Vehicle underbody structure

Abstract

To provide a vehicle lower part structure which can disperse loads and vibrations transmitted from a vehicle anteroposterior direction and a vehicle width direction over an entire vehicle to improve steering stability and NV characteristics of the vehicle.SOLUTION: A vehicle lower part structure 100 includes: a front member 104 located at a front part of a floor panel 102 forming a floor surface of a vehicle; a rear member 106 located at the vehicle rear relative to the front member; a pair of floor side members 108, 110 which connects the front member with the rear member; and a pair of side sills 112, 114 which are disposed at the outer side as seen in a vehicle width direction of the pair of floor side members and extend in a vehicle anteroposterior direction along edges 140, 142 of the floor panel. Each of the pair of floor side members has arc-shaped parts 144, 146, each of which is formed in an arc shape protruding to the outer side in the vehicle width direction, connects the front member with the rear member, and is connected to one of the pair of side sills located at the outer side as seen in the vehicle width direction of the arc-shaped parts.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] A vehicle such as an automobile is provided with a vehicle understructure that connects a front member composed of various members located at the front of the vehicle to a rear member composed of various members located at the rear of the vehicle by floor side members disposed under the floor panel. Such a vehicle understructure distributes loads and vibrations transmitted to the vehicle in the fore-and-aft direction of the vehicle and supports them across the entire frame of the vehicle, thereby suppressing vibrations.

[0003] On the other hand, when the vehicle turns, vibrations and loads (e.g., centrifugal force and inertial force) occur in the vehicle width direction. By distributing the vibrations and loads in the vehicle width direction, it is possible to suppress the vibration of the floor panel, for example, thereby improving the vehicle's noise and vibration (NV) characteristics and further increasing the vehicle's handling stability (maneuverability). For this reason, it is necessary to distribute the vibrations and loads acting in the vehicle's lower structure in the vehicle width direction.

[0004] Patent Document 1 describes a suspension support structure for an automobile. This support structure includes a pair of main side frames 1 extending in the vehicle longitudinal direction, a pair of side sills 2 extending in the vehicle longitudinal direction at a predetermined distance on the outer sides of the main side frames 1 in the vehicle width direction, a plurality of cross members 31-35 extending in the vehicle width direction and spaced apart in the vehicle longitudinal direction, and a plurality of torque boxes 41-43. The multiple cross members 31-35 connect the pair of main side frames 1.

[0005] In the support structure of Patent Document 1, the main side frame 1 and side sill 2 adjacent in the vehicle width direction are connected by multiple torque boxes 41-43, while the cross members 31-35 adjacent in the vehicle front-rear direction are connected by connecting members 37, 38. In this way, this support structure increases the rigidity of the underside of the floor panel while improving the efficiency of energy absorption during a side collision. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4349039 Summary of the Invention [Problem to be solved by the invention]

[0007] In the support structure of Patent Document 1, when loads or vibrations are applied in the vehicle width direction, the loads and vibrations are concentrated around the joints between the main side frame 1 and the cross members 31-36, and it is considered difficult to efficiently transmit these loads and vibrations to the front and rear sides of the joints.

[0008] Furthermore, in the support structure of Patent Document 1, even when loads or vibrations are transmitted from the front of the main side frame 1, no particular effort is made to efficiently transmit these loads and vibrations from one main side frame 1 to the other main side frame 1 and side sill 2, and there is room for improvement.

[0009] Therefore, the support structure of Patent Document 1 is unable to efficiently transmit and distribute load and vibration throughout the vehicle's skeletal members, which may result in torsional vibration of the vehicle body and floor vibration of the floor panel.

[0010] In view of these problems, the present invention aims to provide a vehicle underbody structure that can distribute loads and vibrations transmitted from the vehicle fore-and-aft direction and vehicle width direction throughout the entire vehicle, thereby improving vehicle handling stability and NV characteristics. [Means for solving the problem]

[0011] 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 front member located at the front of the floor panel, a rear member located rearward of the front member, a pair of floor side members connecting the front member and the rear member, and a pair of side sills disposed on the vehicle width outer sides of the pair of floor side members and extending in the fore-and-aft direction of the vehicle along the edges of the floor panel, each of the pair of floor side members having an arc-shaped portion that convex outward in the vehicle width direction and connects the front member and the rear member, and which is connected to one of the pair of side sills located on the vehicle width outer side of the arc-shaped portion. Effect of the Invention

[0012] According to the present invention, a vehicle underbody structure can be provided that can distribute loads and vibrations transmitted from the vehicle fore-and-aft direction and vehicle width direction throughout the vehicle, thereby improving vehicle handling stability and NV characteristics. [Brief description of the drawings]

[0013] [Figure 1] 1 is a bottom view showing a vehicle underbody structure according to an embodiment of the present invention. [Diagram 2] 2 is a diagram showing a state in which a part of the vehicle underbody structure in FIG. 1 is viewed from another direction. [Diagram 3] FIG. 2 is a diagram showing a part of the vehicle underbody structure of FIG. [Figure 4] 4 is a diagram showing a state in which a load or vibration is transmitted from a front member or a rear member to the vehicle underbody structure of FIG. 3. [Diagram 5] 4 is a diagram showing a modified example of the vehicle underbody structure of FIG. 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] A typical configuration of a vehicle underbody structure according to one embodiment of the present invention is a vehicle underbody structure having a floor panel that forms the floor surface of the vehicle, the vehicle underbody structure further comprising a front member located in front of the floor panel, a rear member located rearward of the front member, a pair of floor side members connecting the front member and the rear member, and a pair of side sills disposed on the vehicle width outer sides of the pair of floor side members and extending in the fore-and-aft direction of the vehicle along the edges of the floor panel, each of the pair of floor side members having an arc-shaped portion that convex outward in the vehicle width direction and connects the front member and the rear member, and which is connected to one of the pair of side sills located on the vehicle width outer side of the arc-shaped portion.

