JPS6116536B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a protrusion on one side of a blank tube by hydraulic bulging.

Conventionally, a material tube fitted into a mold is compressed in the axial direction while applying hydraulic pressure inside the material tube, causing a part of the material tube to bulge along the bulge hole on the side of the mold. Hydraulic bulge processing for forming protrusions on a material tube is well known. However, in the above-mentioned conventional hydraulic bulging process, the bulge hole in the mold is configured with a fixed size, so the material tube is compressed in the axial direction to fill it up, thereby causing the bulge. Even if an attempt is made to assist, the effect is not sufficient, and the tip of the bulging protrusion ruptures, or wrinkles occur on the side wall of the protrusion due to buckling, making it difficult to form the bulging protrusion to a sufficient height. That was difficult.

To explain in more detail the case in which a single protrusion is formed on a material pipe using a conventional forming device, Fig. 1a shows the state before the start of forming by the conventional forming device, and Fig. 1b shows the state after the same forming. This indicates the condition. During molding, place the material tube 1 on the lower mold 2, and place the material tube 1 on the upper mold 3.
is clamped onto the lower mold using mold clamping force W. At the same time, the pressurizing rods 4 and 5 are advanced at the same speed from both ends of the material tube 1 by respective hydraulic cylinders (not shown), and brought into contact with both ends of the material tube 1. FIG. 1a shows this state. Next, a high hydraulic pressure p is introduced into the material tube 1 through the bulge hydraulic pressure introduction hole 6 provided in the pressure rod 4, and at the same time, a compressive force F is applied to the pressure rods 4 and 5, so that the material tube 1 is compressed to obtain a T-shaped formed tube 10 as shown in FIG. 1b.

In forming such a material tube, in order to form a protrusion on one side of the material tube, the radius of curvature of the shoulder 3a of the upper die 3 that forms the rising portion 10b of the protrusion 10a must be adjusted.
R ₁ needs to be approximately twice the wall thickness of the material tube 1 or more, and it is not possible to obtain a formed tube having a rising portion 10b with a small radius of curvature. Further, even under appropriate bulge conditions, it is difficult to form the height of the protrusion 10a to be greater than the outer diameter _dp of the material tube 1 because buckling may occur. That is,
The height _H1 of the protrusion 10a corresponds to the amount of compression on one side of the material tube 1, and in consideration of this, insertion portions 4a and 5a are provided at the tips of the pressure rods 4 and 5 to prevent thickening. However, when trying to make the protrusion 10a higher, the extra wall 1 is formed between the tips of the insertion parts 4a and 5a.
0c occurs, and it is unavoidable that buckling occurs on the side surface of the protrusion.

Furthermore, FIGS. 2a and 2b show a case where a conventional molding device is applied to form a camel-shaped molded tube 20 by forming two protrusions 20a, 20a on the raw material tube 1. In this case, the protrusion 20a
The height _H2 is approximately 50% or less of the outer diameter _dp of the material tube 1, and is even lower than the protrusion 10a of the T-shaped formed tube.

When forming the above-mentioned camel-shaped forming tube, the material tube 1 is placed in the molding split mold 11, and the left and right pressure rods 14, 15 are advanced at the same speed at the same time so that both ends of the material tube 1 are brought into contact with each other. Seal the ends. This state is shown in FIG. 2a. Next, high hydraulic pressure p is introduced into the material pipe 1 from the hydraulic pressure introduction hole 16, and at the same time, the pressure rods 14, 1
compressing the material tube 1 by applying a compression force F to 5;
A camel-shaped molded tube 20 as shown in FIG. 2b is obtained.

