JP2000084623A - Hydro forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid a crack due to thinning of a bulged part and to precisely form a bulged part by applying an internal pressure and a axial compression load in the flow direction of a tube stock having a round cross section and forming a roughly flat part to a die face to the part changing from the axial direction of the tube stock to the bulging direction. SOLUTION: A forming die 1 is formed with upper/lower dies 2, 3 split in the axial direction, the upper die 2 is subjected to parting/clamping in the A-B direction. Semicircle shaped die holes 4, 5 are formed in the upper/lower dies 2, 3, a cylindrical hole 7 having the diameter roughly equal to an outer diameter of a tube stock 6 is formed by working with alignment of both die holes 4, 5. A bulged part forming die hole 8 is formed as branched in the direction orthogonal to the axial center of the cylindrical die hole 7. A pressurized fluid is pressure supplied to the cylindrical die hole 7 from pressurized fluid nozzles 11, 12. A roughly flat part 13 is formed at the part where a flow direction of the tube stock 6 is changed from the axial direction to the direction of the bulged part forming die hole 8. The roughly flat part 13 is a roughly triangular, its bottom side is a straight line parallel to the tube stock 6 and its apex is positioned at a face of the bulged part forming die hole 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydroforming apparatus using hydraulic pressure in a bulge processing apparatus, and more particularly to a hydroforming apparatus for forming a bulge on a part of a pipe by hydroforming. .

[0002]

2. Description of the Related Art Conventionally, both ends of a tube material are pressed while applying a liquid pressure to a metal tube material arranged in a mold, and the tube material is caused to flow to form a bulging portion in a part of the tube. As a hydroforming technique, as shown in FIG.
2, a tube material 104 is arranged in a main mold hole 103, and a bulge forming mold hole 105 having a diameter smaller than the diameter of the tube material 104 is formed in a part of the lower mold 102. Using a processing device in which the entire circumference of the intersection of the molding die holes 105 is formed by a curved surface 106 having a small radius, while applying hydraulic pressure to the tube material 104 disposed in the main die hole 103,
Are pressed by punches 107, 107, and the tube material 10 is pressed.
4 is caused to flow and swell into the swelling portion forming die hole 105,
A molding of the bulging portion 108 as shown in FIGS. 14 and 15 is disclosed in, for example, Japanese Utility Model Laid-Open No. 58-66037.

[0003]

Whether or not the above-mentioned bulging portion can be formed into a desired shape, height, or the like depends on how smoothly the material of the tube material flows. You.

In the conventional processing apparatus, the flow of the material due to the hydraulic pressure and the axial pressing loads X and Y from both ends of the tube material 104 has a relatively smooth flow α at the curved surface portion shown in FIG. However, at the portions indicated by B in FIGS. 14 and 15, as shown by the arrow β, after the flow of the material from both sides of the tube material 104 is opposed to each other, the bulge has a smaller diameter than the diameter of the tube material 104. Since the flow becomes a three-dimensional flow flowing into the part forming die hole 105, the flow β portion has a mold surface 106 having a small diameter curved surface (the curved surface 10 in FIG. 15).
With 9), the flow of the raw material (material supply amount) in the direction of the bulging portion forming die hole 105 becomes poor, and it becomes difficult to form the bulging portion 108 shown in FIG.

That is, as shown in FIG. 16C, cracks (cracks) 110 are generated due to the thinning of the bulging portion 108 due to insufficient supply of the material to the bulging portion 108, and the material supply is compensated for. Even if the amount of axial pushing of the tube material in the axial direction is increased, as shown in FIG. 16D, buckling 111 occurs only in the tube material 104, and the crack 110 cannot be prevented. There is a problem that the molding height of the protrusion 108 is limited to a low one.

Therefore, the problem is how to make the flow of the material in the portion indicated by B in FIG. 14 smooth, that is, how to smoothly turn the flow of the opposing material into the bulging portion forming die hole and feed it. However, there has been no hydroforming apparatus that can solve this problem.

[0007] Therefore, an object of the present invention is to provide a hydroform processing apparatus which solves the above-mentioned problems.

