Core for bending hollow member

Abstract

To provide a core for bending a hollow member improved in durability.SOLUTION: The core 100 for bending the hollow member is a core 100 used for bending the hollow member. The core (100) includes a deformable portion (10) disposed so as to include a portion to be bent of a hollow portion of the hollow member, the deformable portion (10) including a base portion (11) made of an elastically deformable non-metal material, the base portion (11) having a longitudinal direction in a first direction, the base portion (11) having a plurality of slits (S) formed therein, the plurality of slits (S) including a first slit S1 recessed in a second direction along a bending shaft during bending and a second slit S1 recessed in a direction opposite to the first slit S2.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a core for bending a hollow member. [Background technology]

[0002] When bending a hollow member, a core is used to suppress cross-sectional deformation of the hollow member. For example, Patent Document 1 describes that a core (mandrel) has a flexible part composed of an inner member made of multiple layers of resin, such as polyvinyl chloride plates, and an outer plate made of spring steel material arranged on the outside of the inner member in the bending direction, and that the flexible part bends together with the hollow member while tightly abutting the inner periphery of the hollow member, thereby making it possible to bend the hollow member without generating wrinkles, sink marks, etc. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 198349 / 1994 Summary of the Invention [Problem to be solved by the invention]

[0004] The core of the hollow member is repeatedly used in bending processes and is repeatedly deformed. The core made of resin as disclosed in the above-mentioned Patent Document 1 is likely to crack or the like when repeatedly deformed, and has durability issues.

[0005] The present invention provides a core for bending a hollow member, which has improved durability. [Means for solving the problem]

[0006] The present invention provides a core for use in bending a hollow member, the core comprising a deformable deformation portion arranged to include a portion of the hollow portion of the hollow member that is to be bent, the deformation portion having a longitudinal direction in a first direction and a base made of an elastically deformable non-metallic material, the base having a plurality of slits cut out from the surface of the base beyond the central axis of the base, the plurality of slits including first slits recessed in a second direction along the bending axis during the bending process, and second slits recessed in the opposite direction to the first slits.

[0007] According to the above configuration, the first slit and the second slit recessed in the opposite direction to the first slit are each formed by being cut out beyond the central axis (axial center), thereby making the stress distribution and strain distribution uniform and improving the durability of the core for bending hollow members.

[0008] The first slits and the second slits may be arranged alternately in the first direction.

[0009] According to the above configuration, the first slits and the second slits are arranged alternately, which further uniforms the stress distribution and strain distribution, thereby further improving the durability of the core for bending hollow members.

[0010] The length of the slit in the second direction may be set based on the ratio to the sum of the length of the slit in the second direction and the thickness of the base, and may be set so that the ratio of the length of the slit to the sum of the thickness of the base and the length of the slit in the second direction is 50% or more and 95% or less.

[0011] According to the above-mentioned configuration, the stress distribution and strain distribution are made uniform, and the durability of the core for bending a hollow member can be improved.

[0012] The length of the slit in the first direction may be set based on a ratio to the sum of the length of the slit in the first direction and the thickness of the base, and may be set so that the ratio of the slit to the sum of the thickness of the base and the length of the slit in the first direction is 5% or more and 60% or less.

[0013] According to the above configuration, it is possible to prevent the base portions that define the slits from coming into contact with each other during bending while ensuring a sufficient contact area with the hollow member, thereby suppressing cross-sectional deformation of the hollow member and improving the durability of the core.

[0014] The deformation section may include a plurality of the deformation sections, which are arranged adjacent to each other in a third direction perpendicular to the first direction and the second direction, and the deformation sections may be arranged such that the slits of adjacent deformation sections are staggered when viewed along the third direction.

[0015] According to the above-described configuration, the contact area with the hollow member can be secured, and the occurrence of wrinkles, sink marks, etc. in the hollow member can be suppressed.

[0016] The hollow portion may further include a straight portion that is arranged in a location different from the portion to be bent, and the deforming portion may be made of resin, while the straight portion may be made of a metal that is less susceptible to deformation than the deforming portion.

