Manufacturing method of automobile component, and automobile component

Abstract

To provide a manufacturing method of automobile components that manufactures automobile components each having a sandwich structure for sandwiching a resin between steel plates at a low cost and that can prevent a resin leakage and resin rupture from occurring during a manufacturing process, and to provide an automobile component capable of being manufactured at a low cost and preventing a resin leakage and resin rupture from occurring during a manufacturing process.SOLUTION: A manufacturing method of automobile components in accordance with the present invention includes a resin encapsulation part molding step S1 of molding a resin encapsulation part 12 that encapsulates a resin 7 in a steel plate 11, a resin filling step S3 of filling the resin encapsulation part 12 with the resin 7 by coating or charging the resin 7 in the resin encapsulation part 12, a patch steel plate installation step S5 of installing a patch steel plate 13 on the steel plate 11 so as to enclose the resin encapsulation part 12, and a press-molding step S7 of press-molding a sandwich structure member 15 having a sandwich structure for sandwiching the resin 7 between the steel plate 11 and patch steel plate 13 into a component shape of an automobile component.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an automobile part having a sandwich structure in which resin is sandwiched between steel plates, and the automobile part. [Background technology]

[0002] Front side members, which are structural components of an automobile, are long parts installed at the front of the vehicle in the longitudinal direction, and absorb the collision energy during a vehicle collision by undergoing axial crushing deformation. Similarly, side sills (rockers) and center pillars are parts that absorb collision energy by bending when a collision load is input from the side of the vehicle body. By absorbing collision energy during a vehicle collision, these parts limit cabin deformation and protect occupants.

[0003] The above-mentioned front side members, side sills (rockers), and center pillars must be able to reliably absorb the energy of a vehicle collision, and require a structure that controls the deformation mode. Since lightweight automobile parts are also required, technologies have been proposed to combine resins with the above-mentioned parts to achieve improved collision energy absorption performance and rigidity while also reducing weight (multi-material parts).

[0004] Patent Document 1 discloses an automobile collision energy absorption component that absorbs collision energy by undergoing axial crushing when a collision load is input from the front or rear of the vehicle body. The automobile collision energy absorption component of Patent Document 1 can also improve vibration damping by absorbing vibrations from the automobile engine and vibrations input to the vehicle body from all directions while the automobile is running. Furthermore, Patent Document 2 discloses a vehicle body frame part that bends when a collision load is input from the side of the vehicle body to absorb collision energy.

[0005] In both of the parts in Patent Documents 1 and 2, resin is applied or affixed to the inner surface of a metal main body member (a cylindrical member, a hat-shaped cross section member, or a U-shaped cross section member), and a metal U-shaped cross section anti-detachment member is arranged to cover the surface of the resin. By arranging resin on the inner surface of the main body member, the resin is sandwiched between the steel plates during axial crushing, in which the part is crushed like an accordion in the axial direction, or bending crushing, in which the part is bent perpendicular to the axial direction, and this increases the bending radius during deformation, making the main body member less likely to break and improving collision energy absorption performance. As described above, the parts in Patent Documents 1 and 2 have a sandwich structure in which resin is sandwiched between a metal main body member and a metal anti-detachment member, thereby preventing fracture of the main body member in the event of axial crushing or bending crushing, thereby improving collision energy absorption performance while also achieving weight reduction. Many methods have been proposed for manufacturing parts having such a sandwich structure in which resin is sandwiched between metal plates.

[0006] Patent Document 1 describes a method for manufacturing a part having a sandwich structure by applying or attaching resin to the inner surface of a cylindrical member, arranging a separation-preventing member to cover the resin, joining the separation-preventing member to the cylindrical member, and then heat-treating these members. Patent Document 1 also describes a method for applying or attaching resin to the separation-preventing member, bringing the resin into contact with the inner surface of the cylindrical member and joining the separation-preventing member to the inner surface of the cylindrical member, and then heat-treating these members.

[0007] Furthermore, Patent Document 3 discloses a frame structure (center pillar) of a vehicle body in which a filler (such as an epoxy resin) is foam-filled into the space between the outer panel and the reinforcement, and describes the following method as an assembly method for the frame structure. First, a sheet of unfoamed filler material is attached to the outer panel side of the reinforcement. The reinforcement with the attached filler material is then attached to the outer panel, and the flanges of both are joined by spot welding. After the entire vehicle body is assembled, the vehicle body is subjected to electrodeposition coating, and the drying heat from this process causes the filler material to foam and harden.

[0008] Furthermore, Patent Document 4 describes the following method as a manufacturing method for a partially composite vibration-damping part for automobiles to prevent automobile noise. First, a resin with vibration-damping properties is applied to a restraining plate made of steel plate or the like, and the solvent in the paint on the restraining plate is evaporated in a drying oven. The restraining plate is then attached to a predetermined position on a steel plate that will form the vehicle body before being press-formed, and heated and pressed. The steel plate with the restraining plate partially adhesively bonded thereto is then press-formed to produce a composite automotive vibration-damping part.

[0009] Patent document 5 also describes a manufacturing method for metal plate components used in automobile bodies, which includes the steps of overlapping first and second metal plates with a resin adhesive therebetween, press-molding the overlapped first and second metal plates, and, after the press-molding step, hardening the resin adhesive. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2020-100183 [Patent Document 2] Japanese Patent Application Publication No. 2020-117039 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-048054 [Patent Document 4] Japanese Patent Application Publication No. 11-141005 [Patent Document 5] Japanese Patent Application Publication No. 2020-183078 Summary of the Invention [Problem to be solved by the invention]

[0011] As described above, various methods have been proposed for manufacturing parts having a sandwich structure in which resin is sandwiched between two metal plates. However, these manufacturing methods have the following problems.

