Abstract
A press forming method for producing a saddle type final product comprises a first process of producing an intermediate product having a processing adjustment section, by cold press working against an ultrahigh tensile strength steel plate, to deform the side wall portions and flange portions at the both sides in the predetermined area, with the cross section of the top plate portion being maintained in a predetermined shape, and a second process of pressing at least the processing adjustment section, by cold press working against the intermediate product, with the cross section of the top plate portion being maintained in the predetermined shape. In at least one of the first process and second process, a processing target of the at least one process is bent in the direction opposite to the opening of the hat-shaped cross section, to produce the saddle type final product
Claims
1. A press forming method for producing a saddle type final product by press working against a steel plate to produce an elongated member of a hat-shaped cross section having an elongated top plate portion, and side wall portions and flange portions at both sides of the top plate portion, and bend a predetermined area of the elongated member in a direction opposite to an opening of the hat-shaped cross section, the press forming method comprising: a first process of producing an intermediate product having a processing adjustment section, by cold press working against an ultrahigh tensile strength steel plate to deform the side wall portions and flange portions at the both sides in the predetermined area of the elongated member, with the cross section of the top plate portion being maintained in a predetermined shape, and a second process of pressing at least the processing adjustment section, by cold press working against the intermediate product, with the cross section of the top plate portion being maintained in the predetermined shape, wherein, in at least one of the first process and second process, a processing target of the at least one process is bent in the direction opposite to the opening of the hat-shaped cross section, to produce the saddle type final product.
2. The press forming method of claim 1, wherein, in the first process, inclined angles of the side wall portions at the both sides relative to the top plate portion are varied in the predetermined area, to deform the side wall portions portion and flange portions at the both sides in the predetermined area.
3. The press forming method of claim 2, wherein the inclined angles of the side wall portions relative to the top plate portion in the predetermined area of the intermediate product are set to be 0 degree to 90 degree.
4. The press forming method of claim 1, wherein a longitudinal dimension of the intermediate product including an extended amount in the longitudinal direction in the predetermined area, which amount is determined by the deformed amount of the side wall portions and flange portions, is set to be 110% of the longitudinal dimension of the final product in the same area as the predetermined area.
5. The press forming method of claim 1, wherein the intermediate product possesses a plurality of processing adjustment sections in the longitudinal direction of the predetermined area.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] [FIG. 1] is a perspective view showing an intermediate product and a final product produced by an embodiment of a press forming method according to the present invention.
[0027] [FIG. 2] is a plan view of an intermediate product produced by an embodiment of a press forming method according to the present invention.
[0028] [FIG. 3] is a side view of an intermediate product produced by an embodiment of a press forming method according to the present invention.
[0029] [FIGS. 4(A)-4(G)] is a sectional view sectioned along A-A line to G-G line in FIG. 2.
[0030] [FIG. 5] is a plan view of a final product produced by an embodiment of a press forming method according to the present invention.
[0031] [FIG. 6] is a side view of a final product produced by an embodiment of a press forming method according to the present invention.
[0032] [FIG. 7] is a sectional view sectioned along A-A line, D-D line and G-G line in FIG. 5.
[0033] [FIG. 8] is a sectional view showing a part of a press apparatus for use in a first process according to an embodiment of the present invention.
[0034] [FIG. 9] is a sectional view showing a part of a press apparatus for use in a second process according to an embodiment of the present invention.
[0035] [FIG. 10] is a plan view of an intermediate product produced by another embodiment of a press forming method according to the present invention.
[0036] [FIG. 11] is a side view of an intermediate product produced by another embodiment of a press forming method according to the present invention.
[0037] [FIGS. 12(A)-12(G)] is a sectional view sectioned along A-A line to G-G line in FIG. 10.
[0038] [FIG. 13] is a plan view of an intermediate product produced by a further embodiment of a press forming method according to the present invention.
[0039] [FIG. 14] is a side view of an intermediate product produced by a further embodiment of a press forming method according to the present invention.
[0040] [FIGS. 15(A)-15(F)] is a sectional view sectioned along A-A line to F-F line in FIG. 13.
[0041] [FIG. 16] is a perspective view showing an intermediate product and a final product produced by a yet further embodiment of a press forming method according to the present invention.
