Metal member and method for manufacturing metal member

Abstract

To provide a metal member that can be manufactured by adding bending to a metal plate while suppressing an occurrence of a damage such as a crack even without forming a structure for removing a portion of a metal material such as a notch and a cutout, and a method for manufacturing such a metal member.SOLUTION: A metal member 1 has a bent part 13 obtained by exerting tight-bending to a metal plate 10, wherein a vertical position of a tip part 16 of the bending has deviation a with respect to a vertical position on a reference plane P on which the two flat parts 11, 12 are overlapped on each other in the bent part 13 with the two flat parts 11, 12 being places with bending unadded thereto in the plate 10 regarding directions located sandwiching the bent part 13 as an upper direction and a lower direction. Also, bending is added to the plate 10 while adding compressing force toward a place 13 to undergo bending to at least a part 11 of one side sandwiching the place 13 to undergo the bending in the plate 10.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a metal component and a method for manufacturing the metal component. [Background technology]

[0002] In recent years, in the field of electrical connection components inside automobiles, etc., from the perspective of space saving, there has been a demand for manufacturing small metal components that include bending of sheet material. Furthermore, high-strength materials have been used as materials for forming metal components. Bending of metal materials when manufacturing small metal components, as well as bending of high-strength metal materials, can be a difficult process. This difficulty increases particularly when bending sheet material at a steep angle or into a complex shape. Examples of bending at a steep angle or into a complex shape include tight bending, in which the sheet surface of a sheet material is bent 180 degrees, and box bending, in which a sheet material is bent into a box shape, both of which are required in the manufacturing process of metal components such as electrical connection terminals.

[0003] When bending a metal plate under difficult conditions, as in the above-described exemplary embodiments, damage to the metal material, such as cracks on the plate surface, is likely to occur at the bent portion. The occurrence of damage, such as cracks, needs to be avoided as much as possible from the viewpoint of ensuring the properties of the metal component being manufactured. Therefore, various methods of bending have been devised to avoid damage to the metal material, such as cracks on the plate surface, even when bending under difficult conditions. Such methods are disclosed, for example, in Patent Document 1 and Patent Document 2. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-25019 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-84487 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, various efforts have been made to prevent damage such as cracks from occurring in the bent portion even when bending metal materials under difficult conditions. However, in Patent Document 1, a notch is formed in the bend line, and a convex portion that protrudes outward in an arc shape corresponding to the notch is formed on the upper surface of the metal plate before bending. Furthermore, in Patent Document 2, a notch is formed in the metal material prior to bending. Forming a notch or notch to prevent damage in this way may complicate the bending process and limit the scope of applications of bending. Removing a portion of the metal material by forming a notch or notch may affect the mechanical strength and other properties of the resulting metal component. It is desirable to be able to bend a metal material and manufacture metal components while preventing damage such as cracks from occurring, without forming special structures such as notches or notches in the metal material.

[0006] In view of the above, an object of the present invention is to provide a metal component that can be manufactured by bending a metal plate while suppressing the occurrence of damage such as cracks, without forming a structure that removes part of the metal material, such as a notch or cutout, and to provide a method for manufacturing such a metal component. [Means for solving the problem]

[0007] The first metal member of the present disclosure has a bent portion formed by tightly bending a metal plate material, and the directions in which two flat portions of the plate material that are not bent are located on either side of the bent portion are defined as up and down, and the vertical position of the tip of the bend in the bent portion is offset from the vertical position of the reference plane on which the two flat portions are superimposed on each other.

[0008] The second metal member of the present disclosure has a bent portion formed by bending a metal plate material, and is manufactured by bending the plate material while applying a compressive force in the direction of the bent portion to at least one portion of the plate material on either side of the bent portion.

[0009] In the method for manufacturing a metal component disclosed herein, when manufacturing a metal component by bending a metal plate, the plate is bent while a compressive force is applied toward the point where the bend is to be applied to at least one side of the plate, sandwiching the point where the bend is to be applied. [Effects of the Invention]

[0010] The first metal member and the second metal member of the present disclosure are metal members that can be manufactured by bending a metal plate while suppressing the occurrence of damage such as cracks, without forming a structure that removes a portion of the metal material, such as a notch or a cutout. Furthermore, the method for manufacturing a metal member of the present disclosure is a method for manufacturing such a metal member. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram illustrating the compression bending process. [Figure 2] FIG. 2 is a cross-sectional view showing the cross-sectional structure of a metal member according to an embodiment of the present disclosure obtained by bending while applying a compressive force. [Figure 3] FIG. 3 is a cross-sectional view showing the cross-sectional structure of a simply bent member obtained by bending a metal member without applying a compressive force. [Figure 4] FIG. 4 is a cross-sectional view showing the structure of an electrical connection terminal as a specific example of a metal member according to an embodiment of the present disclosure. [Figure 5] Figure 5 is a table showing the state of the metal parts obtained when bending was performed under different conditions for 120° bending. CAE results are also shown. Color images will be submitted separately. [Figure 6] FIG. 6 is a table showing the measurement results of the dimensions of each part for each sample in FIG. [Figure 7] FIG. 7 is a table showing the results of approximating the shape of the outer surface of the bent portion for each sample in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Description of the embodiments of the present disclosure] First, an embodiment of the present disclosure will be described. A metal member and a method for manufacturing a metal member according to an embodiment of the present disclosure have the following configuration.

