JP2023038459A - Mold, press device, and method for manufacturing press molding - Google Patents

Abstract

To provide a mold which reduces spring back of a press molding and can improve dimensional accuracy, and has a simple structure.SOLUTION: A mold (10) includes dies (12L, 12R). The dies (12L, 12R) include die shoulders (121L, 121R), and die side faces (122L, 122R). The die side faces (122L, 122R) have a die upper side face (122a), and a die lower side face (122b). The die lower side face (122b) has a shape recessed outward in a width direction of the mold (10) with respect to the die upper side face (122a). When a length from the upper ends of the die shoulders (121L, 121R) to the lower end of the die upper side face (122a) is represented by H1, and a length from the lower end of the die upper side face (122a) to the lower end of the die lower side face (122b) is represented by H2, H1 is larger than a radius of curvature of the die shoulders (121L, 121R) by 5.0 mm or more, and H2/H1 is 1.0 or more and 5.0 or less.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a mold, a press apparatus, and a method of manufacturing a press-formed product for press-working a plate-shaped material.

BACKGROUND ART Press-formed products are widely used as parts constituting automobile bodies and the like. The press-formed product has, for example, a top plate and vertical walls connected to both side edges of the top plate via bent portions. Such a press-formed product is manufactured by subjecting a plate-shaped material (metal plate) to press working. More specifically, a press-formed product is manufactured by drawing or bending a metal plate using a die including a punch and a die.

After molding a metal plate into a press-molded product using a mold, springback occurs when the press-molded product is released from the mold. More specifically, when a metal plate is bent by a die during press working, tensile stress is generated on the outside of the bend and compressive stress is generated on the inside of the bend. Upon removal from the mold, the elastic recovery of the material creates compressive stresses on the outside of the bend and tensile stresses on the inside of the bend. As a result, at the moment the press-molded product is removed from the mold, a moment (wall-opening moment) is generated to open both vertical walls of the press-molded product outward. This moment causes springback of the press-formed product.

A press die is sometimes designed with springback in mind in order to obtain a target dimensional accuracy for a press-formed product. That is, the portion of the mold that forms both vertical walls of the press-formed product is provided inside the target positions of both vertical walls by an amount that is expected to cause the walls to open due to springback. However, it is difficult to exactly match the expected amount of springback with the actual amount of springback. In addition, since the amount of springback is proportional to the strength of the material, the expected amount of springback increases when, for example, a high-strength material such as high-strength steel or ultra-high-strength steel is pressed. When designing a mold based on this estimated amount, the part of the mold that forms both vertical walls of the press-formed product has a negative angle, and there is a possibility that the structure of the mold will not be established. Therefore, it is difficult to obtain the target dimensional accuracy of the press-formed product only by designing the mold in anticipation of springback.

Therefore, techniques have been proposed for obtaining press-formed products with target dimensional accuracy without relying on springback estimates. For example, Patent Literature 1 discloses a method of manufacturing a press-formed product that includes a top plate and two vertical walls, as well as flanges extending outwardly from both vertical walls. The manufacturing method of Patent Document 1 includes, for example, a first press working step of manufacturing an intermediate molded product from a metal plate as a raw material, and a second press working step of manufacturing a final press molded product from the intermediate molded product. . In the first press working step, the metal plate is pressed by the first punch and the first die to form the top plate and the bent portion of the press-formed product, and to form a part of each vertical wall. In the second pressing step, the intermediate product obtained in the first pressing step is pressed by a second punch and a second die to form the remaining portion of each vertical wall and each flange. According to Patent Literature 1, by forming each flange last, it is possible to reduce warping (opening) of each vertical wall due to springback.

For example, Patent Literature 2 discloses controlling the moving direction of a die using a cam mechanism when manufacturing a press-formed product. The manufacturing method of Patent Document 2 includes a push bending process in which the die is lowered toward the material on the punch to bend the material, and a shift process in which the die is moved in a direction approaching the punch using a cam to bend the material. and a bending step. In the bending process, the dies provided on both sides of the punch contact the ends of the material and press the material toward the punch, so that the material is bent upwardly. According to Patent Document 2, by bending the material in this way, it is possible to generate a spring-go component that acts in a direction to cancel the spring-back component.

WO2016/051765 Japanese Patent No. 5808297

In the manufacturing method of Patent Document 1, the top plate and part of each vertical wall of the press-formed product are formed first, and the remaining part of each vertical wall and each flange are formed last, thereby reducing springback. ing. Therefore, in the case of the manufacturing method of Patent Document 1, at least two pressing steps are required in order to prevent deterioration of dimensional accuracy due to springback.

On the other hand, in the manufacturing method of Patent Document 2, a press-formed product can be manufactured in one press working process. However, in the case of the manufacturing method of Patent Document 2, it is necessary to use a cam mechanism to control the moving direction of the die, which poses a problem of complicating the structure of the die.

An object of the present disclosure is to provide a mold that can reduce springback of a press-molded product to improve dimensional accuracy and has a simple structure.

A mold according to the present disclosure is a mold for pressing a plate-shaped material. The mold includes a punch and a die. The punch includes a punch top, a punch side, and a punch shoulder. The punch shoulder constitutes the corner between the punch top surface and the punch side surface. The die includes a die shoulder, a die side, and a die flange face. The die shoulder corresponds to the punch shoulder. The die side corresponds to the punch side. The die flange surface extends outward in the width direction of the mold from the die side surface. The die side has a die top side and a die bottom side. The die upper side surface is continuous with the die shoulder. The die lower side is positioned between the die upper side and the die flange surface. The die lower side surface has a concave shape toward the outside in the width direction of the mold with respect to the die upper side surface. When the length in the vertical direction of the die from the upper end of the die shoulder to the lower end of the upper side of the die is H1, and the length in the vertical direction from the lower end of the upper side of the die to the lower end of the lower side of the die is H2, H1 is the die shoulder. , and H2/H1 is 1.0 or more and 5.0 or less.

A mold according to the present disclosure can reduce springback of a press-molded product and improve dimensional accuracy. Also, the mold according to the present disclosure has a simple structure.

FIG. 1 is a cross-sectional view showing a schematic configuration of a mold according to the first embodiment. 2 is a cross-sectional view showing an enlarged right die of the mold of FIG. 1. FIG. FIG. 3A is a schematic diagram for explaining a method for manufacturing a press-formed product according to the first embodiment. FIG. 3B is a schematic diagram for explaining the method of manufacturing the press-formed product according to the first embodiment. FIG. 3C is a schematic diagram for explaining the method of manufacturing the press-formed product according to the first embodiment. FIG. 3D is a schematic diagram for explaining the method of manufacturing the press-formed product according to the first embodiment. FIG. 3E is a schematic diagram for explaining the method of manufacturing the press-formed product according to the first embodiment. FIG. 3F is a schematic diagram for explaining the method of manufacturing the press-formed product according to the first embodiment. FIG. 3G is a schematic diagram for explaining the method of manufacturing the press-formed product according to the first embodiment. FIG. 4 is a diagram illustrating a press-formed product manufactured by the manufacturing method according to the first embodiment. FIG. 5 is a diagram illustrating another press-formed product manufactured by the manufacturing method according to the first embodiment. FIG. 6 is a diagram illustrating yet another press-formed product manufactured by the manufacturing method according to the first embodiment. FIG. 7 is a partial cross-sectional view of a mold according to a modification of the first embodiment. FIG. 8 is a schematic diagram for explaining a method of manufacturing a mold and a press-molded product that are different from those of the first embodiment. FIG. 9 is a cross-sectional view showing a schematic configuration of a mold according to the second embodiment. 10 is a cross-sectional view showing an enlarged right die of the mold of FIG. 9. FIG. FIG. 11 is a cross-sectional view of a die according to a modification of the second embodiment;

A mold according to an embodiment is a mold for pressing a plate-shaped material. The mold includes a punch and a die. The punch includes a punch top, a punch side, and a punch shoulder. The punch shoulder constitutes the corner between the punch top surface and the punch side surface. The die includes a die shoulder, a die side, and a die flange face. The die shoulder corresponds to the punch shoulder. The die side corresponds to the punch side. The die flange surface extends outward in the width direction of the mold from the die side surface. The die side has a die top side and a die bottom side. The die upper side surface is continuous with the die shoulder. The die lower side is positioned between the die upper side and the die flange surface. The die lower side surface has a concave shape toward the outside in the width direction of the mold with respect to the die upper side surface. When the length in the vertical direction of the die from the upper end of the die shoulder to the lower end of the upper side of the die is H1, and the length in the vertical direction from the lower end of the upper side of the die to the lower end of the lower side of the die is H2, H1 is the die shoulder. , and H2/H1 is 1.0 or more and 5.0 or less (first configuration).

When press-working a plate-shaped material using the mold according to the first configuration, the die is brought relatively close to the punch while the material is placed on the top surface of the punch. As a result, the lower side of the die first comes into contact with the material on the top surface of the punch. The die lower side surface has a concave shape toward the outside in the width direction of the mold with respect to the die upper side surface. Therefore, as the die approaches the punch, the material is guided by the lower side surface of the die and bends into a convex shape on the side opposite to the direction in which the die approaches the punch. When the die is brought closer to the punch, the material contacts the upper side of the die, and the bent material is gradually bent back. As the die and punch move closer together, the deflection of the material is reduced and the material conforms (wraps around) the punch shoulder to form a bend. When the punch and die are finally closed, the flexure of the blank is completely unbent and the blank is clamped between the punch shoulder and the die shoulder and between the punch side and the die upper side.

In this way, the die according to the first configuration bends the material so as to form a convex shape on the side opposite to the direction in which the die approaches the punch, and gradually bends back the deflection of the material as the press working progresses. is configured as As a result, during press working, tensile stress can be generated on the punch side, and compressive stress can be generated on the die side, which is the opposite side of the punch, particularly in the portion of the material that will become the vertical wall of the press-formed product. At the bend formed by the punch shoulder, compressive stress is generated on the punch side and tensile stress is generated on the die side, so the stress generated by the unbending of the deflection cancels out the stress in the bend and reduces the stress in the bend. . When the press-formed product is formed from the raw material, the stress remaining in the bent part and the stress remaining in the unbent part cause a wall-opening moment and a wall-closing moment in the press-formed product after release from the mold. , they cancel each other and the wall opening moment is reduced. Therefore, it is possible to reduce the springback in the press-molded product after releasing the mold. As a result, the dimensional accuracy of the press-formed product can be improved. In addition, when pressing a material using the mold according to the first configuration, it is only necessary to perform a normal mold closing operation, and a cam mechanism or the like for moving the die in a special direction is unnecessary. be. Therefore, the mold can have a simple structure.

In the first configuration, the length in the vertical direction of the die from the upper end of the die shoulder to the lower end of the upper side of the die is H1, and the length in the vertical direction of the die from the lower end of the upper side of the die to the lower end of the lower side of the die is H2. , H2/H1 is set to 1.0 or more and 5.0 or less. As a result, a sufficient length of the lower side surface of the die is ensured, so that the material can be largely deflected over a wide range in the width direction by the lower side surface of the die during press working. Therefore, it is possible to effectively exhibit the effect of canceling out the stress and moment due to the bending return of the deflection. In addition, in the first configuration, H1 is 5.0 mm or more larger than the radius of curvature of the die shoulder, and H2/H1 is set to 1.0 or more and 5.0 or less, so the length of the upper side of the die is secured. can do. Therefore, when the punch and the die are finally closed, the material can be firmly held between the side surfaces of the punch and the upper side surface of the die, and the material can be molded into the shape of the final press-molded product. Therefore, there is no need to perform an additional press working step, and the man-hours and costs in manufacturing the press-formed product can be reduced.

