Body frame part and method of manufacturing the same

Abstract

To provide a vehicle body skeleton component which can improve collision energy absorbed by bending when a collision load is inputted from a side of a vehicle body and a production method of the vehicle body skeleton component.SOLUTION: A vehicle body skeleton component 1 has: a member with a hat-shaped cross section or a member with a U-shaped cross section that has a top plate part 3a, and a pair of vertical wall parts 3c which is continuous from the top plate part 3a via a punch shoulder R part 3b; a resin layer 7 formed on an external surface of at least the punch shoulder R part 3b of the member with a hat-shaped cross section or the member with a U-shaped cross section; and a thin wall patch member 11 which is so provided as to straddle the top plate part 3a and covers a surface of the resin layer 7 from an external surface side, and of which both ends are joined to external surfaces of the pair of vertical wall parts 3c. The coated or pasted resin layer 7 is bonded an external surface of the member with a hat-shaped cross section or the member with a U-shaped cross section and the thin wall patch member 11 at bond strength of 10 MPa or more at a room temperature after being heated, and tensile strength of the thin wall patch member 11 is lower than that of the member with a hat-shaped cross section or the member with a U-shaped cross section.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a body frame part for an automobile, and more particularly to a body frame part that bends to absorb collision energy when a collision load is input from the side of the vehicle body, and a method for manufacturing such a body frame part. [Background technology]

[0002] Many technologies exist for optimizing the shape, structure, materials, etc. of automobile parts to improve the collision energy absorption performance of automobiles. Automobile parts that absorb collision energy are located, for example, on the side of the vehicle body, and absorb collision energy by bending when a collision load is input from the side of the vehicle body. In recent years, many technologies have been proposed that achieve both improved collision energy absorption performance and weight reduction of automobile parts by foaming and filling the interior of automobile parts with a closed cross-sectional structure with resin (such as foamed resin).

[0003] Patent Document 1 discloses a technique in which a filler is filled only between the outer panel and the reinforcement, and the average compressive strength of the filler is set to 4 MPa or more and the maximum bending strength is set to 10 MPa or more. The technique in Patent Document 1 makes it possible to reduce the amount of filler used as much as possible, thereby reducing the weight of the vehicle body and effectively improving collision safety.

[0004] Furthermore, Patent Document 2 discloses a reinforcement structure for a hollow structure (hollow panel) in which a metal reinforcement panel is installed between an inner panel and an outer panel. In the reinforcement structure of Patent Document 2, a second hollow region formed between the outer panel and the reinforcement panel is filled with foam, and cross-sectional shape retaining members are further arranged along the corners of the reinforcement panel. It is claimed that such a reinforcement structure can efficiently reinforce the hollow structure.

[0005] Furthermore, Patent Document 3 discloses a vehicle body frame part having an outer part having a top plate portion and a pair of vertical wall portions continuing from the top plate portion via a punch shoulder R portion (meaning a portion of the molded product), resin applied to the inner surface of the outer part, and a separation prevention member covering the surface of the resin. The resin applied to the inner surface of the outer part extends to at least a predetermined range on both sides of the top plate portion and the vertical wall portions, sandwiching the punch shoulder R portion, and after heating, is bonded to the inner surface with an adhesive strength of 10 MPa or more at room temperature. By bonding the resin to the inner surface of the outer part in this way, the buckling resistance of the part can be improved, thereby improving the collision energy absorption performance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-48054 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-226261 [Patent Document 3] Patent No. 6950871 Summary of the Invention [Problem to be solved by the invention]

[0007] According to Patent Documents 1 and 2, by filling the interior of an automobile part with a foam filler or foam, the strength of the automobile part against bending deformation and the impact energy absorption ability can be improved, and deformation of the automobile part can be suppressed. However, even if the above technology is applied to body frame parts that absorb collision energy by bending when a collision load is input from the side of the vehicle body, there are cases where the components that make up the parts break during the bending process.If the components that make up the parts break, the collision energy absorption performance does not improve as much as expected, which has been an issue.

[0008] Patent Document 3 claims that when a body frame part bends, resin is sandwiched between the metal plates inside the punch shoulder R portion, preventing the bending radius of the punch shoulder R portion from becoming significantly smaller and preventing cracks in the punch shoulder R portion, thereby improving the ability to absorb collision energy. However, since stiffening parts such as bulkheads are placed inside the side sill (rocker), which receives collision loads from the side of the vehicle body, to improve collision characteristics, it can be difficult to install resin and anti-detachment parts inside, assuming the existing side sill structure.

[0009] The present invention has been made to solve the above-mentioned problems, and has an object to provide a body frame part that can be applied to existing side sill structures and that can improve the amount of collision energy absorbed by bending when a collision load is input from the side of the vehicle body, and a method for manufacturing the body frame part. [Means for solving the problem]

[0010] (1) A vehicle body frame part according to the present invention is provided on a side of a vehicle body and bends when a collision load is input from the side of the vehicle body to absorb collision energy. The vehicle body frame part comprises a hat-shaped or U-shaped cross section member having a top plate and a pair of vertical wall portions continuing from the top plate portion via a punch shoulder R portion; a resin layer formed on the outer surface of at least the punch shoulder R portion of the hat-shaped or U-shaped cross section member; and a thin-walled patch member disposed so as to straddle the top plate portion and cover the surface of the resin layer from the outer side, with both ends joined to the outer surfaces of the pair of vertical wall portions. After being heated, the resin layer is adhered to the outer surface of the hat-shaped or U-shaped cross section member and to the thin-walled patch member with an adhesive strength of 10 MPa or more at room temperature, and the tensile strength of the thin-walled patch member is lower than that of the hat-shaped or U-shaped cross section member.

[0011] (2) In addition, in the above (1), the resin layer is formed by coating or pasting a resin.

[0012] (3) Furthermore, in the above (1), the thin patch member is arranged with a gap of 0.2 mm to 3 mm between it and at least the punch shoulder R portion, and the resin layer is formed in the gap by a coating film of electrocoating paint.

[0013] (4) Furthermore, the manufacturing method of a vehicle body frame part according to the present invention is the manufacturing method of a vehicle body frame part described in (2) above, a resin layer thickness determination step of determining a thickness of a resin layer formed by applying or attaching a resin; a resin layer forming step of forming a resin layer on the outer surface of the hat-shaped cross section member or the U-shaped cross section member by applying or pasting resin so that the thickness of the resin layer is determined in the resin layer thickness determining step; a thin patch member joining step of arranging a thin patch member so as to cover the surface of the resin layer formed in the resin layer forming step, and joining both ends of the thin patch member to the outer surface of the vertical wall portion; a heating step of heat-treating the hat-shaped cross-section member or the U-shaped cross-section member provided with the resin layer and the thin-walled patch member, The resin layer thickness determination step includes: Set the base plate thickness, base bending rigidity, and base weight of the hat-shaped cross section member or U-shaped cross section member that serves as the base having the required bending rigidity, The thickness of the resin layer when the plate thickness is thinner than the base plate thickness and the bending rigidity is not reduced to be lower than the bending rigidity of the base is determined as a lower limit value; The upper limit of the thickness of the resin layer is determined when the bending rigidity can be improved to the maximum without increasing the weight from the base weight. The thickness of the resin layer is determined between the above-mentioned lower limit and upper limit.

