AUTOMOBILE IMPACT RESISTANCE ENERGY ABSORPTION PART AND METHOD OF MANUFACTURING AN AUTOMOBILE IMPACT RESISTANCE ENERGY ABSORPTION PART
Patent Information
- Authority / Receiving Office
- MX · MX
- Patent Type
- Patents
- Current Assignee / Owner
- JFE STEEL CORP
- Filing Date
- 2023-02-13
- Publication Date
- 2026-06-12
Smart Images
Figure MX435357B0
Abstract
Description
AUTOMOBILE IMPACT RESISTANCE ENERGY ABSORPTION PART AND METHOD OF MANUFACTURING AN AUTOMOBILE IMPACT RESISTANCE ENERGY ABSORPTION PART FIELD The present invention relates to an automotive impact-resistant energy absorption part and a method for manufacturing the automotive impact-resistant energy absorption part, and more particularly to an automotive impact-resistant energy absorption part that is axially crushed when an impact load is exerted from a front or rear side of the car body to absorb the impact energy, and a method for manufacturing the automotive impact-resistant energy absorption part. BACKGROUND Many techniques exist for improving the impact resistance and energy absorption properties of automobiles, such as optimizing the shape, structure, or materials of automotive parts. Furthermore, in recent years, numerous techniques have been proposed to both improve impact resistance and reduce the weight of car bodies by using foamed resin to fill the interior of closed-section automotive parts. For example, in Patent Literature 1, a technique is disclosed in which, in an automobile structural member having a structure in which an enclosed space is formed inside by aligning the direction of upper portions of hat-shaped cross-section parts such as a side sill, a floor member, a pillar, and overlapping flange portions, the bending strength and torsional stiffness of the automobile structural member are improved while suppressing an increase in weight by filling the interior with a foam filler, and improving the stiffness and crash safety of the automobile body. Furthermore, in Patent Literature 2, a technique is disclosed in which, when an interior space of a closed cross-section shape such as a pillar where hat-shaped cross-section parts meet and flange portions are combined, is filled with a high-stiffness foam body, the high-stiffness foam body is fixed by compression counterforce due to the filling and foaming of the high-stiffness foam body to improve vibration damping performance that suppresses vibration sound transmission, and improve strength, stiffness, and impact resistance energy absorption properties. Patent Literature 3 discloses a carbon fiber reinforced plastic (CFRP) metal composite material in which a reinforcing material formed from CFRP, consisting of a plurality of fiber layers laminated together, is bonded to a metal member surface with a thermosetting adhesive. The CFRP metal composite has a structure that includes a residual shear stress reduction portion with a gradually decreasing thickness from the main body of the reinforcing material toward the outer edge. This portion reduces the residual shear stress generated in the thermosetting adhesive due to a difference in the coefficient of linear thermal expansion between the metal member and the reinforcing material after bonding. Furthermore, Patent Literature 4 discloses an automotive part comprising a front side member that includes: an energy-absorbing portion formed of fiber-reinforced plastic (FRP) having a tubular cross-section that causes sequential axial crushing from an input end by an input load in an axial direction; and a support portion formed continuously with the energy-absorbing portion and formed of FRP, and attached to automotive parts. The energy-absorbing portion has reinforcing fibers oriented equally in a longitudinal direction of the front side member and in a direction perpendicular to the longitudinal direction, the support portion has reinforcing fibers oriented isotropically, and the automotive part can be integrally molded. APPOINTMENT LIST PATENT LITERATURE Patent Literature 1: JP 2006-240134 A Patent Literature 2: JP 2000-318075 A Patent Literature 3: JP 2017-61068 A Patent Literature 4: JP 2005-271875 A BRIEF DESCRIPTION TECHNICAL PROBLEM In accordance with the techniques disclosed in Patent Literatures 1 and 2, it is stated that by filling the interior of an automobile part with a foam filling or foam body, it is possible to improve the resistance to bending deformation, the energy absorption properties of impact resistance and the stiffness against torsional deformation of the automobile part, and to suppress deformation of the automobile part. However, for automotive parts such as a front side member and a crash box that absorb impact resistance energy by bellows-like buckling deformation when an impact resistance load is introduced from the front or rear side of a car and causes axial crushing, even when the technique of filling the inside of the automotive part with a foam filler or foam body is applied, since the foam filler or foam body is simply filled inside the automotive part, the bond strength between the automotive part and the foam filler or foaming agent is insufficient.Consequently, the problem has arisen that the foam filler or foaming agent inside the part is expelled through a gap or similar opening formed at a joint during a collision, hindering improvements in impact resistance and energy absorption properties. Furthermore, the need for an additional foam resin filling process without creating any gaps has also been raised, increasing production costs in automotive part manufacturing. MA / a / ZUZ J / UU10 f J Furthermore, in accordance with the techniques described in Patent Literatures 3 and 4, it is established that flexural strength can be improved by adhering CFRP to the surface of a metal, and a reduction in the hours of labor for assembling parts and a reduction in the weight increase due to a reduction in the number of fastening parts can be achieved by integrally manufacturing parts taking into account the orientation of the CFRP itself. However, even when CFRP is applied to an axially crushing component involving deformation, it exhibits high strength but significantly low elongation. Therefore, a problem has arisen: CFRP rupture and fracture occur as soon as bellows-like deformation begins, and its impact resistance and energy absorption properties are not improved. Furthermore, CFRP is very expensive. The present invention has been made to solve the aforementioned problems, and an object of the present invention is to provide: an automotive impact-resistant energy-absorbing part, such as a front side member and a shock box, which, when an impact-resistant load is introduced from the front or rear side of an automotive body and causes axial crushing, improves the impact-resistant energy-absorbing effect by forming a thick coating film on an outer surface, can function as a vibration-damping material that absorbs the vibration generated in the automotive body, and can reduce additional production processes, thus avoiding a large