KR101987547B1 - Hydroforming apparatus and hydroforming method - Google Patents

Abstract

A hydroforming apparatus according to an embodiment includes: a mold having a cavity provided with a molded tube; A punch unit which is transported from both sides of the mold unit toward both ends of the molded pipe; And a sealing part which is removably mounted on the outer side surfaces of both ends of the molded pipe, wherein the sealing part is mounted on an outer surface of the molded pipe and is compressively deformed by the transfer of the punch part , The spring member generates a reaction force in a direction opposite to the conveying direction of the punch portion, and the contact stress between the punch portion and both ends of the formed pipe can be made uniform by the reaction force.

Description

HYDROFORMING APPARATUS AND HYDROFORMING METHOD BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to a hydraulic pressure molding apparatus and a hydraulic pressure molding method, and more particularly, to a method of manufacturing a hydraulic pressure molding apparatus and a hydraulic pressure molding method by which a uniform contact stress is generated between a punch portion and a molded pipe by a sealing portion including a spring member and a sleeve member To a hydraulic pressure molding apparatus and a hydraulic pressure molding method.

Tube hydroforming is a process for obtaining a desired shape of a pipe using hydraulic pressure and is used for various parts such as automobiles and aircraft.

The advantages of the tubular hydroforming technology are that it can replace existing processes that require complicated metal forming technology while at the same time simplifying the process and integrating parts. In addition, it is possible to reduce the finishing cost and the die cost of the parts, to utilize the excellent material, to improve the workability and to obtain the improved part quality effect.

On the other hand, the hydroforming technology is very sensitive to the internal pressure of the formed tube due to the combination of the material flow in the axial direction and the internal load of the tube, and the sealing of the fluid filled in the tube has an important influence on the formability.

The pressure gradient acting on the punch during asymmetric shape forming using the conventional hydroforming process technique shown in Fig. 1 may appear as shown in Fig.

Specifically, the stress acting on the punch is high in a region where the degree of expansion of the formed tube is small in the asymmetric shape molding, and the stress acting on the punch may be high in the region where the degree of expansion of the formed tube is high.

This results in nonuniform contact stress acting between the punch and the forming tube and pressure leakage at the end of the forming tube, and consequently the shape accuracy of the final formed article is reduced due to the low pressure inside the forming tube.

KR10-2004-0011164, filed on February 19, 2004, discloses a " liquid leakage preventing device for hydraulic molding ".

An object of an embodiment is to provide a hydraulic pressure molding apparatus and a hydraulic pressure molding method capable of preventing pressure leakage generated at an end of a molded pipe by a spring member and improving moldability or shape accuracy using a high molding pressure in a molded pipe .

An object according to an embodiment is to reduce the expansion of a portion where the spring member is located and thereby to concentrate the pressure on a portion to be molded in the formed tube and to prevent the spring member from being uniformly compressed during axial feed of the punch portion, And a reaction force causes an increase in contact between the end portion of the formed pipe and the punch portion, and a hydraulic pressure molding method.

An object of the present invention is to provide a hydraulic pressure molding apparatus and a hydraulic pressure molding method which are easy to mount and remove at both ends of a formed pipe and can maximize the sealing effect of the hydraulic pressure molding process by adding a simple structure.

An object of the present invention is to provide a hydraulic pressure molding apparatus and a hydraulic pressure molding method in which pressure leakage in a molded pipe can be prevented through contact between a cylindrical sleeve member mounted at both ends of a formed pipe and an inclined surface formed corresponding to the punch portion .

An object of the present invention is to provide a hydraulic pressure molding apparatus and a hydraulic pressure molding method capable of preventing pressure leakage at both ends of a formed pipe member so that the load due to the axial directional transfer of the punch member is effectively transmitted to the formed pipe member, .

According to an aspect of the present invention, there is provided a hydroforming apparatus including: a mold having a cavity provided with a molded tube; A punch unit which is transported from both sides of the mold unit toward both ends of the molded pipe; And a sealing part which is removably mounted on the outer side surfaces of both ends of the molded pipe, wherein the sealing part is mounted on an outer surface of the molded pipe and is compressively deformed by the transfer of the punch part , The spring member generates a reaction force in a direction opposite to the conveying direction of the punch portion, and the contact stress between the punch portion and both ends of the formed pipe can be made uniform by the reaction force.

