Vehicle body frontal structure

Abstract

In this vehicle body frontal structure provided with an energy-absorbing member that collapses axially in the event of a frontal collision of the vehicle and thereby absorbs collision energy, the energy-absorbing member is configured by joining a plurality of tubes, extending along the axial direction of the energy-absorbing member, at respective outer peripheral surfaces. A joining member that supports the energy-absorbing member is joined to a vehicle body frontal end of the energy-absorbing member and comprises a tubular part extending to the energy-absorbing member side, and a rib provided at an inner peripheral side of the tubular part and joined or facing a boundary portion of the plurality of tubes at the vehicle body frontal end of the energy-absorbing member.

Description

Front body structure

[0001] The present disclosure relates to a vehicle front body structure.

[0002] Vehicles are equipped with energy-absorbing members that collapse in the event of a collision to absorb the collision load. Conventionally, energy-absorbing members have been made of metal materials such as steel. However, in recent years, in order to reduce the weight of the vehicle body, development of energy-absorbing members made of fiber-reinforced resin composites containing reinforcing fibers, such as carbon fiber, has been progressing. A typical example of an energy-absorbing member is a cylindrical crash box that is placed between the front bumper beam and the body frame at the front of the vehicle body. Furthermore, in order to reduce the weight of the vehicle body, it is being considered to construct not only the crash boxes but also the front side frames using fiber-reinforced resin composites.

[0003] JP 2017-001599 A

[0004] To gradually collapse an energy absorbing member made of a fiber-reinforced resin composite, the joining members supporting the front end of the energy absorbing member must have the resistance necessary to collapse the cross-sectional structure of the energy absorbing member. From the perspective of reducing the vehicle body weight, it is important to reduce the weight of the joining members. Furthermore, to stably collapse the energy absorbing member in the axial direction, the energy absorbing member must have the desired bending rigidity.

[0005] Therefore, the present disclosure has been made in consideration of the above problems, and an object of the present disclosure is to provide a front vehicle body structure that reduces the weight of joining members and that can stably perform axial collapse while ensuring the bending rigidity of the energy absorbing member.

[0006] In order to solve the above problems, according to one aspect of the technology disclosed herein, there is provided a vehicle front structure equipped with an energy absorbing member that absorbs collision energy by axially collapsing during a frontal collision of the vehicle, wherein the energy absorbing member is constructed by joining a plurality of tubes extending along the axial direction of the energy absorbing member at their outer peripheral surfaces, and a joining member that supports the energy absorbing member is joined to the vehicle body front end of the energy absorbing member, and the joining member has a tube portion extending toward the energy absorbing member, and a rib that is provided on the inner peripheral side of the tube portion and is joined to or faces the boundary portion of the plurality of tubes at the vehicle body front end of the energy absorbing member.

[0007] As described above, according to the technique of the present disclosure, it is possible to reduce the weight of the joining member and ensure the bending rigidity of the energy absorbing member while allowing it to stably undergo axial collapse.

[0008] FIG. 1 is a schematic diagram showing the basic configuration of the vehicle body front structure according to the present embodiment; FIG. 2 is a cross-sectional view showing the basic configuration of the vehicle body front structure according to the same embodiment; FIG. 3 is a perspective view showing the configuration of a crash box joint member and a crash box in the vehicle body front structure according to the same embodiment; FIG. 4 is a cross-sectional view showing a joint portion between a front end portion of a crash box and a crash box joint member in the vehicle body front structure according to the same embodiment; FIG. 5 is a cross-sectional view showing another example of a joint portion between a front end portion of a crash box and a crash box joint member in the vehicle body front structure according to the same embodiment; FIG. 6 is an explanatory diagram showing the behavior of a load during axial collapse of the vehicle body front structure according to the same embodiment; FIG. 7 is an explanatory diagram showing the manner in which the vehicle body front structure according to the same embodiment gradually collapses; FIG. 8 is an explanatory diagram showing the manner in which the vehicle body front structure according to the same embodiment gradually collapses;

[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] Below, the basic configuration of the vehicle body front structure according to the present disclosure will be explained, and then application examples of the present disclosure will be explained in detail.

