Method for manufacturing vehicle body structural part, and vehicle body structural part

Abstract

A method for manufacturing a vehicle body structural part in which a prescribed part is disposed in a space on the inner side of a cylindrical molded body composed of a fiber-reinforced resin, said method including: a first step for molding continuous fibers impregnated with a thermoplastic resin into a cylindrical shape, and curing the thermoplastic resin to form a cylindrical molded body composed of a fiber-reinforced resin; a second step for disposing a prescribed part in a space on the inner peripheral side of the cylindrical molded body; and a third step for heating at least a portion of the molded body to melt the thermoplastic resin, forming a plurality of protrusions as projecting toward the inner periphery of the molded body and in contact with the prescribed part, and then curing the thermoplastic resin again.

Description

Manufacturing method of vehicle body structural part and vehicle body structural part

[0001] The technology of the present disclosure relates to a method for manufacturing a vehicle body structural part made of fiber-reinforced resin, and the vehicle body structural part.

[0002] In recent years, with the aim of reducing the weight of automobile bodies such as passenger cars, the use of fiber-reinforced resins, such as carbon fiber reinforced plastics (hereinafter referred to as CFRP), to manufacture structural materials for automobile bodies has been considered. Structural materials made of fiber-reinforced resins have high rigidity and exhibit high strength, particularly against compressive stress or tensile stress acting in the fiber orientation direction. For example, Patent Document 1 discloses a hollow frame made of fiber-reinforced composite material that can be used for center pillars, side sills, and the like in automobile body structures.

[0003] Japanese Patent Application Laid-Open No. 2020-062916

[0004] Here, when a fiber-reinforced resin structural material for a vehicle body is made hollow, it is believed that space can be effectively utilized if predetermined components can be placed in the internal space of the hollow structure. For example, a fuel cell vehicle (FCV) equipped with a fuel cell as a power generation device includes a secondary battery, a hydrogen tank, and other components, and requires space to accommodate these components. For example, an electric vehicle equipped with a turbine engine as a power generation device includes a secondary battery, a turbine engine, a power generation motor, a heat exchanger, and other components, and requires space to accommodate these components. On the other hand, when predetermined components are placed in the internal space of a hollow structure, it is necessary to fix the components to the structural material.

[0005] For example, when fastening components using bolts and nuts, drilling holes for inserting the bolts into a fiber-reinforced resin structural material can cut the fibers, potentially reducing the strength of the structural material. Furthermore, forming holes for inserting the bolts during the manufacturing stage of the structural material can complicate the manufacturing process, requiring ingenuity in the fiber arrangement.

[0006] Therefore, the technology of the present disclosure has been made in consideration of the above problems, and an object of the present disclosure is to provide a body structural part that can easily fix a specified part in the internal space of a hollow molded body made of fiber-reinforced resin and that can suppress a decrease in the strength of the molded body, and a method for manufacturing a body structural part that can efficiently manufacture such a body structural part.

[0007] In order to solve the above-mentioned problems, according to one aspect of the technology of the present disclosure, there is provided a method for manufacturing a vehicle body structural part, including: a first step of molding continuous fibers impregnated with a thermoplastic resin into a cylindrical shape and hardening the thermoplastic resin to form a cylindrical fiber-reinforced resin molded body; a second step of arranging a predetermined part in the space on the inner periphery of the cylindrical molded body; and a third step of heating at least a portion of the molded body to melt the thermoplastic resin, forming a plurality of convex parts that protrude on the inner periphery of the molded body and contact the predetermined parts, and then hardening the thermoplastic resin again.

[0008] In order to solve the above problem, according to another aspect of the technology of the present disclosure, there is provided a vehicle body structural component comprising a cylindrical fiber-reinforced resin molded body and a specified component arranged in the space inside the molded body, the molded body having a plurality of protrusions provided on the inner surface of the molded body that contact the specified component and press down to support the specified component.

[0009] As described above, the technology of the present disclosure can provide a body structural part that can easily fix a specified part in the internal space of a hollow molded body made of fiber-reinforced resin and that can suppress a decrease in the strength of the molded body, as well as a method for manufacturing a body structural part that can efficiently manufacture such a body structural part.

