Vehicle lower part structure

Abstract

To provide a vehicle lower part structure which can inhibit vibration of a cross member.SOLUTION: A vehicle lower part structure 100 according to the invention includes a floor panel 102 forming a floor surface of a vehicle. The vehicle lower part structure further includes: side sills 104 each extending in a vehicle fore and aft direction along an edge 110 of the floor panel; rear side members 124 each of which is disposed below the floor panel and at the inner side of the side sill in a vehicle width direction and extending in the vehicle fore and aft direction; and a second rear cross member 204 which extends in the vehicle width direction and joined to the side sill and the rear side member. The side sill is joined to the rear side member.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vehicle underbody structure. [Background technology]

[0002] Vehicles such as automobiles are equipped with a vehicle underbody structure in which skeletal members such as side sills extending in the vehicle's fore-aft direction are joined by cross members extending in the vehicle's width direction. When a load is applied to the skeletal members during a side collision, the vehicle underbody structure prevents the skeletal members from deforming or moving inwardly of the vehicle.

[0003] Patent Document 1 describes a rear seat mounting support structure for a vehicle. This support structure includes two rear cross members 13, 14. The rear cross member 13 connects the side sills 2 together in the vehicle width direction, and is further connected to the rear side frames 3 via a seat rail member 17. The rear cross member 14 connects the rear side frames 3 together. The joint between the seat rail member 17 and the rear cross member 13 is set at a position corresponding to the mounting portion of the seat rail 20a. In this way, the support structure of Patent Document 1 efficiently distributes the impact load applied to the mounting portion of the rear seat. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-22154 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the vehicle underbody structure, the cross member that connects the frame members such as the side sills arranged on the outer side in the vehicle width direction along the edge of the floor panel is longitudinal in the vehicle width direction. Therefore, the cross member has a large surface area that is locally subjected to vibration, and vibration, especially torsional vibration, is likely to occur. Furthermore, if the floor panel is joined to the cross member, the vibration is transmitted to the floor panel, which deteriorates the ride comfort. Note that the support structure of Patent Document 1 only distributes the impact load applied to the mounting part of the rear seat, and there is room for improvement in suppressing the vibration of the rear cross member.

[0006] In view of the above problems, the present invention has an object to provide a vehicle underbody structure capable of suppressing vibration of a cross member. [Means for solving the problem]

[0007] In order to solve the above problems, a typical configuration of a vehicle understructure according to the present invention is a vehicle understructure having a floor panel that forms the floor surface of the vehicle, the vehicle understructure further comprising a side sill extending in the fore-and-aft direction of the vehicle along the edge of the floor panel, a side member that is positioned below the floor panel on the inside of the side sill in the vehicle width direction and extends in the fore-and-aft direction of the vehicle, and a cross member that extends in the vehicle width direction and is joined to the side sill and the side member, and the side sill is joined to the side member. Effect of the Invention

[0008] According to the present invention, it is possible to provide a vehicle underbody structure capable of suppressing vibration of a cross member. [Brief description of the drawings]

[0009] [Figure 1] 1 is a bottom view showing a vehicle underbody structure according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing a part of the vehicle undercarriage and various suspensions in FIG. 1. [Diagram 3]It is a figure showing a D-D cross section of the vehicle underbody structure in Fig. 2(a) and a comparative example. [Figure 4] It is a figure showing a part of the vehicle underbody structure in Fig. 1 and a modified example. [Diagram 5] It is a figure showing the state of the vehicle underbody structure in Fig. 4(a) viewed from another direction. [Figure 6] It is a figure showing the state of a part of the vehicle underbody structure in Fig. 1 viewed from the front of the vehicle. [Figure 7] It is a figure showing in detail a part of a modified example of the vehicle underbody structure in Fig. 1. [Figure 8] It is a figure showing the state of the vehicle underbody structure in Fig. 7 viewed from another direction. [Figure 9] It is a figure schematically showing another modified example of the vehicle underbody structure in Fig. 1. [Figure 10] It is a figure showing still another modified example of the vehicle underbody structure in Fig. 1.

Mode for Carrying Out the Invention

[0010] In a vehicle underbody structure including a floor panel that forms the floor surface of a vehicle according to an embodiment of the present invention, the vehicle underbody structure further includes a side sill extending in the longitudinal direction of the vehicle along the edge of the floor panel, a side member disposed inside the side sill in the vehicle width direction below the floor panel and extending in the longitudinal direction of the vehicle, and a cross member extending in the vehicle width direction and joined to the side sill and the side member, and the side sill is joined to the side member.

[0011] In the above configuration, the side sill and the side member joined to the cross member are joined to each other. Therefore, while increasing the rigidity of the members supporting the cross member, that is, the support rigidity of the cross member, the load and vibration transmitted to the cross member can be dispersed and released to the side sill and the side member. Accordingly, the vibration of the cross member can be suppressed.

[0012] The cross member may be joined to the side sill and the side member so as to overlap with a joint surface between the side sill and the side member.

[0013] This allows the joint surfaces of the side sill and side member, the joint surfaces of the cross member and side sill, and the joint surfaces of the cross member and side member to be close to or overlap each other. This increases the support rigidity of the cross member. In addition, by joining the cross member to the joint surfaces of the side sill and side member with increased support rigidity, the connection rigidity of the cross member to the side sill and side member can be increased. This allows the vibration of the cross member to be more sufficiently suppressed.

[0014] The cross member may have one or more joints that are joined to the side sill and the side member in a predetermined direction while overlapping each other.

[0015] This allows the cross member to be joined to the side sill and side member in three overlapping pieces (three-piece joint) at the joints, which increases the connection rigidity of the cross member to the side sill and side member, making it possible to more sufficiently suppress vibrations of the cross member, particularly torsional vibrations.

[0016] The one or more joints may include a first joint where the cross member, the side sill and the side member overlap in the vertical direction, and a second joint where the cross member, the side sill and the side member overlap in the vehicle width direction.

[0017] This allows the cross member, side sill and side member to be joined firmly in the vertical and transverse directions by the first and second joints while increasing the joint area of ​​the three members, thereby suppressing vibrations of the cross member, particularly torsional vibrations.

[0018] The first joint may be formed on an upper surface and a lower surface of the side sill.

[0019] As a result, the first joints formed on the upper and lower surfaces of the side sill increase the joint area of ​​the cross member, side sill and side member, and firmly join these three members in the vertical direction, thereby more fully suppressing vibrations of the cross member, especially torsional vibrations.

[0020] The end of the above-mentioned cross member has a widened portion which is widened in the fore-and-aft direction of the vehicle, and the side member is connected to the inner side surface of the side sill on the inner side in the vehicle width direction, and a first joint and a second joint are formed in the widened portion, and the one or more joints of the cross member may further include a third joint formed in the widened portion and overlapping and joined to the side member.

[0021] In this way, the widened portion of the cross member is formed with a third joint where the cross member and the side member are joined in two pieces without overlapping with the side sill, and a first joint and a second joint where the cross member, the side sill and the side member are joined in three pieces. This increases the connection area of ​​the cross member to the side member, thereby increasing the connection rigidity of the cross member. Also, in the cross member, the vibration and load of the side member can be dispersed and easily released from the third joint to the first and second joints via the widened portion. This allows the vibration of the side member to be transmitted to the side sill, thereby suppressing the vibration of the cross member.

