Side sill

Abstract

Provided is a side sill to which a lower portion of a center pillar is to be connected and which is made of a fiber-reinforced resin composite material. The side sill includes a tubular part extending in the front and back directions of a vehicle body. The tubular part comprises a plurality of ridgeline portions each extending in the front and back directions of the vehicle body and a plurality of connecting planar portions each formed between two ridgeline portions adjacent to each other around the axis. The plurality of connecting planar portions each have a recess provided on the outer peripheral surface of the tubular part and extending in the front and back directions of the vehicle body. The vehicle-body inner-side portion of the side sill, which is positioned on the vehicle-body inner side along the vehicle width direction and extends in the upper and lower directions of the vehicle body, has a higher rigidity than the vehicle-body upper-side portion, vehicle-body lower-side portion, and vehicle-body outer-side portion of the side sill.

Description

Side sill

[0001] The technology of the present disclosure relates to a side sill.

[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 using side sills made of fiber-reinforced resin, fiber-reinforced resin has lower ductility than steel, so when a collision load is input to the center pillar and side sill during a side collision, stress is concentrated at the connection between the center pillar and the side sill, and there is a risk that the connection will break.

[0005] 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 side sill that can reduce the risk of the connection between the center pillar and the side sill breaking due to the impact load during a side collision, when the side sill to which the lower part of the center pillar is connected is made of fiber-reinforced resin.

[0006] In order to solve the above problems, according to one aspect of the technology of the present disclosure, there is provided a side sill made of a fiber-reinforced resin composite material to which a lower part of a center pillar is connected, the side sill including a tubular portion extending in the fore-and-aft direction of the vehicle body, the tubular portion having a plurality of ridge portions each extending in the fore-and-aft direction of the vehicle body and a plurality of connecting surface portions formed between two adjacent ridge portions around an axis, the plurality of connecting surface portions each having a recess provided on the outer peripheral surface of the tubular portion and extending in the fore-and-aft direction of the vehicle body, and the rigidity of the inner side surface of the side sill that is positioned on the inner side of the vehicle body in the vehicle width direction and extends in the vertical direction of the vehicle body is greater than the rigidity of the upper side surface, lower side surface and outer side surface of the side sill.

[0007] As described above, according to the technology of the present disclosure, when the side sill to which the lower part of the center pillar is connected is made of fiber-reinforced resin, it is possible to reduce the risk of the connection between the center pillar and the side sill breaking due to the collision load during a side collision.

[0008] FIG. 1 is a schematic diagram showing a vehicle body side structure equipped with a side sill according to the present embodiment; FIG. 2 is an explanatory diagram showing a state in which a connection portion between a center pillar and a side sill is broken due to a collision load; FIG. 3 is a cross-sectional view showing an example of the configuration of a side sill according to the present embodiment; FIG. 4 is an explanatory diagram showing a schematic change in shape of the side sill according to the present embodiment; FIG. 5 is an explanatory diagram showing a modified example of the side sill according to the present embodiment; FIG. 6 is an explanatory diagram showing another modified example of the side sill according to the present embodiment.

[0009] 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.

[0010] First, an outline of a vehicle body side structure equipped with a side sill 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 portion 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] If at least the side sill 6 is made of CFRP, as shown in Figure 2, when a collision load F input during a side collision is applied to the center pillar 3 and the side sill 6, the center pillar 3 may collapse toward the inside of the vehicle body, causing the connection portion 9 between the center pillar 3 and the side sill 6 to break. This is because the ductility of CFRP is smaller than that of steel, close to zero, causing stress to concentrate at the connection portion 9. The side sill 6 according to this embodiment is configured to be able to prevent such breakage of the connection portion 9 between the center pillar 3 and the side sill 6.

[0015] 3 is an explanatory diagram showing an example of the configuration of the side sill 6 according to this embodiment. Fig. 3 shows a cross-sectional view of the side sill 6 in the vicinity of the region where the center pillar 3 is connected, taken along a line perpendicular to the longitudinal direction of the vehicle body.

[0016] The side sill 6 includes an outer circumferential cylindrical portion 10, an inner circumferential cylindrical portion 20, and an intermediate layer 30. Of these, the outer circumferential cylindrical portion 10 and the inner circumferential cylindrical portion 20 are each formed into a hollow cylindrical member made of CFRP and extending along the longitudinal direction of the vehicle body. The illustrated side sill 6 has a double structure formed by the outer circumferential cylindrical portion 10 and the inner circumferential cylindrical portion 20, and has a rectangular cross section perpendicular to the longitudinal direction of the vehicle body.

