Method for manufacturing automotive parts and automotive parts

Abstract

A method for manufacturing a part for an automobile related to the present invention comprises a resin sealing part forming process S1 for forming a resin sealing part (12) for sealing a resin (7) in a steel plate (11), a resin filling process S3 for filling the resin sealing part (12) with resin (7) by applying or filling the resin (7) into the resin sealing part (12), a patch steel plate installation process S5 for installing a patch steel plate (13) to cover the resin sealing part (12) in the steel plate (11), and a press forming process S7 for press forming a sandwich structure member (15) having a sandwich structure in which the resin (7) is sandwiched between the steel plate (11) and the patch steel plate (13) into the shape of a part for an automobile.

Description

Technology Field

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

[0002] The front side member, which is a body frame part of the vehicle, is a long component installed at the front of the vehicle in the front-to-rear direction that absorbs collision energy by undergoing axial crush deformation during a collision. Additionally, the side sill (rocker) and center pillar are components that absorb collision energy by bending when a crash load is applied from the side of the vehicle body. By absorbing collision energy during a collision, these components suppress cabin deformation during the collision, thereby protecting the occupants.

[0003] The above-mentioned front side member, side sill (rocker), and center pillar need to reliably absorb vehicle collision energy, so a structure that controls deformation modes is required. Meanwhile, as lightweighting is also required for automotive parts, a technology (multi-material parts) has been proposed to achieve both improved collision energy absorption performance and stiffness and lightweighting by combining resin with the above-mentioned parts.

[0004] Patent Document 1 discloses a collision energy absorbing component for an automobile that absorbs collision energy by axially compressing when a collision load is input from the front or rear of the vehicle body. The collision energy absorbing component for an automobile according to Patent Document 1 can also improve vibration-damping properties by absorbing vibrations from the automobile engine or vibrations input to the vehicle body from various directions during driving. Additionally, Patent Document 2 discloses a vehicle body frame component that absorbs collision energy by bending when a collision load is input from the side of the vehicle body.

[0005] In all of the parts of Patent Document 1 and Patent Document 2, a resin is applied or attached to the inner surface of a metal main body member (tubular member, hat-shaped cross section member, or U-shaped cross section member), and a metal U-shaped cross section separation prevention member is formed to cover the surface of the resin. By placing the resin on the inner surface of the main body member, the resin is sandwiched between the steel plates during the process of axial crushing, where the part is crushed in a bellows-shaped manner in the axial direction, or bending crash, where it is bent perpendicular to the axial direction. As a result, the bending radius during deformation is expanded, making it difficult for the main body member to break, and the impact energy absorption performance is improved. As described above, the parts of Patent Document 1 and Patent Document 2 have a sandwich structure in which a resin is sandwiched between a metal main body member and a metal anti-detachment member, thereby preventing fracture of the main body member during axial crushing or bending crushing and improving impact energy absorption performance while achieving lightweighting. In addition, many methods for manufacturing parts having such a sandwich structure in which a resin is sandwiched between metal plates have been proposed.

[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 tubular member, forming a detachment prevention member to cover the resin, and then heat-treating the members after bonding the detachment prevention member to the tubular member. Additionally, Patent Document 1 describes a method of applying or attaching a resin to a detachment prevention member, bringing the resin into contact with the inner surface of the tubular member, bonding the detachment prevention member to the inner surface of the tubular member, and heat-treating the members.

[0007] In addition, Patent Document 3 discloses a frame structure (center pillar) of a vehicle body in which a filler material (such as epoxy resin) is foamed into the space between an outer panel and a reinforcement, and the following method is described as an assembly method for the frame structure. First, an unfoamed filler material processed into a sheet shape is attached and set on the outer panel-side surface of the reinforcement. Then, the reinforcement with the attached filler material is set to the outer panel, and the flange portions of both are joined by spot welding. After completing the assembly of the entire vehicle body, an electrodeposition coating is applied to the vehicle body, and the filler material is thermosetting foamed by the drying heat at that time.

[0008] In addition, Patent Document 4 describes the following method as a method for manufacturing a partially composite vibration damping component for automobiles to prevent automobile noise. First, a resin having vibration damping properties is applied to a restraining plate made of steel plates, etc., 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 on a steel plate before press forming that constitutes the vehicle body, and heated and pressure bonded. Then, the steel plate with the restraining plate partially bonded is press-formed to manufacture a partially composite vibration damping component for automobiles.

[0009] In addition, Patent Document 5 describes a method for manufacturing a metal plate member used in an automobile body, comprising a process of overlapping a first and second metal plate through a resin adhesive, a process of press-forming the overlapping first and second metal plates, and a process of curing the resin adhesive after the press-forming process. Prior art literature

[0010] Japanese Published Patent Application No. 2020-100183, Japanese Published Patent Application No. 2020-117039, Japanese Published Patent Application No. 2001-048054, Japanese Published Patent Application No. Hei 11-141005, Japanese Published Patent Application No. 2020-183078 The problem to be solved

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

[0012] First, the manufacturing method of Patent Document 3 limits the locations where resin can be placed in order to foam-fill the filler into the closed sectional space formed in existing parts such as the outer panel of the center pillar and reinforcement. Therefore, the parts that exhibit vibration damping or rigidity cannot be arbitrarily reinforced.

