Vehicle undercarriage

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 Art

[0002] Vehicles such as automobiles have a vehicle underbody structure that joins skeletal members such as side sills extending in the vehicle longitudinal direction of the vehicle with cross members extending in the vehicle width direction. With such a vehicle underbody structure, when a load at the time of a side collision is input to the skeletal members extending in the vehicle longitudinal direction of the vehicle, deformation or movement of this skeletal member inside the vehicle is suppressed.

[0003] Patent Document 1 describes a rear seat mounting support structure of a vehicle. This support structure includes two rear cross members 13 and 14. The rear cross member 13 connects the side sills 2 to each other in the vehicle width direction, and further connects to the rear side frame 3 via a seat rail member 17. The rear cross member 14 connects the rear side frames 3 to each other. The joint portion 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, in the support structure of Patent Document 1, the impact load applied to the mounting portion of the rear seat is efficiently dispersed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, in the understructure of a vehicle, the cross members that connect skeletal members such as side sills, which are positioned along the edge of the floor panel on the outside in the vehicle width direction, are elongated in the vehicle width direction. As a result, the surface area that is locally subjected to vibration is large in the cross members, and vibrations, especially torsional vibrations, are prone to occur. Furthermore, if the floor panel is joined to the cross member, this vibration is transmitted to the floor panel, and this vibration deteriorates the ride comfort. It should be noted that the support structure in Patent Document 1 only distributes the impact load applied to the rear seat mounting part, and there is room for improvement in suppressing vibrations of the rear cross member.

[0006] In view of these problems, the present invention aims to provide a vehicle understructure that can suppress vibrations of the cross member. [Means for solving the problem]

[0007] To solve the above problems, a typical configuration of the vehicle understructure according to the present invention is a vehicle understructure comprising a floor panel that forms the floor surface of a vehicle, wherein the vehicle understructure further comprises a side sill extending in the longitudinal direction of the vehicle along the edge of the floor panel, a side member positioned on the underside of the floor panel and inside the side sill in the vehicle width direction 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, wherein the side sill is joined to the side member. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a vehicle understructure that can suppress vibrations of the cross member. [Brief explanation of the drawing]

[0009] [Figure 1] This is a bottom view showing a vehicle understructure according to an embodiment of the present invention. [Figure 2] Figure 1 shows a portion of the vehicle's understructure and various suspension systems. [Figure 3]Figure 2(a) shows a cross-sectional view of the vehicle's understructure and a comparative example. [Figure 4] Figure 1 shows a portion of the vehicle's understructure and a modified example. [Figure 5] This figure shows the understructure of the vehicle shown in Figure 4(a) from a different direction. [Figure 6] This figure shows a portion of the vehicle's understructure as viewed from the front of the vehicle. [Figure 7] This figure shows in detail a modified example of the vehicle understructure shown in Figure 1. [Figure 8] This figure shows the undercarriage of the vehicle shown in Figure 7, viewed from a different direction. [Figure 9] This figure schematically shows other variations of the vehicle understructure shown in Figure 1. [Figure 10] This figure shows yet another modified example of the vehicle understructure shown in Figure 1. [Modes for carrying out the invention]

[0010] A typical configuration of a vehicle understructure according to one embodiment of the present invention is a vehicle understructure comprising a floor panel that forms the floor surface of a vehicle, wherein the vehicle understructure further comprises a side sill extending in the longitudinal direction of the vehicle along the edge of the floor panel, a side member positioned below the floor panel and inside the side sill in the vehicle width direction 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, wherein the side sill is joined to the side member.

[0011] In the above configuration, the side sills and side members, which are joined to the cross member, are joined to each other. Therefore, the rigidity of the members supporting the cross member, i.e., the support rigidity of the cross member, can be increased, while the loads and vibrations transmitted to the cross member can be distributed and dissipated to the side sills and side members. Consequently, vibrations of the cross member can be suppressed.

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

[0013] Thereby, the joint surface between the side sill and the side member, the joint surface between the cross member and the side sill, and the joint surface between the cross member and the side member can be made close to or overlap each other. For this reason, the support rigidity of the cross member can be increased. Further, by joining the cross member to the joint surface between the side sill and the side member with increased support rigidity, the connection rigidity of the cross member with respect to the side sill and the side member can be increased. Therefore, the vibration of the cross member can be more sufficiently suppressed.

[0014] The above cross member may have one or more joint portions joined to the side sill and the side member so as to overlap in a predetermined direction.

[0015] Thereby, the cross member can be joined in a three-layer manner (triple joint) with the side sill and the side member at the joint portion. For this reason, the connection rigidity of the cross member with respect to the side sill and the side member can be increased, and the vibration of the cross member, particularly torsional vibration, can be more sufficiently suppressed.

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

[0017] Thereby, while increasing the triple joint area by the cross member, the side sill, and the side member, these members can be firmly triple-joined in the vertical direction and the vehicle width direction by the first joint portion and the second joint portion. Therefore, the vibration of the cross member, particularly torsional vibration, can be suppressed.

[0018] The above first joint portion may be formed on the upper and lower surfaces of the side sill.

[0019] As a result, the first joint formed on the upper and lower surfaces of the side sill increases the three-piece joint area between the cross member, side sill, and side member, allowing these members to be firmly joined in the vertical direction. Therefore, vibrations of the cross member, especially torsional vibrations, can be suppressed more effectively.

[0020] The ends of the cross member described above have widened sections formed in the vehicle's longitudinal direction, the side members are connected to the inner side surfaces of the side sills in the vehicle's width direction, the widened sections have first and second joints formed in them, and one or more joints of the cross member may further include a third joint formed in the widened section that overlaps and is joined to the side members.

[0021] Thus, the widened portion of the cross member has a third joint where the cross member and side member are joined together without overlapping with the side sill, and first and second joints where the cross member, side sill, and side member are joined together. This increases the connection area of ​​the cross member to the side member, thereby increasing the connection rigidity of the cross member. Furthermore, the widened portion of the cross member allows vibrations and loads from the side member to be easily dispersed and released from the third joint to the first and second joints. As a result, vibrations from the side member are transmitted to the side sill, suppressing vibrations from the cross member.