[0017] According to the above-described configuration, it is possible to suppress deformation of the portion of the hollow member that does not require deformation (straight portion). [Effects of the Invention]

[0018] According to the core for bending a hollow member according to the present invention, durability can be improved. [Brief explanation of the drawings]

[0019] [Figure 1A] 3A to 3C are diagrams schematically showing bending of a hollow member using a core according to a first embodiment of the present invention. [Figure 1B] 3A to 3C are diagrams schematically showing bending of a hollow member using a core according to a first embodiment of the present invention. [Figure 1C] 3A to 3C are diagrams schematically showing bending of a hollow member using a core according to a first embodiment of the present invention. [Figure 2] FIG. 1 is a perspective view showing a core according to a first embodiment of the present invention. [Figure 3] FIG. 1 is a side view showing a core according to a first embodiment of the present invention. [Figure 4] FIG. 1 is a top view showing a core according to a first embodiment of the present invention. [Figure 5] FIG. 2 is an enlarged schematic view showing a deformed state of the core according to the first embodiment of the present invention. [Figure 6] FIG. 3 is a diagram showing the analysis results of stress distribution in the core according to the first embodiment of the present invention and a core according to a comparative example. [Figure 7] FIG. 3 is a diagram showing the analysis results of strain distribution of the core according to the first embodiment of the present invention and a core according to a comparative example. [Figure 8] FIG. 10 is a perspective view showing a core according to a modified example of the first embodiment of the present invention. [Figure 9A] 5A to 5C are diagrams schematically showing bending of a hollow member using a core according to a modified example of the first embodiment of the present invention. [Figure 9B] 5A to 5C are diagrams schematically showing bending of a hollow member using a core according to a modified example of the first embodiment of the present invention. [Figure 9C] 5A to 5C are diagrams schematically showing bending of a hollow member using a core according to a modified example of the first embodiment of the present invention. [Figure 10] FIG. 6 is a perspective view showing a core according to a second embodiment of the present invention. [Figure 11] FIG. 6 is a side view of a core according to a second embodiment of the present invention. [Figure 12] FIG. 6 is a top view of a core according to a second embodiment of the present invention. [Figure 13] FIG. 10 is a perspective view of a core according to a modified example of the second embodiment of the present invention. [Figure 14A] 10A and 10B are schematic diagrams showing modified examples of slits according to the embodiment of the present invention. [Figure 14B]10A and 10B are schematic diagrams showing modified examples of slits according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] (First embodiment) 1A to 1C, a core 100 for bending a hollow member H (hereinafter referred to as "core 100") in this embodiment is used to bend a hollow member H. FIGS. 1A to 1C are diagrams that schematically show bending of a hollow member H using the core 100. In this embodiment, the hollow member H is an extruded shape formed by extruding a metal such as aluminum.

[0021] As shown in FIG. 1A, core 100 is fitted into hollow portion h1 of hollow member H and is arranged so as to include a portion h2 to be bent (hereinafter referred to as "portion to be bent h2").

[0022] 1B, a bending force is applied to the core 100 together with the hollow member H. The posture of the hollow member H when the bending force is applied is not particularly limited, but for example, the hollow member H is in a state where only the tip end Hb on the opposite side to the base end Ha on the side where the core 100 is inserted is fixed (cantilever state), and a bending force is applied in the Y direction to the base end Ha.

[0023] When the bending process for the hollow member H is completed, the core 100 is removed from the hollow portion h1 of the hollow member H, as shown in FIG. 1C.

[0024] In the following, the longitudinal direction of core 100 when not deformed is referred to as the X direction (an example of a first direction), the bending axis direction (see FIG. 1B) is referred to as the Y direction (an example of a second direction), and the direction perpendicular to the X and Y directions is referred to as the Z direction (an example of a third direction). In addition, the side of core 100 that is positioned during bending and faces hollow member H is referred to as the "tip side." The X direction is parallel to the direction in which core 100 is inserted into and removed from hollow member H.

