Method for manufacturing automotive component

Abstract

This method for manufacturing an automotive component (1) comprises: a resin application step (S1) in which a resin (7) is applied to a pre-molding steel plate (11); a patch steel sheet installation step (S3) in which a patch steel sheet (13) is installed on the steel sheet (11) coated with the resin (7) so as to cover the resin (7); a pre-firing step (S5) for pre-firing a sandwich structural member (15) having a sandwich structure in which the resin (7) is sandwiched between a steel plate (11) and a patch steel plate (13) so that the resin (7) has an elastic modulus of 45 MPa or more and a ductility of 10% or more; and a press-forming step (S7) for press-forming the pre-fired sandwich structural member (15) into the component shape of the automotive component (1).

Description

Technical Field

[0001] This invention relates to a method for manufacturing automotive parts having a sandwich structure formed by sandwiching resin with steel plates. Background Technology

[0002] The front side member, a frame component of a car, is a long component located at the front of the vehicle in the longitudinal direction. It absorbs collision energy during a collision through axial crush deformation. Additionally, the side sills (lockers) and center pillar absorb collision energy by bending when a collision load is input from the side of the vehicle. These components absorb collision energy during a collision, thereby suppressing cabin deformation and protecting the occupants.

[0003] The aforementioned front longitudinal beam, lower longitudinal beam, and center pillar need to reliably absorb vehicle collision energy and require structures that control deformation modes. On the other hand, since automotive components also require lightweighting, technologies have been proposed to date that combine resins in the aforementioned components to achieve a balance between collision energy absorption performance, improved stiffness, and lightweighting (multi-material parts).

[0004] Patent Document 1 discloses a collision energy absorbing component for automobiles that absorbs collision energy by axially crushing when a collision load is input from the front or rear of the vehicle body. The collision energy absorbing component of Patent Document 1 absorbs vibrations from the vehicle engine and vibrations input to the vehicle body from various directions during vehicle movement, thus improving vibration-damping properties. Furthermore, 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] Both Patent Document 1 and Patent Document 2 involve coating or bonding resin onto the inner surface of a metal main body (tubular parts, hat-shaped cross-section parts, or U-shaped cross-section parts), and then placing a metal U-shaped anti-detachment member on the surface covering the resin. By depositing resin on the inner surface of the main body, during axial crushing (forming bellows-shaped depressions) or bending crushing (bending in a direction perpendicular to the axial direction), the resin is sandwiched between steel plates, thus increasing the bending radius during deformation and making it difficult for the main body to break, thereby improving impact energy absorption performance. As described above, the components of Patent Document 1 and Patent Document 2, through a sandwich structure formed by the resin sandwiched between the metal main body and the metal anti-detachment member, prevent the main body from breaking during axial or bending crushing, thereby improving impact energy absorption performance and achieving lightweight design. Furthermore, a method for manufacturing a large number of components with such a sandwich structure formed by sandwiching resin with metal plates has been proposed.

[0006] Patent Document 1 describes a method in which resin is coated or adhered to the inner surface of a cylindrical member, an anti-detachment member is disposed to cover the resin, the anti-detachment member is joined to the cylindrical member, and the members are then subjected to heat treatment, thereby manufacturing a component with a sandwich structure. Patent Document 1 also describes a method in which resin is coated or adhered to the anti-detachment member, the resin is brought into contact with the inner surface of the cylindrical member, the anti-detachment member is joined to the inner surface of the cylindrical member, and the members are then subjected to heat treatment.

[0007] Furthermore, Patent Document 3 discloses a frame structure (center pillar) of a car body formed by foaming filler with filler material (such as epoxy resin) in the space between the outer panel and the reinforcement. As an assembly method for this frame structure, the following method is described: First, a sheet-shaped, unfoamed filler is adhered and placed on the outer panel side of the reinforcement. Then, the reinforcement with the adhered filler is placed on the outer panel, and the flange portions of both are joined together by spot welding. After the overall car body assembly is completed, an electrodeposition coating is applied to the car body, and the aforementioned filler is thermally foamed using the drying heat at this time.

[0008] Furthermore, Patent Document 4 describes a method for manufacturing a partially composite vibration damping component for automobiles used to prevent vehicle noise. First, a vibration-damping resin is coated onto a restraint plate made of steel sheet or the like, and the solvent in the coating on the restraint plate is evaporated in a drying oven. Then, the restraint plate is adhered to a predetermined position on a steel sheet that forms the vehicle body before stamping, and the sheet is heated and pressed together. Finally, the steel sheet with the restraint plate partially bonded together is stamped to manufacture the partially composite vibration damping component for automobiles.

[0009] In addition, Patent Document 5 discloses a method for manufacturing a metal plate component, in which a first metal plate and a second metal plate are overlapped by a resin adhesive, the first metal plate and the second metal plate are stamped, and the resin adhesive is cured after stamping.

[0010] In addition, Patent Document 6 discloses a method for manufacturing a vehicle body, in which a first body component is joined to a second body component via a damping resin adhesive, the damping resin adhesive, which forms the lower part of the joint, is pre-cured in the assembled position of the joint, and then the joint is joined to a third body component in an assembled position.

[0011] Existing technical documents

[0012] Patent documents

[0013] Patent Document 1: Japanese Patent Application Publication No. 2020-100183

[0014] Patent Document 2: Japanese Patent Application Publication No. 2020-117039

[0015] Patent Document 3: Japanese Patent Application Publication No. 2001-048054

[0016] Patent Document 4: Japanese Patent Application Publication No. 11-141005

[0017] Patent Document 5: Japanese Patent Application Publication No. 2020-183078

[0018] Patent Document 6: Japanese Patent Application Publication No. 2021-126930 Summary of the Invention

[0019] The problem that the invention aims to solve

[0020] As described above, various manufacturing methods for components having a sandwich structure formed by sandwiching resin between metal plates have been proposed, but these manufacturing methods have the following problems.

[0021] First, regarding the manufacturing method in Patent Document 3, since the filler is foamed and filled into the closed sectional space of existing components such as the outer panel and reinforcing members formed in the central column, the areas where the resin can be placed are limited. Therefore, it is not possible to arbitrarily strengthen areas that provide vibration damping and rigidity enhancement.

