JP2008149343A - Tube hydroforming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To propose such technique in which the strength is improved while balanced as a whole in terms of an expanded member to be worked. <P>SOLUTION: This invention relates to a tube hydroforming method where, in the cavity 2 of a die which is hermetically sealed, the member 3 to be worked is formed into a shape matching to the inner surface 2a of the cavity by expanding a tubular member 3 to be worked by imparting forming hydraulic pressure p to the inside of the member and closely contacting the member 3 to be worked with the inner surface 2a of the cavity. The member 3 to be worked which is preliminarily formed so that prescribed spaces 5a, 5b ... are formed in the prescribed positions between the outer surface 3a of the member 3 to be worked and the inner surface 2a of the cavity and the circumference of the cross section of the member 3 to be worked is longer than the circumference of the cross section of the cavity 2 is set in the cavity 2 and the forming liquid pressure is imparted to the inside of the member 3 to be worked. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a tube hydroforming technique in which a tubular workpiece is expanded at a molding fluid pressure and molded along a cavity shape.

  2. Description of the Related Art Conventionally, a tube hydroforming technique in which a tubular workpiece is expanded with a molding fluid pressure and molded along a cavity shape has been publicly known, and there is a document disclosing this technique (for example, Patent Document 1). reference.).

  In this tube hydroforming, for example, as shown in FIG. 3, when molding of a corner portion having a small corner R shape is desired, a very large molding fluid pressure is required. Regarding the forming of the part, tube hydroforming was not practical.

  That is, in the example of FIG. 3, the corner portion 51 of the workpiece 50 is brought into close contact with the inner wall 43 of the corner portion 42 of the cavity 41 formed in the mold 40, so that the corner portion 51 has a small corner R shape. In order to reshape, the inner radius R of the corner 51, the plate thickness t of the workpiece 50, the stress σ required for deformation of the workpiece, and the molding fluid pressure p, R = t · σ / p It is necessary to establish a relationship. Here, when R = 3 mm, t = 2.9 mm, and σ = 980 Mpa, the molding fluid pressure p becomes a large number of 950 Mpa, and the corner portions 42 and 51 are in close contact with each other in the well-known tube hydroforming method. The tube cannot be expanded to the level.

  On the other hand, Patent Document 1 discloses a technique capable of forming a corner portion having a very sharp cross section. However, since compression molding is performed by sandwiching the die with a die, the workpiece is uniformly compressed during the compression molding. However, even if the tube hydroforming is performed after that, it is conceivable that deformation due to compression affects and the shape system becomes worse.

  Further, as in Patent Document 1, if compression molding is performed, in the compressed workpiece, residual stress due to compression is generated in the compressed portion, but in the portion that is not compressed, This residual stress will not occur. As a result, non-uniformity of the residual stress occurs, and non-uniformity of the strength occurs such that the strength of the uncompressed portion is weakened.

Further, in Patent Document 1, regarding the formation of the corner R shape, the relative relationship between the shape of the cavity and the workpiece is not considered, and in order to realize a smaller corner R shape, the relative Based on this relationship, it is considered necessary to consider the flow of the workpiece when expanding the workpiece.
Special table 2003-516862 gazette

  Therefore, the present invention proposes a novel tube hydroforming method that enables molding of a smaller corner R shape and can improve the overall balanced strength of the expanded workpiece. To do.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

That is, as described in claim 1,
Inside the cavity of the mold to be sealed, a molding fluid pressure is applied to the inside of the tubular workpiece to expand the tube, and the workpiece is brought into close contact with the inner surface of the cavity, so that the workpiece is attached to the cavity. A tube hydroforming method for forming into a shape along the inner surface,
A predetermined circumferential space is formed at a predetermined position between the outer surface of the workpiece and the inner surface of the cavity, and the sectional circumference of the workpiece is larger than the sectional circumference of the cavity. Set the preformed workpiece in the cavity to be long,
Tube hydroforming, in which a forming fluid pressure is applied to the inside of the workpiece, the workpiece in a range where the predetermined space is formed is brought into close contact with the inner surface of the cavity, and the predetermined space is filled It is a method.

Moreover, as described in claim 2,
The cross-sectional shape of the product finally obtained by the tube hydroforming method has a corner portion of a corner R shape, and in order to form the corner portion, at positions on both sides of the corner portion, The predetermined space is arranged.

  As effects of the present invention, the following effects can be obtained.

  According to the first aspect of the present invention, it is possible to improve the overall strength of the expanded workpiece.

  According to the second aspect of the present invention, it is possible to form a corner portion having a small corner R shape, which has been impossible with conventional tube hydroforming.

  Next, embodiments of the invention will be described.