[0022] The ends of the cross member described above have widened sections formed in the longitudinal direction of the vehicle, and one or more joints of the cross member may further include a fourth joint formed in the widened section that overlaps vertically with the upper surface of the side sill and the floor panel, and a fifth joint formed adjacent to the fourth joint in the widened section that overlaps vertically with the upper surface of the side sill.

[0023] Thus, the widened section of the cross member has a fourth joint where the cross member, the upper surface of the side sill, and the floor panel are joined together in three layers, and a fifth joint where the cross member and the side sill are joined together in two layers without overlapping with the floor panel. This increases the contact area of ​​the cross member with the highly rigid side sill, thereby increasing the support rigidity and connection rigidity of the cross member. Furthermore, the cross member allows vibrations from the floor panel to be easily dispersed and released from the fourth joint to the adjacent fifth joint via the widened section. As a result, vibrations from the floor panel are transmitted to the side sill and cross member, suppressing vibrations of the floor panel. [Examples]

[0024] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. The dimensions, materials, and other specific numerical values ​​shown in these embodiments are merely examples to facilitate understanding of the invention and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to avoid redundant explanations, and elements not directly related to the present invention are omitted from the illustration. In these embodiments, connection includes joining separate members, contact between separate members, and integration where each member becomes the same member.

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

[0026] The vehicle understructure 100 comprises a floor panel 102 that forms the floor surface of the vehicle, a pair of side sills 104 and 106, and a center tunnel 108. The pair of side sills 104 and 106 are spaced apart in the vehicle width direction and extend in the vehicle longitudinal direction along the edges 110 and 112 of the floor panel 102. The center tunnel 108 extends in the vehicle longitudinal direction from the center of the floor panel 102 in the vehicle width direction. The floor panel 102 includes a floor horizontal surface 114 enclosed by dotted line A in the figure, and upward inclined portions 116 and 118, respectively, which are located on the outside of the floor horizontal surface 114 in the vehicle width direction and enclosed by dotted lines B and C in the figure.

[0027] The vehicle understructure 100 further comprises 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. As shown in Figure 1, the vehicle understructure 100 has a symmetrical structure, so unless otherwise necessary, only the structure on the right side in the vehicle width direction will be described below.

[0028] Figure 2 shows a part of the vehicle understructure 100 and various suspensions 132 and 134 from Figure 1. Figure 2(a) shows an enlarged view of the suspension fixing part 120 and its surrounding structure. Figures 2(b) and 2(c) show schematic configurations of typical suspensions 132 and 134 with different pivot axis directions (pivot axis direction).

[0029] The suspension fixing section 120 is the part to which the swinging suspension 132 for the rear wheel 136, as shown in Figure 2(b), is fixed. The suspension 132 has a so-called semi-independent axle structure and includes 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 the front end 144 of the trailing link 138.

[0030] The front end 144 of the trailing link 138 shown in Figure 2(b) is fixed to the suspension fixing part 120. The suspension fixing part 120 is also connected to the inclined portion 146 of the rear side member 124, as shown in Figure 1.

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

[0032] As shown in Figure 1, the inclined portion 146 of the rear side member 124 is a part that inclins outward in the vehicle width direction as it approaches the front of the vehicle. Since the suspension fixing portion 120 is connected to the inclined portion 146 of the rear side member 124, in the vehicle understructure 100, the pivot axis Sa passing through the suspension fixing portion 120 in Figure 2(a) is in a direction that is perpendicular to the inclined portion 146 and inclined forward as it approaches the vehicle width direction.

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

[0034] The vehicle understructure 100, by applying suspensions 132 and 134 to the suspension fixing part 120, will have not only a pivot axis Sa whose pivot axis direction is in a direction that is inclined toward the front of the vehicle as it approaches the inside in the vehicle width direction, but also pivot axes Sb and Sc whose pivot axis direction is in the vehicle width direction or the vehicle longitudinal direction. In addition to pivot axes Sa, Sb and Sc, the vehicle understructure 100 can also be applied to suspensions that have a pivot axis whose pivot axis direction is in a direction that is inclined toward the rear of the vehicle as it approaches the inside in the vehicle width direction, although this is not shown in the illustration.

[0035] Therefore, the rear side member 124 connected to the suspension fixing part 120 receives a load in the direction of the oscillation axis from the suspension 132 via the suspension fixing part 120, for example, when the vehicle is in motion. Furthermore, when the vehicle understructure 100 is applied to the suspension 134, even if an oscillation axis Sc is set with the vehicle's longitudinal direction as the oscillation axis direction, the rear side member 124 receives a load as a vibration component in the vehicle width direction due to vibrations during vehicle operation. In other words, the rear side member 124 receives a load in the direction of the oscillation axis or in the vehicle width direction via the suspension fixing part 120.

[0036] The floor side member 128 connects the rear side member 124 to the front member 162 or front side member 164 located at the front of the vehicle, below the floor panel 102 shown in Figure 1. The front member 162 includes a dash cross member 166 that extends in the vehicle width direction and is positioned between the side sills 104 and 106, and a front suspension frame 168. In the figure, the outer shape of the front suspension frame 168 is shown by a dashed line, and various members that overlap the front suspension frame 168 are shown transparently. In addition, braces 169a and 169b are positioned on the outer side of the dash cross member 166 in the vehicle width direction, and they are inclined outward in the vehicle width direction as they move towards the rear of the vehicle, connecting the dash cross member 166 to the side sills 104 and 106.

[0037] A front side extension 170 is positioned on the 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. In the vehicle understructure 100, on the left side in the vehicle width direction, as shown in Figure 1, the front side extension 174, the front side member 176, and the front suspension 178 are positioned on the front side of the side sill 106.