increase in production cost; and a method for manufacturing the automotive impact-resistant energy-absorbing part. SOLUTION TO THE PROBLEM The inventors have intensively studied a method for solving the aforementioned problems and have discovered that it is possible to improve the impact resistance energy absorption effect without requiring an additional filling process with a filler material such as foam resin, without forming any separation, by using an electroplated paint, which is commonly used in automotive coating processes. The present invention is based on these findings and specifically includes the following configurations. An automotive impact resistance energy absorption portion according to the present invention is provided in a front portion or a rear portion of an automotive body, the automotive impact resistance energy absorption portion being axially crushed when an impact resistance load is introduced from a front or rear side of the automotive body to absorb the impact resistance energy and includes: a tubular member formed by using a hat-shaped section portion including a top portion and a side wall portion;a covering portion made of a material having a lower strength than the tubular member, the covering portion being disposed on the outer surfaces of the top portion and the side wall portion in a part including a corner portion configured to connect the top portion and the side wall portion, with a gap of 0.2 mm or more and 3 mm or less from the outer surface of the top portion, the surface; MA.a.ZUZ J / UU10 f J exterior of the side wall portion and an exterior surface of the corner portion; and a coating film of an electrodeposition paint formed in the separation. A method for manufacturing an automotive impact-resistant energy-absorbing part according to the present invention provided in a front or rear portion of an automotive body, the automotive impact-resistant energy-absorbing part being axially crushed when an impact-resistant load is introduced from a front or rear side of the automotive body to absorb the impact-resistant energy, includes: a part-manufacturing step consisting of manufacturing a pre-coated part including: a tubular member formed by using a hat-shaped section part including a top portion and a side-wall portion;and a covering portion made of a material having a lower strength than the tubular member, the covering portion being disposed on an outer surface of the tubular member in a portion that includes a corner portion configured to connect the top portion and the side wall portion, with a separation of 0.2 mm or more and 3 mm or less from an outer surface of the top portion, an outer surface of the side wall portion and an outer surface of the corner portion;and a coating step consisting of forming a coating layer on a surface of a pre-coated part, including separation by an electrodeposition coating process in a state where the pre-coated part is bonded to the car body, and forming a coating film by thermosetting the coating layer by a paint baking treatment following the electrodeposition coating process. ADVANTAGEOUS EFFECTS OF THE INVENTION According to the present invention, during the compressive deformation of the tubular member that absorbs impact resistance energy by axial crushing when an impact resistance load is applied from the front or rear of the car body, the buckling resistance of the tubular member is enhanced, and bellows-shaped buckling deformation can occur without reducing the deformation resistance of the tubular member. Furthermore, fracture of the flexural portion during buckling deformation of the tubular member can be prevented, and the impact resistance energy absorption properties can be significantly improved. In addition, vibrations from the car engine and vibrations transmitted to the car body from various directions during driving are absorbed, and the vibration damping properties can be enhanced.Furthermore, the coating portion is included in the present invention. Therefore, it is possible to form a coating film of a target thickness by electrodeposition, which is typically used in the coating process for automobile manufacturing, and to manufacture the coating film using a conventional automobile manufacturing line as is. BRIEF DESCRIPTION OF THE FIGURES Figure 1 shows a perspective view illustrating an impact resistance energy absorption part of an automobile in accordance with a first embodiment of the present invention. Figure 2 shows a perspective view illustrating a state before a coating film is formed on the impact-resistant energy-absorbing part of automobiles in accordance with the first embodiment of the present invention. Figure 3 shows a graph that illustrates a relationship between the tensile strength of a steel sheet and the relationship between a critical radius of curvature for fracture and a sheet thickness of the steel sheet. Figure 4 shows an explanatory view of a method for manufacturing an impact-resistant energy absorption part for automobiles in accordance with a second embodiment of the present invention. Figure 5 shows a view illustrating another aspect of the impact resistance energy absorption portion of automobiles according to the present invention (part 1). Figure 6 shows a view illustrating another aspect of the impact resistance energy absorption part of automobiles according to the present invention (part 2). Figure 7 shows a view illustrating another aspect of the impact resistance energy absorption part of automobiles according to the present invention (part 3). Figure 8 shows a view illustrating another aspect of the impact resistance energy absorption part of automobiles according to the present invention (part 4). Figure 9 shows a view illustrating another aspect of the impact resistance energy absorption part of automobiles according to the present invention (part 5). Figure 10 shows a view to describe an axial crush test method in an example. Figure 11 shows a view to describe an impact vibration test method in the example. Figure 12 shows a view illustrating a vibration mode as a target for calculating a character frequency in the evaluation of vibration characteristics by the impact vibration test method in the example. Figure 13 shows a view illustrating a structure of a test specimen used as an example of the invention in the example. Figure 14 shows a view illustrating a structure of a test specimen used as a comparative example in the example. DESCRIPTION OF THE MODALITIES First modality The following describes an energy absorption component for impact resistance of a car in accordance with this standard. Note that, in this description ML / a / ZUZ J / UU10 f J and the drawings, elements that have substantially the same function and configuration are denoted by the same reference numbers, and redundant description is omitted. An automotive impact-resistant energy-absorbing part (1) (Figure 1) according to the present embodiment is provided in a front or rear portion of an automotive body and is axially