[0013] [1] The metal member according to the first embodiment of the present disclosure has a bent portion formed by tightly bending a metal plate material, and the directions in which two flat portions of the plate material that are not bent are positioned on either side of the bent portion are defined as up and down, and the vertical position of the tip of the bend in the bent portion is offset from the vertical position of the reference plane on which the two flat portions are superimposed on each other.

[0014] In the metal member according to the first embodiment, the bent portion subjected to close bending (180° bending) has a vertical offset between the tip of the bend and the reference plane where the two flat portions are superimposed on each other. This offset indicates that a compressive force is being applied to the bent portion, moving one flat portion closer to the other flat portion. The presence of this compressive force relieves the tensile stress that occurs on the outer surface of the bent portion as a result of bending. This reduces the likelihood of damage, such as cracks, occurring on the outer surface of the bent portion due to the tensile stress. This structure in which the tip of the bend is vertically offset from the reference plane can be manufactured by bending a metal material in the vertical direction while applying a compressive force toward the bent portion to one of the flat portions sandwiching the bent portion. This eliminates the need for a special structure, such as a notch or cutout, that removes part of the metal material.

[0015] [2] In the above aspect [1], the magnitude of the deviation may be 10% or more of the thickness of the plate material at the flat portion. A structure in which a large deviation is formed between the tip of the bend and the reference plane indicates that the bending is performed with sufficient compressive force applied to push one flat portion toward the bent portion. This provides a high degree of effectiveness in suppressing damage such as cracking.

[0016] [3] In the above-mentioned aspects [1] or [2], it is preferable that the thickness of the plate material at the tip of the bend is not reduced or the reduction is kept to 20% or less compared to the thickness of the plate material at the flat portion. The fact that the thickness of the plate material at the bent portion is not reduced compared to the flat portion, or that the reduction is kept small, indicates that the tensile stress generated on the outer surface of the bent portion when the plate material is bent is kept small. By reducing the tensile stress, damage such as cracks is less likely to occur at the bent portion.

[0017] [4] In any one of the above aspects [1] to [3], preferably, no cracks are formed on the outer surface of the bent portion. In the metal component according to this embodiment, a compressive force directed toward the bent portion is applied to one flat portion, making it less likely that damage such as cracks will occur on the outer surface of the bent portion. The absence of such damage allows the metal component including the bent portion to maintain high characteristics such as material strength of the metal plate.

[0018] [5] In any one of the above aspects [1] to [4], in a cross section of the metal component cut vertically along the direction in which the flat portion extends from the bent portion, the outer surface of the bent portion may not be approximated by a single arc having a center on the reference plane, but may be approximated by a combination of multiple arcs whose centers are located at different positions. When bending is performed while applying a compressive force that compresses one flat portion toward the bent portion, the position of the center of bending shifts along the way, resulting in bending centered around multiple points. The fact that the outer surface of the bent portion in the cross section is approximated by a combination of multiple arcs provides evidence that there were multiple bending centers when forming the bent portion.

[0019] [6] The metal member according to the second embodiment of the present disclosure has a bent portion formed by bending a metal plate material, and is manufactured by bending the plate material while applying a compressive force toward the bent portion to at least one portion of the plate material on either side of the bent portion.

[0020] When bending a sheet metal in the vertical direction to form a bent portion, applying a compressive force toward the bent portion to at least one side (e.g., the upper side) of the bent portion while bending can minimize the tensile stress generated by bending on the outer surface of the bent portion. This minimizes the occurrence of damage such as cracking during bending without the need to create a special structure that removes part of the metal material, such as a notch or cutout. Metal components manufactured using this method not only minimize the occurrence of damage such as cracking compared to when bending is performed without applying a compressive force, but also exhibit characteristics such as vertical displacement of the bent tip, a shape of the outer surface that indicates the presence of multiple bending centers, and a smooth outer surface of the bent portion.

[0021] [7] In any one of the above aspects [1] to [6], the metal member may constitute an electrical connection terminal. The electrical connection terminal requires a bending structure that requires strict conditions, such as close bending, in order to be formed into a box-like shape or to form elastic contact pieces. By employing the above aspects [1] to [6] in the bending structure, the occurrence of damage such as cracking due to bending can be suppressed, and the electrical connection terminal can fully utilize the properties of the metal material that constitutes the plate material, such as mechanical strength.

[0022] [8] In a method for manufacturing a metal component according to an embodiment of the present disclosure, when manufacturing a metal component by bending a metal plate, the plate is bent while a compressive force is applied toward the point where the bend is to be applied to at least one side of the plate, sandwiching the point where the bend is to be applied.

[0023] In this manufacturing method, when bending a plate material in the vertical direction to form a bent portion, a compressive force is applied toward the bent portion to a portion located on at least one side (e.g., above) of the bent portion while bending. By applying a compressive force while bending in this manner, the tensile stress generated on the surface of the plate material outside the bent portion due to bending can be minimized. This can prevent damage such as cracks from occurring due to bending. To prevent damage, it is not necessary to form a special structure, such as a notch or cutout, in the plate material that removes part of the metal material.

[0024] [Details of the embodiments of the present disclosure] A metal member and a method for manufacturing a metal member according to an embodiment of the present disclosure will be described in detail below with reference to the drawings. The method for manufacturing a metal member according to an embodiment of the present disclosure includes a step of bending a metal plate. The metal member according to an embodiment of the present disclosure can be manufactured by the method for manufacturing a metal member.