When H2/H1 exceeds 5.0, the ratio of the die lower side surface having a concave shape toward the outside in the width direction of the mold occupies an excessive amount, and the die lower side surface bends the material. saturates. Moreover, when H2/H1 exceeds 5.0, the cost of manufacturing the mold increases. Therefore, H2/H1 is preferably 5.0 or less as in the first configuration.

The die bottom side may include a first connecting portion, a second connecting portion, and an intermediate portion. The first connection part is continuously provided at the lower end of the die upper side surface and connects the die lower side surface to the die upper side surface. The second connecting portion includes a lower end of the die lower side and connects the die lower side to the die flange surface. The intermediate portion is arranged between the first connection portion and the second connection portion and is positioned outside the first connection portion in the width direction (second configuration).

The first connecting portion has, for example, an arc shape in a cross-sectional view of the die. In this case, the first connecting portion preferably has a radius of curvature of 1.0 mm or more and 10.0 mm or less (third configuration).

In the third configuration, the radius of curvature of the first connecting portion connecting the die lower side surface to the die upper side surface is set to 10.0 mm or less. In this case, the ratio of the first connection portion and the lower side surface of the die including the first connection portion to the side surface of the die having a predetermined size does not become too large, and the length of the upper side surface of the die can be easily secured. Therefore, when the punch and die are finally closed, the material can be more reliably held between the punch side surface and the die upper side surface.

When the first connecting portion contacts the material during press working, the material may be left with a mark of the first connecting portion biting (biting mark) or a bending habit. On the other hand, in the third configuration, the radius of curvature of the first connecting portion is set to 1.0 mm or more. Therefore, it is possible to avoid leaving bite marks and bending habits on the material.

The intermediate portion may include a curved surface that is concave outward in the width direction of the mold with respect to the first connection portion (fourth configuration). In this case, when the length in the width direction from the lower end of the upper side surface of the die to the lower end of the lower side surface of the die is W2, H2/W2 is preferably 1.0 or more and 5.0 or less (fifth configuration).

When H2/W2 is less than 1.0, that is, when W2 is greater than H2, the effect of bending the material by the die lower side surface saturates. Moreover, when H2/W2 is less than 1.0, the cost of manufacturing the mold increases. On the other hand, when H2/W2 exceeds 5.0, W2 becomes smaller than H2, so the effect of bending the material by the lower side surface of the die becomes small. Therefore, when the intermediate portion of the die lower side surface is mainly curved, it is preferable that H2/W2 is 1.0 or more and 5.0 or less as in the fifth configuration.

The intermediate portion may include an inclined surface that is inclined with respect to the horizontal plane (sixth configuration). The angle formed by the inclined surface with the horizontal plane is preferably (50−θ)° or more and (78−θ)° or less, where θ° is the angle formed by the punch side surface with the vertical plane (seventh configuration). .

When the intermediate portion of the lower side surface of the die is mainly composed of an inclined surface, if the angle of the inclined surface with respect to the horizontal plane is too large, the degree of depression of the lower side surface of the die becomes small. Therefore, the effect of bending the material by the lower side surface of the die is reduced. On the other hand, if the angle of the inclined plane with respect to the horizontal plane is too small, the effect is saturated. In addition, the smaller the angle of the inclined surface with respect to the horizontal plane, the greater the extent of the depression of the lower side surface of the die, which increases the size of the mold and increases the cost of manufacturing the mold. Therefore, the angle formed by the inclined surface included in the intermediate portion with respect to the horizontal plane is (50−θ)° or more, where θ° is the angle formed by the side surface of the punch with respect to the vertical plane as in the seventh configuration. It is preferably (78-θ)° or less.

The clearance between the punch side surface and the die upper side surface when the punch and die are in a closed state may be smaller than the plate thickness of the material (eighth configuration). The clearance is preferably 0.85 times or more and 0.95 times or less the plate thickness (ninth configuration).

In the eighth and ninth configurations, the clearance between the punch side surface and the die upper side surface is smaller than the plate thickness of the material. Therefore, when the punch and die are finally closed, the material is strongly clamped between the side surface of the punch and the upper side surface of the die, and the flexure of the material is more firmly bent back. In this case, a greater tensile stress can be generated on the punch side and a greater compressive stress can be generated on the die side, which is the opposite side of the punch, in the portion of the material that will become the vertical wall of the press-formed product. Therefore, it is possible to enhance the effect of these stresses canceling out the stress in the bent portion. As a result, it is possible to further reduce the springback in the press-formed product after releasing from the mold, and to further improve the dimensional accuracy of the press-formed product.

In the mold according to the embodiment, when the punch and the die are finally closed in the press working of the plate-shaped material, the material is sandwiched between the side surface of the punch and the upper side surface of the die, while the lower side surface of the concave die is substantially Do not touch the material directly. Therefore, the load can be applied intensively to the portion of the material that will be the vertical wall of the press-formed product. In particular, as in the eighth and ninth configurations, when the clearance between the side surface of the punch and the upper side surface of the die is smaller than the plate thickness of the material, the portion of the material that will become the vertical wall of the press-formed product is pressed more strongly. can do.

With a cam mechanism that moves the die obliquely downward, as in Patent Document 2, it is difficult to strongly press the material in the plate thickness direction due to the rigidity of the die. On the other hand, in the eighth and ninth configurations, the cam mechanism is not used, and the clearance between the side surface of the punch and the upper side surface of the die is set smaller than the plate thickness of the material. This makes it possible to strongly press the material in the plate thickness direction. Therefore, it is possible to generate a greater stress in the portion of the material that will become the vertical wall of the press-formed product, and the stress can enhance the effect of canceling out the stress in the bent portion. As a result, it is possible to further reduce the springback in the press-formed product after releasing from the mold, and to further improve the dimensional accuracy of the press-formed product.

The mold may further include a pad corresponding to the top surface of the punch (tenth configuration).

A mold according to the tenth configuration includes a pad in addition to the punch and die. In this case, the die can be brought relatively close to the punch while the material is pressed by the top surface of the punch and the pad. Therefore, it is possible to prevent the positional displacement of the material during press working. Further, by forming the material while pressing the material with the pad, the shape of the top plate of the press-molded product can be accurately formed.

A press apparatus according to an embodiment manufactures a press-molded product from a plate-shaped material. A press device includes the mold described above. The press apparatus is configured such that the punch and die start forming the material while the material placed on the punch top surface is sandwiched between the punch top surface and the pad (eleventh configuration).

The press device further includes a die holder. The die holder integrally and movably supports the die and the pad. The pad is connected to the die holder by a stretchable elastic member (12th configuration).

A manufacturing method according to an embodiment is a method for manufacturing a press-formed product. The manufacturing method includes a first preparation step of preparing the mold, a second preparation step of preparing a plate-shaped material, and a molding step of molding the material into a press-molded product using the mold. In the forming process, after placing the material on the top surface of the punch, the die is moved relatively close to the punch, and the lower side of the die is brought into contact with the material to bend the material. The material is deflected by the upper side of the die by bringing the die closer to the punch and bringing the upper side of the die into contact with the material, and bringing the die closer to the punch while keeping the upper side of the die in contact with the material. and closing the punch and die to clamp the material between the punch shoulder and the die shoulder and between the punch side and the die top side. When the punch and die are completely closed, the material takes a shape along the punch top surface, punch shoulder and punch side surface (13th configuration).

In the manufacturing method described above, in the first preparing step, a mold including a pad in addition to the punch and die may be prepared. In this case, in the forming process, it is preferable that the material placed on the top surface of the punch is held between the top surface of the punch and the pad and bent by the lower side surface of the die (14th configuration).

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each figure, the same or corresponding configurations are denoted by the same reference numerals, and the same description will not be repeated.

<First Embodiment>
[Composition of press device]
FIG. 1 is a cross-sectional view showing a schematic configuration of a mold 10 according to this embodiment. A cross section is a cross section cut along a plane substantially perpendicular to the longitudinal direction of the mold 10 . In the following description, the vertical direction on the paper surface of FIG. 1 is referred to as the vertical direction of the mold 10, and the horizontal direction on the paper surface of FIG. direction is called the width direction of the mold 10 . Also, the left side and right side on the paper surface of FIG. 1 may be simply referred to as the left side and the right side.

The mold 10 is used to press a plate-shaped material (metal plate). By pressing the raw material with the mold 10, it is possible to manufacture a press-molded product, for example, a chassis part of an automobile. Automobile undercarriage parts include, for example, arm parts such as upper arms, lower arms, and trail links, as well as suspension members, torsion beams, and the like.

Referring to FIG. 1, a die 10 is attached to a press device 20 when press working is performed on a material. The mold 10 includes a punch 11, dies 12L and 12R, and a pad 13. In this embodiment, the dies 12L and 12R, which are upper dies of the mold 10, and the pad 13 are vertically moved by the press device 20. As shown in FIG. When a straight line drawn in the vertical direction is projected onto the cross section of the mold 10, the direction of the straight line and the vertical direction of the cross section of the mold 10 match. When the mold 10 is for molding a press-molded product having a linear shape in a side view, the vertical direction and the vertical direction in the cross-sectional view of the mold 10 always match over the entire length of the mold 10. .

Punch 11 includes punch top surface 111, punch shoulders 112L, 112R, and punch side surfaces 113L, 113R.

In the example shown in FIG. 1, the punch top surface 111 is a substantially flat surface. However, the punch top surface 111 may be formed with grooves or steps (steps) extending in the longitudinal direction of the punch 11 . The groove or step may extend over the entire punch top surface 111 or may be provided on a part of the punch top surface 111 in the longitudinal direction of the punch 11 .

Punch shoulders 112L, 112R and punch side surfaces 113L, 113R are provided on both sides of the punch top surface 111 in the width direction of the die 10 . The punch shoulder 112L and the punch side 113L are arranged on the left side of the punch top surface 111. As shown in FIG. The punch shoulder 112R and the punch side 113R are arranged on the right side of the punch top surface 111. As shown in FIG.

The punch shoulders 112L and 112R are provided continuously on the punch top surface 111. As shown in FIG. More specifically, the punch shoulder 112L continues to the left edge of the punch top surface 111, and the punch shoulder 112R continues to the right edge of the punch top surface 111. As shown in FIG. The punch shoulders 112L and 112R form corners (ridge lines) between the punch top surface 111 and the punch side surfaces 113L and 113R, respectively. Each of the punch shoulders 112L and 112R has, for example, a substantially arcuate shape when the punch 11 is viewed in cross section.

Here, in the present embodiment, the term “substantially arcuate” is a concept that includes not only curves forming part of a perfect circle, but also smooth curves such as elliptical curves and spline curves. In this embodiment, for a smooth curve other than a curve forming part of a perfect circle, such as an elliptic curve or a spline curve, the radius of curvature is the radius of a circle that passes through three points: both ends of the curve and the midpoint of the curve. defined by

In cross-sectional view of the punch 11, the punch side 113L extends downward from the left punch shoulder 112L. In cross-sectional view of the punch 11, the punch side 113R extends downward from the right punch shoulder 112R. In the example of the present embodiment, when viewed in cross section of the punch 11, the punch side surfaces 113L and 113R are inclined with respect to the vertical direction so as to separate from each other as they go downward. However, the punch side surfaces 113L and 113R may extend substantially vertically when viewed in cross section of the punch 11 .