[0022] In contrast, the manufacturing method of Patent Document 1 involves applying or attaching resin to the cylindrical member and then covering it with the resin to install the anti-detachment member. This allows the resin to be applied to any location where increased rigidity is desired (e.g., the shoulder R-section of a punch constituting the outer parts of the cylindrical member). However, this manufacturing method requires a separate stamping process for the anti-detachment member, distinct from the stamping process of the cylindrical member, thus increasing manufacturing costs.

[0023] Furthermore, the manufacturing method in Patent Document 1 involves coating or bonding resin onto the stamped component, which sometimes makes it difficult to apply or bond the resin with a uniform thickness on areas where the component surface is given an uneven shape. Therefore, the areas where the resin is coated or bonded are limited to areas with few surface irregularities and a relatively smooth surface.

[0024] In contrast, the manufacturing method in Patent Document 4 coats the steel sheet (constraint plate) with resin before stamping, thus avoiding limitations imposed by the surface irregularities of the resin-coated area after stamping. Furthermore, since the constraint plate is partially bonded to the steel sheet (blank), they are integrally stamped, eliminating the need for an additional stamping process. However, in the aforementioned manufacturing method, after the resin-coated constraint plate is bonded to the steel sheet (blank), it is heated, pressed, and then stamped. Therefore, the resin sometimes completely cures due to heating. If the resin is completely cured, its ductility decreases, and the resin layer may break during stamping. In the case of the impact energy absorption component described above, if the resin layer breaks, it cannot adequately prevent the breakage of the main component during axial or flexural crushing, thus failing to achieve the desired impact energy absorption performance. Additionally, vibration damping may also decrease.

[0025] In contrast, the manufacturing method in Patent Document 5 involves overlapping a first metal plate and a second metal plate using a resin adhesive, followed by stamping and curing of the resin adhesive. Since the resin adhesive is not cured during stamping, resin breakage is avoided. However, if the resin adhesive is not cured before stamping, the surface pressure load during stamping may cause the resin adhesive to leak from the gap between the first and second metal plates. If the resin adhesive leaks from between the metal plates during stamping, the mold becomes contaminated with resin, hindering continuous production.

[0026] Furthermore, in automotive components that absorb collision energy during vehicle collisions, the resin constituting the sandwich structure needs to have a specified thickness to ensure collision energy absorption performance. However, if the resin adhesive is not cured and the components are stamped as in Patent Document 5, the resin leaks out between the two metal plates, making it impossible to achieve the specified resin thickness.

[0027] In contrast, Patent Document 6 describes a method in which a first body component and a second body component are joined using a resin-based decay adhesive, and the decay adhesive is pre-cured by heating or the like before being joined to a third body component. This method prevents the decay adhesive from sagging when assembling a body by bonding stamped automotive parts together; therefore, it cannot prevent resin leakage (or overflow) caused by stamping pressure when the two metal plates holding the resin are stamped.

[0028] The present invention was made to solve the above-mentioned problems, and its object is to provide a method for manufacturing automotive parts that can manufacture automotive parts having a sandwich structure formed by sandwiching resin with steel plates (metal plates) at low cost, and can prevent resin breakage during manufacturing.

[0029] Methods for solving problems

[0030] The inventors have conducted in-depth research on methods to prevent resin breakage and leakage (overflow) in a manufacturing method described in Patent Document 4, which involves forming a sandwich structure on a steel sheet before stamping and then stamping it into a part shape. If the resin is heated before stamping to completely cure it, the resin may break during stamping. On the other hand, if heating is not performed before stamping, the resin will leak from between the steel sheets due to the pressure applied during stamping, making it impossible to ensure the required resin thickness. Furthermore, the leaked resin can contaminate the stamping die, potentially causing problems with part forming and quality.

[0031] If the coating resin is pre-adjusted to high viscosity and high elasticity, resin leakage during stamping can be prevented without pre-stamping heating. However, high viscosity / high elasticity resins have poor coatability, thus extending coating time and reducing productivity. Furthermore, there is the problem of achieving a uniform coating thickness with high viscosity / high elasticity resins.

[0032] Therefore, the inventors realized that by coating a steel plate with a resin of excellent coatability and viscosity, and pre-firing it under heat treatment conditions before stamping, the aforementioned problems could be solved. This invention is based on the above realization and specifically comprises the following structure.

[0033] The first aspect of the present invention provides a method for manufacturing an automotive component, comprising: a resin coating step, wherein a thermosetting resin is coated onto a steel plate before molding; a steel sheet patching step, wherein a steel sheet patch is applied to the resin-coated steel plate in a manner that covers the resin; a pre-firing step, wherein a sandwich structure component is pre-firing in such a manner that the elastic modulus of the resin is 45 MPa or more and the ductility is 10% or more, the sandwich structure component having a sandwich structure formed by sandwiching the resin between the steel plate and the steel sheet patch; and a stamping step, wherein the pre-firing sandwich structure component is stamped into a component shape for an automotive component.

[0034] The second aspect of the present invention provides a method for manufacturing an automotive component, comprising: a resin bonding step, wherein a thermosetting resin, formed into a sheet, is bonded to a steel plate before molding; a patch steel plate setting step, wherein a patch steel plate is set on the steel plate to which the resin is bonded, such that the resin is covered; a pre-firing step, wherein a sandwich structure component is pre-firing in such a way that the elastic modulus of the resin is 45 MPa or more and the ductility is 10% or more, the sandwich structure component having a sandwich structure formed by sandwiching the resin between the steel plate and the patch steel plate; and a stamping forming step, wherein the pre-firing sandwich structure component is stamped into a component shape for an automotive component.

[0035] Alternatively, it may also include a welding process, in which the steel sheet of the automotive component, which has been stamped and formed by the stamping process, is welded to the patch steel sheet.

[0036] The thickness of the resin can be greater than 0.2 mm and less than 3 mm.

[0037] The resin may be a thermosetting rubber-modified epoxy resin.

[0038] Invention Effects

[0039] In this invention, by including a pre-firing process that pre-fires the sandwich structure component to achieve an elastic modulus of 45 MPa or higher and an elongation of 10% or higher, resin overflow and breakage during stamping can be prevented simultaneously. Furthermore, since the sandwich structure is formed and then stamped into a component shape, the main component and the patch can be stamped in a single step. Therefore, compared to conventional methods that stamp each component separately, the number of processes can be reduced, enabling the low-cost manufacture of automotive components with sandwich structures. Attached Figure Description

[0040] Figure 1 This is an explanatory diagram illustrating the manufacturing method of an automotive component according to an embodiment.

