JP2013049068A - Press forming method for plate workpiece - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a press forming method for a plate workpiece which can form a shape that is substantially L-shaped in a plane view and has a step in a height direction in a cross sectional view, without generating surface distortion regardless of a high rigidity member.SOLUTION: The method includes: a preliminary forming step S1 where a temporal top surface 111, which includes a top surface 11 being a substantially L-shape in the plane view and extends over on a side of an inside region M sandwiched by the top surface 11 further than the top surface 11, is set so that a curvature radius of a ridge line RR in a curve of the temporal top surface 111 becomes a first curvature radius and a sandwiched angle of the temporal top surface 111 becomes a first sandwiched angle, and then the temporal top surface 111 and a temporal stepped part 121 having a step in the height direction with respect to the temporal top surface 111 are drawn; and a final forming step S2 where a second curvature radius whose curvature radius of a ridge line R in a curve of the top surface 11 is smaller than a first curvature radius is set so that a sandwiched angle of the top surface 11 becomes a second sandwiched angle smaller than a first sandwiched angle, and then a stepped part 21 is drawn while pushing a top surface scheduled part 99 corresponding to the top surface 11 of the temporal top surface 111.

Description

  The present invention relates to a press-forming method for a plate-like workpiece, and more particularly to a press-forming method for a plate-like workpiece that forms a shape that is substantially L-shaped in a plan view and has a step in the height direction in a cross-sectional view.

As a press-molded product used as an automotive part, for example, a press-molded product having a substantially L-shape in a plan view and a step in a height direction in a cross-sectional view, such as an inner portion of a rear wheel arch of a car. The structure of is known. Specifically, as shown in FIG. 1 (b) which is a cross-sectional view taken along line I (b) -I (b) in FIGS. 1 (a) and 1 (a), a plate-like workpiece such as a steel plate is formed by press forming. A configuration of a press-formed product 10 that is processed and includes a substantially L-shaped elongated top surface 11 and a step portion 21 that has a step in the height direction from the top surface 11 and extends along the top surface 11 is known. is there.
When press-molding the above-described press-molded product 10, the edge of the plate-like workpiece is held by a blank holder, and in this state, the plate-like workpiece is narrowed down using a press die having a die, a blank holder, and a punch. Although the drawing is performed, the stepped portion 21 and the bottom surface 16 are formed by a punch having a substantially square protruding portion in a plan view corresponding to the shape of the stepped portion 21, and is substantially L-shaped in a plan view and high in a sectional view. A shape having a step in the vertical direction is formed.

  When forming a shape with a step in the height direction in cross-sectional view in press molding, for example, if a punch depresses a member to be press-molded, another part of the member will rise from the die, causing surface distortion There is. This lifting of the member is likely to occur when the member is highly rigid.

On the other hand, when manufacturing press-molded products of automobile parts, by pressing and molding a tailored blank material in which a high-strength and high-thickness member and a low-strength and low-thickness member are butt-joined, Manufacturing a molded article having a plurality of portions having different characteristics is performed (see Patent Document 1). In a tailored blank material, it is mainly a high-rigidity part that is used when forming a shape having a step in the height direction in a sectional view.
Therefore, in tailored blanks, in addition to the fact that high-rigidity parts are easily lifted, it is necessary to avoid the elongation of low-rigidity parts even when trying to suppress the lifting by applying high tension with a blank holder. Is small and surface distortion is likely to occur.

  Regarding the shape of the press-molded product to be press-molded, in particular, when the press-molded product 10 having a shape substantially L-shaped in a plan view and having a step in the height direction in a cross-sectional view is formed, the member is lifted. The occurrence of surface distortion due to the surface is remarkable, and surface distortion often occurs on the top surface 11.

JP 2010-36222 A

  The present invention has been made in view of the above, and an object of the present invention is to form a surface that is substantially L-shaped in plan view and has a step in the height direction in cross-sectional view even if the workpiece is a high-rigidity member. An object of the present invention is to provide a press forming method for a plate-like workpiece that can be formed without generation.

