Manufacturing method of arm member

Abstract

To provide a manufacturing method of an arm member which enables an extension part to support a molding member with high support rigidity while securing practically sufficient sectility when the extension part connecting the molding member molded from a base material with a base material crosspiece is cut.SOLUTION: In a manufacturing method of an arm member 1, in a bending molding member 1f or a rear stage molding member 1g, extension parts 510f, 510g, 520f, and 520g include: first extension parts 512f, 514f, 516f, 512g, 514g, and 516g communicating with first outer peripheral edge ends 28f and 28g; second extension parts 512f, 515f, 517f, 512g, 515g, and 517g communicating with second outer peripheral edge ends 128f and 128g; third extension parts 522f, 524f, 526f, 522g, 524g, and 526g communicating with third outer peripheral edge ends 38f and 38g; and fourth extension parts 522f, 525f, 527f, 522g, 525g, and 527g communicating with fourth outer peripheral edge ends 138f and 138g.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing an arm member, and more particularly to a method for manufacturing an arm member used as a component part of a vehicle such as an automobile. [Background technology]

[0002] Conventionally, in vehicles such as automobiles, arm members have been used to mount insulator members such as mount members and bush members that are interposed between engine / transmission components or wheel unsprung components and vehicle body components, to their support members. In addition, there are manufacturing methods for mass-producing such arm members that include a so-called progressive molding process.

[0003] Under these circumstances, Patent Document 1 discloses a manufacturing method for an arm member 1, which includes a blank forming process for obtaining, from a plate-shaped base material 500, which is the member to be processed, a plate-shaped blank formed member 1a having extension portions 300a extending outward from each of both longitudinal ends, and a base material remaining portion 502, which is the remainder of the portion of the base material 500 in which the blank formed member 1a having the extension portions 300a was formed, a burring forming process for obtaining a burred formed member 1b from the blank formed member 1a, a bending forming process for obtaining a bent formed member 1d from the burred formed member 1b, and a separation process for cutting the extension portions 300d at both longitudinal ends to obtain a separated formed member 1e. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2020 / 116320 Summary of the Invention [Problem to be solved by the invention]

[0005] However, according to the study by the present inventor, in the configuration of Patent Document 1, typically, the extending portions 300d at both ends in the longitudinal direction of the connecting wall 210d of the bent formed member 1d are cut to obtain a detached formed member 1e in a state in which the extending portions 300d are detached from the bent formed member 1d. However, the extending portions 300d are not included in the extending portions 300d, but are included in the one end in the longitudinal direction of the connecting wall 210d sandwiched between the first side wall 10d and the second side wall 110d in which the burring hole portion 22d and the burring hole portion 32d are formed correspondingly, and in the burring hole portion 110d ...110d and the burring hole portion 110d are formed correspondingly. Since the extension portion 300d extends through the space between the first side wall 10d and the second side wall 110d toward the other end in the longitudinal direction of the connecting wall 210d sandwiched between the first side wall 10d and the second side wall 110d on which the burring hole portion 132d and the burring hole portion 132d are formed correspondingly, and is connected to one end and the other end of the connecting wall 210d, the space into which the extension portion 300d can extend is relatively narrow, and it is considered that there is a certain limit to increasing the width or number of the extension portion 300d in order to increase the support rigidity of the molded member by the extension portion 300d in the width direction of the connecting wall 210d. In relation to this, the space that can be secured for cutting the extension portion 300d is also relatively narrow, and it is considered that the design of the member that receives the cutting reaction force becomes complicated and the direction in which the cutting member moves is also limited.

[0006] The present invention was made after taking into consideration the above considerations, and aims to provide a manufacturing method for an arm member that can support a molded member on an extension portion with high support rigidity while ensuring practically sufficient cutting ability when cutting the extension portion that connects a molded member molded from a base material to a base material crosspiece portion. [Means for solving the problem]

[0007] In order to achieve the above object, a first aspect of the present invention is a manufacturing method for manufacturing an arm member extending in a longitudinal direction, using a plate-shaped base material, the method including a forming step involving a formed member, an extension portion, and a base material remainder portion which is a portion of the base material other than the formed member and the extension member, the forming step including a bending forming step for obtaining a bent formed member included in the formed member, or a subsequent forming step in addition to the bending forming step for obtaining a subsequent stage formed member included in the formed member at a stage subsequent to the bending forming step, the method including the step of forming the bent formed member or the subsequent stage formed member, The step forming member has a first side wall and a second side wall opposed to each other in a width direction perpendicular to the longitudinal direction, a first hole portion formed on one side of the longitudinal direction in the first side wall and a second hole portion formed on the one side of the longitudinal direction in the second side wall opposed to each other, a third hole portion formed on the other side of the longitudinal direction in the first side wall and a fourth hole portion formed on the other side of the longitudinal direction in the second side wall opposed to each other, and the bending forming member or the rear stage forming member is provided with the extension portion. a first extending portion communicating with a first outer peripheral edge portion which is an outer peripheral edge portion for the first hole portion in the first side wall, a second extending portion communicating with a second outer peripheral edge portion which is an outer peripheral edge portion for the second hole portion in the second side wall, a third extending portion communicating with a third outer peripheral edge portion which is an outer peripheral edge portion for the third hole portion in the first side wall, and a fourth extending portion communicating with a fourth outer peripheral edge portion which is an outer peripheral edge portion for the fourth hole portion in the second side wall, and cutting the extending portions for the bent forming member or the subsequent forming member. The method for manufacturing an arm member further includes a separation process of separating the bent-shaped member or the subsequent-stage formed member from the remaining portion of the base material to obtain a separated formed member, in which, in the separation process, a portion of the first extension portion is cut on the side of the first outer peripheral edge end, a portion of the second extension portion is cut on the side of the second outer peripheral edge end, a portion of the third extension portion is cut on the side of the third outer peripheral edge end, and a portion of the fourth extension portion is cut on the side of the fourth outer peripheral edge end, for the bent-shaped member or the subsequent-stage formed member.

[0008] In addition, in a method for manufacturing an arm member according to a second aspect of the present invention, in addition to the method according to the first aspect, The forming process may include, in addition to the bending process and prior to the separating process, a blank forming process for obtaining a blank forming member included in the formed member and a piercing forming process for obtaining a piercing forming member included in the formed member, in addition to the bending process, the blank forming process and the piercing forming process, and a form forming process for obtaining a foam forming member included in the formed member between the blank forming process and the piercing forming process, or in addition to the bending process, the blank forming process and the piercing forming process, and a form forming process between the piercing forming process and the bending process. The forming step further includes a burring forming step for obtaining a burring formed member included in the formed member, or the forming step includes the blank forming step, the form forming step, the pierce forming step, the burring forming step, and the bending step, in which the blank formed member, the extension portion, and the remaining portion of the base material are obtained from the base material in the blank forming step, and the extension portion extends and connects between the blank formed member and the remaining portion of the base material, and the form forming step obtains the form formed member by further forming the shape of the blank formed member, and the extension portion is , which extends between and communicates with the foam molded member and the remaining base material, and in the piercing process, in the blank molded member or the foam molded member, the first hole portion is formed at one end side which is the negative side of the both ends in the longitudinal direction, the second hole portion is formed at the other end side which is the positive side of the both ends in the longitudinal direction, the third hole portion is formed at one end side which is the negative side of the width direction, and the fourth hole portion is formed at the other end side which is the positive side of the both ends in the longitudinal direction. In the burring forming step, the first hole portion, the second hole portion, the third hole portion, and the fourth hole portion of the pierce forming member are correspondingly formed into a first burring hole portion, a second burring hole portion, a third burring hole portion, and a fourth burring hole portion, respectively, to obtain the burring forming member, and the extension portion extends and communicates between the burring forming member and the remaining base material, and in the bending step, the pierce forming member or the burring forming member isA wall portion that connects in the longitudinal direction an intermediate portion between a portion where the first hole portion or first burring hole portion is formed and a portion where the second hole portion or second burring hole portion is formed, and an intermediate portion between a portion where the third hole portion or third burring hole portion is formed and a portion where the fourth hole portion or fourth burring hole portion is formed is a connecting wall, and the wall portion that stands up in a negative direction in the up-down direction perpendicular to the longitudinal direction and the width direction from the connecting wall and the portion where the first hole portion or first burring hole portion is formed and the third hole portion or fourth burring hole portion is connected to the connecting wall. The bent-shaped member has a first side wall as a wall portion that connects the portion in which the 3rd burring hole portion is formed in the longitudinal direction, and a second side wall that stands up from the connecting wall in the negative direction of the up-down direction so as to face the first side wall in the width direction and connects the portion in which the second hole portion or the second burring hole portion is formed and the portion in which the fourth hole portion or the fourth burring hole portion is formed in the longitudinal direction, and the extension portion extends between and connects the bent-shaped member and the remaining portion of the base material.

[0009] In a manufacturing method of an arm member according to a third aspect of the present invention, in addition to the second aspect, with respect to the bent shaped member, the first extension portion communicates with a portion between one end of the connecting wall on the negative side of the longitudinal direction and a portion corresponding to 7 o'clock counterclockwise when looking at the first hole portion or the first burring hole portion in the positive direction of the width direction, with respect to the first outer circumferential edge end, and the second extension portion communicates with a portion between the one end of the connecting wall on the negative side of the longitudinal direction and a portion corresponding to 7 o'clock counterclockwise when looking at the second hole portion or the second burring hole portion in the negative direction of the width direction, with respect to the second outer circumferential edge end. The third extension portion connects to a portion between the other end of the connecting wall on the positive side of the longitudinal direction and a portion corresponding to 7 o'clock clockwise when looking at the third hole portion or the third burring hole portion in the positive direction of the width direction, and the fourth extension portion connects to a portion between the other end of the connecting wall and a portion corresponding to 7 o'clock counterclockwise when looking at the fourth hole portion or the fourth burring hole portion in the negative direction of the width direction, with respect to the fourth outer peripheral edge end.