[0014] (5) Furthermore, the manufacturing method of a vehicle body frame part according to the present invention is the manufacturing method of a vehicle body frame part described in (3) above, a resin layer thickness determination step of determining the thickness of a resin layer formed by a coating film made of electrodeposition paint; a component manufacturing process for manufacturing a component including the hat-shaped cross section member or the U-shaped cross section member, and a thin-walled patch member disposed on an outer surface side of the hat-shaped cross section member or the U-shaped cross section member, the thin-walled patch member having a gap corresponding to the thickness determined in the resin layer thickness determination process between the thin-walled patch member and at least an outer surface of the punch shoulder R portion; a resin layer forming step of performing electrodeposition coating on the vehicle body to which the part is attached, and forming a resin layer in the gap by a coating film of the electrodeposition paint; a heating step of heat-treating the component on which the resin layer is formed, The resin layer thickness determining step includes: Set the base plate thickness, base bending rigidity, and base weight of the hat-shaped cross section member or U-shaped cross section member that serves as the base having the required bending rigidity, The thickness of the resin layer when the plate thickness is thinner than the base plate thickness and the bending rigidity is not reduced below the bending rigidity of the base is determined as a lower limit value, The upper limit of the thickness of the resin layer is determined when the bending rigidity can be improved to the maximum without increasing the weight from the base weight. The thickness of the resin layer is determined between the above-mentioned lower limit and upper limit. [Effects of the Invention]

[0015] According to the present invention, during the bending process of a hat-shaped cross-section member or a C-shaped cross-section member, the buckling strength is improved, the maximum collision load is increased, cracks are prevented from occurring, and the collision energy absorption performance is improved. Furthermore, the present invention can be applied to side sills that have stiffening parts such as bulkheads arranged inside, so that the collision energy absorption performance can be further improved while utilizing the existing side sill structure. This also makes it possible to accelerate the rise of the load input to the side sill structure at the beginning of a collision, thereby increasing the energy absorption at the beginning of the collision.It also makes it possible to detect the impact on the vehicle earlier, which can speed up the activation of airbags, brakes, and other devices that operate by detecting acceleration during a collision. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a perspective view showing a vehicle body frame part according to an embodiment; [Figure 2] 1 is a cross-sectional view showing a vehicle body frame part according to an embodiment of the present invention; [Figure 3] 1 is a diagram illustrating the bending and crushing process of a conventional vehicle body frame part when a collision load is input from the side of the vehicle body, and is a schematic diagram showing the cross-sectional shape of a portion where bending occurs. [Figure 4] 10A and 10B are diagrams comparing a three-layer structure model according to an embodiment with models of a conventional example and a comparative example. [Figure 5] 1 is a graph showing load-stroke curves of a body frame part having a three-layer structure and a conventional body frame part. [Figure 6] 1 is a graph showing the absorbed energy of a body frame part having a three-layer structure and a conventional body frame part. [Figure 7] FIG. 4 is a cross-sectional view (part 1) showing another aspect of the body frame part according to the embodiment. [Figure 8] FIG. 6 is a cross-sectional view (part 2) showing another aspect of the body frame part according to the embodiment. [Figure 9] FIG. 1 is a diagram illustrating an experimental method in an example. [Figure 10] 1 is a graph showing weight efficiencies (absorbed energy per unit weight) of examples of the present invention, conventional examples, and comparative examples in the working examples. DETAILED DESCRIPTION OF THE INVENTION

[0017] Before describing the vehicle body frame part according to the embodiment of the present invention, the background to the invention will be described below with reference to FIGS.

[0018] [Background to the invention] A conventional body frame part 31 formed from a metal plate such as a steel plate is, for example, a cylindrical member formed by joining an outer part 3, which is a hat-shaped cross section member, and an inner part 5, which is a flat plate-like member, as shown in FIG. 3(a). Such a vehicle body frame component 31 is attached to the side of the vehicle body with the top plate portion 3a of the outer component 3 facing the side of the vehicle body.

[0019] When a collision load is applied from the side of the vehicle body, the collision load is applied to the top plate portion 3a of the outer part 3, and as shown in Figure 3(b), the top plate portion 3a is stretched so as to spread outward, changing the angle of the vertical wall portion 3c. Then, when the buckling strength of the outer part 3 (the collision load at the time when bending occurs) is exceeded, the outer part 3 is crushed, and the body frame part 31 bends, as shown in Figure 3(c). During this bending process (bending crushing process), the body frame part 31 absorbs the collision energy.

[0020] During this process, collision energy is most easily absorbed if bending occurs without cracking the outer part 3. However, if cracks occur in the outer part 3 during the bending process, the deformation resistance to bending decreases and the outer part 3 bends easily, resulting in insufficient absorption of collision energy and preventing the outer part from performing its intended function.

[0021] In the outer part 3, the portion with the highest ability to absorb impact energy during the bending process is the punch shoulder R portion 3b connecting the top plate portion 3a and the vertical wall portion 3c. However, as shown in Figure 3(c), the bending radius of the punch shoulder R portion 3b becomes significantly smaller during the bending process of the outer part 3, so tensile stress concentrates on the outer surface, making it prone to cracking. In particular, when the outer part 3 is a press-formed member with a hat-shaped cross section, the punch shoulder R portion 3b is also the portion that is most susceptible to plastic deformation and work-hardening during the press-forming process. As a result, cracking is more likely to occur in the punch shoulder R portion 3b than in other portions such as the top plate portion 3a and the vertical wall portion 3c due to reduced ductility caused by work hardening during press-forming.

[0022] Furthermore, the high-strength steel sheets that have been adopted in recent years for automotive parts to achieve both crashworthiness and weight reduction have lower ductility than steel sheets of conventional strength. Therefore, for the same thickness, the higher the tensile strength (TS) of the steel sheet, the more likely it is to fracture (crack) at a larger bending radius.

[0023] After extensive research, the inventors came up with the idea that increasing the bending rigidity of the punch shoulder R portion 3b would prevent the bending radius of the punch shoulder R portion 3b from becoming smaller during the process of bending the outer part 3, thereby preventing tensile stress from concentrating on the outer surface and causing cracks.

[0024] The bending rigidity of the punch shoulder R portion 3b is expressed as the product of the Young's modulus E of the material used in the outer part 3 and the second moment of area I of the metal plate (steel plate, etc.) used in the outer part 3. The second moment of area I of a metal plate is proportional to the cube of the thickness of the metal plate, so increasing the thickness of the metal plate used in the outer part 3 can increase the bending rigidity, but this increases the weight of the part.

[0025] Therefore, instead of increasing the thickness of the metal plate used for the outer part 3, they came up with the idea of ​​forming a resin layer with a lower density and a lower Young's modulus than the metal plate on the outer surface of the punch shoulder R portion 3b, where stress concentrates and cracks occur during the bending process. They also came up with the idea of ​​covering the surface of the resin layer with a metal plate, creating a sandwich structure with the resin layer sandwiched between the metal plates, thereby increasing the total thickness. The bending stiffness (EI) of a three-layer (outer part 3 / resin layer / metal plate) sandwich structure can be evaluated using the general formula for the bending stiffness of laminated materials shown in Equation (1) below.

[0026]

number

[0027] In equation (1), L is the width of the laminate, i is the material, n is the number of layers, E i is the Young's modulus of material i, h i is the thickness from the material i=1 to the layer of material i, and λ is the distance from the surface of the material i=1 to the midplane of the laminate.

[0028] FIG. 4 shows the patterns of the cross-sectional structure in the thickness direction of the punch shoulder R portion 3b of the outer part 3, and the results of comparing the total thickness, bending rigidity, and weight for each pattern. FIG. 4(a) shows a model of a single-layer structure consisting of only a metal plate (thickness T0) corresponding to the outer part 3. Figure 4(b) shows the metal plate (thickness T0) corresponding to the outer part 3 and the resin layer (thickness T r This model has a three-layer structure (sandwich structure) in which a thin metal plate (thickness T) is bonded to a metal plate. FIG. 4(c) shows a model of a two-layer structure in which a thin metal plate (thickness T) is bonded to a metal plate (thickness T0) corresponding to the outer part 3.

[0029] In the example of dimensions shown in the figure, the thickness T0 of the metal plate corresponding to the outer part 3 is 1.4 mm, and the thickness T of the resin layer is set so that the bending rigidity of the models in Figs. 4(b) and 4(c) is twice that of the model in Fig. 4(a). r and the thickness T of the thin metal plate.