[0008]

According to a first aspect of the present invention, an internal pressure and an axial compressive load are applied to a tube material in a mold, and a part of the tube material is provided. A hydroforming apparatus for forming a swelling portion, wherein a substantially flat portion is formed on a mold surface of a portion where a flow direction of a tube material changes from an axial direction to a swelling direction.

According to the present invention, in the hydroforming process, the substantially flat portion formed on the mold surface functions as a guide for changing the flow of the tube material in the axial direction relative to the swelling direction. The direction change to
A sufficient material is smoothly supplied in the bulging direction.

According to a second aspect of the present invention, in the first aspect, the bulging portion has a diameter smaller than that of the tube material, the substantially flat portion has a substantially triangular shape, and a base thereof has a bottom side. It is a straight line parallel to the axis of the tube material, and the apex is on the mold surface of the bulging portion.

In the hydroforming process, when a bulged portion having a diameter smaller than that of the tube material is formed, a flow obstruction of the material caused by a difference in diameter between the tube material and the bulged portion is added. Although the swelling property is further deteriorated as compared with the case where the portions have the same diameter, the substantially flat portion is located at the bottom side and the apex is located at the swelling portion side as in the present invention, and the swelling with the tube material is performed. The triangular shape is formed by bridging the parts diagonally to compensate for the difference in diameter, so even if the tube material and the bulging part have different diameters, the flow in the bulging direction of the material is smooth and bulging is easy. It is performed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a front sectional view showing a hydroforming apparatus according to the present invention, and FIG.
It is a line sectional view.

1 and 2, a molding die 1 is divided in an axial direction, and is formed by an upper die 2 and a lower die 3. The upper die 2 is released in the direction of arrows AB by driving means (not shown). And the mold can be clamped. Also, semi-circular mold holes 4 and 5 are formed in both molds 2 and 3, and by making the mold holes 4 and 5 coincide with each other, a cylinder having substantially the same diameter as the outer diameter of the tube material 6 to be processed is formed. The shape hole 7 is formed.

The lower mold 3 is formed with a bulging portion forming die hole 8 in a direction perpendicular to the axis of the cylindrical die hole 7 and communicates with the cylindrical die hole 7 so as to be branched. The part forming die hole 8 is formed as a bottomed hole. Further, the diameter of the bulging portion forming die hole 8 is formed smaller than the diameter of the cylindrical die hole 7, that is, the diameter of the tube blank 6.

Punches 9 and 10 are provided at both ends of the cylindrical mold hole 7.
Are arranged so as to be slidable in the axial direction of the cylindrical mold hole 7 and are moved in the direction of arrow D-E by pressurizing means (not shown). A predetermined axial compression load W is applied to both ends of the tube material 6 set in the hole 7. Further, the punches 9 and 10 are formed with nozzles 11 and 12 for pressurizing a pressurized liquid into the cylindrical mold hole 7, and pressurized liquid of a predetermined pressure is supplied from a pressurized liquid supply source (not shown). Twelve cylindrical mold holes 7
It is designed to be pressed in.

From the cylindrical mold hole 7 to the bulge forming mold hole 8
That is, the tube material 6 set in the cylindrical mold hole 7 is pressed from both ends thereof, and the flow direction of the tube material 6 changes from its axial direction to the direction of the bulging portion forming mold hole 8. Has a substantially flat portion 13 formed therein.

This substantially flat portion 13 is shown in FIGS.
This will be described in more detail. In the direction of the axis F of the cylindrical mold hole 7,
The cylindrical mold hole 7 on the plane G passing through the axis of the protrusion forming mold hole 8
Of the mold surfaces 14 and 15 at the portion that changes from
Radius R₁, R_TwoAnd the R₁, R_TwoStart points a, b
Is the middle point of the curve connecting the bulging portion forming die hole 8 on the mold surface and c
And a line drawn tangentially from the midpoint c to the inner surface of the cylindrical mold hole 7.
The point of intersection with the inner surface of the cylindrical mold hole 7 is d, and the mold surfaces 14,
R larger than radius 15 _Three, R_FourFrom the center c
E and f are the intersections of the drawn curve and the axial line passing through the point d.
, The range surrounded by each of the points c, e, and f is substantially flat.
The surface is formed as a substantially flat portion 13.