[0010] FIG. 3 is a schematic diagram showing the overall configuration of the vehicle body side structure according to the present embodiment; FIG. 4 is a perspective view showing the configuration of a side sill structural part according to the present embodiment; FIG. 5 is a cross-sectional view of the C1 section of the side sill structural part shown in FIG. 2; FIG. 6 is a cross-sectional view of the C2 section of the side sill structural part shown in FIG. 2; FIG. 7 is a horizontal cross-sectional view of region R of the side sill structural part shown in FIG. 2; FIG. 8 is an explanatory diagram showing a modified example of the side sill structural part according to the present embodiment; FIG. 9 is an explanatory diagram showing an example in which a resin is filled in a convex part of the side sill structural part according to the present embodiment; FIG. 10 is an explanatory diagram showing an example in which a fiber-reinforced resin layer is provided on the outer peripheral surface of the side sill structural part according to the present embodiment; and FIG. 11 is an explanatory diagram showing a method for manufacturing a side sill according to the present embodiment.

[0011] Preferred embodiments of the technology of the present disclosure will be described in detail below with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0012] <Vehicle body structural component> First, an outline of a vehicle body structure including a vehicle body structural component according to this embodiment will be described. Fig. 1 is a schematic diagram showing the appearance of a vehicle body side structure 1. The vehicle body side structure 1 shown in Fig. 1 schematically shows a part of the structure of the left side of a vehicle. As shown in Fig. 1, in this specification, the fore-and-aft direction of the vehicle body may be referred to as the X direction, the vehicle width direction as the Y direction, and the vehicle height direction as the Z direction.

[0013] The vehicle body side structure 1 is configured to include a front pillar 2, a center pillar 3, a rear pillar 4, a roof pillar 5, and a side sill 6. The roof pillar 5 extends in the fore-and-aft direction of the vehicle body in the upper part of the vehicle interior space and forms the side portion of the vehicle roof. The side sill 6 extends in the fore-and-aft direction of the vehicle body in the lower part of the side of the vehicle. In this embodiment, the side sill 6 constitutes a part of a vehicle body structural component to which the technology of the present disclosure is applied.

[0014] The front pillar 2 has its lower end connected to the front end of the side sill 6 and its upper end connected to the front end of the roof pillar 5. The front pillar 2 forms the front portion of the vehicle's interior space and is positioned to support the sides of the windshield. The rear pillar 4 has its lower end connected to the rear end of the side sill 6 and its upper end connected to the rear end of the roof pillar 5. The center pillar 3 has its lower end connected to the center of the side sill 6 in the fore-and-aft direction of the vehicle body and its upper end connected to the center of the roof pillar 5 in the fore-and-aft direction of the vehicle body.

[0015] An opening for a front door is formed between the side sill 6, the roof pillar 5, the front pillar 2, and the center pillar 3. In addition, an opening for a rear door is formed between the side sill 6, the roof pillar 5, the rear pillar 4, and the center pillar 3. Each of the structural components that make up the vehicle body side structure 1 may be formed by combining multiple members.

[0016] Next, the configuration of a side sill structural part 11 including the side sill 6 as a vehicle body structural part according to this embodiment will be described in detail.

[0017] 2 to 5 are explanatory diagrams showing an example of the configuration of the side sill structural component 11 according to this embodiment. Fig. 2 shows a perspective view of the side sill structural component 11 as seen from the front outside the vehicle body in the vehicle width direction. Figs. 3 and 4 are cross-sectional views of the side sill structural component 11 shown in Fig. 2 taken along the C1 and C2 sections, respectively, as seen from the front side of the vehicle body to the rear side. Fig. 5 shows a horizontal cross-sectional view (X-Y plane) of region R of the side sill structural component 11 shown in Fig. 2.

[0018] The side sill structural component 11 includes a cylindrical side sill 6 and a component 9 disposed in the space inside the side sill 6. The side sill 6 is a hollow, cylindrical component made of carbon fiber reinforced resin and extending along the longitudinal direction of the vehicle body. The illustrated side sill 6 is molded into a hexagonal prism shape with a hexagonal cross section perpendicular to the longitudinal direction of the vehicle body. A center pillar 3 extending upward is connected to the axial center of the side sill 6.

[0019] The side sill 6 is formed using a fiber reinforced resin in which carbon fiber is impregnated with a thermoplastic resin as a matrix resin.