[0030] The total thickness of each model with the above dimensions and the weight per unit area based on Figure 4(a) are shown in the figure. As shown in Figure 4, Figure 4(b) has a three-layer (outer part 3 / resin layer / thin metal plate) sandwich structure, which increases the apparent plate thickness (total thickness) and improves bending rigidity. The inventors have discovered that by using a low-density resin in part of the three-layer structure, it is possible to reduce the weight of the part compared to Figure 4(c) with the same bending rigidity.

[0031] Since the bending rigidity is effectively improved by the outer part 3, resin layer, and thin metal plate being integrally supported by the load, the outer part 3 and resin layer, and the resin layer and thin metal plate must be bonded with a predetermined strength for the following reasons. For example, in the three-layer structure of Figure 4(b), if the outer part 3, resin layer, and thin metal plate are not bonded at all, the overall bending rigidity is the sum of the bending rigidities of the outer part 3, resin layer, and thin metal plate individually. This is significantly lower than the bending rigidity (bending rigidity calculated by formula (1)) when the outer part 3, resin layer, and thin metal plate are bonded together.

[0032] Therefore, it is important that the outer part 3 and the resin layer are bonded with sufficient strength, and that the resin layer and the thin metal plate are bonded together so that the outer part 3, the resin layer, and the thin metal plate can bear the load as a whole. Furthermore, even if the resin layer is bonded, if it peels off during the bending collapse process at the time of a collision, the bending rigidity will decrease just as if the resin layer were not bonded, so the adhesive must be bonded with sufficient adhesive strength. The inventors have found that if the adhesive strength of the resin in the resin layer is set to 10 MPa or more, the resin layer is less likely to peel off during bending collapse, and the three-layer sandwich structure can be maintained.

[0033] Furthermore, it was found that arranging the resin layer and the thin metal plate on the outside of the punch shoulder R portion 3b, where tensile stress concentrates when the outer part 3 bends, can improve the impact energy absorption effect in the initial stage of the impact, compared to arranging them on the inside. This point will be explained below based on a specific example.

[0034] 5 and 6 show examples of the results of a collision CAE analysis when the structure of FIG. 4(b) (a sandwich structure of three layers (outer part / resin layer / thin metal plate)) is applied to the outer part 3 of the body frame part 31 of FIG. 3. As application examples of the structure of FIG. 4(b), analyses were carried out for the cases where the resin layer and thin metal plate are disposed on the outer surface side of the outer part 3 and for the cases where they are disposed on the inner surface side. As a comparative example, the analysis results for the case where the resin layer and thin metal plate are not disposed on the outer part 3 (structure of FIG. 4(a)) are also shown.

[0035] In this analysis, the outer part 3 of the body frame part 31 was made of steel plate with a tensile strength of 1180 MPa and a plate thickness of 1.2 mm. In the two examples of application of the structure shown in Fig. 4(b), the thickness of the resin layer was set to 1.0 mm, and the thin metal plate was made of steel plate with a tensile strength of 270 MPa and a plate thickness of 0.6 mm.

[0036] In the collision CAE analysis, a collision body (a semi-cylindrical punch) was collided with the top plate portion 3a of the outer part 3, and the relationship (load-stroke curve) between the stroke (mm) from the start of the collision of the collision body and the load (kN) input to the outer part 3 was measured. Figure 5 shows the load-stroke curves for two examples with the structure shown in Figure 4(b) and a comparative example with the structure shown in Figure 4(a). Figure 6 also shows the absorbed energy (kJ) calculated from the load-stroke curves in Figure 5 at a stroke of 10 mm and at a stroke of 40 mm.

[0037] As shown in Figures 5 and 6, the two examples with a three-layer (outer part / resin layer / thin metal plate) sandwich structure can increase the input load to the outer part 3 and significantly improve the absorbed energy compared to the comparative example without a resin layer or thin metal plate.

[0038] In particular, by disposing the resin layer and the thin metal plate on the outside, the bending rigidity of the outer surface of the punch shoulder R portion 3b where tensile stress is concentrated can be increased, which makes it possible to delay the start of deformation of the hat-shaped cross section member at the initial stage of a collision compared to when the resin layer and the thin metal plate are disposed on the inside. Therefore, compared to when a resin layer and a thin metal plate are arranged on the inside, the load rises earlier at the initial stage of a collision (approximately 0.2 msec) (see Figure 5), and the absorbed energy (stroke 0 to 40 mm) can be increased by approximately 4% (see Figure 6). The present invention is based on the above-mentioned findings. The following describes embodiments of the present invention.

[0039] [Embodiment 1] A vehicle body frame part 1 according to one embodiment of the present invention is provided on the side of a vehicle body and absorbs collision energy by bending in a direction intersecting the longitudinal direction when a collision load is input from the side of the vehicle body. As shown in Figures 1 and 2, the vehicle body frame part 1 includes an outer part 3, an inner part 5, a resin layer 7 formed by applying resin to the outer surface of the outer part 3, a tubular member 9 formed by joining the outer part 3 and the inner part 5, and a thin-walled patch member 11.

[0040] The outer part 3 is a hat-shaped cross-section member formed from a metal plate, and has a top plate portion 3a, a pair of vertical wall portions 3c continuing from the top plate portion 3a via punch shoulder R portions 3b, and flange portions 3d continuing from each of the vertical wall portions 3c. The punch shoulder R portions refer to the portions of the hat-shaped cross-section member. The inner part 5 is a flat member formed from a metal plate. A side end of the inner part 5 and the flange portion 3d of the outer part 3 are joined together to form the cylindrical member 9.

[0041] A body frame part 1 having a hat-shaped cross section such as the outer part 3 constitutes part of the body frame of an automobile. The present invention targets body frame parts that are arranged on the left and right sides of the vehicle body to constitute the body frame, and specific examples include A-pillars and B-pillars that extend in the vertical direction of the vehicle body, and rockers (side sills) and roof rails that extend in the longitudinal direction of the vehicle body.

[0042] Examples of types of metal sheets used for the outer part 3 and the inner part 5 include cold-rolled steel sheets, hot-rolled steel sheets, stainless steel sheets, zinc-based plated steel sheets, zinc alloy-based plated steel sheets, aluminum alloy-based plated steel sheets, and aluminum alloy sheets.

[0043] As shown in FIGS. 1 and 2, the resin layer 7 is applied to the outer surfaces of the top plate portion 3a, punch shoulder R portion 3b, and vertical wall portion 3c of the outer part 3. The applied resin layer 7 has a thickness of 8 mm or less after heating, and is adhered to the outer surface of the outer part 3 and the thin patch member 11 with an adhesive strength of 10 MPa or more at room temperature.

[0044] The type of resin in the resin layer 7 may be a thermoplastic, thermosetting, or elastomer type. Examples of thermoplastic resins include vinyl-based (vinyl acetate, vinyl chloride, etc.), acrylic-based, polyamide-based, polystyrene-based, and cyanoacrylate-based resins. Examples of thermosetting resins include epoxy-based, urethane-based, ester-based, phenol-based, melamine-based, and urea-based resins. Examples of elastomer resins include nitro rubber, styrene butadiene rubber, modified silicone, butyl rubber, urethane rubber, and acrylic rubber. In any type of resin, it is preferable that the resin does not break or collapse when subjected to bending deformation.

[0045] The thin patch member 11 is made of a metal plate (e.g., a steel plate) and is arranged so as to straddle the top plate portion 3a, covering the surface of the resin layer 7 from the outer side, and both ends are joined (e.g., spot welded) to the outer surfaces of a pair of vertical wall portions 3c of the outer part 3.

