JP2002239645A - Hydroforming method of metal tube and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydroforming method of a metal tube enabling HF- forming of the metal tube with the strength at which the corner shaping is impossible with the maximum internal pressure of the specification even without remodeling any pressure system in an existing HF-forming device. SOLUTION: By using an axially-pressing punch 3 of double structure having an inner 5 which can be inserted in the metal tube 1 having a liquid filling hole 5a and an outer 6 abutted on a tube end face of the metal tube 1 provided on the outer circumference of the inner 5 in the axial direction in a relatively movable manner, a tip face of the outer 6 is abutted on the tube end face of the metal tube 1 set to a die 2, the metal tube 1 is axially pressed by integrally moving the inner 5 with the outer 6, the liquid is filled in the metal tube 1 through the filling hole 5a, the inner 5 is moved and inserted in the metal tube 1 to increase the forming pressure while the outer 6 is fixed to the position at which the metal tube 1 is axially pressed by the predetermined quantity, and the metal tube 1 is hydroformed in a desired shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for hydroforming a metal tube.

[0002]

2. Description of the Related Art Hydroforming (hereinafter abbreviated to HF as appropriate) molding is a method of forming a hollow closed-section structural part by integrally molding a metal pipe (hereinafter also referred to as a pipe or pipe) by applying an axial force and an internal pressure thereto. The technology to manufacture. Specifically, a metal tube is loaded into a mold, and a liquid is injected into the metal tube to increase the internal pressure of the liquid while applying an axial force. The tube is expanded to a predetermined shape along the inner surface of the mold. This technology is mainly used for the production of automobile parts.

FIG. 5 is a sectional view showing an example of a configuration of a main part of a conventional HF molding apparatus. The HF molding apparatus includes a mold 52 for setting a metal tube 51 to be molded, and a mold 52
And a shaft pressing punch 53 for axially pressing the tube end of the metal tube 51 set on the shaft. The mold 52 is held by a mold holder 54 and is fastened by a press (not shown) so as to oppose the in-pipe pressure of the liquid injected into the metal tube 51. The shaft pressing punch 53 is connected to a shaft pressing cylinder 56 via a shaft pressing punch holder 55. The shaft pressing punch 53 extends through the injection hole 53a through the center axis thereof. The injection hole 53a communicates with an injection passage 56a formed in the shaft pushing cylinder 56 on the shaft pushing cylinder 56 side.

In the conventional HF molding apparatus shown in FIG. 5, a shaft pushing cylinder 56 is driven to axially push the tube end of a metal tube 51 set in a mold 52 by a shaft pushing punch 53 with a shaft pushing force Fn. Meanwhile, water (or a liquid pressure medium such as hydraulic oil) may be injected into the metal pipe 51 through the injection path 56a and the injection hole 53a to apply an internal pressure, thereby applying a cavity (not shown) in the mold 52. The metal tube 51 is expanded inside the box. Here, the maximum value of the shaft pressing force Fn by the shaft pressing punch 53 is generally 1000 kN to 2000 kN.
N, and the in-pipe pressure applied to the metal pipe 51 is 100 to 300 MPa at maximum depending on the apparatus.

[0005]

In the above-described HF molding apparatus, the reason that the pressure inside the pipe of 100 MPa or more is required is that the metal pipe 5 is formed on the corner curved surface (R) in the mold 52 or the like.
In most cases, corner shaping in which 1 is attached is used. For this reason, when the maximum pressure in the specification of the introduced HF molding device is smaller than the internal pressure required for corner shaping of a metal tube having high strength which was not assumed at the beginning of the introduction of the device, The HF molding of the metal tube into a desired shape cannot be performed. As a method to solve this problem, it is conceivable to remodel the existing molding internal pressure system so that it can supply high pressure.However, since the number of mechanical parts to be strengthened is large, it takes time and cost to remodel. There is a concern that this will take place.

Accordingly, a first object of the present invention, which has been made in view of such a point, is to provide a high-pressure system with a specified maximum pressure without modifying a pressure system of an existing HF molding apparatus to a high-pressure system. Even metal pipes that have such strength that corner shaping is not possible can be reliably HF
An object of the present invention is to provide a method for hydroforming a metal tube that can be formed. Further, a second object of the present invention is to provide a metal pipe hydroform forming apparatus appropriately configured so that the above-described forming method can be performed easily and inexpensively.