[0025] (Nakako) Next, the configuration of the core 100 will be described with reference to Figures 2 to 4. As shown in Figures 2 to 4, the core 100 has a deformation section 10 and a tapered section 20. The tapered section 20 is provided closer to the hollow member H than the deformation section 10. The tapered section 20 is tapered so that it becomes thinner towards the tip, so that the core 100 can be inserted more smoothly into the hollow member H than the deformation section 10. Note that the tapered section 20 can also be omitted from the core 100.

[0026] (deformed part) The deformation portion 10 is bellows-shaped and configured to be deformable. When a bending force is applied, the deformation portion 10 is disposed at a position including the bending target portion h2 of the hollow member H described with reference to FIGS. 1A to 1C, and deforms together with the hollow member H.

[0027] The deformation section 10 has a substantially rectangular parallelepiped base 11 with a plurality of slits S formed therein. The base 11 has its longitudinal direction in the X direction and is made of an elastically deformable nonmetallic material. In this embodiment, the material of the base 11 is, for example, a resin such as MC nylon or urethane rubber. The base 11 may be made of a single resin component or a laminate of resin components.

[0028] As shown in Fig. 3, the base 11 has an inner surface 11a, an outer surface 11b, and a side surface 11c. When not deformed, the inner surface 11a and the outer surface 11b are planes perpendicular to the Y direction, and the inner surface 11a and the outer surface 11b face each other in the Y direction. When deformed, the inner surface 11a is the surface that contracts when a bending force is applied, and the outer surface 11b is the surface that is stretched when a bending force is applied. The inner surface 11a and the outer surface 11b are examples of surfaces.

[0029] The side surface 11c is perpendicular to the inner surface 11a and the outer surface 11b and is connected to each of the inner surface 11a and the outer surface 11b.

[0030] The multiple slits S include first slits S1 recessed along the Y direction (from the +Y side to the -Y side) and second slits S2 recessed in the opposite direction to the first slits S1 (from the -Y side to the +Y side). The first slits S1 and the second slits S2 are arranged along the X direction. In this embodiment, the first slits S1 and the second slits S2 are arranged alternately in the X direction.

[0031] The first slit S1 is formed by cutting out from the inner surface 11a to the outer surface 11b along the Y direction. More specifically, the first slit S1 is cut out from the inner surface 11a beyond the central axis AX of the base 11.

[0032] The second slit S2 is formed by cutting out from the outer surface 11b toward the inner surface 11a along the Y direction. More specifically, the second slit S2 is cut out from the outer surface 11b beyond the central axis AX of the base 11.

[0033] As shown in Fig. 3, the thickness N1 of the base 11 in which multiple slits S are formed is constant. Specifically, the base 11 includes horizontal wall portions 11y between adjacent slits S when viewed along the Z direction, and vertical wall portions 11t between the bottom surfaces of the slits S and the inner surface 11a or the outer surface 11b, and the thickness of the horizontal wall portions 11y is equal to the thickness of the vertical wall portions 11t (the length between the bottom surface of the slit S and the inner surface 11a or the outer surface 11b). The thickness of the horizontal wall portions 11y is the length in the X direction of the base 11 between adjacent slits S when viewed along the Z direction. The thickness of the vertical wall portions 11t is the length between the bottom surface of the slit S and the inner surface 11a or the outer surface 11b.

[0034] The length of the slit S in the Y direction (hereinafter referred to as "depth D1") is also constant. The depth D1 of the slit S is set based on the ratio to the length of the base 11 in the Y direction (the sum D1+N1 of the depth D1 of the slit S and the thickness N1 of the base 11 in the Y direction). The lower limit of the depth D1 of the slit S is set so that the ratio of the slit depth (D1) / the total first width thickness (D1+N1) in the Y direction is 50% or more, preferably 60% or more, and more preferably 70% or more. The upper limit of the depth D1 of the slit S is set so that the ratio of the slit depth (D1) / the total first width thickness (D1+N1) in the Y direction is 95% or less, preferably 87.5% or less, and more preferably 80% or less.

[0035] Furthermore, in this embodiment, the length H1 (hereinafter referred to as "width H1") of the slits S (first slits S1 and second slits S2) in the X direction is also constant.