[0046] The resin layer 7 is required at least on the outer surface of the punch shoulder R portion 3b, and from the viewpoint of weight reduction, it is preferable to shorten the vertical wall height (the area to which the resin layer 7 and the thin patch member 11 are applied on the vertical wall portion 3c). Therefore, the thin patch member 11 is bonded to the vertical wall portion 3c of the outer part 3. Alternatively, joining protrusions may be formed at the end of the thin patch member 11 at predetermined intervals in the longitudinal direction, and the joining protrusions may be bonded to the vertical wall portion 3c of the outer part 3.

[0047] The thin patch member 11 is used to form a sandwich structure and does not require high material strength. Therefore, the tensile strength of the thin patch member 11 can be lower than that of the outer part 3 and the inner part 5.

[0048] The resin layer 7 formed by applying resin to the outer surface of the outer part 3 can be bonded to the outer part 3 and the thin patch member 11 by the adhesive properties of the resin itself of the resin layer 7 through heat treatment. In this case, the adhesive strength between the resin of the resin layer 7 and the outer part 3 and the thin patch member 11 can be 10 MPa or more even when returned to room temperature by heat treatment at a predetermined temperature and time. The temperature and time of the heat treatment can be adjusted appropriately depending on the type of resin of the resin layer 7.

[0049] The adhesive strength between the resin of the resin layer 7 and the metal plate (outer part 3, thin patch member 11) can be the maximum shear stress or average shear stress acting at the interface between the metal plate and the resin layer 7. The maximum shear stress or average shear stress can be determined, for example, by determining the boundary conditions under which peeling of the resin layer 7 occurs from a collision experiment of a two-layered rectangular pillar bonded to a metal plate and the resin layer 7, and then performing a collision analysis based on the boundary conditions. Alternatively, the adhesive strength can be measured based on JIS K 6850, "Test method for tensile shear bond strength between adhesive and rigid adherend," and the adhesive strength can be determined as the maximum shear stress or average shear stress acting parallel to the adhesive surface at the interface between the metal plate and the resin layer.

[0050] In addition, the adhesive strength between the resin of the resin layer 7 and the metal plate (outer part 3, thin patch member 11) may be measured by cutting out a portion of the resin layer 7 and the metal plate after bonding, placing them in a tensile testing machine, and clamping the resin layer 7 on one side and the metal plate on the other side, and pulling them. Alternatively, the measurement may be performed by cutting out a portion of the resin layer 7 and the metal plate after bonding, placing them in a tensile tester, and clamping the resin layer 7 on one side and a gripping portion (not shown) formed by bending the metal plate on the other side, and pulling the clamped portion. Alternatively, a gripping part may be joined to the metal plate (outer part 3, thin patch member 11), and the gripping part may be gripped and pulled with a tensile testing machine to measure the adhesive strength between the resin of the resin layer 7 and the outer part 3 and thin patch member 11.

[0051] In the above-described vehicle body frame part 1, resin is applied to the top plate part 3a, punch shoulder R part 3b, and vertical wall part 3c of the outer part 3 to form the resin layer 7, but the present invention is not limited to this. In the present invention, it is sufficient that a resin layer is formed at least on the outer surface of the punch shoulder R part, so vehicle body frame parts 21 and 23 shown in Figures 7(a) and 7(b) may have the resin layer 7 formed only on the outer surface of the punch shoulder R part 3b of the outer part 3.

[0052] In this case, too, by bonding the resin layer 7 to the outer part 3 and the thin patch member 11 with an adhesive strength of 10 MPa or more, the bending rigidity of the punch shoulder R portion 3b is maintained at a high level during the bending collapse process, improving the buckling strength of the outer part 3. This also prevents the bending radius of the punch shoulder R portion 3b from becoming smaller, mitigating stress concentration on the outer surface and preventing cracks from occurring. This improves the ability to absorb collision energy.

[0053] It should be noted that the above-described body frame components 1, 21, and 23 are formed by a tubular member 9 comprised of an outer part 3 and an inner part 5, but the body frame component according to the present invention is not limited to this and may also have only the outer part 3. Furthermore, although the above description has exemplified an outer part 3 that is a hat-shaped cross section, the present invention is not limited to a part having a hat-shaped cross section, and may also be a part having a U-shaped cross section that has a top plate portion and a pair of vertical wall portions that continue from the top plate portion via the punch shoulder R portion.

[0054] Furthermore, the above-described body frame components 1, 21, and 23 are formed by applying resin to the outer surface of the outer component 3 to form the resin layer 7, but the present invention may also be such that a plate-shaped resin is attached to the outer surface of the outer component using an adhesive. Furthermore, a film-like resin having a thickness of about 100 μm, similar to the lamination in a laminated steel sheet, may be attached to the outer surface of the outer part. The adhesive strength between the plate-shaped resin or film-shaped resin and the outer part 3 and thin patch member 11 should be 10 MPa or more at room temperature.

[0055] Furthermore, in another embodiment, the resin layer 7 may be formed by a coating film made of electrodeposition paint. A body frame part of such an embodiment will be specifically described with reference to FIG.

[0056] The body frame part 25 shown in Fig. 8(a) includes a tubular member 9 formed by joining an outer part 3 and an inner part 5, a coating film 13 formed by hardening electrodeposition paint, and a thin patch member 11. The outer part 3 and inner part 5 of the body frame part 25 are similar to the outer part 3 and inner part 5 shown in Fig. 1, so they are denoted by the same reference numerals and their explanations are omitted.

[0057] The coating film 13 on the body frame part 25 is formed by hardening paint by electrodeposition coating, which is a common practice in the painting process of automobile manufacturing. In order to form a coating film 13 of a predetermined thickness during electrodeposition coating, the thin patch member 11 is provided so that a gap of 0.2 mm to 3 mm is formed between it and the outer surface of the outer part 3 before electrodeposition coating.

[0058] When the vehicle body is subjected to electrodeposition coating while the parts, each having a thin-walled patch member 11 attached to a cylindrical member 9 (outer part 3, inner part 5), are attached to the vehicle body, the electrodeposition paint penetrates into the gaps, and when this is heat-treated, the paint hardens to form a coating film 13. Normally, when electrodeposition coating is performed, a coating film of about 0.05 mm is formed on the surface of the steel sheet, but in this example, by providing a predetermined gap on the outer surface side of the outer part 3 and arranging the thin patch member 11, it is possible to form a coating film 13 of a predetermined thickness in the gap. In other words, the thin patch member 11 in this example also functions as a coating film forming member.

[0059] After electroplating, a coating film 13 is formed in the gap between the outer part 3 and the thin patch member 11, thereby forming a sandwich structure consisting of the outer part 3, the coating film 13, and the thin patch member 11 on the outer surface side of the outer part 3. This allows the coating film 13 to function in the same manner as the resin layer 7 of the body frame part 1 (see FIGS. 1 and 2) described above, and suppresses cracks in the punch shoulder R portion 3b of the outer part 3.

[0060] Examples of types of electrodeposition paint include polyurethane-based cationic electrodeposition paint, epoxy-based cationic electrodeposition paint, urethane-based cationic electrodeposition paint, acrylic-based anionic electrodeposition paint, and fluororesin electrodeposition paint.

[0061] As mentioned above, it is sufficient that the resin layer 7 is formed at least on the punch shoulder R portion 3b of the outer part 3, and therefore, even in the case where the electrodeposition paint coating film 13 is made to function as the resin layer 7 as in this example, it is sufficient that the coating film 13 is formed at least on the outer surface of the punch shoulder R portion 3b. Therefore, before painting, the thin patch member 11 should be provided so that there is a gap of at least 0.2 mm to 3 mm between it and the outer surface of the punch shoulder R portion 3b. Therefore, as in the body frame part 27 shown in Figure 8(b), the paint film 13 (resin layer 7) does not need to be formed on the portion other than the outer surface of the punch shoulder R portion 3b.

[0062] In this way, by making the coating film formed by electrodeposition coating function as the resin layer of the present invention, the resin application (or bonding) process can be omitted, and the body frame part of the present invention can be manufactured using conventional automobile production lines.