Therefore, the substantially flat portion 13 is substantially triangular, the base of which is a straight line parallel to the axis of the tube blank 6 and the apex of which is located on the surface of the bulge forming die hole 8. . In addition, the said substantially plane is meant to include a plane and a gentle curved surface having a large radius.

As an example, the diameter of the tube blank 6 is 50 mm.
When the diameter of the bulging portion 6a is 30 mm, the R
₁ and R ₂ were 10 mm, and R ₃ and R ₄ were 24 mm. In the illustrated embodiment, the outer shape of the substantially flat portion 13 is a substantially triangular shape whose bottom is a straight line parallel to the axis of the tube blank 6 and whose apex is on the surface of the bulging portion forming die hole 8. However, the shape is not limited to this outer shape, and any shape may be used as long as it can smoothly change the flow of the tube material facing the axial direction in the bulging direction.

Next, a description will be given of a hydroforming process using the mold 1 described above. First, the upper mold 2 is released, and the tube material 6 is placed in the mold hole 5 of the lower mold 3. Thereafter, the upper mold 2 is tightened to set the tube material 6 in the molding die 1.

Next, the nozzles 11, 1 of the punches 9, 10 will be described.
At the same time, a predetermined pressure is applied to the inside of the tube material 6 by pressurizing the pressurized liquid into the tube material 6 and at the same time, the punches 9 and 10 are moved to the material tube 6 side (arrow D).
Direction), and pressurizes both ends of the tube material 6 to apply a predetermined axial compressive load W to the tube material 6.

Due to the internal pressure and the axial compression load W applied to the tube blank 6, a part of the tube blank 6 swells into the bulging portion forming die hole 8. At this time, the above-mentioned substantially flat portion 1 is attached to the mold surface of the portion where the flow direction of the tube material 6 changes from the axial direction to the bulging direction.
Since the substantially flat portion 13 functions as a guide surface for guiding the flow of the material of the tube material 6 in the axial direction in the swelling direction, the direction change of the material becomes smooth,
A sufficient material is smoothly supplied in the bulging direction. for that reason,
The formation of the bulging portion is facilitated.

Therefore, cracks due to the conventional thinning of the pipe can be avoided, and a large bulging height can be obtained with the same wall thickness. Of course, buckling due to excessive axial load can also be avoided.

By the hydroforming process as described above, a molded product in which a bulging portion (dome) 6a is integrally formed in a part of the tube material 6 as shown in FIGS. 4 to 6 is obtained. A substantially flat portion 6b having the same shape as the substantially flat portion 13 is formed at a portion corresponding to the substantially flat portion 13 in the molding die 1.

Next, the experimental results of hydroforming using the conventional mold and the mold of the present invention will be described. First, as described above, the hydraulic pressure for forming a bulging portion in a part of a tube material by hydroforming is generally represented by the following equation.

Pf = 2 to σB / ρ where Pf is the molding fluid pressure, to is the plate thickness of the tube material, σB is the tensile strength of the tube material, and ρ is the radius of curvature.

Therefore, the diameter of the tube material is 5
cm, plate thickness to is 0.16 cm, tensile strength σB is 3
The molding fluid pressure Pf when a low carbon steel pipe of 000 kg / cm ² is used is calculated by substituting the above value into the above equation with the radius of curvature ρ being the reciprocal of 0.5.
Is 1920 kg / cm ² .

Next, the axial pushing load of the tube material required for molding is controlled by the molding hydraulic pressure 1920 acting as a reaction force.
The pressure is set to be larger than kg / cm ^{2 and not} more than the load obtained by adding the buckling load of the tube material as the molding liquid pressure.

In the embodiment, the sectional area of the tube material (19.63
cm ² ) multiplied by the molding fluid pressure (1920 kg / cm ² ), the buckling stress of the tube material is 37680 kg / cm ^2, and the buckling stress of the tube material is 243 mm ² and the tensile stress is 30 k.
g / mm ² multiplied by 6566 kg (4
4246 kg) is the upper limit of the axial pushing load of the tube material.