[0022] An end of the above-mentioned cross member may have a widening portion that is widened in the fore-and-aft direction of the vehicle, and one or more joints of the cross member may further include a fourth joint formed in the widening portion and joined to the upper surface of the side sill and the floor panel in a vertical direction, and a fifth joint formed in the widening portion adjacent to the fourth joint and joined to the upper surface of the side sill in a vertical direction.

[0023] In this way, the widened portion of the cross member is formed with a fourth joint where the cross member, the upper surface of the side sill, and the floor panel are joined in three places, and a fifth joint where the cross member and the side sill are joined in two places without overlapping with the floor panel. This increases the joint area of ​​the cross member with respect to the highly rigid side sill, thereby increasing the support rigidity and connection rigidity of the cross member. In addition, the cross member can disperse the vibration of the floor panel from the fourth joint to the adjacent fifth joint via the widened portion, making it easier to release it. This allows the vibration of the floor panel to be transmitted to the side sill and cross member, suppressing the vibration of the floor panel. EXAMPLES

[0024] A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. The dimensions, materials, and other specific values ​​shown in the embodiment are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are given the same reference numerals to avoid repeated explanations, and elements not directly related to the present invention are not shown. In this embodiment, connection includes various forms such as joining to join separate members, abutment of separate members, and integration in which each member becomes the same member.

[0025] 1 is a bottom view showing a vehicle underbody structure 100 according to an embodiment of the present invention. The figure shows the vehicle underbody structure 100 as seen from below the vehicle. In each of the figures below, the front-rear direction of the vehicle is indicated by arrows Front and Back, the left and right directions of the vehicle width are indicated by arrows Left and Right, and the top-bottom direction of the vehicle is indicated by arrows Up and Down.

[0026] The vehicle underbody structure 100 includes a floor panel 102 that forms the floor surface of the vehicle, a pair of side sills 104, 106, and a center tunnel 108. The pair of side sills 104, 106 are spaced apart in the vehicle width direction and extend in the vehicle front-rear direction along edges 110, 112 of the floor panel 102. The center tunnel 108 extends in the vehicle front-rear direction at the center of the floor panel 102 in the vehicle width direction. The floor panel 102 includes a floor horizontal surface 114 surrounded by a dotted line A in the figure, and upwardly inclined portions 116, 118 surrounded by dotted lines B, C in the figure, which are respectively disposed on the vehicle width direction outer sides of the floor horizontal surface 114.

[0027] The vehicle underbody structure 100 further includes a pair of suspension fixing parts 120, 122, a pair of rear side members 124, 126, and a pair of floor side members 128, 130. Since the vehicle underbody structure 100 has a bilaterally symmetrical structure as shown in Fig. 1, only the structure on the right side in the vehicle width direction will be described below unless otherwise necessary.

[0028] Fig. 2 is a diagram showing a part of the vehicle underbody structure 100 in Fig. 1 and various suspensions 132, 134. Fig. 2(a) shows an enlarged view of the suspension fixing part 120 and its surrounding structure. Fig. 2(b) and Fig. 2(c) show schematic configurations of general suspensions 132, 134 with different swing axis directions (swing axis line directions).

[0029] The suspension fixing part 120 is a portion to which a swingable suspension 132 for a rear wheel 136 shown in Fig. 2(b) is fixed. The suspension 132 has a so-called semi-independent axle structure, and has a trailing link 138, a coupling profile 140 extending in the vehicle width direction, and a shock absorber 142. The suspension 132 has a swing axis Sb in the vehicle width direction that passes through a front end portion 144 of the trailing link 138.

[0030] 2(b) is fixed to the suspension fixing part 120. In addition, the suspension fixing part 120 is connected to an inclined part 146 of the rear side member 124 as shown in FIG.

[0031] The rear side member 124 is a member located below the floor panel 102 and extending from a rear end 148 of the vehicle forward between the side sill 104 and the center tunnel 108, and extends, for example, on the inner side of the side sill 104 in the vehicle width direction to a position rearward of the side sill 104. Note that the rear side member 124 is not limited to being located on the inner side of the side sill 104 in the vehicle width direction, and may be located on the rear side of the vehicle.

[0032] The inclined portion 146 of the rear side member 124 is a portion that inclines outward in the vehicle width direction as it approaches the front of the vehicle, as shown in Fig. 1. Since the suspension fixing part 120 is connected to the inclined portion 146 of the rear side member 124, in the vehicle undercarriage structure 100, the swing axis Sa passing through the suspension fixing part 120 in Fig. 2(a) is inclined toward the front of the vehicle as it approaches the inside in the vehicle width direction, perpendicular to the inclined portion 146.

[0033] 2(c) is a so-called spring strut independent suspension, and has a wheel carrier 150, a tie rod 152, a lower A-arm link 154, and a shock absorber 156. The suspension 134 has a swing axis Sc that passes through a front end 158 and a rear end 160 of the lower A-arm link 154 in the vehicle longitudinal direction.

[0034] By applying the suspensions 132, 134 to the suspension fixing parts 120, the vehicle underbody structure 100 is not limited to the swing axis Sa whose swing axis direction is inclined toward the front of the vehicle as it moves inward in the vehicle width direction, but has swing axes Sb, Sc whose swing axis direction is in the vehicle width direction or the vehicle front-rear direction. Note that, unlike the swing axes Sa, Sb, Sc, although not shown in the figure, the vehicle underbody structure 100 can also be applied to a suspension having a swing axis whose swing axis direction is inclined toward the rear of the vehicle as it moves inward in the vehicle width direction.

[0035] For this reason, the rear side member 124 connected to the suspension fixing part 120 receives a load in the swing axis direction from the suspension 132 via the suspension fixing part 120 while the vehicle is traveling, for example. Furthermore, when the vehicle underbody structure 100 is applied to the suspension 134, the rear side member 124 receives a load as a vibration component in the vehicle width direction due to vibration while the vehicle is traveling, even if a swing axis Sc is set whose swing axis direction is the vehicle front-rear direction. That is, the rear side member 124 receives a load in the swing axis direction or the vehicle width direction via the suspension fixing part 120.

[0036] The floor side member 128 connects the rear side member 124 to a front member 162 or a front side member 164 located at the front of the vehicle below the floor panel 102 shown in FIG. 1. The front member 162 includes a dash cross member 166 that extends in the vehicle width direction and is disposed between the side sills 104, 106, and a front suspension frame 168. In the drawing, the outer shape of the front suspension frame 168 is shown by a chain line, and various members that overlap with the front suspension frame 168 are shown in transparent form. In addition, braces 169a, 169b that are inclined outward in the vehicle width direction as they approach the rear of the vehicle are disposed on the outer sides of the dash cross member 166 in the vehicle width direction, and connect the dash cross member 166 to the side sills 104, 106.

[0037] A front side extension 170 is disposed on the vehicle front side of the side sill 104. A front suspension 172 is located between the front side member 164 and the front side extension 170. Note that, on the left side in the vehicle width direction of the vehicle underbody structure 100, a front side extension 174 located on the vehicle front side of the side sill 106, a front side member 176, and a front suspension 178 are disposed as shown in FIG.

[0038] Additionally, the front suspension frame 168 is provided with rear fixing points 180, 182 to the floor side members 128, 130, and intermediate fixing points 184, 186 to the front side members 164, 176. Additionally, the front suspension frame 168 is provided with front fixing points 188, 190 to other members located further forward of the intermediate fixing points 184, 186. Although the front side members 164, 176 and the floor side members 128, 130 are described as separate members, this is not limiting, and they may be of an integrated structure.