[0011] <Basic Configuration of Vehicle Body Front Structure> Figures 1 and 2 are explanatory diagrams showing the basic configuration of a vehicle body front structure 1 according to this embodiment. Figure 1 is a schematic diagram of the right front portion of a vehicle body frame viewed from above the vehicle body. Figure 2 is a partial cross-sectional view of the vehicle body front structure 1 shown in Figure 1. In the following description, the front side of the vehicle body may be referred to as the leading end side, and the rear side of the vehicle body may be referred to as the trailing end side.

[0012] The vehicle front body structure 1 includes a bumper beam 3, crash box joint members 10, crash boxes 20, side frame joint members 30, and front side frames 40. The crash box joint members 10 are joined to the bumper beam 3. Front end portions 21 of the crash boxes 20 are joined to the crash box joint members 10, and rear end portions 23 of the crash boxes 20 are joined to the side frame joint members 30. The side frame joint members 30 are joined to rear end portions of the crash boxes 20. Front end portions 41 of the front side frames 40 are joined to the side frame joint members 30. Rear end portions 43 of the front side frames 40 are joined to an appropriate vehicle body framework 5 such as a side member.

[0013] (Bumper Beam) The bumper beam 3 is made of metal such as steel, and is provided inside the front bumper of the vehicle. It has the function of cushioning the impact during a collision and reducing damage to the vehicle body.

[0014] (Crash Box Joint Member) The crash box joint member 10 is disposed opposite the tip end 21 of the crash box 20, to which a collision load is expected to be input, and is fixed to the bumper beam 3 to support the tip end 21 of the crash box 20. The crash box joint member 10 is a molded product made of a metal material such as steel or aluminum, and has higher rigidity than a fiber-reinforced resin molded product. The crash box joint member 10 is fixed to the bumper beam 3 by fastening members such as bolts (not shown) or by welding. However, the joining method is not particularly limited.

[0015] The crash box joining member 10 has a base 11 and a tubular portion 13. The base 11 is a plate-shaped portion that serves as the base of the crash box joining member 10 and is fixed to the bumper beam 3. The tubular portion 13 extends from the base 11 toward the crash box 20. The tubular portion 13 surrounds an end portion 21 on the tip side of the crash box 20 and has an inner circumferential surface that is bonded to the outer circumferential surface of the end portion 21 with an adhesive. In other words, the crash box joining member 10 is bonded to the end portion 21 on the tip side of the crash box 20 with an adhesive.

[0016] (Crash Boxes) The crash boxes 20 are cylindrical components arranged with their axial direction aligned with the front-to-rear direction of the vehicle body. The crash boxes 20 are made of a fiber-reinforced resin composite material, and function as energy absorbing members that absorb the collision energy by receiving a collision load via the bumper beam 3 and collapsing axially when the front of the vehicle collides with a preceding vehicle, an obstacle, or other object. The crash boxes 20 also function to transmit the collision load to the side frame joining members 30 and the front side frames 40.

[0017] A front end 21 of the crash box 20 is supported by a crash box joint member 10, and a rear end 23 of the crash box 20 is supported by a side frame joint member 30. In this embodiment, the crash box 20 is a tubular member whose cross section perpendicular to the axial direction has a rectangular outer shape. The crash box 20 is formed by joining together the outer circumferential surfaces of a plurality of tubes 25 extending along the axial direction. Hereinafter, the term "cross section" refers to a cross section perpendicular to the axial direction.

[0018] The overall dimensions of the crash box 20 may be designed as appropriate depending on the size of the vehicle, the required amount of energy absorption, the weight of the crash box 20, and the like. For example, the axial length of the crash box 20 may be 100 to 200 mm, and each of the two sides of the cross section may be 50 to 100 mm. The thickness of the wall portion of each tube 25 may be, for example, 3 to 5 mm. For example, if the thickness of the wall portion of each tube 25 is 3 to 5 mm, the overall thickness of the joined wall portions will be 6 to 10 mm. However, the dimensions of the crash box 20 are not limited to the above example.

[0019] The crash boxes 20 are made of a fiber-reinforced resin composite material containing at least carbon fiber and a matrix resin, which allows for high strength and lightweight construction. When a collision load is input, the fiber-reinforced resin composite crash boxes 20 exert their load by undergoing axial crushing while continuously breaking, achieving stable energy absorption characteristics with little load fluctuation. Furthermore, the fiber-reinforced resin composite crash boxes 20 have the characteristics of little residual crushing and a large amount of energy absorption per unit weight.