[0025] <Metal component manufacturing method> First, a method for manufacturing a metal member according to one embodiment of the present disclosure will be described. The method for manufacturing a metal member according to this embodiment (hereinafter sometimes simply referred to as a manufacturing method) includes a step of bending a metal plate. The method for manufacturing a metal member according to this embodiment may include steps other than the step of bending the plate, as appropriate, but here, the step of bending the plate will be extracted and described.

[0026] First, as a preliminary preparation, a plate material is prepared as the raw material for the metal member. A flat metal material may be cut into the shape and size required for manufacturing the metal member, and used as the plate material to be processed. The type of metal constituting the plate material is not particularly limited, but when manufacturing an electrical connection member such as an electrical connection terminal as the metal member, copper or a copper alloy can be suitably used. In particular, it is preferable to use a copper alloy such as a Corson alloy, which has high strength and excellent bending workability.

[0027] In the manufacturing method according to this embodiment, a prepared plate material is bent to bend the plate surface to a desired target angle. For example, the target angle is set to 180°, and close bending is performed. At this time, the plate material is bent while applying a compressive force to the plate material in the entire or part of the angle change range from the flat plate state (0°) to the target angle (compression bending). Figure 1 shows a schematic diagram of the state when compressive bending is performed on a plate material 10 in a region midway through the angle change range.

[0028] In FIG. 1 , the state of the sheet material 10 before compression bending in the angle change region is indicated by a dashed line, and the state of the sheet material 10 after compression bending is indicated by a solid line. As described above, the bending angle of the sheet material 10 before and after compression bending is not particularly specified. However, in the illustrated embodiment, the sheet material 10 is pre-bent at a 90° angle and then bent by an additional 30°, resulting in a 120° bend from the initial flat state (120° bend). In this specification, the up-down direction is defined as the direction shown in FIG. 1 , and the upper flat portion 11 is the portion of the sheet material 10 on one side of the bent portion 13, which forms the bend in the sheet material 10, and the lower flat portion 12 is the portion on the other side. In other words, the thickness direction of the lower flat portion 12 is the up-down direction. Within the thickness direction of the lower flat portion 12, the direction corresponding to the outside of the bend is the down direction, and the direction corresponding to the inside of the bend is the up direction. Furthermore, the direction perpendicular to the up-down direction and connecting the lower flat portion 12 and the bent portion 13 is the front-rear direction.

[0029] When performing compression bending, the lower flat portion 12 is fixed, and then a force is applied to the upper flat portion 11 using a jig D. The jig D has a pressing surface D1 that can come into contact with the outer surface 1S of the upper flat portion 11 (the surface located on the outer side of the bend of the bending portion 13), and the pressing surface D1 is inclined at 60° with respect to the surface to which the lower flat portion 12 is fixed. Above the pressing surface D1, a locking surface D2 is provided that forms an angle of 90° with the pressing surface D1 and can come into contact with the upper edge 15 of the upper flat portion 11. A bend can be formed in the plate material 10 by moving the jig D backward while the outer surface 1S of the upper flat portion 11 is in contact with the pressing surface D1 and the upper edge 15 of the upper flat portion 11 is in contact with the locking surface D2.

[0030] When performing this compression bending process, as shown in FIG. 1 , bending is performed while applying a compressive force F to the plate material 10. The compressive force F is applied to at least one portion of the plate material 10 on either side of the bending portion 13, where the bending is to be performed, i.e., at least one of the upper flat portion 11 and the lower flat portion 12, so as to compress the plate material 10 toward the bending portion 13. A method for applying the compressive force F to the upper flat portion 11 may be to apply a downward force and / or a forward force to the upper flat portion 11. A method for applying the compressive force F to the lower flat portion 12 may be to apply an upward force and / or a forward force to the lower flat portion 12. From the viewpoint of simply applying the compressive force F, a method in which a downward / upward force is applied to either the upper flat portion 11 or the lower flat portion 12 is preferred. In particular, a method in which a downward force is applied to the upper flat portion 11 is preferred. In the following description, the mode of applying the compressive force F by applying a downward force to the upper flat portion 11 will be mainly discussed.

[0031] To bend the plate material 10 while applying a compressive force F downward to the upper flat portion 11, the plate material 10 can be bent by using the jig D to apply a compressive force F downward from the engaging surface D2 to the edge 15 of the upper flat portion 11. Specifically, the jig D is positioned lower than when the compressive force F is not applied, and the upper flat portion 11 is pressed downward toward where the bending portion 13 will be provided. Then, the jig D is moved rearward, and the pressing surface D1 presses the outer surface 1S of the upper flat portion 11 to bend the plate material 10 to a predetermined angle (120° in the illustrated embodiment), thereby bending the bending portion 13 while applying the compressive force F. As shown by the excess length δ in Figure 1, the position of the front end of the bent portion 13 moves rearward as the plate material 10 is bent, but if bending is performed without applying a compressive force F, the excess length δ becomes larger, which causes tensile stress on the outer surface 1S of the plate material 10, that is, stress in a direction that pulls the outer surface 1S of the bent portion 13 from the upper flat portion 11 and the lower flat portion 11. However, by applying a compressive force F, the excess length δ can be reduced, and the tensile stress generated on the outer surface 1S of the plate material 10 can be alleviated.