[0036] The width H1 of the slit S is set based on the ratio of the width H1 of the slit S to the sum of the width H1 of the slit S and the thickness N1 of the base 11 in the X direction (hereinafter referred to as the "total width-thickness value (H1+N1)"). The lower limit of the width H1 of the slit S is set so that the width (H1) of the slit S / the total width-thickness value (H1+N1) in the X direction is 5% or more, preferably 20% or more, and more preferably 30% or more. The upper limit of the width H1 of the slit S is set so that the width (H1) of the slit S / the total width-thickness value (H1+N1) in the X direction is 60% or less, preferably 55% or less, and more preferably 50% or less.

[0037] However, the width H1 of the slit S may be set based on the ratio to the length L1 of the deformation portion 10 in the X direction (hereinafter referred to as the entire length L1).

[0038] The upper and lower limit values ​​of the depth D1 and width H1 of the slit S can be arbitrarily combined within the above ranges.

[0039] (Effects of the embodiment) As described above, according to this embodiment, the first slit S1 and the second slit S2 are formed by cutting out beyond the central axis AX. This makes the stress distribution uniform, and also makes the strain distribution uniform. As a result, even if the core 100 is repeatedly deformed, the occurrence of cracks and the like can be suppressed. It is also possible to avoid a situation where permanent deformation (plastic deformation) makes it difficult to insert the core 100 into the hollow member H. In other words, according to this embodiment, the durability of the core 100 can be improved.

[0040] If there are too many slits S or if the width H1 of each slit S is too large (i.e., if the ratio of the width H1 of the slit S to the total width-thickness value (H1+N1) is too large, and the total length of the multiple slits S in the X direction is too long), the contact area of ​​the core 100 with the hollow member H will be reduced, and the core 100 may not function properly. However, as described above, by setting a lower limit for the width H1 of the slits S, it is possible to ensure the contact area with the hollow member H. Furthermore, by setting an upper limit for the width H1 of the slits S, it is possible to prevent the bases 11 that define the slits S from coming into contact with each other during bending, as shown in FIG. 5. Therefore, it is possible to improve the durability of the core 100 while suppressing cross-sectional deformation of the hollow member H.

[0041] Furthermore, since the depth D1 of the slit S is set based on the ratio to the length of the base 11 in the Y direction, the stress distribution and strain distribution are made uniform, and the durability of the core 100 can be improved.

[0042] (Example) Next, the present invention will be further described by way of examples with reference to Figures 6 and 7. However, the present invention is not limited to the following examples.

[0043] To verify the effects of the present invention, a model was created of the configuration of the core 100 described in the first embodiment (the same configuration as only the deforming portion 10 of the core 100). Specifically, a core made of MC nylon with a density ρ=1.22 g / cm^3, Young's modulus E=3530 MPa, and Poisson's ratio V=0.35 was modeled. The slit in the modeled core had a width of 10 mm and a depth of 40 mm.

[0044] A CAE analysis was performed on the stress and strain distributions when a core was fitted into a hollow member (extruded material) measuring 600 mm in length in the X direction, 50 mm in length in the Y direction, and 100 mm in length in the Z direction and bending stress was applied. Specifically, a cylindrical rigid punch (radius 200 mm) was pressed against the hollow member fitted with the core set in a die to perform a bending process (bending state: 60°) (quasi-static analysis). Afterwards, all dies were removed and one end was fixed to perform a springback calculation (static implicit method). The CAE analysis used the general-purpose dynamic explicit method software LS-DYNAR 10.2.0.

[0045] For comparison, cores 91 to 97 having the following configurations were modeled as Comparative Examples 1 to 7, and similar analyses were carried out.

[0046] (Comparative Example 1) As Comparative Example 1, a rectangular parallelepiped core 91 without slits was used.

[0047] (Comparative Example 2) As Comparative Example 2, a core 92 was used that had a fishbone-like structure and multiple slits cut out in two directions. Unlike the slits in core 100 according to the example, the slits in core 92 according to Comparative Example 2 were 10 mm wide and 20 mm deep, and were formed so as not to extend beyond the central axis. The slits in core 92 according to Comparative Example 2 were formed so as to face each other in the Y direction.