[0020] The crash boxes 20 are manufactured by, for example, weaving a plurality of continuous fibers, integrating them with a matrix resin, and curing the weaved fibers. The reinforcing fibers used in the crash boxes 20 may include, in addition to carbon fibers, organic fibers such as glass fibers, ceramic fibers, and aramid fibers.

[0021] The matrix resin used in the crash box 20 may be a thermosetting resin or a thermoplastic resin. When the matrix resin is a thermosetting resin, its main material may be, for example, one or a mixture of two or more of epoxy resin, unsaturated polyester resin, vinyl ester resin, phenolic resin, polyurethane resin, and silicone resin. When using these thermosetting resins as the matrix resin, an appropriate curing agent or reaction accelerator may be added.

[0022] When the matrix resin is a thermoplastic resin, its main material may be, for example, any one or a mixture of two or more of 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, polyetherketone resin, and polyimide resin. Alternatively, the thermoplastic resin may be a copolymer of the above resins. When a mixture of these thermoplastic resins is used as the matrix resin, a compatibilizer may be further added. 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.

[0023] The crash boxes 20 are formed by bonding the outer circumferential surfaces of tubes 25 made of fiber-reinforced resin composite material together with an adhesive. Each tube 25 includes, for example, axial fibers oriented along the axial direction and cross fibers (also called helical fibers) wound in a direction intersecting the axial direction. The cross fibers are wound in directions inclined to the left and right with respect to the axial direction. The axial fibers provide rigidity against loads applied in the axial direction. The cross fibers also provide rigidity against loads applied obliquely with respect to the axial direction. The energy absorption characteristics of the crash boxes 20 can be freely designed by adjusting the number and density of the axial fibers and cross fibers.

[0024] At the tip-side end 21 of the crash box 20, where a collision load is expected to be input, the outer diameter of each tube 25 is constant, and the inner diameter of each tube 25 is tapered toward the end face 27. As a result, the thickness of the wall portion of the tube 25 gradually decreases toward the end face 27. On the other hand, at the rear end 23 of the crash box 20, the wall portion of each tube 25 has a constant thickness. As a result, the strength of the tip-side end 21 of each tube 25 in the axial direction of the crash box 20 is relatively small. Therefore, when an axial load is input to the crash box 20, fracture of each tube 25 is induced from the tip side.

[0025] (Side frame joint member) The side frame joint member 30 is joined to face the tip end portion 41 of the front side frame 40, and supports the tip end portion 41 of the front side frame 40. The side frame joint member 30 is also joined to face the rear end portion 23 of the crash box 20, and supports the rear end portion 23 of the crash box 20. In other words, the side frame joint member 30 is provided between the rear end portion 23 of the crash box 20 and the tip end portion 41 of the front side frame 40.

[0026] The side frame joining member 30 is a molded product made of a metal material such as steel or aluminum, and has higher rigidity than a fiber-reinforced resin molded body. The side frame joining member 30 has a base 31, a first tubular portion 33, and a second tubular portion 35. The base 31 is a plate-shaped portion that serves as the base of the side frame joining member 30. The first tubular portion 33 extends from the base 31 toward the front side frame 40. The second tubular portion 35 extends from the base 31 toward the crash box 20.

[0027] The first tubular portion 33 surrounds the tip-side end 41 of the front side frame 40 and has an inner circumferential surface that is bonded with an adhesive to the outer circumferential surface of the end 41. The second tubular portion 35 surrounds the rear-side end 23 of the crash box 20 and has an inner circumferential surface that is bonded with an adhesive to the outer circumferential surface of the end 23. In other words, the side frame joining member 30 is bonded with an adhesive between the crash box 20 and the front side frame 40. The second tubular portion 35 functions to prevent the crash box 20 from falling over in the event of axial crushing of the crash box 20.

[0028] (Front Side Frame) The front side frame 40 is a cylindrical member whose axial direction is arranged along the front-rear direction of the vehicle body. The front side frame 40 constitutes part of the vehicle body framework and is a member that supports a drive system, such as an engine, a drive motor, and a transmission, that are mounted on the front of the vehicle. In this embodiment, the front side frame 40 is made of a fiber-reinforced resin composite material and functions as an energy absorbing member that axially collapses under a collision load when the front of the vehicle collides with a preceding vehicle, an obstacle, or other object, thereby absorbing the collision energy.

