by a conventional pipe bulge forming method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 2 Pipe hole 3 Branch hole 4 Metal core 5 1st compression piston 6 2nd compression piston 7 Pipe material 8 Branch pipe 9 Fluid passage

Claims (4)

[Claims] 1. A pipe (7) set in a pipe hole (2) of a molding die (1) is compressed at both ends while a hydraulic pressure is applied to both ends of the pipe. ) Branch hole (3)
In the bulge forming method for forming a branch pipe (8) projecting toward the pipe, the branch pipe (8) projects from the pipe material (7) before the branch pipe (8) projects from the pipe material (7). A bulge forming method for a pipe, wherein a side portion is deformed inward in advance. 2. The pipe bulge forming method according to claim 1, wherein a core metal (4) slidable in a hole axis direction is set in a branch hole (3) of the forming die (1). Set the tip (4c) of the gold (4) at the same position as or slightly outside the outer circumference of the pipe (7),
A first step of performing preform molding by compressing both ends of the pipe while increasing the internal pressure while applying fluid pressure to the inside of the pipe, and continuing the first step, connecting the tip end (4c) of the cored bar (4) to the pipe A second step of inwardly moving the pipe side deeper from the outer peripheral position of the pipe (7) to deform the pipe side portion inward; and, following the second step, both ends of the pipe while applying fluid pressure to the inside of the pipe (7). A third step of gradually increasing the internal pressure by compressing the portion to retract the tip (4c) of the cored bar (4) to a position substantially in the first step; and, following the third step, a pipe member (7) While compressing both ends of the pipe while applying fluid pressure to the inside of the pipe, the internal pressure is gradually increased, and the tip (4c) of the cored bar (4) is retracted to a position far away from the outer peripheral position of the pipe material (7) A bulge forming method for a pipe, characterized by forming the pipe by a fourth step. 3. The bulge forming method for a pipe according to claim 2, wherein the core metal (4) is provided with a large-diameter cylindrical base (4a) having an outer diameter corresponding to the inner diameter of the branch hole (3). The small-diameter cylindrical portion (4) protruding from the end face of the diameter cylindrical base (4a) and having an outer diameter smaller than that of the base (4a)
b) and a spherical tip (4) formed at the tip of the small-diameter cylindrical portion (4b).
c) forming a bulge of a pipe. 4. A pipe formed by the pipe bulge forming method according to any one of claims 1 to 3, which is used as a component of an exhaust manifold (11) of an automobile equipped with a multi-cylinder engine (10). A bulge forming method for a pipe, characterized in that the pipe is a letter-shaped pipe (A).