Automobile component production method and automobile component

Abstract

An automobile component production method according to the present invention comprises: a resin encapsulation portion molding step S1 for molding a resin encapsulation portion 12 which is for encapsulating a resin 7 in a steel sheet 11; a resin filling step S3 for applying or filling the resin 7 to / into the resin encapsulation portion 12 to fill the inside of the resin encapsulation portion 12 with the resin 7; a patch steel sheet installation step S5 for installing, to the steel sheet 11, a patch steel sheet 13 in such a manner as to cover the resin encapsulation portion 12; and a press molding step S7 for press molding, into the shape of an automobile component, a sandwich structural member 15 that has a sandwich structure in which the resin 7 is sandwiched between the steel sheet 11 and the patch steel sheet 13.

Description

Manufacturing method of automobile parts and automobile parts

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

[0002] Front side members, which are body frame parts of an automobile, are long parts installed at the front of the vehicle in the longitudinal direction of the vehicle and absorb collision energy during a vehicle collision by undergoing axial crush deformation. Side sills (lockers) and center pillars also absorb collision energy by bending when a crash load is applied 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 vehicle collision energy, and therefore 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 stiffness 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 applied to the front or rear of the vehicle body. The automobile collision energy absorption component of Patent Document 1 can also improve vibration-damping properties by absorbing vibrations from the automobile engine and vibrations applied to the vehicle body from various directions while the vehicle is running. Patent Document 2 also discloses a vehicle body frame component that absorbs collision energy by bending when a collision load is applied to the side of the vehicle body.

[0005] In both of the components disclosed in Patent Documents 1 and 2, a resin is applied or affixed to the inner surface of a metal main body member (tubular member, hat-shaped cross-section member, or U-shaped member), and a metal separation prevention member with a U-shaped cross-section is disposed to cover the surface of the resin. By disposing the 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 a bellows-shaped manner along the axial direction, or during bending crushing, in which the part is bent perpendicular to the axial direction. 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 components disclosed in Patent Documents 1 and 2 have a sandwich structure in which resin is sandwiched between a metal main body member and a metal separation prevention member, thereby preventing the main body member from breaking during axial crushing or bending crushing, improving collision energy absorption performance, and simultaneously 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 a 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 a 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 vehicle frame structure (center pillar) in which a space between an outer panel and a reinforcement is filled with a foamed filler material (such as an epoxy resin), and describes the following method for assembling the frame structure. First, a sheet of unfoamed filler material is attached and set on the surface of the reinforcement facing the outer panel. Then, the reinforcement with the attached filler material is set on the outer panel, and the flange portions of both are joined by spot welding. Then, after completing the assembly of the entire vehicle body, the vehicle body is subjected to electrodeposition coating, and the dry heat generated during this process causes the filler material to undergo thermosetting foaming.

[0008] Furthermore, Patent Document 4 describes the following method for manufacturing 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 furnace. Then, the restraining plate is attached to a predetermined position of a steel plate that will form the vehicle body before press-forming, and heated and pressure-bonded. Then, the steel plate to which the restraining plate has been partially adhesively bonded is press-formed to manufacture a partial composite vibration-damping part for automobiles.

[0009] Furthermore, Patent Document 5 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 hardening the resin adhesive after the press-molding step.

[0010] Japanese Patent Application Laid-Open No. 2020-100183 Japanese Patent Application Laid-Open No. 2020-117039 Japanese Patent Application Laid-Open No. 2001-048054 Japanese Patent Application Laid-Open No. 11-141005 Japanese Patent Application Laid-Open No. 2020-183078

[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 a closed sectional space formed in an existing part such as the outer panel of the center pillar and the reinforcement, the locations where the resin can be placed are limited, and therefore it is not possible to arbitrarily reinforce the parts that are effective in terms of vibration damping and rigidity.

[0013] In contrast, the manufacturing method of Patent Document 1 applies or attaches resin to a tubular member and then attaches a separation-preventing member to cover the resin, allowing resin to be placed in any location where increased rigidity is desired (for example, the punch shoulder R portion of the outer part that constitutes the tubular member). However, this manufacturing method requires molding the separation-preventing member separately from molding the tubular member, which increases the number of processes. Furthermore, the process of applying or attaching resin to the molded tubular member and the process of attaching the molded separation-preventing 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 a roughness shape, and therefore the portion to which the resin is applied or attached is limited to a portion having a relatively smooth surface with few roughness.