[0038] Furthermore, the front suspension frame 168 has rear fixing points 180 and 182 for the floor side members 128 and 130, and intermediate fixing points 184 and 186 for the front side members 164 and 176. In addition, the front suspension frame 168 has front fixing points 188 and 190 for other members located further forward of the vehicle than the intermediate fixing points 184 and 186. Although the front side members 164 and 176 and the floor side members 128 and 130 are shown as separate components, they are not limited to this arrangement and may be integrated into a single structure.

[0039] As described above, the rear side member 124 receives loads in the direction of the oscillation axis or the vehicle width direction via the suspension fixing part 120. Therefore, in order to suppress vibrations of the rear side member 124 in the direction of the oscillation axis or the vehicle width direction, the vehicle understructure 100 employs a configuration in which the floor side member 128 and the suspension fixing part 120 are connected to adjacent areas (see Figure 3(a)) or opposing areas (see Figures 9(a) and 9(b)) of the rear side member 124, respectively.

[0040] Figure 3 shows a DD cross-section of the vehicle understructure 100 in Figure 2(a) and a comparative example. As shown in the DD cross-section of Figure 3(a), the rear side member 124 has a suspension fixing portion 120 connected to its lower surface 192. Also, the rear end portion 194 of the floor side member 128 shown in Figure 2(a) has a bulge portion 196. The bulge portion 196 is a portion that bulges out toward the rear side member 124, as indicated by the dotted line E.

[0041] Furthermore, as shown in Figure 3(a), the bulging portion 196 is connected to the inner side surface 198 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 way, the side member 128 and the suspension fixing portion 120 are connected to adjacent areas of the rear side member 124, namely the inner side surface 198 and lower surface 192 in the vehicle width direction, respectively. Also, the side surface 198 of the rear side member 124 is a side surface that is approximately perpendicular to the direction of the oscillation axis of the oscillation axis Sa (see Figure 2(a)) obtained by tilting the oscillation axis Sb of the suspension 132.

[0042] The comparative vehicle understructure 100A shown in Figure 3(b) differs from the vehicle understructure 100 in that it does not have a floor side member 128. As a result, in the vehicle understructure 100A, the rear side member 124 swings in the direction of the swing axis or vehicle width indicated by arrow F due to the load transmitted from the suspension 132 via the suspension fixing part 120 while the vehicle is running, and vibrates by shifting from its original position as shown by the dotted line G.

[0043] In contrast, in the vehicle understructure 100 shown in Figure 2(a), the load transmitted to the rear side member 124 from the suspension fixing part 120 can be distributed and relieved to the front member 162 or front side member 164 via the floor side member 128, on the upstream side of the load transmission path from the suspension fixing part 120, specifically around the suspension fixing part 120 200 of the rear side member 124.

[0044] Furthermore, as shown in Figure 2(a), the rear end portion 194 of the floor side member 128 has a bulge 196 that connects to the side surface 198 of the rear side member 124, thus increasing the connection area of ​​the floor side member 128 to the rear side member 124. This increases the connection rigidity of the floor side member 128 to the rear side member 124, making the floor side member 128 more receptive to loads from the rear side member 124. Moreover, since the side surface 198 of the rear side member 124 is almost perpendicular to the direction of the oscillation axis of the oscillation axis Sa, the load received by the rear side member 124 can be efficiently received, distributed, and released by the highly rigid floor side member 128.

[0045] As a result, vibrations of the rear side member 124 in the direction of the oscillation axis or the vehicle width direction, particularly vibrations in the load transmission path downstream of the connection point with the floor side member 128, are suppressed. Therefore, the vehicle understructure 100 can reduce torsional vibrations of the vehicle body and floor vibrations of the floor panel 102 caused by vibrations of the rear side member 124.

[0046] As shown in Figure 2(a), in the vehicle understructure 100, the bulging portion 196 of the floor side member 128 bulges out toward the rear side member 124. Therefore, it is not necessary to tilt or curve the rear end portion 194 of the floor side member 128 to bring it closer toward the rear side member 124 by the amount of this bulge. As a result, when the floor side member 128 is subjected to a load from the front-rear direction of the vehicle, deformation that causes it to contract in the front-rear direction of the vehicle can be suppressed.

[0047] The vehicle understructure 100 further includes a first rear cross member 202 and a second rear cross member 204 spaced apart in the longitudinal direction of the vehicle, as shown in Figure 1. The first rear cross member 202 extends in the vehicle width direction and is connected to the 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 the 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 part 120 to be distributed and relieved 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 vibrations of the floor side member 128 in the direction of the swing axis or the vehicle width.

[0049] Furthermore, since the load transmitted to the rear side member 124 can be redirected to the floor side member 128, which is more rigid or heavier 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 Figure 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. This makes it easier for the load transmitted from the rear side member 124 to the rear end 194 of the floor side member 128 to be released towards the first rear cross member 202, thereby suppressing vibration of the floor side member 128. Furthermore, since vibrations are more 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, vibrations of the rear side member 124 and the first rear cross member 202 can also be suppressed. In addition, since the floor side member 128 is connected on top of 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. Furthermore, the floor side member 128 supports the rear side member 124 and is further connected to the first rear cross member 202 and the second rear cross member 204. As a result, the support rigidity of the floor side member 128 is increased, which can suppress vibrations of the rear side member 124 in the direction of the swing axis or the vehicle width.

[0051] As shown in Figure 1, in the vehicle understructure 100, a frame structure is formed by the floor side members 128, 130, the first rear cross member 202, and the second rear cross member 204, and further frame structures are formed by the rear side members 124, 126, the first rear cross member 202, and the second rear cross member 204. Therefore, the overall rigidity of each member constituting these frame structures can be increased, thereby increasing the support rigidity of the rear side members 124, 126 and the floor side members 128, 130.

