JP7513899B2 - Vehicle underbody structure - Google Patents

Description

The present invention relates to a vehicle undercarriage structure.

Vehicles such as automobiles have a vehicle undercarriage that includes a suspension fixing part to which a swinging suspension for the rear wheels is fixed, and a rear side member that extends from the rear end of the vehicle toward the front of the vehicle and is connected to the suspension fixing part.

In such a vehicle undercarriage structure, when the vehicle is traveling, for example due to lateral acceleration (lateral G) when the vehicle turns, the rear side member receives a load in the direction of the suspension's swing axis from the suspension fixing part, causing the rear side member to vibrate in the swing axis direction. When the rear side member vibrates in the swing axis direction, this vibration causes torsional vibration of the vehicle body and floor vibration of the floor panel.

In addition, in the vehicle undercarriage structure, one of the front, rear, left and right wheels may receive a vertical load, such as the inertial force of the vehicle acting on the outer wheel when the vehicle turns. In such cases, torsional vibration occurs with the maximum amplitude point being the underside of the floor panel on the wheel side diagonally opposite the wheel receiving the load. This torsional vibration includes a vertical vibration component and a width-wise vibration component. In the vehicle undercarriage structure, these vibrations cause the underside of the floor to vibrate, making it difficult to improve the vehicle's NV (Noise and Vibration) characteristics and handling stability (maneuverability).

Patent Document 1 describes a suspension support structure for an automobile. This support structure includes a bending member 13 that bends toward the side sill 2 at the front end of the rear frame 12, and a torque box 43. The torque box 43 is disposed behind the bending member 13 and connects the rear frame 12 and the side sill 2. Furthermore, in this support structure, these members have a closed cross-sectional structure, and a trailing arm 7 that constitutes the rear suspension is fixed to the bottom surface by a support bracket 6. In this way, this structure increases the support rigidity of the support bracket 6 in the fore-and-aft direction of the vehicle body.

Japanese Patent No. 4349039

In the support structure of Patent Document 1, vibrations in the swing axis direction of the rear suspension are transmitted from the trailing arm 7 to the rear frame 12 via the support bracket 6, bending member 13, and torque box 43 due to lateral acceleration (lateral G) when the vehicle turns. With such a support structure, there is a risk that these vibrations will cause torsional vibrations of the vehicle body and floor vibrations of the floor panel.

In addition, in the support structure of Patent Document 1, when vibrations having a vibration component in the vehicle width direction occur in the rear frame 12, no special measures are taken to efficiently disperse the vibrations. Therefore, it is difficult to say that the support structure of Patent Document 1 maintains good NV characteristics and handling stability of the vehicle.

In view of these problems, the present invention aims to provide a vehicle underbody structure that can suppress torsional vibrations in the floor panel and improve the vehicle's noise and vibration characteristics and handling stability.

In order to solve the above problems, a representative configuration of the 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 pair of side sills extending in the vehicle longitudinal direction along the edge of the floor panel, a pair of rear side members extending from the rear end of the vehicle to the front end of the vehicle and connected to the rear ends of the pair of side sills, a pair of suspension fixing parts connected to the pair of rear side members and to which a swingable suspension for the rear wheels is fixed, a rear cross member extending in the vehicle width direction and connecting the pair of rear side members, a pair of floor side members connecting the rear cross member to a front member located at the front of the vehicle, and a connecting member that is inserted in an X-shape between the pair of floor side members and connected to each of the pair of floor side members, the rear cross member has a base extending in the vehicle width direction and a pair of first connecting parts that are continuous with both ends of the base and extend diagonally rearward so as to overlap with a virtual area where the connecting member is extended, and the pair of first connecting parts are connected to at least one of the side, upper surface, or lower surface on the inner side in the vehicle width direction of the pair of rear side members.

The present invention provides a vehicle underbody structure that can suppress torsional vibrations in the floor panel and improve the vehicle's noise and vibration characteristics and handling stability.

1 is a bottom view showing a vehicle underbody structure according to an embodiment of the present invention. FIG. 2 is a diagram showing a part of the vehicle undercarriage of FIG. 1 . FIG. 2 is a top view showing a part of the vehicle undercarriage of FIG. 1 . FIG. 2 is a diagram showing a modified example of the vehicle underbody structure of FIG. 1 . FIG. 2 is a diagram showing another modified example of the vehicle underbody structure of FIG. 1 .

A representative 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 pair of side sills extending in the vehicle longitudinal direction along the edge of the floor panel, a pair of rear side members extending from the rear end of the vehicle to the front of the vehicle and connected to the rear ends of the pair of side sills, a pair of suspension fixing parts connected to the pair of rear side members and to which a swingable suspension for the rear wheels is fixed, a rear cross member extending in the vehicle width direction and connecting the pair of rear side members, a pair of floor side members connecting the rear cross member to a front member located at the front of the vehicle, and a connecting member that is inserted in an X-shape between the pair of floor side members and connected to each of the pair of floor side members, the rear cross member having a base extending in the vehicle width direction and a pair of first connecting parts that are continuous with both ends of the base and extend diagonally rearward so as to overlap with a virtual area where the connecting member is extended, and the pair of first connecting parts are connected to at least one of the side, upper surface, or lower surface on the inner side in the vehicle width direction of the pair of rear side members.