[0041] Figure 2 This is an external view of an automotive component that is the subject of the implementation method.

[0042] Figure 3 It is a graph that conceptually represents the relationship between heating time and the viscosity, elastic modulus and ductility of thermosetting resins.

[0043] Figure 4 This is an illustration of another method of manufacturing a car component according to the embodiment.

[0044] Figure 5Figure 1 shows an example of the coating (adhesion) range of the resin in an embodiment.

[0045] Figure 6 Figure 2 shows an example of the coating (adhesion) range of the resin in the embodiment.

[0046] Figure 7 This is an explanatory diagram of the axial crush test of an embodiment.

[0047] Figure 8 This is a diagram (1) showing the pre-curing range of the resin in the comparative examples involved in the embodiments.

[0048] Figure 9 This is a diagram (Figure 2) showing the pre-curing range of the resin in the comparative examples involved in the embodiments. Detailed Implementation

[0049] One embodiment of the present invention provides a method for manufacturing an automotive component having a sandwich structure formed by sandwiching resin between steel sheets. Before describing this embodiment, firstly, using... Figure 2 The automotive component to which this invention is applied will be described.

[0050] Figure 2 The automotive component 1 shown is an example of an automotive component with a sandwich structure, which is the subject of this invention. The automotive component 1 is used in body frame components such as the front longitudinal beam, lower longitudinal beam (lower side beam), and center pillar, and absorbs collision energy by undergoing axial crushing or bending crushing when a collision load is input to the body.

[0051] The automotive component 1 includes an outer component 3, an inner component 5 joined to the outer component 3, a resin 7 coated on the inner surface of the outer component 3, and a patch 9 covering the resin 7 and joined to the inner surface of the outer component 3.

[0052] The outer component 3 is a cap-shaped component formed of steel plate, having a top plate portion 3a, a pair of longitudinal wall portions 3c that are continuous from the top plate portion 3a through a shoulder portion 3b, and flange portions 3d that are continuous from each longitudinal wall portion 3c. The inner component 5 is a flat plate-shaped component formed of steel plate, which is joined to the flange portion 3d of the outer component 3.

[0053] Resin 7 is applied to the inner surfaces of the top portion 3a, shoulder portion 3b, and side wall portion 3c of the outer component 3. A patch 9, formed of steel sheet, is a component that prevents the resin 7 from detaching from the outer component 3 when the automotive component deforms due to a vehicle collision. The patch 9 is disposed on the inner side of the outer component 3 in a manner that covers the resin 7, and both ends of the patch 9 are welded to the inner surface of the side wall portion 3c of the outer component 3.

[0054] The resin 7 is bonded to the outer part 3 and the patch 9 respectively through the pre-firing process S5 described later and the formal firing process performed before or after the body assembly, with a specified adhesive strength. The final adhesive strength after the formal firing process is preferably 10 MPa or more.

[0055] The resin 7 of the automotive component 1 is not limited to resin formed by coating a paint-like material, but can also be resin formed by bonding a material into a sheet shape using an adhesive or the like.

[0056] As described above, the automotive component 1 has a sandwich structure formed by sandwiching resin 7 between an outer component 3 made of steel sheet and a patch 9. This improves the surface rigidity of the top plate portion 3a, shoulder portion 3b, and longitudinal wall portion 3c of the outer component 3, and prevents steel sheet breakage during axial crushing or bending crushing as described above, thus improving the impact energy absorption performance of the automotive component 1. Furthermore, the resin 7 also functions as a vibration damping element, therefore, by having the aforementioned sandwich structure, the vibration damping performance of the automotive component 1 is also improved. Examples of steel sheets used for the outer component 3, inner component 5, and patch 9 include cold-rolled steel sheet, hot-rolled steel sheet, stainless steel sheet, galvanized steel sheet, galvanized alloy steel sheet, and aluminized alloy steel sheet.

[0057] In this embodiment, the method for manufacturing the above-described automotive component 1 will be described. For example... Figure 1 As shown, the manufacturing method of automotive component 1 in this embodiment includes a resin coating process S1, a sheet metal mounting process S3, a pre-firing process S5, a stamping process S7, and a welding process S9. Figure 1 As shown, in this embodiment, resin coating process S1 to welding process S9 are performed in a stamping production line. Figure 1 (a) ~ Figure 1 (f) The manufacturing process of the outer component 3, which has a sandwich structure, is schematically illustrated. Following the welding step S9, in the assembly process carried out on the assembly line, the inner component 5 is joined to... Figure 1 (f) External component 3, capable of manufacturing Figure 2 Automotive parts 1.

[0058] <Resin Coating Process>

[0059] like Figure 1 As shown in (b), the resin coating process S1 is a process of coating resin 7 onto the steel plate 11, which serves as a blank, before the outer part 3 is formed. The steel plate 11, which is punched into the blank shape of the outer part 3 in the blank production line (see reference...) Figure 1(a) The material is transferred to the stamping production line via a feeder with an attached suction rod, a conveyor, or other transfer device. A robot equipped with a dispenser (liquid metering spraying device) is installed on the stamping production line. The dispenser-installing robot applies resin 7 of a specified thickness within a specified range of the steel plate 11 transferred to the stamping production line.

[0060] The method of applying resin 7 is not limited to the method described above. For example, resin 7 can be applied by spraying using a spray nozzle (electrostatic coating), or resin 7 can be applied using a brush or the like. However, since the coating robot using a dispenser can accurately and quantitatively supply the coating amount, it is preferred to apply resin 7 to the steel plate 11 within a specified range and at a specified thickness.

[0061] The scope of the resin coating 7 is preferably set to include areas that effectively improve the impact energy absorption performance of the automotive component 1, and areas that demonstrate effects on vibration damping and rigidity. For example, in Figure 2 In the case of automotive component 1, during axial crushing or bending crushing, the presence of resin at the shoulder 3b of the outer component 3 can improve the impact energy absorption performance of automotive component 1. Therefore, resin 7 can be applied to at least the portion of the steel plate 11 corresponding to the shoulder 3b. Thus, it is possible to achieve the following: Figure 5 (a) In this manner, resin 7 can be applied to the entire area except for the welding portion to the patch 9 and the inner part 5, in a way that includes the portion corresponding to the shoulder 3b. Figure 6 (a) In that case, resin 7 is applied only to the area corresponding to shoulder 3b.