According to one aspect of the present invention, the sealing portion further includes a sleeve member provided in a cylindrical shape and disposed adjacent to both end portions of the formed tube member than the spring member, wherein the sleeve member is configured to be in contact with the punch portion and the sleeve member, Both ends can be sealed.

According to one aspect of the present invention, the contact surfaces of the sleeve member and the punch portion are formed obliquely, and both end portions of the formed tube are positioned between the contact surfaces of the sleeve member and the punch portion. As shown in Fig.

According to one aspect, the inclination angle &thetas; of the contact surface of the sleeve member and the punch portion is determined by the following equation,

At this time,

Fw is a force for deforming both end portions of the formed pipe member by the punching portion,

Fa is an axial force of the punch portion,

Fi is the axial force from the internal pressure of the formed pipe,

Fs is a reaction force generated in the spring member.

According to an aspect of the present invention, there is provided a hydroforming method comprising: mounting a sealing part at both ends of a formed pipe; Providing the shaped tube in a cavity formed in the mold part; Conveying the punch portion toward the inside of both ends of the formed pipe member; Inserting the punch portion into the molded tube; And a step of forming the molded tube according to a cavity shape of the mold part, wherein in the step of inserting the punch part into the molded tube, both ends of the molded tube are expanded by a contact surface shape of the sealing part and the punch part It can be deformed.

According to one aspect of the present invention, in the step of mounting the sealing portion at both ends of the formed tube, the sealing portion may include a sleeve member provided in a cylindrical shape and mounted on outer side surfaces of both ends of the molded tube; And a spring member mounted on an outer surface of the molded tube adjacent to the sleeve member and being compressively deformed by the transfer of the punch portion.

According to one aspect of the present invention, in the step of inserting the punch portion into the forming tube, the spring member generates a reaction force in a direction opposite to the conveying direction of the punch portion, and the reaction force generated in the spring member causes the sleeve member and the sleeve member The punch portion can be closely contacted.

According to one aspect of the present invention, the step of removing the sealing portion from both ends of the formed tube after the step of forming the shaped tube according to the cavity shape of the mold portion may be further included.

According to the hydraulic pressure molding apparatus and the hydraulic pressure molding method according to the embodiment, it is possible to prevent the pressure leakage generated at the end portion of the formed pipe by the spring member and to improve the formability or the shape accuracy by using the high molding pressure in the formed pipe have.

According to the hydraulic pressure molding apparatus and the hydraulic pressure molding method according to the embodiment, the expansion in the portion where the spring member is located is reduced, the pressure is concentrated on the portion to be molded in the formed tube, and the spring member is uniform So that a reaction force generated in the spring member can cause an increase in contact between the end portion of the formed tube and the punch portion.

According to the hydraulic pressure molding apparatus and the hydraulic pressure molding method according to the embodiment, it is easy to mount and remove both ends of the formed pipe, and the sealing effect of the hydraulic pressure molding process can be maximized by adding a simple structure.

According to the hydraulic pressure molding apparatus and the hydraulic pressure molding method according to the embodiment, the pressure leakage in the formed tube can be prevented through the contact between the cylindrical sleeve member mounted at both ends of the formed tube and the inclined surface formed corresponding to the punch portion.

According to the hydraulic pressure molding apparatus and the hydraulic pressure molding method according to the embodiment, it is possible to prevent pressure leakage at both ends of the formed tube, to effectively transmit the load due to the axial direction transfer of the punch to the formed tube, have.

