JP2003071528A - Hydroform processing method for metal tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydroform processing method for a metal tube capable of preventing deterioration of wall thickness as much as possible in the case that a bulge portion is formed on a part in the peripheral direction of the tube in the hydroform processing method for the metal tube used for an exhaust duct or the like of the internal combustion engine, for example. SOLUTION: The hydroform processing method is characterized in that a metal stock material tube is provided inside a forming die and the end portion of the stock material tube is pressed and at the same time, when fluid pressure is given into the stock material tube through the hydroform process to manufacture the metal tube having the bulge portion on the part of the tube, a forcing volume into the forming die in the side to form the bulge portion on at least one part end portion of the stock material tube is made higher compared with the other region. Specifically, for example, at least one end portion of the stock material is formed in the inclined surface and is rammed into the inward direction of the forming die, or, at least one end portion of the stock material tube is expanded and simultaneously, a step portion is formed and the step portion is rammed into the inward direction of the forming die by a tubular body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for hydroforming a metal pipe used for, for example, an exhaust pipe of an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, for example, a metal pipe used as an exhaust pipe of an internal combustion engine has been formed into a desired shape by hydroforming. For example, when merging (collecting) another exhaust pipe 2 with one exhaust pipe 1 as shown in FIG. 11, a bulging portion 1c is formed by hydroforming on a part of the exhaust pipe 1, and the bulging portion 1c is formed. A hole is opened in the projecting portion 1c so that the other exhaust pipe 2 is fitted and connected.

In performing the hydroforming as described above, for example, as shown in FIG. 12 (a), a material pipe 10 having a predetermined thickness cut in advance to a predetermined length is subjected to a predetermined bending process if necessary. Etc. and then placed in the forming die 20 as shown in FIG. 2 (b), and press both ends of the material tube 10 inwardly of the forming die 20 with punches 21 and 22 as shown in FIG. 2 (c). Meanwhile, by supplying a liquid such as water into the material tube 10 through the liquid supply holes 21a and 22a formed in the punches 21 and 22, the material pressure of the material tube 10 follows the inner surface shape of the molding die 20. It is formed into a predetermined shape.

However, even if the both ends of the raw material pipe 10 are pushed into the forming die 20 by the punches 21 and 22 and hydroformed as described above, the material pipe 10 expands in a part in the circumferential direction as shown in the figure. When forming the protruding portion 10c, it is unavoidable that the protruding portion 10c becomes thin, and there is a problem that the strength is lowered, and in some cases, the protruding portion 10c is damaged.

[0005]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above problems, and prevents a decrease in wall thickness as much as possible even when a bulging portion is formed in a part of the pipe in the circumferential direction. It is an object of the present invention to provide a hydroform processing method capable of performing the above.

[0006]

In order to achieve the above object, the method of hydroforming a metal tube according to the present invention has the following constitution. That is, a metal material pipe is placed in a molding die, the end portion of the material pipe is pressed, and a fluid pressure is hydroformed in the material pipe to form a bulge portion that projects radially outward in a part of the pipe. When manufacturing a metal tube having, characterized in that the amount of pushing into the molding die on the side forming the bulging portion of at least one end of the material tube is set to be larger than other regions. To do.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION A method for hydroforming a metal pipe according to the present invention will be described below by taking as an example the case of manufacturing an exhaust pipe having a bulge portion in a circumferential direction of the pipe as shown in FIG. A specific description will be given based on the embodiment shown in the drawings.

FIGS. 1 (a) to 1 (c) are process explanatory views showing an embodiment of a method for hydroforming a metal tube according to the present invention. First, as shown in FIG. 1 (a), a predetermined length is set in advance. The material pipe 10 having a predetermined thickness cut into pieces is bent into a predetermined shape if necessary, and the material pipe 10
The end portion 10b at least on the one end side is obliquely cut so that the side on which the bulging portion is formed becomes longer.

Then, the material pipe 10 is inserted into a forming die 20 as shown in FIG. 1B. For example, the forming die 20 is formed in two and the material pipe is inserted between the forming dies. 1
You can wear 0. In this state, the liquid supply holes 2 formed in the punches 21 and 22 while pressing both ends of the material pipe 10 into the forming die 20 by the punches 21 and 22, respectively.
A liquid such as water is pressure-supplied into the material pipe 10 from 1a and 22a to perform hydroforming. In the case of the drawing, the tips of the punches 21 and 22 are fitted to both ends of the material pipe 10. , A stepped portion 21b formed on the peripheral surface of each punch 21, 22
It is configured to press the end portion of the material pipe 10 with 22b. In the figure, 21c and 22c are seal rings, and 20c is a bulge forming recess.

While pressing both ends of the material tube 10 into the forming die 20 with the punches 21 and 22 as described above,
Material tube 10 by hydroforming
Both ends of the are gradually pushed inward of the molding die 20, and in particular, the end 10b obliquely cut so that the side forming the bulging portion becomes long is swelled by being pushed in order from the most distal end thereof. A larger amount of material is supplied to the side forming the portion to increase the thickness of the bulging portion.