[0062] If the coating thickness of resin 7 is thinner than 0.2 mm, it is difficult to coat resin 7 evenly. Furthermore, if the coating thickness of resin 7 is thicker than 3 mm, it increases costs. For these reasons, the thickness (coating thickness) of resin 7 is preferably 0.2 mm or more and 3 mm or less.

[0063] Regarding the types of resin 7, thermosetting resins can be cited as examples. Examples of thermosetting resins include epoxy resins, polyurethane resins, ester resins, phenolic resins, melamine resins, and urea resins. In particular, thermosetting rubber-modified epoxy resins are preferred because their high ductility after heat curing makes them less prone to breakage during stamping after pre-firing (preheating).

[0064] <Steel Plate Installation Procedure>

[0065] like Figure 1As shown in (c), the patch steel plate setting process S3 is a process of setting the patch steel plate 13 on the steel plate 11 coated with resin 7 by covering it with resin 7. The patch steel plate is a replacement for the patch 9 (refer to...). Figure 2 The blank part before stamping. In the resin coating process S1, the steel plate 11 coated with resin 7 is transferred by a transfer device to a steel plate conveying robot located downstream of the distributor mounting robot. The steel plate conveying robot places the patch steel plate 13 at a predetermined position on the steel plate 11 in a manner covering the resin 7.

[0066] Resin 7 is coated onto steel plate 11, and then a patch steel plate 13 is disposed to cover the resin 7, thereby forming a sandwich structure in which the resin 7 is sandwiched between steel plate 11 and patch steel plate 13. Hereinafter, a sandwich structure having this structure will be described. Figure 1 The component in (c) is called sandwich structure component 15.

[0067] <Pre-firing process>

[0068] like Figure 1 As shown in (d), the pre-firing process S5 is a process of pre-firing the sandwich structure component 15 under heat treatment conditions where the resin 7 is not fully cured. In the resin coating process S1, the resin 7 coated on the steel plate 11 is adjusted to a viscosity suitable for coating. If it is not heated and cured and is directly stamped, the resin 7 will leak from between the steel plate 11 and the sheet steel plate 13 due to the pressure during stamping, resulting in problems such as the inability to ensure the specified resin thickness.

[0069] To prevent leakage of resin 7 during stamping, resin 7 needs to be heated and cured before stamping to achieve a certain viscosity (or elastic modulus). However, as mentioned above, if resin 7 is completely cured before stamping, the resin layer will break during stamping, reducing the impact energy absorption performance of the automotive component 1. Therefore, in the pre-firing process S5, the sandwich structure component 15 is pre-fired to achieve the physical properties of resin 7 suitable for stamping. Figure 3 The physical properties of resins suitable for stamping are described.

[0070] The term "resin leakage" has been used in the description up to this point, but this is a description assuming that the resin is in a fluid state (uncured state) during stamping. In this embodiment, the resin loses its fluidity by pre-firing it before stamping, thus making it difficult for "resin leakage" to occur during stamping after pre-firing. However, if the pre-firing is insufficient, the resin may deform and overflow between the steel sheets. If the overflow is small and the resin does not adhere to the mold, there is no problem in manufacturing. However, if the overflow becomes large, the resin adheres to the mold, making continuous manufacturing difficult, and thus becomes a problem.

[0071] In the following description, the phenomenon of resin having fluidity during stamping and being extruded into the mold by stamping pressure is described as "resin leakage (leakage)". The phenomenon of resin losing fluidity during stamping and being exposed between the steel sheets by stamping pressure, especially the phenomenon where the more resin adheres to the mold, the more resin is exposed, is described as "resin overflow". If the degree of resin exposure is small, and it is overflow to the extent that it does not adhere to the mold, then there is no manufacturing problem, and therefore it is not included in "resin overflow" which is a problem. For example, overflow that is not a problem is defined as overflow from the edge of the steel sheet of the sandwich structure member in a semi-circular shape with a radius (mm) less than 0.5 times the total thickness (mm) of the steel sheet thickness before forming + resin thickness + sheet thickness of the patch.

[0072] Figure 3 This is a conceptual graph representing the relationship between the heating time of a thermosetting resin at 170°C and the resin's viscosity, elastic modulus, and ductility. 170°C is the heat treatment temperature used to heat resins in common structural adhesives used in automobile manufacturing. For reference, the actual heating conditions (formal heating conditions) for fully curing resins in automotive structural adhesives vary slightly depending on the type of resin, but are typically a heating temperature of 150–170°C and a heating time of approximately 15 minutes.

[0073] like Figure 3 As shown in curve A, the resin, which is liquid before heating, gradually solidifies upon heating, and its elastic modulus increases. At this time, as shown in curve B, the viscosity of the resin also increases with the elastic modulus. On the other hand, the ductility of the resin, as shown in curve C, decreases in the opposite direction to the increase in elastic modulus. When the resin is completely cured as the heating time progresses, the changes in elastic modulus and ductility become smaller and gradually approach a near-constant level (the cured region). In addition, as thermosetting resins approach the cured region, their viscosity increases exponentially, and they lose their fluidity and change into a solid.

[0074] The dashed arrow i in the figure represents the range of elastic modulus of resin 7 that prevents resin 7 from overflowing during the stamping of the sandwich structure member 15. That is, if the elastic modulus shown by curve A is higher than that of dashed arrow i, resin overflow during stamping can be prevented. Furthermore, the dashed arrow ii in the figure represents the range of ductility of resin 7 that allows it to follow the deformation of the steel sheet during the stamping of the sandwich structure member 15. That is, if the ductility shown by curve C is higher than that of dashed arrow ii, resin breakage during stamping can be prevented.

[0075] Assuming that the sandwich structure member 15 is heated for the same heating time (e.g., 15 minutes) under existing formal firing conditions, the resin 7 will achieve the properties shown in the cured area, and thus the resin will not overflow between the steel plate 11 and the patch 9 due to the pressure applied during stamping. However, because its ductility is lower than that of the dashed arrow ii, the resin cannot follow the deformation of the steel plate, resulting in the breakage of the resin layer.

[0076] Therefore, by heating the resin under conditions where its elastic modulus is greater than or equal to the dashed arrow i and its ductility is greater than or equal to the dashed arrow ii, the resin can be made to have excellent stamping formability. Figure 3 For example, by setting the heating time in the pre-firing process S5 to a range above the heating time t1 when curve A (elastic modulus) intersects with the dashed line i and below the heating time t2 when curve C (ductility) intersects with the dashed line ii, the elastic modulus and ductility of the heated resin become values ​​suitable for stamping, thus preventing resin overflow and breakage during stamping.