EMBODIMENTS FOR CARRYING OUT THE INVENTION
[0042] Hereinafter, will be explained desirable embodiments of the present invention referring to drawings. FIG. 1 shows an intermediate product 20 produced after a first process (Pf) in an embodiment of a press forming method according to the present invention, and a final product 10 produced after a second process (Ps). In addition to these processes, boring, trimming and so on are arbitrarily performed, drawings of which are omitted in FIG. 1. At the outset, will be explained about a saddle type final product 10 as shown in a lower part of FIG. 1, wherein an elongated member of a hat-shaped cross section having an elongated top plate portion 11, side wall portions 12 and 13, and flange portions 14 and 15 at its both sides, is bent in a direction opposite to the opening of the hat-shaped cross section (upward in FIG. 1) to be formed into the saddle type, and it is served as a vehicle body structural member, for example.
[0043] According to the present embodiment, the top plate portion 11 is formed with a recessed portion 11r in the lateral center, and protruded portions 11p, 11p at its both sides, by which a step portion is formed to extend in the longitudinal direction. Instead of the step, a protruded portion 11p may be formed in the lateral center, and other shapes, or a plate shape (plane) may be employed, as far as a predetermined section modulus can be ensured.
[0044] In order to produce the final product 10 as described above, according to the present embodiment, a cold-rolled steel sheet “SPC1180” with sheet thickness of 1.6 mm is used as the ultrahigh tensile steel plate, and the cold press working is performed by a press apparatus (shown in FIGS. 8 and 9) as described later. At the outset, in the first process (Pf), by means of the cold press working against the ultrahigh tensile steel plate as described above, maintaining a predetermined shape (approximately the same shape as the top plate portion 11 of the final product 10 shown in the lower part of FIG. 1) as indicated by two-dotted chain lines in the upper part of FIG. 1, i.e., maintaining approximately the same shape as the top plate portion 11 without deforming a top plate portion 21, by deforming side wall portions 22 and 23 and flange portions 24 and 25 at its both sides in a predetermined area (M), to form a processing adjustment section 20a, and bending it in the direction opposite to the opening of the hat-shaped cross section, an intermediate product 20 is produced.
[0045] According to the present embodiment, the intermediate product 20 is formed as shown in FIGS. 2-4. That is, by varying the inclined angles of the side wall portions 22 and 23 relative to the top plate portion 21 in the predetermined area (M) of the intermediate product 20, the side wall portions 22 and 23 and flange portions 24 and 25 with the same cross sections as those cross sections as shown in (A), (B), (F) and (G) in FIG. 4 are deformed into the side wall portions 22a and 23a and flange portions 24a and 25a as shown in (C)-(E) in FIG. 4 in the predetermined area (M), and side shapes of the side wall portion 22 and flange portion 24 are deformed into side shapes of the side wall portions 22a and flange portion 24a as shown in FIG. 3 (the side wall portion 23 and flange portion 25 are deformed in the same manner). The processing adjustment section 20a is configured by the side wall portion 22a and 23a, and flange portion 24a and 25a, so that the intermediate product 20 with a bent angle α (e.g., 139 degree) as shown in FIG. 3 is produced.
[0046] Then, in the second process (Ps), by means of the cold press working against the intermediate product 20 as described above, maintaining the cross section of the top plate portion 21 to be the predetermined shape, by pressing the processing adjustment section 20a (so that the processing adjustment section 20a will substantially disappear), and bending it in the direction opposite to the opening of the hat-shaped cross section, to be formed into the saddle type, the final product 10 as described above is produced. Although the top plate portion 11 and the top plate portion 21 with different bent angles being provided are not of the same shape in a strict sense, in such a sense that the top plate portion 21 is maintained to be approximately the same shape as the target top plate portion 11, without deforming the top plate portion 21 (except for varying the bent angle of the top plate portion 21), the first process (Pf) is performed with the cross section of the plate portion 21 being maintained in the predetermined shape, and the second process (Ps) is performed.
[0047] Accordingly, the final product 10 will be formed into the shape as shown in FIGS. 5-7. That is, the cross sections of the side wall portions 22 and 23 and flange portions 24 and 25 as shown in (A), (B), (F) and (G) in FIG. 4, and the cross sections of the side wall portions 22a and 23a and flange portions 24a and 25a as shown in (C)-(E), are deformed into the cross sections of the side wall portions 12 and 13 and flange portions 14 and 15 as shown in FIG. 7, and also the cross sections of the side wall portions 22, 22a and flange portions 24, 24a as shown in FIG. 3 are deformed into the cross sections of the side wall portion 12 and flange portion 14 as shown in FIG. 6 (the cross sections of the side wall portions 23, 23a and flange portions 25, 25a are deformed in the same manner), so that the saddle type final product 10 is formed with the side wall portions 12 and 13 and flange portions 14 and 15 having the same cross section along the whole length, and a bent angle β (e.g., 149 degree) as shown in FIG. 6. Although the final product 10 of the present embodiment is formed in the same cross section along the whole length, such a saddle type final product with its cross section being gradually varied in the longitudinal direction can be formed in the same manner.