[0013] In this regard, the manufacturing method of Patent Document 1 allows resin to be placed in any part where rigidity is to be increased (for example, the punch shoulder R part of the outer part constituting the cylindrical member) because resin is applied or attached to a cylindrical member and then a detachment prevention member is mounted to cover the resin. However, the number of process steps increases because the molding of the detachment prevention member must be performed separately from the molding of the cylindrical member. Furthermore, the manufacturing cost of the part increases because labor is required for the process of applying or attaching resin to the cylindrical member after molding, or for the process of mounting the detachment prevention member after molding on the cylindrical member after molding.

[0014] In addition, since the manufacturing method of Patent Document 1 involves applying or attaching resin to a member after press molding, it may be difficult to apply or attach the resin with a uniform thickness to areas where a roughness shape is imparted to the surface of the member. Therefore, the area where the resin is applied or attached is limited to an area having a relatively smooth surface with little roughness.

[0015] In this regard, the manufacturing methods of Patent Documents 4 and 5 apply resin to a steel plate (restraining plate) prior to press forming, so they are not significantly restricted by the surface irregularity shape of the resin-applied area after press forming. Furthermore, since the restraining plate is partially bonded to a steel plate (blank) and then integrally press-formed, no additional press-forming process is required. However, in the manufacturing method of Patent Document 4, the resin-applied restraining plate is attached to a steel plate (blank), then heated and compressed, and subsequently press-formed; consequently, the resin may completely harden due to the heating. If the resin completely hardens, the ductility of the resin decreases, and there is a risk that the resin layer may fracture during press forming. Moreover, in the case of the impact energy absorbing component described above, if the resin layer is fractured, the fracture of the main body member during axial crushing or bending crushing cannot be sufficiently prevented, and thus the expected impact energy absorption performance cannot be obtained. Additionally, there is a risk that vibration damping performance may be reduced. Meanwhile, in the manufacturing method of Patent Document 5, there was a risk that the resin leaked from the gap between the overlapping surfaces of the metal plates due to the pressure applied during press molding, contaminating the inside of the press machine and damaging the surface quality of the press molded product.

[0016] The present invention has been made to solve the above problems, and its purpose is to provide a method for manufacturing an automotive part having a sandwich structure in which a resin is sandwiched between steel plates, which can be manufactured at a low cost while preventing resin leakage and resin rupture. Furthermore, another objective of the present invention is to provide an automotive part that can be manufactured at a low cost, prevents resin leakage and resin rupture during manufacturing, and achieves the expected collision energy absorption performance. means of solving the problem

[0017] The inventors carefully examined a method to prevent resin breakage in a manufacturing method in which a sandwich structure is formed on a steel plate prior to press forming and then press-formed into a part shape, as described in Patent Documents 4 and 5. If the resin is heated and fully cured prior to press forming, as in the manufacturing method of Patent Document 4, there is a risk that the resin will break during press forming. On the other hand, if heating is not performed prior to press forming, as in the manufacturing method of Patent Document 5, the resin leaks from between the steel plates due to the pressure applied during press forming, making it impossible to secure the required resin thickness. Furthermore, the leaked resin may contaminate the inside of the press mold, potentially causing problems with part forming or quality.

[0018] If a resin adjusted to a high viscosity is applied in advance, heating before press forming is not required, and leakage of the resin during press forming can be prevented. However, since high-viscosity resins have poor spreadability, the application time increases, leading to reduced productivity. Additionally, there is the problem that it is difficult to apply high-viscosity resins with a uniform thickness.

[0019] Therefore, the inventor obtained the insight that the above problem can be solved by forming a structure that encapsulates resin in an automobile part. The present invention is based on this insight and, specifically, is composed of the following components.

[0020] A method for manufacturing an automobile part related to the first aspect of the present invention comprises: a resin-sealing part forming process for forming a resin-sealing part for sealing a resin in a steel plate; a resin filling process for filling the resin-sealing part with resin by applying or filling a resin into the resin-sealing part; a patch steel plate installation process for installing a patch steel plate to cover the resin-sealing part in the steel plate; and a press forming process for 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 shape of an automobile part.

[0021] It is preferable that the viscosity of the above resin be 50 Pa·s or more and 200 Pa·s or less.

[0022] The resin-sealed portion is a concave portion formed by making the steel plate concave, and it is preferable that the depth of the concave portion is 0.2 mm or more and 3 mm or less.

[0023] A method for manufacturing an automobile part related to a second aspect of the present invention comprises: a resin-sealing part forming process for forming a resin-sealing part for encapsulating a resin in a steel plate; a resin attachment process for attaching a sheet-shaped resin formed with a thickness equal to or greater than the height of the perimeter wall of the resin-sealing part into the resin-sealing part; a patch steel plate installation process for installing a patch steel plate to cover the resin-sealing part in the steel plate; and a press forming process for 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 shape of an automobile part.

[0024] It is preferable that the sheet thickness of the above resin be 0.2 mm or more and 3 mm or less.