[0063] As described above, according to this embodiment, by providing the resin layer 7 and the thin patch member 11 on at least the punch shoulder R portion 3b of the outer part 3, cracking of the punch shoulder R portion 3b during a collision can be prevented and the collision energy absorption performance can be improved. Furthermore, by disposing the resin layer 7 and the thin patch member 11 on the outer surface side of the outer part 3, it is possible to apply the present invention to existing side sills in which stiffening parts are disposed inside. Furthermore, since the load can be increased, the energy absorption effect at the beginning of a collision is improved and the impact on the vehicle can be detected quickly, which allows for the earlier activation of airbags, brakes, etc. that detect acceleration during a collision and operate.

[0064] [Embodiment 2] Next, we will explain the method for manufacturing the body frame part described in embodiment 1. The manufacturing method differs between the case where the resin layer 7 is formed by a coated or attached resin, as in the body frame part 1 in Fig. 1, and the case where the resin layer 7 is formed by a coating of electrodeposition paint, as in the body frame part 25 in Fig. 8(a), so each example will be explained below.

[0065] First, the manufacturing method of the body frame part 1 in which the resin layer 7 is formed by the applied or stuck resin includes a resin layer thickness determination process, a resin layer formation process, a thin patch member joining process, and a heating process.

[0066] <Resin layer thickness determination process> The resin layer thickness determination step is a step of determining the thickness of the resin layer 7 formed by applying or attaching a resin. According to the bending rigidity of the laminated material shown in formula (1), if the thickness of the resin layer 7 is too thin, the effect of improving bending rigidity due to the sandwich structure of three layers (outer part 3 / resin layer / metal plate) will be reduced. On the other hand, if the thickness of the resin layer 7 is too thick, the effect of reducing weight will be reduced. Therefore, in order to achieve a good balance between the effects of reducing weight and improving bending rigidity, it is important to set the thickness of the resin layer 7 to an appropriate value. Therefore, in the resin layer thickness determination step, an appropriate thickness of the resin layer 7 is determined by the following method.

[0067] The resin layer thickness determination process in this embodiment includes a step of setting the base plate thickness, base bending rigidity, and base weight of the hat-shaped cross-section member that serves as the base and has the required bending rigidity; a step of determining the lower limit of the thickness of the resin layer 7 when the plate thickness of the hat-shaped cross-section member is thinner than the base plate thickness and the bending rigidity is not reduced below the base bending rigidity; a step of determining the upper limit of the thickness of the resin layer 7 when the bending rigidity can be maximized without increasing the weight more than the base weight; and a step of setting the thickness of the resin layer between the lower limit and upper limit.

[0068] First, as a base for considering the thickness of the resin layer 7, the base plate thickness, base bending rigidity, and base weight are set. Here, an outer part 3 made of a steel plate with a thickness of 1.60 mm was prepared as a hat-shaped cross-section member having the required bending rigidity, and the bending rigidity (specifically, the bending rigidity of the punch shoulder R portion) of the outer part 3 was determined. A flat plate-shaped inner part 5 was also joined to this outer part 3 to form a cylindrical member 9, and the weight of the cylindrical member 9 was determined. The results are shown in the "Base" column of Table 1. The thickness hc (1.60 mm) of the outer part shown in Table 1 is the base thickness, and the bending rigidity (70 GPa / mm 4 ) is the base bending rigidity, and weight (3.59 kg) is the base weight.

[0069] Next, as the outer part 3 constituting the body frame part 1 explained in the first embodiment, a hat-shaped cross section member having a plate thickness thinner than the base plate thickness is prepared. Here, three types of outer parts 3 were prepared: outer part 3 No. 1 with a thickness of 0.80 mm, outer part 3 No. 2 with a thickness of 1.00 mm, and outer part 3 No. 3 with a thickness of 1.20 mm. In addition, a thin-walled patch member 11 made of steel plate with a thickness of 0.40 mm was prepared (common to No. 1 to No. 3).

[0070] Then, using each of the outer parts 3 and thin-walled patch members 11 of the above No. 1 to No. 3, the thickness of the resin layer 7 was adjusted so that the bending rigidity of the punch shoulder R portion 3b was approximately the same as the bending rigidity of the base, thereby constructing a body frame part 1 (A).

[0071] In addition, the body frame part 1 was constructed using each of the outer parts 3 and thin-walled patch members 11 described above as "No. 1" to "No. 3" by adjusting the thickness of the resin layer 7 so that the weight of the body frame part 1 was approximately the same as the weight of the "base" (B).

[0072] Table 1 shows the thickness of the resin layer 7 when the above-mentioned body frame parts 1 A and B are constructed using each of the outer parts 3 No. 1 to No. 3. In addition, the weight of ``Base'' in Table 1 is the sum of the weights of the outer part 3 and the inner part 5 (weight of the tubular member 9), and the weights of ``No.1'' to ``No.3'' are the sum of the weights of the outer part 3, the inner part 5, the resin layer 7 and the thin-walled patch member 11 (weight of the body frame part 1). [Table 1]

[0073] In the case of A of No. 1 to No. 3 shown in Table 1, the thickness of the outer part 3 is thinner than that of the base, a resin with a lower Young's modulus than that of steel is provided as the resin layer 7, and the total thickness of the sandwich structure with the thin patch member 11 is thicker than that of the base, resulting in a bending rigidity (70 GPa mm 4 While maintaining the same level of bending rigidity as the conventional steel sheet, the weight reduction effect is maximized by using a resin with a lower density than steel. The weight reduction rate is 21% for No. 1, 12% for No. 2, and 4% for No. 3. The thickness of the resin layer at A in No. 1 to No. 3 corresponds to the "thickness of the resin layer when the plate thickness is thinner than the base plate thickness and the bending rigidity is not reduced below the base bending rigidity" of the present invention. The thickness of the resin layer at A is set as the lower limit value of the thickness of the resin layer when the outer parts 3 in No. 1 to No. 3 are used to construct a body frame part 1.

[0074] On the other hand, in No. 1 to No. 3, B has a thicker resin layer that is roughly the same weight as the base (3.59 kg), making the total thickness of the sandwich structure thicker than A, thereby maximizing the effect of improving bending rigidity. The bending rigidity improvement rate is 1599% for No. 1, 796% for No. 2, and 171% for No. 3. The thickness of the resin layer at B in No. 1 to No. 3 corresponds to the "thickness of the resin layer when bending rigidity can be improved to the maximum extent without increasing the weight from the base weight" of the present invention. The thickness of the resin layer at B is set as the upper limit of the thickness of the resin layer when a body frame part 1 is constructed using each of the outer parts 3 in No. 1 to No. 3.

[0075] Based on the results in Table 1, the thickness of the resin layer is determined with the lower limit set to the thickness of the resin layer in case A, which allows for the greatest possible weight reduction without a decrease in bending rigidity compared to the <<base>>, and the upper limit set to the thickness of the resin layer in case B, which allows for the greatest possible improvement in bending rigidity without an increase in weight compared to the <<base>>. Therefore, in the case of <<No. 1>> (sheet thickness hc of outer part 3 = 0.80 mm, sheet thickness hp of thin patch member 11 = 0.40 mm), the thickness of resin layer 7 should be set within the range of 0.45 mm to 4.00 mm. Similarly, in the case of <No. 2> (plate thickness hc of hat cross section member = 1.00 mm, plate thickness hp of reinforcing plate = 0.40 mm), the thickness of the resin layer 7 should be set within the range of 0.25 mm to 2.50 mm, and in the case of <No. 3> (plate thickness hc of outer part 3 = 1.20 mm, plate thickness hp of thin patch member 11 = 0.40 mm), the thickness of the resin layer 7 should be set within the range of 0.02 mm to 0.80 mm.