Fig. 1 schematically shows a conventional hydraulic press forming apparatus.
Fig. 2 shows the stress distribution acting on the punch portion in the asymmetric hydroforming.
Figure 3 schematically shows a hydroforming apparatus according to one embodiment.
4 is a flowchart showing a hydroforming method according to one embodiment.
5 (a) to 5 (c) are schematic views of the hydroforming process.
Figure 6 shows the stresses acting on the element at the center of the formed tube.
Figure 7 schematically illustrates the forces acting during the hydroforming process.
8 shows corrugations generated in the spring gap.
Fig. 9 shows an end portion shape of the formed tube by the punch portion and the sleeve member in the hydroforming.
Fig. 10 shows in detail the end deformation of the formed pipe.
Figure 11 shows a process diagram for a hydroforming process.
12 (a) and 12 (b) show a finite element analysis model for a conventional hydroforming apparatus and a hydroforming apparatus according to an embodiment.
Figs. 13 (a) and 13 (b) show the results of the finite element analysis for the stress distribution on the contact surfaces of the tube material formed in the conventional hydraulic press forming apparatus and the hydraulic press forming apparatus according to one embodiment.
Fig. 14 is a graph comparing the stress distribution of the tube material formed in the conventional hydraulic press forming apparatus and the hydraulic press forming apparatus according to one embodiment.
Figs. 15 (a) and 15 (b) show setups for hydroforming experiments on a conventional hydroforming apparatus and a hydroforming apparatus according to an embodiment.
Fig. 16 shows a mold part provided with a cavity for asymmetric shape forming.
17 is a graph showing the pressure inside the formed tube in the conventional hydraulic press forming apparatus and the hydraulic press forming apparatus according to the embodiment.
Figs. 18 (a) and 18 (b) show the final shape of the tube material molded in the conventional hydroforming apparatus and the hydroforming apparatus according to one embodiment.

Hereinafter, embodiments will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In the following description of the embodiments, detailed description of known functions and configurations incorporated herein will be omitted when it may make the best of an understanding clear.

In describing the components of the embodiment, terms such as first, second, A, B, (a), and (b) may be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. When a component is described as being "connected", "coupled", or "connected" to another component, the component may be directly connected or connected to the other component, Quot; may be "connected," "coupled," or "connected. &Quot;

The components included in any one embodiment and the components including common functions will be described using the same names in other embodiments. Unless otherwise stated, the description of any one embodiment may be applied to other embodiments, and a detailed description thereof will be omitted in the overlapping scope.

Fig. 3 schematically shows a hydroforming apparatus according to one embodiment, Fig. 4 is a flowchart showing a hydroforming method according to an embodiment, and Figs. 5 (a) to 5 (c) .

3, the hydroforming apparatus 10 according to an embodiment may include a mold unit 100, a punch unit 200, and a sealing unit 300.

The mold part 100 may include, for example, an upper die 102 and a lower die 104.

At this time, a cavity may be formed so that the formed tube T may be provided inside the upper die 102 and the lower die 104 when they are coupled.

Although not specifically shown, the contact surface between the cavity and the molded tube T can be formed into a shape to be molded.

It is of course also possible to additionally form cavities into which the sealing portions 300 mounted at both ends of the formed tube T can be received when the upper die 102 and the lower die 104 are coupled.

The punch unit 200 may be disposed on both sides of the mold unit 100.

The punch part 200 can be conveyed from both sides of the mold part 100 toward both ends of the formed tube T. [

Specifically, the punch 200 may include a first compartment 202 and a second compartment 204.

The first compartment 202 may be inserted at both ends of the formed tube T in the axial direction of the punch 200.

At this time, the axial transfer may mean that the punch 200 is transferred along the central axis of the forming tube T extending along the longitudinal direction of the formed tube T.

The second compartment 204 may be connected to the first compartment 202 and protrude from both ends of the formed tube T when the punch 200 is axially transported.

In addition, the inclined surface 206 may be formed at a portion of the punch 200 where the first compartment 202 and the second compartment 204 are connected.

For example, if the first compartment 202 and the second compartment 204 are provided as separate parts, they can be connected by fillet welding. Alternatively, when the first compartment 202 and the second compartment 204 are provided as a single part, the interface between the first compartment 202 and the second compartment 204 may be chamfered.

At this time, the both ends of the formed tube T are expanded and deformed by the inclined surface 206 formed at the portion where the first compartment 202 and the second compartment 204 are connected, and the sleeve member of the sealing part 300 330 can be brought into contact with the inclined surface 206 with the formed tube T interposed therebetween. This also means that the sleeve member 330 of the sealing part 300 may be provided with a shape corresponding to the shape of the inclined surface 206.

The inner pressure leaking of the formed tube T can be prevented by the structural feature that the punch portion 200 and the sealing portion 300 are closely contacted at both ends of the formed tube T.

On the other hand, the sealing portion 300 can be mounted on the outer surfaces of both ends of the formed tube T.

The sealing part 300 may be composed of one sealing unit and may be removably mounted from the forming tube T. The sealing part 300 may be removably mounted on the forming tube T, It is possible to easily perform the maintenance of the portable terminal 300.

