Method for manufacturing a hollow part

Abstract

Disclosed is a manufacturing method capable of suppressing occurrence of wrinkles and buckling deformation due to bending in the case where bending processing and cross-sectional processing are performed on a pipe using a press die. The manufacturing method of the present invention includes: applying pressure from the outside of a curved pipe having a curved portion toward the inside of the pipe using a press die, thereby simultaneously performing cross-sectional processing of the curved portion and bending processing for reducing the bending radius of the curved portion.

Description

Technical Field

[0001] This application discloses a method for manufacturing hollow components. Background Technology

[0002] Patent Document 1 discloses a technique for bending or cross-sectionalizing straight tubes using a stamping die (a process that changes the shape of a cross-section intersecting the tube's length direction). In the technique disclosed in Patent Document 1, by simultaneously performing cross-sectional and bending processing on the straight tube, high shape accuracy is ensured in the resulting hollow component. According to the technique disclosed in Patent Document 1, complex processes such as hydroforming are unnecessary; hollow components can be obtained solely through stamping from the outside of the tube, thus improving the productivity of hollow component production.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent No. 6519984 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] According to the inventor's new understanding, when a hollow component with a curved section is obtained by simultaneously processing the cross-section and bending a straight tube as disclosed in Patent Document 1, especially when the bending radius of the curved section is small, poor forming conditions such as wrinkles or buckling are likely to occur on the surface of the curved section.

[0008] Methods used to solve problems

[0009] As one of the means to solve the above-mentioned problems, this application discloses a method for manufacturing a hollow component, comprising: applying pressure from the outside to the inside of a curved tube (bend) having a curved portion (bend) by using a stamping die, thereby simultaneously performing cross-sectional processing of the curved portion and bending processing to reduce the bending radius of the curved portion.

[0010] In the manufacturing method disclosed herein, the stamping die may have an upper metal die and a lower metal die, and the upper metal die and the lower metal die may each have a stamping surface. Alternatively, the upper metal die and the lower metal die may be used to stamp the curved tube from above and below, pressing the stamping surface relative to the curved portion of the curved tube, thereby simultaneously performing the cross-section processing and the bending processing.

[0011] The manufacturing method disclosed herein may also include: obtaining the curved pipe having the aforementioned curved portion by at least performing a bending process on the raw material pipe.

[0012] The manufacturing method disclosed herein may also include: obtaining the curved pipe having the above-mentioned curved portion by performing at least bending and cross-sectional processing on the raw material pipe.

[0013] In the manufacturing method disclosed herein, the bending process performed on the aforementioned raw material tube may also include: applying pressure from the outside of the tube toward the inside of the tube using a stamping die to obtain the aforementioned curved tube.

[0014] In the manufacturing method disclosed herein, the bending process and the cross-sectional processing performed on the aforementioned raw material tube may also include: applying pressure from the outside of the tube toward the inside of the tube using a stamping die to obtain the aforementioned curved tube.

[0015] In the manufacturing method disclosed herein, the aforementioned raw material pipe may also be a straight pipe.

[0016] In the manufacturing method disclosed herein, at the point when the above-mentioned cross-section processing and bending processing are completed, in a cross-section orthogonal to the length direction of the hollow component, the inner wall surface of the stamping die is inclined relative to the outer wall surface of the hollow component, and a gap is generated between the outer wall surface of the hollow component and the inner wall surface of the stamping die.

[0017] Invention Effects

[0018] In the manufacturing method disclosed herein, a curved tube with a curved portion is stamped, and a hollow component is obtained by simultaneously machining the cross-section of the curved portion and reducing its bending radius. Therefore, compared to obtaining a hollow component with a curved portion by stamping a straight tube in one process, defects in the forming of the curved portion can be suppressed. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating an example of the shape of the curved tube 10 along its length.

[0020] Figure 2 This is a schematic diagram illustrating an example of the shape of the hollow component 100 along its length.

[0021] Figure 3 This is a schematic diagram illustrating an example of the cross-sectional shape of the curved tube 10 and the cross-sectional shape of the hollow component 100. (A) Schematic representation Figure 1 Section IIIA-IIIA, (B) is roughly represented. Figure 1 Section IIIB-IIIB, (C) is roughly represented. Figure 1 The IIIC-IIIC view section, (D) is roughly represented. Figure 2 The IIID-IIID view section, (E) is schematically represented. Figure 2 The IIIE-IIIE view section, (F) is roughly represented. Figure 2The shape of the IIIF-IIIF direction view section.

[0022] Figure 4 This is a schematic diagram illustrating an example of the process of stamping a curved tube 10 to obtain a hollow component 100. The diagram shows the shape of the cross-section along the length of the tube. (A) shows the state before the curved tube 10 comes into contact with the metal molds 20 and 30; (B) shows the state immediately after the curved tube 10 comes into contact with the metal molds 20 and 30; and (C) shows the state after the stamping process is completed.