[0048] (Comparative Example 3) Core 93, in which multiple slits not exceeding the central axis were formed, was used as Comparative Example 3. The slits of core 93 according to Comparative Example 3 were 10 mm wide and 20 mm deep, similar to core 92 according to Comparative Example 2, but unlike the slits of core 92 according to Comparative Example 2, they were formed so as not to oppose each other in the Y direction (alternately).

[0049] Comparative Example 4 As Comparative Example 4, a core 94 was used in which a plurality of slits shallower than those of the core 92 according to Comparative Example 2 were formed. The slits according to Comparative Example 4 were 10 mm wide and 10 mm deep.

[0050] (Comparative Example 5) As Comparative Example 5, core 95 was used, which had fewer slits formed therein than core 92 according to Comparative Example 2. The slits according to Comparative Example 5 were 20 mm wide and 20 mm deep.

[0051] (Comparative Example 6) A core 96 having a comb-like structure and multiple slits cut from one direction (inside) was used as Comparative Example 6. The slits of the core 96 according to Comparative Example 6 were 10 mm wide and 40 mm deep, and were formed so as to extend beyond the central axis.

[0052] (Comparative Example 7) As Comparative Example 7, a core 97 was used in which multiple slits were formed by cutting from the opposite side (outside) from that of Comparative Example 6. The slits of the core 97 according to Comparative Example 7 also had a width of 10 mm and a depth of 40 mm, and were formed so as to extend beyond the central axis.

[0053] The configurations (size, material, etc.) of the cores 91 to 97 used in Comparative Examples 1 to 7 other than those described above are the same as those of the Examples.

[0054] (Analysis results) The analysis results are shown in Figures 6 and 7. Figure 6 shows the von Mises stress distribution for the example and comparative examples 1 to 7 when bent at 60 degrees. Figure 7 shows the maximum principal strain distribution for the example and comparative examples 1 to 7 when bent at 60 degrees. In Figure 6, areas with higher stress are shown with lighter colors, and in Figure 7, areas with higher strain are shown with lighter colors.

[0055] 6, it can be seen that stress is concentrated around the bent portion of the longitudinally extending portion in Comparative Examples 1 to 7. On the other hand, it can be seen that in the Examples, unlike Comparative Examples 1 to 7, stress concentration is alleviated and stress distribution is uniform.

[0056] 7, it can be seen that strain is concentrated around the bent portion of the longitudinally extending portion in Comparative Examples 1 to 7. On the other hand, it can be seen that in the Examples, unlike Comparative Examples 1 to 7, the concentration of strain is alleviated and the strain distribution is uniform.

[0057] From the above analysis results, it can be seen that according to the example, the stress distribution is made uniform, the strain distribution is also made uniform, and durability is improved compared to the comparative example.

[0058] (Modification of the first embodiment) A core 100 according to a modification of the first embodiment will be described with reference to Figures 8 and 9A to 9C. As shown in Figures 8 and 9A to 9C, the core 100 according to the modification of the first embodiment has the same configuration as the core 100 according to the first embodiment, except that it further includes a straight portion 30.

[0059] The straight portion 30 has a rectangular parallelepiped shape, and its outer shape when viewed along the X direction is the same as the outer shape of the deformable portion 10.

[0060] The straight portion 30 is made of a material that has a higher elastic modulus and is less likely to deform than the deformable portion 10. In this embodiment, the straight portion 30 is made of a metal such as iron.

[0061] 9A to 9C, when a bending force is applied, the straight portion 30 is arranged in a straight portion h3 other than the bending target portion h2 of the hollow member H. This makes it possible to suppress deformation of the straight portion h3, which does not require deformation of the hollow member H.

[0062] (Second embodiment) Next, a core 100 according to a second embodiment will be described with reference to Figures 10 to 12. The core 100 according to the second embodiment differs from the first embodiment in that it has multiple deformation portions 10. Note that other configurations are the same as those in the first embodiment, and therefore, the same reference numerals are used to designate the same or similar configurations as those in the first embodiment, and detailed description thereof will be omitted.