[0012] First, in the manufacturing method of Patent Document 3, since the filler is foam-filled into the closed cross-sectional space formed in the existing parts such as the outer panel of the center pillar and the reinforcement, the locations where the resin can be placed are limited, which results in the problem that it is not possible to arbitrarily reinforce the areas that are effective in terms of vibration damping and rigidity.

[0013] In contrast, the manufacturing method of Patent Document 1 involves applying or attaching resin to a tubular member and then attaching a separation prevention member to cover the resin, so that resin can be placed in any location where rigidity needs to be increased (for example, the punch shoulder R portion of the outer part that makes up the tubular member). However, the above manufacturing method requires molding the anti-detachment member separately from molding the tubular member, which increases the number of steps. Also, the steps of applying or attaching resin to the molded tubular member and attaching the molded anti-detachment member to the molded tubular member are time-consuming, which increases the cost of manufacturing the part.

[0014] Furthermore, in the manufacturing method of Patent Document 1, since the resin is applied or attached to the member after press molding, it may be difficult to apply or attach the resin with a uniform thickness to a portion of the member surface that has an uneven shape, which causes a problem that the portion to which the resin is applied or attached is limited to a portion that has a relatively smooth surface with few unevenness.

[0015] In contrast, the manufacturing methods of Patent Documents 4 and 5 apply resin to the steel plate (constraint plate) before press forming, and are therefore less subject to restrictions due to the uneven surface shape of the area to which the resin is applied after press forming. Furthermore, after the constraining plate is partially adhesively joined to the steel plate (blank), these are press-formed together, so no additional press forming process is required. However, in the manufacturing method of Patent Document 4, a constraining plate coated with resin is attached to a steel plate (blank), and then heated and pressure-bonded before being press-formed, so the resin may be completely hardened by heating. If the resin is completely hardened, the ductility of the resin decreases, and there is a risk that the resin layer may break during press forming. Furthermore, in the case of the above-mentioned collision energy absorption parts, if the resin layer is broken, the breakage of the main body member during axial or bending crushing cannot be sufficiently prevented, resulting in the problem that the expected collision energy absorption performance cannot be obtained. Also, there is a risk of a decrease in vibration damping performance. On the other hand, in the manufacturing method of Patent Document 5, the pressure applied during press molding can cause resin to leak from gaps between the overlapping surfaces of the metal plates, contaminating the inside of the press and potentially impairing the surface quality of the press-molded product.

[0016] The present invention has been made to solve the above-mentioned problems, and aims to provide a method for manufacturing automobile parts that can produce automobile parts having a sandwich structure in which resin is sandwiched between steel plates at low cost while preventing resin leakage and resin breakage. Another object of the present invention is to provide an automobile part that can be manufactured at low cost, can prevent resin leakage and resin breakage during manufacturing, and can achieve the expected collision energy absorption performance. [Means for solving the problem]

[0017] The inventors have conducted extensive research into methods for preventing resin breakage in manufacturing methods such as those described in Patent Documents 4 and 5, in which a sandwich structure is formed on a steel plate before press-forming and then press-forming into a part shape. If the resin is heated and completely cured before press molding, as in Patent Document 4, there is a risk that the resin will break during press molding. On the other hand, if heating before press molding is not performed, as in Patent Document 5, the resin will leak out from between the steel sheets due to the pressure applied during press molding, making it impossible to ensure the required resin thickness. Furthermore, the leaked resin may contaminate the inside of the press mold, causing problems with part molding and quality.

[0018] If a resin adjusted to a high viscosity is applied in advance, it is possible to prevent resin leakage during press molding without heating before press molding. However, high-viscosity resins have poor applicability, which increases the application time and reduces productivity. Another problem is that it is difficult to apply high-viscosity resins with a uniform thickness.

[0019] The inventors have therefore discovered that the above problem can be solved by providing a structure in which resin is sealed in the automobile part. The present invention has been made based on this finding, and specifically comprises the following configurations.

[0020] (1) A method for manufacturing an automobile part according to the present invention includes a resin encapsulation portion forming step of forming a resin encapsulation portion for encapsulating resin in a steel plate; a resin filling step of applying or filling a resin into the resin encapsulation portion to fill the resin encapsulation portion with the resin; a patch steel plate installation process in which a patch steel plate is installed on the steel plate so as to cover the resin encapsulation portion; and a press-molding process for press-molding a sandwich structural member having a sandwich structure in which the resin is sandwiched between the steel plate and the patch steel plate into the shape of an automobile part.

[0021] (2) In addition, in the above (1), the viscosity of the resin is 50 Pa·s or more and 200 Pa·s or less.

[0022] (3) In the device described in (1) or (2) above, the resin encapsulation portion is a recess formed by recessing the steel plate, The depth of the recess is characterized by being 0.2 mm or more and 3 mm or less.

[0023] (4) The manufacturing method of an automobile part according to the present invention includes a resin encapsulation portion forming step of forming a resin encapsulation portion for encapsulating a resin in a steel plate; a resin pasting step of pasting a sheet-shaped resin formed to a thickness equal to or greater than the height of the peripheral wall of the resin encapsulation portion into the resin encapsulation portion; a patch steel plate installation process in which a patch steel plate is installed on the steel plate so as to cover the resin encapsulation portion; and a press-molding process for press-molding a sandwich structural member having a sandwich structure in which the resin is sandwiched between the steel plate and the patch steel plate into the shape of an automobile part.