[0052] In the vehicle understructure 100 shown in Figure 2(a), we assume that the load transmission path transmitted to the rear side member 124 via the suspension fixing part 120 branches in a direction intersecting the oscillation axis direction of the oscillation axis Sa, for example, to the front or rear of the vehicle. In this case, as shown in Figure 2(a), the vehicle understructure 100 has a first rear cross member 202 and a second rear cross member 204 spaced apart in the longitudinal direction of the vehicle, positioned on either side of the oscillation axis Sa. Therefore, the vehicle understructure 100 can transmit loads transmitted downstream of the branching point of the load transmission path to the first rear cross member 202 or the second rear cross member 204. As a result, vibrations of the rear side member 124 in the oscillation axis direction or vehicle width direction can be suppressed, and torsional vibrations and floor vibrations caused by these vibrations can be reduced.

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

[0054] Furthermore, the floor side member 128, together with the rear side member 124 and the second rear cross member 204, forms a closed section 212 of a triangular truss structure as a frame structure enclosed by the dashed line H in Figure 2(a). This increases the overall rigidity of the floor side member 128, rear side member 124, and second rear cross member 204 by the closed section 212, thereby increasing the support rigidity of the rear side member 124. As a result, vibrations of the rear side member 124 in the oscillation axis direction or vehicle width direction are suppressed, and vibrations of the floor side member 128 are also suppressed, thus reducing torsional vibrations and floor vibrations caused by these vibrations. Moreover, since one of the components of the closed section 212 is the floor side member 128 extending forward of the vehicle, it becomes easier to make adjustments such as distributing the load to the floor side member 128 side to avoid stress concentration.

[0055] Furthermore, in the vehicle understructure 100, the rear side member 124 has an inclined portion 146 as shown in Figure 1, and the side surface 198 of the rear side member 124, which is connected to the rear end portion 194 of the floor side member 128, is formed on this inclined portion 146. Therefore, the connection area between the floor side member 128 and the rear side member 124 can be increased without having to significantly incline the rear end portion 194 of the floor side member 128 to bring it closer to the rear side member 124. As a result, the connection rigidity between the floor side member 128 and the rear side member 124 can be increased.

[0056] Therefore, the vehicle understructure 100 suppresses deformation of the floor side member 128 so as to compress in the longitudinal direction of the vehicle even when subjected to load from the longitudinal direction of the vehicle, while suppressing vibration of the rear side member 124 in the direction of the oscillation axis or the vehicle width direction, thereby reducing torsional vibration and floor vibration caused by this vibration. Furthermore, in the vehicle understructure 100, the rear side member 124, which is 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 vibration of the suspension 132 can also be suppressed.

[0057] Furthermore, the floor side member 128 has a recess 214 that is recessed inward in the vehicle width direction between the rear side member 124 and the front member 162 shown in Figure 1, and is connected to the side surface 198 of the rear side member 124 (see Figure 2(a)) at the recess 214. 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, since 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 can be increased, thereby improving the connection rigidity.

[0058] Here, as shown in Figure 1, the vehicle understructure 100 has floor side members 128 and 130 positioned between the side sills 104 and 106 and the center tunnel 108, respectively. For this reason, the floor panel 102 is divided in the vehicle width direction with the floor side members 128 and 130 as the boundary.

[0059] Therefore, in the vehicle understructure 100, in order to suppress floor vibration, a configuration is adopted in which the floor side members 128 and 130 are positioned close together at intermediate positions 216 and 218 of the floor vibration surface on the floor panel 102. The intermediate position 216 of the floor vibration surface is the 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 is approximately the same as the dimension Lb between the side sill 104 and the floor side member 128.

[0060] Figure 4 shows a part of the vehicle understructure 100 of Figure 1 and a modified example. The floor side member 128 has a front inclined portion 220, a straight portion 222, and a rear inclined portion 224, as shown in Figure 4(a). The front inclined portion 220 is the part that slopes inward in the vehicle width direction as it approaches the rear of the vehicle. The straight portion 222 is the part that extends straight toward the rear of the vehicle from the rear end 226 of the front inclined portion 220. The rear inclined portion 224 is the part that slopes outward in the vehicle width direction as it approaches the rear of the vehicle from the rear end 228 of the straight portion 222.

[0061] In this way, the vehicle understructure 100 has two inclined sections on the floor side member 128, namely a front inclined section 220 and a rear inclined section 224. As a result, even if the connection point between the front member 162 or front side member 164 and the rear side member 124, located at the front and rear of the vehicle, is far from the intermediate position 216 of the floor vibration surface, the degree of inclination and length of the two inclined sections can be adjusted to bring the straight section 222 located between the two inclined sections closer to the intermediate position 216 of the floor vibration surface. Therefore, according to the vehicle understructure 100, floor vibration can be suppressed by bringing the straight section 222 of the floor side member 128 closer to the intermediate position 216 of the floor vibration surface.

[0062] In other words, the floor side member 128, with the front inclined portion 220 and the rear inclined portion 224, can bring the straight portion 222 closer to and position at an intermediate position between the side sill 104 and the center tunnel 108, that is, at an intermediate position 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 way, in the vehicle understructure 100, as shown in Figure 1, the straight portion 222 of the floor side member 128 is positioned overlapping at the intermediate position 216. As a result, the dimensional difference between one side and the other side of the floor vibration surface of the floor panel 102 is reduced with respect to the straight portion 222, meaning that dimensions La and Lb approach the same dimension, thus suppressing floor vibration.

[0064] As shown in Figure 4(a), the floor side member 128 further has a suspension frame connection portion 230. The suspension frame connection portion 230 extends straight forward from the front end 232 of the front inclined portion 220, and the front suspension frame 168 is connected to it at the rear fixing point 180 (see Figure 1). The front end 232 of the front inclined portion 220 is positioned to overlap with the inclined surfaces of the braces 169a and 169b shown in Figure 1 in the vehicle width direction.