compressed when an impact-resistant load is introduced from a front or rear side of the automotive body to absorb the impact-resistant energy. In a state where the impact-resistant energy-absorbing part (1) is attached to the automotive body, a paint coating layer is formed by electrodeposition on a surface thereof, and the coating layer is cured by a paint baking treatment to form a coating film.As illustrated in Figure 1, a coating portion (5) is provided on one side of the outer surface of a tubular member (3) formed using a hat-shaped section portion, and a coating film (13) of an electrodeposited paint is formed in a gap between the hat-shaped section portion and the coating portion (5). Figure 2 illustrates a state of the automotive impact-resistant energy-absorbing portion (1) prior to electrodepositing (hereafter referred to as the pre-coated portion (2)). Each member will be described below with reference to Figures 1 and 2. Tubular member The tubular member (3) is formed from a sheet of metal such as a sheet of steel, and has a tubular shape joining an outer part (7) having a hat-shaped cross-section (hat-shaped section part in the present invention) including a top portion (7a), side wall portions (7b), and corner portions (7c) connecting the top portion (7a) and the side wall portions (7b) with an inner part (9) having a flat sheet shape in the joining portions (10) which are flange portions of the outer part (7). In the course of an impact resistance load being introduced at one end of the automotive impact resistance energy absorption part (1) in the axial direction, the tubular member (3) is axially crushed when the impact resistance load exceeds the buckling strength,The impact resistance energy absorption part of automobiles (1), including said tubular member (3), absorbs impact resistance energy by repeatedly causing a bellows-shaped buckling deformation in the tubular member (3). Part of coating The covering portion (5) is formed from a sheet of metal, such as a sheet of steel, disposed on one side of the outer surface of the outer part (7) in a portion that includes the corner portions (7c) to form a gap (11) of 0.2 mm or more and 3 mm or less, and is joined by spot welding or similar means at the joining portions (12) (see Figure 2). The covering portion (5) may be provided along the entire length of the outer part (7) in the axial direction, but may be provided only along an interval where it is desired that the part MA.a.ZUZ J / UU10 f J of impact resistance energy absorption for automobiles (1) is deformed into a bellows shape. For example, in a case where the impact resistance energy absorption part (1) is installed on the front of an automobile body and it is desired that it deform into a bellows shape in an interval ranging from the front end to a mid-section in the axial direction, the covering portion (5) is sufficient to be provided in this interval of the outer part (7). Furthermore, a portion of the outer part (7) where the covering portion (5) is not provided, for example, an interval from the mid-section to the rear end in the axial direction, is sufficient to be formed, for example, in the form of a cord extending in the axial direction, or to have a large sheet thickness in order to increase resistance to deformation. The coating film (13) of an electrodeposited paint is formed in the separation (11) during electrodeposition, which is a common coating process in automotive manufacturing (see Figure 1). Examples of electrodeposited paint types include cationic polyurethane electrodeposited paint, cationic epoxy electrodeposited paint, cationic urethane electrodeposited paint, anionic acrylic electrodeposited paint, fluororesin electrodeposited paint, and similar products. Electrodeposited coating will be described in detail in a second modality described later. Normally, when electrodeposition coating is performed, a coating film of approximately 0.05 mm is formed on the surface of a steel sheet. However, in the present embodiment, the coating portion (5) is provided on the outer surface side of the outer part (7) on the pre-coated part (2). The electrodeposition paint then enters the gap (11) to form a coating layer, and this coating layer is subjected to heat treatment, resulting in the formation of a coating film (13) with a thickness of 0.2 mm or more and 3 mm or less, as illustrated in Figure 1. The reason why the impact-resistant energy absorption effect of the automotive impact-resistant energy absorption part (1) is improved by the formation of such a coating film (13) will be described below. During the course of an impact resistance load that is introduced at one end of the automotive impact resistance energy absorption part in the axial direction and the tubular member exceeds the buckling resistance and is axially crushed, the automotive impact resistance energy absorption part, including the tubular member formed from a metal sheet, such as a steel sheet, absorbs the impact resistance energy by repeatedly causing a bellows-shaped buckling deformation in the tubular member. However, a bellows-shaped bent part has a small radius of curvature, unique to sheet metal, so the stress is concentrated on the outer surface of the bent part, making fracture likely. If a fracture occurs in the bent part during axial crushing, the impact resistance energy absorption effect is significantly reduced. Therefore, to improve the impact resistance energy absorption effect, it has been necessary to prevent fracture in the tubular member that buckles and deforms in a bellows shape. MA.a.ZUZ J / UUl O f J In particular, in recent years, high-strength steel sheets adopted for automotive parts to achieve both impact resistance characteristics and weight reduction in car bodies have little elongation compared to conventional-strength steel sheets. The relationship between the tensile strength level of the steel sheet and the critical bending radius R for fracture / sheet thickness t of the steel sheet illustrated in Table 1 and Figure 3 (see Reference 1 below) indicates that, for the same sheet thickness, the higher the tensile strength TS of the steel sheet, the more likely fracture is to occur, even with a large bending radius.In other words, when the energy-absorbing component of a car crash, which uses a high-strength steel sheet, bends and deforms into a bellows shape, fracture is likely to occur at the bent end of the bellows shape, increasing the strength of the steel sheet. This has also been a factor hindering the development of improved strength in steel sheets used for impact-resistant energy-absorbing components for weight reduction in car bodies. (Reference 1) Hasegawa Kohei, Kaneko Shinjiro, Seto Kazuhiro, “Cold-rolled and annealed galvanized (GA) high-strength steel sheets for car cabin structures,” JFE Technical Report, No. 30 (August 2012), pp. 6–12. Table 1 MA.a.ZUZ J / UU10 f J Steel Sheet Strength Level Tensile Strength [MPa] RA [-] Class 780 MPa 810 Less than 1 0 Class 980 MPa 1020 10 