At this time, both end portions of the formed tube T are not formed by the mold portion 100 by the sealing portion 300, and only a part of the formed tube T, to which the sealing portion 300 is not attached, As shown in Fig. In other words, the formed tube T may include a non-forming section and a forming section.

Specifically, the sealing portion 300 may include a spring member 310 and a sleeve member 320.

The spring member 310 may be formed of, for example, an elastic material, and may be mounted on the outer surface of the formed tube T.

At this time, the spring member 310 may be compressively deformed when an axial load is applied to the forming tube T by axial feed of the punch 200.

Since the sealing portion 300 includes the spring member 310 as described above, when the axial load is applied to the formed tube T or when the axial movement of the punch 200 is performed, the spring member 310 is uniformly compressively deformed . This means that the spring member 310 can uniformly generate a reaction force and a uniform reaction force generated in the spring member 310 can cause an increase in contact between the formed tube T and the punch 200 .

On the other hand, the sleeve member 320 is provided in a cylindrical shape and can be mounted on both ends of the formed tube T.

In addition, the sleeve member 320 may be made of a non-elastic material and may be maintained in its original shape without being deformed when the punch portion 200 is moved in the axial direction.

At this time, the sleeve member 320 may be disposed adjacent to the spring member 310, and may be attached to both outer ends of the molded tube T than the spring member 310.

More specifically, referring to Fig. 4, the hydroforming process of the hydroforming apparatus 10 according to the embodiment may be as follows.

First, the sealing portion 300 is mounted on both ends of the molded tube T and the molded tube T is provided in the cavity formed in the mold portion 100 (S20).

At this time, the sealing portion 300 may include the spring member 310 and the sleeve member 320 as described above.

Then, the punch unit 200 is fed toward the inside of both ends of the formed tube T (S30), and the punch unit 200 is inserted into the formed tube T (S40).

Referring to FIG. 5A, it can be seen that an inclined surface corresponding to the shape of the inclined surface 206 of the punch 200 is formed on the inner surface of the sleeve member 330, The end portion of the formed tube T can be exposed to the outside by the inner side surface shape.

5 (b), when the punch 200 is moved in the axial direction, the first compartment 202 of the punch 200 is inserted into the inside of the formed tube T, The second compartment 204 may be disposed outside the formed tube T. The second section 204 of the punch unit 200 may be disposed in the cavity of the mold unit 100 while the spring member 320 is compressively deformed by the axial movement of the punch unit 200.

Specifically, the spring member 310 is compressively deformed in the A direction by the axial direction movement of the punch portion 200 in the A direction, and a reaction force in the B direction opposite to the A direction in the spring member 310 can be generated . The direction B is a direction in which the end of the formed pipe B faces the punching part 200. Therefore, the contact stress between the end of the formed tube B and the punch 200 can be increased by the reaction force generated in the spring member 310.

At this time, the spring member 310 is uniformly compressed and deformed, and a uniform contact stress can be generated between the end portion of the formed tube B and the punch 200.

5 (c), when the punch portion 200 is completely inserted into the formed tube T, the end portion of the formed tube T is bent by the inclined surface 206 of the punch portion 200 The inclined surface 206 and the sleeve member 320 come into contact with each other through the deformed formed tube T so that the punch portion 200 and the formed tube T or the punch portion 200 and the sleeve member 320 are deformed, So that both ends of the formed tube T are sealed and pressure leakage at the end of the formed tube T can be prevented.

Thereby, the pressure provided to the formed tube T, for example, the internal pressure P of the formed tube T is concentrated in a portion (molded portion) molded in the tube T, Can be increased.

After both end portions of the formed tube T are sealed in this way, the formed tube T is molded in accordance with the cavity shape of the mold portion 100 by filling the formed tube T with hydraulic oil (S50).

After completion of the hydroforming of the shaped tube T, the sealing portion 300 is removed from both ends of the formed tube T (S60).

Although it is not shown in detail, it is of course possible to remove the punch portion 200 from both ends of the formed tube T before removing the sealing portion 300 from both ends of the formed tube T.

The hydroforming apparatus and the hydraulic pressure forming method according to one embodiment have been described. The analytical analysis for optimizing the hydroforming process using the hydraulic pressure molding apparatus according to one embodiment will be described below.

