JP2008307557A - Two-stage press forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a press forming method by which wall warp is reduced against a high strength material and also stable forming is obtained. <P>SOLUTION: This two-stage press forming method has a first forming stage where a temporary formed body Ff which is provided with a first forming stage where a temporary formed body Ff provided with a short side-wall part 1f is drawn to the target forming shape of a formed member having a hat-shaped cross section which is a product from a metallic blank by inserting a punch into the forming recessed part of a die and a second forming stage where, after housing and holding the temporary formed body Ff in the forming recessed part 7 of the die 8, the formed member is formed from the temporary formed body Ff by inserting the punch 9 into the forming recessed part 7 of the die 8. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a press molding method for structural members such as automobiles and machines, and relates to improvement of the shape of a molded member after a metal base plate is drawn and then released from a molding die.

  In recent years, strengthening and weight reduction of automobile bodies have been promoted with the aim of improving fuel efficiency, environmental considerations, and safety. As one of the means, press-formed members occupying most of the vehicle body structural members are being promoted to increase the strength of steel plates (high tenacity) and to lightweight materials such as aluminum alloy plates.

  Among structural members of automobiles, there are molded members having various cross-sectional shapes, but there is a hat shape as a main cross-sectional shape. As shown in FIG. 15 (solid line), a molded member having a hat-shaped cross section, that is, a hat-shaped channel member has vertical wall portions 53 at both ends of the horizontal wall portion 51 via bent portions 52, A flange portion 55 is coupled to the lower end via a bent portion 54. Such a molded member is a die having a molding recess having a molding surface corresponding to the outer shape of the side wall portion 51, the vertical wall portion 53, and the lower side (flange portion side) bent portion 54 of the molding target shape of the molding member. And a punch having a molding surface corresponding to the inner wall shape 51 of the molding target shape, the bent portion 52 on the upper side (lateral wall portion side), and the inner shape of the vertical wall portion 53. By pressing and holding the metal base plate between the outer peripheral surface (plate pressing surface) and the plate pressing member, moving the punch relative to the die side, and inserting the metal base plate into the forming recess through the punch It is integrally drawn. In addition, on the molding surface of the die, the portion where the lower bent portion 54 is molded at the end of molding, that is, the boundary portion on the outer peripheral surface side of the opening of the molding recess is referred to as the die shoulder, and on the molding surface of the punch, A portion where the upper bent portion 52 of the molding member is molded is referred to as a punch shoulder portion.

  However, when press molding is performed using a metal plate such as a high-strength steel plate or an aluminum alloy plate, elastic recovery (spring back) occurs after molding, and as shown by the two-dot chain line in FIG. The opening width is deformed so as to open larger than the opening width of the forming target shape. The reason for this is due to the angle change of the upper bent portion 52 and the warp of the vertical wall portion 53 (referred to as “wall warp”), but the influence of the wall warp is particularly large.

Various molding methods have been devised for reducing such wall warpage. For example, in Patent Document 1 (Japanese Patent Laid-Open No. 57-134214), a high-strength steel plate having a tensile strength of 35.1 kg / mm ² is used, and a longitudinal shape of a hat-shaped channel member having a target shape in the first forming step is disclosed. Using a punch having a width wider than the width of the punch used to form the temporary molded body in the second molding step, then forming the temporary molded body having a width narrower than the width between the wall portions. It describes how to hit again. According to this two-stage molding method, in the second molding step, the punch rubs the inner side of the vertical wall portion of the temporary molded body in the reverse direction from the flange portion side to the horizontal wall portion side. The stress which generates the wall warp generated in the thickness direction of the part is eliminated, and the wall warp is reduced.

In Patent Document 2 (Japanese Patent Laid-Open No. 2000-271661) and Patent Document 3 (Japanese Patent Laid-Open No. 2006-312184), the die shoulder is divided from the plate holding surface on the die side to form a movable die. A method is described in which punch molding is preceded in a state where the die is retracted, and after the molding of the lateral wall portion (part bottom portion) by the punch has progressed to some extent, the die shoulder portion is molded by pushing out the movable die. According to this method, wall warpage is reduced because tension is applied to the vertical wall portion mainly in the latter half of the molding.
JP-A-57-134214 JP 2000-271661 A JP 2006-312184 A

  However, when a high-strength steel sheet having a tensile strength of 590 MPa or higher is formed, in the press forming method described in Patent Document 1, the temporary molded body formed in the first forming step is warped in the vertical wall portion by the spring back. Therefore, in the second molding step, as shown in FIG. 16, when the temporary molded body Ff is placed on the plate pressing member 63 and inserted into the molding recess 62 of the die 61, the vertical wall of the temporary molded body Ff is placed. The portion 53f may interfere with the die shoulder portion 61d and the member may be broken from that portion, and stable molding cannot be obtained.

  Further, even if the temporary molded body Ff is accommodated in the molding recess of the die 61, if the hat-shaped channel member has a right-angle side wall portion and a vertical wall portion of the molding target shape, the provisional punch F is inserted. When the vertical wall portion 53f of the molded body Ff is counter-rubbed, as shown by the solid line in FIG. 15, the vertical wall portion of the molding target shape of the molded member is inclined so as to form an obtuse angle with respect to the horizontal wall portion. As shown in FIG. 17, in the second forming step, the punch shoulder portion 62p of the punch 62 does not effectively come into contact with the lower half portion of the vertical wall portion 53f of the temporary molded body Ff, and the reverse rubbing hardly occurs. Cannot be effectively suppressed.