[0032] The amount of downward movement of the jig D when bending the plate material 10 can be determined based on the state after the compression bending is completed, as shown in FIG. 1 . Specifically, assuming a state after the compression bending, assuming that the edge 15 of the upper flat portion 11 is bent at a predetermined angle (30° in the illustrated embodiment) without applying the compressive force F, the height position of the edge 15 of the upper flat portion 11 is defined as the neutral position H. The distance by which the edge 15 of the upper flat portion 11 must be compressed downward from the neutral position H to achieve the desired reduction in the excess length δ (compression amount) is set as the push-in amount ΔH. Next, the push-in amount in the state before the compression bending (shown by the dashed line in the figure) is calculated so that the push-in amount ΔH can be achieved after the compression bending. The height position of the jig D is then set so that the engagement surface D2 of the jig D is located at a position that is lowered by the calculated push-in amount from the position corresponding to the height h of the upper flat portion 11 when the compressive force F is not applied, and the bending is then performed using the jig D.

[0033] As described above, in this embodiment, in the compression bending process, the sheet material 10 is bent while applying a compressive force F to the flat portion 11 of the sheet material 10 toward the bent portion 13. If bending were performed without applying the compressive force F, compressive stress would be generated in the sheet material 10 on the inside of the bend, compressing the sheet material 10 from both sides (the upper flat portion 11 side and the lower flat portion 12 side) of the bent portion 13 toward the bent portion 13, whereas tensile stress would be generated on the outside of the bend, pulling the sheet material 10 to both sides across the bent portion 13. When stresses in different directions are generated on the outside and inside (front and back sides) of the sheet material 10, shear deformation occurs, and damage such as cracks and wrinkles is likely to occur on the outer surface 1S where tensile stress is generated. However, if the sheet material 10 is bent while applying the compressive force F toward the bent portion 13, the tensile stress generated on the outside of the bend can be alleviated. Alternatively, compressive stress can be generated in the sheet material 10 even on the outside of the bend. This reduces shear deformation due to bending, and suppresses the occurrence of damage such as cracks and wrinkles on the outer surface 1S. By suppressing damage to the plate material 10, the properties of the plate material 10, such as mechanical strength, can be effectively utilized in the manufactured metal component 1. Since it is not necessary to provide special structures, such as notches or cutouts, that remove part of the metal material of the plate material 10 in order to suppress the occurrence of damage due to bending, it is possible to avoid the influence of the formation of such structures on the properties of the plate material 10. Furthermore, the manufacturing method according to this embodiment can be easily and generally applied to the manufacture of various metal components having bending.

[0034] In the embodiment described above, the process of bending the sheet material 10 through a portion of the angle change range in which the sheet material 10 is bent to the final target angle (for example, the process of bending the sheet material 10 from 90° to 120° out of the bending range from 0° to 180°) is performed as compression bending while applying a compression force F. However, the section in which bending is performed while applying the compression force F is not limited to this, and it is sufficient that bending is performed while applying the compression force F in at least a portion of the process in which the sheet material 10 is bent from a flat state to a state having a desired angle. However, if the process of compressive bending while applying the compression force F is performed only in a portion of the entire angle change range, and further, if the bending angle formed by compressive bending is 110° or more and 145° or less, as in the embodiment shown in the drawings, damage caused by bending can be efficiently suppressed by applying the compression force F. In this way, when bending the plate material 10 by compressive bending only in a partial angle range within the entire angle change range, bending at angles shallower than that angle range can be performed as a pre-bending process without applying compressive force. Also, bending to angles deeper than that angle range can be performed as an additional bending process without applying compressive force. The pre-bending, compressive bending, and additional bending may each be performed in multiple bending processes. The degree of application of compressive force F in the compressive bending process is not particularly limited, but an example of the compression amount of the excess length δ described above is a range of 10% to 25% of the plate thickness.

[0035] <Metal component structure> Next, a description will be given of the metal member 1 according to an embodiment of the present disclosure, which is manufactured by a manufacturing method including a compressive bending step of bending the plate material 10 while applying a compressive force F as described above. Here, we consider a metal member 1 that has been subjected to compressive bending, followed by additional bending, and finally to a tightly bent state.

[0036] A metal member 1 according to a first embodiment of the present disclosure has a bent portion 13 formed by tightly bending a metal plate 10 so that the plate surface is bent 180 degrees. FIG. 2 shows a cross-sectional view of the metal member 1, taken along the front-to-rear direction, of a region including the bent portion 13. In the metal member 1, an upper flat portion 11 and a lower flat portion 12, which are portions of the plate 10 where the plate surface is not bent, are located above and below the bent portion 13. As described above, this metal member 1 is manufactured by bending the plate 10 while applying a compressive force to the upper flat portion 11 in the direction of the bent portion 13. FIG. 3 also shows a cross-sectional view of a simply bent member 1′, which is a metal member manufactured by bending the plate 10 without applying a compressive force to either of the flat portions 11 and 12. Hereinafter, unless otherwise specified, the cross section of the metal member 1 and the simply bent member 1' refers to a cross section of the area including the bent portion 13 cut in the vertical direction along the front-to-back direction, that is, along the direction in which the flat portions 11 and 12 extend from the bent portion 13, as shown in the figure.