[0048] According to the above-described intermediate product 20, as shown in FIG. 3, compressive stresses as indicated by dashed line arrows are applied to the inside of the bent portion in the predetermined area (M), so that tensile stresses as indicated by solid line arrows are remained after the first process (Pf). On the other hand, with respect to the processing adjustment section 20a at the outside of the bent portion, as shown in FIGS. 2-4, the side wall portions 22 and 23 and flange portions 24 and 25 are deformed 3-dimensionally to become the side wall portions 22a and 23a and flange portions 24a and 25a. That is, boundary lines (inside ridge lines) between the top plate portion 21 and the side wall portions 22a and 23a before processing, and boundary lines (outside ridge lines) between the side wall portions 22a and 23a and the flange portions 24a and 25a before processing in the predetermined area (M), are bent after processing, so that they become longer than the boundary lines (inside ridge lines) between the top plate portion 21 and the side wall portions 22 and 23, and boundary lines (outside ridge lines) between the side wall portions 22 and 23 and the flange portions 24 and 25 in the predetermined area (M). Also, in the present embodiment, as shown in FIG. 3, contour lines at the outside of the bent portions of the side wall portions 22a and 23a and the flange portions 24a and 25a after processing become longer than those portions before processing. That is, appeared in FIGS. 2 and 3 are lateral components and longitudinal components of 3-dimensionally deformed amounts created at the side wall portions 22 and 23 and flange portions 24 and 25 in the predetermined area (M). As a result, the tensile stresses are applied to the processing adjustment section 20a as indicated by the dashed line arrows in the lower part of FIG. 3, so that the compressive stresses as indicated by the solid line arrows are remained after the first process (Pf).
[0049] And, according to the final product 10, as shown in FIG. 6, the compressive stresses as indicated by the dashed line arrows are applied to the inside of the bent portion in the predetermined area (M) in the same manner as in FIG. 3, so that tensile stresses as indicated by solid line arrows in the upper part of FIG. 6 are remained after the second process (Ps). However, at the outside of the bent portions, the compressive stresses are applied, when the processing adjustment section 20a is pressed (to substantially disappear), so that the tensile stresses as indicated by the solid line arrows in FIG. 6 are remained after the second process (Ps). As a result, at the inside and outside of the bent portion of the final product 10, only tensile stresses as indicated by the solid line arrows are remained, so that the tensile stresses are balanced as a whole, the spring back or torsion can be prevented from being created. While a figure is omitted herein, in the case where the bending is applied to an intermediate product (not shown) without the above-described processing adjustment section 20a being formed in the same manner as the prior forming method, the tensile stress is remained at the inside of the bent portion, and the compressive stress is remained at the outside of the bent portion, so that the spring back may be created to be returned to the state before bending, or the torsion might be created.
[0050] Hereinafter will be described about apparatuses for use in the first process (Pf) and second process (Ps) as described above. FIG. 8 shows an apparatus for use in the first process (Pf), wherein it is so configured that a work of ultrahigh tensile steel plate is placed on a lower die (Lf), and an upper die (Uf) is driven downward to form the intermediate product 20 by so-called stamping, whereby 500 tons of working force, for example, is applied to the work. The upper die (Uf) is installed with a die 121 having a pressing surface with a predetermined shape (contour of the intermediate product 20), and the lower die (Lf) is installed with a punch 122 and a pad 123 for providing a pressing surface with a similar predetermined shape. With those dies, the side wall portions 22 and 23 and flange portions 24 and 25 are formed to be of the cross sections as shown in (A)-(G) in FIG. 4.