In the above configuration, the suspension fixing part is connected to the rear side member. Therefore, for example, when the vehicle is traveling, the rear side member receives a load in the direction of the swing axis of the suspension from the suspension via the suspension fixing part. Therefore, in the above configuration, the pair of floor side members are connected to each other so as to cross each other by the connecting member, and further, first connection parts are provided at both ends of the base of the rear cross member, extending diagonally rearward so as to overlap with an imaginary area to which the connecting member is extended, and the first connection parts of the rear cross member are connected to at least one of the side, upper surface, or lower surface on the inner side in the vehicle width direction of the rear side member.

In other words, with the above configuration, the rear side member on either the left or right side can be diagonally connected to the floor side member on the opposite side via the first connection part and the connecting member of the rear cross member, thereby increasing the torsional rigidity of the floor panel and suppressing torsional vibration. In addition, the load transmitted from the suspension fixing part to the rear side member on either the left or right side can be dispersed and released to the floor side member on the opposite side via the first connection part and the connecting member of the rear cross member, thereby suppressing floor vibration of the floor panel.

In this way, vibrations and loads can be transmitted between the rear side member on either the left or right side and the floor side member on the opposite side. Furthermore, the load transmitted to the floor side member on the opposite side can be dispersed and released via the floor side member to the front member located at the lower front part of the floor panel, thereby suppressing vibrations in the vehicle width direction of the rear side member. In addition, the load transmitted from the front member located at the lower front part of the floor panel to the floor side member on either the left or right side can also be dispersed and released to the rear side member on the opposite side via the connecting member and the first connection part of the rear cross member. Therefore, according to the above configuration, the torsional vibration of the floor panel can be suppressed, and the torsional vibration of the vehicle body and the floor vibration of the floor panel caused by the vibration of the rear side member can be reduced, thereby improving the noise and vibration characteristics and handling stability of the vehicle.

Each of the pair of suspension fixing parts may overlap a virtual area in a plan view.

In this way, the suspension fixing part is positioned in a position that overlaps with a virtual area that is an extension of the connecting member in a plan view. This makes it easier for vibrations and loads transmitted from the suspension fixing part to the rear side member on either the left or right side to be transmitted to the floor side member on the opposite side via the first connection part of the rear cross member and the connecting member. This makes it easier for vibrations and loads to be transmitted between the rear side member on either the left or right side and the floor side member on the opposite side.

Each of the pair of suspension fixing parts has a support part that supports the swing shaft of the suspension and a bracket that fixes the support part to the rear side member, and the support part overlaps with a midline that extends through the center of the imaginary area in a plan view, and the bracket extends along the midline toward the connecting member.

In this way, the suspension fixing part is positioned so that the support part overlaps the midline in a plan view, and the bracket extends along the midline toward the connecting member. This makes it easier for vibrations and loads transmitted from the support part of the suspension fixing part to the rear side member on either the left or right side via the bracket to be transmitted to the floor side member on the opposite side via the first connection part of the rear cross member and the connecting member. Therefore, with the above configuration, vibrations and loads can be easily transmitted between the rear side member on either the left or right side and the floor side member on the opposite side.

The base of the rear cross member may form a closed cross section, and the rear cross member may further have a pair of second connection portions that are continuous with the pair of first connection portions and are connected to the inner side surfaces of the pair of side sills in the vehicle width direction.

As a result, the rear cross member is connected to a pair of rear side members via a pair of first connection parts, and is further connected to a pair of highly rigid side sills via a pair of second connection parts. This increases the rigidity of the rear cross member, making it possible to suppress vibrations of the pair of floor side members and pair of rear side members connected to the rear cross member. Furthermore, with the above configuration, since the rear cross member is also connected to a pair of highly rigid side sills, vibrations of the rear cross member, rear side members and floor side members can be more sufficiently suppressed.

Each of the pair of floor side members may have a straight rear portion extending in a straight line to which the connecting member is connected, and a rear inclined portion located at the rear end of the straight rear portion, extending diagonally rearward so as to overlap the imaginary area, and connected to each of a pair of first connection portions of the rear cross member.

This makes it easier for the load transmitted from the suspension fixing part to the rear side member on either the left or right side to be transmitted to the floor side member on the opposite side via the first connection part of the rear cross member, the rear inclined part of the floor side member, the rear straight part and the connecting member. Therefore, with the above configuration, it becomes easier to transmit vibrations and loads between the rear side member on either the left or right side and the floor side member on the opposite side.

Each of the pair of floor side members may further have a front inclined portion that is inclined outward in the vehicle width direction from the front end of the rear straight portion toward the front of the vehicle.

As a result, when a load is transmitted from the front member located at the front of the lower side of the floor panel to either the left or right floor side member, this load can be dispersed and released via the front inclined portion, rear straight portion, and connecting member of the floor side member to the floor side member on the opposite side. Here, the front inclined portion is inclined outward in the vehicle width direction from the front end of the rear straight portion toward the front of the vehicle. For this reason, when the front inclined portion is aligned along the extension direction of the connecting member that extends diagonally rearward, vibrations and loads are easily transmitted between the front member and the connecting member.

