PRESS MOLDING DEVICE AND MANUFACTURING METHOD THEREOF

Abstract

A press molding device includes a first die for supporting the work piece and a second die arranged to face the first die. The first die includes a punch including a first molding surface for molding the work piece and a blank holder that is movably arranged along a side surface that extends from the first molding surface of the punch and includes the supporting surface for supporting the end portion of the work piece. The second die includes the die portion that includes the second molding surface that faces the first molding surface and is used for molding the work piece and the trimming portion configured integrally with the die portion. The trimming portion includes the blade portion for cutting the end portion of the work piece. The die portion includes a flow path for circulating a refrigerant to cool the work piece along the second molding surface.

Description

BACKGROUND

1. Technical Field

The present invention relates to a press molding device and a manufacturing method thereof.

2. Related Art

Non-Patent Document 1 discloses a manufacturing method which presses and molds a heated work piece while cooling the heated work piece and then cuts an end portion of the work piece by lowering a trim die. The above-described manufacturing method requires, to prevent the trim die from moving ahead of a pad during molding, to provide a reaction force generation devices such as hydraulic tanker and hydraulic pressure generation device for controlling the hydraulic tanker in a metallic die. Patent Document 1 discloses providing a regulation portion for regulating a posture of the work piece in the trim die and a blank holder so that the work piece does not contact a punch side cutting edge and a die side cutting edge during press molding of the work piece before trimming. Non-Patent Document 1 “Press Technology August 2014” Vol. 52, No. 8, Pages 23-26 Development of a manufacturing method for in-die trim in hot stamp (hot stamping)”, NIKKAN KOGYO SHIMBUN, LTD.

Patent Document 1 Japanese Patent No. 6256571

When press molding such as hot stamp molding (also referred to as hot press molding or PHS) is conducted, to a forming die, a flow path for circulating a refrigerant to cool the work piece is sometimes provided. However, depending on a shape of the work piece, it is sometimes difficult to provide the flow path to the forming die.

A press molding device according to one aspect of the present invention may be a press molding device that presses and molds the heated work piece while cooling the work piece. The press molding device may include a first die for supporting the work piece. The press molding device may include a second die that is arranged to face the first die. The first die may include a punch having a first molding surface for molding the work piece. The second die may include a die portion that includes the second molding surface facing the first molding surface and is used to mold the work piece. The second die may include a trimming portion configured integrally with the die portion. The trimming portion may include a blade portion that cuts an end portion of the work piece. The die portion may include the flow path for circulating the refrigerant to cool the work piece along the second molding surface.

The first die may include a blank holder that is movably arranged along a side surface extending from the first molding surface of the punch and includes a supporting surface for supporting the end portion of the work piece.

The trimming portion may be fixed to a fixed surface of the die portion that faces the blank holder, which fixed surface extends from the second molding surface so that the trimming portion is configured integrally with the die portion.

The trimming portion may be removably fixed to the fixed surface of the die portion.

The trimming portion may include a clamping surface that faces the supporting surface and clamps the end portion of the work piece with the supporting surface and include a protrusion where the clamping surface protrudes toward the blank holder side than the blade.

The second molding surface may include a step portion for folding the work piece and molding a flange portion. The blade may be provided to an inner side of a tangential line that is in contact with a corner portion of the projection and the step portion.

With the end portion of the work piece being clamped between the supporting surface of the blank holder and the clamping surface of the protrusion, the die portion and the trimming portion are moved toward the first die and also the blank holder is moved along the side surface of the punch so that the work piece is pressed and molded with the first molding surface and the second molding surface and the blade may cut the end portion of the work piece before the die portion and the trimming portion reach a bottom dead point.

In the manufacturing method according to one aspect of the present invention, the heated work piece is pressed and molded while being clamped between the first die and the second die and being cooled so that a press-molded article is manufactured. The first die may include the punch having the first molding surface for molding the work piece. The first die may include the blank holder that is movably arranged along the side surface extending from the first molding surface of the punch and includes the supporting surface for supporting the end portion of the work piece. The second die may include the die portion that includes the second molding surface facing the first molding surface and is used to mold the work piece. The second die may include the trimming portion configured integrally with the die portion. The trimming portion may include the blade portion for cutting the end portion of the work piece. The die portion may include the flow path for circulating the refrigerant to cool the work piece along the second molding surface. The manufacturing method may include a step in which with the end portion of the work piece being clamped between the blank holder and the trimming portion, the die portion and the trimming portion are moved toward the first die and also the blank holder is moved along the side surface of the punch so that the work piece is pressed and molded with the first molding surface and the second molding surface, and the blade portion cuts the end portion of the work piece before the die portion and the trimming portion reach the bottom dead point.