  In the present invention, a plate-like workpiece (for example, a plate-like workpiece W described later) is press-molded, and a substantially L-shaped top surface (for example, a ceiling surface 11, a side sill surface 12, and a rear wheel arch surface 13 described later) are seen in plan view. , And a curved portion C) and a step portion (for example, described later) having a step in the height direction with respect to the top surface in a cross-sectional view between an inner region (for example, an inner region M described later) sandwiched between the top surfaces. A press-forming method for a plate-like workpiece for forming a shape having a step portion 21, a side sill surface step portion 22, a rear wheel arch surface step portion 23, and a curved step portion 24), including the top surface and the top A substantially L-shaped temporary ceiling surface (for example, a provisional ceiling surface 111, a provisional side sill surface 112, a provisional rear wheel arch surface 113, and a provisional bending portion CC, which will be described later) extending in a plan view further projecting from the surface to the inner region side. , Bent portion of the temporary surface The temporary ceiling surface and the temporary ceiling are set such that a curvature radius of a ridge line (for example, a ridge line RR described later) is set to a first curvature radius and a sandwich angle of the temporary ceiling surface is a first sandwich angle. A preliminary step for drawing a temporary stepped portion having a step in the height direction with respect to the surface (for example, a temporary stepped portion 121, a temporary side sill stepped portion 122, a temporary rear wheel arch stepped portion 123, and a temporary curved stepped portion 124 described later). A step of forming and capping the top surface with a second radius of curvature having a curvature radius of a ridge line (for example, a ridge line R described later) of the bent portion of the top surface smaller than the first curvature radius. A top surface planned portion that is a portion corresponding to the top surface on the temporary top surface (for example, a top surface planned portion described later) is set so that the angle is a second sandwich angle smaller than the first sandwich angle. 99) a main forming step of drawing the stepped portion while pressing, Characterized in that it contains.

  According to the present invention, first, in the pre-forming step, a temporary L-shaped temporary object is included in a plan view that includes the top surface to be finally formed and projects further to the inner region side sandwiched by the top surface than the top surface. A top surface is set and a temporary step surface and a temporary step portion having a height difference with respect to the temporary top surface are drawn. At this time, the radius of curvature of the ridgeline of the bent portion of the temporary ceiling surface is set to the first curvature radius, and the sandwich angle of the temporary ceiling surface is set to the first sandwich angle.

  Next, in the main forming step, the top surface to be finally formed is set, and the stepped portion is drawn while pressing the planned top surface portion corresponding to the top surface on the temporary top surface. . At this time, the curvature radius of the ridgeline of the bent portion of the top surface is set to a second curvature radius smaller than the first curvature radius, and the sandwich angle of the top surface becomes a second sandwich angle smaller than the first sandwich angle. Is set to

Therefore, according to the present invention, the preliminary shape which greatly deforms the shape from the plate-like workpiece in which the temporary step surface having a substantially L shape in a plan view and the temporary step portion having a height step with respect to the temporary top surface is formed. In the forming step, the first curvature radius larger than the curvature radius (second curvature radius) of the ridgeline of the bent portion of the top surface to be finally formed, and the sandwich angle (second sandwich angle) of the top surface ), The temporary top surface and the temporary stepped portion are drawn.
As will be described later, even if the workpiece is a high-rigidity member, since the curvature radius of the ridgeline of the bent portion of the temporary top surface is large (first curvature radius), the plate-shaped workpiece is unlikely to rise, Surface distortion is unlikely to occur. Further, since the sandwiching angle of the temporary top surface is large (first sandwiching angle), the plate-shaped workpiece is hardly lifted up, and surface distortion is unlikely to occur on the temporary ceiling surface. Therefore, even if the workpiece is a highly rigid member, the temporary top surface including the top surface to be finally formed can be formed without causing surface distortion.