[0015] In contrast, the manufacturing methods of Patent Documents 4 and 5 apply resin to a steel plate (resin constraint plate) before press-forming, so they are less subject to limitations due to the surface irregularities of the resin-coated area after press-forming. Furthermore, the constraining plate is partially adhesively bonded to the steel plate (blank), and then the two are integrally press-formed, eliminating the need for an additional press-forming process. However, in the manufacturing method of Patent Document 4, the resin-coated constraining plate is attached to the steel plate (blank), heated and pressure-bonded, and then press-formed. This can lead to the resin completely curing due to heating. If the resin completely hardens, its ductility decreases, potentially resulting in fracture of the resin layer during press-forming. Furthermore, in the case of a crash energy absorption component such as the one described above, fracture of the main body member during axial or bending crushing cannot be sufficiently prevented, failing to achieve the expected crash energy absorption performance. Furthermore, vibration damping may also be impaired. On the other hand, the manufacturing method of Patent Document 5 involves the risk of resin leaking from gaps between the overlapping surfaces of the metal plates due to the pressure applied during press-forming, contaminating the inside of the press and impairing the surface quality of the press-formed product.

[0016] The present invention has been made to solve the above problems, and its object is to provide a method for manufacturing an automobile part that can manufacture 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. 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.

[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 on steel sheets before press-forming and then press-formed into a part shape. If the resin is heated and completely cured before press-forming, as in the manufacturing method of Patent Document 4, there is a risk of the resin breaking during press-forming. On the other hand, if heating before press-forming is not performed, as in the manufacturing method of Patent Document 5, the resin leaks out from between the steel sheets due to the pressure applied during press-forming, making it impossible to ensure the required resin thickness. Furthermore, the leaked resin may contaminate the inside of the press mold, potentially 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 discovered that the above problems can be solved by providing a structure in which a resin is sealed in an automobile part. The present invention is based on this discovery and specifically comprises the following configurations.

[0020] The manufacturing method for an automotive part according to the first aspect of the present invention includes a resin encapsulation portion molding process for molding a resin encapsulation portion for encapsulating resin in a steel plate; a resin filling process for applying or filling resin into the resin encapsulation portion to fill the resin encapsulation portion with resin; a patch steel plate installation process for installing a patch steel plate 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 automotive part.

[0021] The viscosity of the resin is preferably 50 Pa·s or more and 200 Pa·s or less.

[0022] The resin-encapsulated portion is a recess formed by indenting the steel plate, and the depth of the recess may be 0.2 mm or more and 3 mm or less.

[0023] A manufacturing method for an automotive part according to a second aspect of the present invention includes a resin encapsulation portion molding process for molding a resin encapsulation portion for encapsulating resin in a steel plate; a resin attachment process for attaching sheet-shaped resin shaped to a thickness equal to or greater than the peripheral wall height of the resin encapsulation portion into the resin encapsulation portion; a patch steel plate installation process for installing a patch steel plate on the steel plate so as to cover the resin encapsulation portion; and a press molding process for press-molding a sandwich structure 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 automotive part.

[0024] The thickness of the resin sheet is preferably 0.2 mm or more and 3 mm or less.

[0025] The method may further include a welding step of welding the steel plate press-formed in the press-forming step to the patch steel plate.

[0026] The resin is preferably a thermosetting rubber-modified epoxy resin.

[0027] The automotive part of the present invention comprises 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 in at least the punch shoulder R portion of the hat-shaped cross-section member or the U-shaped cross-section member; a patch member arranged to straddle the top plate portion and cover the resin encapsulation portion; and resin encapsulated in a closed space formed by the resin encapsulation portion and the patch member, wherein 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.

[0028] In the present invention, a resin encapsulation portion is formed in the steel sheet before it is molded into an automotive part. This allows the steel sheet and the patch steel sheet to form a closed space, and resin can be encapsulated within this closed space. This prevents resin leakage during press molding, even without heat treatment before press molding, and prevents resin contamination inside the press mold. Furthermore, since the resin is not thermoset before press molding, the resin does not break during press molding, and the crash energy absorption performance of the manufactured automotive part is not reduced. Furthermore, since the sandwich structure is formed and then press molded into the part shape, the main part and the patch can be press molded simultaneously. This reduces the number of processes compared to conventional methods in which each part was press molded individually, allowing for low-cost production of sandwich-structured automotive parts.