As shown in FIGS. 1A and 1B, in this embodiment,
In the cavity 2 of the mold 1 to be sealed, the molding fluid pressure p is applied to the inside of the tubular workpiece 3 to expand the tube, and the workpiece 3 is brought into close contact with the cavity inner surface 2a. A tube hydroforming method for forming a workpiece 3 into a shape along the cavity inner surface 2a,
.. So that predetermined spaces 5a, 5b... Are formed at predetermined positions between the outer surface 3a of the processed member 3 and the inner surface 2a of the cavity. However, the preformed workpiece 3 is set in the cavity 2 so as to be longer than the circumferential length of the cavity 2;
A molding fluid pressure is applied to the inside of the workpiece 3 to bring the workpiece 3 in a range where the predetermined spaces 5a, 5b... Are formed into close contact with the inner surface 2a of the cavity. 5a, 5b,... Are filled, thereby causing a movement of the material constituting the workpiece 3 in the circumferential direction.

  FIG. 1 (a) shows a state before the tube hydroforming is performed, and FIG. 1 (b) shows that the tube hydroforming is performed so that the workpiece 3 made of metal or the like is along the cavity inner surface 2a. The molded state is shown.

As shown in FIG. 1A, the workpiece 3 is preformed into a cross-sectional shape different from the final product shape before being set in the cavity 2 of the mold 1.
This preforming has a cross-sectional shape so that predetermined spaces 5a, 5b... Are formed at predetermined positions between the outer surface 3a of the workpiece 3 and the inner surface 2a of the cavity, and The cross-sectional peripheral length of the workpiece 3 is made longer than the cross-sectional peripheral length of the cavity 2. The workpiece 3 thus preformed is disposed between the upper mold 1A and the lower mold 1B, and the workpiece 3 is disposed in the cavity 2 by closing both the molds 1A and 1B. It is said.

  In this embodiment, the cross-sectional shape of the product finally obtained by tube hydroforming is a rectangle like the shape of the cavity inner surface 2a shown in FIG. 1 (b). The middle portions of the four sides are recessed inward, that is, pressed in the direction opposite to the tube expansion direction so that the predetermined spaces 5a, 5b,. The cavity 2 is expanded so as to be longer than the circumferential length of the cross section.

  Further, the volumes of the predetermined spaces 5a, 5b,... Are appropriately determined in consideration of the amount of deformation at the time of pipe expansion, and are assumed to be filled by pipe expansion.

  In addition, the specific method of performing the preforming is not particularly limited. For example, according to press molding, the preforming can be performed by a simple and simple operation.

  Furthermore, in the present embodiment, as shown in FIG. 1B, the cross-sectional shape of the product that is the final molding target has corner portions 6a, 6b,. In order to form the corner portions 6a, 6b, etc., as described above, the positions where the corner portions 6a, 6b, etc. are sandwiched, in other words, the corner portions 6a, 6b,. The predetermined spaces 5a, 5b,...

And as shown to Fig.1 (a), by determining the arrangement | positioning about the said predetermined space 5a * 5b ... on the basis of corner part 6a * 6b ..., inside the said to-be-processed member 3 is shown. When the molding fluid pressure is applied and the workpiece 3 is expanded so as to fill the predetermined spaces 5a, 5b. The moving material moves in the circumferential direction toward the corner portions 6a, 6b, ... (material supply to the corner R portion).
Thereby, the corner spaces 8a, 8b,... Formed between the corner portions 6a, 6b,... Of the workpiece 3 and the corner portions 7a, 7b,. The workpiece 3 is expanded.

  Further, as shown in FIG. 1 (a), in the present embodiment, the spaces 5a and 5b are formed by indenting midway portions of the four sides of the workpiece 3 to the inner side. The molding fluid pressure p can be applied to the wide ranges 9a and 9b located on both sides of the corner portion 6a. As a result, a large amount of movement of the workpiece 3 in the circumferential direction can be ensured, and the corner spaces 8a, 8b,... Can be easily filled.

  If it is assumed that the space 5a and 5b are not formed and the middle part of the four sides is contacted with the cavity inner surface 2a in the preliminary molding, the pressure acting on the middle part (molding fluid pressure p) is processed. It becomes impossible to act on the movement of the material which comprises the member 3, and it becomes difficult to fill corner space 8a * 8b ... of corner part 7a * 7b .... Further, since the total pressure (molding fluid pressure p) acting in the vicinity of the corner portions 6a, 6b,... Of the workpiece 3 is small, the corner spaces 8a, 8b,. Will become difficult.