[0010] In addition, in a manufacturing method of an arm member according to a fourth aspect of the present invention, in addition to the second aspect, the shaping step further includes a curl forming step as the subsequent shaping step, and in the curl forming step, an end portion of the first side wall on the negative side in the vertical direction and an end portion of the second side wall on the negative side in the vertical direction are bent so as to face each other in the width direction to obtain a curl forming member having a first folded wall and a second folded wall correspondingly, and the extension portion extends between the curl forming member and the remaining portion of the base material, and for the curl forming member, the first extension portion is disposed between one end portion of the connecting wall on the negative side in the longitudinal direction and the first folded wall relative to the first outer circumferential edge end. the second extension portion connects to a portion between the one end of the connecting wall and the one end of each of the first folded wall and the second folded wall, with respect to the second outer circumferential edge portion; the third extension portion connects to a portion between the other end of the connecting wall on the positive direction side of the longitudinal direction and the other end of each of the first folded wall and the second folded wall, with respect to the third outer circumferential edge portion; and the fourth extension portion connects to a portion between the other end of the connecting wall and the other end of each of the first folded wall and the second folded wall, with respect to the fourth outer circumferential edge portion.

[0011] In addition, in a manufacturing method of an arm member in a fifth aspect of the present invention, in addition to the third or fourth aspects, the first extension portion connects to a portion between 2 o'clock and 6 o'clock counterclockwise when looking at the first hole portion or the first burring hole portion in the positive direction of the width direction with respect to the first outer peripheral edge end, the second extension portion connects to a portion between 2 o'clock and 6 o'clock clockwise when looking at the second hole portion or the second burring hole portion in the negative direction of the width direction with respect to the second outer peripheral edge end, the third extension portion connects to a portion between 2 o'clock and 6 o'clock clockwise when looking at the third hole portion or the third burring hole portion in the positive direction of the width direction with respect to the third outer peripheral edge end, and the fourth extension portion connects to a portion between 2 o'clock and 6 o'clock counterclockwise when looking at the fourth hole portion or the fourth burring hole portion in the negative direction of the width direction with respect to the fourth outer peripheral edge end.

[0012] In addition, in a manufacturing method of an arm member in a sixth aspect of the present invention, in addition to any of the second to fifth aspects, the blank forming member has a first extension plate portion, a second extension plate portion, a third extension plate portion, and a fourth extension plate portion corresponding respectively to the portions in the pierce forming member where the first hole portion, the second hole portion, the third hole portion, and the fourth hole portion are formed, and in the form forming process, a first positioning member is arranged between the first extension plate portion and the second extension plate portion, and a second positioning member is arranged between the third extension plate portion and the fourth extension plate portion, thereby positioning the blank forming member in at least one of the longitudinal direction and the width direction.

[0013] Furthermore, in a manufacturing method of an arm member according to a seventh aspect of the present invention, in addition to any one of the second to sixth aspects, the molding step further includes a burring adjustment step as the subsequent molding step, and in the burring adjustment step, configurations of the first burring hole portion, the second burring hole portion, the third burring hole portion, and the fourth burring hole portion are adjusted while pressing the flanges of each of the first burring hole portion, the second burring hole portion, the third burring hole portion, and the fourth burring hole portion from at least one of the vertical direction and the width direction.

[0014] In addition, in an eighth aspect of the present invention, in addition to any one of the first to seventh aspects, in the separation process, a first cutting member is moved toward the positive side of the width direction while abutting against the first outer peripheral edge end, relative to the bending forming member or the subsequent forming member, to cut a portion of the first extension portion, a second cutting member is moved toward the negative side of the width direction while abutting against the second outer peripheral edge end, to cut a portion of the second extension portion, a third cutting member is moved toward the positive side of the width direction while abutting against the third outer peripheral edge end, to cut a portion of the third extension portion, and a fourth cutting member is moved toward the negative side of the width direction while abutting against the fourth outer peripheral edge end, to cut a portion of the fourth extension portion.

[0015] In addition, in a ninth aspect of the present invention, in addition to any one of the first to eighth aspects, in a manufacturing method of an arm member, when the first side wall and the second side wall are erected from the connecting wall, the first extension portion and the third extension portion are each bent toward the end side of the first side wall on the negative side in the vertical direction, and the second extension portion and the fourth extension portion are each bent toward the end side of the second side wall on the negative side in the vertical direction. Effect of the Invention

[0016] According to a configuration of a first aspect of the present invention, for the bent-formed member or the subsequent-stage formed member, the extension portion includes a first extension portion communicating with a first outer peripheral edge portion that is an outer peripheral edge portion for the first hole portion in the first side wall, a second extension portion communicating with a second outer peripheral edge portion that is an outer peripheral edge portion for the second hole portion in the second side wall, a third extension portion communicating with a third outer peripheral edge portion that is an outer peripheral edge portion for the third hole portion in the first side wall, and a fourth extension portion communicating with a fourth outer peripheral edge portion that is an outer peripheral edge portion for the fourth hole portion in the second side wall, and the extension portion for the bent-formed member or the subsequent-stage formed member and the mother metal are separated by cutting the extension portion for the bent-formed member or the subsequent-stage formed member. The method further includes a separation process in which the remaining material is separated to obtain a separated molded member. In the separation process, for the bent molded member or the subsequent molded member, a portion of the first extension portion is cut on the side of the first outer peripheral edge, a portion of the second extension portion is cut on the side of the second outer peripheral edge, a portion of the third extension portion is cut on the side of the third outer peripheral edge, and a portion of the fourth extension portion is cut on the side of the fourth outer peripheral edge. Therefore, an arm member can be manufactured in a manner in which the molded member is supported by the extension portion with high support rigidity while ensuring sufficient cuttability for practical use when cutting the extension portion connecting the molded member molded from the base material and the base material crosspiece.

[0017] According to the configuration of the second aspect of the present invention, the forming process further includes, in addition to the bending process and the separating process, a blank forming process for obtaining a blank forming member contained in the formed member and a piercing forming process for obtaining a piercing forming member contained in the formed member, in addition to the bending process, the blank forming process, and the piercing forming process, a form forming process for obtaining a foam forming member contained in the formed member between the blank forming process and the piercing forming process, or in addition to the bending process, the blank forming process, and the piercing forming process, a burring forming process for obtaining a burring forming member contained in the formed member between the piercing forming process and the bending process, or the forming process includes the blank forming process, the form forming process, the piercing forming process, the burring forming process, and the bending process, and in such forming processes, the extension portions extend and connect between each of the formed members and the remaining part of the base material, so that the separating process is performed while the extension portions support the formed members with high support rigidity, and the extension portions can be reliably separated.

[0018] According to a configuration of a third aspect of the present invention, for the bent formed member, the first extension portion, with respect to the first outer peripheral edge end, connects to a portion between one end of the connecting wall on the negative side in the longitudinal direction and a portion corresponding to 7 o'clock counterclockwise when looking at the first hole portion or the first burring hole portion in the positive direction in the width direction, the second extension portion, with respect to the second outer peripheral edge end, connects to a portion between one end of the connecting wall and a portion corresponding to 7 o'clock clockwise when looking at the second hole portion or the second burring hole portion in the negative direction in the width direction, and the third extension portion, with respect to the third outer peripheral edge end, connects to a portion between one end of the connecting wall on the negative side in the longitudinal direction of the connecting wall and a portion corresponding to 7 o'clock clockwise when looking at the second hole portion or the second burring hole portion in the negative direction in the width direction. The fourth extension portion connects to the portion between the other end of the connecting wall on the positive side and the portion corresponding to 7 o'clock clockwise when looking at the third hole portion or the third boring hole portion in the positive direction of the width direction, and the fourth extension portion connects to the portion between the other end of the connecting wall and the portion corresponding to 7 o'clock counterclockwise when looking at the fourth hole portion or the fourth boring hole portion in the negative direction of the width direction, relative to the fourth outer peripheral edge end.Therefore, when cutting the extension portion, sufficient cuttability for practical use is ensured, while the extension portion can support the molded member with high support rigidity and the strength of the arm member can be increased.

[0019] According to a configuration of a fourth aspect of the present invention, with respect to the curl forming member, the first extending portion is connected to a portion between one end of the connecting wall on the negative side in the longitudinal direction and one end of each of the first folded wall and the second folded wall on the negative side in the longitudinal direction with respect to the first outer peripheral edge portion, the second extending portion is connected to a portion between one end of the connecting wall and one end of each of the first folded wall and the second folded wall with respect to the second outer peripheral edge portion, and the third extending portion is connected to a portion between the third outer peripheral edge portion and one end of the connecting wall on the negative side in the longitudinal direction with respect to the third outer peripheral edge portion. The fourth extension portion connects to the portion between the other end of the connecting wall and the other end of each of the first folding wall and the second folding wall in the positive longitudinal direction, and the fourth outer peripheral edge portion connects to the portion between the other end of the connecting wall and the other end of each of the first folding wall and the second folding wall, with respect to the fourth outer peripheral edge portion. Therefore, while ensuring sufficient cuttability for practical use when cutting the extension portion, it is possible to cause the extension portion to support the molded member with high support rigidity and to increase the strength of the arm member.

[0020] According to the configuration of the fifth aspect of the present invention, for a bent formed member, the first extension portion connects to a portion between 2 o'clock and 6 o'clock counterclockwise when looking at the first hole portion or first burring hole portion in the positive width direction with respect to the first outer peripheral edge end, the second extension portion connects to a portion between 2 o'clock and 6 o'clock counterclockwise when looking at the second hole portion or second burring hole portion in the negative width direction with respect to the second outer peripheral edge end, the third extension portion connects to a portion between 2 o'clock and 6 o'clock clockwise when looking at the third hole portion or third burring hole portion in the positive width direction with respect to the third outer peripheral edge end, and the fourth extension portion connects to a portion between 2 o'clock and 6 o'clock counterclockwise when looking at the fourth hole portion or fourth burring hole portion in the negative width direction with respect to the fourth outer peripheral edge end. Therefore, the configuration of the extension portion and the configuration for cutting the extension portion can be prevented from becoming complicated, while the extension portion can support the formed member with high support rigidity.

[0021] According to the configuration of the sixth aspect of the present invention, the blank forming member has a first extension plate portion, a second extension plate portion, a third extension plate portion, and a fourth extension plate portion, which respectively correspond to the portions where the first hole portion, the second hole portion, the third hole portion, and the fourth hole portion are formed in the pierce forming member, and in the form forming process, a first positioning member is arranged between the first extension plate portion and the second extension plate portion, and a second positioning member is arranged between the third extension plate portion and the fourth extension plate portion, thereby positioning the blank forming member in at least one of the longitudinal direction and the width direction, thereby improving the processing accuracy in the forming process in which a press shape, etc. is imparted.

