METHOD OF MANUFACTURING A HOLLOW HOUSING PART

Abstract

A manufacturing method is described that can suppress the occurrence of wrinkles and buckling deformations due to bending when bending and cross-sectioning a tube using a press die. The manufacturing method described herein involves applying pressure to a bent tube having a curved portion from the outside of the tube to the inside of the tube using a press die, thereby simultaneously cross-sectioning the curved portion and bending it to reduce its radius of curvature.

Description

METHOD FOR MANUFACTURING A HOLLOW HOUSING PART CJhC Ln / Zznz / E / YIAI Field of invention [1] This application describes a manufacturing method for a hollow housing part. Background of the invention [2] PTL 1 describes a technique for bending and cross-sectioning (processing that transforms the shape of the cross-section intersecting the longitudinal direction of the tube) a straight tube using a press die. In the technique described in PTL 1, high form accuracy for a hollow shell part after processing is ensured by simultaneously performing cross-sectioning and bending on a straight tube. According to the technique described in PTL 1, a hollow shell part can be obtained solely by pressing from the outside of a tube without requiring complex processes such as hydroforming, thereby improving the productivity of the hollow shell part. List of citations Patent literature [3] PTL 1: Japanese Patent Publication No. 6519984 Summary of the invention Technical problem [4] According to a new finding of the inventor hereof, when attempting to obtain a hollow housing piece having a curved portion by simultaneously performing cross-sectioning and bending on a straight tube as described in PTL 1, unsatisfactory shaping, such as wrinkles and buckling, is easily generated on the surface of the curved portion, especially when the radius of curvature of the curved portion is small. PJhC Ln / Zznz / E / YIAI Solution to the problem [5] As a means to solve the above problem, the present application describes a manufacturing method for a hollow housing part, the method comprising applying pressure to a bent tube having a curved portion from the outside of the tube to the inside of the tube using a press die, thereby simultaneously performing cross-sectioning of the curved portion and bending of the curved portion to reduce the radius of curvature of the curved portion. [6] In the manufacturing method described herein, the press die may have an upper die and a lower die, the upper die and the lower die may respectively have pressing surfaces, and cross-sectioning and bending may be performed simultaneously by pressing the bent tube with the upper die and the lower die from above and below and pressing the pressing surfaces against the curved portion of the bent tube. [7] The manufacturing method of the present description may include obtaining the bent tube having the curved portion by at least bending an original tube. [8] The manufacturing method of the present description may include obtaining the bent tube having the curved portion by at least bending and transversely cutting an original tube. [9] In the manufacturing method of the present description, the bending performed on the original tube may include applying pressure from the outside of the tube towards the inside of the tube using a press die to obtain the bent tube.

[10] In the manufacturing method of the present description, the bending and the transverse cutting performed on the original tube may include applying pressure from the outside of the tube towards the inside of the tube using a press die to obtain the bent tube.

[11] In the manufacturing method of the present description, the original tube may be a straight tube.

[12] In the manufacturing method described herein, after the cross-sectioning and bending are completed, in a cross-section orthogonal to the longitudinal direction of the hollow housing part, an inner surface of the press die can be tilted with respect to an outer surface of the hollow housing part, so that a gap can be created between the outer surface of the hollow housing part and the inner surface of the press die. PJhC ίη / ΖΖΠΖ / Ε / ΥΙΛΙ Advantageous effects

[13] In the manufacturing method described herein, a hollow housing part is obtained by pressing a bent tube having a curved portion to reduce the radius of curvature of the curved portion while cross-sectioning the curved portion. This makes it possible to eliminate unsatisfactory shaping of the curved portion compared to obtaining a hollow housing part having a curved portion by pressing a straight tube in a single step. Brief description of the drawings