The angles θ _L and θ _R (°) formed between the punch side surfaces 113L and 113R and the vertical plane may be the same or different. Each of the angles θ _L and θ _R is 0° or more. It is preferable that each of the angles θ _L and θ _R is 20° or less. The angles θ _L and θ _R formed by the punch side surfaces 113L and 113R with the vertical plane are angles (acute angles) formed between the punch side surfaces 113L and 113R and the vertical direction in a cross section obtained by cutting the punch 11 along a plane consisting of the vertical direction and the width direction. side). The vertical plane is a cross section of the mold 10 cut along a plane consisting of the vertical direction and the longitudinal direction, or a plane consisting of the vertical direction and the longitudinal direction. When the vertical plane is projected onto the cross section of the mold 10, it becomes a straight line extending in the vertical direction.

The dies 12L and 12R are positioned above the punch 11 when the die 10 is attached to the press device 20 . Moreover, when the die 10 is attached to the press device 20 , the dies 12 L and 12 R are positioned on both sides of the pad 13 in the width direction of the die 10 . Die 12L is positioned to the left of pad 13 . Die 12R is positioned to the right of pad 13 .

Left die 12L includes die shoulder 121L, die side 122L, and die flange surface 123L. Right die 12R includes die shoulder 121R, die side surface 122R, and die flange surface 123R.

The left die shoulder 121L is provided corresponding to the left punch shoulder 112L. That is, the die shoulder 121L has a shape that allows the material to be sandwiched between itself and the punch shoulder 112L when the punch 11 and the dies 12L and 12R are closed. Similarly, the right die shoulder 121R is provided corresponding to the right punch shoulder 112R. That is, the die shoulder 121R has a shape that allows the material to be held between itself and the punch shoulder 112R when the punch 11 and the dies 12L and 12R are closed.

The die shoulders 121L and 121R are substantially arcuate in cross-sectional view of the dies 12L and 12R, respectively. The radius of curvature of the die shoulders 121L, 121R can be determined in relation to the radius of curvature of the corresponding punch shoulders 112L, 112R. For example, when the radius of curvature of the die shoulder 121L is Rd1, the radius of curvature of the punch shoulder 112L is Rp, and the thickness of the material is t, it is preferable that Rd1≦Rp+t. Similarly, where Rd1 is the radius of curvature of the die shoulder 121R, Rp is the radius of curvature of the punch shoulder 112R, and t is the thickness of the material to be pressed, it is preferable that Rd1≤Rp+t. However, the curvature radius Rd1 of the left die shoulder 121L and the curvature radius Rp of the punch shoulder 112L do not necessarily have to be the same as the curvature radius Rd1 of the right die shoulder 121R and the curvature radius Rp of the punch shoulder 112R.

The left die side surface 122L is provided corresponding to the left punch side surface 113L. That is, the die side surface 122L has a shape that allows the material to be sandwiched between a portion of the die side surface 122L and the punch side surface 113L when the punch 11 and the dies 12L and 12R are closed. The right die side surface 122R is provided corresponding to the right punch side surface 113R. That is, the die side surface 122R has a shape that allows the material to be sandwiched between a portion of the die side surface 122R and the punch side surface 113R when the punch 11 and the dies 12L and 12R are closed. Each of the die sides 122L, 122R has a die top side 122a and a die bottom side 122b.

The die flange surfaces 123L, 123R extend outward in the width direction of the mold from the die side surfaces 122L, 122R. The die flange surface 123L is provided continuously with the left die lower side surface 122b. The die flange surface 123R is provided continuously with the right die lower side surface 122b.

Hereinafter, configurations of the die upper side surface 122a and the die lower side surface 122b will be described with reference to FIG. FIG. 2 is a cross-sectional view showing an enlarged right die 12R of the mold 10. As shown in FIG.

The die upper side surface 122a is provided continuously with the die shoulder 121R. The die upper side surface 122a extends downward from the die shoulder 121R in a cross-sectional view of the die 12R. The die upper side surface 122a has a substantially straight shape in a cross-sectional view of the die 12R.

In a cross section obtained by cutting the die 12R along a plane consisting of the vertical direction and the width direction, the angle formed by the die upper side surface 122a and the vertical direction is substantially equal to the angle θ _R of the punch side surface 113R. In the example of this embodiment, the die upper side surface 122a is inclined with respect to the vertical direction in a cross-sectional view of the die 12R corresponding to the punch side surface 113R. More specifically, the die upper side surface 122a is inclined with respect to the vertical direction so as to widen outward in the width direction of the mold 10 as it goes downward.

The die lower side surface 122b is located between the die upper side surface 122a and the die flange surface 123R. The die lower side surface 122b has a concave shape toward the outside in the width direction of the mold 10 with respect to the die upper side surface 122a. That is, the die lower side surface 122b is a region of the die side surface 122R that is recessed outward in the width direction of the mold 10 compared to the die upper side surface 122a. The die lower side surface 122b is arranged outside in the width direction of the mold 10 from the extension line of the die upper side surface 122a indicated by the two-dot chain line in FIG.

The die lower side surface 122b includes connecting portions 122c, 122d and an intermediate portion 122e. On the die lower side surface 122b, the connecting portions 122c and 122d are provided with an intermediate portion 122e interposed therebetween. The connecting portion 122c is arranged above the intermediate portion 122e. The connecting portion 122d is arranged below the intermediate portion 122e.

The upper connecting portion 122c is provided continuously with the lower end of the die upper side surface 122a. Connection 122c connects die bottom side 122b to die top side 122a. The connecting portion 122c forms a corner between the die upper side surface 122a and the middle portion 122e of the die lower side surface 122b. In the present embodiment, the connecting portion 122c has a substantially arcuate shape when viewed in cross section of the die 12R. The connecting portion 122c smoothly connects the die upper side surface 122a and the die lower side surface 122b. The connection portion 122c preferably has a curvature radius Rd2 of 1.0 mm or more and 10.0 mm or less. More preferably, the curvature radius Rd2 of the connection portion 122c is 1.0 mm or more and 4.0 mm or less.

The lower connecting portion 122d includes the lower edge of the die lower side 122b. The connecting portion 122d connects the die lower side surface 122b to the die flange surface 123R. The connecting portion 122d forms a corner portion between the intermediate portion 122e of the die lower side surface 122b and the die flange surface 123R. In this embodiment, the connecting portion 122d has a substantially arcuate shape when viewed in cross section of the die 12R. The connecting portion 122d smoothly connects the die lower side surface 122b and the die flange surface 123R. The connecting portion 122d preferably has a radius of curvature Rd3 of 1.0 mm or more from the viewpoint of preventing a bite mark from being left on the material. In addition, the connection portion 122d preferably has a radius of curvature Rd3 of 16.0 mm or less from the viewpoint of preventing the mold 10 from increasing in size and reducing costs. More preferably, the curvature radius Rd3 of the connecting portion 122d is 1.0 mm or more and 4.0 mm or less.

The intermediate portion 122e is arranged between the connecting portion 122c and the connecting portion 122d. The intermediate portion 122e is positioned outside the upper connecting portion 122c in the width direction of the mold 10 . That is, the intermediate portion 122e is recessed outward in the width direction of the mold 10 compared to the die upper side surface 122a and the connection portion 122c with the die upper side surface 122a.

In this embodiment, the intermediate portion 122e is mainly composed of a curved surface. This curved surface has, for example, a concave shape toward the outside in the width direction of the mold 10 with respect to the upper connecting portion 122c. The shape of the curved surface forming the intermediate portion 122e is, for example, an arc shape, an elliptical arc shape, a parabolic shape, or the like in a cross-sectional view of the die 12R.

Still referring to FIG. 2, the length in the vertical direction of the die 12R from the upper end of the die shoulder 121R to the lower end of the die upper side surface 122a is defined as the upper height H1 of the die side surface 122R. Also, the length in the vertical direction of the die 12R from the lower end of the die upper side surface 122a to the lower end of the die lower side surface 122b is defined as a lower height H2. The upper end of the die shoulder 121R is the R stop of the die shoulder 121R on the side opposite to the die side surface 122R. In the example of this embodiment, the lower end of the die upper side surface 122a coincides with the upper R stop of the connecting portion 122c of the die lower side surface 122b. Also, the lower end of the die lower side surface 122b is an R stop on the die flange surface 123R side of the connecting portion 122d.

The top height H1 of the die side surface 122R is 5.0 mm or more larger than the radius of curvature Rd1 of the die shoulder 121R. The ratio of the lower height H2 to the upper height H1: H2/H1 is 1.0 or more and 5.0 or less.

The length in the width direction of the mold 10 from the lower end of the die upper side surface 122a to the lower end of the die lower side surface 122b is defined as the concave width W2. The concave width W2 is the depth of the concave die lower side 122b with respect to the die upper side 122a. The ratio of the lower portion height H2 to the concave width W2: H2/W2 is preferably 1.0 or more and 5.0 or less.

When the die 12R is viewed in cross section, the line length L of the intermediate portion 122e of the die lower side surface 122b is preferably 1.03×A or more, preferably 1.08×A or more. It is more preferable to have Parameter A is represented by the following equation.
A=((H2-Rd2-Rd3) ² +(W2-Rd2-Rd3) ² ) ^0.5

Returning to FIG. 1, the left die 12L substantially has a configuration in which the right die 12R is horizontally reversed. That is, the die upper side surface 122a and the die lower side surface 122b have the same basic configuration in the left and right dies 12L and 12R. Therefore, for the left die 12L, detailed description of the die upper side surface 122a and the die lower side surface 122b is omitted. Note that the dies 12L and 12R do not need to have a completely symmetrical shape. The dimensions of each part of the left die 12L may be set within a preferable range like the right die 12R, and may not match the dimensions of each part of the right die 12R.

When the die 10 is attached to the press device 20, the pad 13 is positioned above the punch 11 and between the left and right dies 12L and 12R. At this time, the pad 13 faces the punch top surface 111 . More specifically, the lower surface of pad 13 faces punch top surface 111 . The lower surface of pad 13 has a shape corresponding to punch top surface 111 . In this embodiment, the lower surface of the pad 13 is a flat surface corresponding to the punch top surface 111 . For example, when a groove is formed on the punch top surface 111 , a convex portion corresponding to the groove is formed on the lower surface of the pad 13 . For example, when a stepped portion is formed on the punch top surface 111 , a stepped portion corresponding to the stepped portion is formed on the lower surface of the pad 13 .

The press device 20 is a device that uses the mold 10 to form a press-molded product from a plate-shaped material. The press device 20 includes, for example, a punch holder 21, a bolster 22, a die holder 23, and a slide 24 in addition to the die 10. As shown in FIG.

Bolster 22 supports punch 11 via punch holder 21 . More specifically, a punch holder 21 is fixed to the upper surface of the bolster 22 and the punch 11 is arranged on the punch holder 21 . A plate-shaped spacer may be inserted between the punch holder 21 and the bolster 22 in order to adjust the position of the punch 11 in the vertical direction.

The left and right dies 12L, 12R and pads 13 are supported by slides 24 via die holders 23. As shown in FIG. More specifically, the die holder 23 is fixed to the lower surface of the slide 24, and the dies 12L and 12R are fixed to the lower surface of the die holder 23. As shown in FIG. A plate-like spacer may be inserted between the slide 24 and the die holder 23 to adjust the vertical positions of the dies 12L and 12R. The pad 13 is connected to the die holder 23 by a stretchable elastic member 25 . The elastic member 25 is composed of, for example, a spring or a fluid pressure cylinder such as a gas cylinder. The pad 13 may be attached to an actuator (not shown) included in the press device 20 . However, the method using the elastic member 25 allows the press device 20 to have a simpler structure than the actuator method.