[0051] FIG. 9 shows an apparatus for use in the second process (Ps), wherein it is so configured that the intermediate product 20 is placed on a lower die (Ls), and an upper die (Us) is driven downward to produce the final product 10 by so-called cam-bending, whereby 400 tons of working force, for example, is applied to the intermediate product 20. The upper die (Us) is installed with a die 211 having a pressing surface with a predetermined shape (contour of the final product 10), and the lower die (Ls) is provided with a punch 212 and a pad 213 for providing a pressing surface with a similar predetermined shape. The punch 212 is movably supported by a slider 214 through a slide plate Sp, so as to move close to or remote from the pad 213. Furthermore, the upper die (Us) is installed with a driver 216, so as to be supported in such a manner that an inclined surface (cam surface) of the driver 216 and an inclined surface (cam surface) of the slider 214 are pressed to each other through the slide plate Sp. The lower die (Ls) is provided with a guide member 215, which guides the driver 216 in a vertical direction, and which returns the punch 212 (functions as a return spring). Accordingly, in such a state that the intermediate product 20 is placed on the lower die (Ls), when the upper die (Us) is driven downward, with the driver 216 being guided by the guide member 215 to move downward, the slider 214 is driven toward the pad 213, thereby to produce the final product 10 by the so-called cam-bending (bending by cam).
[0052] According to the above-described embodiment, the inclined angles of the side wall portions 22a and 23a relative to the top plate portion 21 in the predetermined area (M) of the intermediate product 20 is set to be 80 degree as shown in (D) of FIG. 4, which may be set to be a certain angle within a range of 0 degree to 90 degree. As described before, the longitudinal extension in the predetermined area (M) is determined by the 3-dimensional deformed amount created on the side wall portions 22 and 23 and flange portions 24 and 25 of the intermediate product 20. The longitudinal dimension of the intermediate product 20 including the longitudinal extension is set, for example, to be 110% of the longitudinal dimension of the final product 10 in the same area as the predetermined area (M), in conformity with which the inclined angles of the side wall portions 22a and 23a relative to the top plate portion 21 are set. With respect to the above-described 110%, it is provided as an appropriate value according to the present embodiment. However, it is not limited to that rate, but it may be provided in accordance with a property of the ultrahigh tensile steel plate, or shapes of the final product 10 and intermediate product 20, which are resulted from a simulation or various analyzations.
[0053] Furthermore, in the case where the inclined angles of the side wall portions 22a and 23a relative to the top plate portion 21 in the predetermined area (M) of the intermediate product 20 is set to be 0 degree, an intermediate product 30 as shown in FIGS. 10-12 is produced, as will be described hereinafter as another embodiment. That is, according to the intermediate product 30 as shown in FIGS. 10-12, the side wall portions 32 and 33 and flange portions 34 and 35 with the same cross sections as those cross sections shown in (A), (B), (F) and (G) in FIG. 12 are deformed into the side wall portions 32c and 33c and flange portions 34c and 35c shown in (C)-(E) in FIG. 12 in the predetermined area (M), and side shapes of the side wall portion 32 and flange portion 34 are deformed into side shapes of the side wall portions 32c and flange portion 34c as shown in FIG. 11 (the side wall portion 33 and flange portion 35 are deformed in the same manner). Then, a processing adjustment section 30c is configured by the side wall portion 32c and 33c and flange portion 34c and 35c, so that the intermediate product 30 with the bent angle α (e.g., 139 degree) as shown in FIG. 11 is produced.
[0054] In FIGS. 10-12, except for the above-described 30c and so on, corresponding parts to the parts indicated by 20's as shown in FIGS. 2-4 are indicated by 30's, which parts are substantially the same as those parts, and therefore, explanations of which are omitted herein. Also, like in the aforementioned embodiment, the deformation of the intermediate product 30 to the final product 10 is the 3-dimensional deformation, so that the top plate portion 11 and the top plate portion 31 with different bent angles being provided are not of the same shape in a strict sense. However, in such a sense that the top plate portion 31 is maintained to be approximately the same shape as the target top plate portion 11, without deforming the top plate portion 31 (except for varying the bent angle of the top plate portion 31), the first process can be performed, with the cross section of the plate portion 31 being maintained in the predetermined shape.
[0055] According to the above-described intermediate products 20 and 30, the processing adjustment sections 20a and 30a are provided at one section, respectively. However, a plurality of processing adjustment sections may be provided in the longitudinal direction within the predetermined area (M), an embodiment of which is shown in FIGS. 13-15. That is, an intermediate product 40 as shown in FIGS. 13-15 is formed such that the side wall portions 42, 43 and flange portions 44, 45 with the same cross sections as those cross sections as shown in (A), (B) and (F) in FIG. 15 are deformed into the side wall portions 42d, 42e, 43d and 43e and flange portions 44d, 44e, 45d and 45e as shown in (C)-(E) in FIG. 15 in the predetermined area (M), and side shapes of the side wall portion 42 and flange portion 44 are deformed into side shapes of the side wall portions 42d, 42e and flange portions 44d, 44e as shown in FIG. 14 (the side wall portion 43 and flange portion 45 are deformed in the same manner). Therefore, two processing adjustment sections 40d and 40e are configured by the side wall portions 42d, 42e, 43d and 43e and flange portions 44d, 44e, 45d and 45e, so that the intermediate product 40 with the bent angle α (e.g., 139 degree) as shown in FIG. 14 is produced.