Each of the pair of floor side members further has a front straight portion that extends linearly from the front end of the front inclined portion toward the front of the vehicle and is connected to the front member, the front member includes a pair of front side members that are located forward of the pair of side sills, and the rear end of each of the pair of front side members is inclined along the inclination direction of the front inclined portion and is located outboard in the vehicle width direction from the front straight portion.

As a result, when a load is transmitted from the front side member on either the left or right side of the front member to the floor side member, the load can be dispersed and released from the rear end of the front side member through the front straight portion of the floor side member to the front inclined portion. Here, the rear end of the front side member is inclined along the inclination direction of the front inclined portion of the floor side member, and is located further outboard in the vehicle width direction than the front straight portion. This makes it easier to transmit vibrations and loads between the front side member of the front member and the front inclined portion of the floor side member.

The front member further includes a pair of torque boxes that connect the pair of front side members and the pair of side sills, and a connecting member that connects the pair of torque boxes, the pair of torque boxes and the connecting member are connected to each other at a predetermined first connecting surface, the rear surfaces of the pair of torque boxes are inclined so that they are located further rearward in the vehicle as they move outward in the vehicle width direction, and of each of the pair of floor side members, the front inclined portion extends toward the first connecting surface, and the front straight portion is connected to the first connecting surface, and the front inclined portion is wider outward in the vehicle width direction as it moves toward the front of the vehicle.

In this way, the front straight portion of the floor side member is joined to the first connection surface between the torque box and the connecting member, so the connection rigidity of the floor side member, the torque box, and the connecting member can be increased. Also, vibrations and loads transmitted to the floor side member are easily transmitted to the torque box and the connecting member via the front straight portion. In addition, because the front inclined portion becomes wider outward in the vehicle width direction toward the front of the vehicle, the connection area with, for example, the torque box can be increased, so that the load can be transmitted more efficiently.

Furthermore, the rear surface of the torque box is inclined so that it is positioned further rearward in the vehicle width direction as it moves outward, approaching the front inclined portion of the floor side member. Therefore, with the above configuration, the dimensions of the front inclined portion can be reduced, making it easier for vibrations of the front inclined portion and the torque box to be transmitted to the side sill connected to the torque box and released.

The preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. The dimensions, materials, and other specific values shown in the 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 that have substantially the same functions and configurations are given the same reference numerals to avoid duplicated explanations, and elements that are not directly related to the present invention are not shown.

Figure 1 is a bottom view showing a vehicle underbody structure 100 according to an embodiment of the present invention. Figure 2 is a diagram showing a portion of the vehicle underbody structure 100 of Figure 1. The figure shows the vehicle underbody structure 100 as viewed from below the vehicle. In each of the figures below, the front-to-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-to-bottom direction of the vehicle are indicated by arrows Up and Down.

The vehicle underbody structure 100 includes a floor panel 102 that forms the floor surface of the vehicle, a pair of side sills 104, 106, and a pair of rear side members 108, 110. As the vehicle underbody structure 100 has a 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.

The pair of side sills 104, 106 are spaced apart in the vehicle width direction and extend in the vehicle front-rear direction along the edges 112, 114 of the floor panel 102. The pair of rear side members 108, 110 are disposed on the inner side of the pair of side sills 104, 106 in the vehicle width direction, extend from the rear end 116 of the vehicle toward the front of the vehicle, and are connected to the rear end portions 118, 120 of the pair of side sills 104, 106.

The vehicle undercarriage 100 further comprises a pair of suspension fixing parts 122, 124, a front member 126, and a rear cross member (first rear cross member 128). The pair of suspension fixing parts 122, 124 are connected to a pair of rear side members 108, 110, and a swingable suspension for the rear wheels (not shown) is fixed to them. The swing axis of the suspension also passes through the pair of suspension fixing parts 122, 124. Therefore, the rear side members 108, 110 connected to the suspension fixing parts 122, 124 receive a load in the swing axis direction from the suspension via the suspension fixing parts 122, 124, for example, while the vehicle is traveling.

The front member 126 is a member located at the front of the lower side of the floor panel 102, and includes a pair of front side members 130, 132, a pair of torque boxes 134, 136, and a connecting member (torque box connecting member 138). The pair of front side members 130, 132 are located forward of the pair of side sills 104, 106 and extend in the fore-and-aft direction of the vehicle. The pair of torque boxes 134, 136 connect the pair of front side members 130, 132 to the pair of side sills 104, 106. The torque box connecting member 138 connects the pair of torque boxes 134, 136.

The pair of torque boxes 134, 136 and the torque box connecting member 138 are connected to each other at predetermined first connecting surfaces 140, 142. Note that the suspension frame 144 included in the front member 126 overlaps the first connecting surfaces 140, 142 from the underside of the vehicle as shown in the figure.

The vehicle undercarriage 100 further includes a second rear cross member 146, a pair of floor side members 148, 150, and a connecting member 152. As shown in the figure, the second rear cross member 146 is spaced rearward of the first rear cross member 128, extends in the vehicle width direction, and connects the pair of rear side members 108, 110.