[0039] As described above, the rear side member 124 receives a load in the swing axis direction or the vehicle width direction via the suspension fixing part 120. Therefore, in order to suppress vibration of the rear side member 124 in the swing axis direction or the vehicle width direction, the vehicle underbody structure 100 employs a configuration in which the floor side member 128 and the suspension fixing part 120 are connected to adjacent areas of the rear side member 124 (see FIG. 3(a)) or opposing areas (see FIGS. 9(a) and 9(b)).

[0040] Fig. 3 is a diagram showing a DD cross section of the vehicle underbody structure 100 in Fig. 2(a) and a comparative example. As shown in the DD cross section of Fig. 3(a), the rear side member 124 has a lower surface 192 to which the suspension fixing part 120 is connected. In addition, a rear end part 194 of the floor side member 128 shown in Fig. 2(a) has a bulging part 196. The bulging part 196 is a part that bulges out towards the rear side member 124 side as shown by the dotted line E.

[0041] Furthermore, as shown in Fig. 3(a), the bulging portion 196 is connected to a side surface 198 on the inner side in the vehicle width direction adjacent to the lower surface 192 of the rear side member 124 to which the suspension fixing portion 120 is connected. In this manner, the side member 128 and the suspension fixing portion 120 are connected to adjacent regions of the rear side member 124, i.e., the side surface 198 and the lower surface 192 on the inner side in the vehicle width direction, respectively. Furthermore, the side surface 198 of the rear side member 124 is a side surface that is substantially perpendicular to the oscillating axis direction of the oscillating axis Sa (see Fig. 2(a)), which is formed by inclining the oscillating axis Sb of the suspension 132.

[0042] 3(b), the vehicle underbody structure 100A of the comparative example is different from the vehicle underbody structure 100 in that it does not include a floor side member 128. For this reason, in the vehicle underbody structure 100A, the rear side member 124 swings in the swing axis direction or the vehicle width direction indicated by the arrow F due to the load transmitted from the suspension 132 via the suspension fixing part 120 while the vehicle is traveling, and vibrates while shifting from its original position as indicated by the dotted line G.

[0043] In contrast, in the vehicle undercarriage structure 100 of Figure 2(a), the load transmitted from the suspension fixing part 120 to the rear side member 124 can be dispersed and released to the front member 162 or front side member 164 via the floor side member 128 in the periphery 200 of the suspension fixing part 120 of the rear side member 124, i.e., on the upstream side of the load transmission path along which the load is transmitted from the suspension fixing part 120.

[0044] 2(a), the rear end 194 of the floor side member 128 has a bulge 196 connected to a side surface 198 of the rear side member 124, so that the connection area of ​​the floor side member 128 to the rear side member 124 can be increased. This makes it possible to increase the connection rigidity of the floor side member 128 to the rear side member 124, so that the floor side member 128 can more easily receive a load from the rear side member 124. Furthermore, because the side surface 198 of the rear side member 124 is a side surface that is substantially perpendicular to the swing axis direction of the swing shaft Sa, the load received by the rear side member 124 can be efficiently received by the highly rigid floor side member 128, distributed, and released.

[0045] As a result, vibrations of the rear side member 124 in the swing axis direction or vehicle width direction, particularly vibrations in the load transfer path downstream of the connection position of the rear side member 124 with the floor side member 128, are suppressed. Therefore, according to the vehicle underbody structure 100, torsional vibrations of the vehicle body and floor vibrations of the floor panel 102 caused by vibrations of the rear side member 124 can be reduced.

[0046] 2(a), in the vehicle underbody structure 100, the bulging portion 196 of the floor side member 128 bulges toward the rear side member 124, so there is no need to incline or curve the rear end 194 of the floor side member 128 by the amount of this bulging so as to approach the rear side member 124. Therefore, when the floor side member 128 receives a load from the vehicle longitudinal direction, it is possible to suppress deformation such as shrinking in the vehicle longitudinal direction.

[0047] 1, the vehicle undercarriage 100 further includes a first rear cross member 202 and a second rear cross member 204 spaced apart in the vehicle fore-aft direction. The first rear cross member 202 extends in the vehicle width direction and is connected to rear ends 194, 206 of the floor side members 128, 130 and the rear side members 124, 126. The second rear cross member 204 extends in the vehicle width direction and is connected to front ends 208, 210 of the rear side members 124, 126 and the floor side members 128, 130.

[0048] This allows the load transmitted to the rear side member 124 via the suspension fixing portion 120 to be dispersed and released from the rear side member 124 to the floor side member 128, the first rear cross member 202, and the second rear cross member 204. Furthermore, even if the floor side member 128 receives a load from the rear side member 124, the first rear cross member 202 and the second rear cross member 204 can suppress vibration of the floor side member 128 in the swing axis direction or the vehicle width direction.

[0049] Furthermore, since the load transmitted to the rear side member 124 can be dissipated to the floor side member 128, which is more rigid or heavy than the first rear cross member 202 and the second rear cross member 204, vibration of the rear side member 124 can be suppressed while suppressing an increase in the rigidity and thickness of the first rear cross member 202 and the second rear cross member 204.

[0050] As shown in FIG. 2(a), since the first rear cross member 202 is connected to the rear end 194 of the floor side member 128, the rear end 194 of the floor side member 128 is supported by the rear side member 124 and the first rear cross member 202, and the load transmitted from the rear side member 124 to the rear end 194 of the floor side member 128 is easily released to the first rear cross member 202 side, so that the vibration of the floor side member 128 can be suppressed. Furthermore, since the vibration is easily transmitted between the rear side member 124 and the first rear cross member 202 via the rear end 194 of the floor side member 128, the vibration of the rear side member 124 and the first rear cross member 202 can also be suppressed. Furthermore, since the floor side member 128 is connected overlapping the connection surface between the first rear cross member 202 and the rear side member 124, the connection rigidity of the first rear cross member 202 and the rear side member 124 can be increased. In addition, floor side member 128 supports rear side member 124, and is further connected to first rear cross member 202 and second rear cross member 204. This increases the support rigidity of floor side member 128, making it possible to suppress vibration of rear side member 124 in the swing axis direction or vehicle width direction.

[0051] 1, in vehicle underbody structure 100, a frame structure is formed by floor side members 128, 130, first rear cross member 202, and second rear cross member 204, and a frame structure is further formed by rear side members 124, 126, first rear cross member 202, and second rear cross member 204. Therefore, the overall rigidity of each member that constitutes this frame structure can be increased, and the supporting rigidity of rear side members 124, 126 and floor side members 128, 130 can be increased.

[0052] In the vehicle underbody structure 100 of FIG. 2(a), it is assumed that the transmission path of the load transmitted to the rear side member 124 via the suspension fixing part 120 branches in a direction intersecting the swing axis direction of the swing axis Sa, for example, toward the front or rear of the vehicle. In such a case, as shown in FIG. 2(a), in the vehicle underbody structure 100, the first rear cross member 202 and the second rear cross member 204, which are spaced apart in the vehicle longitudinal direction, are disposed at positions sandwiching the swing axis Sa. Therefore, in the vehicle underbody structure 100, the loads transmitted to the downstream side of the branch point of the load transmission path can be transmitted to the first rear cross member 202 or the second rear cross member 204. As a result, the vibration of the rear side member 124 in the swing axis direction or the vehicle width direction can be suppressed, and the torsional vibration and floor vibration caused by this vibration can be reduced.