  Further, in the molding methods described in Patent Documents 2 and 3, although the reduction in wall warpage can be expected when the drawing depth of the molded member is very small compared to the width between the left and right vertical wall portions, the drawing depth can be expected. When the depth becomes deep, excessive tension acts on the vertical wall portion, and the metal base plate is easily broken, and stable press molding cannot be performed.

  The present invention has been made in view of such a problem, and provides a press forming method capable of reducing wall warpage and obtaining stable forming with respect to a metal plate, such as a high-strength steel plate, which is prone to spring back. For the purpose.

  The two-stage press molding method of the present invention is a press molding method for molding a cross-section hat-shaped molded member having a vertical wall portion formed on both sides of a horizontal wall portion via a bent portion from a metal base plate. Each side is provided with a vertical wall part via a bent part, and the interval Waf between the side wall side end parts of the vertical wall part in the molding target shape is between the side wall side end parts of the vertical wall part of the molding target shape of the molding member. A first molding step in which a temporary molded body formed short with respect to the interval Was is drawn from a metal base plate, and molding having a horizontal wall molding surface portion and a vertical wall molding surface portion for molding the horizontal wall portion and the vertical wall portion of the molding member, respectively. A die having a recess and a punch for forming a molding member in cooperation with the molding recess are prepared, and the horizontal wall and the vertical wall of the temporary molded body are formed as a horizontal wall molding surface and a vertical wall molding surface of the molding recess. The temporary molded body so as to face the molding recess After holding housing to have a second forming step of forming the molded member by inserting punch are relatively moved in the molding recess of the die.

  According to this molding method, in the second molding step, molding is performed by relative movement of the punch while the temporary molded body is accommodated and held in the molding concave portion of the die, so that when the temporary molded body is re-molded (restricted) The vertical wall portion of the temporary molded body that is spring-backed does not come into contact with the die shoulder (opening edge) of the molding recess of the die, and press molding can be easily performed in a stable state. Further, in the second molding step, the vertical wall portion of the temporary molded body is bent from the opening side end portion to the horizontal wall portion side end portion by a punch so that the outside is convex along the vertical wall forming surface portion of the die (this Such a bending form is called “reverse bending”), and then bent back. For this reason, tensile stress is applied to the inside of the vertical wall portion of the molded member, and compressive stress is applied to the outside, and stress that causes wall warpage existing in the vertical wall portion of the temporary molded body (compressive stress on the inside and tensile stress on the outside). Stress) is eliminated, wall warpage of the vertical wall portion of the molded member is suppressed, and excellent moldability is obtained.

  In the first forming step, the interval Waf (mm) between the end portions of the vertical wall portions of the vertical wall portion in the forming target shape of the temporary molded body is equal to the end portions of the vertical wall portions of the vertical wall portion of the forming target shape of the forming member. It is preferable to mold the temporary molded body so as to satisfy Was-3t ≦ Waf ≦ Was-3t, where t (mm) is the thickness of the metal base plate with respect to the interval Was (mm).

  By performing the second molding step using a temporary molded body that satisfies the above relationship, as will be apparent from the examples described later, the molding target of the molding member is compared with the case where the molding member is molded in one step. The difference (opening amount) between the opening side end portions of the vertical wall portion of the shape and the same interval interval after molding can be suppressed to about 1/3 or less, and an excellent wall warp improvement effect is obtained. be able to.

  Further, in the molding method, when the vertical wall portion is formed obliquely with respect to the horizontal wall portion so that the target molding shape of the molding member is an obtuse angle between the horizontal wall portion and the vertical wall portion, The interval Wbf between the opening side end portions of the vertical wall portion in the molding target shape of the temporary molded body molded in the first molding step is the interval Was between the side wall side end portions of the vertical wall portion of the molding target shape of the molding member. It is preferable to form the same or less.

  By setting Wbf to be equal to or less than Was, even if the molding target shape of the molded member is an obtuse angle between the horizontal wall portion and the vertical wall portion, in the second molding step, the vertical wall portion of the temporary molded body is Reverse bending and unbending can be performed on the vertical wall portion of the temporary molded body by punching from the opening side end portion to the horizontal wall portion side end portion, and wall warpage in the vertical wall portion of the molded member can be suppressed. However, if Wbf is too small with respect to Wbs, in the second molding step, a large distortion occurs when the opening side end of the vertical wall portion of the temporary molded body and its periphery are reversely bent by the punch. Wbf is preferably set to a length of 80% or more of Wbs.

