JP2001087816A - Press formed member and press forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a press formed member and its forming method having a good formed shape and capable of forming by a conventional press device. SOLUTION: A press formed member is obtained so that many linear recessed parts 11 are press formed for a section e.g. a side wall part 31 of a forming member 30 subjected to bending deformation or bending/bending back deformation in press forming. In the case an interval of the linear recessed parts is P mm and a depth is D mm, a plate thickness of a press forming member is (t) mm, D/P>=0.03×t/1.2, 0.02t<D<=0.5t are satisfied. In a forming method, linear protrusion parts are formed on a forming face of a die, the tip parts of the linear protrusion parts are bitten into a stock, the linear recessed parts having both effects of shape correction and shape forming are press formed for the section subjected to bending deformation or bending/bending back deformation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a press-formed member made of a thin steel sheet, such as a member for an automobile, and a method for forming the same. And the improvement of shape defects (defective dimensional accuracy) such as warpage of the wall portion and change in the angle of the R portion.

[0002]

2. Description of the Related Art A large part of an automobile body is usually composed of a large number of press-formed members formed by pressing a thin steel plate. Various types of these press-formed members formed by draw bending are used. The draw bending forming includes a first forming die having a concave forming surface and a convex forming surface for forming a material metal plate in cooperation with the concave forming surface by relatively moving to the first forming die side. (2) using a mold provided with a plate holding member for holding the material metal plate in a pressed state between the forming die and the plate pressing surface of the first forming die, and using the plate pressing surface of the first forming die and the By moving the second metal mold relatively toward the first molding die, the material metal plate held in a pressed state between the plate holding members is caused to flow from the plate holding surface into the concave molding surface, and the concave molding surface is formed. And a convex molding surface.

[0003] When the above-mentioned draw bending is performed, at the time of forming,
The material metal plate is first subjected to bending deformation at a shoulder transitioning from the plate pressing surface of the first molding die to the concave molding surface, and is subjected to bending back deformation after passing through the shoulder. Such a deformation is called a bending / bending-back deformation. When subjected to the bending and bending-back deformation, the surface portion on the concave molding surface side (outer side surface of the side wall portion of the molding member) is once compressed when passing through the shoulder portion and is stretched after passing, so that tensile stress in the pressing direction is increased. On the other hand, the surface of the molded member on the side of the convex molding surface (the inner surface of the molded member) is stretched once when passing through the shoulder, and is compressed after passing, so that compressive stress remains in the pressing direction and the plate thickness is increased. A stress difference occurs in the direction. On the other hand, the second molding die is bent without being subjected to the bending deformation by the shoulder portion which transitions from the flat top surface to the side portion of the convex molding surface of the second molding die or the first molding die without being bent back. The part that has undergone only deformation (the part molded by the shoulder at the end of molding)
Stresses in different directions remain on the front and back surfaces, and a stress difference occurs in the thickness direction.

[0004] In a part which has undergone such bending deformation or bending-back deformation, the shape of the formed member changes due to the elastic recovery phenomenon after press forming, and the dimension and shape as designed may not be obtained. When such a press-formed member is used, it is difficult to assemble a plurality of members,
There is a problem that joining cannot be performed when joining members (mostly spot welding) after assembly. Further, even if joining can be performed, there is a problem that the dimensions of the entire body or a specific portion of the vehicle body deviate from the design values due to the irregular shape of the members, and a desired design cannot be realized. Such problems are due to the recent increase in the strength of thin steel sheets used for automobile bodies from the viewpoint of weight reduction and safety, and aluminum sheets and the like, which are lightweight but have a significantly lower Young's modulus than steel sheets. There is an increasing problem with the use of materials.

In order to solve such a problem, the following method for improving the shape defect has been employed. For the warpage of the side wall part of the molded member, a method of applying a tensile force to the side wall part at the end of molding to form while molding into the mold. In the process, a method of applying a large compressive force in the thickness direction of the material metal plate (referred to as “determining pressing”). In this case, there is a method in which a molding die (punch) having a convex molding surface in the center of the plate is pressed in a state in which it is completely fixed and the inflow into the concave molding surface is prevented.

[0006]

However, the above-mentioned method requires a special press device, or requires only a step of pulling to be carried out by a normal press. Further, the above method can be carried out relatively easily with a normal press device, but the effect is very small. In addition, the method (1) basically involves pulling the material, and thus has a problem that defects such as breakage are likely to occur in the material during molding. In any case, the conventional method for improving the shape defect has various problems to be implemented by a normal press device.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a press-formed member which has a good formed shape and can be formed by an ordinary press device, and a forming method thereof.