[0023] Figure 5 This is a schematic diagram illustrating an example of the process of stamping a curved tube 10 to obtain a hollow component 100. (A) indicates... Figure 4 The VA-VA direction view section in (B) represents, where (B) indicates... Figure 4 In section (B), the VB-VB direction view section is shown; (C) represents... Figure 4 The VC-VC direction view section in (B) represents, and (D) represents... Figure 4 The VD-VD direction view section in (C), and (E) represents... Figure 4 In the middle (C), the VE-VE direction view section is shown, and (F) represents... Figure 4 The shape of the VF-VF direction view section in (C).

[0024] Figure 6 This is a schematic diagram illustrating an example of the circumferential flow pattern of a tube relative to a stamping die during a stamping process.

[0025] Figure 7 This is a schematic diagram illustrating an example of the shape of a stamping die with an inclination.

[0026] Figure 8 This is a schematic diagram illustrating an example of the shape of the raw material pipe 1. (A) shows the shape along the length direction, and (B) shows... Figure 8 The shape of the view section in the direction of VIIIB-VIIIB in (A).

[0027] Figure 9 This is a diagram illustrating an example of a manufacturing process for a hollow component.

[0028] Figure 10 This is a graph showing the results of the FEA, used to illustrate the stamping conditions for the comparative examples.

[0029] Figure 11 This is a diagram showing the results of the FEA, illustrating an example of a hollow component in the comparative example.

[0030] Figure 12 This is a graph showing the results of the FEA, used to illustrate the stamping conditions of the relevant embodiments. Detailed Implementation

[0031] like Figures 1 to 7 As shown, the manufacturing method of the hollow component 100 includes: applying pressure from the outside to the inside of the curved tube 10 having the curved portion 10a by using stamping dies 20 and 30, thereby simultaneously performing cross-sectional processing of the curved portion 10a and bending processing to reduce the bending radius of the curved portion 10a.

[0032] 1. Bent tube

[0033] 1.1 Shape along the length of the curved tube

[0034] like Figure 1 As shown, the curved tube 10 has a curved portion 10a in at least a portion. A "curved portion" refers to a portion that bends in the shape along the length of the tube. In this application, the "curved tube" may, for example, have a shape that satisfies the relationship R ≤ 250D based on the curvature R of the curved portion and the tube diameter D. The curved tube 10 can be bent in the curved portion 10a either in two dimensions or in three dimensions. Figure 1 The diagram illustrates the shape of the curved tube 10 bending in the vertical direction of the curved portion 10a on the paper surface, but it is also possible for the curved portion 10a to be bent in the depth direction of the paper surface. The bending shape of the curved portion 10a is not particularly limited. For example, the curved tube 10 may also be bent in the curved portion 10a. In addition, it is preferable that the curved tube 10 does not have discontinuous surfaces such as substantial wrinkles or bends in the curved portion 10a.

[0035] The bending radius R of the curved part 10a 10 The (inner bending radius) is not specifically limited, as long as it is greater than the bending radius R described later. 100 Larger is fine. Bending radius R 10 Consider the material, wall thickness, and opening diameter (circular equivalent diameter) of the curved tube 10, as well as the bending radius R described later. 100 The appropriate decision is made accordingly. Furthermore, the curved shape (edge) along the length of the curved section 10a can be formed by a single arc or by a combination of multiple arcs. Additionally, the curvature of the curved section 10a can vary continuously or discontinuously from one end to the other along the length direction.

[0036] exist Figure 1 The diagram shows that the curved tube 10 has only one curved section 10a, but the curved tube 10 can also have a bending radius R. 10 Multiple curved sections 10a, which may be identical or different. When performing stamping processes on multiple curved sections 10a separately (described later), the stamping process can be performed simultaneously using a single metal die or separately using multiple metal dies.

[0037] The curved tube 10 may also have a straight section in addition to the curved section 10a. A "straight section" is a straight part that is substantially without curvature in the shape along the length of the tube. Alternatively, the curved tube 10 may consist of only one or more curved sections 10a.

[0038] The curved tube 10 does not need to be a completely tubular shape. For example, depending on the application, the curved tube 10 may have notches, slits, through holes, intentional irregularities, etc., in a portion. These notches, slits, through holes, irregularities, etc., provided on the curved tube 10 may also remain in the hollow component 100. On the other hand, from the viewpoint of further improving the shape accuracy during the stamping process of the curved portion 10a, the cross-sectional shape of the curved portion 10a may also be an uninterrupted annular shape.

[0039] The length of the curved tube 10 is not particularly limited and can be appropriately determined according to the application. However, if the length of the curved tube 10 is extremely short, it may be difficult to perform the further bending process described later. In the curved tube 10, the length can also be the length L from one end to the other along the length of the tube (the length of the line continuously connecting the centers of the openings (center of view, centroid)). 10 Compared to the opening diameter (equivalent diameter of a circle) D 10 long.