[0017] The outer circumferential cylindrical portion 10 and the inner circumferential cylindrical portion 20 are each formed using a fiber reinforced resin in which carbon fiber is impregnated with a thermoplastic resin or a thermosetting resin as a matrix resin.

[0018] 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.

[0019] 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.

[0020] Examples of thermosetting resins include epoxy resins, unsaturated polyester resins, vinyl ester resins, phenolic resins, polyurethane resins, and silicone resins. The thermosetting resin may be one of the above resins or a mixture of two or more of them. An appropriate curing agent or reaction accelerator may also be added to the thermosetting resin.

[0021] The carbon fibers contain an appropriate ratio of continuous fibers oriented in the longitudinal direction of the vehicle body and continuous fibers oriented in a direction intersecting the longitudinal direction of the vehicle body. The amount of continuous fibers oriented in the longitudinal direction of the vehicle body 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 of the vehicle body can adjust the rigidity against the input load during a side collision, and the amount of energy absorption can be adjusted. Furthermore, the carbon fibers may contain short fibers in addition to the continuous fibers, and may contain fibers other than carbon fibers as reinforcing fibers.

[0022] Because the outer circumferential cylindrical portion 10 and the inner circumferential cylindrical portion 20 are each molded bodies having a cylindrical closed cross-sectional shape, it is possible to maintain the continuity of the fibers not only in the axial direction (forward / backward direction of the vehicle body), but also in the circumferential direction around the axis, thereby increasing rigidity against input loads during a side collision.

[0023] The outer circumferential cylindrical portion 10 has four ridges 11a to 11d extending in the longitudinal direction of the vehicle body and four connecting surfaces 13a to 13d formed between each pair of adjacent ridges 11a to 11d around the axis. The inner circumferential cylindrical portion 20 has four ridges 21a to 21d extending in the longitudinal direction of the vehicle body and four connecting surfaces 23a to 23d formed between each pair of adjacent ridges 21a to 21d around the axis.

[0024] Each of the four connection surfaces 13a to 13d of the outer circumferential cylindrical portion 10 has a flat surface. The thickness of the connection surface 13c on the vehicle body inner side in the vehicle width direction is greater than the thicknesses of the other connection surface 13d on the vehicle body upper side, the connection surface 13c on the vehicle body lower side, and the connection surface 13a on the vehicle body outer side. Therefore, the rigidity of the connection surface 13c on the vehicle body inner side in the vehicle width direction is greater than the rigidity of the other connection surface 13d on the vehicle body upper side, the connection surface 13c on the vehicle body lower side, and the connection surface 13a on the vehicle body outer side. Looking at the side sill 6 as a whole, the rigidity of the vehicle body inner side portion in the vehicle width direction is greater than the rigidity of the other vehicle body upper side portion, the vehicle body lower side portion, and the vehicle body outer side portion.

[0025] The four connection surface portions 23a to 23d of the inner circumferential side cylindrical portion 20 each have a cross-sectional shape that is concave toward the outer circumferential side of the inner circumferential side cylindrical portion 20. Therefore, the four connection surface portions 23a to 23d of the inner circumferential side cylindrical portion 20 each have recesses 25a to 25d that are provided on the outer circumferential side surface of the inner circumferential side cylindrical portion 20 and extend in the fore-and-aft direction of the vehicle body.

[0026] The four ridges 11a to 11d of the outer-periphery-side tubular portion 10 and the four ridges 21a to 21d of the inner-periphery-side tubular portion 20 are in contact with each other. Therefore, the inner-periphery-side tubular portion 20 is fixed in the space on the inner periphery side of the outer-periphery-side tubular portion 10. On the other hand, because the four connection surfaces 23a to 23d of the inner-periphery-side tubular portion 20 have a concave cross-sectional shape, the four connection surfaces 13a to 13d of the outer-periphery-side tubular portion 10 and the four connection surfaces 23a to 23d of the inner-periphery-side tubular portion 20 are spaced apart.

[0027] The intermediate layer 30 is disposed in a region between the connection surfaces 13a to 13d of the outer circumferential side tubular portion 10 and the connection surfaces 23a to 23d of the inner circumferential side tubular portion 20. The intermediate layer 30 is made of a material having a rigidity lower than that of the outer circumferential side tubular portion 10 and the inner circumferential side tubular portion 20. The intermediate layer 30 may be a layer filled with a foam material made of, for example, polyethylene, polystyrene, polypropylene, polyurethane, or the like, but the material constituting the intermediate layer 30 is not limited to the above examples.