Figure 6 shows the stresses acting on the element at the center of the formed tube, Figure 7 schematically shows the forces acting during the hydroforming process, Figure 8 shows the corrugations generated in the spring gap, Fig. 10 shows the end deformation of the formed tube in detail, and Fig. 11 shows a process diagram for the hydroforming step. Fig. 9 shows the end portion shape of the formed tube by the punch portion and the sleeve member in hydroforming.

With reference to Fig. 6, it can be assumed that the formed tube T having the inner wall receiving the internal pressure P is formed. The internal pressure P may be measured, for example, by a pressure sensor connected to a hydraulic pressure intensifier system for generating a high pressure fluid.

During the axial transfer of the punch 200 in the hydroforming process, the axial net stress is represented by the following equation (1).

In this case, P is the internal pressure, r is the radius of the formed tube T, and t is the inner wall thickness of the formed tube T. And Fnet is a balanced axial force.

7, the force acting in the axial direction is represented by the following equation (2).

At this time, in order to simplify the theoretical analysis, it is assumed that there is no frictional force.

Fnet is a balanced axial force, Fa is axial force by the punch 200, Fi is axial force from the inner pressure of the formed tube T, Fs is a reaction force generated from the spring member 310, to be.

The Fa is an adjustable value and can be adjusted as previously programmed.

Further, Fi can be expressed by the following equation (3).

At this time, D is the diameter of the formed tube (T).

Fs can be expressed as the following equation (4).

At this time, K is the spring constant of the spring member 310, and s is the transfer stroke of the punch 200.

When the above equations (2) to (4) are combined, the following equation (5) can be obtained.

If Equation (5) is substituted into Equation (1), the following Equation (6) can be obtained.

8, a spring gap G may exist in the spring member 320 and a wrinkle W may be generated in the formed tube T positioned in the spring gap G. [

The condition for preventing the generation of the corrugations W can be expressed by the following equation (7).

는 폰 미세스 등가응력(von-Mises equivalent stress)이고,

는 성형 관재의 항복응력이다. 그리고

는 스프링 갭(G)에서 축방향 응력으로서,

이다.At this time,

Is the von-Mises equivalent stress,

Is the yield stress of the formed pipe. And

As an axial stress in the spring gap G,

to be.

을 대입하면 다음의 등식 (8)과 같다.Equation (7)

The following equation (8) is obtained.

Thus, by defining the theoretical equations for various parameters (e.g., the inner pressure, the radius of the forming tube, and the transfer stroke of the punch portion) for the formed tube T, ) Can be prevented by using equations (6) and (8).

9 and 10, both ends of the formed tube T can be deformed into a wedge shape to prevent pressure leakage.

Specifically, the wedge bending of the formed tube T mainly occurs at a portion represented by a dotted box in Fig. 10, which is caused by a reaction force of the spring member 310 and a punch This is because the bending moment is maximized by the interaction of the axial force of the part 200.

10, the yield moment M _Y is represented by the following equation (9).

는 성형 관재의 항복응력이다.In this case, 1 is the circumference of the formed tube T, t is the thickness of the tube T,

Is the yield stress of the formed pipe.

In order to simplify the theoretical interpretation of wedge bending, the effect of work hardening is not taken into account. When the force Fw is assumed to be the force for forming the wedge at the end of the formed tube T, the moment at the portion represented by the dotted box in Fig. 10 from Fw is represented by the following equation (10).

Where a is the distance between the point at which the yield moment acts and the bending point of the forming tube.

Therefore, Fw is expressed by the following equation (11).

Since both ends of the formed tube T are deformed into the wedge shape during the hydroforming process, the condition for bending both ends of the formed tube T to prevent pressure leakage can be expressed by the following equation (12).

At this time,? Is the inclined angle of the punch 200.

Therefore, the inclined plane angle of the punch portion 200 can be designed to satisfy the expression (12).

For example, in order to facilitate removal of the punch portion 200 and the sealing portion 300 from the formed tube T after the hydroforming process, the inclined angle of the punch portion 200 may be designed to be 30 degrees.

In this case, substituting equation (11) into equation (12) yields equation (13).

On the other hand, Point A and Point B can be defined by the following equations (14) and (15).