[14] Figure 1 is a schematic diagram to describe an example of the longitudinal shape of a bent tube 10. Figure 2 is a schematic diagram to describe an example of the longitudinal shape of a hollow housing piece 100. Figures 3A to 3F are schematic diagrams to describe examples of the cross-sectional shape of the bent tube 10 and the cross-sectional shape of the hollow shell piece 100. Figure 3A schematically illustrates the cross-sectional shape taken along arrow IIIA-IIIA of Figure 1; Figure 3B schematically illustrates the cross-sectional shape taken along arrow IIIB-IIIB of Figure 1; Figure 3C schematically illustrates the cross-sectional shape taken along arrow IIIC-IIIC of Figure 1; Figure 3D schematically illustrates the cross-sectional shape taken along arrow IIID-IIID of Figure 2; Figure 3E schematically illustrates the cross-sectional shape taken along arrow IIIE-IIIE of Figure 2; and Figure 3F schematically illustrates the shape of the cross section taken along arrow IIIF-IIIF of Figure 2. Figures 4A to 4C are schematic diagrams to describe an example of a process for pressing the bent tube 10 to obtain the hollow shell piece 100. The shape of the cross-section along the longitudinal direction of the tube is illustrated. Figure 4A shows the state before the bent tube 10 abuts the dies 20, 30; Figure 4B shows the state immediately after the bent tube 10 abuts the dies 20, 30; and Figure 4C shows the state after pressing is complete. Figures 5A to 5F are schematic diagrams to describe an example of a process for pressing the bent tube 10 to obtain the hollow shell piece 100. Figure 5A illustrates the cross-sectional shape taken along arrow VA-VA of Figure 4B; Figure 5B illustrates the cross-sectional shape taken along arrow VB-VB of Figure 4B; Figure 5C illustrates the cross-sectional shape taken along arrow VC-VC of Figure 4B; Figure 5D illustrates the cross-sectional shape taken along arrow VD-VD of Figure 4C; Figure 5E illustrates the cross-sectional shape taken along arrow VE-VE of Figure 4C; and Figure 5F illustrates the cross-sectional shape taken along arrow VF-VF of Figure 4C. Figures 6A to 6F are schematic diagrams to describe an example of a flow shape in the circumferential direction of a tube with respect to the press dies during pressing. Figure 7 is a schematic diagram to describe an example of the shapes of press dies with an inclination. Figures 8A and 8B are schematic diagrams to describe an example of the original tube shape 1. Figure 8A illustrates the longitudinal shape, and Figure 8B illustrates the cross-sectional shape taken along arrow VIIIB-VIIIB of Figure 8A. Figure 9 is a diagram illustrating an example of a manufacturing method flow for a hollow shell part. Figure 10 is a diagram illustrating the FEA result to describe the pressing conditions according to the Comparative Example. Figure 11 is a diagram illustrating the FEA result to illustrate an example of a hollow housing part according to the Comparative Example. Figure 12 is a diagram illustrating the FEA result to describe the pressing conditions according to the Example. P JhC Ln / Zznz / E / YIAI Description of the modalities

[15] As illustrated in Figures 1 to 7, the manufacturing method for a hollow shell part 100 includes applying pressure to a bent tube 10 having a curved portion 10a from the outside of the tube to the inside of the tube using a press die 20, 30, thereby simultaneously performing cross-sectioning of the curved portion 10a and bending of the curved portion 10a to reduce the radius of curvature of the curved portion 10a. O JhC Ln / Zznz / E / YIAI

[16] 1. Bent tube 1.1 Longitudinal shape of the bent tube As illustrated in Figure 1, the bent tube 10 has at least a partially curved portion 10a. The curved portion refers to a portion bent along the longitudinal axis of the tube. In this application, the bent tube may have a shape that satisfies, for example, the relationship R = 250D, where R is the radius of curvature and D is the diameter of the tube at the curved portion. The bent tube 10 may be curved in two or three dimensions at the curved portion 10a. Although Figure 1 illustrates a configuration in which the bent tube 10 is curved in the up-to-down direction at the curved portion 10a, the bent tube 10 may be further curved in the off-the-page (depth) direction at the curved portion 10a. The shape of the bend at the curved portion 10a is not particularly restricted. For example, the bent tube 10 may be arced at the curved portion 10a.It should be noted that it is preferable for the bent tube 10 to have substantially no discontinuous surfaces, such as wrinkles or buckling, in the curved portion 10a.

[17] The radius of curvature Rio (inner radius of curvature) in the curved portion 10a is not particularly limited, provided that the radius of curvature Rio is greater than the radius of curvature Rioo described later. The radius of curvature Rio can be adequately determined by taking into account the material, thickness, and diameter of the opening (equivalent circle diameter) of the bent tube 10, as well as the radius of curvature Rioo described later. It should be noted that the bent shape (ridge) in the longitudinal direction in the curved portion 10a may be formed by a single arc or by a plurality of combined arcs. The curvature may also vary continuously or discontinuously in the curved portion 10a from one end in the longitudinal direction to the other end.

[18] Although Figure 1 illustrates a mode in which the bent tube 10 has only one curved portion 10a, the bent tube 10 can have a plurality of curved portions 10a with the same or different radius of curvature Rio. When the pressing described below is performed on each of the plurality of curved portions 10a, the pressing can be performed simultaneously with a single die, or the pressing can be performed separately with a plurality of dies.

[19] The bent tube 10 may have a straight tube portion distinct from the curved portion 10a. The straight tube portion refers to a straight section that is substantially free of bends in the longitudinal shape of the tube. ÓJhC ίη / ΖΖΠΖ / Ε / ΥΙΛΙ Alternatively, the bent tube 10 can be configured by just one or more curved portions 10a.

[20] The bent tube 10 need not be entirely tubular. For example, the bent tube 10 may have a notch, a groove, a through-hole, intentional irregularities, and / or the like in a portion, depending on its application. These notches, grooves, through-holes, irregularities, and / or the like provided in the bent tube 10 may remain in the hollow housing piece 100. On the other hand, the cross-sectional shape of the curved portion 10a may be continuously annular to further increase the accuracy of the shape during pressing of the curved portion 10a.