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

[0066] As shown in Figure 4(a), in the floor side member 128, the suspension frame connection portion 230, which is a different part from the front inclined portion 220, extends straight forward from the front end 232 of the front inclined portion 220. Therefore, in the vehicle understructure 100, compared to the case where the connection portion to the front suspension frame 168 is provided on the front inclined portion 220 itself, it becomes easier to position the rear fixing point 180 of the connection between the suspension frame connection portion 230 and the front suspension frame 168 outward in the vehicle width direction.

[0067] As a result, when a load in the vehicle width direction is applied to the floor side member 128, the load can be easily distributed and relieved from the rear fixing point 180 of the suspension frame connection part 230 to the front fixing point 188 (see Figure 1) of the front suspension frame 168, which is connected to the front side member 176 on the left side in the vehicle width direction. Therefore, vibrations of the front side member 176 itself can be suppressed, and floor vibrations can be suppressed.

[0068] Furthermore, even if the front fixing points 188 and 190 of the front suspension frame 168, which are set on the front side members 164 and 176 in Figure 1, or the torque rod (not shown) connected to the front suspension frame 168, are subjected to a load in the vehicle width direction, this load can be easily distributed and relieved to the floor side members 128 and 130. As a result, vibrations of the front suspension frame 168 are suppressed, and stability during steering can be improved.

[0069] As shown in Figure 4(a), since the suspension frame connection portion 230 extends straight forward from the front end 232 of the front inclined portion 220, when the front inclined portion 220 receives a load from the front, the front inclined portion 220 deforms in the vehicle width direction, which can suppress the rearward movement of front members 162 such as the dash cross member 166 or the front suspension frame 168 shown in Figure 1.

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

[0071] As shown in Figure 4(a), a 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 the connection position 238 to which the second rear cross member 204 is connected. The second rear inclined portion 236 is located behind this connection position 238. Furthermore, the degree of inclination of the first rear inclined portion 234 outward in the vehicle width direction is gentler than the degree of inclination of the second rear inclined portion 236. As a result, when the floor side member 128 is subjected to a load from the front, localized stress concentration is less likely to occur, and deformation in the vehicle width direction caused by this load can be suppressed.

[0072] As shown in Figure 4(a), since the inclination of the first rear inclined section 234 is gentler than that of the second rear inclined section 236, the degree of change in the difference in dimensions in the vehicle width direction between one side and the other side of the floor vibration surface with the first rear inclined section 234 as the boundary is also gentler, thus suppressing floor vibration. If the inclination of the second rear inclined section 236 as well as the first rear inclined section 234 were to be made gentler, the dimensions of the rear inclined section 224 in the vehicle longitudinal direction would increase, and the dimensions of the straight section 222 in the vehicle longitudinal direction would be restricted.

[0073] Therefore, in the vehicle understructure 100, the degree of inclination of the second rear inclined section 236 of the rear inclined section 224 is made steeper and greater than the degree of inclination of the first rear inclined section 234, thereby suppressing an increase in the overall front-to-rear dimensions of the rear inclined section 224 and securing space for arranging the straight section 222 that extends in the front-to-rear direction of the vehicle.

[0074] Furthermore, increasing the degree of inclination of the second rear inclined section 236 tends to cause localized stress concentration in the second rear inclined section 236 when subjected to a load from the front, making it more susceptible to deformation in the vehicle width direction. Therefore, in the vehicle understructure 100, by setting a connection point 238 with the second rear cross member 204 in front of the second rear inclined section 236, the deformation of the second rear inclined section 236 in the vehicle width direction can be suppressed by the second rear cross member 204.

[0075] Furthermore, in the vehicle understructure 100, the vibration surface of the floor panel 102 shown in Figure 1 is divided by the upward inclined portions 116 and 118 with respect to the floor horizontal plane 114, thereby suppressing surface vibration. Moreover, since the upward inclined portions 116 and 118 are provided on the outer side in the vehicle width direction of the floor horizontal plane 114, it becomes easier to position the floor side members 128 and 130 towards the center in the vehicle width direction, and it becomes easier to bend them toward the rear side members 124 and 126 in order to connect them to the rear side members 124 and 126. In the vehicle understructure 100, by positioning the floor side members 128 and 130 at intermediate positions 216 and 218 of the floor vibration surface, the vibration surface of the floor horizontal plane 114 of the floor panel 102 is divided into four almost equally in the vehicle width direction.

[0076] Figure 5 shows the vehicle understructure 100 of Figure 4(a) viewed from a different direction. Figures 5(a) and 5(b) show the floor side members 128 and 130 viewed from diagonally below and diagonally above, respectively.

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

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

[0079] Therefore, in the vehicle understructure 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, thereby improving connection rigidity, suppressing deformation and vibration of the floor side member 128, and also suppressing floor vibration.

[0080] Figures 4(b) and 4(c) are schematic diagrams of the floor side member 128 and a modified floor side member 128A, both embodiments of the present invention. The dashed lines I and J in the figures indicate the state of the floor side members 128 and 128A during a frontal collision.

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

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

[0083] The vehicle understructure 100 further includes a connecting member 254 extending along the front side of the second rear cross member 204, as shown in Figure 4(a), and brackets 256 and 258 located on the outside of the connecting member 254 in the vehicle width direction. The connecting member 254 connects the upper bulge 242 and the bracket 256 by joining the upper surface 244 and front surface 246 of the upper bulge 242. The bracket 256 clamps the rear side frame 124 shown in Figure 1 together with the second rear cross member 204 from above and below, and is also connected to the side sill 104 (see Figure 6).

[0084] Furthermore, in the vehicle understructure 100, as shown in Figure 5(a), the connecting member 254 is connected by sandwiching it in the vehicle width direction at the upper part of the floor side members 128 and 130. This configuration increases the connection surface area between the second rear cross member 204 and the floor side members 128 and 130, thereby increasing the connection rigidity. Moreover, as shown in Figure 5(b), a bracket fixing portion 259 for fixing a rear seat mounting bracket (not shown) is provided in the region spanning the rear end 250 and the upper end 152 of the second rear cross member 204. By arranging this bracket fixing portion 259 and the upper bulge portion 242 of the floor side member 128 to overlap in the vertical direction, vibration of the rear seat (not shown) in the vertical direction can be suppressed.