The summary clause does not necessarily describe all necessary features of the embodiments of the present invention. The present invention may also be a sub-combination of the features described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a drawing for explaining one example of a hot stamp in-die trim method.

FIG. 1B is a drawing for explaining one example of a hot stamp in-die trim method.

FIG. 1C is a drawing for explaining one example of a hot stamp in-die trim method.

FIG. 1D is a drawing for explaining one example of a hot stamp in-die trim method.

FIG. 2 is an enlarged view of a portion of a pad that molds the flange portion of the work piece.

FIG. 3A is a drawing for explaining a press molding device according to the present embodiment.

FIG. 3B is a drawing for explaining a press molding device according to the present embodiment.

FIG. 3C is a drawing for explaining a press molding device according to the present embodiment.

FIG. 4 is an enlarged view of a trimming portion and a portion of a die portion near the trimming portion.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, the present invention will be described through the embodiments of the invention, but the following embodiments do not limit the invention according to the claims. Moreover, not necessarily all combinations of features described in the embodiments are essential to the solution of the invention.

In a hot stamp molding (also referred to as hot press molding, PHS or the like), one possible solution is to cool the press-molded article to have an strength equivalent to 1500 MPa, and then cut thus cooled press-molded article. However, a portion of the press-molded article that has been cooled and then cut has a high strength (hardness) and residual stress, and thus, there is a possibility that a delayed fracture occurs. In order to prevent such delayed fracture, it is considered to cut the work piece in the high temperature condition before being cooled. As a result, the strength (hardness) and the residual stress of the press-molded article are lowered, and thus, the possibility of the occurrence of the delayed fracture can be reduced.

Each of FIG. 1A, FIG. 1B, FIG. 1C, and FIG. 1D is a drawing for explaining one example of the hot stamp in-die trim method in which the work piece in the high temperature condition is cut before being cooled. According to this manufacturing method, the heated work piece is pressed and molded while being cooled, and then the end portion of the work piece is cut by lowering the trim die.

The press molding device includes an upper die 10 and a lower die 30. A work piece 50 is arranged between the upper die 10 and the lower die 30. The upper die 10 includes a die holder 12, a trim die 14, a pad 16, and a reaction force generation device 20 such as hydraulic tanker. A pad 16 includes a flow path 19 that is arranged along a molding surface 16a and is used to circulate a refrigerant such as water for cooling the work piece 50. The lower die 30 includes a punch holder 32, a punch 34, a blank holder 36, and a reaction force generation device 38 such as spring. The punch 34 includes the flow path 39 for circulating the refrigerant such as water for cooling the work piece 50 along a molding surface 34a.

The trim die 14 is fixed to the die holder 12. The pad 16 is coupled to a reaction force generation device 20 so as to be movable in a direction toward and away from the die holder 12. The die holder 12 holds the reaction force generation device 20.

The punch 34 is fixed to the punch holder 32. The blank holder 36 is coupled to the punch holder 32 via the reaction force generation device 38 so as to be movable in a direction toward and away from the punch holder 32.

As illustrated in FIG. 1B, an end portion 52 of the heated work piece 50 is clamped between a clamping surface 14a of the trim die 14 and the supporting surface 36a of the blank holder 36. With this state, the die holder 12 receives a pressing pressure 11 and moves to the lower die 30 side. At this time, the pad 16 receives a hydraulic pressure 17 from the reaction force generation device 20 and moves to the lower die 30 side together with the trim die 14. As a result, the work piece 50 is pressed and molded with the molding surface 16a of the pad 16 and the molding surface 34a of the punch 34.

As illustrated in FIG. 1C, when the pad 16 moves down to the bottom dead point, a hydraulic stroke received by the pad 16 is adjusted and the pad 16 stays at the bottom dead point. The die holder 12 further receives a pressing pressure 11 and moves to the lower die 30 side. At this time, only the trim die 14 moves relative to the punch 34. As a result, the blade portion 14b at a corner of the trim die 14 cuts the end portion 52 of the work piece 50.

According to the above manufacturing method, in order to prevent the trim die 14 from moving ahead of the pad 16 during press molding, it is necessary to control the movement of the pad 16 with the hydraulic pressure of the reaction force generation device 20. However, if the reaction force generation device 20 is installed, it is possible that costs increase. Further, if the reaction force generation device 20 is installed, it is possible that a size of the metallic die becomes large.