Class 1180 MPa 1210 15 Class 1320 MPa 1330 2 0 Class 1470 MPa 1510 2 5 On the other hand, in the present invention, when the tubular member (3) twists and deforms into a bellows shape at the moment of impact, an object is interposed and inserted between two metal sheets in a concave, compressed, flexed portion. This increases the radius of curvature of the concave flexed portion, thus preventing fracture of the bent tip end of the bellows shape. Here, the object interposed between the metal sheets is preferably as lightweight as possible to avoid increasing the weight of the impact-resistant energy-absorbing component. Furthermore, the object is preferably one that can be manufactured using a conventional automotive production line as is, without requiring additional material or processing, such as foam resin or similar materials in the conventional example.In view of the above, in the present invention, an electrodeposition coating is used, which is generally done in automobile manufacturing. Furthermore, in the tubular member (3), a region capable of absorbing a large portion of the impact resistance energy is the corner portion (7c) connecting the top portion (7a) and the sidewall portion (7b). However, the corner portion (7c) is also a region likely to undergo machining, where work hardening occurs when the outer part (7) is pressure-formed, and its elongation is further reduced by work hardening. Therefore, the bent-tip end portion of the bellows shape in the corner portion (7c) is a region where fracture is particularly likely to occur. In view of the foregoing, in the present invention, the coating portion (5) is provided on the outer surface side of the outer part (7), including the corner portions (7c), such that a gap (11) of 0.2 mm to 3 mm is formed between the coating portion (5) and the outer surface. The electroplated coating enters the gap (11) during the electroplating process, and a coating layer of a predetermined thickness can be formed. The coating layer is cured in an electroplating baking process, adheres to the gap (11), and becomes the coating film (13).The impact-resistant energy-absorbing portion (1) of the automotive form, according to this embodiment, can suppress, when the tubular member (3) has buckled and deformed at the moment of impact, the occurrence of fracture of the bent tip portion of a bellows shape by interposing the coating film (13) inside the concave bending portion of the bellows shape to increase the radius of curvature of the concave bending portion. Therefore, the impact-resistant energy-absorbing effect is improved. Note that the appropriate thickness of the coating film (13), which ranges from 0.2 mm to 3 mm, will be described in subsequent examples. The coating film (13) of the impact-resistant energy-absorbing part (1) according to the present embodiment also functions as a vibration-damping material. For example, in a case where the automotive impact-resistant energy-absorbing part (1) is used as a front side member, which is a part that absorbs impact resistance energy by axial crushing, the coating film (13) absorbs the vibration of an automotive engine mounted on the front side member, thereby improving the vibration-damping properties. The advantageous effects of the improved vibration-damping properties will also be described in the examples provided later. As described above, the coating portion (5) is intended to form the coating film (13) of a predetermined thickness during electrodeposition and does not require strength. Therefore, the coating portion (5) can have lower strength and a thinner sheet thickness compared to the outer portion (7) and the inner portion (9). Furthermore, if the strength of the coating portion (5) is too high, it hinders the smooth, bellows-like buckling deformation of the tubular member (3) at the moment of impact. Therefore, the strength is preferably 440 MPa or less, for example. Second modality In the present embodiment, a method for manufacturing the impact-resistant energy-absorbing component of automobiles (1) described in the first embodiment will be described. The method for manufacturing the MA / a / ZUZ J / UU10 f J an automotive impact-resistant energy absorption part (1) according to this embodiment includes a part-making process for manufacturing the pre-coated part (2) wherein the coating part (5) is provided on the tubular member (3), and a coating process for forming a coating layer on the pre-coated part (2) after bonding the pre-coated part (2) to an automotive body and forming the coating film (13) by thermosetting the coating layer by baking treatment. Each process will be specifically described below with reference to Figure 4, which is a cross-sectional view of the automotive impact-resistant energy absorption part illustrated in Figures 1 and 2.Figure 4 shows a cross-sectional view of the automotive impact resistance energy absorption part illustrated in Figures 1 and 2. Part manufacturing process The manufacturing process for the part is a manufacturing process of the pre-coated part (2) wherein the coating portion (5) is provided on the outer surface side of the tubular member (3) formed by joining the outer part (7) and the inner part (9). As illustrated in an example in Figure 4A, the coating portion (5) is installed on the outer surface side of the outer part (7) within a range that includes the corner portions (7c) with a gap (11) of 0.2 mm to 3 mm between the coating portion (5) and the outer surface of the outer part (7), and is joined to the outer surfaces of the side wall portions (7b) by spot welding or similar means. Furthermore, the coating portion (5) can be made contact with the upper portion (7a) of the outer part (7) for further joining (see Figures 6B and 7B).The joining of the outer part (7) and the inner part (9) or the joining of the outer part (7) and the covering part (5) can be done first. Coating process The coating process is a process of forming the coating film (13) in the gap (11). In a state where it is attached to an automobile body, the pre-coated part (2) manufactured in the part manufacturing process described above undergoes an electrodeposition coating, which is generally performed during automobile manufacturing, whereby the coating film (13) is formed in the gap (11). The process will be described hereafter in conjunction with electrodeposition coating and other coating processes used in automobile manufacturing. In general, to improve weather resistance, design, corrosion resistance, and similar properties, a steel sheet used in an automobile body undergoes sequential processes including electroplating, an intermediate coating, a base coat, and a clear coat. Electroplating, the first process applied to the steel sheet, is crucial for enhancing rust prevention on the car body and is widely used. Electroplating involves a process to form a coating layer on the steel sheet by electroplating, followed by a process to cure the coating layer using a drying oven. MA / a / ZUZ J / UUl O f J (oven) or