[0037] In the metal member 1 according to this embodiment, the vertical position of the bend tip 16 at the bent portion 13 is offset from the vertical position of the reference plane P (bend tip offset a). Here, the bend tip 16 refers to the position of the tip of the bend line 17 (a valley fold caused by bending) of the sheet material 10 present inside the bent portion 13. An extrapolated point 18, which is a position on the outer surface 1S extrapolated forward of the bend tip 16, is roughly the most forward-extending position on the outer surface 1S of the bent portion 13. Furthermore, the reference plane P refers to the surface where the upper flat portion 11 and the lower flat portion 12 are superimposed on each other. When the lower surface of the upper flat portion 11 and the upper surface of the lower flat portion 12 are in contact with each other, the contact surface becomes the reference plane P. When these surfaces are not in contact with each other, the reference plane P becomes the vertical position midway between the lower surface of the upper flat portion 11 and the upper surface of the lower flat portion 12.

[0038] The bend tip deviation a occurs because, when forming the bent portion 13, the sheet material 10 is bent while applying a compressive force F to the upper flat portion 11 toward the bent portion 13. This is because, by bending the bent portion 13 while pressing the upper flat portion 11 toward the bent portion 13, the bend line 17, which corresponds to the inner valley of the bend, is also formed as a bent structure toward the pressing direction. The direction in which the bend tip deviation a occurs, i.e., the direction in which the bend tip 16 deviates from the reference plane P, is not particularly limited, but typically coincides with the direction in which the compressive force F is applied when bending. As described above in relation to the manufacturing method, when bending is performed while applying a downward compressive force F to the upper flat portion 11 without applying a compressive force to the lower flat portion 12, the bend tip 16 also deviates downward. The occurrence of the bend tip deviation a thus serves as a trace indicating that bending was performed while applying a compressive force F toward the bent portion 13 to one of the flat portions (here, the upper flat portion 11). By applying the compressive force F that causes the bend tip displacement a to the sheet material 10, the tensile stress applied to the outer surface 1S of the bent portion 13 is alleviated, making it less likely that damage such as cracks or wrinkles will occur on the outer surface 1S. In fact, the outer surfaces of the bent portions of the metal members whose cross-sectional photographs are shown as samples 1 and 2 in Figure 5 are free of cracks, wrinkles, etc., and maintain a smooth surface.

[0039] The magnitude of the bend tip deviation a is not particularly limited. However, it is preferable that it be 10% or more, and even 15% or more, of the thickness t of the sheet material 10 at the flat portions 11, 12 (if there is a difference in thickness between the upper and lower flat portions 11, 12, the average of these thicknesses; the same applies below). There is no particular upper limit to the magnitude of the bend tip deviation a, but from the viewpoint of suppressing excessive influence on the overall shape of the bent portion 13, it is preferable to keep it to, for example, 20% or less of the thickness t of the flat portions 11, 12.

[0040] When the plate material 10 is bent without applying a compressive force, as in the case of the simply bent member 1' in Figure 3, the vertical position of the tip 16 of the bend is aligned with the vertical position of the reference plane P, making it difficult for the tip of the bend to shift. This is because no particular force acts during the bending process to shift the position of the bend in the vertical direction. In this case, as explained above, compressive stress occurs on the inside of the bend in the plate material 10, while tensile stress occurs on the outside of the bend, causing shear deformation and making it more likely that damage such as cracks C will occur on the outside of the bend.

[0041] Furthermore, in the metal member 1 according to this embodiment, the reduction in the thickness t' of the sheet material 10 at the bend tip 16 is likely to be kept small. For example, the thickness t' of the sheet material 10 at the bend tip 16 does not reduce, or the reduction is kept to 20% or less, compared to the thickness t of the sheet material 10 at the flat portions 11 and 12. In other words, the thickness t' at the bend tip 16 remains the same or greater than the thickness t at the flat portions 11 and 12, or, if the thickness reduces, the reduction ((t - t') / t × 100%) is kept to 20% or less. Here, the thickness t' at the bend tip 16 refers to the thickness of the sheet material 10 from the bend tip 16 to the extrapolated point 18 on the outer surface 1S in the cross section. In the metal member 1 according to this embodiment, bending is performed by applying a compressive force F to the (upper) flat portion 11 toward the bent portion 13, which makes it difficult for tensile stress to be applied to the sheet material 10 during bending, and therefore reduces the thickness t' of the bent portion 13. It is particularly preferable that the thickness t' at the tip 16 of the bend is not reduced compared to the thickness t at the flat portions 11 and 12. Even if the thickness t' at the tip 16 of the bend is reduced, it is preferable that the reduction in thickness from the thickness t at the flat portions 11 and 12 be kept to 15% or less, or even 10% or less.

[0042] When the plate material 10 is bent without applying a compressive force, as in the case of the simple bending member 1', the plate thickness t' at the tip 16 of the bend tends to become smaller. This is because the application of tensile stress accompanying bending pulls the metal material in the region on the outer side (front side) of the bend toward the upper and lower flat portions 11, 12. For example, the plate thickness t' at the tip 16 of the bend tends to decrease by more than 20% compared to the plate thickness t at the flat portions 11, 12.