FIG. 2 is an enlarged view of a portion in FIG. 1C surrounded by a reference sign 60. Depending on the press-molded article, a width w of the flange portion 54 of the work piece 50 is very shorter than a depth h of a deep drawing molding and therefore, it is sometimes difficult to secure the strength of the pad 16. Moreover, the pad 16 includes the flow path 19 for circulating the refrigerant such as water for cooling the work piece 50. By forming the flow path 19 inside the pad 16, a thickness 16c of the pad 16 is further reduced. Therefore, if the width of the flange portion of the press-molded article is narrow, it is sometimes more difficult to arrange and process the flow path 19 of the pad 16 while securing the strength of the pad 16.

Therefore, the press molding device according to the present embodiment does not use the hydraulic tanker and trims the work piece during the hot stamp molding process. Further, according to the press molding device, regardless of the shape of the work piece, it is possible to arrange the flow path to the pad while securing the strength of the pad.

With reference to FIG. 3A, FIG. 3B, FIG. 3C, and FIG. 4, the press molding device according to the present embodiment is described.

A hot press molding apparatus presses and molds the heated work piece 500 while cooling the heated work piece 500 to manufacture the press-molded article. The hot press molding apparatus includes the upper die 100 and the lower die 200 as metallic dies. The upper die 100 is one example of the second die. The lower die 200 is one example of the first die. The upper die 100 may function as the first die and the lower die 200 may function as the second die. The lower die 200 supports the work piece 500. The upper die 100 is arranged to face the lower die 200. The work piece 500 may be a plate material. The blank material 500 may be the plate material made of a metal material such as hard steel, mild steel, aluminum, titanium or copper.

The lower die 200 includes a punch holder 202, a punch 204, a blank holder 206, and a reaction force generation device 208 such as spring. The punch 204 faces the upper die 100 and includes the molding surface 204a for molding the work piece 500. The molding surface 204a is one example of the first molding surface. The blank holder 206 is movably arranged along the side surface 204b that extends from the molding surface 204a of the punch 204 to the punch holder 202 side and includes the supporting surface 206a for supporting the end portion 502 of the work piece 500. The punch 204 includes the flow path 209 that is arranged along the molding surface 204a and is used to circulate the refrigerant for cooling the work piece 500.

The upper die 100 includes a die holder 102, a die portion 104, a movable pad 108, and a trimming portion 110. The die portion 104 is fixed to the die holder 102. The die portion 104 includes the molding surface 104a that faces the molding surface 204a of the punch 204 and is sued to mold the work piece 500. The molding surface 104a is one example of the second molding surface. The die portion 104 includes the flow path 109 that is arranged along the molding surface 104a and is used to circulate the refrigerant for cooling the work piece 500. The movable pad 108 includes the flow path 113 for circulating the refrigerant for cooling the work piece 500. The upper die 100 may not include the movable pad 108. The lower die 200 may not include the blank holder 206.

The trimming portion 110 may be configured integrally with the die portion 104. As a result, it is possible to prevent the strength of the die portion 104 from being reduced. The trimming portion 110 is fixed to the fixed surface 104b of the die portion 104 that faces the blank holder 206, which fixed surface 104b extends from the molding surface 104a so that the trimming portion 110 is configured integrally with the die portion 104. The trimming portion 110 may be removably fixed to the fixed surface 104b of the die portion 104 via the bolt 130. Thereby, the replacement of the trimming portion 110 can be facilitated. The trimming portion 110 may be physically integrated with the die portion 104. The trimming portion 110 may be made of the same material as the die portion 104 and may be physically integrated with the die portion 104. Integrally configuring the trimming portion 110 and the die portion 104 is a concept including a form in which the trimming portion 110 and the die portion 104 are separately configured and the trimming portion 110 and the die portion 104 are integrally connected by bolting, bonding and the like besides a form in which the trimming portion 110 and the die portion 104 are made of the same material and physically integrated.

The trimming portion 110 includes the blade 110a for cutting the end portion 502 of the work piece 500. The trimming portion 110 has the blade 110a at the side of the molding surface 104a side. The trimming portion 110 further includes the protrusion 112 that forms a step from the blade 110a to the blank holder 206 side. The protrusion 112 includes the clamping surface 110b that faces the supporting surface 206a of the blank holder 206 and clamps the end portion 502 of the work piece 500 with the supporting surface 206a. The clamping surface 110b protrudes to the blank holder 206 side than the blade 110a. A cross section of the corner of the molding surface 204a side of the protrusion 112 may be curved.