  Further, when the vertical wall portion is formed obliquely with respect to the horizontal wall portion so that an angle formed between the horizontal wall portion and the vertical wall portion is an obtuse angle as a target forming shape of the forming member, in the second forming step, The punch is provided with an expansion / contraction structure in which at least a head thereof expands / contracts in the direction of the vertical wall forming surface portion of the die and engages with a forming concave portion of the die so that a forming member has a forming target shape at the end of forming. The head of the punch can be expanded and contracted so that the vertical wall portion of the temporary molded body comes into contact with the vertical wall molding surface portion of the molding concave portion from the lower portion of the vertical wall portion of the temporary molded body accommodated in the recess. However, the punch can be formed by moving relative to the die side.

  By forming the second forming step in this way, it is not necessary to make Wbf equal to or less than Was as described above, and the interval Wbf between the opening side end portions of the vertical wall portion of the target shape of the temporary molded body is formed as a molded member. Even if it is equivalent to the molding target shape Wbs, the vertical wall portion of the temporary molded body can be easily reversed and bent back, so that the molding is more stable and the moldability can be further improved.

  The punch expansion / contraction structure includes a pair of split punch portions for forming the bent portion and the vertical wall portion on both sides of the horizontal wall portion of the molding member together with the die concave portion of the die, and each split punch portion is a vertical wall molding surface portion of the die. A structure that can be expanded and contracted to the side can be obtained. Moreover, it can be set as the structure provided with the press main body and the press member made to expand-contract to the vertical wall molding surface part side of die | dye in the head.

  According to the two-stage press molding method of the present invention, the second molding step is performed in which the punch is inserted into the molding recess of the die while the temporary molded body molded in the first molding process is accommodated and held in the molding recess of the die. Therefore, when re-molding the temporary molded body in the second molding step, the vertical wall portion of the temporary molded body is reversely bent and bent without the vertical wall portion of the temporary molded body coming into contact with the opening edge of the molding recess of the die. It is possible to return the molded member in which the stress that causes the wall warp, which exists in the vertical wall portion of the temporary molded body, is eliminated, and the wall warp of the vertical wall portion is suppressed can be stably press-molded. .

  First, regarding the molding object of the molding method of the present invention, the molding target shape of the temporary molded body Ff molded by the first molding step and the molding target shape of the molding member Fs molded by the second molding step are shown in FIGS. The description will be given with reference.

  As shown in FIG. 1, the temporary molded body Ff has a hat-shaped cross section, and the vertical wall portions 3f are formed symmetrically at both ends of the horizontal wall portion 1f via bent portions 2f. A flange portion 5f is coupled to the opening side end portion (lower end portion) of 3f via a bent portion 4f. In the figure, Waf is the upper end of the vertical wall 3f of the temporary molded body Ff forming target shape (end on the side of the side of the side wall, that is, the end of the bent side of the side of the side of the side of the side wall) Paf, the inner space between Paf ("upper width"). Wbf is the distance between the lower end of the vertical wall 3f of the target shape to be formed (the opening-side end, that is, the bending-stopped end of the flange-side bent portion on the vertical wall side) Pbf, Pbf ("lower width") "). Hf means the length (referred to as “height”) from the upper surface of the lateral wall 1f of the target shape to the upper surface of the flange 5f.

  As shown in FIG. 2, the molded member Fs molded in the second molding process has a hat-shaped cross section, and the vertical wall portion 3 is formed symmetrically at both ends of the horizontal wall portion 1 via the bent portions 2. In addition, a flange portion 5 is coupled to the opening side end portion (lower end portion) of each vertical wall portion 3 via a bent portion 4. In the figure, Was is a distance (referred to as “upper width”) between the upper end portions Pas and Pas of the vertical wall portion 3 of the forming target shape of the forming member Fs, and Wbs is a lower end portion Pbs of the vertical wall portion 3 of the forming target shape. , Pbs inner space (referred to as “lower width”), Hs is the length (referred to as “height”) from the upper surface of the lateral wall portion 1 of the forming target shape to the upper surface of the flange portion 5, each of which is temporarily formed. It corresponds to Waf, Wbf, and Hf of the body Ff.

The upper width Waf of the molding target shape of the temporary molded body Ff is formed smaller than the upper width Was of the molding target shape of the molding member Fs. As will be apparent from the examples described later, when the thickness of the metal base plate used for forming the temporary molded body Ff is t (mm), Waf (mm) is Was (mm) compared to Was (mm). -3t ≦ Waf ≦ Was-t
It is preferable to set to. Further, it is preferable that the lower width Wbf and the height Hf of the molding target shape of the temporary molded body Ff are equal to or substantially the same as the lower width Wbs and the height Hs of the molding target shape of the molding member Fs, respectively. Further, it is preferable that the bent portions 2f and 4f on the side wall portion side and the flange portion side of the temporary molded body Ff have the same radius of curvature as the bent portions 2 and 4 of the molded member Fs.

  Next, in the first embodiment in which the forming target shape of the forming member Fs is Was = Wbs (upper width = lower width), that is, the hat-shaped channel member in which the angle formed by the horizontal wall portion 1 and the vertical wall portion 3 is a right angle is formed. The two-stage press molding method will be described. This forming method has a first forming step of drawing the temporary formed body Ff and a second forming step of reforming the temporary formed body Ff. The first molding step includes a die and a punch having a molding surface corresponding to the molding target shape, except that the molding target shape of the temporary molded body Ff is set smaller than the molding target shape of the molding member Fs. Is drawn in one step. Since this process is the same as the conventional drawing process performed in one process, its description is omitted. The temporary molded body Ff that has been molded by the first molding step is warped in the vertical wall portion 3f of the temporary molded body Ff as in the conventional case.