  Further, as shown in FIG. 1A, in this embodiment, the cross-sectional peripheral length of the workpiece 3 is longer than the cross-sectional peripheral length of the cavity 2, so Before the forming is performed, the peripheral length of the workpiece 3 remains. The extra perimeter is expanded by the molding fluid pressure p so as to follow the cavity inner surface 2a. And since the extra perimeter is large, a large amount of movement of the material constituting the workpiece 3 in the circumferential direction can be obtained, and a corner portion having a smaller corner R shape can be formed.

  Further, in this way, by securing a large amount of movement of the material constituting the workpiece 3 and securing movement of the material constituting the workpiece 3 by the molding fluid pressure p in a wide range 9a, 9b. In a wide range, a compressive force is applied in the circumferential direction, and the shape freezing property after demolding can be improved. That is, the plastic strain in the circumferential direction is in a compressed state as a whole and has excellent shape freezing property. Further, the strength can be improved and the uniformity of the strength can be improved.

  Further, in the series of pipe expansions described above, a large amount of movement of the material constituting the workpiece 3 can be secured, so the molding fluid pressure p can be set to a pressure lower than the conventional one. . That is, a desired small corner R shape can be obtained with a relatively small molding fluid pressure p. As a result, it is possible to simplify and reduce the size of the apparatus for forming the high-pressure state, and it is possible to reduce the cost.

  As described above, according to the present embodiment, it is possible to form a corner portion having a small corner R shape, which has been impossible with conventional tube hydroforming.

As shown in FIGS. 2 (a) and 2 (b), the second embodiment is a case where tube hydroforming is performed on a workpiece 13 having a substantially U-shaped cross-sectional view, and similar to the first embodiment described above. A predetermined shape is obtained by hydroforming after preforming.
In the preforming, the cross-sectional shape is such that a predetermined space 15a is formed at a predetermined position between the outer surface 13a of the workpiece 13 and the cavity inner surface 12a, and the workpiece The cross-sectional circumference of 13 is longer than the cross-sectional circumference of the cavity 12.

  As in the second embodiment, even in the substantially U-shaped workpiece 13, the molding fluid pressure p is applied to a wide range, that is, the space 15 a is configured to have a wide range, thereby expanding the pipe. It is possible to secure a wide range in which movement of the material constituting the workpiece 13 occurs, and a compressive force is applied in the circumferential direction over a wide range, which can improve the shape freezing property after demolding. it can. That is, the plastic strain in the circumferential direction becomes a compressed state as a whole, and is excellent in shape freezing. Further, the strength can be improved and the uniformity of the strength can be improved.

  Further, as in the second embodiment, with respect to the workpiece 13 configured to be bilaterally symmetric in the cross-sectional view, the space 15a is secured in the left and right central portions, and the workpiece is processed in a direction that expands toward both sides. By forming the material flows 16, 16 constituting the member 3, it is possible to ensure a symmetrical movement of the workpiece 3 and to secure a balance of residual stress after molding. In addition, it is possible to apply a large compressive force to the corner portions 13b and 13b having a large degree of bending in the workpiece 13, and it is possible to ensure a sufficient strength even in particularly weak portions.

(A) is a figure which shows the state before implementing tube hydroforming in Example 1, (b) is a figure which shows the state in which tube hydroforming was implemented in Example 1. FIG. (A) is a figure which shows the state before implementing tube hydroforming in Example 2, (b) is a figure which shows the state in which tube hydroforming was implemented in Example 2. FIG. The figure explaining the shaping | molding of the corner R shape by the conventional tube hydroforming.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal mold | die 2 Cavity 2a Cavity inner surface 3 Work piece 3a Outer surface 5a * 5b Space 6a * 6b Corner part 7a * 7b Corner part 8a * 8b Corner part space p Molding fluid pressure

Claims (2)

Inside the cavity of the mold to be sealed, a molding fluid pressure is applied to the inside of the tubular workpiece to expand the tube, and the workpiece is brought into close contact with the inner surface of the cavity, so that the workpiece is attached to the cavity. A tube hydroforming method for forming into a shape along the inner surface,
A predetermined circumferential space is formed at a predetermined position between the outer surface of the workpiece and the inner surface of the cavity, and the sectional circumference of the workpiece is larger than the sectional circumference of the cavity. Set the preformed workpiece in the cavity to be long,
Tube hydroforming, in which a forming fluid pressure is applied to the inside of the workpiece, the workpiece in a range where the predetermined space is formed is brought into close contact with the inner surface of the cavity, and the predetermined space is filled Method. The cross-sectional shape of the product finally obtained by the tube hydroforming method has a corner portion of a corner R shape, and in order to form the corner portion, at positions on both sides of the corner portion, The tube hydroforming method according to claim 1, wherein the predetermined space is arranged.

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