similar. An example of electrodeposition coating will be described below, and its correspondence with the coating process in this modality will be given. In general electroplating, the first step is a surface pretreatment, such as degreasing, washing, or chemical conversion, applied to an automotive part formed by pressing or similar processes from a sheet of steel. The surface-treated automotive part is then immersed in an electroplating tank containing an electroplating paint. This paint acts as the cathode, and the object to be coated (the automotive part) acts as the anode. Consequently, a coating layer of the electroplating paint forms on the surface of the steel sheet (cationic electroplating coating).The automotive part on whose surface the paint coating layer is formed by electrical conduction electrodeposition in the electrodeposition tank is subjected to further treatment, such as washing, and is transported to a high-temperature drying oven, and the coating layer is cured by a baking treatment. Similarly, when the pre-coated part (2) (see Figure 4A) manufactured in the part manufacturing process of the present embodiment is immersed in the electrodeposition tank described above in a state attached to the car body frame, the electrodeposition paint enters the gap (11), and a coating layer is formed by subsequent electrical conduction. The electrodeposition paint coating layer also forms on the surface of the steel sheet in a region other than the gap (11), but its thickness is as thin as approximately 0.05 mm, so the illustration is omitted. Next, the impact-resistant energy-absorbing portion (1) of the automobile, where the coating layer has formed, is subjected to the baking treatment described above, and the coating layer cures. The coating film (13), having a predetermined thickness, is then fixed to the gap (11) (Figure 4B). Note that the coating film (13) preferably forms in a solid state throughout the gap (11), but it is conceivable that the coating film (13) may form in a state where a void exists in part of the gap (11). Even in such a case, the advantage of the coating film (13) is that it can form in a state where a void exists in part of the gap (11). Even in such a case, the advantageous effects of the present invention can be achieved compared to a case where there is no coating film (13).Therefore, a case where there is a gap in a part of the separation (11) is not excluded. Electroplating has excellent adhesion properties (the ability to extend the coating onto uncoated areas). Therefore, electroplating is particularly effective for interior components with many irregularities (such as parts of a car body frame or engine room). There are several types of electroplating paints, and they are selected based on the coating objective and desired functions (adhesion properties, energy efficiency, corrosion resistance, etc.). Electroplating with a flexible coating film is primarily used for... ML / a / ZUZ J / UU10 f J inner sheet (interior) applies to the automotive impact resistance energy absorption part (1) of the present invention, and as examples of the type, one can name, for example, a cationic polyurethane electrodeposition paint, a cationic epoxy electrodeposition paint, a cationic urethane electrodeposition paint, an anionic acrylic electrodeposition paint, a fluororesin electrodeposition paint, and the like. The automotive part undergoing electroplating is subjected to an intermediate coating, a base coat, and a clear top coat. These coatings are primarily applied using a method called electrostatic painting, which involves spraying a charged coating onto the object to be coated. The intermediate coating masks surface roughness and restricts light transmission, while the base coat and clear top coat provide design benefits such as color, durability, and other advantages.Examples of coatings used for intermediate coating, top-coat base coating, and top-coat clear coating include polyester-melamine paint, acrylic-melamine paint, acrylic-polyester-melamine paint, alkyd-polyester-melamine paint, and the like. In accordance with the above description, and pursuant to the method for manufacturing the automotive impact-resistant energy-absorbing part (1) described herein, the coating part (5) is provided on the tubular member (3). Therefore, the coating film (13) of an electroplated paint is formed in the gap (11) between the tubular member (3) and the coating part (5) during the electroplating process, which is generally carried out in the coating process in automotive manufacturing. Consequently, it is possible to manufacture the automotive impact-resistant energy-absorbing part (1) that has a high impact-resistant energy-absorbing effect without significantly increasing the production cost. In the first and second embodiments, as illustrated in the cross-sectional views of Figure 4, an example has been described in which the joining portions (12) of the coating portion (5) are provided on the side wall portions (7b) of the outer portion (7), and the coating film (13) is formed on the outer surfaces of the top portion (7a), the corner portions (7c), and portions of the side wall portions (7b). However, the present invention is not limited to this. For example, as illustrated in Figure 5, the coating film can be formed mainly on the outer surfaces of the top portion (7a) and the corner portions (7c) and only slightly on the outer surfaces of the side wall portions (7b).Furthermore, as described above, if the coating film forms on the outer surfaces of the corner portions (7c), where fracture is particularly likely to occur upon impact, it can be expected to enhance the impact resistance and energy absorption effect. Therefore, as illustrated in Figure 6, the coating film (13) can form primarily on the outer surfaces of the corner portions (7c). In this process, two coating parts (5) are involved. ML / a / ZUZ J / UUl O f J can be used and the joining portions (12) can each be provided on the top portion (7a) and the side wall portion (7b) (Figure 6A), or a covering portion (5) can be used and brought into contact with the center of the top portion (7a) to be joined, and the joining portions (12) can be provided on the side wall portions (7b) (Figure 6B). Furthermore, as illustrated in Figure 7, the coating film (13) can be formed on the outer surfaces of the side wall portions (7b) and the corner portions (7c). Similar to Figure 6, two coating portions (5) can be used, and joining portions (12) can each be provided on the top portion (7a) and the side wall portion (7b) (Figure 7A). Alternatively, one coating portion (5) can be used and placed in contact with the center of the top portion (7a) to join it, and the joining portions (12) can be provided on the side wall portions (7b) (Figure 7B). Additionally, as illustrated in Figure 8, the coating portion (5) of a hat-shaped cross-section type can be positioned on the outer portion (7) and the inner portion (9), and joined at the joining portions (10). In