[0025] It is preferable to additionally include a welding process for welding the steel plate and the patch steel plate that are press-formed by the above press forming process.

[0026] It is preferable that the above resin is a thermosetting rubber-modified epoxy resin.

[0027] An automotive part related to the present invention comprises a top plate portion, a cross-sectional hat-shaped member or a cross-sectional Ko-shaped member having a pair of longitudinal wall portions continuous from the top plate portion through a punch shoulder R portion, a concave resin-sealing portion formed at least in the punch shoulder R portion of the cross-sectional hat-shaped member or cross-sectional Ko-shaped member, a patch member formed to be positioned to span the top plate portion and cover the resin-sealing portion, and a resin sealed in a closed space formed by the resin-sealing portion and the patch member, wherein the resin is adhered to the cross-sectional hat-shaped member or cross-sectional Ko-shaped member and the patch member with an adhesive strength of 10 MPa or more after heating. Effects of the invention

[0028] In the present invention, by forming a resin-sealing portion on a steel plate before forming it into an automotive part, a closed space can be formed between the steel plate and the patch steel plate, and resin can be sealed within this closed space. As a result, even without performing heat treatment before press forming, it is difficult for the resin to leak during press forming, and the inside of the press mold is not contaminated with resin. Furthermore, since the present invention does not thermoset the resin before press forming, the resin does not break during press forming, and the collision energy absorption performance of the manufactured automotive part is not degraded. In addition, since the part shape is press-formed after forming a sandwich structure, the main body part and the patch can be press-formed simultaneously. Therefore, compared to conventional examples where each part was press-formed individually, the number of process steps can be reduced, allowing for the manufacture of an automotive part having a sandwich structure at a low cost. Brief explanation of the drawing

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

[0030] A method for manufacturing an automobile part related to one embodiment of the present invention is a method for manufacturing an automobile part having a sandwich structure in which a steel plate and a resin are sandwiched between the steel plates. Although the present invention does not limit 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 cross-sectional hat-shaped part having a sandwich structure is described.

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

[0032] <Resin Encapsulation Molding Process>

[0033] The resin-sealing part forming process S1 is a process of forming a resin-sealing part (12) for sealing resin (7) in a steel plate (11), which is a blank material, before forming an outer part (3), as shown in FIG. 1(a). In this embodiment, the steel plate (11) is made concave to form a concave part as the resin-sealing part (12).

[0034] Since the resin (7) is filled within this concave portion, it is desirable to set the range for forming the concave portion to include a location effective for improving the collision energy absorption performance of the automotive part (1), or a location effective for vibration damping and rigidity. For example, in the case of the automotive part (1) of FIG. 2, the collision energy absorption performance of the automotive part (1) can be improved by the resin (7) being adhered to the punch shoulder R portion (3b) of the outer part (3) during the process of axial crushing or bending crushing. Therefore, the concave portion can be formed to include at least the area corresponding to the punch shoulder R portion (3b) in the steel plate (11). In this case, as shown in FIG. 6(a), the concave portion may be formed over the entire area excluding the welded portion with the patch (9) or inner part (5), or as shown in FIG. 7(a), the concave portion may be formed only over the area corresponding to the punch shoulder R portion (3b).

[0035] It is preferable that the depth of the resin-sealed portion (12) be 0.2 mm or more and 3 mm or less. If the depth of the concave portion is shallower than 0.2 mm, it becomes difficult to apply the resin (7) in a uniform thickness within the concave portion. Also, if the depth of the concave portion is deeper than 3 mm, the resin thickness increases, which incurs costs, and at the same time, molding the resin-sealed portion (12) becomes difficult. Since the shape of the resin-sealed portion (12) corresponds to the shape of the resin (7) of the automotive part (1) that is finally manufactured, by making the depth of the resin-sealed portion (12) 0.2 mm or more and 3 mm or less, the thickness of the resin (7) of the automotive part (1) also becomes 0.2 mm or more and 3 mm or less.

[0036] The resin-sealed portion forming process S1 can be performed simultaneously with the blanking process of taking a steel plate (11) from the material. In a general blanking process, the material is cut into a predetermined blank shape while being fixed between a mold consisting of an upper mold and a lower mold. Therefore, by forming a resin-sealed portion forming section for forming the resin-sealed portion (12) on the forming surfaces of the upper and lower molds, the resin-sealed portion (12) can be formed simultaneously with blanking the steel plate (11). As described above, since the resin-sealed portion (12) has a shallow shape with a depth of 0.2 mm or more and 3 mm or less, it can be formed even with a blanking machine of general performance.

[0037] Although the above description explains an example in which the resin-filled portion (12) is formed simultaneously with the blanking of the steel plate (11), it is also acceptable to form the resin-filled portion (12) separately on the steel plate (11) after it has been blanked.

[0038] <Residue-filling process>

[0039] The resin filling process S3 is a process of filling the resin sealing part (12) with resin (7) by applying or filling the resin (7) into the resin sealing part (12) as shown in FIG. 1(b). A steel plate (11) (see FIG. 1(a)) formed with a resin sealing part (12) in a blank line is transferred to a press line by a transfer device such as a bar feeder or conveyor equipped with an adsorption bar. A robot equipped with, for example, a dispenser (liquid quantitative discharge device) is positioned at the inlet side of the press machine in the press line, and the dispenser-equipped robot fills the resin sealing part (12) with resin (7) by applying the resin (7) into the resin sealing part (12).