However, in forming such a camel-shaped tube, the compression of the material tube contributes to the expansion on both sides of the protrusion 10a when forming the T-shaped tube, whereas the compression contributes to the expansion of the tube on both sides of the protrusion 20a. , 20a, and the formed height of the protrusion is inevitably lower than in the case of a T-shaped formed tube. Further, as shown in the figure, a pair of protrusions 20a,
When the protrusions 20a are inclined in directions away from each other, the rising portions 20b, 2 of the protrusions 20a, 20a
0b and the shoulders 13a, 1 of the upper die 13 that molds it
A gap 17 is generated between the protrusions 20a and 3a.
The height of 20a becomes lower.

In view of the above, the present invention is capable of forming a protrusion of sufficient height on the side surface of the tube while preventing buckling and thickening of the material tube, and also reduces the curvature of the rising portion of the protrusion. The purpose is to provide a molding method that allows the radius to be made sufficiently small.

The method of the present invention for achieving the above object is to axially compress a material tube to which hydraulic pressure is applied inside a mold to bulge a part of the material tube to the outside. It consists of a fixed mold with a mold cavity into which a tube is inserted, and a sliding mold that is slidably fitted into a guide groove provided in the fixed mold, and the distal end surface of the sliding mold and the fixed mold are A bulge hole formed between the end face of the guide groove and the material tube that allows one side of the material tube to bulge is shaped in advance to be long in the axial direction, and the material tube is prevented from buckling and thickening due to its compression. In order to prevent this, a core metal with a length that reaches at least the bulging portion is inserted, and while supplying bulge liquid pressure into the material tube, the bulge hole is compressed in the axial direction of the material tube at the same time. The feature is that by narrowing the material tube, a protrusion is formed on the side surface of the material tube while tightening the material tube.

According to the molding method of the present invention, when compressing the material tube to which hydraulic pressure is applied inside the mold in the axial direction, the bulging hole formed in the mold is made to have a long shape in the axial direction in advance, and Since the material tube is compressed in the axial direction and simultaneously narrowed in the axial direction, the initial bulge pressure necessary for the material tube to start expanding can be maintained more fully than in the above conventional example where the size of the expansion hole does not change. In addition, since the bulging portion is pressed in the axial direction of the material tube to tighten it, relative slippage between the material tube and the mold into which it is inserted is reduced compared to the conventional case. As a result, the loss of force due to friction is reduced, and the protrusion can be formed sufficiently high, which not only makes it possible to reduce the radius of curvature at the rising part of the protrusion, but also makes it possible to reduce the loss of force due to friction. Since there is little loss due to friction even when using this material, it is possible to form a protrusion by making the compression effect in the axial direction effective.

Furthermore, since a core bar with a length that reaches at least the bulging portion is inserted into the material tube, and compression molding of the material tube is performed in this state, buckling and protrusions due to compression of the material tube are not formed on the side surface. This core metal reliably prevents thickening of the protrusions, and as a result, the thickening of the protrusions is assisted, making it possible to form higher protrusions.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

3 to 6 show a forming apparatus for forming a tube material into a T-shaped tube. This forming device forms a material tube 1 inserted into the main body of the device into a T-shaped forming tube 21 by the interaction of compressive force F from a pressurizing cylinder device and bulge liquid pressure p.

As can be seen from FIGS. 3 and 5, the molding device main body includes an upper mold support 22 and a lower mold support 23 that overlap vertically, and is fixed in support holes 24 and 25 of both supports 22 and 23. The upper mold 26 and the lower mold 27 are stored, and these molds 26 and 27 are attached to the locking plate 2.
8 and 29 in the support cavities 24 and 25. The pair of molds 26 and 27 are provided with mold cavities 30 and 31 that constitute holes for inserting the material tube,
A fixed end sealing fitting 3 which is one pressure rod is attached to one end of the fitting.
The second sleeve 32a is inserted. This sealing fitting 32 is for sealing the end of the material tube 1 that is pressed by the other pressurizing rod, ie, the core metal 34, and has a hydraulic pressure introduction hole 35 into which the tip of the core metal 34 is inserted. Prepare,
By inserting it, the hydraulic pressure introduction hole 35 and the hydraulic pressure transmission hole 36 in the core bar 34 are brought into communication.