[0053] 2(a), the rear side member 124 is sandwiched between the side sill 104 and the floor side member 128 in the swing axis direction or the vehicle width direction. This allows the load transmitted to the rear side member 124 via the suspension fixing part 120 to be transmitted and dispersed to the highly rigid floor side member 128 and side sill 104. The floor side member 128 is connected upstream of the second rear cross member 204 in the load transmission path that does not pass through the side sill 104.

[0054] Furthermore, the floor side member 128, together with the rear side member 124 and the second rear cross member 204, forms a closed cross section 212 of a triangular truss structure as a frame structure surrounded by a chain line H in FIG. 2(a). This allows the rigidity of the entire floor side member 128, the rear side member 124 and the second rear cross member 204 to be increased by the closed cross section 212, so that the support rigidity of the rear side member 124 can be increased. As a result, vibrations of the rear side member 124 in the swing axis direction or the vehicle width direction are suppressed, and vibrations of the floor side member 128 are also suppressed, so that torsional vibrations and floor vibrations caused by these vibrations can be reduced. Moreover, since one of the components of the closed cross section 212 is the floor side member 128 extending forward of the vehicle, it is easy to make adjustments such as distributing the load to the floor side member 128 side to avoid stress concentration.

[0055] 1, the rear side member 124 has an inclined portion 146, and a side surface 198 of the rear side member 124 connected to a rear end portion 194 of the floor side member 128 is formed on this inclined portion 146. Therefore, even if the rear end portion 194 of the floor side member 128 is not greatly inclined so as to approach the rear side member 124, the connection area between the floor side member 128 and the rear side member 124 can be increased. Therefore, the connection rigidity between the floor side member 128 and the rear side member 124 can be increased.

[0056] Therefore, according to the vehicle understructure 100, even if the floor side member 128 receives a load from the vehicle longitudinal direction, it is possible to suppress deformation such that it shrinks in the vehicle longitudinal direction, while suppressing vibration of the rear side member 124 in the swing axis direction or vehicle width direction, thereby reducing torsional vibration and floor vibration caused by this vibration. Note that in the vehicle understructure 100, the rear side member 124 connected to the suspension fixing part 120 to which the suspension 132 is fixed is sandwiched between the second rear cross member 204 and the side sill 104, so that vibration of the suspension 132 can also be suppressed.

[0057] 1 and the front member 162, the floor side member 128 has a recess 214 recessed inward in the vehicle width direction, and is connected to a side surface 198 (see FIG. 2(a)) of the rear side member 124. This allows the recess 214, which is part of the floor side member 128, to be positioned inward in the vehicle width direction, thereby suppressing surface vibration of the floor panel 102 (described later). In addition, because the floor side member 128 is connected to the side surface 198 of the rear side member 124 at the recess 214, the connection area between the two is increased, thereby increasing the connection rigidity.

[0058] 1, in the vehicle underbody structure 100, floor side members 128, 130 are disposed between the side sills 104, 106 and the center tunnel 108. Therefore, the floor panel 102 is divided in the vehicle width direction with the floor side members 128, 130 as boundaries.

[0059] Therefore, in order to suppress floor vibration, the vehicle underbody structure 100 employs a configuration in which the floor side members 128, 130 are disposed close to and near intermediate positions 216, 218 of the floor vibration surface of the floor panel 102. The intermediate position 216 of the floor vibration surface is a position on the horizontal plane 114 of the floor panel 102 where the dimension La between the center tunnel 108 and the floor side member 128 and the dimension Lb between the side sill 104 and the floor side member 128 are approximately the same.

[0060] 4 is a diagram showing a portion of the vehicle undercarriage structure 100 of FIG. 1 and a modified example. As shown in FIG. 4(a), the floor side member 128 has a front inclined portion 220, a straight portion 222, and a rear inclined portion 224. The front inclined portion 220 is a portion that inclines inward in the vehicle width direction toward the rear of the vehicle. The straight portion 222 is a portion that extends straight from a rear end 226 of the front inclined portion 220 toward the rear of the vehicle. The rear inclined portion 224 is a portion that inclines outward in the vehicle width direction from a rear end 228 of the straight portion 222 toward the rear of the vehicle.

[0061] In this manner, in the vehicle underbody structure 100, two inclined portions, namely the front inclined portion 220 and the rear inclined portion 224, are set in the floor side member 128. As a result, even if the connection position between the front member 162 or the front side member 164 located at the front or rear of the vehicle of the floor side member 128 and the rear side member 124 is away from the intermediate position 216 of the floor vibration plane, the straight portion 222 located between the two inclined portions can be moved closer to the intermediate position 216 of the floor vibration plane by adjusting the inclination degree and length of the two inclined portions. Therefore, according to the vehicle underbody structure 100, the straight portion 222 of the floor side member 128 can be moved closer to the intermediate position 216 of the floor vibration plane, thereby suppressing floor vibration.

[0062] In other words, in the floor side member 128, the front inclined portion 220 and the rear inclined portion 224 allow the straight portion 222 to be positioned close to and at the midpoint between the side sill 104 and the center tunnel 108, i.e., the midpoint 216 in the vehicle width direction of the horizontal floor vibration surface located between the side sill 104 and the center tunnel 108.

[0063] In this manner, in the vehicle underbody structure 100, the straight portion 222 of the floor side member 128 is positioned overlapping at the intermediate position 216 as shown in FIG. 1, so that the dimensional difference between one side and the other side of the floor vibration surface of the floor panel 102, with the straight portion 222 as the boundary, becomes smaller; in other words, the dimensions La and Lb become closer to being the same dimension, thereby suppressing floor vibration.

[0064] As shown in Fig. 4(a), the floor side member 128 further has a sus-fle connection part 230. The sus-fle connection part 230 extends straight from the front end 232 of the front inclined part 220 towards the front of the vehicle, and is connected to the front suspension frame 168 at the rear fixing point 180 (see Fig. 1). The front end 232 of the front inclined part 220 is disposed at a position overlapping in the vehicle width direction with the inclined surfaces of the braces 169a, 169b shown in Fig. 1.

[0065] As a result, the floor side member 128 is supported by the highly rigid front suspension frame 168 via the suspensible connection portion 230. Because of this, vibration of the floor side member 128 itself can be suppressed, and therefore floor vibration of the floor panel 102 connected to the floor side member 128 can also be suppressed.

[0066] 4(a), in the floor side member 128, the suspensory connection part 230, which is a part different from the front inclined part 220, extends in a straight line toward the front of the vehicle from the front end 232 of the front inclined part 220. Therefore, in the vehicle undercarriage structure 100, it is easier to arrange the rear fixing point 180 with the front suspension frame 168, which is connected to the suspensory connection part 230, on the outer side in the vehicle width direction, compared to a case in which a connection part with the front suspension frame 168 is provided in the front inclined part 220 itself.

[0067] As a result, when a load in the vehicle width direction acts on floor side member 128, the load can be easily dispersed and released from rear fixing point 180 of suspensory connection part 230 to front fixing point 188 (see FIG. 1) of front suspension frame 168 connected to front side member 176 on the left side in the vehicle width direction. Therefore, vibration of front side member 176 itself can be suppressed, and floor vibration can be suppressed.

[0068] 1, or a torque rod (not shown) connected to the front suspension frame 168 is subjected to a load in the vehicle width direction, this load can be easily dispersed and released to the floor side members 128 and 130. This suppresses vibration of the front suspension frame 168, improving stability during steering.