[0007]

According to a first aspect of the present invention, a metal tube is loaded in a mold, and the metal tube is axially pushed through a shaft pushing punch. In the metal tube hydroforming method of forming a metal tube by charging a liquid into the tube and increasing the pressure of the liquid inside the tube, the shaft pressing punch can be inserted into the metal tube having the liquid injection hole. Using a double-structured axial pressing punch having an inner and an outer that is provided on the outer periphery of the inner so as to be relatively movable in the axial direction and that can abut on a pipe end face; Abut on the pipe end face of the metal pipe, the inner and outer are moved together to push the metal pipe axially, and a liquid is injected into the metal pipe through the injection hole, thereby forming the metal pipe. At the position where the axis is pushed by a predetermined amount In a state of fixing the serial outer, by inserting into the metal tube by moving the inner, it is characterized in that forming a metal tube into a desired shape.

According to a second aspect of the present invention to achieve the second object, a metal tube is loaded into a mold, the metal tube is axially pushed through a shaft pushing punch, and a liquid is injected into the metal tube. In the metal pipe hydroforming apparatus for forming a metal pipe by increasing the pressure inside the pipe of the liquid, the axial pressing punch comprises an inner insertable into the metal pipe having the liquid injection hole, and an outer periphery of the inner. An outer end which is provided so as to be relatively movable in the axial direction and which can abut on a pipe end face of the metal pipe. And while moving the outer integrally and axially pushing the metal tube, injecting a liquid into the metal tube through the injection hole, fixing the outer at a position where the metal tube is axially pushed by a predetermined amount, Move the above inner By inserting the metal tube by and is characterized by being configured so as to mold the metal tube into a desired shape.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are cross-sectional views showing a schematic configuration of a main part of a first embodiment of an HF molding apparatus according to the present invention. FIG. 1 shows a shaft pressing state, and FIG. It shows the state where it is. This HF molding apparatus basically has the same configuration as that of a conventional HF molding apparatus except for the configuration of a shaft pressing punch, and includes a mold 2 for setting a metal tube 1 to be molded, and a mold 2 And a pressing die 3 for pressing the end of the metal tube 1 set on the metal tube 1. The die 2 is held by a die holder 4 and pressed to oppose the molding pressure of the metal tube 1. (Not shown).

In the present embodiment, the shaft pressing punch 3 includes an inner 5 that can be inserted into the metal tube 1, and an outer 6 that is provided on the outer peripheral side of the inner 5 so as to be in contact with the end surface of the metal tube 1. Having a double structure. The inner 5 is connected to a shaft pushing cylinder 8 via an inner holder 7, and the inner 5 has an injection hole 5 a penetrating along the center axis thereof.
The injection hole 5a is communicated with the injection passage 8a formed in the axial pushing cylinder 8 on the axial pushing cylinder 8 side. On the inner holder 7 side, a shaft pressing force transmitting jig 9 is detachably mounted on the outer periphery of the inner 5. The outer 6 is provided so as to be slidable relative to the inner 5 in the axial direction, and the movement position of the outer 6 is moved in the axial pushing direction by a stopper 10 which can be positioned and can be engaged with and separated from the outer 6. It is installed so as to be fixed at the positioning position.
As shown in the enlarged view of FIG. 2, it is preferable that the stopper 10 has a shape having projections and depressions so that a large number of seating surfaces 10a receive the molding reaction force in a dispersed manner. In addition, inner 5
An O-ring 11 seals the space between the outer case 6 and the outer case 6.

In this embodiment, first, as shown in FIG. 1, a jig 9 for transmitting a shaft pressing force is mounted on the outer periphery of the inner 5 on the shaft pressing cylinder 8 side, and the stopper 10 is attached to the outer 6.
The shaft pushing cylinder 8 is moved in a state of being separated from the inner tube 5, whereby the inner 5 and the outer 6 are integrally moved, and the tip of the inner 5 is inserted into the tube end of the metal tube 1 set in the mold 2. In a slightly inserted state, the tube end face of the metal tube 1 is axially pushed by the outer pressing 6 by the axial pressing force Fn via the axial pressing force transmitting jig 9 by the axial pressing force Fn. A pressure medium such as water or other liquid is injected into the mold 2 to apply pressure, whereby the metal tube 1 is expanded to some extent in a cavity (not shown) in the mold 2.

Thereafter, the movement of the shaft pushing cylinder 8 is temporarily stopped, and as shown in FIG. 2, the stopper 10 is moved to engage with the outer 6, thereby fixing the outer 6 at a predetermined amount of the shaft pushing position. I do. Next, with the outer 6 fixed, the axial pressing force transmitting jig 9 is separated from the inner 5, and in that state, the axial pressing cylinder 8 is driven again to move only the inner 5 while the outer 6 is fixed. Then, the tip portion is further inserted into the metal tube 1, thereby reducing the volume in the metal tube 1 and increasing the molding pressure to perform corner shaping.