[0029] FIG. 1 is an explanatory diagram of a manufacturing method for an automotive part according to an embodiment. FIG. 2 is an external view of an automotive part obtained by the manufacturing method of FIG. 1. FIG. 3(a) is a cross-sectional view of the automotive part of FIG. 2 cut along dashed line A, and FIG. 3(b) is a cross-sectional view of the automotive part of FIG. 2 cut along dashed line B. FIG. 4 is a graph conceptually showing the relationship between the viscosity coefficient, elastic coefficient, and ductility of a resin. FIG. 5 is an explanatory diagram of another aspect of a manufacturing method for an automotive part according to an embodiment. FIG. 6 is a diagram showing an example of a resin application (application) range according to an example (part 1). FIG. 7 is a diagram showing an example of a resin application (application) range according to an example (part 2). FIG. 8 is an explanatory diagram of an axial crushing test according to an example.

[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. Although the present invention is not limited to a specific shape of the automobile part, as an example, in this embodiment, a manufacturing method for 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 manufacturing method for an automotive part in this embodiment includes a resin encapsulation 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 molding step S1 through 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) through 1(e) schematically show the manufacturing process for the outer part 3 at each step. After the welding step S9, an inner part 5 (see FIGS. 2 and 3) is joined to the outer part 3 manufactured in FIG. 1(e) in an assembly process performed on an assembly line, thereby manufacturing the automotive part 1 shown in FIG. 2.

[0032] 1( a), the resin encapsulation portion molding step S1 is a step of molding a resin encapsulation portion 12 for encapsulating the resin 7 in a steel plate 11, which is a blank material (blank) before molding the outer part 3. In this embodiment, the resin encapsulation portion 12 is formed by recessing the steel plate 11 to form a recess.

[0033] Since the recess is filled with resin 7, it is desirable to set the area where the recess is formed so as to include a portion that is effective in improving the collision energy absorption performance of the automotive part 1 and a portion that is effective in improving 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, thereby improving the collision energy absorption performance of the automotive part 1. Therefore, it is desirable to form the 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, the recess may be formed over the entire steel plate 11 except for the welded portion with the patch 9 or the inner part 5, as shown in Figure 6(a), or it may be formed only in the portion that corresponds to the punch shoulder R portion 3b, as shown in Figure 7(a).

[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. Furthermore, if the depth of the recess is deeper than 3 mm, the resin becomes thicker, which increases costs and makes molding the resin encapsulation portion 12 difficult. Since the shape of the resin encapsulation portion 12 corresponds to the shape of the resin 7 in the final manufactured automotive part 1, by setting the depth of the resin encapsulation portion 12 to 0.2 mm or more and 3 mm or less, the thickness of the resin 7 in the automotive part 1 also becomes 0.2 mm or more and 3 mm or less.

[0035] The resin encapsulation portion molding process S1 can be performed simultaneously with the blanking process in which the steel plate 11 is extracted from the raw material. In a typical blanking process, the raw 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 portion molding section for molding the resin encapsulation portion 12 on the molding surfaces of the upper die and lower die, the resin encapsulation portion 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, so it can be molded even with a blanking machine with 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 Step> As shown in FIG. 1( b), the resin filling step S3 is a step of applying or filling the resin encapsulation portion 12 with resin 7, thereby filling the resin encapsulation portion 12 with the resin 7. 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 suction bar feeder or a conveyor. On the entry side of the press machine in the press line, a robot equipped with, for example, a dispenser (a device for discharging a fixed quantity of liquid) is disposed. This dispenser-equipped robot applies the resin 7 into the resin encapsulation portion 12, thereby filling the resin encapsulation portion 12 with the 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 painting), or the resin 7 may be applied using a brush or the like. However, the method using a dispenser is more preferable because it allows for accurate supply of the amount of 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 preferred as the type of resin 7. Using a thermosetting resin is efficient because the resin 7 can be cured during the heating process for curing the electrodeposition coating on the vehicle body. Examples of thermosetting resins include epoxy resins, urethane resins, ester resins, phenolic resins, melamine resins, and urea resins. In particular, thermosetting rubber-modified epoxy resins are preferred because they have high ductility after heat curing, making the cured resin 7 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] Figure 4 is a graph conceptually showing the relationship between the viscosity of a resin and its ductility and modulus of elasticity. 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, taking into account the properties of the resin described above, the inventors investigated the appropriate viscosity of resin 7 in this embodiment from the following three perspectives.