the present embodiment, the tubular member (3) is used as an example, comprising the outer portion (7) having a hat-shaped cross-section and the inner portion (9) having a flat sheet shape, but the present invention is not limited to this. As illustrated in the examples in Figure 9, the present embodiment is also applicable to a tubular member formed by facing the hat-shaped portions of the section and combining the flange portions. Figure 9A shows an example where the covering portion (5) of the aspect illustrated in Figure 5 is provided on each of the facing hat-shaped portions.Similarly, Figure 9B shows an example where the coating portion (5) of the polished appearance in Figure 6A is provided, Figure 9C shows an example where the coating portion (5) of the polished appearance in Figure 7B is provided, and Figure 9D shows an example where the coating portion (5) of the polished appearance in Figure 8 is provided. Note that in Figure 9, the coating portion (5) of the polished appearance in Figure 8 is provided on each of the facing parts of the hat-shaped section. Note that in Figure 9, the outer parts (7) are denoted by the same reference numbers as those in Figures 4 through 8, and the inner parts (9) are denoted by the corresponding reference numbers for the outer parts (7).Furthermore, Figure 9 illustrates examples where the outer part (7) and the inner part (9) are hat-shaped section parts that have the same shape, but the inner part (9) can also be a hat-shaped section part that has a different shape than the outer part (7). Examples Experiments were carried out to confirm the advantageous effects of the automobile impact resistance energy absorption part (1) in accordance with the present invention, and the results thereof will be described below. In the present example, the impact resistance energy absorption part of automobiles according to the present invention was used as a test sample, and the following tests were performed: ML / a / ZUZ J / UUl O f J Evaluation of the energy absorption characteristics of impact resistance by means of an axial crushing test and the evaluation of the damping characteristics by measuring a frequency response function and calculating a characteristic frequency in an impact vibration test. In the axial crushing test, as illustrated in Figure 10, a load was applied to a test specimen (21) that included the tubular member (3) in the axial direction at a test speed of 17.8 m / s. A load stroke curve was then measured, indicating the relationship between load and stroke (amount of axial crushing deformation) when the test specimen (21) underwent axial crushing deformation of 80 mm from a test specimen length (an axial length L₀ of the test specimen (21)) of 200 mm to 120 mm. Additionally, high-speed camera images were taken to observe the state of deformation and the presence or absence of fracture in the tubular member (3). Furthermore, the energy absorbed during a stroke from 0 to 80 mm was obtained from the measured load stroke curve. Furthermore, the energy absorbed in a stroke from 0 to 80 mm was obtained from the measured load stroke curve. On the other hand, in the impact vibration test, as illustrated in Figure 11, an acceleration sensor (manufactured by Ono Sokki Co., Ltd.: NP-3211) was attached to the hanging test specimen (21) near an edge on the inside side of the upper portion (7a) of the outer part (7). An impact vibration was then applied to the inside side of the lateral portion 7b of the outer part (7) of the test specimen (21) using an impact hammer (manufactured by Ono Sokki Co., Ltd.: GK-3100). The impact force and acceleration generated in the test specimen (21) were fed into an FFT analyzer (manufactured by Ono Sokki Co., Ltd.: CF-7200A), and a frequency response function was calculated. In this case, the frequency response function was calculated by averaging and five-stroke curve fitting.Next, a vibration mode analysis was performed using the calculated frequency response function, and a character frequency was obtained for the same mode. Figure 12 illustrates a target vibration mode. Figure 13 illustrates the structure and shape of the test specimen (21), which is the automotive impact-resistant energy absorption portion (1) (Figure 1 and Figure 4B), where the coating film (13) is formed according to the first and second embodiments described above. The test specimen (21) includes the tubular member (3) where the outer portion (7) and the inner portion (9) are joined by spot welding, and the coating portion (5) is bonded to the outer surfaces of the side wall portions (7b) of the outer portion (7). The coating film (13) is formed between the outer portion (7) and the coating portion (5). Figure 13 illustrates an example where the gap (11) formed from the top portion (7a), the corner portions (7c), and to the side wall portions (7b), and between them and the coating portion (5) is 3 mm. However, in the present example, test specimens (21) were also prepared with a gap (11) of 2 mm, 1 mm, and 0.2 mm, and the test was performed by changing the thickness of the coating film (13) formed at the gap (11). In addition, as comparative examples, as illustrated in Figure 14, samples are prepared MA / a / ZUZ J / UU10 f J of test (31) including the tubular member (3) and the coating portion (5) and in which the coating film (13) is not formed, and the axial crush test and the impact vibration test were carried out in a manner similar to the examples of the invention. Table 2 illustrates the structures of the test specimens (21) that are the examples of the invention and the test specimens (31) that are the comparative examples, the conditions of the coating films, and the weights of the test specimens, in addition to the results of the calculation of the energy absorbed when the axial crush test was carried out, and the results of the character frequency obtained by the impact vibration test. MA / a / ZUZ J / UU10 f J Table 2 Vibration characteristics [Character frequency] [Hz] 430 340 340 310 00 01 155 175 155 155 155 350 Absorbed energy [Test speed 17.8 m / s] [kJ / kg] 7.4 7.9 9.6 9.7 6.0 5.9 7.8 6.3 [kJ] 0.6 9.5 11.2 6.5 7.0 8.5 Presence or absence of fracture in tubular member Absence Absence Absence Absence Absence Absence Absence Absence Presence Presence Presence Presence Test sample weight [kg] 1.28 1.21 1.21 1.17 1.10 1.19 1.08 1.09 96 0 1.28 Coating film Thickness [mm] CO OI OI 0.2 iiii 0.05 CO Presence or absence Presence Presence Presence Presence Presence Absence Absence Absence Absence Absence Absence Presence Structure Separation between (1) and (2) CO OI OI 0.2 CO OI 1 CO (3) Inner part Sheet thickness [mm] OI OI OI OI OI OI OI OI OI OI OI Material [MPa] 590 590 590 590 590 590 590 590 590 590 590 590 (2) Coating part Sheet thickness [mm] 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 i 0.5 Material [MPa] 270 270 440 270 270 270 270 270 270 < 780 (1) Outer part Sheet thickness [mm] 1.2 OI OI OI OI OI OI OI OI OI Material [MPa] 590 590 590 1180 1180 590 590 