[0008]

In describing the present invention, first, an experiment for improving shape defects based on the present invention will be described. It is considered that most of the shape defects of the press-formed member are caused by residual stress generated on the surface portion of the formed member due to bending deformation or bending-back deformation at the time of forming, and a stress difference occurs in a thickness direction. . For this reason,
The present inventor uses a mold having a linear projection formed on a molding surface, and by making the linear projection bite into a molding member during press molding, material movement in the plane or in the sheet thickness direction. Compressive deformation occurs, and the residual stress on the surface of the molded member and the difference in stress in the thickness direction can be reduced or eliminated, and the molding failure is corrected and improved. An experiment was conducted to improve the warpage of the side wall of the U-shaped member.

[0009] As shown in FIG.
The sample steel plate W (sheet thickness 0.8
mm, 1.2 mm, and 1.6 mm, a high-strength galvanized steel sheet of 440N class with a plate width of 40 mm and a length of 250 mm each) and hold the upper die 141 above the plate holding member 142. The lower die (punch) 143 was pushed into the sample steel plate W, and the U-shaped member 145 was drawn and formed. At this time, the width d (bending width) of the punch used was 48 m.
m, the bending radius of the upper end R of the punch was 5 mm, the pressing depth of the punch was 67 mm, and the urging force of the plate pressing member 142 was about 1 tonf. When the U-shaped member 145 is removed from the mold after the press molding, as shown in FIG. 12, the stress difference generated in the thickness direction of the side wall portions 146 bent on both sides of the bottom wall portion 147 is removed. Then, the side wall portion 146 was warped outward.

In order to correct the warpage of the side wall 146, as shown in FIG. 11, an inner die 148 is provided inside the side wall 146 of the U-shaped member 145, and outer dies 149 and 149 are provided on both outer sides. Pressure was applied by a press in the direction of the arrow in the figure. The U
On the surface of the inner mold 148 or the outer mold 149 facing the inner surface or the outer surface of the side wall portion 146 of the shaped member 145, a linear protrusion 150 having a regular triangular cross section having a height of 1 mm is provided in the width direction (horizontal direction) of the sample steel plate W. ) Or lengthwise (vertically). The case where pressure is applied using the inner mold 148 and the flat outer dies 149 and 149 on which the linear protrusions 150 are formed is called inner pressurization, and conversely, the flat inner mold 148 and the linear protrusions are used. Outer die 14 formed with 150
The case where the pressure is applied by using the pressure of 9, 149 is referred to as outer pressure. FIG. 11 shows an inner mold 1 having a horizontal linear projection 150 formed thereon.
48 shows an example of the inner pressurization using No. 48.

The mold is pressurized with various pressing forces to cause the tip of the linear projection 150 to bite into the steel plate W at various depths. Then, the mold is removed and the warpage δ in the side wall 146 is removed.
, And the wall warpage improvement rate was examined based on this. The wall warpage improvement rate is defined as (δA) where δA is the amount of warpage of the side wall portion of the U-shaped member after press forming, and δB is the amount of warpage after correcting the warpage by performing inner pressing or outer pressing. −δ
B) / δA × 100 (%). From this equation, when the warpage amount δB after correction is 0, the wall warp improvement rate is 100%. FIG. 12 shows the U-shaped member after demolding,
A dashed line indicated by the side wall portion 146 in FIG. 12 is a linear concave portion 151 formed by biting the linear projection portion 150.
Is represented. FIG. 12A shows a linear recess 151 formed when the linear projection 150 is oriented horizontally, and FIG. 12B shows a linear recess 151 formed when the linear projection 150 is oriented vertically. The warpage amount δ is
As shown in FIG. 12 (A), the maximum separation amounts δ1 and δ2 at each side wall portion 146 are measured from a straight line connecting the punch shoulder and the die shoulder at the R stop (the end of the radius), and δ = (δ1 + δ2)
/ 2.

FIG. 14 shows an example of the above experimental results. FIG.
No. 4 indicates that the direction of the linear projection is horizontal, and the interval (pitch P)
Using three types of outer dies of 1, 5 and 10 mm, the outer pressing is performed by changing the rolling force variously, and linear recesses of various depths D are formed in each outer die by biting the linear projections. It is the graph which arranged the relationship between the wall warpage improvement rate at the time of forming in the side wall part, and D / P. From FIG. 14, the relationship between D / P and the wall warpage improvement rate is as follows.
When the plate thickness t is t = 0.8 mm, it is represented as a solid line,
When t = 1.2 mm, it is represented as a broken line, and t = 1.
In the case of 6 mm, it is represented as a dashed line. Than this,
When the D / P is the same value, the warpage improvement effect decreases as the plate thickness increases, and the minimum D / P required to make the wall warp improvement rate 100% is represented by 0.03 t / 1.2. You can see that. That is, D / P is 0.03t / 1.2.
Thus, the warpage is almost completely corrected. Here, D / P is determined in relation to t / 1.2 as described above for the following reason. That is, shape defects such as wall warpage are based on the stress difference in the cross section of the plate thickness. When the plate thickness is reduced, the distribution of the stress becomes shallower in the plate thickness direction (toward the center). As the thickness increases, the depth increases. Therefore, the minimum D / P (minimum D / P) can be changed depending on the plate thickness t. For example, the minimum D / P is small for a thin plate, while the minimum D / P is large for a thick plate. It is based on the reason that it becomes. In addition, when the inner press having the linear projections formed in the horizontal direction was used and the inner pressurization was performed in the same manner as above, substantially the same results as above were obtained. The same shape correction effect was obtained when the outer or inner press was performed using an outer mold or an inner mold whose linear projections were vertically oriented (not shown).