  As shown in FIG. 3, the second forming step includes a horizontal wall forming surface portion 1 d for forming the horizontal wall portion 1 of the forming member Fs, a vertical wall forming surface portion 3 d for forming the vertical wall portion 3, and a lower end side of the vertical wall portion 3. A die 8 having a molding recess 7 in which a die shoulder 4d for molding the bent portion 4 is formed, and a lateral wall portion of the molding member Fs in cooperation with the lateral wall molding surface portion 1d and the vertical wall molding surface portion 3d of the die 8. 1 and a vertical wall forming surface portion 1p for forming the vertical wall portion 3 and a vertical wall forming surface portion 3p, and further includes a punch shoulder portion 2p for forming a bending portion 2 connecting the horizontal wall portion 1 and the vertical wall portion 3 of the forming member Fs. This is performed using a molding die provided with a punch 9. For the punch 9 as well, the interval Wasp of the portion corresponding to Was of the forming target shape Was of the forming member Fs is called “upper width”, and the interval Wbsp of the portion corresponding to Wbs of the forming target shape of the forming member Fs is “ In this embodiment, Wasp = Wbsp = Was = Wbs.

  The punch 9 is provided with an accommodating member 11 for accommodating the temporary molded body Ff in the molding recess 7 of the die 8 at the center of the punch 9 so as to be movable up and down. The housing member 11 can be moved up and down by lifting means such as a hydraulic cylinder such as hydraulic or pneumatic pressure. Further, a plate pressing member (blank holder) 12 is provided that presses and holds the metal base plate (flange portion of the temporary molded body) between the lower surface of the die 8 (opening outer peripheral surface of the molding recess). The plate pressing member 12 is urged upward by a fluid pressure cylinder, an elastic member, or the like, but the upper surface of the plate pressing member 12 is the punch 8 until the metal base plate is pressed and clamped between the lower surface of the die 8. The position is regulated so as to be in a certain positional relationship with respect to the upper surface of, for example, the same surface.

  In this embodiment, the die 8 is fixed to the upper frame of the press device, the punch 9 is attached to a ram provided at the lower portion of the press device, and the punch 9 is moved to the die side to form the molding recess 7 of the die 8. Molding is performed by insertion. Of course, contrary to this embodiment (same in other embodiments below), the punch 9 is fixed to the lower frame of the press device, the die 8 is attached to the ram provided at the upper portion of the press device, and the die 8 is attached. The punch 9 may be moved to the punch 9 side so that the punch 9 is inserted into the molding recess 7 of the die 8. In this case as well, the plate pressing member 12 is urged upward, but the upper surface of the plate pressing member 12 is against the upper surface of the punch 8 until the metal base plate is pressed between the lower surface of the die 8. The position is regulated so as to be in a certain positional relationship, for example, flush.

  The molding operation in the second molding step will be described with reference to FIGS. First, as shown in FIG. 3, the punch 9 and the plate pressing member 12 are made to stand by to the lower limit, and the temporary molded body Ff molded in the first molding process is placed on a mounting table provided on the upper portion of the housing member 11. To raise. Next, as shown in FIG. 4, the punch 9 and the plate pressing member 12 are raised to the die side while the housing member 11 is raised. At this time, the temporary molded body Ff placed on the housing member 11 is pushed into the molding concave portion 7 of the die 8 against the warp of the vertical wall portion 3f. Further, as shown in FIG. 5, the flange portion 5f of the temporary molded body Ff is pressed and clamped by the plate pressing member 12, and the punch 9 is further raised. At this time, the vertical wall portion 3f of the temporary formed body Ff is bent by the punch shoulder 2p so that the outside is convex, and is bent back by the vertical wall forming surface portion 3p of the punch 9. Then, as shown in FIG. 6, when the punch 9 is raised to the ascending limit, the temporary molded body Ff is formed into the forming member Fs, and the forming ends. Thereafter, the punch 9 and the plate pressing member 12 are lowered while the accommodating member 11 is lowered into the punch 9, and the molding member Fs is released from the die 8. In addition, by forming the lower width Wbf of the molding target shape of the temporary molded body Ff to the same extent as the lower width Wbs of the molding target shape of the molding member Fs, the spring wall of the vertical wall portion 3f of the temporary molded body Ff is moved outward by the spring back. In order to open, the temporary molded body Ff is placed on the housing member 11, the housing member 11 is raised, and the temporary molded body Ff is housed in the molding recess 7 of the die 8, whereby the elastic force of the vertical wall portion 3 f is obtained. Thus, the temporary molded body Ff is naturally held in the molding recess 7. For this reason, after accommodating the temporary molded object Ff in the shaping | molding recessed part 7, you may descend | lower the accommodating member 11. FIG.

