Manufacturing method of automobile parts and automobile parts

Abstract

To provide a method for manufacturing an automobile part having a sandwich structure in which resin is sandwiched between steel plates at low cost, while preventing resin leakage and resin breakage during manufacturing. Also provided is an automobile part that can be manufactured at low cost and prevents resin leakage and resin breakage during manufacturing. [Solution] The manufacturing method for automotive parts according to the present invention is characterized by comprising a resin encapsulation portion molding process S1 in which a resin encapsulation portion 12 for encapsulating resin 7 in a steel plate 11 is molded, a resin filling process S3 in which resin encapsulation portion 12 is applied or filled with resin 7 to fill the resin encapsulation portion 12 with resin 7, a patch steel plate installation process S5 in which a patch steel plate 13 is installed on the steel plate 11 so as to cover the resin encapsulation portion 12, and a press molding process S7 in which a sandwich structure member 15 having a sandwich structure in which resin 7 is sandwiched between the steel plate 11 and the patch steel plate 13 is press molded into the part shape of the automotive part.

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] The front side member, which is a structural component of an automobile, is a long part installed at the front of the vehicle in the longitudinal direction of the vehicle, and absorbs the collision energy during a vehicle collision by undergoing axial crushing deformation. In addition, the side sill (rocker) and center pillar are parts that absorb collision energy by bending when a collision load is input from the side of the vehicle body. By absorbing the collision energy during a vehicle collision, these parts suppress cabin deformation during the collision and protect the occupants.

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

[0004] Patent Document 1 discloses an automobile collision energy absorption part that absorbs collision energy by axially collapsing when a collision load is input from the front or rear of the vehicle body. The automobile collision energy absorption part of Patent Document 1 can also improve vibration damping by absorbing vibrations from the automobile engine and vibrations input to the vehicle body from each direction while the vehicle 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 anti-detachment member with a U-shaped cross-section is disposed so as to cover the surface of the resin. By disposing 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 in an accordion-like manner in the axial direction, or bending crushing, in which the part is bent perpendicular to the axial direction, so that the bending radius during deformation is enlarged, 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 crush or bending crush, improving collision energy absorption performance while also achieving weight reduction. Many methods have been proposed for manufacturing components 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 sticking resin to the inner surface of a cylindrical member, arranging a separation prevention member to cover the resin, joining the separation prevention member to the cylindrical member, and then heat-treating these members. Patent Document 1 also describes a method for applying or sticking resin to the separation prevention member, abutting the resin against the inner surface of the cylindrical member and joining the separation prevention member to the inner surface of the cylindrical member, and 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 epoxy resin) is foamed and filled into the space between the outer panel and the reinforcement, and describes the following method for assembling the frame structure. First, a sheet of unfoamed filler is attached to the surface of the reinforcement facing the outer panel. The reinforcement with the attached filler is then attached to the outer panel, and the flanges of both are joined by spot welding. After the assembly of the entire vehicle body is completed, the vehicle body is electrocoated, and the drying heat used in this process causes the filler to foam and harden.

[0008] Furthermore, Patent Document 4 describes the following method as a manufacturing method for a partial composite vibration-damping part for automobiles to prevent automobile noise. First, a resin having vibration-damping properties is applied to a restraining plate made of a steel plate or the like, and the solvent in the paint on the restraining plate is evaporated in a drying oven. After that, the restraining plate is attached to a predetermined position of a steel plate that is to be press-formed to form the vehicle body, and heated and pressed. Then, the steel plate to which the restraining plate is partially bonded is press-formed to produce a composite vibration-damping part for an automobile.

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

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

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

[0012] First, in the manufacturing method of Patent Document 3, since the filler is foamed and 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. Therefore, there is a problem that the parts that show the effect of vibration damping and rigidity cannot be reinforced arbitrarily.

[0013] In contrast, the manufacturing method of Patent Document 1 involves applying or attaching resin to a tubular member and then attaching an anti-detachment member to cover the resin, making it possible to place resin in any location where rigidity needs to be increased (for example, the punch shoulder R portion of the outer part that constitutes 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 parts.