[0069] As shown in FIG. 4(a), the suspension connection portion 230 extends in a straight line from the front end 232 of the front inclined portion 220 toward the front of the vehicle. Therefore, when the front inclined portion 220 receives a load from the front, the front inclined portion 220 deforms in the vehicle width direction, preventing the front member 162, such as the dash cross member 166 and the front suspension frame 168 shown in FIG. 1, from moving rearward.

[0070] 1, the suspension connection part 230 is the front end part of the floor side member 124, and is connected to the upper surface and rear surface of the dash cross member 166. Furthermore, the front suspension frame 168 is connected to the upper part of the suspension connection part 230. In other words, the floor side member 124 is sandwiched between the dash cross member 166 and the front suspension frame 168 in the vertical direction.

[0071] As shown in FIG. 4(a), the second rear cross member 204 is connected to the rear inclined portion 224 of the floor side member 128. The rear inclined portion 224 has a first rear inclined portion 234 and a second rear inclined portion 236. The first rear inclined portion 234 is located forward of a connection position 238 at which the second rear cross member 204 is connected. The second rear inclined portion 236 is located rearward of the connection position 238. The first rear inclined portion 234 is inclined outward in the vehicle width direction at a gentler rate than the second rear inclined portion 236. Therefore, when the floor side member 128 receives a load from the front, stress is less likely to be concentrated locally, and deformation in the vehicle width direction due to this load can be suppressed.

[0072] 4(a), since the inclination degree of the first rear inclined portion 234 is gentler than that of the second rear inclined portion 236, the degree of change in the dimensional difference in the vehicle width direction between one side and the other side of the floor vibration surface bounded by the first rear inclined portion 234 also becomes gentle, so that floor vibration can be suppressed. If the inclination degrees of not only the first rear inclined portion 234 but also the second rear inclined portion 236 were made gentle, the dimension of the rear inclined portion 224 in the vehicle fore-aft direction would become large, and the dimension of the straight portion 222 in the vehicle fore-aft direction would be limited.

[0073] Therefore, in the vehicle undercarriage structure 100, the inclination of the second rear inclined portion 236 of the rear inclined portion 224 is made steeper than the inclination of the first rear inclined portion 234, thereby preventing the overall fore-aft dimension of the rear inclined portion 224 from becoming larger, and ensuring space for arranging the straight portion 222 extending in the fore-aft direction of the vehicle.

[0074] Furthermore, if the degree of inclination of the second rear inclined portion 236 is increased, when a load is received from the front, stress tends to be locally concentrated on the second rear inclined portion 236, making the second rear inclined portion 236 more likely to deform in the vehicle width direction. Therefore, in the vehicle underbody structure 100, by setting a connection position 238 with the second rear cross member 204 in front of the second rear inclined portion 236, the deformation of the second rear inclined portion 236 in the vehicle width direction can be suppressed by the second rear cross member 204.

[0075] 1 is provided on the outer side of the floor horizontal plane 114 in the vehicle width direction, it becomes easier to arrange the floor side members 128, 130 toward the center in the vehicle width direction, and it becomes easier to bend them toward the rear side members 124, 126 in order to connect them to the rear side members 124, 126. Note that, in the vehicle undercarriage structure 100, the floor side members 128, 130 are arranged at the middle positions 216, 218 of the floor vibration surface, so that the vibration surface of the floor horizontal plane 114 of the floor panel 102 is divided into four parts approximately equally in the vehicle width direction.

[0076] Fig. 5 is a diagram showing the vehicle underbody structure 100 of Fig. 4(a) as viewed from another direction. Fig. 5(a) and Fig. 5(b) are diagrams showing the floor side members 128 and 130 as viewed obliquely from below and above, respectively.

[0077] The second rear inclined portion 236 has a side surface 240 shown in FIG. 4(a), FIG. 5(a), and FIG. 5(b). In FIG. 4(a), only the portion showing the side surface 240 is a side view, and the remaining portion is a top view. An upwardly bulging portion 242 is formed on the side surface 240 of the second rear inclined portion 236. As shown in FIG. 4(a), the second rear cross member 204 is connected to an upper surface 244 (see FIG. 5(a)) of the upwardly bulging portion 242 and a front surface 246. In the upwardly bulging portion 242, a front end 248 shown in FIG. 4(a) is inclined or arc-shaped in a side view in order to increase the connection area with the second rear cross member 204. In accordance with the shape of the front end 248 of the upwardly bulging portion 242, a rear end 250 of the second rear cross member 204 shown in FIG. 5(b) is also inclined. Furthermore, an upper end 252 of the second rear cross member 204 extends rearward and abuts against an upper surface 244 of the upward bulge 242, thereby increasing the connection area therebetween.

[0078] Here, when the rear inclined portion 224 of the side sill 104, the rear side member 124 and the floor side member 128 are connected by the second rear cross member 204, if the rear inclined portion 224 does not have an upward bulge 242, the second rear cross member 204 will be connected to the upper surface of the rear inclined portion 224. In such a configuration, the connection area between the rear inclined portion 224 and the second rear cross member 204 cannot be secured, making it difficult to suppress deformation of the rear inclined portion 224 in the vehicle width direction.

[0079] Therefore, in the vehicle undercarriage structure 100, by providing an upward bulge 242 on the second rear inclined portion 236 of the rear inclined portion 224, the connection area between the second rear cross member 204 and the rear inclined portion 224 is increased and the connection rigidity is improved, thereby suppressing deformation and vibration of the floor side member 128 and also suppressing floor vibration.

[0080] 4(b) and 4(c) are both examples of the present invention, and are schematic diagrams of a floor side member 128 and a modified floor side member 128A. Note that dashed lines I and J in the drawings indicate the states of the floor side members 128 and 128A at the time of a frontal collision.

[0081] The floor side member 128A of the modified example in Fig. 4(c) differs from the floor side member 128 in that the rear inclined portion 224A is inclined at a constant degree of inclination from the rear end 228 of the straight portion 222 outward in the vehicle width direction. In the floor side member 128A, depending on the degree of inclination of the rear inclined portion 224A, there is a risk that the rear end 228 of the straight portion 222 will be significantly deformed inward in the vehicle width direction during a frontal collision, as shown by the dashed line J in Fig. 4(c).

[0082] In contrast, the floor side member 128 in Fig. 4(b) has a rear inclined portion 224 formed by a first rear inclined portion 234 and a second rear inclined portion 236 which have different degrees of inclination. Therefore, the floor side member 128 can suppress deformation of the rear end 228 of the straight portion 222 inward in the vehicle width direction during a frontal collision, as shown by the dashed dotted line I in Fig. 4(b).

[0083] As shown in Fig. 4(a), the vehicle undercarriage structure 100 further has a connecting member 254 extending along the vehicle front side of the second rear cross member 204, and brackets 256, 258 located on the vehicle width direction outer sides of the connecting member 254. The connecting member 254 connects the upper bulging portion 242 and the bracket 256 by being joined to an upper surface 244 and a front surface 246 of the upper bulging portion 242. The bracket 256 holds the rear side frame 124 shown in Fig. 1 together with the second rear cross member 204 from above and below, and is also connected to the side sill 104 (see Fig. 6).