[0022] According to the configuration of the seventh aspect of the present invention, the molding process further includes a burring adjustment process as a subsequent molding process, in which the configurations of the first burring hole portion, the second burring hole portion, the third burring hole portion, and the fourth burring hole portion are adjusted while pressing the flanges of each of the first burring hole portion, the second burring hole portion, the third burring hole portion, and the fourth burring hole portion in at least one of the vertical and width directions, thereby improving the shape and coaxiality accuracy of the burring holes, which can improve the support strength, etc. of the insulator member.

[0023] According to the configuration of the eighth aspect of the present invention, in the separation process, a first cutting member is moved in the positive width direction while abutting against the first outer peripheral edge end of the bent formed member or the subsequent formed member to cut a portion of the first extension portion, a second cutting member is moved in the negative width direction while abutting against the second outer peripheral edge end to cut a portion of the second extension portion, a third cutting member is moved in the positive width direction while abutting against the third outer peripheral edge end to cut a portion of the third extension portion, and a fourth cutting member is moved in the negative width direction while abutting against the fourth outer peripheral edge end to cut a portion of the fourth extension portion, so that the extension member can be reliably cut while ensuring sufficient strength for practical use of the components that cut the extension member.

[0024] According to the configuration of the ninth aspect of the present invention, in the bending molding process, when the first side wall and the second side wall are raised from the connecting wall, the first extension portion and the third extension portion are each bent toward the end side of the first side wall on the negative side in the vertical direction, and the second extension portion and the fourth extension portion are each bent toward the end side of the second side wall on the negative side in the vertical direction. Therefore, it is possible to prevent the extension portions from unnecessarily interfering with the molding process and reducing the processing accuracy of the molded part. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a side view showing a lower arm manufactured by a manufacturing method for a lower arm in an embodiment of the present invention. [Diagram 2] FIG. 2 is a view taken along the Z1 arrow in FIG. 1, and is a plan view of a lower arm manufactured by the manufacturing method for a lower arm in this embodiment. [Diagram 3] 3 is a view taken along the Z2 arrow in FIG. 1, and is a bottom view of the lower arm manufactured by the manufacturing method for the lower arm in this embodiment. [Figure 4] FIG. 4 is a view taken along the X arrow in FIG. 1, and is a front view of a lower arm manufactured by the manufacturing method for a lower arm in this embodiment. [Diagram 5] FIG. 5 is a vertical cross-sectional view taken along line AA in FIG. [Figure 6]FIG. 6 is a vertical cross-sectional view taken along line BB of FIG. [Figure 7] FIG. 7 is a plan view showing formed members obtained in sequence from a plate-shaped base material in each process when the lower arm produced by the lower arm manufacturing method of this embodiment is produced by a progressive forming method. [Figure 8] FIG. 8 corresponds in position to the CC vertical sectional view of FIG. 7, and is a partial vertical sectional view of a configuration including a positioning member used in the manufacturing method of the lower arm in this embodiment. [Figure 9] FIG. 9 is a longitudinal sectional view taken along line DD of FIG. [Figure 10] Figure 10 is a diagram showing the positional relationship of the feed bar portion to be connected to the formed member to obtain a lower arm by the manufacturing method of a lower arm in this embodiment, Figure 10(a) is a side view positionally corresponding to the Y1 arrow view of Figure 7, Figure 10(b) is a partially enlarged view of Figure 10(a) showing a first example of the positional relationship of the connection of the feed bar portion to the formed member, and Figure 10(c) is a partially enlarged view of Figure 10(a) showing a second example of the positional relationship of the connection of the feed bar portion to the formed member. [Figure 11] Figure 11 corresponds to Figures 10(b) and 10(c) in terms of the position of the molded member, and is a partial side view showing a configuration including a cutting member applied in a separation process that cuts and separates the feed rail used in the manufacturing method of the lower arm in this embodiment. [Figure 12] FIG. 12 is a vertical cross-sectional view of a configuration including an insert member used in an additional adjustment step of the burring hole portion that is applied in the manufacturing method of the lower arm in this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, a manufacturing method of an arm member according to an embodiment of the present invention will be described in detail with reference to Fig. 1 to Fig. 12 as appropriate, taking a lower arm, which is a component part of a suspension system of a vehicle such as an automobile, as an example. In the drawings, the x-axis, y-axis, and z-axis form a three-axis orthogonal coordinate system. The x-axis direction may be called the longitudinal direction, the y-axis direction the width direction, and the z-axis direction the up-down direction or height direction.

[0027] FIG. 1 is a side view showing a lower arm manufactured by the manufacturing method of the lower arm in this embodiment. FIG. 2 to FIG. 4 are, correspondingly, a view taken along the Z1 arrow in FIG. 1, which is a plan view of the lower arm manufactured by the manufacturing method of the lower arm in this embodiment, a view taken along the Z2 arrow in FIG. 1, which is a bottom view of the lower arm manufactured by the manufacturing method of the lower arm in this embodiment, and a view taken along the X arrow in FIG. 1, which is a front view of the lower arm manufactured by the manufacturing method of the lower arm in this embodiment. FIG. 5 and FIG. 6 are, correspondingly, a vertical sectional view taken along the line AA in FIG. 1 and a vertical sectional view taken along the line BB in FIG. 1. In FIG. 1, FIG. 4, and FIG. 5, the reference characters of some components located symmetrically to the components shown in the drawings may be written in parentheses.

[0028] First, as shown in Fig. 1 to Fig. 6, the lower arm 1 is typically an arm member made of metal such as iron, which has a U-shape that opens mainly toward the negative direction of the z-axis in a vertical cross section cut on the yz plane and extends with the x-axis direction as the longitudinal direction. The lower arm 1 has a shape that is plane-symmetrical with respect to a plane that is parallel to the yz plane and passes through the center of the lower arm 1 in the longitudinal direction, and is also plane-symmetrical with respect to a plane that is parallel to the xz plane and passes through the center of the lower arm 1 in the y-axis direction as the width direction perpendicular to the longitudinal direction. Note that the lower arm 1 does not necessarily have to be limited to such a symmetrical shape, and may have an asymmetrical shape, as long as it has a configuration that has a U-shape that opens mainly toward the negative direction of the z-axis in a vertical cross section cut on the yz plane and extends with the x-axis direction as the longitudinal direction so that a hole portion, etc., described later, can be provided.

[0029] Specifically, the lower arm 1 mainly comprises a first side wall 10 located on the negative side of the y axis and parallel to the xz plane, a second side wall 110 parallel to the xz plane and located on the positive side of the y axis and facing the first side wall 10, and a connecting wall 210 located on the positive side of the z axis and connecting the first side wall 10 and the second side wall 110 at their ends on the positive side of the z axis.

[0030] Specifically, the first side wall 10 is composed of an intermediate side wall portion 12, an extended side wall portion 14 connected to the intermediate side wall portion 12 and having a vertical length longer than the vertical length of the intermediate side wall portion 12 (length in the z-axis direction) on the negative side of the x-axis relative to the intermediate side wall portion 12, an extended side wall portion 16 connected to the intermediate side wall portion 12 and having a vertical length longer than the vertical length of the intermediate side wall portion 12 on the positive side of the x-axis relative to the intermediate side wall portion 12, and a folded wall 40 folded from an end portion of the first side wall 10 on the negative side of the z-axis toward the positive side of the y-axis. Note that, when it is not necessary to increase the vertical length of the extended side wall portions 14 and 16 due to requirements such as the layout of the components of the lower arm 1, the vertical length of the extended side wall portions 14 and 16 may be set to be equal to or shorter than the vertical length of the intermediate side wall portion 12. Also, when there is no large requirement for the strength and rigidity of the lower arm 1, the folded wall 40 may be omitted.

[0031] The intermediate side wall 12 is a plate-like side wall having a constant vertical length, the extended side wall 14 is a plate-like side wall having a vertical length that gradually increases toward the negative x-axis side and an end portion on the negative x-axis side terminates in a semicircular shape that is convex toward the positive x-axis direction in a side view in the y-axis direction, and the extended side wall 16 is a plate-like side wall having a vertical length that gradually increases toward the positive x-axis side and an end portion on the positive x-axis side terminates in a semicircular shape that is convex toward the positive x-axis direction in a side view in the y-axis direction.

[0032] The extended side wall portion 14 has a burring hole portion 22 penetrating the extended side wall portion 14 in the y-axis direction, and the burring hole portion 22 has a cylindrical side wall-shaped flange 24 erected from the extended side wall portion 14 toward the positive direction of the y-axis while drilling the extended side wall portion 14 in the y-axis direction, and a through hole 26 defined radially inward of the burring hole portion 22 with respect to the flange 24. In addition, an outer peripheral edge portion 28 of the extended side wall portion 14, which is a portion that terminates in a semicircular shape convex toward the negative direction of the x-axis, is a cut end surface where the base material is cut in the manufacturing method of the lower arm 1. Note that if the requirements for strength and rigidity of the lower arm 1 are not large, the flange 24 may be omitted, and in such a case, the burring hole portion 22 becomes a through hole 26 that only penetrates the extended side wall portion 14.

[0033] The extended side wall portion 16 has a burring hole portion 32 penetrating the extended side wall portion 16 in the y-axis direction, similar to the extended side wall portion 14, and the burring hole portion 32 has a cylindrical side wall-shaped flange 34 erected from the extended side wall portion 16 toward the positive direction of the y-axis while drilling the extended side wall portion 16 in the y-axis direction, and a through hole 36 defined radially inward of the burring hole portion 32 with respect to the flange 34. In addition, an outer peripheral edge portion 38 of the extended side wall portion 16, which is a portion that terminates in a semicircular shape convex toward the positive direction of the x-axis, is a cut end surface where the base material is cut in the manufacturing method of the lower arm 1. Note that if the requirements for strength and rigidity of the lower arm 1 are not large, the flange 34 may be omitted, and in such a case, the burring hole portion 32 becomes a through hole 36 that only penetrates the extended side wall portion 16.