As shown in FIGS. 5 and 6, the fixed upper mold 26 has a guide groove 38 cut therethrough vertically, and a sliding upper mold 39 slidably fitted into the guide groove 38. There is. This sliding upper mold 39 comes into contact with the upper surface of the core bar 34 and the material tube 1 into which it is inserted, and furthermore, the leading end surface 39a and the guide groove 3 in the fixed upper mold 26
A bulging hole 40 for forming a protrusion on the side surface of the material tube is formed between the end surface 38a of the material tube and the end surface 38a of the material tube.
This bulging hole 40 has an elliptical shape in the state before molding as shown in FIGS. 3 and 6, and is formed by the movement of the sliding upper mold 39 in the state after molding as shown in FIG. It becomes circular.

Sliding guide body 41 fixed to the sliding upper mold 39
, which guides the sliding movement of the upper sliding mold 39, is inserted into a sliding groove 42 provided in the upper mold supporting body 22, and is inserted between the sliding guide body 41 and the spring seat 43 facing it. A spring 44 compressed therebetween urges it to return to a position where it abuts against a stopper 45.

The pressurizing cylinder device 50 that drives the sliding upper mold 39 and the core metal 34 eliminates the reaction force caused by the bulge hydraulic pressure introduced into the molding device main body, and maintains the sealing state at both ends of the material tube 1. while cylinder 5
1, and is provided with a hydraulic pressure supply port 54 for introducing hydraulic pressure into a drive chamber 53 to drive the pressurizing piston 52, and also has a hydraulic pressure introduction hole 56. Insert the tip of the reaction force erasing rod 55 into the pressure piston 52 through the cylinder end wall 57,
It is configured to supply bulge hydraulic pressure to the hydraulic pressure introduction hole 56.

Next, a molding method using the apparatus configured as described above will be explained.

First, the fixed upper mold 26, the sliding upper mold 39, etc. are raised together with the upper mold support 22, and in this state,
The material tube 1 into which the core bar 34 has been inserted is inserted into the mold cavity 3 of the lower mold 27.
1, and the pressure cylinder device 50 is driven to insert the tip of the core metal 34 into the sealing metal fitting 32, and at the same time, both ends of the material tube 1 are clamped between the core metal 34 and the sealing metal fitting 32 to seal the gap. state. At the same time, the upper die support 22 is lowered together with the members attached thereto, placed on the lower die support 23, and clamped with a clamping force W by a clamping press (not shown) (Fig. 3). . After that, high pressure bulge liquid pressure p is applied from a pressure intensifier (not shown) to the liquid pressure introduction holes 35 and 56 of the sealing fitting 32 and the reaction force erasing rod 55 to remove the reaction force and remove the reaction force from both ends of the material tube 1. Initial bulge pressure p ₁ is introduced into the material tube 1 while maintaining the sealing state at .

Next, the pressurizing piston 52 is driven by the compression force F,
When the material tube 1 is compressed in the axial direction through the core metal 34, the portion of the material tube 1 facing the oblong expansion hole 40 starts to bulge due to the interaction of this compression and bulge liquid pressure. Since the sliding upper mold 39 moves forward at the same time as the material tube 1 is compressed by the core bar 34, the distal end surface 39a of the sliding upper mold 39 presses the bulged portion and tightens the fixed upper mold 26. The axial side wall portion of the bulging protrusion 21a is formed in cooperation with the end surface 38a of the guide groove 38, and the bulging portion is plastically deformed from an elliptical shape to a circular shape and moves outward. Increase the protrusion height. As the above process progresses, the bulge hydraulic pressure p and the compression force F rapidly increase, and when the molding is completed, the hydraulic pressure reaches the bulge final pressure p _f and the pressing force reaches the final compression force F _f , and the pressurizing piston 5
2, the bulging portion becomes a cylindrical protrusion 21a having approximately the same diameter as the material pipe diameter, and the T-shaped formed pipe 21
a is formed.