[0040] 1.2 Cross-sectional shape of the curved tube

[0041] The cross-sectional shape (opening shape) of the curved tube 10 is not specifically defined. Figure 3 In Figures (A), (B), and (C), it is indicated that the cross-sectional shape of the curved tube 10 is circular. However, in addition to a circle, it can have various shapes such as ellipse, flat circle, polygon, polygon containing a circle, and combinations of these shapes. The cross-sectional shape of the curved tube 10 can be appropriately determined by taking into account factors such as the insertion capability into the stamping dies 20 and 30.

[0042] The cross-sectional shape of the curved pipe 10 can be either a shape that remains unchanged from one end to the other along the pipe's length direction, or a shape that changes continuously or discontinuously from one end to the other along the pipe's length direction. Furthermore, when the curved pipe 10 has a curved section 10a and a straight section, the curved section 10a and the straight section can have the same cross-sectional shape or different cross-sectional shapes. Moreover, when the curved pipe 10 has multiple curved sections 10a, each curved section 10a can have the same cross-sectional shape or different cross-sectional shapes.

[0043] The thickness (wall thickness) of the curved tube 10 is not specifically limited and can be appropriately determined according to the application. The thickness of the curved tube 10 can also vary for each section.

[0044] 1.3 Material of the curved tube

[0045] The material of the curved tube 10 can be any material that can be stamped, and can be appropriately determined according to the application. For example, it can also be made of metals such as steel, iron, aluminum, titanium, and magnesium. The manufacturing method disclosed herein can be applied to high-strength steel tubes made of high-strength steel with a tensile strength of 440 MPa or more, 590 MPa or more, or 780 MPa or more as measured at room temperature according to JIS Z 2241:2011, or high-strength steel tubes made of ultra-high-strength steel with a tensile strength of 980 MPa or more.

[0046] 1.4 Methods for obtaining curved tubes

[0047] There are no particular limitations on the method used to obtain the curved tube 10. For example, it can also be obtained by... Figure 8 The starting material tube 1 shown in (A) and (B) is subjected to at least a bending process to obtain a curved tube 10 having a curved portion 10a. Alternatively, the curved tube 10 having a curved portion 10a can also be obtained by performing at least a bending process and a cross-sectional processing on the starting material tube 1.

[0048] When the curved tube 10 is obtained from the raw material tube 1, the shape of the raw material tube 1 is not particularly limited. For example, it can also be as follows: Figure 8 As shown in (A), the raw material pipe 1 is a straight pipe. Alternatively, the raw material pipe 1 may also have a curved section with a larger bending radius compared to the curved section 10a of the curved pipe 10. Alternatively, the raw material pipe 1 may have both a curved section and a straight section. The cross-sectional shape of the raw material pipe 1 is not particularly limited, except... Figure 8 Besides the circle shown in (B), there can be various shapes such as ellipse, flat circle, polygon, polygon containing circle, and combinations of these shapes. The cross-sectional shape of the raw material pipe 1 can be a shape that remains the same from one end to the other along the length of the pipe, or it can change continuously or discontinuously from one end to the other along the length of the pipe.

[0049] There is no particular limitation on the bending method of the raw material tube 1. For example, the curved tube 10 can also be obtained by stamping the raw material tube 1 from the outside. That is, the bending process performed on the raw material tube 1 can also include applying pressure from the outside to the inside of the tube using a stamping die to obtain the curved tube 10. In addition, the raw material tube 1 can also be cross-sectionally processed using a stamping die. That is, the bending process and cross-sectional processing performed on the raw material tube 1 can also be obtained by applying pressure from the outside to the inside of the tube using a stamping die to obtain the curved tube 10. In either case, it is sufficient to distinguish between the stamping die (first metal die) used to obtain the curved tube 10 from the raw material tube 1 and the stamping dies 20 and 30 (second metal dies) used to obtain the hollow component 100 from the curved tube 10, as described later. Specifically, the bending radius of the stamping surface used to form the curved portion is larger in the first metal die compared to the second metal die. In this way, by simply changing the metal mold, the same stamping machine can be used to perform stamping processes from the raw material tube 1 to the curved tube 10 and from the curved tube 10 to the hollow component 100. That is, the manufacturing equipment for the curved tube 10 and the manufacturing equipment for the hollow component 100 can be shared, thereby improving productivity.

[0050] Alternatively, pressure can be applied to the raw material tube 1 from the outside to the inside of the tube using a stamping die, while simultaneously performing bending and cross-section processing, thereby obtaining a curved tube 10. This further improves the shape accuracy when the curved tube 10 is manufactured.

[0051] When the raw material tube 1 is bent to obtain the curved tube 10, the minimum bending radius (R) that will not cause buckling or wrinkling can be determined in advance by experiments or FEM analysis before the actual bending of the raw material tube 1 is performed. 10min That is, when bending the raw material pipe 1, the bending process is carried out to achieve a pre-determined minimum bending radius R. 10min The above bending radius R 10 This can further suppress the occurrence of bending or wrinkling of the curved tube 10.