[0043] Furthermore, in the metal member 1 according to this embodiment, the outer surface 1S (front edge) of the bent portion 13 is likely to have a vertically asymmetric shape in cross section. In particular, the outer surface 1S in the direction of the flat portion to which the compressive force F was applied during bending (upward in the above-described embodiment) across the reference plane P is likely to have a gently bent shape with a larger radius of curvature than the outer surface 1S in the other direction (downward in the above-described embodiment). This vertical asymmetry means that the shape of the outer surface 1S of the bent portion 13 in cross section cannot be approximated by a single arc centered on the reference plane P. In particular, as shown by the approximate curves in the cross-sectional photographs of samples 1 and 2 in FIG. 7, the outer surface 1S of the bent portion 13 is likely to have a shape approximated by multiple arcs with centers at different positions. At least one of the centers of the multiple arcs is located outside the reference plane P. In the metal member 1 of this embodiment, bending is caused by applying a compressive force F to the (upper) flat portion 11 toward the bending portion 13, so that the center of bending (the point around which the plate material 10 is bent) does not remain at one location on the reference plane P, but moves to multiple locations with different positions in the vertical direction as the bending progresses.

[0044] When the plate material 10 is bent without applying a compressive force, as in the case of the simple bending member 1', the outer surface 1S of the bent portion 13 tends to have a cross-sectional shape that is symmetrical above and below the reference plane P, or a shape close to that. In particular, the shape of the outer surface 1S tends to be approximated by a single arc having its center on or near the reference plane P. This is because the center point of the bending is fixed at one location throughout the entire bending process.

[0045] Another structural feature of the metal member 1 according to this embodiment compared to the simply bent member 1' is that the outer surface 1S of the bent portion 13 in the direction of the flat portion to which the compressive force F was applied during bending (upward in the embodiment described above) is more likely to protrude outward than the outer surfaces 1S of the flat portions 11 and 12 (see indicated area B in the close-contact bent side photographs of Samples 1 and 2 in FIG. 5). Also, the surface of the plate material 10 outside the bent portion 13 is more likely to maintain a smooth surface with fewer irregularities (see the close-contact bent surface photographs of Samples 1 and 2 in FIG. 5).

[0046] As described above, the metal member 1 according to the first embodiment of the present disclosure has various structural features, including a deviation in the vertical position of the bent tip 16 from the reference plane P, due to bending the sheet material 10 while applying a compressive force F toward the bent portion 13 to the sheet material 10, compared to a simply bent member 1' obtained by bending the sheet material 10 without applying a compressive force. However, depending on parameters such as the material and thickness of the sheet material 10 and the magnitude of the applied compressive force F, or when the bending angle is less than 180°, the resulting metal member 1 may not clearly exhibit these structural features, even if the metal member 1 is manufactured by bending the sheet material 10 while applying a compressive force F toward the bent portion 13 to the sheet material 10. In this way, even when the metal member 1 does not exhibit clear structural features, it still falls under the category of a metal member according to the second embodiment of the present disclosure.

[0047] The metal member according to the second embodiment of the present disclosure has a bent portion 13 obtained by bending a metal plate material 10, and is manufactured by bending the plate material 10 while applying a compressive force toward the bent portion 13 to at least one portion of the plate material 10 on either side of the portion that will become the bent portion 13. Even if the obtained metal member 1 is observed alone and does not have clear structural features like the metal member 1 according to the first embodiment, structural features can be extracted by comparing it with a simply bent member 1' obtained by using the same plate material 10 but bending it to the same angle without applying a compressive force to the plate material 10. The structural features may be the same as those listed above for the metal member 1 according to the first embodiment.

[0048] That is, the following points can be mentioned as structural features of the metal member according to the second embodiment compared with the simply bent member 1'. It is preferable that the metal member according to the second embodiment has at least one of the following features. The outer surface 1S of the bent portion 13 has little or no damage such as cracks or wrinkles. The vertical position of the bent tip 16 is offset from the vertical position of the reference plane P. The reduction in the thickness t' of the plate material 10 at the tip 16 of the bend is kept small. The outer surface 1S of the bent portion 13 has a vertically asymmetric shape. In particular, the shape is approximated by a plurality of arcs whose centers are located at different positions. The outer surface 1S of the bent portion 13 in the direction of the flat portion to which the compressive force F is applied is positioned, and is shaped to protrude outward compared to the outer surfaces 1S of the flat portions 11 and 12. The surface of the plate material 10 outside the bent portion 13 remains smooth with few irregularities.

[0049] The type of component specifically constituting the metal member 1 according to the embodiment of the present disclosure is not particularly limited, and various bent components can be formed. Among these, forming an electrical connection terminal is preferable. As a specific example of an electrical connection terminal, FIG. 4 shows a schematic structure of a female terminal 5. The female terminal 5 has a clamping portion 52 formed in a rectangular cylindrical shape with an open front. The inside of the bottom surface of the clamping portion 52 has a resilient contact piece 51 that acts as a spring and is folded back toward the inside rear. When a flat tab of a male terminal 6, which is a mating electrical connection member, is inserted into the clamping portion 52, the resilient contact piece 51 presses the male terminal 6 against the ceiling surface of the clamping portion 52. This establishes electrical contact between the resilient contact piece 51 and the male terminal 6, and the male terminal 6 is clamped and held within the clamping portion 52. In this female terminal 5, a tight bend is formed at the point where the elastic contact piece 51 is folded backward from the bottom surface of the clamping portion 52 (shown surrounded by a dashed line in the figure), and this tight bend point can be formed as the bent portion 13 of the metal member 1 according to the embodiment of the present disclosure described above. [Example]

[0050] Examples are shown below. Here, the relationship between the application of compressive force when bending a plate material and the structure of the resulting metal material was investigated. However, the present invention is not limited to these examples.