Although the shape correcting effect of the linear concave portion is not always clear, it is presumed as follows. During the draw-bending process, the inside (the punch side) of the side wall portion 146 of the U-shaped member undergoes the bending / bending deformation, so that a compressive stress remains and the outside (the die side) a tensile stress remains. At the time of press forming, as shown in FIG. 13A, the linear projections 150 bite into the inside of the side walls 146 (in the width direction of the plate and the direction perpendicular to the pressing direction) to form the linear recesses 151. Then, compressive deformation occurs in the thickness direction of the side wall portion 146 and the stress difference in the thickness direction is reduced, so that the warpage of the side wall portion 146 after mold release is improved. On the other hand, as shown in FIG.
When the linear concave portion 151 is formed laterally by the bite of the linear protrusion 150 outside the surface, the tensile stress is relaxed by the compression deformation due to the movement of the material caused by the bite of the protrusion on the outer surface portion, Further, since the compressive deformation occurs in the thickness direction, the stress difference in the thickness direction is reduced, and the warpage of the side wall portion is improved. In addition, when the linear projection 151 is formed along the length direction (the direction parallel to the pressing direction) of the side wall portion 146 by the biting of the linear protrusion portion 150 inside or outside the side wall portion 146 (FIG. 12B). )), Compressive deformation occurs in the thickness direction, and the stress difference in the thickness direction is reduced, so that the warpage of the side wall portion is improved.

The present invention based on the above findings is as follows. The press-formed member according to the present invention described in claim 1 is a press-formed member in which a linear concave portion is press-formed at a portion which has undergone bending deformation or bending-back deformation during press forming, and When the interval between the concave portions is Pmm, the depth is Dmm, and the plate thickness of the press-formed member is tmm,
D / P ≧ 0.03 × t / 1.2 and 0.02t <D ≦
0.5t.

According to the present invention, since the predetermined linear concave portion is press-formed at the portion where the press-formed member has undergone the bending deformation or the bending-back deformation, at the time of press-forming the linear concave portion, the molded member is formed. Material movement occurs on the surface, and the residual stress and the stress difference in the sheet thickness direction generated on the surface of the molded member due to bending deformation or bending / unbending deformation are relaxed or eliminated, resulting from these residual stresses and stress differences. Shape defects can be corrected and improved. The linear concave portion is not limited to the entire portion subjected to the bending deformation or the bending / unbending deformation, but may be formed in a part corresponding to a portion where the shape change of the molded member is particularly problematic. Note that, as described below, the linear concave portion can be formed at the same time as press forming by performing press forming using a mold having a predetermined linear protrusion formed on a forming surface, but after press forming. For example, pressure molding may be performed using a pressure roller.

In the present invention, the D / P of the linear concave portion
Is set to 0.03 × t / 1.2 or more based on the result obtained in the previous experiment, and D / P of the linear concave portion is set to 0.03 × t / 1.2. If it is less than 100%, a sufficient shape correction effect of a wall warpage improvement rate of almost 100% cannot be obtained, so that the D / P of the linear concave portion is 0.03 × t.
/1.2 or more, preferably 0.05 × t / 1.2 or more. Also, the reason why D is set to 0.02 t to 0.5 t is that if the depth of the linear concave portion is too shallow, it becomes difficult for the material to flow on the surface portion of the molded member, so that the residual stress on the surface portion can be reduced and the plate thickness can be reduced. It is difficult to eliminate the stress difference in the direction, and it is also difficult to stably form a predetermined linear concave portion. For this reason,
D is more than 0.02t, preferably 0.04t or more, more preferably 0.07t or more. On the other hand, if the depth of the linear concave portion is too deep, the fatigue strength and impact resistance will be significantly deteriorated due to the notch effect, and if a surface-treated steel plate such as a plated steel plate is used as a material metal plate, the plating film etc. Of the surface-treated film is likely to be broken or peeled off, and the corrosion resistance is deteriorated. For this reason, the upper limit of D is set to 0.5 t, preferably 0.4 t, and more preferably 0.3 t.
In the present invention, the thickness t of the press-formed member is not particularly limited. In the present invention, a cold-rolled steel sheet, a hot-rolled steel sheet, and further, any of such as a plated steel sheet as an original plate can be used, and not only a steel sheet but also an aluminum plate or the like can be used. Any material from about 0.5 mm to a maximum of about 6 mm can be adopted. Preferably it is about 0.5 to 2 mm.