[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 acts as a lid to seal the resin 7 into 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 molded, the resin is less likely to leak into the press.

[0043] However, in Figure 1(c), the patch steel plate 13 is simply placed on the steel plate 11. 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 press molding. Leakage of the resin 7 during press molding is undesirable because it can contaminate the press machine or prevent the desired resin thickness from being achieved. Therefore, it is preferable that the resin 7 have a viscosity above a certain level that prevents leakage from the 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 the dashed arrow i in Figure 4. The dashed arrow i indicates that resin leakage during press molding can be prevented if the viscosity of the resin 7 is in the region to the right of the dashed arrow i. In other words, from the perspective of preventing resin leakage, it is preferable that the viscosity of the resin 7 be a or higher.

[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 section 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 above-mentioned method if the viscosity of the resin 7 is in the region to the left of the dashed arrow ii. In other words, from the perspective of a viscosity suitable for application or filling, it is preferable that the viscosity of the resin 7 be b or less.

[0045] If the ductility of resin 7 is too low, resin 7 may not be able to follow deformation during press molding, resulting in the risk of fracture of the resin layer. Resin layer fracture is undesirable because it reduces the collision energy absorption performance of the automotive component 1, as described above. Therefore, resin 7 preferably has a certain level of ductility that allows it to deform during press molding without fracture. The ductility range of resin 7 that allows resin 7 to follow the deformation of the steel sheet during press molding is indicated by the dashed arrow iii in Figure 4. The dashed arrow iii indicates that if the ductility of resin 7 is in the region above dashed arrow iii, resin fracture during press molding can be prevented. In other words, from the perspective of preventing resin fracture, it is preferable for the ductility of resin 7 to be c or higher. Resin ductility is correlated with the viscosity of the resin. Therefore, in the example shown in Figure 4, in order to achieve ductility of resin 7 of c or higher, the viscosity of resin 7 must be d or lower.

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

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

[0048] <Patch Steel Plate Installation Process> As shown in FIG. 1( c), 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. The patch steel plate 13 is a blank material prior to press-forming into the patch 9 (see FIG. 2) of the automotive part 1. The steel plate 11 whose resin encapsulation portion 12 is filled with resin 7 is transferred by a transfer device to a steel plate transport robot arranged downstream of the dispenser mounting robot. The steel plate transport robot installs the 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 acts as a lid, sealing in the resin 7 in the resin encapsulation portion 12. 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-forming process> The press-forming process S7 is a process in which the sandwich structural member 15 shown in Figure 1(c) is press-formed into the shape of an automotive part. Here, as shown in Figure 1(d), the sandwich structural member 15 is press-formed into the shape of the outer part 3 of the automotive part 1. By placing the patch steel plate 13 so as to cover the resin encapsulation portion 12, the resin 7 is sealed in the closed space formed by the resin encapsulation portion 12 and the patch steel plate 13, so that the resin 7 is less likely to leak from between the steel plate 11 and the patch steel plate 13 even when pressurized during press-forming. 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-forming.

[0051] <Welding Process> As shown in Fig. 1(e) , the welding process S9 is a process of welding the steel plate 11 press-formed in the press-forming process S7 to the patch steel plate 13. The part press-formed in the press-forming process S7, as shown in Fig. 1(d), is transferred to the press exit side by a transfer device. A robot equipped with a spot welding gun is disposed 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 a 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, since 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, it is preferable to fix the patch steel plate 13 to the steel plate 11.

[0053] The part shown in Figure 1(e) is transferred to an assembly line, and an inner part 5 is joined to form an automotive part 1 as shown in Figures 2 and 3. The automotive part 1 obtained by the manufacturing method of this embodiment will be specifically described below. Note that the x marks in Figure 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 round portions 3b, and flange portions 3d continuing from each of the vertical wall portions 3c. The top plate portion 3a, punch shoulder round portions 3b, and vertical wall portions 3c of the outer part 3 are formed with resin encapsulation portions 12 that are 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 forms a sandwich structure to improve the rigidity of the automotive part 1.