[0077] As an example of specific heat treatment conditions, it is preferable to set the heating temperature to 140~210°C, which is at the same level as the existing formal firing conditions, and the heating time to 4 seconds~35 seconds. By pre-firing under such heat treatment conditions, the viscosity of resin 7 is about 40~90% of that of the cured region, and the ductility of resin 7 is about 2~7 times that of the cured region.

[0078] Detailed descriptions will be provided in the embodiments described later. As suitable physical properties for stamping, i.e., properties that prevent resin spillage and breakage during stamping, the elastic modulus is 45 MPa or higher, and the elongation is 10% or higher. In the above description, a lower limit for the elastic modulus is specified from the viewpoint of preventing resin spillage during stamping, and a lower limit for the elongation is specified from the viewpoint of preventing resin breakage during stamping; however, this does not mean that there are no upper limits for the elastic modulus and elongation.

[0079] like Figure 3 As shown, generally speaking, the elastic modulus and ductility of a resin have the following relationship: in the same resin, the higher the elastic modulus, the lower the ductility, and vice versa. Therefore, if a lower limit value for the elastic modulus is specified from the viewpoint of preventing resin overflow, then the value of ductility at this point ( Figure 3 The value at heating time t1 becomes the upper limit of ductility. Furthermore, if a lower limit of ductility is specified from the viewpoint of preventing resin breakage, then the value of the elastic modulus at this time (…) Figure 3The value at heating time t2 becomes the upper limit of the elastic modulus. Thus, by specifying the lower limits of the elastic modulus and ductility, the ranges of elastic modulus and ductility suitable for stamping are naturally determined.

[0080] By pre-firing the resin 7 to achieve properties suitable for stamping, as described above, the elastic modulus of the resin 7 can be higher than that during coating, preventing resin overflow during stamping. Furthermore, the high ductility of the resin 7 can be maintained, preventing resin layer breakage caused by stamping. Additionally, compared to heating the sandwich structure member 15 under existing formal firing conditions (e.g., 15 minutes), the heating time is extremely short, ranging from 4 to 35 seconds, thus shortening the manufacturing time.

[0081] There are no particular limitations on the pre-firing method. For example, one could consider heating the sandwich structure component 15 by inserting it into a high-temperature furnace (oven) where the atmosphere temperature is kept constant, or by heating the sandwich structure component 15 using electric heating or high-frequency induction heating.

[0082] The above is an example of using a device such as an oven located on the inlet side of the stamping press, i.e., upstream of the stamping press in the stamping production line, to perform the pre-firing process S5. However, the pre-firing process S5 can also be performed as follows: Figure 4 The process is carried out inside the stamping press as shown. As... Figure 4 In the case of pre-firing, for example, the following method can be considered: preheat the forming mold for stamping process S7 to a specified temperature using direct electrification heating or high frequency induction heating, load the sandwich structure component 15 on the heated forming mold and wait for a specified time (4 to 35 seconds).

[0083] <Stamping process>

[0084] Stamping process S7 is a process in which the sandwich structure component 15, pre-fired in the aforementioned pre-firing process S5, is stamped into the shape of an automotive component. Here, as... Figure 1 As shown in (e), the sandwich structure member 15 is stamped into the shape of the outer part 3 of the automotive part 1. By pre-firing the sandwich structure member 15 in the pre-firing process S5, the viscosity of the resin 7 is higher than that during coating, so even when pressure is applied during stamping, the resin 7 will not leak or overflow between the steel plate 11 and the patch steel plate 13. In addition, since the resin 7 is not completely cured, the ductility of the resin 7 is maintained at a high level, which can prevent the resin layer from cracking due to stamping.

[0085] <Welding Process>

[0086] like Figure 1 As shown in (f), welding process S9 is the process of welding the steel sheet 11 of the automotive component 1, which has been stamped in stamping process S7, to the patch steel sheet 13. In stamping process S7, the stamped component is transferred by a transfer device to the outlet side of the stamping machine. A robot equipped with a spot welding gun is located at the outlet side of the stamping machine. The robot uses this spot welding gun to spot weld the patch steel sheet 13 (patch 9) to the steel sheet 11 (outer component 3). Figure 1 (f) marked with an × symbol).

[0087] When the sandwich structure member 15 is stamped, the resin 7 is pressed against the steel plate 11 and the patch steel plate 13 under high surface pressure. Then, through the formal firing process described later, it is bonded to the steel plate 11 and the patch steel plate 13 with a specified bonding strength. Therefore, the welding process S9 can be omitted. However, the automotive component 1 of this embodiment absorbs collision energy through axial crushing or bending crushing. If the patch 9 peels off from the resin 7 during deformation, the collision energy absorption characteristics will be reduced. Therefore, it is preferable to fix the patch steel plate 13 to the steel plate 11.

[0088] Figure 1 The component of (f) is transferred to the assembly line and formed by joining the inner component 5. Figure 2 The automotive component 1. The resin 7 of the automotive component 1, manufactured as described above, is fully cured through a subsequent formal firing process, thereby bonding it to the outer component 3 and the patch 9 with a specified strength. Hereinafter, an example of using electrodeposition coating, which is commonly performed in automobile manufacturing, to carry out the formal firing process will be described.

[0089] In the internal component 5 and Figure 1 After the components in (f) are joined to manufacture automotive component 1, automotive component 1 is assembled as a car body. The car body is immersed in an electrodeposition coating, and after a coating layer is formed on the surface by electrodeposition, it is transferred to a drying oven or similar heat treatment process. Through this drying heat, the resin 7 of automotive component 1 is completely cured. As described above, the drying process of the electrodeposition coating performed on the car body assembled using automotive component 1 can be positioned as the formal firing process of this embodiment.

[0090] The formal firing process for automotive component 1 is not limited to the above, and can also be carried out before body assembly. For example, automotive component 1 before body assembly can be placed in a high-temperature furnace (oven) with a constant atmosphere temperature for heating, or electric heating or high-frequency induction heating can be used to heat automotive component 1 before body assembly.