[0085] Figure 6 shows a view of a portion of the vehicle understructure 100 shown in Figure 1, from the front of the vehicle. As shown in Figure 6, the vehicle understructure 100 sandwiches the rear side frame 124 and the side sill 104 between the lower surface 260 of the outer end of the second rear cross member 204 and the upper surface 262 of the outer end of the bracket 256.

[0086] Figure 7 is a detailed diagram showing a modified version of the vehicle understructure 100 of Figure 1. Figure 7(a) is a bottom view of a part of the modified vehicle understructure 100A. Figure 7(b) shows the vehicle understructure 100A of Figure 7(a) viewed from diagonally below. Figure 8 shows the vehicle understructure 100A of Figure 7 viewed from another direction.

[0087] The modified vehicle understructure 100A differs from the above-described vehicle understructure 100 in that it includes a second rear cross member 204A, which is a component including connecting members 254 and brackets 256 and 258, instead of the second rear cross member 204.

[0088] In the vehicle understructure 100A, as shown in Figure 7(a), 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, which are joined to the second rear cross member 204A, are joined to each other.

[0089] Therefore, in the vehicle understructure 100A, the rigidity of the member supporting the second rear cross member 204A, i.e., the support rigidity of the second rear cross member 204A, can be increased, while the load and vibration transmitted to the second rear cross member 204A can be distributed and released to the side sill 104 and rear side member 124. Consequently, vibration of the 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 enclosed by the dotted line K in the figure, where the lower flange 268, side sill 104, and rear side member 124 of the second rear cross member 204A overlap in the vertical direction.

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

[0092] This increases the area of ​​joint between the three components, the second rear cross member 204A, the side sill 104, and the rear side member 124, while allowing these components to be firmly joined in the vertical and vehicle width directions by the first joint 264 and the second joint 266. Therefore, in the vehicle understructure 100A, the connection rigidity of the second rear cross member 204A to the side sill 104 and the rear side member 124 can be increased, thereby suppressing vibrations of the second rear cross member 204A, especially torsional vibrations.

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

[0094] Thus, the widened portion 276 of the second rear cross member 204A has a third joint portion 278 which is joined to the rear side member 124 in a two-piece configuration, and a first joint portion 264 and a second joint portion 266 which are joined to the side sill 104 and the rear side member 124 in a three-piece configuration. Therefore, the connection area of ​​the second rear cross member 204A to the rear side member 124 can be increased, thereby increasing the connection rigidity of the second rear cross member 204A.

[0095] Furthermore, the second rear cross member 204A allows vibrations and loads from the rear side member 124 to 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 from the rear side member 124 are transmitted to the side sill 104, suppressing vibrations of the second rear cross member 204A.

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

[0097] The fifth joint 284 is the area enclosed by the dotted line O in the figure, and is adjacent to the fourth joint 282. It does not overlap with the floor panel 102, and is joined to the upper flange 288 of the second rear cross member 204A and the upper surface 286 of the side sill 104 in the vertical direction. The fifth joint 284 is not limited to this, and may be joined to three parts so as to overlap with the floor panel 102. Alternatively, as a modification, 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 three parts.

[0098] When spot welding four or more plates, the stability of the welding process decreases, increasing joining costs and time. Therefore, instead of joining four plates, by separating the part of the second rear cross member 204A that joins the side sill 104 in three pieces from the part that joins the floor panel 102 in three pieces, welding work and welding time can be shortened compared to joining the second rear cross member 204A, side sill 104, rear side member 124, and floor panel 102 in four pieces. Moreover, by arranging the fourth joint 282, which is a three-piece joint that joins the floor panel 102, and another first joint, which is a modified version of the fifth joint 284 that joins the side sill 104, adjacent to each other, vibrations of the floor panel 102 can be easily dispersed and released from the other first joint to the adjacent fourth joint 282. As a result, vibrations of the floor panel 102 can be transmitted to the side sill 102 and the second rear cross member 204A, suppressing vibrations of the floor panel 102. Furthermore, if the joining cost and joining time are acceptable, the second rear cross member 204A, side sill 104, rear side member 124, and floor panel 102 may be joined together in a four-piece configuration.

[0099] The vehicle understructure 100A also has other joints 290 and 292. Joint 290 is the area enclosed by the dotted line P in Figure 8, and is joined to the floor panel 102, the rear side member 124, and the second rear cross member 204A in a three-piece overlapping manner in the vertical direction. Joint 292 is joined to the side sill 104 and the rear side member 124 in a two-piece overlapping manner in the vertical direction, as shown in Figures 7(a) and 7(b). However, joint 292 is not limited to this, and the second rear cross member 204A may be extended to join to the side sill 104 and the rear side member 124 in a three-piece overlapping manner.

[0100] The rear side member 124 shown in Figure 7(b) has an inner side surface 296 adjacent to the side flange 294 of the second rear cross member 204A, an upper flange 298 continuous with the inner side surface 296, a side flange 300 continuous with the lower surface 280, and a lower flange 302 continuous with the side flange 300. Here, the rear side member 124 forms a closed cross section with the upper 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 shared with the inner side surface 272 of the side sill 104. Because the rear side member 124 is cantilevered, the side flange 300 and the lower flange 302 are provided on its lower surface 280 to increase the contact area with the side sill 104.

[0101] In the vehicle understructure 100A, the second rear cross member 204A is joined to the side sill 104 and the rear side member 124 such that it overlaps with the joint surface between the side sill 104 and the rear side member 124, i.e., the locations of the first joint 264 and the second joint 266 where three pieces are joined together.

[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 in close proximity or overlapping. This increases the support rigidity of the second rear cross member 204A. Furthermore, by joining the second rear cross member 204A to the joint surfaces of the side sill 104 and the rear side member 124, which now have 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. Consequently, vibrations of the second rear cross member 204A can be suppressed more effectively.