The slide 24 is configured to be movable up and down with respect to the punch 11 by, for example, a mechanical or hydraulic mechanism (not shown) provided in the press device 20 . As the slide 24 moves up and down, the die holder 23 also moves up and down. As the die holder 23 moves up and down, the dies 12L and 12R and the pad 13 move up and down with respect to the punch 11 . That is, the dies 12L, 12R and the pad 13 are integrally and movably supported by the die holder 23. As shown in FIG.

[Manufacturing method of press-molded product]
A method of manufacturing a press-molded product using the mold 10 will be described below with reference to FIGS. 3A to 3G. 3A to 3G are schematic diagrams for explaining the method of manufacturing a press-molded product. A method for manufacturing a press-formed product according to the present embodiment includes a step of preparing a mold 10, a step of preparing a plate-shaped material, and a forming step of forming the material into a press-formed product using the mold 10. Prepare.

(First preparation step)
A metal mold 10 (FIGS. 1 and 2) configured as described above is prepared in order to manufacture a press-molded product. The die 10 is attached to the press device 20 before starting press working of the material.

(Second preparation step)
Further, when manufacturing a press-formed product, a plate-shaped material M is prepared as shown in FIG. 3A. The material M is a metal plate, typically a steel plate. The plate thickness t of the material M is, for example, 0.8 mm or more and 4.0 mm or less. The material M has, for example, a tensile strength of 270 MPa or more and 1470 MPa or less. When the press-formed product to be manufactured is an arm part among automobile underbody parts, the tensile strength of the material M is usually 590 MPa or more. When the press-formed product to be manufactured is a frame part such as a ladder frame for an automobile, the tensile strength of the material M is usually 590 MPa or more. When the press-formed product to be manufactured is a substantially U-shaped reinforcing part for the front floor tunnel portion among automobile body frame parts, the tensile strength of the material M is usually 590 MPa or more.

(Molding process)
Next, using the mold 10, the material M is press-formed into a press-molded product. The molding process includes steps (a) to (d). The steps (a) to (d) will be specifically described below.

(Step (a))
As shown in FIG. 3B, when starting press working of the material M, the dies 12L, 12R and the pad 13 attached to the press device 20 are positioned at the top dead center. In this state, the material M is placed on the punch top surface 111 . In step (a), after the material M is placed on the punch top surface 111, the dies 12L and 12R are moved relatively close to the punch 11, and each die lower side surface 122b is brought into contact with the material M, whereby the material M bend the

More specifically, as shown in FIG. 3C, after the material M is placed on the punch top surface 111, the slide 24 is lowered to move the dies 12L and 12R supported by the slide 24 onto the material M and the punch. Lower towards 11. At this time, the pad 13 also descends toward the material M and the punch 11 together with the dies 12L and 12R. The pad 13 contacts and presses the material M on the punch top surface 111 . More specifically, the pad 13 presses the portion of the material M located in the center in the width direction of the mold 10 from above.

As shown in FIG. 3D, the slide 24 is further lowered while the material M is sandwiched between the pad 13 and the punch top surface 111 . At this time, the dies 12L and 12R are lowered relative to the pad 13 by contraction of the elastic member 25 connecting the pad 13 to the slide 24 . As a result, the die lower side surfaces 122b of the die side surfaces 122L and 122R come into contact with the material M. As shown in FIG. Each die lower side surface 122b contacts the material M at a concave intermediate portion 122e after contacting the material M at a connection portion 122d with the die flange surfaces 123L and 123R. As the dies 12L and 12R descend, the material M is guided by the concave intermediate portion 122e, and is greatly bent so as to form a convex shape on the side opposite to the direction in which the dies 12L and 12R approach the punch 11, that is, upward. go. The portion of the material M sandwiched between the pad 13 and the punch top surface 111 does not float, and the molding of the material M proceeds. The state in which the material M is sandwiched between the pad 13 and the punch top surface 111 is maintained until the completion of molding.

(Step (b))
In step (b), the dies 12L and 12R are brought closer to the punch 11 while the material M is bent, and the upper side surfaces 122a of the dies are brought into contact with the material M. As shown in FIG. More specifically, as shown in FIG. 3E, the dies 12L and 12R are further lowered to bring the connecting portion 122c of each die lower side surface 122b to the die upper side surface 122a into contact with the material M. As shown in FIG. Thereafter, when the dies 12L and 12R are further lowered, each die upper side surface 122a contacts the material M.

(Step (c))
In step (c), the dies 12L and 12R are brought closer to the punch 11 while keeping the die upper side surfaces 122a in contact with the material M, so that the die upper side surfaces 122a bend the material M back. As shown in FIG. 3F, as the dies 12L, 12R are lowered, the flexure of the material M is bent back between the die upper side surfaces 122a and the punch side surfaces 113L, 113R. The deflection of the material M gradually reduces as the dies 12L and 12R descend and the dies 12L and 12R approach the punch 11. As shown in FIG. Also, the material M winds around the punch shoulders 112L and 112R.

(Step (d))
In step (d), as shown in FIG. 3G, the punch 11 and the dies 12L, 12R are closed, and between the punch shoulders 112L, 112R and the die shoulders 121L, 121R, and between the punch side surfaces 113L, 113R and the left and right die upper side surfaces. The material M is sandwiched between 122a, 122a. As a result, the material M becomes the press-molded product 30 . More specifically, by causing the dies 12L and 12R to reach the bottom dead center, the material M is pressed between the punch shoulders 112L and 112R and the die shoulders 121L and 121R, forming bent portions of the press-formed product. be. In addition, the material M is pressed between the punch side surface 113L and the die upper side surface 122a of the left die 12L, and between the punch side surface 113R and the die upper side surface 122a of the right die 12R. is formed. At this time, the ends of the material M, that is, the lower ends of the vertical walls of the press-formed product 30 are not in contact with the die side surfaces 122L and 122R. When the dies 12L and 12R reach the bottom dead center, the deflection of the material M is completely bent back to form both vertical walls of the press-formed product 30.例文帳に追加

When the die 12L reaches the bottom dead center and the punch 11 and the die 12L are in a completely closed state, the clearance between the punch side face 113L and the die upper side face 122a of the die 12L is greater than the plate thickness t of the material M. is preferably small. Similarly, when the die 12R reaches the bottom dead center and the punch 11 and the die 12R are in a closed state, the clearance between the punch side face 113R and the die upper side face 122a of the die 12R is the plate thickness t of the material M. is preferably smaller than More preferably, the clearance between the punch side surfaces 113L, 113R and the left and right die upper side surfaces 122a, 122a is 0.85 times or more and 0.95 times the plate thickness t of the material M. The clearance between punch shoulders 112L, 112R and die shoulders 121L, 121R is typically equal to the clearance between punch sides 113L, 113R and left and right die upper sides 122a, 122a.

The entire material M contacts the punch 11 when the dies 12L and 12R reach the bottom dead center and the punch 11 and the dies 12L and 12R are completely closed. When the punch 11 and the dies 12L, 12R are completely closed, the blank M takes a shape along the punch top surface 111, punch shoulders 112L, 112R, and punch side surfaces 113L, 113R. Therefore, in a cross section obtained by cutting the punch 11 and the material M after molding on a plane consisting of the vertical direction and the width direction, the portions of the material M that are in contact with the punch side surfaces 113L and 113R, that is, both vertical walls of the press-formed product 30 with the vertical direction (acute angle side) is substantially the same as the angles θ _L and θ _R of the punch side surfaces 113L and 113R.

[Press molded product]
FIG. 4 is a diagram illustrating a press-formed product 30 manufactured by the manufacturing method according to this embodiment. The press-formed product 30 has a substantially U-shape in cross-sectional view. The press-formed product 30 includes a top plate 31, left and right vertical walls 32L and 32R, and left and right bent portions 33L and 33R. The upper end of the left vertical wall 32L is connected to the left edge of the top plate 31 via the left bent portion 33L. The upper end of the right vertical wall 32R is connected to the right edge of the top plate 31 via the right bent portion 33R. The lower ends of the vertical walls 32L and 32R are free ends.

In the press-formed product 30 shown in FIG. 4, the top plate 31 has a flat shape. However, when the punch top surface 111 is provided with a groove or a stepped portion, the top plate 31 of the press-formed product 30 is formed with a grooved portion or a stepped portion corresponding to the punch top surface 111 . The top plate 31 may be provided with one or more through holes. The through hole may be a simple round hole, or may be a hole (burring hole) formed by burring and having a protruded hole edge. The through-holes in the top plate 31 can be formed after the press-molded product 30 is molded by the mold 10 .

A press-formed product 30 shown in FIG. 4 has a linear shape when viewed from the top plate 31 side (in plan view). Moreover, the press-formed product 30 shown in FIG. 4 has a linear shape when viewed from the side of the vertical wall 32L or the vertical wall 32R (in a side view). However, as shown in FIG. 5, the press-formed product 30 may have a curved or bent shape in plan view. Alternatively, as shown in FIG. 6, the press-formed product 30 may have a curved or bent shape when viewed from the side.

The shape of the press-formed product 30 may be a combination of two or more types of linear portions and curved portions or bent portions in plan view. Further, the shape of the press-formed product 30 may be a shape in which two or more types of linear portions and curved portions or curved portions are combined in a side view. Further, the press-formed product 30 may have a shape such as a three-pronged shape or a four-pronged shape in plan view, in which a portion having a substantially U-shaped cross section branches into a plurality of branches. The press-formed product 30 may have a uniform cross-sectional shape over its entirety, or may have a cross-sectional shape that changes along the way.

[effect]
When press working is performed using the die 10 according to the present embodiment, the plate-shaped material M is greatly bent by each die lower side surface 122b in the process of being formed into the press-formed product 30. As shown in FIG. Each die lower side surface 122b has a concave shape outward in the width direction with respect to the die upper side surface 122a, thereby guiding and bending the material M so as to form an upward convex shape. As the dies 12L and 12R approach the punch 11, the material M comes into contact with the upper side surfaces 122a of the dies, and the material M is gradually bent back. The deflection of the material M decreases as the dies 12L and 12R approach the punch 11, and remains in the gaps between the punch side surfaces 113L and 113R and the die upper side surfaces 122a. When the punch 11 and the dies 12L, 12R are finally closed, the flexure of the material M is completely bent back and disappears. and each die upper side surface 122a.

As described above, in the present embodiment, the material M is bent and bent back so as to form an upwardly convex shape during the press working process. As a result, during press working, a tensile stress is generated on the side of the punch 11, particularly in the portions of the material M that will become the vertical walls 32L and 32R of the press-formed product 30, and on the side of the dies 12L and 12R opposite to the punch 11. Compressive stress can occur. On the other hand, at the bent portions 33L and 33R formed by the punch shoulders 112L and 112R, compressive stress is generated on the punch 11 side and tensile stress is generated on the die 12L and 12R side during press working. Therefore, the stress generated by bending back the deflection of the material M cancels out the stress in the bent portions 33L and 33R, thereby reducing the stress in the bent portions 33L and 33R. Due to the stress remaining in the bent portions 33L and 33R and the stress remaining in the unbent portion at the bottom dead center of the molding, the press-formed product 30 removed from the mold 10 has a wall-opening moment and a wall-closing moment. cancel each other out. Therefore, it is possible to reduce the wall opening moment that occurs in the press-molded product 30 when the mold is released. As a result, springback in the press-formed product 30 can be reduced, and the dimensional accuracy of the press-formed product 30 can be improved. Further, when the material M is press-worked using the die 10, it is only necessary to lower the dies 12L and 12R directly below. Therefore, a cam mechanism or the like for moving the dies 12L and 12R in a particular direction is not required, and the mold 10 can be of a simple structure.