[0024] (5) In addition, in the above (4), the thickness of the resin sheet is 0.2 mm or more and 3 mm or less.

[0025] (6) Furthermore, in the above (1) or (4), the method is characterized in that it further comprises a welding step of welding the steel plate press-formed by the press-forming step to the patch steel plate.

[0026] (7) In addition, in the above (1) or (4), the resin is a thermosetting rubber-modified epoxy resin.

[0027] (8) The automobile part according to the present invention includes a hat-shaped cross section member or a U-shaped cross section member having a top plate portion and a pair of vertical wall portions continuing from the top plate portion via a punch shoulder R portion; a concave resin encapsulation portion formed at least in the punch shoulder R portion of the hat-shaped cross section member or the U-shaped cross section member; a patch member disposed across the top plate portion and covering the resin encapsulation portion; a resin sealed in a closed space formed by the resin sealing portion and the patch member; The resin is characterized in that after being heated, it is adhered to the hat-shaped cross section member or the U-shaped cross section member and the patch member with an adhesive strength of 10 MPa or more. [Effects of the Invention]

[0028] In the present invention, by forming a resin encapsulation portion in the steel sheet before forming it into an automotive part, a closed space can be formed between the steel sheet and the patch steel sheet, and resin can be encapsulated in this closed space. This makes it difficult for resin to leak during press forming, even without performing a heat treatment before press forming, and prevents the inside of the press mold from being contaminated with resin. Furthermore, since the present invention does not involve heat curing of the resin prior to press molding, the resin will not break during press molding, and the collision energy absorption performance of the manufactured automobile parts will not be reduced. Furthermore, since the sandwich structure is formed and then pressed into the part shape, the main body and patch can be press-formed simultaneously, which reduces the number of processes compared to conventional methods in which each part is press-formed individually, allowing for the low-cost production of sandwich-structured automotive parts. [Brief explanation of the drawings]

[0029] [Figure 1] 1A to 1C are explanatory diagrams of a manufacturing method for an automobile part according to an embodiment. [Figure 2] 2 is an external view of an automobile part obtained by the manufacturing method of FIG. 1. [Figure 3] 3(a) is a cross-sectional view of the automobile part of FIG. 2 taken along dashed line A, and FIG. 3(b) is a cross-sectional view of the automobile part of FIG. 2 taken along dashed line B. As shown in FIG. [Figure 4] 1 is a graph conceptually showing the relationship between viscosity, elastic modulus, and ductility of a resin. [Figure 5] 10A to 10C are explanatory diagrams of another aspect of the manufacturing method of an automobile part according to the embodiment. [Figure 6]FIG. 1 is a diagram showing an example of the range of application (attachment) of resin according to an embodiment (part 1). [Figure 7] FIG. 10 is a diagram showing an example of the range of application (attachment) of resin according to the embodiment (part 2). [Figure 8] FIG. 1 is an explanatory diagram of an axial crushing test according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0030] A manufacturing method for an automobile part according to one embodiment of the present invention is a method for manufacturing an automobile part having a sandwich structure in which resin is sandwiched between steel plates. The present invention does not limit the shape of the automobile part, but as an example, in this embodiment, a case where an automobile part 1 (see FIG. 2) having a hat-shaped cross section with a sandwich structure will be described.

[0031] As shown in Fig. 1, the method for manufacturing an automotive part in this embodiment includes a resin encapsulation portion molding step S1, a resin filling step S3, a patch steel plate installation step S5, a press molding step S7, and a welding step S9. By performing the resin encapsulation portion molding step S1 to the welding step S9, a part with a hat-shaped cross section having a sandwich structure, i.e., the outer part 3 shown in Fig. 2, can be manufactured. Figs. 1(a) to 1(e) schematically show the manufacturing process of the outer part 3 in each step. After the welding process S9, in the assembly process carried out on the assembly line, the inner part 5 (see FIGS. 2 and 3) is joined to the outer part 3 manufactured in FIG. 1(e), thereby forming the automotive part 1 shown in FIG.

[0032] <Resin encapsulation molding process> As shown in FIG. 1(a), the resin encapsulation portion molding step S1 is a step of molding a resin encapsulation portion 12 for encapsulating resin 7 in a steel plate 11, which is a blank material before the outer part 3 is molded. In this embodiment, the steel plate 11 is recessed to form the resin encapsulation portion 12 .

[0033] Since resin 7 is filled into this recess, it is desirable to set the area in which the recess is formed so as to include areas that are effective in improving the collision energy absorption performance of the automotive part 1 and areas that are effective in vibration damping and rigidity. For example, in the case of the automotive part 1 shown in Figure 2, the resin 7 is bonded to the punch shoulder R portion 3b of the outer part 3 during axial crushing or bending crushing, which can improve the collision energy absorption performance of the automotive part 1, so it is advisable to form a recess in the steel plate 11 so as to include at least the portion corresponding to the punch shoulder R portion 3b. In this case, as shown in Figure 6(a), a recess may be formed over the entire part except for the welded portion with the patch 9 or inner part 5, or as shown in Figure 7(a), a recess may be formed only in the portion corresponding to the punch shoulder R portion 3b.

[0034] The depth of the resin encapsulation portion 12 is preferably 0.2 mm or more and 3 mm or less. If the depth of the recess is shallower than 0.2 mm, it becomes difficult to apply a uniform thickness of resin 7 inside the recess. If the depth of the recess is deeper than 3 mm, the resin becomes thicker, which increases costs and makes it difficult to mold resin encapsulation portion 12. The shape of the resin encapsulation portion 12 corresponds to the shape of the resin 7 of the final manufactured automotive part 1, so by making the depth of the resin encapsulation portion 12 between 0.2 mm and 3 mm, the thickness of the resin 7 of the automotive part 1 will also be between 0.2 mm and 3 mm.