[0034] The folded wall 40 is composed of an intermediate folded wall 42 folded from the end of the intermediate side wall 12 on the negative side of the z axis toward the positive side of the y axis, an inclined folded wall 44 connected to the intermediate folded wall 42 and folded from the end of the extended side wall 14 on the negative side of the z axis toward the positive side of the y axis, and an inclined folded wall 46 connected to the intermediate folded wall 42 and folded from the end of the extended side wall 16 on the negative side of the z axis toward the positive side of the y axis. The portion where the inclined folded wall 44 terminates on the negative side of the x axis becomes a longitudinal end 45 connected to the outer circumferential edge 28 of the extended side wall 14, and the portion where the inclined folded wall 46 terminates on the positive side of the x axis becomes a longitudinal end 47 connected to the outer circumferential edge 38 of the extended side wall 16.

[0035] The second side wall 110 has components, which correspond to the respective components of the first side wall 10, namely the intermediate side wall portion 112, the extended side wall portions 114 and 116, the flange 124 and through hole 126 of the burring hole portion 122, the outer peripheral edges 128 and 138, the flange 134 and through hole 136 of the burring hole portion 132, the intermediate folded wall portion 142, the inclined folded wall portions 144 and 146, and the longitudinal ends 145 and 147 of the folded wall 140, facing each other on the positive side of the y-axis. Incidentally, only one of the pair of burring holes 22 and 122 and the pair of burring holes 32 and 132 may be provided as necessary.

[0036] However, in the second side wall 110, the flange 124 of the burring hole portion 122 and the flange 134 of the burring hole portion 132 are erected toward the negative direction of the y axis, and the intermediate bent wall portion 142 and the inclined bent wall portions 144 and 146 of the bent wall 140 are bent toward the negative direction of the y axis, which is different from that in the first side wall 10. In other words, the flange 24 of the burring hole portion 22 and the flange 124 of the burring hole portion 122 face each other on the inner side in the width direction of the lower arm 1, and the flange 34 of the burring hole portion 32 and the flange 134 of the burring hole portion 132 face each other on the inner side in the width direction of the lower arm 1. Moreover, the intermediate bent wall portion 42 and the inclined bent wall portions 44 and 46 of the bent wall 40 and the intermediate bent wall portion 142 and the inclined bent wall portions 144 and 146 of the bent wall 140 correspond to each other on the inner side in the width direction of the lower arm 1. Moreover, the through hole 26 of the burring hole portion 22 and the through hole 126 of the burring hole portion 122 have a coaxial central axis that is the C1 axis parallel to the y-axis direction, and the through hole 36 of the burring hole portion 32 and the through hole 136 of the burring hole portion 132 have a coaxial central axis that is the C2 axis parallel to the y-axis direction, and typically, an outer tubular portion of a bush member, which is an insulator member, is inserted into the through holes 26 and 126 and the through holes 36 and 136 correspondingly. In addition, when only one of the pairs of burring hole portions 22 and 122 and the pair of burring hole portions 32 and 132 is provided, a through hole may be provided at the location where the other pair should be provided, and a separate collar member may be attached around the through hole by welding or the like.

[0037] The connecting wall 210 consists of an intermediate connecting wall portion 212, an inclined connecting wall portion 214 that connects to the intermediate connecting wall portion 212 and is inclined so as to rise toward the positive side of the z-axis as it moves toward the negative side of the x-axis relative to the intermediate connecting wall portion 212, and an inclined connecting wall portion 216 that connects to the intermediate connecting wall portion 212 and is inclined so as to rise toward the positive side of the z-axis as it moves toward the positive side of the x-axis relative to the intermediate connecting wall portion 212.

[0038] The intermediate connecting wall portion 212 is an upper wall portion parallel to the xy plane that connects the ends of the intermediate side walls 12 and 112 on the positive side of the z axis.

[0039] The inclined connecting wall 214 is an upper wall connecting the ends of the extended side wall portions 14 and 114 on the positive side of the z-axis, and the end where the inclined connecting wall portion 214 terminates on the negative side of the x-axis becomes a longitudinal end portion 222 where the outer circumferential edge portion 28 of the extended side wall portion 14 and the outer circumferential edge portion 128 of the extended side wall portion 114 are connected. Note that the longitudinal end portion 222 may be provided with a protrusion depending on the specifications.

[0040] The inclined connecting wall 216, like the inclined connecting wall 214, is an upper wall connecting the ends of the extended sidewalls 16 and 116 on the positive side of the z-axis, and the end where the inclined connecting wall 216 terminates on the positive side of the x-axis becomes a longitudinal end 232 where the outer circumferential edge 38 of the extended sidewall 16 and the outer circumferential edge 138 of the extended sidewall 116 are connected. Note that the longitudinal end 232 may be provided with a protrusion depending on the specifications.

[0041] Next, a method for manufacturing the lower arm 1 by a series of progressive press forming steps will be described in detail with reference to Figs.

[0042] FIG. 7 is a plan view showing a formed member obtained in sequence from a plate-shaped base material in each process when a lower arm manufactured by the manufacturing method of the lower arm in this embodiment is manufactured by a progressive molding method. FIG. 8 corresponds to the CC vertical section of FIG. 7 in terms of position, and is a partial vertical section of a configuration including a positioning member applied in the manufacturing method of the lower arm in this embodiment. FIG. 9 is a DD vertical section of FIG. 7. FIG. 10 is a diagram showing the positional relationship of a feed bar portion to be connected to a formed member to obtain a lower arm by the manufacturing method of the lower arm in this embodiment, FIG. 10(a) is a side view corresponding in position to the Y1 arrow view of FIG. 7, FIG. 10(b) is a partial enlarged view of FIG. 10(a) showing a first example of the positional relationship of the feed bar portion to be connected to the formed member, and FIG. 10(c) is a partial enlarged view of FIG. 10(a) showing a second example of the positional relationship of the feed bar portion to be connected to the formed member. Fig. 11 corresponds to Fig. 10(b) and Fig. 10(c) in terms of the position of the formed member, and is a partial side view showing a configuration including a cutting member applied in a separation process for cutting and separating the feed bar used in the manufacturing method of the lower arm in this embodiment. Fig. 12 is a vertical cross-sectional view of a configuration including an insert member applied in an additional burring adjustment process of the burring hole portion applied in the manufacturing method of the lower arm in this embodiment, and corresponds to Fig. 5 in terms of the position. In Fig. 7, the feed direction Y of the base material is shown to face the positive direction of the y axis. In Fig. 10(a) and Fig. 12, the symbols of some components located symmetrically to the components shown in the figures may be shown in parentheses.

[0043] First, in the blank forming process shown in FIG. 7 on the most negative side of the y-axis, a blank forming member 1a, a remaining base material 502, and feed bars 510a and 520a, each of which is a single piece and plate-shaped, are formed from a base material 500, which is a plate-shaped workpiece made of metal such as iron. Note that the remaining base material 502 has a number of positioning holes 504 for positioning the base material 500 when it is advanced in the feed direction Y, which are formed during blank processing. Protrusions (not shown) are inserted into the positioning holes 504 in each forming process to determine position. Note that in the drawing, the blank forming member 1a, the remaining base material 502, and the end materials other than the feed bars 510a and 520a are not shown.

[0044] Here, the blank formed member 1a is a plate-like member having a longitudinal direction in the x-axis direction and an outer contour of the lower arm 1, and typically has a shape that is plane-symmetrical with respect to a plane that is parallel to the yz plane and passes through the center of the blank formed member 1a in the longitudinal direction, and is plane-symmetrical with respect to a plane that is parallel to the xz plane and passes through the center of the blank formed member 1a in the y-axis direction as the width direction perpendicular to the longitudinal direction. In the blank formed member 1a, extended plate portions 14a, 16a, 114a, and 116a, and outer peripheral portions 28a, 38a, 128a, and 138a are formed correspondingly as component portions corresponding to the extended sidewall portions 14, 16, 114, and 116, and the outer peripheral portions 28, 38, 128, and 138 of the lower arm 1.

[0045] The feed rail 510a typically has a base 512a that protrudes from the remaining base material 502 extending in the y-axis direction on the negative side of the x-axis toward the positive side of the x-axis, facing the middle part of the extension plate parts 14a and 114a of the blank formed member 1a in the y-axis direction, a branch part 514a that branches from the base 512a toward the negative side of the y-axis, and a connecting part 516a that connects the branch part 514a and the outer circumferential edge part 28a of the extension plate part 14a of the blank formed member 1a. The base 512a is wider in the y-axis direction than the branch part 514a and the connecting part 516a, and is connected integrally to the remaining base material 502. The connecting part 516a is connected integrally to the outer circumferential edge part 28a of the extension plate part 14a, which is the blank cut end surface when the blank formed member 1a is formed, and is integrated with the blank formed member 1a. The portion where the connecting portion 516a connects to the outer peripheral edge 28a of the extension plate 14a may be curved toward the outer peripheral edge 28a due to requirements in blanking, etc. Also, the feed bar 510a may extend such that its position (height) in the z-axis direction gradually decreases in the negative direction of the z-axis from the portion of the remaining base material 502 where the base portion 512a connects to the portion of the outer peripheral edge 28a of the extension plate 14a where the connecting portion 516a connects.

[0046] Here, when the connecting portion 516a is connected to the outer peripheral edge portion 28a on the negative side of the y-axis of the extension plate portion 14a so as to wrap around, the extension length of the branch portion 514a in the negative direction of the y-axis becomes longer, and the extension length of the connecting portion 516a in the positive direction of the x-axis becomes longer, and the connecting portion of the connecting portion 516a to the outer peripheral edge portion 28a tends to require an additional portion that bends toward the outer peripheral edge portion 28a. On the other hand, when the connecting portion 516a is connected to the outer peripheral edge portion 28a on the positive side of the y-axis of the extension plate portion 14a so as to wrap around the limited space between the outer peripheral edges 28a and 128a of the extension plate portions 14a and 114a in a top view, the extension length of the branch portion 514a becomes shorter, but the extension length of the connecting portion 516a in the positive direction of the x-axis becomes longer, and the handling tends to become complicated.