  FIG. 7 is a schematic cross-sectional view of the molded member Fs in a state of being constrained by the molding die at the end of molding, and M1 is a bending moment generated by bending back the upper bending portion 2f of the temporary molded body Ff. Yes, M2 is a bending moment generated in the bending portion 2 on the upper side of the forming member Fs in the second forming step. M3 is a bending moment generated in the vertical wall portion 3f of the temporary molded body Ff, and M4 is a bending moment generated by reverse bending and bending back of the vertical wall portion of the forming member Fs by the punch in the second forming step. Yes, M1 and M2 cancel each other, and M3 and M4 cancel each other. For this reason, the deformation | transformation from the shaping | molding target shape of the shaping | molding member Fs after a 2nd shaping | molding process is suppressed.

  Regarding the molding method of the above embodiment, the optimum range of the upper width Waf of the temporary molded body Ff was examined by the following experiment. A high strength steel plate of 780 MPa class having a thickness t = 1.2 mm was used as the metal base plate. A temporary molded body Ff having the dimensions shown in Table 1 below (molding target dimension) was molded in the first molding step. The plate pressing force of the metal base plate in this forming was 3 tonf. Using the obtained temporary molded body Ff, a molded member Fs having a dimension (molding target dimension) shown in the same table was molded in the second molding process. The pushing force of the housing member in the second molding step was 1 tonf.

  After the molding of the second molding process was completed, the actual lower width Wbs ′ was measured for the molded member Fs after the release, and the opening amount ΔW was calculated from (Wbs′−Wbs). The ratio of the opening amount of the molding member Fs molded by the molding method of the embodiment to the opening amount of the molding member Fs (sample No. 7) molded only by the second molding step corresponding to the conventional molding method (mouth The opening ratio was determined. These values are also shown in Table 1. In addition, a thing with an opening amount of a negative value shows that the vertical wall part has deform | transformed inside the shaping | molding target shape.

  From Table 1, in Sample Nos. 2 to 4, (Was-Waf) / t is 1.3 to 3.0, that is, Waf is in the range of (Was-1.3t) to (Was-3.0t). It can be seen that the opening amount is about 1/3 or less as compared with the one-step molding. Since the amount of opening is almost proportional to the material strength, setting Waf within the range of (Was-t) to (Was-3t) is equivalent to forming a 270 MPa grade mild steel sheet in one step. It is inferred that the amount of mouth opening will occur.

  Next, the forming target shape of the forming member Fs is Was <Wbs (upper width <lower width), that is, the angle formed by the horizontal wall portion 1 and the vertical wall portion 3 is an obtuse angle, and the vertical wall portion 3 is oblique to the horizontal wall portion 1. A two-stage press molding method according to the second embodiment, in which the hat-shaped channel member formed in (1) is to be molded, will be described. As in the first embodiment, this embodiment includes a first molding step for drawing the temporary molded body Ff and a second molding step for remolding the temporary molded body Ff. The molding target shape of the temporary molded body Ff molded by the first molding step is set to be smaller (Waf <Was) than the molding target shape of the molding member Fs, and the molding target of the temporary molded body Ff is set. Except that the lower width Wbf of the shape is set to be equal to or lower than the upper width Was of the forming target shape of the forming member Fs (Wbf ≦ Was), it is the same as in the first embodiment.

  In the second molding step of this embodiment, the basic configuration of the die and punch used is the same as that of the first embodiment, but the shape of the molding surface is as shown in FIG. 8 according to the molding target shape of the molding member Fs. In addition, the vertical wall molding surface portion 3p is formed obliquely with respect to the horizontal wall molding surface portion 1p. Of course, the upper width Wasp of the punch 9 is set to the upper width Was of the forming target shape of the forming member Fs, and the lower width Wbsp of the punch 9 is set to the lower width Wbs of the forming target shape. In addition, in order to avoid complexity, the shaping | molding site | part similar to the die | dye and punch concerning 1st Embodiment attaches | subjects the same code | symbol.

  Here, the molding operation in the second molding step of the second embodiment will be described. First, the temporary molded body Ff is accommodated and held in the molding concave portion 7 of the die 8 using a housing member (not shown). Next, as shown in FIG. 8, when the plate pressing member 12 is raised together with the punch 9, the flange portion 5 f of the temporary molded body Ff is pressed and sandwiched by the lower surface of the die 8 by the plate pressing member 12, and the temporary molded body Ff is Elastic deformation is performed in the molding recess 7 so as to obtain a molding target shape. On the other hand, the punch shoulder 2p of the punch 9 comes into contact with the lower bent portion 4f of the temporary molded body Ff. When the punch 9 is further raised, the vertical wall portion 3f of the temporary molded body Ff is reversely bent by the punch shoulder 2p of the punch 9, and then the reverse bent portion is the vertical wall forming surface portion 3p and the vertical wall forming surface portion 3d of the die 8. It is sandwiched between and bent back. Thereby, even when the vertical wall portion 3 of the forming member Fs is formed obliquely, the bending moment generated from the horizontal wall portion 1 to the vertical wall portion 3 is canceled out similarly to FIG. 7, and the deformation of the forming member Fs is suppressed. Is done.