In the mold 10 according to the present embodiment, H2/H1 is 1.0 or more and 5.0 or less, where H1 is the upper height of the die side surfaces 122L and 122R and H2 is the lower height of the die side surfaces 122L and 122R. is set. As a result, a sufficient length of the concave die lower side surface 122b is ensured on each of the die side surfaces 122L and 122R. can let Therefore, it is possible to effectively exhibit the effect of canceling out the stress due to bending back of the deflection.

In the mold 10 according to this embodiment, the top height H1 of the die side surface 122L is set to be 5.0 mm or more larger than the radius of curvature Rd1 of the die shoulder 121L, and the top height H1 of the die side surface 122R is set to the radius of curvature of the die shoulder 121R. Rd1 is increased by 5.0 mm or more, and the ratio of the lower height H2 to the upper height H1: H2/H1 is set to 1.0 or more and 5.0 or less for each of the die side surfaces 122L and 122R. there is Therefore, the length of each die upper side surface 122a can be ensured. Therefore, when the punch 11 and the dies 12L, 12R are finally closed, the material M can be firmly held between the punch side surfaces 113L, 113R and the die upper side surfaces 122a. As a result, the portion of the material M that is bent during press working can be bent back, and the material M can be formed into the shape of the final press-formed product 30 . Therefore, it is possible to reduce the man-hours and costs in manufacturing the press-formed product 30 without performing an additional press working step.

In order to cancel the stress of the bent portions 33L and 33R generated during press working and the moment generated at the time of release by bending back, each die upper side surface 122a in the vicinity of the punch shoulders 112L and 112R and the punch side surfaces 113L and 113R should be aligned. It is important to clamp the material M firmly between them. In the mold 10 according to this embodiment, as described above, the length of each die upper side surface 122a is appropriately ensured, so that the punch side surfaces 113L, 113R and each die upper side surface 122a firmly sandwich the material M. can do. Therefore, the stress of the bent portions 33L and 33R generated during press working and the moment generated during mold release can be effectively canceled by bending back.

When H2/H1 exceeds 5.0, the concave die lower side surface 122b occupies a large proportion of each of the die side surfaces 122L and 122R, and the effect of bending the material M by each die lower side surface 122b is saturated. Moreover, when H2/H1 exceeds 5.0, the cost for manufacturing the mold 10 and the like also increases. Therefore, H2/H1 is preferably 5.0 or less.

In the mold 10 according to the present embodiment, the radius of curvature of the connection portion 122c of each die lower side surface 122b that connects to the die upper side surface 122a is preferably set to 10.0 mm or less. In this case, in each of the die side surfaces 122L and 122R having a predetermined size, the connection portion 122c and the proportion of the connection portion 122c occupied by the die lower side surface 122b are not too large, and the length of the die upper side surface 122a is ensured. easier to do. Therefore, when the punch 11 and the dies 12L, 12R are finally closed, the material M can be more reliably held between the punch side surfaces 113L, 113R and the die upper side surfaces 122a.

Moreover, in the present embodiment, it is preferable that the radius of curvature of the connecting portion 122c is set to 1.0 mm or more. As a result, when the connecting portion 122c comes into contact with the material M during press working, it is possible to prevent the material M from having bite marks or bending peculiarities.

In this embodiment, the intermediate portion 122e of each die lower side 122b includes a curved surface. The intermediate portion 122e has a concave shape outward in the width direction of the mold 10 with respect to the connection portion 122c on the die upper side surface 122a side of the die lower side surface 122b. In this case, on each of the die side surfaces 122L and 122R, the ratio of the lower height H2 to the concave width W2: H2/W2 is preferably 1.0 or more and 5.0 or less. As H2/W2 becomes smaller, the effect of bending the material M by each concave die lower side surface 122b is improved. However, when H2/W2 is less than 1.0, the effect of bending the material M is saturated. Moreover, when H2/W2 is less than 1.0, the cost of manufacturing the mold 10 and the like increases. On the other hand, if H2/W2 exceeds 5.0, the width W2 of the recess becomes smaller than the height H2 of the lower portion, so the effect of bending the material M is reduced.

In this embodiment, the larger the line length L of the intermediate portion 122e of the die lower side surface 122b, the larger the recess of the die lower side surface 122b. The greater the depression of the die lower side surface 122b, the greater the deflection of the material M during press working. In this case, when the material M is firmly sandwiched between the die upper side surface 122a and the punch side surfaces 113L and 113R, the stress of the bent portions 33L and 33R generated during press working and the moment generated during mold release are bent back. can be more effectively counteracted by That is, the greater the wire length L, the better the dimensional accuracy of the press-formed product 30 . Therefore, the line length L is preferably at least 1.03 times the parameter A, more preferably at least 1.08 times.

In the mold 10 according to this embodiment, the clearance between the punch side surfaces 113L and 113R and the die upper side surfaces 122a is smaller than the plate thickness t of the material M when the punch 11 and the dies 12L and 12R are closed. is preferred. It is particularly preferable that the clearance between the punch side surfaces 113L, 113R and each die upper side surface 122a is 0.85 times or more and 0.95 times or less the plate thickness t. As a result, when the punch 11 and the dies 12L, 12R are finally closed in the forming process, the material M is strongly held between the punch side surfaces 113L, 113R and the die upper side surfaces 122a, and the material M is more reliably flexed. bent back to In this case, a greater tensile stress can be generated on the punch 11 side and a greater compressive stress can be generated on the die 12L and 12R side in the portions of the material M that will become the vertical walls 32L and 32R of the press-formed product 30 . Therefore, it is possible to enhance the effect of these stresses canceling out the stresses of the bent portions 33L and 33R. As a result, the springback in the press-formed product 30 can be further reduced, and the dimensional accuracy of the press-formed product 30 can be further improved.

When the material M is pressed by the die 10 according to this embodiment, when the punch 11 and the dies 12L and 12R are finally closed, the material M is sandwiched between the punch side surfaces 113L and 113R and the die upper side surfaces 122a. be done. On the other hand, each die lower side 122b does not substantially contact the blank M. As a result, the load can be applied in a concentrated manner to the portions of the material M that will be the vertical walls 32L and 32R of the press-formed product 30 . In particular, when the clearance between the punch side surfaces 113L, 113R and each die upper side surface 122a is smaller than the plate thickness t of the material M, the portions of the material M that become the vertical walls 32L, 32R of the press-formed product 30 are strengthened. can be pressed.

Each die lower side 122b does not substantially contact the material M when the punch 11 and dies 12L, 12R are fully closed. That is, the portions of the material M that will be the lower ends of the vertical walls 32L, 32R of the press-formed product 30 are not sandwiched between the punch side surfaces 113L, 113R and the die side surfaces 122L, 122R. However, in this portion, only elastic deformation occurs during press working, and no plastic deformation occurs. Therefore, the punch 11 and the dies 12L, 12R are not sandwiched between the punch side surfaces 113L, 113R and the die side surfaces 122L, 122R. When closed, the material M is formed into a shape along the punch 11. - 特許庁

When the punch 11 and the dies 12L and 12R are completely closed and the material M is formed into the press-formed product 30, the lower ends of the vertical walls 32L and 32R of the press-formed product 30 are formed into punch side surfaces 113L and 113L as shown in FIG. 3G. 113R is desirable. That is, it is desirable that the punch side surfaces 113L, 113R have a shape that contacts the entire vertical walls 32L, 32R of the press-formed product 30 when the punch 11 and the dies 12L, 12R are completely closed. However, the punch side surfaces 113L and 113R may have a shape that does not come into contact with the vertical walls 32L and 32R of the press-formed product 30 only at their lower portions. For example, as shown in FIG. 7, the punch side surfaces 113L and 113R may be configured such that only their lower portions have an angle smaller than the opening angle of the vertical walls 32L and 32R. The opening angles of the vertical walls 32L, 32R correspond to the angles θ _L , θ _R formed between the punch side surfaces 113L, 113R and the vertical plane. In this case, when the punch 11 and the dies 12L, 12R are completely closed, the lower ends of the vertical walls 32L, 32R do not contact the punch side surfaces 113L, 113R.

A mold 10 according to this embodiment includes a pad 13 in addition to a punch 11 and dies 12L and 12R. The press device 20 is configured such that the punch 11 and the dies 12L and 12R start forming the material M while the material M placed on the punch top surface 111 is sandwiched between the punch top surface 111 and the pad 13. ing. Therefore, when the material M is pressed using the die 10 and the press device 20, the dies 12L and 12R are brought closer to the punch 11 while the material M is held between the punch top surface 111 and the pad 13. be able to. More specifically, while the material M placed on the punch top surface 111 is sandwiched between the punch top surface 111 and the pad 13, the material M can be deflected by each die lower side surface 122b. Therefore, it is possible to prevent the positional deviation of the material M during press working. Further, by forming the material M while the material M is pressed by the pad 13, the shape of the top plate 31 of the press-formed product 30 can be formed with high accuracy.

For example, as shown in FIG. 8, in order to suppress the wall opening of the press-formed product, preforming is performed so as to swell the material M in a convex shape, and a general punch 41 and a die are applied to the preformed material M. Pressing at 42L and 42R is also conceivable. However, in this case, since a preforming step is required in which the material M is expanded in advance in a step separate from the pressing step, the mold for preforming and the man-hours and costs associated with manufacturing the press-formed product increase. In addition, since the target shape in the preforming step is a relatively gentle convex shape, the amount of deformation of the material M during preforming is within the range of elastic deformation, especially when the strength of the material M is high. Therefore, the material M does not have a gently convex shape after the mold is released from the preforming, but has a flat shape. That is, it is difficult to form the material M into a convex shape in the preforming process.

On the other hand, in the present embodiment, the material M is not preformed, and the material M is formed into the press-formed product 30 in one step. Therefore, the man-hours and cost for manufacturing the press-formed product 30 can be suppressed. Moreover, since the material M is not preformed, the problem of difficulty in forming the material M does not occur.

<Second embodiment>
FIG. 9 is a cross-sectional view of the mold 10A according to the second embodiment. The mold 10A has substantially the same configuration as the mold 10 (FIGS. 1 and 2) according to the first embodiment. The mold 10A differs from the mold 10 according to the first embodiment only in the configuration of the die side surfaces 122L and 122R.

FIG. 10 is a cross-sectional view showing an enlarged right die 12R of the mold 10A. In the mold 10A, the basic configuration of the die side surfaces 122L, 122R of the left and right dies 12L, 12R is common. Therefore, only the configuration of the die side surface 122R of the right die 12R will be described with reference to FIG. 10, and the detailed description of the die side surface 122L of the left die 12L will be omitted.