[0035] The resin encapsulation portion molding step S1 can be performed simultaneously with the blanking step of extracting the steel plate 11 from the material. In a typical blanking process, the material is sandwiched and fixed between dies consisting of an upper die and a lower die, and then cut into a predetermined blank shape. Therefore, by providing a resin encapsulation molding section for molding the resin encapsulation section 12 on the molding surfaces of the upper die and lower die, the resin encapsulation section 12 can be molded simultaneously with blanking the steel plate 11. As described above, the resin encapsulation portion 12 has a shallow shape with a depth of 0.2 mm to 3 mm, and therefore can be molded even with a blanking machine of general performance.

[0036] In the above, an example has been described in which the resin encapsulation portion 12 is formed simultaneously with blanking of the steel plate 11, but the resin encapsulation portion 12 may be formed separately on the steel plate 11 after blanking.

[0037] <Resin filling process> The resin filling step S3 is a step of applying or filling the resin 7 into the resin encapsulation portion 12, thereby filling the resin encapsulation portion 12 with the resin 7, as shown in FIG. 1(b). The steel plate 11 (see FIG. 1(a)) on which the resin encapsulation portion 12 has been formed on the blank line is transferred to the press line by a transfer device such as a feeder with a suction bar or a conveyor. At the entrance side of the press machine in the press line, a robot equipped with, for example, a dispenser (a device for dispensing a fixed quantity of liquid) is placed, and this dispenser-equipped robot applies resin 7 into the resin encapsulation section 12, thereby filling the resin encapsulation section 12 with resin 7.

[0038] The method of applying resin 7 is not limited to the above, and for example, resin 7 may be applied by spraying with a spray nozzle (electrostatic coating), or resin 7 may be applied using a brush, etc. However, the method using a dispenser is more preferable because it allows for accurate supply of the amount of resin 7 required to fill resin encapsulation portion 12. Alternatively, the resin 7 may be injected into the resin encapsulation portion 12 to fill it.

[0039] A thermosetting resin is preferable as the type of resin 7. If a thermosetting resin is used, it is efficient because the resin 7 can be cured in the heating process for curing the electrodeposition coating of the vehicle body. Examples of thermosetting resins include epoxy-based, urethane-based, ester-based, phenol-based, melamine-based, and urea-based resins. In particular, thermosetting rubber-modified epoxy resins are suitable because they have high ductility after being cured by heat, making the cured resin 7 less likely to break.

[0040] The resin 7 used in the resin filling step S3 is adjusted in advance to an appropriate viscosity. The appropriate viscosity of the resin 7 in this embodiment will be described below with reference to FIG.

[0041] FIG. 4 is a graph conceptually showing the relationship between the viscosity of a resin and the ductility and elastic modulus. As shown by curve A in Figure 4, as the viscosity of the resin increases, the modulus of elasticity also increases. On the other hand, as shown by curve B, the ductility of the resin decreases inversely with the increase in modulus of elasticity. In other words, the higher the viscosity of the resin, the lower the ductility of the resin. Therefore, the inventors have considered the properties of the above resin and investigated the appropriate viscosity of resin 7 in this embodiment from the following three points of view.

[0042] First, if the viscosity of the resin 7 is too low, there is a risk that the resin 7 will leak into the press due to the pressure applied during press molding. As will be described in detail later, in this embodiment, the patch steel plate 13 installed in the patch steel plate installation step S5 serves as a lid to seal the resin 7 in the resin sealing section 12 (see FIG. 1(c)). In this way, by sealing the resin 7 between the steel plate 11 and the patch steel plate 13, even when the member of FIG. 1(c) is press-formed, the resin is less likely to leak into the press.

[0043] However, the patch steel plate 13 in Figure 1(c) is simply placed on the steel plate 11, and if the viscosity of the resin 7 is too low, the resin 7 may leak from the gap between the steel plate 11 and the patch steel plate 13 due to the pressure applied during pressing. If the resin 7 leaks during press molding, it can contaminate the press machine and make it impossible to ensure the specified resin thickness, which is undesirable. Therefore, it is preferable that resin 7 has a viscosity above a certain level so that resin 7 does not leak from resin encapsulation portion 12 even when subjected to pressure during press molding. The viscosity range that can prevent resin leakage during press molding is shown by dashed arrow i in Figure 4. Dashed arrow i indicates that resin leakage during press molding can be prevented if the viscosity of resin 7 is in the region to the right of dashed arrow i. That is, from the viewpoint of preventing resin leakage, it is preferable that the viscosity of the resin 7 is set to a or more.

[0044] On the other hand, if the viscosity of the resin 7 is too high, the thickness of the resin 7 will not be uniform when the resin 7 is applied or filled in the resin filling step S3, making it difficult to fill the resin encapsulation portion 12 with the resin 7. Therefore, it is preferable that the resin 7 has a viscosity below a certain level that ensures a uniform thickness when applied or filled. The viscosity range in which the resin 7 can be appropriately applied (filled) is shown by the dashed arrow ii in Figure 4. The dashed arrow ii indicates that the resin 7 can be applied or filled by the method described above if the viscosity of the resin 7 is in the region to the left of the dashed arrow ii. That is, from the viewpoint of viscosity suitable for application or filling, it is preferable that the viscosity of the resin 7 is set to b or less.