As described above, in the present embodiment, the molding pressure is increased by inserting the inner 5 into the metal tube 1.
3.5 mm, thickness 2.0 mm, length 500 mm, when expanding 1.5 times in a cavity 2.0 times the outer diameter, the outer diameter of the inner 5 is 40 mm Approximately 300MPa when 70mm is inserted into tube 1.
Becomes For this reason, a reaction force against the molding pressure acts on the shaft pressing punch 3, but the shaft pressing punch 3 according to the present embodiment is used.
Has a double structure of the inner 5 and the outer 6, the reaction force acting on the shaft pressing punch 3 is about 900 kN in total of the reaction forces on the inner 5 and the outer 6. Therefore, if the shaft pressing force is 1000 kN or more in specification, it is not necessary to power up the shaft pressing force system.

[0014] In addition, by increasing the molding pressure,
The tightening force of the mold 2 by the press will also increase. At this time, the necessary tightening force is calculated by multiplying the molding area by the vertical projection area of the mold 2 where the pressure is applied. Can be. Therefore, when the above-mentioned projected area of the part to be HF-molded is small, even if the molding pressure increases, it may fall within the maximum tightening force in the specifications of the equipment. Further, when the projection area is large and the tightening force exceeds the maximum tightening force in the specification of the equipment, it can be easily dealt with by using a known mechanical tightening method. FIG. 3 is a sectional view showing a schematic configuration of a main part of a second embodiment of the HF molding apparatus according to the present invention. In the present embodiment, the cylinder part 12 is formed on the outer
Is connected to the inner shaft pushing hydraulic system 13, and the inner 5 is formed with a piston portion 14 slidable in the cylinder chamber 12 a, and the inner shaft pushing hydraulic system 1 is formed.
3, the inner 5 is moved relative to the outer 6 by supplying and discharging oil to and from the cylinder chamber 12a.

A portion of the outer 6 having the cylinder portion 12 is slidably disposed in a hydraulic cylinder 15 fixed to the apparatus, and one of the hydraulic cylinders 15 defined by the cylinder portion 12 is provided. A hydraulic system 16 for pushing the shaft is connected to the cylinder chamber 15a, and a hydraulic system 17 for returning the shaft is connected to the other cylinder chamber 15b. The inner 6 and the inner 5 are integrally moved in the shaft pushing direction, and oil is supplied from the shaft returning hydraulic system 17 to the other cylinder chamber 15b so that the outer 6 and the inner 5 are integrally moved in the shaft returning direction. Other configurations are the same as those of the first embodiment.

As described above, first, the shaft pushing hydraulic system 1
By supplying oil from cylinder 6 to one cylinder chamber 15a, outer 6 and inner 5 are integrally moved in the axial pushing direction, and the pipe end of the metal pipe set in the mold is the same as in the first embodiment. With the tip of the inner 5 slightly inserted into the metal pipe, the outer end of the inner pipe 5 is axially pushed by a predetermined amount, and water is injected into the metal pipe through the injection hole 5a to apply pressure. Expand the metal pipe to some extent in the cavity.

Thereafter, the supply of oil from the shaft pushing hydraulic system 16 is stopped to fix the outer 6 to the predetermined amount of the shaft pushing position, and in this state, the inner shaft pushing hydraulic system 13 Oil is supplied to the chamber 12a and the inner 5
Is moved with respect to the outer 6 and its tip is further inserted into the metal tube, thereby reducing the volume in the metal tube and increasing the molding pressure to perform corner shaping.

In the present embodiment, similarly to the first embodiment, the inner 5 is inserted into the metal pipe to increase the molding pressure, so that the inner shaft pushing hydraulic system 13 and the shaft pushing hydraulic system 16 are relatively formed. A low-power one can be used, and the configuration can be simple and inexpensive.

[0019]

FIG. 4 shows the geometry of the HF forming process and the specifications of the metal tube in the embodiment. Table 1 shows the specifications of the HF molding apparatus. In FIG. 4, reference numeral 18 indicates an outline of the metal tube before molding, reference numeral 19 indicates an outline of the metal tube after molding, and reference numeral 20 indicates a corner R portion to be subjected to corner shaping.

[0020]

[Table 1]

The metal tube has a yield stress of about 400 MPa, 5
00MPa, 600MPa and 800MPa 4
For each of these metal tubes, a corner R
When rb is 5 mm, Table 2 shows the results of HF molding performed using the axial pressing punch of the present invention example under each condition, and the results of HF molding performed using the conventional axial pressing punch as a comparative example. Is shown in comparison with. The state of the corner shaping is determined by visual observation. A mark ○ indicates that the shape is sufficient, and a mark X indicates that the shape is insufficient. Table 3 shows the specifications of the shaft pressing punch of the present invention example and the shaft pressing punch of the comparative example.