[0084] In addition, in the vehicle underbody structure 100, as shown in FIG. 5(a), the connecting member 254 is connected so as to be sandwiched in the vehicle width direction by the upper part of the floor side members 128, 130. With this configuration, the connection surface between the second rear cross member 204 and the floor side members 128, 130 can be increased, and therefore the connection rigidity between them can be increased. Furthermore, as shown in FIG. 5(b), a bracket fixing portion 259 for fixing a rear seat mounting bracket (not shown) is provided in an area spanning the rear end portion 250 and the upper end portion 152 of the second rear cross member 204. Then, by arranging this bracket fixing portion 259 and the upward bulging portion 242 of the floor side member 128 so as to overlap in the vertical direction, it is possible to suppress the rear seat (not shown) from vibrating in the vertical direction.

[0085] Fig. 6 is a diagram showing a state in which a portion of the vehicle underbody structure 100 in Fig. 1 is viewed from the front of the vehicle. As shown in Fig. 6, in the vehicle underbody structure 100, the rear side frame 124 and the side sill 104 are sandwiched between a lower surface 260 of the outer end of the second rear cross member 204 and an upper surface 262 of the outer end of the bracket 256.

[0086] Fig. 7 is a detailed view of a portion of a modified example of the vehicle underbody structure 100 of Fig. 1. Fig. 7(a) is a bottom view of a portion of the modified vehicle underbody structure 100A. Fig. 7(b) shows the vehicle underbody structure 100A of Fig. 7(a) as viewed obliquely from below. Fig. 8 is a view showing the vehicle underbody structure 100A of Fig. 7 as viewed from another direction.

[0087] The modified vehicle underbody structure 100A differs from the above-described vehicle underbody structure 100 in that, instead of the second rear cross member 204, a second rear cross member 204A is provided as a member including a connecting member 254 and brackets 256, 258.

[0088] 7(a), in the vehicle underbody structure 100A, the second rear cross member 204A is joined to the side sill 104 and the rear side member 124, and the side sill 104 is joined to the rear side member 124. In other words, the side sill 104 and the rear side member 124 joined to the second rear cross member 204A are joined to each other.

[0089] Therefore, in vehicle underbody structure 100A, the rigidity of the members supporting second rear cross member 204A, i.e., the supporting rigidity of second rear cross member 204A, can be increased, while the load and vibration transmitted to second rear cross member 204A can be dispersed and released to side sill 104 and rear side member 124. Therefore, vibration of second rear cross member 204A can be suppressed.

[0090] The second rear cross member 204A has a first joint 264 shown in Figures 7(a) and 7(b) and a second joint 266 shown in Figure 7(b). The first joint 264 is the area surrounded by dotted line K in the figure, where a lower flange 268 of the second rear cross member 204A, the side sill 104, and the rear side member 124 overlap in the vertical direction.

[0091] The second joint 266 is the area surrounded by dotted line L in Figure 7(b), where a side flange 270 of the second rear cross member 204A, an inner side surface 272 of the side sill 104, and a side flange (not shown) of the rear side member 124 overlap in the vertical direction.

[0092] This increases the three-piece joint area of ​​the second rear cross member 204A, the side sill 104 and the rear side member 124, while firmly joining these three members in the vertical and vehicle width directions by the first joint portion 264 and the second joint portion 266. Therefore, in the vehicle underbody structure 100A, the connection rigidity of the second rear cross member 204A to the side sill 104 and the rear side member 124 is increased, making it possible to suppress vibrations, particularly torsional vibrations, of the second rear cross member 204A.

[0093] A widened portion 276 that is widened in the vehicle front-rear direction is formed at a lower end 274 of the second rear cross member 204A. A first joint 264 and a second joint 266 are formed at the widened portion 276, and a third joint 278 is also formed. The third joint 278 is an area surrounded by dotted line M in Figures 7(a) and 7(b), does not overlap with the side sill 104, and is where a lower flange 268 of the second rear cross member 204A and a lower surface 280 of the rear side member 124 are joined together.

[0094] In this way, the widened portion 276 of the second rear cross member 204A is formed with a third joint 278 which is joined together with the rear side member 124, and a first joint 264 and a second joint 266 which are joined together, i.e., the side sill 104 and the rear side member 124. This increases the connection area of ​​the second rear cross member 204A to the rear side member 124, thereby increasing the connection rigidity of the second rear cross member 204A.

[0095] Furthermore, in the second rear cross member 204A, vibrations and loads of the rear side member 124 can be easily dispersed and released from the third joint 278 to the first joint 264 and the second joint 266 via the widened portion 276. As a result, vibrations of the rear side member 124 are transmitted to the side sill 104, and vibrations of the second rear cross member 204A can be suppressed.

[0096] 8, the widened portion 276 of the second rear cross member 204A is formed with a fourth joint 282 and a fifth joint 284. The fourth joint 282 is the area surrounded by dotted line N in the figure, and is joined to an upper flange 288 of the second rear cross member 204A, an upper surface 286 of the side sill 104, and a floor panel 102 (not shown) while overlapping in the vertical direction.

[0097] The fifth joint 284 is a portion surrounded by a dotted line O in the figure, adjacent to the fourth joint 282, does not overlap with the floor panel 102, and is joined to an upper flange 288 of the second rear cross member 204A and an upper surface 286 of the side sill 104 while overlapping in the vertical direction. Note that the fifth joint 284 is not limited to this, and may be joined in three pieces so as to overlap with the floor panel 102. Alternatively, as a modified example, the fifth joint 284 may function as another first joint formed on the upper surface 286 of the side sill 104 by extending the rear side member 124 so as to overlap between the upper flange 288 of the second rear cross member 204A and the upper surface 286 of the side sill 104 and joining the three pieces.

[0098] When four or more plates are spot-welded, the stability of the welding process is reduced, and the joining cost and joining time increase. Instead of joining four plates, the second rear cross member 204A is divided into a portion where the side sill 104 is joined to the floor panel 102 and a portion where the floor panel 102 is joined to the side sill 104. This reduces the welding work and the welding time compared to the case where the second rear cross member 204A, the side sill 104, the rear side member 124, and the floor panel 102 are joined to four plates. Moreover, by arranging the fourth joint 282 as a three-piece joint joined to the floor panel 102 and the other first joint as a three-piece joint which is a modified example of the fifth joint 284 joined to the side sill 104 adjacent to each other, the vibration of the floor panel 102 can be dispersed from the other first joint to the adjacent fourth joint 282, making it easier to escape. Therefore, the vibration of the floor panel 102 is transmitted to the side sill 102 and the second rear cross member 204A, and the vibration of the floor panel 102 can be suppressed. If the joining costs and joining time are tolerable, the second rear cross member 204A, the side sill 104, the rear side member 124, and the floor panel 102 may be joined together in four pieces.

[0099] The vehicle lower structure 100A also has other joints 290, 292. The joint 290 is an area surrounded by dotted line P in Fig. 8, and is joined to the floor panel 102, the rear side member 124, and the second rear cross member 204A by overlapping them in the vertical direction. The joint 292 is joined to the side sill 104 and the rear side member 124 by overlapping them in the vertical direction, as shown in Figs. 7(a) and 7(b). However, the joint 292 is not limited to this, and the second rear cross member 204A may be extended to join the three together with the side sill 104 and the rear side member 124.

[0100] The rear side member 124 shown in FIG. 7(b) has an inner side surface 296 adjacent to the side surface flange 294 of the second rear cross member 204A, an upper surface flange 298 continuing with the inner side surface 296, a side surface flange 300 continuing with the lower surface 280, and a lower flange 302 continuing with the side surface flange 300. Here, the rear side member 124 forms a closed cross section with the upper surface flange 298, the lower surface 280, the inner side surface 296, and the inner side surface 272 of the side sill 104. The outer side surface is also used as the inner side surface 272 of the side sill 104. Since the rear side member 124 is cantilevered, the side surface flange 300 and the lower flange 302 are provided on the lower surface 280 of the rear side member 124, thereby increasing the joining area with the side sill 104.