[0015] In the above configuration, the front member, the rear member, and the side sill are connected to the floor side member by an arc-shaped portion that is convex on the vehicle width direction outer side. The term "arc-shaped" is not limited to a circular arc-shaped portion that is a part of a circle, but also includes an arc-shaped portion that is a part of an ellipse. Therefore, when a load or vibration is transmitted from the vehicle front-rear direction or the vehicle width direction, the load or vibration is transmitted between the front member and the side sill and between the rear member and the side sill through the arc-shaped floor side member. This makes it possible to efficiently disperse the load or vibration by preventing it from concentrating locally when transmitting the load or vibration between the front member and the side sill and between the rear member and the side sill. Therefore, according to the above configuration, it is possible to improve the vehicle's NV (Noise and Vibration) characteristics by suppressing the vibration of the floor panel while improving the vehicle's steering stability (maneuverability).

[0016] It is preferable that the front ends of the arcuate portions of the pair of floor side members are connected to each other in the vehicle width direction, and the rear ends are connected to each other in the vehicle width direction.

[0017] As a result, the front member, rear member and pair of side sills are connected to one another via the arc-shaped portions of the pair of floor side members, so that loads transmitted in the vehicle longitudinal direction and vehicle width direction can be efficiently distributed between the pair of side sills, between the pair of arc-shaped portions, and between the front member and rear member.

[0018] The above-mentioned front member includes a pair of front side members located forward of the pair of side sills, each of the pair of front side members having a tail portion connected to the arc-shaped portion, the tail portion being inclined inward in the vehicle width direction toward the rear of the vehicle so as to be approximately perpendicular to the tangent direction of the arc-shaped portion.

[0019] In this way, the tail portions of the pair of front side members are inclined so as to be substantially perpendicular to the tangent direction of the arcuate portions of the pair of floor side members and are connected to the arcuate portions, so that the load and vibration transmitted from the tail portions of the pair of front side members can be reliably transmitted to the arcuate portions of the pair of floor side members and can be efficiently dispersed to the pair of side sills and the rear member via the arcuate portions.

[0020] The vehicle underbody structure may further include a pair of braces connecting the pair of floor side members and the pair of side sills, respectively, and each of the pair of braces may be joined in an arcuate shape to the arcuate portion.

[0021] In this way, the floor side member and the side sill are connected via a brace that is joined in an arc to the arc portion of the floor side member, which makes it possible to prevent loads and vibrations from concentrating locally between the side sill and the arc portion, and to efficiently transmit and disperse these loads and vibrations.

[0022] Each of the pair of floor side members further has a bulge portion formed in an arc-shaped portion and bulging toward the bottom of the vehicle, and the bulge portion has a lower surface to which a suspension fixing portion that fixes a swaying suspension for the front wheels is fixed, and an inclined surface that slopes downward from the fore-and-aft direction of the vehicle toward the lower surface.

[0023] In this way, a bulge that bulges out towards the bottom of the vehicle is formed in the arc-shaped portion of the floor side member, the suspension fixing part is fixed to the underside of the bulge, and furthermore, inclined surfaces are formed on the front and rear of the underside of the bulge. Therefore, when loads or vibrations are transmitted from the suspension fixing part, these loads and vibrations can be efficiently transmitted and dispersed from the underside of the bulge of the arc-shaped portion of the floor side member via the inclined surfaces to the front member, side sill and rear member.

[0024] The bulge may be formed in an arc shape along the arc portion.

[0025] As a result, when load or vibration is transmitted from the suspension fixing part, the load or vibration can be efficiently transmitted and dispersed to the side sill via the arc-shaped bulge. Also, the load or vibration transmitted from one suspension fixing part can be transmitted and dispersed to the other floor side member via the arc-shaped bulge of one floor side member.

[0026] The above-mentioned vehicle undercarriage structure further includes a center tunnel extending upwardly in the fore-and-aft direction of the vehicle at the center of the floor panel in the vehicle width direction, a pair of floor cross members extending in the vehicle width direction on the upper surface of the floor panel and connecting the center tunnel to each of the pair of side sills, and a reinforcing member provided inside the center tunnel in a position overlapping the pair of floor cross members when viewed from the vehicle width direction, wherein the center tunnel is positioned so as to overlap the area where the front ends of the arc-shaped portions of the pair of floor side members are connected via the front member and the area where the rear ends are connected via the rear member, and each of the pair of floor cross members is positioned so as to overlap the area where the arc-shaped portions and side sills are connected.

[0027] Therefore, when loads or vibrations are transmitted from the vehicle's fore-and-aft direction or width direction, these loads and vibrations can be transmitted and dispersed not only to the arc-shaped portions of the floor side members, but also to the center tunnel and the pair of floor cross members.In addition, the floor panel can divide the floor vibration surface into four between the pair of arc-shaped portions, with the center tunnel and the pair of floor cross members as boundaries, thereby suppressing floor vibration. EXAMPLES

[0028] Preferred embodiments 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 embodiments 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.