[0063] 10 and 12, in this embodiment, the core 100 has three deformed portions 10. The tapered portion 20 is integrally formed and is provided closer to the tip than the three deformed portions 10.

[0064] The three deformation portions 10 are arranged adjacent to each other along the Z direction. Hereinafter, the three deformation portions 10 will be referred to as the "first deformation portion 10a," the "second deformation portion 10b," and the "third deformation portion 10c," in that order from the -Z side.

[0065] As shown in FIGS. 11 and 12, the three deformation sections 10 are arranged such that adjacent slits S are staggered when viewed along the Z direction.

[0066] Specifically, the slits S of the first deformation portion 10a and the slits S of the second deformation portion 10b do not overlap when viewed along the Z direction. That is, the slits S of the first deformation portion 10a and the base portion 11 of the second deformation portion 10b are adjacent to each other in the Z direction.

[0067] Furthermore, the slits S of the second deformation portion 10b and the slits S of the third deformation portion 10c do not overlap when viewed along the Z direction. That is, the slits S of the second deformation portion 10b and the base 11 of the third deformation portion 10c are adjacent to each other in the Z direction.

[0068] In other words, when viewed along the Z direction, the three deformation sections 10 are arranged so that adjacent slits S in the Z direction do not overlap, and the slit S of one deformation section 10 is adjacent to the base 11 of an adjacent deformation section 10.

[0069] The slits S of the first deformation portion 10a and the slits S of the third deformation portion 10c overlap when viewed in the Z direction. In other words, the slits S of one deformation portion 10 overlap with the slits S of the adjacent deformation portion 10 when viewed in the Z direction.

[0070] (Effects of the second embodiment) The hollow member H may develop wrinkles, sink marks, etc. at the locations where the slits S of the core 100 disposed in the hollow portion h1 are formed. As in the present embodiment, by arranging the slits S alternately in the direction (Z direction) perpendicular to the bending axis direction (Y direction), for example, the base 11 of the second deformation portion 10b is located in a position adjacent in the Z direction to the slits S of the first deformation portion 10a and the third deformation portion 10c. This allows the reinforcing member 1 to secure a contact area with the hollow member H, thereby suppressing the development of wrinkles, sink marks, etc. in the hollow member H.

[0071] (Modification of the second embodiment) Next, a core 100 according to a modification of the second embodiment will be described with reference to Fig. 13. As shown in Fig. 13, the core 100 according to the modification of the second embodiment has the same configuration as the core 100 according to the second embodiment except that it further includes a straight section 30.

[0072] The straight portion 30 according to the modified example of the second embodiment is integrally formed and connected to the base end sides of the three deformed portions 10.

[0073] As described in the modified example of the first embodiment, the straight portion 30 is made of a material that is less susceptible to deformation than the deformable portion 10, such as a metal such as iron. Also, as described in the modified example of the first embodiment, during bending (when a bending force is applied to the hollow member H), the straight portion 30 is arranged in the straight portion h3 of the hollow member H other than the bending target portion h2 of the hollow member H (see FIGS. 9A to 9C). This makes it possible to suppress the occurrence of wrinkles, sink marks, and the like in the hollow member H, while also suppressing deformation of the straight portion h3, which does not require deformation of the hollow member H.

[0074] In the second embodiment, the number of deformation portions 10 that the core 100 has is not limited to three, and may be two or four or more.

[0075] (Other variations) In each of the above embodiments, the width H1 of the slits S is the same, but the width H11 of the first slit S1 and the width H12 of the second slit S2 may be different. For example, as shown in Fig. 14A, the width H11 of the first slit S1 may be smaller than the width H12 of the second slit S2. Alternatively, the width H11 of the first slit S1 may be larger than the width H12 of the second slit S2.

[0076] In addition, in each of the above embodiments, the depth D1 of the first slit S1 and the depth D12 of the second slit S2 are the same, but as long as the first slit S1 and the second slit S2 both have depths that exceed the central axis AX, the depth D11 of the first slit S1 and the depth D12 of the second slit S2 may be different. For example, as shown in Fig. 14B, the depth D11 of the first slit S1 may be greater than the depth D12 of the second slit S2. Alternatively, the depth D11 of the first slit S1 may be smaller than the depth D12 of the second slit S2.