[21] The length of the bent tube 10 is not particularly limited and can be appropriately determined according to its application. However, when the length of the bent tube 10 is extremely short, it can be difficult to carry out the further bending process described below. In the bent tube 10, the length LIO from one end in the longitudinal direction of the tube to the other end (the length of the line continuously connecting the centers of the opening (the centers of the Figures)) can be greater than the opening diameter (the equivalent diameter of the circle) Dio.

[22] 1.2 Shape of the cross-section of the bent tube The shape of the cross-section (opening shape) of the bent tube 10 is not particularly restricted. Figures 3A, 3B, and 3C illustrate that the cross-sectional shape of the bent tube 10 is circular, but the cross-sectional shape can take on various forms, such as a circular shape, an elliptical shape, a flattened circular shape, a polygonal shape, a rounded polygonal shape, and a combination of these shapes. The cross-sectional shape of the bent tube 10 can be appropriately determined by considering its insertion into the press die 20, 30, or similar device.

[23] The cross-sectional shape of the bent tube may be the same without change from one end to the other along the tube's length, or it may change continuously or discontinuously along the tube's length. It should be noted that when the bent tube 10 has a straight tube portion as well as a curved portion 10a, the curved portion 10a and the straight tube portion may have the same cross-sectional shapes or they may have different cross-sectional shapes. Furthermore, when the bent tube 10 has a plurality of curved portions 10a, the curved portions 10a may have the same cross-sectional shapes or they may have different cross-sectional shapes.

[24] The thickness (wall thickness) of the bent tube 10 is not particularly limited and can be appropriately determined according to its application. The thickness of the bent tube 10 may differ from one portion to another.

[25] 1.3 Material of the bent tube The material of the bent tube 10 can be appropriately determined according to its application, provided the material can be pressed. For example, the bent tube 10 can be made of metal, such as steel, iron, aluminum, titanium, and magnesium. The manufacturing method described herein can also be applied to a high-strength steel tube made of high-strength steel having a tensile strength of 440 MPa or more, 590 MPa or more, or 780 MPa or more, measured at room temperature in accordance with JIS Z 2241:2011, and to a high-strength steel tube made of ultra-high-strength steel with a tensile strength of 980 MPa or more. Q JhC ίη / ΖΖΠΖ / Ε / ΥΙΛΙ

[26] 1.4. Method of obtaining bent tube. The method for obtaining a bent tube 10 is not particularly limited. For example, a bent tube 10 having a curved portion 10a can be obtained by bending at least one original tube (a starting material tube) 1 as illustrated in Figures 8A and 8B. Furthermore, a bent tube 10 having a curved portion 10a can be obtained by bending and cross-sectionally cutting an original tube 1.

[27] When a bent tube 10 is obtained from an original tube 1, the shape of the original tube 1 is not particularly restricted. For example, as illustrated in Figure 8A, the original tube 1 can be a straight tube. Alternatively, the original tube 1 can have a curved portion with a radius of curvature greater than the curved portion 10a of the bent tube 10. Alternatively, the original tube 1 can have both a curved portion and a straight portion. The shape of the cross-section of the original tube 1 is not particularly restricted, and in addition to the circular shape illustrated in Figure 8B, the cross-section can take various forms, such as an elliptical shape, a flattened circular shape, a polygonal shape, a rounded polygonal shape, and a combination of these shapes.The shape of the cross-section of the original tube 1 may have the same shape without changing from one end in the longitudinal direction of the tube to the other end, or it may change continuously or discontinuously from one end in the longitudinal direction of the tube to the other end.

[28] The method of bending the original tube 1 is not particularly limited. For example, the bent tube 10 can be obtained by crimping the original tube 1 from the outside. ÓJhC Ln / Zznz / E / YIAI of the tube. In other words, the bending performed on the original tube 1 may include applying pressure from the outside of the tube to the inside of the tube using a press die to obtain the bent tube 10. In addition, the cross-sectioning may be performed using a press die on the original tube 1. In other words, the bending and cross-sectioning performed on the original tube 1 may include applying pressure from the outside of the tube to the inside of the tube using a press die to obtain the bent tube 10. In either case, a press die (first die) for obtaining the bent tube 10 from the original tube 1 and a press die 20, 30 (second die) for obtaining the hollow shell piece 100 from the bent tube 10 described below may be used separately.Specifically, the first die can have a pressure surface with a larger radius of curvature to form a curved portion than the second die. In this way, simply by replacing the die, the pressing to transform the original tube 1 into the bent tube 10 and the pressing to transform the bent tube 10 into the hollow shell piece 100 can also be performed using the same press. In other words, the manufacturing equipment for the bent tube 10 and the manufacturing equipment for the hollow shell piece 100 can be shared to improve productivity.