[0029] 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.

[0030] The vehicle underbody structure 100 includes a floor panel 102 that forms the floor surface of the vehicle, and a front member 104. 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.

[0031] The front member 104 is a member located at the front of the lower side of the floor panel 102, and has a pair of front side members 120, 122, a pair of apron side members 124, 126, a suspension frame 128, a pair of torque boxes 130, 132, and a connecting member 133.

[0032] The vehicle underbody structure 100 further includes a rear member 106 and a pair of side sills 112, 114. The rear member 106 is a member located rearward of the front member 102, and includes a rear cross member 134 that extends in the vehicle width direction and connects the pair of side sills 112, 114, and a pair of rear side members 136, 138. As shown in the figure, the pair of rear side members 136, 138 are arc-shaped and convex outward in the vehicle width direction, and are connected to the rear cross member 134 from the rear side of the vehicle.

[0033] The vehicle underbody structure 100 further includes a pair of floor side members 108, 110. As shown in the figure, the pair of side sills 112, 114 are disposed on the outer sides of the pair of floor side members 108, 110 in the vehicle width direction, and extend in the vehicle front-rear direction along edges 140, 142 of the floor panel 102. The pair of floor side members 108, 110 are members that connect the front member 104 and the rear member 106 below the floor panel 102, and have arc-shaped portions 144, 146.

[0034] The vehicle underbody structure 100 further includes a pair of braces 116, 118. The arc-shaped portions 144, 146 are arc-shaped convex outward in the vehicle width direction, connect the front member 104 and the rear member 104, and are further connected to side sills 112, 114 located on the outer side in the vehicle width direction via braces 116, 118 (described later). Note that the term "arc-shaped" is not limited to a circular arc-shaped portion that is a part of a circle, but also includes an arc-shaped portion that is a part of an ellipse.

[0035] Here, front ends 148, 150 of the arcuate portions 144, 146 are connected to each other in the vehicle width direction via a connecting member 133 which is the front member 104. In addition, rear ends 152, 154 of the arcuate portions 144, 146 are connected to each other in the vehicle width direction via a rear cross member 134 which is the rear member 106.

[0036] The vehicle underbody structure 100 further includes a center tunnel 156, a pair of floor cross members 158, 160, and a reinforcing member 162. The center tunnel 156 extends in the vehicle front-rear direction, protruding upward at the center of the floor panel 102 in the vehicle width direction. The pair of floor cross members 158, 160 extend in the vehicle width direction on the upper surface of the floor panel 102 and connect the center tunnel 156 to each of the pair of side sills 112, 114. The reinforcing member 162 is provided inside the center tunnel 156 at a position overlapping the pair of floor cross members 158, 160 when viewed from the vehicle width direction.

[0037] The center tunnel 156 is disposed so as to overlap an area 164 where the front ends 148, 150 of the arc-shaped portions 144, 146 of the pair of floor side members 108, 110 are connected via the front member 104, and an area 166 where the rear ends 152, 154 are connected via the rear member 106. The pair of floor cross members 158, 160 are disposed so as to overlap areas 168, 170 where the arc-shaped portions 144, 146 and the side sills 112, 114 are connected.

[0038] The pair of floor side members 108, 110 further have bulging portions 172, 174. The bulging portions 172, 174 are formed in front portions 176, 178 including the front ends 148, 150 of the arc-shaped portions 144, 146, and are portions that bulge out toward the bottom of the vehicle.

[0039] Fig. 2 is a diagram showing a state where a part of the vehicle underbody structure 100 in Fig. 1 is seen from another direction. Fig. 2 shows the bulging portion 172 of the floor side member 108 and its surroundings. Fig. 3 is a diagram showing a part of the vehicle underbody structure 100 in Fig. 1. Note that Fig. 3 shows a state where the suspension frame 128 is omitted from the vehicle underbody structure 100 in Fig. 1.

[0040] The bulging portion 172 is formed with a lower surface 180 and inclined surfaces, namely a first inclined surface 182, a second inclined surface 184, and a third inclined surface 186 shown in Fig. 3, as shown in Fig. 2. A suspension fixing part 190 for fixing a swinging suspension 188 for the front wheels is fixed to the lower surface 180. The suspension 188 is composed of, for example, the suspension frame 128 including the suspension fixing part 190, and a suspension tower 192 shown in Fig. 1.

[0041] The first inclined surface 182 inclines downward from the rear of the vehicle toward the lower surface 180 and is connected to the lower surface 180. The second inclined surface 184 inclines downward from the front of the vehicle toward the lower surface 180 and is connected to the lower surface 180. The third inclined surface 186 inclines downward from the lower flange 194 of the floor side member 108 toward the lower surface 180 as shown in FIG. 3, and is connected to the lower surface 180, the first inclined surface 182, and the second inclined surface 184.

[0042] A lower flange 194 of the floor side member 108 is joined to the torque box 130 and the connecting member 133 shown in Fig. 3. As shown by the dotted line in Fig. 2, an inner side surface 196 of the bulging portion 172 is generally trapezoidal. Furthermore, the bulging portion 172 is formed in an arc shape along the arc-shaped portion 144 as shown in Fig. 3.