[0014] In addition, 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 the part where the surface of the member has an uneven shape. Therefore, there is a problem that the part to which the resin is applied or attached is limited to a part having 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 constraint plate is partially adhesively joined to the steel plate (blank), these are integrally press formed, so no additional press forming process is required. However, in the manufacturing method of Patent Document 4, the resin-coated restraining plate is attached to a steel plate (blank), and then heated and pressed together before being press-molded, so the resin may be completely cured by heating. If the resin is completely cured, the ductility of the resin decreases, and there is a risk that the resin layer may break during press molding. Furthermore, in the case of the above-mentioned collision energy absorbing parts, if the resin layer is broken, the breakage of the main body member during axial or bending crush cannot be sufficiently prevented, so that the expected collision energy absorbing performance cannot be obtained. Also, there is a risk of the vibration damping performance being reduced. On the other hand, in the manufacturing method of Patent Document 5, there is a risk that the resin may leak from gaps between overlapping surfaces of the metal sheets due to pressure during press molding, contaminating the inside of the press machine and impairing the surface quality of the press-molded product.

[0016] The present invention has been made to solve the above-mentioned problems, and has an object to provide a method for manufacturing automobile parts, which 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 which can be manufactured at low cost, which is capable of preventing resin leakage and resin breakage during manufacturing, and which has the expected performance of absorbing collision energy. [Means for solving the problem]

[0017] The inventors have thoroughly investigated 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 in a steel plate before press molding and then press molded 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 is not performed before press molding 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 that has been adjusted to a high viscosity in advance is applied, it is possible to prevent the resin from leaking during press molding without the need for 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 discovered that the above problems can be solved by providing an automobile part with a structure in which resin is sealed therein. The present invention has been made based on such findings, 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 a 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) Moreover, 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 above-described (1) or (2), 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 the 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 molded to a thickness equal to or greater than a peripheral wall height 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 in which a sandwich structural member having a sandwich structure in which the resin is sandwiched between the steel plate and the patch steel plate is press-molded into the shape of an automobile part.

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

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

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

[0027] (8) The present invention also provides an automobile part, comprising: 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. Effect of the Invention

[0028] In the present invention, by forming a resin encapsulation portion in the steel sheet before it is molded into an automobile 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 molding, and prevents the inside of the press mold from being contaminated with resin, even if heat treatment is not performed before press molding. Furthermore, since the present invention does not involve heat curing of the resin prior to press molding, the resin does not break during press molding, and the collision energy absorbing performance of the manufactured automobile parts does not decrease. Furthermore, since the sandwich structure is formed and then pressed into the part shape, the main body part and the patch can be press-molded at the same time, which reduces the number of steps compared to the conventional example in which each part was press-molded individually, making it possible to manufacture automotive parts with a sandwich structure at low cost. [Brief description of the drawings]

[0029] [Figure 1] 1 is an explanatory diagram of a manufacturing method for an automobile part according to an embodiment of the present invention; [Diagram 2] 2 is an external view of an automobile part obtained by the manufacturing method of FIG. 1. [Diagram 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. [Diagram 5] FIG. 4 is an explanatory diagram of another aspect of the manufacturing method for 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. 2 is a diagram showing an example of the range of application (attachment) of resin according to the embodiment (part 2). [Figure 8] FIG. 4 is an explanatory diagram of an axial crushing test according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] The 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. Although the present invention is not limited to the shape of the automobile part, as an example, in this embodiment, a case of manufacturing an automobile part 1 (see FIG. 2) having a hat-shaped cross section with a sandwich structure will be described.