According to a second aspect of the present invention, there is provided the press-formed member according to the first aspect, wherein a side wall portion subjected to bending and bending-back deformation is formed on both sides of the bottom wall portion. A linear concave portion is press-formed at the portion. According to the present invention, since the predetermined linear concave portion is press-formed on the side wall portion subjected to the bending and bending deformation, the residual stress and the stress in the plate thickness direction generated on the surface portion of the side wall portion by the bending and bending deformation. The difference is relaxed or eliminated, and the warpage generated in the side wall portion due to the residual stress or the stress difference is corrected. As a result, the assembly, joining, and shape stability of the press-formed member are secured.

According to a third aspect of the present invention, there is provided the press-formed member according to the first aspect, wherein a curved surface portion subjected to bending deformation or bending-back deformation is formed around the bottom wall portion. A linear concave portion is formed in the curved surface portion by pressure molding. According to the present invention, since the linear concave portion is press-formed on the curved surface portion which has been subjected to the bending deformation or the bending / unbending deformation, the residual stress or the plate generated on the surface portion of the curved surface portion due to the bending deformation or the bending / bending unfolding deformation. The stress difference in the thickness direction is relaxed or eliminated, and the expansion of the radius of curvature generated in the curved surface portion due to the residual stress or the stress difference is corrected,
A press-formed member having a curved surface portion having an intended radius of curvature is obtained.

According to a fourth aspect of the present invention, there is provided the press-formed member according to any one of the first to third aspects, wherein a line subjected to bending deformation or bending-back deformation is drawn in a direction perpendicular to the pressing direction. The recess is press-formed. According to the present invention, since the linear concave portion is formed in a direction perpendicular to the pressing direction in the portion subjected to the bending deformation or the bending and bending deformation, the pressing direction is caused by the bending deformation or the bending and bending deformation on the surface of the molded member. The residual stress generated at the surface is divided transversely,
Stress differences in the thickness direction can be effectively reduced or eliminated, and shape defects can be effectively corrected.

The press forming method according to the fifth aspect is characterized in that:
Press forming in which a second forming die having a second forming surface is relatively moved to a first forming die having a first forming surface, and a material metal plate is formed by cooperation of the first forming surface and the second forming surface. A method, wherein a linear projection is provided on the first molding surface or the second molding surface or both, and the linear projection is formed on a portion which has undergone bending deformation or bending-back deformation during press molding. D / P ≧ 0.03 × t / 1.2, when the interval between the linear recesses is Pmm, the depth is Dmm, and the thickness of the press-formed member is tmm, And 0.02t <D ≦ 0.5t. According to the present invention, the shape forming of the press-formed member and the formation of the linear concave portion having the shape correcting effect are simultaneously performed at the time of press forming. Can be efficiently corrected and improved, and the method for producing a press-formed member of the present invention is excellent in productivity.

According to a sixth aspect of the present invention, the press forming method according to the fifth aspect of the present invention is performed in any one of the steps when press-forming a raw metal plate in a plurality of steps. Also in the present invention, as in the case of the fifth aspect, it is possible to efficiently correct and improve the molding defect together with the shape molding by using a normal press device, and it is excellent in productivity.

The invention according to claim 7 is the invention according to claim 5 or 6.
Press forming method, wherein a linear projection is formed on the first forming surface or the second forming surface of the first forming surface or the second forming surface having a smaller moving speed relative to the material metal plate during the press forming. It is. According to the present invention, since the linear projections are formed on the molding surface having the smaller relative movement speed of the material metal plate during the press forming, the linear projections are formed when the material metal plate is molded. The sliding amount of the material metal plate on the formed molding surface side is smaller than the molding surface side on which the linear projections are not formed, so that galling hardly occurs on the molding surface side on which the linear projections are formed. And the moldability is improved.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a main part of a press-molding die for forming the flared U-shaped member 30 shown in FIG. 2, and an upper die (die) 1 having a concave molding surface 2 formed on a lower surface. And a lower mold having a convex forming surface 4 which is provided to be able to approach and separate from the upper mold 1 and cooperates with the concave forming surface 2 to form the material steel plate W when approaching the upper mold 1. (Punch) 3, and a predetermined pressure is applied to the outer peripheral portion of the lower die 3 between the raw steel plate W and a plate pressing surface 6 formed of the lower surface of the outer peripheral portion of the concave molding surface 2 of the upper die 1. A plate holding member 5 that is pressed by a key is provided.