[29] In addition, bending and cross-sectioning P JhC ίη / ZZΖΠZ / E / YΙΛΙ can be performed simultaneously on the original tube 1 by applying pressure from the outside of the tube to the inside of the tube using a press die to obtain the bent tube 10. This further improves the accuracy of the shape of the bent tube 10.

[30] In the case of obtaining the bent tube 10 by bending at least the original tube 1, the minimum bending radius (Riomin) at which no buckling or wrinkling occurs can be confirmed in advance by experiments or FEM analysis before actually bending the original tube 1. In other words, when bending the original tube 1, the occurrence of buckling and wrinkling in the bent tube 10 can be further suppressed by bending the original tube 1 so that the bending radius Rio becomes the minimum bending radius Riomin or greater, which has been confirmed in advance.

[31] It should be noted that the method for obtaining a bent tube 10 is not limited to the method of pressing from the outside of the tube using the press die described above. For example, a bent tube 10 can be obtained by performing a conventionally known bending process, such as rotary draw bending (tube bender), tube draw bending, tube compression bending, intrusion bending, and tube rolling bending. However, as described above, from the point of view of standardizing manufacturing equipment and improving the C JhC ίη / ZZΖΠZ / E / YΙΛΙ productivity, it is preferable to obtain the bent tube 10 from the original tube 1 by the method of pressing from the outside of the tube using a press die. PJhC Ln / Zznz / E / YIAI

[32] 2. Press matrix The press die can be any die, provided it is capable of simultaneously performing the cross-sectioning of the curved portion 10a and the bending of the curved portion 10a to reduce the radius of curvature. The material of the press die is not particularly limited, and a general-purpose die material can be used. The press die can be configured by a plurality of dies, in which case, by moving the plurality of dies relative to each other, pressure can be applied from the outside of the bent tube 10 to the inside of the tube. For example, as illustrated in Figure 4A, the press die can have an upper die 20 and a lower die 30. In this case, the upper die 20 and the lower die 30 can have press surfaces 20a and 30a, respectively.As illustrated in Figures 4B and 4C, cross-sectioning and bending can be performed simultaneously by pressing the bent tube 10 from above and below using the upper die 20 and the lower die 30 and pressing the pressing surfaces 20a, 30a against the curved portion 10a of the bent tube 10.

[33] The shape of the press die corresponds to the shape of the hollow shell piece 100. As illustrated in Figures 4A to 4C and 5A to 5F, for example, when the press die includes an upper die 20 and a lower die 30, the upper die 20 may have a bottom 21 opposite the upper end lia of the bent tube 10 and a side wall 22 opposite the side 12 of the bent tube 10; the lower die 30 may have a bottom 31 opposite the lower end 11b of the bent tube 10 and a side wall 32 opposite the side 12 of the bent tube 10; and as illustrated in Figures 5D to 5F and 6F, with the upper matrix 20 and the lower matrix 30 closed, the entire circumference (perimeter) of the hollow housing portion 100 can be enclosed by the bottoms 21, 31 and the side walls 22, 32.

[34] In the manufacturing method described herein, after the cross-sectioning and bending of the bent tube 10 is completed, in a cross-section orthogonal to the longitudinal direction of the hollow shell part 100, an inner surface of the press die may be inclined with respect to an outer surface of the hollow shell part 100, thereby creating a gap between the outer surface of the hollow shell part 100 and the inner surface of the press die. For example, in a cross-section orthogonal to the longitudinal direction of the hollow shell part 100, a portion of the inner wall of the press die may have a portion that is convex outward relative to the outer wall of the hollow shell part 100.Consider a case where the entire circumference of the hollow housing piece 100 is enclosed by the inner wall of the press die 40 upon completion of cross-sectioning and bending by the press die 40 as illustrated in Figure 7.In this case, as illustrated in Figure 7, in a cross-section orthogonal to the longitudinal direction of the hollow shell piece 100, the hollow shell piece 100 may have: a corner portion lOOx of a small radius of curvature; and a side lOOy and a bottom lOOz of large radii of curvature, and the inner wall of the press die 40 may have: a portion 40a that is convex outwards with respect to the outer wall of the side lOOy of the hollow shell piece 100; a portion 40b that is convex outwards with respect to the outer wall of the bottom lOOz of the hollow shell piece 100; and a portion 40c that is convex outwards with respect to the outer wall of the corner portion lOOx of the hollow shell piece 100.In portions 40a to 40c illustrated in Figure 7, in a cross-section orthogonal to the longitudinal direction of the hollow housing piece 100, the inner surface of the press die is inclined with respect to the outer surface of the hollow housing piece 100, thus creating a gap between the outer surface of the hollow housing piece 100 and the inner surface of the press die. In this way, the surface of the hollow housing piece 100 can be prevented from sinking inward by inclining the inner surface of the press die with respect to the outer surface of the hollow housing piece 100 to create a gap between the outer surface of the hollow housing piece 100 and the inner surface of the press die, in a cross-section orthogonal to the longitudinal direction of the hollow housing piece 100.