Based on the above processing conditions, the molding liquid pressure is set to 1
As a result of performing hydroforming with the axial pressing load of the tube material set to 920 kg / cm ² and the axial pressing load of the tube material set to 44000 kg, the axial pressing amount of the tube material was 30 mm in the conventional mold, and FIG. As shown in FIG. 16A, a crack 110 was generated at the top of the bulging portion 108, whereas in the mold having the substantially flat portion 13 according to the present invention, the axial pushing amount of the tube material was 50 mm, and FIG. As shown in
The bulging portion 6a was accurately formed without cracking.

The molding fluid pressure was set to 1920 kg / cm ^2, and the axial pushing load of the tube material was 50,000 kg / cm ^2.
As a result of the hydroforming with the setting of the conventional molding die, the axial pushing amount of the tube material is 50 mm,
As shown in FIG. 16D, a crack 110 occurred at the top of the bulging portion 108 and a buckling 111 occurred. This increases the axial pushing amount of the tube material by 20 mm as compared with FIG. 16C, but the material is not supplied to the top of the bulging portion 108 due to the buckling phenomenon of the tube material, and cracks 110 occur. It seems to have done.

On the other hand, in the mold having the substantially flat portion 13 according to the present invention, the axial pushing amount of the tube material is 60 mm, and the bulging portion 6a is accurately formed as shown in FIG. Then, buckling 6c was formed in 6 parts of the tube material. In this example, the axial pushing amount is 10 mm compared to FIG.
Although the increase was made, the increase was only buckling 6c, which was an unnecessary load increase for forming the bulging portion.

FIG. 8 shows a second embodiment.
Shows an example in which a bent tube is formed and a bulged portion 6a is formed in a part thereof. The forming die in this embodiment has a split die for forming the tube blank 6 and a bulging portion forming die hole for forming the bulging portion 6a in one of the dies. In (2), the mold surface of the portion where the flow direction of the tube material 6 changes from the axial direction to the bulging direction is formed in a substantially flat portion similar to the above.

Then, as in the above-described embodiment, the both ends of the tube blank 6 are pressed with a punch while applying a predetermined hydraulic pressure to the inside of the tube blank 6, so that the flow of the blank in the substantially flat portion is performed in the same manner as in the above embodiment. Is performed smoothly to form the bulging portion 6a. FIG.
In the figure, 6b is a substantially flat portion on the tube blank 6 side formed by the substantially flat portion of the mold.

In the embodiment, the bending radius R _{5 of the} tube blank 6 is
Was 75 mm, and the diameter of the bulging portion 6a was 30 mm.
Also in this example, the bulging portion 6a could be formed accurately without cracking.

FIGS. 9 to 12 show still another four embodiments, each showing a molded product. FIG. 9 is a diagram in which one bulging portion 6a is formed so as to be inclined with respect to the axis of the tube blank 6, and
FIG. 10 shows two bulging portions 6a which are inclined with respect to the axis of the tube material 6 and are branched on both sides. FIG. 11 shows two bulging portions 6a with respect to the axis of the tube material 6. FIG. 12 shows a bulge formed on both sides in the direction orthogonal to the tube material. FIG. Fig. 5 shows a bulged portion 6a further inclined and branched.

In the embodiments shown in FIGS. 9 to 12, a mold is formed corresponding to the molded product, and the flow direction of the tube material during the hydroforming is changed from the axial direction to the swelling direction. The mold surface of the portion that changes to is formed in a substantially flat portion similar to the above.

In each of the embodiments, the material flows smoothly as in the previous embodiment. 9 to 12, reference numeral 6b denotes a substantially flat portion on the tube blank 6 side formed by the substantially flat portion of the molding die.

Also in these examples, each bulging portion 6a could be formed accurately without cracking.

[0040]

As described above, according to the first aspect of the present invention, the formation of the bulging portion is facilitated, and the cracking due to the thinning of the bulging portion as in the prior art is avoided, and accurate Bulges can be formed. Furthermore, if the wall thickness is the same as that of the related art, a bulging portion having a larger bulging height can be formed.