[0045] If the ductility of the resin 7 is too low, the resin 7 may not be able to follow the deformation during press molding, and the resin layer may break. If the resin layer breaks, the collision energy absorption performance of the automotive part 1 will decrease, as described above, which is undesirable. Therefore, it is preferable that resin 7 has a certain level of ductility that does not break even when deformed during press forming. The ductility range of resin 7 that allows resin 7 to follow the deformation of the steel sheet during press forming is shown by dashed arrow iii in Figure 4. Dashed arrow iii indicates that if the ductility of resin 7 is in the region above dashed arrow iii, resin breakage during press forming can be prevented. That is, from the viewpoint of preventing resin breakage, it is preferable that the ductility of the resin 7 is c or more. Since the ductility of resin is correlated with the viscosity of resin, in the example shown in FIG. 4, in order to make the ductility of resin 7 c or more, the viscosity of resin 7 needs to be d or less.

[0046] From the above three viewpoints, the suitable viscosity range of resin 7 in this embodiment is from a to b, and from d to d. In the example of Fig. 4, d is smaller than b, so the suitable viscosity range of resin 7 in this case is from a to d. Furthermore, since the shape of curve B changes depending on the properties of the resin, d may be greater than b depending on the properties of the resin. In this case, the appropriate viscosity range of resin 7 is a or more and b or less.

[0047] Considering the above, in this embodiment, the suitable viscosity range of resin 7 in resin filling step S3 is set to 50 Pa s or more and 200 Pa s. By adjusting the viscosity of resin 7 within this range, if it is a general resin, resin 7 can be applied or filled in resin filling step S3, and leakage or breakage of resin 7 will not occur in the subsequent press molding step S7.

[0048] <Patch steel plate installation process> The patch steel plate installation process S5 is a process of installing a patch steel plate 13 on the steel plate 11 whose resin encapsulation portion 12 is filled with resin 7, as shown in Figure 1(c). Here, the patch steel plate 13 is a blank material before being press-formed into the patch 9 (see Figure 2) of the automotive part 1. The steel plate 11, with the resin encapsulation section 12 filled with resin 7, is transferred by a transfer device to a steel plate transport robot located downstream of the dispenser mounting robot. The steel plate transport robot places a patch steel plate 13 at a predetermined position on the steel plate 11 so as to cover the resin encapsulation section 12.

[0049] By installing the patch steel plate 13, the patch steel plate 13 becomes a lid, sealing in the resin 7 inside the resin encapsulation portion 12. In addition, the resin 7 is sandwiched between the bottom of the resin encapsulation portion 12 and the patch steel plate 13, forming a sandwich structure. Hereinafter, the member having this sandwich structure shown in FIG. 1(c) will be referred to as a sandwich structure member 15.

[0050] <Press molding process> The press-forming step S7 is a step of press-forming the sandwich structural member 15 shown in Fig. 1(c) into the shape of an automobile part. Here, as shown in Fig. 1(d), the sandwich structural member 15 is press-formed into the shape of the outer part 3 of the automobile part 1. By placing the patch steel plate 13 so as to cover the resin encapsulation portion 12, the resin 7 is encapsulated in the closed space formed by the resin encapsulation portion 12 and the patch steel plate 13, so even when pressure is applied during press molding, the resin 7 is less likely to leak out from between the steel plate 11 and the patch steel plate 13. Furthermore, because the resin 7 is in a state before it is heated and hardened, the resin layer is less likely to break during press molding.

[0051] <Welding process> As shown in FIG. 1(e), the welding step S9 is a step of welding the steel sheet 11 press-formed in the press-forming step S7 and the patch steel sheet 13 together. The part press-formed in the press forming process S7 (Fig. 1(d)) is transferred to the press exit side by a transfer device. A robot equipped with a spot welding gun is placed at the press exit side, and this spot welding gun-equipped robot spot-welds the patch steel plate 13 (patch 9) to the steel plate 11 (outer part 3) (the part marked with an X in Fig. 1(e)).

[0052] When the sandwich structural member 15 is press-formed, the resin 7 is subjected to high surface pressure and is pressed against the steel plate 11 and the patch steel plate 13, and then undergoes the heating process described below to be bonded to the steel plate 11 and the patch steel plate 13 with a predetermined adhesive strength, so the welding process S9 can be omitted. However, the automotive part 1 of this embodiment absorbs collision energy by axial crushing or bending crushing, and if the patch 9 peels off from the resin 7 during the deformation process, the collision energy absorption characteristics will decrease, so it is preferable to fix the patch steel plate 13 to the steel plate 11.

[0053] The part shown in Fig. 1(e) is transferred to an assembly line and joined with an inner part 5 to become an automotive part 1 as shown in Fig. 2 and Fig. 3. The automotive part 1 obtained by the manufacturing method of this embodiment will be specifically described below. Note that the x marks in Fig. 2 indicate spot welds.

[0054] The automotive part 1 in FIG. 2 is intended to be used in body frame parts such as front side members, side sills (rockers), and center pillars, and is a part that absorbs collision energy by bending or collapsing axially when a collision load is applied to the vehicle body.

[0055] As shown in FIG. 2, the automobile part 1 includes an outer part 3, an inner part 5, a patch 9, and a resin 7 (see FIG. 3(a)).

[0056] The outer part 3 (the hat-shaped cross-section member of the present invention) is formed by pressing a steel plate 11, and has a top plate portion 3a, a pair of vertical wall portions 3c continuing from the top plate portion 3a via punch shoulder R portions 3b, and flange portions 3d continuing from each of the vertical wall portions 3c. The top plate portion 3a, punch shoulder R portion 3b and vertical wall portion 3c of the outer part 3 are formed with a resin encapsulation portion 12 that is recessed inward.