[0052] Furthermore, the method for obtaining the curved tube 10 is not limited to the stamping process using a stamping die from the outside of the tube described above. For example, the curved tube 10 can also be obtained by performing known bending processes such as rotary bending (tube bending machine), stretch bending, pressure bending, press bending, and roll bending. However, as mentioned above, from the viewpoint of improving productivity by sharing manufacturing equipment, it is preferable to obtain the curved tube 10 from the raw material tube 1 by the stamping process using a stamping die from the outside of the tube.

[0053] 2. Stamping dies

[0054] The stamping die only needs to be able to simultaneously perform the cross-sectional machining of the curved section 10a and the bending machining to reduce the bending radius of the curved section 10a. The material of the stamping die is not particularly limited; common materials can be used as metal dies. The stamping die can also be composed of multiple metal dies. In this case, by moving these multiple metal dies relative to each other, pressure can be applied from the outside of the curved tube 10 toward the inside. For example, as... Figure 4 As shown in (A), the stamping die can also have an upper metal die 20 and a lower metal die 30. In this case, the upper metal die 20 and the lower metal die 30 are assumed to have stamping surfaces 20a and 30a, respectively. Figure 4 (B) and Figure 4 As shown in (C), by pressing the curved tube 10 from the top and bottom with the upper metal mold 20 and the lower metal mold 30, the stamping surfaces 20a and 30a are pressed relative to the curved portion 10a of the curved tube 10, thereby enabling the simultaneous processing of the cross section and the bending process.

[0055] The shape of the stamping die corresponds to the shape of the hollow component 100. For example... Figure 4 (A) to (C) and Figure 5 As shown in (A) to (F), for example, when the stamping die is composed of an upper metal die 20 and a lower metal die 30, the upper metal die 20 may also have a bottom 21 opposite to the upper end 11a of the curved tube 10 and a side wall portion 22 opposite to the side portion 12 of the curved tube 10, and the lower metal die 30 may also have a bottom 31 opposite to the lower end 11b of the curved tube 10 and a side wall portion 32 opposite to the side portion 12 of the curved tube 10, as shown in (A) to (F). Figure 5 (D)~(F) and Figure 6 As shown in (F), the hollow component 100 can also be surrounded by the bottom 21, 31 and the side wall portions 22, 32 when the upper metal mold 20 and the lower metal mold 30 are closed.

[0056] According to the manufacturing method of this disclosure, at the point where the cross-sectional machining and bending of the curved tube 10 are completed, in a cross-section orthogonal to the longitudinal direction of the hollow component 100, the inner wall surface of the stamping die is inclined relative to the outer wall surface of the hollow component 100, creating a gap between the outer wall surface of the hollow component 100 and the inner wall surface of the stamping die. For example, in a cross-section orthogonal to the longitudinal direction of the hollow component 100, a portion of the inner wall of the stamping die may have a portion convex outward relative to the outer wall of the hollow component 100. Figure 7As shown, this considers the case where the cross-sectional machining and bending machining performed by the stamping die 40 are completed, and the hollow component 100 is completely surrounded by the inner wall of the stamping die 40. In this case, as illustrated, in a cross-section orthogonal to the length direction of the hollow component 100, the hollow component 100 may also have a corner portion 100x with a small radius of curvature, a side portion 100y with a large radius of curvature, and a bottom portion 100z. The inner wall of the stamping die 40 may also have a portion 40a that convexes outward relative to the outer wall of the side portion 100y of the hollow component 100, a portion 40b that convexes outward relative to the outer wall of the bottom portion 100z of the hollow component 100, and a portion 40c that convexes outward relative to the outer wall of the corner portion 100x of the hollow component 100. Figure 7 In portions 40a to 40c shown, in a cross-section orthogonal to the length direction of the hollow component 100, the inner wall surface of the stamping die is inclined relative to the outer wall surface of the hollow component 100, creating a gap between the outer wall surface of the hollow component 100 and the inner wall surface of the stamping die. Thus, by inclining the inner wall surface of the stamping die relative to the outer wall surface of the hollow component 100 in a cross-section orthogonal to the length direction of the hollow component 100, and creating a gap between the outer wall surface of the hollow component 100 and the inner wall surface of the stamping die, it is possible to suppress the inward concavity of the wall surface of the hollow component 100.

[0057] In the manufacturing method disclosed herein, as described later, the bending radius R of the curved portion 10a of the curved tube 10 is achieved by stamping using a stamping die. 10 The bending process is reduced in size, thereby obtaining a hollow part 100 with a curved portion 100a. Here, the bending radius R of the stamping surface of the stamping die is... M (Refer to Figure 4 The bending radius R of the curved portion 100a of the hollow component 100 can also be greater than that of the hollow component 100. 100 Small.