As illustrated in FIG. 3A, with the end portion 502 of the work piece 500 being clamped between the supporting surface 206a of the blank holder 206 and the clamping surface 110b of the protrusion 112 and a portion of the work piece 500 being clamped between the movable pad 108 and the punch 204, the pressing pressure 111 is added to the die holder 102. As a result, as illustrated in FIG. 3B, the die portion 104 and the trimming portion 110 move toward the lower die 200 and the blank holder 206 moves along the side surface 204b of the punch 204.

The work piece 500 is clamped between the die portion 104 and the punch 204, is pressed with the molding surface 204a and the molding surface 104a, and is molded to a predetermined shape. Further, as illustrated in FIG. 3C, before the die portion 104 and the trimming portion 110 reach the bottom dead point, the blade 110a cuts the end portion 502 of the work piece 500. The blade 110a may cut the end portion 502 of the work piece 500 immediately before the die portion 104 and the trimming portion 110 reach the bottom dead point. When the upper die 100 functions as the first die, the work piece 500 in the clamped state moves toward the lower die 200 that functions as the second die, and then is molded and cut.

The heated work piece 500 is molded toward the molding surface 204a of the punch 204 while being pressed. If the work piece 500 contacts with the blade 110a while the work piece 500 is pressed, the blade 110a is likely to be abraded due to the friction with the work piece 500. Therefore, the trimming portion 110 includes the protrusion 112 where the clamping surface 110b protrudes to the blank holder 206 side than the blade 110a. As a result, before the work piece 500 is cut and during pressing of the work piece 500, the work piece 500 is less likely to contact the blade 110a. Therefore, it is possible to prevent the abrasion of the blade 110a due to the friction with the work piece 500.

The trimming portion 110 is fixed to the fixed surface 104b of the die portion 104 that faces the blank holder 206, which fixed surface 104b extends from the molding surface 104a. The trimming portion 110 is fixed to the die portion 104 instead of the die holder 102. As a result, the width of the die portion 104 is not limited to the width of the flange portion of the press-molded article. Therefore, it is possible to provide the flow path 109 for circulating the refrigerant such as water inside the die portion 104 without the limitation in the width of the flange portion of the press-molded article. As a result, even if the flow path 109 is provided, it is possible to prevent the reduction in the strength of the die portion 104.

Further, in the press molding device according to the present embodiment, it is not necessary to provide the hydraulic tanker for adjusting positions of the trimming portion 110 and the die portion 104. Therefore, it is possible to reduce a size of the metallic die.

As illustrated in FIG. 4, the molding surface 104a of the die portion 104 includes the step portion 104c for folding the work piece 500 and molding the flange portion. The step portion 104c is formed by standing from an end portion for molding the flange portion of the molding surface 104a. As illustrated in a portion enclosed by a reference sign 612, the blade 110a may be provided inside a virtual tangential line 610 that is in contact with the corner portion 112d of the protrusion 112 and the step portion 104c. The blade 110a may be provided inside a tangent plane that is in contact with the corner portion 112d and the step portion 104c. As a result of a molding analysis, as in the case of the work piece 500 illustrated in FIG. 4, there is a case where a result is obtained in which a molding analysis line is present outside the tangential line. In this case, the blade 110a may be provided outside the tangential line 610 as long as the blade 110a is provided inside the molding analysis line. As a result, it is possible to surely prevent the work piece 500 from being in contact with the blade 110a and being dragged before the blade 110a cuts the work piece 500. Therefore, it is possible to more surely prevent the abrasion of the blade 110a.

While the embodiments of the present invention have been described, the technical scope of the invention is not limited to the above described embodiments. It is apparent to persons skilled in the art that various alterations and improvements can be added to the above-described embodiments. It is also apparent from the scope of the claims that the embodiments added with such alterations or improvements can be included in the technical scope of the invention.

The operations, procedures, steps, and stages of each process performed by an apparatus, system, program, and method shown in the claims, embodiments, or diagrams can be performed in any order as long as the order is not indicated by “prior to,” “before,” or the like and as long as the output from a previous process is not used in a later process. Even if the process flow is described using phrases such as “first” or “next” in the claims, the specification, or diagrams, it does not necessarily mean that the process must be performed in this order.