[0029] A tip end 41 of the front side frame 40 is supported by a side frame joint member 30, and a rear end 43 of the front side frame 40 is supported by a support plate 50. The side frame joint member 30 is connected to the rear end 23 of the crash box 20. The support plate 50 is fixed to the tip end of the body frame 5. In this embodiment, the front side frame 40 is a tubular member whose cross section perpendicular to the axial direction has a rectangular outline. The front side frame 40 is formed by joining a plurality of tubes 45 extending along the axial direction at their outer circumferential surfaces.

[0030] The overall dimensions of the front side frame 40 may be designed appropriately depending on the size of the vehicle, the required energy absorption capacity and rigidity, the weight of the front side frame 40, and the like. For example, the axial length of the front side frame 40 may be 500 to 1,000 mm, and the dimensions of each of the two sides of the cross section may be 100 to 200 mm. The thickness of the wall portion of each tube 45 may be, for example, 5 to 10 mm. For example, if the thickness of the wall portion of each tube 45 is 5 to 10 mm, the overall thickness of the joined wall portions will be 10 to 20 mm. However, the dimensions of the front side frame 40 are not limited to the above example.

[0031] The fiber-reinforced resin composite material constituting the front side frame 40 may be the same as the fiber-reinforced resin composite material constituting the crash boxes 20. Similarly to the crash boxes 20, the thickness of the wall portion of each tube 25 at the tip-side end 41 of the front side frame 40 gradually decreases toward the end face 47. Meanwhile, the thickness of the wall portion of each tube 45 at the rear end 43 of the front side frame 40 is constant. This results in a relatively small strength in the axial direction of each tube 45 at the tip-side end 41 of the front side frame 40. Therefore, when an axial load is applied to the front side frame 40, fracture of each tube 45 is induced from the tip side.

[0032] The rear end 43 of the front side frame 40 is supported by a tubular portion 51 of the support plate 50. The tubular portion 51 surrounds the rear end 43 of the front side frame 40 and has an inner circumferential surface that is bonded with an adhesive to the outer circumferential surface of the end 43. The tubular portion 51 functions to prevent the front side frame 40 from collapsing in the event of axial crushing of the front side frame 40.

[0033] <Application example> In the vehicle front body structure according to the present disclosure, at least one of the crash box joining members 10 and the side frame joining members 30 that support the tip-side ends of the crash boxes 20 and the front side frames 40 of the vehicle front body structure 1 described above has a tubular portion that extends towards the supported crash box 20 or front side frame 40, and a rib that is provided on the inner periphery of the tubular portion and that is joined to or faces the boundary portion between multiple tubes at the vehicle front end of the crash box 20 or the front side frame 40.

[0034] In one embodiment, the crash box joining member 10 may have a tubular portion 13 extending toward the crash box 20, and a rib provided on the inner periphery of the tubular portion 13 and joined to or facing the boundary portion between the multiple tubes 25 at the end 21 on the tip side of the crash box 20. In another embodiment, the side frame joining member 30 may have a tubular portion (first tubular portion) 33 extending toward the front side frame 40, and a rib provided on the inner periphery of the first tubular portion 33 and joined to or facing the boundary portion between the multiple tubes 45 at the end 41 on the tip side of the front side frame 40.

[0035] In yet another embodiment, the crash box joining member 10 may have a tubular portion 13 extending toward the crash box 20 and a rib provided on the inner periphery of the tubular portion 13 and joined to or facing the boundary portion between multiple tubes 25 at the tip end 21 of the crash box 20, and the side frame joining member 30 may have a tubular portion (first tubular portion) 33 extending toward the front side frame 40 and a rib provided on the inner periphery of the first tubular portion 33 and joined to or facing the boundary portion between multiple tubes 45 at the tip end 41 of the front side frame 40.

[0036] 1 and 2 show examples in which the technology of the present disclosure is applied to a structure in which crash boxes 20 are supported by crash box joint members 10, and a structure in which front side frames 40 are supported by side frame joint members 30. Below, the vehicle body front structure 1 according to this embodiment will be described in detail using the structure in which crash boxes 20 are supported by crash box joint members 10 as an example.