[0043] 3, the arc-shaped portions 144, 146 of the pair of floor side members 108, 110 have the above-mentioned front portions 176, 178 and rear portions 198, 200. The front portions 176, 178 extend closer to the side sills 112, 114 as they move toward the rear of the vehicle. The rear portions 198, 200 are located further rearward than the front portions 176, 178, and extend farther away from the side sills 112, 114 as they move toward the rear of the vehicle.

[0044] 3 are located, for example, further forward of the side sills 112 and 114, and further have tail portions 202 and 204. The tail portions 202 and 204 are indirectly connected to the front portions 176 and 178 of the arc-shaped portions 144 and 146 via the connecting member 133 and the torque boxes 130 and 132.

[0045] In addition, the tail portions 202, 204 are inclined inward in the vehicle width direction as they approach the rear of the vehicle, as shown by dotted lines C and D, so as to be approximately perpendicular to the tangent directions A and B near the front ends 148, 150 of the front portions 176, 178 of the arcuate portions 144, 146 shown in Figure 3.

[0046] The connecting member 133 has a front portion 206 and a rear portion 208. The front portion 206 has extensions 210, 212 that extend outward in the vehicle width direction beyond the rear portion 208. Outer side surfaces 214, 216 of the extensions 210, 212 are connected to the torque boxes 130, 132. In addition, rear surfaces 218, 220 of the extensions 210, 212 are inclined along front portions 176, 178 of the arc-shaped portions 144, 146 of the floor side members 108, 110, and are joined to the arc-shaped portions 144, 146.

[0047] Furthermore, the tail portions 202, 204 of the front side members 120, 122 are joined to front surfaces 222, 224 of the extension portions 210, 212 of the connecting member 133 and front surfaces 226, 228 of the torque boxes 130, 132. Furthermore, the tail portions 202, 204 of the front side members 120, 122 face the vicinity of the front ends 148, 150 of the inclined front portions 176, 178 of the floor side members 108, 110 at the front and rear of the joint surfaces of the torque boxes 130, 132 and the connecting member 133, i.e., the surfaces along the outer side surfaces 214, 216 of the extension portions 210, 212.

[0048] Furthermore, both side surfaces 230, 232 of the rear surface 208 of the connecting member 133 are inclined inward in the vehicle width direction toward the rear of the vehicle.

[0049] Below, a description will be given of brace 116 and its surroundings. Brace 118 has the same configuration and function as brace 116. Brace 116 has a front brace portion 234, a rear brace portion 236, and a lower surface portion 238 shown in FIG.

[0050] The front brace portion 234 is a portion that extends along the front portion 176 of the floor side member 108 and connects the front portion 176 to the side sill 112. The front portion 176 of the floor side member 108 extends in an arc shape that convexly faces outward in the vehicle width direction. The front brace portion 234 extends in an arc shape that convexly faces inward in the vehicle width direction, and is joined so as to be continuous with a side surface 240 of the front portion 176 on the outer side in the vehicle width direction. As a result, the front portion 176 and the front brace portion 234 are joined to each other so as to have an S-shaped curved shape in a plan view as shown in FIG. 3.

[0051] The rear brace portion 236 is a portion that extends along the rear portion 198 of the floor side member 108 and connects the rear portion 198 to the side sill 112. The rear portion 198 of the floor side member 108 extends in an arc shape that convexly faces outward in the vehicle width direction. The rear brace portion 236 extends in an arc shape that convexly faces inward in the vehicle width direction, and is joined so as to be continuous with a side surface 242 of the rear portion 198 on the outer side in the vehicle width direction. As a result, the rear portion 198 and the rear brace portion 236 are joined to each other so as to have an S-shaped curved shape in a plan view as shown in FIG. 3.

[0052] 3, the lower surface portion 238 of the brace 116 is a portion that joins a lower surface 244 of the side sill 112 and a lower surface 246 of the floor side member 108. The lower surface portion 238 spans the front portion 176 and the rear portion 198 of the floor side member 108, and is joined to a lower surface 248 of the front portion 176 and a lower surface 250 of the rear portion 198. The lower surface portion 238 of the brace 116 has a side surface 252 on the inner side in the vehicle width direction joined in an arc to the arc-shaped portion 144 of the floor side member 108.

[0053] Furthermore, as shown in FIG. 3, the lower surface portion 238 of the brace 116 joins a lower surface 244 of the side sill 112 and a lower surface 246 of the floor side member 108 over a larger area on the rear brace portion 236 side than on the front brace portion 234 side.

[0054] Here, floor cross member 158 shown in Fig. 3 is disposed so as to overlap brace 116 in plan view. Therefore, in order to increase the connection rigidity between brace 116 and floor cross member 158, for example, in joint areas 254, 256 shown by diagonal lines in Fig. 4(a), a lower surface 258 of floor panel 102, lower flanges 260, 262 of brace 116, and upper flanges 264, 266 of floor side member 108 are overlapped and joined in three pieces.

[0055] Fig. 4 is a diagram showing how loads and vibrations are transmitted from the front member 104 and the rear member 106 to the vehicle underbody structure 100 of Fig. 3. The chain line E shown in Fig. 3 indicates a transmission path when a load in the vehicle width direction is transmitted from the brace 116 to the vehicle underbody structure 100. The chain line F shown in Fig. 4(a) indicates a transmission path when a load toward the rear of the vehicle is transmitted from the front side member 120, which is the front member 104, to the vehicle underbody structure 100. The chain line G shown in Fig. 4(b) indicates a transmission path when a load toward the front of the vehicle is transmitted from the rear side member 136, which is the rear member 106, to the vehicle underbody structure 100.