  In the main forming step, the radius of curvature of the ridgeline of the bent portion of the top surface is set to the second curvature radius, and the sandwich angle of the top surface is set to the second sandwich angle. The radius of curvature of the ridgeline of the bending portion of the top surface and the sandwiching angle of the top surface correspond to the shape to be finally formed. In the case of “forming from a plate-like workpiece in one step”, it may be a molding condition in which the plate-like workpiece is likely to be lifted (as a result, surface distortion is likely to occur). However, since the temporary top surface and the temporary stepped portion are already formed in the preforming step, forming the top surface and the stepped portion from this shape may require a relatively small shape change. Moreover, since the molding is performed while pressing the planned top surface corresponding to the top surface, the top surface to be finally formed is formed without causing surface distortion even if the work is a high-rigidity member. be able to.

  According to the present invention, a press forming method for a plate-like workpiece capable of forming a shape that is substantially L-shaped in a plan view and has a step in a height direction in a cross-sectional view without occurrence of surface distortion even if the workpiece is a highly rigid member. Can provide.

It is a figure which shows the whole structure of the press molded product shape | molded by the press molding method of the plate-shaped workpiece | work which concerns on one Embodiment of this invention. a is a top view and b is an I (b) -I (b) cross-sectional view of a. a is a schematic diagram showing the lifting of a workpiece during press molding, and b is a schematic diagram showing the details thereof. a is a graph showing the relationship between the radius of curvature of the ridgeline of the substantially L-shaped top surface and the amount of surface strain, and b is a graph showing the relationship between the sandwich angle of the substantially L-shaped top surface and the amount of surface strain. a is a top view showing the shape of the press-formed product in the preforming step, and b is a top view showing the shape of the press-formed product in the main forming step. It is sectional drawing which shows the shape change in each process of the press-formed product in the VV cross section of FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing an overall configuration of a press-formed product formed by the plate-shaped work press forming method according to the present embodiment. FIG. 2 is a schematic diagram showing the lifting of the workpiece during press molding. FIG. 3 is a graph showing the relationship between the radius of curvature of the ridgeline of the approximately L-shaped top surface and the amount of surface distortion, and the relationship between the sandwich angle of the approximately L-shaped top surface and the amount of surface strain. FIG. 4 is a top view showing the shape of the press-formed product in each step of the preforming step and the main forming step. FIG. 5 is a cross-sectional view showing a shape change in each step of the press-formed product in the VV cross section of FIG.

First, the overall configuration of a press-formed product 10 formed by using the plate-shaped workpiece press forming method of the present embodiment will be described.
1, the arrow X direction is the front-rear direction of the press-formed product 10, the arrow Y direction is the up-down direction of the press-formed product 10, and the arrow Z direction is the height direction of the press-formed product 10.

As shown in FIG. 1, in the press forming method of the present embodiment, a press-formed product 10 having a shape that is substantially L-shaped in a plan view and has a step in the height direction in a sectional view from a plate-like workpiece W such as a steel plate. Molded. The plate-like workpiece W may be a tailored blank material in which a high-rigidity portion Wa and a low-rigidity portion Wb are butt-joined at the joining surface 19.
This press-molded product 10 is a side surface plate used for an inner portion of a rear wheel arch of an automobile, and has a top surface 11 having a substantially L shape in plan view extending in the front-rear direction and the vertical direction of the press-molded product 10 and the top surface. 11 and extending in a substantially L shape in plan view, and having a step in the height direction from the top surface 11 and connected to the step 21 on the side opposite to the side connected to the top surface 11. And a bottom surface 16.