[0031] The manufacturing method for an automobile part in this embodiment includes a resin encapsulation part 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, as shown in Fig. 1. By carrying out the above-mentioned resin encapsulation part molding step S1 to welding step S9, a part having a hat-shaped cross section with a sandwich structure, i.e., the outer part 3 in Fig. 2, can be manufactured. Figs. 1(a) to 1(e) are schematic diagrams showing the manufacturing process of the outer part 3 in each step. After the welding process S9, in an assembly process performed on an assembly line, an inner part 5 (see FIGS. 2 and 3) is joined to the outer part 3 manufactured in FIG. 1(e), thereby forming the automobile 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 in FIG. 2, since the resin 7 is bonded to the punch shoulder R portion 3b of the outer part 3 during axial crushing or bending crushing, the collision energy absorption performance of the automotive part 1 can be improved, so it is advisable to form a recess so as to include at least the portion of the steel plate 11 that corresponds to the punch shoulder R portion 3b. In this case, as shown in FIG. 6(a), a recess may be formed over the entire part except for the welded parts with the patch 9 and the inner part 5, or as shown in FIG. 7(a), a recess may be formed only in the part corresponding to the punch shoulder R part 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 the resin 7 in the recess with a uniform thickness. On the other hand, if the depth of the recess is deeper than 3 mm, the resin becomes thick, which increases the cost and makes it difficult to mold the 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 carried out simultaneously with a blanking step in which the steel plate 11 is extracted from a material. In a typical blanking process, the material is sandwiched and fixed between a metal mold consisting of an upper mold and a lower mold, and then cut into a predetermined blank shape. By providing a resin encapsulation molding section for molding the resin encapsulation section 12 on the molding surfaces of the upper mold and the lower mold, the resin encapsulation section 12 can be molded at the same time as the steel sheet 11 is blanked. 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 encapsulation portion 12 with the resin 7, as shown in FIG. 1(b). The steel sheet 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, for example, a robot equipped with a dispenser (a device for dispensing a fixed amount 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 the resin 7 is not limited to the above, and for example, the resin 7 may be applied by spraying with a spray nozzle (electrostatic coating), or the resin 7 may be applied using a brush, etc. However, the method using a dispenser is more preferable because it allows accurate supply of a fixed amount of the resin 7 required to fill the 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 during the heating process for curing the electrodeposition coating of the vehicle body. Examples of thermosetting resins include epoxy, urethane, ester, phenol, melamine, and urea resins. In particular, thermosetting rubber-modified epoxy resins are preferable because they have high ductility after being cured by heating, and therefore the cured resin 7 is less likely to break.

[0040] The resin 7 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 elastic modulus also increases. On the other hand, as shown by curve B, the ductility of the resin decreases inversely with the increase in the elastic modulus. In other words, the ductility of the resin decreases as the viscosity of the resin increases. 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 standpoints.

[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. In this embodiment, the specific details will be described later, but the patch steel plate 13 installed in the patch steel plate installation process S5 serves as a lid to seal the resin 7 in the resin sealing section 12 (see FIG. 1(c)). By sealing the resin 7 between the steel plate 11 and the patch steel plate 13 in this manner, even when the member in FIG. 1(c) is press-molded, the resin is less likely to leak into the press.

[0043] 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 out 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 out during press molding, it is not preferable because it may soil the press machine or make it impossible to ensure a predetermined resin thickness. Therefore, it is preferable that resin 7 has a certain level of viscosity that 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 Fig. 4. Dashed arrow i indicates that if the viscosity of resin 7 is in the region to the right of dashed arrow i, resin leakage during press molding can be prevented. 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 so that the thickness is uniform 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 Fig. 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 cannot follow the deformation during press molding, and the resin layer may break. If the resin layer breaks, the collision energy absorption performance of the automobile part 1 decreases, as described above, which is not preferable. Therefore, it is preferable that the resin 7 has a certain level of ductility that does not break even if it is deformed during press forming. The ductility range of the resin 7 that allows the resin 7 to follow the deformation of the steel sheet during press forming is shown by the dashed arrow iii in Fig. 4. The dashed arrow iii indicates that if the ductility of the resin 7 is in the region above the dashed arrow iii, it is possible to prevent the resin from breaking during press forming. That is, from the viewpoint of preventing resin breakage, it is preferable that the ductility of 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, it is necessary to make the viscosity of resin 7 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 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. In addition, since the shape of curve B changes depending on the properties of the resin, d may be larger than b depending on the properties of the resin. In this case, the appropriate viscosity range of resin 7 is equal to or larger than a and equal to or smaller than b.

[0047] In consideration of the above, in this embodiment, the suitable viscosity range of resin 7 in resin filling step S3 is set to 50 Pa s to 200 Pa s. By adjusting the viscosity of resin 7 within the above 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 having the resin encapsulation portion 12 filled with resin 7, as shown in Fig. 1(c). Here, the patch steel plate 13 is a blank material before the patch 9 (see Fig. 2) of the automotive part 1 is press-formed. The steel plate 11 with the resin 7 filled in the resin encapsulation portion 12 is transferred by a transfer device to a steel plate transport robot arranged 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 portion 12.

[0049] By installing the patch steel plate 13, the patch steel plate 13 becomes a lid, and the resin 7 in the resin encapsulation portion 12 is encapsulated. 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.