[0056] As described above, the front member 104 and the rear member 106 are connected by the arc-shaped portions 144, 146 of the floor side members 108, 110, and further, the side sills 112, 114 are connected to the arc-shaped portions 144, 146 via the braces 116, 118.

[0057] Therefore, as shown by the chain line E in Fig. 3, the chain line F in Fig. 4(a), and the chain line G in Fig. 4(b), when a load or vibration is transmitted from the vehicle longitudinal direction or the vehicle width direction, the load or vibration is transmitted between the front member 104 and the side sills 112, 114 and between the rear member 106 and the side sills 112, 114 via the arc-shaped floor side members 108, 110. This makes it possible to prevent the load or vibration from concentrating locally when transmitting the load or vibration between the front member 104 and the side sills 112, 114 and between the rear member 106 and the side sills 112, 114 and to efficiently disperse the load or vibration. Therefore, according to the vehicle underbody structure 100, it is possible to improve the NV characteristics of the vehicle by suppressing the vibration of the floor panel 102 while improving the vehicle handling stability.

[0058] The tail portions 202, 204 of the front side members 120, 122 are inclined (see dotted lines C, D) approximately perpendicular to the tangent directions A, B near the front ends 148, 150 of the arcuate portions 144, 146 of the floor side members 108, 110, and are indirectly connected to the front portions 176, 178 of the arcuate portions 144, 146.

[0059] As a result, the load and vibration transmitted from the tail portions 202, 204 of the front side members 120, 122 can be reliably transmitted to the front portions 176, 178 of the arc-shaped portions 144, 146, and can be further efficiently distributed to the side sills 112, 114 and the rear member 106 via the arc-shaped portions 144, 146.

[0060] The floor side members 108, 110 and the side sills 112, 114 are connected via braces 116, 118 that are joined in an arc to the arc-shaped portions 144, 146. This makes it possible to prevent loads and vibrations from concentrating locally between the side sills 112, 114 and the arc-shaped portions 144, 146, and allows these loads and vibrations to be efficiently transmitted and dispersed.

[0061] In addition, since the floor side members 108, 110 and the side sills 112, 114 are connected via braces 116, 118, it is possible to increase the number of support points for the pair of floor side members 108, 110. As a result, the load and vibration transmitted from one rear side member 136, 138 to the other floor side member 108, 110 can be efficiently transmitted and dispersed to the highly rigid side sills 112, 114, while suppressing vibration of the floor side members 108, 110 themselves.

[0062] Bulging portions 172, 174 that bulge out toward the bottom of the vehicle are formed on the arc-shaped portions 144, 146 of the floor side members 108, 110. In addition, in the bulging portion 172, a suspension fixing portion 190 is fixed to a lower surface 180 as shown in Fig. 2, and further, a first inclined surface 182 and a second inclined surface 184 are formed on the front and rear of the lower surface 180 of the bulging portion 172.

[0063] Therefore, when loads or vibrations are transmitted from the suspension fixing portion 190, these loads and vibrations can be efficiently transmitted and dispersed from the underside 180 of the bulge portion 172 of the arc-shaped portion 144, via the first inclined surface 182 and the second inclined surface 184, to the front member 104, the side sill 112 and the rear member 106.

[0064] Furthermore, the bulging portions 172, 174 are formed in an arc shape along the arc-shaped portions 144, 146. Therefore, when a load or vibration is transmitted from the suspension fixing portion 190, the load or vibration can be efficiently transmitted to the side sill 112 via the arc-shaped bulging portion 172 and dispersed. Also, the load or vibration transmitted from one suspension fixing portion 190 can be transmitted to the other floor side member 110 via the arc-shaped bulging portion 172 of one floor side member 108 and dispersed.

[0065] The center tunnel 156 is disposed so as to overlap an area 164 (see FIG. 1) where the front ends 148, 150 of the arc-shaped portions 144, 146 are connected to each other via the front member 104, and an area 166 where the rear ends 152, 154 are connected to each other via the rear member 106. Furthermore, the floor cross members 158, 160 are disposed so as to overlap areas 168, 170 where the arc-shaped portions 144, 146 and the side sills 112, 114 are connected to each other.

[0066] Therefore, when loads or vibrations are transmitted from the vehicle's fore-and-aft direction or width direction, these loads and vibrations can be transmitted and dispersed not only to the arc-shaped portions 144, 146 of the floor side members 108, 110 but also to the center tunnel 156 and floor cross members 158, 160. Furthermore, the floor panel 102 can divide the floor vibration surface into four between the pair of arc-shaped portions 144, 146, with the center tunnel 156 and floor cross members 158, 160 as boundaries, thereby suppressing floor vibration.

[0067] Furthermore, the front portion 176 and rear portion 198 of the floor side member 108 are connected to the side sill 112 by a front brace portion 234 and a rear brace portion 236 of the brace 116 which extend along the arcuate front portion 176 and rear portion 198 of the floor side member 108, respectively.