[0028] In the side sill 6, the outer circumferential tubular portion 10 determines the outer shape of the side sill 6, and the connecting surface 13c of the outer circumferential tubular portion 10 on the vehicle body inner side functions to absorb a collision load during a side collision. The inner circumferential tubular portion 20 functions to make the cross section of the side sill 6 easily crush evenly upon receiving the collision load during a side collision, dispersing stress over a wide area of ​​the side sill 6 and absorbing the energy of the collision load. The intermediate layer 30 functions to transmit the load received by the outer circumferential tubular portion 10 to the inner circumferential tubular portion 20 and to increase the amount of energy absorption of the collision load by being compressed by the load.

[0029] 4 is an explanatory diagram schematically illustrating the change in shape of the side sill 6 according to this embodiment when a collision load F is applied to the side sill 6 during a side collision. When the collision load F is applied to the side sill 6, the inner tubular portion 20 begins to deform due to the collision load F. The connecting surface portion 13c on the vehicle body inner side of the outer tubular portion 10 has greater rigidity than other portions and is therefore less likely to deform when subjected to the collision load F transmitted via the inner tubular portion 20. Therefore, the inner tubular portion 20 is more likely to be crushed by the collision load F. At this time, because the outer peripheral surface of each connecting surface portion of the inner tubular portion 20 is provided with a recess, each connecting surface portion of the inner tubular portion 20 deforms toward the axial center.

[0030] This allows the cross section of the inner tubular portion 20 to be crushed evenly, distributing stress over a wide area of ​​the side sill 6. Furthermore, the cross section of the inner tubular portion 20 is crushed evenly, which absorbs the energy of the collision load. Therefore, it is possible to prevent breakage of the connection portion between the center pillar 3 and the side sill 6 due to stress concentration at the connection portion.

[0031] The configuration of the side sill 6 according to this embodiment can be modified in various ways. Some of the modifications will be described below.

[0032] FIG. 5 shows a modified side sill 6A in which the shape of the inner tubular portion 20 has been changed. Each of the connecting surfaces 27a-27d of the inner tubular portion 20 of the side sill 6A has a substantially flat surface. Each of the connecting surfaces 27a-27d has recesses 29a-29d provided on the outer surface of the inner tubular portion 20 and extending in the longitudinal direction of the vehicle. The recesses 29a are formed as portions with a relatively small layer thickness. The outer tubular portion 10 has the same configuration as the outer tubular portion 10 of the side sill 6 according to the above embodiment. An intermediate layer 30 is provided in the region between the outer tubular portion 10 and the inner tubular portion 20.

[0033] Even with the side sill 6A shown in FIG. 5, when a collision load is input during a side collision, the recesses 29a-29d of the inner tubular portion 20 trigger deformation of the connecting surfaces 27a-27d of the inner tubular portion 20 toward the axial center. This causes the cross section of the inner tubular portion 20 to crush evenly, dispersing stress over a wide area of ​​the side sill 6A. Furthermore, the uniform crushing of the cross section of the inner tubular portion 20 also contributes to energy absorption of the collision load. This prevents stress concentration at the connecting portion between the center pillar 3 and the side sill 6A, thereby preventing breakage of the connecting portion.

[0034] FIG. 6 shows a modified side sill 6B that is configured using a single tubular portion 40 instead of a double structure. The tubular portion 40 of the side sill 6B is configured similarly to the inner tubular portion 20 of the modified side sill 6A shown in FIG. 5. A reinforcing plate 49 is joined to the inner surface of the tubular portion 40, which is located on the inner side of the vehicle body in the vehicle width direction, on the inner side of the connection surface 43c. The reinforcing plate 49 is provided to increase the rigidity of the inner portion of the side sill 6B that is located on the inner side of the vehicle body in the vehicle width direction and extends in the vertical direction of the vehicle body, compared to the rigidity of the upper, lower, and outer portions of the side sill 6B. From the perspective of weight reduction, the reinforcing plate 49 is preferably a CFRP plate, but may also be a metal plate.

[0035] Even with the side sill 6B shown in FIG. 6, when a collision load is input during a side collision, the recesses 45a to 45d of the tubular portion 40 cause each of the connecting surfaces 43a to 43d of the tubular portion 40 to deform toward the axial center. This causes the cross section of the tubular portion 40 to crush evenly, distributing stress over a wide area of ​​the side sill 6B. Furthermore, the even crushing of the cross section of the tubular portion 40 allows for energy absorption of the collision load. Therefore, fracture of the connecting portion between the center pillar 3 and the side sill 6B due to stress concentration at the connecting portion can be suppressed.