[0050] <Press molding process> The press forming process S7 is a process for 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 that even if pressure is applied during press molding, the resin 7 is unlikely to leak out from between the steel plate 11 and the patch steel plate 13. In addition, since the resin 7 is in a state before being heated and hardened, the resin layer is unlikely to break during press molding.

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

[0052] In addition, 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, so that it is bonded to the steel plate 11 and the patch steel plate 13 with a predetermined adhesive strength, and therefore 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 in Fig. 1(e) is transferred to an assembly line, and an inner part 5 is joined to produce an automobile part 1 as shown in Fig. 2 and Fig. 3. The automobile 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 automobile 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 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] 3(a), the resin 7 is filled in the closed space formed by the resin filling portion 12 and the patch 9. A sandwich structure is formed in the portion filled with the resin 7, i.e., the top plate portion 3a of the outer part 3, the punch shoulder R portion 3b, and the vertical wall portion 3c. However, the sandwich structure of this embodiment is not one in which the resin 7 is simply sandwiched between the patch 9 and the outer part 3 from above and below, but one in which the periphery of the resin encapsulation portion 12 is also covered with the patch 9 and the outer part 3 to encapsulate it. For this reason, the peripheral portion 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 in FIG. 3(a) and FIG. 3(b), a gap is depicted between the outer part 3 and the patch 9, but this is for the purpose of making it easier to identify each member, 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 member made of a steel plate, and is joined to the flange portion 3d of the outer part 3 by welding.

[0061] As described above, the automobile 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 the patch 9, which are made of steel plate. 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 in the process of axial crush or bending crush as described above, thereby exhibiting high collision energy absorption performance.

[0062] As described above, the automobile part 1 does not leak resin or break during the manufacturing process, so it has good manufacturability and stably exhibits the expected collision energy absorbing performance. Furthermore, since the resin 7 also functions as a vibration-damping material that absorbs vibrations, the above 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] Automotive part 1 manufactured using the manufacturing method of this embodiment needs to be treated to harden resin 7 (heat treated if resin 7 is a thermosetting resin) before or after assembly of the vehicle body. Hardening resin 7 bonds resin 7 to outer part 3 and resin 7 to patch 9 with a predetermined adhesive strength. The final adhesive strength after hardening is preferably 10 MPa or more.

[0064] When the resin 7 is a thermosetting resin, it is possible to harden 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 to a vehicle body and the vehicle body is subjected to electrodeposition coating, the resin 7 of the automobile part 1 is completely hardened during the heating process for drying the electrodeposition paint, which is efficient.

[0065] The method of heating the automobile part 1 is not limited to the above, and may be performed before the assembly of the vehicle body. For example, the automobile part 1 before the assembly of the vehicle body may be heated by being placed in a high-temperature furnace (oven) in which the atmospheric temperature is kept constant, or the automobile part 1 before the assembly of the vehicle body may be heated by using 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 resin 7 adheres to the outer part 3 and the patch 9 with a predetermined adhesive strength due to the adhesive ability of the resin itself. Note that 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 since these heat treatment conditions differ depending on the type of resin 7, it is advisable to adjust them appropriately so that the adhesive strength of the resin 7 after heating becomes a predetermined value (for example, 10 MPa or more).

[0067] 2 is one 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 filled into the steel plate 11 and the patch steel plate 13, so that when these are press-molded into a part shape, the resin 7 does not leak into the press. In addition, since the resin 7 is not cured before press molding, the resin 7 does not break during molding. Therefore, the automobile part 1 having the required collision energy absorption performance and vibration damping properties can be stably manufactured.

[0069] Furthermore, compared with 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 molding of the resin encapsulation portion 12 can also be performed simultaneously with the blanking of the steel plate 11, which does not increase the number of steps and is efficient.

[0070] In addition, since 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 the case where the resin 7 is applied to a part after press forming. This makes it possible to reduce variations in the collision energy absorption performance and vibration damping performance of the automotive part 1.