[0047] The feed bar 510a further has a branch portion 515a branching off from the base portion 512a toward the positive side of the y-axis, and a connecting portion 517a connecting the branch portion 515a and the outer peripheral edge portion 128a of the extension plate portion 114a of the blank forming member 1a. The branch portion 515a and the connecting portion 517a are symmetrical with the branch portion 514a and the connecting portion 516a about a plane passing through the center of the base portion 512a in the y-axis direction and parallel to the xz plane (typically, the plane coincides with a plane passing through the center of the blank forming member 1a in the y-axis direction and parallel to the xz plane). In addition, the feed bar portion 520a is symmetrical to the feed bar portion 510a with respect to a plane passing through the longitudinal center of the blank forming member 1a parallel to the yz plane, and has a base portion 522a protruding toward the negative side of the x-axis from the portion of the remaining base material 502 extending in the y-axis direction on the positive side of the x-axis, a branch portion 524a branching off from the base portion 522a toward the negative side of the y-axis, a connecting portion 526a connecting the branch portion 524a and the outer peripheral edge portion 38a of the extension plate portion 16a of the blank forming member 1a, a branch portion 525a branching off from the base 522a toward the positive side of the y-axis, and a connecting portion 527a connecting the branch portion 525a and the outer peripheral edge portion 138a of the extension plate portion 116a of the blank forming member 1a. In addition, in consideration of the material, plate thickness, and the like, if the required mechanical characteristics and the like are satisfied, the base portion 512a may be divided corresponding to the branch portions 514a and 515a and may be independent of each other.

[0048] Next, the pierce forming process shown next to the blank forming process on the positive side of the y axis in Fig. 7 is performed successively by feeding and moving a portion of the blank forming member 1a after the blank forming process. In this pierce forming process, a pierce forming member 1b is formed having extended plate portions 14b, 16b, 114b and 116b in which the pair of burring hole portions 22 and 122 of the lower arm 1 and the pair of burring hole portions 32 and 132 can be formed, as well as the pair of through holes 22b and 122b, and the pair of through holes 32b and 132b, are formed corresponding to the extended plate portions 14a, 16a, 114a and 116a formed in the blank forming member 1a. In this pierce forming process, the feed bar portions 510a and 520a connected to the blank forming member 1a are maintained, and like the feed bar portions 510a and 520a, the pierce forming member 1b is connected to the remaining base material portion 502 via the feed bar portion 510b having branch portions 514b and 515b and connecting portions 516b and 517b, and the feed bar portion 520b having branch portions 524b and 525b and connecting portions 526b and 527b.

[0049] Here, if a more precise shape is to be given to the blank formed member 1a between the blank forming process and the piercing process, a forming process may be provided between these processes in which press forming is performed to give the blank formed member 1a a required shape. When the forming process is provided, as shown by virtual lines for convenience in Fig. 7, it is preferable to respectively arrange a pair of positioning members 402 fixed on a lower mold 400 as shown in Fig. 8 between the extension plate parts 14a and 114a and between the extension plate parts 16a and 116a in order to position the blank formed member 1a in the x-axis direction and the y-axis direction during press forming, etc. Such a pair of positioning members 402 can be arranged in a configuration having a more appropriate size, etc., when the connecting parts 516b, 517b, 526b, and 527b of the feed rail parts 510a and 520a are not arranged between the extension plate parts 14a and 114a and between the extension plate parts 16a and 116a. The pair of positioning members 402 may be applied to a piercing process or a burring process, if necessary. The positioning by the pair of positioning members 402 may be performed in at least one of the x-axis direction and the y-axis direction, if necessary.

[0050] Next, the burring forming process shown next to the pierce forming process on the positive side of the y-axis in Fig. 7 is performed after the pierce forming process by sending and moving a portion of the pierce forming member 1b. In this burring forming process, burring is performed on the pair of through holes 22b and 122b and the pair of through holes 32b and 132b formed in the pierce forming member 1b, and a burring formed member 1c is obtained in which a pair of burring hole portions 22c and 122c and a pair of burring hole portions 32c and 132c corresponding to the pair of through holes 22b and 122b are formed. As shown representatively in Fig. 9, the burring hole portion 32c has a flange 34c erected from the burring forming member 1c around the central axis Cc. In addition, in the burring forming process, the feed bars 510b and 520b connected to the pierce forming member 1b are maintained as feed bars 510c and 520c, and the burring forming member 1c is connected to the remaining base material 502 through the feed bar 510c having the branched portions 514c and 515c and the connecting portions 516c and 517c, and the feed bar 520c having the branched portions 524c and 525c and the connecting portions 526c and 527c, as in the case of the feed bars 510b and 520b. Note that the burring forming process can be omitted as necessary, but when the burring forming process is performed, it is also possible to combine the pierce forming process with the burring forming process, form the pair of through holes 22b and 122b and the pair of through holes 32b and 132b in the burring forming process, and then form the pair of burring holes 22c and 122c and the pair of burring holes 32c and 132c corresponding to these.

[0051] Next, in Fig. 7, the first pre-bending process shown next to the burring process on the positive side of the y-axis is performed after the burring process by sending and moving the burring member 1c. In this first pre-bending process, a portion of a predetermined width having a center line that is a straight line connecting the base 512c of the feed bar 510c and the base 522c of the feed bar 520c connected to the burring member 1c is made into a connecting wall 210d, and a first pre-bending member 1d is obtained by bending the burring member 1c so that the first side wall 10d and the second side wall 110d are raised from the connecting wall 210d shown in the first pre-bending member 1d. However, in the primary pre-bending member 1d, the first side wall 10d and the second side wall 110d are each set to an angle greater than 90 degrees with respect to the connecting wall 210d, and are inclined surfaces inclined in the opening direction with respect to the connecting wall 210d. The pair of burring holes 22c and 122c and the pair of burring holes 32c and 132c in the burring member 1c are also maintained in the primary pre-bending member 1d as the pair of burring holes 22d and 122d and the pair of burring holes 32d and 132d, but with respect to the feed rails 510c and 520c connecting to the burring member 1c, the first side wall 10d and the second side wall 110d shown in the primary pre-bending member 1d are inclined toward the connecting wall 210d. As the guide rails are raised from 0d and bent, in particular the branch portions 514c, 515c, 524c and 525c and the connecting portions 516c, 517c, 526c and 527c are bent toward the ends of the first side wall 10d and the second side wall 110d on the negative side of the z-axis, thereby resulting in guide rail portions 510d and 520d each having bent branch portions 514d, 515d, 524d and 525d and connecting portions 516d, 517d, 526d and 527d.

[0052] 7, the secondary pre-bending process shown next to the primary pre-bending process on the positive side of the y-axis is performed successively by sending and moving a portion of the primary pre-bending member 1d after the primary pre-bending process. In this secondary pre-bending process, the primary pre-bending member 1d is bent so that the first side wall 10d and the second side wall 110d are raised from the connecting wall 210d to obtain a secondary pre-bending member 1e having a first side wall 10e and a second side wall 110e. However, the connecting wall 210d, the pair of burring holes 22d and 122d, and the pair of burring holes 32d and 132d in the primary pre-bending member 1d are maintained in the secondary pre-bending member 1e as the connecting wall 210e, the pair of burring holes 22e and 122e, and the pair of burring holes 32e and 132e. However, with regard to the feed rails 510d and 520d connected to the primary pre-bending member 1d, the first side wall 10d and the second side wall 110d of the primary pre-bending member 1d are maintained as the feed rails 510d and 520d connected to the primary pre-bending member 1d. As the lower arm 1 is raised from the connecting wall 210d and bent, in particular the branch portions 514d, 515d, 524d, and 525d and the connecting portions 516d, 517d, 526d, and 527d are bent by the end portions on the negative side of the z-axis of the first side wall 10d and the second side wall 110d, thereby obtaining the feed bar portions 510e and 520e having the branch portions 514e, 515e, 524e, and 525e and the connecting portions 516e, 517e, 526e, and 527e, which are bent more. At least one of the first pre-bending process and the second pre-bending process can be omitted when the bending process is easy due to the material or shape of the lower arm 1.

[0053] 7, the bending process shown next to the positive side of the y-axis of the secondary pre-bending process is performed successively by sending and moving a portion of the secondary pre-bending member 1e after the secondary pre-bending. In this bending process, the first side wall 10e and the second side wall 110e of the secondary pre-bending member 1e are pressed toward the positive and negative sides of the y-axis, and the first side wall 10e and the second side wall 110e are bent so that the angles formed by the first side wall 10e and the second side wall 110e with respect to the connecting wall 210e are each about 90 degrees, thereby obtaining a bent member 1f having the first side wall 10f, the second side wall 110f and the connecting wall 210f. The connecting wall 210e, the pair of burring holes 22e and 122e, and the pair of burring holes 32e and 132e in the secondary pre-bending member 1e are maintained in the bending member 1d as the connecting wall 210f, the pair of burring holes 22f and 122f, and the pair of burring holes 32f and 132f. However, with regard to the feed bar portions 510e and 520e connected to the secondary pre-bending member 1e, the first side wall 10e and the second side wall 110e of the secondary pre-bending member 1e are closer to the connecting wall 210e. As the guide rails 510f and 520f are bent, in particular the branch portions 514e, 515e, 524e, and 525e and the connecting portions 516e, 517e, 526e, and 527e are bent more toward the ends of the first side wall 10e and the second side wall 110e, which is on the negative side of the z-axis, so as to align with the first side wall 10e and the second side wall 110e, thereby obtaining guide rail portions 510f and 520f each having more bent branch portions 514f, 515f, 524f, and 525f and connecting portions 516f, 517f, 526f, and 527f.

[0054] Here, when the bent walls 40 and 140 are provided on the lower arm 1, a curl forming process may be provided after the bending process, in which the bent walls 40g and 140g are formed on the first side wall 10f and the second side wall 110f of the bending member 1f. In the curl forming process, the ends of the first side wall 10f and the second side wall 110f of the bending member 1f on the negative side of the z-axis are pressed to obtain a curl forming member 1g having bent wall portions 40g and 140g bent corresponding to the positive and negative sides of the y-axis. The other configurations of the curl forming member 1g are the same as those of the bending member 1f, and the feed bars 510g and 520g connected to the curl forming member 1g are also the same as the feed bars 510f and 520f connected to the bending member 1f. The curl forming process is typically included in a series of steps of the progressive forming method, like the above forming process.