In the above-described forming, the core metal 34 is inserted into the material tube 20 along its entire length, and the material tube is compressed in this state. It is possible to actively prevent thickening on the side where no protrusions are formed, while assisting in building up the thickness to the protrusions.

After the molding is completed, the high liquid pressure inside the tube is released, the pressurizing piston 52 is moved back, and the mold clamping force W is released to raise the upper mold support 22, and the T-shaped molding with the core bar 34 fitted is performed. The tube 21 can be taken out from the lower mold 27.

In addition, although the case where the attachment and detachment of the core metal 34 is performed in a separate process from the molding has been described above, by lengthening the stroke of the pressure piston 52, the attachment and detachment of the core metal 34 can be performed in a series of flows in the molding process. It can be performed.

As shown in FIGS. 5 and 6, the sliding upper mold 39 used for the above molding has a width S ₀ equal to the diameter d ₀ of the material tube.
, the left and right edges 39b, 39b of the tip surface 39a and the left and right ends 39d, 39d of the contact surface 39c with the material tube 1 are extremely thin, and the mechanical strength of the sliding upper mold 39 is therefore reduced. However, durability becomes an issue.

FIGS. 7 and 8 show a solution to this problem, in which the thickness S ₁ of the sliding upper mold 59 is made slightly smaller than the outer diameter d ₀ of the material tube 1, for example, by about 1 to 20%. This prevents thinning of both left and right edges 59b and 59d of the distal end surface 59a of the sliding upper die 59 and the contact surface 59c with the material tube. Note that it is natural that the shape of the fixed upper mold 60 needs to be changed in accordance with the sliding upper mold 59.

FIGS. 9 and 10 show a case where a raw material tube 1 is processed into a camel-shaped forming tube 61 having two protrusions 61a, 61a, and the apparatus is similar to the above-mentioned T-shaped forming tube forming apparatus. The differences are that a pair of guide grooves 63, 63 are cut in the fixed upper mold 62 in a state of facing each other, that sliding upper molds 64, 64 are inserted into each guide groove 63, 63, and that each guide groove 63, This is because the bulging holes 65, 65 formed at 63 are inclined in directions away from each other, and the pressure rods 66, 67 that drive the sliding upper molds 64, 64 are arranged symmetrically. Other than that, the configuration is almost the same. Note that in FIGS. 9 and 10, illustrations of the upper mold support, the lower mold support, etc. are omitted.

To form a camel-shaped molded tube using the above-mentioned apparatus, as in the case of forming the T-shaped molded tube, first, the fixed upper mold 62 is raised and the material tube 1 is placed in the mold cavity 69 of the lower mold 68, and then The left and right pressure rods 66, 67 are brought close to each other, and both ends of the material tube 1 are pressed against the pressure rods 66, 67.
After that, bulge hydraulic pressure is introduced from the hydraulic pressure introduction hole 70 of one pressure rod 66, and at the same time, the material tube 1 is clamped with the left and right pressure rods 66, 67 to form a sealed state (Fig. 9). It is compressed in the axial direction, thereby obtaining a camel-shaped formed tube 61 (FIG. 10). In the above-mentioned forming process, the bulging holes 65, 65 change from an elliptical shape to a circular shape as in the case of the T-shaped formed pipe, and the protrusion 61a is changed while the material pipe is being thickened accordingly. is formed.

Therefore, when forming the protrusion 61a, in order to actively prevent the formation of a thick part and the occurrence of buckling,
Insertion portions 66a and 67a as core metals in the pressure rods 66 and 67 are each formed to have a length that can reach the bulging portion of the material tube and support that portion from the inside.

Further, the sliding upper molds 64, 64 can be fastened to the sliding guide body similarly to the molding apparatus shown in FIGS. 3 to 5.