[0051] (Sample preparation) Three types of specimens were prepared by tight bending of plate material. First, a 0.20 mm thick Corson alloy plate material was cut into a length of 20 mm and a width of 5 mm. Then, the plate material was bent in the longitudinal direction and pre-bent to 90°. In this case, the radius of curvature of the bent part was set to R = 0.1 mm on the inside of the bend. No compressive force was applied to the plate material during pre-bending. After pre-bending, the upper part of the upper flat part was cut off so that the edge height h of the upper flat part was 3.5 mm.

[0052] Next, a 120° bending was performed using compression bending. As shown in Figure 1, jig D was positioned below neutral position H, so that the upper flat portion was pressed downward from a height of 3.5 mm. This applied a compressive force to the upper flat portion toward the bent portion, while bending the sheet material. The downward pressing amount ΔH of the upper flat portion was 0.30 mm for Sample 1, 0.15 mm for Sample 2, and 0 mm (no pressing) for Sample 3. The excess length δ was converted to a compression amount of 0.05 mm for Sample 1, 0.025 mm for Sample 2, and 0 mm (no compression) for Sample 3. After completing the 120° bending for each sample, an additional bending was performed without applying a compressive force, resulting in a tight bending state.

[0053] (Test Method) For each of Samples 1 to 3, the appearance of the sample after 120° bending and the final sample after close bending was observed with a stereo microscope, photographs were taken, and the condition was analyzed. Furthermore, the final sample after close bending was cut in the vertical direction along the front-to-back direction at the center of the bent part. The obtained cross section was then observed with a metallurgical microscope, photographs were taken, and the condition was analyzed.

[0054] For reference, analysis was also performed using CAE (Computer Aided Engineering). Specifically, the manufacturing process of Sample 1 (with compression) and Sample 3 (without compression) was reproduced by simulation using elastic-plastic analysis with the finite element method (FEM). The obtained simulation results were used to analyze the shape of the sample and the distribution of stress.

[0055] (Test results) Figure 5 summarizes the test results in table format. For samples 1 to 3, from the top to bottom, the following photographs are shown: side view after 120° bending, side view after close bending, surface view after close bending, cross-sectional view after close bending, and the presence or absence of cracks determined from the cross-sectional view after close bending. The side view was taken from the side of the thickness of the sample, and the surface view was taken from the front of the bent portion. CAE shows the cross-sectional shape and stress distribution in the cross-section for the state after 120° bending (104° bending without compression) and the state after close bending. Furthermore, Figure 6 shows the results of measuring dimensions at key positions on the cross-sectional view after close bending for samples 1 to 3. Furthermore, Figure 7 shows the results of approximating the outer surface of the bent portion with an arc for the cross-sectional view after close bending for samples 1 to 3.

[0056] The photographs in Figure 5 compare Samples 1 and 2, which were bent while compressive force was applied, with Sample 3, which was bent without compressive force. First, looking at the side view photograph after 120° bending, we can see that the inner edge of the bend in Sample 3 remains flat, whereas in Samples 1 and 2, the inner edge of the bend is recessed downward at the front (indicated by symbol A). This is due to the compressive force applied when Samples 1 and 2 were bent 120°. Next, looking at the side view photograph after close bending, we can see that the outer surface above the bent portion in Sample 3 is flat, whereas in Samples 1 and 2, it protrudes upward (indicated by symbol B). Furthermore, looking at the surface photograph after close bending, we can see that Sample 3 has multiple wrinkle-like streaks extending horizontally, creating surface irregularities. In contrast, Samples 1 and 2 have few similar wrinkle-like streaks, indicating that they maintain a smoother surface than Sample 3.

[0057] Furthermore, looking at the cross-sectional photographs after close bending, sample 3 shows obvious cracks on the outside of the bend (shown as C), whereas no such cracks are observed in samples 1 and 2, and the outer surface of the bent portion remains smooth. Also, in sample 3, the bend line of the sheet material present on the inside of the bend (the black stripe-like area between the upper and lower flat portions; shown as D) extends generally horizontally, whereas in samples 1 and 2, the bend line curves downward as it moves forward. Furthermore, looking at the shape of the outer surface of the bent portion (the front edge), sample 3 is nearly symmetrical from top to bottom, except for the cracked area, whereas samples 1 and 2, and especially sample 1, are asymmetrical from top to bottom, with a gentler bend shape with a larger radius of curvature at the top than at the bottom.

[0058] The presence or absence of cracks and the differences in the shape of the bend line and outer surface of the bent part depending on whether or not compressive force is applied are largely reproduced by CAE. Furthermore, the CAE results show that when no compressive force is applied, stress is concentrated near the crack (indicated by the symbol C) (the areas with high stress are shown in red in the color diagram). This suggests that the application of stress to the outer surface during bending leads to the occurrence of cracks, and that applying compressive force while bending can alleviate that stress and prevent cracks from occurring.