[0068] Therefore, loads and vibrations transmitted to the side sill 112 in the vehicle width direction can be transmitted to the front member 104 via the front brace portion 234 of the brace 116 and the front portion 176 of the floor side member 108, as shown by the dashed line E in Figure 3. In addition, these loads and vibrations can be transmitted to the rear member 106 via the rear brace portion 236 of the brace 116 and the rear portion 198 of the floor side member 108, as shown by the dashed line E.

[0069] Also, the load and vibration transmitted from the front member 104 to the floor side member 108 can be efficiently transmitted to the highly rigid side sill 112 via the front portion 176 of the floor side member 108 and the front brace portion 234 of the brace 116, as shown by the dashed line F in Fig. 4(a). Furthermore, the load and vibration transmitted from the rear member 106 to the floor side member 108 can be efficiently transmitted to the side sill 112 via the rear portion 198 of the floor side member 108 and the rear brace portion 236 of the brace 116, as shown by the dashed line G in Fig. 4(b).

[0070] In this way, the vehicle undercarriage structure 100 can prevent loads and vibrations transmitted from the vehicle's fore-and-aft direction and width direction from concentrating locally, and can efficiently distribute these loads and vibrations, thereby improving the vehicle's handling stability while suppressing vibration of the floor panel 102 and improving the vehicle's NV characteristics.

[0071] In addition, the front brace portion 234 of the brace 116 is joined so as to be continuous with a side surface 240 on the outer side in the vehicle width direction of the front portion 176 of the floor side member 108, and the rear brace portion 236 is joined so as to be continuous with a side surface 242 on the outer side in the vehicle width direction of the rear portion 198 of the floor side member 108.

[0072] This prevents load and vibration from concentrating locally at the joint surface between the front brace portion 234 and the front portion 176 of the floor side member 108 and the joint surface between the rear brace portion 236 and the rear portion 198 of the floor side member 108, thereby improving the efficiency of transmission of load and vibration.

[0073] Because the front portion 176 of the floor side member 108 and the front brace portion 234 of the brace 116 are arc-shaped, localized concentration of load and vibration at these locations is reduced, and the efficiency of transmission of load and vibration can be improved. In addition, when the arc-shaped front portion 176 and the arc-shaped front brace portion 234 are joined together, they form an S-shaped curved shape in a plan view. This makes it possible to avoid localized concentration of load and vibration at the joint surface between the front portion 176 of the floor side member 108 and the front brace portion 234, and improve the efficiency of transmission of load and vibration.

[0074] Because the rear portion 198 of the floor side member 108 and the rear brace portion 236 of the brace 116 are arc-shaped, localized concentration of load and vibration at these locations can be reduced, improving the efficiency of transmission of the load and vibration. In addition, when the arc-shaped rear portion 198 and the arc-shaped rear brace portion 236 are joined together, they form an S-shaped curved shape in a plan view. This makes it possible to avoid localized concentration of load and vibration at the joint surface between the rear portion 198 of the floor side member 108 and the rear brace portion 236, improving the efficiency of transmission of the load and vibration.

[0075] The underside portion 238 of the brace 116 straddles the front portion 176 and the rear portion 198 of the floor side member 108 and is joined to undersides 248, 250 of the front portion 176 and the rear portion 198. Furthermore, a side surface 252 of the underside portion 238 extends along these arc-shaped front portion 176 and rear portion 198. Therefore, when vibrations or loads are transmitted between the brace 116 and the floor side member 108, it is possible to prevent the vibrations or loads from concentrating locally on the underside portion 238 of the brace 116, thereby improving the transmission efficiency of the load or vibration.

[0076] The floor side member 108 is connected to the side sill 112 and the front side member 120 via the torque box 130 joined to a side surface 240 on the outer side in the vehicle width direction of the front part 176 of the floor side member 108. This makes it possible to increase the efficiency of transmission of vibrations and loads between the side sill 112 and the front member 104, which includes the front side member 120 and the torque box 130.

[0077] The underside portion 238 of the brace 116 joins the underside 244 of the side sill 112 and the underside 246 of the floor side member 108 over a larger area on the rear brace portion 236 side than on the front brace portion 234 side. This increases the efficiency of vibration and load transmission on the rear brace portion 236 side of the brace 116, thereby improving the efficiency of load and vibration transmission between the side sill 112 and the rear member 106.

[0078] The floor cross member 158 is joined to the upper surface of the floor panel 102, and is arranged so as to overlap the brace 116 in a plan view. Therefore, a closed cross section is formed by the lower surface 238 of the brace 116, the side sill 112, the outer side surfaces 240, 242 of the floor side member 108 in the vehicle width direction, and the floor cross member 158, thereby increasing rigidity.

[0079] Both side surfaces 230, 232 of the rear surface portion 208 of the connecting member 133 are inclined inward in the vehicle width direction toward the rear of the vehicle. This makes it easier to transmit load and vibration transmitted from the front end 148 of one floor side member 108 to the tail portion 204 of the other front side member 122. In addition, both side surfaces 230, 232 of the rear surface portion 208 are sandwiched between the floor side members 108, 110, making it easier to transmit load and vibration from the front end 148 of one to the front end 150 of the other.