[0057] A patch 9 is disposed on the outside of the outer part 3 so as to cover the resin encapsulation portion 12, and an end of the patch 9 is welded to the outer surface of the vertical wall portion 3c of the outer part 3. The patch 9 is formed by pressing a patch steel plate 13, and is a member that prevents the resin 7 from coming off the outer part 3 and improves the rigidity of the automobile part 1 by forming a sandwich structure.

[0058] In Figure 2, the resin encapsulation portion 12 is shown by two lines (the part covered by the patch 9 is shown by two fine dashed lines), of which the inner line indicates the outer edge of the bottom of the resin encapsulation portion 12, and the outer line indicates the upper edge of the resin encapsulation portion 12.

[0059] As shown in Fig. 3(a), resin 7 is filled in the closed space formed by the resin encapsulation portion 12 and the patch 9. A sandwich structure is formed in the portion encapsulated with resin 7, i.e., the top plate portion 3a, punch shoulder R portion 3b, and vertical wall portion 3c of the outer part 3. However, the sandwich structure of this embodiment does not simply sandwich the resin 7 between the patch 9 and the outer part 3 from above and below, but also covers the periphery of the resin 7 in the resin encapsulation portion 12 with the patch 9 and the outer part 3 to create an encapsulated state. Therefore, the peripheral edge of the resin encapsulation portion 12 needs to be in contact with the outer part 3 to form an encapsulated state, and as a result, a sandwich structure is not formed at both axial ends of the automotive part 1 (see FIG. 3(b)). Note that although FIGS. 3(a) and 3(b) show a gap between the outer part 3 and the patch 9, this is to make it easier to identify each component, and in reality, the patch 9 is in contact with the outer part 3 as described above.

[0060] The inner part 5 is a flat plate-shaped member made of steel plate, and is joined to the flange portion 3d of the outer part 3 by welding.

[0061] As described above, the automotive part 1 obtained by the manufacturing method of this embodiment has a sandwich structure in which the resin 7 is sandwiched between the outer part 3 and patch 9, which are formed from steel plates. This improves the surface rigidity of the top plate portion 3a, punch shoulder R portion 3b, and vertical wall portion 3c of the outer part 3, and prevents the steel plate from breaking during the axial crushing or bending crushing process described above, thereby demonstrating high collision energy absorption performance.

[0062] As described above, the automobile part 1 does not leak or break during the manufacturing process, so it is easy to manufacture and stably exhibits the expected collision energy absorption performance. Furthermore, since the resin 7 also functions as a vibration-damping material that absorbs vibrations, the sandwich structure improves the vibration-damping performance of the automobile part 1. Examples of the types of steel sheets used for the outer part 3, the inner part 5 and the patch 9 include cold-rolled steel sheets, hot-rolled steel sheets, stainless steel sheets, zinc-based plated steel sheets, zinc alloy-based plated steel sheets and aluminum alloy-based plated steel sheets.

[0063] The automotive part 1 manufactured using the manufacturing method of this embodiment must be treated to harden the resin 7 (heat treated if the resin 7 is a thermosetting resin) before or after assembly of the vehicle body. Hardening the resin 7 bonds the resin 7 to the outer part 3 and the resin 7 to the patch 9 with a predetermined adhesive strength. The final adhesive strength after hardening is preferably 10 MPa or more.

[0064] If the resin 7 is a thermosetting resin, it is possible to cure the resin 7 by utilizing the heating process of electrodeposition coating, which is commonly performed in automobile manufacturing. If the automobile part 1 before the heat treatment is assembled onto a vehicle body and then electrodeposition coating is performed on the vehicle body, the resin 7 of the automobile part 1 is completely cured during the heating process for drying the electrodeposition paint, which is efficient.

[0065] The method for heating the automotive component 1 is not limited to the above, and the automotive component 1 may be heated before the assembly of the vehicle body. For example, the automotive component 1 before the assembly of the vehicle body may be heated by being placed in a high-temperature furnace (oven) in which the ambient temperature is maintained constant, or the automotive component 1 before the assembly of the vehicle body may be heated by electrical heating or high-frequency induction heating.

[0066] In either case, by heat treating the automotive part 1 at a predetermined temperature for a predetermined time, the adhesive properties of the resin 7 allow it to bond to the outer part 3 and the patch 9 with a predetermined adhesive strength. The heat treatment conditions for completely curing the resin 7 are, for example, a heating temperature of 150 to 170°C and a heating time of about 15 minutes, but these heat treatment conditions vary depending on the type of resin 7, so they should be adjusted appropriately so that the adhesive strength of the resin 7 after heating reaches a predetermined value (for example, 10 MPa or more).

[0067] 2 is an example of an automobile part that can be manufactured by the manufacturing method of this embodiment, and does not limit the shape of the automobile part 1. As another example, the outer part 3 may be a member having a U-shaped cross section instead of a hat-shaped cross section.

[0068] As described above, according to this embodiment, the resin 7 is sealed in the steel plate 11 and the patch steel plate 13, so when they are press-molded into a part shape, the resin 7 does not leak into the press. Furthermore, because the resin 7 is not cured before press-molding, the resin 7 does not break during molding. Therefore, it is possible to stably manufacture an automotive part 1 that has the required collision energy absorption performance and vibration damping properties.