As shown in FIG. 10, in this embodiment, the intermediate portion 122e of the die lower side surface 122b includes an inclined surface 122f that is inclined with respect to the horizontal plane. A horizontal plane is a cross section when the mold 10 is cut along a plane perpendicular to the vertical direction. When the horizontal plane is projected onto the cross section of the mold 10, it becomes a straight line in the horizontal direction. In the example of this embodiment, the entire intermediate portion 122e is an inclined surface 122f. The inclined surface 122f descends from the connection portion 122c with the die upper side surface 122a toward the outside in the width direction of the mold 10A. On the die side surface 122R, the ratio of the lower height H2 to the upper height H1: H2/H1 is 1.0 or more and 5.0 or less, as in the first embodiment. Further, as in the first embodiment, the top height H1 of the die side surface 122R is 5.0 mm or more larger than the radius of curvature Rd1 of the die shoulder 121R. Even with such a configuration, as in the first embodiment, springback in the press-formed product 30 (FIGS. 4 to 6) can be reduced, and the dimensional accuracy of the press-formed product 30 can be improved. .

On the die side surface 122R, the inclined surface 122f forms an angle ψ (°) with the horizontal plane. The angle ψ is the angle (acute angle side) formed between the inclined surface 122f and the width direction in a cross section obtained by cutting the die 12R along a plane consisting of the vertical direction and the width direction.

In the die side surface 122R, if the angle ψ of the inclined surface 122f is too large, the degree of depression of the die lower side surface 122b with respect to the die upper side surface 122a becomes small. Therefore, the effect of bending the material by the die lower side surface 122b is reduced during press working. The angle ψ is preferably (78−θ _R )° or less in order to sufficiently exhibit the effect. On the other hand, when the angle ψ of the inclined surface 122f becomes small, the effect of bending the material during press working increases, but if the angle ψ is too small, the effect saturates. In addition, as the angle ψ of the inclined surface 122f becomes smaller, the degree of depression of the die lower side surface 122b becomes larger. Therefore, the angle ψ formed by the inclined surface 122f with respect to the horizontal plane is preferably (50−θ _R )° or more. Also on the left die side surface 122L (FIG. 9), the angle of the inclined surface 122f is preferably (50−θ _L )° or more and (78−θ _L )° or less, similarly to the right die side surface 122R. θ _L and θ _R are angles formed by the punch side surfaces 113L and 113R with the vertical plane, respectively, as described in the first embodiment. The angle ψ of the inclined surface 122f may be the same or different between the left and right die side surfaces 122L and 122R.

In the die side surface 122R, the respective curvature radii Rd2 and Rd3 of the connection portion 122c of the die lower side surface 122b to the die upper side surface 122a and the connection portion 122d of the die lower side surface 122b to the die flange surface 123R are the same as in the first embodiment. can be set. Similarly, in the die side surface 122L (FIG. 9), the respective curvature radii Rd2 and Rd3 of the connection portion 122c of the die lower side surface 122b to the die upper side surface 122a and the connection portion 122d of the die lower side surface 122b to the die flange surface 123L are: It can be set in the same manner as in the first embodiment. The clearance between the punch side surfaces 113L, 113R and each die upper side surface 122a can also be set in the same manner as in the first embodiment.

In the examples shown in FIGS. 9 and 10, the entire intermediate portion 122e of each die lower side surface 122b is formed of an inclined surface 122f. However, part of the intermediate portion 122e may be the inclined surface 122f. For example, as shown in FIG. 11, on the die side surfaces 122L and 122R, between the connecting portion 122c between the die upper side surface 122a and the die lower side surface 122b and the inclined surface 122f, there is a width direction in the cross-sectional view of the mold 10A. A straight surface 122g may be provided that extends to . Alternatively, the connecting portion 122c and the inclined surface 122f may be connected via a curved surface (not shown).

Although the embodiments according to the present disclosure have been described above, the present disclosure is not limited to the above embodiments, and various modifications can be made without departing from the scope of the present disclosure.

For example, in each of the embodiments described above, the dies 12L and 12R are arranged above the punch 11 with the die 10 attached to the press device 20 . Further, when the material M is pressed, the dies 12L and 12R are moved toward the punch 11. As shown in FIG. However, contrary to the above embodiments, the dies 12L and 12R may be arranged below the punch 11 when the material M is pressed. Alternatively, the dies 12L and 12R may be brought relatively close to the punch 11 by moving the punch 11 toward the dies 12L and 12R.

The molds 10, 10A according to each of the embodiments described above include symmetrical dies 12L, 12R. However, the left die 12L and the right die 12R need not have strictly symmetrical shapes and dimensions.

In the first embodiment described above, the intermediate portion 122e of each die lower side surface 122b is mainly configured by a curved surface. On the other hand, in the above-described second embodiment, the intermediate portion 122e of each die lower side surface 122b is mainly composed of a straight inclined surface 122f. A mold according to the present disclosure can also be configured by combining these embodiments. That is, in one of the dies 12L and 12R, the middle portion 122e of the die lower side surface 122b is mainly curved, as in the first embodiment (FIG. 2), and in the other of the dies 12L and 12R, the intermediate portion 122e of the second embodiment is formed. As shown in FIG. 10 or 11, the intermediate portion 122e of the die lower side surface 122b may be composed mainly of the inclined surface 122f. Alternatively, only one of the dies 12L, 12R may be provided with the concave die lower side surface 122b and the other of the dies 12L, 12R may not be provided with the concave die lower side surface 122b.

The molds 10 and 10A according to each of the above embodiments are provided with pads 13 . However, the molds 10 and 10A do not have to be provided with the pad 13 . For example, when the width of the punch top surface 111 (the top plate 31 of the press-formed product 30) is relatively short when the molds 10 and 10A are viewed in cross section, or when the punch top surface 111 has no grooves or steps. In the case of having a flat shape, even if the upper die is composed only of the dies 12L and 12R, the press-formed product 30 with high dimensional accuracy can be obtained in one process.

However, when the width of the punch top surface 111 is relatively long when the dies 10 and 10A are viewed in cross section, or when the punch top surface 111 is provided with grooves, steps, etc., the die 12L and the die Pad 13 is preferably present between 12R. Alternatively, the die 12L may be provided with a die top surface extending from the die shoulder 121L to the die 12R side, and the die 12R may be provided with a die top surface extending from the die shoulder 121R to the die 12L side. Alternatively, by integrally forming the dies 12L and 12R, the connecting portion with the dies 12L and 12R can be the die top surface. Also, another mold may be provided between the dies 12L and 12R. The top plate 31 of the press-formed product 30 is given a predetermined shape by sandwiching the material M between the pad 13, the top surface of the die, or another mold between the dies 12L and 12R, and the top surface 111 of the punch. It is possible to obtain the press-formed product 30 with good dimensional accuracy in one process.

Between the molds 10 and 10A provided with the die top surface and the molds 10 and 10A provided with the pad 13, the latter is preferable. In the case of the dies 10 and 10A provided with the die top surface, the material M is sandwiched between the die top surface and the punch top surface 111 when the dies 12L and 12R reach the bottom dead center. The material M on the punch top surface 111 cannot be pressed by the die top surface. On the other hand, in the case of the molds 10 and 10A provided with the pad 13, the material M on the punch top surface 111 can be pressed by the pad 13 from the initial stage of press working. By forming the material M in a state where the material M is pressed by the pad 13, it is possible to prevent the positional deviation of the material M during press working and prevent unexpected deformation behavior of the material M on the punch top surface 111. (behavior of deflection) can be suppressed. Also, the shape of the top plate 31 of the press-formed product 30 can be formed with high accuracy. Therefore, it is preferable that the molds 10 and 10A are provided with the pads 13 as in the above embodiments.

In the first embodiment, the intermediate portion 122e of each die lower side surface 122b is formed by a curved surface that smoothly continues from the upper connecting portion 122c to the lower connecting portion 122d. In the second embodiment, the intermediate portion 122e of each die lower side surface 122b is substantially composed of a single inclined surface 122f continuous from the upper connecting portion 122c to the lower connecting portion 122d. However, the shape of the intermediate portion 122e is not limited to these. For example, the intermediate portion 122e may be provided with a step.

The present disclosure will be described in more detail below by way of examples. However, the present disclosure is not limited to the following examples.

[First embodiment]
In order to confirm the effect of the present disclosure, the mold 10 according to the first embodiment (FIGS. 1 and 2) or the mold 10A according to the second embodiment (FIGS. 9 and 10) was used, and the tensile strength TS = A CAE analysis was carried out for press forming of a material (steel plate) having a thickness of 1180 MPa and a plate thickness of t=1.6 mm into a press-formed product 30 having a substantially U-shaped cross section. In the press-formed product 30, the bend R (curvature radius inside the bend) of the bent portions 33L and 33R was set to 8.0 mm, and the opening angle θ of the vertical walls 32L and 32R was set to 5°. The bending R of the bent portions 33L, 33R corresponds to the radius of curvature Rp of the punch shoulders 112L, 112R. The opening angle θ _{of the vertical walls 32L, 32R corresponds to the angles θ L , θ R of} the punch side surfaces 113L, 113R described in the above embodiment.

Commercially available software (LS-DYNA ver971 rev7.12, manufactured by ANSYS) is used for CAE analysis, molding analysis and springback analysis are performed, and the amount of change in the opening angle of the vertical walls 32L and 32R after springback Δθ (°) was evaluated. Δθ is the opening angle θ of the vertical walls 32L and 32R in the press-molded product 30 before removal from the mold 10 (before release), and the vertical angle θ after removal from the molds 10 and 10A (after release). It is the difference from the opening angle θ (°) of the walls 32L and 32R. A smaller Δθ means that the springback is reduced and the dimensional accuracy of the press-formed product 30 is improved.

Table 1 shows the analysis results (Nos. 1 to 18) when using the mold 10 (FIGS. 1 and 2) according to the first embodiment. In the mold 10, the intermediate portion 122e of the die lower side surface 122b is mainly composed of curved surfaces. In this analysis, the line length L of the intermediate portion 122e of the die lower side surface 122b on the left and right die side surfaces 122L, 122R was set to 1.08×A. Parameter A is represented by the following equation.
A=((H2-Rd2-Rd3) ² +(W2-Rd2-Rd3) ² ) ^0.5

The radius of curvature Rd1 of the die shoulders 121L and 121R was 9.6 mm, and the radius of curvature Rd3 of the connecting portion 122d of the die lower side surface 122b to the die flange surfaces 123L and 123R was 4.0 mm. For comparison, Table 1 also shows analysis results (comparative example) when using a general mold, that is, a mold in which the die side surfaces 122L and 122R are not provided with the concave die lower side surfaces 122b. .

As shown in Table 1, the amount of change Δθ in the opening angle of the vertical walls 32L and 32R after springback is All of 1 to 18 were smaller than the comparative example. However, the top height H1 of the die side surfaces 122L, 122R is 3.0 mm larger than the radius of curvature Rd1 of the die shoulders 121L, 121R. 1 (H1-Rd1=3.0), the amount of change Δθ in the opening angle exceeded 7.0°, and the effect of reducing Δθ was small. This is because the length of each die upper side surface 122a is short, so that each die upper side surface 122a cannot sufficiently hold down the material when the punch 11 and the dies 12L and 12R are closed (bottom dead center). it is conceivable that.

On the other hand, the top height H1 of the die side surfaces 122L and 122R is 5.0 mm larger than the radius of curvature Rd1 of the die shoulders 121L and 121R. 3 (H1-Rd1=5.0), the amount of change Δθ in the opening angle was 5.0° or less. No. Δθ in 3 is 4.6°, which is less than half of the comparative example. The top height H1 of the die side surfaces 122L, 122R is 12.0 mm larger than the radius of curvature Rd1 of the die shoulders 121L, 121R. 2 (H1-Rd1=12.0), the opening angle variation Δθ was 2.1°, which was smaller. From this result, in order to effectively reduce the springback and significantly improve the dimensional accuracy of the press-formed product 30, the upper height H1 of the die side surfaces 122L, 122R should be less than the radius of curvature Rd1 of the die shoulders 121L, 121R. should also be increased by 5.0 mm or more (H1-Rd1≧5.0).