[0020] Examples of thermoplastic resins include polyethylene resin, polypropylene resin, polyvinyl chloride resin, ABS resin (acrylonitrile-butadiene-styrene copolymer synthetic resin), polystyrene resin, AS resin (acrylonitrile-styrene copolymer synthetic resin), polyamide resin, polyacetal resin, polycarbonate resin, polyester resin, PPS (polyphenylene sulfide) resin, fluororesin, polyetherimide resin, polyether ketone resin, and polyimide resin.

[0021] The thermoplastic resin may be one of the above resins or a mixture of two or more of them. Alternatively, the thermoplastic resin may be a copolymer of the above resins. When the thermoplastic resin is a mixture, a compatibilizer may be used in combination. Furthermore, a flame retardant such as a bromine-based flame retardant, a silicon-based flame retardant, or red phosphorus may be added to the thermoplastic resin.

[0022] The carbon fibers contain an appropriate ratio of continuous fibers oriented in the longitudinal direction of the side sill 6 and continuous fibers oriented in a direction intersecting the longitudinal direction. The amount of continuous fibers oriented in the longitudinal direction can adjust the tensile stress generated when a load is input due to a side collision. The amount of continuous fibers oriented in a direction intersecting the longitudinal direction can adjust the rigidity against the input load during a side collision, thereby adjusting the amount of energy absorption. Furthermore, the carbon fibers may contain short fibers in addition to continuous fibers, and may contain fibers other than carbon fibers as reinforcing fibers.

[0023] Because the side sill 6 is a molded body having a cylindrical closed cross-sectional shape, it is possible to maintain the continuity of the fibers not only in the axial direction (longitudinal direction), but also in the circumferential direction around the axis, thereby increasing rigidity against input loads during a side collision.

[0024] The component 9 disposed in the space on the inner periphery of the side sill 6 is not particularly limited. For example, the vehicle to which the vehicle body side structure 1 is applied may be an electric vehicle equipped with a turbine engine generator, and the predetermined component 9 may be a heat exchanger. The heat exchanger is provided to cool the high-temperature exhaust gas emitted from the turbine engine. In other words, the component 9 is connected to a pipe through which the exhaust gas is introduced, a pipe through which the exhaust gas is discharged, and a pipe through which cooling water is circulated (not shown).

[0025] The vehicle to which the vehicle body side structure 1 is applied may be a fuel cell vehicle, and the predetermined component 9 may be a hydrogen tank. That is, a pipeline for discharging hydrogen is connected to the component 9 (not shown). In both the electric vehicle and the fuel cell vehicle described above, the area inside the vehicle body in the vehicle width direction beyond the side sill 6 is the area under the floor of the passenger compartment, and multiple secondary batteries are arranged in this area.

[0026] The side sill 6 has a plurality of protrusions 13 provided on the inner peripheral surface of the side sill 6, which contact the component 9 and press down to support the component 9. In this embodiment, recesses 14 are formed on the outer peripheral surface of the side sill 6, thereby forming the protrusions 13 on the inner peripheral surface of the side sill 6. The side sill 6 has five protrusions 13 aligned along the fore-and-aft direction of the vehicle on the surface of the side sill 6 facing outward from the vehicle in the vehicle width direction. Each of the protrusions 13 extends along the height direction of the vehicle.

[0027] Each of the protrusions 13 contacts the component 9 and presses and supports the component 9 between itself and the inner circumferential surface of the side sill 6 that is on the vehicle body side in the vehicle width direction. As will be described later, each of the protrusions 13 is formed by placing the component 9 in the space on the inner circumferential side of the molded body (6a) of the side sill 6 that has been molded once, and then forming a recess 14 on the outer circumferential surface side of the side sill 6. Therefore, the protrusions 13 and the component 9 contact each other without any gaps being generated between them.

[0028] To reliably support the component 9 using the protrusions 13, it is necessary to provide at least one protrusion 13 on each of the front and rear sides of the component 9, but there are no other limitations on the number or positions of the protrusions 13. Furthermore, the shape of each protrusion 13 does not have to extend along the height direction of the vehicle body. However, if the protrusions 13 have a shape that extends along the height direction of the vehicle body, and the outer peripheral surface of the component 9 has a curved shape such as a cylindrical shape, each protrusion 13 can reliably press down on the outer peripheral surface of the component 9 even if the height position of the component 9 is shifted.