[0069] Furthermore, compared to the conventional manufacturing method in which the outer part 3 and the patch 9 are press-formed separately, the present embodiment allows the outer part 3 and the patch 9 to be press-formed simultaneously, thereby improving the productivity of the automotive part 1. The resin encapsulation portion 12 can also be formed simultaneously with the blanking of the steel plate 11, which does not increase the number of processes and is therefore efficient.

[0070] Furthermore, because the resin 7 is applied to the steel plate 11, which is the blank material before the outer part 3 is press-formed, the resin 7 can be applied in a uniform thickness without being restricted by the uneven surface shape of the part, as compared to when the resin 7 is applied to a part after press forming. This reduces variations in the collision energy absorption performance and vibration damping performance of the automotive part 1.

[0071] The above manufacturing method involves applying or filling the resin encapsulation portion 12 with paint-like resin 7 to fill the resin encapsulation portion 12 with resin 7, but instead of this resin filling step S1, it may also be possible to include a resin pasting step in which resin 7 molded in a sheet shape is pasted inside the resin encapsulation portion 12. When attaching the sheet-shaped resin 7, for example, laminating equipment can be used to attach the sheet-shaped resin 7 inside the resin encapsulation portion 12. At this time, it is preferable to temporarily fix the resin 7 inside the resin encapsulation portion 12 using adhesive tape or a glue. Also, when installing the patch steel plate 13, it is preferable to temporarily fix the resin 7 and the patch steel plate 13 using adhesive tape or a glue. However, if the sheet-shaped resin 7 itself has initial adhesive strength on both sides, it is not necessary to use the adhesive tape or a glue.

[0072] In the above case, if the sheet thickness of the resin 7 is thinner than the peripheral wall height (recess depth) of the resin encapsulation portion 12, the resin 7 and the patch steel plate 13 will not come into contact when the patch steel plate 13 is installed, and a sandwich structure cannot be formed. Therefore, the thickness of the resin 7 applied in the resin application process should be the same as or greater than the peripheral wall height of the resin encapsulation portion 12. However, if the sheet thickness of resin 7 greatly exceeds the height of the peripheral wall of resin encapsulation portion 12, the gap between patch steel plate 13 and steel plate 11 will become large when patch steel plate 13 is installed, and resin 7 will be more likely to protrude from the gap during press forming. Therefore, it is more preferable that the sheet thickness of resin 7 be approximately the same as the height of the peripheral wall. The thickness of the resin 7 sheet is preferably set to 0.2 mm or more and 3 mm or less, similarly to when the resin 7 is applied.

[0073] 1, the resin filling step S3 and the patch steel plate installation step S5 are performed in the same press line where the sandwich structural member 15 is press-formed into the part shape, but these steps do not necessarily have to be performed in the same press line. For example, a production line for manufacturing the sandwich structural member 15 and a press line for press-forming the sandwich structural member 15 into the part shape may be provided separately. In this case, after the steps up to the patch steel plate installation step S5 are performed in the production line for the sandwich structural member 15, the manufactured sandwich structural member 15 can be transferred to the press line by a transfer device, where the press-forming step S7 and subsequent steps are performed.

[0074] Furthermore, the welding step S9 does not necessarily have to be performed within the press line. For example, after the press forming step S7, the part shown in Fig. 1(d) may be transferred to an assembly line, and the welding step S9 may be performed when the inner part 5 is joined on the assembly line.

[0075] Furthermore, in the example of Figure 1, the resin filling process S3 and the patch steel plate installation process S5 are performed on the entry side of the press machine, but as shown in Figure 5, these processes may also be performed inside the press machine. [Example]

[0076] The effects of the manufacturing method of the present invention will be described based on specific examples. In this example, a resin encapsulation portion 12 was formed in a steel plate 11 having a tensile strength of 1470 MPa and a thickness of 1.4 mm, as shown in Fig. 6(a) or Fig. 7(a). Then, resin 7 was applied (or attached) as shown in Fig. 6(b) or Fig. 7(b). Then, a patch steel plate 13 having a tensile strength of 270 MPa and a thickness of 0.4 mm was installed as shown in Fig. 6(c) or Fig. 7(c) to form a sandwich structural member 15. The depth of the resin encapsulation portion 12 and the thickness of the resin 7 were set in the range of 0.2 to 3 mm. Note that Figure 6 shows an example in which resin 7 is applied to the entire steel plate 11 (excluding the portion to be welded after press forming) (resin / area "all" in Table 1), while Figure 7 shows an example in which resin 7 is applied only to the portion of the steel plate 11 that may become the punch shoulder R portion 3b of the outer part 3 (resin / area "shoulder" in Table 1).

[0077] The sandwich structural member 15 was press-molded into the shape of the outer part 3 shown in Fig. 2, and its press formability was evaluated. Here, the presence or absence of resin 7 protruding from the outer part 3 and patch 9 after press molding was observed.

[0078] Thereafter, the inner part 5 was welded to the press-formed outer part 3 to assemble the automobile part 1 shown in Fig. 2, and then heated at 170°C for 15 minutes. An axial crushing test was then carried out on the heated automobile part 1.

[0079] In the axial crush test, a load was applied to the automotive part 1 in the axial direction at a test speed of 17.8 m / s, and the test piece length was reduced from 200 mm to 120 mm, resulting in an axial crush deformation of 80 mm, and the load-stroke curve was measured to determine the absorbed energy, as shown in Fig. 8. In addition, the state of deformation and the presence or absence of fracture in the outer part 3 were observed using a high-speed camera. Table 1 shows the structure of each evaluation part, as well as the evaluation results of press formability and axial crushing test.