[0091] In any case, by heating the automotive component 1 at a specified temperature and for a specified time, the resin 7 bonds to the outer component 3 and the patch 9 with a specified adhesive strength through the adhesive properties of the resin itself. The heat treatment conditions in the above-mentioned formal firing process, even the heat treatment conditions for complete curing of the resin 7, are as described above: a heating temperature of 150~170°C and a heating time of about 15 minutes. However, these heat treatment conditions vary depending on the type of resin 7, and can therefore be appropriately adjusted so that the adhesive strength of the heated resin 7 reaches a specified value (e.g., 10 MPa or more).

[0092] As described above, according to this embodiment, since the sandwich structure member 15 is pre-fired and then stamped into a component shape under heat treatment conditions before the resin 7 is fully cured, the stamping process can be performed without leakage or overflow of the resin 7, and the breakage of the resin 7 during molding can also be prevented. Therefore, it is possible to manufacture an automotive component 1 with the required impact energy absorption performance and vibration damping properties.

[0093] Furthermore, compared to existing manufacturing methods that separately stamp out the external component 3 and the patch 9, this embodiment can complete a series of processes within a stamping production line, thereby improving the productivity of the automotive component 1.

[0094] Furthermore, since the resin 7 is applied to the blank, i.e., the steel sheet 11, before the outer component 3 is stamped, the resin 7 can be applied with a uniform thickness without being limited by the surface irregularity of the component, compared to the case where the resin 7 is applied to the component after stamping. As a result, deviations in the collision energy absorption performance and vibration damping performance of the automotive component 1 can be reduced.

[0095] The above-described manufacturing method involves coating the steel plate 11 with a coating-like resin 7. However, a resin bonding process can be performed instead of the resin coating step S1, where the resin 7 is bonded to a sheet. When bonding the sheet-like resin 7, for example, a lamination device is used to bond the sheet-like resin 7 to the steel plate 11. In this case, adhesive tape or adhesive can be used to pre-fix the resin 7 to the steel plate 11. Furthermore, when the patch steel plate 13 is provided to cover the resin 7, adhesive tape or adhesive can also be used to pre-fix the resin 7 to the patch steel plate 13. However, if the sheet-like resin 7, such as double-sided tape, has inherent adhesive strength, the aforementioned adhesive tape or adhesive is not required.

[0096] It has been explained that the coating thickness of resin 7 is preferably 0.2 mm or more, which allows for a uniform coating thickness. However, when the resin 7 is bonded in sheet form, the thickness of resin 7 is not limited to this. The lower limit of the resin 7 thickness in this invention is simply that the resin 7 can be uniformly formed; in the case of sheet-like resin 7, the sheet thickness can also be around 20 μm. From a cost perspective, the upper limit of the sheet thickness of resin 7 is preferably set to 3 mm or less, similar to the coating case.

[0097] The sheet-like resin 7 has a certain degree of hardness, so it is less likely to leak during stamping compared to the coating-like resin 7. However, by pre-firing, the hardness can be adjusted to be suitable for the stamping process S7 (hardness that does not cause overflow). However, if the sheet-like resin 7 has a hardness that can withstand stamping (resin 7 does not overflow) and is not damaged during stamping, the pre-firing process S5 can be omitted.

[0098] in addition, Figure 1 An example is the resin coating process S1 to the pre-firing process S5 performed within a stamping production line that stamps the sandwich structure component 15 into a part shape. However, these processes do not necessarily need to be performed within the same stamping production line. For example, a manufacturing production line for producing the sandwich structure component 15 and a stamping production line for stamping the sandwich structure component 15 into a part shape can be set up separately. In this case, after performing the resin coating process S1 to the pre-firing process S5 on the manufacturing production line of the sandwich structure component 15, the manufactured sandwich structure component 15 can be transferred to the stamping production line using a transfer device to perform the stamping process S7.

[0099] Furthermore, welding process S9 does not necessarily need to be performed within the stamping production line. For example, it can be performed after stamping process S7. Figure 1 (e) The component is transferred to the assembly line, and welding process S9 is performed when the internal component 5 is joined on the assembly line.

[0100] Example

[0101] The effects of the manufacturing method of the present invention will be explained based on specific embodiments. In this embodiment, for a steel plate 11 with a thickness of 1.4 mm and a tensile strength of 1470 MPa, as... Figure 5 (a) or Figure 6 As shown in (a), after applying or pasting resin 7, as Figure 5 (b) or Figure 6As shown in (b), a 0.4 mm thick sheet steel plate 13 with a tensile strength of 270 MPa is used to form a sandwich structure component 15. The coating thickness (or sheet thickness) of the resin 7 is set in the range of 0.2 to 3 mm. Then, the sandwich structure component 15 is pre-fired under various heating methods and heat treatment conditions (heating temperature 140 to 210 °C, heating time 4 to 35 seconds). The heating method is any one of electric heating (electric), high-temperature furnace (oven), or mold heating (heating the forming mold used in the stamping process to a specified temperature by electric heating or high-frequency induction heating). Figure 5 This is an example where resin 7 is coated on the entire steel plate 11 (excluding the parts that are welded after stamping) (the resin / range in Table 1 is "full"). Figure 6 This is an example where resin 7 is applied only to the shoulder 3b of the steel plate 11, which can become the outer part 3 (resin / range in Table 1, "shoulder").

[0102] The pre-fired sandwich structure component 15 is stamped into shape as follows: Figure 2 The shape of the outer component 3 is shown, and its stamping formability is evaluated. Here, it is observed whether resin 7 overflows from the outer component 3 and the patch 9 after stamping.

[0103] Regarding the evaluation of resin overflow, the situation where no resin overflows from the steel plate at all, or where there is slight overflow but the resin does not adhere to the mold, is defined as "none". The situation where resin overflows significantly from the steel plate and adheres to the mold is defined as "yes". Specifically, overflow in a semi-circular arc shape with a radius (mm) less than 0.5 times the total thickness (mm) of the steel plate edge of the sandwich structure component before molding (steel plate thickness + resin thickness + sheet steel plate thickness) is evaluated as "none", which is different from overflow that is a manufacturing problem.

[0104] Then, the inner component 5 is welded onto the stamped outer component 3 to assemble it. Figure 2 After the automotive component 1 was fired, it was heated at 170°C for 15 minutes to carry out the formal firing process. Then, the automotive component 1 that had undergone the formal firing process was subjected to an axial crush test.