[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. 3A , the resin 7 is enclosed in a closed space formed by the resin encapsulation portion 12 and the patch 9. A sandwich structure is formed in the enclosed portion, i.e., the top plate portion 3 a, punch shoulder R portion 3 b, and vertical wall portion 3 c of the outer part 3. 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; rather, the patch 9 and the outer part 3 also cover the resin 7 in the resin encapsulation portion 12, creating an enclosed state. Therefore, the peripheral edge of the resin encapsulation portion 12 must be in contact with the outer part 3 to form an enclosed state. As a result, a sandwich structure is not formed at both axial ends of the automotive part 1 (see FIG. 3B ). While FIGS. 3A and 3B depict a gap between the outer part 3 and the patch 9, this is for ease of identification. In reality, the patch 9 contacts the outer part 3, as described above.

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

[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 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 during the axial crush or bending crush process described above, thereby demonstrating high collision energy absorption performance.

[0062] As described above, this automotive part 1 is easy to manufacture because the resin does not leak or break during the manufacturing process, and the expected collision energy absorption performance is stably exhibited. 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 automotive part 1. Examples of types of steel sheets used for the outer part 3, inner part 5, and patch 9 include cold-rolled steel sheets, hot-rolled steel sheets, stainless steel sheets, galvanized steel sheets, zinc alloy-plated steel sheets, and aluminum alloy-plated steel sheets.

[0063] The automotive part 1 manufactured using the manufacturing method of this embodiment must be subjected to a process to harden the resin 7 (heat treatment 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 use the heating process of electrodeposition coating, which is commonly performed in automobile manufacturing, to cure the resin 7. If the automobile part 1 before the heat treatment is assembled to 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 using direct electrification 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] In the above-described manufacturing method, the resin encapsulation portion 12 is filled with the resin 7 by applying or filling the resin encapsulation portion 12 with a paint-like resin 7. However, instead of the resin filling step S1, a resin pasting step may be provided in which the resin encapsulation portion 12 is pasted with the resin 7 formed in a sheet shape. When pasting the sheet-like resin 7, the sheet-like resin 7 can be pasted into the resin encapsulation portion 12 using, for example, laminating equipment. In this case, the resin 7 may be temporarily fixed into the resin encapsulation portion 12 using adhesive tape or a glue. Furthermore, when installing the patch steel plate 13, the resin 7 and the patch steel plate 13 may be temporarily fixed using adhesive tape or a glue. However, if the sheet-like resin 7 itself has initial adhesive strength on both sides, the adhesive tape or glue is not required.

[0072] In the above case, if the thickness of the resin 7 sheet 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 thickness of the resin 7 sheet significantly exceeds the peripheral wall height of the resin encapsulation portion 12, the gap between the patch steel plate 13 and the steel plate 11 will become larger when the patch steel plate 13 is installed, making it more likely that the resin 7 will protrude from that gap during press forming. Therefore, it is more preferable that the thickness of the resin 7 sheet be approximately the same as the peripheral wall height. As in the case of applying the resin 7, the thickness of the resin 7 sheet is preferably 0.2 mm or more and 3 mm or less.

[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-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 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-molding 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.

[0076] The effects of the manufacturing method of the present invention will be described based on specific examples. In these examples, a resin encapsulation portion 12 was formed on a 1.4 mm thick steel plate 11 with a tensile strength of 1470 MPa, as shown in FIG. 6(a) or FIG. 7(a). Resin 7 was then applied (or attached) as shown in FIG. 6(b) or FIG. 7(b). Finally, a 0.4 mm thick patch steel plate 13 with a tensile strength of 270 MPa 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 within the range of 0.2 to 3 mm. FIG. 6 shows an example in which resin 7 was applied to the entire steel plate 11 (excluding the portion to be welded after press forming) (resin / range "All" in Table 1). FIG. 7 shows an example in which resin 7 was applied only to the portion of the steel plate 11 that would become the punch shoulder R portion 3b of the outer part 3 (resin / range "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 crushing test, as shown in Figure 8, 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 crushing deformation of 80 mm. The load-stroke curve was measured and the absorbed energy was determined. In addition, the deformation state and the presence or absence of fracture in the outer part 3 were observed using a high-speed camera. The configuration of each evaluated part, the evaluation results of press formability, and the evaluation results of the axial crushing test are shown in Table 1.