According to the second aspect of the present invention, the flow of the material is smoothed to facilitate the formation of the bulging portion even when the bulging portion having a diameter smaller than that of the tube material is formed. Can be molded.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a molding die showing a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line CC in FIG.

FIG. 3 is a view for explaining a substantially flat portion in FIG. 1;

FIG. 4 is a front view showing a molded product molded by the molding die of FIG. 1;

FIG. 5 is a sectional view taken along line HH in FIG. 4;

FIG. 6 is a bottom view of FIG. 4;

FIG. 7 is a perspective view of FIG. 4;

FIG. 8 is a front view of a molded product showing another embodiment of the present invention.

FIG. 9 is a front view of a molded product showing still another embodiment of the present invention.

FIG. 10 is a front view of a molded product according to still another embodiment of the present invention.

FIG. 11 is a front view of a molded product according to still another embodiment of the present invention.

FIG. 12 is a front view of a molded product showing still another embodiment of the present invention.

FIG. 13 is a front sectional view showing a conventional molding die.

FIG. 14 is a front view of a molded product molded by the molding die of FIG. 13;

FIG. 15 is a side view of FIG. 14;

FIG. 16 is an explanatory cross-sectional view of a molding state of a bulging portion, where (a)
(B) is based on the mold of the present invention, and (c) and (d) are based on the conventional mold.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Molding die 2, 3 ... Upper and lower molds 4, 5 ... Mold hole 6 ... Tube material 8 ... Swelling part molding die hole 9, 10 ... Punch 11, 12 ... Pressurized liquid nozzle 13 ... Substantially flat part

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[Procedure amendment]

[Submission date] July 23, 1999 (1999.7.2)
3)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

[0008]

To SUMMARY OF THE INVENTION To solve the above problems, a first invention according to claim 1, adds pressure and axial compressive load to the tube material in the mold, from a portion of the pipe material A hydroform processing apparatus for branching and forming a cylindrical bulge,
A substantially flat portion is formed on a mold surface of a portion where the flow direction of the tube material changes from the axial direction to the bulging direction.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0040

[Correction method] Change

[Correction contents]

[0040]

As described above, according to the first aspect of the present invention, the tubular bulging portion is branched from a part of the tube material.
This facilitates the formation of the swelling portion, avoids the cracks caused by the thinning of the swelling portion as in the prior art, and allows the accurate swelling portion to be formed. Furthermore, if the wall thickness is the same as that of the related art, a bulging portion having a larger bulging height can be formed. ────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 24, 1999 (1999.9.2)
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

[0008]

According to a first aspect of the present invention, a circular section in a mold is provided.
Adding pressure and axial compressive load to the tube material having, a hydroforming device for branching a circular cylindrical bulged portion from a portion of the tube stock, the bulging direction flow direction of the pipe material in the axial direction A substantially flat portion is formed on the mold surface of the portion that changes to.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0040

[Correction method] Change

[Correction contents]

[0040]

It seems because the foregoing, according to the first aspect of the present invention, it becomes easy to branching a circular cylindrical bulged portion from a portion of tube material having a circular cross-section, wherein Cracking due to thinning of the bulging portion as in the prior art can be avoided, and an accurate bulging portion can be formed. Furthermore, if the wall thickness is the same as that of the related art, a bulging portion having a larger bulging height can be formed.

Claims (2)

[Claims] 1. A hydroforming apparatus for applying an internal pressure and an axial compressive load to a tube material in a mold to form a bulge in a part of the tube material, wherein a flow direction of the tube material is expanded from an axial direction. A hydroform processing apparatus, wherein a substantially flat portion is formed on a mold surface of a portion that changes in an outgoing direction. 2. The swelling portion has a diameter smaller than that of the tube material, the substantially flat portion has a substantially triangular shape, a bottom side of the swelling portion is a straight line parallel to an axis of the tube material, and a vertex is swelled. 2. The hydroforming apparatus according to claim 1, wherein the apparatus is located on a mold surface of the part.