[0076] <Resin layer formation process> The resin layer forming step is a step of forming the resin layer 7 on the outer surface of the outer part 3 by applying or pasting resin to the thickness determined in the resin layer thickness determining step. In this embodiment, first, the outer part 3 and the inner part 5 are joined together to form the tubular member 9. Then, resin is applied or attached to the outer surface of the outer part 3, specifically, the outer surfaces of the top plate portion 3a, punch shoulder R portion 3b, and vertical wall portion 3c, to form the resin layer 7, so as to have the thickness determined in the resin layer thickness determination step. At this time, a liquid resin may be applied to the outer surface of the outer part 3, or a plate-like resin may be attached (bonded) to the outer surface of the outer part 3 using an adhesive.

[0077] <Thin-walled patch member joining process> The thin patch member joining step is a step in which the surface of the resin layer 7 formed in the resin layer forming step is covered with a thin patch member 11, and both ends of the thin patch member 11 are joined to the outer surface of the vertical wall portion 3c of the outer part 3 by spot welding or the like. At this time, the thin patch member 11 is adhered to the surface of the resin layer 7 by pasting or by using an adhesive.

[0078] <Heating process> The heating step is a step of heat treating the cylindrical member 9 (outer part 3, inner part 5) provided with the resin layer 7 and the thin patch member 11. By the heat treatment, the resin layer 7 and the outer part 3, and the resin layer 7 and the thin patch member 11 are bonded with sufficient adhesive strength (10 MPa or more), and the body frame part 1 of FIG. 1 can be manufactured. The body frame parts 21 and 23 shown in Figs. 7(a) and 7(b) can also be manufactured in a similar manner.

[0079] Next, a method for manufacturing a body frame part 25 in which the resin layer 7 is formed by a coating of electrodeposition paint will be described. The method for manufacturing the body frame part 25 includes a resin layer thickness determination step, a part manufacturing step, a resin layer formation step, and a heating step.

[0080] <Resin layer thickness determination process> The resin layer thickness determination step is a step of determining the thickness of the resin layer 7 formed by the coating film 13 made of electrodeposition paint. The resin layer thickness determination step in this example is performed in the same manner as the resin layer thickness determination step described in the manufacturing method of the body frame part 1. When the resin layer 7 is formed by the coating film 13 of electrodeposition paint, it is preferable to set the thickness to 0.20 mm or more and 3.00 mm or less due to manufacturing characteristics, as described in Embodiment 1. Therefore, the thickness of the resin layer 7 in this case should be between the above-mentioned lower limit and upper limit values, and should be 0.20 mm or more and 3.00 mm or less.

[0081] <Parts manufacturing process> The part manufacturing process is a process for manufacturing a part having an outer part 3 and a thin patch member 11 disposed on the outer surface side of the outer part 3. In this embodiment, first, the outer part 3 and the inner part 5 are joined together to form the tubular member 9. Then, a thin patch member 11 is placed on the outer surface of the outer part 3 so as to straddle the top plate 3a of the outer part 3, and the end of the thin patch member 11 is joined to the outer surface of the vertical wall 3c of the outer part 3 by spot welding or the like. At this time, a gap corresponding to the thickness determined in the resin layer thickness determination step is provided between the outer surface of the outer part 3 and the thin patch member 11.

[0082] <Resin layer formation process> The resin layer forming step is a step of performing electrodeposition coating on the vehicle body to which the above-mentioned parts are attached, and forming a resin layer in the gap by a coating film of the electrodeposition paint. When the vehicle body with the above-mentioned parts attached thereto is immersed in an electrodeposition tank containing electrodeposition paint, the electrodeposition paint penetrates into the gaps and forms a coating film 13. This coating film 13 then forms a resin layer 7.

[0083] <Heating process> The heating step is a step of heat treating the part on which the resin layer 7 is formed. The vehicle body immersed in the electrodeposition bath is heated to harden the surface coating. At this time, the vehicle body and the part on which the resin layer 7 is formed are also heated, and the resin layer 7 is bonded to the outer part 3 and the resin layer 7 to the thin patch member 11 with sufficient adhesive strength (10 MPa or more), thereby producing the vehicle body frame part 25 shown in Fig. 8(a). The body frame part 27 in FIG. 8(b) can also be manufactured in a similar manner.

[0084] The above two examples are examples of manufacturing a body frame part made up of an outer part 3 that is a hat-shaped cross section member, but the same can be said for manufacturing a body frame part made up of a U-shaped cross section member.

[0085] As described above, according to the second embodiment, by providing a resin layer thickness determination process for determining an appropriate thickness of the resin layer, it is possible to manufacture a body frame part that can achieve a balanced effect of both weight reduction and improved bending rigidity. [Example]

[0086] Experiments were conducted to confirm the effects of the vehicle body frame part according to the present invention, and the results are described below. In this example, an experiment was carried out to evaluate the collision energy absorption characteristics of the vehicle body frame part according to the present invention in the process of bending when a collision load is applied from the side of the vehicle body.

[0087] In the experiment, various test specimens were created using a cylindrical member 9 (conventional structure) consisting of an outer part 3, which is a hat-shaped cross-section member with an axial length of 700 mm, and an inner part 5, which is a flat plate-like member, as shown in Figure 9. As an example of the invention, a resin layer 7 and a thin patch member 11 covering the surface of the resin layer 7 were provided within a range of 200 mm from the center of the outer surface of the outer part 3, and test specimens corresponding to the body frame parts 1, 21, 23, 25, and 27 described in the embodiment were prepared. Both ends of the thin patch member 11 were joined to the outer surface of the vertical wall part 3c of the outer part 3 by spot welding.

[0088] Furthermore, a test specimen consisting of only the cylindrical member 9 was prepared as a conventional example. Furthermore, as comparative examples, test specimens not having the thin patch member 11 and test specimens having a resin adhesive strength of less than 10 MPa were prepared. In this example, the adhesive strength was determined as the maximum shear stress or average shear stress acting on the interface between the steel plate used in the outer part 3 and the resin layer 7, which was determined based on a collision experiment of a two-layered rectangular pillar formed by bonding the steel plate and the resin layer 7 together.

[0089] The outer part 3 of each test specimen was made of steel plate with a thickness of 1.2 mm or 1.4 mm and a tensile strength of 980 MPa. The inner part 5 of each test specimen was made of steel plate with a thickness of 1.2 mm and a tensile strength of 590 MPa. The thin patch member 11 was made of so-called mild steel plate with a thickness of 0.6 mm and a tensile strength of 270 MPa. The resin of the resin layer 7 was either epoxy-based or urethane-based.

[0090] In the experiment, as shown in Figure 9, a collision body 15 (a semi-cylindrical punch, radius of curvature of the R part = 100 mm) was collided with each test body from the outer part 3 side towards the inner part 5 side at a speed of 15.3 m / s, and the collision body 15 was pushed 150 mm into the test body. At this time, a load-stroke curve showing the relationship between the stroke amount and the load after the collision body 15 collided with the test body was measured, and the absorbed energy from a stroke of 0 to 100 mm was calculated from the load-stroke curve. Note that the distance between the axial supports supporting the inner part 5 side when the load was applied was 500 mm.

[0091] Table 2 shows the plate thickness of the outer part 3 and the thin patch member 11, the type of resin in the resin layer 7, adhesive strength, and other conditions of each test specimen for the invention example, conventional example, and comparative example, the test specimen weight, and the bending rigidity of the punch shoulder R portion 3b calculated using formula (1). In calculating the bending rigidity, L in formula (1) was set to be equivalent to 200 mm.

[0092] [Table 2]

[0093] In the range of resins in Table 2, "outer" indicates the outer part 3, and "punch shoulder R" indicates the punch shoulder R portion 3b of the outer part 3. Furthermore, the test weight in Table 2 is the sum of the weights of the outer part 3, inner part 5, thin patch member 11, and resin layer 7 for test specimens having the resin layer 7 and thin patch member 11 (Invention Examples 1 to 8, Comparative Examples 2 and 3). It is the sum of the weights of the outer part 3, inner part 5, and resin layer 7 for test specimens having the resin layer 7 but not the thin patch member 11 (Comparative Example 1), and it is the sum of the weights of the outer part 3, inner part 5, and resin layer 7 for test specimens not having the resin layer 7 (Conventional Examples 1 and 2).