At this time, Fy is a force for yielding the forming tube when the internal pressure is zero,

Py is the pressure to yield the forming tube when the axial force is zero.

A process diagram for the hydroforming process as shown in Fig. 11 can be obtained by combining the above-described equations (8), (13) to (15).

Specifically, Fig. 11 shows the forming-limit curve on the graph of the internal pressure of the forming tube with respect to the axial force of the punch portion. The lines on the graph are shown based on a single loading path.

11, the safe forming process range is surrounded by wrinkling, sealing and yielding lines, and the load path follows the safe forming process range, Can be obtained. In other words, it can be seen that the parameters of the formed tube T, the punch 200 and the sealing part 300 are preferably designed such that the load path is included within the safe molding process range.

Hereinafter, the results of the finite element analysis for the conventional hydraulic press forming apparatus and the hydraulic press forming apparatus according to one embodiment will be described.

Figs. 12 (a) and 12 (b) show a conventional hydroforming apparatus and a finite element analysis model for a hydroforming apparatus according to an embodiment, and Figs. 13 (a) FIG. 14 is a graph showing the results of the finite element analysis for the stress distribution on the contact surface of the tube material formed in the hydroforming apparatus according to the embodiment. FIG. This is a graph comparing the stress distribution.

In particular, referring to Fig. 13 (a), it can be confirmed that the pressure gradient relative to the contact surface between the formed tube and the punch portion is not uniform when the hydroforming process is carried out using the conventional hydroforming apparatus. On the other hand, referring to Fig. 13 (b), when the hydroforming process is carried out using the hydroforming apparatus according to the embodiment including the sealing portion, it is confirmed that the pressure gradient with respect to the contact surface between the formed tube and the punch portion is uniform Can be confirmed.

14, when a hydroforming process is performed using a conventional hydroforming apparatus, the contact stresses between the formed pipe and punch portions at 0 °, 90 °, and 180 ° are 62.5, 23.8, 67.80 MPa.

This can lead to fluid leakage or pressure leakage into the area to be less pressurized in the formed tube, and this nonuniform pressure distribution is mainly caused by the asymmetric molding configuration.

On the other hand, in the hydroforming apparatus according to an embodiment, it can be seen that the contact stress between the formed pipe and the punch portion becomes substantially uniform through the interaction of the axial force of the punch portion and the reaction force of the spring member.

Hereinafter, a molding test for a conventional hydraulic press forming apparatus and a hydraulic press forming apparatus according to one embodiment will be described.

15 (a) and 15 (b) show setups for hydroforming experiments on a conventional hydroforming apparatus and a hydroforming apparatus according to an embodiment, and Fig. 16 shows a mold section having cavities for asymmetric shape forming (A) and 18 (b) are graphs showing the pressure inside the molded tube in the conventional hydraulic pressure molding apparatus and the hydraulic pressure molding apparatus according to the embodiment, and FIGS. 18 The final shape of the tube formed in the hydroforming apparatus according to the present invention is shown.

15 (a) is a set-up for a hydraulic pressure molding test on a conventional hydraulic pressure molding apparatus, in which a formed tube T is provided in a cavity formed in a mold section 100 and a punch section 200 are transported.

15 (b) is a set-up for the hydroforming test of the hydroforming apparatus according to an embodiment, in which a molded tube T mounted with sealing portions 300 at both ends is formed in a cavity The punch 200 is axially transferred to both ends of the formed tube T to seal both ends of the formed tube T. [

16, in the hydroforming apparatus according to the embodiment, the mold part 100 is provided with a cavity C1 to be formed with a formed tube T at its center, and a sealing part 300 is provided at both ends A cavity C2 may be provided. At this time, the target shape of the formed tube T can be machined in the cavity C1.

Referring to FIG. 17, the pressure inside the molded pipe in the conventional hydraulic press forming apparatus and the hydraulic press forming apparatus according to one embodiment were compared. As a result, in the conventional hydraulic press apparatus, the process was stopped at a maximum internal pressure of about 25.4 MPa , The maximum internal pressure of the hydroforming apparatus according to the embodiment is about 44.9 MPa, which is about 20 MPa higher than that of the conventional hydraulic press forming apparatus.

