JP2001009528A - Hydraulic form processing method and hydraulic forming die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a burst when an inner pressure is loaded and not to cause a pinching either by giving an inner pressure in the pipe inside and a pushing force in the pipe axial direction after divided dies are clamped in a state that a pipe is mounted on the dies, one part of the dies is activated so as to push the pipe for deformation and one part of the dies into which the pipe is pushed, is returned again to its original position. SOLUTION: Die clamping is completed by lowering an upper die 2 in a state that a pipe 1 is mounted on a bottom die 3. In that case, activation parts 4 and 5 being respectively built-in on the intermediate portions in the upper and bottom dies are left in a condition that they are drawn inside of each die (original position). Then, the activation parts 4, 5 are moved in a direction where the pipe is pushed in, namely, to inner side than original positions for deforming the pipe 1. Thereby, distance between a corner part 6, which is of the final angular cross sectional shape, and a pipe material is reduced. Then, the activation parts 4, 5 are again withdrawn into original positions of each die. After then, the hydraulic form processing will be completed by applying an axial pushing and an inner pressure against the pipe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for manufacturing an engine cradle or the like for an automobile part. A pipe is put into a divided mold, the mold is clamped, and the internal pressure and the pipe shaft are put in the pipe. The present invention relates to a hydroforming method for forming into a predetermined shape by applying a pressing force in a direction and a mold used for the processing.

[0002]

2. Description of the Related Art In recent years, hydroforming technology has attracted attention in the automotive field as one of the means of cost reduction and weight reduction by reducing the number of parts, and has already been adopted in actual vehicles in Europe and the United States, and has been applied by domestic companies as well. Is under consideration. The hydroforming technology not only controls the basic three axes, ie, mold clamping, internal pressure, and pushing in the tube axis direction, but also, for example, bulging as disclosed in JP-A-7-155857. For forming by controlling the height of the portion,
Processing of a complicated shape has been made possible by, for example, a method of compressing a pre-expanded portion in the tube axis direction as disclosed in Japanese Patent No. 96347.

[0003]

One of the problems of the hydroforming technique is prevention of burst at a corner or the like. For example, when the pipe 1 is expanded from a circular cross section to have a square cross section as shown in FIGS. 2 (a) and 2 (b), contact starts from a side portion as shown in FIG. 2 (b). When the internal pressure is further increased, the portion that first comes into contact with the internal pressure is gripped by the frictional force, and the elongation concentrates on the free corner 6, and before reaching the target radius of curvature of the corner R, the corner 6 is bent. May burst.

As a means generally used to solve the above-mentioned problem, as shown in FIG. 3A, a pre-process such as pressing is performed in a separate step before hydroforming. That is, it is a method of forming a shape as close as possible to the final shape of the hydroform processing by a press or the like, and starting contact from a position close to the corner portion 6 at an initial time when the internal pressure of the hydroform is applied, thereby preventing a burst. . However, this method involves one additional step, which is disadvantageous in terms of cost. In addition, as shown in FIG. 3B, depending on the shape of the pre-processing, the end of the pipe 1 is sandwiched between the upper and lower dies during mold clamping. , So-called pinching may occur.

[0005]

Means for Solving the Problems The present inventors prevent the above-mentioned burst at the time of hydroform internal pressure load,
Moreover, as a result of various studies on a method that does not cause pinching and does not increase the number of steps as in the conventional pre-processing method and a mold for performing the method, the present invention has been completed. The gist of the present invention will be described below.