[0029] Even if the convex portion 13 is not shaped to extend along the height direction of the vehicle body, but is a plurality of convex portions 13 arranged along the height direction of the vehicle body, any one of the convex portions 13 can reliably press down the outer surface of the part 9.

[0030] Furthermore, by deforming the molded body (6a) of the side sill 6 made of fiber-reinforced resin containing continuous fibers to form the convex portion 13, the orientation direction of the continuous fibers in the side portion of the convex portion 13 is aligned with the vehicle width direction. Therefore, in the event of a side collision of the vehicle, it is possible to increase the amount of energy absorption of the collision load input to at least the side sill 6. This makes it possible to suppress damage to components located in the area under the floor of the vehicle interior, such as the secondary battery.

[0031] 6, the convex portions 13 may be provided on both the outer and inner surfaces of the vehicle body in the vehicle width direction. However, when the sum of the convex portions 13 in the vehicle width direction is the same, providing the convex portions 13 only on the outer surface of the vehicle body in the vehicle width direction maximizes the height of the convex portions 13, thereby enabling a greater amount of energy absorption during a side collision.

[0032] 7, resin 15 may be disposed in recesses 14 that form the respective protrusions 13. Filling the recesses 14 with resin 15 can prevent a deterioration in the appearance due to the provision of multiple protrusions 13 and a decrease in the bonding strength when another member is bonded further to the outer periphery of the side sill 6. From the viewpoint of ease of manufacture, it is preferable that the resin 15 be the same type of thermoplastic resin as the matrix resin of the fiber-reinforced resin.

[0033] 8, a fiber-reinforced resin layer 17 containing continuous fibers may be provided around the outer periphery of the side sill 6 in addition to the resin 15 disposed in the recess 14. This makes it possible to prevent a decrease in the strength of the side sill 6 as a whole.

[0034] At least one of the recesses 14 may be provided with an energy absorbing member having an energy absorbing function instead of the resin 15. The energy absorbing member absorbs the collision load by crushing under the impact of the collision load during a side collision. For example, the energy absorbing member is a multi-layer composite material formed using a carbon fiber reinforced resin that uses a thermosetting resin or a thermoplastic resin and carbon fiber, and can achieve high strength and light weight.

[0035] For example, the energy absorption member has a cylindrical shape. A fiber-reinforced resin energy absorption member absorbs a collision load by collapsing and breaking progressively from the tip side when a collision load is input. Compared to a steel plate crash box, a fiber-reinforced resin energy absorption member breaks progressively at smaller intervals, so it can achieve stable energy absorption characteristics with less load fluctuation. Furthermore, a fiber-reinforced resin energy absorption member has the characteristics of leaving relatively little residual crush and absorbing a large amount of collision load per unit weight.

[0036] The energy absorbing member may have a tapered portion that narrows toward the end portion on the outer side of the vehicle body. This tapered portion makes it easier for peeling to occur between the multiple layers that make up the energy absorbing member when a collision load is transmitted to the tip side of the energy absorbing member. This provides a trigger for the tip side of the energy absorbing member to break, making it easy to gradually break the energy absorbing member. Note that the shape of the energy absorbing member is not limited to a cylindrical shape, and various configurations can be adopted.

[0037] <Method of Manufacturing Vehicle Body Structural Part> Next, an example of a method of manufacturing the side sill structural part 11 as the vehicle body structural part according to this embodiment will be described.

[0038] 9 is an explanatory diagram showing the manufacturing process of the side sill structural component 11. First, a cylindrical molded body 6a made of fiber-reinforced resin is molded by a conventional method such as braiding, filament winding, sheet winding, or lay-up, or by cold press molding or hot press molding (first step). The molding method for the molded body 6a is not particularly limited, but because a thermoplastic resin is used as the matrix resin, a method is adopted in which the matrix resin is heated to form a molten fiber-reinforced resin and then cooled in that state.

[0039] Next, a predetermined component 9 is positioned and placed in the space on the inner periphery of the cylindrical compact 6a (second step). At this time, for example, a water-soluble positioning member may be used for positioning and placing the predetermined component 9. The water-soluble positioning member may be, for example, an expendable salt core, but is not particularly limited as long as it can be removed by washing with water in a subsequent step.