The top surface 11 has an elongated side sill surface 12 linearly extending in the front-rear direction of the press-formed product 10 and an elongated rear wheel arch surface 13 extending from the terminal side surface 12 s of the side sill surface 12 in the vertical direction of the press-formed product 10. . The side sill surface 12 and the rear wheel arch surface 13 are formed so as to be connected to each other at a substantially right angle, and the top surface 11 is formed in a substantially L shape in a plan view extending in the front-rear direction and the vertical direction of the press-formed product 10. Yes. The curved portion C of the side sill surface 12 and the rear wheel arch surface 13 has a ridge line R on the side of the inner region M sandwiched between the side sill surface 12 and the rear wheel arch surface 13, and the ridge line R has a radius of curvature r. 2 is formed into a curve having a radius of curvature r0 (curvature radius r = second radius of curvature r0).
The ridge line S of the side sill surface 12 on the inner region M side is formed so as to be smoothly connected to one end of the ridge line R, and the ridge line T of the rear wheel arch surface 13 on the inner region M side is smoothly connected to the other end of the ridge line R. Shaped to connect. The sandwiching angle φ between the ridgeline S and the ridgeline T is formed into the second sandwiching angle φ0 (the sandwiching angle φ = the second sandwiching angle φ0).
The rear wheel arch surface 13 is shaped so as to gradually curve from the up-down direction of the press-formed product 10 toward the front-rear direction of the press-formed product 10 as the distance from the bent portion C increases.
The rear wheel arch surface 13 may have a small step in the height direction with respect to the side sill surface 12 at the position of the terminal side surface 12s.

  The step portion 21 extends in the inner region M in a substantially L shape in plan view along the side sill surface 12 and the rear wheel arch surface 13, and the side sill surface 12, the rear wheel arch surface 13 constituting the top surface 11, and A side sill step portion 22 connected to the side sill surface 12, a rear wheel arch step portion 23 connected to the rear wheel arch surface 13, and a bend portion C are formed so as to have a step in the height direction in a sectional view from the bent portion C. And a curved stepped portion 24 connected to the.

The side sill step portion 22 is formed so as to be smoothly connected to the side sill surface 12 via the ridge line S, and is similarly formed to be smoothly connected to the bottom surface 16. The rear wheel arch step portion 23 is formed so as to be smoothly connected to the rear wheel arch surface 13 via the ridge line T, and is similarly formed to be smoothly connected to the bottom surface 16.
The curved step portion 24 is formed so as to be smoothly connected to the bent portion C via the ridge line R, and is similarly formed to be smoothly connected to the bottom surface 16. The curved stepped portion 24 is formed into a curved surface that is concavely curved toward the inner region M.
The side sill step portion 22 is shaped so as to be smoothly connected to one end of the curved step portion 24, and the rear wheel arch step portion 23 is shaped to be smoothly connected to the other end of the curved step portion 24.

  The plate-like workpiece W may be a tailored blank material in which the high-rigidity portion Wa and the low-rigidity portion Wb are butt-joined at the joint surface 19 as described above, and the joint surface 19 crosses the rear wheel arch surface 13. Thus, the press-formed product 10 extends linearly in the front-rear direction. The rear wheel arch surface 13 includes a high rigidity rear wheel arch surface 13a and a low rigidity rear wheel arch surface 13b. Similarly, the rear wheel arch surface step portion 23 includes a high rigidity rear wheel arch surface step portion 23a and a low rigidity rear wheel arch surface step portion 23b. Similarly, the bottom surface 16 includes a high-rigidity bottom surface 16a and a low-rigidity bottom surface 16b.

  As described above, the press-molded product 10 is a side surface plate used for an inner portion of a rear wheel arch of an automobile. The step portion 21 and the bottom surface 16 are portions that can be seen only when the door is opened, and may be provided with notches, screw holes, etc. for attaching functional parts when attached to the automobile by welding. In addition, a bead necessary for increasing rigidity may be provided. On the other hand, since the top surface 11 (side sill surface 12 and rear wheel arch surface 13) is a design surface that is always visible on the side surface of the automobile, the smoothness of the surface is important.

  Next, in order to solve the above-mentioned problems and press-form a shape that is substantially L-shaped in plan view and has a step in the height direction in cross-section without causing surface distortion even if the work is a highly rigid member The present inventors have first elucidated “a substantially L-shaped top surface when press-molding a plate-like workpiece, which is substantially L-shaped in plan view and has a step in the height direction in sectional view. The mechanism of the occurrence of surface distortion in the vicinity of the bent portion (lift of the outer surface) will be described.