[0094] The absorbed energy (kJ) and weight efficiency (kJ / kg) for strokes from 0 to 100 mm are also listed in the absorbed energy column of Table 2. Weight efficiency indicates the absorbed energy per unit weight, and is the value obtained by dividing the absorbed energy by the weight of the test specimen.

[0095] Conventional Examples 1 and 2 used test specimens corresponding to a conventional body frame part 31 (see Figure 3) consisting only of a tubular member 9. As shown in Table 2, cracks were observed in the upper part of both Conventional Example 1 (outer part 3 plate thickness 1.2 mm) and Conventional Example 2 (outer part 3 plate thickness 1.4 mm), which used test specimens with conventional structures. In addition, the absorbed energy in the stroke from 0 to 100 mm was 2.60 kJ for Conventional Example 1 and 3.43 kJ for Conventional Example 2.

[0096] In contrast, Example 1 of the invention used a test specimen corresponding to a vehicle frame part 1 (see Figure 1), and the plate thickness of the outer part 3 was 1.2 mm, the same as in Conventional Example 1. In Example 1 of the invention, resin was applied to a thickness of 1.0 mm from the top plate portion 3a to the vertical wall portion 3c of the outer part 3 to form a resin layer 7, and a thin patch member 11 was disposed so as to cover the surface of the resin layer 7. In addition, the adhesive strength between the resin layer 7 and the outer part 3 and the thin patch member 11 was set to 11.9 MPa, which is within the range of the present invention (10 MPa or more).

[0097] The bending rigidity of Example 1 is 117.5 × 10 -5 GPa m 4 The bending rigidity of Conventional Example 1, which has the same plate thickness of the outer part 3 (5.9 × 10 -5 GPa m 4 ) is significantly improved. The absorbed energy in the stroke range of 0 to 100 mm was 3.87 kJ, which was 49% higher than that of Conventional Example 1. Furthermore, no cracks occurred in the outer part 3 during the bending process. The test weight of Inventive Example 1 was 3.32 kg, which was 0.29 kg heavier than the test weight of Conventional Example 1 (=3.03 kg), but the weight efficiency was 1.17 kJ / kg, which was 36% better than Conventional Example 1 (=0.86 kJ / kg).

[0098] Furthermore, Example 1 of the present invention had improved absorbed energy compared to Example 2 of the prior art, which had a similar test weight, and both the weight efficiency of Example 1 of the present invention (= 1.17 kJ / kg) and the weight efficiency of Example 2 of the prior art (= 1.02 kJ / kg) were improved.

[0099] As described above, in Example 1, the resin layer 7 and the thin patch member 11 were disposed on the outer surface of the outer part 3, and the resin layer 7 was bonded to the outer part 3 and the thin patch member 11 with an adhesive strength of 10 MPa or more, thereby improving the collision energy absorption performance. This is because, as mentioned above, the three-layer structure improved the bending rigidity of the punch shoulder R portion 3b, suppressing cracking of the punch shoulder R portion 3b during the bending process and improving the buckling strength.

[0100] Inventive Examples 2 and 3, test specimens corresponding to the body frame part 1 (see FIG. 1) were used, similar to Inventive Example 1. In Inventive Examples 2 and 3, the thickness of the resin layer 7 was set to 2 mm or 3 mm, and the bending rigidity of the punch shoulder R portion 3b was increased to 2.1 times or 3.6 times that of Inventive Example 1, respectively. In invention examples 2 and 3, no fractures (cracks) occurred during the bending process, and the absorbed energy was 4.35 kJ and 4.82 kJ, respectively, which were 12% and 25% higher than the absorbed energy (=3.87 kJ) in invention example 1. Furthermore, the weight efficiency of invention examples 2 and 3 was 1.29 kJ / kg and 1.40 kJ / kg, and the thicker the resin layer 7, the higher the weight efficiency.

[0101] Inventive Example 4, a test specimen corresponding to a body frame part 21 (see FIG. 7(a)) was used. In Inventive Example 4, the area to which the resin of the resin layer 7 was attached was limited to only the punch shoulder R portion 3b of the outer part 3, and the adhesive strength was set to 21.5 MPa, which is within the range of the present invention (10 MPa or more). In Example 4, no fractures (cracks) occurred during the bending process, and the absorbed energy was 3.71 kJ. The absorbed energy of Example 4 was 4% lower than that of Example 1 (3.87 kJ), but 43% higher than that of Conventional Example 1 (2.60 kJ). In addition, the weight efficiency of Example 4 was 1.13 kJ / kg, which was 3% lower than that of Example 1 (1.17 kJ / kg), but 32% higher than that of Conventional Example 1 (0.86 kJ / kg).

[0102] Inventive Example 5 used a test specimen corresponding to a body frame part 23 (see Figure 7(b)). In Inventive Example 5, the area to which the resin of the resin layer 7 was applied was limited to only the punch shoulder R portion 3b of the outer part 3, minimizing the area covered by the thin patch member 11. The adhesive strength of the resin of the resin layer 7 was set to 10.5 MPa, which is within the range of the present invention (10 MPa or more). In Example 5, no fractures (cracks) occurred during the bending process, and the absorbed energy was 3.71 kJ, the same as in Example 4. In Example 5, the area covered by the thin patch member 11 is smaller than in Example 4, so the weight of the thin patch member 11 is reduced, resulting in a lighter test weight. Therefore, the weight efficiency (= 1.18 kJ / kg) was improved over Example 4 (= 1.13 kJ / kg). The weight efficiency was also improved compared to Example 1 (= 1.17 kJ / kg), which has the same resin layer thickness.

[0103] Inventive Examples 6 and 7, test specimens corresponding to a body frame part 25 (see Figure 8(a)) were used. In Inventive Examples 6 and 7, a thin patch member 11 was provided on the outer surface of the outer part 3 so as to leave a gap of 0.2 mm or 0.5 mm between the outer surface and the thin patch member 11. Electrodeposition paint was allowed to penetrate into the gap during electrodeposition coating, and the paint was cured in a baking process to form a coating film 13 (resin layer 7) with a thickness of 0.2 mm or 0.5 mm. The adhesive strength of the coating film 13 (resin layer 7) was set to 12.1 MPa and 13.5 MPa, which are within the range of the present invention (10 MPa or more). No fractures (cracks) occurred during the bending process in Inventive Examples 6 and 7. The absorbed energy of Inventive Examples 6 and 7 was 3.49 kJ and 3.63 kJ, which were 34% and 40% higher than that of Conventional Example 1 (=2.60 kJ), respectively. Furthermore, the weight efficiency of Inventive Examples 6 and 7 was 1.07 kJ / kg and 1.11 kJ / kg, which were 25% and 29% higher than that of Conventional Example 1 (=0.86 kJ / kg), respectively.

[0104] Inventive Example 8 used a test specimen corresponding to a body frame part 27 (see Figure 8(b)). In Inventive Example 8, the area where the coating film 13 was formed was limited to the punch shoulder R part of the outer part, minimizing the area covered by the thin patch member 11. The thickness of the coating film 13 (resin layer 7) was 0.5 mm, the same as Inventive Example 7, and the adhesive strength was 15.7 MPa, which is within the range of the present invention (10 MPa or more). No fractures (cracks) occurred during the bending process in Example 8. The absorbed energy of Example 8 was 3.48 kJ, which was 4% lower than that of Example 7 (=3.63 kJ), but the weight efficiency was the same as that of Example 7, 1.11 kJ / kg.