[0037] Fig. 3 is a perspective view showing the configuration of the crash box joint member 10 and the crash box 20 in the vehicle body front structure 1. Figs. 4 and 5 are cross-sectional views showing the joint portion between the tip end 21 of the crash box 20 and the crash box joint member 10, and show the cross section at the position intersecting two recesses 17a, 17b of the recesses 17a to 17d of the crash box joint member 10 shown in Fig. 3.

[0038] As described above, the crash box 20 is formed by joining multiple axially extending tubes 25a-25d at their respective outer circumferential surfaces. In the example shown in FIG. 3 , the crash box 20 is formed by joining four tubes 25a-25d, each having a rectangular cross section. However, the number of tubes is not particularly limited as long as two or more tubes are joined. The crash box 20 formed by joining multiple tubes 25a-25d includes a cross-shaped portion (cross portion) in the pattern shape in a planar view of the cross section. In the example shown in FIG. 3 , the center of the cross section of the crash box 20 is formed as a cross-shaped portion. Note that the crash box 20 may also be a cylindrical member whose cross section perpendicular to the axial direction has a circular or other shape.

[0039] The crush box 20 is formed by joining a plurality of cylinders 25a to 25d, which increases the bending rigidity of the crush box 20 against axial crushing. Therefore, the crush box 20 can be stably crushed in the axial direction.

[0040] The crash box 20 is formed by joining the outer peripheries of the cylinders 25a to 25d, each made of a fiber-reinforced resin composite, with an adhesive. When a predetermined collision load is applied to the crash box 20, the adhesive layer may peel off or shear. The adhesive may be, for example, an epoxy resin, but is not particularly limited.

[0041] The crash box joining member 10 includes a base 11, a tubular portion 13, and a rib 15 provided on the inner periphery of the tubular portion 13. The rib 15 is bonded to or faces the boundary between the multiple tubes 25a to 25d at the tip end 21 of the crash box 20. For example, as shown in FIG. 4, the rib 15 may be provided facing the boundary between the tubes 25a and 25b. Alternatively, as shown in FIG. 5, the rib 15 may be sandwiched between and bonded to the boundary between the tubes 25a and 25b. As long as the rib 15 faces the boundary between the tubes 25a and 25b, the rib 15 and the crash box 20 may be spaced apart. The pattern of the rib 15 in a plan view includes a cross-shaped portion (cross portion), the same as the pattern on the end surface 27 of the crash box 20. Furthermore, the four recesses 17a to 17d formed by the rib 15 are provided in positions facing the ends of the respective tubes 25a to 25d of the crash box 20.

[0042] The crash box joining member 10 has the ribs 15, which increases the strength of the crash box joining member 10 while suppressing an increase in the weight of the crash box joining member 10. Therefore, the strength required for axial crushing of the crash boxes 20 can be obtained while reducing the weight of the vehicle body.

[0043] The height (axial length) of the rib 15 of the crash box joining member 10 may be shorter than the height of the tubular portion 13. This allows the crash box joining member 10 to be further lightened while still retaining the function of the rib 15 to separate the tubes 25a to 25d of the crash box 20. On the other hand, as shown in Figure 5, when the rib 15 is sandwiched and joined at the boundary between the tubes 25a, 25b, the height (axial length) of the rib 15 may be the same as the height of the tubular portion 13, or may be greater than the height of the tubular portion 13.

[0044] The tip end 23 of the crash box 20 is joined to the crash box joining member 10 with an adhesive. The rigidity of the adhesive is smaller than the rigidity of the crash box joining member 10 and the crash boxes 20, so that when a collision load is input to the crash box joining member 10 via the bumper beam 3, the adhesive undergoes shear failure at an early stage. The adhesive may be, for example, an epoxy resin, but is not particularly limited to this.