[0040] The method of applying the resin (7) is not limited to the above; 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, etc. Above all, the method of using a dispenser is more preferable because it can supply a precise amount of resin (7) with high precision to fill the resin sealing part (12). Alternatively, the resin (7) may be injected into the resin sealing part (12) to fill it.

[0041] As for the type of resin (7), a thermosetting type is preferred. Using a thermosetting resin 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 resin, urethane resin, ester resin, phenolic resin, melamine resin, and urea resin. In particular, a thermosetting rubber-modified epoxy resin is preferred because it has high ductility after heat curing, so the cured resin (7) does not easily break.

[0042] The resin (7) in the resin filling process S3 is adjusted to an appropriate viscosity in advance. The appropriate viscosity of the resin (7) in this embodiment will be explained below using FIG. 4.

[0043] FIG. 4 is a graph conceptually showing the relationship between the viscosity, ductility, and elastic modulus of a resin. As shown by curve A in FIG. 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 in opposition to the increase in elastic modulus; that is, as the viscosity of the resin increases, the ductility of the resin decreases. Therefore, considering the properties of the resin, the inventor examined the appropriate viscosity of the resin (7) in the present embodiment from the following three perspectives.

[0044] First, if the viscosity of the resin (7) is excessively low, there is a risk that the resin (7) may leak out of the press machine due to the pressure applied during press molding. Specifically, as will be described later, in this embodiment, the patch steel plate (13) installed in the patch steel plate installation process S5 acts as a cover, and the resin (7) is sealed within the resin sealing part (12) (see FIG. 1(c)). In this way, by sealing the resin (7) with the steel plate (11) and the patch steel plate (13), it becomes difficult for the resin to leak out of the press machine even when the member of FIG. 1(c) is press molded.

[0045] However, since the patch steel plate (13) of FIG. 1(c) is merely placed on the steel plate (11), if the viscosity of the resin (7) is excessively low, there is a possibility that the resin (7) may leak from the gap between the steel plate (11) and the patch steel plate (13) due to the pressure applied during pressing. If the resin (7) leaks during press molding, it is undesirable because the press machine may become contaminated or the required resin thickness cannot be secured. Therefore, it is desirable for the resin (7) to have a viscosity of at least a certain level so that it does not leak from the resin encapsulation part (12) even when subjected to pressure during press molding. The viscosity range that can prevent resin leakage during press molding is indicated by the dashed arrow i in FIG. 4. The dashed arrow i indicates that if the viscosity of the resin (7) is in the region to the right of the dashed arrow i, resin leakage during press molding can be prevented. That is, from the perspective of preventing resin leakage, it is desirable to make the viscosity of the resin (7) a or higher.

[0046] Meanwhile, if the viscosity of the resin (7) is excessively high, when the resin (7) is applied or filled in the resin filling process S3, the thickness of the resin (7) does not become uniform, and it becomes difficult to fill the resin encapsulation part (12) with the resin (7). Therefore, it is desirable for the resin (7) to have a viscosity below a certain level such that the thickness becomes uniform when applied or filled. The viscosity range in which the resin (7) can be appropriately applied (filled) is indicated by the dashed arrow ii in FIG. 4. The dashed arrow ii indicates that if the viscosity of the resin (7) is in the region to the left of the dashed arrow ii, the resin (7) can be applied or filled using the method described above. That is, from the perspective of a viscosity suitable for application or filling, it is desirable to make the viscosity of the resin (7) b or less.

[0047] If the ductility of the resin (7) is excessively low, the resin (7) cannot follow the deformation during press forming, and there is a risk that the resin layer will break. If the resin layer breaks, the collision energy absorption performance of the automotive part (1) is reduced as described above, which is undesirable. Therefore, it is desirable for the resin (7) to have a certain level of ductility so that it does not break even when deformed during press forming. The range of ductility of the resin (7) that allows the resin (7) to follow the deformation of the steel plate during press forming is indicated by the dashed arrow iii in FIG. 4. The dashed arrow iii indicates that if the ductility of the resin (7) is in the upper region above the dashed arrow iii, the resin can be prevented from breaking during press forming. That is, from the perspective of preventing resin breakage, it is desirable to make the ductility of the resin (7) c or higher. Since the ductility of the resin is correlated with the viscosity of the resin, in the example shown in FIG. 4, in order to make the ductility of the resin (7) greater than or equal to c, it is necessary to make the viscosity of the resin (7) less than or equal to d.

[0048] From the perspective of the three points above, the preferred viscosity range of the resin (7) in this embodiment is a or greater and b or less, and d or less. In the example of FIG. 4, since d is smaller than b, the preferred viscosity range of the resin (7) in this case is a or greater and d or less. Also, since the shape of curve B changes according to the properties of the resin, there are cases where d becomes larger than b depending on the properties of the resin. In this case, the appropriate viscosity range of the resin (7) is a or greater and b or less.