  That is, as shown in FIG. 2A, when press forming (drawing) is performed on the plate-like workpiece W using the punch 200 and the die 300, the lower surface 201 of the punch 200 is formed to form a stepped portion. When the protruding portion 202 protruding from the point contacts the point E on the plate-like workpiece W and pushes the plate-like workpiece W downward, the protruding portion (ridge line portion) 302 provided on the upper surface 301 of the die 300 is supported as a fulcrum. (See FIG. 2B), the point G on the plate-like workpiece W opposite to the point E with respect to the protruding portion (ridge line portion) 302 is lifted upward. That is, when the force PE is applied to the point E with the point E as the force point, the force PG corresponding to the force PE is applied to the point G, which is the action point, according to the “leverage principle” with the protruding portion (ridge line portion) 302 as a fulcrum. Join. Therefore, the point G rises from the die upper surface 301 against the tension by the blank holder applied to the plate-like workpiece W in the H direction.

As shown in FIG. 2 (b), in order to elucidate the phenomenon of the lifting of the plate-like workpiece W in more detail, “To form the ridge line R of the bent portion C of the press-formed product 10 to be press-formed”. A curve F on the plate-like workpiece W corresponding to the ridgeline portion 302 "provided on the upper surface 301 of the die 300, a point E on the plate-like workpiece W with which the projecting portion 202 of the punch 200 contacts, and a plate that becomes a lift point A virtual workpiece piece that is a part of the plate-like workpiece W including the point G on the rectangular workpiece W is considered, and this is referred to as a workpiece piece 500. When the force PE is applied to the point E by the projecting portion 202 of the punch 200 coming into contact with the workpiece piece 500, the workpiece piece 500 is pressed against the ridgeline portion 302 provided on the upper surface 301 of the die 300. Since the ridge line portion 302 is shaped into a curve having a curvature radius r corresponding to the ridge line R and having a second curvature radius r0, the work piece 500 is pressed against the ridge line portion 302, whereby the ridge line portion 302 is pressed against the ridge line portion 302. The corresponding curve F (that is, the arc) has a curvature radius r that is the second curvature radius r0, and the sandwich angle φ is the second sandwich angle φ0.
The bent workpiece piece 500 has a bending rigidity that is increased as compared with a flat plate having the same size and the same rigidity. Therefore, the force PG applied to the point G on the plate-like workpiece W is increased. It floats greatly from the die upper surface 301 against the tension of the blank holder applied in the H direction to the workpiece W. Since the point G is located in the vicinity of the bent portion of the substantially L-shaped top surface, the surface distortion occurs in the vicinity of the bent portion C of the substantially L-shaped top surface, that is, the top surface 11 due to the occurrence of the rising of the point G. Occur. The lift becomes more prominent as the work piece 500, that is, the corresponding part of the plate-like work W is a highly rigid member, and surface distortion is likely to occur.

  As shown in FIG. 3, the degree of occurrence of surface distortion (surface distortion amount) on the top surface 11 that is the design surface is the radius of curvature of the ridge line R of the bent portion C of the substantially L-shaped top surface and the substantially L-shaped top surface. It was found that there was a close correlation with the included angle. That is, as shown in FIG. 3A, the surface distortion amount (height) of the top surface 11 increases as the radius of curvature of the ridge line R of the bent portion C of the substantially L-shaped top surface increases (in other words, the bending). The degree of curvature of the ridgeline R of the part C is smaller and the closer it is to a straight line), the smaller it is. Further, as shown in FIG. 3B, the surface distortion amount (height) of the top surface 11 increases as the sandwich angle of the substantially L-shaped top surface increases (in other words, the bending of the substantially L-shaped top surface). The smaller the ratio of the length of the “arc” of the ridgeline R of the part C to the “circumference having the same radius of curvature as that arc”, the smaller.