The side surfaces of the concave forming surface 2 and the convex forming surface 4 are tapered surfaces 7 and 8, and the tapered surface 8 on the side of the convex forming surface 4 has a pressing direction as shown in FIG. A large number of linear projections 10 each having a triangular cross section are provided at predetermined intervals (pitch) in a direction perpendicular to the vertical direction.

In order to press-mold using the above-mentioned mold, first, as shown in FIG. 1, the upper die 1 is raised to the top dead center, and the plate holding member 5 is raised to the position where the material steel plate W is carried in. In this state, the material steel plate W is introduced onto the plate holding member 5. Then, the upper die 1 is lowered to hold the material steel plate W between the plate pressing surface 6 of the upper die 1 and the plate pressing member 5, and further to the bottom dead center against the urging force of the plate pressing member 5. Pressing down and forming the material steel sheet W between the concave forming surface 2 and the convex forming surface 4 of the lower mold 3 while flowing the material steel plate W into the concave forming surface 2,
As shown in FIG. 2, a U-shaped member 30 is obtained in which the side walls 31 are drawn and formed on both sides of the bottom wall 32 formed by the top of the convex forming surface 4.

At the time of press molding, since the linear projections 10 are formed on the tapered surface 8 of the convex molding surface 4 of the lower mold 3 in a direction perpendicular to the pressing direction, the upper mold 1 is Is reached, the linear projection 1 is formed on the inner surface of the side wall 31 of the U-shaped member 30.
A number of linear recesses are juxtaposed in the side wall 31 at a predetermined depth and pitch. Due to the formation of the linear concave portions, the residual stress on the surface portion of the side wall portion 31 caused by the bending-back deformation and the stress difference generated in the plate thickness direction are reduced.
The warpage of the side wall 31 of the U-shaped member 31 removed from the mold after molding is reduced, and the shape accuracy is improved. In FIG.
The linear recess 11 formed by the linear protrusion 10 is represented by a center line in the length direction for convenience. Also,
In the figure, the linear concave portion 11 is drawn on the outer surface side of the side wall portion 31 for convenience, but is actually formed on the inner surface side of the side wall portion 31. When the depth of the linear concave portion is D mm, the pitch is P mm, and the thickness of the material steel plate is t mm, D / P ≧
0.03t / 1.2, and 0.02t <D ≦ 0.5t.

In the above embodiment, the linear projection 10 is formed on the tapered surface 8 of the convex molding surface 4 of the lower mold 3.
May be formed on the side of the tapered surface 7 of the concave molding surface 2. Or you may form in both. However, forming the linear projections 10 on the side of the lower mold 3 has an advantage that galling is less likely to occur during press molding, and is easy to form.

The tapered surface portion 8 or the tapered surface portion 7
The formation direction of the linear projections 10 in the above is not limited to the direction perpendicular to the pressing direction as in the above embodiment, but may be the inclination direction of the tapered surface portion substantially parallel to the pressing direction. That is, as shown in FIG. 3, as a linear projection 10 passing through a point O on a plane P1 constituting the tapered surface portion 8, a straight line a passing through the point O and perpendicular to the plane P1 and passing through the point O in the pressing direction. A plane P2 defined by the parallel straight line b may be formed in a direction of an intersection line intersecting the plane P1. Also,
The linear projection 10 may be in any direction between the direction perpendicular to the pressing direction shown in FIG. 1 and the inclined direction of the tapered surface shown in FIG. Further, the linear projection may be a mixture of these directions. However, the linear projection is perpendicular to the pressing direction and / or
Or, forming in parallel (including the case of being substantially vertical and substantially parallel) makes it easier to manufacture a mold than forming in any direction. In FIG. 3, the linear projection 10 is represented by a center line in the length direction.

Further, the linear projection in the present invention is not limited to a continuous linear shape as in the above embodiment,
As shown in FIG. 6, a linear projection 10A having an intermittent portion 13 in the middle may be used. Also, as shown in FIG. 5, the cross-sectional shape of the linear projection is not limited to (A) a triangle,
(B) truncated triangular shape, (C) triangular shape with arcuate head,
(D) An appropriate shape such as a flared mountain shape can be adopted. When a linear projection having such a triangular or substantially triangular cross section is provided, the tip of the linear projection easily penetrates into the material surface, causing the material to flow smoothly on the surface, A linear recess having a triangular or substantially triangular cross section with a predetermined depth and a predetermined pitch can be easily and stably formed.

The location where the linear projection 10 is formed is not limited to the tapered surfaces 7 and 8, but a shoulder or an upper die which forms a transition from the tapered surface 8 of the lower die 3 to a flat top surface. A predetermined linear concave portion can be formed in the bent R portion of the U-shaped member 30 by forming the bent R portion forming the transition from the tapered surface portion 7 to the bottom flat surface. The stress change in the thickness direction can be reduced or eliminated, and the angle change at the bending R portion can also be suppressed.