[0105] Comparative Example 1 used a test specimen corresponding to the body frame part 1 (see Figure 1) as in Invention Example 1, but without the thin patch member 11, only a 1.0 mm thick resin was used as the resin layer 7 and attached to the outer part 3 with an adhesive strength of 10.9 MPa. In Comparative Example 1, cracking (fracture) occurred during the bending process, and the absorbed energy was 2.72 kJ. In Comparative Example 1, the absorbed energy was only 5% higher than that of Conventional Example 1 (=2.60 kJ), but 30% lower than that of Inventive Example 1 (=3.87 kJ). In addition, the weight efficiency of Comparative Example 1 was 0.88 kJ / kg, which was lower than that of Inventive Example 1. This is because Comparative Example 1 has a two-layer structure without a thin-walled patch member 11, and therefore the bending rigidity cannot be improved as much as that of Invention Example 1, which has a three-layer structure, and the buckling strength of the outer part 3 during bending collapse cannot be sufficiently improved.

[0106] Comparative Examples 2 and 3 used test specimens corresponding to the body frame part 1 (see FIG. 1) as in Example 1, but the adhesive strength of the resin layer 7 was set outside the range of the present invention (less than 10 MPa). Comparative Example 2 had an adhesive strength of 0 MPa (a state in which the resin layer 7 was not adhered to the outer part 3 and the thin patch member 11), and Comparative Example 3 had an adhesive strength of 9 MPa. In Comparative Examples 2 and 3, cracks (fractures) occurred during the bending process, and the absorbed energy was 2.78 kJ in Comparative Example 2 and 2.84 kJ in Comparative Example 3. The weight efficiency was 0.84 kJ / kg in Comparative Example 2 and 0.86 kJ / kg in Comparative Example 3, both of which were low results. In Comparative Example 3, the resin layer 7 peeled off from the outer part 3. As mentioned above, to achieve high bending rigidity with a three-layer structure, the three layers must bear the load together, but in Comparative Examples 2 and 3, the resin layer 7 was not bonded or had weak adhesive strength, so the three layers could not bear the load together during bending collapse. Therefore, the bending rigidity of Comparative Examples 2 and 3 was only improved by 13% and 17%, respectively, compared to Conventional Example 1, and the bending rigidity was not improved as much as in Invention Example 1, and the buckling strength of the outer part 3 during bending collapse was not sufficiently improved.

[0107] Fig. 10 is a graph comparing the weight efficiency (kJ / kg) of Inventive Examples 1 to 8, Conventional Examples 1 and 2, and Comparative Examples 1 to 3 in Table 2. As shown in Fig. 10, Inventive Examples 1 to 8 have a higher weight efficiency of absorbed energy than Conventional Examples 1 and 2 and Comparative Examples 1 to 3.

[0108] As described above, the vehicle body frame part according to the present invention has been shown to be able to efficiently improve the collision energy absorption performance when a collision load is input from the side and the collision energy is absorbed by bending. Furthermore, it has been shown that the weight efficiency of the absorbed energy is high, which makes it possible to reduce the weight of the vehicle body frame part. [Explanation of symbols]

[0109] 1 Body frame parts 3 Outer parts 3a Top plate 3b Punch shoulder R part 3c Vertical wall section 3d flange part 5 Inner parts 7 Resin layer 9 Cylindrical member 11 Thin-walled patch member 13 Paint film 15 Collision body (Kamaboko-shaped punch) 21 Body frame parts (other aspects 1) 23 Body frame parts (other aspects 2) 25 Body frame parts (other aspects 3) 27 Body frame parts (other aspects 4) 31 Body frame parts (conventional example)

Claims

1. A vehicle body frame part that is provided on a side of a vehicle body and bends when a collision load is input from the side of the vehicle body to absorb collision energy, a hat-shaped or U-shaped cross section member having a top plate portion attached toward a side of the vehicle body and a pair of vertical wall portions continuing from the top plate portion via a punch shoulder R portion; a resin layer formed on at least the outer surface of the punch shoulder R portion of the hat-shaped cross section member or the U-shaped cross section member; a thin patch member disposed across the top plate portion to cover the surface of the resin layer from the outer surface side, and both ends of the thin patch member joined to the outer surfaces of the pair of vertical wall portions; the resin layer is adhered to the outer surface of the hat-shaped cross section member or the U-shaped cross section member and the thin-walled patch member with an adhesive strength of 10 MPa or more at room temperature after being heated, A vehicle body frame part, wherein the thin patch member has a lower tensile strength than the hat-shaped cross section member or the U-shaped cross section member.

2. 2. The vehicle body frame part according to claim 1, wherein the resin layer is formed by coating or pasting a resin.

3. the thin patch member is disposed at least between the punch shoulder R portion and the thin patch member with a gap of 0.2 mm to 3 mm; 2. The vehicle body frame part according to claim 1, wherein the resin layer is formed in the gap by a coating film made of an electrodeposition paint.

4. The method for manufacturing a vehicle body frame part according to claim 2, a resin layer thickness determination step of determining a thickness of a resin layer formed by applying or attaching a resin; a resin layer forming step of forming a resin layer on the outer surface of the hat-shaped cross section member or the U-shaped cross section member by applying or pasting resin so that the thickness of the resin layer is determined in the resin layer thickness determining step; a thin patch member joining step of arranging the thin patch member so as to cover the surface of the resin layer formed in the resin layer forming step, and joining both ends of the thin patch member to the outer surface of the vertical wall portion; a heating step of heat-treating the hat-shaped cross-section member or the U-shaped cross-section member provided with the resin layer and the thin-walled patch member, The resin layer thickness determination step includes: Set a base plate thickness, base bending rigidity, and base weight of the hat-shaped cross section member or the U-shaped cross section member that serves as a base having the required bending rigidity, The thickness of the hat-shaped cross section member or the U-shaped cross section member is thinner than the base plate thickness, and a thickness of the resin layer when the bending rigidity of the hat-shaped cross section member or the U-shaped cross section member provided with the resin layer and the thin patch member is not reduced below the bending rigidity of the base is determined as a lower limit value. The thickness of the resin layer is determined as an upper limit value when the weight of the hat-shaped cross section member or the U-shaped cross section member provided with the resin layer and the thin-walled patch member can be increased to the maximum extent without increasing from the base weight, A method for manufacturing a vehicle body frame part, wherein the thickness of the resin layer is determined between the lower limit value and the upper limit value.

5. The method for manufacturing a vehicle body frame part according to claim 3, a resin layer thickness determination step of determining the thickness of a resin layer formed by a coating film made of electrodeposition paint; a component manufacturing process for manufacturing a component including the hat-shaped cross section member or the U-shaped cross section member, and a thin-walled patch member disposed on an outer surface side of the hat-shaped cross section member or the U-shaped cross section member, the thin-walled patch member having a gap corresponding to the thickness determined in the resin layer thickness determination process between the thin-walled patch member and at least the outer surface of the punch shoulder R portion; a resin layer forming step of performing electrodeposition coating on the vehicle body to which the part is attached, and forming a resin layer in the gap by a coating film of the electrodeposition paint; a heating step of heat-treating the component on which the resin layer is formed, The resin layer thickness determining step includes: Set a base plate thickness, base bending rigidity, and base weight of the hat-shaped cross section member or the U-shaped cross section member that serves as a base having the required bending rigidity, The thickness of the hat-shaped cross section member or the U-shaped cross section member is thinner than the base plate thickness, and a thickness of the resin layer when the bending rigidity of the hat-shaped cross section member or the U-shaped cross section member provided with the resin layer and the thin patch member is not reduced below the bending rigidity of the base is determined as a lower limit value. The thickness of the resin layer is determined as an upper limit value when the weight of the hat-shaped cross section member or the U-shaped cross section member provided with the resin layer and the thin-walled patch member can be increased to the maximum extent without increasing from the base weight, A method for manufacturing a vehicle body frame part, wherein the thickness of the resin layer is determined between the lower limit value and the upper limit value.

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