[0103] Here, at point Q of the vehicle understructure 100 shown in Figure 2(a), the rear side member 124 is connected to the first rear cross member 202 and the floor side member 128, thereby increasing the support rigidity of the second rear cross member 204A. At point Q, the floor side member 128, the first rear cross member 202, and the rear side member 124 are joined together in a three-piece configuration, overlapping in the vertical direction. Adjacent to the region including point Q where these three pieces are joined, there are regions where the rear side member 124 and the floor side member 128 are joined together in a two-piece configuration, a region where the floor panel 102 is also joined in a three-piece configuration, and a region where the first rear cross member 202 and the floor side member 128 are joined together in a two-piece configuration. This allows for a more substantial increase in the support rigidity of the second rear cross member 204A.

[0104] In Figure 2(a), the dotted line R in the vehicle understructure 100 indicates the joining region between the side sill 104 and the rear side member 124. In this joining region, a recess 304 is provided at the rear of the rear of the side sill 104, and the 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 longitudinal and width directions of the vehicle, thereby increasing the support rigidity of the second rear cross member 204A.

[0105] Furthermore, the rear portion 307 of the widened section 276 of the second rear cross member 204A, as shown in Figure 2(a), extends in a direction substantially perpendicular to the inner side surface 296 of the rear side member 124 (see Figure 7(b)). The rear portion 307 of the widened section 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 on the inside of the outer portion 307b in the vehicle width direction. As shown in Figure 2(a), this inner portion 307a has a greater degree of inclination than the outer portion 307b and is inclined to follow the rear inclined portion 224 of the floor side member 128 (see Figure 4(a)). This configuration increases the contact area between the widened section 276 and the front end portion 208 of the rear side member 124, while also facilitating the transmission of vibrations transmitted to the widened section 276 to the front side of the floor side member 128. Furthermore, if the inner portion 307a of the rear portion 307 of the widened portion 276 is inclined along the pivot axis Sa that passes through the suspension fixing portion 120, vibrations transmitted from the suspension fixing portion 120 to the rear side member 124 are more 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 understructure 100, the front side member 164, floor side member 128, and rear side member 124 are shown as separate components, but the vehicle is not limited to this and may be an integrated structure. In this specification, the term "side member" refers to a concept that includes all of the front side member 164, floor side member 128, and rear side member 124.

[0107] Figure 9 schematically shows other modifications of the vehicle understructure 100 of Figure 1. In the vehicle understructures 100B and 100C shown in Figure 9(a), when the oscillation axes Ta and Tb are in the vehicle width direction and the vehicle longitudinal 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 the vehicle width direction, i.e., the side surfaces 308 and 310, respectively. Even with such vehicle understructures 100B and 100C, vibrations of the rear side member 124 in the oscillation axis direction or the vehicle width direction can be suppressed.

[0108] In the vehicle understructures 100D and 100E shown in Figure 9(b), when the oscillation axes Ta and Tb are in the vehicle width direction and the vehicle longitudinal direction, the floor side member 128 and the suspension fixing part 120 are connected to the vertically opposing regions of the rear side member 124, namely the upper surface 312 and the lower surface 314, respectively. Even with such vehicle understructures 100D and 100E, vibrations of the rear side member 124 in the oscillation axis direction or the vehicle width direction can be suppressed.

[0109] In the vehicle understructures 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 this configuration. For example, when the shock absorber 142 of the suspension 132 (see Figure 2(a)) 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 longitudinal direction is smaller than the width dimension of the suspension fixing part 120 in the vehicle longitudinal direction.

[0110] In the vehicle understructures 100F and 100G shown in Figure 9(c), when the oscillation axes Ta and Tb are in the vehicle width direction and the vehicle longitudinal direction, the floor side member 128 and the rear side member 124 are arranged to face each other in the vehicle width direction via the suspension fixing part 120 and are connected to the suspension fixing part 120, respectively. Even with such vehicle understructures 100F and 100G, vibrations of the rear side member 124 in the oscillation axis direction or the vehicle width direction can be suppressed.

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

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

[0113] Therefore, even if the connection point between the front member 162 or front side member 164 and the rear side member 124, as shown in Figure 1, located at the front and rear of the vehicle on the floor side member 128B, is located further away from the intermediate position 216 of the floor vibration surface (see Figure 1), floor vibration can be suppressed by adjusting the degree of inclination and length of the two inclined sections, namely the front inclined section 220A and the rear inclined section 224, to bring the straight section 222 located between the two inclined sections closer to the intermediate position 216 of the floor vibration surface.

[0114] In the vehicle understructure 100, as shown in Figure 1, 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 side sill 104, are located outward 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 inward in the vehicle width direction from the intermediate position 216, and the rear end position is located outward in the vehicle width direction from the intermediate position 216.

[0115] However, the modifications are not limited to those shown in Figure 10(a). Although not shown, one of the front and rear ends of the floor side member may be positioned further outward in the vehicle width direction than the intermediate position 216. Alternatively, one of the front and rear ends of the floor side member may be located at the intermediate position 216. When the front end 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 section 222. When the rear end 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 section 222.

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

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

[0118] In the vehicle understructure 100I shown in Figure 10(c), the rear side member 124B is positioned on the rear side of the side sill 104B, and the side sill 104B and the rear side member 124B are joined to each other, with the side sill 104B and the rear side member 124B being joined to the second rear cross member 204B. Furthermore, as shown in the figure, the joining surfaces 324 of the side sill 104B and the rear side member 124B, the joining surface 326 of the second rear cross member 204B and the side sill 104B, and the joining surface 328 of the second rear cross member 204B and the rear side member 124B are brought into close proximity.

[0119] Therefore, in the vehicle understructure 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 are distributed and released to the side sill 104B and rear side member 124B. Consequently, vibration of the second rear cross member 204B can be suppressed.