Next, the press molding method according to the present embodiment will be described in detail below.
As shown in FIGS. 4 and 5, the press forming method according to the present embodiment is a press forming having a substantially L shape in plan view and a step in the height direction in cross section from a plate-like workpiece W such as a steel plate. In the drawing of the product 10, the top surface 11 and the stepped portion 21 to be finally formed are divided into a plurality of processes, so that the top surface of the press-formed product 10, particularly the design surface, at the end of the final molding. 11 can prevent the occurrence of surface distortion. Specifically, the press molding method according to the present embodiment includes the top surface 11 and has a substantially L-shaped temporary top surface in a plan view that projects from the top surface 11 to the inner region M side sandwiched by the top surface 11. 111 so that the curvature radius r of the ridge line RR that is the ridge line of the curved portion CC of the temporary ceiling surface 111 is the first curvature radius r1 and the sandwiching angle φ of the temporary ceiling surface 111 is the first sandwiching angle φ1. The preliminary molding step S1 to obtain the intermediate press-formed product 100 by drawing the temporary step surface 121 and the provisional step portion 121 having a step in the height direction with respect to the temporary top surface 111, and the top surface 11, The curvature radius r of the ridge line R, which is the ridge line of the bent portion C of the top surface 11, is a second curvature radius r0 smaller than the first curvature radius r1, and the sandwich angle φ of the top surface 11 is greater than the first sandwich angle φ1. The top surface 11 of the provisional top surface 111 is set to be a small second sandwiching angle φ0. And a final molding step S2 for drawing the stepped portion 21 to complete the press-molded product 10 while pressing the planned top surface portion 99 corresponding to the above.

  In the preliminary forming step S1, the temporary top surface 111 and the temporary stepped portion 121 are drawn from the plate-like workpiece W to obtain the intermediate press-formed product 100. The temporary top surface 111 includes a top surface 11 to be finally formed, that is, a side sill surface 12, a rear wheel arch surface 13, and a bent portion C (see FIG. 4B), and is further higher than the top surface 11. It is set so as to project to the inner region M side sandwiched between the surfaces 11. That is, the provisional side sill surface 112, the provisional rear wheel arch surface 113, and the provisional bending portion CC of the provisional top surface 111 project from the side sill surface 12, the rear wheel arch surface 13 and the bending portion C to the inner region M side (see FIG. 4 (b)).

Similarly, the temporary side sill surface 112 and the temporary rear wheel arch surface 113 are formed so as to be connected to each other at substantially right angles, and the temporary top surface 111 is substantially L-shaped in a plan view extending in the front-rear direction and the vertical direction of the press-formed product 100. It is formed into a shape. The ridge line RR of the temporary bending portion CC is formed into a curve whose curvature radius r is the first curvature radius r1 (curvature radius r = first curvature radius r1).
The ridge line SS of the temporary side sill surface 112 on the inner region M side is formed so as to be smoothly connected to one end of the ridge line RR, and the ridge line TT of the temporary rear wheel arch surface 113 on the inner region M side is connected to the other end of the ridge line RR. Molded to connect smoothly. The sandwiching angle φ between the ridge line SS and the ridge line TT is formed into the first sandwiching angle φ1 (the sandwiching angle φ = the first sandwiching angle φ1).

  The provisional stepped portion 121 is substantially L-shaped in a plan view along the provisional side sill surface 112 and the provisional rear wheel arch surface 113 in the provisional inner region MM sandwiched between the provisional side sill surface 112 and the provisional rear wheel arch surface 113. The temporary side sill surface 112, the temporary rear wheel arch surface 113, and the temporary curved portion CC that form the temporary top surface 111 are formed to have a step in the height direction in a cross-sectional view and connected to the temporary side sill surface 112. A temporary side sill step portion 22, a temporary rear wheel arch step portion 123 connected to the temporary rear wheel arch surface 113, and a temporary curved step portion 124 connected to the temporary bend portion CC are provided.