[35] In the manufacturing method described herein, as described below, a hollow shell piece 100 having a curved portion 100a is obtained by pressing with a press die to make a bend that reduces the radius of curvature Rio of a curved portion 10a of a bent tube 10. The radius of curvature Rm of the pressing surface of the press die (see Figure 4A) may be less than the radius of curvature Rioo of the curved portion 100a of the hollow shell piece 100.

[36] When the bent tube 10 has a curved portion 10a that is convex downwards as illustrated in Figures 4B and 5A to 5C, at least two locations of one and the other longitudinal ends of the curved portion 10a of the bent tube 10 may rest against the lower die 30 and at least one other location of one and the other longitudinal ends of the curved portion 10a of the bent tube 10 may abut against the upper die 20, immediately after the curved portion 10a abuts against the upper die 20 and the lower die 30. In this way, at least three locations of the bent tube 10 abut against the press die immediately after the press die abuts the bent tube 10, thereby suppressing misalignment of the bent tube 10 with respect to the press die during pressing.

[37] It should be noted that Figures 4A to 4C illustrate a pressing mode in which the curved portion 10a of the bent tube 10 and the curved portion 100a of the hollow housing piece 100 are convex downwards, but the pressing can be performed so that the curved portion 10a of the bent tube 10 and the curved portion 100a of the hollow housing piece 100 are convex upwards. However, the workability of the pressing is considered superior when the tube is convex downwards because the bent tube 10 can be easily positioned and placed in the lower die 30. Furthermore, the pressing direction of the press die is not limited to the up-down direction as illustrated in Figures 4A to 4C and can be, for example, a horizontal direction. However, when considering workability, productivity, and the like, the pressing direction of the press die can be set as the up-down direction.A press machine known as a press machine can be used in which... PJhC Ln / Zznz / E / YIAI installs the press matrix.

[38] 3. Cross-section In the manufacturing method described herein, a cross-section is performed that changes the cross-sectional shape of the curved portion 10a of the bent tube 10 by applying pressure from the outside of the tube to the inside of the tube using the press die 20, 30. In other words, by pressing the pressure surface 20a, 30a of the pressure die 20, 30 against the curved portion 10a from the outside, the curved portion 10a creates a flow of material in the circumferential (peripheral) direction of the tube within the curved portion 10a, thus changing the cross-sectional shape of the curved portion 10a. For example, as illustrated in Figures 5A to 5F, the cross-sectional shape of the curved portion 10a can be transformed from a first shape (e.g., a circular shape) to a second shape (e.g., an elliptical shape, a polygonal shape, a rounded polygonal shape, or a combination of these shapes) by cross-section.

[39] Pressure is applied from the outside of the tube to the inside of the tube during cross-sectioning. In other words, in the manufacturing method described herein, pressure is not applied from the inside of the tube to the outside of the tube, as in hydroforming, and the cross-sectional shape of the curved portion 10a of the bent tube 10 is transformed solely by pressing from the outside of the tube. It should be noted that a core die or similar device may be installed inside the tube, for example, at the ends of the tube or similar device for cross-sectioning. This may further prevent dents, crushing, and / or similar defects at the ends of the tubes and / or similar devices.

[40] In the manufacturing method described herein, after the cross-sectioning is completed, a space may or may not be created between the outer wall of the hollow housing piece 100 and the press die in a cross-section orthogonal to the longitudinal direction of the hollow housing piece 100.

[41] It should be noted that, in the manufacturing method described herein, cross-sectioning a portion other than the part that is bent to become the curved portion 100a is optional. When a hollow shell piece 100 is obtained having a straight tube portion as well as the curved portion 100a, cross-sectioning may or may not be performed on the straight tube portion. When cross-sectioning is performed on the straight tube portion, a different cross-section can be made between the curved portion 10a and the straight tube portion. Furthermore, when the bent tube 10 has a plurality CJhC ίη / ZZΖΠZΖ / E / YΙΛΙ of curved portions 10a, the same cross-sectioning or a different cross-sectioning can be performed between one curved portion 10a and the other curved portion 10a. PJhC ίη / ΖΖΠΖ / Ε / ΥΙΛΙ

[42] 4. Folded In the manufacturing method described herein, pressing involves bending that reduces the radius of curvature Rio of the curved portion 10a of the bent tube 10. In other words, pressing the press surfaces 20a, 30a of the press dies 20, 30 against the curved portion 10a from the outside of the tube creates a flow of material in the longitudinal direction of the tube in the curved portion 10a and reduces the radius of curvature Rio of the curved portion 10a. For example, as illustrated in Figures 1 and 2, bending transforms the curved portion 10a of a radius of curvature Rio into the curved portion 100a of a radius of curvature Rioo.