FIGS. 11a to 11d show a method of forming a protrusion-formed tube 71 having four protrusions by repeating the above-mentioned method of processing the camel-shaped formed tube, as shown in FIG. 11a. , while compressing the material tube 1 in the axial direction while applying bulge hydraulic pressure, the fixed upper mold 7
The sliding upper molds 73, 73 that slide against the molds 2 are driven toward the center, thereby forming a camel-shaped forming tube 74 as shown in FIG. It is mounted on the second fixed upper mold 75 in which holes 76, 76 corresponding to the protrusions 74a, 74a are formed, and in this state, as shown in FIG. In addition, both ends of the camel-shaped forming tube 74 are compressed in the axial direction, and the sliding upper molds 77, 77 are driven toward the center, thereby forming the protrusion 7 of the camel-shaped forming tube as shown in FIG.
4a, a new protrusion 74b on the outside of 74a,
A protrusion-formed tube 71 can be obtained by molding 74b.

Next, examples of the method of the present invention will be described.

As a material tube, the outer diameter is 19 mm, the wall thickness is 1.4 mm, and the total length is 100 mm.
mm copper tube was used, and the molding conditions were as follows: The distance l between the fixed upper mold and the sliding upper mold was 58 mm using the apparatus shown in Figures 3 to 6, and the radius of curvature of the shoulders of the upper molds was 58 mm.
R ₂ is approximately 1mm, initial pressure p ₁ of bulge hydraulic pressure is 200Kg/cm ² ,
The final pressure pf was 500 Kg/cm ² and the final compression force acting on the pressurizing piston was approximately 17 tons. The T-shaped molded tube thus obtained has a total length of 62 mm and a protrusion height of approximately
It was 20mm. In addition, in the conventional method, it was necessary to set the above initial pressure to at least 400Kg/ ^cm2 , but
According to the present invention, this can be reduced to 200Kg/cm ² , which is less than half of the conventional value.
By lowering the initial pressure in this way, it is possible to reduce the frictional force between the material tube and the mold due to the compression of the material tube, thereby making it easier to form the protrusion.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing how T-shaped and camel-shaped tubes are formed using a conventional forming apparatus, and FIGS. 5 is a cross-sectional view taken along the line A-A in FIG. 3, FIG. 6 is a plan view of the fixed upper mold and the sliding upper mold, and FIG. 7 and FIG. Fig. 8 is a sectional view and a partial plan view showing examples of different structures of a fixed upper mold and a sliding upper mold, and Figs. 9 and 10 show an embodiment in which a camel-shaped molded tube is formed using a molding apparatus based on the present invention. Cross-sectional views, FIGS. 11a to 11d are cross-sectional views showing how the multi-projection formed tube is formed. 1... Raw pipe, 21, 61, 71... Molded pipe,
21a, 61a, 74a, 74b...protrusion, 34
... Core metal, 36 ... Hydraulic pressure transmission hole, 39, 59, 6
4...Sliding upper mold, 40, 65...Bulging hole.

Claims (1)

[Claims] 1 When compressing a material tube to which hydraulic pressure is applied inside in the mold in the axial direction to bulge a part of the material tube outward, the mold is placed in a fixed mold having a mold cavity into which the material tube is inserted. A material tube consisting of a mold and a sliding mold slidably fitted into a guide groove provided in the mold, and formed between the tip end face of the sliding mold and the end face of the guide groove in the fixed mold. The bulge hole that allows the bulge on one side is made in advance in a long shape in the axial direction, and the material tube has a length that reaches at least the bulge part in order to prevent buckling and thickening caused by compression of the material tube. By inserting a core bar and supplying bulge hydraulic pressure into the material tube, the bulge hole is narrowed in the axial direction at the same time as the material tube is compressed in the axial direction, while the material tube is being thickened. A method for forming a protrusion on the side surface of a tube by hydraulic bulge processing, which is characterized by forming a protrusion on the side surface of a material tube.