[0077] Furthermore, the thickness N1 of the base portion 11 may be uniform as described in the above embodiment, or may not be uniform as shown in Figures 14A and 14B. For example, as shown in Figure 14A, the thickness N11 of the vertical wall portion 11t may be smaller than the thickness N12 of the horizontal wall portion 11y. Alternatively, as shown in Figure 14B, the thickness N11 of the vertical wall portion 11t may be smaller than the thickness N12 of the horizontal wall portion 11y.

[0078] In the above embodiment, the first slits S1 and the second slits S2 are alternately arranged in the X direction. However, the first slits S1 and the second slits S2 do not have to be alternately arranged in the X direction. For example, a combination of a first arrangement pattern in which two first slits S1 and two second slits S2 are adjacently arranged and a second arrangement pattern in which one first slit S1 and one second slit S2 are adjacent may be used. Specifically, the slits S may be arranged such that the first arrangement pattern, the second arrangement pattern, the second arrangement pattern, and the first arrangement pattern are repeated along the X direction. That is, the first slits S1 and the second slits S2 may be arranged according to a regularity in the X direction. However, the first slits S1 and the second slits S2 may be arranged randomly in the X direction, and the arrangement of the first slits S1 and the second slits S2 can be changed as appropriate.

[0079] Furthermore, the side surfaces that define the slit S may or may not be perpendicular to the bottom surface that defines the slit S.

[0080] In the description of each of the above embodiments, expressions such as parallel, vertical, orthogonal, identical, and equal include not only strict parallel, vertical, orthogonal, identical, and equal, but also, for example, substantially parallel, vertical, orthogonal, identical, and equal. [Explanation of symbols]

[0081] 10 Deformation section 11 Base 11a Inner surface (surface) 11b Outer surface (surface) 30 Straight section 100 Core (for bending) AX center axis D1 Depth (length of the slit in the second direction) H hollow member h1 hollow part h2 Bending target area h3 Straight section H1 Width (length of the slit in the first direction) N1 Wall thickness (length of base in 1st direction) S slit S1 First slit S2 Second slit

Claims

1. A core used in bending a hollow member, a deformable deformation portion disposed to include a portion to be bent in the hollow portion of the hollow member; The deformation portion is The first direction is a longitudinal direction, and the base portion is made of an elastically deformable nonmetallic material; The base portion has a plurality of slits cut out from the surface of the base portion beyond the central axis of the base portion, A core for bending a hollow member, wherein the plurality of slits include first slits recessed in a second direction along the bending axis during the bending process, and second slits recessed in the opposite direction to the first slits.

2. The core for bending a hollow member according to claim 1 , wherein the first slits and the second slits are arranged alternately in the first direction.

3. a length of the slit in the second direction is set based on a ratio to a total value of the length of the slit in the second direction and a thickness of the base portion, 3. The core for bending a hollow member according to claim 1 or 2, wherein in the second direction, a ratio of the length of the slit to the sum of the thickness of the base and the length of the slit is set to be 50% or more and 95% or less.

4. a length of the slit in the first direction is set based on a ratio to a total value of the length of the slit in the first direction and a thickness of the base portion, 3. The core for bending a hollow member according to claim 1 or 2, wherein in the first direction, a ratio of the length of the slit to the sum of the thickness of the base and the length of the slit is set to be 5% or more and 60% or less.

5. A plurality of the deformation portions are provided, the plurality of deformation portions are arranged adjacent to each other in a third direction perpendicular to the first direction and the second direction, 3. The core for bending a hollow member according to claim 1, wherein the deformed portions are arranged such that the slits of adjacent deformed portions are staggered with respect to the slits of the adjacent deformed portions when viewed along the third direction.

6. The bending member further includes a straight portion disposed in a portion of the hollow portion different from the portion to be bent, the deformation portion is made of resin, The core for bending a hollow member according to claim 1 or 2, wherein the straight portion is made of a metal that is less susceptible to deformation than the deforming portion.

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