A pair of floor side members 148, 150 connect the first rear cross member 128 and the front member 126 located at the front of the vehicle below the floor panel 102. The connecting member 152 is placed in an X-shape between the pair of floor side members 148, 150 below the floor panel 102 and is connected to each of the pair of floor side members 148, 150. In other words, the connecting member 152 extends diagonally rearward from each of the pair of floor side members 148, 150, intersects with each other at a predetermined intersection point 154, and is further connected to each of the floor side members 148, 150 on the opposite side.

The first rear cross member 128 has a base 156, a pair of first connecting portions 158, 160, and a pair of second connecting portions 162, 164. The base 156 extends in the vehicle width direction and forms a closed cross section together with the floor panel 102. The base 156 has, for example, a U-shaped cross section with an open upper surface, and forms a closed cross section by overlapping the upper surface with the floor panel 102. Note that the cross section of the base 156 is not limited to a rectangular shape, but may also be a cylindrical shape.

The pair of first connection parts 158, 160 are continuous with both ends 166, 168 of the base 156 and extend obliquely rearward so as to overlap with an imaginary region 170 (see FIG. 2) that is an extension of the connecting member 152. The pair of first connection parts 158, 160 are also connected to the vehicle width direction inner side surfaces 172, 174 of the pair of rear side members 108, 110. Although not shown, the pair of first connection parts 158, 160 are not limited to being connected to the vehicle width direction inner side surfaces 172, 174 of the pair of rear side members 108, 110, but may be connected to the upper or lower surfaces, and may further be connected to at least one of the side surfaces 172, 174, the upper surface, or the lower surface.

The connecting member 152 has a pair of rear portions 176, 178 that extend diagonally rearward from the intersection point 154 shown in FIG. 1, and a pair of front portions 180, 182 that extend diagonally forward from the intersection point 154. Here, the imaginary region 170 to which the connecting member 152 shown in FIG. 2 is extended is the region located between the front virtual line A and the rear virtual line B.

The front virtual line A extends obliquely rearward through the front edge 184 of the rear portion 176 of the connecting member 152. The rear virtual line B extends obliquely rearward through the rear edge 186 of the rear portion 176 of the connecting member 152. Also shown in FIG. 2 is a middle line C that is located between the front virtual line A and the rear virtual line B and extends through the center of the imaginary area 170.

As shown in FIG. 2, the first connection portion 158 extends diagonally backward so as to overlap with the imaginary area 170. The first connection portion 160 also extends diagonally backward so as to overlap with an imaginary area (not shown).

Therefore, in the vehicle undercarriage structure 100, the rear side members 108, 110 on either the left or right side can be diagonally connected to the floor side members 148, 150 on the opposite side via the first connection parts 158, 160 of the first rear cross member 128 and the connecting member 152, thereby increasing the torsional rigidity of the floor panel 102 and suppressing torsional vibration. In addition, the load transmitted from the suspension fixing parts 122, 124 to the rear side members 108, 110 on either the left or right side can be dispersed and released to the floor side members 148, 150 on the opposite side via the first connection parts 158, 160 of the first rear cross member 128 and the connecting member 152, thereby suppressing floor vibration of the floor panel 102.

In this way, the vehicle undercarriage structure 100 can transmit vibrations and loads between the rear side members 108, 110 on either the left or right side and the floor side members 148, 150 on the opposite side. Furthermore, the load transmitted to the floor side members 148, 150 on the opposite side can be dispersed and released to the front member 126 via the floor side members 148, 150, so vibrations of the rear side members 108, 110 in the vehicle width direction can be suppressed. Furthermore, the load transmitted from the front member 126 to the floor side members 148, 150 on either the left or right side can be dispersed and released to the rear side members 108, 110 on the opposite side via the connecting member 152 and the first connecting parts 158, 160 of the first rear cross member 128.

The pair of second connection parts 162, 164 of the first rear cross member 128 are continuous with the pair of first connection parts 158, 160 and are connected to the vehicle widthwise inner side surfaces 188, 190 of the pair of side sills 104, 106.

Therefore, the first rear cross member 128 is connected to a pair of rear side members 108, 110 via a pair of first connection parts 158, 160, and is further connected to a pair of highly rigid side sills 104, 106 via a pair of second connection parts 162, 164. This increases the rigidity of the first rear cross member 128, making it possible to suppress vibrations of the pair of floor side members 148, 150 and the pair of rear side members 108, 110 connected to the first rear cross member 128. In particular, since the first rear cross member 128 is also connected to a pair of highly rigid side sills 104, 106, vibrations of the first rear cross member 128, the rear side members 108, 110, and the floor side members 148, 150 can be more sufficiently suppressed.

In addition, in the first rear cross member 128, not only the base 156 that forms a closed cross section by being overlapped with the floor panel 102, but also the pair of first connecting portions 158, 160 and the pair of second connecting portions 162, 164 may be made to have a closed cross section structure, so that this closed cross section structure can function as a bulkhead.

The pair of suspension fixing parts 122, 124 have support parts 192, 194 and brackets 196, 198 as shown in FIG. 1. The support parts 192, 194 support the swing shaft of the suspension (not shown). The brackets 196, 198 fix the support parts 192, 194 to the rear side members 108, 110. As shown in FIG. 2, the support part 192 overlaps with a midline C that extends through the center of the imaginary area 170 in a plan view. The bracket 196 extends along the midline C toward the rear part 176 of the connecting member 152.