[0105] Axial crush test such as Figure 7 As shown, a load was input along the axial direction of automotive component 1 at a test speed of 17.8 m / s. The load-stroke curve was measured when the test piece underwent 80 mm axial crushing deformation, reducing its length from 200 mm to 120 mm, to determine the absorbed energy. Additionally, the deformation state and whether the outer component 3 fractured were observed using a high-speed camera. Table 1 shows the evaluation results of the structure of each evaluated component, the pre-sintering heat treatment conditions, the stamping formability, and the axial crushing test results.

[0106] [Table 1]

[0107] Invention Example A uses a dispenser to dispense resin 7 in a thickness of 0.2 mm. Figure 5 (a) An example of coating within the area, overlapping patch 9, and pre-firing at 200°C for 13 seconds. The test specimen weighed 1.17 kg, and no resin overflowed after pressing. In addition, the axial crush test results showed that the base material (outer part 3) did not break, the absorbed energy was 13.4 kJ, and the EA / weight (energy absorbed per unit weight) was 11.5 kJ / kg.

[0108] Invention Example B involves using an adhesive tape to bond a 1mm thick sheet of resin 7. Figure 5 (a) An example of pre-fixing within the range of overlap patch 9 and pre-firing in an oven at 150°C for 5 seconds. The test specimen weighed 1.21 kg, and no resin overflowed after pressing. In addition, the axial crush test results showed no parent material fracture, an absorbed energy of 15.5 kJ, and an EA / weight of 12.8 kJ / kg.

[0109] Invention Example C utilizes a dispenser to distribute resin 7 in a 3mm thickness. Figure 5 (a) An example of coating within the range of (a), overlapping patch 9, and pre-firing for 25 seconds using a mold heated to 200°C. The test specimen weighed 1.33 kg, and no resin overflowed after pressing. In addition, the axial crush test results showed no parent material fracture, absorbed energy of 18.9 kJ, and EA / weight of 14.2 kJ / kg.

[0110] Invention Example D uses a dispenser to distribute resin 7 in a 1mm thickness. Figure 6 (a) An example of coating within the area, overlapping patch 9, and pre-firing at 170°C for 8 seconds. The test specimen weighed 1.21 kg, and no resin overflowed after pressing. In addition, the axial crush test results showed no parent material fracture, absorbed energy of 15.5 kJ, and EA / weight of 12.8 kJ / kg.

[0111] In Invention Example E, resin 7 is dispensed using a dispenser at a thickness of 0.2 mm. Figure 5 An example of coating within the area of ​​(a), overlapping patch 9, and pre-firing at 140°C for 6 seconds. The test specimen weighed 1.17 kg, and no resin overflowed after pressing. Furthermore, the axial crush test showed no breakage of the base material. The absorbed energy was lower than that of Invention Example A, but higher than Comparative Example A (without resin 7) described later, at 11.9 kJ, with an EA / weight of 10.2 kJ / kg.

[0112] Invention Example F utilizes a dispenser to dispense resin 7 in a thickness of 0.2 mm. Figure 5An example of coating within the area of ​​(a), overlapping patch 9, and pre-firing at 210°C for 35 seconds. The test specimen weighed 1.17 kg, and no resin overflowed after pressing. Furthermore, the axial crush test showed no matrix fracture. The absorbed energy was 13.0 kJ higher than Comparative Example A (without resin 7) described later, with EA / weight of 11.1 kJ / kg.

[0113] Invention example G utilizes a dispenser to dispense resin 7 in a thickness of 0.2 mm. Figure 5 The example was prepared by coating within the area of ​​(a), overlapping patch 9, and pre-firing at 170°C for 4 seconds. The test specimen weighed 1.17 kg, and no resin overflowed after pressing. In addition, the axial crush test showed no fracture of the base material. The absorbed energy was 12.0 kJ, which was higher than that of Comparative Example A (without resin 7) described later, and EA / weight was 10.3 kJ / kg.

[0114] In Invention Example H, a dispenser is used to dispense resin 7 in a thickness of 0.2 mm. Figure 5 The example was prepared by coating within the area of ​​(a), overlapping patch 9, and pre-firing at 170°C for 15 seconds. The test specimen weighed 1.17 kg, and no resin overflowed after pressing. In addition, the axial crush test showed no fracture of the base material. The absorbed energy was 12.9 kJ, which was higher than that of Comparative Example A (without resin 7) described later, and EA / weight was 11.0 kJ / kg.

[0115] Comparative Example A is an example without resin 7. In Comparative Example A, which does not have a sandwich structure, the axial crush test confirmed the fracture of the base material. Furthermore, the absorbed energy was 10.7 kJ, and the energy absorption per kilogram (EA / kg) was 9.2 kJ / kg.

[0116] Comparative Example B is an example where resin 7 is present but not pre-fired. In the coated state, the unpre-fired resin significantly overflows during stamping. Furthermore, the highly fluid resin tends to scatter, raising concerns about potential damage to the apparatus and testing equipment; therefore, an axial crush test was not performed.

[0117] Comparative Example C uses a dispenser to apply resin 7 in a 0.2 mm thickness. Figure 5 An example of coating within the area of ​​(a), overlapping patch 9, and then formally fired in an oven at 170°C for 900 seconds (15 minutes). The test specimen weighed 1.17 kg, and no resin overflowed after pressing. However, the axial crush test confirmed the fracture of the base material, and compared with Comparative Example A, almost no increase in absorbed energy was observed.

[0118] Comparative Example D uses a dispenser to apply resin 7 in a 0.2 mm thickness. Figure 5(a) An example of coating within the area, overlapping patch 9, and pre-firing at 170°C for 45 seconds. The test specimen weighed 1.17 kg, and no resin overflowed after pressing. In addition, the axial crush test confirmed the fracture of the base material, and compared with Comparative Example A, almost no increase in absorbed energy was observed.

[0119] As described above, in Invention Examples A to H, no resin 7 overflow occurred during stamping. Furthermore, although it is impossible to visually evaluate whether resin 7 fractured during stamping, Invention Examples A to H all exhibited higher energy absorption performance than Comparative Examples A to D.