[0055] Specifically, as shown in Fig. 10(a), the curl forming member 1g has a substantially similar structure to the lower arm 1 having the burring holes 22, 32, 122, and 132 and the bent walls 40 and 140, and the extended side walls 14g and 16g have through holes 26g and 36g for the burring holes 22g and 32g, and the extended side walls 14g and 16g have outer peripheral edges 28g and 38g. The inclined bent wall 44g has a longitudinal end 45g on the negative side of the x-axis, and the inclined bent wall 46g has a longitudinal end 47g on the positive side of the x-axis. The inclined connecting wall 214g has a longitudinal end 222g on the negative side of the x-axis, and the inclined connecting wall 216g has a longitudinal end 232g on the positive side of the x-axis. In the curl forming member 1g, a connecting portion 516g of a feed bar portion 510g, which has a branch portion 514g connecting to a base portion 512g and a connecting portion 516g connecting to the branch portion 514g, connects to the outer peripheral edge portion 28g of the extended side wall portion 14g on the negative side of the x-axis, and a connecting portion 517g of a feed bar portion 510g, which has a branch portion 515g connecting to the base portion 512g and a connecting portion 517g connecting to the branch portion 515g, connects to the outer peripheral edge portion 128g of the extended side wall portion 114g on the negative side of the x-axis, A branch portion 524g connected to the base portion 522g and a connecting portion 526g connected to the branch portion 524g of the feed bar portion 520g are connected to the outer peripheral edge portion 38g of the expanded side wall portion 16g of the forming member 1g on the positive side of the x-axis, and a branch portion 525g connected to the base portion 522g and a connecting portion 527g connected to the branch portion 525g of the feed bar portion 520g are connected to the outer peripheral edge portion 138g of the expanded side wall portion 116g of the curl forming member 1g on the positive side of the x-axis. In the drawing, the symbol Cg indicates the central axis of the burring hole portions 32g and 132g that define the through holes 36g and 136g, and the symbol Cg' indicates the central axis of the burring hole portions 22g and 122g that define the through holes 26g and 126g.

[0056] 10(b), the connection range α corresponds to the maximum range in which the connecting portion 526g of the feed bar 520g can connect to the outer peripheral edge 38g of the expanded side wall 16g. In more detail, the maximum range in which the connecting portion 526g can connect to the outer peripheral edge 38g of the expanded side wall 16g corresponds to the entire range in which the outer peripheral edge 38g exists, so that when viewed in the positive direction of the y-axis along the central axis Cg of the burring hole 32g, i.e., the through hole 36g, the counterclockwise limit of the connecting portion 526g of the feed bar 520g is defined by the longitudinal end 232g of the inclined connecting wall 216g, and the clockwise limit of the connecting portion 526g of the feed bar 520g is defined by the longitudinal end 47g of the inclined bent wall 46g. Thus, the connection range α in the figure is the range of the outer peripheral edge 38g sandwiched between the longitudinal end 232g of the inclined connecting wall 216g and the longitudinal end 47g of the inclined bent wall 46g. Similarly, although not shown, the connection range α for the connecting portion 527g of the feed bar 520g is the range of the outer peripheral edge 138g sandwiched between the longitudinal end 232g of the inclined connecting wall 216g and the longitudinal end 147g of the inclined bent wall 146g. Similarly, the connection range α for the connecting portion 516g of the feed bar 510g is the range of the outer peripheral edge 28g sandwiched between the longitudinal end 222g of the inclined connecting wall 214g and the longitudinal end 45g of the inclined bent wall 44g, and the connection range α for the connecting portion 517g of the feed bar 510g is the range of the outer peripheral edge 128g sandwiched between the longitudinal end 222g of the inclined connecting wall 214g and the longitudinal end 145g of the inclined bent wall 144g. If the curl forming step is not provided, the bent walls 40g and 140g do not exist, and in such a case, the connection range α for the bending member 1f may be set to the same range as the connection range α for the curl forming member 1g.In other words, when viewed in the positive direction of the y axis along the burring hole portion 32f, i.e., the central axis Cf of the through hole not shown in the figure, it can be evaluated that the counterclockwise limit of the connecting portion 526f of the feed bar portion 520f is determined by the longitudinal end portion 232f of the inclined connecting wall portion 216f, and the clockwise limit of the connecting portion 526f of the feed bar portion 520f corresponds to the 7 o'clock position in the counterclockwise direction; and when viewed in the negative direction of the y axis along the burring hole portion 132f, i.e., the central axis Cf of the through hole not shown in the figure, it can be evaluated that the clockwise limit of the connecting portion 527f of the feed bar portion 520f is determined by the longitudinal end portion 232f of the inclined connecting wall portion 216f, and the counterclockwise limit of the connecting portion 527f of the feed bar portion 520f corresponds to the 7 o'clock position in the counterclockwise direction. Furthermore, when viewed in the positive direction of the y-axis along the burring hole portion 22f, i.e., the central axis Cf' of the through hole not shown in the figure, it can be evaluated that the clockwise limit of the connecting portion 516f of the feed bar portion 510f is determined by the longitudinal end portion 222f of the inclined connecting wall portion 214f, and the counterclockwise limit of the connecting portion 516f of the feed bar portion 510f corresponds to the 7 o'clock position in the counterclockwise direction; and when viewed in the negative direction of the y-axis along the burring hole portion 122f, i.e., the central axis Cf' of the through hole not shown in the figure, it can be evaluated that the counterclockwise limit of the connecting portion 517f of the feed bar portion 510f is determined by the longitudinal end portion 222f of the inclined connecting wall portion 214f, and the clockwise limit of the connecting portion 517f of the feed bar portion 510f corresponds to the 7 o'clock position in the clockwise direction. Here, the main reference numerals are shown in the bent member 1f in FIG. 7, and the 7 o'clock position in the clockwise direction is representatively shown in FIG. 10(b).

[0057] Furthermore, as shown representatively in Figure 10(c), the connection range β corresponds to a narrower range in which the connecting portion 526g of the feed bar portion 520g can connect to the outer peripheral edge portion 38g of the extended side wall portion 16g, compared to the connection range α shown representatively in Figure 10(b), and is defined as an angular range of 120 degrees (30 degrees + 90 degrees) between 2 o'clock and 6 o'clock clockwise when viewed in the positive direction of the y-axis along the central axis Cg of the boring hole portion 32g, i.e., the through hole 36g. This is because, when the connecting portion 526g is connected to the outer peripheral edge portion 38g on the side of the longitudinal end 232g of the inclined connecting wall portion 216g before 2 o'clock, it may be possible to shorten the overall length of the branch portion 524g and the connecting portion 526g, but the design of the feed bar portion 520g that can achieve both the cuttability of the connecting portion 526g and the formability of the branch portion 524g and the connecting portion 526g tends to become complicated, particularly due to the complicated handling of the connecting portion 526g.For example, when the connecting portion 526g is connected to the outer peripheral edge portion 38g of the extended side wall portion 16g at the 2 o'clock position, in the burring forming member 1a, which is the initial formed state of the curl forming member 1g, it is possible to shift the connection position from the end portion on the negative side of the y-axis direction of the extension plate portion 116a in the positive direction of the y-axis by a length of approximately 1 / 2 the radius of the extension plate portion 116a. On the other hand, if the connecting portion 526g is connected to the outer peripheral edge portion 38g on the side of the longitudinal end 47g of the inclined folded wall portion 46g rearward of 6 o'clock, the overall length of the branch portion 524g and the connecting portion 526g will be longer, the variation in the shapes of the branch portion 524g and the connecting portion 526g will increase, and the additional portion connecting and connecting the connecting portion 526g to the outer peripheral edge portion 38g will become larger, which tends to complicate the design of the feed bar portion 520g that can achieve both the cuttability of the connecting portion 526g and the formability of the branch portion 524g and the connecting portion 526g.Similarly, the connection range β is defined for the connecting portion 527g of the feed bar portion 520g, and the connecting portion 516g and the connecting portion 517g of the feed bar portion 520g, but the connection range β corresponds to the range between 2 o'clock and 6 o'clock counterclockwise when viewed in the negative direction of the y axis along the central axis Cg of the through hole 136g for the connecting portion 527g, between 2 o'clock and 6 o'clock counterclockwise when viewed in the positive direction of the y axis along the central axis Cg' of the through hole 26g, and between 2 o'clock and 6 o'clock clockwise when viewed in the negative direction of the y axis along the central axis Cg' of the through hole 126g for the connecting portion 517g. The connection range β in the bending member 1f when the curl forming step is not provided can be applied to the bending member 1f in the same manner as the connection range β in the curl forming member 1g.

[0058] In addition, the connection range γ shown representatively in Figure 10(c) corresponds to a range that narrows the clockwise limit of the range in which the connecting portion 526g of the feed bar portion 520g can connect to the outer peripheral edge portion 38g of the extended side wall portion 16g compared to the connection range β, and is defined as an angular range of 90 degrees (30 degrees + 60 degrees) between 2 o'clock and 5 o'clock clockwise when viewed in the positive direction of the y-axis along the central axis Cg of the boring hole portion 32g, i.e., the through hole 36g. Here, the reason why the limit of the connection range γ on the clockwise side is narrowed from 6 o'clock to 5 o'clock on the counterclockwise side with respect to the connection range β is to shorten the length of the branch portion 524g and the connecting portion 526g, reduce the additional portion that connects the connecting portion 526g to the outer peripheral edge portion 38g, and further improve the formability while suppressing the shape variation, and to simplify the movement of the cutting member to the connecting portion 526g to further improve its cuttability, and to facilitate the insertion of a jig or a die from above and below into the burring hole portions 32g and 132g, which contributes to the convenience of adjusting their shapes, etc. In addition, the connection range γ is also specified in the same manner as the connection range β for the connecting portion 527g of the feed bar portion 520g, and the connecting portion 516g and the connecting portion 517g of the feed bar portion 510g. In addition, the connection range γ in the bending member 1f when the curl forming process is not provided can be applied to the bending member 1f in the same manner as the connection range γ in the curl forming member 1g.