[0058] In such Figure 4 (B) and Figure 5 When the curved tube 10 has a downwardly convex curved portion 10a as shown in (A) to (C), after the curved tube 10 is brought into close contact with the upper metal mold 20 and the lower metal mold 30 respectively, at least two points along the length of one end and the other end of the curved portion 10a of the curved tube 10 are brought into contact with the lower metal mold 30, and at least one point along the length of the curved portion 10a other than one end and the other end is brought into contact with the upper metal mold 20. In this way, by bringing the stamping die into close contact with the curved tube 10 and then bringing the curved tube 10 into contact with the stamping die at least three points, it is possible to suppress the positional deviation of the curved tube 10 relative to the stamping die during the stamping process.

[0059] In addition, Figure 4In diagrams (A) to (C), a stamping process is shown to make the curved portion 10a of the curved tube 10 and the curved portion 100a of the hollow component 100 convex downwards. However, stamping can also be performed to make the curved portion 10a of the curved tube 10 and the curved portion 100a of the hollow component 100 convex upwards. However, it is conceivable that the downward convex configuration makes it easier to place and position the curved tube 10 onto the lower metal die 30, resulting in better workability during stamping. Furthermore, the stamping direction of the stamping die is not limited to... Figure 4 The vertical direction shown in (A) to (C) can also be, for example, horizontal. However, considering workability or productivity, it is preferable to set the stamping direction of the stamping die to vertical. The press that houses the stamping die can adopt a known structure.

[0060] 3. Section machining

[0061] In the manufacturing method disclosed herein, pressure is applied from the outside to the inside of the tube using stamping dies 20 and 30, thereby performing cross-sectional processing to change the cross-sectional shape of the curved portion 10a of the curved tube 10. That is, by pressing the stamping surfaces 20a and 30a of the stamping dies 20 and 30 relative to the curved portion 10a from the outside, material flow in the circumferential direction of the tube is generated in the curved portion 10a, thus changing the cross-sectional shape of the curved portion 10a. For example, as... Figure 5 As shown in (A) to (F), the cross-sectional shape of the curved part 10a can also be changed from a first shape (e.g., a circle) to a second shape (e.g., an ellipse, a polygon, a polygon containing a circle, or a combination of these shapes) by cross-sectional processing.

[0062] In the cross-section processing, pressure is applied from the outside of the tube to the inside. That is, in the manufacturing method of this disclosure, pressure is not applied from the inside of the tube to the outside as in hydroforming; instead, the cross-sectional shape of the curved portion 10a of the curved tube 10 is changed only by stamping from the outside of the tube. Furthermore, during cross-section processing, a core metal mold or similar material may be provided, for example, at the tube end or other locations on the inside of the tube. This further suppresses depressions or collapses at the tube end or other locations.

[0063] In the manufacturing method disclosed herein, when the cross-section is completed, in the cross-section orthogonal to the length direction of the hollow component 100, a gap may or may not be generated between the outer wall of the hollow component 100 and the stamping die.

[0064] Furthermore, in the manufacturing method disclosed herein, the cross-sectional machining of the portion other than the part that is bent to form the curved section 100a is arbitrary. When a hollow component 100 having both curved sections 100a and straight sections is obtained, cross-sectional machining may or may not be performed on the straight sections. When cross-sectional machining is performed on the straight sections, different cross-sectional machining may be performed on the curved section 10a and the straight section. Furthermore, when the curved tube 10 has multiple curved sections 10a, the same cross-sectional machining may be performed on one curved section 10a and different cross-sectional machining on the other curved sections 10a.

[0065] 4. Bending process

[0066] In the manufacturing method disclosed herein, the bending radius R of the curved portion 10a of the curved tube 10 is adjusted by stamping. 10 A smaller bending process. That is, by pressing the stamping surfaces 20a and 30a of the stamping dies 20 and 30 relative to the curved portion 10a from the outside of the tube, material flow in the length direction of the tube is generated in the curved portion 10a, thereby reducing the bending radius R of the curved portion 10a. 10 To become smaller. For example, as Figure 1 and 2 As shown, the bending radius R is achieved through bending processing. 10 The curved part 10a has a bending radius R 100 The curve 100a changes.

[0067] During the bending process, pressure is applied from the outside of the tube to the inside. That is, in the manufacturing method disclosed herein, pressure is not applied from the inside of the tube to the outside as in hydraulic forming, but the bending radius of the curved portion 10a of the curved tube 10 is reduced only by stamping from the outside of the tube.

[0068] In the manufacturing method disclosed herein, when the bending process is completed, a gap may or may not be generated between the outer wall of the hollow component 100 and the stamping die in the longitudinal direction of the hollow component 100.

[0069] Furthermore, in the manufacturing method disclosed herein, the bending process for portions other than the curved section 10a is arbitrary. For example, if the curved tube 10 has a straight section, a gentle bending process can be performed on the straight section without causing wrinkles or bending.