Here, specific results of a molding example using the mold shown in FIG. 1 will be described. A material SGAC4 is formed by using a lower mold 3 having a tapered surface portion 8 on which a linear projection 10 having a height of 0.2 mm and a pitch of 3 mm and having a sectional shape shown in FIG.
40-45 / 45, 0.8mm thick steel sheet (high-strength alloyed hot-dip galvanized steel sheet) with 150mm U-shaped recess
At the bottom dead center of the upper die 1 so that the distal end of the linear projection 10 bites into the material steel plate, and a linear recess (depth D of 20% of the plate thickness t) is formed. D = 0.16mm, D
/P=0.053), the warpage hardly occurred on the side wall 31 of the U-shaped member 30. this is,
The linear recess is a requirement of the present invention, that is, D / P ≧ 0.03.
This is because xt / 1.2 and 0.02t <D ≦ 0.5t are satisfied. The inclination angle of the tapered surface portion 8 (the angle formed by the tapered surface forming the tapered surface portion and a straight line passing through a point on the tapered surface portion and parallel to the pressing direction) was 5 °.

Further, some products are not limited to the U-shaped cross section as in the molding object of the above-mentioned embodiment, but have a curved surface portion having a large radius of curvature, such as a door or a roof. Even in the case of such a molded member, when the molded member is removed from the mold after press molding, a portion subjected to bending deformation or bending-back deformation is deformed due to a residual stress or a stress difference in a thickness direction in a surface portion. Usually, the radius of curvature becomes larger than the radius of curvature.

In such a case, as shown in FIG. 6, for example, using a mold in which linear projections 20 are juxtaposed in a direction perpendicular to the pressing direction on a curved surface 28 formed on the top of the lower mold 23. By press molding, a predetermined linear concave portion can be easily formed on the curved surface portion of the molded member that has undergone bending deformation or bending / bending-back deformation during molding, and the change in curvature can be prevented. Of course, the linear projection 2
0 may be formed on the curved surface of the bottom molding surface of the upper die. In FIG. 6 (same in FIG. 7), the linear projection 20 is represented by a center line in the extending direction for convenience of explanation.

The direction of the linear projections 20 is not limited to the direction perpendicular to the pressing direction. As shown in FIG. It may be formed. That is, the linear projection 20 passing through the point O on the curved surface C constituting the curved portion 28 is
May be formed in a direction of an intersecting line between the curved surface C and a plane P defined by a normal line a of the curved surface C passing through the point O and a straight line b passing through the point O and parallel to the pressing direction. Further, the linear projection 20 and the linear projection 20 shown in FIG. 6 may be provided side by side. By press-molding using such a mold, the linear projections 20 are formed.
Bites into the curved surface of the molded member, and a predetermined linear concave portion can be radially pressed from the center of the bottom of the curved surface of the molded member.

In the above-described embodiment, the molding into the product shape and the formation of the linear concave portion by the biting of the linear projection portion 10 are simultaneously performed in one step. When a product is formed by a draw (rough forming) process and a restriking (finish forming) process of drawing and bending into a U-shaped cross section, a mold having a linear projection formed in any of the processes is used. Thus, a linear concave portion may be formed to prevent a change in shape.

Hereinafter, an embodiment will be described in which the warpage generated on the side wall portion of the molded member during the rough molding in the finish molding of the product in the restriking process is improved. As shown in FIG. 9, the molded member in this embodiment includes a side wall portion 81,
Reference numeral 81 denotes a U-shaped member 80 formed by bending both sides of the bottom wall portion 82 at right angles.

FIG. 8 is a front view of a half part of a mold for restrik molding, and shows a convex molding surface 5 having a square cross section.
And a convex molding surface 54 of the lower mold 53.
A horizontal mold 51 formed on the front surface with a flat molding surface 52 for finish-molding the side wall portion 81 of the U-shaped member 80 in cooperation with the side surface portion.
And a driving mechanism 68 for moving the horizontal mold 51 on the mold base 60 so as to be able to advance and retreat to the lower mold 53 side.
The lower mold 53 is erected on the mold base 60,
On the side surface of the convex molding surface 54, a number of linear projections 10 project at predetermined intervals in a direction perpendicular to the pressing direction at the time of draw molding. Further, after the horizontal die 51 advances to the lower die 53 side, a return member 69 for pulling the horizontal die 51 backward is attached to a heel member 66 erected at the end of the mold base 60.