[0059] Next, the separation step shown in Fig. 11 is performed by feeding and moving the bending forming member 1f or the curl forming member 1g, which is provided as necessary, after the bending forming step shown on the most positive side of the y axis in Fig. 7, but the curl forming member 1g is shown as a representative in the figure. In this separation step, parts of the feed bars 510g and 520g connected to the curl forming member 1g are cut to separate the curl forming member 1g from the remaining base material portion 502, thereby obtaining a separation formed member. In addition, since this separation formed member can be considered to be substantially the lower arm 1, it is shown in the figure by a phantom line and reference symbol 1'.

[0060] Specifically, as representatively shown in the figure, the base 522g of the feed rail 520g and the flanges 34g and 134g of the curl forming member 1g are placed on the support mold 450, and the support mold 450 is fixed by being clamped between the extension plate parts 16g and 116g. In this state, the cutting member 452, which is supported so as to be movable so as to enter the opening 454 of the support mold 450, is moved from the negative side of the y-axis toward the connecting part 526g of the feed rail 520g, and a part of the connecting part 526g overlapping with the cutting member 452 is cut so as to be partially punched out, and the connecting part 526g is separated from the curl forming member 1g. At this time, the part 452a of the cutting member 452 moves along the outer peripheral edge part 38g while abutting against it, and breaks the part of the connecting part 526g on the outer peripheral edge part 38g side. On the other hand, for connecting portion 527g of feed bar portion 520g, a cutting member (not shown) facing cutting member 452 on the positive side of the y-axis is moved from the positive side of the y-axis toward connecting portion 527g of feed bar portion 520g, and a part of connecting portion 527g is cut so as to be partially punched out, similar to connecting portion 526, and connecting portions 526g and 527g, i.e., feed bar portion 520g, are separated from curl forming member 1g. Cut pieces (not shown) of separated connecting portions 526g and 527g are discharged to the outside through gap portion 456 of support mold 450 and discarded. In this way, in order to easily cut the connecting parts 526g and 527g by moving the cutting member 452 and a cutting member (not shown) in the y-axis direction, the range in which the connecting parts 526g and 527g can connect and connect to the outer peripheral parts 38g and 138g is preferably a connecting range β, and more preferably a connecting range γ. Similarly, the connecting parts 516g and 517g of the feed bar part 510g other than the connecting parts 526g and 527g of the feed bar part 520g are also cut off from the curl forming member 1g by a cutting member (not shown), but the cutting member for the connecting part 516g is moved from the negative side of the y-axis toward the connecting part 516g, and the cutting member for the connecting part 517g is moved from the positive side of the y-axis toward the connecting part 517g. The timing of cutting the connecting parts 516g, 517g, 526g, and 527g may all be the same, or some may be the same and the others may be different, as necessary.

[0061] Furthermore, before the above-mentioned separation step, a burring adjustment step may be provided to adjust the shape of the pair of burring holes 22f and 122f and the pair of burring holes 32f and 132f in the bend forming member 1f, or the pair of burring holes 22g and 122g and the pair of burring holes 32g and 132g in the subsequent curl forming member 1g that is provided as necessary, but Fig. 12 shows the curl forming member 1g as a representative example. Note that the burring adjustment step is typically included in the series of steps of the progressive type forming method, like the above-mentioned forming steps.

[0062] Specifically, as shown representatively in the figure, the contact dies 410 and 420 are abutted against the flanges 24g, 34g, 124g, and 134g of the burring hole portions 22g, 32g, 122g, and 132g of the curl forming member 1g in the z-axis direction and pressed down from the z-axis direction, while the insertion members 432a and 432b are inserted into the through holes 26g, 36g, 126g, and 136g of the burring hole portions 22g, 32g, 122g, and 132g in the y-axis direction. The insert members 432a and 432b are pressed through a pressing mechanism (not shown) in the guide members 434a and 434b, and slide in contact with the wall surfaces of the through holes 26g, 36g, 126g and 136g, and the configurations of the burring holes 22g, 32g, 122g and 132g, such as the shape and coaxiality of the through holes 26g, 36g, 126g and 136g, are adjusted. In this way, in order to make the contact dies 410 and 420 contact the flanges 24g, 34g, 124g and 134g in the z-axis direction, the range in which the connecting portion 526g can connect to the outer periphery 38g is preferably the connecting range β, and more preferably the connecting range γ. Note that the pressing by the contact dies 410 and 420 may be performed from at least one of the z-axis direction and the y-axis direction, as necessary.

[0063] In addition, the extension portion such as the above-mentioned feed rail portion can be used as part of the support portion when manually moving the workpiece between processes and when setting it up at each process in a tandem-type multiple press molding process, and can be used as part of the support portion when automatically moving the workpiece between processes and when setting it up at each process in a series of transfer-type press molding processes.

[0064] In the manufacturing method of the arm member 1 of the present embodiment described above, for the bending formed member 1f or the rear-stage formed member 1g, the extension portions 510f, 510g, 520f, and 520g are formed into first extension portions 512f, 514f, 516f, 512g, 514g, and 516g communicating with the first outer peripheral edge portions 28f and 28g which are the outer peripheral edge portions for the first hole portions 22f and 22g in the first side walls 10f and 10g, and second extension portions 128f and 128g which are the outer peripheral edge portions for the second hole portions 122f and 122g in the second side walls 110f and 110g. a third extension portion 522f, 524f, 526f, 522g, 524g, and 526g communicating with a third outer peripheral edge portion 38f and 38g which is an outer peripheral edge portion for the third hole portion 32f and 32g in the first side wall 10f and 10g, and a fourth extension portion 522f, 525f, 527f, 522g, 525g, and 527g communicating with a fourth outer peripheral edge portion 138f and 138g which is an outer peripheral edge portion for the fourth hole portion 132f and 132g in the second side wall 110f and 110g, The present invention further includes a separation step of cutting the extensions 510f, 510g, 520f, and 520g of the bent-formed member 1f or the subsequent-stage formed member 1g to separate the bent-formed member 1f or the subsequent-stage formed member 1g from the remaining base material 502, thereby obtaining a separated formed member. In the separation step, the first extensions 512f, 514f, 516f, 512g, 514g, and 516g are cut off on the first outer peripheral edge ends 28f and 28g sides of the bent-formed member 1f or the subsequent-stage formed member 1g, and the second extensions 512f, 515f, 517f, 512g are cut off on the second outer peripheral edge ends 128f and 128g sides of the bent-formed member 1f or the subsequent-stage formed member 1g. , 515g and 517g are cut, and portions of the third extensions 522f, 524f, 526f, 522g, 524g and 526g are cut on the side of the third outer peripheral edge ends 38f and 38g, while portions of the fourth extensions 522f, 525f, 527f, 522g, 525g and 527g are cut on the side of the fourth outer peripheral edge ends 138f and 138g. Therefore, when cutting the extensions 510f to 510g and 520f to 520g connecting the molded members 1a to 1g molded from the base material 500 to the base material crosspiece 502, sufficient cutting ability is ensured for practical use,The arm member 1 can be manufactured in a state in which the molded members 1a to 1g are supported with high support rigidity by the extension portions 510f to 510g and 520f to 520g.

[0065] In addition, the present invention is not limited to the above-described embodiment in terms of the type, shape, arrangement, number, etc. of the components, and it goes without saying that the components can be appropriately modified within the scope of the gist of the invention, such as by appropriately replacing them with components that achieve the same functional effects. [Industrial Applicability]

[0066] As described above, the present invention provides a manufacturing method for an arm member that can support a molded member on an extension portion with high support rigidity while ensuring sufficient cutting ability for practical use when cutting the extension portion that connects a molded member formed from a base material to a base material crosspiece portion.Therefore, due to its versatile and universal nature, it is expected that the method will be widely applicable to the field of strength parts for vehicles, etc. [Explanation of symbols]

[0067] 1. Lower arm 1a...Blank forming member 1b…Piercing forming member 1c…Burring forming part 1d…First pre-bending member 1e…Secondary pre-bending member 1f…Bent forming member 1g...Curl forming member 10, 10d to 10g…First side wall 12...Intermediate side wall 14, 16…Extended side wall 14a, 14b, 14g, 16a, 16b, 16g...Extension plate section 22, 22c to 22g, 32, 32c to 32g... Burring hole section 22b, 32b...Through hole 24, 24g, 34, 34g...Flanges 26, 26g, 36, 36g...through hole 28, 28a, 28f, 28g, 38, 38a, 38f, 38g...Outer periphery 40, 40g...Bent wall 42...Intermediate folded wall section 44, 44g...Inclined bent wall 45, 45g...Long end 46, 46g...Inclined bent wall 47, 47g...Long end 110, 110d to 110g…Second side wall 112...Intermediate side wall 114, 116...extended side wall portion 114a, 114b, 114g, 116a, 116b, 116g...extension plate section 122, 122c to 122g, 132, 132c to 132g... Burring hole section 122b, 132b...Through hole 124, 124g, 134, 134g...Flanges 126, 126g, 136, 136g...through hole 128, 128a, 128f, 128g, 138, 138a, 138f, 138g...Outer periphery 140, 140g...Bent wall 142...Intermediate folded wall section 144, 144g...Inclined bent wall 145, 145g...Long end 146, 146g...Inclined bent wall 147, 147g...Long end 210, 210d, 210e...Connecting walls 212...Intermediate connecting wall 214, 214g...Slanted connecting wall part 216, 216g...Slanted connecting wall part 222, 222g, 232, 232g...Long end 400…lower mold 402... Positioning member 410, 420... Hit type 432a, 432b...insertion member 434a, 434b...Guide members 450…support type 452...Cutting member 454…Opening 456...Void part 500...Base material 502…Remaining base material 504…Positioning hole 510a to 510g, 520a to 520g...Feed bar section 512a to 512g, 522a to 522g...base 514a to 514g, 524a to 524g...Branch 515a to 515g, 525a to 525g...Branch 516a to 516g, 526a to 526g… Contact Department 517a to 517g, 527a to 527g… Contact Department