[0080] [Table 1]

[0081] In Example 1 of the invention, a 0.2 mm deep resin encapsulation section 12 was formed in a steel plate 11 within the range shown in Figure 6(a), and resin 7 was applied to a thickness of 0.2 mm inside the resin encapsulation section 12 using a dispenser. The test weight was 1.12 kg, and no resin overflowed after pressing. Furthermore, as a result of the axial crushing test, there was no fracture of the base material (outer part 3), and the absorbed energy was 12.6 kJ, resulting in an EA / weight (energy absorption per unit weight) of 11.3 kJ / kg.

[0082] In Example 2 of the present invention, a 1 mm deep resin encapsulation section 12 was molded into a steel plate 11 within the range of Figure 6(a), and a 1 mm thick sheet-like resin 7 was temporarily fixed inside the resin encapsulation section 12 with adhesive tape. The test weight was 1.16 kg, and no resin overflowed after pressing. Furthermore, as a result of the axial crushing test, there was no fracture of the base material, and the absorbed energy was 14.5 kJ, resulting in an EA / weight of 12.5 kJ / kg.

[0083] In Example 3 of the invention, a 3 mm deep resin encapsulation section 12 was formed in a steel plate 11 within the range of Figure 6(a), and resin 7 was applied to a thickness of 3 mm using a dispenser within the resin encapsulation section 12. The test weight was 1.27 kg, and no resin overflowed after pressing. Furthermore, as a result of the axial crushing test, there was no fracture of the base material, and the absorbed energy was 17.7 kJ, with EA / weight (energy absorption per unit weight) being 13.9 kJ / kg.

[0084] In Example 4 of the invention, a 1 mm deep resin encapsulation section 12 was formed in a steel plate 11 within the range of Figure 7(a), and resin 7 was applied to a thickness of 1 mm inside the resin encapsulation section 12 using a dispenser. The test weight was 1.16 kg, and no resin overflowed after pressing. Furthermore, as a result of the axial crushing test, there was no fracture of the base material, and the absorbed energy was 14.5 kJ, with EA / weight (energy absorption per unit weight) being 12.5 kJ / kg.

[0085] Comparative Example 1 is an example without resin 7. In the case of Comparative Example 1 without a sandwich structure, the base material fracture was observed as a result of the axial crushing test. In addition, the absorbed energy was 10 kJ, and EA / weight was 9.0 kJ / kg.

[0086] Comparative Example 2 is an example in which resin 7 was applied to the range shown in Figure 6(a) without forming resin encapsulation portion 12 on steel plate 11. In the case of Comparative Example 2 without resin encapsulation portion 12, resin overflow was confirmed after pressing. Furthermore, no increase in absorbed energy was observed in Comparative Example 2 compared to Comparative Example 1.

[0087] As described above, no leakage (extrusion) of the resin 7 occurred during press molding in any of the invention examples 1 to 4. Furthermore, all of the invention examples 1 to 4 exhibited higher energy absorption performance than the comparative example. [Explanation of symbols]

[0088] 1. Automotive parts 3 Outer parts 3a Top plate 3b Punch shoulder R part 3c Vertical wall section 3d flange part 5 Inner parts 7. Resin 9 Patch 11 Steel plate 12 Resin encapsulation part 13 Patch steel plate 15 Sandwich structural members

Claims

1. a resin encapsulation portion forming step of forming a resin encapsulation portion for encapsulating resin in the steel plate; a resin filling step of applying or filling a resin into the resin encapsulation portion to fill the resin encapsulation portion with the resin; a patch steel plate installation process in which a patch steel plate is installed on the steel plate so as to cover the resin encapsulation portion; and a press-molding process for press-molding a sandwich structural member having a sandwich structure in which the resin is sandwiched between the steel plate and the patch steel plate into the shape of an automobile part.

2. 2. The method for manufacturing an automobile part according to claim 1, wherein the viscosity of the resin is 50 Pa·s or more and 200 Pa·s or less.

3. The resin encapsulation portion is a recess formed by recessing the steel plate, 3. The method for manufacturing an automobile part according to claim 1, wherein the depth of the recess is 0.2 mm or more and 3 mm or less.

4. a resin encapsulation portion forming step of forming a resin encapsulation portion for encapsulating resin in the steel plate; a resin pasting step of pasting a sheet-shaped resin formed to a thickness equal to or greater than the height of the peripheral wall of the resin encapsulation portion into the resin encapsulation portion; a patch steel plate installation process in which a patch steel plate is installed on the steel plate so as to cover the resin encapsulation portion; a press-molding process for press-molding a sandwich structural member having a sandwich structure in which the resin is sandwiched between the steel plate and the patch steel plate into the shape of an automobile part.

5. 5. The method for manufacturing an automobile part according to claim 4, wherein the resin sheet has a thickness of 0.2 mm or more and 3 mm or less.

6. 5. The method for manufacturing an automobile part according to claim 1, further comprising a welding step of welding the steel plate press-formed in the press-forming step to the patch steel plate.

7. 5. The method for manufacturing an automobile part according to claim 1, wherein the resin is a thermosetting rubber-modified epoxy resin.

8. a hat-shaped or U-shaped cross-section member having a top plate portion and a pair of vertical wall portions continuing from the top plate portion via a punch shoulder R portion; a concave resin encapsulation portion formed at least in the punch shoulder R portion of the hat-shaped cross section member or the U-shaped cross section member; a patch member disposed across the top plate portion and covering the resin encapsulation portion; a resin sealed in a closed space formed by the resin sealing portion and the patch member; The automotive part is characterized in that the resin is adhered to the hat-shaped cross section member or the U-shaped cross section member and the patch member with an adhesive strength of 10 MPa or more after being heated.

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