The driving mechanism 68 includes a base member 61 which moves up and down between a top dead center and a bottom dead center, and a side surface of a convex molding surface 54 of a lower mold 53 interlocked with the elevation of the base member 61. A cam member 67 is provided for moving the horizontal die 51 forward and backward so as to approach and separate the flat molding surface 52. The cam member 67
Are provided at both ends of the base member 61, a first tapered surface 65 is formed at a lower end portion, and an outer side surface portion is guided by a side surface of a heel member 66 erected on the mold base 60 to ascend and descend. Is configured. When the base member 61 descends to the vicinity of the bottom dead center or to the bottom dead center via the urging support member 62 attached to the base member 61, the lower mold 53 is formed in a convex shape. A pressing member 63 is provided which cooperates with the top of the surface 54 to press and hold the bottom wall 82 of the U-shaped member 80. The urging support member 62 and the return member 69 are constituted by an elastic body such as a spring or rubber capable of obtaining a relatively large expansion and contraction amount, a fluid cylinder, and the like.

As the cam member 67 descends, the upper end of the horizontal die 51 comes into contact with a first tapered surface 65 formed at the lower end of the cam member 67, and receives the rearward biasing force of the return member 69. A second tapered surface 70 for moving the horizontal mold 51 toward the lower mold 53 side is formed. In addition, a wear-resistant material is appropriately attached to the sliding surface of the member.

In order to finish form the U-shaped member 80 using the above-mentioned mold, first, as shown in FIG. 8, the base member 61 of the drive mechanism 68 is raised to the top dead center, The roughly-formed U-shaped member 80 in which the side wall portion 81 is warped is introduced onto the lower mold 53. And the base member 6
1 is lowered, and the lower surface of the pressing member 63 supported by the base member 61 via the urging support member 62 is placed on the top of the convex forming surface 54 of the lower mold 53. 8
2 is brought into contact with the upper surface. Further, the base member 61 is lowered to the bottom dead center against the elastic force of the urging support member 62, and the bottom wall 82 of the U-shaped member 80 is pressed to the pressing member 63 and the top of the convex forming surface 54 of the lower mold 53. And pressurized state.

On the other hand, the cam member 67 provided on the base member 61 descends as the base member 61 descends, so that the first tapered surface 65 of the cam member 67 contacts the second tapered surface 70 of the horizontal die 51, and As the member 61 descends, the horizontal mold 51 advances to the lower mold 53 side. When the base member 61 reaches the bottom dead center, as shown in FIG. 9, the planar molding surface 52 formed on the front surface of the horizontal die 51 is provided on the side surface of the convex molding surface 54 of the lower die 53. The side wall portions 81 of the U-shaped member 80 are pressed against the large number of linear protrusions 10 so that the linear protrusions 10 bite into the side wall portions 81 and finish forming is completed. Thereafter, when the base member 61 is raised, the pressing member 63 is raised to open the bottom wall portion 82 of the U-shaped member 80, and the horizontal die 51 is pulled backward by the return member 69 and retreats to the original position. Return and end molding.

A large number of linear recesses having a predetermined depth and pitch are formed in the side wall portion 81 of the U-shaped member 80 in the direction perpendicular to the pressing direction at the time of draw molding by the biting of the linear projections 10. Is done. The linear recesses reduce the residual stress on the surface portion of the side wall portion 81 and the stress difference in the plate thickness direction, correct the warpage of the side wall portion 81 of the U-shaped member 80 taken out of the mold, and improve the shape accuracy. .

Here, the concrete results of the example of the restriking molding using the above-mentioned mold will be described below. Material SGAC440
First, a U-shaped member 80 having a recess depth of 150 mm was roughly formed by draw bending using a material steel sheet (high-strength alloyed hot-dip galvanized steel sheet) having a thickness of -45/45 and a thickness of 0.8 mm. However, the side wall portion 81 was warped. This U
The shaped member 80 was supplied to a mold for restriking. Lower mold 53
A large number of linear protrusions 10 having a height of 0.2 mm and a pitch of 3 mm and having the shape shown in FIG. The base member 61 is lowered to the bottom dead center. At the bottom dead center, the tip of the linear protrusion 10 is cut into the side wall 81 of the U-shaped member 80, and the depth D is 20% of the plate thickness t (D = 0.16mm,
D / P = 0.053).
The warpage of the side wall portion 81 of the shaped member 80 has been almost eliminated.
This is because the linear concave portion is a requirement of the present invention, that is, D / P ≧
0.03 × t / 1.2 and 0.02t <D ≦ 0.5t
Is satisfied.

In the above embodiment, the linear projections 10 are formed on the side surfaces of the convex molding surface 54 of the lower mold 53. However, the linear projections may be formed on the flat molding surface 52 of the horizontal mold 51. Good.
The direction in which the linear protrusions are formed is not limited to the direction perpendicular to the pressing direction during drawing (horizontal direction) as shown in the figure, but may be formed in the direction parallel to the pressing direction (vertical direction). Often,
Alternatively, it may be formed in an oblique direction between the horizontal direction and the vertical direction.