Claims

1. A manufacturing method for manufacturing an arm member extending in a longitudinal direction, comprising a molding process using a plate-shaped base material, the molding process including a molded member, an extension portion, and a base material remainder portion which is a portion of the base material other than the molded member and the extension member, the method comprising the steps of: The forming step includes a bending forming step for obtaining a bent formed member included in the formed member, or a subsequent forming step for obtaining a subsequent stage formed member included in the formed member at a stage subsequent to the bending forming step in addition to the bending forming step, The bending shaping member or the rear-stage shaping member has a first side wall and a second side wall opposed to each other in a width direction perpendicular to the longitudinal direction, a first hole portion formed on one side of the longitudinal direction in the first side wall and a second hole portion formed on the one side of the longitudinal direction in the second side wall opposed to each other, and a third hole portion formed on the other side of the longitudinal direction in the first side wall and a fourth hole portion formed on the other side of the longitudinal direction in the second side wall opposed to each other, For the bending forming member or the subsequent forming member, the extension portion includes a first extension portion communicating with a first outer peripheral edge end portion which is an outer peripheral edge end portion for the first hole portion in the first side wall, a second extension portion communicating with a second outer peripheral edge end portion which is an outer peripheral edge end portion for the second hole portion in the second side wall, a third extension portion communicating with a third outer peripheral edge end portion which is an outer peripheral edge end portion for the third hole portion in the first side wall, and a fourth extension portion communicating with a fourth outer peripheral edge end portion which is an outer peripheral edge end portion for the fourth hole portion in the second side wall, The method further includes a separation step of cutting the extension portion relative to the bent-formed member or the subsequent-stage formed member to separate the bent-formed member or the subsequent-stage formed member from the remaining portion of the base material to obtain a separated formed member, A manufacturing method for an arm member, in which, in the cutting process, a portion of the first extension portion is cut on the side of the first outer peripheral edge end, a portion of the second extension portion is cut on the side of the second outer peripheral edge end, a portion of the third extension portion is cut on the side of the third outer peripheral edge end, and a portion of the fourth extension portion is cut on the side of the fourth outer peripheral edge end, for the bending forming member or the subsequent forming member.

2. The forming process further includes, in addition to the bending process and the preceding stage of the separating process, a blank forming process for obtaining a blank forming member included in the forming member and a piercing forming process for obtaining a piercing forming member included in the forming member, a form forming process for obtaining a foam forming member included in the forming member between the blank forming process and the piercing forming process, in addition to the bending process, the blank forming process and the piercing forming process, or a burring forming process for obtaining a burring forming member included in the forming member between the piercing forming process and the bending process, in addition to the bending process, the blank forming process and the piercing forming process, Or the forming step includes the blank forming step, the form forming step, the piercing forming step, the burring forming step, and the bending forming step, In the blank forming step, the blank formed member, the extension portion, and the remaining portion of the base material are obtained from the base material, and the extension portion extends between and communicates with the blank formed member and the remaining portion of the base material; In the foam molding step, the foam molded member is obtained by further molding the shape of the blank molded member, and the extension portion extends between and communicates with the foam molded member and the remaining base material, In the pierce forming step, the blank forming member or the foam forming member is provided with the first hole formed at one end side, which is the negative side of the two ends in the longitudinal direction, the second hole formed at the other end side, which is the positive side of the two ends in the longitudinal direction, the third hole formed at one end side, which is the negative side of the two ends in the width direction, and the fourth hole formed at the other end side, which is the positive side of the two ends in the longitudinal direction, to obtain a pierce forming member, and the extension portion extends between and connects the pierce forming member and the remaining base material, In the burring forming step, the first hole portion, the second hole portion, the third hole portion, and the fourth hole portion of the pierce forming member are correspondingly formed into a first burring hole portion, a second burring hole portion, a third burring hole portion, and a fourth burring hole portion to obtain the burring formed member, and the extension portion extends between and communicates between the burring formed member and the remaining portion of the base material, In the bending process, a wall portion that connects a portion where the first hole portion or first burring hole portion is formed and an intermediate portion where the second hole portion or second burring hole portion is formed, and an intermediate portion where the third hole portion or third burring hole portion is formed and an intermediate portion where the fourth hole portion or fourth burring hole portion is formed, in the longitudinal direction of the pierce forming member or the burring forming member, is a connecting wall, and a wall portion that stands up in a negative direction in the up-down direction perpendicular to the longitudinal direction and the width direction from the connecting wall and connects the portion where the first hole portion or first burring hole portion is formed and an intermediate portion where the second hole portion or second burring hole portion is formed and an intermediate portion where the third hole portion or third burring hole portion is formed and an intermediate portion where the fourth hole portion or fourth burring hole portion is formed is a connecting wall.

2. The method for manufacturing an arm member as described in claim 1, wherein the bent shaped member has a first side wall which is a wall portion that connects the portion in which the second hole portion or second burring hole portion is formed and the portion in which the fourth hole portion or fourth burring hole portion is formed in the longitudinal direction, and the second side wall is a wall portion that stands up from the connecting wall in the negative direction of the up-down direction so as to face the first side wall in the width direction and connects the portion in which the second hole portion or second burring hole portion is formed and the portion in which the fourth hole portion or fourth burring hole portion is formed in the longitudinal direction, and the extension portion extends between and connects the bent shaped member and the remaining portion of the base material.

3. With respect to the bent shaped member, the first extension portion is connected to a portion between one end of the connecting wall on the negative side of the longitudinal direction and a portion corresponding to 7 o'clock counterclockwise when looking at the first hole portion or the first burring hole portion in the positive direction of the width direction, with respect to the first outer circumferential edge portion, and the second extension portion is connected to a portion between one end of the connecting wall and a portion corresponding to 7 o'clock clockwise when looking at the second hole portion or the second burring hole portion in the negative direction of the width direction, with respect to the second outer circumferential edge portion, 3. A manufacturing method for an arm member as described in claim 2, wherein the third extension portion connects, with respect to the third outer peripheral edge end, to a portion between the other end of the connecting wall on the positive side of the longitudinal direction and a portion corresponding to 7 o'clock clockwise when looking at the third hole portion or the third burring hole portion in the positive direction of the width direction, and the fourth extension portion connects, with respect to the fourth outer peripheral edge end, to a portion between the other end of the connecting wall and a portion corresponding to 7 o'clock counterclockwise when looking at the fourth hole portion or the fourth burring hole portion in the negative direction of the width direction.

4. The forming step further includes a curl forming step as the latter forming step, In the curl forming step, an end portion of the first side wall on the negative side in the vertical direction and an end portion of the second side wall on the negative side in the vertical direction are bent to face each other in the width direction, thereby obtaining a curl forming member having a first bent wall and a second bent wall corresponding to each other, and the extension portion extends between the curl forming member and the remaining portion of the base material, 3. The method for manufacturing an arm member according to claim 2, wherein the first extension portion connects, with respect to the first outer circumferential edge portion, to a portion between one end of the connecting wall on the negative side of the longitudinal direction and one end of each of the first folded wall and the second folded wall on the negative side of the longitudinal direction; the second extension portion connects, with respect to the second outer circumferential edge portion, to a portion between the one end of the connecting wall and the one end of each of the first folded wall and the second folded wall; the third extension portion connects, with respect to the third outer circumferential edge portion, to a portion between the other end of the connecting wall on the positive side of the longitudinal direction and the other end of each of the first folded wall and the second folded wall on the positive side of the longitudinal direction.

5. 5. The method for manufacturing an arm member according to claim 3 or 4, wherein, for the bent formed member, the first extension portion connects to a portion between 2 o'clock and 6 o'clock counterclockwise when looking at the first hole portion or the first burring hole portion in the positive direction of the width direction with respect to the first outer peripheral edge end, the second extension portion connects to a portion between 2 o'clock and 6 o'clock clockwise when looking at the second hole portion or the second burring hole portion in the negative direction of the width direction with respect to the second outer peripheral edge end, the third extension portion connects to a portion between 2 o'clock and 6 o'clock clockwise when looking at the third hole portion or the third burring hole portion in the positive direction of the width direction with respect to the third outer peripheral edge end, and the fourth extension portion connects to a portion between 2 o'clock and 6 o'clock counterclockwise when looking at the fourth hole portion or the fourth burring hole portion in the negative direction of the width direction with respect to the fourth outer peripheral edge end.

6. the blank forming member has a first expansion plate portion, a second expansion plate portion, a third expansion plate portion, and a fourth expansion plate portion, which respectively correspond to portions of the pierce forming member where the first hole portion, the second hole portion, the third hole portion, and the fourth hole portion are formed, A manufacturing method for an arm member as described in claim 5, wherein in the form molding process, a first positioning member is arranged between a first extension plate portion and a second extension plate portion, and a second positioning member is arranged between a third extension plate portion and a fourth extension plate portion for the blank molding member, thereby positioning the blank molding member in at least one of the longitudinal direction and the width direction.

7. The molding step further includes a burring adjustment step as the latter forming step, 5. The method for manufacturing an arm member according to claim 3 or 4, wherein in the burring adjustment process, configurations of the first burring hole portion, the second burring hole portion, the third burring hole portion, and the fourth burring hole portion are adjusted while pressing a flange of each of the first burring hole portion, the second burring hole portion, the third burring hole portion, and the fourth burring hole portion from at least one of the vertical direction and the width direction.

8. 5. A manufacturing method for an arm member as described in claim 3 or 4, wherein in the separation process, a first cutting member is moved toward the positive side of the width direction while abutting against the first outer peripheral edge end with respect to the bending forming member or the subsequent forming member to cut a portion of the first extension portion, a second cutting member is moved toward the negative side of the width direction while abutting against the second outer peripheral edge end to cut a portion of the second extension portion, a third cutting member is moved toward the positive side of the width direction while abutting against the third outer peripheral edge end to cut a portion of the third extension portion, and a fourth cutting member is moved toward the negative side of the width direction while abutting against the fourth outer peripheral edge end to cut a portion of the fourth extension portion.

9. 5. A method for manufacturing an arm member as described in claim 3 or 4, wherein in the bending forming process, when the first side wall and the second side wall are erected from the connecting wall, the first extension portion and the third extension portion are each bent toward the end side of the first side wall on the negative side in the vertical direction, and the second extension portion and the fourth extension portion are each bent toward the end side of the second side wall on the negative side in the vertical direction.

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