[0080] The rear surfaces 218, 220 of the extensions 210, 212 of the connecting member 133 are inclined along the front portions 176, 178 of the arc-shaped portions 144, 146 of the floor side members 108, 110, so that the joint area with the arc-shaped portions 144, 146 can be increased. Furthermore, the rear surfaces 218, 220 of the extensions 210, 212 are joined to the arc-shaped portions 144, 146, and the outer side surfaces 214, 216 are connected to the torque boxes 130, 132. In this way, the extensions 210, 212 are welded to the arc-shaped portions 144, 146 and the torque boxes 130, 132 in a substantially L-shaped manner in plan view, for example, so that the joint rigidity can be increased.

[0081] The tail portions 202, 204 of the front side members 120, 122 are joined to front surfaces 222, 224 of the extension portions 210, 212 of the connecting member 133 and front surfaces 226, 228 of the torque boxes 130, 132. This allows loads and vibrations to be transmitted from the front side members 120, 122 to the torque boxes 130, 132 and the connecting member 133.

[0082] The tail portions 202, 204 of the front side members 120, 122 face the inclined front portions 176, 178 of the floor side members 108, 110 in front of and behind the joint surface between the torque boxes 130, 132 and the connecting member 133. This makes it easier to transmit loads and vibrations from the front of the vehicle to the floor side members 108, 110, and further allows the loads and vibrations to be transmitted over the entire front surfaces of the front portions 176, 178. Moreover, since the inclination directions indicated by dotted lines C and D of the tail portions 202, 204 of the front side members 120, 122 overlap with the joint surface, the loads and vibrations can be transmitted more efficiently.

[0083] Front ends 148, 150 of the floor side members 108, 110 are clamped between the connecting member 133 and the torque boxes 130, 132. Therefore, vibration of the floor side members 108, 110 themselves in the vehicle width direction can be suppressed.

[0084] In the vehicle underbody structure 100, the front member 104 is disposed at the front of the lower side of the floor panel 102, and the floor side members 108, 110 are disposed below the floor panel 102, but the present invention is not limited to this. As an example, the front member 104 may be disposed at the front of the upper side of the floor panel 102, and the floor side members 108, 110 may be disposed above the floor panel 102. When the floor side members 108, 110 are disposed above the floor panel 102, the bulging portions 172, 174 of the floor side members 108, 110 may be caused to bulge toward the top of the vehicle, and the suspension fixing portions 190, 268 may be fixed to the upper surfaces of the bulging portions 172, 174.

[0085] Fig. 5 is a diagram showing a modified example of the vehicle underbody structure 100 of Fig. 3. The modified vehicle underbody structure 100A shown in Fig. 5(a) differs from the vehicle underbody structure 100 in that the front ends 148A, 150A of a pair of floor side members 108A, 110A are connected to each other in the vehicle width direction without the interposition of a connecting member 133A. Note that the front ends 148A, 150A of the pair of floor side members 108A, 110A may be integrated with each other.

[0086] Although not shown in the drawings, rear ends 152, 154 of a pair of floor side members 108A, 110A of the vehicle underbody structure 100A may be connected or integrated with each other in the vehicle width direction without the interposition of the rear cross member 134. Furthermore, the pair of floor side members 108A, 110A may be integrated with the connecting member 133A.

[0087] The pair of floor side members 108, 108A, 100, 110A of the vehicle underbody structure 100, 100A may be integrated with the front side members 120, 122. In this case, the connecting members 133, 133A are also integrated with the pair of floor side members 108, 108A, 100, 110A and the front side members 120, 122.

[0088] The arc-shaped portions 144, 146 of the pair of floor side members 108, 108A, 100, 110A of the vehicle underbody structure 100, 100A may be directly joined to the pair of side sills 112, 114, respectively, without the pair of braces 116, 118. In such a case, the front member 104, the rear member 106 and the pair of side sills 112, 114 are connected to each other via the arc-shaped portions 144, 146 of the pair of floor side members 108, 108A, 100, 110A. Therefore, the load transmitted from the vehicle front-rear direction and the vehicle width direction can be efficiently distributed between the pair of side sills 112, 114, between the pair of arc-shaped portions 144, 146, and between the front member 104 and the rear member 106.

[0089] In the connecting member 133 of the vehicle undercarriage 100, the extensions 210, 212 and the front portion 206 may be integral with the torque boxes 130, 132. Also, the extension 210 may be separate from the connecting member 133. Furthermore, the connecting member 133 including the extension 210 may be integral with the pair of floor side members 108, 110.

[0090] In addition, in brace 116, front brace portion 234 and rear brace portion 236 are joined to arcuate portion 144 along the ridge lines of side surfaces 240, 242 of arcuate portion 144, which suppresses localized concentration of load and vibration, making it easier to transmit load and vibration.

[0091] The arc-shaped portions 144, 146 and the side sills 112, 114 of the vehicle underbody structures 100, 100A may be disposed adjacent to each other without being connected. Even in such a case, it is possible to suppress vibration of at least the floor panel 102, and further, when the side sills 112, 114 deform or move inward in the vehicle width direction during a side collision and come into contact with the arc-shaped portions 144, 146, it is possible to transmit load and vibration to the entire vehicle.

[0092] 5(b) is equipped with integrated arc-shaped floor side members 108B and 110B. In the vehicle underbody structure 100B, the bulging portion 172A of the floor side member 108B bulges toward the suspension fixing portion 190 of the suspension frame 128 and is fixed thereto, and then extends to the bulging portion 174A of the floor side member 110B while maintaining the same height, and the bulging portion 174A is fixed to the other suspension fixing portion 268.