[0101] In the vehicle undercarriage structure 100A, the second rear cross member 204A is joined to the side sill 104 and the rear side member 124 so as to overlap the joint surfaces between the side sill 104 and the rear side member 124, i.e., the first joint 264 and the second joint 266 where the three pieces are joined.

[0102] This allows the joint surfaces of the side sill 104 and the rear side member 124, the joint surfaces of the second rear cross member 204A and the side sill 104, and the joint surfaces of the second rear cross member 204A and the rear side member 124 to be close to or overlap each other. This makes it possible to increase the support rigidity of the second rear cross member 204A. In addition, by joining the second rear cross member 204A to the joint surface of the side sill 104 and the rear side member 124, which has increased support rigidity, the connection rigidity of the second rear cross member 204A to the side sill 104 and the rear side member 124 can be increased. This makes it possible to more sufficiently suppress vibration of the second rear cross member 204A.

[0103] Here, at point Q of the vehicle underbody structure 100 shown in FIG. 2(a), the rear side member 124 is connected to the first rear cross member 202 and the floor side member 128, so that the support rigidity of the second rear cross member 204A can be increased. At point Q, the floor side member 128, the first rear cross member 202, and the rear side member 124 are joined in three pieces by overlapping in the vertical direction. Adjacent to the area including point Q where the three pieces are joined, there are an area where the rear side member 124 and the floor side member 128 are joined in two pieces, an area where the floor panel 102 is also joined in three pieces, and an area where the first rear cross member 202 and the floor side member 128 are joined in two pieces. This makes it possible to more sufficiently increase the support rigidity of the second rear cross member 204A.

[0104] 2(a) indicates the joining area between the side sill 104 and the rear side member 124. In this joining area, a recess 304 is provided behind the rear part of the side sill 104, and a protrusion 306 of the rear side member 124 is joined to this recess 304. This allows the rear side member 124 and the side sill 104 to be joined in the vehicle fore-and-aft direction and the vehicle width direction, thereby increasing the support rigidity of the second rear cross member 204A.

[0105] In addition, the rear portion 307 of the widened portion 276 of the second rear cross member 204A shown in FIG. 2(a) extends in a direction substantially perpendicular to the inner side surface 296 (see FIG. 7(b)) of the rear side member 124. Furthermore, the rear portion 307 of the widened portion 276 has an inner portion 307a and an outer portion 307b. The inner portion 307a is continuous with the outer portion 307b and is located inside the outer portion 307b in the vehicle width direction. As shown in FIG. 2(a), the inner portion 307a has a greater degree of inclination than the outer portion 307b, and is inclined so as to follow the rear inclined portion 224 (see FIG. 4(a)) of the floor side member 128. This configuration increases the joint area between the widened portion 276 and the front end portion 208 of the rear side member 124, while facilitating the transmission of vibration transmitted to the widened portion 276 to the front side of the floor side member 128. Furthermore, when the inner portion 307a of the rear portion 307 of the widened portion 276 is inclined along the swing axis Sa passing through the suspension fixing portion 120, vibrations transmitted from the suspension fixing portion 120 to the rear side member 124 are easily transmitted to the floor side member 128. The suspension fixing portion 120 may also be joined to the side sill 104 by a bracket (not shown).

[0106] In the vehicle underbody structure 100, the front side member 164, the floor side member 128, and the rear side member 124 are each separate bodies, but this is not limited thereto and they may be of an integrated structure. In this specification, the term "side member" is a concept that includes all of the front side member 164, the floor side member 128, and the rear side member 124.

[0107] Fig. 9 is a diagram showing a schematic diagram of another modified example of the vehicle understructure 100 of Fig. 1. In the vehicle understructures 100B and 100C shown in Fig. 9(a), when the swing axes Ta and Tb are in the vehicle width direction and the vehicle front-rear direction, the floor side member 128 and the suspension fixing part 120 are connected to the regions of the rear side member 124 that face each other in the vehicle width direction, i.e., the side surfaces 308 and 310, respectively. Even in such vehicle understructures 100B and 100C, it is possible to suppress vibration of the rear side member 124 in the swing axis direction or the vehicle width direction.

[0108] 9(b), when the swing axes Ta, Tb are in the vehicle width direction and the vehicle front-rear direction, the floor side member 128 and the suspension fixing part 120 are connected to areas of the rear side member 124 that face each other in the vertical direction, i.e., the upper surface 312 and the lower surface 314, respectively. Even with such vehicle understructures 100D, 100E, it is possible to suppress vibration of the rear side member 124 in the swing axis direction or the vehicle width direction.

[0109] In the vehicle undercarriage structures 100, 100B to 100E, the floor side member 128 and the suspension fixing part 120 are connected to adjacent or opposing areas of the rear side member 124, respectively, but this is not limited to the above. As an example, when a shock absorber 142 (see FIG. 2(a)) of the suspension 132 is fixed to the suspension fixing part 120, the floor side member 128 and the shock absorber 142 may be connected to adjacent or opposing areas of the rear side member 124, respectively. The width dimension of the shock absorber 142 in the vehicle front-rear direction is smaller than the width dimension of the suspension fixing part 120 in the vehicle front-rear direction.

[0110] 9(c), when the swing axes Ta, Tb are in the vehicle width direction and the vehicle front-rear direction, the floor side member 128 and the rear side member 124 are disposed to face each other in the vehicle width direction via the suspension fixing part 120, and are connected to the suspension fixing part 120. Even with such vehicle understructures 100F, 100G, it is possible to suppress vibration of the rear side member 124 in the swing axis direction or the vehicle width direction.

[0111] Figure 10 is a diagram showing yet another modified example of the vehicle underbody structure 100 of Figure 1. Figure 10(a) shows modified floor side members 128B, 130A. As shown in the figure, the floor side members 128B, 130A have a symmetrical structure, so here, the structure of the floor side member 128B will be described.

[0112] The floor side member 128B differs from the above-described floor side member 128 in that it has a front inclined portion 220A that inclines outward in the vehicle width direction toward the rear of the vehicle instead of the front inclined portion 220. In the floor side member 128B, a straight portion 222 extends straight from a rear end 226A of the front inclined portion 220A toward the rear of the vehicle, and a suspension connection portion 230 extends straight from a front end 232A of the front inclined portion 220A toward the front of the vehicle.

[0113] Therefore, even if the connection position between the front member 162 or front side member 164 shown in Figure 1, which is located at the front or rear of the vehicle of the floor side member 128B, and the rear side member 124 is located away from the intermediate position 216 (see Figure 1) of the floor vibration surface, by adjusting the degree of inclination and length of the two inclined portions, i.e., the front inclined portion 220A and the rear inclined portion 224, the straight portion 222 located between the two inclined portions can be brought closer to the intermediate position 216 of the floor vibration surface, thereby suppressing floor vibration.

[0114] 1, in the vehicle underbody structure 100, the front end position of the floor side member 128, i.e., the connection position between the front side member 164 and the floor side member 128, and the rear end position of the floor side member 128, i.e., the connection position between the floor side member 128 and the rear side member 124 or the side sill 104, are located outside in the vehicle width direction from the intermediate position 216 of the floor vibration surface. On the other hand, when the modified floor side member 128B is applied, the front end position of the floor side member 128B is located inside in the vehicle width direction from the intermediate position 216, and the rear end position is located outside in the vehicle width direction from the intermediate position 216.