As a result, vibrations and loads transmitted from the support parts 192, 194 of the suspension fixing parts 122, 124 to the rear side members 108, 110 on either the left or right side via the brackets 196, 198 are easily transmitted to the floor side members 148, 150 on the opposite side via the first connection parts 158, 160 and the connecting member 152 of the first rear cross member 128. This makes it easier to transmit vibrations and loads between the rear side members 108, 110 on either the left or right side and the floor side members 148, 150 on the opposite side.

The brackets 196, 198 are formed to extend along the midline C shown in FIG. 2, but if the brackets 196, 198 are rectangular, the corners of the rectangle that face the connecting member 152 should be positioned so that they overlap the midline C. This can improve the efficiency of transmitting vibrations and loads in the inclined direction along which the midline C extends. The brackets 196, 198 may be joined to the undersides of the pair of rear side members 108, 110, the undersides of the pair of side sills 104, 106, or the underside of the first rear cross member 128.

As shown in FIG. 1, the floor side members 148, 150 have rear straight portions 200, 202 and rear inclined portions 204, 206. The rear straight portions 200, 202 extend linearly and are connected to the connecting member 152. The rear inclined portions 204, 206 are located at the rear ends 208, 210 of the rear straight portions 200, 202, extend obliquely rearward so as to overlap the imaginary area 170 (see FIG. 2), and are further connected to the first connection portions 158, 160 of the first rear cross member 128, respectively.

As a result, in the vehicle undercarriage structure 100, the load transmitted from the suspension fixing parts 122, 124 to the rear side members 108, 110 on either the left or right side can be easily transmitted to the floor side members 148, 150 on the opposite side via the first connection parts 158, 160 of the first rear cross member 128, the rear inclined parts 204, 206 of the floor side members 148, 150, the rear straight parts 200, 202, and the connecting member 152.

The floor side members 148, 150 further have front inclined portions 212, 214 and front straight portions 216, 218. The front inclined portions 212, 214 are inclined outward in the vehicle width direction from the front ends 220, 222 of the rear straight portions 200, 202 toward the front of the vehicle. The front straight portions 216, 218 extend linearly from the front ends 224, 226 of the front inclined portions 212, 214 toward the front of the vehicle and are connected to the front member 126.

The front straight portions 216, 218 are also connected to the first connecting surfaces 140, 142 of the front member 126, to which the torque boxes 134, 136 and the torque box connecting member 138 are connected, as shown in FIG. 1.

Therefore, in the vehicle undercarriage structure 100, when a load is transmitted from the front member 126 to the floor side members 148, 150 on either the left or right side, the load can be dispersed and released to the opposite floor side member 148, 150 via the front straight portions 216, 218, front inclined portions 212, 214, rear straight portions 200, 202, and connecting member 152 of the floor side members 148, 150. Also, in the vehicle undercarriage structure 100, if the front inclined portions 212, 214 are inclined outward in the vehicle width direction from the front ends 220, 222 of the rear straight portions 200, 202 toward the front of the vehicle and are aligned in the direction of extension of the connecting member 152, vibrations and loads are easily transmitted between the front member 126 and the connecting member 152.

In addition, the rear ends 228, 230 of the front side members 130, 132 of the front member 126 are inclined along the inclination direction of the front inclined portions 212, 214, and are positioned outboard in the vehicle width direction relative to the front straight portions 216, 218. This makes it easier to transmit vibrations and loads between the front side members 130, 132 of the front member 126 and the front inclined portions 212, 214 of the floor side members 148, 150.

Therefore, in the vehicle undercarriage structure 100, when a load is transmitted from the front side members 130, 132 on either the left or right side of the front member 126 to the floor side members 148, 150, this load can be dispersed and released from the rear ends 228, 230 of the front side members 130, 132 through the front straight portions 216, 218 of the floor side members 148, 150 to the front inclined portions 212, 214.

Figure 3 is a top view showing a portion of the vehicle underbody structure 100 of Figure 1. In the figure, a portion of the vehicle underbody structure 100 is shown through the floor panel 102. The vehicle underbody structure 100 further includes a center tunnel 232, a front seat cross member 234, and a rear seat cross member 236. The center tunnel 232 extends in the vehicle front-rear direction at the center of the floor panel 102 in the vehicle width direction and protrudes upward.

The front seat cross member 234 is a member that extends in the vehicle width direction and connects the pair of side sills 104, 106, and has multiple front seat mounting brackets 238 installed on its upper surface. The rear seat cross member 236 is spaced from the front seat cross member 234 to the rear of the vehicle, extends in the vehicle width direction, and connects the pair of side sills 104, 106, and has multiple rear seat mounting brackets 240 installed on its upper surface.

Here, the center tunnel 232 has a tunnel portion 242 that protrudes upward from the floor panel 102. For example, the tunnel portion 242 protrudes less from the floor panel 102 the further toward the rear of the vehicle. For this reason, the floor panel 102 is prone to surface vibration at a position rearward of the lower end 244 of the tunnel portion 242. Therefore, in the vehicle undercarriage structure 100, the intersection point 154 of the connecting member 152 is positioned rearward of the lower end 244 of the tunnel portion 242, thereby suppressing surface vibration of the floor panel 102.