No. 4 in which the radius of curvature Rd2 of the connecting portion 122c between the die upper side surface 122a and the concave die lower side surface 122b is 1.0 mm. 4, the change amount Δθ of the opening angle was 1.8°, which was significantly smaller than that of the comparative example. In addition, No. 1 in which the radius of curvature Rd2 of the connecting portion 122c is 10.0 mm. 5, the amount of change Δθ in the opening angle was 3.6°, which was significantly smaller than that of the comparative example. On the other hand, no. In No. 11, the amount of change Δθ in the opening angle was 7.0° or less, but exceeded 5.0°. No. In No. 11, although the effect of reducing Δθ was obtained, the extent of the effect was low. Smaller than 5. Therefore, when the radius of curvature Rd2 of the connection portion 122c is 10.0 mm or less, the springback is more effectively reduced, and the dimensional accuracy of the press-formed product 30 is further improved.

No. 5, in which the radius of curvature Rd2 of the connecting portion 122c is 0.5 mm. In No. 10, the amount of change Δθ in the opening angle is 1.7°, and the radius of curvature Rd2 is 1.0 mm. 4 and almost the same. However, no. In 10, the bending habit remained in the material. Therefore, it is preferable that the curvature radius Rd2 of the connection portion 122c is 1.0 mm or more.

No. 1 in which the ratio of the lower height H2 to the upper height H1 on the die side surfaces 122L and 122R: H2/H1 is 1.0. 6, the amount of change Δθ in the opening angle was 2.8°, which was significantly smaller than that of the comparative example. Moreover, No. 1, which has an H2/H1 ratio of 3.0. 2, the amount of change Δθ in the opening angle was 2.1°, which was significantly smaller than that of the comparative example. On the other hand, no. In No. 12, the amount of change Δθ in the opening angle exceeded 7.0°, and the effect of reducing Δθ was small. Therefore, it can be said that by setting H2/H1 to 1.0 or more, the springback is effectively reduced, and the dimensional accuracy of the press-formed product 30 is significantly improved.

No. 1, in which the ratio of the lower height H2 to the upper height H1: H2/H1 on the die side surfaces 122L and 122R is 5.0. 7, the amount of change Δθ in the opening angle was 0.8°, which was significantly smaller than that of the comparative example. No. with H2/H1 set to 6.0. In No. 14, the amount of change Δθ in opening angle is 0.8°. was equivalent to 7. That is, when H2/H1 exceeds 5.0, the effect of reducing springback and the accompanying effect of improving the dimensional accuracy of the press-formed product 30 are saturated. Further, if H2/H1 exceeds 5.0, the size of the die 10 increases due to the lengthening of the die lower side surface 122b, and the cost of the die 10 increases. Therefore, it can be said that the dimensional accuracy of the press-formed product 30 can be efficiently improved by setting H2/H1 to 5.0 or less.

No. 1 in which the ratio of the lower height H2 to the concave width W2 on the die side surfaces 122L and 122R: H2/W2 is 1.0. 8, the amount of change Δθ in the opening angle was 1.3°, which was significantly smaller than that of the comparative example. No. 1, in which H2/W2 is 2.0. 2, and No. 2 with H2/W2 of 5.0. 9, the amounts of change Δθ in the opening angle are 2.1° and 3.2°, respectively, which are significantly smaller than those of the comparative example. On the other hand, no. In No. 13, the amount of change Δθ in the opening angle was 7.0° or less, but exceeded 5.0°. No. In No. 13, although the effect of reducing Δθ was obtained, the extent of the effect was low. Smaller than 9. Therefore, in order to more effectively reduce springback and further improve the dimensional accuracy of the press-formed product 30, H2/W2 is preferably 5.0 or less.

No. with H2/W2 set to 0.5. In No. 15, the amount of change Δθ in the opening angle is 1.3°. Equivalent to 8. That is, when H2/W2 is less than 1.0, the effect of reducing springback and the accompanying effect of improving the dimensional accuracy of the press-formed product 30 are saturated. Also, if H2/W2 is less than 1.0, the width W2 of the recess becomes large relative to the height H2 of the lower portion, which increases the size of the mold 10 and increases the cost of the mold 10 . Therefore, in order to improve the dimensional accuracy of the press-formed product 30 more efficiently, it is preferable that H2/W2 is 1.0 or more.

No. In 16 to 18, the clearance CL between the punch side surfaces 113L and 113R and each die upper side surface 122a when the punch 11 and the dies 12L and 12R are closed is smaller than the plate thickness t of the material. No. The clearance CL at 16 to 18 is 0.97 times (CL/t = 0.97), 0.95 times (CL/t = 0.95), and 0.85 times (CL/t) the plate thickness t, respectively. t=0.85). No. 1 with CL/t of 0.97. In No. 16, the amount of change Δθ in opening angle is 2.0° and CL/t is 1.00. slightly less than 2. On the other hand, no. In No. 17, the amount of change Δθ in the opening angle is 1.2°. 2 was significantly smaller. No. 1 with CL/t of 0.85. In No. 18, the amount of change Δθ in the opening angle was further reduced to 0.6°. Therefore, in order to further improve the dimensional accuracy of the press-formed product 30, the clearance CL is preferably smaller than the plate thickness t of the material, and is 0.85 to 0.95 times the plate thickness t. is particularly preferred.

Table 2 shows the analysis results (Nos. 19 to 36) when using the mold 10A (FIGS. 9 and 10) according to the second embodiment. In the mold 10A, an intermediate portion 122e of the die lower side surface 122b is mainly composed of a straight inclined surface 122f. Hereinafter, for convenience of explanation, the die 10A is referred to as a straight type, and the die 10 in which the intermediate portion 122e of the die lower side surface 122b is mainly curved is referred to as a curved type.

In this analysis, the line length L of the intermediate portion 122e of the die lower side surface 122b on the left and right die side surfaces 122L and 122R is 1.00×A because the intermediate portion 122e is linear. Parameter A is represented by the following equation. The radius of curvature Rd1 of the die shoulders 121L and 121R was 9.6 mm, and the radius of curvature Rd3 of the connecting portion 122d of the die lower side surface 122b to the die flange surfaces 123L and 123R was 4.0 mm.
A=((H2-Rd2-Rd3) ² +(W2-Rd2-Rd3) ² ) ^0.5

The comparative examples in Table 2 are the same as the comparative examples in Table 1. As shown in Table 2, the amount of change Δθ in the opening angle of the vertical walls 32L and 32R after springback is All of 19 to 36 were smaller than the comparative example. However, the top height H1 of the die side surfaces 122L, 122R is 3.0 mm larger than the radius of curvature Rd1 of the die shoulders 121L, 121R. 19 (H1-Rd1=3.0), curve type No. 1 (Table 1), the amount of change Δθ in the opening angle exceeded 7.0°, and the effect of reducing Δθ was small.

On the other hand, the top height H1 of the die side surfaces 122L and 122R is 5.0 mm larger than the radius of curvature Rd1 of the die shoulders 121L and 121R. 21 (H1-Rd1=5.0), the amount of change Δθ in the opening angle was 5.0° or less. No. Δθ in No. 21 is 4.8°, which is less than half that of the comparative example. The top height H1 of the die side surfaces 122L, 122R is 12.0 mm larger than the radius of curvature Rd1 of the die shoulders 121L, 121R. 20 (H1-Rd1=12.0), the opening angle variation Δθ was 2.9°, which was smaller. From this result, in the case of the linear type mold 10A as well as the curved type mold 10, in order to effectively reduce the springback and improve the dimensional accuracy of the press-formed product 30, the die side surface 122L, The top height H1 of 122R must be 5.0 mm or more larger than the radius of curvature Rd1 of the die shoulders 121L and 121R (H1-Rd1≧5.0).

No. 4 in which the radius of curvature Rd2 of the connecting portion 122c between the die upper side surface 122a and the concave die lower side surface 122b is 1.0 mm. In No. 22, the amount of change Δθ in the opening angle was 2.1°, which was significantly smaller than in the comparative example. In addition, No. 1 in which the radius of curvature Rd2 of the connecting portion 122c is 10.0 mm. 23, the amount of change Δθ in the opening angle was 4.1°, which was significantly smaller than that of the comparative example. On the other hand, no. In No. 29, the amount of change Δθ in the opening angle was 7.0° or less, but exceeded 5.0°. No. In No. 29, although the effect of reducing Δθ was obtained, the extent of the effect was low. Smaller than the 23. Therefore, in the case of the straight type mold 10A as well as the curved type mold 10, when the curvature radius Rd2 of the connection portion 122c is 10.0 mm or less, the springback is effectively reduced, and the press-formed product 30 is formed. It can be seen that the dimensional accuracy is further improved.

No. 5, in which the radius of curvature Rd2 of the connecting portion 122c is 0.5 mm. In No. 28, the amount of change Δθ in the opening angle is 1.9°, and the radius of curvature Rd2 is 1.0 mm. slightly reduced compared to 22. However, no. In 28, the bending habit remained in the material. Therefore, even in the case of the linear type mold 10A, the radius of curvature Rd2 of the connecting portion 122c is preferably 1.0 mm or more.

No. 1 in which the ratio of the lower height H2 to the upper height H1 on the die side surfaces 122L and 122R: H2/H1 is 1.0. In No. 24, the amount of change Δθ in the opening angle was 4.6°, which was significantly smaller than that of the comparative example. Moreover, No. 1, which has an H2/H1 ratio of 3.0. 20, the amount of change Δθ in the opening angle was 2.9°, which was significantly smaller than that of the comparative example. On the other hand, no. In No. 30, the amount of change Δθ in the opening angle exceeded 7.0°, and the effect of reducing Δθ was small. Therefore, in the case of the linear type mold 10A as well as the curve type mold 10, by setting H2/H1 to 1.0 or more, the springback is effectively reduced, and the dimensional accuracy of the press-formed product 30 is reduced. can be said to improve significantly.

No. 1, in which the ratio of the lower height H2 to the upper height H1: H2/H1 on the die side surfaces 122L and 122R is 5.0. 25, the amount of change Δθ in the opening angle was 1.8°, which was significantly smaller than that of the comparative example. No. with H2/H1 set to 6.0. In No. 32, the amount of change Δθ in the opening angle is 1.8°. 25. That is, when H2/H1 exceeds 5.0, the effect of reducing springback and the accompanying effect of improving the dimensional accuracy of the press-formed product 30 are saturated. Also, even in the linear type mold 10A, if H2/H1 exceeds 5.0, the size of the mold 10A increases due to the lengthening of the die lower side surface 122b, which increases the cost of the mold 10A. Therefore, it can be said that the dimensional accuracy of the press-formed product 30 can be efficiently improved by setting H2/H1 to 5.0 or less.