A molding experiment was conducted on the two-stage press molding method of the second embodiment. When the shape of the molded member having an obtuse angle between the horizontal wall portion 1 and the vertical wall portion 3 is represented by Was = k × Wbs (where k is a constant satisfying 0 <k <1), k is 0.00. In the case of about 9, by setting the Waf and Wbf of the temporary molded body as shown in the following formula, the same result as in Table 1 was obtained.
Waf = Wbf = 0.9 × Was = 0.9 × k × Wbs

  On the other hand, when k is reduced to 0.8 or less and the vertical wall portion has a greater obtuse angle with respect to the horizontal wall portion, setting Wbf according to the above formula causes Wbf to be considerably smaller than Wbs. There was a tendency for bending wrinkles (bending inward locally after mold release due to excessive reverse bending) in the vertical wall near the die shoulder during the two molding steps. Even when molding a molded member having such a large obtuse angle, it is possible to improve wall warpage in the entire range of the vertical wall portion by using a temporary molded body in which Wbf is equal to Wbs without generating bending wrinkles. A possible two-stage press molding method will be described with reference to the following third embodiment.

  Also in the two-stage press molding method according to the third embodiment, as described above, the molding target shape of the molding member Fs is an obtuse angle between the horizontal wall portion and the vertical wall portion, and the vertical wall portion is oblique to the horizontal wall portion. The formed hat-shaped channel member is an object to be molded. This molding method also includes a first molding step for drawing the temporary molded body Ff and a second molding step for remolding the temporary molded body Ff. As in the first and second embodiments, the molding target shape of the temporary molded body Ff molded by the first molding step is set to have a smaller upper width (Waf <Was) than the molding target shape of the molding member Fs. Is done.

  In the second molding step of the third embodiment, the die is the same as that of the second embodiment, but the punch structure is different, and this point will be mainly described. As shown in FIG. 9, the punch 9 includes left and right divided punch portions 9 </ b> L and 9 </ b> R divided into right and left along the center line of the forming recess 7, and the divided punch portions 9 </ b> L and 9 </ b> R are formed into a vertical wall of the die 8. It has an expansion / contraction structure provided with expansion / contraction means for advancing / retreating in the direction (lateral direction) of the surface portion 3d. In the figure, 1pL and 1pR are divided horizontal wall molding surface portions of the divided punch portions 9L and 9R, respectively. As the expansion / contraction means, a fluid pressure cylinder, an elastic member such as a spring, or a mechanical expansion / contraction mechanism such as a cam can be used.

  When the left and right divided punch portions 9L and 9R are integrated with the interval between the two divided punch portions being reduced, the left and right divided punch portions 9L and 9R are interposed via the horizontal wall portion 1, the upper bent portion 2, and the vertical wall portion 3 of the forming target shape of the forming member Fs. A molding surface is formed so as to engage with the molding recess 7 of the die 8. The upper width (maximum upper width: maximum Wasp) of the left and right divided punch portions 9L and 9R required for molding in the second molding step is Wbs, and as shown in FIG. The upper width (Wasp) is Was and the lower width (Wbsp) is Wbs. Accordingly, the expansion / contraction width ΔS of the divided punch portion necessary for molding is set to (Wbs−Was). Of course, the maximum upper width may be set to Wbs or more in consideration of maintenance and the like.

  Here, the molding operation in the second molding step of the third embodiment will be described with reference to FIGS. First, the temporary molded body Ff is accommodated in the molding recess 7 of the die 8 by an accommodation member (not shown). After the provisional molded body Ff is accommodated in the molding recess 7, as shown in FIG. 9, the left and right divided punch portions 9L and 9R are expanded outward to raise the punch 9. Thereby, the expanded punch shoulders 2p of the left and right divided punch portions 9L and 9R press the lower end portion on the opening side of the vertical wall portion 3f of the temporary molded body Ff against the vertical wall forming surface portion 3d of the die 8. Further, as shown in FIG. 10, the left and right divided punch portions 9 </ b> L and 9 </ b> R are expanded to raise the punch 9 while pressing the vertical wall portion 3 f of the temporary molded body Ff against the vertical wall forming surface portion 3 d of the die 8. As a result, the vertical wall portion 3f is reversely bent and bent back from the lower end portion to the upper end portion, and a bending moment in the direction opposite to the bending moment causing the wall warp in the vertical wall portion 3f of the temporary molded body Ff is generated. . Then, as shown in FIG. 11, the gap between the left and right divided punch portions 9L and 9R disappears at the end of molding, and the two are integrated to form the temporary molded body Ff into the molding target shape of the molding member Fs. The distribution state of the bending moment in the cross section of the molded member Fs in this state is the same as in FIG. 7, and the bending moments cancel each other, so that the warp of the vertical wall portion 3 of the molded member Fs after release is corrected.

  In the third embodiment, in the second molding step, the vertical wall portion 3f of the temporary molded body Ff accommodated in the die 8 is viewed from below using the punch 9 provided with the divided punch portions 9L and 9R that expand and contract to the left and right. Although the reverse bending and the bending back were performed to the upper part, the punch 9 shown in FIG. 12 can be used as a punch 9 which performs the said reverse bending and a bending return as a modification of 3rd Embodiment. The punch 9 includes a punch body 9M having a molding surface for forming the temporary molded body Ff into a molding target shape of the molding member Fs in cooperation with the molding recess 7 of the die 8, and a punch shoulder 2p of the punch body 9M. An expansion / contraction structure provided with a pair of left and right pressing members 14L, 14R that extend in the direction (lateral direction) of the vertical wall molding surface portion 3d of the die 8 and expansion / contraction means that expands / contracts the pressing members 14L, 14R. Have. As the expansion / contraction means, an expansion / contraction mechanism using a fluid structure, an elastic member such as a spring, or a mechanical structure such as a cam can be used. In the illustrated example, the expansion and contraction mechanism is formed by supplying and discharging fluid pressure to and from the storage cylinders of the pressing members 14L and 14R.