The temporary side sill step portion 122 is formed so as to be smoothly connected to the temporary side sill surface 112 via the ridge line SS, and is similarly formed to be smoothly connected to the bottom surface 16. The temporary rear wheel arch step portion 123 is formed so as to be smoothly connected to the temporary rear wheel arch surface 113 via the ridge line TT, and is similarly formed to be smoothly connected to the bottom surface 16.
The temporary curved stepped portion 124 is formed so as to be smoothly connected to the temporary bent portion CC via the ridge line RR, and is similarly formed to be smoothly connected to the bottom surface 16. The temporary curved stepped portion 124 is formed into a curved surface that is concavely curved toward the temporary internal region MM.
The temporary side sill step portion 122 is formed so as to be smoothly connected to one end of the temporary curved step portion 124, and the temporary rear wheel arch step portion 123 is formed so as to be smoothly connected to the other end of the temporary curved step portion 124. The

As shown in FIG. 4A, the planned top surface 99 is a portion finally formed on the top surface 11 in the main molding step S2 on the temporary top surface 111 (the top planned portion indicated by the dot portion). 99, and the ridgeline S, the ridgeline T, the ridgeline R, and the step portion 21 indicated by a broken line). On the temporary top surface 111, a portion other than the top surface planned portion 99 is a non-top surface planned portion 98, and is formed on the step portion 21 and the bottom surface 16 in the main forming step S2 (see FIG. 5).
Moreover, it is preferable that the shape which is finally shape | molded by the top | upper surface 11 is previously shape | molded in the preforming process S1.

In the main molding step S2, the stepped portion 21 is drawn and formed by leaving the intermediate press-formed product 100 (temporary top surface 111) to the top surface 11, that is, the side sill surface 12, the rear wheel arch surface 13, and the bent portion C. The press-molded product 10 to be molded is completed.
The ridgeline R of the bending portion C of the top surface 11 is a curve having a second curvature radius r0 whose curvature radius r is smaller than the first curvature radius r1 (curvature radius r = second curvature radius r0).
Further, the ridge line S of the side sill surface 12 on the inner region M side is smoothly connected to one end of the ridge line R, and the ridge line T of the rear wheel arch surface 13 on the inner region M side is smoothly connected to the other end of the ridge line R. ing. The sandwiching angle φ between the ridge line S and the ridge line T is set to a second sandwiching angle φ0 smaller than the first sandwiching angle φ1 (squeezing angle φ = second sandwiching angle φ0).
Then, the stepped portion 21 is drawn while pressing the planned top surface portion 99 on the temporary top surface 111 corresponding to the top surface 11 set in this way with the pad 250.

Therefore, according to the press molding method according to the present embodiment, the plate-like shape of molding the temporary step surface 121 having a step in the height direction with respect to the temporary top surface 111 and the temporary top surface 111 in a substantially L shape in plan view. In the pre-forming step S1 in which a large shape deformation is performed from the workpiece W, the radius of curvature r of the ridge line RR that is the bent portion ridge line of the temporary top surface 111 is finally set to the ridge line R that is the bent portion ridge line of the top surface 11 to be formed. The first curvature radius r1 is larger than the second curvature radius r0, and the sandwiching angle φ of the temporary top surface 111 is the second sandwiching angle of the top surface 11 to be finally formed. The temporary top surface 111 and the provisional stepped portion 121 are drawn as a first sandwiching angle φ1 that is larger than the sandwiching angle φ0.
When the temporary top surface 111 is formed, even if the work is a high-rigidity member, the curvature radius r of the ridge line RR is large (first curvature radius r1). Is unlikely to occur, and surface distortion on the provisional top surface 111 is unlikely to occur. Further, since the sandwiching angle φ of the temporary ceiling surface 111 is large (the first sandwiching angle φ1), the plate-like workpiece W hardly rises at the portion of the temporary ceiling surface 111, and surface distortion on the temporary ceiling surface 111 occurs. Hateful. Therefore, even if the workpiece is a high-rigidity member, the temporary top surface 111 including the top surface 11 to be finally formed can be formed without causing surface distortion.