FIG. 1A shows one end 10 of the material tube 10.
Although the whole b was cut obliquely, for example, as shown in FIG. 2 (a), a substantially half portion of one end portion 10b of the raw material tube 10 on the side where the bulging portion is formed is formed into a flat surface perpendicular to the axis and the rest May be formed on the inclined surface so as to be gradually shorter than that, or the remaining substantially half portion may be formed on the inclined surface so as to be gradually longer than that as shown in FIG. .

In the case of FIG. 2 (a), hydroforming may be performed in the same manner as in the case of FIG. 1, and first, the flat surface on the side where the bulge is formed is the step 22b of the punch 22.
And is pushed inward of the molding die 20 to abut on the side of the molding die 20, and more material is supplied to the side forming the bulging portion to increase the thickness of the bulging portion.

In the case of FIG. 2B, first, FIG.
As shown in FIG. 4, when the step portion 22b of the right punch 22 is pressed into the forming die 20 so that the tip end portion of the inclined surface of the raw material tube 10 abuts, the meat in the vicinity of the inclined surface is indicated by the arrow in the figure. As described above, the thickness is increased by being pushed into the side where the bulging portion is formed. Then, when it is pushed in a predetermined amount, as shown in FIG. 3 (b), substantially the entire right end portion of the raw material tube comes into contact with the step portion 22b of the right punch 22, and the liquid supply holes 21a of the punches 21 and 22 are continued.
When both punches 21 and 22 are pushed toward the inside of the molding die 20 while supplying a liquid such as water from the material 22a to the material tube 10 under pressure, the bulging portion side is thickened as shown in FIG. 3 (c). The bulging portion 10c is formed while being pressed.

In the above embodiment, the bulging portion forming recess 20c having substantially the same shape as the bulging portion to be formed is formed in the molding die 20, but the recess 20c is formed as shown in FIG. 4, for example. The movable die 24 may be formed large so as to open on one side surface side, and the movable die 24 may be provided in the recess 20c so as to be movable in the direction of the arrow in the drawing. Initially, as shown in FIG.
4 is pressed against the raw material pipe 10 to fix the raw material pipe, and when the punches 21 and 22 are pushed toward the inside of the forming die 20 in that state, the meat in the vicinity of the inclined surface in the drawing is the same as in the above embodiment. As shown by the arrow, it is pushed into the side forming the bulging portion to increase the thickness. Then, as shown in FIG. 7B, when the step portion 22b of the right punch 22 abuts on the substantially entire circumference of the right end portion of the raw material tube or is pushed in the vicinity thereof, each punch 21.
While the liquid such as water is being pressure-supplied into the material tube 10 from the two liquid supply holes 21a and 22a, both punches 21 and 22 are further pushed inward of the molding die 20, and at the same time, the movable die 24 is moved. When it is gradually retracted in the direction of the arrow in FIG.
As the bulging portion side is increased in thickness, the bulging portion 1 as shown in FIG.
0c is formed.

In the embodiment of FIG. 1 as well, similar to FIG. 4, the bulging portion forming recess 20c is formed to be large so as to open to one side surface of the molding die 20, and the recess 20c has the same shape as described above. The movable mold 24 may be provided.

In each of the above embodiments, the punches 21 are provided at both ends.
The bulging portion was formed by hydroforming while pushing it inward at 22 in the forming die 20, but one end of the material pipe 10 was previously expanded by hydroforming and the material pipe 10 was expanded. It is also possible to form a stepped portion and form the bulging portion by hydroforming while pushing the stepped portion toward the inside of the molding die 20 with a tubular body or the like.

FIG. 5 and FIG. 6 show an example thereof,
First, as shown in FIG. 6A, the material pipe 10 in which one end 10b side is obliquely cut so that the side forming the bulging portion becomes long
5A is set in the forming die 20 as shown in FIG.
・ Place 22. The inner surface 20a of the forming die 20 on the one end 10b side of the raw material tube 10 is formed to be slightly larger than the outer diameter of the raw material tube 10, and a cylindrical body 23 is provided between the outer peripheral surface of the raw material tube 10 and the inner surface of the forming die 20. Deploy. As in the embodiment of FIG. 4, a concave portion 20c for forming a bulge portion is formed in the molding die 20, one end side of which opens to one side surface side of the molding die 20,
A movable die 24 is provided in the recess 20c so as to be movable in the direction of the arrow in the figure.

The cylindrical body 23 and the movable die 24 are initially positioned in the state shown in FIG. 5 (a), and in that state, both punches 2 are moved.
When liquids such as water are pressure-supplied into the material pipe 10 from the liquid supply holes 21a and 22a of the punches 21 and 22 while pressing the parts 1 and 22 toward the inside of the forming die 20, a part of the material pipe 10 is formed. Is expanded as shown in FIGS. 5B and 6B, and a step portion 10d is formed in the material pipe 10, and the end portion on the left side of the cylindrical body 24 in the drawing abuts on the step portion 10d. It becomes a state.