The connecting member 152 has its rear portions 176, 178 positioned behind the rear seat cross member 236 while overlapping the intersection 154 with the rear seat cross member 236. This allows the surface vibration of the floor panel 102 to be more sufficiently suppressed at a position rearward of the lower end 244 of the tunnel portion 242.

Furthermore, in the connecting member 152, the rear seat mounting brackets 240a, 240b installed on the rear seat cross member 236 and the rear parts 176, 178 are arranged to be stacked in the vertical direction near the intersection 154. This increases the rigidity of the underside of the front seat (not shown) that receives the load when the occupant sits down, suppressing the vibration transmitted to the occupant and improving the NV characteristics. Moreover, since the rear seat mounting brackets 240a, 240b that receive the weight of the occupant and the rear parts 176, 178 are stacked in the vertical direction near the intersection 154 of the connecting member 152, the vibration transmitted to the occupant can be more sufficiently suppressed than when the front seat mounting bracket 238 is stacked on the front parts 180, 182 of the connecting member 152.

The rear seat mounting bracket 240 may be positioned not only so as to overlap vertically with the intersection 154 and rear portions 176 and 178 of the connecting member 152, but also so as to overlap vertically with a specified area 246 surrounded by the rear portion 176, front portion 180 and floor side member 148 of the connecting member 152 in a plan view.

The direction in which the floor side members 148, 150 extend changes at the position where they overlap the front seat cross member 234 in a plan view. That is, the front ends 220, 222 (see FIG. 1) of the rear straight portions 200, 202 overlap the front seat cross member 234 in the vertical direction. The front inclined portions 212, 214 are inclined outward in the vehicle width direction from the front ends 220, 222 of the rear straight portions 200, 202 toward the front of the vehicle. In this way, in the vehicle undercarriage structure 100, the positions where the extension direction of the floor side members 148, 150 changes and where stress is likely to concentrate are reinforced by the front seat cross member 234, making it easier to transmit loads and vibrations at these positions.

Although the above floor side members 148, 150, connecting member 152 and rear side members 108, 110 are arranged below the floor panel 102, this is not limiting and they may be arranged above the floor panel 102.

Figure 4 shows a modified example of the vehicle underbody structure 100 of Figure 1. The modified vehicle underbody structure 100A differs from the above vehicle underbody structure 100 in that it includes a pair of floor side members 148A, 150A instead of the pair of floor side members 148, 150.

In the vehicle undercarriage structure 100A, as shown in the figure, the rear surfaces 248, 250 of the pair of torque boxes 134, 136 are inclined so that they are located further rearward in the vehicle width direction as they move outward in the vehicle width direction. In addition, the front inclined portions 212A, 214A of the pair of floor side members 148A, 150A are inclined outward in the vehicle width direction as they move from the front ends 220, 222 of the rear straight portions 200, 202 toward the front of the vehicle, and the inclination degree of each outer side portion 213, 215 is adjusted so that the width in the vehicle width direction becomes wider toward the front of the vehicle. Note that the inclination degree of the inner side portions 217, 219 of the front inclined portions 212A, 214A may be adjusted instead of the outer side portions 213, 215 so that the width in the vehicle width direction becomes wider toward the front of the vehicle.

In addition, in the vehicle undercarriage structure 100A, the front inclined portions 212A, 214A extend toward the first connecting surfaces 140, 142, and the front straight portions 216A, 218A extend in a straight line from the front ends 224A, 226A of the front inclined portions 212A, 214A toward the front of the vehicle and are connected to the first connecting surfaces 140, 142.

In this way, the front straight portions 216A, 218A of the floor side members 148A, 150A are joined to the first connecting surfaces 140, 142 between the torque boxes 134, 136 and the torque box connecting member 138, thereby increasing the connection rigidity of these floor side members 148A, 150A, the torque boxes 134, 136, and the torque box connecting member 138. As a result, in the vehicle underbody structure 100A, vibrations and loads transmitted to the floor side members 148A, 150A are easily transmitted to the torque boxes 134, 136 and the torque box connecting member 138 via the front straight portions 216A, 218A.

The front straight portions 216A, 218A are continuous with the front inclined portions 212A, 214A, which are wider outward in the vehicle width direction toward the front of the vehicle. Therefore, the front straight portions 216A, 218A are wider in the vehicle width direction than the front straight portions 216, 218 (see FIG. 1) of the vehicle undercarriage structure 100. This allows the front inclined portions 212A, 214A to have a larger connection area with the torque boxes 134, 136 and the torque box connecting member 138, so that vibrations and loads can be transmitted more efficiently. Note that the connection area may be increased by only increasing the width of the front straight portions 216A, 218A in the vehicle width direction without increasing the width of the front inclined portions 212A, 214A in the vehicle width direction.