[0080]

[0081] In Example 1, a 0.2 mm deep resin encapsulation portion 12 was formed in a steel plate 11 within the range shown in Figure 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. 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, a 1 mm deep resin encapsulation section 12 was formed in a steel plate 11 within the range shown in Figure 6(a), and a 1 mm thick sheet-like resin 7 was temporarily fixed in the resin encapsulation section 12 with adhesive tape. The test weight was 1.16 kg, and no resin overflowed after pressing. In addition, the results of the axial crushing test showed no base material fracture, and the absorbed energy was 14.5 kJ, resulting in an EA / weight ratio of 12.5 kJ / kg.

[0083] Inventive Example 3, a 3 mm deep resin encapsulation portion 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 3 mm inside the resin encapsulation portion 12 using a dispenser. The test weight was 1.27 kg, and no resin overflowed after pressing. In addition, the results of the axial crushing test showed 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 portion 12 was formed in a steel plate 11 within the range shown in Figure 7(a), and resin 7 was applied to a thickness of 1 mm inside the resin encapsulation portion 12 using a dispenser. The test weight was 1.16 kg, and no resin overflowed after pressing. In addition, the results of the axial crushing test showed 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 axial crushing test showed fracture of the base material. The absorbed energy was 10 kJ, and the EA / weight was 9.0 kJ / kg.

[0086] Comparative Example 2 is an example in which resin 7 was applied to the area 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 Examples 1 to 4. In addition, all of Examples 1 to 4 exhibited higher energy absorption performance than the comparative example.

[0088] According to the present invention, a method for manufacturing an automobile part can be provided that can manufacture an automobile part having a sandwich structure in which resin is sandwiched between steel plates at low cost while preventing resin leakage and resin rupture. Furthermore, according to the present invention, an automobile part can be manufactured at low cost, can prevent resin leakage and resin rupture during manufacturing, and can achieve the expected collision energy absorption performance.

[0089] REFERENCE SIGNS LIST 1 Automotive part 3 Outer part 3a Top plate part 3b Punch shoulder R part 3c Vertical wall part 3d Flange part 5 Inner part 7 Resin 9 Patch 11 Steel plate 12 Resin encapsulated part 13 Patch steel plate 15 Sandwich structural member

Claims

1. A method for manufacturing an automotive part, comprising: a resin encapsulation part forming step of forming a resin encapsulation part for encapsulating resin in a steel plate; a resin filling step of applying or filling resin into the resin encapsulation part to fill the resin encapsulation part with resin; a patch steel plate installation step of installing a patch steel plate so as to cover the resin encapsulation part on the steel plate; and a press forming step of press forming a sandwich structure member having a sandwich structure in which the resin is sandwiched between the steel plate and the patch steel plate into the part shape of an automotive part.

2. The method for manufacturing an automotive 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 method for manufacturing an automotive part according to claim 1 or 2, wherein the resin encapsulation part is a recess formed by denting the steel plate, and the depth of the recess is 0.2 mm or more and 3 mm or less.

4. A method for manufacturing an automotive part, comprising: a resin encapsulation part forming step of forming a resin encapsulation part for encapsulating resin in a steel plate; a resin pasting step of pasting a sheet-shaped resin formed to have the same thickness as or a thickness exceeding the peripheral wall height of the resin encapsulation part into the resin encapsulation part; a patch steel plate installation step of installing a patch steel plate so as to cover the resin encapsulation part on the steel plate; and a press forming step of press forming a sandwich structure member having a sandwich structure in which the resin is sandwiched between the steel plate and the patch steel plate into the part shape of an automotive part.

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

6. The method for manufacturing an automotive part according to claim 1 or 4, further comprising a welding step of welding the steel plate and the patch steel plate press formed by the press forming step.

7. The method for manufacturing an automotive part according to claim 1 or 4, wherein the resin is a thermosetting rubber-modified epoxy resin.

8. An automotive part having a cross-sectional hat-shaped member or a cross-sectional U-shaped member having a top plate portion and a pair of vertical wall portions continuous 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 cross-sectional hat-shaped member or the cross-sectional U-shaped member; a patch member disposed so as to straddle the top plate portion and covering the resin encapsulation portion; and a resin encapsulated in a closed space formed by the resin encapsulation portion and the patch member, wherein the resin is adhered to the cross-sectional hat-shaped member or the cross-sectional U-shaped member and the patch member with an adhesive strength of 10 MPa or more after being heated.

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