[0070] In the manufacturing method disclosed herein, the bending process described above and the cross-section processing described above are performed simultaneously. That is, during the stamping process, by simultaneously allowing material flow in the circumferential direction and in the longitudinal direction at the curved portion 10a of the curved tube 10, high shape accuracy is ensured in the hollow component 100. The cross-section processing and bending process of the tube using a stamping die are performed, for example, by... Figure 6The process is carried out as shown in (A) to (F). Figure 6 The shapes shown in (A) to (F) are similar to Figure 5 The corresponding shapes shown in (A) and (D) illustrate the transformation of a circular tube cross-section into a rectangular cross-section containing a circle. For example... Figure 6 As shown in (A) to (F), the tube is brought into contact with at least one of the upper metal mold 20 and the lower metal mold 30. Figure 6 In step (A), the upper metal mold 20 and the lower metal mold 30 are brought close together, and while a portion of the tube flows, it is inserted into the inner side of the upper metal mold 20 and the lower metal mold 30, so that the tube does not bite into the gap between the upper metal mold 20 and the lower metal mold 30, thus allowing the forming to proceed. Figure 6 (B)~(E)), by closing the upper metal mold 20 and the lower metal mold 30, the cross-sectional processing and bending processing of the tube can be completed. Figure 6 (F)). In addition, in the manufacturing method disclosed herein, it is sufficient that the section machining and bending machining are performed simultaneously at a certain point in time, and it is not necessary for the start and completion times of the section machining to be strictly simultaneous with the start and completion times of the bending machining.

[0071] When the hollow component 100 is obtained by performing the above-described stamping process on the curved tube 10, before actually performing the stamping process on the curved tube 10, the minimum bending radius (R) that will not cause bending or wrinkling can be confirmed in advance through experiments or FEM analysis. 100min That is, when stamping the curved tube 10, bending is performed to achieve a pre-determined minimum bending radius R. 100min The above bending radius R 100 This can further suppress the occurrence of bending or wrinkling of the hollow component 100.

[0072] 5. Hollow shell part

[0073] 5.1 Shape along the length of the hollow component

[0074] like Figure 2 As shown, the hollow component 100 has a curved portion 100a at least in one part. As described above, since the hollow component 100 is formed by stamping a tube, it can also be described as a "press-formed tube". The length direction of the hollow component 100 can correspond to the length direction of the tube before stamping. The hollow component 100 can be bent in both two dimensions and three dimensions at the curved portion 100a. For example, in... Figure 2The diagram illustrates a shape in which the hollow component 100 is bent in the vertical direction of the curved portion 100a on the paper surface, but it is also possible for the curved portion 100a to be bent in the depth direction of the paper surface. The bending shape of the curved portion 100a is not particularly limited. For example, the hollow component 100 may also be bent in the curved portion 100a. By changing the shape of the stamping surface of the aforementioned stamping dies 20 and 30, the bending shape of the hollow component 100 can be easily changed.

[0075] The bending radius R of the curved part 100a 100 The (inner bending radius) is not specifically limited, as long as it is greater than the bending radius R mentioned above. 10 Small is acceptable. Furthermore, the curved shape (edge) along the length of the curved section 100a can be formed by a single arc or by a combination of multiple arcs. Additionally, the curvature of the curved section 100a can change continuously or discontinuously from one end of the length direction towards the other.

[0076] exist Figure 2 The diagram shows that the hollow component 100 has only one curved section 100a, but the hollow component 100 can also have a bending radius R. 100 Multiple curves 100a that are the same or different.

[0077] The hollow component 100 may also have a straight tube portion in addition to the curved portion 100a. Alternatively, the hollow component 100 may consist of only one or more curved portions 100a.

[0078] The hollow component 100 does not need to be entirely tubular. For example, the hollow component 100 may also have a notch or slit in a portion. In addition, the hollow component 100 may also have a through hole or intentional protrusions in a portion.

[0079] The length of the hollow component 100 is not particularly limited and can be appropriately determined according to the application. The length of the hollow component 100 can be the same as or different from the length of the curved tube 10. For example, the length of the hollow component 100 can be shorter than the length of the curved tube 10 by processes such as increasing the opening diameter (circular equivalent diameter) of the curved tube 10 in addition to the bending and cross-section processing disclosed in this disclosure. Alternatively, the length of the hollow component 100 can be longer than the length of the curved tube 10 by processes such as thinning the tube thickness or reducing the tube diameter.

[0080] 5.2 Cross-sectional shape of hollow components

[0081] The cross-sectional shape (opening shape) of the hollow component 100 is not specifically defined. Figure 3In the diagram, (D), (E), and (F) indicate that the cross-sectional shape of the hollow component 100 is polygonal or elliptical. However, in addition to these, it can also be circular, flattened circular, polygonal containing circles, or combinations of these shapes. The cross-sectional shape of the hollow component 100 can be appropriately determined according to its application. By changing the shape of the stamping surfaces of the aforementioned stamping dies 20 and 30, the cross-sectional shape of the hollow component 100 can be easily changed.