Furthermore, the rear surfaces 248, 250 of the torque boxes 134, 136 are inclined so that they are positioned further rearward in the vehicle width direction, so that they approach the front inclined portions 212A, 214A of the floor side members 148A, 150A. As a result, in the vehicle undercarriage structure 100A, the dimensions in the direction in which the front inclined portions 212A, 214A extend can be reduced, making it easier for the vibrations of the front inclined portions 212A, 214A and the vibrations of the torque boxes 134, 136 to be transmitted to the side sills 104, 106 connected to the torque boxes 134, 136 and released. In addition, by reducing the dimensions in the direction in which the front inclined portions 212A, 214A extend, it becomes easier to transmit vibrations and loads between the connecting member 152 and the torque boxes 134, 136.

In addition, because the widths of the front inclined portions 212A, 214A and the front straight portions 216A, 218A are increased outward in the vehicle width direction, it becomes easier to position the suspension fixing portions 251a, 251b of the suspension frame 144 outward in the vehicle width direction, improving the vehicle's handling stability. Furthermore, the suspension fixing portions 251a, 251b are positioned adjacent to the rear surfaces 248, 250 of the torque boxes 134, 136 along the inclined direction of the rear surfaces 248, 250. Therefore, in the vehicle undercarriage structure 100A, vibrations of the suspension fixing portions 251a, 251b are more easily released toward the side sills 104, 106.

Figure 5 shows another modified example of the vehicle underbody structure 100 of Figure 1. The modified vehicle underbody structure 100B differs from the above vehicle underbody structure 100 in that it includes a pair of side sill connectors 252, 254 and a pair of braces 256, 258.

In addition, in the vehicle undercarriage structure 100B, the pair of side sills 104, 106 and the pair of torque boxes 134, 136 are connected to each other at predetermined second connecting surfaces 260, 262. The pair of side sill connecting parts 252, 254 branch outward in the vehicle width direction from the pair of floor side members 148, 150, and further the front end portions 264, 266 are connected to the second connecting surfaces 260, 262.

As a result, the vehicle undercarriage structure 100B increases the connection rigidity between the pair of side sills 104, 106 and the pair of torque boxes 134, 136, while making it easier for vibrations transmitted from the connecting member 152 via the pair of floor side members 148, 150 to escape to the pair of side sills 104, 106 and the pair of torque boxes 134, 136.

The vehicle lower structure 100B further includes a plurality of bridging portions 268a, 268b, 270a, and 270b. The side sill connecting portion 252 and the front portion 180 of the connecting member 152 overlap in the extension direction of the front portion 180 of the connecting member 152 via the floor side member 148. The bridging portions 268a and 268b are disposed inside the floor side member 148 and function as bulkheads by bridging between the rear end portion 272 of the side sill connecting portion 252 and the front portion 180 of the connecting member 152 in the extension direction. This increases the rigidity between the connecting member 152 and the side sill connecting portion 252 while improving the efficiency of vibration and load transmission.

The side sill connecting portion 254 and the front portion 182 of the connecting member 152 overlap in the extension direction of the front portion 182 of the connecting member 152 via the floor side member 150. The bridging portions 270a and 270b are disposed inside the floor side member 150 and function as bulkheads by bridging between the rear end portion 274 of the side sill connecting portion 254 and the front portion 182 of the connecting member 152 in the extension direction. This increases the rigidity between the connecting member 152 and the side sill connecting portion 254 while improving the efficiency of vibration and load transmission.

The pair of braces 256, 258 are disposed at the rear ends 208, 210 of the rear straight sections 200, 202, extend obliquely rearward so as to overlap the imaginary area 170 (see FIG. 2), and are further connected to the first connection parts 158A, 160A of the first rear cross member 128A, respectively. Similarly to the pair of braces 256, 258, the first connection parts 158A, 160A also extend obliquely rearward so as to overlap the imaginary area 170, and are further connected to the pair of rear side members 108, 110.

As a result, in the vehicle undercarriage structure 100B, the load transmitted from the suspension fixing parts 122, 124 to the rear side members 108, 110 on either the left or right side can be easily transmitted to the floor side members 148, 150 on the opposite side via the first connection parts 158A, 160A of the first rear cross member 128A, the pair of braces 256, 258, the floor side members 148, 150 and the connecting member 152.

In addition, in the first rear cross member 128A, both ends 166A, 168A of the base 156A, which extends in the vehicle width direction and forms a closed cross section, are inclined diagonally rearward as shown in the figure, so that it functions as a bulkhead and can efficiently transmit vibrations and loads.

As described above, the vehicle substructures 100, 100A, and 100B suppress the torsional vibration of the floor panel 102, thereby reducing the torsional vibration of the vehicle body and the floor vibration of the floor panel 102 caused by the vibration of the rear side members 108 and 110, thereby improving the NV characteristics and handling stability of the vehicle.

Although the preferred embodiment of the present invention has been described above with reference to the attached drawings, it goes without saying that the present invention is not limited to such an example. It is clear that a person skilled in the art can come up with various modified or revised examples within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

The present invention can be used in vehicle undercarriage structures.