In the above embodiment, the base member 61
Of the horizontal die 51 via the cam member 67 to lower the die 53
Side, but without the cam member 67, the horizontal type 5 can be moved by an appropriate telescopic member such as a hydraulic cylinder.
1 may be moved forward and backward.

It is needless to say that the press molding die may be subjected to a known surface treatment such as chromium plating or ceramic coating, heat treatment, or the like. The press apparatus for carrying out the present invention is not particularly limited, and any type of press such as a hydraulic press, a mechanical press, and a counter hydraulic press can be used.

[0047]

According to the press-formed member of the present invention, a predetermined linear concave portion is formed under pressure in a portion which has been subjected to bending deformation or bending-back deformation. Since the residual stress and the stress difference in the thickness direction generated in the surface portion of the molded member can be reduced or eliminated, the defective shape of the molded member can be improved, and the defective assembly due to the defective shape of the molded member can be improved. In addition, it is possible to prevent poor joining of a plurality of molded members. In particular,
From the viewpoint of weight reduction and safety, it is possible to effectively prevent remarkable shape defects when using high-tensile thin steel sheets (high-tensile steel) used for automobile bodies. It is enormous. Further, according to the forming method of the present invention, it is possible to form a predetermined linear concave portion in a portion that has undergone bending deformation or bending-back deformation together with shaping of a shape by using a normal pressing device. Excellent productivity as a member manufacturing method.

[Brief description of the drawings]

FIG. 1 is a sectional view of a press-molding die according to an embodiment.

FIG. 2 shows a perspective view of a U-shaped member to be molded.

FIG. 3 is a perspective view of a lower mold in which linear protrusions are juxtaposed in an inclined direction.

FIG. 4 is a partial cross-sectional perspective view of a linear projection having an intermittent portion.

FIG. 5 is a cross-sectional view showing the cross-sectional shape of various linear projections.

FIG. 6 is a perspective view of a lower mold in which linear projections are formed on a curved surface formed on the top of the lower mold in a direction perpendicular to the pressing direction.

FIG. 7 is a perspective view of a lower mold in which linear projections are formed radially from the center of the top of the curved surface.

FIG. 8 is a half-part front view at the time of starting molding of a mold for restorative molding according to another embodiment.

FIG. 9 is a half-part front view of a rest-like molding die according to another embodiment at the end of molding.

FIG. 10 is an explanatory view of draw bending of a U-shaped member.

FIG. 11 is an explanatory view of an outline of a test procedure for improving a shape defect of a U-shaped member.

FIG. 12 is a perspective view after a shape defect improvement experiment of a U-shaped member.

FIG. 13 is an explanatory diagram of an operation of a linear concave portion.

FIG. 14 is a graph showing the results of an experiment for improving the shape defect of a U-shaped member.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper mold 2 Concave molding surface 3,23,53 Lower mold 4,54 Convex molding surface 6 Plate holding surface 10,10A, 20 Linear projection 11,151 Linear recess 31,81 Side wall 32,82 Bottom wall Department

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Koichi Kani 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Toshinari Funabiki 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation

Claims (7)

[Claims] 1. A press-formed member in which a linear concave portion is press-formed at a portion which has undergone bending deformation or bending-back deformation during press forming, wherein the distance between the linear concave portion is Pmm and the depth is D / P ≧ 0.03 × t /
1.2 and a press-formed member in which 0.02t <D ≦ 0.5t. 2. A press-formed member in which a side wall portion subjected to bending and bending back deformation is formed on both sides of a bottom wall portion, wherein a linear concave portion is press-formed on the side wall portion. Press molded parts. 3. A press-formed member having a curved surface portion subjected to bending deformation or bending-back deformation around a bottom wall portion, wherein a linear concave portion is pressure-formed in the curved surface portion. Press-formed member described in 1. 4. The press-formed member according to claim 1, wherein a linear concave portion is press-formed in a direction perpendicular to the pressing direction in a portion subjected to bending deformation or bending-back deformation. . 5. A metal mold plate comprising: a first molding die having a first molding surface; a second molding die having a second molding surface being relatively moved to a first molding die having a first molding surface; and a cooperating operation between the first molding surface and the second molding surface. A press forming method, wherein a linear projection is provided on the first forming surface and / or the second forming surface, and the wire is subjected to a bending deformation or a bending and bending deformation at the time of press forming. The linear projections are cut into the linear recesses, and the distance between the linear recesses is P mm and the depth is D.
mm and the thickness of the press-formed member tmm, D / P
≧ 0.03 × t / 1.2 and 0.02t <D ≦ 0.5
Press molding method as t. 6. A press forming method for performing the press forming method according to claim 5 in any of the steps when press forming a material metal plate in a plurality of steps. 7. A first molding surface or a second molding surface during press molding.
7. The press forming method according to claim 5, wherein a linear projection is formed on a forming surface having a smaller relative movement speed with respect to the material metal plate among the forming surfaces.