[0082] The cross-sectional shape of the hollow component 100 can be a shape that remains the same from one end to the other along the length of the tube, or it can be like... Figure 3 As shown in (D) to (F), the shape changes continuously or discontinuously from one end to the other along the length of the tube. Furthermore, when the hollow component 100 has a curved section 100a and a straight section, the curved section 100a and the straight section can have the same cross-sectional shape or different cross-sectional shapes. Furthermore, when the hollow component 100 has multiple curved sections 100a, each curved section 100a can have the same cross-sectional shape or different cross-sectional shapes.

[0083] The thickness (wall thickness) of the hollow component 100 is not specifically limited and can be appropriately determined according to the application. The thickness of the hollow component 100 can also vary for each part.

[0084] As described above, in the manufacturing method of the hollow component 100 disclosed herein, a curved tube 10 having a curved portion 10a is stamped, and while the cross-section of the curved portion 10a is machined, the bending radius of the curved portion 10a is reduced. Therefore, compared to obtaining the hollow component 100 having a curved portion 100a from a straight tube through a single stamping process, defects in the forming of the curved portion 100a can be suppressed.

[0085] Furthermore, the manufacturing method of this disclosure can also be applied, for example, in the case of manufacturing a tapered tube. That is, a tapered tube as a hollow component 100 can be obtained by machining the cross section using the manufacturing method of this disclosure, or a tapered tube can be used as a curved tube 10 for obtaining the hollow component 100.

[0086] 5.3 An example of the use of hollow components

[0087] The hollow component 100 obtained by the manufacturing method of this disclosure has applications spanning multiple fields. For example, it can be used as a bumper beam, suspension component, side rail, trailing arm, upper arm, pillar, torsion beam, door anti-collision beam, dashboard beam, and other automotive parts.

[0088] 6. Summary

[0089] As described above, the method of this disclosure involves simultaneously performing bending and sectioning operations on a pre-bent curved tube 10 using a stamping die, thereby changing the cross-sectional shape of the curved portion 10a of the curved tube 10 and reducing the bending radius of the curved portion 10a, thus manufacturing a hollow component 100 with a curved portion 100a having a smaller bending radius. As also described above, the method of this disclosure can also include a pre-preparation step for the curved tube 10 as a step different from the bending and sectioning operations using a stamping die described above. For example, as... Figure 9 As shown, a curved tube 10 with a curved portion 10a can also be obtained by at least performing a bending process (pre-bending) on ​​the raw material tube 1 (which can also be a straight tube as described above). Then, the obtained curved tube 10 can be placed from the outside of the stamping die into the inside of the stamping die, and then the bending process and section processing described above can be performed simultaneously to change the cross-sectional shape of the curved portion 10a of the curved tube 10 and reduce the bending radius of the curved portion 10a (formal forming), thereby obtaining a hollow component 100 with a specified curved portion 100a. As in the method of this disclosure, bending and section processing are performed simultaneously on the pre-bent curved tube 10 using a stamping die, thereby suppressing wrinkles or buckling, and enabling the manufacture of a hollow component 100 with a curved portion 100a having a small bending radius.

[0090] Example

[0091] Hereinafter, the effects of the method for manufacturing the hollow component of the present invention will be described in more detail while showing embodiments.

[0092] 1. Comparative Example

[0093] like Figure 10 As shown, for a straight pipe (980MPa grade steel pipe, φ38.1mm, thickness 1.0mm, length 600mm), a stamping die is used to simultaneously perform cross-section processing and bending processing. By changing the cross-sectional shape of the straight pipe while bending it with a specified bending radius, a hollow component is obtained through only one formal forming process.

[0094] The experimental results show that, for the aforementioned straight tubes, section processing and bending using stamping dies can be performed without wrinkles or buckling up to a bending radius of approximately 700 mm. However, if the bending radius is less than 700 mm, buckling deformation was confirmed on the surface of the hollow component. For example, according to... Figure 11 The FEM analysis results also show that, with the bending radius set to 570 mm, buckling deformation occurred at the central part (bending center) along the length of the hollow component.

[0095] 2. Example

[0096] like Figure 12As shown, by performing a bending process (pre-bending) on ​​the same straight tube as the comparative example using a stamping die, a bent tube with a bending radius of 700 mm was obtained. Then, a formal forming process was performed on the bent tube using a stamping die to simultaneously perform cross-section processing and bending, reducing the bending radius of the bent portion to 570 mm. No wrinkles or buckling were found in the curved portion of the resulting hollow component.

[0097] Based on the above results, it can be concluded that, when using the same straight tube as the starting blank, performing pre-bending followed by stamping can suppress wrinkles and buckling in the final hollow component compared to performing stamping in a single process. Furthermore, while the pre-bending method using stamping has been described above, similarly, when pre-bending is performed using methods other than stamping (such as hydroforming), subsequent stamping can also suppress wrinkles and buckling in the curved portion, resulting in a hollow component with high shape accuracy.