EXPLANATION OF REFERENCES

• 10 upper die
• 12 die holder
• 14 trim die
• 14 a clamping surface
• 14 b blade portion
• 16 pad
• 16 a molding surface
• 16 c thickness
• 19 flow path
• 20 reaction force generation device
• 30 lower die
• 32 punch holder
• 34 punch
• 34 a molding surface
• 36 blank holder
• 36 a supporting surface
• 38 reaction force generation device
• 39 flow path
• 50 work piece
• 52 end portion
• 54 flange portion
• 100 upper die
• 102 die holder
• 104 die portion
• 104 a molding surface
• 104 b fixed surface
• 104 c step portion
• 108 movable pad
• 109 flow path
• 110 trimming portion
• 110 a blade portion
• 110 b clamping surface
• 112 protrusion
• 112 d corner portion
• 113 flow path
• 130 bolt
• 200 lower die
• 202 punch holder
• 204 punch
• 204 a molding surface
• 204 b side surface
• 206 blank holder
• 206 a supporting surface
• 208 reaction force generation device
• 209 flow path
• 500 work piece
• 502 end portion
• 610 tangential line

Claims

1. A press molding device that presses and molds a work piece that has been heated while cooling the work piece, the press molding device comprising: a first die for supporting the work piece; anda second die arranged to face the first die, whereinthe first die includes:a punch including a first molding surface for molding the work piece, anda blank holder that is movably arranged along a side surface extending from the first molding surface of the punch and includes a supporting surface for supporting an end portion of the work piece;the second die includes;a die portion that includes a second molding surface that faces the first molding surface and is used to mold the work piece and a fixed surface that extends to an outside from a tip portion of the second molding surface and faces the supporting surface of the blank holder anda trimming portion that is configured integrally with the die portion;the trimming portion includes:a blade portion for cutting the end portion of the work piece;the die portion includes:a flow path for circulating a refrigerant to cool the work piece along the second molding surface;the trimming portion is configured integrally with the die portion by being fixed to the fixed surface; andthe trimming portion includes a clamping surface that faces the supporting surface and clamps the end portion of the work piece with the supporting surface and further includes a protrusion where the clamping surface protrudes toward the blank holder side than the blade portion.

2. The press molding device according to claim 1 wherein the second molding surface includes a step portion for folding the work piece and molding a flange portion; andthe blade portion is provided inside a tangential line that is in contact with a corner portion of the protrusion and the step portion.

3. The press molding device according to claim 1 wherein with the end portion of the work piece being clamped between the supporting surface of the blank holder and the clamping surface of the protrusion, the die portion and the trimming portion are moved toward the first die and the blank holder is moved along the side surface of the punch so that the work piece is pressed and molded with the first molding surface and the second molding surface and, before the die portion and the trimming portion reach a bottom dead point, the blade portion cuts the end portion of the work piece.

4. The press molding device according to claim 1, wherein the fixed surface of the die portion continuously extends from a tip portion of the second molding surface to an outside.

5. The press molding device according to claim 1 wherein the trimming portion is removably fixed to the fixed surface of the die portion.

6. A method for manufacturing a press-molded article by pressing and molding a work piece that has been heated while clamping the work piece between a first die and a second die and cooling the work piece, the method comprising: pressing and molding the work piece with the first molding surface and the second molding surface and before a die portion and a trimming portion reach a bottom dead point, cutting an end portion of the work piece with a blade portion by moving the die portion and the trimming portion toward the first die and moving a blank holder along a side surface of a punch with the end portion of the work piece being clamped between a supporting surface of the blank holder and a clamping surface of the trimming portion, whereinthe first die includes the punch that includes the first molding surface for molding the work piece and the blank holder that is movably arranged along the side surface that extends from the first molding surface of the punch and includes the supporting surface for supporting the end portion of the work piece;the second die includes the die portion including the second molding surface that faces the first molding surface and is used for molding the work piece and a fixed surface that extends to an outside from a tip portion of the second molding surface and faces the supporting surface of the blank holder, and the trimming portion that is configured integrally with the die portion;the trimming portion includes the blade portion for cutting the end portion of the work piece;the die portion includes a flow path for circulating a refrigerant to cool the work piece along the second molding surface;the trimming portion is configured integrally with the die portion by being fixed to a fixed surface; andthe trimming portion includes the clamping surface that faces the supporting surface and clamps the end portion of the work piece with the supporting surface and further includes a protrusion where the clamping surface protrudes toward the blank holder side than the blade portion.

7. The method for manufacturing the press-molded article according to claim 6 wherein the trimming portion is removably fixed to the fixed surface of the die portion.