[0115] 10(a), one of the front end position and the rear end position of the floor side member may be located outside the intermediate position 216 in the vehicle width direction (not shown). One of the front end position and the rear end position of the floor side member may be located at the intermediate position 216. When the front end position of the floor side member is at the intermediate position 216, for example, the front side member 164 is connected to the front end of the straight portion 222. When the rear end position of the floor side member is at the intermediate position 216, for example, the rear side member 124 is connected to the rear end of the straight portion 222.

[0116] In the vehicle underbody structure 100H shown in Fig. 10(b), a rear side member 124A is joined to the underside of a floor panel 102A, while a side surface 316 of the floor panel 102A, a side sill 104A, and a side surface 318 of the rear side member 124A are joined together in a vehicle width direction. The inner side of the floor panel 102A in the vehicle width direction is joined to a center tunnel 108A and a reinforcing member 320. A cross member 322 extending in the vehicle width direction above the floor panel 102A is disposed between the side sill 104A and the center tunnel 108A.

[0117] In this vehicle underbody structure 100H, the load and vibration transmitted to the cross member 322 can be dispersed and released to the side sill 104A and the rear side member 124A via the three-piece joined locations, thereby suppressing the vibration of the cross member 322. Furthermore, since the vibration of the floor panel 102A can be dispersed and released to the side sill 104A, the rear side member 124A, and the cross member 322, the vibration of the floor panel 102A can be suppressed.

[0118] In the vehicle underbody structure 100I shown in Fig. 10(c), a rear side member 124B is disposed on the vehicle rear side of the side sill 104B, and the side sill 104B and the rear side member 124B, which are joined to the second rear cross member 204B, are joined to each other. Furthermore, as shown in the figure, a joint surface 324 between the side sill 104B and the rear side member 124B, a joint surface 326 between the second rear cross member 204B and the side sill 104B, and a joint surface 328 between the second rear cross member 204B and the rear side member 124B are brought into close proximity to each other.

[0119] Therefore, in the vehicle underbody structure 100I, the support rigidity of the second rear cross member 204B is increased, while the load and vibration transmitted to the second rear cross member 204B can be dispersed and released to the side sill 104B and the rear side member 124B. Therefore, vibration of the second rear cross member 204B can be suppressed.

[0120] The vehicle underbody structure 100 may have a plurality of suspension fixing parts corresponding to a plurality of swing axes. In such a case, it is sufficient to connect the suspension fixing part 120 and the floor side member 128 corresponding to any one of the swing axes to an adjacent or opposing area of ​​the rear side member 124. This makes it possible to suppress vibration of the rear side member 124 in the swing axis direction or the vehicle width direction.

[0121] Although the preferred embodiment of the present invention has been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such an embodiment. It is clear that a person skilled in the art can think of various modifications or alterations within the scope of the claims, and it is understood that these also naturally belong to the technical scope of the present invention. [Industrial Applicability]

[0122] The present invention can be used in a vehicle underbody structure. [Explanation of symbols]

[0123] 100, 100B~100I…Vehicle underbody structure 102, 102A…Floor panel 104, 104A, 104B, 106...Side sill 108, 108A...Center tunnel 110, 112…Edge of floor panel 114…Floor horizontal surface 116, 118...Upward slope 120, 122…Suspension fixing part 124, 124A, 124B, 126...Rear side member 128, 128A, 128B, 130, 130A...Floor side members 132, 134…Suspension 136...Right rear wheel 138…trailing link 140…Coupling profile 142, 156...Shock absorber 144…Front end of trailing link 146…Sloped part of rear side member 148…Rear end of vehicle 150…Wheel carrier 152…Tie rod 154…Lower A-arm link 158…Front end of lower A-arm link 160…Rear end of lower A-arm link 162…Front member 164, 176...Front side member 166…Dash cross member 168…Front suspension frame 169a, 169b…Brace 170, 174…Front side extension 172, 178…Front suspension 180, 182... Rear fixed point 184, 186...Intermediate fixed points 188, 190...Front fixed point 192, 280, 314...Underside of rear side member 194, 206…Rear end of floor side member 196…bulge 198…Side of rear side member 200…Suspension area 202…First rear cross member 204, 204A, 204B...Second rear cross member 208, 210...Front end of rear side member 212...Closed section 214…Floor side member recess 216, 218...Middle position of floor vibration surface 220, 220A…Front inclined section 222…Straight section 224, 224A…Rear inclined section 226, 226A…Rear end of front inclined part 228…Rear end of straight section 230…Susfle connection part 232, 232A…Front end of front inclined part 234…First rear incline 236…Second rear incline 238…Second rear cross member connection position 240…Side of second rear incline 242...Upward bulge 244…Upper surface of upper bulge 246…Front of upper bulge 248…Front end of upper bulge 250…Rear end of second rear cross member 252…Upper end of second rear cross member 254…Connecting member 256, 258… bracket 259…Bracket fixing part 260…Underside of outer end of second rear cross member 262...Top surface of outer end of bracket 264...1st joint 266...Second joint 268…Lower flange of second rear cross member 270, 294...Side flange of second rear cross member 272…Inner side of side sill 274…Lower end of second rear cross member 276…Wide section 278...Third joint 282…4th joint 284...5th joint 286…Top surface of side sill 288…Upper flange of second rear cross member 290, 292...other joints 296…Inner surface of rear side member 298…Upper surface of rear side member 300…Side flange of rear side member 302…Lower flange of rear side member 304…Side sill recess 306…Rear side member protrusion 307…Rear part of widening section 307a…Inner part of rear of widening section 307b…Outer part of rear of widening section 308, 310...Side of rear side member 312…Upper surface of rear side member 316…Side of floor panel 318…Side of rear side member 320…Reinforcing member 322…Cross member 324, 326, 328…Joint surface

Claims

1. A floor panel that forms a floor surface of the vehicle; a side sill extending in a vehicle front-rear direction along an edge of the floor panel; a side member disposed below the floor panel and on the inner side of the side sill in the vehicle width direction, the side member extending in the vehicle front-rear direction; A cross member joined to the side sill, The side member has an upwardly bulging portion that bulges upward, A vehicle underbody structure, wherein the cross member is connected to the upward bulge portion.

2. The cross member is disposed forward of the upward bulge portion, 2. The vehicle underbody structure according to claim 1, wherein a rear end of the cross member is connected to a front end of the upward bulge portion.

3. The front end of the upward bulge portion is inclined or arcuate in side view, 3. The vehicle underbody structure according to claim 2, wherein a rear end of the cross member is inclined to match a front end of the upwardly bulging portion.

4. the side member has a recessed portion that is recessed below a front end of the upper bulge portion from a front side of the upper bulge portion, 4. The vehicle underbody structure according to claim 2, wherein the cross member has a protrusion connected to the recess.

5. The side member has an inclined portion that inclines outward in the vehicle width direction toward the rear, 5. The vehicle underbody structure according to claim 1, wherein the upward bulge is provided on the inclined portion.

6. The side member has a straight portion extending in the front-rear direction on a front side of the inclined portion, 6. The vehicle underbody structure according to claim 5, wherein the inclined portion extends from the front side to the rear side of the cross member, and the inclination angle of the rear side of the cross member is greater than the inclination angle of the front side of the cross member.

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