The sum of the angle ψ (°) of the inclined surface 122f of the die lower side surface 122b on the die side surfaces 122L and 122R and the opening angle θ (°) of the vertical walls 32L and 32R of the press-formed product 30: No when ψ+θ is 50° . 26, the amount of change Δθ in the opening angle was 1.4°, which was significantly smaller than that of the comparative example. No. in which ψ+θ is 78°. 27, the amount of change Δθ in the opening angle was 4.4°, which was significantly smaller than that of the comparative example. On the other hand, no. In No. 31, the amount of change Δθ in the opening angle was 7.0° or less, but exceeded 5.0°. No. In No. 31, although the effect of reducing Δθ was obtained, the extent of the effect was low. Smaller than the 27. Therefore, in order to effectively reduce the springback and further improve the dimensional accuracy of the press-formed product 30 in the linear type mold 10A, the angle ψ of the inclined surface 122f is (78−θ)° or less. is preferred.

of the inclined surface 122f and the opening angle .theta. In No. 33, the amount of change Δθ in the opening angle is 1.4°. 26. That is, when ψ+θ is less than 50°, the effect of reducing springback and the accompanying effect of improving the dimensional accuracy of the press-formed product 30 are saturated. Moreover, if ψ+θ is less than 50°, the size of the mold 10A increases, and the cost of the mold 10A increases. Therefore, in order to improve the dimensional accuracy of the press-formed product 30 more efficiently, it is preferable that the angle ψ of the inclined surface 122f is (50−θ)° or more.

No. In 34 to 36, the clearance CL between the punch side surfaces 113L and 113R and each die upper side surface 122a is smaller than the plate thickness t of the material. No. The clearance CL at 34 to 36 is 0.97 times (CL/t = 0.97), 0.95 times (CL/t = 0.95), and 0.85 times (CL/t) the plate thickness t, respectively. t=0.85). No. 1 with CL/t of 0.97. In No. 34, the amount of change Δθ in opening angle is 2.8°, and CL/t is 1.00. slightly less than 20. On the other hand, no. In No. 35, the amount of change Δθ in the opening angle is 1.9°. significantly smaller than 20. No. 1 with CL/t of 0.85. 36, the amount of change Δθ in the opening angle was further reduced to 1.2°. Therefore, in the case of the linear type die 10A as well as the curved type die 10, in order to further improve the dimensional accuracy of the press-formed product 30, the clearance CL should be smaller than the plate thickness t of the material. It is preferably 0.85 times or more and 0.95 times or less the plate thickness t, particularly preferably.

[Second embodiment]
A CAE analysis was performed on the molds 10 and 10A under the same basic conditions as in the first embodiment, and differences in effects depending on the presence or absence of the pad 13 and the presence or absence of the die top surface were verified. Table 3 shows the analysis results.

Comparative example in Table 3, No. 2, and no. 20 are comparative examples in the first embodiment, and Nos. 2, and no. 20. No. The conditions of P2 were the same as those of No. 1 except that the mold 10 was not provided with the pads 13 . It is the same as the condition of 2. No. The conditions of P20 were the same as those of No. 1 except that the mold 10A was not provided with the pads 13. 20 conditions. No. The conditions of D2 are the same as those of No. 1 except that the dies 12L and 12R are provided with die top surfaces in place of the pad 13. It is the same as the condition of 2. No. The conditions of D20 are the same as those of No. D20 except that the pads 13 are replaced with the die top surfaces of the dies 12L and 12R. 20 conditions. No. 2, No. P2, No. In D2, the line length L of the intermediate portion 122e of the die lower side surface 122b of the left and right die side surfaces 122L and 122R was set to 1.08×A.

As shown in Table 3, the amount of change Δθ in the opening angle of the vertical walls 32L and 32R after springback is P2, No. D2, No. D20, and No. All P20 values were smaller than those of the comparative example.

However, no. In P2, No. 1 with pad 13; Δθ is larger than that of 2. In addition, no pad 13 is used. In P20, No. 1 with pad 13; Δθ is larger than that of 20. Therefore, in order to further reduce the springback and improve the dimensional accuracy of the press-formed product 30 more efficiently, it is preferable to provide the pad 13 for pressing the material between the left and right dies 12L and 12R.

No. 4, in which die top surfaces are provided on the dies 12L and 12R instead of the pad 13; In D2, No. 1 with pad 13; Although Δθ was larger than that of No. 2, No. 2 had no pad 13 and no die top surface. Δθ became smaller than that of P2. In addition, No. 1 has die top surfaces instead of pads 13 on dies 12L and 12R. In D20, No. 1 with pad 13; Δθ was larger than that of No. 20, but No. 2 had no pads 13 and no die top surface. Δθ became smaller than that of P20. Therefore, in order to further reduce springback and improve the dimensional accuracy of the press-formed product 30 more efficiently, it is preferable that there is a die top surface for holding down the material, and it is more preferable that there is a pad 13 .

[Third embodiment]
A CAE analysis was performed on the mold 10 under the same basic conditions as in the first example, and differences in effects depending on the size of the line length L of the intermediate portion 122e of the die lower side surface 122b were verified. Table 4 shows the analysis results. Table 4 shows values obtained by dividing the wire length L by the parameter A expressed by the following equation.
A=((H2-Rd2-Rd3) ² +(W2-Rd2-Rd3) ² ) ^0.5

Comparative examples in Table 4 and No. 2 are comparative examples in the first embodiment, and No. 1, respectively. 2. No. 200 conditions are No. 2, the line length L is 1.08 times the parameter A, but H2/W2 is No. 2 different. No. The condition of No. 201 is that the line length L is 1.01 times the parameter A, and the depression of the intermediate portion 122e (die lower side surface) is No. 201. It is less than 200 and almost linear. No. The condition of 202 is that the line length L is 1.03 times the parameter A, and the depression of the intermediate portion 122e (die lower side surface) is No. 202; less than 200. No. The condition of 203 is that the line length L is 1.06 times the parameter A, and the depression of the intermediate portion 122e (die lower side surface) is No. 203; 202 but no. less than 2 No. In the condition of 204, the line length L is 1.10 times the parameter A, and the depression of the intermediate portion 122e (die lower side surface) is the largest in Table 4.

As shown in Table 4, the amount of change Δθ in the opening angle of the vertical walls 32L and 32R after springback is 200, No. 201, No. 202, No. 203, and No. In all of 204, it became smaller than the comparative example.

In descending order of wire length L, that is, No. 204, No. 200, No. 203, No. 202, No. Since Δθ is smaller in the order of 201, it can be said that the longer the line length L is, the more preferable it is. That is, the larger the wire length L, the larger the depression of the intermediate portion 122e (the lower side surface of the die), and the greater the deflection of the material M during press working. The greater the deflection of the material M during press working, the greater the stress in the bent portions 33L and 33R generated during press working when the material M is firmly held between the die upper side surface 122a and the punch side surfaces 113L and 113R. The moment generated at the time of mold release can be canceled more effectively by bending back.

As shown in Table 4, no. 200, and No. In 202 to 204, the amount of change Δθ in the opening angle was remarkably smaller than in the comparative example. No. 4, in which the line length L is 1.08 times or more of the parameter A. 200, and No. At 204, Δθ is even smaller. Therefore, the line length L is preferably 1.03 times the parameter A or more, and more preferably 1.08 times the parameter A or more.

No. 2, No. 200, the line length L is 1.08 times the parameter A; 2 is No. H2/W2 is smaller than 200. No. 2, the amount of change Δθ in the opening angle is No. smaller than 200.

10, 10A: mold 11: punch 111: punch top surface 112L, 112R: punch shoulder 113L, 113R: punch side surface 12L, 12R: die 121L, 121R: die shoulder 122L, 122R: die side surface 122a: die upper side surface 122b: Die Lower Sides 122c, 122d: Connection Part 122e: Intermediate Part 122f: Inclined Surface 123L, 123R: Die Flange Surface 13: Pad 20: Press Device 30: Press Molded Product

Claims (14)

A mold for pressing a plate-shaped material,
a punch including a punch top surface, a punch side surface, and a punch shoulder defining a corner between the punch top surface and the punch side surface;
a die including a die shoulder corresponding to the punch shoulder, a die side surface corresponding to the punch side surface, and a die flange surface extending outward from the die side surface in the width direction of the mold;
with
The die side surface is
a die upper side surface continuously provided to the die shoulder;
a die lower side surface disposed between the die upper side surface and the die flange surface and having a concave shape outward in the width direction with respect to the die upper side surface;
has
Let H1 be the length in the vertical direction of the die from the upper end of the die shoulder to the lower end of the upper side of the die, and H2 be the length in the vertical direction from the lower end of the upper side of the die to the lower end of the lower side of the die. , H1 is 5.0 mm or more larger than the radius of curvature of the die shoulder, and H2/H1 is 1.0 or more and 5.0 or less. A mold according to claim 1,
The lower side of the die is
a first connecting portion continuously provided to the lower end of the die upper side surface and connecting the die lower side surface to the die upper side surface;
a second connecting portion including the lower end of the die lower side surface and connecting the die lower side surface to the die flange surface;
an intermediate portion disposed between the first connection portion and the second connection portion and positioned outside the first connection portion in the width direction;
Including molds. A mold according to claim 2,
The mold, wherein the first connecting portion has an arcuate shape with a radius of curvature of 1.0 mm or more and 10.0 mm or less in a cross-sectional view of the die. The mold according to claim 2 or 3,
The mold, wherein the intermediate portion includes a curved surface that is concave outward in the width direction with respect to the first connecting portion. A mold according to claim 4,
A mold, wherein H2/W2 is 1.0 or more and 5.0 or less, where W2 is the length in the width direction from the lower end of the die upper side surface to the lower end of the die lower side surface. The mold according to claim 2 or 3,
The mold, wherein the intermediate portion includes an inclined surface that is inclined with respect to a horizontal plane. A mold according to claim 6,
The mold, wherein the angle formed by the inclined surface with the horizontal plane is (50-θ)° or more and (78-θ)° or less, where θ° is the angle formed between the side surface of the punch and the vertical plane. The mold according to any one of claims 1 to 7,
A mold, wherein a clearance between the side surface of the punch and the upper side surface of the die when the punch and the die are in a closed state is smaller than the plate thickness of the material. A mold according to claim 8,
The mold, wherein the clearance is 0.85 times or more and 0.95 times or less the plate thickness. A mold according to any one of claims 1 to 9, further comprising:
A die comprising a pad corresponding to said punch top surface. A press device for forming a press-formed product from a plate-shaped material,
A mold according to claim 10,
The press device is configured to start forming the material with the punch and the die while the material placed on the top surface of the punch is sandwiched between the top surface of the punch and the pad. , press equipment. The press apparatus according to claim 11, further comprising:
A die holder that movably supports the die and the pad integrally,
The press device, wherein the pad is connected to the die holder by an elastic member that can expand and contract. A method for manufacturing a press-molded product,
A first preparation step of preparing the mold according to any one of claims 1 to 10;
a second preparation step of preparing a plate-shaped material;
A molding step of molding the material into the press-molded product using the mold;
with
The molding step includes
After placing the material on the top surface of the punch, the die is brought relatively close to the punch, and the lower side surface of the die is brought into contact with the material to bend the material;
bringing the die closer to the punch while the material is bent, and bringing the upper side surface of the die into contact with the material;
bringing the die closer to the punch while the die upper side is in contact with the material, thereby bending back the flexure of the material with the die upper side;
closing the punch and die to clamp the material between the punch shoulder and the die shoulder and between the punch side and the die top side;
including
The method of manufacturing, wherein the blank conforms to the top surface of the punch, the shoulder of the punch, and the sides of the punch when the punch and the die are fully closed. 14. The manufacturing method according to claim 13,
In the first preparation step, the mold according to claim 10 is prepared,
In the forming step, the material placed on the top surface of the punch is held between the top surface of the punch and the pad, and the material is bent by the lower side surface of the die.

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