[0006] The gist of the present invention is that, with the tube attached to the mold, the divided mold is clamped, then a part of the mold is operated, the tube is pushed in to deform it, and then the pushed metal is pressed. After returning a part of the mold to the original position again, a hydroforming method characterized by applying the internal pressure inside the tube and the pushing force in the axial direction of the tube, and dividing the tube with the tube attached to the mold In the mold for hydroforming for deforming the tube, the part of the mold is moved inward from the original position, the tube is deformed by pushing the tube, and the mold is returned to the original position. A mold for hydroforming, which has a returning function. In the present invention, the divided mold refers to a mold divided into two, three, or more.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example in which a tube is processed from a circular cross section to a square cross section. The present invention will be described in detail with reference to this example. First, the upper mold 2 is lowered with the tube 1 attached to the lower mold 3, and the mold clamping is completed (→). At this time, the operating parts 4 and 5 incorporated in the intermediate portions in the upper and lower dies, respectively, are kept in their original positions (the original positions). Next, the operating units 4 and 5 are moved in the direction in which the pipe is pushed in, that is, inside the original position, to deform the pipe 1 (). Thereby, the corner portion 6 of the final square cross-sectional shape
And the distance between the tube material is reduced. Next, the operating units 4 and 5 are again operated.
Is drawn into each mold at the original position (). Thereafter, hydroforming is completed by applying axial pressing and internal pressure (illustrated by an arrow) to the tube ().
According to this method, contact starts from a point close to the corner from the initial point of the internal pressure load, and a burst at a corner or the like as described above can be prevented.

The present invention does not require a separate step such as pre-processing, so that the number of steps does not increase, the number of equipment does not need to be increased, and the cost is excellent. In addition, since processing is performed in a state in which the mold is closed, there is no possibility of pinching.
The effect of the present invention can be obtained by any means, such as a mechanical type or a hydraulic type, for driving the operating units 4 and 5.

[0009]

[Embodiment 1] FIGS. 4 and 5 show an embodiment of the present invention. FIG. 4 shows an example in which a straight pipe having a circular cross section is machined into a square cross section. In the conventional method (shown by (a) and (b) in FIG. 4), the outer diameter is 6 mm.
0.5mm x 1.6mm steel pipe with 400 corners
What was bursting at atmospheric pressure can be loaded up to about 700 atm by the example of the present invention (shown in (c), (d) and (e) of FIG. 4), and the corner R can be machined more sharply. In addition, the drive part of the metal mold | die of this invention example was controlled using the mechanical means (rack and pinion system).

Embodiment 2 FIG. 5 shows an example in which a 90 ° bent pipe (steel pipe: outer diameter 60.5 mm × sheet thickness 1.6 mm) is subjected to hydroforming processing. When the gap 6 with the gap 3 was large, bursting occurred at about 300 atm from the position. However, according to the present invention, that is, in this case, as shown in FIG. The internal shape can be crushed before the internal pressure is applied, the gap inside the bend is reduced, and the internal pressure is applied. Could be obtained. still,
The drive unit of the mold of this example was controlled using hydraulic means.

[0011]

According to the present invention, it is possible to hydroform a shape which could not be processed due to a conventional burst due to a neck, thereby contributing to the effect of reducing the number of parts and reducing the weight as described above. Further, since the number of steps does not increase, there is no cost disadvantage. In addition, in the hydroforming process, it is necessary to fill the inside of the pipe with liquid etc. after the mold is clamped, so if the step of pushing the working part, which is the point of the present invention, is provided within the filling time, the cycle time will also increase It can be processed without performing, and the productivity does not decrease.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view and a longitudinal sectional side view of a hydroforming method and a mold according to the present invention.

FIG. 2 is a longitudinal sectional view illustrating a burst problem in a conventional method.

FIG. 3 is a longitudinal sectional view of a conventional method for performing pre-processing in another step.

FIG. 4 is a longitudinal sectional view and a longitudinal sectional side view in the case of forming a square section from a circular section, which is an example of the present invention.

FIG. 5 is a cross-sectional view of a conventional method and a method of hydroforming a bent tube and an example of a die according to the present invention.

FIG. 6 is a sectional view taken along line BB in FIG. 5 (c).

[Explanation of symbols]

 1 Tube 2 Upper die 3 Lower die 4 Upper die built-in drive unit 5 Lower die built-in drive unit 6 Clearance (corner part)

Claims (2)

[Claims] 1. With the tube attached to the mold, the divided mold is clamped, then a part of the mold is operated, the tube is pushed in to deform, and then a part of the pushed mold. After returning to the original position again, the internal pressure inside the pipe and the pushing force in the axial direction of the pipe are applied. 2. A hydroforming processing mold for clamping a divided mold while the tube is mounted on the mold and deforming the tube, wherein a part of the mold is located inside an original position. A working mold for operating a hydroform, wherein the working part has a function of pushing the pipe and deforming the pipe, and the working part has a function of returning to the original position again.