[0049] Considering the above, in this embodiment, the preferred viscosity range of the resin (7) in the resin filling process S3 is set to 50 Pa·s or higher and 200 Pa·s or higher. By adjusting the viscosity of the resin (7) to within the above range, if it is a general resin, the resin (7) can be applied or filled in the resin filling process S3, and leakage or breakage of the resin (7) does not occur in the subsequent press molding process S7.

[0050] Patch Steel Plate Installation Process

[0051] The patch steel plate installation process S5 is a process of installing a patch steel plate (13) on a steel plate (11) in which the resin (7) is filled in the resin-sealed portion (12), as shown in FIG. 1(c). The patch steel plate (13) is a blank material before press forming a patch (9) (see FIG. 2) of an automotive part (1). The steel plate (11) in which the resin (7) is filled in the resin-sealed portion (12) is transferred by a transfer device to a steel plate conveyor robot positioned downstream of a dispenser-mounted robot. The steel plate conveyor robot installs the patch steel plate (13) at a predetermined position on the steel plate (11) to cover the resin-sealed portion (12).

[0052] By installing the patch steel plate (13), the patch steel plate (13) becomes a cover, and the resin (7) inside the resin sealing part (12) is sealed. Additionally, the resin (7) is sandwiched between the bottom part of the resin sealing part (12) and the patch steel plate (13), forming a sandwich structure. Hereinafter, the member of FIG. 1(c) having this sandwich structure is referred to as a sandwich structure member (15).

[0053] Press forming process

[0054] The press forming process S7 is a process of press forming the sandwich structure member (15) of FIG. 1(c) into the shape of a part for an automobile. Here, as shown in FIG. 1(d), the sandwich structure member (15) is press formed into the shape of an outer part (3) of an automobile part (1). By installing a patch steel plate (13) to cover the resin encapsulation part (12), the resin (7) is enclosed in the closed space formed by the resin encapsulation part (12) and the patch steel plate (13), so it is difficult for it to leak from between the steel plate (11) and the patch steel plate (13) even when pressurized during press forming. In addition, since the resin (7) is in a state before heat curing, it is difficult for the resin layer to break due to press forming to occur.

[0055] Welding Process

[0056] The welding process S9 is a process of welding the steel plate (11) and the patch steel plate (13) that were press-formed by the press forming process S7, as shown in FIG. 1(e). The part of FIG. 1(d) that was press-formed in the press forming process S7 is transported to the exit side of the press machine by a transfer device. A robot equipped with a spot welding gun is positioned at the exit side of the press machine, 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 (part marked with an × in FIG. 1(e)).

[0057] When the sandwich structural member (15) is press-formed, the resin (7) is pressed against the steel plate (11) and the patch steel plate (13) under high surface pressure, and further, through the heating process described later, it is bonded to the steel plate (11) and the patch steel plate (13) with a predetermined adhesive strength, so the welding process S9 may be omitted. Above all, the automotive part (1) of this embodiment absorbs collision energy by axial crushing or bending crushing, and since the collision energy absorption characteristics are reduced if the patch (9) is peeled off from the resin (7) during the deformation process, it is preferable to fix the patch steel plate (13) to the steel plate (11).

[0058] The part of FIG. 1(e) is transferred to an assembly line, and by joining an inner part (5), it becomes the automobile part (1) shown in FIG. 2 and FIG. 3. The automobile part (1) obtained by the manufacturing method of the present embodiment will be described in detail below. Also, the × mark in FIG. 2 indicates a spot weld.

[0059] The automotive part (1) of 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 axially crushing when a collision load is applied to the car body.

[0060] As shown in FIG. 2, the automotive part (1) is equipped with an outer part (3), an inner part (5), a patch (9), and a resin (7) (see FIG. 3(a)).

[0061] The outer part (3) (the cross-sectional hat-shaped member of the present invention) is formed by press-forming a steel plate (11) and has a top plate portion (3a), a pair of longitudinal wall portions (3c) that are continuous from the top plate portion (3a) through the punch shoulder R portion (3b), and flange portions (3d) that are continuous from each longitudinal wall portion (3c). In the top plate portion (3a), the punch shoulder R portion (3b), and the longitudinal wall portions (3c) of the outer part (3), a resin-filled portion (12) with a concave shape that is recessed inward is formed.

[0062] On the outer side of the outer part (3), a patch (9) is formed to cover the resin-sealed portion (12), and the end of the patch (9) is welded to the outer surface of the longitudinal wall portion (3c) of the outer part (3). The patch (9) is a press-formed patch steel plate (13) and is a component that prevents the resin (7) from escaping from the outer part (3) and forms a sandwich structure to improve the rigidity of the automotive part (1).

[0063] In FIG. 2, the resin-sealed portion (12) is shown with two lines (the part covered by the patch (9) is shown with two fine dashed lines), but the inner line represents the outer edge of the bottom portion of the resin-sealed portion (12), and the outer line represents the upper edge of the resin-sealed portion (12).