  The pressing members 14L and 14R are retracted and accommodated in the vertical wall molding surface portion 3p of the punch body 9M at the end of molding, and the retracted positions where the outer end portions thereof are flush with the vertical wall molding surface portion 3p (see FIG. 14). And the outer width Wout expands and contracts between the extension position (see FIG. 12) at which the outer width Wout extends to the lower width Wbs of the target shape of the forming member Fs. That is, the maximum outer width (maximum Wout) of the pressing members 14L and 14R is Wbs, and the minimum outer width (minimum Wout) is approximately Was. Of course, the maximum Wout may be greater than or equal to Wbs and the minimum Wout may be less than Was in consideration of maintenance or the like.

  A molding operation in the second molding step when the punch 9 provided with the pressing members 14L and 14R is used will be described with reference to FIGS. First, the temporary molded body Ff is accommodated in the molding recess 7 of the die 8 by an accommodation member (not shown). After the provisional molded body Ff is accommodated in the molding recess 7, as shown in FIG. 12, the left and right pressing members 14L, 14R are extended outward so that Wout is maximized, and the punch 9 is raised. Thereby, the top part of the extended left and right pressing members 14L and 14R presses the lower end part on the opening side of the vertical wall part 3f of the temporary molded body Ff against the vertical wall molding surface part 3d of the die 8. Further, as shown in FIG. 13, the punches 9 are raised while the top portions of the left and right pressing members 14 </ b> L and 14 </ b> R are extended to press the vertical wall portion 3 f of the temporary molded body Ff against the vertical wall forming surface portion 3 d of the die 8. Thereby, the vertical wall portion 3f is reversely bent and bent back from the lower end portion to the upper end portion, and a bending moment in a direction opposite to the bending moment causing the wall warp in the vertical wall portion 3f of the temporary molded body Ff is generated. Then, as shown in FIG. 14, at the end of molding, the left and right pressing members 14L, 14R are reduced in the molding surface of the punch body 9M, and the temporary molded body Ff is molded into the molding target shape of the molding member Fs by the punch body 9M. Is done. The distribution state of the bending moment in the cross section of the molded member Fs in this state is the same as in FIG. 7, and the bending moments cancel each other, so that the warp of the vertical wall portion of the molded member Fs after the mold release is corrected.

  In the third embodiment and its modification, the left and right pressing members 14L, 14R provided at the maximum upper width of the left and right divided punch portions 9L, 9R and the head of the punch body 9M at the start of molding in the second molding step. Is set to be approximately equal to the lower width Wbs of the molding target shape of the molding member Fs, and reverse bending is performed from the lower end portion on the opening side of the vertical wall portion 3f of the temporary molded body Ff to the upper end portion, and bending back is performed. However, the punch shoulder is not limited to the lower end portion of the vertical wall portion 3f of the temporary molded body Ff, and includes a lower portion including the lower end portion, preferably a lower region within about 20% of the height of the temporary molded body Ff from the lower end portion. It is also possible to perform reverse bending and unbending by pressing the top portion of the portion or the pressing member against the vertical wall portion 3f of the temporary molded body Ff.