[0093] In this manner, in the vehicle underbody structure 100B, the suspension fixing parts 190, 268 are connected to each other in the vehicle width direction by the integrated arc-shaped floor side members 108B, 110B. This allows loads and vibrations to be efficiently transmitted between the suspension fixing parts 190, 268 or between the suspension fixing parts 190, 268 and the side sills 112, 114.

[0094] 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]

[0095] The present invention can be used in a vehicle underbody structure. [Explanation of symbols]

[0096] 100, 100A, 100B... vehicle underbody structure, 102... floor panel, 104... front member, 106... rear member, 108, 108A, 108B, 110, 110A, 110B... floor side member, 112, 114... side sill, 116, 118... brace, 120, 122... front side member, 124, 126... apron side member, 128... suspension frame, 130, 132... torque box, 133, 133A... connecting member, 134... rear cross member, 136, 138... rear side member , 140, 142...Edge of floor panel, 144, 146...Arrow portion, 148, 148A, 150, 150A...Front end of arc portion, 152, 154...Rear end of arc portion, 156...Center tunnel, 158, 160...Floor cross member, 162...Reinforcing member, 164, 166, 168, 170...Area, 172, 172A, 174, 174A...Bulging portion, 176, 178...Front portion of arc portion, 180...Lower surface of bulging portion, 182...First inclined surface, 184...Second inclined surface, 186...Third inclined surface, 188...Suspension, 190, 268...Suspension 192 ... suspension tower, 194 ... lower flange of floor side member, 196 ... inner side of bulge, 198, 200 ... rear of arc-shaped portion, 202, 204 ... tail of front side member, 206 ... front portion of connecting member, 208 ... rear portion of connecting member, 210, 212 ... extension, 214, 216 ... outer side of extension, 218, 220 ... rear of extension, 222, 224 ... front of extension, 226, 228 ... front of torque box, 230, 232 ... both sides of rear portion of connecting member, 234 ... front brace portion, 236 ...rear brace portion, 238...underside of brace, 240...front side of floor side member on the outer side in the vehicle width direction, 242...rear side of floor side member on the outer side in the vehicle width direction, 244...underside of side sill, 246...underside of floor side member, 248...front underside of floor side member, 250...rear underside of floor side member, 252...side of underside of brace, 254, 256...joint area, 258...underside of floor panel, 260, 262...lower flange of brace, 264, 266...upper flange of floor side member

Claims

1. In a vehicle underbody structure including a floor panel that forms a floor surface of a vehicle, the vehicle underbody structure further includes: a front member located in front of the floor panel; a rear member located rearward of the front member; a pair of floor side members connecting the front member and the rear member; a pair of side sills disposed on vehicle width direction outer sides of the pair of floor side members and extending in a vehicle front-rear direction along edges of the floor panel, the rear member includes a rear cross member extending in a vehicle width direction and connecting the pair of side sills, Each of the pair of floor side members is a vehicle underbody structure including an arc-shaped portion that is convex outward in a vehicle width direction, connects the front member and the rear member, and is connected to one of the pair of side sills that is located outward in the vehicle width direction of the arc-shaped portion.

2. 2. The vehicle underbody structure according to claim 1, wherein the front ends of the arc-shaped portions of the pair of floor side members are connected to each other in the vehicle width direction, and the rear ends of the arc-shaped portions of the pair of floor side members are connected to each other in the vehicle width direction.

3. the front member includes a pair of front side members located forward of the pair of side sills, each of the pair of front side members has a tail portion connected to the arc-shaped portion, 3. The vehicle underbody structure according to claim 1, wherein the tail portion is inclined inwardly in a vehicle width direction toward the rear of the vehicle so as to be substantially perpendicular to a tangent direction of the arc-shaped portion.

4. The vehicle underbody structure further includes a pair of braces connecting the pair of floor side members and the pair of side sills, respectively.

4. The vehicle underbody structure according to claim 1, wherein each of the pair of braces is joined to the arc-shaped portion in an arc shape.

5. Each of the pair of floor side members further has a bulge portion formed on the arc-shaped portion and bulging toward a lower portion of the vehicle, The bulging portion has a lower surface to which a suspension fixing part for fixing a swingable suspension for a front wheel is fixed; 5. The vehicle underbody structure according to claim 1, further comprising an inclined surface that is inclined downward from the vehicle front-rear direction toward the lower surface.

6. The vehicle underbody structure according to claim 5, wherein the bulging portion is formed in an arc shape along the arc-shaped portion.

7. The vehicle undercarriage further comprises: a center tunnel extending upward in a vehicle front-rear direction at a center of the floor panel in a vehicle width direction; a pair of floor cross members extending in a vehicle width direction on an upper surface of the floor panel and connecting the center tunnel to each of the pair of side sills; a reinforcing member provided inside the center tunnel at a position overlapping the pair of floor cross members as viewed from the vehicle width direction, the center tunnel is disposed so as to overlap a region where the front ends of the arc-shaped portions of the pair of floor side members are connected to each other via the front member and a region where the rear ends of the arc-shaped portions of the pair of floor side members are connected to each other via the rear member, 7. The vehicle underbody structure according to claim 2, wherein each of the pair of floor cross members is disposed so as to overlap an area where the arc-shaped portion and the side sill are connected.

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