[43] Pressure is applied from the outside of the tube to the inside of the tube during bending. In other words, in the manufacturing method described herein, pressure is not applied from the inside of the tube to the outside of the tube, as by hydroforming, and the radius of curvature of the curved portion 10a of the bent tube 10 is reduced only by pressing from the outside of the tube.

[44] In the manufacturing method described herein, once the bending is completed, a space may or may not be created between the outer wall of the hollow housing part 100 and the press die in a longitudinal direction of the hollow housing part 100.

[45] It should be noted that, in the manufacturing method described herein, bending a portion other than the curved portion 10a is optional. For example, when the bent tube 10 has a straight tube portion, a gentle bend may be applied to the straight tube portion to the extent that no creasing or buckling occurs.

[46] In the manufacturing method described herein, the bending described above is performed simultaneously with the cross-sectioning described above. In other words, during pressing, the material flow in the circumferential (peripheral) direction of the tube and the material flow in the longitudinal direction of the tube proceed simultaneously in the curved portion 10a of the bent tube 10, thus ensuring high form accuracy of the hollow housing piece 100. The cross-sectioning and bending of the tube using the press die are performed, for example, according to a flow as illustrated in Figures 6A to 6F. The mode illustrated in Figures 6A to 6F corresponds to the mode illustrated in Figures 5A and 5D and illustrates a case of transforming the cross-section of a circular tube into a section PJhC Ln / Zznz / E / YIAI rounded rectangular cross-section. As illustrated in Figures 6A to 6F, the tube can be brought into contact with at least one of the upper die 20 and the lower die 30 (Figure 6A), the upper die 20 and the lower die 30 can be brought close together and a portion of the tube is inserted into the upper die 20 and the lower die 30 while flowing, forming continues without biting the tube in the space between the upper die 20 and the lower die 30 (Figures 6B to 6E), and cross-sectioning and bending of the tube can be completed by closing the upper die 20 and the lower die 30 (Figure 6F).It should be noted that, in the manufacturing method described herein, provided that cross-sectioning and bending can be performed simultaneously at a given time, the start and end times of cross-sectioning and the start and end times of bending do not have to be strictly simultaneous.

[47] When the hollow housing part 100 is obtained by pressing the bent tube 10, the minimum Rioomin radius of curvature where no buckling or wrinkling occurs can be confirmed by experiments, FEM analysis, or similar methods before actually pressing the bent tube 10. In other words, when pressing the bent tube 10, the occurrence of buckling and wrinkling in the hollow housing part 100 can be further suppressed by bending the bent tube 10 so that the radius of curvature Rioo becomes the minimum radius of curvature Rioomír. or more that has been confirmed in advance.

[48] ​​5. Part of the hollow casing 5.1 Longitudinal shape of the hollow housing piece As illustrated in Figure 2, the hollow shell piece 100 has at least a partially curved portion 100a. As described above, the hollow shell piece 100 can be referred to as a press-formed tube because the tube has been formed by pressing. The longitudinal direction of the hollow shell piece 100 can correspond to the longitudinal direction of the tube before pressing. The hollow shell piece 100 can be curved in two or three dimensions at the curved portion 100a. For example, Figure 2 illustrates that the hollow shell piece 100 is curved in the top-down direction of the paper at the curved portion 100a, but it can curve further away from the paper at the curved portion 100a. The bent shape at the curved portion 100a is not particularly restricted. For example, the hollow shell piece 100 can be arched at the curved portion 100a.The bent shape of the hollow housing piece 100 can be easily changed by changing the shapes of the press surfaces of the press die 20, 30 described above.

[49] The Rioo radius of curvature (inner radius of curvature) in the curved portion 100a is not particularly limited as long as the Rico radius of curvature is less than the Rio radius of curvature described above. It should be noted that the folded shape (ridge) in the longitudinal direction of the curved portion 100a may be formed by a single arc or by a plurality of combined arcs. The curvature may also vary continuously or discontinuously in the curved portion 100a from one end in the longitudinal direction to the other.

[50] Although Figure 2 illustrates a mode in which the hollow shell piece 100 has only one curved portion 100a, the hollow shell piece 100 can have a plurality of curved portions 100a with equal or different Rioo curvature radii.

[51] The hollow housing piece 100 may have a straight tube portion other than the curved portion 100a. Alternatively, the hollow housing piece 100 may be configured from only one or more curved portions 100a.

[52] Hollow housing piece 100 need not be completely tubular throughout. For example, hollow housing piece 100 may have a notch or a groove in one part. Hollow housing piece 100 may also have a through-hole or intentional irregularities in one part.