It is a cross-sectional view of the temporary molded object which is a shaping | molding object of the 1st shaping | molding process which concerns on embodiment of this invention. It is a cross-sectional view of a forming member (hat-shaped channel member) that is a forming target of the second forming step according to the embodiment of the present invention. It is sectional explanatory drawing which shows arrangement | positioning of the die | dye, a punch, and a temporary molded object in the shaping | molding preparation period of the 2nd shaping | molding process concerning 1st Embodiment. It is a section explanatory view showing arrangement of a die, a punch, and a temporary fabrication object in the forming start period of the 2nd forming process concerning a 1st embodiment. It is sectional explanatory drawing which shows the shaping | molding state of the temporary molded object in the shaping | molding middle stage of the 2nd shaping | molding process concerning 1st Embodiment. It is a section explanatory view showing the molding state of a temporary fabrication object at the end of fabrication of the 2nd fabrication process concerning a 1st embodiment. It is sectional explanatory drawing which shows the distribution state of the bending moment which arises in the shaping | molding member restrained by the shaping die at the time of completion | finish of a shaping | molding of a 2nd shaping | molding process. It is sectional explanatory drawing which shows arrangement | positioning of the die | dye, a punch, and a temporary molded object in the shaping | molding start stage of the 2nd shaping | molding process concerning 2nd Embodiment. It is sectional explanatory drawing which shows arrangement | positioning of the die | dye, a punch, and a temporary molded object in the shaping | molding start stage of the 2nd shaping | molding process concerning 3rd Embodiment. It is sectional explanatory drawing which shows the shaping | molding state of the temporary molded object in the shaping | molding middle stage of the 2nd shaping | molding process concerning 3rd Embodiment. It is sectional explanatory drawing which shows the shaping | molding state of the temporary molded object at the time of completion | finish of shaping | molding of the 2nd shaping | molding process concerning 3rd Embodiment. It is sectional explanatory drawing which shows arrangement | positioning of the die | dye, a punch, and a temporary molded object in the shaping | molding start stage of the 2nd shaping | molding process concerning the modification of 3rd Embodiment. It is sectional explanatory drawing which shows the shaping | molding state of the temporary molded object in the shaping | molding middle stage of the 2nd shaping | molding process concerning the modification of 3rd Embodiment. It is sectional explanatory drawing which shows the shaping | molding state of the temporary molded object at the time of completion | finish of shaping | molding of the 2nd shaping | molding process concerning the modification of 3rd Embodiment. It is sectional drawing of the shaping | molding target shape and deformation | transformation shape after shaping | molding of the hat-shaped channel member draw-drawn by 1 process by the conventional press molding method. It is sectional drawing which shows the state of the temporary molded object of the molding preparation period in the 2nd shaping | molding process of the conventional two-stage press molding method. Sectional drawing which shows the shaping | molding state of the temporary molded object of the shaping | molding initial stage in the 2nd shaping | molding process in the 2nd shaping | molding process at the time of shaping | molding the shaping | molding member of the shaping target shape in which the vertical wall part spread outside using the conventional 2 step press molding method It is.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1f Horizontal wall part 2,2f, 4,4f Bending part 3,3f Vertical wall part 3d, 3p Vertical wall shaping part 7 Molding recessed part 8 Die 9 Punch 11 Housing member 12 Plate pressing member Ff Temporary molding Fs Molding member

Claims (6)

A press molding method for molding a hat-shaped molded member having a vertical wall portion formed on both sides of a horizontal wall portion via a bent portion, from a metal base plate,
A vertical wall portion is provided on each side of the horizontal wall portion via a bent portion, and the distance Waf between the horizontal wall side ends of the vertical wall portion in the molding target shape is the side wall side end of the vertical wall portion of the molding target shape of the molding member A first forming step of drawing a temporary formed body formed short with respect to the interval Was between the parts from the metal base plate;
Preparing a die having a molding concave portion having a horizontal wall molding surface portion and a vertical wall molding surface portion for molding the horizontal wall portion and the vertical wall portion of the molding member, respectively, and a punch for molding the molding member in cooperation with the molding concave portion; The temporary molded body is accommodated and held in the molding concave portion so that the horizontal wall portion and the vertical wall portion of the temporary molded body face the horizontal wall molding surface portion and the vertical wall molding surface portion of the molding concave portion, and then the molding concave portion of the die A two-stage press forming method comprising a second forming step of forming the forming member by relatively moving the punch into the insert.   In the first forming step, the interval Waf (mm) between the end portions of the vertical wall portions of the vertical wall portion in the forming target shape of the temporary molded body is equal to the end portions of the vertical wall portions of the vertical wall portion of the forming target shape of the forming member. The temporary molded body is drawn so as to satisfy Was-3t ≦ Waf ≦ Was-t, where t (mm) is the thickness of the metal base plate with respect to the interval Was (mm). The two-stage press molding method described in 1.   The vertical wall portion is formed obliquely with respect to the horizontal wall portion so that the angle formed by the horizontal wall portion and the vertical wall portion is an obtuse angle as a target forming shape of the forming member, and is temporarily formed in the first forming step. The interval Wbf between the opening side ends of the vertical wall portion in the molding target shape of the molded body is formed to be equal to or less than the interval Was between the side wall side end portions of the vertical wall portion of the molding target shape of the molding member. The two-stage press molding method described in 1 or 2.   The vertical wall portion is formed obliquely with respect to the horizontal wall portion so that an angle formed by the horizontal wall portion and the vertical wall portion is an obtuse angle as a target forming shape of the forming member, and in the second forming step, the punch is at least The head has an expansion / contraction structure that expands and contracts in the direction of the vertical wall molding surface of the die and engages with the molding recess of the die so that the molding member has a molding target shape at the end of molding, and is accommodated in the molding recess of the die. The punch head is expanded and contracted so that the vertical wall portion of the temporary molded body comes into contact with the vertical wall molding surface portion of the molding recess from the lower part of the opening side of the vertical wall portion of the temporary molded body. The two-stage press molding method according to claim 1, wherein the molding is performed by relatively moving the mold to the die side.   The expansion / contraction structure of the punch includes a pair of divided punch portions for forming the bent portion and the vertical wall portion on both sides of the horizontal wall portion of the molding member together with the molding concave portion of the die, and each divided punch portion is on the side of the vertical wall forming surface portion of the die. The two-stage press molding method according to claim 4, wherein the two-stage press molding method can be freely expanded and contracted.   5. The two-stage press molding method according to claim 4, wherein the punch expansion / contraction structure includes a punch main body and a pressing member at its head that is extendable to a vertical wall molding surface portion side of the die.

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