[0064] As shown in FIG. 3(a), resin (7) is sealed in the closed space formed by the resin sealing part (12) and the patch (9). A sandwich structure is formed in the part where the resin (7) is sealed, namely the top plate part (3a), the punch shoulder R part (3b), and the side wall part (3c) of the outer part (3). Above all, the sandwich structure of this embodiment is not only simply sandwiching the resin (7) between the patch (9) and the outer part (3) from the top and bottom, but also creating a sealed state in which the surrounding area of ​​the resin (7) in the resin sealing part (12) is covered by the patch (9) and the outer part (3). For this reason, the periphery edge portion of the resin encapsulation portion (12) needs to form an encapsulation state by bringing the patch (9) into contact with the outer part (3), and as a result, a sandwich structure is not formed at both axial ends of the automotive part (1) (see FIG. 3(b)). In FIG. 3(a) and FIG. 3(b), it is depicted as if there is a gap between the outer part (3) and the patch (9), but this is to make it easier to identify each component, and in reality, as described above, the patch (9) is in contact with the outer part (3).

[0065] The inner part (5) is a flat plate-shaped member formed of steel plate and is welded to the flange portion (3d) of the outer part (3).

[0066] As described above, the automobile part (1) obtained by the manufacturing method of the present embodiment has a sandwich structure in which a resin (7) is sandwiched between an outer part (3) formed from a steel plate and a patch (9). As a result, the surface rigidity of the top plate part (3a), punch shoulder R part (3b), and vertical wall part (3c) of the outer part (3) is improved, and since the breakage of the steel plate during the process of axial crushing or bending crushing as described above is prevented, it exhibits high collision energy absorption performance.

[0067] As described above, this automotive part (1) does not leak resin or break during the manufacturing process, so it has good manufacturability and stably exhibits the expected collision energy absorption performance. In addition, since the resin (7) also functions as a vibration damping material that absorbs vibrations, the vibration damping performance of the automotive part (1) is improved by providing the sandwich structure. Examples of steel sheets used for the outer part (3), inner part (5), and patch (9) include cold rolled steel sheet, hot rolled steel sheet, stainless steel sheet, galvanized steel sheet, zinc alloy plated steel sheet, and aluminum alloy plated steel sheet.

[0068] The automobile part (1) manufactured using the manufacturing method of the present embodiment requires a treatment to cure the resin (7) before or after assembly of the vehicle body (heat treatment if the resin (7) is a thermosetting resin). By curing the resin (7), the resin (7) and the outer part (3) and the resin (7) and the patch (9) are bonded with a predetermined bonding strength. A final bonding strength after curing is preferably 10 MPa or more.

[0069] When the resin (7) is a thermosetting resin, the resin (7) can be cured using the heating process of electrodeposition coating, which is generally practiced in automobile manufacturing. When the automobile part (1) is assembled to the car body before heat treatment and electrodeposition coating is performed on the car body, the resin (7) of the automobile part (1) is completely cured during the heating process to dry the electrodeposition paint, so it is efficient.

[0070] The method of heating the automotive part (1) is not limited to the above and may be performed before the car body assembly. For example, the automotive part (1) before the car body assembly may be heated by loading it into a high-temperature furnace (oven) in which the atmosphere temperature is maintained constant, or the automotive part (1) before the car body assembly may be heated using direct electrification heating or high frequency induction heating.

[0071] In any case, by heat-treating the automotive part (1) at a predetermined temperature and for a predetermined time, the resin (7) is bonded to the outer part (3) and the patch (9) with a predetermined adhesive strength due to the adhesive ability of the resin itself. 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 vary depending on the type of resin (7), it is preferable 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).

[0072] The automobile part (1) shown in FIG. 2 is an example of an automobile part that can be manufactured by the manufacturing method of the present embodiment, and the shape of the automobile part (1) is not limited. As another example, the outer part (3) may be a cross-sectional K-shaped member instead of a cross-sectional hat shape.

[0073] As described above, according to the present embodiment, since the resin (7) is enclosed in the steel plate (11) and the patch steel plate (13), the resin (7) does not leak out of the press machine when these are press-molded into a part shape. Also, since 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) equipped with the necessary collision energy absorption performance and vibration damping properties.

[0074] In addition, compared to the conventional manufacturing method in which the outer part (3) and the patch (9) were press-molded separately, the present embodiment can press-mold the outer part (3) and the patch (9) simultaneously, thereby improving the productivity of the automotive part (1). Regarding the molding of the resin-filled part (12), since it can be performed simultaneously with the blanking of the steel plate (11), there is no increase in the number of processes, and it is efficient.

[0075] In addition, since the resin (7) is applied to the steel plate (11), which is a blank material before press forming the outer part (3), the resin (7) can be applied with a uniform thickness without being restricted by the surface irregular shape of the part compared to when the resin (7) is applied to the part after press forming. This allows for a reduction in the deviation of the collision energy absorption performance and vibration damping performance of the automotive part (1).