[0098] 3. Supplement

[0099] Furthermore, regarding the reason why poor forming conditions such as wrinkling or buckling occur in the curved portion of a hollow component when a straight tube is stamped only once in a single process, as in the comparative example, resulting in a hollow component with a small bending radius, the following can be considered. That is, it can be reasoned that even if bending and sectioning are performed simultaneously on the straight tube using a stamping die, the bending radius of the stamping surface of the stamping die is too small. Therefore, at the center of the tube's length direction, the material cannot flow smoothly in the circumferential direction of the tube, resulting in buckling deformation such as inward indentation (which only occurs during bending before sectioning).

[0100] In contrast, as shown in the embodiment, instead of a straight pipe, a pre-bent curved pipe is subjected to bending and cross-section processing simultaneously through stamping. This suppresses the aforementioned wrinkles and buckling, and allows the manufacture of hollow components with curved sections having small bending radii. That is, when considering bending processes with small bending radii that could cause wrinkles or buckling, by simultaneously performing cross-section processing along with bending, the pipe material can flow appropriately not only along the length of the pipe but also in the circumferential direction, thus preventing wrinkles or buckling.

[0101] Furthermore, the method disclosed herein, such as obtaining a curved tube from a raw material tube and then performing bending and cross-sectional processing on that curved tube, can be described as performing the bending process in segments. Here, it is generally believed that even segmenting the cold bending process would have no effect. However, based on the inventor's new understanding and inferences based on this understanding, it is conceivable that if the bending process is segmented, deformation in subsequent bending processes can be dispersed to locations different from those bent in previous processes. That is, it is conceivable that by dispersing the deformation during bending, the occurrence of buckling or wrinkling in the final hollow component can be suppressed. Previously, even those skilled in the art would not easily predict the effects of such segmentation of the bending process. Originally, those skilled in the art, from the viewpoint of production efficiency, generally wanted to minimize the number of processes.

[0102] Label Explanation

[0103] 1. Starting material tube; 10. Bent tube; 10a. Bent section; 11a. Upper end; 11b. Lower end; 12. Side section; 20. Upper metal mold (stamping die); 21. Bottom; 22. Side wall section; 30. Lower metal mold (stamping die); 31. Bottom; 32. Side wall section; 100. Hollow shell part; 100a. Bent section.

Claims

1. A method of manufacturing a hollow member, characterized by comprising:

2. The method of manufacturing according to claim 1, characterized in that, At least bending processing is performed on the raw pipe to make it a minimum bending radius R that does not cause buckling and wrinkling 10min The bending radius above, whereby a curved pipe having a curved portion is obtained; and By using a press die, a pressure is given to the curved pipe having the curved portion described above from the outside of the pipe toward the inside of the pipe, thereby simultaneously performing the cross-sectional processing of the curved portion and the bending processing of making the bending radius of the curved portion smaller than the bending radius R 10min described above. the press die has an upper die and a lower die, the upper die and the lower die each have a press surface, the upper die and the lower die press the press surfaces against the curved portion of the curved pipe from above and below, thereby simultaneously performing the cross-sectional processing and the bending processing.

3. The method of manufacturing according to claim 1, characterized in that, the method of manufacturing includes obtaining the curved pipe having the curved portion by performing at least the bending processing and the cross-sectional processing on the raw pipe.

4. The method of manufacturing according to claim 2, characterized in that, the method of manufacturing includes obtaining the curved pipe having the curved portion by performing at least the bending processing and the cross-sectional processing on the raw pipe.

5. The method of manufacturing according to claim 1, characterized in that, the bending processing performed on the raw pipe includes: using a press die to apply pressure from the outside of the pipe toward the inside of the pipe to obtain the curved pipe.

6. The method of manufacturing according to claim 2, characterized in that, the bending processing performed on the raw pipe includes: using a press die to apply pressure from the outside of the pipe toward the inside of the pipe to obtain the curved pipe.

7. The method of manufacturing according to claim 3, characterized in that, the bending processing and the cross-sectional processing performed on the raw pipe include: using a press die to apply pressure from the outside of the pipe toward the inside of the pipe to obtain the curved pipe.

8. The method of manufacturing according to claim 4, characterized in that, the bending processing and the cross-sectional processing performed on the raw pipe include: using a press die to apply pressure from the outside of the pipe toward the inside of the pipe to obtain the curved pipe.

9. The method of manufacturing according to any one of claims 1 to 8, characterized in that, the raw pipe is a straight pipe.

10. The method of manufacturing according to any one of claims 1 to 8, characterized in that, at the point in time when the cross-sectional processing and the bending processing are completed, the inner wall surface of the press die is inclined with respect to the outer wall surface of the hollow member in a cross section orthogonal to the length direction of the hollow member, and a gap is generated between the outer wall surface of the hollow member and the inner wall surface of the press die.

11. The method of manufacturing according to claim 9, characterized in that, at the point in time when the cross-sectional processing and the bending processing are completed, the inner wall surface of the press die is inclined with respect to the outer wall surface of the hollow member in a cross section orthogonal to the length direction of the hollow member, and a gap is generated between the outer wall surface of the hollow member and the inner wall surface of the press die. ​

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