[0045] 4 and 5, a gap S is provided between the tip end faces of the cylinders 25a to 25d of the crash boxes 20 and the bottom surfaces 19 of the respective recesses 17a to 17d of the crash box connecting member 10. Therefore, until the collision load input to the crash box connecting member 10 exceeds a predetermined load, the bottom surfaces 19 of the recesses 17a to 17d of the crash box connecting member 10 and the tip end faces of the cylinders 25a to 25d of the crash boxes 20 are maintained apart. Furthermore, when the collision load input to the crash box connecting member 10 exceeds the predetermined load, the bottom surfaces 19 of the recesses 17a to 17d of the crash box connecting member 10 come into contact with the tip end faces of the cylinders 25a to 25d of the crash boxes 20, and axial crushing of the crash boxes 20 begins.

[0046] The load at which the bottom surfaces 19 of the recesses 17a to 17d of the crash box connecting member 10 come into contact with the tip end surfaces of the tubes 25a to 25d of the crash boxes 20 is the sum of the load that can cause shear failure of the adhesive plus the load that can move the crash box connecting member 10 the length of the gap S. Therefore, by adjusting the rigidity of the adhesive and the length of the gap S, the load at which axial collapse of the crash boxes 20 begins can be adjusted.

[0047] Furthermore, as the crash box joining member 10 moves toward the crash box 20, the rib 15 penetrates into the boundary between the tubes 25a to 25d of the crash box 20, separating the tubes 25a to 25d. As shown in FIG. 4 , even if the rib 15 is provided facing the boundary between the tubes 25a and 25b, the rib 15 is pressed against the boundary between the tubes 25a and 25b, thereby penetrating the boundary between the tubes 25a to 25d of the crash box 20. By providing a groove C at the boundary between the tubes 25a and 25b, the rib 15 can be reliably inserted into the boundary between the tubes 25a and 25b. The groove C can be provided, for example, by performing post-processing such as polishing on the tip end of each of the tubes 25a and 25b. On the other hand, as shown in FIG. 5, when the rib 15 is joined by being sandwiched in the groove C at the boundary between the cylinders 25a and 25b, the cylinders 25a to 25d of the crash box 20 are reliably separated by the rib 15.

[0048] Furthermore, the corners of the bottom surface 19 of the recesses 17a to 17d of the crash box connecting member 10 are curved (see FIGS. 4 and 5). Therefore, when the end 21 on the tip side of the crash box 20 begins to axially collapse due to the collision load input through the crash box connecting member 10, the end 21 is prevented from spreading outward as it is crushed, and the broken cylinders 25a to 25d of the crash box 20 can be axially collapsed while being rolled inward.

[0049] The structure for supporting the vehicle body front end of the front side frame 40 with the side frame joint member 30 is configured in the same manner as the structure for supporting the crash boxes 20 with the crash box joint member 10. As a result, when a collision load is input, the front side frame 40, which is made up of multiple tubes 45a-45d, is split, and each tube 45a-45d of the broken front side frame 40 is rolled inward and subjected to axial crushing. In particular, because the axial length of the front side frame 40 is longer than the axial length of the crash boxes 20, this embodiment is an effective configuration that increases the bending rigidity of the front side frame 40 against axial crushing and allows the side frame joint member 30 to gradually crush the front side frame 40.

[0050] <Load Characteristics> The configuration of the vehicle body front structure 1 according to this embodiment has been described above. Next, the load characteristics of the vehicle body front structure 1 will be described.

[0051] Figure 6 shows the load characteristics of the vehicle body front structure 1 shown in Figures 1 and 2. Figures 7 to 11 show the vehicle body front structure 1 undergoing sequential collapse in chronological order. The load characteristics show the behavior of the load when the rear end of the front side frame 40 is fixed to a support base and an axial surface load is applied from the crash box joint member 10 toward the front side frame 40. The horizontal axis shows the stroke amount (axial collapse length) of the vehicle body front structure 1. The vertical axis shows the developed load. In the load characteristics shown in Figure 6, the sum of the loads at each stroke amount indicates the amount of energy absorbed when the vehicle body front structure 1 axially collapses up to that stroke amount.

[0052] In the vehicle body front structure 1 of this embodiment, the load increases during a first stroke period T1 after the start of the stroke, and a relatively small load peak appears. The first stroke period T1 indicates the period until the adhesive bonding the crash boxes 20 and the crash box bonding members 10 shears (the state shown in FIG. 7 ). The peak at the end of the first stroke period T1 indicates the timing (stroke amount) at which the adhesive shears.