[0040] Next, at least the region of the molded body 6a where the convex portions 13 (concave portions 14) are to be formed is heated to melt the thermoplastic resin, and a portion of the molten molded body 6a is deformed from the outer periphery to the inner periphery to form a plurality of convex portions 13 (concave portions 14) that protrude toward the inner periphery of the molded body 6a and come into contact with the part 9 (third step). The convex portions 13 can be formed using, for example, a molding die, but the method for forming the convex portions 13 is not particularly limited.

[0041] Next, the molded body 6a is cooled, and the thermoplastic resin is hardened again to obtain the side sill structural part 11 (third step). At an appropriate timing after the thermoplastic resin has hardened, the water-soluble positioning member is removed by washing with water or the like.

[0042] When filling the recess 14 with resin 15 (see FIG. 7), after forming the protrusion 13 with a molten thermoplastic resin, the thermoplastic resin is filled into the recess 14 before hardening again, and the thermoplastic resin is hardened simultaneously with cooling of the molded body 6a. This allows for a strong bond between the resin 15 filled into the recess 14 and the side sill 6. Alternatively, after cooling the molded body 6a to form the side sill structural component 11, molten thermoplastic resin may be placed in the recess 14 and further cooled to harden the thermoplastic resin.

[0043] Furthermore, when arranging an energy absorbing member in the recess 14, after forming the protrusion 13 with a molten thermoplastic resin, a fiber-reinforced resin energy absorbing member that has been pre-molded is arranged in the recess 14 before the thermoplastic resin is hardened again. This allows the energy absorbing member arranged in the recess 14 to be firmly bonded to the side sill 6. Alternatively, after the molded body 6a is cooled to form the side sill structural component 11, the energy absorbing member may be bonded to the recess 14 using an adhesive or the like.

[0044] Furthermore, a fiber-reinforced resin layer 17 (see FIG. 8) made by further winding continuous fibers and curing them with resin may be formed on the outer periphery of the side sill 6. This gives the outer periphery of the side sill structural part 11 a seamless, cylindrical, closed cross section, eliminating any areas that become weak when a collision load is input during a side collision, thereby improving the strength or rigidity of the side sill structural part 11.

[0045] <Effects> As described above, the side sill structural component 11 according to this embodiment can utilize the internal space of the hollow closed cross-section structure formed by using the CFRP molded body 6a. This allows for the placement of a component 9, such as a heat exchanger provided in an electric vehicle equipped with a turbine generator or a hydrogen tank provided in a fuel cell vehicle. Furthermore, the side sill structural component 11 according to this embodiment supports the component 9 placed in the internal space by pressing down on it with the multiple protrusions 13 formed by modifying the shape of the molded body 6a. Therefore, a structure that supports the component 9 can be realized without breaking the fibers of the CFRP molded body 6a.

[0046] Furthermore, the side sill structural component 11 according to this embodiment has a plurality of protrusions 13 formed by deforming the shape of the molded body 6a, so that the orientation direction of the continuous fibers in the side portions of the protrusions 13 is the vehicle width direction, thereby increasing the amount of energy absorption of the collision load input during a side collision.

[0047] Furthermore, the side sill structural component 11 according to this embodiment has the protrusions 13 only on the surface on the outer side of the vehicle body in the vehicle width direction, which maximizes the height of the protrusions 13 that press and support the component 9 arranged in the internal space, thereby enabling greater energy absorption during a side collision.

[0048] The side sill structural component 11 according to this embodiment may also include resin 15 filled in at least one of a plurality of recesses 14 formed on the outer periphery of the molded body 6a by the plurality of protrusions 13. Filling the recess 14 with resin 15 allows the surface of the side sill 6 around the recess 14 to be flat, thereby preventing a decrease in strength or rigidity of the side sill 6. An energy absorbing member may also be disposed in at least one of the plurality of recesses 14. Disposing an energy absorbing member in the recess 14 increases the amount of energy absorbed during a side collision.