[0076] The above manufacturing method involves applying or filling a resin (7) in the form of a paint to the resin-sealing part (12) to fill the resin-sealing part (12) with the resin (7). However, instead of this resin filling process S1, a resin attachment process may be provided in which a resin (7) formed into a sheet shape is attached to the resin-sealing part (12). When attaching the sheet-shaped resin (7), for example, the sheet-shaped resin (7) can be attached to the resin-sealing part (12) by using a laminating facility. At that time, the resin (7) can be temporarily fixed to the resin-sealing part (12) using adhesive tape or adhesive. Also, when installing the patch steel plate (13), the resin (7) and the patch steel plate (13) can be temporarily fixed using adhesive tape or adhesive. Above all, if there is initial adhesive force on both sides of the sheet-shaped resin (7) itself, there is no need to use the above adhesive tape or adhesive.

[0077] In the above case, if the sheet thickness of the resin (7) is thinner than the perimeter wall height (concave depth) of the resin encapsulation part (12), the resin (7) and the patch steel plate (13) do not come into contact when the patch steel plate (13) is installed, and thus a sandwich structure cannot be formed. Therefore, the thickness of the resin (7) applied during the resin application process is equal to or greater than the perimeter wall height of the resin encapsulation part (12). Above all, if the sheet thickness of the resin (7) significantly exceeds the perimeter wall height of the resin encapsulation part (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 easily pushed out from the gap during press molding. Therefore, it is more desirable to make the sheet thickness of the resin (7) equal to the perimeter wall height. The sheet thickness of the resin (7) is preferably 0.2 mm or more and 3 mm or less, just like when applying the resin (7).

[0078] Additionally, in the example of FIG. 1, the resin filling process S3 and the patch steel plate installation process S5 were performed within a press line that press-forms the sandwich structural member (15) into a part shape, but these processes do not necessarily need to be performed within the same press line. For example, a manufacturing line for manufacturing the sandwich structural member (15) and a press line for press-forming the sandwich structural member (15) into a part shape may be kept separate. In that case, after performing the patch steel plate installation process S5 in the manufacturing line of the sandwich structural member (15), the manufactured sandwich structural member (15) is transferred to the press line by a transfer device, and the press-forming process S7 and subsequent steps are performed.

[0079] In addition, the welding process S9 does not necessarily have to be performed within the press line. For example, after performing the press forming process S7, the part of FIG. 1(d) is transferred to the assembly line, and the welding process S9 may be performed when joining the inner part (5) at the assembly line.

[0080] In addition, although the example in FIG. 1 shows an example in which the resin filling process S3 and the patch steel plate installation process S5 are performed at the inlet side of the press machine, as shown in FIG. 5, these processes may be performed inside the press machine.

[0081] Examples

[0082] The effects of the manufacturing method of the present invention will be explained based on specific examples. In this example, a resin-sealed portion (12) was formed on a steel plate (11) with a thickness of 1.4 mm and a tensile strength of 1470 MPa as shown in FIG. 6(a) or FIG. 7(a). Then, a resin (7) was applied (or attached) as shown in FIG. 6(b) or FIG. 7(b). Then, a patch steel plate (13) with a thickness of 0.4 mm and 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-sealed portion (12) and the thickness of the resin (7) were set in the range of 0.2 to 3 mm. FIG. 6 is an example in which resin (7) is applied to the entire steel plate (11) (excluding the part to be welded after press forming) (resin range “entire” in Table 1), and FIG. 7 is an example in which resin (7) is applied only to the part that can become the punch shoulder R part (3b) of the outer part (3) in the steel plate (11) (resin range “shoulder part” in Table 1).

[0083] The above sandwich structure member (15) was press-molded into the shape of the outer part (3) shown in FIG. 2, and the press-molding properties were evaluated. Here, the presence or absence of resin (7) being pushed out from the outer part (3) and patch (9) after press-molding was observed.

[0084] After that, the inner part (5) was welded to the press-formed outer part (3) to assemble it into the automobile part (1) of FIG. 2, and then heated at 170°C for 15 minutes. Then, an axial crushing test was performed on the automobile part (1) after heating.

[0085] In the axial crushing test, as shown in FIG. 8, a load was applied in the axial direction of the automotive part (1) at a test speed of 17.8 m / s, and the load-stroke curve was measured when the length of the test specimen was axially crushed by 80 mm from 200 mm to 120 mm, and the absorbed energy was calculated. In addition, the deformation state and the presence or absence of fracture of the outer part (3) were observed by high-speed camera photography. The results of the evaluation of the composition and press formability of each evaluated part and the results of the axial crushing test are shown in Table 1.

[0086]

[0087] Invention Example 1 is an example in which a resin-sealed portion (12) with a depth of 0.2 mm is formed in a steel plate (11) within the range of FIG. 6(a), and a resin (7) is applied to the resin-sealed portion (12) with a thickness of 0.2 mm using a dispenser. The weight of the test specimen was 1.12 kg, and there was no resin extrusion after pressing. Also, 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, so the EA / weight (energy absorption per unit weight) was 11.3 kJ / kg.

[0088] Invention Example 2 is an example in which a resin-sealed portion (12) with a depth of 1 mm is formed in a steel plate (11) within the scope of FIG. 6(a), and a sheet-shaped resin (7) with a thickness of 1 mm is temporarily fixed within the resin-sealed portion (12) with adhesive tape. The weight of the test specimen was 1.16 kg, and there was no resin extrusion after pressing. In addition, as a result of the axial crushing test, there was no fracture of the base material, and the absorbed energy was 14.5 kJ, so the EA / weight was 12.5 kJ / kg.