In this state, the movable die 24 is gradually retracted in the direction of the arrow in FIG.
22 and the cylindrical body 23 are pressed toward the inside of the molding die 20, the liquid supply holes 21a.
A bulging portion 10c is formed as shown in FIG. 5 (c) by pressurizing and supplying a liquid such as water from the material pipe 22a into the material pipe 10.

When expanding the diameter of a part of the raw material tube 10 as described above, the end portion 10b of the raw material tube 10 is formed obliquely so that the bulging portion side becomes longer, so that more bulging portion side is formed. When the material is supplied to increase the wall thickness and the bulging portion is formed, the cylindrical body 24 pushes the stepped portion 10d of the raw material tube 10 so that it can be pushed in reliably.

When the pipe prepared as described above is used as the exhaust pipe 1 and a hole is formed in the bulged portion 1c formed in the exhaust pipe 1 to connect another exhaust pipe 2 as shown in FIG. Has an advantage that the back pressure to the engine can be reduced because the pipe diameter of the end portion 1b on the downstream side of the collecting portion is expanded. In the figure, 3 is a downstream side exhaust pipe connected to the end portion 1b.

In the above embodiment, the step portion 10d is
The approximately half portion on the side where the bulging portion is formed is formed into a flat surface that is substantially parallel to the circumferential direction, and the remaining approximately half portion is an inclined surface that is inclined to the side opposite to the bulging portion. Step 10 as in (a)
The entire d may be formed flat in the circumferential direction, or the bulging portion side may be formed into a flat surface that is substantially parallel to the circumferential direction as shown in FIG. You may make it an inclined surface which inclines to.

Further, in each of the above-described embodiments, the treatment or operation for increasing the thickness is performed only on one end of the material pipe 10, particularly on the end near the site where the bulge is formed. You may make it apply to both sides. In the above embodiment, the case where a plurality of (two in the case of the figure) exhaust pipes are combined (merged) into one exhaust pipe has been described as an example. However, one exhaust pipe is provided with a plurality of exhaust pipes. It is also applicable when branching to.

Further, the present invention can be applied to the case where a bent portion of an exhaust pipe or the like bent in a U shape is expanded, and the material pipes 10 to 10 shown in FIG. As shown in the drawings, the present invention can be applied to the case of manufacturing the exhaust pipe 1 or the like whose sectional shape gradually changes as shown in FIGS.

[0025]

As described above, in the method of hydroforming a metal tube according to the present invention, the amount of pushing into the molding die on the side forming the bulging portion of at least one end of the raw material tube is as described above. Since it is made larger than other regions, it is possible to prevent the wall thickness of the bulging portion from decreasing as much as possible, and it is possible to form the bulging portion satisfactorily even in a thin material tube. Has the effect of.

[Brief description of drawings]

FIG. 1 is a process explanatory view showing an embodiment of a method for hydroforming a metal tube according to the present invention.

2A and 2B are front views showing a modification example of a material pipe.

FIG. 3 is a process explanatory view showing another embodiment of the method for hydroforming a metal tube according to the present invention.

FIG. 4 is a process explanatory view showing still another embodiment of the method for hydroforming a metal tube according to the present invention.

FIG. 5 is a process explanatory view showing still another embodiment of the method for hydroforming a metal tube according to the present invention.

6A to 6C are front views showing a processed state of the material pipe according to the embodiment.

FIG. 7 is a front view of an example in which the pipe obtained by the above embodiment is used as a collecting pipe.

8 (a) and 8 (b) are front views showing another example of a state where the material pipe is being processed midway.

FIG. 9 is a front view of another material pipe.

FIG. 10 is a front view of an exhaust pipe whose sectional shape is gradually changed.

FIG. 11 is a front view showing a configuration example of a conventional collecting pipe.

FIG. 12 is a process explanatory view showing an example of a conventional method of hydroforming a metal tube.

[Explanation of symbols]

1, 2 exhaust pipe 1c bulge 10 material tube 10a, 10b ends 10c bulge 10d step 20 Mold 21,22 punch 21a, 22a Liquid supply hole 21b, 22b Steps 21c, 22c Seal ring 23 cylinder 24 mobile

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Naoki Shimizu             Gunma Prefecture Isesaki City Toyatsuka Town 1069-1 Sankei Gi             Ken Kogyo Co., Ltd.

Claims (3)

[Claims] 1. A metal pipe in which a metal material pipe is arranged in a molding die, an end portion of the material pipe is pressed, and a fluid pressure is hydroformed in the material pipe to have a bulge portion in a part of the pipe. In manufacturing, the amount of pushing into the molding die on the side forming the bulging portion of at least one end of the material pipe is set to be larger than other regions of the metal pipe. Hydroforming method. 2. The method of hydroforming a metal tube according to claim 1, wherein at least one end of the material tube is formed into an inclined surface and is pushed inward of the forming die. 3. The metal pipe according to claim 1, wherein at least one end portion of the material pipe is expanded in diameter, a step portion is formed, and the step portion is pushed toward the inside of the forming die by the cylindrical body. Hydroforming method.