[53] The length of the hollow housing piece 100 is not The length of the hollow shell piece 100 is particularly limited and can be appropriately determined according to its application. The length of the hollow shell piece 100 can be equal to or different from the length of the bent tube 10. For example, the length of the hollow shell piece 100 can be shorter than the length of the bent tube 10 by a process of enlarging the diameter of the opening (equivalent circle diameter) relative to the diameter of the opening of the bent tube 10, or by other processes, in addition to the bending and cross-sectioning described herein. Alternatively, the length of the hollow shell piece 100 can be longer than the length of the bent tube 10 by a process of thinning the tube thickness relative to the bent tube 10, reducing the tube diameter, or by other processes. ÓJhC ίη / ΖΖΠΖ / Ε / ΥΙΛΙ

[54] 5.2. Shape of the cross-section of the hollow housing part The cross-sectional shape (opening shape) of the hollow housing piece 100 is not particularly limited. Figures 3D, 3E, and 3F illustrate the cross-sectional shape of the hollow housing piece 100 as either polygonal or elliptical, but the cross-sectional shape can take on various forms, such as polygonal, elliptical, circular, flattened circular, rounded polygonal, and combinations thereof. The cross-sectional shape of the hollow housing piece 100 can be appropriately determined according to its application. The cross-sectional shape of the hollow housing piece 100 can be easily changed by altering the shape of the pressing surfaces of the press die 20, 30 described above.

[55] The cross-sectional shape of the hollow shell piece 100 may be the same without change from one end in the longitudinal direction of the tube to the other end, or it may change continuously or discontinuously from one end in the longitudinal direction of the tube to the other end, as illustrated in Figures 3D to 3F. When the hollow shell piece 100 has a straight tube portion, as well as the curved portion 100a, the curved portion 100a and the straight tube portion may have the same cross-sectional shapes or they may have different cross-sectional shapes. Furthermore, when the hollow shell piece 100 has a plurality of curved portions 100a, the curved portions 100a may have the same cross-sectional shapes or they may have different cross-sectional shapes.

[56] The thickness (wall thickness) of the hollow housing piece 100 is not particularly limited and can be appropriately determined according to its application. The thickness of the hollow housing portion 100 can vary from portion to portion.

[57] As described above, in the method of manufacturing the hollow housing part 100 of the present description, a bent tube 10 having a curved portion 10a is pressed to reduce the radius of curvature of the curved portion 10a while forming a cross-section in the curved portion 10a. This makes it possible to eliminate the unsatisfactory forming in the curved portion 100a that occurs when a hollow housing part 100 having a curved portion 100a is obtained by pressing a straight tube in a single step.

[58] It should be noted that the manufacturing method described herein can also be applied, for example, to the manufacture of a tapered tube. In other words, a tapered tube can be obtained as part 100 of a hollow shell by cross-sectioning according to the manufacturing method described herein, or a tapered tube can be used as a bent tube 10 to obtain part 100 of the hollow shell. PJhC Ln / Zznz / E / YIAI

[59] 5.3 Application examples of the hollow housing part The application of the hollow housing part 100 obtained by the manufacturing method described herein is diverse. For example, it can be used in automotive parts such as a bumper beam, a suspension member, a side rail, a trailing arm, an upper arm, a post, a torsion beam, a door impact beam, and an instrument panel beam. Q JhC Ln / Zznz / E / YIAI

[60] 6. Summary As described above, the method herein is for manufacturing a hollow casing piece 100 having a curved portion 100a with a small radius of curvature using a press die and simultaneously performing bending and cross-sectioning on a pre-bent tube 10 to change the cross-sectional shape of the curved portion 10a of the pre-bent tube 10 while reducing the radius of curvature of the curved portion 10a. As described above, the method herein may also include a process of preparing the pre-bent tube 10 in advance as a separate process from the bending and cross-sectioning using the press die above.For example, as illustrated in Figure 9, a bent tube 10 having a curved portion 10a can be obtained by bending (pre-bending) an original tube 1 (as described above, the original tube 1 can be a straight tube). The resulting bent tube 10 can then be placed into the press die from outside the die, and the bending and cross-sectioning described above can be performed simultaneously to reduce the radius of curvature of the curved portion 10a while changing the cross-sectional shape of the curved portion 10a of the bent tube 10 (main forming), thus obtaining a hollow shell piece 100 having a predetermined curved portion 100a.As in the method described herein, by simultaneously performing bending and cross-sectioning using a press die on a previously bent tube 10, a hollow housing piece 100 can be formed having a curved portion 100a of a small radius of curvature manufactured while suppressing wrinkles and buckling. P JhC ίη / ΖΖΠΖ / Ε / ΥΙΛΙ Examples

[61] From here on, the effects of the manufacturing method of the hollow housing part of the present description are described in more detail with examples.

[62] 1. Comparative example As illustrated in Figure 10, a hollow shell piece was obtained by main forming in a process by simultaneously performing cross-sectioning and bending using a press die on a straight tube (980 MPa class steel tube, φ38.1 mm, thickness 1.0 mm, length 600 mm) to change the shape of the cross-section of the straight tube while bending it at a predetermined bend radius.