[0071] The above-described 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, a resin pasting step may be provided in which resin 7 molded into a sheet shape is pasted inside the resin encapsulation portion 12. When attaching the sheet-like resin 7, for example, lamination equipment can be used to attach the sheet-like resin 7 inside the resin encapsulation portion 12. At that time, it is preferable to temporarily fix the resin 7 inside the resin encapsulation portion 12 using an 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 an adhesive tape or a glue. However, if the sheet-like resin 7 itself has initial adhesion on both sides, it is not necessary to use the adhesive tape or the 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 is set to be the same as or greater than the peripheral wall height of the resin encapsulation portion 12. However, if the sheet thickness of the resin 7 greatly exceeds the peripheral wall height of the resin encapsulation portion 12, the gap between the patch steel plate 13 and the steel plate 11 becomes large when the patch steel plate 13 is installed, and the resin 7 is likely to protrude from the gap during press molding. Therefore, it is more preferable that the sheet thickness of the resin 7 is approximately the same as the peripheral wall height. The thickness of the sheet of resin 7 is preferably set to 0.2 mm or more and 3 mm or less, similarly to the case where resin 7 is applied.

[0073] 1, the resin filling step S3 and the patch steel plate installation step S5 are performed in a press line in which the sandwich structural member 15 is press-molded 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-molding the sandwich structural member 15 into the part shape may be provided separately. In that 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 may be transferred to the press line by a transfer device, where the press molding step S7 and subsequent steps are performed.

[0074] In addition, the welding step S9 does not necessarily have to be performed in 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 FIG. 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 FIG. 5, these processes may be performed inside the press machine. EXAMPLES

[0076] The effects of the manufacturing method of the present invention will now be described based on specific examples. In this embodiment, a resin encapsulation portion 12 was formed on 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). After that, 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 structure 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 part shape of the outer part 3 shown in Fig. 2, and its press moldability was evaluated. Here, the presence or absence of protrusion of the resin 7 from the outer part 3 and the 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 the automobile part 1 was heated at 170°C for 15 minutes. An axial crushing test was then performed 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 changed from 200 mm to 120 mm, causing 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 deformation state and the presence or absence of fracture in the outer part 3 were observed using a high-speed camera. Table 1 shows the composition of each evaluation part, as well as the evaluation results of press formability and axial crush test.

[0080] [Table 1]

[0081] In Example 1, a resin encapsulation portion 12 of 0.2 mm depth was formed in a steel plate 11 in the range of Fig. 6(a), and resin 7 was applied to the resin encapsulation portion 12 with a thickness of 0.2 mm using a dispenser. The test weight was 1.12 kg, and no resin overflowed after pressing. In addition, the axial crush test showed no fracture of the base material (outer part 3), and the absorbed energy was 12.6 kJ, with EA / weight (energy absorption per unit weight) being 11.3 kJ / kg.

[0082] In Example 2, a 1 mm deep resin encapsulation portion 12 was formed in a steel plate 11 in the range of Fig. 6(a), and a 1 mm thick sheet-like resin 7 was temporarily fixed in the resin encapsulation portion 12 with adhesive tape. The test weight was 1.16 kg, and there was no resin overflow after pressing. In addition, the axial crush test resulted in no base material fracture, and the absorbed energy was 14.5 kJ, with EA / weight being 12.5 kJ / kg.

[0083] In Example 3, a resin encapsulation portion 12 with a depth of 3 mm was formed in a steel plate 11 in the range of Fig. 6(a), and resin 7 was applied to the resin encapsulation portion 12 with a thickness of 3 mm using a dispenser. The test weight was 1.27 kg, and no resin overflowed after pressing. In addition, the axial crush test resulted in no breakage 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, a resin encapsulation portion 12 with a depth of 1 mm was formed in a steel plate 11 in the range of Fig. 7(a), and resin 7 was applied to the resin encapsulation portion 12 with a thickness of 1 mm using a dispenser. The test weight was 1.16 kg, and no resin overflowed after pressing. In addition, the axial crush test resulted in no breakage 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 was fractured 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 the resin 7 is applied to the range of FIG. 6(a) without forming the resin encapsulation portion 12 on the steel plate 11. In the case of Comparative Example 2 without the resin encapsulation portion 12, overflow of the resin was confirmed after pressing. Furthermore, in Comparative Example 2, no increase in absorbed energy was observed compared to Comparative Example 1.

[0087] As described above, no leakage (protrusion) 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 13 Patch Steel Plate 15 Sandwich structural members

Claims

1. a resin encapsulation portion molding step of molding 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 molding step of molding a resin encapsulation portion for encapsulating resin in the steel plate; a resin pasting step of pasting a sheet-shaped resin molded to a thickness equal to or greater than a peripheral wall height 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.

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.

Images