In the main forming step S2, the curvature radius r of the ridge line R, which is the ridge line of the bent portion of the top surface 11, is set to the second curvature radius r0, and the sandwiching angle φ of the top surface 11 is set to the second sandwiching angle φ0. The These settings correspond to the shape of the press-formed product 10 (top surface 11) to be finally formed, but the shape of the press-formed product 10 (top surface 11) to be finally formed is determined. In the case of forming from the plate-shaped workpiece W in one step, it may be a molding condition in which the plate-shaped workpiece is likely to be lifted (as a result, surface distortion is likely to occur).
However, according to the press forming method according to the present embodiment, the top surface 11 and the stepped portion 21 to be finally formed are divided into a plurality of steps, and the temporary top surface 111 and the temporary stepped portion 121 are already formed in the preliminary forming step S1. Since it is formed, forming the top surface 11 and the stepped portion 21 as the design surface from this shape may be a relatively small shape change. In addition, since molding is performed while pressing the planned top surface portion 99 corresponding to the top surface 11, the top surface to be finally formed is free from surface distortion even if the workpiece is a highly rigid member. Can be molded.

  According to the press molding method according to the present embodiment, the shapes of the top surface 11 and the stepped portion 21 of the press molded product 10 to be finally molded are molded in a plurality of steps, and the remaining portions in the main molding step S2 Therefore, the occurrence of bending and twisting of the entire press-formed product 10 can be effectively suppressed.

  Further, according to the press forming method according to the present embodiment, the shapes of the temporary top surface 111 and the temporary stepped portion 121 formed in the pre-forming step S1 are the same as those of the press-formed product 10 to be finally formed in the main forming step S2. Without being constrained by the shapes of the top surface 11 and the stepped portion 21, the extent to which the temporary top surface 111 is projected to the inner region M side and how the shape of the temporary stepped portion 121 is set are appropriately selected. be able to. For example, the temporary side sill surface 112 and its ridgeline SS may be made to coincide with the side sill surface 12 and its ridgeline S, with all the protrusions of the temporary ceiling surface 111 toward the inner region M side as the temporary rear wheel arch surface 113 side.

  Further, according to the press forming method according to the present embodiment, the plate-like workpiece W is a tailored blank material in which the high-rigidity portion Wa and the low-rigidity portion Wb are joined (for example, the plate-like workpiece W has the high-rigidity portion Wa and the low-rigidity portion). The portion Wb is a tailored blank material butt-joined at the joint surface 19, and the substantially rigid L-shaped temporary ceiling surface 111 and the temporary ceiling surface 111 are formed in a plan view with the high-rigidity portion Wa. However, since the high-rigidity portion Wa does not lift from the die 300, the low-rigidity portion Wb does not stretch. Therefore, it is possible to effectively suppress the occurrence of a shift in the shape of the press-formed product 10.

  It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention. For example, the shape of the top surface planned portion 99 that is finally formed on the top surface 11 may be formed also in the main forming step S2.

DESCRIPTION OF SYMBOLS 11 ... Top surface 21 ... Step part 99 ... Top surface planned part 111 ... Temporary top surface 121 ... Temporary step part M ... Internal area R ... Ridge line W ... Plate-shaped workpiece

Claims (1)

A plate-like workpiece is press-molded, and includes a substantially L-shaped top surface in a plan view, and a step portion having a height step with respect to the top surface in a cross-sectional view in an internal region sandwiched between the top surfaces. Press forming method of a plate-like work for forming a different shape,
In the plan view including the top surface and projecting further to the inner region side than the top surface, the curvature radius of the ridge line of the bent portion of the temporary ceiling surface is set to the first curvature radius. In addition, pre-molding is performed such that the provisional step and the provisional step portion having a step in the height direction with respect to the provisional ceiling surface are drawn by setting the sandwich angle of the provisional ceiling surface to be the first angle. Process,
A second radius of curvature of the ridgeline of the bent portion of the top surface is set to a second radius of curvature smaller than the first radius of curvature, and a sandwich angle of the top surface is smaller than the first sandwich angle. A main forming step of drawing the stepped portion while setting the pinching angle and pressing a planned top surface portion corresponding to the top surface on the temporary top surface;
A press forming method for a plate-like workpiece including

Images