[63] As a result of the experiment, with respect to the straight tube described above, cross-sectioning and bending using a press die were possible without generating wrinkles or buckling up to a bending radius of approximately 700 mm. However, when the bending radius fell below 700 mm, buckling deformation was observed on the surface of the hollow casing piece. For example, as is clear from the FEM analysis results illustrated in Figure 11, when the bending radius is set to 570 mm, buckling deformation occurs in the longitudinal center portion (the center portion of the bend) of the hollow casing piece. ÓJhC ίη / ΖΖΠΖ / Ε / ΥΙΛΙ

[64] 2. Example As illustrated in Figure 12, after obtaining a bent tube with a bend radius of 700 mm per bend (pre-bending) using a press die on a straight tube similar to the Comparative Example, the main forming process is carried out. This involves cross-sectioning and bending simultaneously on the bent tube using a press die to reduce the bend radius of the curved portion to 570 mm. No wrinkling or buckling was observed in the curved portion of the resulting hollow casing piece.

[65] Based on the above results, it can be said that even when using the same straight tube as the original, wrinkles and buckling in the final hollow housing piece can be suppressed by pre-bending and pressing, rather than pressing in a single step. It should be noted that, although pre-bending is performed by pressing in the manner described above, even when pre-bending is performed by a method other than pressing (hydroforming or similar), a hollow housing piece with high form accuracy can be obtained while suppressing wrinkles and buckling of the curved portion by subsequent pressing similar to the method described above. CJhC ίη / ΖΖΠΖ / Ε / ΥΙΛΙ

[66] 3. Supplementary Notes It should be noted that, as in the comparative example, when a hollow casing piece with a small radius of curvature is obtained in a single step by pressing a straight tube only once, the reason for unsatisfactory forming, such as wrinkling and buckling in the curved portion of the hollow casing piece, can be considered as follows. That is, it is considered that even when simultaneous bending and cross-sectioning are performed on a straight tube using a press die, the radius of curvature of the press die's pressing surface is too small for the material to flow smoothly in the circumferential (peripheral) direction of the tube, and the material is dented inwards, resulting in buckling deformation in the longitudinal central portion of the tube (because bending occurs only before cross-sectioning).

[67] Conversely, as illustrated in the Example, by simultaneously bending and cross-sectioning a pre-bent tube instead of a straight tube, a hollow casing piece can be manufactured that has a curved portion with a small radius of curvature while suppressing the wrinkling and buckling described above. In other words, when wrinkling and buckling are expected to occur due to bending at a small radius of curvature, performing the cross-sectioning simultaneously with the bending allows the tube material to flow properly not only in the longitudinal direction of the tube but also in the circumferential (peripheral) direction of the tube, which can prevent wrinkling and buckling.

[68] It should be noted that the method described herein may also be considered, for example, as dividing a bending process into obtaining a bent tube from an original tube and bending and cross-sectioning the bent tube. In general, it was believed that dividing the process of Side wall djhc Ln / zznz / E / YiAi Lower die (press die) Bottom Side wall 100 Hollow Housing Pieces 100a Curved portion

Claims

1. A manufacturing method for a hollow housing part, the method comprising applying pressure to a bent tube having a curved portion from the outside of the tube to the inside of the tube using a press die, thereby simultaneously performing cross-sectioning of the curved portion and bending of the curved portion to reduce the radius of curvature of the curved portion.

2. The manufacturing method according to claim 1, wherein the press die has an upper die and a lower die, the upper die and the lower die respectively having pressing surfaces, and the cross-sectioning and bending are performed simultaneously by pressing the bent tube with the upper die and the lower die from above and below and pressing the pressing surfaces against the curved portion of the bent tube; 3. The manufacturing method according to claim 1 or 2, comprising obtaining the bent tube having the curved portion by bending at least one original tube.

4. The manufacturing method according to claim 1 or 2, comprising obtaining the bent tube having the curved portion at least by bending and cross-sectioning an original tube, 5. The manufacturing method according to claim 3, wherein the bending performed on the original tube comprises applying pressure from the outside of the tube to the inside of the tube using a press die to obtain the bent tube.

6. The manufacturing method according to claim 4, wherein the bending and cross-sectioning performed on the original tube comprises applying pressure from the outside of the tube to the inside of the tube using a press die to obtain the bent tube.

7. The manufacturing method in accordance with any of claims 3 to 6, wherein the original tube is a straight tube.

8. The manufacturing method according to any of claims 1 to 7, wherein upon completion of the cross-sectioning and bending, in a cross-section orthogonal to the longitudinal direction of the hollow housing piece, an inner surface of the press die is inclined with respect to an outer surface of the hollow housing piece, thereby creating a space between the outer surface of the hollow housing piece and the inner surface of the press die.

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