086 1180 1180 590 Example of invention 1 Example of invention 2 Example of invention 3 Example of invention 4 Example of invention 5 Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Comparative example 5 Comparative example 6. θ IT ML / a / ZUZ J / UU10 f J In each of the invention examples 1 to 5, the test specimen (21) (Figure 13) was used, including the coating portion (5) and the coating film (13), and the strength (material) of the outer portion (7) and the coating portion (5), and the thickness of the coating film (13) were modified. On the other hand, in comparative examples 1 to 4, the test specimen (31) (Figure 14) was used, which includes the coating portion (5) but is not formed with the coating film (13), and the strength (material) and thickness of the outer portion (7), as well as the separation (11) between the outer portion (7) and the coating portion (5), were modified.In comparative example 5, a coating film was formed without including the coating part (5). In comparative example 6, the coating part (5) and the coating film (13) were included in a similar way to the test sample (21), but the strength of the material of the coating part (5) exceeds that of the material of the outer part (7) and the inner part (9). For test specimens formed with the coating film (13), the weight of the test specimen illustrated in Table 2 is the sum of the respective weights of the outer part (7), the inner part (9), the coating part (5), and the coating film (13). For test specimens without the coating film (13) (comparative examples 1 to 4), the weight of the test specimen is the sum of the respective weights of the outer part (7), the inner part (9), and the coating part (5). In comparative example 1, the weight of the test specimen was 1.08 kg, and the absorbed energy was 6.5 kJ. In addition, the character frequency was 155 Hz. In comparative example 2, the thickness of the outer sheet (7) and the separation between the outer part (7) and the coating part (5) were modified with respect to those of comparative example 1, and the weight of the test sample was 1.19 kg, and the absorbed energy was 7.0 kJ, which was increased compared to comparative example 1. The character frequency was 175 Hz. In comparative example 3, a high-strength steel sheet of class 980 MPa was used for the outer part (7), and the weight of the test specimen was 1.08 kg. The absorbed energy was 8.1 kJ, which was even higher compared to comparative example 2, but fracture occurred in the tubular member (3). The characteristic frequency was 155 Hz. In comparative example 4, a high-strength steel sheet of class 1180 MPa was used for the outer part (7), and the weight of the test specimen was 1.09 kg. The absorbed energy was 8.5 kJ, which was even higher compared to comparative example 3, but fracture occurred in the tubular member (3). The characteristic frequency was 155 Hz. In comparative example 5, a high-strength steel sheet of class 1180 MPa was used for the outer part (7), and a coating film was formed without installing the coating part (5). The thickness of the coating film (13) was 0.05 mm. The weight of the test specimen was 0.96 kg, and the absorbed energy was 8.7 kJ, which was increased compared to comparative example 4, but fracture occurred in the tubular member (3). The characteristic frequency was 155 Hz. MA.a.ZUZ J / UUl O f J In comparative example 6, the strength of the coating material (5) exceeded that of the outer (7) and inner (9) material (tubular member (3)), and a coating film (13) with a thickness of 3 mm was formed. The test specimen weighed 1.28 kg, and the absorbed energy was 8.1 kJ, which was higher compared to comparative example 1, but a fracture occurred in the tubular member (3). The characteristic frequency was 350 Hz. In example 1 of the invention, test specimen (21) was used, where a steel sheet with a steel sheet strength of 590 MPa-class was used for the outer part (7), and the coating film thickness (13) was 3 mm. The absorbed energy in example 1 of the invention was 11.1 kJ. The absorbed energy was significantly improved compared to the absorbed energy (= 6.5 kJ) in comparative example 1, where the same material was used but without the coating film (13), and no fracture occurred in the tubular member (3). Furthermore, the absorbed energy was significantly improved compared to the absorbed energy in comparative example 2. Additionally, the absorbed energy was significantly improved even compared to comparative example 3 (= 8.1 kJ), where a high-strength steel sheet of 980 MPa was used for the outer part (7), and comparative example 4 (= 8.5 kJ), where a high-strength steel sheet of 1180 MPa was used for the outer part (7). The weight of the test specimen (= 1.28 kg) in the invention example 1 increased compared to comparative example 1 (= 1.08 kg), comparative example 3 (= 1.08 kg) and comparative example 4 (= 1.09 kg). But the energy absorbed per unit weight obtained by dividing the energy absorbed by the weight of the test specimen was 8.7 kJ / kg, which improved compared to comparative example 1 (= 6.0 kJ / kg), comparative example 3 (= 7.5 kJ / kg) and comparative example 4 (= 7.8 kJ / kg). Furthermore, the character frequency in invention example 1 was 430 Hz, which increased significantly compared to comparative example 1, comparative example 3, and comparative example 4 (= 155 Hz). In example 2 of the invention, the same material was used as in example 1, and the thickness of the coating film (13) was fixed at 2 mm. The weight of the test specimen was 1.21 kg, lighter than that of example 1 (1.28 kg). The energy absorbed in example 2 was 9.0 kJ, an improvement over the energy absorbed (7.0 kJ) in comparative example 2, which has the same shape but a larger outer sheet thickness (7). Fracture did not occur in the tubular member (3). Furthermore, the energy absorbed per unit weight in example 2 of the invention was 7.4 kJ / kg, an improvement over comparative example 2 (5.9 kJ / kg). Furthermore, the character frequency in invention example 2 was 340 Hz, which increased significantly compared to comparative example 2 (= 175 Hz). In example 3, the thickness of the coating film (13) was fixed at 2 mm, similarly to example 2, and the strength of the steel sheet of the coating portion (5) was fixed at 440 MPa. In comparative example 6, where the strength of the steel sheet of the coating portion (5) was 780 MPa, exceeding the strength of the steel sheet of the outer portion (7), a fracture occurred in the tubular member (3), but no fracture occurred in example 3. Furthermore, the energy absorbed in the tubular member (3) was reduced. MA / a / ZUZ J / UU10 f J significant. Furthermore, the energy absorbed in invention example 3 was 9.5 kJ, which was an improvement compared to comparative example 6 (= 8.1 kJ). In the example of Invention 4, a high-strength steel sheet with a steel sheet strength of class 1180 MPa was used for the outer part (7), and the thickness of the coating film (13) was fixed at 1 mm. The energy