[0089] Invention Example 3 is an example in which a resin-sealed portion (12) with a depth of 3 mm is formed in a steel plate (11) within the range of FIG. 6(a), and a resin (7) is applied to the resin-sealed portion (12) with a thickness of 3 mm using a dispenser. The weight of the test specimen was 1.27 kg, and there was no resin extrusion after pressing. In addition, as a result of the axial crushing test, there was no fracture of the base material, and the absorbed energy was 17.7 kJ, so the EA / weight (energy absorption per unit weight) was 13.9 kJ / kg.

[0090] Invention Example 4 is an example in which a resin-sealed portion (12) with a depth of 1 mm is formed in a steel plate (11) within the range of FIG. 7(a), and a resin (7) is applied to the resin-sealed portion (12) with a thickness of 1 mm using a dispenser. The weight of the test specimen was 1.16 kg, and there was no resin extrusion after pressing. In addition, as a result of the axial crushing test, there was no fracture of the base material, and the absorbed energy was 14.5 kJ, so the EA / weight (energy absorption per unit weight) was 12.5 kJ / kg.

[0091] Comparative Example 1 is an example without resin (7). In the case of Comparative Example 1, which does not have a sandwich structure, fracture of the base material was observed as a result of the axial crushing test. Also, the absorbed energy was 10 kJ, and the EA / weight was 9.0 kJ / kg.

[0092] Comparative Example 2 is an example in which resin (7) is applied to the area of ​​FIG. 6(a) without forming a resin-sealed portion (12) on the steel plate (11). In the case of Comparative Example 2, which does not have a resin-sealed portion (12), it was confirmed that the resin was pushed out after pressing. In addition, no increase in absorbed energy was observed in Comparative Example 2 compared to Comparative Example 1.

[0093] As described above, in Invention Examples 1 to 4, no leakage (extrusion) of the resin (7) occurred during press molding. Also, Invention Examples 1 to 4 all exhibited higher energy absorption performance than the Comparative Example.

[0094] Industrial applicability

[0095] According to the present invention, a method for manufacturing an automotive part having a sandwich structure in which a resin is sandwiched between steel plates can be provided, which prevents resin leakage and resin rupture and can be manufactured at a low cost. Furthermore, according to the present invention, an automotive part can be provided that can be manufactured at a low cost, prevents resin leakage and resin rupture during manufacturing, and achieves the expected collision energy absorption performance. Explanation of the symbols

[0096] 1 : Automotive parts 3 : Outer parts 3a : Top plate 3b : Punch Shoulder R Part 3c: Longitudinal wall 3d : Flange section 5 : Inner parts 7 : Suzy 9 : Patch 11 : Steel plate 12: Resin encapsulation part 13 : Patch steel plate 15: Sandwich structural member

Claims

Claim 1 A method for manufacturing an automobile part, comprising: a resin sealing portion forming process for forming a resin sealing portion for sealing a resin in a steel plate; a resin filling process for filling the resin sealing portion with resin by applying or filling the resin into the resin sealing portion; a patch steel plate installation process for installing a patch steel plate to cover the resin sealing portion in the steel plate; and a press forming process for 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 shape of an automobile part. Claim 2 A 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. Claim 3 A method for manufacturing an automobile part according to claim 1 or 2, wherein the resin-sealed portion is a concave portion formed by making the steel plate concave, and the depth of the concave portion is 0.2 mm or more and 3 mm or less. Claim 4 A method for manufacturing an automobile part, comprising: a resin-sealing portion forming process for forming a resin-sealing portion for encapsulating resin in a steel plate; a resin attachment process for attaching a sheet-shaped resin formed with a thickness equal to or greater than the height of the perimeter wall of the resin-sealing portion to the resin-sealing portion; a patch steel plate installation process for installing a patch steel plate to cover the resin-sealing portion in the steel plate; and a press forming process for press forming 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. Claim 5 A 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. Claim 6 A method for manufacturing an automotive part according to claim 1 or 4, further comprising a welding process for welding the steel plate press-formed by the press-forming process and the patch steel plate. Claim 7 A method for manufacturing an automotive part according to claim 1 or 4, wherein the resin is a thermosetting rubber-modified epoxy resin. Claim 8 An automotive part comprising: a cross-sectional hat-shaped member or a cross-sectional Ko-shaped member having a top plate portion and a pair of longitudinal wall portions continuous from the top plate portion through a punch shoulder R portion; a concave resin-sealing portion formed at least in the punch shoulder R portion of the cross-sectional hat-shaped member or the cross-sectional Ko-shaped member; a patch member formed to be positioned across the top plate portion and covering the resin-sealing portion; and a resin sealed in a closed space formed by the resin-sealing portion and the patch member, wherein the resin is adhered to the cross-sectional hat-shaped member or the cross-sectional Ko-shaped member and the patch member with an adhesive strength of 10 MPa or more after heating.

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