18 (a) and 18 (b), the final shapes of the conventional hydroforming apparatus and the hydroforming apparatus according to the embodiment were compared. As a result, in the conventional hydraulic press apparatus, It can be confirmed that it is low. This is because the molded tube can not be precisely molded due to the low internal pressure in the tube. On the other hand, in the hydroforming apparatus according to the embodiment, it is confirmed that the degree of molding is very close to the target shape due to the high internal pressure in the formed tube.

As described above, in the hydraulic pressure molding apparatus and the hydraulic pressure molding method according to the embodiment, the sealing portion can prevent the pressure leakage due to the increase of the contact between the punch portion and the molded tube, thereby increasing the pressure acting inside the molded tube have. Further, it is possible to perform hydroforming of a complicated component by hydroforming the formed pipe with the set pressure, and the shape accuracy of the final product can be increased.

Although the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, And various modifications and changes may be made thereto without departing from the scope of the present invention. Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the claims set forth below, fall within the scope of the present invention.

10: Hydraulic molding device
100: mold part
200: punch portion
300: sealing part
310: spring member
320; Sleeve member

Claims (8)

A mold having a cavity provided with a molded tube;
A punch unit which is transported from both sides of the mold unit toward both ends of the molded pipe; And
A sealing portion removably mounted on the outer side surfaces of both ends of the molded pipe;
Lt; / RTI >
The sealing portion
A spring member mounted on an outer surface of the formed tube and being compressively deformed by the transfer of the punch portion;
Lt; / RTI >
The spring member generates a reaction force in a direction opposite to the conveying direction of the punch portion and the contact stress between the punch portion and the both end portions of the formed tube becomes uniform by the reaction force,
The von Mises equivalent stress determined by the inner pressure of the formed tube, the radius of the formed tube and the thickness of the formed tube is set to be smaller than the yield stress of the formed tube,
Wherein the sealing portion further includes a sleeve member which is provided in a cylindrical shape and is disposed adjacent to both ends of the molded tube member than the spring member, both ends of the molded tube member are sealed by the contact between the punch portion and the sleeve member,
The inclination angle? Of the contact surface of the sleeve member and the punch portion is determined by the following equation,

At this time,
Fw is a force for deforming both end portions of the formed pipe member by the punching portion,
Fa is an axial force of the punch portion,
Fi is the axial force from the internal pressure of the formed pipe,
And Fs is a reaction force generated in the spring member.
delete The method according to claim 1,
Wherein a contact surface of the sleeve member and the punch portion is formed obliquely,
Both end portions of the formed tube are positioned between the contact surfaces of the sleeve member and the punch portion, and both ends of the formed tube are deformed to expand into a wedge shape by the transfer of the punch portion.
delete Attaching a sealing part to both ends of the formed tube;
Providing the shaped tube in a cavity formed in the mold part;
Conveying the punch portion toward the inside of both ends of the formed pipe member;
Inserting the punch portion into the molded tube; And
Forming the formed tube according to a cavity shape of the mold part;
Lt; / RTI >
Wherein in the step of inserting the punch portion into the forming tube,
Both end portions of the formed tube are expanded and deformed by the contact surface shape of the sealing portion and the punch portion,
The von Mises equivalent stress determined by the inner pressure of the formed tube, the radius of the formed tube and the thickness of the formed tube is set to be smaller than the yield stress of the formed tube,
In the step of mounting the sealing portions at both ends of the formed tube,
The sealing portion
A sleeve member provided in a cylindrical shape and mounted on outer side surfaces of both ends of the molded tube; And
A spring member mounted on an outer surface of the molded tube adjacent to the sleeve member and being compressively deformed by the transfer of the punch portion;
Lt; / RTI >
The inclination angle? Of the contact surface of the sleeve member and the punch portion is determined by the following equation,

At this time,
Fw is a force for deforming both end portions of the formed pipe member by the punching portion,
Fa is an axial force of the punch portion,
Fi is the axial force from the internal pressure of the formed pipe,
And Fs is a reaction force generated in the spring member.
delete 6. The method of claim 5,
Wherein in the step of inserting the punch portion into the forming tube,
Wherein the spring member generates a reaction force in a direction opposite to the conveying direction of the punch portion and the sleeve member and the punch portion are in close contact with each other by a reaction force generated in the spring member.
6. The method of claim 5,
After the step of forming the forming tube according to the cavity shape of the mold part,
Removing the sealing portion from both ends of the formed tube;
Further comprising the steps of:

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