[0022]

[Table 2]

[0023]

[Table 3]

As is clear from Table 2, in the case of metal pipes of 400 MPa and 500 MPa, corner shaping was possible even with a conventional punching punch as a comparative example, but in the case of metal pipes of 600 MPa and 800 MPa. However, it was impossible to completely shape the conventional shaft pressing punch. On the other hand, in the case of the axial pressing punch of the present invention, the metal pipes having all the yield stresses could be completely shaped.

[0025]

According to the present invention, an inner body capable of inserting a shaft pressing punch into a metal pipe having a liquid injection hole, and the metal provided on the outer periphery of the inner body so as to be relatively movable in the axial direction. As a double structure having an outer that can be in contact with the pipe end face of the pipe, the outer end face is brought into contact with the pipe end face of the metal pipe, and the inner and outer are moved together to push the metal pipe axially. In addition, the liquid is injected into the metal pipe through the injection hole, and the inner is moved and inserted into the metal pipe while the outer is fixed at a position where the metal pipe is axially pushed by a predetermined amount. A metal having a strength that can increase the molding pressure without converting the pressure system in the existing HF molding apparatus to a high-pressure system, and therefore makes corner shaping impossible at the maximum pressure in the pressure system. Surely HF into a desired shape even in the case of
It can be molded and can be implemented simply and inexpensively.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of a main part of a first embodiment of an HF molding apparatus according to the present invention.

FIG. 2 is a cross-sectional view showing a state where corner shaping is performed.

FIG. 3 is a sectional view showing a schematic configuration of a main part of a second embodiment of the HF molding apparatus according to the present invention.

FIG. 4 is a diagram showing dimensional specifications of a metal tube before and after expansion used in the example.

FIG. 5 is a sectional view showing a schematic configuration of a main part of a conventional HF molding apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal tube 2 Die 3 Shaft pushing punch 4 Mold holder 5 Inner 5a Injection hole 6 Outer 7 Inner holder 8 Shaft pushing cylinder 8a Injection channel 9 Shaft pushing force transmission jig 10 Stopper 11 O-ring 12 Cylinder part 12a Cylinder chamber 13 Inner shaft pushing hydraulic system 14 Piston section 15 Hydraulic cylinder 15a, 15b Cylinder chamber 16 Axis pushing hydraulic system 17 Axis returning hydraulic system 18 Outline of metal pipe before molding 19 Outline of metal tube after molding 20 Corner R section

Claims (2)

[Claims] 1. A metal tube is loaded into a mold, the metal tube is axially pushed through a shaft pushing punch, and a liquid is charged into the metal tube to increase the pressure of the liquid in the tube, thereby forming the metal tube. In the hydroforming method of a metal tube to be formed, as the shaft pressing punch, an inner insertable into a metal tube having the liquid injection hole and an outer periphery of the inner are provided so as to be relatively movable in an axial direction. Using a double-structured axial pressing punch having an outer that can be in contact with the pipe end face of the metal pipe, the tip face of the outer pipe is brought into contact with the pipe end face of the metal pipe, and the inner and outer parts are integrally formed. While moving and axially pushing the metal tube, injecting a liquid into the metal tube through the injection hole and moving the inner in a state where the outer is fixed at a position where the metal tube is axially pushed by a predetermined amount. Said gold A method for hydroforming a metal pipe, wherein the metal pipe is formed into a desired shape by inserting the metal pipe into a metal pipe. 2. A metal tube is loaded in a mold, and the metal tube is pressed by a shaft pressing punch, and a liquid is injected into the metal tube to increase the pressure of the liquid in the tube, thereby forming the metal tube. In the metal pipe hydroforming apparatus, the shaft pressing punch is provided with an inner insertable into the metal pipe having the liquid injection hole, and the inner press is provided on the outer periphery of the inner so as to be relatively movable in the axial direction. An outer end which can be in contact with the pipe end face of the metal pipe, wherein the tip end face of the outer pipe is brought into contact with the pipe end face of the metal pipe to move the inner and outer parts together to push the metal pipe axially. By simultaneously injecting a liquid into the metal tube through the injection hole, and fixing the outer at a position where the metal tube is axially pushed by a predetermined amount, moving the inner and inserting the inner tube into the metal tube. ,metal The hydroforming molding apparatus of the metal tube, characterized by being configured so as to mold into a desired shape.