100, 100A, 100B...vehicle lower structure, 102...floor panel, 104, 106...side sill, 108, 110...rear side member, 112, 114...edge of floor panel, 116...rear end of vehicle, 118, 120...rear end of side sill, 122, 124...suspension fixing part, 126...front member, 128, 128A...first rear cross member, 130, 132...front side member, 134, 136...torque box, 138...torque box connecting member, 140, 142...first connecting surface, 144...suspension frame, 146... Second rear cross member, 148, 148A, 150, 150A...floor side member, 152...connecting member, 154...intersection, 156, 156A...base, 158, 158A, 160, 160A...first connection portion, 162, 164...second connection portion, 166, 166A, 168, 168A...both ends of base, 170...imaginary area, 172, 174...side of rear side member, 176, 178...rear of connecting member, 180, 182...front of connecting member, 184...front edge of rear, 186...rear edge of rear, 188, 190...side of side sill, 192, 194...support portion , 196, 198... bracket, 200, 202... rear straight portion, 204, 206... rear inclined portion, 208, 210... rear end of rear straight portion, 212, 212A, 214, 214A... front inclined portion, 213, 215... outer side portion of front inclined portion, 216, 216A, 218, 218A... front straight portion, 217, 219... inner side portion of front inclined portion, 220, 222... front end of rear straight portion, 224, 224A, 226, 226A... front end of front inclined portion, 228, 230... rear end of front side member, 232... center tunnel, 234... front seat Cross member, 236... rear seat cross member, 238... front seat mounting bracket, 240, 240a, 240b... rear seat mounting bracket, 242... tunnel section, 244... lower end of tunnel section, 246... specified area, 248, 250... rear surface of torque box, 251a, 251b... suspension fixing section, 252, 254... side sill connection section, 256, 258... brace, 260, 262... second connection surface, 264, 266... front end of side sill connection section, 268a, 268b, 270a, 270b... bridging section, 272, 274... rear end of side sill connection section

Claims (8)

In a vehicle underbody structure including a floor panel that forms a floor surface of a vehicle, the vehicle underbody structure further includes:
A pair of side sills extending in a vehicle front-rear direction along edges of the floor panel;
a pair of rear side members extending from a rear end of the vehicle toward a front side of the vehicle and connected to rear ends of the pair of side sills;
a pair of suspension fixing portions connected to the pair of rear side members and to which a swingable suspension for a rear wheel is fixed;
a rear cross member extending in a vehicle width direction and connecting the pair of rear side members;
a pair of floor side members connecting the rear cross member and a front member located at the front part of the vehicle;
a connecting member that is inserted between the pair of floor side members in an X-shape and connected to each of the pair of floor side members,
The rear cross member is
A base portion extending in a vehicle width direction;
a pair of first connection portions continuous with both ends of the base portion and extending obliquely rearward so as to overlap an imaginary region obtained by extending the connecting member;
a pair of first connection portions connected to at least one of a side surface, an upper surface, or a lower surface on inner sides in a vehicle width direction of the pair of rear side members, said pair of first connection portions being connected to at least one of a side surface, an upper surface, or a lower surface on inner sides in a vehicle width direction of the pair of rear side members. The vehicle underbody structure according to claim 1, characterized in that each of the pair of suspension fixing parts overlaps the virtual area in a plan view. Each of the pair of suspension fixing parts is
a support portion for supporting a swing shaft of the suspension;
a bracket for fixing the support portion to the rear side member,
The support portion overlaps with a middle line extending through a center of the virtual area in a plan view,
3. The vehicle underbody structure according to claim 2, wherein the bracket extends along the midline toward the connecting member. The base of the rear cross member forms a closed cross section,
4. A vehicle undercarriage structure as claimed in claim 1, wherein the rear cross member further has a pair of second connection portions which are continuous with the pair of first connection portions and connected to the vehicle width directional inner side surfaces of the pair of side sills. Each of the pair of floor side members is
a rear straight portion to which the connecting member is connected, the rear straight portion extending straightly;
5. A vehicle undercarriage structure as claimed in any one of claims 1 to 4, characterized in that it has a rear inclined portion located at the rear end of the rear straight portion, extending diagonally rearward so as to overlap the imaginary area, and connected to each of a pair of first connection portions of the rear cross member. The vehicle underbody structure according to claim 5, characterized in that each of the pair of floor side members further has a front inclined portion that inclines outward in the vehicle width direction from the front end of the rear straight portion toward the front of the vehicle. Each of the pair of floor side members further includes a front straight portion that extends linearly from a front end of the front inclined portion toward the front side of the vehicle and is connected to the front member,
the front member includes a pair of front side members located forward of the pair of side sills,
7. The vehicle underbody structure according to claim 6, wherein the rear end portions of the pair of front side members are inclined along the inclination direction of the front inclined portion and are positioned outboard in the vehicle width direction relative to the front straight portion. The front member further comprises:
a pair of torque boxes connecting the pair of front side members and the pair of side sills;
a connecting member connecting the pair of torque boxes,
The pair of torque boxes and the connecting member are connected to each other at a predetermined first connecting surface,
The rear surfaces of the pair of torque boxes are inclined so as to be positioned rearward of the vehicle as they go outward in the vehicle width direction,
In each of the pair of floor side members, the front inclined portion extends toward the first connecting surface, and the front straight portion is connected to the first connecting surface,
8. The vehicle underbody structure according to claim 7, wherein the front inclined portion has a width that is wider outward in a vehicle width direction toward the front of the vehicle.

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