[0049] Furthermore, according to the manufacturing method for the side sill structural component 11 of this embodiment, by using CFRP with a thermoplastic resin as the matrix resin, the molded body 6a is molded once, and the component 9 is placed in the internal space. After that, the thermoplastic resin is heated and melted, and deformation can be applied from the outside. This makes it easy to form multiple protrusions 13 that can reliably press and support the component 9 placed in the internal space. Furthermore, with the protrusions 13 formed in this manner, the fibers of the molded body 6a are not broken, and therefore a decrease in the strength or rigidity of the side sill 6 can be prevented.

[0050] Although the preferred embodiments of the technology of the present disclosure have been described in detail above with reference to the accompanying drawings, the technology of the present disclosure is not limited to these examples. It is clear that a person skilled in the art of the technology to which the present disclosure pertains can conceive of various modified or altered examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure.

[0051] For example, in the above embodiment, a side sill structural part is used as an example of a vehicle body structural part, but the technology of the present disclosure is not limited to such an example. For example, the vehicle body structural part may be a center pillar structural part or a front pillar structural part. Even if the vehicle body structural part is a center pillar structural part or a front pillar structural part, it is possible to effectively utilize the internal space of the cylindrical closed cross-sectional shape and easily form a protrusion that can reliably support a part placed in the internal space.

[0052] In the above embodiment, the protrusions that press down and support the components are formed on the side surfaces in the vehicle width direction, but the technology of the present disclosure is not limited to this example. For example, the protrusions may be formed on both the top and bottom surfaces in the vehicle height direction, or on either one of the top and bottom surfaces. Even with such protrusions, it is possible to easily form protrusions that can reliably support components placed in the internal space.

[0053] REFERENCE SIGNS LIST 1: Vehicle body side structure 3: Center pillar 6: Side sill 6a: Molded body 9: Part 11: Side sill structural part 13: Convex portion 14: Concave portion 17: Fiber-reinforced resin layer

Claims

1. A method for manufacturing an automobile body structural part, comprising: a first step of molding continuous fibers impregnated with a thermoplastic resin into a cylindrical shape, and hardening the thermoplastic resin to form a cylindrical fiber-reinforced resin molded body; a second step of arranging a specified part in the space on the inner periphery of the cylindrical molded body; and a third step of heating at least a part of the molded body to melt the thermoplastic resin and form a plurality of protrusions that protrude on the inner periphery of the molded body and contact the specified parts, and then hardening the thermoplastic resin again.

2. A method for manufacturing a vehicle body structural part as described in claim 1, wherein in the third step, at least a portion of the molded body in which the thermoplastic resin is melted by heating is deformed from the outer periphery to the inner periphery to form the multiple convex portions, and at least one of the concave portions formed on the outer periphery of the molded body is filled with resin, and then the thermoplastic resin is hardened again.

3. The method for manufacturing a vehicle body structural part as described in claim 1, wherein the vehicle body structural part is a side sill in which the axial direction of the molded body is arranged along the fore-and-aft direction of the vehicle body, and in the third step, the multiple protrusions are provided on at least the surface of the molded body facing outward from the vehicle body in the vehicle width direction.

4. A method for manufacturing a vehicle body structural part as described in claim 3, wherein in the third step, at least a portion of the molded body in which the thermoplastic resin has been melted by heating is deformed from the outer periphery to the inner periphery to form the multiple convex portions, an energy absorbing member is placed in at least one of the concave portions formed on the outer periphery of the molded body, and then the thermoplastic resin is hardened again.

5. A vehicle body structural component comprising: a cylindrical fiber-reinforced resin molded body; and a specified part arranged in the space inside the molded body, the molded body having a plurality of protrusions provided on the inner peripheral surface of the molded body, which contact the specified part and press down to support the specified part.

6. The vehicle body structural part according to claim 5, wherein the vehicle body structural part is a side sill in which the axial direction of the molded body is arranged along the longitudinal direction of the vehicle body, and the plurality of protrusions are provided on at least the surface of the molded body on the outer side of the vehicle body in the vehicle width direction.

7. The vehicle body structural part according to claim 6, wherein at least one of a plurality of recesses formed on the outer periphery of the molded body by the plurality of protrusions is provided with a resin or energy absorbing material.

8. The vehicle body structural part according to claim 5, wherein the matrix resin of the fiber reinforced resin is a thermoplastic resin.

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