[0053] During the subsequent second stroke period T2, the load decreases. This second stroke period T2 refers to the period until the tip-side end faces 27 of the cylinders 25a to 25d of the crash boxes 20 come into contact with the bottom surfaces 19a to 19d of the recesses 17a to 17d of the crash box joint member 10 (the state shown in FIG. 8 ). During the second stroke period T2, the crash box joint member 10 and the crash boxes 20 are moving relative to each other, and the load decreases. However, even after shear failure of the adhesive occurs, a load equivalent to the stroke until the tip-side end faces 27 of the cylinders 25a to 25d of the crash boxes 20 come into contact with the bottom surfaces 19a to 19d of the recesses 17a to 17d of the crash box joint member 10 is generated.

[0054] In the following third stroke period T3, the load increases and reaches a peak again. The third stroke period T3 indicates the period from the start of axial crushing of the crash box 20 until the adhesive bonding the front side frame 40 and the side frame joint member 30 is shear-fractured. The peak at the end of the third stroke period T3 indicates the timing (stroke amount) at which the adhesive is shear-fractured.

[0055] During the subsequent fourth stroke period T4, the load decreases. The fourth stroke period T4 refers to the period until the tip end faces 47 of the tubes 45a to 45d of the front side frame 40 abut against the bottom surfaces 39a to 39d of the recesses 37a to 37d of the side frame joint member 30 (the state shown in FIG. 9 ). During the fourth stroke period T4, the side frame joint member 30 and the front side frame 40 are moving relative to each other, and the load decreases. However, even after shear failure of the adhesive occurs, a load is generated corresponding to the stroke until the tip end faces 47 of the tubes 45a to 45d of the front side frame 40 abut against the bottom surfaces 39a to 39d of the recesses 37a to 37d of the side frame joint member 30.

[0056] In the following fifth stroke period T5, the load increases and reaches a peak again. The fifth stroke period T5 indicates the period until the axial collapse of the crash boxes 20 begins. The peak at the end of the fifth stroke period T5 indicates the timing (stroke amount) at which the axial collapse of the crash boxes 20 begins.

[0057] During the subsequent sixth stroke period T6, the load remains at a substantially constant value. The sixth stroke period T6 represents the period during which the axial collapse of the crash boxes 20 progresses (the state shown in FIG. 10 ). In this embodiment, the axial collapse of the crash boxes 20, which have a uniform cross section in the axial direction, occurs, so the load remains at a substantially constant value. The end of the sixth stroke period T6 represents the timing (stroke amount) at which the axial collapse of the crash boxes 20 ends.

[0058] In the following seventh stroke period T7, the load increases and reaches a peak again. The seventh stroke period T7 indicates the period until the axial collapse of the front side frame 40 begins. The peak at the end of the seventh stroke period T7 indicates the timing (stroke amount) at which the axial collapse of the front side frame 40 begins.

[0059] During the subsequent eighth stroke period T8, the load remains at a substantially constant value. The eighth stroke period T8 is the period during which the axial collapse of the front side frame 40 progresses (the state shown in FIG. 11 ). In this embodiment, the front side frame 40 has a uniform cross section in the axial direction, so the load remains at a substantially constant value.

[0060] As described above, the vehicle front body structure 1 according to this embodiment is constructed by joining the outer peripheral surfaces of multiple cylinders of the crash boxes 20 and the front side frames 40. This increases the bending rigidity of the crash boxes 20 and the front side frames 40. Furthermore, the crash box joining members 10 and the side frame joining members 30 each have a cylindrical portion extending toward the crash boxes 20 or the front side frames 40, respectively, and a rib located on the inner periphery of the cylindrical portion that joins to or faces the boundary between the multiple cylinders at the vehicle front end of the crash boxes 20 or the front side frames 40. This allows the crash box joining members 10 and the side frame joining members 30 to be lightweight while still providing the resistance necessary to axially crush the crash boxes 20 or the front side frames 40. This allows the vehicle front body structure 1 to be lightweight while still providing stable axial crushing of the crash boxes 20 or the front side frames 40.