[0036] 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.

[0037] For example, in the above embodiment, the layer thickness was increased or a reinforcing plate 49 was provided to increase the rigidity of the inner side surface (13c, 49) of the side sill that is disposed on the inner side of the vehicle body in the vehicle width direction and extends in the vertical direction of the vehicle body, but the technology of the present disclosure is not limited to such examples. For example, the rigidity may be increased by providing a three-dimensional uneven shape on the inner connection surface 13c or the reinforcing plate 49. Furthermore, the rigidity may be increased by increasing the proportion of continuous fibers that are oriented at 0 degrees or 90 degrees relative to the fore-aft direction of the vehicle body as the continuous fibers that make up the inner connection surface 13c or the reinforcing plate 49.

[0038] In the above embodiment, the space on the inner periphery side of the inner periphery side tubular portion 20 or the tubular portion 40 is hollow, but the technology of the present disclosure is not limited to such an example. For example, by arranging a material identical to the intermediate layer 30 in the space on the inner periphery side of the inner periphery side tubular portion 20 or the tubular portion 40, it is possible to increase the amount of energy absorption without inhibiting the inner periphery side tubular portion 20 or the tubular portion 40 from collapsing toward the axial center.

[0039] In the above embodiment, the cross-sectional shape of the side sill is rectangular, but the cross-sectional shape of the side sill is not limited to a rectangular shape and may be a polygon, such as a hexagon or octagon.

[0040] DESCRIPTION OF SYMBOLS 1: Vehicle body side structure 2: Front pillar 3: Center pillar 4: Rear pillar 5: Roof pillar 6: Side sill 9: Connection portion 10: Outer peripheral cylindrical portion 11a to 11d: Ridge portion 13a to 13d: Connection surface portion 20: Inner peripheral cylindrical portion 21a to 21d: Ridge portion 23a to 23d: Connection surface portion 25a to 25d: Recessed portion 27a to 27d: Connection surface portion 29a to 29d: Recessed portion 30: Intermediate layer 40: Cylindrical portion 43a to 43d: Connection surface portion 45a to 45d: Recessed portion 49: Reinforcement plate

Claims

1. A side sill made of fiber-reinforced resin to which a lower part of a center pillar is connected, the side sill comprising a tubular portion extending in the fore-and-aft direction of a vehicle body, the tubular portion having a plurality of ridge portions each extending in the fore-and-aft direction of the vehicle body and a plurality of connecting surface portions each formed between two of the ridge portions adjacent around an axis, the plurality of connecting surface portions each having a recess provided on the outer peripheral surface of the tubular portion and extending in the fore-and-aft direction of the vehicle body, and a rigidity of an inner side surface of the side sill that is disposed on the inner side of the vehicle body in the vehicle width direction and extends in the vertical direction of the vehicle body is greater than the rigidity of an upper side surface, a lower side surface and an outer side surface of the side sill.

2. The side sill according to claim 1, wherein the side sill has a dual structure including an outer circumferential cylindrical portion and an inner circumferential cylindrical portion extending in the fore-and-aft direction of the vehicle body, the inner circumferential cylindrical portion has the multiple ridge portions, the multiple connecting surface portions and the multiple recesses, and the rigidity of the inner side surface of the outer circumferential cylindrical portion is greater than the rigidity of the upper side surface, the lower side surface and the outer side surface of the outer circumferential cylindrical portion.

3. The side sill according to claim 2, wherein each of the plurality of connecting surface portions has a cross-sectional shape that is concave toward the outer periphery of the cylindrical portion.

4. The side sill according to claim 2, wherein a member having a rigidity smaller than the rigidity of each of the outer peripheral side cylindrical portion and the inner peripheral side cylindrical portion is disposed in the region between the outer peripheral side cylindrical portion and the inner peripheral side cylindrical portion.

5. The side sill as described in claim 1, wherein the rigidity of the vehicle body inner side surface of the tubular portion having the multiple ridge portions, the multiple connecting surface portions and the multiple recesses is greater than the rigidity of the vehicle body upper side surface, the vehicle body lower side surface and the vehicle body outer side surface of the tubular portion.

6. The side sill as claimed in claim 1, wherein the tubular portion has a rectangular cross-sectional shape with four of the ridge portions and four connecting surface portions formed on each of two of the ridge portions adjacent to each other around the axis, and each of the four connecting surface portions has the recess on a surface facing the outer periphery of the tubular portion.

7. The side sill according to claim 1, wherein the recess is a portion having a relatively small layer thickness.

Images