absorbed in the example of Invention 4 was 11.2 kJ, and no fracture occurred in the tubular member (3). The absorbed energy was significantly improved compared to the comparative example 4 (= 8.5 kJ) where a steel sheet of the same material was used for the outer part (7) and fracture occurred. Furthermore, the weight of the test specimen in example 4 was 1.17 kg, lighter than that of example 1, and the absorbed energy per unit weight (= 9.6 kJ / kg) was improved compared to example 1 (= 8.7 kJ / kg) and comparative example 4 (= 7.8 kJ / kg).Furthermore, the character frequency in invention example 4 was 310 Hz, which increased significantly compared to the comparative example 4 (= 155 Hz). In example 5 of the invention, using the same material as in example 4, the thickness of the coating film (13) was fixed at 0.2 mm, which is approximately the same thickness as a lamination on a standard rolled steel sheet, and the weight of the test specimen was 1.10 kg. The energy absorbed in example 5 of the invention was 10.7 kJ, and the energy absorbed per unit weight was 9.7 kJ / kg, which was an improvement compared to comparative example 5 (9.1 kJ / kg) where a 0.05 mm coating film was formed without including the coating portion (5). Furthermore, fracture occurred in the tubular member in comparative example 5, but no fracture occurred in example 5 of the invention. Additionally, the characteristic frequency in example 5 was 280 Hz, which was an increase compared to comparative example 5 (155 Hz). Note that, although not illustrated in the table, in a case where the separation between the outer part (7) and the coating part (5) was set at 4 mm or more—that is, in a case where the coating film (13) was formed to a thickness of 4 mm or more—sufficient drying could not be achieved during the electroplating coating oven treatment, and coating dripping occurred, with the dry coating film not forming until a predetermined separation. Therefore, in the present invention, the suitable thickness of the coating film (13) was set between 0.2 mm and 3 mm. Thus, it has been shown that the impact resistance energy absorption part of automobiles (1) according to the present invention can effectively improve the impact resistance energy absorption effect while suppressing a weight increase in a case where an impact resistance load is introduced in the axial direction and causes axial crushing, and the frequency of character when an impact is applied increases and the vibration damping properties can be improved. Note that the reason why vibration damping properties improve with an increase in characteristic frequency is as follows. When the characteristic frequency of the tubular member (3), which is an impact-resistant element such as the front side element described above, falls within the vibration frequency range of a motor mounted on the element, it ML / a / ZUZ J / UU10 f J produces sympathetic vibration and increases vibration. For example, when the engine is running at 4000 rpm, which is a high normal driving speed, the crankshaft rotates at the same speed, and in a four-stroke engine, the explosion and vibrations occur once every two rotations. Therefore, the vibration frequency is 133 Hz in a four-cylinder engine, 200 Hz in a six-cylinder engine, and 267 Hz in an eight-cylinder engine. Consequently, with a characteristic frequency of approximately 280 Hz or higher, as in the present invention, the sympathetic vibration described above can be reliably prevented, and the vibration damping properties are improved. Industrial applicability According to the present invention, it is possible to provide: an automotive impact-resistant energy absorption part, such as a front side member and a shock box, which, when an impact-resistant load is introduced from the front or rear side of an automotive body and causes axial crushing, improves the impact-resistant energy absorption effect by forming a thick coating film on an outer surface, can function as a vibration damping material that absorbs the vibration generated in the automotive body, and can reduce additional production processes, thus avoiding a large increase in production cost; and a method for manufacturing the automotive impact-resistant energy absorption part. LIST OF REFERENCE SIGNS AUTOMOBILE IMPACT RESISTANCE ENERGY ABSORPTION PART PRE-COATED PART TUBULAR MEMBER COATING PART EXTERIOR PART 7a UPPER PORTION 7b LATERAL PORTION 7c CORNER PORTION INTERIOR PART 9a UPPER PORTION 9b LATERAL PORTION 9c CORNER PORTION JOINT PORTION (TUBULAR MEMBER) SEPARATION JOINING PART (COVERING PART) COATING FILM TEST SAMPLE (EXAMPLE OF INVENTION) SAMPLE TRIAL (COMPARATIVE EXAMPLE)
Claims
CLAIMS 1. An automobile impact resistance energy absorption part to be provided in a front portion or a rear portion of an automobile body, the automobile impact resistance energy absorption part being axially crushed when an impact resistance load is exerted from a front side or a rear side of the automobile body to absorb the impact resistance energy, and comprising: a tubular member formed using a hat-shaped section portion including a top portion and a sidewall portion;a coating portion made of a material of lower strength than the tubular member, the coating portion disposed over the outer surfaces of the top portion and the side wall portion in a portion including a corner portion configured to connect the top portion and the side wall portion, with a gap equal to or greater than 0.2 mm and equal to or less than 3 mm from the outer surface of the top portion, the outer surface of the side wall portion and an outer surface of the corner; and a coating film of an electroplated paint formed in the gap.
2. A method for manufacturing an automotive impact-resistant energy-absorbing part positioned on a front or rear portion of an automotive body, the automotive impact-resistant energy-absorbing part being axially crushed when an impact-resistant load is exerted from a front or rear side of the automotive body to absorb the impact-resistant energy, the method comprising: a part-making step for manufacturing a pre-coated part including: a tubular member formed using a hat-shaped section part including a top portion and a side-wall portion;and a covering portion made of a material having a lower strength than the tubular member, the covering portion being disposed on an outer surface of the tubular member in a portion that includes a corner portion configured to connect the top portion and the side wall portion, with a spacing of 0.2 mm or more and 3 mm or less from an outer surface of the top portion, an outer surface of the side wall portion and an outer surface of the corner portion;and a coating step consisting of forming a coating layer on a surface of a pre-coated part, including separation by an electrodeposition coating process in a state where the pre-coated part is fixed to the car body, and forming a coating film by thermosetting the coating layer by a paint baking treatment after the electrodeposition coating process.