[0061] Furthermore, in the vehicle body front structure 1 according to this embodiment, at least a part of the rib of the joining member may be sandwiched and joined to the boundary portions of the multiple tubes of the energy absorbing member, thereby reliably dividing the tubes of the energy absorbing member by the rib of the joining member, and allowing the broken energy absorbing member to be axially crushed while being rolled inward into each recess.

[0062] Furthermore, in the vehicle body front structure 1 according to this embodiment, the rib of the joining member may be provided opposite the boundary portion of the tube of the energy absorbing member. In this way, the rib of the joining member is pressed against the boundary portion of the tube of the energy absorbing member, thereby entering the boundary portion of the tube of the energy absorbing member and separating the tube of the energy absorbing member.

[0063] Furthermore, in the vehicle body front structure 1 according to this embodiment, the vehicle body front end of the energy absorbing member collapses inward into the recess surrounded by the rib of the joining member, which prevents the broken energy absorbing member from scattering, and also increases the developed load as the broken energy absorbing member packs inward, thereby increasing the amount of energy absorbed.

[0064] Furthermore, in the vehicle body front structure 1 according to this embodiment, the rib pattern of the joining member includes a cross-shaped portion. This increases the strength of the joining member while reducing its weight. Furthermore, the cross-shaped portion of the rib pattern of the joining member can also be used as a marker for aligning the front end of the energy absorbing member with the vehicle body front side end. For example, as shown in FIG. 5 , the crash box 20 can be aligned with the crash box joining member 10 by sandwiching the rib 15 of the crash box joining member 10 into the groove C at the boundary between the cylinders 25a and 25b of the crash box 20. This improves the joining accuracy between the outer peripheral surface of the tip end of the crash box 20 and the inner peripheral surface of the cylinder portion 13 of the crash box joining member 10. Therefore, even if the surface accuracy of the outer peripheral surface of the energy absorbing member formed by, for example, a winding method or a braiding method is low, the alignment accuracy between the energy absorbing member and the joining member can be improved.

[0065] 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.

[0066] DESCRIPTION OF SYMBOLS 1: Vehicle body front structure 3: Bumper beam 10: Crash box joining member 11: Base 13: Cylindrical portion 15: Rib 17a, 17b, 17c, 17d: Recessed portions 19a, 19b, 19c, 19d: Bottom surface 20: Crash box 21: End portion 25a, 25b, 25c, 25d: Cylinder 27: End surface 30: Side frame joining member 31: Base 33: First cylindrical portion 37a, 37b, 37c, 37d: Recessed portions 39a, 39b, 39c, 39d: Bottom surface 40: Front side frame 41: End portion 45a, 45b, 45c, 45d: Cylinder 47: End surface S: Gap

Claims

1. A vehicle front structure equipped with an energy absorbing member that absorbs collision energy by axially collapsing during a frontal collision of the vehicle, wherein the energy absorbing member is configured by joining a plurality of tubes extending along the axial direction of the energy absorbing member at their respective outer circumferential surfaces, and a joining member that supports the energy absorbing member is joined to the vehicle body front end of the energy absorbing member, and the joining member has a tube portion extending toward the energy absorbing member, and a rib that is provided on the inner circumferential side of the tube portion and is joined to or faces the boundary portion of the plurality of tubes at the vehicle body front end of the energy absorbing member.

2. The vehicle body front structure according to claim 1, wherein at least a portion of the rib is sandwiched and joined to the boundary portion of the plurality of tubes.

3. A vehicle body front structure according to claim 1, wherein at least a portion of the rib penetrates into the boundary portion between the plurality of tubes due to a load generated during a frontal collision of the vehicle.

4. A vehicle front structure as described in claim 1, wherein the load generated during a frontal collision of the vehicle causes the front end of the energy absorbing member to collapse inward into the recess surrounded by the rib.

5. The vehicle front body structure according to claim 1, wherein the pattern shape of the rib includes a cross-shaped portion.

6. The vehicle front structure according to claim 1, wherein the vehicle front structure comprises a bumper beam, front side frames, crash boxes arranged between the bumper beam and the front side frames, crash box joint members supporting the vehicle front end portions of the crash boxes, and side frame joint members supporting the vehicle front end portions of the front side frames, the energy absorbing member being at least one of the front side frames and the crash boxes, and the joint member being at least one of the crash box joint members and the side frame joint members supporting at least one of the front side frames and the crash boxes.

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