[0056] In FIGS. 13-15, except for the above-described 40d, 40e and so on, corresponding parts to the parts indicated by 20's as shown in FIGS. 2-4 are indicated by 40's, which parts are substantially the same as those parts, and therefore, explanations of which are omitted herein.
[0057] In each of the above-described embodiments, the intermediate products 20, 30 and 40 are formed to be bent. Instead, as shown in FIG. 16, for example, the bending may not be performed in a first process (Pfx), but it may be performed only in the second process (Ps). That is, in the first process (Pfx) as shown in FIG. 16, by means of the cold press working against the ultrahigh tensile steel plate, maintaining a predetermined shape of a top plate portion 51 without deforming it, by deforming side wall portions 52 (numeral to the opposite wall portion is omitted) and flange portions 54 (numeral to the opposite flange portion is omitted) at its both sides in the predetermined area (M) to form a processing adjustment section 50a, an intermediate product 50 is produced.
[0058] Then, in the second process (Ps), by means of the cold press working against the intermediate product 50 as described above, by pressing the processing adjustment section 50a (so that the processing adjustment section 50a will substantially disappear), and bending it in the direction opposite to the opening of the hat-shaped cross section, to be formed into the saddle type, the final product 10 as described above is produced. In the second process (Ps), with the top plate portion 51 being maintained to be a predetermined shape (except for variations before and after the bending), it is formed to be bent in the direction opposite to the opening of the hat-shaped cross section.
[0059] Contrary to the embodiment as shown in FIG. 16, the bending may not be performed in the second process, but it may be performed only in the first process. For example, in the first process (Pf) as shown in FIG. 1, maintaining the cross section of the top plate portion 21 to be a predetermined shape, by deforming the side wall portions 22a, 23a and flange portions 24a, 25a at its both sides in the predetermined area (M), to form the processing adjustment section 20a, and bending it in the direction opposite to the opening of the hat-shaped cross section, the intermediate product 20 may be produced, and in the second process (Ps), by means of the cold press working against the intermediate product 20, maintaining the cross section of the top plate portion 21 to be the predetermined shape, by pressing the processing adjustment section 20, without bending it, the final product 10 as shown in FIG. 1 may be produced.
[0060] As described above, in any embodiments as described above, by varying the inclined angles of the side wall portions 22 and 23 relative to the top plate portion 21 in the predetermined area (M) of the intermediate product 20, the side wall portions 22 and 23 and flange portions 24 and 25 are deformed to form the processing adjustment section 20a and so on, and in the second process (Ps), by pressing the processing adjustment section 20a (so that the processing adjustment section 20a and so on will substantially disappear), the final product 10 is formed. Therefore, the 3-dimensional deformed amount, which is created when bending, can be absorbed by the shape of the intermediate product 20 itself, so that beads or the like are not required to be formed separately. Although the processing adjustment section 20a and so on do not disappear completely, and a pressed mark such as a discolored portion for example will be remained, any trouble will not be caused in the use of the product. In any embodiments, such a product that is formed with flanges or the like at both of opposite ends of the final product 10 can be produced by the processes including the first process (Pf, Pfx) and second process (Ps).
DESCRIPTION OF CHARACTERS
[0061] 10 final product [0062] 20, 30, 40, 50 intermediate product [0063] 11, 21, 31, 41, 51 top plate portion [0064] 12, 22, 32, 42, 52 side wall portion [0065] 13, 23, 33, 43, 53 side wall portion [0066] 14, 24, 34, 44, 54 flange portion [0067] 15, 25, 35, 45, 55 flange portion [0068] 20a, 30c, 40d, 40e, 50a processing adjustment section [0069] Pf first process [0070] Ps second process [0071] Uf, Us upper die [0072] Lf, Ls lower die [0073] 121, 211 die [0074] 122, 212 punch [0075] 123, 213 pad [0076] 214 slider [0077] 216 driver