[0059] Furthermore, we will examine the results of measuring the dimensions of each cross-section of Samples 1 to 3 in Figure 6. Here, we measured the dimensions of the locations numbered 1 to 4 in the cross-sectional photographs (Dimensions 1 to 4), and the results are summarized. First, we will examine the position of the bend tip in detail. In each cross-sectional photograph, the vertical position of the bend tip corresponding to the forward end of the bend line is represented by a line marked "Dimension 3." The bend tip deviation is defined as "Dimension 4," which corresponds to the distance between the position of the line marked "Dimension 3" and a reference plane P located midway between the lower surface of the upper flat portion and the upper surface of the lower flat portion. For Sample 3, to which no compressive force was applied, the vertical position of the bend tip (the line marked "Dimension 3") and the vertical position of the reference plane P coincide. In other words, the bend tip deviation is 0 mm. In contrast, for Samples 1 and 2, which were bent while compressive force was applied, the position of the bend tip was shifted downward from the position of the reference plane P. The bend tip deviation measured as Dimension 4 was 0.035 mm for both Samples 1 and 2, which is 18% of the plate thickness. In this way, it was confirmed that by bending the plate material while applying a downward compressive force to the upper flat portion, the position of the tip of the bend shifts downward relative to the reference plane P. The plate thickness was calculated as the average value of "dimension 1", which corresponds to the thickness of the upper flat portion, and "dimension 2", which corresponds to the thickness of the lower flat portion.

[0060] Next, we focus on the thickness. In Figure 6, "Dimension 1" and "Dimension 2" correspond to the thickness at the upper and lower flat sections, respectively. Furthermore, "Dimension 3" corresponds to the thickness at the tip of the bend. Furthermore, the thickness change and percentage change of "Dimension 3" are shown, based on the average thickness of "Dimension 1" and "Dimension 2." For all samples, the thicknesses at the two flat sections, i.e., "Dimension 1" and "Dimension 2," match the thickness of the raw material, 0.20 mm, within an error range. However, the thickness at the tip of the bend, i.e., "Dimension 3," differs significantly between samples. First, for Sample 3, which was not subjected to compressive force, the thickness at the tip of the bend is significantly smaller than the thickness at the flat section. The percentage reduction in thickness is over 20%. In contrast, for Sample 2, which was bent while compressive force was applied, the thickness at the tip of the bend decreased, but the percentage reduction in thickness was 12%, keeping it below 20%. Furthermore, in Sample 1, which was bent under a large compressive force, the thickness at the tip of the bend was actually greater than the thickness at the flat part, and the thickness change was a positive value. This demonstrates that bending a sheet material while applying a compressive force can suppress the reduction in thickness at the bent part.

[0061] Finally, we examine the results of approximating the outer surface of the bent section with a circular arc in Figure 7. In Figure 7, the cross-sectional photographs of each specimen show the shape of the outer surface (front edge) of the bent section approximated by a circular arc. The shape of the outer surface is generally approximated forward of the tip of the bend. First, for specimen 3, to which no compressive force was applied, the shape of the outer surface can be well approximated by a single circular arc centered on the reference plane. On the other hand, for specimens 1 and 2, which were bent under compressive force, the outer surfaces of both specimens have asymmetric shapes, so a single circular arc cannot adequately approximate the shape of the outer surface. Instead, the outer surface can be approximated as a series of multiple circular arcs centered at different points—three for specimen 1 and two for specimen 2—with different centers. This suggests that the bending center shifted during the bending process when the plate was bent under compressive force.

[0062] Although the embodiments of the present disclosure have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0063] 1 Metallic parts 1' Simple bending member 10 Board material 11 Upper flat part 12 Lower flat part 13 Bending section 15 Edge of upper flat part 16 Tip of bend 17 Bending Lines 18 extrapolation points 1S outer surface 5 female terminals 51 Elastic contact piece 52 clamping section 6 male terminals a) Bending tip deviation h Height of upper flat part t Plate thickness at flat part t' Plate thickness at the tip of the bend C crack D Jig D1 Pressing surface D2 Locking surface F Compression force H Neutral position ΔH Push-in amount P reference plane δ Excess length

Claims

1. The bent portion is made by closely bending a metal plate material. The directions in which two flat portions, which are not bent, of the plate material are positioned on either side of the bent portion are defined as upper and lower. A metal member, wherein the vertical position of the tip of the bend in the bent portion is offset from the vertical position of a reference plane where the two flat portions are superimposed on each other.

2. The metal member according to claim 1 , wherein the magnitude of the deviation is 10% or more of the thickness of the plate material at the flat portion.

3. 3. The metal component according to claim 1, wherein the thickness of the plate material at the tip of the bend is not reduced or the reduction is kept to 20% or less compared to the thickness of the plate material at the flat portion.

4. 3. The metal member according to claim 1, wherein no cracks are formed on the outer surface of the bent portion.

5. 3. The metal member according to claim 1, wherein in a cross section of the metal member cut in an up-down direction along the direction in which the flat portion extends from the bent portion, the outer surface of the bent portion cannot be approximated by a single arc having a center on the reference plane, but is approximated by connecting multiple arcs whose centers are located at different positions.

6. The bent portion is formed by bending a metal plate material. A metal component manufactured by bending the plate material while applying a compressive force toward the bent portion to at least one portion of the plate material on either side of the bent portion.

7. The metal member according to claim 1 , which constitutes an electrical connection terminal.

8. When manufacturing a metal part by bending a metal plate, A method for manufacturing a metal component, comprising: bending the plate material while applying a compressive force toward the portion to be bent to at least one portion of the plate material on either side of the portion to be bent.

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