[0120] Furthermore, the elastic modulus and ductility of the pre-fired resins in the examples in Table 1 were investigated using the following method. First, the gap between two steel plates was adjusted to 0.2 mm, and uncured resin was added between them. After heating under the pre-fired conditions in Table 1, the steel plates were peeled off to create a 0.2 mm thick resin plate. Next, this plate-shaped resin was processed into a dumbbell shape (JIS No. 6 dumbbell) to create a test piece. A tensile test was conducted at a tensile speed of 2 mm / min until the resin fractured. The elongation between the gauge marks at the point of resin fracture was divided by the initial gauge mark distance (=20 mm) to obtain a percentage, which was used as the ductility of the test piece. In addition, the slope of the stress (tensile strength) between the strain variables 0 and 0.005 in the elastic region was calculated from the stress-strain curve obtained from the above tensile test, and this slope was used as the elastic modulus of the test piece. The results are shown in Table 1.

[0121] As described above, the elastic modulus and ductility of the pre-fired resin under various pre-firing conditions were measured. The results showed that the elastic modulus was 45 MPa or higher and the ductility was 10% or higher. That is, if the physical properties of the pre-fired resin are an elastic modulus of 45 MPa or higher and a ductility of 10% or higher, then as shown in Table 1, it can be seen that there is no resin overflow when the sandwich structure component is stamped, and it shows high energy absorption performance (no resin fracture occurs) in the axial crush test.

[0122] When comparing examples B to D, none of them met the conditions of an elastic modulus of 45 MPa or more and an elongation of 10% or more. Resin overflow occurred when the elastic modulus was less than 45 MPa, and resin breakage occurred when the elongation was less than 10%. Therefore, when neither the elastic modulus nor the elongation is met, it is impossible to simultaneously prevent resin overflow and breakage during stamping.

[0123] As described above, it can be seen that by pre-firing the sandwich structure component with an elastic modulus of 45 MPa or more and an elongation of 10% or more after pre-firing, the overflow and breakage of resin during stamping can be suppressed.

[0124] The test pieces used in the tensile test were prepared under the condition that the resin thickness was the thinnest within the range of resin thickness (0.2 mm to 3 mm) specified in this invention, i.e., the assumed minimum ductility. Therefore, it is assumed that if the resin thickness is within the range specified in this invention, the ductility will not be lower than that described in Table 1 when pre-fired under the same heating conditions, and resin breakage will not occur.

[0125] However, Patent Document 6 described above illustrates a technique for suppressing resin sagging caused by gravity by locally pre-curing the resin. Therefore, an investigation was conducted into whether such a technique could suppress resin overflow during stamping, and the results are shown in Table 2.

[0126] [Table 2]

[0127] Comparative Examples E-H in Table 2 are comparative examples related to the technology in Patent Document 6. The resin thickness, resin placement area, heating temperature, and heating time are the same as those in Invention Examples A-D in Table 1, except that the area for resin curing is limited. In Patent Document 6, the resin in the lower region is pre-cured in the assembled position, but in Comparative Examples E-H, as... Figure 8 , Figure 9 As shown, the resin on the outer periphery of the coated (adheded) resin is pre-cured. Figure 8 This is an example where resin 7 is coated on the entire steel plate 11 (excluding the parts that are welded after stamping) (the resin / range in Table 2 is "full"). Figure 9 This is an example where resin 7 is applied only to the portion of the steel plate 11 that can become the shoulder 3b of the outer part 3 (resin / range in Table 2, "shoulder"). Additionally, as a heating method, high-frequency induction heating is used, referring to Patent Document 6.

[0128] As described above, the sandwich structure component 15, in which only the outer peripheral portion of the resin 7 is pre-cured, is stamped into... Figure 2 The shape of the outer component 3 is shown, and its stamping formability is evaluated, that is, whether the resin 7 overflows from the outer component 3 and the patch 9 after stamping.

[0129] As a result, as shown in Table 2, Comparative Examples E to H were unable to suppress resin overflow during stamping. This is believed to be because the strong pressure applied to the resin during stamping caused the pre-cured portion to break under the internal pressure.

[0130] As stated above, while the technology in Patent Document 6 is effective in preventing resin sagging due to gravity, it cannot prevent resin overflow caused by the strong pressure applied during stamping. Therefore, even compared to the technology in Patent Document 6, the present invention is superior as a method for manufacturing automotive parts with a sandwich structure.

[0131] Industrial applicability

[0132] According to the present invention, a method for manufacturing an automotive component is provided, which manufactures an automotive component having a sandwich structure formed by sandwiching resin with steel plates (metal plates) at low cost, and can prevent resin breakage during manufacturing.

[0133] Label Explanation

[0134] 1. Automotive parts

[0135] 3 External components

[0136] 3a Top plate section

[0137] 3b Shoulder

[0138] 3c Longitudinal wall section

[0139] 3D flange

[0140] 5 Internal components

[0141] 7 Resin

[0142] 9 Patch

[0143] 11 Steel Plate

[0144] 13. Patch steel plate

[0145] 15. Sandwich structure components.

Claims

1. A manufacturing method of an automobile component, comprising: a resin coating step of coating a thermosetting resin on a steel sheet before forming; a patch steel sheet setting step of setting a patch steel sheet on the steel sheet on which the resin is coated in a manner of covering the resin; a pre-baking step of pre-baking a sandwich structure member having a sandwich structure formed by sandwiching the resin with the steel sheet and the patch steel sheet in a manner of making an elastic modulus of the resin 45 MPa or more and ductility 10% or more; and a press forming step of press forming the sandwich structure member after the pre-baking into a component shape of the automobile component.

2. A manufacturing method of an automobile component, comprising: a resin sticking step of sticking a thermosetting resin formed into a sheet shape on a steel sheet before forming; a patch steel sheet setting step of setting a patch steel sheet on the steel sheet on which the resin is stuck in a manner of covering the resin; a pre-baking step of pre-baking a sandwich structure member having a sandwich structure formed by sandwiching the resin with the steel sheet and the patch steel sheet in a manner of making an elastic modulus of the resin 45 MPa or more and ductility 10% or more; and a press forming step of press forming the sandwich structure member after the pre-baking into a component shape of the automobile component.

3. The manufacturing method of the automobile component according to claim 1 or 2, wherein the manufacturing method of the automobile component further comprises a welding step of welding the steel sheet and the patch steel sheet of the automobile component press formed by the press forming step.

4. The manufacturing method of the automobile component according to any one of claims 1 to 3, wherein a thickness of the resin is 0.2 mm or more and 3 mm or less.

5. The manufacturing method of the automobile component according to any one of claims 1 to 4, wherein the resin is a thermosetting rubber-modified epoxy resin. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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