[0120] The vehicle understructure 100 may have multiple suspension fixing points corresponding to multiple pivot axes. In such cases, the suspension fixing point 120 and floor side member 128 corresponding to any one of the pivot axes can be connected to adjacent or opposing areas of the rear side member 124, respectively. This makes it possible to suppress vibrations of the rear side member 124 in the pivot axis direction or the vehicle width direction.

[0121] Preferred embodiments of the present invention have been described above with reference to the attached drawings, but it goes without saying that the present invention is not limited to such examples. It is clear to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of the present invention. [Industrial applicability]

[0122] This invention can be used in the undercarriage of a vehicle. [Explanation of symbols]

[0123] 100, 100B~100I…Vehicle understructure 102, 102A… Floor panel 104, 104A, 104B, 106... Side sill 108, 108A... Center Tunnel 110, 112... Edge of floor panel 114... Floor horizontal plane 116, 118...Upward slope 120, 122... Suspension mounting parts 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 absorbers 144... Front end of trailing link 146... Inclined section of the rear side member 148... Rear end of the vehicle 150... Wheel carrier 152...Tie rod 154...Lower A-arm link 158... Front end of the lower A-arm link 160...Rear end of the lower A-arm link 162…Front Member 164, 176… Front side members 166... ​​Dash Cross Member 168…Front suspension frame 169a, 169b... braces 170, 174... Front side extensions 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 the rear side member 200... Around the suspension 202...First rear cross member 204, 204A, 204B... Second rear cross member 208, 210... Front end of rear side member 212...Closed section 214… Recess of floor side member 216, 218...Intermediate positions of the floor vibration plane 220, 220A... Front inclined section 222...Straight section 224, 224A... Rear inclined section 226, 226A... Rear end of the front sloping section 228...Rear end of the straight section 230... Suspension frame connection 232, 232A... Front end of the front sloping section 234...First rear inclined section 236...Second rear inclined section 238...Connection position of the second rear cross member 240...Side view of the second rear inclined section 242...Upward bulge 244... Upper surface of the upward bulge 246...Front view of the upper bulge 248... Front end of the upward bulge 250...Rear end of the second rear cross member 252... Upper end of the second rear cross member 254…Connecting member 256, 258… brackets 259...Bracket fixing part 260...Underside of the outer end of the second rear cross member 262... Upper surface of the outer end of the bracket 264...1st joint 266...Second joint 268... Lower flange of the second rear cross member 270, 294... Side flange of the second rear cross member 272... Inner side of the side sill 274... Lower end of the second rear cross member 276... Widening section 278...Third joint 282…4th joint 284...5th joint 286... Top surface of the side sill 288... Upper flange of the second rear cross member 290, 292... Other joints 296...Inner side of the rear side member 298... Upper surface of the rear side member 300... Rear side member side flange 302... Lower flange of the rear side member 304... Recess in the side sill 306... protruding part of the rear side member 307...Rear of the widened section 307a...Inner part of the rear of the widened section 307b... Rear outer portion of the widened section 308, 310... Side of the rear side member 312... Upper surface of the rear side member 316…Side of the floor panel 318... Side of the rear side member 320…Reinforcement member 322... Cross member 324, 326, 328…Joint surface

Claims

1. Floor panels that form the floor surface of the vehicle, A side sill extending in the vehicle's longitudinal direction along the edge of the floor panel, A side member is positioned on the underside of the floor panel, on the inside of the side sill in the vehicle width direction, and extends in the vehicle longitudinal direction. In a vehicle understructure comprising a cross member joined to the side sill, The aforementioned side member is An inclined section extending outward in the width direction of the vehicle, It has a connecting portion that connects the inclined portion and the side sill, The cross member is connected to the inclined portion, forming a frame structure enclosed by the inclined portion and the connecting portion. The side member has a portion that connects to the side sill rearward from the cross member, The vehicle understructure is characterized in that the cross member is connected to the aforementioned portion.

2. The vehicle understructure according to claim 1, characterized in that the frame structure is a truss structure.

3. The vehicle understructure according to claim 1 or 2, characterized in that the cross member has a widened portion that widens toward the side member and is connected to the side member.

4. A floor panel that forms the floor surface of a vehicle, A side sill extending in the vehicle's longitudinal direction along the edge of the floor panel, A side member is positioned on the underside of the floor panel, on the inside of the side sill in the vehicle width direction, and extends in the vehicle longitudinal direction. In a vehicle understructure comprising a cross member joined to the side sill, The aforementioned side member is An inclined section extending outward in the width direction of the vehicle, It has a connecting portion that connects the inclined portion and the side sill, The cross member is connected to the inclined portion, forming a frame structure enclosed by the inclined portion and the connecting portion. The aforementioned side sill has a recess at the rear that is recessed outward in the vehicle width direction, The vehicle understructure is characterized in that the side member has a protrusion connected to the recess.

5. The side member has a portion that extends forward of the protrusion and is connected to the side sill. The vehicle understructure according to claim 4, characterized in that the cross member is connected to the aforementioned portion.

6. A floor panel that forms the floor surface of a vehicle, A side sill extending in the vehicle's longitudinal direction along the edge of the floor panel, A side member is positioned on the underside of the floor panel, on the inside of the side sill in the vehicle width direction, and extends in the vehicle longitudinal direction. In a vehicle understructure comprising a cross member joined to the side sill, The aforementioned side member is An inclined section extending outward in the width direction of the vehicle, It has a connecting portion that connects the inclined portion and the side sill, The cross member is connected to the inclined portion, forming a frame structure enclosed by the inclined portion and the connecting portion. A rear cross member is provided behind the aforementioned cross member. The vehicle understructure is characterized in that the inclined portion of the side member is connected to the rear cross member.

7. The inclined portion of the side member has a bulge that protrudes outward in the vehicle width direction, The vehicle understructure according to claim 6, characterized in that the bulging portion is connected to the connecting portion.

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